Switch

1 . A switch comprising:

a static contact;

a static iron core partially forming a cavity, wherein the cavity has a first opening on a side facing the static contact and a second opening on a side away from the static contact;

a moving iron core, wherein the moving iron core comprises a narrow part passing through the first opening of the cavity and a widened part immediately adjacent to the narrow part and away from the static contact relative to the narrow part, wherein a cross-sectional size of the narrow part is smaller than that of the widened part, and a platform is formed at a boundary between the narrow part and the widened part and protruding outwards from a periphery of the narrow part, and the moving iron core passes through the cavity through the first opening and the second opening of the cavity;

a moving contact fixedly arranged on the moving iron core, wherein the platform abuts against the static iron core when the moving contact is in contact with the static contact;

a coil arranged in the cavity and surrounding a part of the moving iron core;

a permanent magnet arranged in the cavity and adjacent to the coil;

a reset piece connected to the moving iron core, wherein the reset piece exerts an elastic force on the moving iron core away from the static contact when the static contact is in contact with the moving contact,

wherein the static iron core, the moving iron core and the permanent magnet form a closed magnetic circuit when the static contact is in contact with the moving contact.

2 . The switch according to claim 1 , wherein there is no air gap between the permanent magnet and the static iron core, and there is no air gap between the permanent magnet and the moving iron core when the moving contact is in contact with the static contact.

3 . The switch according to claim 2 , wherein the moving iron core passes through the static iron core along a center line of the static iron core.

4 . The switch according to claim 3 , wherein the permanent magnet comprises a first permanent magnet and a second permanent magnet, the first permanent magnet and the second permanent magnet are oppositely arranged with respect to the center line and spaced apart, and magnetic poles of respective ends of the first permanent magnet and the second permanent magnet facing the moving iron core are the same, and when the static contact is in contact with the moving contact, the first permanent magnet and the second permanent magnet are in contact with the moving iron core respectively.

5 . The switch according to claim 4 , wherein the permanent magnet is arranged on a side of the coil near or away from the static contact.

6 . The switch according to claim 4 , wherein the static iron core is provided with a protruding part at the first opening and protruding towards an interior of the static iron core in a direction parallel to the center line of the static iron core, and when the moving contact is in contact with the static contact, the platform abuts against the protruding part.

7 . The switch according to claim 6 , wherein the protruding part is made of a ferromagnetic material.

8 . The switch according to claim 4 , wherein the permanent magnet is arranged on a side of the coil near the static contact, and the position of the permanent magnet is set so that when the static contact is in contact with the moving contact, a side surface of the permanent magnet near the static contact is flush with the platform of the moving iron core.

9 . The switch according to claim 1 , wherein the widened part and the narrow part are integrally formed and are made of a magnetic conductive material.

10 . The switch according to claim 1 , wherein the moving iron core comprises an outer part and an inner part, wherein the inner part continuously extends through the cavity and has a same cross-sectional size as that of the narrow part, the outer part surrounds a part of the inner part to form the widened part, and the outer part is made of a magnetic conductive material.

11 . The switch according to claim 1 , wherein the reset piece is a spring, one end of the reset piece is fixed and the other end of the reset piece is connected to an end of the moving iron core facing the static contact, and when the moving contact is in contact with the static contact, the spring is in a compressed state.

12 . The switch according to claim 1 , wherein the moving iron core is provided with an accommodating part near the moving contact, and a contact spring is arranged in the accommodating part, and one end of the contact spring is connected with the moving contact and the other end of the contact spring is fixed to the moving iron core.