JPS6044957B2 - sewing machine control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention includes a sewing machine head incorporating a 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 has a motor for the purpose of the sewing machine, a clutch/brake coil for transmitting the transmission force of the motor to the sewing machine, and an electromagnetic coupling mechanism using a magnetic circuit, lining, etc., 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 system will be described below. Figure 1 shows the structure of an electromagnetic clutch/motor, particularly an electromagnetic coupling, 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). fly foil 2
The brake friction disk 3 is fixed on the stationary side and constantly rotates due to the drive of the motor. A clutch lining 6 and a brake lining 7 are attached to the clutch disc 4 and the brake disc 5, respectively, and these are attached to a spline 9 fixed to a clutch shaft 8.
The structure is such that the upper part can be moved independently in the thrust direction. 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, when a thread trimming command signal is generated, for example, based on a signal of pressing down on a sewing machine pedal, the clutch coil 10 is energized, and the clutch disk 4 is energized by the magnetic circuit. moves to the clutch friction disk 1 side, and 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 is transmitted to the clutch via the clutch disk 4 and splines 9. axis 8
is driven, and the sewing machine connected to the clutch shaft 8 via a pulley and a 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 it reaches the set speed. When the rotational speed further increases beyond the set speed, the clutch coil 10 is turned off and the brake coil 11 is energized, the brake disc 5 is moved toward the brake friction disc 3 by the magnetic circuit, and is brought into pressure contact with the surface of the brake lining 7, thereby decelerating the clutch shaft 8 via the brake disc 5 and the spline 9. Become. As described above, acceleration and deceleration are performed, but when the set speed is stable, only the clutch coil 10 is energized to maintain operation, 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 fixed because there is a gap in the thrust direction. In this state, when a position signal for stopping (hereinafter referred to as a stop position signal) is generated from the position detector, the brake coil 11 is energized to full voltage, and the Mitashin is decelerated and stopped as described above. However, 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 greatest variation, and the stopping accuracy is significantly reduced. It is causing the deterioration of the 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 stop time) as much as possible in order to improve stopping accuracy. As a measure, further increase the magnetomotive force of 1 brake coil.

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

The following two points are possible, 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, a different problem from the above is that in conventional products, a difference occurs in the brake force as the excitation current of the brake coil changes due to an increase or decrease in the conduction voltage, and the stopping position moves according to the power supply voltage. It had the disadvantage that it would cause problems.

In other words, if the power supply voltage increases, the brake force will increase and the vehicle will stop at a position earlier than usual, and in the opposite case, the brake force will increase even more and the vehicle will stop at a position later than usual. As mentioned above, especially 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 removal device and the sewing machine needle. However, the current situation is that a perfect one has not yet been provided.The present invention solves the above-mentioned conventional drawbacks, provides a high stopping precision, and provides an inexpensive one.

Embodiments of the present invention will be described below with reference to the block diagram shown in FIG. In the embodiment, the application is applied to a sewing machine model in which the intermediate thread trimming solenoid is driven from when the thread trimming command signal is generated and the sewing machine is driven until the sewing machine stops (i.e., during the thread trimming process). state In Fig. 2, numeral 21 indicates a position detector for detecting the needle position of the sewing machine, which corresponds to the needle down position and is used to generate a first position signal (hereinafter referred to as needle down position signal) for starting the thread trimming process. This signal corresponds to the needle up position (hereinafter referred to as needle up position signal) and a second position signal (hereinafter referred to as needle up position signal) for ending the thread trimming process.

22 is a thread trimming command circuit that generates a signal to start thread trimming, 23 is a speed control circuit, and 24 is a circuit for driving the thread trimming solenoid and applying a low bias current to the brake coil.

Further, reference numerals 25, 26, and 27 each represent a driver circuit, and each load of a clutch coil 28, a brake coil 29, and a thread trimming solenoid 30 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 22, the speed control circuit 23 controls the clutch coil 28 via the driver circuit 25 if the needle down position signal is generated from the position detector 21. Alternatively, the brake coil 29 is actuated by outputting the BRl signal to excite the brake coil 29 via the driver circuit 26, and a constant low speed operation is started.

On the other hand, when the thread trimming command signal is output, the thread trimming drive circuit 24 attracts the thread trimming solenoid 30 via the lower liver circuit 27 if the needle down position signal is generated as well as the BR2 signal. is output to the driver circuit 26, and the driver circuit 26 uses the BR2 signal to output a small excitation current when the power supply voltage is high, and a large excitation current when the power supply voltage is low, according to the power supply voltage for excitation of the various solenoids. , operates to apply to the brake coil 29.

When the sewing machine further rotates and the needle up position signal is detected, the thread trimming drive circuit 24 first turns off the thread trimming solenoid 30 via the driver circuit 27 to end the thread trimming operation and disable the BR2 signal. However, on the other hand,
The speed control circuit 23 turns off the clutch coil 28 and outputs the R1 signal to energize the brake coil 29 to full voltage via the driver circuit 26, thus stopping the sewing machine. Finish the thread cutting process. As mentioned above, one feature of the present invention is that by energizing the brake coil 29 with a low current during the thread cutting process,
The brake disc is moved toward the brake friction disc 3 side with a slight force to eliminate the variation in the stopping position caused by the movement between the brake gaps as described above.

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 clutch current, 5 is the brake current, and 6 is the thread trimming signal. 7 shows the solenoid suction signal, and 7 shows the time course of the sewing machine rotation speed in 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 30 is attracted, the brake coil 29 is energized with a low current, and the clutch coil 28 is energized. The sewing machine starts the circuit.

When the sewing machine further accelerates and exceeds the thread trimming set speed N1, the clutch coil current is cut off and the speed control circuit 2
Based on the BR signal from 3, the brake coil current increases and the sewing machine decelerates. Incidentally, part 3 represents a decrease in speed due to an increase in the mechanical load on the thread cutting device. As mentioned above, the speed control during the thread cutting section is
This is done by controlling the clutch coil 28 according to the speed control circuit 23 or controlling the brake coil 29 based on the R1 signal while the brake coil 29 is excited with a low current by the BR2 signal.

Here, the bias current value to the brake coil 29 is controlled according to the power supply voltage for various solenoids.

That is, in the same figure, the brake coil 29 normally has 1
2 when the power supply voltage is low and 3 when it is high, and the clutch coil 28 is excited with a low current of 1'', 2'', and 3'' for the current to the brake coil 29.
A current is applied to maintain the set thread cutting speed N1. Is this the state?The needle up position signal N
At the moment u is detected, the clutch current is cut off, and the brake current is caused by the inductance of the coil, and even though it rises slowly, it tries to reach the final current value determined by the power supply voltage.In this process, the sewing machine It will stop after a slip time T.

As mentioned above, one of the features of the present invention is that the excitation current value to the brake coil 29 during the thread cutting process is automatically adjusted in accordance with the change in the power supply voltage, so that the excitation current value is automatically adjusted in accordance with the change in the power supply voltage. The purpose is to absorb the change in the brake coil current, especially in the rising process, during the berthing time T1 described above, and to keep the burr angle constant according to the burr time T1, and to excite the brake coil 29. The change value of the current value is determined experimentally by adding a circuit that allows the above-mentioned angle to be as limited as possible with respect to the change in the power supply voltage.

Here, a specific circuit example of the driver circuit 26 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, some circuits attempt to automatically adjust the excitation current of the brake coil 29 according to the power supply voltage. In FIG. 4, one end of the brake coil BRK is connected to the DC power supply voltage +V, and during sewing other than the thread trimming process, the brake coil BRK is connected to the BRl from the speed control circuit 23.
controlled only via transistor TRl by a signal;
Transistor TR2 is in a cut-off state. As described above, during the thread cutting process, in addition to the control based on the transistor TR1, control is performed based on the BR2 signal. The BR2 signal opens the potential at point a from ゜゜L゛ via the open collector buffer ICl, and activates the low current excitation circuit to the brake coil 29. The operation of the above-mentioned low current excitation circuit will be described below.

First, the potential at point b is low resistor R1 and constant voltage diode ZD.
The potential at point c is fixed to a constant potential, and the potential at point c takes the value obtained by dividing the power supply voltage +V by R2 and R3.Therefore, the potential at point c is proportional to the power supply voltage +■. 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 the point a becomes lower when the potential at the point c rises, and becomes higher when the potential at the point c rises.

The above point a is connected to the base of the transistor TR2, and the circuit of the transistor TR2 and the low resistor R6 allows a current according to the potential of the above point a to flow through the brake coil BRX.
will flow. In other words, the above operation first detects the rise (fall) of the power supply voltage +■, lowers (raises) the collector potential of the transistor TR3, and
2, the excitation current to the brake coil BRK is decreased (increased). Next, at the time when the needle up position signal is detected, the BR signal disappears, the transistor TR2 is cut off, and the transistor TRl is turned on by the front signal R1, and the brake coil B
A total voltage of 10 V is applied to RK, and the sewing machine stops.

As is clear from the above description, the present invention moves the brake disc so as to be in contact with the brake friction disk by applying low current excitation to the brake coil during the thread cutting and glueing process section, and In addition to preventing variations in the final stop position due to variations in position,
The purpose is to improve the accuracy of the needle stop position by automatically adjusting the excitation current value to the brake coil in a direction that cancels out changes in the brake force due to changes in current and voltage.

As described above, according to the present invention, the accuracy of stopping the needle position after the thread cutting process is significantly improved by adding a small amount of circuitry compared to the conventional one, and therefore, an inexpensive and high-performance product is provided. It can be done, and the effects are extremely large.

Brief Description of the Drawings 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, and Fig. 3 is a time chart showing the operation of the present invention. , FIG. 4 is a circuit diagram showing a specific configuration of a brake coil driver circuit.

21...Position detector, 22...Thread trimming command circuit, 23...Speed control circuit, 24...
・Low bias current supply circuit, 25, 26, 27...
...Driver circuit, 28...Clutch coil, 29...Brake coil, 30...
・Thread cutting 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 one of the bases is connected to the drive power supply voltage of the brake coil, and the output signal is displaced in the opposite direction in response to a change in the input voltage. control means including brake bias means at the output of the amplifier circuit and a second transistor sustained at the output of a buffer which receives the brake bias signal; The sewing machine is driven at a low speed by energizing the clutch coil or the brake coil by the first transistor in response to a command signal, and the thread trimming solenoid is energized and the brake bias is energized by generation of the first position signal. turning on a signal to open the output end of the buffer, and energizing the brake coil with a low current through the second transistor based on the output signal of the amplifier circuit;
Generation of the second position signal deenergizes the thread trimming solenoid, turns off the clutch coil, and deactivates the first position signal.
A sewing machine control device configured to turn on a transistor to stop the sewing machine.