JPS5836596B2 - Automatic control device for electric sewing machines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic leg device for an electric sewing machine, and particularly to an electric sewing machine that uses a series commutator motor (universal motor) to position a sewing needle at a fixed position such as top dead center or bottom dead center. The present invention relates to an automatic control device for stopping the operation.

Traditionally, electric motors use a universal electric motor as the drive source. Shin is put into practical use.

1. Generally, when basting (or basting),
The stitch spacing is increased.

Therefore, in order to enable basting stitches in such an electric sewing machine, it is necessary to park an arbitrary intermediate sewing needle at a predetermined position (preferably near the top dead center).

SUMMARY OF THE INVENTION Therefore, a primary object of the present invention is to provide an automatic control device for an electric sewing machine that can reliably stop a sewing needle at a predetermined position during basting, for example.

In summary, the present invention provides a method for detecting when the sewing needle has reached a predetermined position, such as top dead center (or bottom dead center), to achieve the above-mentioned purpose during the basting (or basting) operation mode. This is an automatic control device for electric sewing machines that detects this and applies reverse phase braking to the universal drive motor.

The above objects and other objects and features of this invention will become more apparent from the following detailed description with reference to the drawings. It is a schematic diagram of an electric sewing machine.

According to the structure, a sewing machine arm AM that houses various mechanisms is formed on the upper surface of the thin bed BS, and further below the bed BS (or on the outside of the sewing machine arm) there is a series rectifier for driving. A child electric motor M is provided.

A belt B1 is applied to a pulley IJMP provided on the rotating shaft of the electric motor M, and the driving force from this belt B1 is transmitted to the belt B2 at a certain speed ratio via an intervening pulley.

This belt B2 is further placed around a pulley SP formed on the main shaft SH, which serves as a drive source for the various mechanisms described above, and rotationally drives this pulley, ISP, and therefore the main shaft SH.

The main shaft SH is connected to the nail bar NR via a crank CR, and drives the needle bar NR in the vertical direction in accordance with its rotation.

In addition, a sewing needle NDL is fitted into the lower end of the needle bar NR, and a bobbin thread (bobbin thread bobbin) wound around an inner hook and a bobbin is arranged below the bed BS opposite to the position of the sewing needle NDL. be done.

Therefore, the sewing needle NDL stitches the lower thread and upper thread near its bottom dead center, and is then returned to its top dead center, and repeats this operation in accordance with the rotation of the main shaft SH.

Although not shown, in relation to the driving electric motor M,
For example, it has a pedal and is provided with a controller to control the speed of the electric motor M in accordance with pedal depression.

Further, in this embodiment, the sewing needle NDLo is controlled to stop near the top dead center, and a magnet MG is fixedly provided at a predetermined portion of the pulley SP of the main shaft SH for the purpose of detecting the position of the sewing needle NDL.

1. When this magnet MG reaches a position corresponding to the top dead center position of the sewing needle NDL when it is displaced in accordance with the rotation of the pulley IJSP, it is led to a position opposite to this magnet MG in the arm AM. A switch LS is fixedly provided.

That is, the magnet MG provided on the pulley SP and the reed switch LS detect that the sewing needle NDL has reached the top dead center.

It should be noted that in FIG. 1, only essential parts related to the present invention are shown, and other parts are omitted.

FIG. 2 is an electrical circuit diagram showing a preferred embodiment of the invention.

In the configuration, the plug PL is connected to, for example, a commercial power source to supply power to the electric motor M.

A series circuit of a thyristor SCR and a motor M including field coils F1 and F2 is inserted between one end and the other end of the plug PL.

Further, at both ends of the plug PL, for applying a set voltage (gate signal) to the gate electrode of the thyristor SCH,
A series circuit of a semi-fixed resistor r1 and a variable resistor r3 and a rectifying diode D1 are inserted.

A resistor r2 and a semi-fixed resistor r4 (semi-fixed to compensate for variations in each component) are connected between the connecting point of the semi-fixed resistor r1 and variable resistor r3 and the connecting point of variable resistor r3 and diode D1. The series circuit with the

These resistors r1 and r3 provide normal (Normal
A set voltage is provided during the %-mode operation, and a relatively low set voltage during the Basting mode operation is provided by resistors r2 and r4.

A capacitor C1 for stabilizing the low speed rotation range is connected in parallel to the resistor r3.

The slider of this variable resistor r3 (slides according to the depression of the pedal of the controller) is the mode changeover switch SW.
The basting mode contact B of this switch SW12 is connected to the connection point between the resistors r2 and r4.

Therefore, each of the set voltages is switched by this switch SW12, and the thyristor S is connected via the diode D2.
Provided to the gate electrode of CR.

A parallel circuit including a bias resistor r5 and a protective capacitor C2 (to prevent malfunction when a pulse-like voltage component is applied) is inserted between the gate electrode and cathode electrode of this thyristor SCH.

A mode changeover switch SWII which is manually switched in conjunction with the mode changeover switches SW1 and SW2, and a normally closed switch SW2 which is opened by depressing a pedal of the controller, are provided at both ends of the plug PL. A reed switch LS and a relay R disposed within the arm AM are inserted.

One normally open contact Ra 1 of the relay R is connected in parallel to the reed switch LS, and the other normally open contact Ra 1 is connected in parallel to the reed switch LS.
2 is connected in parallel to the semi-fixed resistor r4.

Disconnected, two normally closed contacts of relay R, Rb 1 and Rb
2 are respectively inserted between one field winding F1 and the armature and between the other field winding F2 and the armature.

Further, one normally open contact Ra 3 of this relay R is inserted between the connection point of the normally closed contact Rb 1 and the armature, and the connection point of the normally closed contact Rb 2 and the field winding F2. It will be done.

The remaining normally open contact Ra 4 is the normally closed contact Rb.
The connection point between the l button and the field winding F1, and the normally closed contact Rb
2 and the connection point of the armature.

The operation of the above structure will be explained below with reference to FIGS. 1 and 2.

In the case of Normal mode, first, manually operate the mode selector switches SWI 1 and SW.
12 to the contact N side.

Then, the plug PL is connected to a commercial power source.

Next, gradually depress the pedal of the controller (not shown).

Therefore, the setting voltage v1 generated by the voltage dividing circuit of the semi-fixed resistor r1 for high speed setting and the variable resistor r3 according to the depression is applied to the selector switch SWI2 and the diode D2.
is applied to the gate electrode of the thyristor SCR via the thyristor SCR.

Therefore, a gate signal flows through this thyristor SCR, and the thyristor SCR is turned on.

Therefore, the electric motor M starts rotating, and a back electromotive voltage v2 is generated.

The back electromotive force v2 of the motor M is compared with the set voltage v1, and the motor M reaches a constant speed when the value of (V1-v2) becomes the trigger voltage of the thyristor SCR.

That is, if back electromotive voltage V2>setting voltage v1, thyristor SCR is not turned on.

Therefore, the electric motor M operates such that the back electromotive force v2 is constant, and the rotation speed is controlled according to the depression of the pedal (and therefore the value of the variable resistor r3).

In this way, normal operations, such as lock stitching, for example, are achieved.

In the case of Basti■ mode, at this time, do not switch, but manually press the mode selector switch SW11 button and SW1 button.
2 to the contact B side, and the plug PL is connected to the commercial power source.

Therefore, the set voltage V1 applied to the gate electrode of the thyristor SCR is given a divided voltage (relatively low) by the resistors r2 and r4.

Therefore, the conduction angle of the thyristor SCR becomes small, and the electric motor M rotates at a predetermined low speed.

Here, let us assume that the position of the sewing needle NDL has not yet reached the top dead center (predetermined) position.

In this case, the magnet MG of the pulley SP is connected to the reed switch LS.
will not be closed.

Therefore, relay R is not energized at all, and its normally open contact Ra
1 to Ra 4 are open 1″!, normally closed contacts Rbl,
Rb2 is a closed it.

Therefore, the voltage v1 set by the resistors r2 and r4 turns on the thyristor SCR, and the motor M rotates.

Accordingly, the pulley SP is rotationally driven via the bells Bl and B2, the main shaft SH rotates, and the sewing needle NDL moves.

Therefore, the pedal is released, but unless the magnet MG is still facing the reed switch LS at this time, the relay R will not be energized.

Therefore, the electric motor M rotates at a relatively low rotational speed, and the sewing needle NDL reciprocates once, sews one stitch, and reaches the top dead center position again.

Next, let us assume that the sewing needle NDL reaches the top dead center (predetermined) position.

As described above, when the sewing needle NDL reaches the top dead center, the magnet MG of the pulley SP faces the reed switch LS, and the reed switch LS is closed.

Therefore, the power from the plug PL is connected to the selector switch SWII.
, open/close switch SW2 linked to the pedal of the controller
and the relay R is energized via the closed reed switch LS, and the normally open contacts Ra 1 to Ra 4 are closed or
Normally closed contacts Rbl and Rb2 are opened.

Therefore, the reed switch LS is self-held by the normally open contact Ra 1 and the normally open contact Ra 2 connected in parallel with the semi-fixed resistor r4 is closed.

Therefore, the set voltage V1 applied via the changeover switch SWI2 and the diode D2 is cut off, and the thyristor SCR is turned off.

Furthermore, normally closed contacts Rbli- and Rb2 are opened,
Since normally open contacts Ra 3 and Ra 4 are closed at the same time, the residual back electromotive force V generated when the motor M is rotating by inertia (by turning off the thyristor SCR)
The polarity of 2 is reversed.

Therefore, the differential voltage (V1-V2) becomes (0-(-V2)) even though the set voltage V1 is zero, and a positive gate signal is applied to the gate electrode of the thyristor SCH.

That is, the back electromotive force V2 of the motor M is applied to the relay contact Ra.
2 is on, the current does not flow in the diode D1 direction, but flows through the plug PL to the half-lock resistor rlj,-
It is applied to the gate electrode of the thyristor SCH through the B-side contact of the switch SWI 2 and the diode D2 through the resistor r2 and the resistor r2.

This is because the impedance of the plug PL is low, for example, about 50 ohms, while the potential of the motor M is relatively high.
This is because this diode D1 is in a reverse bias state.

In this way, a positive gate voltage due to the back electromotive voltage V2 is applied to the gate electrode of the thyristor SCR.

Therefore, the thyristor SCR causes the turn-on motor M to rotate again.

However, at this time, the conduction polarity of the motor M is determined by the relay contacts Ra 3y Ra 4 and Rbl, Rb2.
Therefore, the electric motor M will rotate in the opposite direction to the direction in which it was currently rotating due to inertia in the housing, and the rotation due to inertia will be rapidly decelerated.

Accordingly, the residual back electromotive voltage V2 caused by the motor M suddenly decreases, and the thyristor SCR is turned off.

As described above, according to this embodiment, it is detected that the sewing needle NDL has reached the top dead center (or a predetermined position for the above-mentioned purpose), and the main circuit of the electric motor M is cut off, and the residual reverse rotation due to inertia is stopped. Since anti-phase braking is applied by the electromotive force, the motor M and therefore the sewing needle NDL instantly
definitely stopped.

Therefore, there is no need to take into consideration the inertia of the electric motor and sewing machine in order to keep the sewing needle in place during, for example, basting (or basting). What could not be achieved is
It can be done faster.

Therefore, the workability and sewing torque are dramatically improved.

Furthermore, after the sewing needle has stopped at the fixed position, in order to disable (disable) the position detection circuit of this sewing needle (including the reed switch LS and magnet MG, etc.), for example, the handwheel must be rotated by hand later on. It can be used safely without any risk of the electric motor M suddenly starting to rotate.

It goes without saying that the relay and its contacts in the above-described embodiments may be replaced with semiconductor switching elements that respond to the opening and closing of the reed switch LS, for example.

Furthermore, in the above-mentioned embodiment, reverse phase braking is performed by reversing the polarity of the armature of the motor; Of course, it can also be realized in the same way.

Furthermore, the above-mentioned predetermined position of the sewing needle includes any case other than top dead center or bottom dead center, and the magnet for detecting the position is
It may be provided on any member that operates synchronously with the main shaft.

At this time, it goes without saying that the reed switch must also be provided at its predetermined position so as to face the magnet.

It is also pointed out that in addition to using a reed switch and a magnet for this position detection, various methods such as a proximity switch method or a photoelectric method can be applied.

As described above, according to the present invention, the sewing needle can be reliably stopped at a predetermined position with a simple configuration and operation, and a more effective electric sewing machine can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an illustrative view of the main parts of an electric sewing machine that forms the background of this invention and in which this invention can be implemented. FIG. 2 is an electrical circuit diagram showing a preferred embodiment of the invention. In the figure, M is a series commutator motor, MP, sp are pulleys, SH is the main shaft, NDL is a sewing needle, LS is a reed switch, MG is a magnet, R is a relay, Ra1 to Ra4 are normally open contacts, Rbl, Rb2 is a normally closed contact, SWI 1, SW1
2 is a mode changeover switch, SW2 is an open/close switch linked to the pedal, and SCR is a thyristor.

Claims (1)

[Scope of Claims] 1. An AC power supply, a series-wound commutator motor energized by the AC power supply, a main shaft driven by the series-wound commutator motor, and a sewing needle connected to the main shaft. An automatic control device for an electric sewing machine, comprising: a series circuit including the AC power supply, a thyristor, and the series-wound commutator motor; a mode switching device for switching the electric sewing machine between a relatively high-speed operation mode and a relatively low-speed operation mode; means, first control means for controlling the electric motor by applying a variable first set voltage to the gate of the thyristor during the relative high speed operation mode; A second controller that controls the electric motor by applying a second set voltage.
anode side connected to the gate of the thyristor;
There is a can between the electric motor and the AC power source. l
a means for detecting when the sewing needle has reached a predetermined position; and a means for detecting when the sewing needle has reached a predetermined position; conductive means to disable the second control means from applying the set voltage to the gate of the thyristor; An automatic leg device for an electric sewing machine, comprising means for reversely connecting an armature of the machine and applying a counter electromotive force generated in the armature to the gate of the thyristor. 2. The second control means includes a series circuit of first and second resistors connected in parallel to the series connection of the thyristor and the electric motor, and a connection point between the first and second resistors and the thyristor. The automatic control device for an electric sewing machine according to claim 1, wherein the automatic control device is connected to a gate. 3. The unidirectional conductive means capable of conducting current includes a series connection of an on-off switch and a diode, the anode of the diode is connected to the gate of the thyristor via the second resistor, and the cathode of the diode is connected to the electric motor. 3. The automatic control device for an electric sewing machine according to claim 2, wherein the on/off switch is connected between the second resistor and the second resistor. 4. The position detecting means detects whether or not the sewing needle has reached the predetermined position based on the rotational position of the main shaft or the position of a member that operates synchronously with the main shaft. The automatic control device for an electric sewing machine according to any one of Item 3. 5. The position detection means includes a magnetic element substantially fixed to the main shaft or a member that operates in synchronization with the main shaft, and is arranged at a position facing the magnetic element when the sewing needle reaches the predetermined position. An automatic control device for an electric sink according to claim 4, comprising a reed switch.