JPS6150475B2 - - Google Patents

Description

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

Conventional needle position stop control devices for electric sewing machines are equipped with a needle position detection switch that detects when the needle bar has reached a predetermined position. The switch closes and the needle bar automatically stops at a predetermined position. However, once the needle bar has stopped at a predetermined position, if the needle bar is forcibly moved and the needle position detection switch is opened, the electric motor is driven and the needle bar moves suddenly, potentially endangering the worker. .

Furthermore, when the electric motor is stopped, if the needle bar is stuck in the fabric and locked, the electric motor continues to be energized with the needle position detection switch open, which poses a risk of the electric motor overheating.

An object of the present invention is to eliminate both of the above-mentioned drawbacks of conventional devices with a simple structure, so that after the needle bar has been stopped at a predetermined position, the needle bar can be moved by mistake or as required for work. To provide a needle specified position stop control device which does not drive a needle bar and automatically deenergizes an electric motor when the needle bar is locked while being driven. In order to achieve such an object, the present invention connects the AC power supply 2 to the main switch 3 and the semiconductor means 10 and 12 with control electrodes.
a main motor circuit that supplies a motor current to the DC motor 4 via the main motor circuit, and a trigger signal generating means 6 that outputs a trigger signal for controlling the energization phase to the semiconductor means.
6, and a speed instruction signal generator 46, 4 which is actuated by the closing of the main switch and provides a signal indicating the rotational speed of the electric motor to the trigger signal generation means.
8, 50, 140, a switch means 101 which is switched between a first state for instructing to start the electric motor and a second state for instructing to stop the electric motor; first bias signal generating means 104, 106 for generating a first bias signal instructing to stop the trigger signal; and second bias signal generating means 124 connected to the switch means and generating a second bias signal for the trigger signal generating means. , a first charging/discharging element 116 connected to the outputs of the first bias signal generating means 104, 106, and a first charging/discharging element 116 connected to the first charging/discharging element, the output of which changes between the first and second states. a first logic means 118 and a second charging/discharging element 1 connected to the output of the second bias signal generating means 124;
28, a needle position detection switch 122 which is connected in parallel to the second charge/discharge element and closes when it detects that the needle bar has come to a predetermined position; and the first logic means 1.
a second logic means 120 whose input is connected to the output of 18 and the second charging/discharging element, whose output is connected to the input of the first bias signal generating means, and which changes between the first and second states; The first bias signal generating means 104 and 106 are configured such that when the switch means 101 is in the second state and the first bias signal generating means 104 and 106 are in the second state,
A first bias signal is generated only when the output of the logic means 120 is in the first state, and is applied to the trigger signal generation means 66 to stop the trigger signal, and is applied to the first logic means 118 to start the first charge. The discharge element 116 changes the output of the first logic means from the first state to the second state after a predetermined time when the first bias signal is applied, and returns to the first state when the first bias signal is no longer applied. The second bias signal generating means 124 generates the second bias signal when the switch means 101 is in the first state, and the second bias signal generating means 124 generates the second bias signal when the switch means 101 is in the first state,
48, 50, and 140, and also to the second charging/discharging element 128 to charge the element, and the speed instruction signal generating means normally operates when the second bias signal is applied from the second bias signal generating means 124. Generates a speed instruction signal to instruct driving, and
If a bias signal is not applied, a speed instruction signal instructing low speed rotation is generated, and the second charge/discharge element 1
28 applies a third bias signal to the second logic means 12 while the second bias signal is applied and for a predetermined time after the second bias signal is cut off.
0, the needle position detection switch 122 disables the third bias signal when closed, and the second logic means 120 causes the output of the first logic means 118 to be in the first state and the third bias signal to be The present invention provides a needle specified position stop control device for an electric sewing machine, characterized in that the output is in the second state only when a bias signal is applied, and is in the first state otherwise.

The present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is a circuit diagram of a typical example of a needle specified position stop control device for an electric sewing machine according to the present invention and a speed control device for an electric motor to which the same is applied, and FIG. 2 and FIG. It is a time chart showing signal waveforms of each part to explain the operation.

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,
10 and 12 are thyristors for controlling the energization phase of the motor current given to the DC motor from the AC power supply;
is a rectifying diode for extracting the back electromotive force of the motor 4, 40 is a resistor for detecting the back electromotive force, 48,1
40 is a resistor for setting the speed of the motor, 50 is a resistor 40
As a servo amplifier that inputs the back electromotive force detected by the resistor 46 and the voltage indicating the speed set by the resistor 46, and outputs a speed instruction voltage that makes this deviation a predetermined value (for example, zero) based on these deviations. Functioning linear amplifiers, 54 and 56 are resistors and capacitors to stabilize the output of the linear amplifiers to prevent disturbances in the motor; 66 is a non-inverting input to which a sawtooth voltage is input via terminal 70; A comparator inputs the output voltage of the linear amplifier 50, 80 is a switch element such as an SBS element that conducts and generates a pulse in response to the output of the comparator, and 82 is a primary winding.
The pulse transformer is connected to the output of the SBS element and has a secondary winding connected to the gate electrodes of the thyristors 10 and 12. Here, the resistor 18 is for detecting the back electromotive force of the motor, and the resistors 24, 2
8, 32, 36 and capacitors 22, 26 have the function of protecting the gate electrodes of the thyristors 10, 12, and the resistor 52 determines the gain of the linear amplifier by the ratio determined by the resistor 44. Further, the resistors 72 to 78 divide the DC voltage applied through the resistor 78 and apply 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, the voltage of the comparator is This ensures that the thyristor is energized by applying a small predetermined correction divided voltage to the inverting input. Further, the diode 88 absorbs the 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.

The capacitor 56 and the diode 60 respond to the DC current signal from the terminal 62 to apply a signal to the inverting input of the comparator 66 to start and stop the motor, and also to prevent the thyristor from suddenly turning into a large energizing phase when starting the motor. This is a circuit to prevent conduction.

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 motor 4 will be described. When the thyristors 10 and 12 are energized by the output pulse from the pulse transformer 82, the output power of the AC power source 2 is transmitted to the main switch 3, the thyristor 10, the motor 4, flows through the diodes 20, 16, and in the negative half cycle the thyristor 1
2, the current flows through the electric motor 4, diodes 20 and 14, and the main switch 3, but the diode 2
Since there are 0 and 37, there is no flow to the resistors 38 and 40. When the motor rotates due to the 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 8, resistor 18, diode 37, and resistor 38, as shown by the dotted line. , 40 to the other end of the motor.

Therefore, the voltage between the terminals _of the motor 4 is as shown in _FIG . (t ₂ - _{t 3} ), an AC power supply voltage appears, but the AC power supply voltage is blocked by the diodes 20 and 37, so the resistor 4
Only a back electromotive force appears between the zero terminals as shown in FIG.

The voltage between the terminals of resistor 40 is applied to non-inverting input 50a of linear amplifier 50 via resistors 42 and 44. On the other hand, the DC power supply voltage +V is applied to the inverting input 50b.
A speed setting voltage V _s obtained by dividing _cc by a resistor 48 and a resistor 46 is applied via a resistor 44 . Here, the DC power supply + _Vcc is provided by 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. Then, a voltage is output that keeps the difference between the speed setting voltage and the back electromotive force constant (for example, zero). In addition, the speed setting voltage V set by the resistor 46
The larger the value of _s , the higher the rotation speed of the electric motor. Also, the inverting input 50b of the amplifier 50
A resistor 54 and a capacitor 56, which are connected in parallel between the amplifier and the output, are used to moderate fluctuations in the output when the input of the amplifier changes suddenly, thereby preventing disturbances in the motor.

Now, if the DC current from the terminal 62 is set to zero, the output voltage of the amplifier is superimposed on the correction voltage V _p applied via the resistor 74 and applied to the inverting input of the comparator 66 as a speed instruction voltage. is compared with the sawtooth wave voltage (FIG. 3b) applied to the non-inverting input via the resistor 63. The phase of this sawtooth wave voltage is synchronized with each half cycle of the output voltage of the AC power supply 2 (FIG. 3A). Also,
When the speed instruction voltage that is the sum of the output voltage of the amplifier 50 and the correction voltage is V _a , V _a is a predetermined value between V _p and the maximum value V _n of the sawtooth wave voltage. When the value of the sawtooth wave voltage reaches the speed instruction voltage V _a (FIG. 3C), the comparator 66 outputs a signal at that time {time t ₁ ), and the SBS element 80 becomes conductive in response to the output signal. A sharp pulsed current is passed through the primary winding of the pulse transformer 82. Therefore, a pulse signal is induced in the secondary winding, and the diodes 30, 34 and resistors 32, 36
The trigger signal is applied as a trigger signal to each gate of the thyristors 10 and 12 through the thyristors 10 and 12, thereby energizing each thyristor (FIG. 3D). Therefore, if the main switch 3 is turned on, the thyristor is energized at a conduction angle determined by the speed instruction voltage _Va , and the motor is operated at a predetermined speed.

By changing the set value of any one of the resistors 46, 48, and 140, the speed instruction voltage V _a can be set to any value between the minimum value V _p and the maximum value V _n , and the speed of the motor can be adjusted to any value. It can be speed.

Next, starting and stopping operations of the electric motor will be explained. Assuming that a DC current of a predetermined value is input from the terminal 62 to instruct the stop, the capacitor 5
6 is charged and its terminal voltage is applied to the inverting input of the comparator 66 via the resistor 72, and since the voltage at the inverting input exceeds the maximum value of the voltage at the non-inverting input, the comparator does not output a pulse signal and the motor is not driven. When a DC current instructing startup, 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 _a is applied, so that the voltage at the inverting input of the comparator 66 is less than the maximum value of the voltage at the non-inverting input, the motor is started, and the resistor 4
It is driven at a speed determined by values of 6, 48, and 140.

A case will be described in which when the motor is operated at a speed determined by the speed setting voltage V _s determined by the resistors 46, 48, and 140 in this manner, the rotational speed of the motor fluctuates due to changes in load or the like.
Now, if the load increases and the rotation speed decreases, the back electromotive force of the motor decreases and the voltage across the terminals of the resistor 40 decreases, so the output voltage of the amplifier 50 decreases and the speed instruction voltage V _a 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 _Vs. Further, when the load decreases and the rotational speed increases, the back electromotive force increases, so the output voltage of the amplifier 50 increases, and the speed instruction voltage V _a 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 changes in the load or power supply voltage, this is detected by the back electromotive force and negative feedback control is performed, so that the rotational speed is always determined by the speed setting voltage V _s . The speed can be maintained stably. 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. A simple and inexpensive speed control device can be provided.

By the way, when starting the electric motor, the voltage input to the non-inverting input 50a is small compared to the speed setting voltage V _s determined by the resistor 48 until the rotation speed of the motor reaches the target rotation speed, so the output voltage of the amplifier 50 is small and the speed instruction voltage V _a 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 to the motor and driving it rapidly. To prevent this, a circuit consisting of a resistor 54, a capacitor 56, and a diode 60 is added. Next, the operation of this circuit will be explained.

First, when the main switch 3 is closed while the switch 101 is open, the NAND gate 1
04 has its input f connected to the DC power supply +V _cc at the terminal 114
However, since a high level (hereinafter referred to as H level) signal is applied to the input e from the NAND gate 120, its output maintains a low level (hereinafter referred to as L level). , therefore H inverted by the inverter 106
The level output is applied via the resistor 108, diode 110, and terminal 62 to a series circuit of resistors 74 and 76 as a voltage instructing to stop the motor, and this terminal voltage is applied via the resistor 72 to the inverting input of the comparator 66. given to. Since this voltage is larger than the maximum value V _n of the sawtooth wave voltage applied to the non-inverting input, the comparator 66 does not output and therefore the thyristors 10 and 1
In case 2, no gate pulse is applied, so no motor current flows, and the motor remains in a stopped state.

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

When the operating switch 101 is closed, the input f of the NAND gate 104 becomes L level, so the output becomes H level. Therefore, the output of the inverter 106 becomes L level, and the current flowing from the terminal 62 to the resistors 74 and 76 via the resistor 108 is cut off, so that the potential of the inverting input of the comparator 66 decreases. On the other hand, since the charge in the capacitor 56 is discharged through the resistors 74, 76, and 54, this terminal voltage begins to gradually decrease. Therefore, the speed indicating voltage V _a starts to gradually decrease from the maximum value V _n , the thyristor is energized at a small conduction angle, and the motor is started slowly and increases to a predetermined rotational speed. In this way, rush rotation of the electric motor is prevented.

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

In FIG. 1, a switch 101 instructs to stop and start the electric motor 4 depending on its open and closed states, and the electric motor is started by closing the switch 101 while the main switch 3 is closed. Ru. Reference numeral 122 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. The NAND gates 104, 118, 120 are known C-
It is a MOS type logic integrated circuit.

First, a state in which the electric motor is stopped will be explained.

When switch 101 is open, terminal 1
Since the DC voltage + _Vcc applied to the NAND gate 104 is configured to keep the input f of the NAND gate 104 at the H level and the input e also at the H level, the output of the NAND gate 104 goes to the L level, and the inverter 106 Inverted H level output is resistor 10
8. Since it is applied from the terminal 62 to the resistors 74 and 76 via the diode 110, the inverting input level of the comparator 66 becomes higher than the maximum value V _n of the non-inverting input level, and the comparator 66 does not generate an output signal. Thyristors 10 and 12 are non-conductive and the motor remains stopped. At this time, since the capacitor 116 is charged by the H level output of the inverter 106, the inputs a and b of the NAND gate 118 are both at the H level, and the output thereof is at the L level. On the other hand, since the output of the inverter 124 is at the L level, the input d of the NAND gate 120 is at the L level because the capacitor 128 is not charged. Therefore, inputs c and d of NAND gate 120 are both at L level, and its output is at H level.

The signal waveforms of each part of the needle designated position stop control device 100 are as shown in FIG.

Next, starting the electric motor will be explained.

When the switch 101 is closed to instruct startup, the input f of the NAND gate 104 becomes L level, and the output of the NAND gate 104 becomes H level regardless of the input e.
Since the output inverted by the inverter 106 becomes the L level, the capacitor 1
16 is discharged through the diode 117, and the inputs a and b of the NAND gate 118
both become L level, and their output becomes H level. On the other hand, until now the resistor is 108 and the diode is 110.
Since the current instructing the stop flowing through the terminal 62 is cut off, the charge stored in the capacitor 56 is gradually discharged through the resistors 74 and 76, and the potential of the inverting input of the comparator 66 gradually decreases. Since it falls below the maximum value V _n of the sawtooth wave applied to the non-inverting input, the comparator starts outputting a pulse signal at the slow phase of half a cycle of the AC power supply, and thyristor 1
0 and 20 at a small conduction angle to start the motor.

On the other hand, since the switch 101 is closed,
Since the input of the inverter 124 is at L level,
The output of the inverter 124 becomes H level, and current flows to the resistor 46 via the diode 132, the terminal 134, and the resistor 140, so the speed setting voltage V is determined by the terminal voltage of the resistor 46 divided by the resistor 140 and the resistor 46. The rotational speed of the motor increases to the speed controlled by _s , and the motor continues to rotate while maintaining this speed. By varying the resistance value of the resistor 140 in this state, the motor can be set to a desired rotation speed. Also switch 1
By closing 01, the H level output of the inverter 124 charges the capacitor 128 via the diode 125 and the resistor 126, and continues charging while the motor is rotating. Therefore, the input d of the NAND gate 120 becomes H level, and becomes L level only while the needle bar passes through the top dead center and the switch 122 is closed (for example, between times t ₂ and t ₃ ) (see FIG. 4). i), its output becomes H level as shown in FIG. 4i, but since the input f of the NAND gate 104 maintains L level, its output maintains H level (FIG. 4d).

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

As mentioned above, when the electric motor continues to rotate at a constant speed, switch 101 is activated to instruct it to stop.
When is opened at time _t4 , the input f of the NAND gate 104 and the input of the inverter 124 change from the L level to the H level, so the output of the inverter 124 becomes the L level, and the diode 132 and the terminal 134
The speed setting voltage that was applied to the resistor 140 via the power supply +Vcc is no longer applied, and the speed setting voltage _Vs is changed to the voltage that is constantly applied to the resistor 48 from the power supply + _Vcc , that is, the electric sewing machine rotates at a low speed with no inertia. Since there is only voltage, the speed of the motor begins to decrease, and eventually it will rotate at a low speed with no inertia. Furthermore, since the output of the inverter 124 becomes L level, the charging current that has been applied to the capacitor 128 via the diode 125 and the resistor 126 is cut off, so that the charge that has been stored in the capacitor 128 is transferred to the resistors 130 and 131. After that, the voltage gradually discharges, and the terminal voltage generated in the resistor 131 continues to maintain the input d of the NAND gate 120 at the H level. Input c also remains at H level since inputs a and b of NAND gate 118 are both at L level, so the output of NAND gate 120 is L level.
Continue level. Therefore, even if the input f of the NAND gate 104 becomes H level due to the opening of the switch 101, the output of the NAND gate 104 will remain at the H level and the L level output of the inverter 106 will continue to instruct activation. The electric motor will continue to rotate at the above-mentioned speed without inertia.

Further, the electric motor continues to rotate and, for example, when the needle position detection switch 122 provided at the top dead center closes at time _t5 and the resistor 131 is short-circuited, the NAND gate 120 is closed.
Since the input d of becomes L level, NAND gate 1
The output of 20 changes to H level, and the NAND gate 10
The two inputs of 4 are both at H level. Therefore, the output of the NAND gate 104 changes to the L level, and the H level output inverted by the inverter 106 is transferred to the resistor 1.
08, the motor tries to stop because a current is applied to the terminal 62 via the diode 110 to instruct the motor to stop.

At this time, the H level output of the inverter 106 immediately changes the input a of the NAND gate 118 to the H level, and at the same time, the input a of the NAND gate 118 is transferred to the capacitor 116 through the resistor 112.
Start charging. Here, the input b of the NAND gate 118 connected in parallel to the capacitor 116 is
It takes a time constant τ ₂ determined by the capacitor 116 and the resistor 112 to reach the predetermined threshold voltage (corresponding to the H level) (FIG. 4f), so the output of the inverter 106 continues for a period of τ ₂ . If the H level is maintained, both of the two inputs of the NAND gate 118 will be at the H level, and the input c of the NAND gate 120 will change from the H level to the L level. However, in this case, the speed of the motor is not sufficiently reduced, and the hand position detection switch 122 opens again at time t ₆ after τ ₁ hour, which is shorter than τ ₂ .
Therefore, the input d of the NAND gate 120 becomes H level again at time _t6 , and the NAND gate 10
Since the input e of 4 becomes L level again, the output of NAND gate 104 changes to H level and inverter 1
The output of 06 is inverted to L level and instructs the motor to start up again, and at the same time, the charge stored in the capacitor 116 is discharged via the diode 117.

Here, the time constant τ ₂ is sufficiently larger than τ ₁ ,
The operator of the electric sewing machine quickly tries to move the needle position after the electric sewing machine has completely stopped for a period slightly longer than the period during which the needle position detection switch 122 is open when the electric motor is rotating at low speed. It is assumed that capacitor 116 has previously been set to a value that will complete charging and change the output of NAND gate 118 to L level.

When the electric motor continues to rotate and is sufficiently decelerated, the needle position detection switch 122 is closed again at time _t7 , and a current is applied to the terminal 62 to instruct the stop, causing the thyristors 10 and 12 to become non-conducting. Therefore, the motor will stop immediately. Therefore, switch 1
22 remains closed without being opened again.
Therefore, the input d of the NAND gate 120 becomes L level, and the inputs e and f of the NAND gate 104 both become H level, so the output of the NAND gate 104 becomes L level, and the H level output inverted by the inverter 106 passes through the resistor 108 and diode 110. A current is applied to the terminal 62 as a stop instruction through the resistor 112, and at the same time, the capacitor 11 is supplied through the resistor 112.
Charge 6. Therefore, at time t ₈ τ ₂ hours after time t ₇ , input b of NAND gate 118 reaches H level and its output becomes L level, so L level is input to input c of NAND gate 120 . Therefore, both inputs c and d of the NAND gate 120 are at L level.

In this state, if the operator operates the pulley of the sewing machine to forcibly move the needle position and opens the needle position detection switch 122, the capacitor 12
8 is discharging its residual charge through resistors 130 and 131, so the input d of NAND gate 120 changes to H level. However, since the input c of the NAND gate 120 is at L level, the NAND gate 120
Since the output of 0 maintains the H level, NAND gate 1
The operating state of inverter 04 does not change, therefore, the output of inverter 106 continues to maintain the H level that instructs to stop. In this way, the electric motor once stopped is prevented from restarting even if the needle position is manually moved immediately after stopping, and it can be moved freely by hand to change it to the desired position at any time.

Note that the potential of the capacitor 128 changes from the time _t4 when the discharge starts, depending on the capacitance of the capacitor 128 and the resistor 13.
τ determined by the value of 0,131 Time after ₃ hours
At _t10 , the threshold level (H level) of the NAND gate 120 is reached. Furthermore, even if you turn off the power once after the needle bar has stopped at a predetermined position, then accidentally move the pulley to open the switch 122, and then turn on the power, the switch 101 remains open and the capacitor 128 remains open. Since the input d of the NAND gate 120 is not charged and therefore the input d of the NAND gate 120 is at the L level regardless of the state of the switch 122, the output of the NAND gate 120 is at the H level.
Therefore, both inputs e and f of the NAND gate 104 are H.
level, the inverter 106 outputs an H level signal instructing to stop, and therefore the electric motor remains stopped, and there is no danger of the needle bar being driven inadvertently.

Next, a description will be given of the operation of stopping the electric motor when the needle bar is stuck in the fabric or the like and becomes locked and does not move.

In order to stop the rotating electric motor, start switch 1
When 01 is opened, the charge in the capacitor 128 is discharged through the resistors 130 and 131, and a terminal voltage is generated across the resistor 131 by the discharge current of the capacitor 128, causing the input d of the NAND gate 120 to go to H level. keep it. In this state, when the needle bar reaches the top dead center, the needle position detection switch 122 connected in parallel with the resistor 131 is closed, and the electric motor is stopped. However, if the needle bar is locked before reaching the position where the needle position detection switch 122 is closed (top dead center), the input d of the NAND gate 120 is high because the switch 122 remains open. Since the input c is at the H level, the output remains at the L level, and therefore the output of the NAND gate 104 is kept at the H level, so no signal is output to instruct the motor to stop, so the motor continues to rotate. It continues to maintain the activated state in an attempt to continue. However, when the start switch 101 is opened, charging to the capacitor 128 has been stopped, so the charge that has been stored up to now is transferred to the resistors 130, 1
31, and eventually discharges for a predetermined time τ
After ₃ , the terminal voltage of resistor 131 becomes NAND gate 12.
When the voltage drops below the threshold voltage of input d of 0, the input of NAND gate 120 becomes L level, so the output changes from L level to H level, and an H level signal is given to input e of NAND gate 104, so NAND gate 104 becomes L level. Output the level. Therefore, the L level output of NAND gate 104 is output from inverter 1.
06, and the H level output provides a current to the terminal 62 via the resistor 108 and the diode 110 to instruct the motor to stop, and the motor immediately stops.

If the switch 101 is opened in this manner, even if the needle bar is locked, the power supply to the motor is automatically cut off after a predetermined period of time, thereby preventing the risk of the motor overheating.

As described above, the needle position stop control device for electric sewing machines 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. , furthermore,
If the needle bar is locked after opening switch 101, or if the needle bar is locked,
If 01 is opened, the supply current to the motor is automatically cut off after a predetermined period of time, and heat shielding of the motor is prevented.

The needle 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 the drawing]

FIG. 1 is a circuit diagram of a typical example of a needle specified position stop control device for an electric sewing machine according to the present invention and a speed control device for a DC motor to which the same is applied, and FIGS. This is a tire chart showing signal waveforms of various parts to explain the operation of the speed control device. Explanation of symbols, 2... AC power supply, 3... Main switch, 4... DC motor, 50... Linear amplifier, 66... Comparator, 80... SBS element, 82...
...Pulse transformer, 122...Needle position detection switch.

Claims (1)

[Claims] 1. A DC motor 4 from an AC power supply 2 via a main switch 3 and semiconductor means 10 and 12 with control electrodes.
a main motor circuit that supplies a motor current to the main motor; a trigger signal generating means 66 that outputs a trigger signal for controlling the energization phase to the semiconductor means; Speed instruction signal generators 46, 48, 50, 140 that provide signals instructing the rotational speed, and a switch means 101 that can be switched between a first state instructing to start the motor and a second state instructing it to stop. first bias signal generating means 104, 106 connected to the switch means and generating a first bias signal for instructing the trigger signal generating means to stop the motor; a second bias signal generating means 124 that generates a second bias signal; a first charging/discharging element 116 connected to the outputs of the first bias signal generating means 104 and 106; and a first charging/discharging element 116 connected to the first charging/discharging element. a first logic means 118 whose output changes between a first and a second state; a second charging/discharging element 128 connected to the output of the second bias signal generating means 124; A needle position detection switch 122 that is connected in parallel to the discharge element and closes when it detects that the needle bar has come to a predetermined position.
The input is connected to the output of the first logic means 118 and the second charging/discharging element, and the output is connected to the input of the first bias signal generating means.
and a second logic means 120 that changes between a second state and a second state.
The first bias signal generating means 104, 106
generates the first bias signal only when the switch means 101 is in the second state and the output of the second logic means 120 is in the first state;
The trigger signal is applied to the trigger signal generating means 66 to stop the trigger signal and is also applied to the first logic means 118, and when the first charge/discharge element 116 receives the first bias signal, the first charge/discharge element 116 activates the first logic means after a predetermined period of time when the first bias signal is applied. changing the output from a first state to a second state;
When the first bias signal is no longer applied, it returns to the first state, and the second bias signal generating means 124 generates the second bias signal when the switch means 101 is in the first state, and generates the speed instruction. The speed instruction signal generating means receives a second bias signal from the second bias signal generating means 124, and the speed instruction signal generating means receives a second bias signal from the second bias signal generating means 124. When the second bias signal is not applied, it generates a speed instruction signal that instructs normal operation, and when the second bias signal is not applied, it generates a speed instruction signal that instructs low speed rotation, and the second charge/discharge element 128 generates a speed instruction signal that instructs normal operation. A third bias signal is applied to the second logic means 120 for a predetermined period of time while the second bias signal is being applied and for a predetermined time after the second bias signal is cut off, and when the hand position detection switch 122 is closed, the third bias signal is applied to the second logic means 120. the bias signal is disabled, and the second logic means 120 is configured to disable the first logic means 1.
18 is in the first state and the output is in the second state only when the third bias signal is applied, and the output is in the first state otherwise. Stop control device. 2. In claim 1, from when the first charge/discharge element 116 is given the first bias signal until the output of the first logic means 118 changes from the first state to the second state. A needle specified position stop control device for an electric sewing machine, wherein the predetermined period is slightly longer than a period during which the needle position detection switch 122 is open when the electric motor is rotating at a low speed.