JPS6242473B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a malfunction prevention circuit for a control circuit of an electronic sewing machine.

Electronic sewing machines have also recently become more multi-functional.
For example, when basting, use the foot controller 1
If you press the button twice, the sewing machine will start at 1 regardless of how long you press the button.
They are starting to have functions such as rotation. In order to achieve these functions, it depends on an electronic control circuit, and many flip-flop circuits are used in the control circuit.

Figure 1 is a block circuit diagram showing a conventional example of a control circuit for such an electronic sewing machine, in which 1 is an AC power supply, 2 is
3 and 4 are a field coil and an Amachia coil that constitute the universal motor 2, respectively, 5 is a thyristor unit that drives the universal motor 2, 6 is a trigger circuit that triggers the thyristor of the thyristor unit 5, and 7 is an Amathia coil 4. 8 is a drive circuit for the brake thyristor 7, 9 is a foot controller, and 10 outputs an output signal when the needle of the sewing machine is in the upper or lower position. A needle position detection circuit 11 sends a required signal to the trigger circuit 6 of the thyristor unit 5 or the drive circuit 8 of the brake thyristor 7 according to signals from the foot controller 9, the needle position detection circuit 10, etc., and adjusts the rotation speed of the sewing machine. This is a control circuit with a built-in flip-flop that performs control and braking. Note that the needle position detection circuit 10 usually includes a magnet attached to the main shaft (not shown) of the sewing machine and a reed relay or Hall element attached to the main body.

FIG. 2 is a waveform diagram of each part for explaining the operation of the device shown in FIG. 1. First, when the foot controller 9 is turned on, a signal is sent from the control circuit 11 to the trigger circuit 6, which operates and As shown in FIG. 2d, a trigger signal synchronized with the power supply is sent to the thyristor unit 5. Therefore, the thyristor unit 5 conducts at a predetermined phase angle and drives the universal motor 2. When the universal motor 2 starts rotating, the main shaft of the sewing machine connected to the motor 2 rotates, and each time the sewing machine needle passes a predetermined stop position, the needle position detection circuit 10 operates, and the second
As shown in Figure b, a low ("L") level signal is output.
When the foot controller 9 is turned off in this rotating state, its output signal goes to the "L" level as shown in FIG. 2a.
The sewing machine is still rotating, and when it reaches a predetermined stop position, the brake thyristor is activated from the control circuit 11 in response to the "L" level signal from the foot controller 9 and the "L" level signal from the needle position detection circuit 10. A brake signal as shown in FIG. 2C is sent to the drive circuit 8. During the high (“H”) level of this brake signal, the brake thyristor 7
conducts, the brake is applied to the universal motor 2, and the sewing machine decelerates. However, if you overrun the predetermined stopping angle, the brake signal will disappear;
The sewing machine is driven again at a gentle speed. When the needle reaches the designated stop position again, the brakes are applied to the sewing machine in the same way as before. Since the sewing machine has already decelerated considerably before this second brake, the second brake stops the sewing machine at a predetermined needle stop position, and the output of the needle stop position detection circuit 10 is as shown in FIG. 2b. It remains at L” level. However, even in this case, the universal motor 2
In order to avoid burning out the brake thyristor 7.
is controlled by a control circuit 11 so that it operates only for a certain period of time.

By the way, the control circuit 11 in the conventional circuit shown in FIG. 1 has a built-in flip-flop circuit, and in devices such as sewing machines that cannot be grounded, the flip-flop circuit of the control circuit 11 may malfunction due to static electricity, causing the foot controller 9 to malfunction. The sewing machine may rotate once even when the is off.

This invention has been made in view of the above points, and the output of the foot controller 9, the output of the needle position detection circuit 10, and the brake signal are logically ANDed, and the trigger circuit 6 of the thyristor unit 5 is activated whenever the sewing machine is stopped. The purpose of this invention is to eliminate the drawbacks of the conventional circuit by stopping the operation of the circuit.

FIG. 3 is a block circuit diagram showing an embodiment of the present invention, in which parts equivalent to those of the conventional example shown in FIG. In the figure, reference numeral 12 denotes a static electricity malfunction prevention circuit, which takes the AND of the output of the foot controller 9, the output of the needle position detection circuit 10, and the brake signal from the control circuit 11, and sends the output to the trigger circuit 6a. The output of the trigger circuit 6a is controlled by the AND output.

As can be seen from the waveform diagram in FIG. 2, when the sewing machine is stopped, the output signal of the foot controller 9, the output signal of the needle position detection circuit 10, and the brake signal to the brake thyristor drive circuit 8 are all "L".
It's on the level. Moreover, both of these three signals are at the "L" level only when the sewing machine is stopped. Therefore, if the logical product of these three signals is taken and the sending of the trigger signal from the trigger circuit 6a is inhibited when all three signals are at "L" level, the above-mentioned erroneous rotation can be avoided. can be prevented.

If the needle stop position is only at top dead center, for example, it is sufficient to use one AND circuit to logically multiply the three signals as in the embodiment shown in Fig. 3, but if the needle stop position is only at top dead center, For a type in which one of the modes is arbitrarily selected at the bottom dead center, an electrostatic malfunction prevention circuit as shown in FIG. 4 may be used.
FIG. 4 shows an example in which all the circuits are NOR circuits, and it is well known that an equivalent circuit can be constructed using other logic elements. In the figure, 2
1 to 24 are all NOR circuits, 25 is a transistor, and 26 is a trigger capacitor. A is the upper position stop mode selection signal, B is the upper position detection circuit output, C is the lower position stop mode selection signal, D is the lower position detection signal, E is the brake signal, and F is the foot controller output signal.

As detailed above, in this invention, an electrostatic malfunction prevention circuit having no internal memory element such as a flip-flop is constructed, and the trigger signal to the thyristor for driving the sewing machine motor is forcibly blocked when the sewing machine is stopped. Therefore, the thyristor control circuit includes a flip-flop circuit, and even if this circuit malfunctions due to static electricity, the sewing machine will not rotate incorrectly. Therefore, the margin against power supply noise and radiation noise of the sewing machine is increased, and restrictions on circuit board patterns, wiring, etc. are relaxed. Moreover, this malfunction prevention circuit is composed of simple gates and can be easily integrated into an integrated circuit (IC).If it is integrated into an IC together with other control circuits, it can be realized virtually without any space or cost burden.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing a conventional electronic sewing machine control circuit, FIG. 2 is a waveform diagram of each part to explain its operation, FIG. 3 is a block circuit diagram showing an embodiment of the present invention, and FIG. 4 FIG. 2 is a circuit diagram showing only a malfunction prevention circuit section according to another embodiment of the present invention. In the figure, 1 is an AC power supply, 2 is a universal motor (sewing machine motor), 4 is an Amachia coil,
5 is a thyristor unit, 6 and 6a are trigger circuits, 7 is a brake thyristor, 8 is a brake thyristor drive circuit, 9 is a foot controller,
10 is a needle position detection circuit, 11 is a control circuit, 12 is a static electricity malfunction prevention circuit (gate circuit), and 21 to 24 are NOR circuits forming this static electricity malfunction prevention circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1 A sewing machine motor connected to an AC power supply, a thyristor unit that drives and controls the sewing machine motor,
A trigger circuit that triggers the thyristor of this thyristor unit, a brake thyristor connected between both ends of the Amachia coil of the sewing machine motor,
A brake thyristor drive circuit that drives the brake thyristor, a foot controller that controls the rotation speed of the sewing machine motor, a needle position detection circuit that outputs an output when the sewing machine needle is at a predetermined stop position, the foot controller and the needle position. An electronic sewing machine control circuit including a control circuit that receives a signal from a detection circuit and sends a necessary signal to the trigger circuit and the brake thyristor drive circuit, and has a built-in flip-flop circuit,
A gate circuit is provided that outputs an output only when there is no output signal from the foot controller, there is an output signal from the needle position detection circuit, and there is no input signal to the brake thyristor drive circuit. An electronic sewing machine control circuit characterized in that the operation of the trigger circuit is stopped.