Oil free air compressor is a micro reciprocating piston compressor. When the compressor crankshaft rotates driven by a single shaft motor, the piston with self lubrication without adding any lubricant will move back and forth through the transmission of the connecting rod, and the working volume composed of the inner wall of the cylinder, the cylinder head and the top surface of the piston will change periodically. When the piston of the piston compressor starts to move from the cylinder head, the working volume in the cylinder gradually increases. At this time, the gas pushes the inlet valve along the inlet pipe and enters the cylinder until the working volume reaches the maximum, and the inlet valve is closed; When the piston of the piston compressor moves in the opposite direction, the working volume in the cylinder decreases and the gas pressure increases. When the pressure in the cylinder reaches and is slightly higher than the exhaust pressure, the exhaust valve opens and the gas is discharged from the cylinder until the piston moves to the limit position, and the exhaust valve closes. When the piston of the piston compressor moves in the opposite direction again, the above process repeats. That is, the crankshaft of the piston compressor rotates once, the piston reciprocates once, and the process of intake, compression and exhaust is realized successively in the cylinder, that is, a working cycle is completed. The structural design of single shaft and double cylinder makes the gas flow of the compressor twice that of a single cylinder at a certain rated speed, and has been well controlled in vibration and noise control. Working principle of the whole machine: when the motor runs, the air enters the compressor through the air filter. The compressor compresses the air. The compressed gas enters the air storage tank through the air flow pipeline by opening the check valve, and the pointer of the pressure gauge rises to 8 bar,. When it is greater than 8 bar, the pressure switch automatically closes after sensing the pressure of the channel, the motor stops working, and the solenoid valve discharges the air pressure in the compressor head to 0. At this time, the air switch pressure declaration and the gas pressure in the air storage tank are still 8 ￠ bar, and the gas exhausts through the ball valve to drive the connected equipment to work. When the air pressure in the air storage tank drops to 5 ￠ bar, the pressure switch opens automatically through induction, and the compressor starts working again