JPS58143797A - Controller for stoppage at designated position of needle for motor sewing machine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a one-designated-position stop control device for an electric sewing machine, and more particularly to an improved one-designated-position stop control device that does not cause this operation.

Conventional one-specified position stop control devices for electric sewing machines are equipped with a needle position detection switch that detects when the needle bar is at a predetermined position. When the detection switch closes, the needle bar automatically stops at a predetermined position. However, once the rod has stopped at a predetermined position, if the needle bar is forcibly moved and the needle position cover detection switch is opened, the electric motor will be driven and the needle bar will suddenly move, potentially endangering the operator. was there.

In addition, when the motor was stopped, the needle bar would remain stuck in the fabric and become locked, and the motor would continue to be energized with the needle position detection switch open, creating a risk of the motor overheating. .

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of conventional devices, and the needle bar is not driven even if the needle bar is moved by mistake or as required for work after the needle bar has been stopped at a predetermined position. An object of the present invention is to provide a one-specified position stop control device that does not cause problems.

Another object of the present invention is to provide a one-point stop control device that automatically de-energizes the electric motor if the needle bar is locked during operation.

Hereinafter, the present invention will be explained in detail with reference to the illustrated drawings. FIG. 1 is a circuit diagram of a typical example of an electric sewing machine m1 designated position stop control device according to the present invention and a speed control device for an electric motor to which the same is applied, and FIGS. 2 and 6 show the operation of the speed control device of FIG. 1. FIG. 2 is a time chart showing signal waveforms of each part for explaining. FIG.

In FIG. 1, reference number 2 is an AC power supply, 3 is a main switch, 4 is a DC motor, 6 is a field winding of the DC motor,
8 is a flywheel diode flo, 12 is a thyristor for controlling the energization phase of the motor current given to the DC motor from the AC power source, 20 is a rectifying diode for taking out the back electromotive force of the motor 4, and 40 is for detecting the back electromotive force. resistance, 4
Reference numeral 8 indicates a resistor for setting the speed of the motor, and reference numeral 50 indicates an input box for inputting the back electromotive force detected by the resistor 40 and the voltage indicating the speed set by the variable resistor 46. Based on these deviations, this deviation is set to a predetermined value (for example, zero). ), 54.56 is a resistor and capacitor to stabilize the output of the linear J111Is to prevent disturbances in the motor, and 66 is its non-inverting input. A comparator to which a sawtooth wave voltage is input through the terminal TO and the output voltage of the linear amplifier 50 is input to the inverting input. 80 is a switching element, for example, an 8BB element, which conducts and generates all pulses in response to the output of the comparator. , 82 has a primary winding connected to the output of the EIB8 element, and a secondary winding connected to the thyristor 10 .
It is a pulse transformer connected to 12 date electrodes.

Here, the resistor 1Bt'i is used to detect the back electromotive force of the motor, and the resistors 24 and 28°32.36, and the capacitor 22
．． 26 has the function of protecting the r-) electrode of the thyristor 10.12, and the resistor 52 determines the gain of the linear amplifier by the ratio determined by the resistor 44. Also resistance 72
78 divides the DC voltage applied through the resistor 78 and applies it to the inverting input of the comparator 66 together with the output voltage of the linear amplifier 50, so that even when the output voltage of the linear amplifier is zero, it is applied to the inverting input of the comparator 66. A slight predetermined partial voltage for correction is applied to ensure the conduction of the thyristor. Also,
The diode P88 absorbs the entire back electromotive force of the pulse transformer 82. The terminal 62 is a terminal for inputting a direct current signal for instructing start/stop of the electric motor, and a method for generating this signal will be described in detail later.

Capacitor 56 and diode 60 are terminal 6'! A signal is applied to the inverting input of the comparator 66 in order to start and stop the motor in response to the DC current signals of This is a circuit to prevent this.

The operation of the circuit shown in FIG. 1 will be explained below. First, a method for detecting the back electromotive force of the electric a4 will be described. pulse transformer 8
When the thyristor 10.12 is energized by the output pulse from the thyristor 2, the output current of the AC power supply 2 is, as shown by the solid line in the figure, the main switch 3, the thyristor 10, the motor 4, Daio)'20.1
6, and in the negative half cycle it flows through the thyristor 12, the motor 4, the diode 20.14, and the main switch 3t, but the diode r20.37
Because of this, it does not flow to resistance 38.40. When the p-motor rotates due to energization of the thyristor, a back electromotive force is generated between its terminals, and the current generated by this back electromotive force flows from one end of the motor to diode P8, resistor 18,
It flows to the other end of the motor via diode 37 and resistor 38.40.

Therefore, the voltage between the terminals of the electric motor 4 is as shown in FIG.
1g), only the back electromotive force appears, and during the period when the thyristor is energized (t2 to t3), the AC power supply voltage appears, but of this, the AC power supply voltage is the diode (20.1g).
37, only a back electromotive force appears between the terminals of the resistor 40 as shown in FIG.

The voltage across the terminals of the resistor 40 is applied to the non-inverting input 5Qa of the linear amplifier 50 via the resistors 42 and 44. On the other hand, the inverting input 50b has a current power supply voltage of 10 V. A speed setting voltage v8 divided by resistors 48 and 46 is applied via resistor 44. Here, the bow [: DC power supply terminal ■. . is provided with the output of the AC power supply 2 via the main switch 3 and a rectifier and smoothing circuit (not shown). Therefore, the output voltage of the amplifier 50 becomes a voltage that is almost inversely proportional to the speed setting voltage, and also varies depending on the back electromotive force detected by the resistor 40, such that the smaller the back electromotive force is, the lower the value becomes, and the larger the back electromotive force is, the higher the value becomes. , outputs a voltage that keeps the difference between the speed setting voltage and the back electromotive force constant (for example, zero). Note that the speed setting voltage V is set by the resistor 46.

The larger the value, the higher the rotation speed of the electric motor. Furthermore, a resistor 54 and a capacitor 56 connected in parallel between the inverting input 50b and the output of the amplifier 50 are used to moderate the fluctuation of the output when the input of the amplifier changes suddenly, thus preventing disturbances in the motor pI. be able to.

Now, when the DC current from the terminal 62 is set to zero, the output voltage of the amplifier is superimposed on the correction voltage v0 applied via the resistor 74, and is applied as a speed instruction voltage to the inverting input of the comparator 66, and from the terminal TO. It is compared with the sawtooth wave voltage (FIG. 3) applied to the non-inverting input through resistor 68t. The phase of this sawtooth wave voltage is the output voltage (
It is synchronized with each half cycle of Fig. 6a)). (9) If the speed instruction voltage t-va is the sum of the output voltage of the amplifier 50 and the correction voltage, va is V. and the maximum value of the sawtooth voltage v! It is a predetermined value between n. Comparator 6
6 is when the value of the sawtooth wave voltage reaches the speed instruction voltage va (
e→) in Fig. 3, output a signal at that time (time t), and
The BEI element 80 becomes conductive in response to the output signal and causes a sharp pulse-like current to flow through the primary winding of the pulse transformer 82. Therefore, a pulse signal is induced in the secondary winding and the diode
0.34 and the thyristor 10 through the resistor 32°36.
It is applied as a trigger signal on each of the 12 dates to energize each thyristala (see FIG. 6). Therefore main switch 3
is turned on, the thyristor is energized at a conduction angle determined by the speed instruction voltage V, and the motor is operated at a predetermined speed.

Incidentally, by changing the setting value of the resistor 48, the speed instruction voltage vat can be set to any value between the minimum value v0 and the maximum value 9rLvm, and the motor speed can be set to any desired speed.

Next, starting and stopping operations of the electric motor will be explained.

Now, assuming that a DC current of a predetermined value is input from the terminal 62 to instruct a stop, the capacitor 56 is charged and the terminal voltage is applied to the inverting input of the comparator 660 via the resistor 72, and the voltage at the inverting input is Since the voltage exceeds the maximum value of the non-inverting input, the comparator does not output a pulse signal and the motor is not driven. When a DC current instructing start-up, that is, a signal with a current value of zero, is applied from the terminal 62, the capacitor 56 is not charged and only the speed instruction voltage V is applied to the comparator 66.
The voltage at the inverting input of is less than the maximum of the voltage at the non-inverting input and the motor is started and driven at a speed determined by the value of resistor 48.

Speed setting voltage v8 determined by resistor 4B in this way
A case will be described in which, when the motor is operated at a speed determined by , the rotational speed of the motor fluctuates due to changes in load, etc. Now, if the load increases 11 and the rotational speed decreases, the back electromotive force of the motor decreases and the voltage across the terminals of the resistor 40 decreases, so the amplifier 50
The output voltage decreases, and the speed instruction voltage V& also decreases. Therefore, the energization phase of the thyristor advances, increasing the rotational speed of the motor and maintaining it at the speed determined by the speed setting voltage (6). Again, when the load decreases and the rotational speed increases,
Since the back electromotive force increases, the output voltage of the amplifier 50 increases, and the speed instruction voltage (2) also increases. Therefore, the energization phase of the thyristor is delayed, and the rotational speed of the motor is reduced and maintained at the original rotational speed.

In this way, even if the rotational speed of the motor fluctuates due to fluctuations in the load or power supply voltage, the rotational speed is always stabilized at the speed determined by the speed setting voltage VS by detecting it using the back electromotive force and performing negative feedback control. It can be maintained at

Moreover, the present invention does not use the output signal of the rotary generator as a signal indicating the speed of the electric motor, but uses the rotational electromotive force of the electric motor and detects it with a simple configuration. By the way, when starting the electric motor, the non-inverting input 50aK is used until the rotation speed of the motor reaches the target rotation speed compared to the speed setting voltage V determined by the resistor 48. Since the input voltage is small, the output voltage of the amplifier 5o is small, and the cutting speed instruction voltage vIL is also small, so there is a risk that the thyristor will be energized at an extremely early phase, causing a large current to flow in the motor and driving it rapidly.

To prevent this, a resistor 54 and a capacitor 5
6, a circuit consisting of a diode P2O is added.

Next, the operation of this circuit will be explained.

First, when the main switch 3 is closed, the output of the AC power supply 2 is transferred from the DC voltage +v0° terminal 114 smoothed by a rectifier and smoothing circuit (not shown) to the resistor 118, the diode 122, and the terminal 62 to stop the motor. A voltage indicating this is applied to the series body of resistors γ4 and γ6. As a result, the voltage applied to the inverting input of the comparator 66 via the resistor 72t is larger than the maximum value v of the sawtooth wave voltage applied to the non-inverting input, so the comparator 66 outputs Therefore, since the date pulse is not applied to the thyristors 10 and 12, the motor current does not flow and the motor remains in a stopped state.

At this time, the capacitor 56 is being charged by the direct current applied via the terminal 62.

Here, when the start switch 101 is closed, the transistor 106 is made conductive via the resistor 102, so the DC current that had previously flowed from the terminal 114 to the diode 122 via the resistor 118 now flows to the transistor 106, and the Since the current flowing from 62 to resistors 74 and 76 is cut off, the potential at the inverting input of comparator 66 decreases.

On the other hand, the charge in the capacitor 56 is transferred to the resistor 74°76.5
4, the terminal voltage begins to gradually decrease. Therefore, the speed instruction voltage va begins to gradually decrease from the maximum value vm, and the thyristor is gradually energized at a small conduction angle, and eventually becomes energized at a conduction angle determined by the set voltage v6, and the motor is gradually started. It increases at a predetermined rotational speed f. In this way, rush rotation of the electric motor is prevented.

Next, a one-specified position stop control device 100 according to the present invention, which reliably stops the needle bar at a predetermined needle position and prevents the above-mentioned malfunction when applied to such a motor speed control device lamination machine, will be described.

In the figure, a switch 101 instructs to stop and drive the electric motor 4 depending on its open and closed states, and when the main switch 3 is closed, the switch 101
The electric motor is started by closing 01. 154 is a known needle position detection switch that is closed when the needle bar reaches a predetermined position, for example, top dead center, and is opened when it leaves top dead center.

Next, the operation of this circuit will be explained. First, we will explain the state in which the electric motor is stopped. When the switch 101 is open, the DC voltage +vca applied to the terminal 114 is applied to the terminal 6 via the resistor 118 and the diode 122.
2, it is applied to the resistor 74°76, so the comparator 66
The inverting input level of is higher than the maximum value of the non-inverting input level V, and the comparator 66 does not output. The thyristor is therefore non-conducting and the motor is not started.

At this time, from the resistor 118 to the resistor 124, 128°144
Since current is applied to the base of transistor 146 through resistor 152 and transistor 146 is conducting, the base of transistor 126 is shorted through resistor 152 so that transistor 126 is non-conducting.

Here, since resistors 128 and 144 have high resistance, terminal 6
Since the influence 41 on the output voltage of 2 is extremely small, it is irrelevant to the operation of the comparator 66.

Also, at this time, the capacitor 142 is charged via the Htl 28.

Next, the starting operation of the electric motor will be explained.

When the start switch 101 is closed, the electric voltage V is applied. .

is applied to the transistor 106 via the switch 101 and the resistor 102 to make it conductive, so the current that was being output from the resistor 118 to the terminal 62 via the diode 122t- now flows to the collector of the transistor 106. The current flowing from the terminal 62 to the series body of resistors 74 and 76 and the capacitor 56 is cut off. Therefore, as the capacitor 56 begins to discharge its charged charge, the potential at the inverting input of the comparator smoothly falls below the maximum value of the sawtooth waveform applied to the non-inverting input, so that the comparator At the late phase of the half cycle of the alternating current power supply, a pulse signal begins to be output, which is applied via the pulse transformer 82t to the dates of the thyristors 10, 12, energizing them with a small conduction angle and starting the motor. At this time, switch 1
When 01 is closed, the power supply current flows through switch 1o1 and diode
Because it flows to the resistor 140 via the p136 terminal 134,
Controlled by the speed setting voltage v8 determined by the terminal voltage of the resistor 140, the motor reaches the next speed and continues to maintain a constant speed. When the switch 101 is closed, the capacitor 148 is connected via the switch 101 and the diode 104.
is charged, and its terminal voltage is applied to the collector of the transistor 146 via the resistor 15 (l), and
5D and 152 to the base of the transistor 126, the transistor 146 is supplied with a base bias current, and the transistor 126 is supplied with a collector current, so that they are in a non-conducting state. On the other hand, the needle position detection switch 154 opens and closes as the motor rotates, but since no base bias is applied to the transistor 126, the transistor 126 remains non-conducting regardless of whether the needle position detection switch is opened or closed. .

By closing the switch f-1 (N), the capacitor 14
The charge stored in the diode 13o.

It is discharged through the resistor 124 and the transistor 10& at time i.

Next, the stopping operation of the electric motor will be explained.

When the motor continues to rotate at a constant speed in the above state, when the start switch 101 is opened, the voltage is applied to the resistor 140 via the switch 101 and the diode 136.
Since the current is cut off, the speed setting voltage v6#ia Rt source + Vca applied to the inverting input of the amplifier 500
However, the voltage decreases to a predetermined value determined by the voltage applied to the resistor 48. It is assumed that the speed setting voltage V at this time is adjusted so that the motor rotates at a low speed with no inertia.

On the other hand, when the switch 101 is opened, the switch 101
Transistor 106 provided via resistor 102
Since the base current of the transistor 106 is cut off, the transistor 106 becomes non-conductive, and the power supply current applied to the terminal 114 flows through the resistor 1.
18 to the diode 122, attempting to raise the potential at the terminal 62 to a value that stops the motor.

However, when the switch 101 is opened, the charge in the capacitor 148 that has been charged through the switch 101 and the diode V2O3 starts discharging through the resistors 150 and 152, giving a base bias to the transistor 126 and discharging it. In order to conduct, the power supply current from the terminal 114 is passed through the resistor 118, the color resistor 124. ) is divided into nine registers 126.

Therefore, the potential of the terminal 62 is the power supply voltage +v0° and the resistor 118
and 124, and this voltage is the voltage divided by comparator 66
The motor is set to a value sufficiently lower than the maximum value of the sawtooth wave voltage at the non-inverting input of the motor, and lower than the output voltage of the amplifier 50, which is determined by the speed setting voltage V, It will rotate at a low speed with no inertia determined by .

Eventually, when the needle bar of the sewing machine reaches a predetermined position t (top dead center in this case), the needle position detection switch 154 closes and the transistor 126 is closed to short-circuit the base of the transistor 126.
The base bias from capacitor 148 is cut off and becomes non-conductive. Therefore, from terminal 114 to resistors 118, 12
The current that was flowing through transistor 126 through resistor 128 is cut off and instead flows through resistor 128 to resistor 144, transistor 146, and capacitor 142.

Since the current flowing through the resistor 128 is smaller than the collector current of the transistor 126, the potential at the terminal 62 rises, and the voltage applied to the inverting input of the comparator 66 changes to a sawtooth waveform applied to the non-inverting input. When the voltage reaches its maximum value, it will stop generating its output pulses, and the U machine will stop immediately.

Here, the needle position detection switch 154 closes at the top dead center, and the base of the transistor 126 is short-circuited, causing the transistor 12
6 is non-conducting, and when the motor is stopped by applying a voltage exceeding V to the inverting input of the comparator 66 from the terminal 62 through the resistor 118 and the diode 122t from the terminal 114, the current from the terminal 114 flows from resistor 118 to diode 122 and is shunted to provide charging current to capacitor 142 via resistors 124 and 128. Then, the potential of the capacitor 142 gradually increases, and this potential causes the transistor 146 to conduct through the resistor 144.
8 charges are rapidly discharged through the low resistance 150.

Therefore, even if the operator manually moves the needle position immediately after the motor stops and the needle position detection switch 154 is opened, the capacitor 148 has already finished discharging, so the transistor 126 will not become conductive. , the motor will therefore remain in a stopped state.

After the transistor 126 becomes non-conductive and before the transistor 146 becomes conductive, the resistor 128 and the capacitor 1
The reason why the delay is caused by 42 is that when the switch 101 is opened by a stop operation while the motor is running at high speed, a deceleration period occurs in which the motor decelerates to a low speed with no inertia. Due to inertia, the needle position detection switch 154 opens for a short time and then opens again as the electric motor rotates, repeating the state once or several times. However, during this period, after the hand position detection switch is closed and the transistor 126 becomes non-conductive, the capacitor 142 starts to be charged and is gradually charged via the resistor 128, and eventually the potential of the capacitor 142 reaches the resistor 1.
44 to a value sufficient to cause transistor 146't- to conduct through diode 2130, the needle position switch opens again, transistor 126 becomes conductive again, and the charge on capacitor 142 is transferred to diode 2130. Since the base bias of the transistor 146 does not reach the value required for conducting current, the charge in the capacitor 148 is discharged by the transistor 126 via the base bias of the transistor 126 without inadvertently shortening the discharge period. It is possible to continue applying current. Therefore, the electric motor, which has been sufficiently decelerated to a low speed with no inertia, can be reliably stopped at the next closing of the needle position detection switch.

In this way, after the needle bar has stopped at a predetermined position (top dead center), even if the pulley of the sewing machine is forcibly moved to move the needle bar and open the switch 154, the capacitor 148 has already discharged, so the transistor 126 Since no base bias is applied and the motor remains non-conducting, the motor remains stopped. Therefore, even if the pulley is moved by mistake, the needle bar will not be driven, thereby preventing danger to the operator. If you want to move the needle bar up after the electric motor has stopped, you can move the pulley by hand.

Next, the operation of stopping the electric motor in the case where the needle bar is stuck in the fabric etc. and becomes locked and does not move will be explained.

In conventional devices, in such a case, the needle position detection switch remains open and current continues to be supplied to the motor, causing the motor to overheat, which is dangerous. In the device of the present invention, when such a situation occurs, the motor current is automatically cut off. The operation will be explained below.

When the start switch 101 is opened to stop the motor being driven, the capacitor 148 starts discharging its charge as described above, giving a base bias to the transistor 126 and making it conductive, driving the motor at low speed with no inertia. do. In this state, if the needle bar is locked to the fabric and does not move, the needle position detection switch 154 remains open and the base of the transistor 126 remains ungrounded. However, after opening the capacitor 148Fi switch 101, the charged charge is transferred to the resistor 150 with a predetermined time constant.
152t-, the terminal voltage gradually decreases, and eventually, after a predetermined time, when the discharge is completed, the bias current applied to the base of the transistor 126 also stops, so the transistor 126 detects the needle position. Although the switch 154 is in an open state, it becomes non-conductive. Therefore, the electric motor will stop immediately. ``In this way, even if the needle bar is locked after opening the switch 101, the supply current to the motor is automatically cut off after a predetermined time, so the danger of the motor overheating is prevented.

As described above, the electric sewing needle specified position stop control device according to the present invention prevents the dangerous situation in which the electric motor is driven and the needle bar moves even if the pulley is moved by mistake after the needle bar has stopped at a predetermined position. Further, when the needle bar is locked after opening the switch 101, the supply current to the motor is automatically cut off after a predetermined period of time, thereby preventing the motor from overheating.

The one-specified position stop control device according to the present invention can be applied not only to the motor speed control circuit shown in FIG. 1, but also to other types of speed control circuits.

[Brief explanation of drawings]

The circuit diagrams of typical examples of the control device, FIGS. 2 and 6, are time charts showing signal waveforms of various parts for explaining the operation of the speed control device of FIG. 1. Explanation of symbols 2... AC power supply, 3... Main switch, 4... DC motor, 50... Linear amplifier, 66... Comparator,
80... BBB element, 82... Pulse transformer, 1
54...Needle position detection switch. Representatives: Asamura and 4 people

Claims (1)

[Claims] A DC motor (4) is connected to an AC power supply (2) via a main switch (3) and semiconductor means with control electrodes (10, 12).
A main motor circuit that supplies a motor current to the semiconductor means, and a trigger signal generator that outputs a trigger signal for controlling the energization phase to the semiconductor means! (66), a speed instruction signal generator (4B, 50
140), and a bias signal generator (114) which is activated by the closing of the main switch to generate a bias signal and supplies the bias signal to the trigger signal generating means as a stop signal for instructing the motor to stop. a switch means (101), one end of which is connected to the output of the bias signal generator and is switched between a closed state for instructing to start the motor and an open state for instructing to stop the motor; a first switching element (106) connected and having its control electrode connected to the other end of the switching means;
A charge/discharge element (14) connected to the other end of the switch means
B), a second switching element (126) connected to the output of the bias signal generator and whose control electrode is connected to the photodischarge element, and a needle bar connected to the control electrode of the second switching element (126); A needle position detection switch (154) which closes when it detects that the needle has reached a predetermined position is deflected, and when the switch means is in the closed state, the first switching element applies the needle position detection switch (154) to its control electrode via the switch means. A bias signal is applied to conduct and invalidate the stop signal, and when the switch means is in a closed state, the speed signal generator receives the bias signal and generates a signal instructing normal operation via the switch means. A signal is applied to the trigger signal generating means, and when the switch means is in an open state, a signal is given to the trigger signal generating means that cuts off the bias signal and instructs low speed operation, and when the switch means is closed, the charging/discharging element is When the switch means is in the open state, it is charged by the bias signal applied through the switch means, and when the switch means is switched to the open state, a discharge current is applied to the control electrode of the second switching element for a predetermined period of time. conduction, and when the second switching element becomes conductive, it invalidates the stop signal, and when the needle position detection switch is closed, it invalidates the discharge current from the charging/discharging element and renders the second switching element non-conductive. Electric sewing machine M1 specified position stop control device that makes % mold.