Autoinjector comprising: - a reservoir module comprising a reservoir (110) containing fluid product and a piston (111), and comprising a needle (112), - an engine module comprising: - a body (201), - a piston rod (210) adapted to cooperate with the piston (111) of said reservoir (110), said piston rod (210) being movable between a rest position and an injection position in which said piston rod (210) has moved the piston (111) of the reservoir (110) for injecting the fluid product through said needle (112), - an injection spring (220) to urge said piston rod (210) towards its injection position, - a lock which blocks said piston rod (210) in the rest position, said lock comprising a wire (230) connected on one side to said piston rod (210) and on the other side to a toothed winding wheel (240 ), a locking member (260) cooperating with a tooth (241) of said toothed winding wheel (2 40), said locking member (260) being movable, in particular pivoting, between a locking position, in which it prevents rotation of the winding wheel (240) in the direction of the actuating force (Fa) exerted by said injection spring (220) on said piston rod (210), and an actuating position, in which said rotation of the winding wheel (240) is possible. Autoinjecteur comportant : - un module réservoir comportant un réservoir (110) contenant du produit fluide et un piston (111), et comportant une aiguille (112), - un module moteur comportant : - un corps (201), - une tige de piston (210) adaptée à coopérer avec le piston (111) dudit réservoir (110), ladite tige de piston (210) étant déplaçable entre une position de repos et une position d'injection dans laquelle ladite tige de piston (210) a déplacé le piston (111) du réservoir (110) pour injecter le produit fluide à travers ladite aiguille (112), - un ressort d'injection (220) pour solliciter ladite tige de piston (210) vers sa position d'injection, - une serrure qui bloque ladite tige de piston (210) en p
