Step 1 Determine the cylinder diameter/rod diameter
Condition 1
The oil pressure P and flow Q supplied by the hydraulic cylinder in the control loop of the hydraulic system of the equipment or device are known, and their working conditions require the action mode (push, pull, both push and pull) of the output force of the hydraulic cylinder on the load and the size of the corresponding force (thrust F1, pull F2, thrust F1 and pull F2) (extra resistance that may exist in the load should be considered). For the three different modes of action of load output force, the primary method of cylinder diameter/rod diameter is as follows:
(1) The operation mode of output force is thrust F1:
Initial cylinder diameter D: according to the given system oil pressure P (pay attention to the flow channel pressure loss of the system), the cylinder diameter D is theoretically calculated to meet the requirements of thrust F1, and the cylinder diameter D is initially determined after the standard cylinder diameter series is rounded.
Initial fixed rod diameter D: when the action mode of the output force given by the conditions is thrust F1, the selection principle requires that the rod diameter is in the speed ratio of 1.46 ~ 2 (speed ratio: The ratio between the effective acting area of the piston cavity of the hydraulic cylinder and the effective acting area of the piston rod cavity), the rod diameter D should be selected according to the corresponding hydraulic cylinder series speed ratio standard, taking into account the hydraulic cylinder back pressure and the pressure stability of the piston rod.
(2) When the mode of action of output force is force F2:
Assuming cylinder diameter D, rod diameter D is theoretically calculated based on the given system oil pressure P (pay attention to the pressure loss of the system along the way), which meets the requirements of tensile force F2. After entering the standard rod diameter series, the rod diameter D is preliminarily determined, and then the initial rod diameter D is determined after relevant strength verification.
(3) The working mode of output force is thrust F1 and pull F2:
The cylinder diameter D and rod diameter D are compared and calculated by referring to the above two methods (1) and (2), and the hydraulic cylinder diameter and rod diameter standard series are selected.
Condition 2
The mode of action (push, pull, both push and pull) and the magnitude of the corresponding force (thrust F1, pull F2, thrust F1 and pull F2) required by the equipment or device for the output force of the hydraulic cylinder on the load should be known (additional resistance that may exist in the load should be considered). However, the parameters such as oil pressure P and flow rate Q supplied to the hydraulic cylinder by the control loop of the equipment or the hydraulic system of the device are unknown. Aiming at the three different modes of action of the load output force, the primary method of the cylinder diameter/rod diameter is as follows:
(1) According to the industry specifications or characteristics of the equipment or device, determine the rated pressure P of the hydraulic system; The rated pressure of the hydraulic system of special equipment or device depends on the specific working condition. It is generally recommended to choose from medium low pressure or medium high pressure.
(2) According to the operation characteristics of the equipment or device, clear the working speed requirements of the hydraulic cylinder.
(3) Refer to "Condition 1" cylinder diameter/rod diameter primary method for selection.
Step 2 Select the travel or installation mode
According to the requirements of the overall design of equipment or device system, the installation method and stroke S are determined. The specific determination principles are as follows:
Step 2
The determination principle of installation mode:
(1) Flange installation
It is suitable for fixed installation of hydraulic cylinder in the working process, and its force is in the same axis with the supporting center. Its installation location has end, middle, or end three, how to choose depends on acting on the load of the main force on the piston rod compression (push) stress, tensile stress (la), general compression stress using the tail (push), middle flange installation, tensile stress (la) and end, middle flange installation, Determine the end, middle or tail flange installation should be combined with the overall structural design requirements of the system and long stroke compression (push) force conditions of the hydraulic cylinder bending stability.
(2) Hinge installation
It is divided into tail single (double) earring installation and end, middle or tail trunnion installation. It is suitable for the working condition of hydraulic cylinder in which the force causes the machine component to be moved along the same motion plane to curve motion path. When the machine member is driven to operate at an Angle, the force to realize the turning moment is proportional to the Angle of the force generated by the lever arm of the machine connecting rod mechanism and the hinge installation.
A) Rear single (double) earring installation
Tail single earring installation is the most common installation method in hinged installation conditions. It is suitable for the installation conditions of single earring when the piston rod ends move along a curve along the same motion plane during the working process, and the piston rod will move along a path of no more than 3° on both sides of an actual motion plane or the structural design needs. At this time, tail and rod end spherical bearings can be used for installation, but attention should be paid to the pressure load that the spherical bearing installation is allowed to bear.
The installation of tail double earring is suitable for the working condition that the piston rod end presents a curving motion path along the same motion plane. It can be used at any Angle in the same motion plane, and the longitudinal bending caused by the lateral load caused by the "folding force" of the piston rod must be fully considered in the long stroke thrust condition.
B) End, middle or tail trunnion mounting
The central fixed trunnion installation is the most commonly used trunnion installation. The trunnion position can be arranged to balance the weight of the cylinder block or in any position between the end and tail to meet the needs of a variety of applications. The trunnion pin is designed for shear load only and should not be subjected to bending stress. It should be installed with a rigid mounting support seat as long as the trunnion and with support bearings as close to the trunnion shoulder end face as possible in order to minimize bending stress.
C) The installation of tail trunnion is similar to that of tail double earrings, and the selection method is the same as above.
D) End trunnion installation is suitable for hydraulic cylinders with smaller rod diameters than those with hinge points at the tail or middle position. The influence of hydraulic cylinder overhang weight must be considered for cylinder with long stroke end trunnion installation. In order to ensure the effective bearing capacity of the support bearing, it is suggested that the stroke of the hydraulic cylinder should be controlled within 5 times of the cylinder diameter.
(3) Foot frame installation
Suitable for fixed installation in the working process of the hydraulic cylinder, its installation is not in the same plane with the center of the cylinder axis plane condition, so when the hydraulic cylinder of load stress, foot rack installation cylinder will produce a turning torque, such as the hydraulic cylinder is not very good and the installed components are fixed or load it not in the right direction, The overturning torque will produce a large lateral load on the piston rod. When choosing this type of installation, the components installed must be well positioned, fastened and properly guided to the load. The installation mode selection position has two kinds of end and side bracket installation.
The principle of determining the itinerary
(1) Trip S= actual maximum working trip Smax+ trip abundance △S;
Trip abundance △S= trip allowance △S1+ trip allowance △S2+ Trip allowance △S3.
(2) the determination principle of travel wealth △S
Under general conditions, comprehensive consideration should be given to: the travel allowance required by the manufacturing error of the installation size of the system structure △S1, the travel allowance that the hydraulic cylinder may need at the beginning of the travel during the actual work △S2 and the travel allowance that the hydraulic cylinder may need at the end △S3 (note that the hydraulic cylinder has buffer function requirements: The size of travel abundance △S will have a direct impact on the buffer function, it is suggested to reduce travel abundance △S) as far as possible;
(3) For hydraulic cylinders with long stroke (beyond the longest stroke allowed by each series of samples of this product) or specific working conditions, the stability of hydraulic cylinders should be checked according to their specific working conditions (load characteristics, installation methods, etc.).
(4) Hydraulic cylinders with ultra-short stroke (beyond the shortest stroke permitted by certain installation methods of the product sample series).
Step 3 Select the end bit buffer
Buffering at both ends or at one end should be considered for the following conditions:
(1) When the hydraulic cylinder piston runs in full stroke and its round-trip moving speed is greater than 100mm/s, both ends should be buffered.
(2) when the single yearning (return) speed of the hydraulic cylinder piston is greater than 100mm/s and runs to the end of the stroke, one end or both ends of the buffer should be selected.
(3) Other specific working conditions.
Step 4 Select an oil port type and diameter
(1) Oil port type:
The choice of internal thread type, flange type and other special types is determined by the connection pipe in the system.
(2) Diameter selection principle of oil outlet:
Under the condition of known medium flow rate in the connection pipeline between the system and the hydraulic cylinder, the medium flow rate through the oil port is generally not more than 5mm/s. At the same time, pay attention to the factor of speed ratio and determine the diameter of the oil port.
Step 5 Select conditions in specific conditions
(1) Working medium
Normal medium is mineral oil, other media must pay attention to its influence on the sealing system, the material characteristics of each component and other conditions.
(2) Ambient or medium temperature
Normal working medium temperature is -20℃ to +80℃, beyond this working temperature, attention must be paid to its influence on the sealing system, material properties of each component and cooling system Settings.
(3) High operation accuracy
For servos or other hydraulic cylinders with low starting pressure requirements above medium high pressure, attention must be paid to their influence on sealing system, material properties and detailed design of each component.
(4) Zero leakage
For the hydraulic cylinder with special pressure holding requirements, we must pay attention to its influence on sealing system, material properties of each component and other conditions.
(5) Working pressure and speed, such as
A) Medium and low pressure system, piston round-trip speed ≥70~80mm/s
B) High pressure, high pressure system, piston round-trip speed ≥100~120mm/s
Attention must be paid to the influence of sealing system, material properties of each component, coupling structure and mating accuracy.
(6) The working environment of high frequency vibration: attention must be paid to its influence on the material characteristics of each component, the coupling structure and detail design.
(7) Low-temperature icing or pollution of the working environment, such as
1) High dust environment;
2) Water spray, acid fog or salt fog and other environments.
Attention must be paid to the effects on the sealing system, the material properties of each component, the surface treatment of the piston rod and the protection of the product.
Step 6 Selection of seal quality
1.No specific working conditions, specific quality requirements, according to the company's standard sealing system, if necessary, please contact our technical department (0578-3162333) for further information;
Situation
2. In specific working conditions as mentioned above, without specified quality requirements, the sealing system shall be adopted according to our company's specific sealing system;
3. It is recommended that the sealing system be adopted by our company's professional engineers for the specific working conditions and specified quality requirements as mentioned above;
4. The failure of the sealing system of the hydraulic cylinder has serious consequences (such as affecting safety, not easy to replace, and large economic losses, etc.). It is recommended that the sealing system be recommended by the professional engineers of the company.
5. For the hydraulic cylinder sealing system supporting export, it is recommended to adopt well-known sealing quality with good interchangeability and easy to purchase by our professional engineers according to the working conditions.
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Step 7 Select other features
(1) exhaust valve
According to the working position of the hydraulic cylinder, it is normally set at the highest point of the final silting of air in the end of the two cavities. After the exhaust of air, it can prevent crawling, protect the seal, and slow down the deterioration of oil.
(2) Oil leakage port
In the working environment where oil leakage is strictly prohibited, due to the long stroke of the hydraulic cylinder or some working conditions, the oil is silted behind the dustproof ring during the round trip to prevent leakage after a long time of work, and the leakage port must be set at the position where the oil is silted.
