Nowadays, many people have understood the usefulness of such a tool as a screwdriver, and they have little idea, for example, of carrying out repairs in an apartment without it. Naturally, its failure is a great annoyance. Immediately the question arises, how to troubleshoot the screwdriver.
Screwdriver device scheme.
Of course, you can take the tool to the workshop, but if you urgently need it, you should think about how to get out of the situation yourself. Nothing remains to be done, only to repair the screwdriver on your own. In some cases, almost any person can perform such an operation. To do this, you must familiarize yourself with its design and have basic knowledge of electrical engineering and mechanics.
Parts of the screwdriver that can fail
Screwdrivers of any brand are based on a similar design and differ only in the layout details. In general, this tool consists of a body, a cartridge, an electrical and mechanical part. The type and design of the housing can be very different, but the cartridge is used for all cam type and is located on the torque shaft of the gearbox.
The electric part is represented by an electric motor, a switch of the direction of rotation, as well as a start button with a speed controller. The main element of not only the electrical part, but the whole screwdriver, is the electric motor. Commonly used collector single-phase motor. The engine is started through a starting capacitor. Like all engines of this type, it consists of a stator, a rotor and contact brushes. Rotational motion on the main shaft of the screwdriver is transmitted from the motor shaft through a gearbox.
The device gears gearbox screwdriver.
The start button plays the role of a switch that provides power to the engine. The button is combined with a power regulator that allows you to change the speed of rotation of the electric motor. The controller has an electronic version, usually on the basis of a special generator (transistor) placed on the control board. Speed adjustment is done by changing the force of the button; this changes the signal to open the transistor, which, in turn, changes the voltage of the motor.
Switching the direction of rotation of the motor shaft is made by changing the polarity on the electrical input. The regulator itself is usually represented in the form of a lever with which the contacts on the terminals are thrown. The motor is reversed.
The mechanical part consists of a gearbox and a mechanical force regulator. The gearbox is designed to reduce the speed of rotation transmitted from the motor shaft to the main shaft of the screwdriver. Usually used planetary gear type. Such a reducer consists of a ring and sun gear, satellites and a carrier. The number of satellites and carrier depends on the number of stages, that is, the smoothness of the change in speed. In screwdrivers, gearboxes with two or three stages are used. The principle of operation of planetary gearboxes is simple - the sun gear is located on the motor shaft and transmits the rotation of the satellite, which, in turn, transmits the rotation to the ring gear located on the main shaft through the carrier. When transmitting rotation from a small gear to a large rotational speed decreases.
Mechanical force regulator provides a change in the load transmitted to the screw when working with a screwdriver. The regulator operates in the range of up to 16 positions, which makes it possible to use it effectively when tightening the screws into materials of very different hardness and brittleness. In the mechanical part, the system of bearings in which all the rotating shafts are pressed is particularly noteworthy.Back to table of contents
Electrical components of the screwdriver.
The main manifestations of faults screwdrivers on the electrical part include:
- When you press the start button, the tool does not turn on.
- No power adjustment; the direction of rotation does not change.
- The tool works, but there is sparking or crackling and clicking.
If the screwdriver does not turn on when you press the start button, you should check the operability of the electrical parts. It should start with checking the batteries with a tester (multimeter). The voltage measured at the output terminals should correspond to the rated voltage indicated on the housing. If the voltage is absent or insufficiently charged batteries. If the voltage does not appear even after using the charger, the case is opened and the quality of the rations and the integrity of the wiring are checked. The voltage on each element is checked, which must be at least 0.9-1 V. If any element does not produce the required voltage, it should be replaced.
The next step should be to check the health of the start button. The tester checks the operation of the contacts of the button. If the supply voltage after pressing the button is not observed, then you should first try to clean the contacts with emery cloth, and if this does not help, then replace the button.Back to table of contents
The electrical circuit of the screwdriver.
After checking all the elements responsible for the power supply, the motor is checked. First of all, the condition of the contact brushes is visually assessed, since their wear is a fairly common phenomenon. If wear of brushes is observed, they should be replaced. The next step is to check the performance of the starting capacitor. If its actual capacity does not match the nominal value indicated on the case, it is replaced by a similar capacitor with the same capacity.
With the integrity of all contact and starting elements, as well as the reliability of soldering and lead wires, the motor itself is tested. For this, the anchor is removed and its visual inspection is carried out. Damage or electrical short between windings will be immediately noticed. In the absence of obvious signs, the integrity of each winding is checked separately. If the integrity of the winding is broken, then the anchor must be replaced or rewound the winding with a specialist on special equipment. Repair anchors of the electric motor on their own is not made.
Back to table of contents
Lack of adjustment of speed of rotation and reverse
In the case when the screwdriver is turned on, but the rotational speed does not change with any button press, you should look for faults in the speed regulator system. The reason for such a malfunction may be: malfunction of the start button, failure of the transistor, partial wear of the contact brushes of the electric motor. The work of all contacts of the start button is checked by the tester. If it fails, it will be difficult and more expedient to change it.
The quality of the transistor on the control panel is checked visually (by color change) or by measuring the magnitude of the input and output signals. The integrity of the entire circuit in the speed controller system is checked.
For the impossibility of changing the direction of rotation of the electric motor, the lever regulator or contact brushes of the electric motor are responsible. The regulator is checked with a tester with a different location of the lever.
The cause of sparks, cod or clicks, as a rule, is a partial abrasion or combustion of the contact brushes of the electric motor.
It is recommended to change the brushes, if their length is reduced by 40% or more of the original length.Back to table of contents
Faults in the mechanical part of screwdrivers
Scheme of the internal structure of the screwdriver.
Characteristic signs of the appearance of faults in the mechanical part of the screwdriver are:
- the appearance of extraneous sounds in the form of a rattle, hum, etc .;
- noticeable vibration of the main shaft with a chuck;
- full or periodic stop of the screwdriver (jamming).
In order to repair the screwdriver, special attention should be paid to the bearings on which the engine anchor and main shaft are located. Failure of the armature bearings causes noise, and jamming is usually caused by the destruction of the main shaft bearing.
Vibration, noise can be caused by faults in the screwdriver gearbox.
The most frequent reasons for them are:
- deformation of the shaft of the gearbox;
- damage to gear teeth;
- the destruction of the pin mounting satellite and some others.
To find out the reasons, you should disassemble the gearbox, which is located in a plastic case in the form of two halves. Sometimes malfunctions are caused by misalignment of the satellite axes. In this case, you can repair the screwdriver by installing these axes into the sockets of the carrier without replacement. Most often, malfunctions are caused by the destruction of the gearbox elements or their irreversible deformation. Such parts require replacement.Back to table of contents
To repair the screwdriver on your own, you need to prepare the following tools:
- tester or multimeter;
- electric probe;
- sandpaper or emery bar;
- soldering iron.
Screwdriver is a very useful tool needed in the household. You can not despair if it is out of order. It is necessary to find out the cause of the malfunction and repair it yourself. To repair the screwdriver at home is quite real.