Automatic centering device

The utility model relates to an automatic centering device. The device comprises an overtravel sensor, a centering sensor and a contact sensor which are arranged on a mobile device, the overtravel sensor, the centering sensor and the contact sensor are correspondingly arranged; when the moving device decelerates to get close to a medium fixed supply point to be contacted; firstly, signal butt joint of the contact sensor and the contact sensor is realized; after signal butt joint, the moving device automatically changes speed and decelerates again; mobile device proceeding, the centering sensorand the centering sensor are in signal butt joint; a medium taking opening in the moving device is aligned with the medium fixed supply point, the moving device stops immediately to achieve centering, and after the moving device is in overtravel, the overtravel sensor and the overtravel sensor achieve signal butt joint, and then the moving device moves reversely till the centering sensor and thecentering sensing piece ac