JPS5849115B2 - Electric sewing machine control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sudden braking control device for an electric sewing machine.

It has traditionally been desirable for electric sewing machines to be able to brake suddenly for safety and other reasons.

In order to apply sudden braking in this way, it is conceivable to use a mechanical braking method, such as an electromagnetic clutch, as is already done in industrial sewing machines.

However, in such a device that is mechanically stopped, since it has a movable part for that purpose, changes occur over time due to wear, for example, and it becomes impossible to make a sudden stop reliably.

At the same time, such a mechanical braking device requires a large amount of space and a complicated mechanism, and cannot be used in electric sewing machines that are required to be inexpensive and compact, such as household sewing machines. It has the disadvantage that it cannot be obtained.

Therefore, the main object of the present invention is to provide a control device for an electric sewing machine which eliminates the above-mentioned drawbacks and which reliably applies sudden braking.

In summary, in an electric sewing machine in which the speed is controlled by controlling the phase of an AC power source to energize a motor and controlling its conduction angle or conduction angle, when a foot controller switch is released, the motor is activated. This is a control device in which a diode is connected in parallel to either the armature or the field coil so as to short-circuit either the armature or the field coil in the opposite direction and apply dynamic braking.

The above objects and other objects and features of the 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 this 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 outside.

A bell I-Bl is applied to a pulley IJMP provided on the rotating shaft of the electric motor M, and the driving force from the bell 1 and B1 is transmitted to the belt B2 at a certain speed ratio via the intervening pulley.

This belt B2 is further passed around a pulley SP formed on the main shaft SH which serves as a driving 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 the needle bar NR via a crank CR, and drives the needle bar NR in the vertical direction in accordance with its rotation.

Further, 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, this 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.

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 an embodiment of the present invention.

In the configuration, a thyristor SCRI, a field coil FC of an electric fflM, an amateur AM, a thyristor SCR2, and a resistor R4 are installed at both ends of the plug PL connected to the commercial power supply.
series circuit is connected.

The thyristors SCR1 and SCR2 are connected in opposite directions.

Here, the resistor R4 is a current limiting resistor.

This thyristor SCR1 is connected to the foot controller (
(not shown), the conduction angle is changed by the electric ffl
Performs speed control of M.

Diodes D3 and D5 in opposite directions are connected in parallel to the thyristors SCR1 and SCR2, respectively.

Furthermore, a bias resistor R is connected between the gate electrode and cathode electrode of each of the thyristors SCR1 and SCR2.
A parallel circuit of 2 and R3 and protective capacitors C2 and C3 is connected.

A diode D4, which is a feature of the present invention, is connected in parallel to the amateur AM of the electric motor M in the opposite direction to the thyristor SCRI and in the same direction as the thyristor SCR2.

Further, a series circuit including a switch SWI, a resistor Rl, an iJ variable resistor VRI, and a diode D1 is connected to both ends of the plug PL.

The switch SW1 is linked to a pedal (not shown) of the controller, similar to the switch SW2 described later, and when the pedal is depressed, the Normal mode (connection between contacts N and O) is established and opened. This establishes the brake mode (connection between contacts B and O).

Further, the slider of the variable resistor VRi changes its position in accordance with the depression of the pedal, and applies the gate voltage of the cyrisk SCRI via the diode D2.

Note that a stabilizing capacitor C1 at a small conduction angle is connected in parallel to the variable resistor VR1.

The diode D1 is a rectifying diode.

Further, a series circuit including a diode D7, a semi-fixed resistor VR2, a resistor R5, and a switch SW2 is connected to both ends of the plug PL.

The semi-fixed resistor VR2 is for braking setting, and the voltage from its slider is applied to the cyrisk S through the diode D6.
It is given as the gate voltage of CR2.

Note that a stabilizing capacitor C4 at a small conduction angle is connected in parallel to this semi-fixed resistor VR2.

The diode D7 is a rectifying diode.

The operation of the above structure will be explained below.

First, Norm presses the foot controller pedal.
The al mode will be explained.

In this case, both switches SWI and SW2 are set to Norm.
Switched to al mode.

Therefore, the series circuit including the semi-fixed resistor VR2 is cut off.

Therefore, thyristor SCR2 is in an off state.

On the other hand, a certain voltage (corresponding to the amount of depression of the foot controller pedal, that is, the position of the slider) is generated in the variable resistor VRI by the current applied from the plug PL via the switch SW1.

The voltage from this variable resistor VR1 causes the thyristor S to
CRI is turned on, plug PL - thyristor SCR
1-field a coil FC-amateur AM-diode D5
- A closed circuit of the plug PL is formed.

Therefore, the electric motor 3 is rotated at a speed corresponding to the depression of the pedal, and the sewing needle NDL shown in FIG. 1 is driven one time in the vertical direction.

It is assumed that the controller pedal is then released to interrupt or end sewing.

At this point, both switches sw1 and sw2 are switched to the brake mode.

Therefore, the series circuit including variable resistor VRI is cut off.

Therefore, thyristor SCRI is turned off.

On the other hand, a certain voltage (preset by adjusting the slider position) is generated in the semi-fixed resistor VR2 by the current applied from the plug PL via the switch SW2.

The voltage from this semi-fixed resistor VR2 causes the thyristor S to
CR2 turns on, plug PL single-lens flow (to prevent motor burnout) resistor R4 - thyristor SCR2 - diode D
A closed circuit of 4-field coil FC-diode D3-plug PL is constructed.

Therefore, the armature AM of the electric motor M is short-circuited, a DC voltage is applied to the field coil FC, and the kinetic energy of the armature is DC-braked.

Therefore, so-called dynamic braking is applied to the electric motor M, and the sewing needle NDL shown in FIG. 1 is suddenly stopped.

Note that although the field coil FC is kept in an excited state, a slight time lag occurs when the pedal is next depressed, but this does not pose any problem in practice.

Although the embodiment uses a half-wave rectifier circuit, a full-wave rectifier circuit can also have the same effect.

Furthermore, it goes without saying that the same sudden braking effect can be obtained even if the diode D4 inserted in parallel with the amateur AM is placed in parallel with the field coil FC.

As described above, according to the present invention, a diode is connected in parallel in the opposite direction to the first semiconductor phase control circuit to either the armature or field coil of a motor that is energized by a phase-controlled current. Since the sewing machine is configured to apply dynamic braking, sudden braking of the sewing needle is possible without the need for a special switch circuit to cut off the power supply.

Therefore, it is particularly suitable for household sewing machines that are required to be inexpensive and compact.

[Brief explanation of drawings]

FIG. 1 is a schematic illustration of an electric sewing machine that forms the background of this invention and in which this invention can be practiced. FIG. 2 is an electrical circuit diagram showing an embodiment of the present invention. In the figure, M is a DC motor, NDL sewing needle, AM is an armature, FC is a field coil, SCRI, SCR2 is a passive risk, D1 to D7 are diodes, VRI is a variable resistor, VR2 is a semi-fixed resistor, SW1 and SW2 are switching It's a switch.

Claims (1)

[Scope of Claims] 1. An electric motor including at least a field winding and an armature connected in series; a sewing needle driven by the electric motor; an AC power source; an anode side connected to one end of the AC power source, and the field a first semiconductor phase control circuit whose cathode side is connected to the winding side, and which controls the phase of the AC power source and applies it to the motor; and controls the conduction angle of the first semiconductor phase control circuit to control the speed of the motor. An electric sewing machine comprising speed regulating means for manually adjusting the speed of the electric sewing machine, the electric sewing machine comprising: a first unidirectional element connected in parallel to the armature of the electric motor in a direction opposite to the direction of the first semiconductor phase control circuit; , an anode side is connected to the other end side of the AC power source, a cathode side is connected to the armature side, and the first unidirectional element is connected from the other end of the AC power source when the manual speed regulating means is not operated. a second semiconductor phase control circuit that allows current to flow through the semiconductor phase control circuit; and second and third unidirectional elements connected in antiparallel to the first semiconductor phase control circuit and the second semiconductor phase control circuit, respectively. . A control device for an electric sewing machine, which applies dynamic braking to the electric motor to suddenly stop the sewing needle when the manual speed regulating means changes to a non-operating state. 2. The control device for an electric sewing machine according to claim 1, wherein the fourth to third unidirectional elements are diodes.