简体中文
EnglishHOT CALL：+86-578-2083777
NEWS
新闻动态
How much do you know about excavator hydraulic cylinders
With the development of modern industry, hydraulic transmission technology has been greatly applied and developed in many industries around the world, such as loaders, bulldozers and road rollers for construction machinery; forklifts, belt conveyors and truck cranes for lifting and transporting machinery; construction machinery Pile driver, hydraulic jack and leveler, etc.; agricultural machinery, automobile industry, mining machinery, metallurgical machinery...
Basic knowledge of hydraulic cylinder
With the development of modern industry, hydraulic transmission technology has been greatly applied and developed in many industries around the world, such as loaders, bulldozers and road rollers for construction machinery; forklifts, belt conveyors and truck cranes for lifting and transporting machinery; construction machinery Pile driver, hydraulic jack and leveler, etc.; agricultural machinery, automobile industry, mining machinery, metallurgical machinery...
Hydraulic transmission equipment is usually composed of four components: power, execution, control and auxiliary. And the hydraulic cylinder can realize linear reciprocating motion or less than 360. The hydraulic mechanism of reciprocating oscillating motion is simple in structure and reliable in work. It is also the main executive element widely used in hydraulic systems. It is the hydraulic pressure energy generated by the prime mover driving the hydraulic pump in the form of mechanical energy, and then it can directly drive the load. Reciprocating motion or less than 360. An energy conversion device for the mechanical energy of reciprocating swing motion. To understand hydraulic cylinders, we must know the following basic knowledge.
1. Classification and composition of hydraulic cylinders
Hydraulic cylinders can be divided into four types: piston cylinders, plunger cylinders, swing cylinders and special cylinders according to their structure; according to their rated pressure, they can be divided into high pressure and super high pressure hydraulic cylinders, medium and high pressure hydraulic cylinders and medium and low pressure hydraulic cylinders.
1. Cylinder: The cylinder is the main part of the hydraulic cylinder. It forms a closed cavity with the cylinder head, piston and other parts to push the piston to move. There are 8 types of commonly used cylinder structures, which are usually selected according to the connection form of the cylinder and the end cover. Materials generally require sufficient strength and impact toughness, and good welding performance for welding. Therefore, commonly used materials are: 25, 45, ZG200~400, 1Cr18Ni9 and so on. Cylinder blanks are mostly cold-drawn or hot-rolled seamless steel pipes, so the process is usually quenched and tempered (ensure the strength of the cylinder so that it can withstand oil pressure without deformation and damage) → honing or boring and rolling (ensure the inner diameter of the cylinder The roughness, roundness, cylindricity and straightness, etc. of the piston will not change after long-term reciprocating motion) → Car (ensure the design size requirements such as the full length of the cylinder) → Drill (process the oil outlet hole to ensure entry and exit Oil circuit) → clamp
2. Cylinder head: The cylinder head is installed at both ends of the hydraulic cylinder and forms a tight oil cavity with the cylinder barrel. Usually there are multiple connection methods such as welding, thread, bolt, snap key and tie rod. Generally, the selection is based on factors such as working pressure, connection method of the cylinder, and use environment.
3. Piston rod: The piston rod is the main component of the hydraulic cylinder to transmit force. The material is generally medium carbon steel (such as No. 45 steel). When the oil cylinder is working, the piston rod is subjected to thrust, tension or bending moment, so it is necessary to ensure its strength; and the piston rod often slides in the guide sleeve, the fit should be appropriate, too tight, the friction is too large, too loose, and easy It causes jamming and unilateral wear, which requires proper surface roughness, straightness and roundness. Therefore, the process of piston rod is usually rough turning → quenching and tempering → semi-finishing turning → quenching → pre-plating grinding → chrome plating → post-plating grinding → finishing turning.
4. Piston: The piston is the main element that converts hydraulic energy into mechanical energy. Its effective working area directly affects the force and movement speed of the hydraulic cylinder. There are many forms of connection between the piston and the piston rod. Commonly used are snap ring type, bushing type and nut type. When there is no guide ring, the piston uses high-strength cast iron HT200~300 or ductile iron; when there is a guide ring, the piston uses high-quality carbon steel No. 20, No. 35 and No. 45.
5. Guide sleeve: The guide sleeve acts as a guide and support for the piston rod. It requires high matching accuracy, low friction resistance, good wear resistance, and can withstand the pressure, bending force and impact vibration of the piston rod. A sealing device is installed inside to ensure the sealing of the rod cavity of the cylinder, and a dust ring is installed on the outside to prevent impurities, dust and moisture from being brought to the sealing device and damaging the seal. Metal guide sleeves generally use bronze, gray cast iron, ductile iron and oxide cast iron with low friction coefficient and good wear resistance; non-metallic guide sleeves can use polytetrafluoroethylene and polychlorotrifluoroethylene.
6. Cushioning device: The piston and piston rod have great momentum when they are driven by hydraulic pressure. When they enter the end cover and bottom of the cylinder, they will cause mechanical collisions, resulting in great impact pressure and noise. The buffer device is used to avoid such collisions. Its working principle is to make the oil (all or part) in the low pressure chamber of the cylinder tube convert kinetic energy into heat energy through throttling, and the heat energy is carried out of the hydraulic cylinder by the circulating oil. The structure of the buffer device is divided into two types: constant throttle area buffer device and variable throttle buffer device.
2. The main parameters of the hydraulic cylinder
The main parameters of hydraulic cylinders include pressure, flow, size specifications, piston stroke, movement speed, push-pull force, efficiency and hydraulic cylinder power.
1. Pressure: Pressure is the pressure of oil on a unit area. The calculation formula p=F/A, that is, the load acting on the piston divided by the effective working area of the piston. It can be seen from the above formula that the establishment of the pressure value is produced by the existence of the load. On the effective working area of the same piston, the greater the load, the greater the pressure required to overcome the load. In other words, if the effective working area of the piston is constant, the greater the oil pressure, the greater the force generated by the piston. The rated pressure we usually talk about is the pressure at which the hydraulic cylinder can work for a long time. According to the rated pressure, the hydraulic cylinder pressure classification is shown in the following table: unit MPa
The maximum allowable pressure refers to the ultimate pressure that the hydraulic cylinder can withstand at an instant; and the pressure test pressure refers to the test pressure that the hydraulic cylinder needs to withstand when checking the quality of the hydraulic cylinder. Most of these two pressures are less than or equal to 1.5 times the rated pressure.
2. Flow rate: Flow rate is the volume of effective cross-sectional area of oil passing through the cylinder in a unit time. The calculation formula Q=V/t=vA, where V represents the volume of oil consumed in one stroke of the hydraulic cylinder piston, t represents the time required for one stroke of the hydraulic cylinder piston, v represents the movement speed of the piston rod, and A represents the effective work of the piston area.
3. Piston stroke: Piston stroke refers to the distance traveled between the two poles when the piston reciprocates. Generally, after satisfying the stability requirements of the oil cylinder, a standard stroke similar to it is selected according to the actual working stroke.
4. The movement speed of the piston: the movement speed is the distance that the pressure oil pushes the piston to move in a unit time, which can be expressed as v=Q/A.
5. Size specifications: The size specifications mainly include the inner and outer diameters of the cylinder, the piston diameter, the piston rod diameter and the cylinder head size, etc. These dimensions are calculated according to the use environment of the hydraulic cylinder, the installation form, the required push-pull force and the stroke, etc. , Design and verification.
3. Common problems and maintenance of hydraulic cylinders
As a component and a working device, hydraulic cylinders, like all mechanical equipment, will inevitably produce varying degrees of wear, fatigue, corrosion, loosening, aging, deterioration or even damage in their structural parts during long-term operation. This phenomenon makes the working performance and technical condition of the hydraulic cylinder deteriorate, which directly causes the failure or even failure of the entire hydraulic equipment. Therefore, it is very important to eliminate and repair common problems in the daily work of hydraulic cylinders.
Fourth, the development trend of hydraulic cylinders
With the in-depth popularization of hydraulic technology and the increasing expansion of application fields and occasions, new requirements have been continuously raised for the working performance, structure, scope of use, manufacturing accuracy, appearance, materials, and test methods of hydraulic cylinders. Therefore, hydraulic cylinders are continuously promoted. Development and progress.
Its general trend is:
1. High pressure and miniaturization.
High pressure is an effective way to reduce the radial size and weight of the hydraulic cylinder, and reduce the volume of the entire hydraulic device.
2, new material, lightweight.
With high pressure, miniaturization, and the test of the environment in which hydraulic cylinders are used, new materials and light weight have become one of the solutions.
3. Novel structure composite.
In order to adapt to the expansion of the application range of hydraulic cylinders, various hydraulic cylinders with novel structures are constantly appearing, such as automatic control hydraulic cylinders, self-locking hydraulic cylinders, steel cable hydraulic cylinders, peristaltic hydraulic cylinders and composite hydraulic cylinders.
4, high performance, multiple varieties.
5. Energy saving and corrosion resistance.
【Statement】
Disclaimer: The above article is partly reprinted from the web editor. The purpose of reprinting is to convey more information. If it involves the content of the work, copyright and other issues, please contact us in time. We will take appropriate measures as soon as possible to avoid causing both parties Unnecessary economic losses.
With the development of modern industry, hydraulic transmission technology has been greatly applied and developed in many industries around the world, such as loaders, bulldozers and road rollers for construction machinery; forklifts, belt conveyors and truck cranes for lifting and transporting machinery; construction machinery Pile driver, hydraulic jack and leveler, etc.; agricultural machinery, automobile industry, mining machinery, metallurgical machinery...
Hydraulic transmission equipment is usually composed of four components: power, execution, control and auxiliary. And the hydraulic cylinder can realize linear reciprocating motion or less than 360. The hydraulic mechanism of reciprocating oscillating motion is simple in structure and reliable in work. It is also the main executive element widely used in hydraulic systems. It is the hydraulic pressure energy generated by the prime mover driving the hydraulic pump in the form of mechanical energy, and then it can directly drive the load. Reciprocating motion or less than 360. An energy conversion device for the mechanical energy of reciprocating swing motion. To understand hydraulic cylinders, we must know the following basic knowledge.
1. Classification and composition of hydraulic cylinders
Hydraulic cylinders can be divided into four types: piston cylinders, plunger cylinders, swing cylinders and special cylinders according to their structure; according to their rated pressure, they can be divided into high pressure and super high pressure hydraulic cylinders, medium and high pressure hydraulic cylinders and medium and low pressure hydraulic cylinders.
1. Cylinder: The cylinder is the main part of the hydraulic cylinder. It forms a closed cavity with the cylinder head, piston and other parts to push the piston to move. There are 8 types of commonly used cylinder structures, which are usually selected according to the connection form of the cylinder and the end cover. Materials generally require sufficient strength and impact toughness, and good welding performance for welding. Therefore, commonly used materials are: 25, 45, ZG200~400, 1Cr18Ni9 and so on. Cylinder blanks are mostly cold-drawn or hot-rolled seamless steel pipes, so the process is usually quenched and tempered (ensure the strength of the cylinder so that it can withstand oil pressure without deformation and damage) → honing or boring and rolling (ensure the inner diameter of the cylinder The roughness, roundness, cylindricity and straightness, etc. of the piston will not change after long-term reciprocating motion) → Car (ensure the design size requirements such as the full length of the cylinder) → Drill (process the oil outlet hole to ensure entry and exit Oil circuit) → clamp
2. Cylinder head: The cylinder head is installed at both ends of the hydraulic cylinder and forms a tight oil cavity with the cylinder barrel. Usually there are multiple connection methods such as welding, thread, bolt, snap key and tie rod. Generally, the selection is based on factors such as working pressure, connection method of the cylinder, and use environment.
3. Piston rod: The piston rod is the main component of the hydraulic cylinder to transmit force. The material is generally medium carbon steel (such as No. 45 steel). When the oil cylinder is working, the piston rod is subjected to thrust, tension or bending moment, so it is necessary to ensure its strength; and the piston rod often slides in the guide sleeve, the fit should be appropriate, too tight, the friction is too large, too loose, and easy It causes jamming and unilateral wear, which requires proper surface roughness, straightness and roundness. Therefore, the process of piston rod is usually rough turning → quenching and tempering → semi-finishing turning → quenching → pre-plating grinding → chrome plating → post-plating grinding → finishing turning.
4. Piston: The piston is the main element that converts hydraulic energy into mechanical energy. Its effective working area directly affects the force and movement speed of the hydraulic cylinder. There are many forms of connection between the piston and the piston rod. Commonly used are snap ring type, bushing type and nut type. When there is no guide ring, the piston uses high-strength cast iron HT200~300 or ductile iron; when there is a guide ring, the piston uses high-quality carbon steel No. 20, No. 35 and No. 45.
5. Guide sleeve: The guide sleeve acts as a guide and support for the piston rod. It requires high matching accuracy, low friction resistance, good wear resistance, and can withstand the pressure, bending force and impact vibration of the piston rod. A sealing device is installed inside to ensure the sealing of the rod cavity of the cylinder, and a dust ring is installed on the outside to prevent impurities, dust and moisture from being brought to the sealing device and damaging the seal. Metal guide sleeves generally use bronze, gray cast iron, ductile iron and oxide cast iron with low friction coefficient and good wear resistance; non-metallic guide sleeves can use polytetrafluoroethylene and polychlorotrifluoroethylene.
6. Cushioning device: The piston and piston rod have great momentum when they are driven by hydraulic pressure. When they enter the end cover and bottom of the cylinder, they will cause mechanical collisions, resulting in great impact pressure and noise. The buffer device is used to avoid such collisions. Its working principle is to make the oil (all or part) in the low pressure chamber of the cylinder tube convert kinetic energy into heat energy through throttling, and the heat energy is carried out of the hydraulic cylinder by the circulating oil. The structure of the buffer device is divided into two types: constant throttle area buffer device and variable throttle buffer device.
2. The main parameters of the hydraulic cylinder
The main parameters of hydraulic cylinders include pressure, flow, size specifications, piston stroke, movement speed, push-pull force, efficiency and hydraulic cylinder power.
1. Pressure: Pressure is the pressure of oil on a unit area. The calculation formula p=F/A, that is, the load acting on the piston divided by the effective working area of the piston. It can be seen from the above formula that the establishment of the pressure value is produced by the existence of the load. On the effective working area of the same piston, the greater the load, the greater the pressure required to overcome the load. In other words, if the effective working area of the piston is constant, the greater the oil pressure, the greater the force generated by the piston. The rated pressure we usually talk about is the pressure at which the hydraulic cylinder can work for a long time. According to the rated pressure, the hydraulic cylinder pressure classification is shown in the following table: unit MPa
The maximum allowable pressure refers to the ultimate pressure that the hydraulic cylinder can withstand at an instant; and the pressure test pressure refers to the test pressure that the hydraulic cylinder needs to withstand when checking the quality of the hydraulic cylinder. Most of these two pressures are less than or equal to 1.5 times the rated pressure.
2. Flow rate: Flow rate is the volume of effective cross-sectional area of oil passing through the cylinder in a unit time. The calculation formula Q=V/t=vA, where V represents the volume of oil consumed in one stroke of the hydraulic cylinder piston, t represents the time required for one stroke of the hydraulic cylinder piston, v represents the movement speed of the piston rod, and A represents the effective work of the piston area.
3. Piston stroke: Piston stroke refers to the distance traveled between the two poles when the piston reciprocates. Generally, after satisfying the stability requirements of the oil cylinder, a standard stroke similar to it is selected according to the actual working stroke.
4. The movement speed of the piston: the movement speed is the distance that the pressure oil pushes the piston to move in a unit time, which can be expressed as v=Q/A.
5. Size specifications: The size specifications mainly include the inner and outer diameters of the cylinder, the piston diameter, the piston rod diameter and the cylinder head size, etc. These dimensions are calculated according to the use environment of the hydraulic cylinder, the installation form, the required push-pull force and the stroke, etc. , Design and verification.
3. Common problems and maintenance of hydraulic cylinders
As a component and a working device, hydraulic cylinders, like all mechanical equipment, will inevitably produce varying degrees of wear, fatigue, corrosion, loosening, aging, deterioration or even damage in their structural parts during long-term operation. This phenomenon makes the working performance and technical condition of the hydraulic cylinder deteriorate, which directly causes the failure or even failure of the entire hydraulic equipment. Therefore, it is very important to eliminate and repair common problems in the daily work of hydraulic cylinders.
Fourth, the development trend of hydraulic cylinders
With the in-depth popularization of hydraulic technology and the increasing expansion of application fields and occasions, new requirements have been continuously raised for the working performance, structure, scope of use, manufacturing accuracy, appearance, materials, and test methods of hydraulic cylinders. Therefore, hydraulic cylinders are continuously promoted. Development and progress.
Its general trend is:
1. High pressure and miniaturization.
High pressure is an effective way to reduce the radial size and weight of the hydraulic cylinder, and reduce the volume of the entire hydraulic device.
2, new material, lightweight.
With high pressure, miniaturization, and the test of the environment in which hydraulic cylinders are used, new materials and light weight have become one of the solutions.
3. Novel structure composite.
In order to adapt to the expansion of the application range of hydraulic cylinders, various hydraulic cylinders with novel structures are constantly appearing, such as automatic control hydraulic cylinders, self-locking hydraulic cylinders, steel cable hydraulic cylinders, peristaltic hydraulic cylinders and composite hydraulic cylinders.
4, high performance, multiple varieties.
5. Energy saving and corrosion resistance.
【Statement】
Disclaimer: The above article is partly reprinted from the web editor. The purpose of reprinting is to convey more information. If it involves the content of the work, copyright and other issues, please contact us in time. We will take appropriate measures as soon as possible to avoid causing both parties Unnecessary economic losses.
NEWS
Address：
No.95 Xianxia Road, Liandu District, Lishui City, Zhejiang Province, China
E-mail：
379052306@qq.com
Telephone：
86-578-2083777
COPYRIGHT © 2020 ZHEJIANG ZHONGMING ENGINEERING MACHINERY CO., LTD. SERVICE PROVIDER：@JCSW