Automatic door-closing trigger for fireproof door

The utility model adopts the technical scheme as follows: an automatic door-closing trigger for a fireproof door comprises a housing body, a walking rod and an electromagnet fixed on a bottom plate of the housing body, and is characterized in that a fan-shaped pendulum piece capable of driving the walking rod is positioned on an upper shaft of the bottom plate of the housing body, a spring is pivotally connected between the fan-shaped pendulum piece and the bottom plate, the pendulum piece is hollowed out to form an arc groove, a raised pin is fixed on the pendulum piece, a manual shifting rod capable of leaning against the raised pin to apply the force and a shifting fork are movably positioned on a raised shaft of the bottom plate, the raised shaft is positioned in the arc groove of the fan-shaped pendulum piece, the shifting fork can be butted against on a step surface in the arc groove of the fan-shaped pendulum piece, an extending arm of the shifting fork is connected with the electromagnet through a hin