JP2008023047A - Bobbin thread tension control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bobbin thread tension control device for appropriately controlling the tension of the bobbin thread of a sewing machine. <P>SOLUTION: A bobbin thread tension device 30 includes a flexible tension spring 31 (a leaf spring) made of a magnetic material on the outer periphery of a bobbin case 27 which holds a bobbin 26 slackly fitted in a shuttle hook 24. Prescribed tension is applied to the bobbin thread 8 by directly clasping the bobbin thread 8 between an end (a clasping part) of the tension spring 31 and the outer periphery of the bobbin case 27. One end of an electromagnet 32 is disposed at a position close to the tension spring 31 on the outer side of the bobbin case 27, and an electric current according to the sewing speed is applied to the electromagnet 32. When the electric current is distributed to the electromagnet 32, the tension spring 31 is attracted with the magnetic force generated in the electromagnet 32, and is moved in a direction in which the energization force to the outer periphery of the bobbin case 27 is reduced, that is a direction separated from the outer periphery. Accordingly, the tension of the bobbin thread can be adjusted in real time within the range of initial tension. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a bobbin thread tension control device that controls the bobbin thread tension of a sewing machine.

Generally, a sewing machine is provided with a needle drive mechanism for reciprocating a sewing needle up and down, and a shuttle mechanism for performing sewing in cooperation with the sewing needle in the sewing machine bed. The hook mechanism has a hook made up of a rotating outer hook and a non-rotating inner hook provided inside the outer hook, and the inner hook has a lower thread on a spindle projecting from the inner hook. A bobbin as a supply source is rotatably mounted, and a bobbin case is detachably attached.
By the way, it is not preferable that the lower thread pulled out from the bobbin is pulled out more than necessary or the necessary amount is not pulled out compared to the upper thread, and an appropriate amount is supplied according to the sewing conditions. Is desirable. Therefore, conventionally, a configuration has been adopted in which a plate spring is provided on the bobbin case, and the lower thread is sandwiched between the plate spring and the bobbin case, thereby applying a constant tension to the lower thread.
In addition, in a sewing machine having a so-called vertical hook that rotates coaxially with the lower shaft that rotates fully in conjunction with the main shaft (upper shaft), the bottom of the sewing machine that adjusts the tension of the lower thread fed from the inside of the hook. A yarn tension control device is known (see, for example, Patent Document 1).

The conventional lower thread tension control device includes an elastic body (for example, a disc spring) that contacts the end surface of the bobbin between the inner bottom portion of the bobbin case and the end surface of the bobbin facing the bobbin case. An annular permanent magnet that is adjacently movable in the thrust direction is provided, and an electromagnet disposed opposite to the outer bottom of the bobbin case is provided outside the bobbin case. Then, with the electromagnet approaching the outside (end wall portion) of the bobbin case, a current corresponding to the sewing speed is passed through the coil of the electromagnet, and magnetized to a polarity opposite to that of the permanent magnet. The permanent magnet moves in the thrust direction (direction toward the end face of the bobbin) in response to the repulsive force corresponding to. As a result of the permanent magnet pressing the end surface of the bobbin via the elastic body, a braking force corresponding to the sewing speed acts on the bobbin, and a predetermined tension is applied to the lower thread. In other words, the conventional lower thread tension control device adjusts the repulsive force acting on the permanent magnet provided inside the hook by controlling the current flowing to the electromagnet provided outside the hook, and rotates the bobbin. The tension of the lower thread fed from the bobbin is controlled by increasing or decreasing the resistance.
JP 05-68764 A

  However, when the lower thread is pulled out with the braking force applied to the rotation of the bobbin due to the compression, the tension is consumed by tightly binding the bundle of lower threads wound around the bobbin to obtain the desired lower thread tension. That is not always easy. That is, the conventional lower thread tension control device has a problem that the desired lower thread tension cannot always be obtained even if the bobbin is pressed. Further, even when the bobbin is compressed to adjust the tension of the lower thread, there is a problem that a time delay occurs until an actual change appears in the lower thread tension due to the binding of the lower thread. Further, since the bundle of lower threads wound around the bobbin is tightly bound, a large force is required for the subsequent withdrawal of the lower threads, resulting in a problem that the subsequent lower thread tension increases. .

  An object of the present invention is to appropriately control the tension of the lower thread.

  In order to solve the above-described problem, the invention according to claim 1 is provided with a bobbin case for holding a bobbin, and a lower thread that is provided on an outer peripheral part or an inner peripheral part of the bobbin case and is pulled out from the bobbin by a clamping part. A lower thread tension applying means and a lower thread tension adjusting means disposed on the outside of the bobbin case, and either the clamping part or the lower thread tension adjusting means is made of a magnetic material, and The bobbin thread tension adjusting means adjusts the bobbin thread tension by adjusting the magnetic force applied to the clamping portion.

  According to a second aspect of the present invention, in the first aspect of the present invention, the clamping portion of the lower thread tension applying means is a leaf spring made of a magnetic material.

  According to a third aspect of the present invention, in the first aspect of the present invention, the holding portion of the lower thread tension applying means is a roller made of a magnetic material, and the lower thread tension applying means includes a spring that provides rotational resistance to the roller. It is characterized by having.

  The invention according to claim 4 is the invention according to claim 1, wherein the holding portion of the lower thread tension applying means is a flexible piece made of a magnetic material formed from a part of the peripheral wall of the bobbin case, The bobbin thread tension applying means has a pressing part made of a magnetic material harder than a nonmagnetic material or the flexible piece while being in contact with the holding part, and holding the bobbin thread between the holding part and the pressing part. Features.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the clamping portion includes a permanent magnet.

  According to a sixth aspect of the present invention, in the invention according to any one of the first to fifth aspects, the lower thread tension control device includes an electromagnet, and the magnetic force is changed by changing a current flowing through the electromagnet. It is characterized by doing.

  According to a seventh aspect of the present invention, in the invention according to any one of the first to fifth aspects, the lower thread tension control device includes a permanent magnet, and a clamping portion between the permanent magnet and the lower thread tension applying means. The magnetic force is adjusted by changing the distance between and.

  According to the first aspect of the present invention, the lower thread pulled out from the bobbin is directly clamped by the clamping part of the lower thread tension applying means provided on the outer peripheral part or the inner peripheral part of the bobbin case. Further, the bobbin thread tension is adjusted by adjusting the magnetic force applied to the pinching portion formed of a magnetic material from the bobbin thread tension adjusting means disposed outside the bobbin case. That is, it is possible to adjust the lower thread tension by controlling the force directly clamping the lower thread drawn from the bobbin from the outside of the bobbin case. Therefore, when tension is applied to the lower thread, the lower thread wound around the bobbin is not tightly wound around the bobbin. Thereby, the time delay until the desired tension is applied to the lower thread can be eliminated, and the responsiveness when changing the lower thread tension can be improved. Further, it is possible to solve the problem that after the predetermined tension is applied to the lower thread, the subsequent lower thread tension generally increases due to the tight binding. That is, by appropriately adjusting the magnetic force applied to the holding portion from the lower thread tension adjusting means, the lower thread tension can be appropriately controlled, and a desired lower thread tension can be obtained.

  According to the invention described in claim 2, in addition to obtaining the same effect as that of the invention described in claim 1, in particular, the holding part of the lower thread tension applying means is a leaf spring made of a magnetic material. One end of the leaf spring is attached to the outer peripheral portion or inner peripheral portion of the bobbin case, and the other end is urged toward the bobbin case, thereby holding the lower thread between the other end of the leaf spring and the bobbin case. can do. When a magnetic force is generated in the lower thread tension adjusting means, the other end side of the leaf spring formed of a magnetic material is attracted and attracted to the lower thread tension adjusting means.

In other words, since the lower thread tension adjusting means is disposed outside the bobbin case and generates magnetic force, for example, when a leaf spring is provided on the outer periphery of the bobbin case, the lower thread tension adjusting means is turned OFF and the magnetic force is adjusted. When it does not occur, the force to pinch the lower thread becomes maximum and the lower thread tension becomes maximum. Further, when the lower thread tension adjusting means is ON, the other end of the leaf spring is attracted to the lower thread tension adjusting means side against the biasing force of the leaf spring in accordance with the action of the magnetic force by the lower thread tension adjusting means. As a result, the lower thread tension is reduced as a result of a decrease in the force for clamping the lower thread. That is, the lower thread tension can be adjusted within the range of the maximum value of the lower thread tension determined by the urging force of the leaf spring, that is, the initial tension.
On the other hand, when the leaf spring is provided on the inner periphery of the bobbin case, the clamping force is minimized and the lower thread tension is minimized when the lower thread tension adjusting means is OFF. Further, when the lower thread tension adjusting means is ON, the pinching force increases as the action of the magnetic force increases. That is, the tension can be adjusted in a range larger than the initial tension by increasing the action of the magnetic force.

  According to the invention described in claim 3, in addition to obtaining the same effect as that of the invention described in claim 1, in particular, the holding portion of the lower thread tension applying means is a roller made of a magnetic material, and lower thread tension applying The means includes a spring that provides rotational resistance to the roller. That is, the bobbin thread pulled out from the bobbin is pinched by the roller and the bobbin case made of a magnetic member that is a pinching part. When a magnetic force is generated in the lower thread tension adjusting means, a roller made of a magnetic member is attracted to the lower thread tension adjusting means. Therefore, for example, when the roller is provided on the inner peripheral portion of the bobbin case, the lower thread tension can be adjusted in a range larger than the initial tension. On the other hand, when the roller is provided on the outer peripheral portion of the bobbin case, the bobbin thread tension can be adjusted within a range smaller than the initial tension. Further, the rotation resistance is applied to the roller by the spring, so that the lower thread is fed out from the bobbin, and the lower thread tension is increased.

According to the fourth aspect of the invention, the same effect as that of the first aspect of the invention can be obtained, and in particular, the flexible piece made of a magnetic material formed from a part of the peripheral wall of the bobbin case is a lower thread It functions as a clamping part of the tension applying means. Further, the lower thread is sandwiched between the flexible piece made of the magnetic material and the pressing portion made of a non-magnetic material in contact with the flexible piece or a magnetic material harder than the flexible piece. Then, when the magnetic force of the lower thread tension adjusting means is generated, the flexible piece made of a magnetic material is attracted to the lower thread tension adjusting means side, that is, outside the bobbin case.
That is, when the presser part is formed of a non-magnetic material, the presser part does not react even if a magnetic force is generated in the lower thread tension adjusting means. Therefore, the presser part that does not react to the magnetic force and the flexible piece attracted by the magnetic force Can adjust the force to clamp the lower thread.

On the other hand, when the presser part is formed of a magnetic material harder than the flexible piece, when a magnetic force is generated in the lower thread tension adjusting means, the flexible piece and the presser part both receive an attractive force in a direction attracted by the magnetic force. However, the flexible piece is easily bent by a magnetic force weaker than that of the pressing portion, whereas the pressing portion is not deformed. Therefore, the force for holding the lower thread can be adjusted by the pressing portion and the flexible piece. .
Therefore, when the pressing portion is provided on the outer peripheral portion of the bobbin case, it is possible to apply a tension larger than the initial tension to the lower thread by adjusting the magnetic force of the lower thread tension adjusting means. In addition, when a presser is provided on the inner periphery of the bobbin case, the initial tension becomes the maximum tension, and the lower thread tension is adjusted by increasing or decreasing the magnetic force of the lower thread tension adjusting means within the range of the initial tension. Can do.

According to the invention described in claim 5, the same effect as that of any one of the inventions described in claims 1 to 4 can be obtained, and in particular, since the clamping portion includes a permanent magnet, By making the polarity of the permanent magnet and the polarity of the magnetic force generated by the bobbin thread tension adjusting means different or the same polarity, not only an attractive force but also a repulsive force can be applied to the clamping portion. That is, even when the clamping part is provided on the outer peripheral part of the bobbin case, not only is the suction part sucked in a direction away from the outer periphery of the bobbin case, but the clamping part is pressed against the outer periphery of the bobbin case. Yarn can be clamped. Even when the clamping part is provided on the inner peripheral part of the bobbin case, the clamping part can be removed not only in the inner peripheral side of the bobbin case but also in a direction away from the inner periphery.
In other words, regardless of whether the clamping part is provided on the outer peripheral part or the inner peripheral part of the bobbin case, the lower thread tension adjusting means adjusts the magnetic force generated so that the magnitude can be increased or decreased based on the initial tension. The tension can be adjusted, and the range of adjustable bobbin thread tension can be greatly expanded.

  According to the sixth aspect of the present invention, the same effect as the first aspect of the present invention can be obtained. In particular, the lower thread tension control device includes an electromagnet, and the electromagnet The magnetic force of the lower thread tension adjusting means is changed by changing the current passed through the thread. That is, by controlling the current flowing through the electromagnet, the value and polarity of the magnetic force generated by the electromagnet can be quickly and appropriately adjusted. Further, for example, when a current having a magnitude corresponding to the sewing speed is passed through the electromagnet, a lower thread tension corresponding to the sewing speed can be applied.

  According to the invention described in claim 7, in addition to obtaining the same effect as the invention described in any one of claims 1 to 5, in particular, the lower thread tension control device includes a permanent magnet, The magnetic force of the bobbin thread tension adjusting means is adjusted by changing the distance between the permanent magnet and the clamping portion. That is, the magnetic force acting on the sandwiching portion can be increased by increasing the distance between the sandwiching portion and the permanent magnet, and the magnetic force acting on the sandwiching portion by increasing the distance between the sandwiching portion and the permanent magnet. Can reduce the effects of

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. However, in the following description, various preferable limitations for implementing the present invention are given, but the scope of the invention is not limited to the following embodiments.
Here, in the following description, a direction in which an upper shaft 2 described later extends is a Y-axis direction, a direction perpendicular to the Y-axis direction and a needle bar 6 (described later) moves up and down is a Z-axis direction, Y A direction orthogonal to both the axial direction and the Z-axis direction is defined as an X-axis direction.

(First embodiment: overall configuration)
The configuration of the first embodiment will be described in detail with reference to FIGS.
In the present embodiment, the sewing machine 1 including a vertical hook 21 that rotates coaxially with the lower shaft 9 disposed in the sewing machine bed will be described as an example.
As shown in FIG. 1, a sewing machine 1 according to the present embodiment is arranged in a sewing machine motor (not shown) which is a main drive source of the sewing machine 1 and a sewing machine arm which is connected to the sewing machine motor and forms an upper part of a sewing machine frame (not shown). An upper shaft 2 provided, a needle driving mechanism 10 that is provided at the tip of the upper shaft 2 and drives a needle bar 6 that holds a sewing needle 7 up and down at the lower end, and a sewing machine bed that forms a lower portion of a sewing machine frame (not shown) A lower shaft 9 interlocked with the upper shaft 2, a hook mechanism 20 provided in the sewing machine bed and forming a seam in cooperation with the needle driving mechanism, and a lower thread 8 supplied from the hook mechanism 20 A bobbin thread tension device 30 as a bobbin thread tension control device that adjusts the tension, and a control unit (not shown) that controls the operation of each of the mechanisms 10, 20, and 30 are provided.

(Sewing frame)
A sewing machine frame (not shown) is a machine frame that is substantially U-shaped when viewed as a whole, and includes a sewing machine bed that forms the lower part of the machine frame, a vertical trunk that is erected upward from one end of the sewing machine bed, and a sewing machine frame. And a sewing machine arm extending substantially in parallel with the sewing machine bed from the upper part of the vertical body in the same direction as the sewing machine bed.
An upper shaft 2 extending along the longitudinal direction of the sewing machine arm, that is, the Y-axis direction is rotatably provided inside the sewing machine arm. In addition, a lower shaft 9 extending along the longitudinal direction of the sewing bed, that is, the Y-axis direction is rotatably provided inside the sewing bed.
The lower shaft 9 is connected to the upper shaft 2 via the vertical axis 11 and the bevel gear 12, and rotates in conjunction with the upper shaft 2 (see FIG. 1).

(Needle drive mechanism)
The needle drive mechanism 10 includes an upper shaft 2 that is a main shaft that is rotationally driven by a sewing machine motor, a rotary weight 3 that is fixedly mounted at the tip of the upper shaft 2, and one end fixedly mounted at an eccentric position of the rotary weight 3. A crank rod 4, a needle bar holder 5 connected to the other end of the crank rod 4, and a needle bar 6 supported by the needle bar holder 5 and holding a sewing needle 7 at the lower end are provided (see FIG. 1). ).
When the upper shaft 2 and the rotary weight 3 are rotated by driving the sewing machine motor, one end of the crank rod 4 connected to the eccentric position of the rotary weight 3 performs a circular motion of the circular orbit. A needle bar 6 connected to the other end portion of the crank rod 4 via a needle bar holder 5 is supported so as to be movable only in the vertical direction, and only the vertical movement component of the circular motion is transmitted to the needle bar 6 and the needle. The bar 6 and the sewing needle 7 reciprocate up and down. An upper thread is inserted through a threader (not shown) provided at the lower end of the sewing needle 7.

(Hook mechanism)
As shown in FIGS. 1 to 3, the shuttle mechanism 20 is provided at the tip of the lower shaft 9 in the sewing machine bed, and is a vertical shuttle 21 (hereinafter simply referred to as the shuttle 21) that rotates coaxially with the lower shaft 9. ).
The hook 21 is constituted by an outer hook 22 that is coaxially rotated with the lower shaft 9 coaxially with the lower shaft 9, and a non-rotating inner hook 24 that is loosely fitted coaxially with the lower shaft 9 inside the outer hook 22. (See FIG. 2 and FIG. 3).
The outer hook 22 includes a sharpened sword tip (not shown) in a part of the outer periphery thereof in the rotation direction.
A support shaft 25 that extends coaxially with the lower shaft 9 protrudes from the inner hook 24.
A bobbin 26 as a lower thread supply source around which the lower thread 8 is wound is mounted on the support shaft 25 in a loosely fitted state and is rotatably supported.

A bobbin case 27 is detachably attached to the tip of the support shaft 25.
The bobbin case 27 is formed in a substantially cylindrical shape with one end opened and a connecting portion with the support shaft 25 at the center of the other end. The bobbin case 27 functions as a holding member that holds the bobbin 26 inside the inner hook 24 by being mounted so that the inner bottom thereof faces the inner bottom of the inner hook 24.
A notch 19 for passing the lower thread 8 is provided in the peripheral wall of the bobbin case 27, and an outer peripheral part of the bobbin case 27, which is outside the notch 19, applies tension to the lower thread 8, which will be described later. A tension spring 31 of the lower thread tension device 30 is attached along the outer periphery of the bobbin case 27 (see FIGS. 4 and 5).
When the upper shaft 2 and the lower shaft 9 interlocked with the upper shaft 2 perform full rotation by driving the sewing machine motor, the inner hook 24 loosely fitted inside the outer hook 22 remains in a stopped state. The outer hook 22 connected to the shaft 9 rotates around the shaft in synchronization with the vertical movement of the sewing needle 7. At that time, the sword traps the loop of the upper thread formed by the raising of the sewing needle 7, and the seam is formed by entanglement of the upper thread and the lower thread 8 drawn from the bobbin 26 in the inner hook 24. .

(Lower thread tension device)
The lower thread tension device 30 functions as a lower thread tension control device in the present embodiment that adjusts the tension applied to the lower thread 8 (hereinafter referred to as lower thread tension).
The lower thread tension device 30 is provided on the outer peripheral portion of the bobbin case 27, and is disposed on the outer side of the bobbin case 27, and a tension spring 31 as a lower thread tension applying means for sandwiching the lower thread 8 drawn from the bobbin 26. And an electromagnet 32 as lower thread tension adjusting means for generating magnetic force (see FIGS. 1 and 4).

As shown in FIG. 4, the tension spring 31 is a flexible leaf spring made of a magnetic material (magnetic body), and is formed in a substantially arc shape along the outer peripheral portion of the peripheral wall of the bobbin case 27. . One end of the tension spring 31 is fixed to a part of the peripheral wall (outer peripheral portion) of the bobbin case 27 with a screw, and the other end is urged so as to press the outer peripheral portion of the bobbin case 27.
In the present embodiment, a tension (lower thread tension) is applied to the lower thread 8 by sandwiching the lower thread 8 between the other end of the tension spring 31 and the outer peripheral portion of the bobbin case 27. That is, in the present embodiment, the other end portion of the tension spring 31 that is biased to the outer peripheral portion of the bobbin case 27 functions as a clamping portion that clamps the lower thread. Specifically, the shape and elastic force of the tension spring 31 are such that the tension (hereinafter referred to as initial tension) applied to the lower thread 8 when the electromagnet 32 (described later) is OFF is about 0.49 [N]. Is set.

The electromagnet 32 is disposed in the vicinity of the tension spring 31 around the edge of the outer hook 22 (see FIGS. 3 to 5). The electromagnet 32 includes a coil 33 in which conductive wires are wound in multiple layers, and a yoke 34 inserted into the coil 33.
The yoke 34 is disposed such that its longitudinal direction is orthogonal to the extending direction of the lower shaft 9, that is, the Y-axis direction in the sewing machine bed. One end (front end) of the yoke 34 is arranged in a position not in contact with the rotating outer hook 22 and at a position close to the other end of the above-described tension spring 31 that functions as a clamping portion in the vicinity of the edge of the outer hook 22. (See FIGS. 3 to 5). The other end of the yoke 34 is fixed to the inside of the sewing machine bed via the attachment arm 35.

The position close to the end of the tension spring 31 where one end of the yoke 34 is disposed is the magnetic force generated on the one end side of the yoke 34 when the distance between the clamping part and the yoke 34 is the current flowing through the coil 33. Therefore, it is desirable that the tension spring 31 made of a magnetic material can be separated from the outer peripheral portion of the bobbin case 27 (see FIGS. 3 to 5).
Note that one end of the yoke 34 that exerts a suction force on the tension spring 31 by magnetic force is originally movable with the other end of the tension spring 31 as a clamping portion that clamps the lower thread 8 together with the outer peripheral portion of the bobbin case 27. Although it is preferable to arrange in the direction, that is, in the direction facing the outer peripheral portion of the peripheral wall of the bobbin case 27 or the outer hook 22, in this embodiment, the tension spring 31 is arranged to avoid interference with the rotating outer hook 22. It is arranged offset at a position where a sufficient magnetic force can be exerted.

  Furthermore, a current having a magnitude corresponding to the rotational speed of the upper shaft 2 flows through the electromagnet 32 (coil 33) in the present embodiment by a control unit (not shown) that detects the rotational speed of the upper shaft 2. . That is, the lower thread tension device 30 as the lower thread tension control device in the present embodiment includes the electromagnet 32 and changes the current flowing through the electromagnet 32 to change the magnetic force applied to the other end of the tension spring 31 that is the clamping portion. Is supposed to change. Thus, a magnetic force having a magnitude corresponding to the rotational speed of the upper shaft 2 is generated at the tip of the electromagnet 32 (yoke 34), and the other end (clamping portion) of the tension spring 31 is on the tip side of the yoke 34. A suction force having a magnitude corresponding to the sewing speed is applied.

  The other end (clamping portion) of the tension spring 31 is attracted to the distal end side of the electromagnet 32 (yoke 34) by the attraction force and resists the biasing force of the tension spring 31 toward the outer peripheral portion of the bobbin case 27. Suction is performed in a direction away from the outer peripheral portion of the bobbin case 27 (in the direction of arrow B in FIG. 5), which is the direction in which the tension spring 31 is movable. As a result, the tension (including the initial tension) applied to the lower thread 8 decreases. That is, the amount of decrease in the bobbin thread tension from the initial tension can be adjusted to a desired value according to the attractive force due to the magnetic force of the electromagnet 32 and the magnitude of the current (current value) flowing through the electromagnet 32. That is, the lower thread tension device 30 adjusts the lower thread tension by adjusting the magnetic force applied to the clamping portion.

  A control unit (not shown) is electrically connected to electrical components provided in the sewing machine 1, that is, various actuators such as a sewing machine motor and various sensors, and performs centralized control thereof. Such a control unit is electrically connected to a potentiometer or a rotary encoder that detects the rotational speed of the upper shaft 2 to detect the rotational speed of the upper shaft 2, that is, the sewing speed, and has a current corresponding to the sewing speed. Is controlled to flow through the coil 33 of the electromagnet 32.

(Description of sewing machine operation)
Next, based on FIG.4 and FIG.5, the operation | movement of the sewing machine 1 in 1st Embodiment provided with the said structure is demonstrated in detail.
First, the bobbin 26 is mounted on the support shaft 25 of the inner hook 24 and the bobbin case 27 is attached. At this time, the lower thread 8 is passed through the notch 19 of the bobbin case 27 and set so that the lower thread 8 is clamped by the outer peripheral part of the bobbin case 27 and the clamping part of the tension spring 31.
Here, no current flows through the coil 33 before starting sewing, and no magnetic force is generated in the electromagnet 32. For this reason, the clamping part of the tension spring 31 will be in the state urged | biased by the outer peripheral part side of the bobbin case 27 with the set urging | biasing force. That is, the initial tension that is the maximum tension in the present embodiment is applied to the lower thread 8 that is clamped by the clamping portion and the outer peripheral portion of the bobbin case 27.

Next, when sewing is started by driving the sewing machine motor, a current corresponding to the detected rotational speed of the upper shaft 2, that is, the sewing speed, flows through the coil 33 of the electromagnet 32. As a result, a magnetic force having a strength corresponding to the sewing speed is generated in the electromagnet 32 (yoke 34), and the tension spring 31 moves from the tension spring 31 toward one end of the yoke 34 (in the direction of arrow A in FIG. 5). A suction force corresponding to the sewing speed is applied.
Here, one end of the yoke 34 that exerts a magnetic force on the tone spring 31 is provided at a position shifted (offset) from the movable direction (direction of arrow B in FIG. 5) in which the clamping portion of the tone spring 31 bends. Since the one end of the tension spring 31 is fixed, the sandwiching portion (the other end of the tension spring 31) does not bend in the direction of arrow C in FIG. That is, the tension spring 31 is attracted in the direction of the arrow B by a magnetic force (component force) having a magnitude corresponding to the component in the direction of the arrow B in FIG. 5 of the attractive force acting on the tension spring 31 from the tip of the yoke 34. The Rukoto.

In addition, the bobbin case 27 in the present embodiment is formed of a nonmagnetic material and is provided as a rigid body that is sufficiently hard and difficult to be deformed as compared with the flexible tension spring 31. For the magnetic force, the tension spring 31 is a member that is more easily bent. That is, in this embodiment, only the tension spring 31 reacts to the magnetic force generated by the electromagnet 32, and the outer hook 22, the inner hook 24, the bobbin case 27, and the like do not move or deform.
The lower thread 8 is directly clamped (pressed) by the magnetic force (attraction force) generated by the current value corresponding to the sewing speed, and the tension is controlled. That is, the optimum tension is applied to the lower thread 8 due to changes in the sewing conditions due to the sewing speed, stepped portion sewing, and the like.

(Effect of 1st Embodiment)
As described above, according to the sewing machine 1 according to the present embodiment, the lower thread 8 wound around the bobbin 26 is not controlled, and the lower thread 8 drawn out from the bobbin 26 is directly clamped to increase the tension. The desired bobbin thread tension can be obtained for control. Further, there is no change in the lower thread 8 wound around the bobbin 26, and the lower thread tension after the wound lower thread 8 is tightened (tightened) does not increase. Further, since the tension is controlled by directly pinching the lower thread 8, there is no time delay until the lower thread tension changes. Furthermore, the responsiveness can be improved by adopting the electromagnet 32 as means for adjusting the bobbin thread tension, and the bobbin thread tension can be changed in real time, for example, for each needle. Accordingly, the bobbin thread tension can be appropriately controlled.

In this embodiment, the tension spring 31 is sucked until the lower thread tension is 0 [N], that is, the lower thread 8 is released by the suction force corresponding to the sewing speed. That is, the lower thread tension device 30 of the sewing machine 1 according to the present embodiment can adjust the lower thread tension in the range of 0 to 0.49 [N] according to the sewing speed.
In addition, since the tension spring 31 is configured to apply an initial tension (about 0.49 [N] in the present embodiment), the bobbin thread tension does not disappear even during a power failure or disconnection.

  Further, the current passed through the coil 33 of the electromagnet 32 by the control unit is a value corresponding to the rotational speed of the upper shaft 2, that is, the sewing speed, but the value corresponding to the sewing speed corresponds to the rotational speed of the upper shaft 2. The current may be increased or decreased, or a current having a predetermined value corresponding to a predetermined rotation speed may be supplied. It is also possible to cause a constant current to flow according to the sewing speed. Further, the polarity of the magnetic force generated at the tip of the yoke 34 (for example, N pole or S pole) may be reversed by reversing the direction of the current flowing through the coil 33.

The bobbin case 27 is made of a non-magnetic material in the present embodiment, but the bobbin case 27 is a rigid body that is sufficiently strong, that is, sufficiently hard as compared with the flexible spring 31. Moreover, since it is installed in an arrangement that does not block between the tension spring 31 and the electromagnet 32, it may be made of a magnetic material.
Further, since the lower thread tension is controlled by the action of magnetic force, the lower thread tension can be controlled in a non-contact manner, and there is no need to provide power supply means for the bobbin case 27 and the shuttle 21.
Moreover, in this embodiment, since a permanent magnet is not used as the lower thread tension adjusting means, no magnetic force is generated unless an electric current is passed through the electromagnet 32, and iron powder or the like does not adhere.

  Moreover, the permanent magnet 40 can also be used as the bobbin thread tension adjusting means. In this case, as shown in FIG. 15, by changing (adjusting) the distance between the permanent magnet 40 and the clamping part of the tension spring 31, the magnetic force acting on the clamping part is changed (adjusted). In order to change the distance, in addition to adjusting with a screw or the like, the permanent magnet can be moved away from and in contact with the clamping portion using an actuator. In this way, the magnetic force applied to the holding portion can be adjusted according to the sewing speed by driving the actuator in accordance with the sewing speed by the control unit that detects the sewing speed, and the lower speed corresponding to the sewing speed can be adjusted. Yarn tension can be applied.

(Second Embodiment)
Next, a second embodiment to which the present invention is applied will be described with reference to FIGS. In the following description of the present embodiment, in the second to fifth embodiments, the same components as those in the first embodiment described above are denoted by the same reference numerals, and redundant descriptions are omitted.
The second embodiment is different from the first embodiment in that the bobbin case 27 is made of a magnetic material (hereinafter referred to as a bobbin case 27a) and a magnet (permanent magnet) 36 is attached to the tension spring 31 (FIG. 6 to 8).

  That is, a magnet 36 that is a permanent magnet is attached to the outer peripheral side of the arc of the tension spring 31 that is attached to the outer peripheral portion of the bobbin case 27 made of a magnetic material and is formed in a substantially arc shape. Therefore, in the initial state, that is, in the state where the electromagnet 32 is OFF (the current is not flowing through the coil 33), the magnet 36 provided on the tension spring 31 is placed on the bobbin case 27 made of a magnetic material with the tension spring 31 interposed therebetween. The tension spring 31 is sucked and pressed against the outer peripheral portion of the bobbin case 27. According to this configuration, since the initial tension of the tension spring 31 is determined by the attractive force of the magnet 12 attached to the tension spring 31, the initial tension varies depending on the tightening torque of the screw for fixing the tension spring 31. Can be reduced. In other words, by using the lower thread tension applying means other than the leaf spring as in the first embodiment, the initial tension set in advance does not fluctuate due to the adjustment work of the operator, and the stable initial tension of the lower thread is maintained. Can be granted.

  When the bobbin thread tension is controlled, the magnet 12 (permanent magnet) affixed to the tension spring 31 has a polarity opposite to that of the magnet 12 (for example, the S (N) pole if the magnet 12 is an N (S) pole). By generating a magnetic force in the electromagnet 32 and attracting the magnet 12 attached to the tension spring 31, the attraction force between the bobbin case 27 and the tension spring 31 is changed to change the bobbin thread tension. ing.

(Effect of 2nd Embodiment)
According to the second embodiment, it is possible to apply a magnetic force to the magnet 12 affixed to the tension spring 31 by changing the polarity of the magnetic force generated by the electromagnet 32, and not only the attractive force but also the repulsive force acts. It can also be made. Accordingly, in addition to reducing the tension applied by the bobbin thread tension applying means, it is possible to apply a tension equal to or higher than the initial tension, so that it is possible to ensure a large control range of the adjustable tension.
Moreover, the permanent magnet 40 can also be used as the bobbin thread tension adjusting means. In this case, as shown in FIG. 15, by changing (adjusting) the distance between the permanent magnet 40 and the magnet 36, the magnetic force acting on the clamping portion is changed (adjusted). In order to change the distance, in addition to adjusting with a screw or the like, the permanent magnet 40 can be moved away from the holding portion by using an actuator. In this way, the magnetic force applied to the holding portion can be adjusted according to the sewing speed by driving the actuator in accordance with the sewing speed by the control unit that detects the sewing speed, and the lower speed corresponding to the sewing speed can be adjusted. Yarn tension can be applied.

(Third embodiment)
Next, based on FIG. 9 thru | or FIG. 11, 3rd Embodiment to which this invention is applied is described.
In the first and second embodiments, the initial tension of the lower thread 8 is applied by directly clamping it with the tension spring 31 (leaf spring), whereas in the third embodiment, the roller 37 is used. Is different from the above embodiments (see FIGS. 9 to 11).
That is, a roller 37 made of a magnetic material is provided inside the bobbin case 27. The roller 37 is disposed in the vicinity of the inner peripheral portion inside the bobbin case 27, and is supported so as to be rotatable about a shaft portion 41 parallel to the central axis of the bobbin case 27. Further, both ends of the shaft portion 41 are supported so as to be slidable along a long hole along the radial direction of the bobbin case 27.
Leaf springs 42 and 42 are attached to the shaft portion of the roller 37. The leaf springs 42 and 42 are adapted to give a rotational resistance (torque) to the roller 37 by frictional resistance with the shaft portion 41. Then, by holding the lower thread 8 between the inner wall of the bobbin case 27 and the peripheral surface of the roller 37, tension is applied to the lower thread 8.
Since the roller 37 is made of a magnetic material, when a current flows through the electromagnet 32 (coil 33) and a magnetic force is generated, the roller 37 is attracted toward the electromagnet 32 side, that is, the outside of the bobbin case 27. Therefore, the roller 37 provided inside the bobbin case 27 is sucked toward the inner peripheral portion of the peripheral wall of the bobbin case 27. As a result, the lower thread tension applied to the lower thread 8 clamped between the roller 37 and the bobbin case 27 can be adjusted by the rotational resistance of the leaf spring 42 and the attractive force of the roller 37 by the magnetic force.

(Effect of the third embodiment)
According to the third embodiment, the same effects as those of the first embodiment can be obtained, and in particular, the lower thread tension applying means is rotated by the roller 37 made of a magnetic material as a clamping portion and the roller 37. For example, when the roller 37 is provided on the inner peripheral portion of the bobbin case 27, the lower thread tension is adjusted in a range larger than the initial tension. be able to. On the other hand, when the roller 37 is provided on the outer peripheral portion of the bobbin case 27, the lower thread tension can be adjusted within a range smaller than the initial tension. Further, the bobbin thread tension increases due to the rotational resistance by the leaf spring 42 and the attractive force of the roller 37 by the magnetic force.

In the present embodiment, no permanent magnet is used as the bobbin thread tension adjusting means. Therefore, no magnetic force is generated unless an electric current is passed through the electromagnet 32, and iron powder or the like does not adhere.
Further, by using a lower thread tension applying means other than the leaf spring as in the first embodiment, the initial tension set in advance is not changed by the adjustment work of the operator, and a stable initial tension of the lower thread is obtained. Can be granted.
Moreover, the permanent magnet 40 can also be used as the bobbin thread tension adjusting means. In this case, as shown in FIG. 15, by changing (adjusting) the distance between the permanent magnet and the holding portion of the roller 37, the magnetic force acting on the holding portion is changed (adjusted). In order to change the distance, in addition to adjusting with a screw or the like, the permanent magnet 40 can be moved away from the holding portion by using an actuator. In this way, the magnetic force applied to the holding portion can be adjusted according to the sewing speed by driving the actuator in accordance with the sewing speed by the control unit that detects the sewing speed, and the lower speed corresponding to the sewing speed can be adjusted. Yarn tension can be applied.

(Fourth embodiment)
Next, based on FIG.12 and FIG.13, 4th Embodiment to which this invention is applied is described.
In the first and second embodiments, the initial tension of the lower thread 8 is fixed by sticking the tension spring 31 along the outside of the bobbin case 27. However, in the fourth embodiment, the peripheral wall of the bobbin case 27 is fixed. This embodiment is different from the above embodiments in that a slit is provided in a part of the film, and a flexible piece 38 made of a flexible magnetic material is formed by making the thickness thinner than other parts.
A pressing portion, that is, a thread pressing portion 39 that is in contact with the flexible piece 38 and is formed of a rigid body of a nonmagnetic material is fixed to the outside of the flexible piece 38.
The lower thread 8 is passed between the flexible piece 38 and the thread pressing portion 39, and the lower thread 8 is sandwiched between the flexible piece 38 and the thread pressing portion 39.

(Effect of 4th Embodiment)
The bobbin thread tension control method after the bobbin case 27 is set in the shuttle 21 is the same as that in the first embodiment. That is, the bobbin thread tension changes by adjusting the strength of the magnetic force generated in the electromagnet 32.
The thread retainer 39 is a non-magnetic material and is a rigid material, so that the change due to the magnetic force does not occur.
Therefore, in the fourth embodiment, the flexible piece 38 provided in the bobbin case 27 reacts to the magnetic force. Therefore, when the magnetic force is increased, the flexible piece 38 is attracted and pulled to the outside of the bobbin case 27 and is pressed by the thread pressing portion 39. Conversely, when the magnetic force becomes weak, the force for pinching the lower thread 8 becomes weaker, and the lower thread tension becomes weaker.

The thread pressing portion 39 may be formed of a magnetic material that is harder than the flexible piece.
Moreover, the permanent magnet 40 can also be used as the bobbin thread tension adjusting means. In this case, as shown in FIG. 15, by changing (adjusting) the distance between the permanent magnet 40 and the holding part of the flexible piece 38, the magnetic force acting on the holding part is changed (adjusted). In order to change the distance, in addition to adjusting with a screw or the like, the permanent magnet 40 can be moved away from the holding portion by using an actuator. In this way, the magnetic force applied to the holding portion can be adjusted according to the sewing speed by driving the actuator in accordance with the sewing speed by the control unit that detects the sewing speed, and the lower speed corresponding to the sewing speed can be adjusted. Yarn tension can be applied.

(Fifth embodiment)
Next, a fifth embodiment to which the present invention is applied will be described with reference to FIG.
In the first and second embodiments, the initial tension of the lower thread 8 is applied by fixing the tension spring 31 along the outside of the bobbin case 27. However, in the fifth embodiment, the bobbin case 27 is different from the above-described embodiment in that a tension spring 31a is fixed to the inner periphery of 27.
The bobbin case 27 is made of a nonmagnetic material. For this reason, when a magnetic force is generated in the electromagnet 32, the magnetic force passes through the bobbin case 27, and the magnetic force acts only on the tension spring 31 a fixed inside the bobbin case 27.

A lower thread 8 is passed between the tension spring 31 a and the bobbin case 27.
In the subsequent lower thread tension control method, as in the first embodiment, the lower thread tension is changed by adjusting the strength of the magnetic force.

(Effect of 5th Embodiment)
In the fifth embodiment, it is the tension spring 31a provided on the inner periphery of the bobbin case 27 that reacts to the magnetic force. Since the bobbin case 27 is made of a nonmagnetic material, it does not change due to magnetic force. For this reason, when the magnetic force is increased, the tension spring 31 a is pulled and pressed against the inner periphery of the bobbin case 27. Then, the lower thread 8 passed between the tension spring 31a and the bobbin case 27 is sandwiched, and the lower thread tension increases. On the contrary, if the magnetic force is weakened, the force for pinching the lower thread 8 becomes weaker, and the lower thread tension becomes weaker.

  In addition, the permanent magnet 40 can also be used as the bobbin thread tension adjusting means. In this case, as shown in FIG. 15, by changing (adjusting) the distance between the permanent magnet 40 and the holding part of the flexible piece 38, the magnetic force acting on the holding part is changed (adjusted). In order to change the distance, in addition to adjusting with a screw or the like, the permanent magnet 40 can be moved away from the holding portion by using an actuator. In this way, the magnetic force applied to the holding portion can be adjusted according to the sewing speed by driving the actuator in accordance with the sewing speed by the control unit that detects the sewing speed, and the lower speed corresponding to the sewing speed can be adjusted. Yarn tension can be applied, and the magnetic force can be adjusted for each needle.

It is a disassembled perspective view which shows schematic structure of this invention (1st Embodiment). It is the schematic which shows the principal part structure (front view) of this invention (1st Embodiment). It is the schematic which shows the principal part structure (side view) of this invention (1st Embodiment). It is an enlarged view which shows the principal part structure of this invention (1st Embodiment). It is operation | movement explanatory drawing which shows operation | movement of the lower thread tension device in this invention (1st Embodiment). It is the schematic which shows the principal part structure of this invention (2nd Embodiment). It is a disassembled perspective view which shows the principal part structure (side view) of this invention (2nd Embodiment). It is operation | movement explanatory drawing which shows operation | movement of the lower thread tension device in this invention (2nd Embodiment). It is the schematic which shows the principal part structure of this invention (3rd Embodiment). It is a disassembled perspective view which shows the principal part structure (side view) of this invention (3rd Embodiment). It is operation | movement explanatory drawing which shows operation | movement of the lower thread tension device in this invention (3rd Embodiment). It is the schematic which shows the principal part structure of this invention (4th Embodiment). It is a schematic perspective view which shows the principal part structure of this invention (4th Embodiment). It is the schematic which shows the principal part structure of this invention (5th Embodiment). It is the schematic which shows the lower thread tension device (permanent magnet) in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sewing machine 2 Upper shaft 3 Rotating weight 4 Crank rod 5 Needle bar holding 6 Needle bar 7 Sewing needle 8 Lower thread 9 Lower shaft 10 Needle drive mechanism 19 Cutting part 20 Hook mechanism 21 Hook (vertical hook)
22 Outer pot 24 Inner pot 25 Support shaft 26 Bobbin 27 Bobbin case (non-magnetic material)
27a Bobbin case (magnetic material)
30 Lower thread tension device (lower thread tension control device)
31 Tone spring (lower thread tension applying means, clamping part, magnetic material, leaf spring)
32 Electromagnet (lower thread tension adjusting means)
33 Coil 34 Yoke 35 Mounting arm 36 Magnet (permanent magnet)
37 Roller (lower thread tension applying means, clamping part, magnetic material)
38 Flexible piece (lower thread tension applying means, clamping part, magnetic material)
39 Yarn presser (presser)
40 Permanent magnet (lower thread tension adjusting means)

Claims (7)

A bobbin case for holding the bobbin;
A lower thread tension applying means provided on an outer peripheral part or an inner peripheral part of the bobbin case and holding the lower thread pulled out from the bobbin by a holding part;
Bobbin thread tension adjusting means disposed on the outside of the bobbin case,
Either the clamping part or the lower thread tension adjusting means is made of a magnetic material, and the lower thread tension adjusting means adjusts the lower thread tension by adjusting the magnetic force applied to the clamping part. Lower thread tension control device.   2. The lower thread tension control device according to claim 1, wherein the holding part of the lower thread tension applying means is a leaf spring made of a magnetic material.   2. The lower thread tension control device according to claim 1, wherein the holding part of the lower thread tension applying means is a roller made of a magnetic material, and the lower thread tension applying means has a spring that gives rotational resistance to the roller. . The holding part of the lower thread tension applying means is a flexible piece made of a magnetic material formed from a part of the peripheral wall of the bobbin case,
The lower thread tension applying means has a pressing portion made of a magnetic material harder than a nonmagnetic material or the flexible piece while being in contact with the holding portion,
The lower thread tension control device according to claim 1, wherein the lower thread is clamped by the clamping part and the pressing part.   The bobbin thread tension control device according to any one of claims 1 to 4, wherein the clamping portion includes a permanent magnet.   The lower thread tension control device according to any one of claims 1 to 5, wherein the lower thread tension control device includes an electromagnet, and the magnetic force is changed by changing a current flowing through the electromagnet. .   6. The lower thread tension control device includes a permanent magnet, and adjusts the magnetic force by changing a distance between the permanent magnet and a holding portion of the lower thread tension applying means. The lower thread tension control device according to any one of the above.

Images