Detailed maintenance methods of imported electric screwdrivers

1. Repair tools

Two multimeters (one for analog and one for digital, analog is indispensable), diagonal pliers, needle-nose pliers, soldering iron, soldering iron stand. Flux, tin wire, tin suction device, fine sandpaper, heat shrinkable sleeve, wire stripper, flat screwdriver (one for small and medium), Phillips screwdriver (one for small and medium, plus a screwdriver with rubber handle), art Knife.

Second, the working principle of the circuit

1. Process

Input (protector, micro switch) → rectifier → filter → positive and negative switch → motor → clutch

2. The normal parameters of each electronic component

(1). Power cord: measure the DC resistance value, the normal value is close to zero; common faults: open circuit or poor contact (broken).

(2) Micro switch: measure the resistance value between normally open (resistance approaches infinity) and normally closed (resistance approaches zero); common faults: poor contact (burning black), buttons cannot be reset normally, the body rupture.

(3) Protector: measure resistance value; normal is zero; it can automatically reset after light overload, and it will be permanently invalid when it is too large. It can also be disconnected (thermal protector) in case of high temperature, and it can also be automatically reset after normal temperature.

(4) Rectifier bridge: Short-circuit the output terminals (+, -), and measure the output terminal (+, -) DC resistance (about 15K).

(5) Positive and negative switch: The pin corresponding to the toggle key is a common pin, and the two gears corresponding to the toggle key are connected.

Three, circuit detection analysis

When you get an electric batch of unknown cause, you should do preliminary inspection first, as follows:

Set the multimeter to the (×1K) position to zero, turn on (press) the micro switch, and measure the DC resistance of the input terminal. Under normal circumstances, it is about 15K (the digital multimeter is adjusted to the diode to be measured, and the voltage drop is 1.0. Left and right), this value can indicate that the electric batch circuit part is working normally. Another way to check the circuit is to open the electric batch and short-circuit the two poles of the motor. Under normal circumstances, the measured input DC resistance value is slightly smaller than the preliminary test. Maximum value (the motor DC resistance value is not included in the calculation).

Fourth, the components of the motor

1. Basic components: armature (rotor), carbon brush holder, motor front cover, bearing, magnet (stator), carbon brush, motor gasket.

(1) Armature: The most important part of the electric batch, like the "heart", the state of the armature will determine whether the electric batch can work normally. The quality of the armature: We can know by measuring its DC resistance. Under normal circumstances, the DC resistance (220V) between two adjacent poles of the armature commutator is about 15 ohms larger (due to different manufacturers, the value is different, and the larger DC resistance exceeds 20 ohms).

Damage characteristics and failure analysis: A. Judging from the appearance whether the commutator of the armature is obviously worn or not, the more severely worn armature has a lot of noise during operation: B is to see whether the central axis of the armature becomes smaller (install the bearing Later, when the bearing can shake left and right) is obvious, the armature rotation center is unstable and the noise is also louder. C. Many armatures cannot work normally due to the open circuit of the adjacent two poles of the commutator. When there are multiple disconnections, the motor cannot start; when one is disconnected, the motor can work, but if the carbon brush just touches the disconnection, the motor will stop working.

(2) Carbon brush holder: Judging from the appearance whether it is damaged and internal carbonization (burning black).

(3) The front cover of the motor: Judging from the appearance, it is damaged.

(4) Stator: Judging from the appearance whether the internal disk is damaged or displacing elements (resulting in magnetic asymmetry), and at the same time, a flat-head screwdriver can be placed inside the magnet to check the size of its magnetism. If the magnetism is too small, replace it. New magnet.

(5) Bearing: Judging from the rotating bearing, there is a jam phenomenon. When the internal friction is strong, the motor crying noise is louder.

(6) Carbon brush: When the carbon brush is worn to the remaining two or three millimeters, replace it with a new one (replace regularly).

(7) Gasket: Fix the armature to prevent it from shaking up and down to ensure stability. Appropriate number of spacers; the armature will not shake up and down, and the armature can be twisted with a small force

Five, clutch

1. Common faults of clutch: (1). Unable to jam the screwdriver head: A drive shaft is broken, replace the drive shaft (the groove becomes larger and automatically falls off); (2). Missing, add new ones.

2. The drive shaft is damaged: (1). The head of the screwdriver is severely worn out and needs to be replaced; (2). Internal fracture (The test method is to install the fan blade into the clutch, then jam it, twist the drive shaft with a flat-head screwdriver, judge the sense of tripping, and determine whether it is good or bad.)