The usefulness and convenience of using a screwdriver for repairs in the house is not in doubt. With this tool, the joining of wooden elements is much faster and easier. Self-repair of screwdrivers has become a necessity for many.
Scheme of the device cordless screwdriver.
Any, even the highest quality, tool ever fails. There are many reasons for this. Repair of an automatic screwdriver is not an exception to the rule; it is a completely natural phenomenon, and you need to prepare for it in advance.
Possible faults and design features of screwdrivers
The screwdriver is used for tightening (unscrewing) fasteners (mainly screws). It is sometimes used for drilling, but this is undesirable and can lead to failure. Unlike a drill, a screwdriver has a mechanism for stopping rotation when a load occurs; In addition, the rotation speed of its cartridge is noticeably lower than that of the drill.
Despite the variety of types and forms, all screwdrivers have very similar designs, which differ mainly in the build quality, appearance and layout of the elements. Main elements: case with handle; cartridge mounted on the shaft; electrical and mechanical parts.
Screwdrivers can be powered by electricity from the network or their own batteries. In general, the electrical part includes an electric motor, a reverse rotation mechanism (directional shift lever); trigger (button) with speed control and power cord or battery. Most often, when powered from the mains, a single-phase AC motor for a voltage of 220 V is used. A starting capacitor is used to start the engine. The engine itself consists of a stator, a collector rotor and contact brushes. Rotation from the motor shaft to the main shaft with a chuck is transmitted through the gearbox.
Screwdriver battery connection diagram.
The trigger mechanism combines the trigger button and power control. The regulator is made on the base of the transistor and changes the current that feeds the motor to the contact brushes. By changing the input current is provided by the regulation of the speed of rotation of the motor. The start button is designed so that a change in its pressing force leads to a change in the signal to the power regulator transistor.
The torsion direction switch cartridge provides reverse engine. This is done by moving the lever, due to which the contact elements are transferred on the input connectors, which changes the polarity of the signal.
The basis of the mechanical scheme of the screwdriver is the gearbox, bearing system and load limiting mechanism. The planetary gearbox is installed to reduce the number of revolutions during the transmission of rotation from the electric motor to the cartridge. The basis of the gear - gears (ring and solar); satellites and carrier, and their number is determined by the number of stages of rotation speed of the cartridge. In household tools 2 or 3 steps are provided. The work of planetary gearboxes is based on the fact that the sun gear mounted on the motor shaft drives the satellite, which, with the help of a carrier, rotates the ring gear mounted on the main shaft. When transmitting rotation (from gear with a smaller diameter to gear with a larger diameter), the rotation speed decreases.
The mechanism of regulation (limitation) of the force changes the load applied to the fastening element. The regulator is able to function within up to 15 positions, and this makes it possible to optimize the process when screwing fasteners into materials of different density and strength. A special role is played by bearings in which all rotating shafts are placed. They provide smooth and reliable operation of all rotating elements of the tool.Back to table of contents
Types of electrical faults
Table of characteristics of screwdrivers.
Electrical faults in screwdrivers can manifest themselves in the following form: the tool does not turn on when the start button is pressed; the speed of rotation of the cartridge is not adjustable; unable to change the direction of rotation when moving the lever; when the screwdriver is working, there is noticeable sparking and there is a crash and clicks.
In circumstances in which the tool does not want to turn on when you press the start button, you need to check the entire electrical circuit along the chain (from simple to complex). The first step is to check the battery. The tester measures the voltage at the battery output. If the voltage is below the normalized value (indicated on the battery case), then you should first try to charge the battery. If charging did not help, then the entire battery is removed and the voltage on each cell is measured (the voltage should be 1.2 V). Repair in this case consists in replacing the defective battery.
The second element in the electrical circuit in turn is a push-button switch. With the help of the device, the operability of moving and fixed contacts is evaluated. When the electric signal does not pass after pressing the button switch, first of all it is necessary to clean the contacts with a fine sanding sandpaper.
If the malfunction persists, it is impractical to repair the button and it should be replaced.
Very often, tool repair is to replace the brushes, as they are subject to active wear and burning. First, you should visually assess the condition of the contact brushes. If wear of the brush is noticeable by more than 40% in length, then it must be replaced. The repair consists in removing the brush holder from the case, removing the damaged one and installing it in exactly the same but new one. In addition, capacitor breakdown is common; therefore, it is necessary to check the capacity of the starting capacitor. If the capacitance value does not match (indicated on the case), the capacitor is replaced with a new one with the same capacity.
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The last one to check is the electric motor as the most complex element of the electrical part. If damage to the contact and trigger mechanisms is not detected, and there is no doubt about the reliability of the soldering and the integrity of the supply wires, then the electric motor is tested.
Charger circuit for the screwdriver.
Disassembly of the engine begins with the extraction of the armature from the stator. A visual inspection of the contact part of the collector and the winding is performed. Mechanical damage or electrical circuit and breakdown of the insulation of the wire are noticeable by discoloration and the presence of soot. Repair anchors themselves are not carried out. He is either trusted by professionals or replaced by new ones. If no visual damage is found, then an ohmmeter checks the operation of all windings separately.
Similarly, the state of the stator windings is checked. Repair it consists in winding winding, then you have to use the services of the workshop.Back to table of contents
Repair of power control and reverse mechanisms
There is a situation when the instrument turns on normally, but the rotation is not regulated by different pressing of the push-button switch. In this case, the cause of the damage must be clarified in the engine rotation control mechanism. The main reasons for such damage may be the failure of the push-button switch, the breakdown of the transistor, the destruction of the armature brushes.
The operability of the contact system of the launch button is checked using a tester. Repair is not made, and it should be changed.
The integrity of the transistor located on the control panel is checked by inspection (by color change) or by measuring the voltage and current of the input and output signals.
Then you should check the integrity of all rations and the condition of all elements in the circuit of the speed controller circuit.
Malfunctions in the mechanism of reverse rotation of the electric motor may occur due to damage to the lever mechanism or the destruction of the armature brushes. The efficiency of the contact system of the mechanism is estimated by an ohmmeter with different fixation of the flag.Back to table of contents
The failure of the elements responsible for the rotation of the screwdriver manifests itself as suspicious sounds, in particular, squeaking, humming and others; perceptible vibration of the driving axle with a chuck; final or temporary stop of rotation of the cartridge (jamming). The repair of the tool, in this case, consists in checking and replacing the bearings in which the engine anchor and main shaft are located. Wear or damage to the armature bearings cause noise, and tool seizure is usually due to the wear of the bearing located on the main shaft.
Mechanical damage, tool vibrations, hum are often the result of damage to the elements in the tool reducer. Typical faults: the curvature of the axis of the gearbox; damage to gear elements; collapse of the mounting of satellites on the axis, etc. Repair begins with the disassembly of the gearbox, which is placed in a plastic housing consisting of two halves. Sometimes violations in the work due to a change in the centering of the axes of the satellites. Such repair screwdriver is done by returning these axes in their nests. Violations are usually due to damage to the parts of the gearbox, as well as their significant curvature. These structural elements are not repaired, but are replaced by new ones.
If you need to repair the screwdriver on your own, you should have the usual tools and devices:
- a mallet;
- keys set;
- sanding paper;
- soldering kit.
Any tool can break, but it is not a tragedy. Repair of automatic screwdrivers can be done independently, having understood their design and having understood the basic principles of repair.