JPS62247784A - Speed control circuit for motor - Google Patents

Abstract

PURPOSE:To widen a speed control range by altering a frequency of output signal of a speed-detecting circuit or timing-pulse generation circuit. CONSTITUTION:A speed signal proportional to a motor rotating speed is outputted from any of frequency generator FG1 or FG2 selected by a changeover switch SW. A sample reset pulse generation circuit 2 generates a sample pulse and a reset pulse simultaneously with a speed signal and a serrate-wave genera tion circuit 3 generates a serrate-wave voltage simultaneously with a reset pulse. A sample-and-hold circuit 4 samples a serrate-wave voltage by a sample pulse. A comparator 13 compares an error signal of a sample-and-hold voltage and a rotating-speed setting voltage with a reference triangular wave to give a comparison signal to FET 14.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a motor speed control circuit applied to power tools such as electric drills and electric screwdrivers.

(Prior art) In general, power tools such as electric screwdrivers and drills
A speed control circuit is provided that functions to rotate at a low speed to facilitate bit alignment when drilling a hole or tightening a screw, and then to rotate at a high speed.

However, a wider speed control range and lower speed rotation are desired in order to accommodate the wide variety of materials used and Hakugaku.

Currently, there is a mechanical two-stage switching configuration using gear switching to meet this demand.
The problem with type b is that not only is the structure not in a cylinder, but it is also difficult to use multiple stages, and moreover, it causes a lot of controversy. Furthermore, in power tools equipped with a feedback control circuit, if you try to widen the speed control range of the motor to meet the above requirements, the stable point of the feedback system will be deviated, and the control circuit will not be stable, causing the motor to wobble and result in stable rotation. The problem was that it was not possible to obtain

(Objective of the Invention) The present invention solves the above-mentioned conventional problems.By switching electrical signals, a wide speed control range and low speed control are possible without using a mechanical two-stage mechanism. The purpose is to provide a motor speed control circuit suitable for power tools.

(Structure of the Invention) The present invention provides a speed detection circuit that outputs a signal proportional to the rotational speed of a motor, a timing pulse generation circuit that generates a timing pulse based on the speed signal from the speed detection circuit, and the timing pulse generation circuit. a frequency-voltage conversion circuit that converts the speed signal of the motor from frequency to voltage using timing pulses; and an error that amplifies the difference between the frequency-voltage converted signal from the frequency-voltage conversion circuit and the voltage of the speed variable circuit. The frequency-voltage conversion circuit includes an amplifier circuit, a comparison circuit that compares the error amplified signal with a predetermined reference triangular wave, and a switching circuit that supplies driving power to the motor using the output of the comparison circuit. a sawtooth wave generation circuit that generates/initializes a sawtooth wave using the timing pulse of the timing pulse generation circuit; and a Ringer hold circuit that holds the voltage of the sawtooth wave at that time using the timing pulse of the timing pulse generation circuit. In this motor speed control circuit, the speed detection circuit or the timing pulse generation circuit is provided with conversion means for converting the frequency of the timing pulse into a plurality of n times different frequencies.

With this configuration, by appropriately switching and using the frequency of the timing pulse, the Daruma can be controlled over a wide range and at low speeds.

(Embodiment) FIG. 1 shows a motor speed control circuit according to a first embodiment of the present invention, and FIG. 2 shows its time chart.

In FIG. 1, a speed detection circuit 1 that outputs a signal proportional to the number of rotations of a DC motor M is connected to a rotating shaft of the motor M and outputs pulses of different frequencies per rotation as described later. - Wave number generator FG1. FG2, these frequency power generation 1!
rG1. Changeover switch SW for selecting FGt
, an operational amplifier OP1, resistors R and R8, and capacitors CF and C8. The frequency power generation I
FGt and FG2 constitute conversion means for converting the frequency of the timing pulse described later into a plurality of different frequencies.

In this speed detection circuit 1, the frequency generators FG1 and FG2 having different numbers of output pulses per rotation of the motor M are as follows:
As shown in Fig. 3, it is sufficient to use motors arranged side by side on the motor shaft, and here, the number of output pulses per rotation is equal to the frequency generator FG1.
Two types of frequency generators with double FG2 are used.

On the other hand, the rimble reset pulse generation circuit 2, which is a timing pulse generation circuit that generates timing pulses such as rimple pulses and reset pulses, includes a trapezoidal wave circuit 11 that generates a trapezoidal wave, and a hysteresis comparator OP.
2 and a sample reset pulse generator 2 consisting of an IC.
It consists of a, sample reset pulse generation/l
The trapezoidal wave circuit 114 inputs the trapezoidal wave to the device 2a,
It consists of a tj flow source 11, a capacitor OR, etc.

A tooth wave is formed by the reset pulse of the sample/reset pulse generator 2a! The tooth-shaped wave generation circuit 3 is composed of a constant current source T2, a constant current source T2, a non-pull pulse of the ripple reset pulse generator 2a, and generates a saw-tooth wave electric current.
The simple hold circuit 4 that samples and holds the
It is composed of buffers 4a, 4b, a capacitor C11, and the like.

A speed variable circuit 7 for setting an appropriate speed 1α of the motor M
consists of a resistor Rx1, a variable resistor VR, a buffer 78, etc., and its output is an error amplifier 12 as an error amplifying circuit.
It is compared with the output from the non-pull hold circuit 4, and the difference between the two and the two is inverted and amplified. Furthermore, the output of error amplifier 12 is! It is compared with the reference triangular wave from the IL triangular wave generation circuit 5 by a comparator 13 as a comparison circuit,
When the output of the comparator 3 is 1 level, the output circuit 8 is driven. Then, a power MOS field effect transistor (FFT) 14 constituting a switching circuit is turned on by the output of this output circuit 8, and the motor M
is now driven.

In addition, the speed signal of motor M is expressed as frequency-electric IT, (F-V
) The F-V conversion circuit for conversion is composed of a sawtooth wave generation circuit 3 and a sample hold circuit 4. Furthermore, a battery B is used as a power source for the motor M.

Further, the lock protection circuit 9 is a circuit for stopping the drive of the motor M when the rotation speed of the motor M becomes less than a set value, and when an overload is applied to the motor M, the rotation speed of the motor M decreases. Therefore, the output frequency of the frequency power generator IFG1 or FG2 becomes smaller, and the output voltage of the ripple hold circuit 4 becomes higher. However, the lock protection circuit 9 uses the voltage divided by the resistors R1 and R1
5, when the rotation speed drops below the setting 11,
This is to cut off the output of the comparator 13 and stop the motor M. The output circuit 8 also includes a booster circuit 1.
0 is connected. Next, based on FIGS. 1 and 2, explain (!ll). (a) to (i) in FIG. The waveform of iQ is shown.A speed signal proportional to the rotation speed of motor M is output from either the frequency generator Il!FG1 or FG2 selected by the changeover switch SW, and the output speed signal is output from the OBEANZO 01.
)1, it is amplified by R, /R8 times. This speed signal]
As shown in FIG. 2(a), which corresponds to
l) The output of 1 is input to the hysteresis comparator OP2, and from this comparator 01)2 the output is input to the hysteresis comparator OP2 as shown in FIG.
An h-shaped pulse with a frequency proportional to the rotation number is obtained as shown in FIG. Using this square wave, the ring reset pulse generating circuit 20 and the trapezoidal wave circuit 11 generate a trapezoidal wave as shown in FIG. 2(C). The rise of this trapezoidal wave is compared with the standard fffrfV1°V2 and V3 from the reference voltage generation circuit 6. The timing at which Fig. 2(d)) occurs is determined.

On the other hand, in the sawtooth wave generation circuit 3, ]+JC■ is charged by a constant current l1i12, and when a reset pulse is generated, the charge charged in the capacitor CI is discharged, and the second
A sawtooth wave as shown in Figure (f) is generated. In the ripple hold circuit 4, when a non-pull pulse occurs,
[bold]nden)ic,.

By charging or discharging, the current sawtooth wave electric power is held for 1 non-pull. , Therefore, the sample-and-hold circuit 4 has a ripple-hold voltage as shown in FIG.
A DC signal proportional to the rotational speed as shown in (+) is output.

In the error amplifier 12, the voltage 8 set by the speed 1a variable circuit 7 and the output type IT-V o of the sample hold circuit 4 are
The difference is inverted and amplified to RA/RN times, and the output is shown in Figure 2 (
h), the base wall triangular wave generating circuit 50M quasi-triangular wave is compared with the inverter 13 to obtain a square wave as shown in FIG. 2(i), and this square wave is output through the output circuit 8 to The FET gate output voltage shown in FIG. 2 (j) is obtained, and the power supply to the motor M is controlled by pulse wide modulation (PWM) using the FET 14.

As mentioned above, the frequency of the signals of each part is twice that of the frequency r/i generator FG+ signal in the case of the frequency sporadic city machine IG2, so the duty of the gate signal of t l T 14 is also becomes smaller. Shift switch S
By manually switching W to the frequency power generation IN F G 2 side, the feedback system becomes stable even when the rotation speed of the motor M is low, and is suitable for rotation speeds lower than conventional ones.
be able to control it.

In addition, in FIG. 2 ((+) to (j)), the waveform in the case of the frequency generator FG2 is shown by a thick line.

Second Embodiment FIG. 4 shows a motor speed control circuit according to a second embodiment of the present invention, FIG. 5 shows its time chart, and FIG. 6 shows the configuration of an optical encoder as a conversion means in this embodiment. show. The speed detection circuit 1 is provided with a light Tn]-da E1. F2
is provided, and this light n'-da E1. E2 is motor M
+A of 2 scales or more in an annular row fixed to the rotating shaft of
It consists of a slit disk 101 with slits in it, a light emitting element 102 made of an FD or the like, sandwiching the slit disk 101, and a light receiving element F103 made of a phototransistor or the like paired with the light emitting element F102. Disk 10
Different numbers of output pulses are obtained per revolution of the motor. For example, in the case of FIG. 6, the slit interval of the slit disc 101 of the slit disk F2 is 1/2 for the light Tn]-da[1, and the number of output pulses per rotation is 2. It's doubled.

In this configuration, the changeover switch SW is connected to the optical encoder F.
By switching to the 2 side, the frequency of the signals in each part of the circuit is doubled, and as in the first embodiment, the feedback system becomes stable even during low speed operation, and proper control is possible down to lower speeds. .

Third Embodiment FIG. 7 shows a motor control circuit according to a third embodiment of the present invention, FIG. 8 shows its time chart, and FIG. 9! a)
9 shows the configuration of the frequency doubling circuit as the conversion means in this embodiment, and FIG. 9(b) shows the relationship between the input and output of this circuit. In this embodiment, a frequency doubling circuit FC is provided after the output of the hysteresis comparator 01)2 of the monthly reset pulse generating circuit 2 as a timing pulse generating circuit. frequency doubling circuit)7C[,1
As shown in FIG. 9(a), an exclusive OR circuit (exc
lusiveOR) 201, 202, 203 and resistance [<
, ] and a capacitor C, and as shown in FIG. 9(b), two outputs can be obtained for each input.

In addition, in FIG. 7, from the A side of the changeover switch SW to the B side
The arrangement is such that switching to the side causes the frequency 2 (8 digitizing circuit FC to be removed from the circuit).

In this configuration, by switching the switching switch (SW) from the 8 side to the A side, the frequency of the bind-off of each part of the circuit is doubled, and the same effect as in each of the above embodiments and 11 can be obtained.

(Effects of the Invention) As described above, according to the present invention, the motor speed detection circuit or the timing pulse generation circuit is provided with a conversion means for converting the frequency of the timing pulse into a plurality of different frequencies. Therefore, by appropriately switching and selectively using this conversion means, the following effects can be obtained.

(1) The speed controllable rotational speed can be reduced to 1/2 or less than that of the conventional system. Therefore, compared to conventional ones, it is possible to operate at a lower speed and more stably, and therefore, when applied to a power tool, it is possible to improve operability and workability.

(2) By dividing the speed control range into narrow sections, delicate speed adjustments can be made within each range, and speed stability is also improved.

(3) Compared to a mechanical type using gears, etc., the configuration is simpler, smaller, and lighter, and the number of project names is reduced.

In other words, in the case of a conventional mechanical type, if the speed switching range is multi-stage, the number of gears increases, the configuration becomes complicated, the shape becomes large, and the noise tends to increase, but with the present invention, Since this can be done by processing electrical signals, the configuration is simple, compact and lightweight, and there is no increase in noise.

[Brief explanation of drawings]

FIG. 1 is a speed control circuit diagram of a motor according to the first embodiment of the present invention, FIG. 2 (a) to (61) are tie 18 chart diagrams thereof, and FIG. FIG. 4 is a block diagram of a frequency generator as a two-stage conversion stage, FIG. 4 is a speed control circuit diagram of a motor according to a second embodiment of the present invention, and FIGS.
J) is a time chart thereof, FIG. 6 is a configuration diagram of an optical encoder as a conversion means in the second embodiment, and FIG.
The figure shows a motor speed control 611- according to the third embodiment of the present invention.
Figures 8 (a) to (j) are time charts, and Figures 9 (a) (b) '+ are circuit diagrams of the frequency doubling circuit as the first stage of conversion in the third embodiment. And its human power 111 Bamboo drawing C. 1...Speed detection circuit, 2...Rin1 reset pulse generation circuit (timing pulse generation circuit), 3...
Sawtooth wave generation circuit, 4... Limbo Ruld circuit, 1
2...Error amplifier C1fli difference amplification circuit), 13.
...] Comparator (comparison circuit), 14...11 [(
switching circuit), M...motor, EGl, FC
2... Frequency power generation II (conversion means), Fl, l-2.
・・Optical encoder, 101 ・・Slit disk, FC・
...Frequency doubling circuit (conversion means). Figure 9 Hidete*,,'a Ml-1 [Book (method) July 1986
January Σ Date 1, Indication of the case 1986 Patent Application No. 91490 2, Name of the invention - Evening speed control circuit 3, Relationship with the case by the person making the amendment Name of the patent applicant (583) Matsushita Electric Works Co., Ltd. 4. Address of the agent: 5 Shin Matsuoka Building, 1-10-3 Nishihonmachi, Nishi-ku, Osaka City; Date of amendment order: June 24, 1985; 6. [Simplified explanation of drawings 1] Column 7, Contents of amendment (1) Specification No. 15, Line 1, Figure 2 (a) to (j)
” is corrected to “Figure 2 is 1.” (2) “Figure 5 (a) to (”) on page 15, lines 4 to 5.
1 is corrected to [Figure 5 is 1] Jo (3) [Figure 8 (a) to l) on page 15, line 8 of the same page is corrected to ``Figure 8 is''.

Claims (1)

[Claims] 1. A speed detection circuit that outputs a signal proportional to the rotation speed of the motor, a timing pulse generation circuit that generates a timing pulse based on the speed signal from the speed detection circuit, and a timing pulse generation circuit that a frequency-voltage conversion circuit that converts a motor speed signal into frequency-voltage using a timing pulse; and an error amplification circuit that amplifies the difference between the frequency-voltage converted signal from the frequency-voltage conversion circuit and the voltage of the speed variable circuit. a comparison circuit that compares the error amplified signal with a predetermined reference triangular wave; and a switching circuit that supplies driving power to a motor using the output of the comparison circuit, A motor configured with a sawtooth wave generation circuit that generates a sawtooth wave using the timing pulse of the pulse generation circuit, and a sample hold circuit that samples and holds the voltage of the sawtooth wave at that time using the timing pulse of the timing pulse generation circuit. 1. A speed control circuit for a motor, characterized in that said speed detection circuit or said timing pulse generation circuit is provided with conversion means for converting a frequency of a timing pulse into a plurality of mutually different frequencies. 2. The motor speed control circuit according to claim 1, wherein frequency generators each having a different number of output pulses are used as the conversion means. 3. The motor speed control circuit according to claim 1, wherein an encoder having a slit disk having slits each having a different number of output pulses is used as the conversion means. 4. The motor speed control circuit according to claim 1, wherein a frequency doubling circuit is used as the conversion means.