Linear vibration motor and method for manufacturing linear vibration motor

A linear vibration motor, comprising:

• a cylinder having a through-hole with a first open end at a first end in a first direction and a second open end at a second end in the first direction;
• a mover magnet accommodated in the through-hole of the cylinder and movable between the first open end and the second open end;
• a first stator magnet disposed closer to the first open end in the first direction than the mover magnet and arranged so as to generate a repulsive magnetic force against the mover magnet;
• a second stator magnet disposed closer to the second open end in the first direction than the mover magnet and arranged to generate a repulsive magnetic force against the mover magnet;
• a coil conductor at an outer circumferential surface of the cylinder;
• and
• a casing that accommodates the cylinder, the mover magnet, the first stator magnet, the second stator magnet, and the coil conductor,
• wherein a length A of the cylinder in the first direction, a length B of the casing in the first direction, and a length C of the first stator magnet and the second stator magnet in the first direction satisfy a relationship of A+2C<B,
• wherein the casing includes a side wall extending in the first direction, a first end wall connected to the side wall, and a second end wall connected to the side wall and located opposite to the first end wall,
• wherein the first end wall, the second end wall, a first portion of the side wall connected to the first end wall and having a predetermined length, and a second portion of the side wall connected to the second end wall and having a predetermined length comprise magnetic bodies,
• wherein the first end wall has a first recess that opens toward the first open end,
• wherein the second end wall has a second recess that opens toward the second open end,
• wherein the first stator magnet is at least partially accommodated in the first recess, and is attracted to the first end wall with a magnetic force, and
• wherein the second stator magnet is at least partially accommodated in the second recess, and is attracted to the second end wall with a magnetic force.

A method for manufacturing a linear vibration motor, the method comprising:

• preparing a cylinder having a through-hole, and including a polygonal flange at an outer circumferential surface thereof;
• placing a coil conductor on the outer circumferential surface of the cylinder and positioning the coil conductor with the flange;
• inserting the first stator magnet, the mover magnet, and the second stator magnet into the through-hole such that magnetic poles of the first stator magnet, the mover magnet, and the second stator magnet arranged to cause the mover magnet to repel the first stator magnet and the second stator magnet;
• inserting the cylinder having the coil conductor, the first stator magnet, the mover magnet, and the second stator magnet into a casing comprising a magnetic body, having a rectangular prism shape, and having one of side surfaces extending in a longitudinal direction open such that the polygonal flange is brought into contact with an inner wall surface of the casing to restrict rotation of the cylinder inside the casing;
• and
• drawing out an end portion of the coil conductor from the opening of the casing and sealing the opening with a lid comprising a magnetic body,
• wherein a length A of the cylinder in a longitudinal direction, a length B of the casing in the longitudinal direction, and a length C of the first stator magnet and the second stator magnet in the longitudinal direction satisfy a relationship of A<B<A+2C or A+2C<B,
• wherein the cylinder restricts movement of the first stator magnet and the second stator magnet in a plane perpendicular to the longitudinal direction, and a repulsive magnetic force between the mover magnet and the first stator magnet and the second stator magnet restricts movement of the first stator magnet and the second stator magnet in the longitudinal direction.