JPS6044956B2 - 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 position of a sewing machine needle, and a position detector for driving the sewing machine head. In a sewing machine drive system that mainly includes a motor that rotates, a clutch and brake coil that transmits the rotational force of the motor to the sewing machine, and a magnetic coupling section that connects with a magnetic circuit and has a braking mechanism, The purpose of this invention is to improve the precision with which the sewing machine needle is stopped at a certain position by effective speed control means based on the control of the clutch and brake coil in the cutting process.

A conventional example of this type of sewing machine needle positioning method will be described below.

FIG. 1 shows the structure of an electromagnetic clutch motor, especially the magnetic coupling part, as an example of a motor for carrying out the above-mentioned control J. Hereinafter, the speed control method and the sewing machine needle will be explained according to the same figure. This section describes the final positioning method. In FIG. 1, a clutch friction disk 1 is fixed to a flywheel 2 of a motor and constantly rotated by the motor.

On the other hand, the brake friction disk 3 is fixed on the load side (stationary side). A clutch lining 6 and a brake lining 7 are attached to the clutch disk 4 and the brake disk 5, respectively, and these are attached to a spline 9 fixed to a clutch shaft 8 in a structure that is independent of each other and movable in the thrust direction. ing. 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 includes a pulley,
It is connected to the sewing machine's crankshaft via a belt. In the magnetic coupling section configured as described above, when a thread trimming command signal is generated, for example, based on a signal of depressing a pedal of a sewing machine, 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 by sliding on the disk 1 of the clutch lining 6 according to the excitation current value of the clutch coil, and the male spline 9 of the clutch disk is transferred. The clutch shaft 8 is driven through the clutch shaft 8, and the crankshaft of the sewing machine head, which is connected to the clutch shaft 8 through the pulley belt, begins to rotate. Normally, in the thread cutting process, the sewing machine is set to a low speed, and until the set speed is reached, the sewing machine is accelerated according to the excitation force of the coupling section as described above, and when the rotational speed further increases beyond the set speed, the sewing machine Coil 10 is turned off,
The brake coil is energized and its magnetic circuit. The brake disc 5 moves toward the brake friction disc 3 and the brake lining 7 is brought into pressure contact with the disc 3, thereby decelerating the clutch shaft 8 via the brake disc 5 and the spline 9. As mentioned above, the rotation of the sewing machine head accelerates and decelerates. However, in a stable rotational state at a constant set speed, operation is maintained by energizing almost only the clutch coil, and the brake coil is almost not energized.

Therefore, in such a state, it can be said that the position of the brake disc 5, which is movable on the spline, cannot be determined because there is a gap in the thrust direction of the spline. In such a 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 excited by the full voltage of the power supply, and the sewing machine is decelerated and stopped as described above, but in this process, at the time when the stop position signal is generated, there is no position on the spline of the brake disc 5. Since the position is not fixed, the travel time corresponding to the maximum gap with the brake friction disk 3 appears as the largest variation during braking, and is a factor that significantly deteriorates stopping accuracy. Furthermore, in order to improve stopping accuracy, it is necessary to make the time it takes for the sewing machine head to stop after the stop position signal is generated (hereinafter referred to as the "verification time") as short as possible.

As a countermeasure for this, (1) further increase the magnetomotive force of the brake coil. (2) Reduce the current inductance of the brake coil 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 control unit, and are not a good idea. On the other hand, as a problem different from the above, in the conventional example, a difference occurs in the braking force due to changes in the excitation current of the brake coil due to fluctuations such as increases or decreases in the power supply voltage, and the stopping position moves according to the above power supply voltage. It had the disadvantage of causing

In other words, if the power supply voltage increases, the braking force will increase and you will stop at a position closer to you than usual, and in the opposite case, the slack will increase even more and you will stop at a position further back than usual. It will be stopped at . As mentioned above, high precision is required, especially regarding the needle stop position after the thread trimming process, 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 a complete version is not provided.

The present invention eliminates the above-mentioned drawbacks of the conventional sewing machine and provides a control device for a sewing machine that has high stopping accuracy and is inexpensive.

Hereinafter, embodiments of the present invention will be described according to the block diagram shown in FIG.

Note that this example is applicable to sewing machine models 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., 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 generates a first position signal (hereinafter referred to as needle down position signal) for starting the thread trimming process. ) and a second position signal (
(hereinafter referred to as the needle top position signal), and
2 shows a thread trimming command circuit that generates a signal to start thread trimming.

23 is a speed control circuit, 24 is a brake bias circuit that applies a low bias current to the brake coil for only one section,
Reference numeral 25 indicates a circuit for driving the thread cutting solenoid.

Furthermore, 26, 27, and 28 are each clutch coil 1
0, a brake coil 11, and a thread trimming solenoid 12 are connected as loads to a drive control section (hereinafter referred to as a driver) that drives and controls the loads. The operation of the sewing machine drive system configured as described above is 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 10 via the driver 26 if the needle down position signal is generated from the position detector 21. Alternatively, it outputs a braking BRl signal, operates to excite the brake coil 11 via the driver 27, and starts constant low-speed operation.

On the other hand, when the thread trimming command signal is output, the thread trimming solenoid drive circuit 25 attracts the thread trimming solenoid 12 via the driver 28 if the needle down position signal is generated as described above.

From this thread cutting drive state, the position detector 2
When the needle up position signal is generated from 1, at this point the brake bias circuit 24 outputs a BR2 signal for braking,
The driver 27 is operated by the BR2 signal to apply a small excitation current to the brake coil 11 when the voltage is high, and to apply a large excitation current to the brake coil 11 when the voltage is low, depending on the various solenoid excitation power supply voltages. Further, when the sewing machine rotates and the needle up position signal passes, first the drive circuit 25 of the thread trimming solenoid is connected to the driver 28.
The brake bias circuit 24 operates to turn off the thread trimming solenoid 12 and terminate the thread trimming operation via the brake bias circuit 24.
inhibits the BR2 signal, and the speed control circuit 23 turns off the clutch coil 10 and outputs the BR1 signal, which excites the brake coil 11 via the driver 27 with full voltage and current. Therefore, the sewing machine is stopped, thus completing the thread cutting process. As mentioned above, one feature of the present invention is that by exciting the brake coil with a low current for a certain period immediately before the end of the thread cutting process, the brake disc can be moved toward the brake friction disc side with a small force. This eliminates the variation in the stopping position due to the movement between the brake gaps as described above, and the excitation section of the brake coil lasts until the maximum travel time and speed of the brake disc stabilize at a constant speed. Determined by adding the time. The operation of the embodiment of the present invention described above is further shown in a time course diagram in FIG. 3, and a detailed explanation of the invention will be added to the same figure below.
In Fig. 3, ST is the thread trimming command signal, ND is the needle down position signal, NU is the needle up position signal, CL is the clutch current, BR is the brake current, and TR is the thread trimming solenoid. R indicates the suction signal, and R indicates 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, a current flows to the clutch coil.
As soon as the sewing machine starts rotating, the thread trimming solenoid is sucked.

Further, when the sewing machine accelerates and exceeds the thread trimming set speed N1, the clutch coil current is cut off, current flows to the brake coil, and the sewing machine decelerates. Note that part A in the figure represents a decrease in speed due to an increase in the mechanical load on the thread cutting device. The sewing machine further rotates and the needle top position signal N
When U occurs, the brake coil is normally excited by a low current as shown in 1 in the same figure, 2 if the power supply voltage is low, and 3 if the voltage is high, and the clutch coil is excited by the above brake coil current. Correspondingly, currents such as 1'', 2'', and 3'' are applied to try to maintain the set thread cutting speed N1.

At the point when the upper position signal NU passes from this state, the clutch current is cut off, and the brake current tries to reach the final current value determined by the power supply voltage, although the rise is quite slow due to the inductance of the coil. In such a process, the sewing machine will stop after the threading time T1. As mentioned above, one feature of the present invention is that
By automatically adjusting the excitation current value of the brake coil in a certain section before the sewing machine stops, such as the needle top position signal generation section, in response to changes in the power supply voltage, the excitation current value is automatically adjusted in response to changes in the power supply voltage. The above-mentioned completion time T1
This is intended to absorb changes in the brake coil current, especially in the rising process, and to maintain a constant angle of overflow according to the overflow time T1.

The change value of the excitation current value of the brake coil is experimentally determined by adding a circuit that makes the above-mentioned overburden angle a limited constant with respect to the change in the power supply voltage. Here, a specific circuit example of the driver 27 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 according to the power supply voltage.

In FIG. 4, one end of the brake coil BRK is connected to the DC power supply voltage +■, and normally it is controlled only via the transistor TRl by the BRl signal from the speed control circuit, and the transistor TR2 is in a cut-off state. ing. Next, as described above, in the generation section of the needle up position signal, the BR2 signal is output from the brake bias circuit, and the BR2 signal is output from the brake bias circuit.
The signal is passed through the open collector buffer ICl and is opened from the potential ゜゜L'' at point a, activating the low current excitation circuit to the brake coil. The operation of the above-mentioned low current excitation circuit will be described below.

First, the potential at point b is determined by the resistance R1 and the constant voltage diode ZD.
The potential at point c takes the value obtained by dividing the power supply voltage +V by R2 and R3, and is therefore proportional to the power supply voltage +■. The point c is connected to the base of the transistor TR3, and the point c is connected to the base of the transistor TR3.
Due to the circuit of R3 and the 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 transition. The brake coil BRK is connected to the base of the brake coil BRK, and is connected to the base of the brake coil BRK by a circuit including the transistor TR2 and the resistor R6.
will flow. That is, the above operation first detects an increase (decrease) in the power supply voltage +V, decreases (increases) the collector potential of the transistor TR3, and reduces the collector potential of the transistor TR2.
As a result, the excitation current to the brake coil BRK is decreased (increased). Next, when the needle up position signal passes, the BR2 signal disappears, the transistor TR2 is cut off, and the BRl signal turns on the transistor TRl, causing the brake coil BRK to
A total voltage of V is applied and the sewing machine stops. An embodiment of the present invention has been described above, but as is clear from the above, the present invention provides the following advantages: By applying low current excitation to the brake coil and moving the brake disc so as to be in contact with the brake friction disk, it is possible to prevent variations in the final stop position due to variations in the position of the brake disc, and also to prevent This is based on the idea of increasing the accuracy of the stop position of the needle by automatically adjusting the excitation current value in a direction that cancels out the fluctuations in the brake force caused by fluctuations in the power supply voltage. As described above, according to the present invention, by adding a small amount of circuitry compared to the conventional one, the needle positioning accuracy after the thread cutting process is greatly improved, and therefore, an inexpensive and high-performance sewing machine is provided. It is something that can be done.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the structure of the magnetic coupling part, Figure 2 is a cross-sectional view showing the structure of the magnetic coupling part.
The figure is a block diagram of a control device in an embodiment of the present invention,
FIG. 3 is a time course diagram showing the operation of the device of the present invention, and FIG. 4 shows a specific circuit of the brake coil drive control section. 10...Clutch coil, 11...Brake coil, 12...Thread trimming solenoid, 21
...position detector, 22 ... thread trimming command circuit, 23 ... speed control circuit, 24 ... brake bias circuit, 25 ... thread trimming solenoid Drive circuit, 26, 27, 28... Drive control section.

Claims (1)

[Claims] 1 A sewing machine equipped with a thread trimming device incorporating a thread trimming solenoid, a sewing machine shaft, and a first position signal that rotates together 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 that changes the speed of an output shaft by magnetic coupling thereof; a thread trimming command means that outputs a thread trimming command signal; and a thread trimming command means that drives the brake coil. A first transistor is arranged in parallel with the first transistor, the base of which is connected to the drive power supply voltage of the brake coil, and the output voltage shifts in the opposite direction in response to a change in the input voltage. At the output end of an amplifier circuit such as
The other is equipped with a control means including a brake bias means having a second transistor connected to an output end of a buffer that receives a brake bias signal, and the control means controls the clutch coil according to the thread trimming command signal. Alternatively, the brake coil is energized by the first transistor to drive the sewing machine at a low speed, the thread trimming solenoid is energized by the generation of the first position signal, and the second
Upon generation of the position signal, the brake bias signal is turned on to open the output end of the buffer, and the second transistor energizes the brake coil with a low current based on the output signal of the amplifier circuit. A control device for a sewing machine that deenergizes the thread trimming solenoid, turns off the clutch coil, and turns on the first transistor to stop the sewing machine when a position signal passes.