The primary function of the vibration motor is to alert the user to incoming calls. Vibration motors are normally classified into cylinder type and button type. Here, we will look at how the cylinder type works.
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| An electrical current applied to the coil in the direction of the arrow (see Figure 1) generates upward force on the left side of the coil and downward force on the right side , causing the coil to revolve clockwise. |
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Principles of vibration
An offset counterweight is fitted to the end of the motor shaft. When the shaft turns, the imbalance in the counterweight causes the handset to vibrate. Figure 4 shows the internal structure of the motor, while Table 1 shows the criteria.
| Counter Weight
|
Speed[rpm]
|
Vibration[N]
|
| 4CH |
R2.5×L3.5×180° |
9500 |
1.50 |
| R3.0×L3.5×150° |
9500 |
2.18 |
| 4CR |
R3.0×L4.0×150° |
9500 |
2.56 |
| 4.4CH |
R3.0×L4.0×150° |
7400 |
1.91 |
| R3.0×L4.0×150° |
8500 |
2.37 |
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The counterweight is designed to provide strong vibrations from a small motor within a compact handset. Tungsten alloy is often chosen for its high specific gravity (see Table 1).
| Element[Symbol] |
Specific Gravity[g/cm3] |
| Namiki Tungsten(W) |
18.1 |
| Pure Tungsten(W) |
19.3 |
| Iron(Fe) |
7.9 |
| Gold(Au) |
19.3 |
|
| Element[Symbol] |
Specific Gravity[g/cm3] |
| Silver（Ag） |
10.5 |
| Copper（Cu） |
9.0 |
| Lead（Pb） |
11.4 |
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The commutation process involving the commutator and brushes is the basic principle at the heart of the DC motor. Motor performance depneds the efficiency of this process. The commutator and brushes works as follows.
| ♦Communicater |
Commutator: Supplies electrical current from the brush to the armature, and performs commutation together with the brush. Commutators are often made from tough pitch copper or silver cladding, although Namiki uses metallic commutators clad with a thin, super-reliable Pd-Ag-Au-Pt alloy. |
| ♦Brush |
Brushes : Supply electrical current from the power source to the commutator, and also perform commutation with the commutator. The brush material is chosen to match the commutator. For instance, silver-carbon or noble-metal brushes are normally used with silver-clad or gold-clad commutators.. Namiki uses metallic brushes clad in Au-Ag-Pt alloy. |
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| A key feature of Namiki motors is the use of resin bearings for the motor shafts instead of conventional metal bearings. By using a single piece of resin for both front and rear, Namiki has succeeded in reducing the total number of components, thus speeding up the manufacturing process, saving space, and cutting production costs. Resinous bearings also generate less friction than conventional metal bearings and are able to transmit the rotation force of the rotor and magnet with more efficiency. |
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| Clearance of at least 0.5 mm in both thrust and radial directions must be provided around the counter weight when mounting the motor in the handset. If the clearance is insufficient, the counterweight could come into contact with the outer casing when the unit is dropped, bending the shaft and preventing proper operation. |
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