JPH1066381A - Motor controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize stabilized r.p.m. control insusceptible to power supply frequency by correcting the conduction angle of a switching element for controlling the speed of an AC motor depending on the fluctuation of power supply frequency. SOLUTION: The motor controller comprises a circuit 6 for charging a capacitor 4 in the positive direction during positive half-cycle of an AC power supply 1, a circuit 7 for charging the capacitor 4 in the negative direction during negative half-cycle of the AC power supply 1 starting from the end of positive half- cycle charging of the positive charging circuit 6 and triggering a bidirectional switching element 2, a circuit 8 for charging a capacitor 5 in the negative direction during negative half-cycle of the AC power supply 1, and a second positive charging circuit 9 for charging the capacitor 5 in the positive direction during positive half-cycle of the AC power supply 1 starting from the end of negative half-cycle charging of the negative charging circuit 8 and triggering the bidirectional switching element 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device for controlling the rotation speed of an AC motor applied to an electric power tool or the like, and more particularly to a method for controlling the conduction angle of a switching element whose full-wave phase is controlled in accordance with a fluctuation of a power supply frequency. The present invention relates to a motor control device capable of correcting by means of a motor.

[0002]

2. Description of the Related Art FIG. 8 is a circuit diagram of a conventional motor control device used for controlling the speed of an AC motor such as a power tool. In the figure, an AC motor M
And a triac TA for speed control are connected in series. A series circuit of a variable resistor VR and a capacitor C is connected in parallel to both ends of the AC power supply e, and a gate and a cathode of the triac TA are connected to both ends of the capacitor C via a diac DA. The diac DA, the variable resistor VR, and the capacitor C constitute a full-wave phase control circuit.

[0003] On both ends of the triac TA, an on / off switch SW for short-circuiting the triac TA to apply the full voltage of the AC power supply e to rotate the AC motor M at full speed is connected in parallel.

In this configuration, as shown in FIG. 9, when a positive half cycle voltage 121 of an AC power supply e is applied,
The charging voltage of the capacitor C changes as shown by a curve 122 in FIG. 9 according to the time constant with the variable resistor VR. And
When the charging voltage of the capacitor C reaches the gate trigger voltage vg of the diac DA, the diac DA is triggered and the triac TA is turned on at the same time. From this point on, the power in the hatched area of the positive half cycle is changed to the AC motor. M.

The negative half cycle voltage 1 of the AC power source e
When 23 is applied, the charging voltage of the capacitor C changes as shown by a curve 124 in FIG. 9 according to the time constant with the variable resistor VR, and the charging voltage of the capacitor C changes to the gate trigger voltage vg of the diac DA. When it reaches, Diac DA
Is also triggered, the triac TA is also turned on, and from this point on, the power in the shaded area of the negative half cycle is supplied to the AC motor M. Accordingly, AC motor M rotates at a speed corresponding to the conduction angle.

On the other hand, when the variable resistor VR is changed in a direction in which the resistance value increases or decreases, the time constant also changes, so that the slopes of the charging curves 122 and 124 of the capacitor C change in a falling direction or a rising direction. . Since the conduction angle of the current flowing through the triac TA changes in the decreasing or increasing direction (the direction in which the hatched area in the positive half cycle decreases or increases), the rotation speed of the AC motor must be controlled. Can be.

[0007]

In the above-mentioned conventional motor control circuit, the phase control section is composed of only the variable resistor VR and the capacitor C, so that the charging characteristic (time constant) of the capacitor C does not change. Nevertheless, if the power supply frequency used changes to 50 Hz or 60 Hz, the conduction angle of the triac changes depending on the power supply frequency, and there is a disadvantage that stable motor speed control cannot be performed.

That is, as shown in FIG. 10A, a voltage waveform 131 at a power supply frequency of 60 Hz and a voltage waveform 131 at a power supply frequency of 50 H
The charge characteristic 133 of the capacitor C for a positive half cycle (or a negative half cycle) with the voltage waveform 132 of z is:
Although the conduction angle of the triac TA with respect to each of the voltage waveforms 131 and 132 is different irrespective of the power supply frequency, when the charging voltage of the capacitor C reaches the gate trigger voltage vg of the triac TA, 60H
The conduction region of the triac TA at z and 50 Hz is as shown in FIGS.
z becomes larger.

As a result, when the resistance value of the variable resistor VR is changed at the same interval, the rotation speed of the AC motor becomes higher at 50 Hz. It becomes inconvenient to use. For example, when the rotational speed of the motor is controlled by changing the resistance value of the variable resistor VR in conjunction with the stroke operation of the switch used in the power tool, the relationship between the switch stroke at 60 Hz and 50 Hz and the motor rotational speed is shown in FIG. Become like

As is apparent from FIG.
There is a large difference between the shift range at 0 Hz and the shift range at 50 Hz, and it is necessary to change the stroke operation of the switch according to the power supply frequency.

The present invention has been made to solve such a conventional problem, and corrects the conduction angle of a switching element for controlling the speed of an AC motor in accordance with the fluctuation of the power supply frequency. It is an object of the present invention to provide a full-wave phase control type motor control device which enables stable control of the number of revolutions independent of the motor speed.

[0012]

A motor control device according to a first aspect of the present invention is a motor control device for controlling the rotation speed of an AC motor connected to an AC power supply via a bidirectional switching element for speed control. A first and a second capacitor for storing a charging voltage for triggering the bidirectional switching element during a positive and a negative half cycle of the AC power supply; and a first capacitor for the positive half cycle of the AC power supply. A first positive charging circuit for charging in each cycle in a positive direction, and a charging end point of a positive half cycle by the first positive charging circuit for each cycle of the first capacitor during a negative half cycle of the AC power supply A first negative charging circuit that charges the bidirectional switching element when the charging voltage reaches the gate trigger voltage of the bidirectional switching element. , Second to charge every cycle negative direction in a negative half cycle of the AC power source and the second capacitor
And charging the second capacitor in the positive direction from the end of negative half-cycle charging by the second negative charging circuit every cycle during the positive half-cycle of the AC power supply, and
A second positive charging circuit that triggers the bidirectional switching element when the charging voltage reaches the gate trigger voltage of the bidirectional switching element.

In accordance with the present invention, the first negative charging circuit causes the first capacitor to charge the first capacitor every cycle during the negative half cycle of the AC power supply from the end of the positive half cycle by the first positive charging circuit. A second positive charging circuit for charging the second capacitor in a negative direction every cycle during a negative half cycle of the AC power supply;
Is charged in the positive direction from the end of the negative half cycle by the second negative charging circuit every cycle during the positive half cycle of the AC power supply, and the charging voltage of the first capacitor or the second capacitor is increased. Since the conduction angle at the point when the gate trigger voltage of the bidirectional switching element is reached is triggered in synchronization with the positive and negative half-cycle waveforms, the conduction angle of the bidirectional switching element is subject to fluctuations in the power supply frequency. Accordingly, the rotation speed of the AC motor can be controlled stably independent of the power supply frequency.

According to a second aspect of the present invention, in the motor control device according to the first aspect, the first positive charging circuit includes a limiter circuit for limiting a charging voltage of the first capacitor, and The negative charging circuit includes a limiter circuit that limits the charging voltage of the second capacitor.

According to the present invention, a negative or positive voltage exceeding the breakdown voltage of the first and second capacitors is prevented from being accumulated, so that the destruction of the first and second capacitors can be prevented and the capacitance can be reduced. I can do it.

According to a third aspect of the present invention, in the motor control device according to the first or second aspect, when the voltage of the AC power supply decreases, the first negative charging circuit operates in the negative half cycle period. A constant voltage circuit for making the current for charging the first capacitor in the negative direction constant and for the second positive charging circuit to make the current for charging the second capacitor in the positive direction constant during the positive half cycle; It is provided.

According to the present invention, even if the power supply voltage fluctuates in the decreasing direction, the rotation speed of the AC motor can be stably controlled without being affected by the fluctuation of the voltage.

According to a fourth aspect of the present invention, in the motor control device according to the first or third aspect, the first negative charging circuit and the second positive charging circuit include a variable resistor.

According to a fifth aspect of the present invention, there is provided the motor control device according to the first or fourth aspect, wherein the first negative charging circuit and the second positive charging circuit have a resistance value including a variable resistance. Has a circuit for changing logarithmically.

According to the fourth and fifth aspects of the present invention, it is possible to obtain a characteristic in which the rotational speed of the AC motor changes in a bow-like manner, and it is possible to reduce the rate of change in the speed of the AC motor when it starts up. Can be improved.

According to a sixth aspect of the present invention, in the motor control device according to the first or fourth aspect, the bidirectional switching element includes a main bidirectional switching element for switching a power supply circuit of the AC motor, Triggered by one negative charging circuit and a second positive charging circuit;
And an auxiliary bidirectional switching element for turning on the main bidirectional switching element.

According to the present invention, the gate current of the bidirectional switching element can be reduced, the current consumption of the first negative charging circuit and the second positive charging circuit can be reduced, and the heat generation can be reduced.

According to a seventh aspect of the present invention, in the first aspect, the first capacitor is charged by the first negative charging circuit upon triggering of the bidirectional switching element in the negative half cycle. The first gate trigger circuit, which is turned on by a voltage, is used to trigger the bidirectional switching element in the positive half cycle.
And a second gate trigger circuit that is turned on by the charging voltage of the second capacitor by the positive charging circuit.

According to the present invention, the charging current of the first and second capacitors can be reduced while securing the gate current of the bidirectional switching element, and the first negative charging circuit and the second positive charging circuit are provided. Current consumption is small, and the heat generation can be reduced.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 is a circuit diagram of a motor control device according to Embodiment 1 of the present invention. In the figure, a motor control device triggers an AC power supply 1, a bidirectional switching element (triac) 2 for speed control, an AC motor 3, and a bidirectional switching element 2 during positive and negative half cycle periods of the AC power supply 1. And second capacitors 4 and 5 for storing a charging voltage, a first positive charging circuit 6, a first negative charging circuit 7, and a second negative charging constituting a full-wave phase control circuit Circuit 8 and second positive charging circuit 9
Is provided.

The AC power supply 1 has a bidirectional switching element 2
The AC motor 3 is connected via the. The first capacitor 4 is connected in parallel to both ends of the AC power supply 1 via a diode D1 and a resistor R2. The first capacitor 4, the diode D1, and the resistor R2 constitute a first positive charging circuit 6 that charges the first capacitor 4 in a positive direction every cycle during a positive half cycle of the AC power supply 1. .

The first negative charging circuit 7 switches the first capacitor 4 every cycle during the negative half cycle of the AC power supply 1,
The battery is charged in the negative direction (reverse direction) from the end of the positive half-cycle charging by the first positive charging circuit 6, and bidirectionally when the charging voltage reaches the gate trigger voltage of the bidirectional switching element 2. The switching element 2 is triggered, and includes a series circuit of an NPN transistor Q1, a diode D3, and a variable resistor VR. The first negative charging circuit 7 is connected between the connection point between the first capacitor 4 and the diode D1 of the first positive charging circuit 6 and the anode of the bidirectional switching element 2. .

The second capacitor 5 is connected in parallel to both ends of the AC power supply 1 via a diode D2 and a resistor R2. The second capacitor 5, the diode D2 and the resistor R2 charge the second capacitor 5 in the negative direction every cycle during the negative half cycle of the AC power supply 1.
Of the negative charging circuit 8 of FIG.

The second positive charging circuit 9 switches the second capacitor 5 every cycle during the positive half cycle of the AC power supply 1,
The battery is charged in a positive direction (reverse direction) from the end of the charge in the negative half cycle by the second negative charge circuit 8, and bidirectionally when the charge voltage reaches the gate trigger voltage of the bidirectional switching element 2. This triggers the switching element 2, and includes a series circuit of a PNP transistor Q2, a diode D4, and a variable resistor VR. The second positive charging circuit 8 is connected between the connection point of the second capacitor 5 and the diode D2 of the second negative charging circuit 8 and the anode of the bidirectional switching element 2. .

The gate of the bidirectional switching element 2 is connected to the bases of the transistors Q1 and Q2. Also,
A protection capacitor C1 and a resistor R1 are connected in parallel between the gate and the gate-side terminal of the bidirectional switching element 2.

In this configuration, the power supply frequency is 50 Hz
When the AC motor 3 is controlled using the AC power supply 1, the voltage waveform of the AC power supply 1 has a sine waveform shown by a solid line in FIG. In the AC power supply voltage V1 of 50 Hz, the diode D1 of the first positive charging circuit 6 conducts during a period in which the point P side shown in FIG. 1 is a positive half cycle (time points T0 to T4 in FIG. 2). A charging current flows through the path of AC power supply 1 → resistor R1 → diode D1 → capacitor 4 → AC power supply 1, and the charging current causes the first capacitor 4 to have a charging curve 21 shown by a solid line in FIG. Charged in the positive direction.

During a period in which the point P side shown in FIG. 1 is a negative half cycle (time points T4 to T8 in FIG. 2), the diode D3 and the transistor Q1 of the first negative charging circuit 7 become conductive, AC power supply 1 → capacitor 4 → transistor Q1 → diode D3 → variable resistor VR
→ AC motor 3 → Charging current flows through the path of AC power supply 1,
Due to this charging current, the first capacitor 4 is turned on as shown in FIG.
As shown by a charge curve 22 shown by a solid line, reverse charging is performed in the negative direction from the positive maximum charging voltage. At this time, a base current flows through the transistor Q1, but this base current does not trigger the gate of the bidirectional switching element 2 because it is small. Further, the AC motor 3 is not rotated by this charging current.

After the first capacitor 4 is reversely charged with a negative half cycle voltage, the charged voltage V2 gradually decreases at a time constant determined by the resistance value of the variable resistor VR, and enters the negative region. , When the gate trigger voltage -vg of the bidirectional switching element 2 is reached (time T6), FIG.
Is applied to the gate of the bidirectional switching element 2 so that the bidirectional switching element 2
Is turned on, and a current having a waveform 23 shown by a solid line in FIG. 2E is supplied to the AC motor 3 from the time T6 to a time T8 at which the negative half cycle ends.

On the other hand, during the period (points T0 to T4 in FIG. 2) in which the point P side shown in FIG.
When the diode D4 and the transistor Q2 of the positive charging circuit 8 conduct, the AC power supply 1 → AC motor 3
A charging current flows through a path of → variable resistance VR → transistor Q2 → AC power supply 1, and the charging current causes the second capacitor 5 to move in a positive direction as shown by a charging curve 24 shown by a solid line in FIG. It is being charged. At this time, a base current flows through the transistor Q2, but since the base current is small, the gate of the bidirectional switching element 2 is not triggered. Further, the AC motor 3 is not rotated by this charging current.

As the second capacitor 5 is charged in the forward direction with the positive half cycle voltage, the charged voltage V2 gradually increases with a time constant determined by the resistance value of the variable resistor VR and enters the positive region. After that, when the gate trigger voltage vg of the bidirectional switching element 2 is reached (time T2), FIG.
When the positive trigger voltage shown by the solid line in (d) is applied to the gate of the bidirectional switching element 2, the bidirectional switching element 2 is turned on, and from this time T2 to the time T4 at which the positive half cycle ends, FIG. Is supplied to the AC motor 3. Thus, AC motor 3 is rotated at a speed corresponding to the electric power in the conduction angle region of both waves shown in waveforms 26 and 23.

In the period during which the point P side shown in FIG. 1 is a negative half cycle (time T4 to T8 in FIG. 2), the second
When the diode D2 of the negative charging circuit 8 is turned on, a charging current flows through a path of AC power supply 1 → capacitor 4 → diode D1 → resistor R1 → AC power supply 1, so that the second capacitor 5 The battery is reversely charged in the negative direction as indicated by the charge curve 25 shown by the solid line in FIG. Then, in the positive half cycle, the second positive charging circuit 8 operates in the same manner as described above.

In the first negative charging circuit 7 and the second positive charging circuit 8, when the variable resistance VR is variably operated to reduce the resistance value, the power supply voltage V1
, The time constant in the positive or negative half cycle becomes smaller, so that the charging time of the second capacitor 5 or the first capacitor 4 until reaching the gate trigger voltage vg or -vg of the bidirectional switching element 2 is shortened. The charging curve 24 or the charging curve 22 rises in the direction of the arrow. As a result, the conduction angle of the current flowing through the bidirectional switching element 2 increases, and the rotation speed of the AC motor 3 increases.

When the resistance of the variable resistor VR is decreased, the time constant in the positive or negative half cycle of the power supply voltage V1 becomes large. The charging time of the second capacitor 5 or the first capacitor 4 until reaching the trigger voltage vg or -vg becomes longer, and the charging curve 24 or the charging curve 22 falls in the direction opposite to the arrow. As a result, the conduction angle of the current flowing through the bidirectional switching element 2 decreases, and the rotation speed of the AC motor 3 decreases.

Next, a case where an AC motor is controlled using an AC power supply having a power supply frequency of 60 Hz will be described. In this case, the voltage waveform of the AC power supply 1 is a sine waveform indicated by a broken line in FIG. In the AC power supply voltage V1 of 50 Hz, the diode D1 of the first positive charging circuit 6 conducts during the period in which the point P side shown in FIG. 1 is a positive half cycle (time T0 to T3 in FIG. 2). , A charging current flows through a path of AC power supply 1 → resistor R1 → diode D1 → capacitor 4 → AC power supply 1;
2 is a charge curve 2 shown by a broken line in FIG.
The battery is charged in the positive direction as shown in FIG.

During a period in which the point P side shown in FIG. 1 is a negative half cycle (time points T3 to T7 in FIG. 2), the diode D3 and the transistor Q1 of the first negative charging circuit 7 become conductive, AC power supply 1 → capacitor 4 → transistor Q1 → diode D3 → variable resistor VR
→ AC motor 3 → Charging current flows through the path of AC power supply 1,
Due to this charging current, the first capacitor 4 is turned on as shown in FIG.
As shown in a charging curve 28 indicated by a broken line, reverse charging is performed in the negative direction from the positive maximum charging voltage. At this time, a base current flows through the transistor Q1, but this base current does not trigger the gate of the bidirectional switching element 2 because it is small. Further, the AC motor 3 is not rotated by this charging current.

After the first capacitor 4 is reverse-charged with a negative half cycle voltage, the charge voltage V2 gradually decreases at a time constant determined by the resistance value of the variable resistor VR and enters a negative region. 2 (d) when the gate trigger voltage -vg of the bidirectional switching element 2 is reached (time T5).
Is applied to the gate of the bidirectional switching element 2 so that the bidirectional switching element 2
Is turned on, and a current having a waveform 29 shown by a broken line in FIG. 2E is supplied to the AC motor 3 from time T5 to time T7 at which the negative half cycle ends.

On the other hand, during the period (points T0 to T3 in FIG. 2) in which the point P side shown in FIG.
When the diode D4 and the transistor Q2 of the positive charging circuit 8 conduct, the AC power supply 1 → AC motor 3
A charging current flows through a path of → variable resistance VR → transistor Q2 → AC power supply 1, and the charging current causes the second capacitor 5 to move in a positive direction as shown by a charging curve 30 shown by a broken line in FIG. It is being charged. At this time, a base current flows through the transistor Q2, but since the base current is small, the base of the bidirectional switching element 2 is not triggered. Further, the AC motor 3 is not rotated by this charging current.

When the second capacitor 5 is charged in the forward direction with a positive half cycle voltage, the charged voltage V2 gradually increases with a time constant determined by the resistance value of the variable resistor VR and enters the positive region. After that, when the voltage reaches the gate trigger voltage vg of the bidirectional switching element 2 (time T1), FIG.
When the positive trigger voltage shown by the broken line in (d) is applied to the gate of the bidirectional switching element 2, the bidirectional switching element 2 is turned on, and from this time T1 to the time T3 at which the positive half cycle ends, FIG. Is supplied to the AC motor 3. As a result, AC motor 3 is rotated at a speed corresponding to the electric power in the conduction angle region of both waves shown in waveforms 32 and 29.

In the period during which the point P side shown in FIG. 1 is a negative half cycle (time T3 to T7 in FIG. 2), the second
When the diode D2 of the negative charging circuit 8 is turned on, a charging current flows through a path of AC power supply 1 → capacitor 4 → diode D1 → resistor R1 → AC power supply 1, so that the second capacitor 5 The battery is reversely charged in the negative direction as indicated by the charging curve 31 shown by the broken line in FIG. Then, in the positive half cycle, the second positive charging circuit 8 operates in the same manner as described above.

In the first negative charging circuit 7 and the second positive charging circuit 8, when the variable resistance VR is variably operated to reduce the resistance value, the power supply voltage V1
, The time constant in the positive or negative half cycle becomes smaller, so that the charging time of the second capacitor 5 or the first capacitor 4 until reaching the gate trigger voltage vg or -vg of the bidirectional switching element 2 is shortened. The charging curve 24 or the charging curve 22 rises in the direction of the arrow. As a result, the conduction angle of the current flowing through the bidirectional switching element 2 increases, and the rotation speed of the AC motor 3 increases.

When the resistance of the variable resistor VR is decreased, the time constant at the time of the positive or negative half cycle of the power supply voltage V1 becomes large. The charging time of the second capacitor 5 or the first capacitor 4 until reaching the trigger voltage vg or -vg becomes longer, and the charging curve 24 or the charging curve 22 falls in the direction opposite to the arrow. As a result, the conduction angle of the current flowing through the bidirectional switching element 2 decreases, and the rotation speed of the AC motor 3 decreases.

As is apparent from the above description, the first positive charging circuit 6, the first negative charging circuit 7, the second negative charging circuit 8, and the second positive charging circuit 9 are bidirectionally connected. By incorporating the switching element 2 in the full-wave phase control circuit, the conduction angle of the bidirectional switching element 2 can be corrected according to the fluctuation of the power supply frequency. For this reason, even if the power supply frequency is 50 Hz or 60 Hz, the conduction angles of the bidirectional switching elements 2 become substantially equal.

Therefore, the motor control device according to the present embodiment is applied to a motor control circuit of an AC power tool such as bolting, and the resistance value of the variable resistor VR is changed in conjunction with the stroke operation of a switch used in the power tool. When the rotation speed of the motor is controlled, the relationship between the switch stroke at 60 Hz and 50 Hz and the rotation speed of the motor is as shown in FIG. As is apparent from FIG. 3, the shift range is almost the same between the power supply frequency of 60 Hz and the power supply frequency of 50 Hz. As a result, there is almost no need to change the stroke operation of the switch according to the power supply frequency, and the usability of the power tool is good. become.

(Embodiment 2) FIG. 4 is a circuit diagram of a motor control device according to Embodiment 2 of the present invention. The same components as in FIG. 1 are denoted by the same reference numerals as in FIG. The description of the operation will be omitted, and portions different from FIG. 1 will be mainly described.

As is apparent from FIG. 4, the present embodiment 2
Are characterized in that the first limiter circuit 10 is connected in parallel to both ends of the first capacitor 4 in the first positive charging circuit 6, and the second limiter circuit in the second negative charging circuit 8
A second limiter circuit 11 is connected in parallel to both ends of the capacitor 5, and an auxiliary bidirectional switching element 2 for turning on the bidirectional switching element 2 with a small gate current.
b and the main bidirectional switching element 2a that is turned on as the auxiliary bidirectional switching element 2b is turned on. The first negative charging is performed so that the rotational speed of the AC motor 3 has a lower bow-like speed characteristic. The resistor R3 is connected in parallel to the variable resistor VR of the circuit 7 and the second positive charging circuit 9, so that the combined resistance value of the two resistors varies logarithmically.

Both terminals of the main bidirectional switching element 2a are connected between the AC motor 3 and the AC power supply 1, and both terminals of the auxiliary bidirectional switching element 2b are connected with the main bidirectional switching element gate between one terminals. ing. Further, between the gates of the bidirectional switching element 2 and the auxiliary bidirectional switching element 2b and the gate side terminal, protective capacitors C11 and C12 and resistors R11 and R11 are provided, respectively.
12 are connected in parallel.

The first limiter circuit 10 limits the charging voltage when the first capacitor 4 is charged with a negative half cycle voltage in the reverse direction every cycle so as not to exceed the withstand voltage of the first capacitor 4. The Zener diode ZD1 having the opposite polarity with respect to the voltage of the negative half cycle.
And a diode D5 connected in series to the zener diode ZD1 with the opposite polarity. The diode D5 prevents the Zener diode ZD1 from conducting in the forward direction when charging the first capacitor 4 in the positive direction.

The second limiter circuit 11 limits the charging voltage when the second capacitor 5 is charged in the reverse direction every cycle with a positive half cycle voltage so as not to exceed the withstand voltage of the second capacitor 5. The Zener diode ZD which has the opposite polarity with respect to the positive and negative half cycle voltages.
2 and a diode D6 connected in series with the zener diode ZD2 in reverse polarity. The diode D6 prevents the Zener diode ZD2 from conducting in the forward direction when charging the second capacitor 5 in the positive direction.

In this configuration, the first negative charging circuit 7
Then, if the value of the variable resistor VR is increased, the negative half-cycle voltage causes the negative charging voltage V
2, the conduction angle of the main bi-directional switching element 2a including the auxiliary bi-directional switching element 2b is reduced. Here, even if the conduction angle becomes zero, the resistance of the variable resistor VR is further reduced. As the value is increased, the terminal voltage V2 of the first capacitor 4 does not reach negative but increases in the positive direction.

When the positive terminal voltage of the first capacitor 4 becomes larger than the Zener voltage of the Zener diode ZD1, the Zener diode ZD1 conducts, and the positive charging voltage of the first capacitor 4 is reduced by the diode D5. And discharge through the Zener diode ZD1. As a result, a negative voltage exceeding the breakdown voltage is prevented from being accumulated in the first capacitor 4, so that the destruction of the first capacitor 4 can be prevented, and the first capacitor 4 can be prevented from being destroyed.
It is not necessary to increase the capacity of the first capacitor 4 more than necessary, and the capacity of the first capacitor 4 can be reduced.

Similarly, in the second positive charging circuit 9,
When the value of the variable resistor VR is increased, the rising gradient of the negative charging voltage V2 of the second capacitor 5 due to the negative half cycle voltage becomes gentle, and the main bidirectional switching element including the auxiliary bidirectional switching element 2b is provided. Although the conduction angle of 2a becomes smaller, if the value of the variable resistor VR is further increased even if the conduction angle becomes zero, the terminal voltage V2 of the second capacitor 5 does not reach positive, It increases in the negative direction.

When the negative terminal voltage of the second capacitor 5 becomes higher than the Zener voltage of the Zener diode ZD2, the Zener diode ZD2 conducts, and the positive charging voltage of the second capacitor 5 is reduced by the diode D6. And discharge through the Zener diode ZD2. As a result, a negative voltage exceeding the withstand voltage is not accumulated in the second capacitor 5, so that the destruction of the second capacitor 5 can be prevented, and the second capacitor 5 can be prevented from being damaged.
It is not necessary to increase the capacity of the second capacitor 5 more than necessary, and the second capacitor 5 can be reduced in capacity.

On the other hand, when the variable resistor R2 is variably operated,
The combined resistance value of the variable resistor RV and the resistor R3 is represented by a curve 5 in FIG.
It changes exponentially as shown in FIG. Therefore, by operating the variable resistor RV, the rotation speed of the AC motor has a characteristic that changes in a lower bow as shown by a curve 52 in FIG. Accordingly, the rate of change in speed at the time of startup of the AC motor 3 is small, and the number of revolutions gradually increases. Therefore, it is suitable for an electric tool that performs a tightening operation while positioning a bolt, such as a bolt. .

A two-stage configuration of a bidirectional switching element 2 for switching the power supply circuit of the AC motor 3 is a main bidirectional switching element 2a and an auxiliary bidirectional switching element 2b for turning on the main bidirectional switching element 2a. , The gate current of the bidirectional switching element can be reduced, and the resistor R3, the variable resistor RV and the transistors Q1, Q
2 reduces the current consumption and reduces the heat generated by these elements.

(Embodiment 3) FIG. 6 is a circuit diagram of a motor control device according to Embodiment 3 of the present invention. The same components as those in FIGS. 1 and 4 are denoted by the same reference numerals as in FIG. The description of the configuration and operation will be omitted, and portions different from those in FIGS. 1 and 4 will be mainly described.

As is apparent from FIG. 6, the third embodiment
The first and second gate trigger circuits 12 for triggering the bidirectional switching element 2
13 is provided, and a constant voltage circuit 14 common to the first negative charging circuit 7 and the second positive charging circuit 9 is provided.

The first gate / trigger circuit 12 is turned on by the charging voltage of the first capacitor 4 by the first negative charging circuit 7 when the bidirectional switching element 2 is triggered in the negative half cycle. NPN transistor TR1, PNP transistor TR2, capacitor C1,
C2, diode D7 and zener diode ZD5
And so on. The second gate / trigger circuit 13 triggers the bidirectional switching element 2 in the positive half cycle by the second positive charging circuit 9
Is conducted by the charging voltage of the capacitor 5 of
PN transistor TR3, PNP transistor TR4,
It is composed of capacitors C3 and C4, a diode D8, a Zener diode ZD6, and the like.

The constant voltage circuit 14 is a circuit for making the voltage for charging the first capacitor 4 in the positive direction and the voltage for charging the second capacitor 5 in the negative direction constant when the voltage of the AC power supply 1 decreases. The series circuit is composed of zener diodes ZD3 and ZD4 connected in series with each other in polarity. The series circuit is connected between the ground side of the AC power supply 1 and one end of the variable resistor RV via a resistor R4.

Next, the operation when the constant voltage circuit 14 is provided will be described. First, in the case where the second negative charging circuit 8 and the second positive charging circuit 9 operate and the constant voltage circuit 14 is not provided, as shown in FIG. When the state is reduced from the solid line state to the state shown by the broken line, as shown in FIG. 7B, the inclination of the charge curve 31 in the negative direction of the capacitor 5 becomes gentle, and the charge curve 30 in the positive direction also becomes gentle. However, the time point T2 when the positive charging voltage V2 reaches the gate trigger voltage vg of the bidirectional switching element 2 is the same.

However, when the thyristor is turned on at time T2 when the power supply voltage is high as shown by the solid line, the voltage V3 supplied to the AC motor 3 is in the conduction region shown by the solid line in FIG. On the other hand, when the power supply voltage decreases as shown by the broken line, the voltage V3 supplied to the AC motor 3
Is a conduction region indicated by a broken line in FIG. As a result, the rotation speed of the AC motor is lower than at a high power supply voltage.

On the other hand, when the constant voltage circuit 14 is provided, the charging voltage to the capacitor 5 is made constant by the Zener diode ZD3 and the resistor R4, so that the voltage is made constant even when the power supply voltage becomes low. Capacitor 5 depending on voltage
Will be charged in the positive direction.

Accordingly, the inclination of the charge curve 30 in the positive direction of the capacitor 5 when the power supply voltage is low is as shown in FIG.
As shown in the figure, the slope becomes the same as the positive charge curve 25 to the capacitor 5 at the time of the high power supply voltage, and the positive charge voltage V2 at the time of the low power supply voltage becomes the gate trigger voltage vg of the bidirectional switching element 2. Time T1 to reach
Moves before the time point T2. As a result, FIG.
As shown in the figure, a conduction region at the time of a low power supply voltage indicated by a broken line,
The conduction regions at the time of the high power supply voltage indicated by the solid line are substantially equal.
Therefore, even if the power supply voltage changes in the decreasing direction, it is possible to prevent the rotation speed of the AC motor from decreasing.

The function of such a constant voltage circuit 14 is similarly performed when the first positive charging circuit 6 and the first negative charging circuit 7 operate, and changes in a direction in which the power supply voltage decreases. However, it is possible to prevent the rotational speed of the AC motor from decreasing.

Further, by providing the first and second gate trigger circuits 12 and 13 for triggering the bidirectional switching element 2 during the positive and negative half cycle periods of the AC power supply 1, the gate current can be reduced. At the same time, the current consumption of the charging circuit is reduced, and the heat generated by the charging circuit can be reduced.

The bidirectional switching element used in the present invention is not limited to a triac, and a semiconductor element such as a MOS transistor can be used.

[0071]

According to the present invention, the first negative charging circuit causes the first capacitor to charge the first capacitor every cycle during the negative half cycle of the AC power supply from the end of the positive half cycle by the first positive charging circuit. Charge in the negative direction and the second positive charging circuit
A second negative charging circuit for charging the capacitor in the negative direction every cycle during the negative half cycle of the AC power supply; and a second negative charging circuit for charging the second capacitor every cycle during the positive half cycle of the AC power supply. Bidirectional switching is performed at the conduction angle at the time when the charging voltage of the first capacitor or the second capacitor reaches the gate trigger voltage of the bidirectional switching element, by charging in the positive direction from the end of the negative half cycle by the charging circuit. Since the elements are triggered in synchronization with the positive and negative half-cycle waveforms, the conduction angle of the bidirectional switching element can be corrected according to the fluctuations in the power supply frequency, and the rotation speed of the AC motor can be controlled stably independent of the power supply frequency. it can.

Further, according to the present invention, the first positive charging circuit and the second negative charging circuit are provided with limiter circuits for limiting the charging voltage of each capacitor. Excessive negative or positive voltage is not accumulated, so that destruction of the first and second capacitors can be prevented and the capacitance can be reduced.

Further, according to the present invention, when the voltage of the AC power supply decreases, the first negative charging circuit keeps the voltage for charging the first capacitor in the negative direction constant during the negative half cycle. In addition, since the second positive charging circuit has a constant voltage circuit for keeping the voltage for charging the second capacitor in the positive direction constant during the positive half cycle, the power supply voltage may fluctuate in a decreasing direction. However, the rotation speed of the AC motor can be stably controlled without being affected by the fluctuation of the voltage.

Further, according to the present invention, the first negative charging circuit and the second positive charging circuit have a circuit for changing the resistance value including the variable resistance logarithmically, so that the rotation of the AC motor is reduced. It is possible to obtain a characteristic in which the speed changes like a lower bow, and it is possible to reduce the speed change rate when the AC motor starts up, thereby improving the usability of the power tool or the like.

Further, according to the present invention, since the bidirectional switching element is composed of the main bidirectional switching element and the auxiliary bidirectional switching element, the gate current of the bidirectional switching element can be reduced and the first negative switching element can be used. The current consumption of the charging circuit and the second positive charging circuit is reduced, and the heat generation can be reduced.

Further, according to the present invention, the first gate trigger circuit is used to trigger the bidirectional switching element in the negative half cycle, and the second gate is used to trigger the bidirectional switching element in the positive half cycle. Since the trigger circuit is used, the gate current of the bidirectional switching element can be reduced, and the current consumption of the first negative charging circuit and the second positive charging circuit is reduced, and the heat generation thereof is also reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a motor control device according to a first embodiment of the present invention.

2 (a) to 2 (e) are waveform diagrams of each part of the motor control device shown in FIG.

FIG. 3 is a characteristic diagram showing a relationship between a stroke of the motor control device shown in FIG. 1 and a motor rotation speed.

FIG. 4 is a circuit diagram of a motor control device according to a second embodiment of the present invention.

5 is a characteristic diagram illustrating a relationship between a resistance value of a variable resistor of the motor control device illustrated in FIG. 4 and a rotation speed of an AC motor.

FIG. 6 is a circuit diagram of a motor control device according to a third embodiment of the present invention.

7 (a) to 7 (e) are waveform diagrams of respective parts of the motor control device shown in FIG.

FIG. 8 is a circuit diagram of a conventional motor control device used for speed control of an AC motor such as a power tool.

FIG. 9 is an explanatory waveform diagram of the conventional motor control device shown in FIG.

10 (a) to 10 (c) are waveform diagrams of respective parts of the conventional motor control device shown in FIG.

11 is a characteristic diagram showing a relationship between a stroke and a motor rotation speed of the conventional motor control device shown in FIG.

[Explanation of symbols]

 Reference Signs List 1 AC power supply 2 Bidirectional switching element 2a Main bidirectional switching element 2b Auxiliary bidirectional switching element 3 AC motor 4 First capacitor 5 Second capacitor 6 First positive charging circuit 7 First negative charging circuit Reference Signs List 8 second negative charging circuit 9 second positive charging circuit 10 first limiter circuit 11 second limiter circuit 12 first gate trigger circuit 13 second gate trigger circuit 14 constant voltage circuit RV variable Resistance R3 Resistance

Claims (7)

[Claims] 1. A motor control device for controlling a rotation speed of an AC motor connected to an AC power supply via a bidirectional switching element for speed control, wherein the bidirectional switching element is connected to a positive and a negative of the AC power supply. First and second capacitors for storing a charging voltage for triggering in a half cycle period, and a first positive charge for charging the first capacitor in a positive direction every cycle during a positive half cycle period of the AC power supply. And charging the first capacitor in the negative direction from the end of the positive half-cycle charging by the first positive charging circuit every cycle during the negative half-cycle period of the AC power supply. A first negative charging circuit for triggering the bidirectional switching element when the gate trigger voltage of the bidirectional switching element is reached; A second negative charging circuit for charging in a negative direction every cycle during a negative half cycle period of the power supply; and a second negative charging circuit for charging the second capacitor every cycle during a positive half cycle period of the AC power supply. A second positive charge that charges in the positive direction from the end of the charge in the negative half cycle according to the above, and triggers the bidirectional switching element when the charging voltage reaches the gate trigger voltage of the bidirectional switching element. And a circuit. 2. The first positive charging circuit includes a limiter circuit that limits a charging voltage of a first capacitor, and the second negative charging circuit limits a charging voltage of a second capacitor. The motor control device according to claim 1, further comprising a limiter circuit. 3. When the voltage of the AC power supply drops, the first negative charging circuit keeps the current for charging the first capacitor in the negative direction constant during the negative half cycle period, 3. The positive charging circuit according to claim 1, further comprising a constant voltage circuit for maintaining a constant current for charging the second capacitor in the positive direction during the positive half cycle.
The motor control device according to any one of the preceding claims. 4. The first negative charging circuit and the second negative charging circuit
4. The motor control device according to claim 1, wherein the positive charging circuit includes a variable resistor. 5. The first negative charging circuit and the second negative charging circuit.
The motor control device according to claim 1, wherein the positive charging circuit includes a circuit that logarithmically changes a resistance value including a variable resistance. 6. The bi-directional switching element is triggered by a main bi-directional switching element for switching a power circuit of an AC motor, the first negative charging circuit and the second positive charging circuit, The motor control device according to claim 1, further comprising an auxiliary bidirectional switching element for turning on the main bidirectional switching element. 7. A method according to claim 1, wherein a first gate trigger circuit that is turned on by a charging voltage of a first capacitor by said first negative charging circuit is used for triggering said bidirectional switching element in a negative half cycle, 2. A second gate trigger circuit which is turned on by a charging voltage of a second capacitor by the second positive charging circuit is used as a trigger of the bidirectional switching element in a half cycle of the step (c). The motor control device according to any one of the preceding claims.