piston body accordingly the manufacturing cost of the air compressor can be reduced to achieve an economical design and the weight of the air compressor can be reduced to facilitate the compressor being carried onto a vehicle application_number US 201514686779 A description referring to fig1 through 4 an air compressor of weight reduction type according to one embodiment of the present invention is shown which generally comprises a main housing 1 a cylinder 3 joined to the main housing 1 a power mechanism mounted to the main housing 1 and a piston body 25 fitted in the cylinder 3 and driven by the power mechanism to conduct reciprocating motion within the cylinder 3 the piston body 25 contains a piston head 26 being integrally formed therewith the power mechanism includes a motor 21 a small gear 22 a large gear 23 a counterweight 28 fixed with a crankpin 24 and a cooling fan 27 the main housing 1 which can be made of plastic is provided with a first portion 11 and a second portion 12 see fig3 the first portion 11 is provided for mounting the motor 21 fitted with a small gear 22 at an axle thereof a cooling fan 27 is provided at a rear end of the axle of the motor 21 the large gear 23 is provided with the counterweight 28 being fixed with a crankshaft 281 and.