Pneumatic motor is a kind of pneumatic actuator for continuous rotary motion. It is an energy conversion device that converts the pressure energy of compressed air into rotary mechanical energy. Its function is equivalent to motor or hydraulic motor. It outputs torque to drive the actuator for rotary motion. Vane type, piston type and gear type pneumatic motors are widely used in pneumatic transmission.
Working principle of piston pneumatic motor
It is mainly composed of: motor shell, connecting rod, crankshaft, piston, cylinder, valve, etc. The compressed air enters into the valve core to make it rotate. At the same time, by the valve core rotation, the compressed air is successively sent into the surrounding cylinders. Due to the expansion of the compressed air in the cylinder, the piston connecting rod and crankshaft are pushed to rotate. When the piston is pushed to the "bottom dead center", the valve core also turns to the first exhaust position. The expanded gas is discharged directly from the cylinder through the exhaust port of the valve. At the same time, all the remaining gas in the piston cylinder is discharged from the exhaust port of the valve core distribution valve. After such reciprocating circulation, the crankshaft can rotate continuously. Its work mainly comes from gas expansion work.

 

   

 
Working principle of vane pneumatic motor
As shown in the figure is the working principle of bidirectional vane type pneumatic motor. The compressed air is input through hole a, and a small part enters the bottom of the blade through the slots of the sealing cover at both ends of the stator (not shown in the figure). The blade is pushed out to make the blade close to the inner wall of the stator, and most of the compressed air enters the corresponding sealing space and acts on the two blades. Due to the unequal extension length of the two blades, there is a torque difference, which makes the blades and the rotor rotate in a counter clockwise direction, and the gas after work is discharged from the hole B on the stator.
If the input direction of the compressed air is changed (that is, the compressed air enters from hole B and discharges from hole a), the rotation direction of the rotor can be changed.
      
 

Figure-1 vane motor with bidirectional rotation
(a) Structure（ b) Function symbol
Working principle of vane pneumatic motor
Pneumatic motor is a prime mover which uses compressed air as working medium. It is a power device which uses the expansion of compressed air to convert pressure energy into mechanical energy.
Although different types of air motors have different structures and working principles, most of them have the following characteristics:
1. Stepless speed regulation. As long as the opening of the intake valve or the exhaust valve is controlled, that is, the flow of compressed air is controlled, the output power and speed of the motor can be adjusted. The purpose of adjusting speed and power can be achieved.
2. It can rotate forward or reverse. Most of the air motors can realize the forward and reverse rotation of the output shaft of the air motor as long as they simply use the control valve to change the direction of the motor's intake and exhaust, and can change the direction instantaneously. In the case of forward and reverse conversion, the impact is very small. One of the main advantages of air motor reversing operation is that it has the ability to rise to full speed almost instantaneously. The vane type air motor can rise to full speed in one and a half revolutions; The piston air motor can reach full speed in less than a second. Using the control valve to change the direction of air intake can achieve positive and negative. It has the advantages of short time, high speed, small impact and no need to unload.
3. Work safety, not affected by vibration, high temperature, electromagnetic, radiation, etc. it is suitable for harsh working environment, and can work normally under inflammable, explosive, high temperature, vibration, humidity, dust and other adverse conditions.
4. It has the function of overload protection, and will not fail due to overload. When overload occurs, the speed of the motor only decreases or stops. When the overload is removed, the motor can immediately resume normal operation without any damage to the parts. It can run continuously at full load for a long time with small temperature rise.
5. It has high starting torque and can be started directly with load. It starts and stops quickly. It can be started with load. Start and stop quickly.
6. Wide range of power and speed. The power is as small as several hundred watts and as large as tens of thousands of watts; The speed can be from zero to ten thousand revolutions per minute.
7. Easy to operate, easy to maintain and repair. The pneumatic motor has the advantages of simple structure, small volume, light weight, high horsepower, easy operation and convenient maintenance.
8. Using air as the medium, there is no difficulty in supply, the used air does not need to be treated, put into the atmosphere without pollution, compressed air can be centralized supply, long-distance transmission
Because of the above characteristics, the air motor can work in humid, high temperature, high dust and other harsh environment. In addition to being used as power in rock drilling, drilling, loading and other equipment in mining machinery, it is also widely used in shipbuilding, metallurgy, chemical industry, papermaking and other industries.
Air motor is the best substitute for explosion-proof motor. In addition to the standard model, we also have the model of air motor equipped with reducer, with reduction ratio from 10:1 to 60:1.
Features include:
1) Variable speed;
2) Explosion proof - no electric spark;
3) No heating during operation;
4) It will not burn out;
5) Both positive and negative directions are OK.
Pneumatic motor is divided into one-way and two-way forms. For the unidirectional pneumatic motor, the rotation and stop of the motor can be controlled only by opening and closing the air inlet.
The bidirectional pneumatic motor has two air intakes and one main exhaust port. When the motor works, the air is supplied from one air inlet, and the other air inlet is the auxiliary exhaust port. If the motor rotation direction needs to be changed, the air inlet and the auxiliary exhaust port only need to be exchanged. Therefore, the selected control valve must have the above functions to make the motor work normally. Three position four-way valve or three position five way valve is recommended. During the pipeline layout, the diameter of the pipeline between the gas source and the gas motor (including pipeline accessories, control valve, oil mist device, etc.) shall not be less than the minimum inner diameter corresponding to the motor, and the pipeline shall not have serious throttling phenomenon. The pipe joint should be firm, sealed and free of leakage, otherwise the pneumatic motor can not achieve the expected performance.
   
 
 

As shown in the figure is the structural schematic diagram of vane type pneumatic motor. It is mainly composed of stator, rotor, blade and shell. The stator is provided with an air distribution slot hole for air inlet and exhaust. The rotor is milled with long grooves. The slot is equipped with blades. Both ends of the stator are covered with sealing covers. The rotor and stator are installed eccentrically. In this way, the blade sliding along the radial direction and the inner cavity of the shell form the working chamber of the pneumatic motor.
The working principle of pneumatic motor is similar to that of hydraulic motor. The compressed air enters from a. It acts on the blades on both sides of the working chamber. Due to the eccentric installation of the rotor, the torque difference generated by the air pressure acting on the blades on both sides causes the rotor to rotate counterclockwise. When the eccentric rotor rotates, the volume of the working chamber changes, resulting in a pressure difference on the blades of the adjacent working chamber, which is used to drive the rotor to rotate. The gas after work is discharged from the output port. If the compressed air input direction is changed, the rotation direction of the rotor can be changed.
As shown in figure a, the vane type pneumatic motor adopts the structure form that does not expand the compressed air, that is, the non expansion type, and the working principle is described above. The vane type pneumatic motor shown in Fig. B adopts the structure form of maintaining the compressed air expansion stroke. When the rotor turns to the position of exhaust port C, the compressed air in the working chamber will exhaust once, and then the rest of the compressed air will continue to expand until the rotor turns to the position of output port B for secondary exhaust. The pneumatic motor with this structure can effectively use part of the compressed air expansion energy, improve the output power. Compared with the expansion type pneumatic motor, the non expansion type pneumatic motor has higher air consumption and lower efficiency; The output power per unit volume is large, the volume is small and the weight is light.
The vane type pneumatic motor is generally used in the range of medium and small capacity and high speed rotation. Its air consumption is larger than that of piston type, with small volume, light weight and simple structure. The output power is 0.1-20kw and the speed is 500-25000r / min. In addition, the characteristics of vane air motor are not good when it starts and runs at low speed. When it is used under the speed of 500r / min, it must be equipped with a deceleration mechanism. Vane type pneumatic motor is mainly used in mining machinery and pneumatic tools.
Ruinuohong precision machinery technology has the first technology and equipment processing pneumatic motor rotor and stator (cylinder).