JPH0331478B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of driving a sewing machine that can stop a sewing machine needle at a predetermined position and can vary the speed to any desired speed.

Conventionally, a sewing machine driving device employing an electromagnetic clutch/brake system as shown in FIG. 1 has been proposed.

That is, 10 is a sewing machine, 12 is a sewing machine pulley, 14 is a drive motor including an electromagnetic clutch 16 and an electromagnetic brake 18, and 20 is a motor pulley, and the pulley 20 and the sewing machine pulley 12 are connected by a belt 22. .

24 is a position detector attached to sewing machine 10 for detecting the needle position of the sewing machine, and 26 is similarly attached to sewing machine 1.
This is a speed detector that detects the driving speed of the sewing machine attached to the sewing machine.

28 is a foot pedal for operating the sewing machine 10; 30;
32 is a detection circuit for detecting the operation of the pedal 28; 32 is a motor speed control circuit for controlling the electromagnetic clutch 16 and the electromagnetic brake 18 to obtain a desired sewing speed according to operation commands of the pedal 28; 34 is a motor speed control circuit for controlling the sewing machine 10; This is a sewing machine control circuit that controls needle stop position, automatic thread trimming, etc.

Next, to explain the operation, the foot pedal 28
When the electromagnetic clutch 16 is depressed, the electromagnetic clutch 16 is energized and electromagnetically coupled to the flywheel 36 connected to the rotor of the drive motor 14 which is connected to a power source (not shown) and is constantly driven to rotate. The sewing machine 10 is rotationally driven via an electric motor pulley 20, a belt 22, and a sewing machine pulley 12.

Next, by changing the amount of depression of the foot pedal 28, an electromagnetic signal is obtained from the motor speed control circuit 32 based on the speed command VC of the pedal detection circuit 30 and the detection signal FG of the speed detector 26 attached to the sewing machine 10. The clutch excitation current is controlled, and the sewing machine rotational speed is controlled to an arbitrary speed according to the amount of pedal depression.

When the foot pedal 28 is returned to the neutral position, the sewing machine control circuit 34 outputs an ultra-low speed command for positioning, and at the same time, based on the position detection signal (UP or DN) of the position detector 24, the sewing machine When the needle is detected, a stop signal BK is output, the electromagnetic brake 18 is excited, and the driving of the sewing machine 10 is stopped. A timing chart of the above operation is shown in FIG.

In this way, conventional sewing machine drive devices keep the drive motor constantly rotating regardless of whether the sewing machine is running or stopping, which consumes unnecessary power, and because it uses a flywheel with large inertia, it cannot rotate forward or reverse. The rotational direction of the clutch cannot be changed at any time, and the friction type electromagnetic clutch suffers from wear and has a short lifespan.

In order to eliminate this drawback, a low-inertia print motor is used as the sewing machine drive motor and is driven by direct current, and the electromagnetic clutch 16 is omitted, so that the print motor is directly started and stopped in response to the operation of the foot pedal 28. A variable speed sewing machine drive device has also been proposed. However, since this device uses a DC motor, its control characteristics are very good, but the brushes wear out and have a short lifespan, requiring maintenance, and the device starts and stops each time the foot pedal is operated. Therefore, there are disadvantages such as a large starting current, a large power supply capacity, and a large and expensive drive control circuit.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to operate a sewing machine at variable speed by using an AC induction motor as a drive motor and driving this with an inverter connected in series to a converter. An object of the present invention is to provide an easy-to-operate sewing machine driving method that can promote energy saving by performing regenerative braking by using a converter as an inverter during deceleration.

In order to achieve the above object, the present invention provides an inverter that supplies alternating current of variable voltage and variable frequency to an alternating current motor that drives a sewing machine, and rectifies and supplies alternating current from an alternating current power source to the inverter, and also enables the inverter to regenerate a motor speed control circuit that has a converter capable of converting power on the AC power source side when braking, and performs control to apply braking to the AC motor;
A position detector attached to the sewing machine detects the preset needle position of the sewing machine, and a signal corresponding to the pedal movement of the sewing machine is used to command the set speed and control the thread cutting operation. , and a sewing machine control circuit that issues a stop signal based on the signal that detects the needle position of the position detector, and when the sewing machine's rotational speed is decelerated, the converter is switched in response to the speed command to regenerate power and stop the sewing machine in the needle down position. After that, control the thread cutting operation,
It detects the needle-up position, applies braking to stop it, switches the phase of the alternating current supplied to the electric motor, reverses the rotation, returns the needle to the needle-up position, and stops the needle.

Hereinafter, preferred embodiments of the present invention will be described based on FIGS. 3 to 8.

In FIG. 3, parts corresponding to those in FIG. 1 are given the same reference numerals and detailed explanations are omitted. However, in the configuration of FIG. 1, the drive motor 14 is an AC induction motor, and the electromagnetic clutch 16 is omitted. The sewing machine has a rotor 40 manufactured to have low inertia, such as a cup shape, opposing the stator 38 of the induction motor, and the motor speed control circuit 32 includes a variable voltage/frequency inverter circuit. Reference numeral 10 is constructed so that a sewing machine driving electric motor 14 can perform variable speed operation and stop at a fixed position.

Pedal detection circuit 3 connected to foot pedal 28
0 is shown in detail in FIG. 4, and its configuration will be explained below.

In FIG. 4, the detection circuit 30 includes an optical sensor section 50 consisting of photo interrupters 42, 44, a shielding plate 46 and a resistor 48 that move between the photointerrupters, a magnet 52 that moves together with the shielding plate 46, A Hall element 54 magnetically coupled to the magnet 52 to generate a speed command during sewing operation, a resistor 56 connected to the Hall element 54, and a Hall element 54
The generated speed command is amplified to generate the speed command signal VC.
The shielding plate 46 and the magnet 52 are interlocked with the foot pedal 28.

When the foot pedal 28 is depressed, the degree of magnetic coupling between the magnet 52 and the Hall element 54 varies depending on the magnitude of the depression, and the value of the speed command signal VC changes and the shielding plate 46 is lowered. Then, the outputs of the photo interrupters 42 and 44 become "1" and "0", respectively, and the control circuit 3 outputs operation command signals S ₁ and S ₂ indicating that the sewing operation is in progress.
2. Further, when the foot pedal 28 is in the neutral state as shown in _FIG .
This is determined by the control circuit 32 when both S ₂ become "0". Further, when the foot pedal 28 is "kicked back", that is, rotated in the opposite direction to the direction of depression, the sewing thread is cut, and the shield plate 4
6 rises, the operation command signals S ₁ and S ₂ become "0" and "1", respectively, and the control circuit 32 determines that the "kickback" state is present.

Further, the position detector 24 outputs a needle up position signal UP and a needle down position signal DN indicating the position of the sewing machine needle, and the outputs of the position detector 24 and the pedal detection circuit 30 respectively control the speed of the electric motor 14 for driving the sewing machine. It is also supplied to a sewing machine control circuit 34 that controls various solenoids (not shown) of the sewing machine.

As shown in FIG. 5, the sewing machine control circuit 34 includes operation signal storage circuits (hereinafter referred to as FF circuits) 62 and 64 having a flip-flop circuit configuration to which operation command signals S ₁ and S ₂ of the pedal detection circuit 30 are supplied. The positive output of the FF circuit 62 is directly connected to the speed control circuit 32 through the OR circuit 66 to the star signal SRT.
A brake signal is sent to the speed control circuit 32 via the brake one shot circuit 68.
Sent as BK. In other words, the operation command signal
When S ₁ becomes "1" and the positive output of the FF circuit 62 becomes "1", the speed control circuit 32 outputs a speed command signal.
Drive control of the sewing machine 10 is performed based on VC.

The positive output of the FF circuit 64 is directly connected to the system control circuit 3.
2 as a low speed command signal LLKO, and is also supplied to the OR circuit 66 and the sewing machine control circuit 70. This FF circuit 64 operates when the foot pedal 28 is in the "kickback" state, that is, after the sewing machine has stopped, when cutting the sewing thread, and when the speed command signal _S2 becomes "1", the FF circuit 64 is activated. When the positive output becomes "1", the low speed command signal LLKO is first supplied to the speed control circuit 32 to raise the sewing machine needle, then the sewing machine mechanism control circuit 70 performs thread trimming and wiper control, and finally the sewing machine needle Stops at the top position. FF circuit 6 to stop the sewing machine at the upper position when the sewing machine needle is not at the upper position.
An upper position signal UP is supplied to the reset input of No. 4 via a NAND circuit 72. At this time, the positive output of the FF circuit 62 is supplied to the other input of the NAND circuit 72 via an inverter 74 so that no trouble will occur even if the foot pedal 28 is erroneously depressed.

The brake one shot circuit 68 supplies the brake signal BK to the speed control circuit 32 for a predetermined period of time from when the positive outputs of the FF circuits 62 and 64 are inverted from "1" to "0", respectively, to control the sewing machine 1.
This is to stop 0 immediately.

The sewing machine control circuit 34 also includes a low speed detection circuit 76 to which the upper position detection signal UP and the lower position detection signal DN of the position detector 24 are supplied. This circuit detects that the rotation of the sewing machine 10 has reached a low speed based on the period of the lower position detection signal DN, and sends a low speed detection signal.
This is for outputting LDN and resetting the FF circuit 62, the details of which are shown in FIG. That is, the flip-flop 78 has the upper position detection signal UP and lower position detection signal DN of the position detector 24 supplied to the set terminal s and the reset terminal r, respectively.
, a fixed resistor 80, a variable resistor 82, and a charging capacitor 8 connected to its positive output terminal Q.
A time constant circuit 86 consisting of 4 and this time constant circuit 8
6, and a NOR circuit 90 to which the output of the inverter 88 and the positive output of the flip-flop 78 are supplied. Note that 92 is a diode for rapid discharge of the capacitor 84.

Therefore, the positive output of flip-flop 78 is the seventh
As shown in Figure A, the upper position detection signal is set to "1" by the upper position detection signal UP.
Therefore, the charging voltage of the capacitor 84 becomes "0" due to the lower position detection signal DN.
As shown in FIG. When the charging voltage decreases), the charging voltage exceeds the standard predetermined value, and at this point, the output of the inverter 88 returns from "1" to "0" as shown in FIG. A low speed detection signal LDN indicating this is output, and the FF circuit 62 is reset.

Next, the motor speed control circuit 32 which is supplied with each output of the sewing machine control circuit 34 and the speed command signal VC of the pedal detection circuit 30 and drives the sewing machine driving electric motor 14 will be explained with reference to FIG.

That is, the speed command signal VC of the magnetic sensor section 60 of the pedal detection circuit 30, the start command signal SRT of the sewing machine control circuit 34, and the stop preparation command signal
A command circuit 92 to which IMCO and low speed command signal LLKO are supplied, a voltage control circuit 94 and a slip correction frequency control circuit 96 to which voltage and frequency command signals obtained from this command circuit 92 are respectively supplied.
A thyristor converter 100 is connected in series to the output side of the converter 100 via a smoothing circuit 102 to which the output of the voltage control circuit 94 is supplied as an ignition control signal and converts a three-phase AC voltage from an AC power source into a DC voltage. and a thyristor inverter power circuit 104 to which the output of the slip correction frequency control circuit 96 is supplied as an ignition control signal, and a brake circuit 106 to which the output of the command circuit 92 and the brake signal BK of the sewing machine control circuit 34 are supplied. The output of the inverter power circuit 104 is supplied to the induction motor 14 for driving the sewing machine.
At the same time, the electromagnetic brake 18 is controlled by the output of the brake circuit 106.

Note that the detection signal FG from the speed detector 26 is supplied to the slip correction frequency control circuit 96 for servo control. Further, the output end of the inverter power circuit 104 is connected to the voltage control circuit 94 via a transformer 108, and stabilization is achieved by voltage return. The output of the converter 110 is supplied, and the detected output cuts off the converter drive current and stops the sewing machine drive motor 14.

Then, the start signal of the sewing machine control circuit 34
The voltage and frequency are adjusted by the voltage control circuit 94 and the frequency control circuit 96 according to the output of the command circuit 92 based on SRT and each speed command signal LLKO, IMCO, and VC, and the rotational speed of the sewing machine drive motor 14 is kept within a predetermined reference value. and brake circuit 1
The electromagnetic brake 18 is excited by the output of 06 to stop the sewing machine needle at the stop position.

Although not clearly shown in the figure, the transistor drive circuit 9 is activated by the user's switch operation, etc.
By supplying a predetermined command signal to the main circuit transistor 8, the phase of the voltage supplied from the main circuit transistor to the motor 14 is switched, thereby moving the sewing machine needle in the stopped state to an arbitrary position in the vertical direction.

A preferred embodiment of the present invention has the above configuration,
The effect will be explained below.

When starting sewing work, the foot pedal 28 is depressed to bring the magnet 52 close to the Hall element 58, and the magnetic sensor section 60 causes the motor speed control circuit 3 to move.
At the same time, the photo interrupter 42 outputs the operation signal _S1 of "1" to the sewing machine control circuit 34. Along with this, a start signal SRT of "1" is output from the sewing machine control circuit 34 to the speed control circuit 32, and the driving of the sewing machine drive motor 14 is started. Then, in the speed control circuit 32, the voltage and frequency are converted into voltage and frequency corresponding to the speed commanded by the voltage control circuit 94 and the frequency control circuit 96, and the sewing machine drive motor 14 is rotated at a predetermined speed.

If you want to slow down during sewing work, use the foot pedal 28.
By returning the value, the value of the sewing speed command signal VC decreases, and therefore, the voltage control circuit 94 and the frequency control circuit 96 convert the converter 100 and the inverter 104 into an inverter and a converter, respectively, and regenerate the induction motor 14 as a generator. By performing the control, the speed is rapidly decelerated and stabilized at a desired medium speed rotation according to the amount of depression.

During such sewing work, if the sewing direction is to be changed with the sewing machine needle stuck into the fabric, that is, in the needle down state, the foot pedal 28 is returned to the "neutral" state, and the pedal detection circuit 30 sends a message to the sewing machine control circuit 34. An operation command signal of “0” is sent to the FF circuit 62 of
Output S ₁ . Since the FF circuit 62 continues to output the start signal SRT of "1" to the speed control circuit 32 until it is ready to stop, the rotational speed of the sewing machine drive motor 14 is lower than the normal sewing speed as shown in FIG. maintained at a low predetermined speed.

During this stop preparation period, the low speed detection circuit 76
As described above, the capacitor 84 is charged based on the upper position detection signal UP and the lower position detection signal DN from the position detection circuit 24 only during the period in which the positive output of the flip-flop 78 is "1". Then, the speed of the motor 14 decreases, the repetition period T becomes longer, and only in the section where the charging voltage of the capacitor 84 exceeds a predetermined value Vth, the output of the inverter 88 sends an output signal of "0" to the NOR circuit 90.
Therefore, the positive output of flip-flop 78 is "0".
At the moment when this occurs, the reset signal LDN for the FF circuit 62 is obtained from the NOR circuit 90, and the direction change conditions are met, in which the rotational speed of the sewing machine drive motor 14 reaches a predetermined low speed and the sewing machine needle is in the lower position. At this point, a brake signal BK of "1" is obtained from the brake one shot circuit 68, and the sewing machine drive motor 14 is stopped via the brake circuit 106 of the speed control circuit 32.

When thread trimming is to be performed after sewing, the foot pedal 28 is depressed to output a thread trimming signal _S2 of "1" from the photo interrupter 44 to the FF circuit 64 of the sewing machine control circuit. In response, a start signal of "1" is sent from the FF circuit 64 to the speed control circuit 32.
SRT and low speed signal LLKO (medium speed signal if necessary)
In some cases, the sewing machine outputs IMCO) and operates the sewing machine mechanism control circuit 70 to control thread trimming, thread sweeping, etc. The FF circuit 64 receives an upper position detection signal of "1" from the position detector 26.
The sewing machine drive motor 14 is reset by UP.
stops with the sewing machine needle in the upper position.

When it is desired to move the stopped sewing machine needle from the lower position to the upper position, for example, a switching means such as a switch is used to direct the voltage control circuit 94 and frequency control circuit 96 of the motor speed control circuit 32 to a predetermined position. By supplying a command signal and sending a phase switching signal to the main circuit transistor, the sewing machine needle can be quickly and easily moved to a desired vertical position without adding a control means such as a reversing motor.

In the above embodiment, a case has been described in which the speed command and the driving command are operated by the foot pedal 28, but they may be operated by an external driving switch signal.

Further, the sewing machine driving motor is not limited to a three-phase induction motor, but may be a single-phase induction motor.

As described above, according to the present invention, the motor speed control circuit includes an inverter, and the motor can be reversed by switching the phase.

The automatic thread trimming mechanism in a sewing machine uses the rotation of the main shaft of the sewing machine to cut the thread after the needle lifts away from the workpiece cloth and reaches the top dead center, which is a high position. The position where the needle position is detected and the brake is applied to stop is considerably lower than top dead center. With only forward rotation like conventional equipment,
If the needle stops at this low position, it may get caught or get stuck when, for example, you are putting in or taking out a sewing item. Therefore, a special mechanism must be installed to return the needle stop position to near the top dead center, or the needle can be returned manually while watching the needle. There was a drawback that I had no choice but to do so.

In contrast, by operating the pedal to cut the thread, detecting the needle position, and applying braking to stop the thread, even if the needle stops at a low position, the electric motor can be reversed. Since the needle can be returned to near the top dead center and stopped, it will not get caught even when sewing thick cloth. Furthermore, since the induction motor with the drive device is configured to be driven by an inverter circuit, it is possible to steplessly change the speed to any drive speed, and moreover, it is possible to command the sewing machine speed without using a speed detector or the like to detect the sewing machine speed. Since the speed can be controlled at a constant speed at a frequency of , there is no need for an unstable variable speed motor or a complicated control circuit as in conventional devices.

In addition, in the case of sudden deceleration or stopping, regenerative braking can be used in conjunction with an inverter and converter, significantly extending the life of the brake unit compared to braking only with conventional mechanical friction brakes. It is possible to save energy, and the brake part can be made smaller, so the moment of inertia of the output shaft is reduced.
It can fully meet the sudden acceleration and deceleration requirements required for sewing work.

Furthermore, since it uses an AC induction motor, there is no need for maintenance and inspection as with DC motors.

Furthermore, by applying a variable voltage converter and a variable frequency inverter circuit, when starting the sewing machine by operating the foot pedal, there is no starting current flowing each time unlike a DC motor, and there is no effect on the power supply. It has the advantage of requiring less power and capacity, and since the induction motor is driven by an inverter, it is not affected by frequencies such as 50Hz and 60Hz, so it has excellent features such as unification of control equipment. It is possible to perform ideal control as a method of driving a sewing machine.

As described above, according to the present invention, since electric power can be regenerated to the power supply, it is possible to save energy in an industrial sewing machine that has extremely high accuracy in starting and stopping, and it is also possible to stop the sewing machine using regenerative braking. Since the needle position stop position can be returned by reverse rotation of the electric motor, there is an effect that a sewing machine driving method that is easy to handle with a simple sewing machine configuration can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing a conventional sewing machine drive device, Fig. 2 is an explanatory diagram showing the relationship between the waveforms and rotational speed of each part of the fixed position stop device in the sewing machine, and Fig. 3
4 is a schematic configuration diagram showing a preferred embodiment of the sewing machine driving device according to the present invention, FIG. 4 is an explanatory diagram showing the detailed configuration of the pedal detection circuit shown in FIG. 3, and FIG.
6 is an explanatory diagram showing the detailed configuration of the sewing machine control circuit shown in FIG. 3, FIG. 6 is an explanatory diagram showing the detailed configuration of the low speed detection circuit in FIG. 5, and FIG.
FIG. 8 is an explanatory diagram showing waveforms of various parts of the low speed detection circuit shown in the figure, and FIG. 8 is an explanatory diagram showing details of the motor speed control circuit shown in FIG. 3. The same members in each figure are given the same reference numerals, 10 is a sewing machine, 14 is a sewing machine drive motor, 18 is an electromagnetic brake, 24 is a position detector, 28 is a foot pedal,
30 is a pedal detection circuit, 32 is a motor speed control circuit, 34 is a sewing machine control circuit, 76 is a low speed detection circuit, 100 is a thyristor converter, and 104 is a thyristor inverter.

Claims (1)

[Scope of Claims] 1. An inverter that supplies alternating current of variable voltage and variable frequency to an alternating current motor that drives a sewing machine and that can switch the phase; and an inverter that rectifies and supplies alternating current from an alternating current power source to the inverter; a motor speed control circuit that is attached to the sewing machine and has a converter capable of converting power on the AC power source side when the sewing machine performs regenerative braking, and that controls a braking means to brake and stop the AC motor; A position detector detects a preset needle position of the sewing machine, and a signal corresponding to the pedal motion of the sewing machine is used to command a set speed and control the thread cutting operation. In a method of driving a sewing machine, the sewing machine control circuit is equipped with a sewing machine control circuit that issues a stop signal based on a signal that detects the needle position of a position detector, and when the sewing machine is stopped, the converter is switched according to the speed command when the rotational speed is reduced, and the electrical power is changed. a first step of regenerating the sewing machine; a second step of controlling the thread cutting operation after stopping the sewing machine at the needle down position, detecting the needle up position, and applying braking to stop the sewing machine; After the second step, a third step of switching the phase of the alternating current supplied to the electric motor to reverse the rotation, return the needle to the needle-up position, and stop the needle. How to drive a sewing machine.