How to Increase Life Time of Coin Vibration Motor

How to Increase Life Time of Coin Vibration Motor

   China's flat vibration motor for mobile phones has developed rapidly, and many companies have formed large-scale production. With the development of mobile phone performance, manufacturers have increased their lifespan from the initial 45,000 times (that is, 2 seconds, 2 seconds to 1 cycle) to 100,000 times, and some manufacturers require 150,000 times or more. Its longevity has become an important threshold for entering high-demand mobile phone companies.    

   The motor is a commutator type permanent magnet DC motor. The brush and commutator determine the life of the motor. The paper describes an effective method to improve the life of the flat vibration motor for mobile phones.

    1) The shunt resistance between the commutators is an important measure to improve the commutation and reduce the spark according to the commutation theory. At present, the main method is to print carbon film resistors on the PCB or to mount carbon film resistors on the PCB. The value is O. Between 6 and 1.2KΩ. There are also shunt capacitors that reduce the inductive reactance of the commutation loop. It would be better if the corresponding varistor effect was used.

    2) Winding type and connection. Motor windings should be arranged in a plane regardless of whether they use three coils or two coils. Do not overlap them to reduce the mutual inductance and facilitate commutation. The connection between the winding and the commutator must be calculated by the calculation and reversed by an angle in order to reduce the influence of the armature reaction on the commutation.

    3) Brush design. The brush is 9 O° between two points. I hope that the distance between the two points will be as small as possible. In the case of high-speed rotation of the motor, the distance is the linear speed of the motor, and the belt conveyor is a few tenths of a millimeter apart. The whole life will be ten kilometers away, and the degree of wear of the brush and commutator should be proportional to it.

    4) Reduce the electrical load. Reducing the electrical load is an effective way to increase the life of the motor. The motor's rated current is reduced from the initial 80mA to 45mA.

    5) Reduce the impact of electromagnetic interference. The goal is to reduce the influence of external electromagnetic interference on the motor and reduce the influence of electromagnetic interference caused by the motor commutator on the mobile phone circuit. The design uses the inter-electrode capacitance for absorption, which is achieved by adding the inter-electrode capacitance to the chip capacitor or the sieving machine design on the flexible circuit board FPC.

    6) Pay attention to the calculation of the dimension chain. Guaranteed axial dimension vibration table clearance and brush and commutator pressure value are the main part of the motor size chain calculation, and also the key to ensure the normal operation of the motor.

 The surface of the brush slides on the surface of the commutator by a certain contact force, and the stability of the contact resistance is ensured. The commutator is scratched by the scraping force of the brush (higher hardness), which is accompanied by mechanical wear and erosion, Complex damage processes such as environmental electrochemical corrosion, so the rational selection of materials is another key to improving the life of the motor.

    1) Commutator material. The part is achieved by gold plating of the PCB board. There are currently two methods in gold plating technology: one is to first plate a layer of nickel on the substrate (required between 3um and 5um), and then gold plating; the other is directly plated with gold on the substrate. I agree with the previous view that gold plating is reliable. Those who oppose it think that after nickel plating, nickel interferes with the magnetic circuit and forms an axial magnetic pulling force. The author believes that controlling the inner diameter of the magnetic steel and the size of the commutator piece reduces the influence of the magnetic pull force, and it is better to plate the gold after nickel plating. Existing precious metal composite materials are used to punch out the commutator segments and then combine a layer of circuit boards. This design makes the motor last longer.

    2) Brush material. At present, the Japanese composite code is SP-1, and China has corresponding product output. Pay attention to its "expensive/cheap metal composites" and its many studies. mainly:   

    (1) The change rule of the commutator and brush material pairing selection and contact resistance.

    (2) The effect of alloy crystal structure on workability, nanocrystalline technology.

    (3) Surface hardness distribution state and wear.

    (4) Surface residual pressure and stability of contact resistance.

    (5) The influence of the composite interface structure on the electrical and thermal conductivity.

    (6) Temperature rise of the electrical contact surface and changes in working conditions.

    (7) Electrical erosion treatment.

    (8) Surface film structure.

    (9) Surface finish and environmental conditions.

    3) Selection of non-metallic materials. Non-metallic materials used in the internal structure and external installation of the motor, such as plastics, mold release agents, lubricants, adhesives, glues and patches, are required to contain no silicon or sulfur. When silicon or sulfur is exposed to normal temperature or high temperature, the low-molecular-weight silicon and sulfur compound organic gases volatilized on the contact surface, causing corrosion of the commutating component and a decrease in lifetime.

3 production environment

    The motor is a labor-intensive product. Many processes are performed manually by workers. The strict requirements of the manufacturing process, the protection of the environment and the cleaning of components are essential to improve product quality.

    1) Strictly follow the operating procedures, keep the environment clean, and wear finger cots for workers.

    2) Pay attention to the cleaning of parts.

    3) The brush and commutator should be inspected before assembly, and there is no dirt on the surface to enter the assembly.

4 brush adjustment.

    The contact between the brush and the commutator is achieved by adjusting the height of the brush, and the magnitude of the contact pressure directly affects the operation and life of the motor. For this point, all enterprises are guaranteed by adjusting the adjustment value through many experiments, but due to the influence of brush materials, processing accuracy, environment and other factors, they should also pay attention to it at any time. At present, there are two methods for brush adjustment: one is to adjust the height of the display by using a CCD camera; the other is to adjust the pressure required to press the brush to the estimated height. The former uses more than the latter.

From net forwarded by www.vibrationmotor.net