JPH02154790A - Set position stopping device for sewing machine - Google Patents

Abstract

PURPOSE:To exactly stop an upper shaft in a prescribed position regardless of sewing speed by effectively utilizing back electromotive force generated by a sewing machine for braking when the rotary phase of the upper shaft is a phase in a prescribed range. CONSTITUTION:A notched part 58 of a prescribed open angle and a switching board 56 having an expanding part 60 are adhered to a rotary body 54 fixed to a sewing machine shaft 14. Two switches A and B are composed of the switching board 56 and terminals 67a, 68a and 69a, to which connecting lines L4, L5 and L6 brought into contact with this switching board are connected. Only when an activation stopping switch 40 is in a stop position S2 and an upper shaft 14 is in the phase range corresponding to an above mentioned open angle 62, by these switches, a power source circuit 70 is opened and a control circuit 74 is opened. Then, when the upper shaft 14 goes to the prescribed position, a sewing machine motor 20 is exactly stopped by the back electromotive force generated in an internal part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a set position stopping device for a sewing machine, and more particularly to one that brakes the rotation of a sewing machine motor using a back electromotive force generated by the sewing machine motor.

[Prior art]

In general, a normal sewing machine is configured to stop the upper shaft of the sewing machine when the sewing needle is in the needle down position when changing the sewing direction, and also to stop the upper shaft of the sewing machine when the sewing direction is changed. When the needle is taken out from the sewing position, the upper shaft of the sewing machine is stopped when the sewing needle is at the sewing position.

For example, in an electronically controlled zigzag sewing machine, there is a timing signal generator that outputs a timing signal for counting when the upper axis is in phase just before the sewing needle reaches the counting position, and a timing signal generator that outputs a timing signal for counting when the sewing needle is in the upper axis phase just before the sewing needle reaches the needle down position. When the sewing machine motor is stopped by operating the start/stop switch, when the recording position is specified, the timing signal generator outputs a timing signal for recording. Based on the timing signal, first the rotational speed of the sewing machine motor is reduced to a low speed (for example, 150 rpm), and then the power supply circuit of the sewing machine motor is cut off, thereby stopping the sewing needle at the set position.

On the other hand, when the boot, which is connected to the sewing machine motor via a timing belt, and the upper shaft of the sewing machine are operatively connected by a spring clutch, and the sewing needle is stopped at the sewing position, for example, when the sewing needle is at the sewing position, the By engaging the claw provided on the frame with the claw provided on the spring clutch side, the spring of the spring clutch releases the restraint of the upper shaft, and the setting position stops the upper shaft (sewing needle) at a predetermined stop phase. Some sewing machines are equipped with a stop mechanism.

[Problem to be solved by the invention]

As mentioned above, when stopping the upper shaft at a predetermined stop phase based on the timing signal from the timing signal generator, the rotation speed of the sewing machine motor is controlled to a low speed, and the power supply circuit Since the control is to shut off the upper shaft, what is the control to stop the upper shaft at a predetermined phase? jHf
In addition, the timing signal generator requires various kinds of expensive sensors, which increases the cost, and the sewing needle stops at a different position depending on whether the sewing speed is high or low. There are problems such as.

Sewing machines equipped with a set position stop mechanism instantly stop the rotation of the upper shaft, so there is almost no misalignment when the sewing needle stops, but this stop mechanism is complex and requires a large number of parts, including a spring clutch. Because of this structure, there are problems such as being expensive and requiring a great deal of labor to assemble and adjust these parts.

SUMMARY OF THE INVENTION An object of the present invention is to provide an inexpensive and simple setting position stopping device for a sewing machine that can improve stopping position accuracy.

[Means for Solving the Problem] As shown in the configuration diagram of FIG. 1, the setting position stop device for a sewing machine according to the present invention has a power supply circuit connected to a DC motor as a sewing machine motor, and a power supply circuit connected to the DC motor. a braking circuit that forms a closed circuit; a selection switch that is interposed between the power supply circuit and the braking circuit and selectively closes both circuits;
An auxiliary circuit that connects the braking circuit side terminal and the power supply circuit side terminal of the selection switch, a first switch installed in the auxiliary circuit, a second switch installed in the braking circuit, and a switch operated on the upper shaft of the sewing machine. the first switch is opened and the second switch is closed when the rotational phase of the upper shaft is in a phase within a predetermined range that includes at least a predetermined stop position of the upper shaft and precedes this stop position; , and switching means for closing the first switch and opening the second switch at other times.

[Effect]

In the set position stop device for a sewing machine according to the present invention, by operating the selection switch to selectively close the power supply circuit, the sewing machine motor receives a drive current from the power supply circuit and rotates. At this time, since the upper shaft of the sewing machine rotates with the rotation of the sewing machine motor, the switching means operatively connected to the upper shaft of the sewing machine determines that the rotational phase of the upper shaft during rotation is at least at a predetermined stop position of the upper shaft. When the phase is within a predetermined range that includes and precedes this stop position, a first switch provided in the auxiliary circuit is opened and a second switch provided in the braking circuit is closed. Further, when the rotational phase of the upper shaft during rotation is outside the predetermined range, the switching means closes the first switch and opens the second switch.

When the selection switch is operated to open the power supply circuit in order to stop the sewing machine motor, the braking circuit is closed by the selection switch.

However, at this time, when the rotational phase of the upper shaft is outside the predetermined range, the second switch is opened, so the braking circuit does not become a closed circuit, and when the first switch is closed, the auxiliary circuit becomes a closed circuit, and the power supply circuit becomes a closed circuit via the auxiliary circuit and the braking circuit side terminal of the selection switch, and the sewing machine motor continues to rotate.

After that, when the rotational phase of the upper shaft falls within a predetermined range, the first switch is opened and the second switch is closed, so the power supply circuit becomes an open circuit and drive current is supplied to the sewing machine motor. The braking circuit becomes a closed circuit.

As a result, the sewing machine motor rotates by inertia, functions as a generator, and generates a back electromotive voltage according to the inertia rotation speed. This back electromotive force causes a back electromotive current to flow through the braking circuit to the armature coil of the sewing machine motor, which generates a braking torque that causes the sewing machine motor to rotate in the opposite direction to the inertial rotation of the sewing machine motor. A brake is applied to the inertial rotation of the sewing machine motor. Since this back electromotive voltage is proportional to the inertial rotation speed of the sewing machine motor, a large braking torque is generated when the inertia rotation speed is large.

Therefore, the sewing machine motor is stopped immediately by this braking torque, so that the upper shaft can be accurately stopped at a predetermined stop position.

〔Effect of the invention〕

According to the set position stopping device for a sewing machine according to the present invention, as explained above, when the rotational phase of the upper shaft is within a predetermined range, the back electromotive force generated in the sewing machine motor is effectively utilized for braking. The upper shaft can be accurately stopped at a predetermined stop position regardless of the sewing speed, and the accuracy of the stop position can be significantly improved.

Further, the set position stopping device can be made inexpensive and simple in structure using only circuits and switches.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

In this embodiment, the present invention is applied to an electronically controlled zigzag sewing machine.

As shown in FIG. 2, a head 4 is provided at the left end of the arm 2 of the sewing machine M, and a needle bar 6 is disposed vertically within the head 4. The needle bar support 8 is attached to a support 8 so as to be movable up and down, and the upper end of the needle bar support 8 is pivotally connected to a machine frame 10 via a pin 12. Thereby, the needle bar 6 and the needle bar support 8 can swing left and right about the bin 12. A sewing machine upper shaft 14 extending in the left-right direction within the arm portion 2 is rotatably supported by a machine frame 10, and is connected to a sewing machine motor 20 (a direct current motor) via a pulley 16 and a timing belt 18 fixed to the right end of the sewing machine upper shaft 14. (See Figure 4). When the sewing machine upper shaft 14 rotates with the rotation of the sewing machine motor 20, the needle bar 6 is driven up and down via the needle bar crank 22 and link mechanism fixed to the left end of the sewing machine upper shaft 14, and the needle bar swings. The needle bar support 8 is
and the needle bar 6 is driven to swing.

Built into the bed portion 26 are a vertical feed drive device for vertically moving the feed dog 2 for cloth feeding, and a back and forth feed drive device for moving the feed dog 28 back and forth. It is driven by a feeding stepping motor (path shown), and the vertical feeding drive device is driven by a sewing machine motor 20. still,
30 is a sewing needle, 32 is a presser bar, 34 is a presser foot, and 36 is a balance.

A start/stop button 38 for controlling start and stop of the sewing machine motor 20 is provided on the jaw provided on the head 4.
The pillar section 42 has a pattern selection switch 44 consisting of a numeric keypad.
, a feed amount adjustment knob 46 that adjusts the feed amount of the work cloth, a needle swing amount adjustment knob 48 that adjusts the amount of needle swing of the sewing needle 30,
A speed adjustment knob 50 for controlling the sewing speed is provided. As shown in FIG. 4, a start/stop switch (switch for switching between two circuits) 40 is connected to the start/stop button 3, and each time this button 38 is pressed, the switch 40 starts. (the common terminal S1 and the terminal S3 are closed as shown by the broken line) and the stop side (the common terminal S1 and the terminal S2 are closed as shown by the solid line).

Next, the set position stop device 52 for stopping the sewing machine upper shaft 14 at a predetermined stop phase (stop position) will be explained based on FIGS. 2 to 4.

A circular rotating body 54 is fixed to the sewing machine upper shaft 14,
An annular switch plate 56 made of a conductive material such as a copper plate is attached to the left side surface of the rotating body 54 with adhesive or the like.

A notch 58 having a predetermined opening angle (for example, approximately 70 degrees) with respect to the axis of the upper shaft 14 of the sewing machine is formed on the outer periphery of the switch plate 56, and on the inner periphery of the notch 58, the upper shaft 14 of the sewing machine An overhang 60 having a predetermined opening angle with respect to the axis is formed, and the notch 58 and the overhang 60 are in the same phase with respect to the upper shaft 14 of the sewing machine. Here, the range of the phase of the upper shaft 14 of the sewing machine corresponding to the predetermined opening angle is defined as a braking range 62, and the range of the phase of the upper shaft 14 of the sewing machine other than the braking range 62 is the drive range of the sewing machine motor (hereinafter referred to as the drive range). ) 64.

On the other hand, three electric contacts 67, 68, and 69 are respectively attached to the mounting member 66 attached to the machine frame 10, and the tips of each electric contact 67, 68, and 69 are bent into a substantially V-shape. Contact points 67a, 68a, and 69a are formed respectively, and each contact point 67
a, 68a, and 69a are arranged in a line on a line extending radially outward from the upper shaft 14 of the sewing machine, and are in contact with the switch plate 56.

That is, as shown in the fourth article, the contact 67a of the electric contactor 67
is provided at a position that faces the notch 58 when the phase is in the braking range 62 and contacts the switch plate 56 when the phase is in the driving range 64, and the contact 68a of the electric contact 68 is in the phase of the braking range 62 and the driving range 64. Switch plate 5 is always in phase
The contact 6 of the electrical contact 69 is provided at a position in contact with the contact 6
9a is the switch plate 56 only when the phase is in the braking range 62.
(the overhanging portion 60).

Here, the position of each contact 67a, 68a, 69a is the fourth
As shown in the figure, when the sewing machine upper shaft 14 is in the position approximately at the center of the braking range 62, the needle bar 6 is in the recording position, and the sewing machine upper shaft 14 at this time is in the set stop position. As shown in the figure, the phase of the sewing machine upper shaft 14 at the start position of the braking range 62 is taken as the braking start position, and the braking range 6
The phase of the sewing machine upper shaft 14 at the end position of 2 is defined as the braking end position. Therefore, the braking range 62 is a predetermined range that includes at least the stop position of the sewing machine upper shaft 14 and precedes this stop position.

Next, a drive/brake circuit for controlling the drive and braking of the sewing machine motor 20 will be explained based on FIG. 4.

The positive side terminal P1 of the sewing machine motor 20 is connected to the common terminal Sl of the start/stop switch 40 via the connection line LL, and the negative side terminal P2 of the sewing machine motor 20 is connected to the connection line L.
The positive terminal of the DC power supply 76 is connected to the terminal S3 of the start/stop switch 40 via the connection line L3, and these connection lines L
1, L2, and L3 constitute a power supply circuit 70.

In addition, the terminal S3 of the start/stop switch 40 is connected to the connection line L3.
Terminal S2 of the start/stop switch 40 is connected to a contact 68a via a connection line L5, and an auxiliary circuit 72 is formed by these connection lines L4 and L5. ing.

Further, the negative terminal P2 of the sewing machine motor 20 is connected to the contact point 69a via the connecting wire L6, and the connecting wires L1 and L5
and L6 constitute a braking circuit 74. Note that the connection line L1 is shared by the power supply circuit 70 and the brake circuit 74, and the connection line L5 is shared by the auxiliary circuit 72 and the brake circuit 74.

Here, the first switch A is configured by the contact 67a and the contact 68a, and this first switch A is interposed in the auxiliary circuit 72, and the second switch B is configured by the contact 68a and the contact 69a, This second switch B is interposed in the braking circuit 74.

Next, the drive side of the sewing machine motor 20 in the drive/control circuit? I
The operation of the brake control and the braking control will be explained based on FIGS. 4 to 6.

When the start/stop button 3 is operated to switch the start/stop switch 40 to the starting side in order to start sewing, the power supply circuit 70 becomes a closed circuit, and the sewing machine motor 20 receives DC power a.
Rotates by direct current from 9I76. This results in
The upper shaft 14 of the sewing machine is rotated via the timing belt 18 and the pulley 16, and the needle bar 6 is driven up and down, and the feed dog 28 is driven, thereby sequentially forming stitches on the workpiece cloth. At this time, due to the rotation of the upper shaft 14 of the sewing machine, the first switch A is opened in the braking range 62 and closed via the switch plate 56 in the driving range 64. Further, the second switch B is closed via the switch plate 56 in the braking range 62, and is opened in the driving range 64.

Then, when the start/stop button 38 is operated to switch the start/stop switch 40 to the stop side upon completion of sewing, the power supply circuit 70 becomes an open circuit.

However, at this time, when the upper shaft 14 of the sewing machine is in the phase shown in FIG. Since the switch (composed of SL and terminal S2) is also closed, the power supply circuit 70 becomes a closed circuit via the auxiliary circuit 72 and the stop side switch of the start-stop switch 40, and the sewing machine motor 20 continues. and rotate.

Then, as the sewing machine motor 20 rotates, the sewing machine upper shaft 1
4 rotates, and the first switch A and second switch B switch to the sixth
When the braking start position of the braking range 62 shown in the figure is reached, the first switch A is opened and the second switch B is closed.

As a result, the power supply circuit 70 becomes an open circuit, and the sewing machine motor 20 is not supplied with direct current from the DC power supply 76 (
At the same time, the braking circuit vr74 becomes a closed circuit. As a result, the sewing machine motor 20 rotates by inertia, functions as a generator, and generates a back electromotive voltage according to the inertia rotation speed.

This back electromotive force causes a back electromotive current to flow through the armature coil of the sewing machine motor 20 through the braking circuit 74, and a braking torque is generated in the sewing machine motor 20 to rotate the sewing machine motor 20 in a direction opposite to the direction of inertial rotation of the sewing machine motor 20. This braking torque applies a brake to the inertial rotation of the sewing machine motor 20. Therefore, as the sewing machine motor 20 is immediately stopped by this braking torque, the sewing machine upper shaft 14 can be accurately stopped at the predetermined stop position shown in FIG. 4 before reaching the braking end position. Moreover, this back electromotive force is proportional to the inertial rotation speed of the sewing machine motor 20, and when the inertia rotation speed is large, a large braking torque is generated. It is possible to accurately stop at the stop position, and the accuracy of the stop position can be significantly improved. Moreover, the power supply circuit 70
, the auxiliary circuit 72, the braking circuit 74, the first switch A, and the second switch B are only provided, so the set position stop device 5
2 can be constructed inexpensively and simply.

Note that the first switch A and the second switch B are each configured with a limit switch, and the first limit switch is opened corresponding to the braking range 62 shown in FIG.
4, and a second cam for closing the second limit switch corresponding to the braking range 62 and opening it corresponding to the driving range 64 on the sewing machine. It may also be provided on the shaft 14.

A switch plate similar to the switch plate 56 is attached to the right side of the rotating body 54 with a phase difference of approximately 180 degrees from the switch plate 56, and three electric wires each having a contact point that contacts this switch plate are attached. Contacts may be provided opposite the electrical contacts 67 to 69, and each of these contacts may be connected to the aforementioned drive/brake circuit, respectively, when the needle down position is instructed.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a configuration diagram of the present invention, FIG. 2 is a perspective view of the sewing machine showing the internal mechanism of the arm section, FIG. 3 is an enlarged perspective view of the main part, and FIG. The figure is a drive/brake circuit diagram, and FIGS. 5 and 6 are partial circuit diagrams illustrating the timing of switching the first switch and the second switch after switching the start/stop switch to the stop side, respectively. M...Sewing machine, 20...Sewing machine motor, 4°...Start/stop switch, 52...Setting position stop device, 5
6... Switch plate, 58... Notch, 60... Overhang, 62... Braking range, 64... Driving range, 67~
69... Electric contact, 70... Power supply circuit, 72... Auxiliary circuit, 74... Braking circuit, 76... DC power supply. Patent applicant: Brother Industries, Ltd.

Claims (1)

[Claims] (1) A power supply circuit connected to a DC motor as a sewing machine motor, a braking circuit connected to the DC motor forming a closed circuit, and interposed between the power supply circuit and the braking circuit, and both these circuits a selection switch that selectively closes the selection switch; an auxiliary circuit that connects a braking circuit side terminal and a power supply circuit side terminal of the selection switch; a first switch interposed in the auxiliary circuit; an interposed second switch operatively connected to the upper shaft of the sewing machine, when the rotational phase of the upper shaft is within a predetermined range of phases that includes at least a predetermined stop position of the upper shaft and precedes the stop position; opening the first switch and opening the second switch;
A setting position stop device for a sewing machine, comprising a switching means for closing a switch, and for otherwise closing the first switch and opening the second switch.