Voice coil motor structure diagram_Structural form of voice coil motor

Voice coil motor structure diagram

The voice coil motor is a special form of direct drive motor that can directly convert electrical energy into linear motion mechanical energy without the need for any intermediate conversion mechanism transmission device. The principle is: a cylindrical winding is placed in a uniform air gap magnetic field, and the winding is energized to generate electromagnetic force to drive the load to move back and forth in a straight line. By changing the strength and polarity of the current, the magnitude and direction of the electromagnetic force can be changed. Therefore, the voice coil motor can move in a linear or rotary form. It has the advantages of high response, high speed, high acceleration, simple structure, small size, good force characteristics, and easy control. The structure of the Tongmao voice coil motor is mainly composed of a stator and a mover. The stator includes an outer yoke, an annular magnetic steel, a magnetic isolation ring and an inner yoke, and the mover consists of a voice coil winding and a winding bracket.

The traditional voice coil motor structure has a cylindrical coil, an air gap formed by the cylindrical center rod and the permanent magnet surrounding the center rod, and a soft iron shell covering the magnet and the center rod. The coil moves along the axial direction of the cylinder in the air gap.

Depending on the coil stroke, the axial length of the coil can exceed the axial length of the magnet, that is, a long voice coil structure. Sometimes, depending on the stroke, the magnet can be longer than the coil, that is, a short voice coil structure. The voice coil length in the long voice coil structure is greater than the sum of the working air gap length and the maximum stroke length; while the working air gap length in the short voice coil structure is greater than the sum of the voice coil length and the maximum stroke length. The long voice coil structure makes full use of the magnetic density, but since only a part of the coil in the voice coil is in the working air gap, the electrical power is not fully utilized; the short voice coil structure is just the opposite. Compared with the two structures, the former allows a smaller magnet system, so the volume of the voice coil motor can also be relatively small; the latter is larger in size, but has less power consumption and can allow a larger voice coil current. Compared with the short coil configuration, the long voice coil configuration can provide a better power-to-efficiency ratio and good heat dissipation. The short voice coil configuration has a shorter electrical time delay, a smaller mass, and generates a smaller armature reaction force.

The structure of voice coil motor

1. Traditional voice coil motor

In the traditional structure, the voice coil motor is a cylindrical coil, with an air gap formed by the cylindrical center rod and the magnet surrounding the center rod, and a soft iron shell covering the magnet and the center rod. The coil moves along the axial direction of the cylinder in the air gap.

In traditional voice coil motors, the coil stroke can be divided into long voice coil structure and short voice coil structure, that is, the axial length of the coil can exceed the axial length of the magnet, that is, the long voice coil structure. Sometimes, depending on the stroke, the magnet can be longer than the coil, that is, the short voice coil structure.

2. Voice coil motor with concentrated flux structure

In motion control, sometimes the force required is greater than what a traditional mobile voice coil motor can provide, and the traditional structure of the voice coil motor cannot meet the requirements. To solve this problem, it is necessary to improve the working efficiency of the voice coil motor. To this end, its structure should be reasonably designed to minimize magnetic circuit leakage. When designing a voice coil motor, it is always hoped that the magnetic lines of force of the magnet steel pass through the air gap as much as possible to increase the air gap flux density and thus generate the greatest possible magnetic force. The use of concentrated flux technology can make the air gap flux density of the manufactured motor equal to or even greater than the residual amount in the magnet.

3. Voice coil motor with magnetic cross access structure

If peak output force is required at the smallest possible diameter, a proprietary cross-access magnetic circuit technology can be used. Compared with conventional structures and concentrated flux structures, its performance characteristics remain unchanged, but the axial dimension is longer, but the diameter dimension is reduced, the magnet mass is smaller, but the coil tends to be heavier. The outstanding advantages of the cross-access magnetic circuit voice coil are small coil leakage inductance and very short electrical time delay.

The material selection of voice coil motor is also very important. The selection of voice coil motor material needs to consider system performance, working environment, processing and cost. The coil is generally made of copper or aluminum wire wound on a non-ferromagnetic winding drum, and a polymer film is coated on the outside for insulation. The conductivity of aluminum wire is half that of copper wire, but the weight is one-third of that of copper wire. It can be selected according to the specific heat dissipation and usage. Most magnetic materials are hard magnets, neodymium iron boron and samarium cobalt. The air gap of the magnet used to accommodate the coil must be large enough, that is, the magnet must work at a lower load line, usually B/H=1. 0~2. 0. In addition, the magnetic material should have high coercive force and a fairly good demagnetization curve to improve the working efficiency of the magnetic circuit.