Common sense of pneumatic transmission

(1) Overview of Pneumatic Transmission

Pneumatic transmission and hydraulic transmission are collectively referred to as fluid transmission, and both use pressurized fluid (gas or liquid) as working medium to transmit power or control signals. Pneumatic transmission is a technology that uses compressed air as working medium to transmit and control pressure or signal, so as to realize mechanization and automation of production. Its transmission and control principles are basically the same as hydraulic transmission, but the working characteristics and application occasions of these two systems are also different due to the huge differences in working media and their characteristics.

(2) The basic principle, composition and characteristics of pneumatic transmission.

1. Working principle of pneumatic transmission

The basic working principles of pneumatic transmission and hydraulic transmission are similar (omitted).

2. Composition of pneumatic transmission system

A typical pneumatic transmission system consists of four parts: pneumatic generator, executive component, control component and auxiliary component (Figure 2-70).

Figure 2-70 Composition of Pneumatic Transmission and Control System

1- motor; 2- air compressor; 3- gas tank; 4- pressure control valve; 5- logic element; 6- directional control valve; 7— Flow control valve; 8— Travel valve; 9— Cylinder; 10- muffler; 1 1- Mr. You; 12- water separation air filter

(1) air pressure generator

Air pressure generating device, referred to as air source device for short, is an energy device for obtaining compressed air. Its main part is air compressor, in addition to air source purification equipment. The air compressor converts the mechanical energy provided by the prime mover into the pressure energy of air, and the air source purification equipment is used to reduce the temperature of compressed air and remove moisture, oil and pollution impurities in the compressed air. In factories and mines that use a lot of pneumatic equipment, air source devices are often concentrated in compressor stations (commonly known as air compressor stations), and then compressed air is evenly distributed and supplied to all gas consumption points (branches, workshops, gas equipment, etc.) by the compressor stations. ).

(2) the operative part

The actuator is an energy conversion device, which uses compressed air as the working medium to convert the pressure energy of compressed air into mechanical energy. The actuating elements include: a cylinder that does linear reciprocating motion, a pneumatic motor that does continuous rotary motion and a swing motor that does discontinuous rotary motion.

(3) control elements

The control element, also known as the control, calculation and detection element, is used to control the pressure, flow rate and flow direction of compressed air flow, so that the actuator can complete the predetermined motion law. Control elements include: various pressure valves, directional valves, flow valves, logic elements, injection elements, travel valves, converters and sensors.

(4) Auxiliary components

Auxiliary components are some devices needed for purifying, lubricating, silencing and connecting compressed air. Auxiliary components include: water filter, oil mist filter, muffler and various pipeline accessories.

3. The characteristics of pneumatic transmission

Compared with other transmission and control methods, pneumatic transmission has the following main advantages and disadvantages:

Advantages of (1) pneumatic transmission

1) The pneumatic device is simple in structure, easy to carry and easy to install and maintain. Low pressure level and safe use.

2) The adjustment of output force and working speed is very easy. The working speed of the cylinder is generally 50 ~ 500mm/s, which is faster than the hydraulic and electric modes.

3) High reliability and long service life.

4) Use the compressibility of air to store energy and realize centralized gas supply.

5) Full pneumatic control has fire-proof, moisture-proof and explosion-proof capabilities. Compared with hydraulic pressure, pneumatic method can be used in high temperature occasions.

6) Due to the small airflow loss, compressed air can be supplied centrally and transported over a long distance.

(2) shortcomings of pneumatic transmission

1) Due to the compressibility of air, the change of load can easily change the running speed of the cylinder.

2) When the hydraulic cylinder moves at low speed, the low-speed stability of the hydraulic cylinder is not as good as that of the hydraulic cylinder because of the large ratio of friction to thrust.

3) Although the output force of the oil cylinder can meet the working requirements in many applications, its output force is smaller than that of the hydraulic cylinder.

4) At present, the transmission efficiency of pneumatic transmission is low.