JP2008136571A - Bobbin thread tension controller of sewing machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To give tension of an appropriate level to a bobbin thread at timing desired by a user. <P>SOLUTION: The bobbin thread tension controller 1 of a sewing machine includes: a bobbin case 4 composed of a magnetic material; a thread pull-out groove for pulling out the bobbin thread to the outer side of the bobbin case; a tension imparting part for imparting the tension to the bobbin thread by clamping the bobbin thread with the outer peripheral surface of the bobbin case; a flexible part forming a part of the outer peripheral surface of the bobbin case, formed at a position facing the tension imparting part and formed so as to be bent in the radial direction of a hook; an exciting coil 6 provided on the outer periphery of a lower shaft 3 composed of the magnetic material; an inner cylinder part 51 provided between the exciting coil and the hook and composed of a non-magnetic material; an outer cylinder part 52 provided on the outer periphery of the inner cylinder part and composed of the magnetic material; and a connection part 24 provided to a position facing the lower shaft in the hook and composed of the non-magnetic material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a lower thread tension control device for a sewing machine.

2. Description of the Related Art Conventionally, there has been known a sewing machine that forms a seam by entwining an upper thread passed through a sewing needle and a lower thread of a bobbin held by a hook. In such a sewing machine, a bobbin thread tension control device 100 as shown in FIG. 5 has been proposed to change the tension applied to the bobbin thread in accordance with a change in the sewing speed.
As shown in FIG. 5, in the bobbin thread tension control device 100, a permanent magnet 104 is provided in a bobbin case 103 of a bobbin 102 held by the inner hook 101, and the permanent magnet 104 is located at a position facing the permanent magnet 104. An electromagnet 105 is provided at a distance from 104. When a magnetic field is generated around the electromagnet 105 by energizing the electromagnet 105, the permanent magnet 104 is moved away from or close to the electromagnet 105 under the influence of the magnetic field of the electromagnet 105. When the permanent magnet 104 is separated from the electromagnet 105, the permanent magnet 104 presses the bobbin 102 around which the lower thread is wound through the disc spring 106 toward the bottom of the inner hook 101, so that the bobbin 102 rotates due to friction with the inner hook 101. The speed drops and tension is applied to the lower thread. On the other hand, when the permanent magnet 104 approaches the electromagnet 105, the permanent magnet 104 does not press the disc spring 106, so the bobbin 102 around which the lower thread is wound is not pressed toward the bottom of the inner hook 101, and the bobbin No. 102 maintains the rotation speed without being affected by friction with the inner hook 101, and tension is not applied to the lower thread.
By utilizing such a principle, the tension applied to the lower thread can be controlled by appropriately adjusting the magnitude of the current flowing through the electromagnet 105 and the direction in which the current flows (see, for example, Patent Document 1). .
JP-A-5-68764

However, in the lower thread tension control device described above, the bobbin thread is pressed against the bottom of the inner hook to decelerate the rotation of the bobbin, thereby applying tension to the lower thread, but the lower thread has a certain degree of elasticity. For this reason, there is a problem that even if the bobbin is pressed against the inner hook, the lower thread only stretches and the tension desired by the user cannot be applied to the lower thread.
Further, since the timing for applying tension to the lower thread is delayed in time by the extension of the lower thread due to elongation of the lower thread, it is not possible to apply tension to the lower thread at the timing desired by the user. There was a problem.
Also, if the bobbin is pulled while the bobbin is pressed against the bottom of the inner hook, the bobbin thread wound around the bobbin is tightened by the bobbin, and a larger force than usual is required to feed the bobbin thread. For this reason, there was a problem that the tension of the lower thread after that increased.

  Accordingly, the present invention has been made to solve the above-described problems, and provides a lower thread tension control device for a sewing machine that can apply an appropriate magnitude of tension to a lower thread at a timing desired by a user. Objective.

  The invention according to claim 1 is accommodated in a hook formed of a magnetic material, holds a bobbin around which a lower thread is wound, and is formed on a bobbin case made of a magnetic material and an outer peripheral surface of the bobbin case. A bobbin pull-out groove for pulling out the bobbin thread wound around the bobbin, and an outer peripheral surface of the bobbin case provided to face a part of the bobbin pull-out groove, The lower thread is sandwiched between the outer peripheral surface and tension is applied to the lower thread, the tension applying portion made of a non-magnetic material, a part of the outer peripheral surface of the bobbin case, and the portion having the thread extraction groove, And a flexible portion formed at a position facing the tension applying portion and capable of bending in the radial direction of the hook, and rotating the hook about its axis, Provided on the outer periphery of the lower shaft An excitation coil, an outer periphery of the lower shaft and provided between the excitation coil and the shuttle, an inner cylinder portion made of a non-magnetic material, and an outer periphery of the inner cylinder portion. It is provided with the outer cylinder part which consists of material, and the connection part which is provided in the position facing the said lower shaft in the said hook, and consists of a nonmagnetic material.

According to the first aspect of the present invention, when the exciting coil is energized, the magnetic lines of force generated from the exciting coil pass from the lower shaft made of the magnetic material through the inside of the hook to the outer peripheral surface of the bobbin case made of the magnetic material. It is transmitted. When the magnetic lines of force are transmitted to the outer peripheral surface of the bobbin case, the flexible part forming a part of the outer peripheral surface of the bobbin case bends toward the outside of the hook under the influence of the magnetic field lines, and the tension applying part made of a non-magnetic material is It does not deform under the influence of magnetic field lines. When the flexible portion bends toward the outside of the hook, the flexible portion presses the tension applying portion, and tension is applied to the lower thread drawn out from the yarn drawing groove.
As a result, by changing the amount of current applied to the exciting coil, the strength of the magnetic force also changes, and the tension applied to the lower thread can be changed. Tension control can be performed.
Also, by controlling the tension of the lower thread by such a method, the tension of the lower thread can be directly controlled, so that the tension desired by the user can be given to the lower thread, and there is also a time delay. Does not occur. In addition, since control is not performed on the lower thread wound around the bobbin, the lower thread wound around the bobbin is not tightened on the bobbin, and a larger force than usual is required to feed the lower thread. There will be no such thing.
Therefore, an appropriate magnitude of tension can be applied to the lower thread at a timing desired by the user.

  According to a second aspect of the present invention, in the lower thread tension control device of the sewing machine according to the first aspect, the current to be applied to the exciting coil is an alternating current.

  According to the second aspect of the present invention, by applying an alternating current to the exciting coil, no residual stress remains even after the energization to the exciting coil is cut off and the generation of magnetic field lines is eliminated.

  A third aspect of the present invention is the lower thread tension control device of the sewing machine according to the first or second aspect, further comprising a control device that controls the amount of current that is applied to the exciting coil, wherein the control device is capable of sewing. When the process is completed, the energization to the exciting coil is stopped while gradually reducing the amount of current.

  According to the third aspect of the present invention, when the sewing is finished, the control device stops energization to the exciting coil while gradually reducing the current amount, so that the magnetic circuit remains magnetized to one polarity. It can be prevented from becoming a state.

According to the first aspect of the present invention, by changing the amount of current applied to the exciting coil, the strength of the magnetic force can be changed, and the tension applied to the lower thread can be changed. The bobbin thread tension can be controlled simply by controlling.
Also, by controlling the tension of the lower thread by such a method, the tension of the lower thread can be directly controlled, so that the tension desired by the user can be given to the lower thread, and there is also a time delay. Does not occur. In addition, since control is not performed on the lower thread wound around the bobbin, the lower thread wound around the bobbin is not tightened on the bobbin, and a larger force than usual is required to feed the lower thread. There will be no such thing.
Therefore, an appropriate magnitude of tension can be applied to the lower thread at a timing desired by the user.

  According to the second aspect of the present invention, by applying an alternating current to the exciting coil, no residual stress remains even after the energization to the exciting coil is cut off and the generation of magnetic field lines is eliminated.

  According to the third aspect of the present invention, when the sewing is finished, the control device stops energization to the exciting coil while gradually reducing the current amount, so that the magnetic circuit remains magnetized to one polarity. It can be prevented from becoming a state.

Hereinafter, an embodiment of a lower thread tension control device of a sewing machine according to the present invention will be described.
(Configuration of sewing thread lower tension control device)
As shown in FIGS. 1 to 4, a lower thread tension control device 1 (hereinafter referred to as a lower thread tension control device 1) of the sewing machine is disposed below a sewing machine table T on which a sewing product is placed, A bobbin case 4 that holds a bobbin around which a lower thread is wound from a part of a hook 2 that entangles a lower thread wound around a bobbin B with an upper thread passed through a sewing needle, and a lower shaft 3 that rotates the hook 2 It is provided over.

(Pot)
First, the hook 2 will be described. As shown in FIGS. 1 and 2, the hook 2 is provided below the sewing needle in the sewing machine table T, and is driven to rotate by a sewing machine motor which is a drive source for moving the sewing needle up and down. The lower shaft 3 is fixed. In other words, the vertical movement of the sewing needle and the rotation of the hook 2 operate in synchronization, and when the sewing needle descends, the hook 2 catches the upper thread passed through the sewing needle and is held by the hook 2 Entangled the lower thread.

The hook 2 has a sword tip that captures an upper thread loop formed by an upper thread passed through a sewing needle, and stores an outer hook 21 fixed to a rotatable hook shaft (lower shaft) 3 and a bobbin B. A bobbin case 4 is held inward, and an inner hook 22 is rotatably held inward of the outer hook 21.
The inner hook 22 is formed with a recess (not shown) that is fitted into a projection (not shown) fixed to the sewing machine frame. The recess is fitted into the projection, and the outer shaft 21 is rotated by rotating the lower shaft 3. It rotates around the axis of the lower shaft 3.

The inner hook 22 has a support shaft 23 formed on the same axis as the lower shaft 3, and the bobbin case 4 is passed through the support shaft 23. The bobbin case 4 is supported by the support shaft 23 and rotates relative to the outer hook 21 by the rotation of the lower shaft 3. The inner pot 22 is formed of a magnetic material such as iron or steel that allows passage of magnetic lines formed by the exciting coil 6 to be described later, except for a part thereof. However, the bottom portion 22a of the inner hook 22 is formed of a non-magnetic material that is not affected by the lines of magnetic force generated by the exciting coil 6, such as aluminum or copper.
The outer hook 21 is formed of a magnetic material (iron, steel, etc.) that allows the magnetic lines of force formed by the exciting coil 6 to pass through, except for a part. However, the connecting portion 24 of the outer hook 21 with the lower shaft 3 is a non-magnetic material (aluminum, copper, etc.) whose inner layer 24a facing the outer periphery of the lower shaft 3 is not affected by the lines of magnetic force generated by the exciting coil 6. The outer layer 24b formed on the outer side of the inner layer 24a is made of a magnetic material (iron, steel, etc.) that allows the magnetic lines of force formed by the exciting coil 6 to pass therethrough.

(Bottom axis)
The lower shaft 3 is rotatable around the axis and is connected to the shuttle 2 via a connecting portion 24. The lower shaft 3 is made of a magnetic material (iron, steel, etc.) that passes the magnetic lines of force formed by the exciting coil 6.

(Bearing metal)
A bearing metal 5 is provided on the outer periphery of the lower shaft 3 so as to be adjacent to the connecting portion 24 of the hook 2. The bearing metal 5 is provided on the outer periphery of the lower shaft 3 and between the exciting coil 6 and the shuttle 2, and is made of a non-magnetic material (aluminum, copper, etc.) that is not affected by the lines of magnetic force generated by the exciting coil 6. A two-layer structure including an inner cylinder portion 51 and an outer cylinder portion 52 that is provided on the outer periphery of the inner cylinder portion 51 and is made of a magnetic material (iron, steel, etc.) that passes the magnetic lines formed by the exciting coil 6. It is said that. With such a structure, the magnetic lines of force generated by the exciting coil 6 can pass only through the outer cylindrical portion 52 outside the bearing metal 5.

(Excitation coil)
The exciting coil 6 is provided adjacent to the bearing metal 5 so as to surround the outer periphery of the lower shaft 3. The exciting coil 6 is composed of an electromagnet, and generates a magnetic field around it when energized. As shown by the arrow in FIG. 4, the magnetic lines of force generated by the generated magnetic field pass through the lower shaft 3 provided with the exciting coil 6, pass through the outer side from the support shaft 23 of the shuttle 2, and pass through the outer layer 24 b of the connecting portion 24. A magnetic circuit that returns to the exciting coil 6 through the outer cylindrical portion 52 is formed.

(Bobbin case)
The bobbin case 4 is made of a magnetic material that allows the magnetic lines of force formed by the exciting coil 6 to pass through, for example, a material such as iron or steel.
As shown in FIG. 3, a thread drawing groove 41 for pulling out the lower thread wound around the bobbin B to the outside of the bobbin case 4 is formed on the outer peripheral surface of the bobbin case 4.
The bobbin case 4 is provided on the outer peripheral surface of the bobbin case 4 so as to face a part of the thread drawing groove 41. A tension spring 42 is attached by a set screw 43. The tension spring 42 is made of a non-magnetic material (aluminum, copper, etc.) that is not affected by the magnetic lines of force generated by the exciting coil 6. Even if a magnetic field is generated by energizing the exciting coil 6, the magnetic spring 42 There is no deformation under the influence. The tension spring 42 can change the tension applied to the lower thread by changing the degree of fastening of the set screw 43 to the bobbin case 4.

The bobbin case 4 forms a part of the outer peripheral surface of the bobbin case 4 including the portion where the thread drawing groove 41 is formed, is formed at a position facing the tension spring 42, and is bent in the radial direction of the hook 2. A flexible portion 44 is formed so as to be able to be removed.
The flexible portion 44 is formed by forming a notch in the outer peripheral surface of the bobbin case 4, is formed so that the proximal end side is continuous with the outer peripheral surface of the bobbin case 4, and the distal end side is separated from the outer peripheral surface of the bobbin case 4. It is formed to be a free end. In addition, since the flexible portion 44 is a part of the bobbin case 4, it is made of a magnetic material (iron, steel, etc.) that allows the magnetic lines of force formed by the exciting coil 6 to pass therethrough as with the bobbin case 4.

  Thereby, the flexible part 44 can bend in the radial direction of the shuttle 2 with the base end side as a fulcrum. Specifically, in a state where the exciting coil 6 is not energized, the flexible portion 44 is located along the outer peripheral surface of the bobbin case 4 (the state of the flexible portion 44a in FIG. 3A). When the exciting coil 6 is energized and a magnetic field is generated around it, it is elastically deformed toward the outside of the hook 2 due to the influence of the lines of magnetic force, and is slightly projecting from the outer peripheral surface of the bobbin case 4 (FIG. 3A). The state of the flexible portion 44b in FIG. Note that the flexible portion 44a and the flexible portion 44b in FIG. 3 (a) are the same as the flexible portion 44, and are simply given different reference numbers for the purpose of explaining the movement of the flexible portion 44. is there.

(Control device)
The exciting coil 6 is connected to a control device (not shown) that controls the driving of the sewing machine. The control device controls the amount of current to be applied to the exciting coil 6 according to the tension to be applied to the lower thread, and when it is desired to increase the tension to be applied to the lower thread, the amount of current to be applied to the exciting coil 6 is determined. Increase it. The exciting coil 6 is energized with an alternating current so that the magnetic circuit is not magnetized to one side.
In addition, when the sewing is finished, the control device performs energization control to the excitation coil 6 so as to stop energization to the excitation coil 6 while gradually decreasing the amount of current.

(Function and effect)
As shown in FIG. 4, when the excitation coil 6 is energized, a magnetic field is generated around the excitation coil 6, and the magnetic field lines of this magnetic field pass from the lower shaft 3 made of a magnetic material through the support shaft 23 of the shuttle 2, It is transmitted to the outer peripheral surface of the bobbin case 4 made of a magnetic material. When the magnetic lines of force are transmitted to the outer peripheral surface of the bobbin case 4, the flexible portion 44 made of a magnetic material forming a part of the outer peripheral surface of the bobbin case 4 is bent toward the outside of the hook 2 under the influence of the magnetic lines of force. The tone spring 42 made of a magnetic material is not deformed by the influence of the lines of magnetic force. When the flexible portion 44 bends toward the outside of the hook 2, the flexible portion 44 presses the tension spring 42, and tension is applied to the lower thread pulled out from the thread drawing groove 41. The magnetic lines of force transmitted to the flexible portion 44 are transmitted to 52 through the outer layer 24b of the connecting portion without returning to the inside of the hook 2 because the bottom portion 22a of the inner pot 22 is formed of a non-magnetic material. Eventually it returns to the exciting coil 6.

In addition, by changing the amount of current flowing through the exciting coil 6, the strength of the magnetic force also changes, the force with which the flexible portion 44 presses the tension spring 42 also changes, and the tension applied to the lower thread can be changed. The bobbin thread tension can be controlled simply by controlling the energization amount to the exciting coil 6.
Also, by controlling the tension of the lower thread by such a method, the tension of the lower thread can be directly controlled, so that the tension desired by the user can be given to the lower thread, and there is also a time delay. Does not occur. Further, since control is not performed on the lower thread wound around the bobbin B, the lower thread wound around the bobbin B is not tightened on the bobbin B, and a force larger than usual for unwinding the lower thread. Is no longer necessary.
Therefore, an appropriate magnitude of tension can be applied to the lower thread at a timing desired by the user.

In addition, by applying an alternating current to the exciting coil 6, no residual stress remains even after the energization of the exciting coil 6 is cut off and the generation of magnetic field lines is eliminated.
In addition, since the control device stops energizing the exciting coil 6 while gradually reducing the amount of current when the sewing is completed, the magnetic circuit is prevented from being magnetized to one polarity. Can do.
In addition, by using an electromagnet as the exciting coil 6 that forms the magnetic field, current is not supplied when the tension is not adjusted, so that iron powder or the like does not adhere and maintenance is easy.
Also, by setting information on tension control in advance in the memory of the control device, there is almost no manual operation, so that the tension of the lower thread can be controlled in a relatively stable state.
Further, the tension applied to the lower thread can be easily adjusted only by controlling the magnetic force by the exciting coil 6, that is, the energization amount to the exciting coil 6.

Further, in the process in which the magnetic lines of force are transmitted from the lower shaft 3 to the hook 2, the inner cylinder portion 51 of the bearing metal 5 provided around the lower shaft 3 is made of a nonmagnetic material, so that the magnetic lines of force leak around the lower shaft 3. It is transmitted only in the axial direction of the lower shaft 3. Thereby, the loss of magnetic lines of force is reduced, and the tension of the lower thread can be controlled with a small amount of energization.
Further, since the connecting portion 24 that connects the lower shaft 3 and the hook 2 is made of a non-magnetic material, the lines of magnetic force transmitted to the outside of the hook 2 do not return to the outer cylinder portion 52 without returning to the inner side of the lower shaft 3 or the hook 2. It is transmitted. As a result, the lines of magnetic force that have once passed through the flexible portion 44 do not hinder the outward bending of the flexible portion 44.
In addition, since the exciting coil 6 can be provided at a position away from the hook 2, there is no need to newly attach the outer periphery of the hook 2 or the bobbin case 4. Does not interfere with work.
Further, since the tension of the lower thread can be controlled simply by distinguishing the material forming each part from a magnetic material or a non-magnetic material, the shape of the hook 2 is high and versatility is high.

(Other)
The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the magnetic circuit is configured such that the direction of the magnetic force line is directed from the inside to the outside of the hook 2, but the magnetic circuit may be configured so that the magnetic line of force is directed from the outside to the inside of the hook. In this case, the tension spring outside the outer peripheral surface of the bobbin case may be formed of a magnetic material, and the rigidity may be increased without forming a flexible portion in the bobbin case. As a result, the tension spring affected by the lines of magnetic force can bend toward the outer peripheral surface of the bobbin case inside the tension spring, and tension can be applied to the lower thread.

The front view which carried out the cross sectional view of a part of the lower thread tension control device of the sewing machine provided below the sewing machine table. Sectional drawing of a pot. (A) is a top view of a bobbin case, (b) is a side view of a bobbin case. The front view which looked at a part of the lower thread tension control device of the sewing machine which showed the direction of the line of magnetic force generated from the exciting coil. Sectional drawing of the lower thread tension control apparatus of the sewing machine in a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lower thread tension control apparatus 2 Sewing machine 4 Bobbin case 6 Excitation coil 24 Connection part 41 Thread extraction groove 42 Tone spring (tension applying part)
44 Flexible part 51 Inner cylinder part 52 Outer cylinder part B Bobbin

Claims (3)

A bobbin case made of a magnetic material, which is housed in a hook made of a magnetic material and holds a bobbin around which a lower thread is wound;
A thread drawing groove formed on the outer peripheral surface of the bobbin case and for drawing out the lower thread wound around the bobbin to the outside of the bobbin case;
Tension made of a non-magnetic material that is provided on the outer peripheral surface of the bobbin case so as to face a part of the thread pull-out groove and sandwiches the lower thread with the outer peripheral surface of the bobbin case to apply tension to the lower thread. A granting unit;
A part of the outer peripheral surface of the bobbin case, which is a part having the thread drawing groove, is formed at a position facing the tension applying portion, and can be bent in the radial direction of the hook. A formed flexible portion;
An exciting coil provided on the outer periphery of the lower shaft made of a magnetic material, rotating the hook around its axis,
An outer cylinder of the lower shaft, and provided between the exciting coil and the hook, and an inner cylinder portion made of a non-magnetic material;
An outer cylinder portion provided on an outer periphery of the inner cylinder portion and made of a magnetic material;
A connecting portion provided at a position facing the lower shaft in the hook, and made of a non-magnetic material;
A bobbin thread tension control device for a sewing machine comprising:   2. The bobbin thread tension control device of the sewing machine according to claim 1, wherein an electric current supplied to the exciting coil is an alternating current. A control device for controlling the amount of current flowing through the exciting coil;
3. The bobbin thread tension control device according to claim 1, wherein when the sewing is finished, the control device stops energization of the exciting coil while gradually reducing the amount of current. 4.

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