JPS6044958B2 - sewing machine control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a sewing machine head having a built-in thread cutting device, a position detector attached to the sewing machine head and generating a position signal corresponding to the needle position of the sewing machine, and a position detector for driving the sewing machine head. In the sewing machine drive system, which includes a motor for cutting, a clutch/brake coil for transmitting the rotational force of the motor to the sewing machine, and an electromagnetic coupling mechanism using a magnetic circuit, lining, etc., it is particularly useful for the thread cutting process. The purpose of this invention is to provide an effective speed control means based on the control of the clutch/brake coil described above to further improve the accuracy with which the sewing machine needle is stopped at a fixed position.

A conventional example of such a sewing machine needle positioning method will be described below.

Fig. 1 shows the structure of an electromagnetic clutch motor, particularly the electromagnetic coupling part, as an example of a motor for performing the above control, and the clutch friction disk 1 is attached to the output shaft of the motor (not shown). The brake friction disc 3 is fixed to the flywheel 2 and constantly rotates by the drive of a motor, while the brake friction disc 3 is fixed on the stationary side. A clutch lining 6 and a brake lining 7 are attached to the clutch disc 4 and the brake disc 5, respectively, and are configured to be movable independently in the thrust direction on a spline 9 fixed to a clutch shaft 8. . Further, the clutch coil 10 and the brake coil 11 each have a magnetic circuit for moving the clutch disk 4 toward the clutch friction disk 1 side and the brake disk 5 toward the brake friction disk 3 side. Note that the clutch shaft 8 is interlocked with the sewing machine via a pulley and a belt. In the magnetic coupling section configured as described above,
First, for example, when a thread trimming command signal, such as that based on a signal from pressing down on a sewing machine pedal, is generated, the clutch coil 10 is energized, and its magnetic circuit moves the clutch disc 4 toward the clutch friction disc 1. The rotational force of the motor is decelerated and transmitted through the surface of the clutch lining 6 according to the excitation current of the clutch coil 10, and the clutch shaft 8 is driven via the clutch disc 4 and splines 9. The sewing machine connected via the pulley and belt begins to rotate.

Normally, in the thread cutting process, the sewing machine is set to a low speed, and the sewing machine accelerates as described above until the set speed is reached. When the rotational speed further increases beyond the set speed, the Clazzi coil 10 is turned off and the brake coil 11 is turned off. is excited, and the magnetic circuit moves the brake disc 5 toward the brake friction disc 3 and presses the surface of the brake lining 7, thereby decelerating the clutch shaft 8 via the brake disc 5 and the spline 9. . As described above, acceleration and deceleration are performed, but when the speed is stabilized at a constant set speed, the operation is maintained mostly by energizing only the clutch coil 10, and the brake coil 11 is almost not energized. In such a state, it can be said that the position of the brake disc 5 is not determined because there is a gap in the thrust direction. In this state, when a position signal for stopping is generated from the position detector (hereinafter referred to as a stop position signal), the brake coil 11 is energized to full voltage, and the sewing machine decelerates and stops as described above. But,
In this process, since the position of the brake disc 5 at the time when the above-mentioned stop position signal is generated is not determined, the travel time corresponding to the maximum gap appears as the largest variation, which significantly deteriorates the stopping accuracy. This is a contributing factor. In addition, it is considered necessary to shorten the time from when the stop position signal is generated until the sewing machine stops (hereinafter referred to as the "verification time") as much as possible in order to improve stopping accuracy. 1. Further increase the magnetomotive force of the brake coil.

2. To reduce the inductance of the brake coil current and shorten the rise time of the current.

There are two possibilities, but both of them lead to an increase in the price of the brake coil or its drive circuit, and are not a good idea. On the other hand, as a different problem from the above, in conventional products, a difference occurs in the brake force due to changes in the excitation current of the brake coil due to increases or decreases in the power supply voltage, etc.
This has the disadvantage that the stop position moves according to the power supply voltage.

In other words, if the power supply voltage increases, the brake force will increase and the vehicle will stop at a position closer to you than usual.
In the opposite case, the slippage will be even greater and the vehicle will stop at a later position than usual. As mentioned above, particularly regarding the needle stop position after the thread trimming process, high precision is required in order to prevent risks such as needle breakage due to interference between the thread wiper and the sewing machine needle. The current situation is that nothing complete has been provided yet. The present invention eliminates the above-mentioned drawbacks of the conventional art, provides a high stopping precision, and is inexpensive.

Embodiments of the present invention will be described below with reference to the block diagram shown in FIG.

In addition, in this embodiment, the application is applied to a sewing machine model in which the thread trimming solenoid is driven during the period from when the thread trimming command signal is generated and the sewing machine is driven until the sewing machine stops (i.e., thread trimming step). It is stated as follows. In Figure 2, 2
1 is a speed generator attached to the sewing machine head and detects the sewing machine speed; 22 is a first position signal (hereinafter referred to as needle down position signal) corresponding to the needle down position and used to start the thread trimming process; a position detector which generates a second position signal (hereinafter referred to as needle up position signal) corresponding to the position and for terminating the thread trimming process; 23, a thread trimming command circuit which generates a signal to start the thread trimming process; 24; 25 is a speed control circuit; 25 is a waveform shaping circuit for shaping the signal from the speed generator 21 into a rectangular wave; 26 is a waveform shaping circuit for measuring the period of the rectangular wave from the waveform shaping circuit 25; An acceleration/subtraction judgment circuit for determining acceleration or deceleration by comparison with the measurement cycle;
27 is a thread trimming load reduction detection circuit for detecting a reduction in thread trimming load based on the judgment signal of the acceleration/deceleration judgment circuit 26;
28 is a thread cutting drive circuit.

Furthermore, 29, 30, 31 each indicate a driver circuit,
Each load of a clutch coil 32, a brake coil 33, and a thread trimming solenoid 34 is connected to each driver circuit. The operation of the sewing machine drive system configured as described above is performed as follows. First, when a thread trimming command signal is output from the thread trimming command circuit 23, the speed control circuit 2
4 outputs the clutch coil 32 or the BRl signal via the driver circuit 29 according to the actual speed signal from the speed generator 21 when the needle down position signal is generated from the position detector 22, and outputs the BRl signal to the driver. The brake coil 33 is actuated to be energized via the circuit 30, and constant low speed operation is started.

On the other hand, when the thread trimming command signal is output, the thread trimming drive circuit 28 generates a needle lower position signal in the same manner as described above, and in turn, suctions the thread trimming solenoid 34 via the driver circuit 31, and The load reduction detection circuit 27 is activated.

Here, the acceleration/deceleration determination circuit 26 is the waveform shaping circuit 25.
Measurement of the period of the actual speed signal TG from the speed generator 21 whose waveform has been shaped by Output. The thread trimming load reduction detection circuit 27, which has become active as described above, detects the time rotation input after the acceleration signal AC is in the deceleration speed state due to an increase in the thread trimming load, and outputs the BR2 signal to the driver circuit 30. However, the driver circuit 30 operates according to the power supply voltage for excitation of various solenoid by the above-mentioned BR2 signal, so that when the power supply voltage is high, a small excitation current is applied to the brake coil 33, and when the power supply voltage is low, a large excitation current is applied to the brake coil 33. do. When the sewing machine further rotates and the needle up position signal is detected, first, the thread trimming drive circuit 28 turns off the thread trimming solenoid 34 via the driver circuit 31 to complete the thread trimming operation and reduce the thread trimming load. The detection circuit 27 is inhibited from operating, and therefore the BR2 signal is inhibited, while the speed control circuit 24 turns off the clutch coil 32 and outputs the BRl signal to the brake coil 33 via the driver circuit 30. is energized to full voltage, and the sewing machine is therefore stopped, thus completing the thread cutting process.

As mentioned above, one feature of the present invention is that in the thread cutting process, the sewing machine detects the point in time when the sewing machine switches from the process of deceleration due to an increase in the thread cutting load to an acceleration state due to a decrease in the thread cutting load, and By energizing the brake coil 33 with a low current from the time of change to the end of the remaining thread cutting process, the brake disc is moved toward the brake friction disc side with a slight force, and the movement between the brake gaps as described above is performed. There are some methods that attempt to eliminate variations in the stopping position based on

The operation of the application example of the present invention described above is further shown in a time chart in FIG. 3, and a detailed explanation of the invention will be added below to the same figure.

In FIG. 3, 1 is the thread trimming command signal, 2 is the needle down position signal, 3 is the needle up position signal, 4 is the actual speed signal after waveform shaping, and 5 is the acceleration signal. 6 shows the clutch current, 7 shows the brake current, 8 shows the thread trimming solenoid suction signal, and 9 shows the time course of the sewing machine rotational speed during the thread cutting process.

First, if the thread trimming command signal ST is generated and the needle down position signal ND is generated, the thread trimming solenoid 34 is attracted, the clutch coil 32 is energized, and the sewing machine is accelerated.

When the sewing machine further accelerates and exceeds the thread trimming set speed N1, the clutch coil current is cut off, the brake coil 33 is energized, and the sewing machine is decelerated, and as the thread trimming load increases, the deceleration state is changed as shown in Section 4. maintained. When the sewing machine further rotates, the thread trimming load rapidly decreases and the sewing machine begins to accelerate, causing the actual speed signal TG after the waveform shaping to
By actually measuring the cycle and comparing it with the previous measured cycle, acceleration is detected, and an acceleration signal AC is output, and at this point the brake coil 33 is excited with a low current. Here, the bias current value to the brake coil 33 is controlled according to the power supply voltage for various solenoids. That is, in the figure, the brake coil 33 is normally as shown in 1.
When the power supply voltage is low, a low current such as 2 is excited, and when it is high, a low current is excited as shown in 3, and the clutch coil 32 is energized with a current of 1'', 2'', or 3'' corresponding to the current to the brake coil 33. In this state, when the needle up position signal Nu is detected, the clutch current is cut off, and the brake current is turned off even though the rise is quite slow due to the inductance of the coil. The final current value determined by the voltage is about to be reached, and in this process the sewing machine comes to a halt after a deadening time T1.

As mentioned above, one of the features of the present invention is that the excitation current value to the brake coil 33 is adjusted according to the change in the power supply voltage between the time when the acceleration due to the reduction of the thread trimming load is detected and the end of the thread trimming process. By automatically adjusting the brake coil current according to the change in the power supply voltage, the change in the brake coil current, especially in the rising process, during the full time T1 is absorbed, and the variation according to the full time T1 is adjusted. It tries to keep the angle constant,
The value of change in the excitation current value of the brake coil 33 is determined experimentally by adding a circuit that allows the above-mentioned angle to be as limited as possible with respect to changes in the power supply voltage.

Here, a specific circuit example of the driver circuit 30 in FIG. 2 is shown in FIG. 4, and a detailed explanation of the invention will be added below with reference to the same figure.

As mentioned above, this circuit attempts to automatically adjust the excitation current of the brake coil 33 according to the power supply voltage. In FIG. 4, one side of the brake coil BRK is connected to the DC power supply voltage +■, and in normal operation, it is controlled only via the transistor TRl by the BRl signal from the speed control circuit 24, and the transistor TR2 is in a cut-off state. As described above, after the acceleration due to the reduction of the thread cutting load is detected, in addition to the control based on the transistor TR1, control based on the front tracking R2 signal is performed. The BR2 signal changes the potential at point a from "L" to open via the open collector buffer ICl, and activates the low current excitation circuit to the brake coil 33.The operation of the low current excitation circuit will be described below.

First, the potential at point b is fixed at a constant potential by the resistor t/LRl and the voltage regulator diode ZD, and the potential at point C takes the value obtained by dividing the power supply voltage +■ by R2 and R3. The potential is proportional to the power supply voltage +V, and the point c is connected to the base of the transistor TR3, and the transistor T
Due to the circuit of R3 and resistors R4 and R5, the potential at point a becomes lower when the potential at point c rises, and becomes higher when the potential at point c rises.

The above point a is connected to the base of the transistor TR2, and the above point a is connected to the base of the transistor TR2.
A current according to the potential at the point flows through the brake coil BRK. In other words, the above operation is performed when the power supply voltage +■
Detecting the rise (fall) of , the collector voltage of the transistor TR3 is lowered (raised), and the excitation current to the brake coil BRK is decreased (increased) by the transistor TR2. Next, at the time when the needle up position signal is detected, the BR2 signal disappears and the transistor TR
2 is cut off and + is applied to the brake coil BRK.
■The full voltage will be applied and the sewing machine will stop.

An embodiment of the present invention has been described above, and as is clear from this, the present invention is capable of reducing the thread trimming load from the deceleration state of the sewing machine rotation speed due to an increase in the thread trimming load in the thread trimming process. The brake disc is brought into contact with the brake friction disc by detecting the switching point to the acceleration state due to the decrease and applying low current excitation to the brake coil during the section from the detection point to the end of the thread cutting process. ) to prevent variations in the final stop position due to variations in the position of the brake disc, and to prevent variations in the final stop position due to variations in the position of the brake disc. This is intended to improve the accuracy of the stop position of the needle by automatically adjusting the excitation current value to cancel out the fluctuations in the brake force caused by fluctuations in the power supply voltage. As mentioned above, according to the present invention, compared to the conventional one,
By adding the wasca circuit, the accuracy of stopping the needle position after the thread cutting process is greatly improved, and therefore an inexpensive and high-performance product can be provided, and its effects are extremely large.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of an electromagnetic coupling section in a conventional sewing machine control device, Fig. 2 is a block diagram according to an embodiment of the present invention, Fig. 3 is a time chart showing the operation of the present invention, and Fig. 4 is a FIG. 2 is a circuit diagram showing a specific configuration of a brake coil driver circuit. 21...Speed generator, 22...Position detector, 23...Thread trimming command circuit, 24...Speed control circuit, 26...Acceleration/deceleration determination circuit , 27...
...Thread trimming load reduction detection circuit, 28... Thread trimming drive circuit, 29, 30, 31... Driver circuit, 32... Clutch coil, 33...・
・Brake coil, 34...Thread trimming solenoid.

Claims (1)

[Claims] 1 A sewing machine having a thread trimming device with a built-in thread trimming solenoid, a sewing machine shaft, and a first position signal that rotates with the sewing machine shaft and that corresponds to the needle down position and a second position signal that corresponds to the needle up position. a clutch motor that includes a clutch coil and a brake coil and changes the speed of an output shaft by magnetic coupling thereof; a thread trimming command means that outputs a thread trimming command signal; A first transistor is arranged in parallel with the first transistor, and its base is set such that one inputs the power supply voltage for driving the brake coil and the output signal shifts in the opposite direction in response to a change in the input voltage. control means including a brake bias means having a second transistor connected to the output end of the amplifier circuit and the other end connected to the output end of a buffer which inputs the brake bias signal; a speed detector that outputs an actual speed signal, and acceleration/deceleration determining means that determines acceleration/deceleration of the sewing machine by measuring a period of the speed signal, and the control means controls the clutch according to the thread trimming command signal. The brake coil is energized by the coil or the first transistor to drive the sewing machine at a low speed, and the thread trimming solenoid is energized by the generation of the first position signal, and the acceleration/deceleration determining means When measurement of acceleration/deceleration of the sewing machine is started and the state is changed from a deceleration state to an acceleration state, the brake bias signal is turned on, and the control means opens the output end of the buffer based on the brake bias signal, and the amplifier circuit The second transistor energizes the brake coil with a low current based on the output signal of the second transistor, and upon generation of the second position signal, the thread trimming solenoid is deenergized, the clutch coil is turned off, and the first transistor is turned off. on,
and a sewing machine control device configured to stop the sewing machine by turning off the brake bias signal.