JPS5943195B2 - Automatic control device for electric sewing machines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic control device for an electric sewing machine, and in particular, for example, in an electric sewing machine using a DC motor (series-wound, split-wound, double-wound, etc.), the sewing needle is moved to the top dead center, bottom dead center, etc. The present invention relates to an automatic control device that stops at a fixed position.

2. Description of the Related Art Conventionally, electric sewing machines using a universal electric motor as a drive source have been put into practical use.

Also, 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 using a DC motor that can reliably stop a sewing needle at a predetermined position during, for example, basting. To summarize, the present invention provides that when the sewing needle is in the basting (or basting) operation mode, the sewing needle is at the top dead center (
This is an automatic control device for an electric sewing machine that detects that the sewing machine has reached a predetermined position to achieve the above-mentioned purpose, such as (or bottom dead center), and applies reverse phase braking to the driving DC motor.

The above objects and other objects and features of the present invention will become more apparent from the following detailed description with reference to the drawings.

FIG. 1 is a schematic illustration of an electric sewing machine that forms the background of this invention and in which this invention is implemented.

In the structure, a sewing machine arm AM is formed on the upper surface of the sewing machine bed BS, and a sewing machine arm AM that houses various mechanisms therein is formed.
A driving DC motor M is provided on the outside. A belt B1 is attached to the pulley MP provided on the rotating shaft of the electric motor M.
is applied, and the driving force from belt B1 is transmitted to 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 SP and therefore the main shaft SH. The main shaft SH
is connected to needle bar NR via crank CR, and drives needle bar NR in the vertical direction in accordance with its rotation. Also,
A sewing needle NDL is fitted into the lower end of the needle bar NR, and a lower thread (lower thread bobbin) wound around an inner hook and a bobbin is disposed below the sewing machine bed BS opposite to the position of the sewing needle NDL. 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. Further, although not shown in the drawings, a controller is provided in connection with the driving electric motor M, for example, having a pedal and controlling the speed of the electric motor M in accordance with depression of the pedal.

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

Further, when this magnet MG is displaced in accordance with the rotation of the pulley SP, when the magnet MG reaches a position corresponding to the top dead center position of the sewing needle NDL, a reed switch LS is moved to a position opposite to the magnet MG in the sewing machine arm AM. 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.

Regarding the configuration, the plug PL is connected to, for example, a commercial power source to supply power to the electric motor M. A full-wave rectifying diode D1 is provided between one end and the other end of the plug PL, and a series circuit of a thyristor SCR and a motor M is inserted between both ends of the full-wave rectifying diode D1. Further, the thyristor S is connected to both ends of the full-wave rectifier diode D1.
A series circuit of a semi-fixed resistor rl and a variable resistor R3 is inserted for applying a set voltage (gate signal) to the gate electrode of the CR. Furthermore, a resistor R2 and a semi-fixed resistor R are connected across the full-wave rectifier diode D1 in parallel with the series circuit.
4 (semi-fixed to correct variations in each component) is connected in series. This resistance rl and R3
The setting voltage for normal (NOrmal) mode operation is applied by resistors R2 and R4, and the basting is
ng) Provides a relatively low set voltage during mode operation. The slider of the variable resistor R3 (slides in response to depression of the pedal of the controller) is a mode changeover switch SW.
The basting mode contact B of this switch SWl2 is connected to the connection point between the resistors R2 and R4. Therefore, each set voltage is switched by this switch SWl2 depending on the high speed operation mode (NOrmal) or the low speed operation mode (Basting), and is applied to the gate electrode of the thyristor SCR via the diode D2. A parallel circuit including a bias resistor R5 and a protective capacitor C1 (to prevent malfunction when a pulsed voltage component is applied) is inserted between the gate electrode and cathode electrode of the thyristor SCR.

Further, at both ends of the rectifier diode D1, there is a mode changeover switch SWll which is manually switched in conjunction with the mode changeover switch SWl2, and a normally closed switch SW2 which is opened by depressing the pedal of the controller.
and a reed switch LS disposed within the arm AM;
Relays R1 and R2 are inserted.

One normally open contact R1al of the relay R1 is connected in parallel to the reed switch LS, and the other normally open contact R1
a2 is connected in parallel to the semi-fixed resistor R4.

In addition, the two normally closed contacts Rlbl and Rl of relay R1
b2 is the electric motor M (armature thereof) and the thyristor SCR.
The other normally closed contact Rlb3 is inserted between the cathode of the controller switch SW2 and the negative side of the motor M (armature of the motor M) and the full-wave rectifier diode D1.
is inserted between contact point X and contact point Y of . and the remaining two normally open contacts Rla3 and Rla of the relay R1.
4 are the electric motor M and the normally closed contact R1b1, respectively.
and the negative side of the full-wave rectifier diode D1, and between the connection point between the motor M and the normally closed contact Rlb2 and the cathode side of the thyristor SCR. Further, the relay R2 includes one normally open contact R2a, which is the contact 0 of the switch SW2.
and contact X. A series circuit of a delay resistor R6 and a capacitor C2 is connected in parallel to both ends of this relay R2. The operation of the above configuration will be explained below with reference to FIGS. 1 and 2. NOr
In the case of the mal mode, first, the mode changeover switches SWll and SWl2 are sequentially switched to the contact N side by manual operation.

Then, the plug PL is connected to a commercial power source. Next, the pedal of the controller (shown in the figure (1)) is gradually depressed. Therefore, the set voltage generated by the voltage dividing circuit of the semi-fixed resistor rl for high speed setting and the variable resistor R3 corresponding to the pedal depression is applied. 1 is applied to the gate of the thyristor SCR via the changeover switch SWl2 and the diode D2.Therefore, a gate current flows through the thyristor SCR and the thyristor SCR is turned on.Therefore, the electric motor M starts rotating. A back electromotive current V2 is generated. This back electromotive voltage V2 of the motor M is compared with the set voltage V1 (V1-
When the value of V2) becomes the voltage of the thyristor SCR, the motor M has a constant speed. That is, if back electromotive voltage V2>setting voltage V1, thyristor SCR will not turn 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. B
In the asting mode, first, the mode changeover switches SWll and SWl2 are manually switched 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, the position of the sewing needle NDL is still at the top dead center (
Let's assume a case in which the object does not reach the specified position.

First, the user depresses the pedal of the controller to start the sewing machine, and in response, the switch SW2 is switched to the contact Y side. Therefore, relay R1 is deenergized, relay R2 is energized, normally open contact R2a is turned on, and this switch SW
2 is short-circuited and relay R2 is self-held. at the same time,
After capacitor C2 is charged and the controller pedal is released, this relay R2 connects resistor R6 and capacitor C2.
It will be deenergized after a delay time corresponding to the discharge time constant. In this case, the magnet MG of the pulley SP does not close the lead switch LS, so the relay R1 is not energized, its normally open contacts Rla2 to Rla4 remain open, and the normally closed contacts R1Bl and Rlb2 are closed. It remains as it was.

Therefore, the voltage V1 set by the resistors R2 and R4 turns on the thyristor SCR, and the motor M rotates.
In response, pulley SP is rotationally driven via belts Bl and B2, main shaft SH rotates, and sewing needle NDL moves. Therefore, the pedal is released, but if the magnet MG is not yet facing the reed switch LS at this time,
Relay R1 is never energized. Therefore, electric motor M
is rotated at a relatively low rotational speed, and the sewing needle NDL is 1
It goes back and forth to sew 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 and therefore the full-wave rectifier diode D1 energizes the relay R1 through the changeover switch SWll, switch SW2 and the closed reed switch LS, and the normally open contacts R1al to Rla4 are closed. Normally closed contact R1Bl,
Rlb2 is opened. Therefore, the reed switch LS is self-held by the normally open contact Rlal, and the semi-fixed resistor R4
A normally open contact Rla2 connected in parallel with is closed. Therefore, the relatively low set voltage 1 applied via the changeover switch SWl2 and the diode D2 is cut off, and the thyristor SCR is turned off. Furthermore, since the normally closed contacts Rlbl and Rlb2 are closed, and the normally open contacts Rla3 and Rla4 are closed at the same time, the remaining The polarity of the back electromotive current V2 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 SCR. Therefore, the thyristor SCR is turned on again, causing the electric motor M to rotate. however,
At this time, the conduction polarity of the motor M is determined by each of the relay contacts Rl.
Since the directions are reversed by trigram a3, Rla4 and R1Bl, Rlb2, the electric motor M will now rotate in the opposite direction to the direction in which it has been rotating due to inertia, and the rotation due to inertia will suddenly increase. Slowed down. Depending on the electric,
The residual back electromotive force V2 caused by the machine M suddenly decreases, the thyristor SCR is turned off, and the motor M and therefore the sewing needle NDL are stopped. }, when the pedal is released, switch SW2 moves from contact point Y to X, but
During this movement, the power supply to the reed switch LS is cut off, the relay R2 is deenergized, and the power supply to the relay R1 is also cut off.

However, the resistor R6 and capacitor C of the delay circuit
2, the relay R2 is held for a while after the pedal is released, as described above. Therefore, normally open contact R2
Since a remains held for a while, the reed switch LS continues to be energized without being affected by the disconnection of the circuit caused by the movement of the contact of the switch SW2. Therefore, even if the controller pedal is depressed and immediately released, the reed switch LS continues to be energized, and the electric motor M and therefore the main shaft SH rotate at a low speed and stop at a fixed position. As described above, according to this embodiment, the sewing needle NDL is at the top dead center (or at a predetermined position).
, the main circuit of the motor M is cut off, and reverse phase braking is applied by the residual counter electromotive force of the rotation due to inertia.
L is instantly and reliably 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 basting (or basting). Things that could not be done can now be done faster. Therefore, workability and sewing torque are dramatically improved. Furthermore, after the sewing needle has stopped at the normal position, in order to disable (invalidate) the sewing needle's position detection circuit (including reed switch LS, magnet MG, etc.) can be used safely without the risk of the electric motor M suddenly starting to rotate.

Once the pedal of the controller is depressed, the main shaft will rotate approximately once and stop, regardless of whether the pedal is continued or released, and the sewing needle will surely be located at the top dead center, bottom dead center, or near the dead center. The sewing of the first stitch is completed. In the above embodiment, reverse phase braking is performed by reversing the polarity of the armature of the motor; however, this also applies even if the polarity of the field winding of the separately excited motor is reversed. The same can be achieved.

In addition, the relay and its contacts are, for example, reed switch LS.
Of course, it may be replaced by a semiconductor switching element that responds to the opening or closing of the switch. Furthermore, the above-mentioned predetermined position of the sewing needle includes any case other than the top dead center or the bottom dead center, and the magnet for detecting the position may be provided on any member that acts 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 type or a photoelectric type 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 DC motor, MP and SP are pulleys, SH is a main shaft, NDL is a sewing needle, LS is a reed switch, MG is a magnet, Rl and R2 are relays, and R1a1 to R1A
4, R2a is a normally open contact, Rlbl, Rlb2, Rlb3
is a normally closed contact, D1 is a full-wave rectifier diode, SWll, S
Wl2 is a mode changeover switch, SW2 is an open/close switch linked to the pedal, SCR is a thyristor, and Cl and C2 are capacitors.

Claims (1)

[Scope of Claims] 1. An AC power supply, a circuit for rectifying the AC power supply, a DC motor energized by the output of the AC circuit, a main shaft driven by the DC motor, and a main shaft driven by the DC motor. An automatic control device for an electric sewing machine including a connected sewing needle,
mode switching means for switching the electric sewing machine between a relatively high-speed operation mode and a relatively low-speed operation mode; a first control means for controlling the DC motor in the relatively high-speed operation mode; and a first control means for controlling the DC motor in the relatively low-speed operation mode. a second control means for controlling the electric motor; a means for detecting that the sewing needle has reached a predetermined position; and a means for disabling the second control means in response to the output of the position detection means in the relative low speed operation mode. An automatic control device for an electric sewing machine, comprising switching means for braking the DC motor in reverse phase. 2. The automatic control device for an electric sewing machine according to claim 1, wherein the first control means includes speed adjustment means for the DC motor. 3. The automatic control device for an electric sewing machine according to claim 2, wherein the speed adjusting means includes a pedal and a variable resistor interlocked with the pedal. 4. The pedal further includes a switch contact, wherein the pedal is self-retained by depressing the pedal during the relatively low speed operating mode, and the self-retaining is performed with a certain delay time by depressing the pedal. The automatic control device for an electric sewing machine according to claim 3, wherein the automatic control device is released. 5. Claims characterized in that the position detection 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. An automatic control device for an electric sewing machine according to items 1 to 4. 6. The position detecting means includes a magnetic element substantially fixed to the main shaft or a member acting in synchronization with the main shaft, and is arranged at a position facing the magnetic element when the sewing needle reaches the predetermined position. 6. An automatic control device for an electric sewing machine according to claim 1, further comprising a reed switch. 7. The automatic control device for an electric sewing machine according to claim 1, wherein the switching means further disables the position detection means by its operation. 8. The automatic control device for an electric sewing machine according to any one of claims 1 to 7, wherein the switching means is a relay. 9. The automatic control device for an electric sewing machine according to any one of claims 1 to 8, wherein the switching means is a semiconductor element.