JPS6334717B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power tool in which the phase of a motor is controlled according to a computer program.

Conventionally, in the case of power tools whose phase is controlled by a computer, the trigger point of the SCR or triax for motor control of the power tool is phase 0 of the power supply frequency.
Since the phase is controlled according to the number of clock pulses counted from the point in time, even if the same power tool is used in areas with different power supply frequencies, no trigger pulse will be generated, or even if a trigger pulse is generated, the settings will not be correct. Trigger pulses occur in different phases, making it impossible to control the motor according to the settings. Therefore, when using power tools in regions with different frequencies, it is necessary to use a computer controller with a program created to match the frequency of the region. The drawback was that it required the use of power tools dedicated to each power frequency.

An object of the present invention is to eliminate the above-mentioned drawbacks of the conventional power tool by providing a computer-controlled phase-controlled power tool that can be used even in regions with different power supply frequencies such as 50 Hz and 60 Hz.

Next, the configuration of an embodiment of the present invention is shown in FIGS. 1 and 2.
This will be explained using figures.

A ferrite magnet 2 is located on the outer periphery of the armature shaft tip 1 that rotates together with the armature A1 of the series commutator motor M1 for power tools, which is connected to a 50Hz or 60Hz AC power supply via the main switch SW1 and the triax TRI1. For example, the magnetically sensitive element 3 of an SDME type magnetic resistor, which is embedded in the magnet 2 and attached to the fixed part of the motor M1 facing the same magnet 2, increases its resistance value every time the magnet 2 approaches, and resistors R1 and R2 The comparator Q1 of the OP amplifier IC, whose reference voltage is set at
As a result, the comparator Q1 generates a pulse with a frequency corresponding to the rotation speed of the electric motor M1, and this rotation speed detector 4 uses another magnetic/optical sensor. It can be used as a rotation speed detector.

In addition, the +5V DC voltage from the constant voltage power supply circuit 5 connected to the AC power supply via the step-down transformer T1 is supplied as a power source to each circuit, and also controls the electric motor M1 of the power tool according to a preset program. A microcomputer, i.e., a CPU,
It is also supplied to the power terminals of the microcomputer 6, which consists of RAM, ROM, I/O ports, clock generators, system controllers, etc. A reference time generator CPG1 is connected to generate a clock pulse CP of .

On the other hand, the input port of microcomputer 6
IC7 has an output corresponding to the rotational speed of motor M1 from the comparator Q1, and an output corresponding to the rotation speed of motor M1 from the comparator Q1, and a
A synchronizing output from a power frequency detection circuit 8 consisting of a diode D1 and a Zener diode ZD1 connected to the next side is input, and this power frequency detection circuit 8 is connected to a monostable multivibrator.
ICQ2, resistors R11, R12, capacitor C3,
OP amplifier ICQ3, resistors R13, R14, R
15, comparator 1 consisting of capacitor C4
2. That is, a comparator 12 as a frequency discrimination circuit that discriminates whether the frequency of the AC power source is 50Hz or 60Hz.
is connected to each power supply frequency output terminal provided on the output port IC9 of the microcomputer 6. In this case, for the purpose of explanation, the clock pulse CP from the reference time generator CPQ1 is
If the frequency F is 2.4MHz, the number of clock pulses per half cycle of the power supply E when the power supply frequency is 50Hz is 2.4MHz / 50Hz x 2 = 24000 pulses, and the operating characteristics of the power tool at the power supply frequency of 50Hz and 60Hz are the same at 50Hz. and the 60Hz output terminal of a program that makes the operating characteristics of the power tool the same at 50Hz and 60Hz power supply frequencies, assuming that the number of clock pulses per half cycle of power supply E at 60Hz power supply frequency is 2.4MHz / 60Hz x 2 = 20000 pulses. In this case, a digital changeover switch 13, in this case, a bilateral switch, is switched according to a change in the power supply frequency output from the comparator 12.
A digital changeover switch 13 consisting of ICQ4, Q5 and an inverter Q6 is connected, and the output from the digital changeover switch 13 via a resistor R3 is as follows.
Resistor R4 and photocoupler PC in constant voltage power supply circuit 5
It controls on/off the Darlington connected transistors Tr1 and Tr2 connected through the light emitting diode LED 1, and also controls the triac TRI1.
The trigger point of the photo-silicon controlled rectifier elements PSCR1 and PSCR2 connected to the trigger circuit 10 is controlled.

In the figure, X and Y are the power supply connection terminals of the power tool, F1 is the field coil of the series commutator motor M1, R is the resistor, and C is the capacitor. followed by a serial number.

Next, the operation of this embodiment will be explained.

First, with the power supply connection terminals X and Y of the power tool connected to an AC power source, if the power supply frequency is 50Hz, the capacitor C4 voltage is generated by a 50Hz pulse output with a pulse width determined by the resistor R11 and capacitor C3 from the waveform shaping circuit 11. Vc is the dividing resistance R
14, reference voltage of comparator 12 by R15
Therefore, the output of the comparator 12 is at H level, and only the bilateral switch ICQ4 of the digital changeover switch 13 is conductive _. An output corresponding to the 50Hz program is supplied, and the trial
TRI1 is phase-controlled by a program with a clock pulse count of 24,000 pulses per half cycle of power supply E1, which makes the operating characteristics of the power tool the same at 50Hz and 60Hz, and power supply connection terminals X and Y are connected to a 60Hz AC power supply. Then, the period of the pulse output from the waveform shaping circuit 11 becomes shorter and the capacitor C4
The voltage Vc becomes higher than the reference voltage V _R , the output of the comparator 12 becomes L level, and the bilateral switch of the digital changeover switch 13
Only ICQ5 becomes conductive, and transistors Tr1 and Tr
An output corresponding to the program for the power supply frequency 60Hz of the microcomputer 6 is supplied to the trigger circuit 10 via the trigger circuit 2 via the trigger circuit 10.
The number of clock pulses per half cycle of power supply E2 is 20,000 to make the operating characteristics of the power tool the same at 60Hz.
The phase is controlled by the pulse program.

Therefore, when the AC power supply is 50Hz, when the main switch SW1 is turned on, the clock generator terminal of the microcomputer 6 receives the frequency F=2.4MHz from the reference time generator CPG1.
In addition to the clock pulse CP, input port IC7 of the microcomputer 6 receives pulses with a frequency proportional to the power frequency from the power frequency detection circuit 8 and the rotational speed of the motor M1 from the rotational speed detector 4. , microcomputer 6
is a motor M1 with a preset lash current limit, slow start, and is unaffected by load conditions.
According to a program such as constant speed operation, clock pulses CP are counted from the phase 0 point of each half cycle of the power supply frequency, and when this count value reaches, for example, the trigger point of triax TRI1 necessary for constant speed operation, the output of the microcomputer 6 is Port IC9
An output corresponding to the 50Hz program is generated from the 50Hz output terminal of the trigger circuit 10, and the triac TRI1 is turned on via the gate pulse CP1 from the photocoupler PC1 of the trigger circuit 10, and the 50Hz power supply E1 shown by the solid line in Fig. 2 is turned on. clock pulse CP
The phase is controlled according to the count value of .

That is, when the power supply E1 frequency is 50Hz, the clock pulse CP frequency F from the reference time generator CPG1 is
Since 2.4MHz is being generated, output port IC9
The output terminal for 50 Hz generates an output corresponding to the program of the microcomputer 6 which sets the number of clock pulses per half cycle of the power supply E1 to 2.4 MHz/50 Hz x 2 = 24000 pulses.
1 trigger point is phase controlled with 24,000 pulses calculated as a 180° phase angle of a half cycle of power supply E1.

Next, when this power tool is used with a 60Hz AC power source, when the main switch SW1 is turned on, the clock generator connection terminal of the microcomputer 6 is connected to the clock generator connection terminal of the microcomputer 6, =2.4MHz clock pulse CP is input and output port IC9
The output terminal for 60Hz generates an output corresponding to the program of the microcomputer 6 which sets the number of clock pulses per half cycle of the power supply E2 to 2.4MHz/60Hz x 2 = 20000 pulses as shown by the dotted line in Figure 2, and therefore, Frequency of power supply E2
In the case of 60Hz, triac TRI1 is the gate pulse GP2 generated by the 60Hz program.
It is controlled in the same phase as when the power supply frequency is 50Hz.

Next, the effects of the present invention will be explained.

The present invention provides a motor for driving an electric tool connected to an AC power supply via an SCR or a triax, and a trigger point of the SCR or triax that is controlled in phase by the number of clock pulses counted from phase 0 of the power supply frequency.
A microcomputer having a program for each power supply frequency to perform phase control with the same characteristics at each power supply frequency of 60Hz, a reference time generator that supplies clock pulses of a constant frequency to the microcomputer, and a reference time generator that controls the rotation speed of the motor. a rotation speed detector that detects and supplies the rotation speed detection signal to the microcomputer; a frequency discrimination circuit that discriminates whether the frequency of the AC power supply is 50 Hz or 60 Hz and generates the frequency discrimination signal; a changeover switch for switching the program of the microcomputer to a program corresponding to the discriminated power supply frequency based on each frequency-specific output signal from the circuit; The above is determined by the output from the computer.
A phase-controlled power tool is provided with a trigger circuit for phase-controlling the trigger point of an SCR or a triax.

As a result, the present invention improves the operating characteristics of a phase control power tool that phase-controls the rotation speed of a motor using the number of clock pulse counts.
Even if the power frequency is converted from one region to the other, it will always remain constant, and the operator will not notice the change in the power frequency, which can easily happen when carrying a power tool from one region of 50Hz or 60Hz to the other. This has the effect of effectively preventing work errors due to changes in motor characteristics when working.

[Brief explanation of the drawing]

Fig. 1 is an electrical circuit diagram of an embodiment of the present invention;
The figure is a waveform diagram. 4... Rotation detector, 5... Constant voltage power supply circuit, 6
...Microcomputer, 7...Input port
IC, 8... Power frequency detection circuit, 9... Output port, 10... Trigger circuit, 11... Waveform shaping circuit, 12... Comparator, 13... Digital changeover switch, M1... Series commutator motor, CPG
1...Reference time generator, TRI1...Triack.

Claims (1)

[Claims] 1 A power tool drive motor connected to an AC power source via an SCR or a triax, and the
A microcontroller with programs for each power supply frequency that controls the trigger point of the SCR or triax by the count number of clock pulses from the phase 0 point of the power supply frequency, and performs phase control with the same characteristics at each power frequency of 50Hz and 60Hz. a computer, a reference time generator that supplies clock pulses of a constant frequency to the microcomputer, a rotational speed detector that detects the rotational speed of the motor and supplies the rotational speed detection signal to the microcomputer, and the AC power supply. The frequency of
A frequency discrimination circuit that discriminates between 50 Hz and 60 Hz and generates the frequency discrimination signal, and a program of the microcomputer that corresponds to the discriminated power supply frequency based on each frequency output signal from the frequency discrimination circuit. and a trigger circuit that controls the phase of the trigger point of the SCR or triact by the output from the microcomputer corresponding to the program for each power frequency switched by the changeover switch. Features of phase control power tools.