A simple circular metal part that guides the piston to perform linear reciprocating motion in the cylinder. Air in the engine cylinder converts thermal energy into mechanical energy through expansion; gas is compressed by the piston in the compressor cylinder to increase the pressure. The casings of turbines, rotary piston engines, etc. are also commonly referred to as "cylinders". Application fields of cylinder: printing (tension control), semiconductor (spot welding machine, chip grinding), automation control, robot, etc.
1. Cylinder type:
①Single-acting cylinder: There is only one end of the piston rod, the air is supplied from the side of the piston to generate air pressure, and the air pressure pushes the piston to generate thrust to extend, and returns by spring or its own weight.
②Double-acting cylinder: Alternately supply air from both sides of the piston to output force in one or two directions.
③Diaphragm type cylinder: The diaphragm is used instead of the piston, the force is output in only one direction, and the spring is used for reset. It has good sealing performance but short stroke.
④ Impact cylinder: This is a new type of element. It converts the pressure energy of the compressed gas into the kinetic energy of the high-speed (10~20m/s) motion of the piston, so as to do work.
⑤Rodless cylinder: The general term for cylinders without piston rods. There are two types of magnetic cylinders and cable cylinders.
The cylinder that does reciprocating swing is called a swing cylinder. The inner cavity is divided into two by the blades, and air is supplied to the two cavities alternately. The output shaft swings, and the swing angle is less than 280°. In addition, there are rotary cylinders, gas-hydraulic damping cylinders and stepping cylinders.
2. Cylinder structure:
The cylinder is composed of cylinder barrel, end cover, piston, piston rod and seal, etc.
(1) End cover
The end caps are provided with inlet and exhaust ports, and some are also provided with buffer mechanisms in the end caps. The rod side end cover is provided with a sealing ring and a dust ring to prevent air leakage from the piston rod and prevent external dust from mixing into the cylinder. There is a guide sleeve on the end cover of the rod side to improve the guiding accuracy of the cylinder, bear a small amount of lateral load on the piston rod, reduce the bending amount when the piston rod is extended, and prolong the service life of the cylinder. Guide bushes usually use sintered oil-impregnated alloy, forward-inclined copper castings. In the past, malleable cast iron was commonly used for end caps. In order to reduce weight and prevent rust, aluminum alloy die-casting was often used, and brass materials were used for micro cylinders.
The piston is the pressurized part in the cylinder. In order to prevent the left and right cavities of the piston from blowing gas from each other, a piston sealing ring is provided. The wear-resistant ring on the piston can improve the guiding of the cylinder, reduce the wear of the piston sealing ring, and reduce the frictional resistance. The wear-resistant ring length is made of polyurethane, polytetrafluoroethylene, cloth-lined synthetic resin and other materials. The width of the piston is determined by the size of the sealing ring and the necessary length of the sliding part. The sliding part is too short, which can cause early wear and seizure. The material of the piston is usually aluminum alloy and cast iron, and the material of the plug is usually aluminum alloy and cast iron, and the piston of the small cylinder is made of brass.
(3) Piston rod
The piston rod is the most important force-bearing part in the cylinder. Usually high carbon steel is used with hard chrome plating on the surface, or stainless steel is used to prevent corrosion and improve the wear resistance of the seal.
(4) Sealing ring
The sealing of the parts in the rotary or reciprocating motion is called dynamic seal, and the seal of the stationary part is called static seal. The connection methods of the cylinder barrel and the end cover mainly include the following:
Integral type, riveting type, threaded connection type, flange type, pull rod type.
When the cylinder is working, the oil mist in the compressed air is used to lubricate the piston. There are also a small number of lube-free cylinders.
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