JPS5949833B2 - Speed control device for electric motor for sewing machine with basting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a speed control device for a motor for a sewing machine with a basting device.

A motor control device for an electric sewing machine capable of performing basting stitches is disclosed in Japanese Patent Application No. 137546/1983 filed on November 16, 1976 by the same applicant as the present applicant. Since many gate elements and transistors are used, the circuit becomes complicated and expensive, the braking device of the motor does not work properly and smooth operation is difficult, and the motor is forced to stop due to heavy loads. There was a risk that the motor would burn out if it was stopped.

The main aim of the invention is to eliminate the above-mentioned drawbacks.

Other objects and features of the present invention, as well as operations and effects of the speed control device according to the present invention, will be described in detail below regarding preferred embodiments of the present invention, illustrated by way of example with reference to the accompanying drawings. The explanation will make it clear.

The drawing is a circuit diagram of a preferred embodiment of the speed control device according to the present invention. a main motor circuit that supplies a motor current to the DC motor 4 via a first trigger voltage setting means having, for example, a controller 5 for setting a first trigger voltage for triggering the semiconductor element; a second trigger voltage setting means including a semi-fixed resistor 17 and a diode 18 for setting a second trigger voltage for triggering the device; and a second trigger voltage setting means for supplying the first and second trigger voltages to the control electrode of the semiconductor device. Capacitor 22 Programmable Union Transistor (PUT)
) 21; switching means comprising, for example, a single-pole double-throw switch 13 switched between a first and a second state; and switching means, for example a transistor, for disabling said second trigger voltage setting means. 38; second switching means, e.g. a transistor 60, for controlling the operation of said first switching means; and third switching means, e.g. a thyristor 65, for controlling the operation of said second switching means. and a braking means having, for example, a coil 85, for electromagnetically braking the electric motor, and a braking means having, for example, a transistor 80 and a thyristor 84, for generating a signal for activating the braking means for a predetermined period of time following the cooling of the semiconductor element. 1 signal generating means, and a needle position detecting means 44 having, for example, reed switches 45 and 46 for detecting that a needle (not shown) has come to a predetermined position.

Furthermore, a second switching means comprising, for example, a transistor 69 and a Zener diode 50 provides a signal for controlling the first switching means when a predetermined period of time has elapsed after the shutoff of the semiconductor element.
It includes a signal generating means and a motor voltage detecting means having, for example, a Zener diode 30 for detecting the motor voltage.
The controller 5 is, for example, a variable resistor 1 for controlling the speed of an electric motor.
1, a semi-fixed resistor 12, and a single-pole single-throw switch 10 linked to a slider a of a variable resistor 11.The switch 10 has a semi-fixed resistor 12, and a single-pole single-throw switch 10 that is connected to a slider a of a variable resistor 11. When the switch 10 positions the slider a at a terminal b and its resistance value r is maximized, It opens and closes when it moves slightly toward the terminal C side. The reed switch 45 of the needle position detection means 44 detects when the needle comes to a designated position, for example, the upper designated position, and closes it, and the reed switch 46 detects and closes the needle when it comes to, for example, the lower designated position. However, the single-pole double-throw switch 47 specifies the needle stop position as either the upper designated position or the lower designated position.

Next, the operation of the circuit will be explained.

First, the continuous stitch mode will be explained. Move the movable piece of the switch 13 for selecting continuous stitching and basting stitch to the terminal e side of the continuous stitching mode, and press the slider a of the variable resistor 11.
is located at terminal b, its resistance value r is maximized, and when main switch 2 is closed with switch 10 open,
The power supply current from AC power supply 1 is passed through diodes 6, 7, 8, 9.
The signal is full-wave rectified by a full-wave rectifier circuit consisting of the following, and flows from the terminal 87 to the Zener diode 37 via the protective resistor 15, but does not flow to the controller 5 because the switch 10 is open. The voltage between the terminals of the Zener diode 37 exhibits a trapezoidal waveform with a constant maximum value every half cycle of the power supply voltage, and is applied to the collector of the transistor 38 via the protective resistor 16 and the semi-fixed resistor 17, as well as the resistor 48 and the capacitor 70. The voltage is applied to the collector of the transistor 69 through the protective resistor 49 and to the collector of the transistor 60 through the protective resistor 49. By the way, since both transistors 60 and 69 are in an off state with no base bias applied, the voltage between the terminals of the Zener diode 37 is applied to the cathode of the Zener diode 50 via the resistors 48 and 49. Since this applied voltage is set to exceed the breakover voltage of the Zener diode 50, the Zener diode 50 becomes conductive and a bias current is applied to the base of the transistor 38 via the bias resistor 5L and the backflow prevention diode 52. Transistor 38 conducts with its collector grounded. Therefore, the current flowing through the resistors 16 and 17 flows to the collector-emitter circuit of the transistor 38, and does not flow to the circuit of the diode 18, the resistor 20, and the capacitor 22. ) does not conduct, the thyristor 3 remains non-conductive, and the motor 4 does not start. Further, when the needle is at the position specified by the switch 47, for example, the movable piece of the switch 47 is inserted into the terminal f, the upper specified position is selected, and the reed switch 4
6 is closed, the Zener diode 37
The voltage between the terminals of is applied to the base of the transistor 38 via the resistors 48 and 49, the switch 47, the reed switch 46, and the resistor 5L diode 52, thereby making the transistor 38 conductive. Next, when the slider a of the variable resistor 11 is moved slightly toward the terminal c side, the switch 10 is closed, and the full-wave rectified current is passed from the terminal 87 to the overcurrent protection resistor 14, the switch 10, and the resistor 1.
1, 12, and one side is diode 1 through switch 13.
9, resistor 20, and capacitor 22, and the other flows to diode 39, resistor 40, and the base of transistor 38, as well as diodes 41, . Flows into resistor 42 and the base of transistor 60.

Therefore, the transistor 38 continues to conduct, keeping its collector potential at the ground potential, and the transistor 60 changes from a closed state to a conductive state, and the current flowing through the resistor 49 to the Zener diode 50 or the switch 47 is now turned off by the transistor. 60 collector-emitter circuit. Here, the resistors 43 and 59 are used to prevent base current from flowing in due to a small collector cutoff current when the transistors 38 and 60 are off, or to prevent the transistors from malfunctioning due to induced charges or the like. Due to the conduction of the transistor 38, the current flowing through the resistors 16, 17, the diode 19, and the capacitor 22 continues to be cut off. The capacitor 22 is charged with a predetermined time constant determined by the resistance value of the capacitor 22 and the capacitance of the capacitor 22. However, since the resistance value of the variable resistor 11 is near the maximum value, the charging current to the capacitor 22 is small, and the resistance value of the semi-fixed resistor 12 is adjusted appropriately so that the charging charge is at most slightly lower than the breakover voltage of the PUT. Therefore, PUT is not conductive, and accordingly, thyristor 3 is also not conductive, and the motor remains stationary. Here, the characteristics of PUT2l will be explained. The breakover voltage of the PUT 2l changes depending on the gate voltage, and has a characteristic that as the gate voltage increases, the breakover voltage also increases, and conversely, as the gate voltage decreases, the breakover voltage also decreases. The gate voltage of PUT in this circuit is a full-wave rectified voltage that is converted into a trapezoidal waveform voltage by a Zener diode 28 via a resistor 25, and this trapezoidal waveform voltage is converted to a trapezoidal waveform voltage by a resistor 26.
, 27. By the way, in the above state, the voltage between the terminals of the capacitor 22 rises at a constant slope during the half cycle of the power supply voltage, but when the power supply voltage suddenly drops near the end of the half cycle, the gate voltage of the PUT 2l, that is, the resistor 26, Since the voltage at the connection point 27 also drops in the same way, the breakover voltage of PUT 2l also drops, and therefore current flows between the anode and cathode of PUT, and the charge in capacitor 22 that has been charged up to now is transferred to PU
It is discharged through T, and the voltage between its terminals drops to zero.
Therefore, the discharge current of the capacitor 22 flows between the PUT 2l and the gate and cathode of the thyristor 3, but this current value is so small that it does not trigger the thyristor 3. In this manner, capacitor 22 is discharged after each half cycle of AC, thereby preventing the accumulation of residual charge in capacitor 22 from intermittently and unnecessarily triggering the thyristor.

Next, when the resistance value of the variable resistor 11 is slightly decreased to a predetermined value, the charging voltage of the capacitor 22 reaches the breakover voltage of the PUT 2l for the first time near its maximum value, making the PUT conductive.

Therefore, the capacitor 22 instantly discharges its charge through the PUT and supplies it to the gate of the thyristor 3, but this discharge current is of sufficient value to trigger the thyristor 3, and the thyristor is Electricity is applied at a certain angle (corresponding to the conduction period) to supply a pulsating current to the motor 4, starting the motor and causing it to rotate at a low speed. When the resistance value of the variable resistor 11 is further decreased, the charging current to the capacitor 22 increases,
The phase at which the charging voltage of the capacitor 22 reaches the breaker over-voltage of the PUT 2l advances, and therefore the flow phase angle of the thyristor 3 increases, increasing the rotational speed of the motor.

By adjusting the resistance value of the variable resistor 11 in this manner, the rotation speed of the electric motor can be continuously controlled from low speed to high speed.

Here, the resistor 23 and capacitor 24 prevent the thyristor 3 from malfunctioning due to noise, etc., the diode 34 removes the flash voltage generated across the motor, and the thermal protector 36 prevents the thyristor 3 from malfunctioning due to noise etc., and the thermal protector 36 prevents the thyristor 3 from malfunctioning due to noise etc. It has a switch that opens the circuit and cuts off the motor current to prevent overload operation.

When the thyristor 3 is energized, the energizing current is supplied to the motor 4 via the diode 29, and on the other hand, the voltage dividing resistor 61. A bias resistor 66 is applied to the base of a PNP transistor 69 to make the transistor 69 conductive, and a voltage dividing resistor 71 . It is supplied to the NPN transistor 80 via the smoothing resistor 74 and the bias resistor 76 to reverse bias the transistor 80 and keep the transistor 80 non-conductive.

Further, the current is supplied to the gate of the thyristor 65 via the resistors 61 and 62 to energize the thyristor 65, but since the movable piece of the switch 3 is not on the terminal d side, no energizing current flows. Here, the Zener diode 67 slices the energized voltage divided by the resistor 6], and the capacitor 68 smoothes the sliced voltage to stably turn on the transistor 69. Further, the capacitor 72 smoothes the voltage divided by the resistor 71, the Zener diode 73 applies the smoothed voltage as a constant maximum voltage between the emitter and base of the transistor 80, and the capacitor 79 smooths the voltage divided by the resistor 71.
, diode J and V, and resistor 78. While this charging is being carried out, transistor 8
Since the emitter and base of 0 are kept at the same potential, transistor 80 is not conductive. When the transistor 69 is conductive, the current flowing through the resistor 48 passes through the capacitor 70 and flows into the collector-emitter circuit of the transistor 69. However, since the transistor 60 is conductive, the current flowing through the resistor 48 is further shunted to the resistor 49. The current flows through the collector-emitter circuit of transistor 60. Here, since the resistance value of the resistor 49 is much smaller than that of the resistor 48, the divided voltage of the resistor 49 is also small, and therefore the charging voltage of the capacitor 70 is also small.
Next, the stopping operation of the electric motor will be explained.

The resistance value r of variable resistor 1 in the state of high-speed operation of electric machine 4
Gradually increasing , the motor shifts from high-speed operation to low-speed operation, and when slider a of variable resistor 11 is further positioned at terminal b, switch 10 opens, and controller 5, switch 13, diode 19, and resistor 220 The charging current flowing to the capacitor 22 via the switch 13, the diode 39, the bias current flowing to the base of the transistor 38 via the diode 40, and the bias current flowing to the base of the transistor 38 via the switch 3, the diode 41, and the resistor 42. The bias current flowing to the base of transistor 60 is cut off. Therefore, the transistors 38 and 60 become non-conducting, and the resistance up to now]6,
] 7 to the collector of the transistor 38, the current flows through the diode 18 and the resistor 20 to the capacitor 2.
In order to charge the thyristor 2, the PUT 2l continues to be triggered and continues to conduct the thyristor 3. At this time, it is assumed that the value of the semi-fixed resistor 17 is adjusted so as to conduct the thyristor at an extremely small energization phase angle and rotate the motor at an extremely low speed with no inertia. Also, due to the non-conduction of the transistor 60, the current flowing from the resistor 48 to the resistor 49 and the collector of the transistor 60 is suddenly cut off, and the resistor 4 parallel to the capacitor 70 is cut off.
9. Since the series circuit of the transistor 60 disappears, the voltage divided by the capacitor 70 increases, and the capacitor 70 is connected to the resistor 48.
The charging voltage is determined by the resistance value of the Zener diode 50 and the capacitance of the capacitor 70.
The voltage will rise slowly until it reaches the breakover voltage of . Note that since the thyristor 3 continues to be conductive, the transistor 69 continues to be conductive, and the transistor 80 remains non-conductive. Eventually, as the electric motor 4 rotates, the needle bar reaches the position specified by the switch 47, for example, the upper specified position, and the reed switch 46 closes.
A bias current is supplied to the base of the transistor 38 through the 9 switch 47, the reed switch 46, and the 5L diode 52, making the transistor 38 conductive. Therefore, the current that was charging the capacitor 22 through the diode 18 and the resistor 20 is cut off, causing the thyristor 3 to become non-conducting and the motor to maintain the motor current. will be cut off. When the thyristor 3 becomes non-conductive, the base bias of the transistor 69 and the charging current of the capacitor 68 that have been applied through the resistors 61 and 66 are cut off, so the capacitor 68 transfers the charged charge to the resistor 66 and the transistor 6. The transistor 69 is discharged at a predetermined time constant through a base-emitter circuit of .9 and continues to be conductive until the discharge is completed.
Therefore, the charging voltage of capacitor 70 continues to rise during that time. Furthermore, due to the non-conduction of the thyristor 3, the current that was charging the capacitor 79 through the resistors 71, 74, the diode 7.7, and the resistor 78 is cut off, so that the capacitor 79 is ,75
The photoelectric charge is discharged through the transistor 80 to make the transistor 80 conductive. Therefore, the capacitor 79 is charged. The electric charge is applied to the gate of a switching element, such as a thyristor 84, through the emitter-collector resistor 81 of the transistor 80, making the thyristor conductive. Therefore, the full-wave rectified current from the terminal 87 flows to the electromagnetic brake solenoid 85, and the electric motor is activated. The disk (not shown) attached to the shaft (not shown) is adsorbed, the rotation of the shaft is forcibly stopped, and the rotation of the electric motor is immediately stopped. Therefore, the needle bar stops at the upper designated position and the reed switch 46 is kept closed. After that, when the discharge of the accumulated charge in the capacitor 79 is completely completed, the capacitor 83 discharges the charge through the resistor 82, and when the discharge is completed and the potential between the cathode and gate of the thyristor 84 becomes equal, the thyristor automatically to return to the cut-off state and release the electromagnetic brake. Also capacitor 68
When the discharge of the transistor 69 is completed, the transistor 69 becomes non-conductive.
Charging to capacitor 70 is stopped. In addition, resistance 81, 8
2. The capacitor 83 prevents the thyristor 84 from malfunctioning due to noise between the gate and cathode of the thyristor 84, and the diode 86 prevents the thyristor 84 from malfunctioning due to noise between the gate and cathode of the thyristor 84.
This reduces the pulsation of the current flowing through the thyristor 84 and prevents the thyristor 84 from malfunctioning. By dynamically operating the electromagnetic brake reliably at the designated position in this manner, the needle bar is accurately and promptly stopped at the designated position after the switch 10 is released. Here, a case where the needle bar is forcibly stopped outside the designated position due to a heavy load or the like will be explained.

When the needle bar is forcibly stopped at a location other than the designated position, that is, the upper or lower designated position, the reed switches 45 and 4
6 is in an open state, the transistor 38 is not given a base bias through the reed switch and is in a non-conducting state, and the capacitor 22 is charged through the resistors 16, 17, the diode 18, and the resistor 20, and the thyristor 3 is in a conductive state. Continue to do so. However, as described above, when the switch 10 is opened, the transistor 60 becomes non-conductive and the charging potential of the capacitor 70 increases, so that it eventually reaches the breakover voltage of the Zener diode 50 and makes the Zener diode 50 conductive. Therefore, transistor 38 is resistor 49
, Zener diode 50, resistor 51, , diode 5
Since the base bias is applied through the conductive capacitor 22 and the charging of the conductive capacitor 22 is interrupted, the thyristor 3 is interrupted, and at the same time, the solenoid 85 is energized and the electromagnetic brake is activated. In this way, even if the needle bar is forcibly stopped outside the designated position, the thyristor 3 is automatically cut off after a predetermined period of time, thereby preventing damage to the motor. Next, a description will be given of a circuit that performs a feedback effect on motor speed changes due to load fluctuations. As mentioned above, the breakover voltage of PUT 2l varies depending on the gate voltage, and this circuit utilizes this to perform a feedback effect. When the motor 4 starts to rotate, a magnetic field is generated because the energy stored in the field winding 32 is circulated through the flywheel diode 33 when the thyristor 3 is cut off, and therefore the armature rotates while cutting off the magnetic field. A rotational electromotive force appears between the terminals of the motor 4. This back electromotive force is detected by the Zener diode 30 and applied to the gate of the PUT 2l, but the Zener diode 37 detects only the back electromotive force and does not detect the energizing voltage of the thyristor 3. That is, when the thyristor 3 is conductive, the potentials of the anode and cathode of the Zener diode 30 are equal, but when the thyristor 3 is turned off, the anode and cathode of the Zener diode 30 are connected in the opposite direction to the back electromotive force. A back electromotive force appears in between. In this way, the gate of PUT2l is connected to the resistor 26, 2 of the voltage between the terminals of the Zener diode 28.
7 divided voltages and back electromotive force are given. Therefore, when the load on the motor increases and the rotational speed slows down, the back electromotive force decreases, the gate voltage of PUT2l decreases, the breakover voltage of PUT also decreases, and the energization phase of thyristor 3 advances, increasing the rotational speed of the motor. . Furthermore, when the load on the motor decreases and the rotation speed increases, the back electromotive force increases and the gate voltage of the PUT increases, so the breakover voltage of the PUT increases, delaying the energization phase of the thyristor 3 and reducing the rotation speed of the motor. . As described above, the speed fluctuations of the motor due to load fluctuations are greatly reduced by the feedback effect.
Note that the capacitor 31 removes noise contained in the back electromotive force, and the resistor 35 prevents a current exceeding the rated value from flowing through the Zener diode 30. Next, sew one stitch (
This section explains the basting (basting) mode.

If the needle bar is now in the upper designated position, for example, press the release switch 46.
is closed and the switch 47 is connected to the terminal f, move the movable piece of the switch 13 that selects continuous stitching and basting stitch to the terminal d side of the basting mode, and turn the variable resistor of the controller 5]1. Move slider a slightly from terminal B to terminal C.
When the switch 10 is closed, the full-wave rectified voltage is applied from the terminal 87 to the smoothing capacitor 53 through the controller 5 and the switch 13, as well as to the smoothing resistor 54.
, is applied to the resistor 55, and the divided voltage of the resistor 55 is applied to the cathode of the Zener diode 56 and the anode of the thyristor 65, but the thyristor 65 is not triggered and the divided voltage is below the breakover voltage of the Zener diode 56. Zener diode 56 is not conductive. Further, the transistor 38 includes resistors 48, 49, a switch 47,
Reed switch 46, resistor 51. Since a base bias is applied through the diode 52 and conductive, the capacitor 22 is not charged and continues to turn off the thyristor 3, keeping the motor in a stationary state. When the slider of the variable resistor 11 is further moved to the terminal C side and its resistance value r is lowered to a predetermined value or less,
The divided voltage of the resistor 55 reaches the breakover voltage of the Zener diode 56 and makes the Zener diode 56 conductive. Therefore, a current is applied to the base of the transistor 60 via the Zener diode 56, the resistor 57, and the diode 58, and the transistor 60 becomes conductive. . Then until now resistance 4
9. The current flowing through the switch 47 and the read switch 46 flows to the collector-emitter of the transistor 60, so the transistor 38 becomes non-conductive and the resistor 17
The current flowing from the collector to the emitter of the transistor 38 passes through the diode 8 and the resistor 20 to the capacitor 2.
It flows to 2. Therefore, the thyristor 3 is energized at a small flow phase angle to start the electric motor 4 and rotate it at a very low speed. As the electric motor rotates, the needle bar leaves the upper designated position and moves toward the lower designated position, opening the lowering shield switch 46. Further, when the thyristor 3 is energized, the current begins to charge the capacitor 63 through the diode 29 and the resistors 61 and 62, and when the charging voltage eventually reaches the trigger voltage of the thyristor 65, the thyristor 65 becomes conductive and the cathode potential of the Zener diode 56 Since the voltage is set to zero, the transistor 60 becomes non-conductive. Then, the resistors 48, 4 are connected to the terminal f of the switch 47.
9, the terminal voltage of the Zener diode 37 is applied, but since the reed switch 46 is open, the transistor 3
No. 8 is not given a base bias and remains non-conductive. Here, the time when the charging voltage of the capacitor 63 reaches the trigger voltage of the thyristor 65 is that the needle bar leaves the upper specified position and opens the reed switch 46, and then the needle bar approaches the upper specified position again and opens the reed switch 46. It is assumed that the time constants of the circuit including the resistors 6], 62, and the capacitor 63 are adjusted so that the time is until the circuit is closed. Further, when the thyristor 3 is energized, the capacitor 79 is charged via the resistor 71, the seven-hole diode J and the resistor 78, and the resistor 78.

Eventually, the needle bar rises from the lower designated position to the upper designated position and when it reaches the upper designated position, the reed switch 46 closes again, so the transistor 38 closes the reed switch 4.
A base bias is applied again through the capacitor 6 to cut off the charging current to the conductive capacitor 22. Therefore, since the thyristor 3 becomes non-conductive, the motor current is cut off, and the charging current to the capacitor 79 is also cut off, so the transistor 80 becomes conductive and triggers the thyristor 84.
Solenoid 85 is energized and activates the electromagnetic brake to immediately stop the electric motor. Therefore, the needle bar stops at the upper designated position and one stitch is completed. When sewing the next stitch,
This is accomplished by once opening the switch]0 to make the thyristor 65 non-conductive, then closing it again and moving the slider of the variable resistor 11 to the terminal C side. In addition, if the needle bar is forcibly stopped at a position other than the designated position due to a heavy load or the like during one stitch, even if the switch 10 is kept closed, the transistor 60 will cause the thyristor 65 to conduct as the motor starts. Since it becomes non-conductive, the charging voltage of the capacitor 70 rises after a predetermined time and reaches the breakover voltage of the Zener diode 50 and becomes conductive, giving a base bias to the transistor 38 and making the thyristor 3 non-conductive. Furthermore, after the needle bar has stopped at the designated position, with switch 10 opened, the flywheel of the sewing machine is immediately turned to move the needle bar out of the designated position and the corresponding reed switch, for example, reed switch 46, is activated.
When the transistor 60 is turned off, the transistor 60 is in a non-conducting state, and the transistor 69 is in a conducting state until a predetermined time has elapsed after the thyristor 3 is turned off and the discharge of the capacitor 68 is completed. The capacitor 70 continues to be charged until the capacitor 69 becomes non-conductive, and soon the charging voltage reaches the Zener diode 50.
The breakover voltage is reached, causing transistor 38 to conduct, thereby preventing starting of the motor.

Furthermore, when the flywheel is rotated and the transistor 69 is already non-conductive due to the completion of discharging the capacitor 68, the voltage of the Zener diode 37 is applied to the Zener diode 50 via the resistors 48 and 49. biases conductive transistor 38, thereby preventing restart of the motor.

[Brief explanation of the drawing]

The figure shows a circuit diagram of a typical embodiment of a speed control device for a motor for a sewing machine with a basting device according to the present invention.

Claims (1)

[Claims] 1. A main motor circuit that supplies motor current from an AC power source to a DC motor via a main switch, a full-wave rectifier circuit, and a semiconductor element with a control electrode, and for triggering the semiconductor element individually. first and second trigger voltage setting means for setting the first and second trigger voltages, and applying the first and second trigger voltages set by the first and second trigger voltage setting means to the control electrodes of the semiconductor element. a trigger voltage supply means for supplying a trigger voltage, a switching means for switching between a first and a second state, a first switching means for disabling said second trigger voltage setting means, and said first switching means. a second switching means for controlling the operation of the second switching means;
a third switching means for controlling the operation of the switching means; a braking means for electromagnetically braking the electric motor; and a first signal generation for generating a signal for activating the braking means for a predetermined period of time subsequent to the interruption of the semiconductor element. and a needle position detection means for detecting that the needle is at a predetermined position, and the first trigger voltage setting means is configured such that the main switch is closed and the switching means is in the first state. When applying the first trigger voltage to the trigger voltage supply means, applying a first bias to the first switching means and applying a second bias to the second switching means, and when in the second state, A third bias is applied to the second switching means and a fourth bias is applied to the third switching means, and the second trigger voltage setting means sets the second trigger voltage to the trigger voltage supply means when the main switch is closed. and when the needle position detection means detects that the needle has come to a predetermined position, it applies a fifth bias to the first switching means, and the first switching means determines whether either the first bias or the fifth bias is present. When applied, the second switching means becomes conductive and disables the second trigger voltage setting means; when either the second bias or the third bias is applied, the second switching means becomes conductive and disables the fifth bias; A speed control device for a motor for a sewing machine with a basting device, wherein the third switching means disables the third bias as long as the fourth bias is applied once the semiconductor element becomes conductive. 2. In claim 1, furthermore, when the semiconductor element is conducting and a predetermined period of time has elapsed after the second switching element is turned off, the first switching means
a second signal generating means for applying a bias; the first switching means becomes conductive when the sixth bias is applied, disabling the second trigger voltage setting means;
A speed control device for a motor for a sewing machine with a basting device, wherein the switching means disables the sixth bias when conductive. 3. In claim 1, further comprising means for detecting a motor voltage, and the trigger voltage supply means includes a charging circuit connected to the first and second trigger voltage setting means;
a switching element with a control electrode that is connected to the charging circuit and becomes conductive when the charging voltage of the charging circuit reaches a predetermined value to discharge the charged charge and supply a trigger voltage to the semiconductor element; The motor voltage detected by the detection means is applied to the control electrode of the switching element with a control electrode, and the switching element with a control electrode changes the predetermined conduction value according to the motor voltage and increases the motor voltage. A speed control device for a motor for a sewing machine with a basting device, characterized in that the speed control device acts to delay the phase in which the semiconductor element is conductive and to advance the phase in which the semiconductor element is conductive when the motor voltage decreases.