JPS6334716B2 - - 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. The trigger pulses occur in different phases and the motor cannot be controlled as set. Therefore, when using a power tool in an area with a different frequency, the computer program must be changed or adjusted to match the frequency of the area. The drawback was that it required the use of a computer-controlled power tool with a program created by the user.

An object of the present invention is to provide a computer-controlled power tool that can be used without changing the computer program even in regions with different power frequencies such as 50Hz and 60Hz. It consists in removing.

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 attached to the outer periphery of the armature shaft tip 1 that rotates together with the armature A1 of the series-wound 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. is embedded,
The magnetically sensitive element 3 of, for example, an SDME type magnetic resistor, which is attached to the fixed part of the series commutator motor M1 facing the magnet 2, increases its resistance value every time the magnet 2 approaches, and resistors R1 and R2 As a result, an H level output is generated from the comparator Q1 of the OP amplifier IC whose reference voltage is set at A pulse with a frequency corresponding to the rotation speed of the series-wound commutator motor M1 is generated, and the rotation speed detector 4 may be a rotation speed detector using another magnetic or optical sensor. can.

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 is also used to control the series commutator motor M1 of the power tool using a preset program. A microcomputer that controls according to
The power is also supplied to the power terminals of the microcomputer 6, which includes a CPU, RAM, ROM, I/O port, clock generator, system controller, etc.

On the other hand, the input port of microcomputer 6
IC7 has an output corresponding to the rotational speed of electric 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.
ICQ6, resistors R13, R14, capacitor C5,
OP amplifier ICQ7, resistors R15, R16, R
17. Comparator 1 consisting of capacitor C6
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 the clock generator connection terminal of the microcomputer, and a first reference time generator CPG1 that generates a 2MHz clock pulse for the power supply frequency of 50Hz, and
A second reference time generator CPG2 that generates a 2.4MHz clock pulse for 60Hz is connected via a digital changeover switch 13, in this case, a digital changeover switch 13 consisting of bilateral switches ICQ4, Q5 and an inverter Q6. The reference time generators CPG1 and CPG2 are formed by crystals CR1 and CR2 for each oscillation frequency, inverters Q2 and Q3, buffer amplifiers Q4 and Q5, resistors R3 and R4, and capacitors C1 and C2.

The output from the output port IC9 of the microcomputer 6 via the resistor R5 turns on and off the Darlington-connected transistors Tr1 and Tr2, which are connected to the constant voltage power supply circuit 5 via the resistor R6 and the light emitting diode LED of the photocoupler PC1. In addition to controlling the trigger circuit 1 of the triax TRI1
Photosilicon controlled rectifier connected to 0
Controls the trigger point of PSCR1 and PSCR2.

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 frequency is 50Hz, the voltage on capacitor C6 is generated by a 50Hz pulse output with a pulse width determined by resistor R13 and capacitor C5 from waveform shaping circuit 11. Vc is the divided voltage R1
6. Reference voltage of comparator 12 by R17
Therefore, the output of the comparator 12 is at H level, and only the bilateral switch ICQ8 of the digital changeover switch ₁₃ is conductive. 2MHz clock pulse CP1 is input, and the power supply connection terminals
When Y is connected to a 60Hz AC power supply, the pulse period output from the waveform shaping circuit 11 is short and the capacitor C6 voltage Vc becomes higher than the reference voltage _VR , and the output of the comparator 12 becomes L level. , only the bilateral switch ICQ9 of the digital changeover switch 13 is conductive, and the microcomputer 6 has the first switch corresponding to the power frequency of 50Hz.
A 2MHz clock pulse CP1 from a reference time generator CPG1 is input.

Therefore, when the AC power source is 50Hz, when the main switch SW1 is turned on, the clock generator connection terminal of the microcomputer 6,
〓〓 is the frequency F1 from the first reference time generator CPG1.
=2MHz clock pulse (CP1 in Figure 2) is input, and the input port IC7 of the microcomputer 6 receives the power frequency from the power frequency detection circuit 8 and the series commutator motor M from the rotation speed detector 4.
A pulse with a frequency proportional to the number of revolutions is input,
As a result, the microcomputer 6 has a preset rush current limit, slow start,
Clock pulses CP1 are counted from the phase 0 point of each half cycle of the power supply frequency according to a program such as series-wound commutator motor M1 constant-speed operation that is not affected by the load condition, and this count value is used as a trigger for the triac TRI1 necessary for constant-speed operation, for example. When the point is reached,
An output is generated from the output port IC9 of the microcomputer 6, and the triax TRI1 is turned on via the gate pulse GP1 from the photocoupler PC1 of the trigger circuit 10, and the 50Hz power supply E1 shown by the solid line in FIG. 2 receives the count value of the clock pulse CP1. The phase is controlled according to .

That is, when the power supply E1 frequency is 50Hz and the clock pulse CP1 frequency F1 from the first reference time generator CPG1 is 2MHz, the number of clock pulses per half cycle of the power supply E1 is set as 2MHz/50Hz×2=20000 pulses by the program of the microcomputer 6. At the same time, the triggering point of the triax TRI1 is phase-controlled with 20,000 pulses converted as a 180° phase angle of a half cycle of the power source E1.

Next, when using this power tool with a 60Hz AC power supply, when the main switch SW1 is turned on, the clock generator connection terminal of the microcomputer 6 is connected to the second reference time generator.
As a result of inputting a clock pulse with frequency F2 = 2.4MHz from CPG2 (CP2 in Figure 2), the number of clock pulses per half cycle of power supply E2, shown by the dotted line in Figure 2, is 2.4MHz/60Hz x 2 = 20000 pulses. Therefore, even when the frequency of the power source E2 is 60 Hz, the triac TRI1 can perform the same phase control via the gate pulse GP2 using the same program as when the power source frequency is 50 Hz.

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

The present invention has a power tool drive motor connected to an AC power supply via an SCR or a triax, and a program for controlling the phase of the trigger point of the SCR or triax by the number of clock pulses counted from the phase 0 point of the power supply frequency. a microcomputer, each reference time generator for 50Hz and 60Hz, which supplies the microcomputer with clock pulses of different frequencies for each power supply frequency in order to perform phase control with the same characteristics at each power supply frequency of 50Hz and 60Hz; a rotation speed detector that detects the rotation speed and supplies the rotation speed detection signal to the microcomputer; a frequency discrimination circuit that discriminates whether the frequency of the AC power source is 50 Hz or 60 Hz and generates the frequency discrimination signal;
a changeover switch that switches each of the reference time generators for 50Hz and 60Hz to a reference time generator corresponding to the discriminated power supply frequency according to each frequency output signal from the frequency discrimination circuit; and a trigger circuit for controlling the phase of the triggering point of the SCR or triact by the output from the microcomputer corresponding to the reference time generator for each power supply frequency.

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, CPG2...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 microcomputer with a program that controls the phase of the SCR or triax trigger point by the number of clock pulses counted from phase 0 of the power supply frequency;
Each reference time generator for 50Hz and 60Hz supplies clock pulses of different frequencies for each power supply frequency in order to perform phase control with the same characteristics at each power supply frequency of Hz and 60Hz, and a reference time generator for detecting the rotational speed of the motor and detecting the rotational speed of the motor. a rotation speed detector that supplies a detection signal to the microcomputer; a frequency discrimination circuit that discriminates whether the frequency of the AC power source is 50 Hz or 60 Hz and generates a frequency discrimination signal; By the output signal
A changeover switch for switching each reference time generator for 50Hz and 60Hz to a reference time generator corresponding to the differentiated power supply frequency, and the microcomputer corresponding to the reference time generator for each power supply frequency switched by the changeover switch. The above by the output from
A phase control power tool characterized by comprising a trigger circuit for phase controlling the trigger point of an SCR or a triax.