JP2005073811A - Thread breakage detector of sewing machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thread breakage detector capable of keeping a distance between a magnetic field detection sensor and a permanent magnet member fixed, stabilizing needle thread tension, improving thread breakage detection accuracy, reducing the number of components, becoming advantageous in terms of a manufacture cost, and smoothly hooking needle thread to a rotary disk. <P>SOLUTION: The thread breakage detector 19 comprises: a thread tension pedestal 21 fixed to a thread tension frame 13 and provided with an attaching base plate 21a to which the rotary disk 20 approaches facing each other; a plurality of permanent magnet pieces 22 attached to a surface orthogonal to the axial center of the rotary disk 20; the magnetic field detection sensor 23 attached to an inner surface on the opposite side of the surface facing the rotary disk 20 in the attaching base plate 21a for detecting a magnetic field generated from the permanent magnet pieces 22; and a controller for detecting the breakage of a needle thread on the basis of detection signals from the magnetic field detection sensor 23. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  According to the present invention, a permanent magnet member and a magnetic field detection sensor are provided in a thread tensioner with a rotary dish for adjusting the tension of an upper thread supplied from a thread supply source of a sewing machine to a sewing needle, and the thread breakage of the upper thread is detected. It relates to what I did.

  2. Description of the Related Art Conventionally, a sewing machine is provided with a thread tensioner that applies tension to an upper thread supplied to a sewing needle from a thread supply source such as a thread spool and adjusts the upper thread tension. A general thread tensioner has a pair of thread tension plates and a thread tension spring that elastically biases one of the pair of thread tension plates to the other, and the upper thread between the pair of thread tension plates. Thus, the tension of the upper thread is applied to the upper thread, and the tension of the upper thread can be adjusted by changing the spring force of the thread tension spring by rotating the thread tension knob.

  By the way, some industrial sewing machines are provided with a separate thread trimmer detector that detects when the upper thread is broken, but the applicant of the present application has filed and commercialized a thread breakage detector with a thread tensioner. (For example, refer to Patent Document 1). In this thread breakage detecting device, a thread tension main body member is fixed to a thread tension frame, a shaft member protrudes from the thread tension main body member, and a disk-shaped spacer, felt material, rotary dish, felt material is formed on the shaft member. The pressing members are externally fitted in this order. The pressing member is elastically biased to the rotary dish by the thread tension spring, and the upper thread is hung and sandwiched between a pair of the rotary dishes.

  When the upper thread is pulled out during sewing, the rotary dish holding the upper thread rotates, and rotational resistance is applied to the rotary dish by a felt material or the like, so that tension is applied to the upper thread. A plurality of permanent magnet pieces are attached to the rotary plate at equal intervals in the circumferential direction, and a magnetic field detection sensor for detecting the magnetic field of the permanent magnet piece is attached to the outer surface of the thread tension body member on the rotary plate side. A change is detected to detect the rotation / stop of the rotary dish, and when the rotary dish stops despite sewing, it is possible to detect thread trimming of the upper thread.

By the way, the spacer prevents interference between the magnetic field detection sensor attached to the thread tension main body member and the felt material, and keeps the distance between the magnetic field detection sensor and the permanent magnet piece in the rotation axis direction of the rotary dish constant, It is an important member that takes the pedestal of the rotary dish.
JP 2002-369990 A

  However, in the yarn breakage detecting device of Patent Document 1, since the spacer is externally fitted to the shaft member and assembled into an unstable state, there is a possibility that the spacer may rattle and the posture may not be stable. The upper thread tension becomes unstable, and the distance between the permanent magnet piece attached to the rotary dish using the spacer as a base and the magnetic field detection sensor attached to the thread tension main body member cannot be kept constant and varies. May occur, and the yarn breakage detection accuracy may deteriorate. Further, the number of parts including the spacer of the thread tension device is increased, which is disadvantageous in terms of production cost.

  In addition, in the thread tension device provided in the yarn breakage detecting device, the outer peripheral portion of the rotary dish is exposed to the outside, so that it is well suited when an upper thread is to be hung between a pair of rotary dishes. Therefore, there is a possibility that the upper thread may be hung between the members other than between the pair of dishes (for example, between the spacer and the felt material). That is, there is a problem that it is difficult to smoothly thread the upper thread on the rotary dish.

  The object of the present invention is to keep the distance between the magnetic field detection sensor and the permanent magnet member constant, stabilize the upper thread tension, increase the thread breakage detection accuracy, reduce the number of parts, and increase the production cost. An object of the present invention is to provide a yarn breakage detecting device capable of smoothly hanging an upper thread on a plate.

  A thread breakage detecting device for a sewing machine according to claim 1, further comprising a thread tensioner with a rotary tray for applying an upper thread supplied to a sewing needle from a thread supply source of the sewing machine and adjusting a tension of the upper thread. A thread tension pedestal fixed to the thread tension frame of the sewing machine and having a mounting base plate on which the rotary plate approaches in a facing manner, and a permanent magnet member attached to a surface orthogonal to the axis of the rotary plate And a magnetic field detection sensor for detecting a magnetic field emitted from the permanent magnet member, and a detection signal from the magnetic field detection sensor. The magnetic field detection sensor is attached to the inner surface of the mounting base plate opposite to the surface facing the rotary dish. And yarn breakage detection control means for detecting yarn breakage of the upper thread.

  The upper thread fed from a thread supply source such as a thread spool during sewing is supplied to the sewing needle via the rotary dish (hanging on the rotary dish). When the upper thread is pulled out during sewing, the rotary dish rotates, and the magnetic field of the permanent magnet member detected by the magnetic field detection sensor changes. A rotational resistance is added to the rotary dish to give tension to the upper thread, and the upper thread tension can be adjusted by changing the rotational resistance. If thread breakage of the upper thread occurs during sewing, the upper thread is not supplied to the sewing needle from the thread supply source, so the rotary dish stops rotating. At this time, since the magnetic field of the permanent magnet member detected by the magnetic field detection sensor does not change, the yarn breakage detection control means detects the yarn breakage of the upper thread based on the detection signal from the magnetic field detection sensor.

  Since the thread tension pedestal is fixed to the thread tension frame and the mounting plate of the thread tension pedestal is in a stable state, the rotary plate is arranged so as to approach the mounting plate so as to face each other. Since the magnetic field detection sensor is attached to the inner surface opposite to the surface facing the rotary dish, the upper thread tension applied to the upper thread is stable, and the rotary dish between the magnetic field detection sensor and the permanent magnet member Since the distance in the rotation axis direction is kept constant, the yarn breakage detection accuracy is improved.

  The thread breakage detection device for a sewing machine according to a second aspect of the present invention is the invention according to the first aspect, wherein the thread tension pedestal has a peripheral wall having a tip fixedly provided on an outer peripheral portion of the mounting base plate. The base end portion is fixed to the thread tension frame. A magnetic field detection sensor and components and wiring necessary for the mounting thereof are disposed in an internal space surrounded by the mounting base plate and the peripheral wall of the thread tension pedestal so as to be covered from the outside.

  A thread breakage detection device for a sewing machine according to a third aspect is the invention according to the second aspect, wherein a sensor mounting recess is formed on the mounting base plate from the inner surface side, and the magnetic field detection sensor is accommodated in the sensor mounting recess. It is what. The magnetic field detection sensor is positioned and easily assembled in the sensor mounting recess of the mounting base plate, and the distance between the magnetic field detection sensor and the permanent magnet member in the rotation axis direction of the rotary plate can be set to an appropriate distance.

  A thread breakage detecting device for a sewing machine according to a fourth aspect is characterized in that, in the invention of the third aspect, a sensor substrate is fixed to the inner surface of the mounting base plate, and the magnetic field detection sensor is mounted on the sensor substrate. is there. By fixing the sensor substrate to the inner surface of the mounting base plate, the sensor board is assembled in a state where the magnetic field detection sensor is accommodated in the sensor mounting concave portion of the mounting base plate. This sensor substrate is disposed in a state of being covered with a space inside the thread tension base.

  A thread breakage detecting device for a sewing machine according to a fifth aspect of the present invention is the sewing machine according to any one of the first to fourth aspects, wherein the rotary dish is rotatably fitted around a thread tension shaft fixed to a thread tension frame. Is configured to be inserted through the mounting base plate. A thread tension shaft is fixed to the thread tension frame and the mounting base plate is inserted, and a rotary dish is externally fitted to the thread tension shaft, and the rotary dish is disposed so as to be opposed to the mounting base plate.

  The thread breakage detection device for a sewing machine according to a sixth aspect is characterized in that, in the invention according to any one of the first to fifth aspects, an escape recess is formed on the mounting base plate to escape the outer peripheral portion of the rotary dish. . Since the outer peripheral portion of the rotary dish is escaped by the relief recess formed in the mounting base plate and is not exposed to the outside, the upper thread is smoothly applied to the rotary dish.

  The thread breakage detection device for a sewing machine according to a seventh aspect of the present invention is the invention according to the sixth aspect, wherein the rotary plate is provided with a pressing member that approaches from the opposite side to the mounting base plate. An escape recess is formed to escape the outer peripheral portion. The outer periphery of the rotary dish is escaped by the relief recess formed in the pressing member approaching in an opposing manner from the opposite side of the mounting plate, so that the upper thread is smoothly applied to the rotary dish so as not to be exposed to the outside. become.

  The thread breakage detection device for a sewing machine according to claim 8 is the sewing machine according to any one of claims 1 to 7, wherein the permanent magnet members are arranged in a ring shape at equal intervals in the circumferential direction around the rotation axis of the rotary dish. It is characterized by comprising a permanent magnet piece. During sewing, when the upper thread is supplied to the sewing needle and the rotary plate is rotating, changes in the magnetic field from the plurality of permanent magnet pieces to the magnetic sensor can be detected every short time, while the upper thread breaks and the sewing needle is In a state where the supply is stopped and the rotary dish is stopped rotating, the magnetic field does not change, so it can be determined that the yarn breakage has occurred.

  According to the thread breakage detection device for a sewing machine according to claim 1, the apparatus includes a rotary dish, a thread tension pedestal, a permanent magnet member, a magnetic field detection sensor, and a thread breakage detection control means, and in particular, the thread tension pedestal is fixed to the thread tension frame. Therefore, the mounting plate of the thread tension pedestal is in a stable state, and the rotary plate is disposed so as to be opposed to the mounting plate so that the mounting plate is opposite to the surface facing the rotary plate. Since the magnetic field detection sensor is attached to the inner surface on the side, the upper thread tension applied to the upper thread is stabilized, and the distance between the magnetic field detection sensor and the permanent magnet member in the rotational axis direction of the rotary plate is kept constant. The detection accuracy can be increased, and furthermore, since the mounting base plate corresponding to the spacer, which has been separately provided conventionally, is provided integrally with the thread tension base, the number of parts can be reduced, which is advantageous in production cost.

  According to the thread breakage detecting device for a sewing machine according to claim 2, the thread tension pedestal has a peripheral wall having a distal end portion fixedly provided on an outer peripheral portion of the mounting base plate, and a base end portion of the peripheral wall is used as a thread tension frame. Because it is fixed to the thread tension pedestal, the magnetic field detection sensor and the components and wiring necessary for its installation can be covered and arranged from the outside in the space enclosed by the thread tension pedestal mounting base plate and peripheral wall. Can be used effectively to improve the appearance.

  According to the thread breakage detecting device for a sewing machine according to claim 3, the sensor mounting recess is formed on the mounting base plate from the inner surface side, and the magnetic field detection sensor is accommodated in the sensor mounting recess. The magnetic field detection sensor can be positioned and assembled easily, and the distance between the magnetic field detection sensor and the permanent magnet member in the rotation axis direction of the rotary plate can be set to an appropriate distance, and the magnetic field detection sensor can reliably detect the magnetic field of the permanent magnet member. can do.

  According to the thread breakage detecting device of the sewing machine according to the fourth aspect, the sensor substrate is fixed to the inner surface of the mounting base plate, and the magnetic field detection sensor is attached to the sensor substrate, so that the sensor substrate is fixed to the inner surface of the mounting base plate. Thus, the sensor mounting recess of the mounting base plate can be easily assembled in a state where the magnetic field detection sensor is accommodated, and the sensor substrate can be disposed in a state of being covered with the space inside the thread tension base.

  According to the thread breakage detecting device for a sewing machine according to claim 5, the rotary dish is rotatably fitted on the thread tension shaft fixed to the thread tension frame, and the thread tension shaft is inserted through the mounting base plate. Therefore, it can arrange | position so that a rotary dish can be rotated and it approaches to an attachment base plate in the opposing shape.

  According to the thread breakage detecting device of the sewing machine of claim 6, since the escape recess is formed on the mounting base plate so as to escape the outer peripheral portion of the rotary plate, the outer peripheral portion of the rotary plate is not exposed to the outside, The upper thread can be smoothly applied.

  According to the thread breakage detecting device for a sewing machine according to claim 7, the rotary plate is provided with a pressing member that approaches the counter plate from the side opposite to the mounting base plate, and the pressing member is provided with a relief recess that allows the outer peripheral portion of the rotary plate to escape. Since it is formed, the upper thread can be smoothly applied to the rotary dish without exposing the outer peripheral portion of the rotary dish to the outside.

  According to the thread breakage detecting device of the sewing machine according to the eighth aspect, since the permanent magnet members are arranged annularly at equal intervals in the circumferential direction around the rotary shaft of the rotary plate, the upper thread is supplied to the sewing needle during sewing and the rotary needle is rotated. While the plate is rotating, changes in the magnetic field from a plurality of permanent magnet pieces to the magnetic sensor can be detected reliably every short time, the upper thread breaks and is not supplied to the sewing needle, and the rotary plate stops rotating. In this state, since the magnetic field does not change, it can be reliably determined that thread breakage has occurred.

  The thread breakage detection device for a sewing machine according to the present embodiment includes a multi-sewing machine capable of embroidery sewing, and a rotary dish with a rotary dish that adjusts the tension of the upper thread by applying an upper thread supplied to the sewing needle from the thread supply source of the sewing machine. A thread tension pedestal that has a thread tensioner and is fixed to the thread tension frame of the sewing machine, and has a mounting plate that is close to the rotary dish, and is attached to a surface perpendicular to the axis of the rotary dish. And a magnetic field detection sensor for detecting a magnetic field emitted from the permanent magnet member, and a detection signal from the magnetic field detection sensor. Is a yarn breakage detecting device provided with yarn breakage detection control means for detecting the yarn breakage of the upper thread based on the above.

  As shown in FIG. 1, in the multi-needle sewing machine M, a leg portion 1 that supports the entire sewing machine is provided, and a leg column portion 2 is erected from a rear end portion of the leg portion 1. The arm portion 3 extends forward from the top of the arm. A needle bar case 4 with a synthetic resin cover is attached to the front side of the arm part, and a cylinder bed 5 extends from the lower part of the pedestal column part 2 to the lower side of the front needle bar case 4.

  The needle bar case 4 accommodates six needle bars 10 in the left and right rows, the sewing needle 11 is attached to the lower end of each needle bar 10, and the needle bar case 4 has six balances 12 on the left and right sides. It is mounted in a row. A synthetic resin thread tension frame 13 that is slightly inclined rearward and upward is fixed to the upper end of the needle bar case 4, and six thread tensioners 14 are provided on the thread tension frame 13. Six piece stands 15 are provided on the upper side of the arm portion 3, and yarn pieces (not shown) as six yarn supply sources are attached to the piece stands 15, and upper yarns (not shown) extending from the respective yarn pieces. Is applied to the corresponding thread tensioner 14 and the balance 12 and supplied to the sewing needle 11.

  Here, the needle bar case 4 is driven to move in the left-right direction integrally with the thread tension frame 13 by a case drive mechanism (not shown), whereby one needle out of the six needle bars 10 and the balance 12 is driven. The rod 10 and the balance 12 are switched to the use position. When the sewing machine motor 50 (see FIG. 5) is driven, the needle bar 10 and the balance 12 at the use position are driven up and down to cooperate with a rotary hook (not shown) provided in the cylinder bed 5 to A stitch is formed on the work cloth disposed on the upper side of the bed 5 by the upper thread and the lower thread.

  The work cloth to be used for sewing is held in a state of being stretched on an embroidery frame (not shown), and this embroidery frame is attached to the frame mounting base 16 and set. The frame mount 16 is driven to move in the left-right direction by a left-right drive mechanism (not shown) provided inside the movable case 17, and the front-rear drive mechanism (not shown) provided inside the leg portion 1. Is driven to move in the front-rear direction. In this way, the embroidery frame is moved forward and backward and left and right together with the frame mounting base 16, and the work cloth is fed. The multi-needle sewing machine M is provided with a liquid crystal display 18 for displaying various screens in order to operate / stop the multi-needle sewing machine M, select an embroidery pattern, and the like.

  Next, a thread breakage detecting device 19 provided with a thread tensioner 14 with a rotary tray 20 that is threaded with an upper thread to be supplied to each sewing needle from each thread supply source of the multi-needle sewing machine M and adjusts the tension of the upper thread. This will be described in detail. Note that the upper side of FIG.

  As shown in FIGS. 2 to 4, the yarn breakage detecting device 19 is fixed to the rotary dish 20 on which the upper thread is hung and the thread tension frame 13, and the mounting base in which the rotary dish 20 approaches in an opposing manner from above. A plurality of thread tension pedestals 21 having a plate 21a and a plurality of permanent magnet members that are attached to the lower surface perpendicular to the axis of the rotary dish 20 and are annularly arranged at equal intervals in the circumferential direction around the rotation axis of the rotary dish 20 The permanent magnet piece 22 and a magnetic field detection sensor 23 (hole) for detecting a magnetic field emitted from the permanent magnet piece 22 is attached to the inner surface (lower surface) of the mounting base plate 21a opposite to the upper surface on the side facing the rotary dish 20. Element) and a control device 40 (see FIG. 5) corresponding to yarn breakage detection control means for detecting yarn breakage of the upper thread based on a detection signal from the magnetic field detection sensor 23. This control device 40 determines that there is no thread breakage when there is a change in the detection signal based on the magnetic field detection signal from the magnetic field detection sensor 23 during sewing of the multi-needle sewing machine M, and the detection signal changes. When there is no thread, it is determined that there is a thread break.

  The yarn breakage detecting device 19 includes a thread tension shaft 24, a sensor substrate 25, a pair of felt members 26 and 27, a pressing member 28, a spring receiving ring 29, and a thread tension spring 30 including a compression coil spring. And a thread tension knob 31. The thread tension pedestal 21, the pressing member 28, the thread tension knob 31 and the like are made of synthetic resin.

  The thread tension pedestal 21 includes a disc-shaped mounting base plate 21a, a peripheral wall 21b having a distal end portion (upper end portion) fixedly provided on an outer peripheral portion of the mounting base plate 21a, and a base end portion (lower end portion) of the peripheral wall 21b. The flange 21c is fixed to the thread tension frame 13 with a plurality of screws 21g. A shaft insertion hole 21d through which the thread tension shaft 24 is inserted is formed at the center of the mounting base plate 21a, and an escape recess 21e formed of a circular recess that allows the outer periphery of the lower plate 20a of the rotary dish 20 to escape over the entire upper surface. Is formed. A felt material 26 that is pressed against the lower surface of the rotary dish 20 is attached to the escape recess 21e.

  In the mounting base plate 21a, a sensor mounting recess 21f is formed from the inner surface side below the rotation path of the plurality of permanent magnet pieces 22, and the magnetic field detection sensor 23 is accommodated in the sensor mounting recess 21f. The mounting base plate 21a is provided with a plurality of mounting pins 25a protruding downward from the inner surface, and the sensor board 25 is positioned on the mounting pins 25a and fixed to the inner surface of the mounting base plate 21a with, for example, an adhesive. A magnetic field detection sensor 23 is attached to the substrate 25.

  In addition, a sheet-like shock absorbing rubber is mounted between the mounting base plate 21a and the sensor substrate 25, and the shock absorbing rubber absorbs vibrations caused by the rotation of the rotary dish 20 so that the sensor substrate 25 does not easily vibrate. A lead wire 32 extending from the control device 40 of the multi-needle sewing machine M is connected to the sensor substrate 25 via a connector 33, and the lead wire contact and the magnetic field detection sensor 23 are connected by a signal wire wired to the sensor substrate 25. Has been.

  The lower end of the thread tension shaft 24 is fixed to the thread tension frame 13 on the inner side of the thread tension pedestal 21, and is configured to be inserted through the insertion hole 21d of the mounting base plate 21a, and the lower half is approximately the thread tension pedestal 21. The upper half part protrudes to the upper side of the thread tension pedestal 21.

  The thread tension shaft 24 has a shaft portion 24a on the lower side of about 5/7 of the total length and a screw portion 24b on the upper side of about 2/7 of the total length, and is a shaft portion on the upper side of the thread tension pedestal 21. A rotary dish 20 is rotatably fitted on 24a, a pressing member 28 is fitted on the rotary dish 20 so as to be movable up and down, and felt materials 26 and 27 are also fitted. Further, a spring receiving ring 29 is externally fitted to the threaded portion 24b so as to be movable up and down, and a thread tension knob 31 is screwed on the upper side thereof in an external fitting shape. A split groove 24 c is formed in the upper half of the thread tension shaft 24.

  The thread tension knob 31 includes a peripheral wall 31a, an upper wall 31b, and a cylindrical portion 31c extending downward from the upper wall 31b on the inner side of the peripheral wall 31a. The cylindrical portion 31c is screwed to the screw portion 24b, and a spring. The receiving ring 29 can be received from below.

  The pressing member 28 has a peripheral wall 28a and a bottom wall 28b. A spring receiving portion 28c that is recessed downward is formed on the bottom wall 28b. A thread tension spring 30 is mounted between the spring receiving portion 28c and the spring receiving ring 29. The pressing member 28 is elastically biased downward by the thread tension spring 30. The pressing member 28 approaches the rotary plate 20 from the upper side opposite to the mounting base plate 21a, contacts the felt material 27, and presses the felt material 27 against the rotary plate 20. An annular relief recess 28d is formed in the vicinity of the outer periphery of the bottom wall 28b of the pressing member 28 to allow the outer periphery of the upper plate 20b of the rotary dish 20 to escape.

  The rotary plate 20 is connected by engaging a pair of thin metal plates 20a and 20b back to back, and a plurality of permanent magnet pieces 20 are attached to the lower surface of the lower plate 20a. The upper thread is hung over the entire circumference of the thread guide groove 20c having a substantially V-shaped cross section. The plurality of permanent magnet pieces 22 are arranged such that, for example, a plurality of N poles and a plurality of S poles are alternately arranged with a N pole and a S pole so that the direction of the magnetic field is directed to the direction of the rotation axis of the rotary dish 20. Are arranged in a ring shape.

  Here, a control system including the control device 40 will be described based on the block diagram of FIG. The control device 40 includes a microcomputer including a CPU 41, a ROM 42, and a RAM 43, an input / output interface 44, and a driver 45 for the sewing machine motor 50, which are connected by a bus. The magnetic field detection sensor 23 is connected to the input / output interface 44, and although not shown, various other sensors and switches are connected.

  The ROM 42 stores a thread breakage detection control program and other various control programs. This thread breakage detection control program receives a detection signal from the magnetic field detection sensor 23 during sewing and detects that a change (change) in the magnetic field of the permanent magnet piece 22 has occurred. This is a program for determining that there is yarn breakage by detecting that no change in the magnetic field of the permanent magnet piece 22 has occurred.

The operation and effect of the yarn breakage detection device 19 described above will be described.
First, when the upper thread is set, the pair of trays 20a and 20b of the rotary tray 20 is inserted from the side of the thread breakage detection device 19 so that the upper thread is inserted between the thread tension base 21 and the pressing member 28. Insert the upper thread in between and wrap it around for about 1 turn. Then, the upper thread is hung on a predetermined thread hooking portion such as the balance 12 and set through the sewing needle 11.

  The set upper thread is clamped between the pair of dishes 20a and 20b of the rotary dish 20 by the elastic biasing force of the thread tension spring 30, and sewing is performed in this state, and when the upper thread is unwound from the thread spool, The rotary dish 20 rotates with almost no sliding between the yarn and the rotary dish 20. At this time, rotational resistance is applied to the rotary plate 20 by the felt members 26 and 27 pressed against the rotary plate 20 by the elastic biasing force of the thread tension spring 30, and tension is applied to the upper thread. Here, by rotating the thread tension knob 31 and changing the spring force of the thread tension spring 30, the rotational resistance of the rotary dish 20, that is, the upper thread tension can be adjusted.

  Now, during sewing, when the upper thread is supplied and the rotary dish 20 is rotating, it is projected to the magnetic field detection sensor 23 from the permanent magnet piece 22 in which the N pole and the S pole are alternately arranged on the rotary dish 20. The direction of the magnetic field to be switched is changed every short time, and the controller 40 detects that the magnetic field has been switched (changed), whereby it is determined that there is no yarn breakage. On the other hand, when the thread breakage occurs, the upper thread is not supplied from the thread spool to the sewing needle, so that the rotary dish 20 stops rotating. In this case, the permanent magnet piece 22 detected by the magnetic field detection sensor 23 is no longer changed in magnetic field, and the control device 40 detects that there is no change in the magnetic field, so that it is determined that there is yarn breakage.

  According to this thread breakage detecting device 19, the rotary dish 20, the thread tension pedestal 21, the plurality of permanent magnet pieces 22, and the magnetic field detection sensor 23 are provided. In particular, the thread tension pedestal 21 is fixed to the thread tension frame 13. The mounting base plate 21a of the thread tension pedestal 21 is in a stable state, and the rotary plate 20 is disposed so as to be opposed to the mounting base plate 21a. The inner surface of the mounting base plate 21a opposite to the rotary plate 22 side. Since the magnetic field detection sensor 23 is attached to the upper thread, the upper thread tension applied to the upper thread is stabilized, and the distance between the magnetic field detection sensor 23 and the permanent magnet piece 22 in the rotation axis direction (vertical direction) of the rotary dish 20 is constant. In this case, the thread breakage detection accuracy can be increased, and the mounting base plate 21a corresponding to a spacer that has been separately provided in the past is provided integrally with the thread tension base 21 so that the number of parts can be reduced. It can be manufactured cost-effective.

  Since the thread tension pedestal 21 has a peripheral wall 21b whose tip is fixedly provided on the outer periphery of the mounting base plate 21a, and the base end of the peripheral wall 21b is fixed to the thread tension frame 13, the thread tension pedestal 21 The magnetic field detection sensor 23 and the sensor board 25, the mounting pins 25a, the lead wires 32, and the connector 33 necessary for mounting the magnetic field detection sensor 23 are covered in the space surrounded by the mounting base plate 21a and the peripheral wall 21b. The inside of the thread tension pedestal 21 can be used effectively, and the appearance can be improved.

  Since the sensor mounting recess 21f is formed on the mounting base plate 21a from the inner surface side, and the magnetic field detection sensor 23 is accommodated in the sensor mounting recess 21f, the magnetic field detection sensor 23 is positioned in the sensor mounting recess 21f of the mounting base plate 21a. The magnetic field detection sensor 23 and the permanent magnet piece 22 are easily assembled, and the distance in the rotation axis direction of the rotary dish 20 is set to an appropriate distance so that the magnetic field detection sensor 23 can reliably detect the magnetic field of the permanent magnet piece 22. Can do.

  Since the sensor substrate 25 is fixed to the inner surface of the mounting base plate 21a, and the magnetic field detection sensor 23 is mounted on the sensor substrate 25, the sensor of the mounting base plate 21a is secured by fixing the sensor substrate 25 to the inner surface of the mounting base plate 21a. The magnetic field detection sensor 23 can be easily assembled in the mounting recess 21f. Since the rotary dish 20 is rotatably fitted on a thread tension shaft 24 fixed to the thread tension frame 13, and the thread tension shaft 24 is inserted through the mounting base plate 21a, the rotary dish 20 can be rotated. Thus, the mounting base plate 21a can be disposed so as to be opposed to each other.

  Since the escape recess 21e that allows the outer peripheral portion of the lower plate 20a of the rotary dish 20 to escape is formed in the mounting base plate 21a, and the escape recess 28d that allows the outer periphery of the upper plate 20b of the rotary dish 20 to escape is formed on the pressing member 28. It is possible to smoothly thread the upper thread between the pair of plates 20a and 20b of the rotary plate 20 so that the outer peripheral portion of the rotary plate 20 is not exposed to the outside.

  As for the mounting direction of the plurality of permanent magnet pieces 22, even if the plurality of N poles and the plurality of S poles are not arranged so that the N poles and the S poles are alternately positioned, they are all arranged in the same direction. You may set up. Since the change of the magnetic field can be detected by rotating the rotary dish 20, it is possible to detect the rotation / stop of the rotary dish 20. Further, as the permanent magnet member, instead of the plurality of permanent magnet pieces 22, a single annular magnet piece having a plurality of poles alternately magnetized in the circumferential direction of the rotary dish 20 may be provided. In addition, the present invention can be implemented with various modifications without departing from the spirit of the present invention, and can be applied as a yarn breakage detection device for various sewing machines such as household sewing machines and industrial sewing machines.

It is a perspective view of the multi-needle sewing machine provided with the thread breakage detection apparatus which concerns on the Example of this invention. It is a longitudinal cross-sectional view of a thread breakage detection device. It is the III-III sectional view taken on the line of FIG. It is the IV-IV sectional view taken on the line of FIG. It is a block diagram of a control system including a control device.

Explanation of symbols

M Multi-needle sewing machine 13 Thread tension frame 14 Thread tensioner 19 Thread breakage detector 20 Rotary dish 21 Thread tension pedestal 21a Mounting base plate 21b Perimeter wall 21f Sensor mounting recess 22 Permanent magnet piece 23 Magnetic field detection sensor 25 Sensor substrate 21e, 28d Relief recess 31 PRESSING MEMBER 40 CONTROL DEVICE

Claims (8)

In a thread breakage detection device for a sewing machine having a thread tensioner with a rotary dish that adjusts the tension of an upper thread that is applied to a sewing needle from a thread supply source of the sewing machine.
A thread tension pedestal fixed to the thread tension frame of the sewing machine and having a mounting base plate in which the rotary plate approaches in an opposing manner;
A permanent magnet member attached to a surface orthogonal to the axis of the rotary plate;
A magnetic field detection sensor for detecting a magnetic field emitted from the permanent magnet member, attached to the inner surface of the mounting base plate opposite to the surface facing the rotary dish;
Thread breakage detection control means for detecting thread breakage of the upper thread based on a detection signal from the magnetic field detection sensor;
A yarn breakage detecting device for a sewing machine comprising:   The thread tension pedestal includes a peripheral wall having a distal end portion fixedly provided on an outer peripheral portion of the mounting base plate, and a base end portion of the peripheral wall is fixed to a thread tension frame. The thread breakage detecting device for the sewing machine as described.   3. A thread breakage detection device for a sewing machine according to claim 2, wherein a sensor mounting recess is formed on the mounting base plate from the inner surface side, and the magnetic field detection sensor is accommodated in the sensor mounting recess.   The thread breakage detection device for a sewing machine according to claim 3, wherein a sensor substrate is fixed to an inner surface of the mounting base plate, and the magnetic field detection sensor is attached to the sensor substrate.   The rotary plate is rotatably fitted on a thread tension shaft fixed to a thread tension frame, and the thread tension shaft is configured to pass through the mounting base plate. The thread breakage detection device for a sewing machine according to any one of the above.   The thread breakage detecting device for a sewing machine according to any one of claims 1 to 5, wherein a relief recess for allowing the outer peripheral portion of the rotary dish to escape is formed in the mounting base plate.   7. The rotary dish is provided with a pressing member that approaches in an opposing manner from the side opposite to the mounting base plate, and an escape recess is formed in the pressing member that allows the outer periphery of the rotary dish to escape. Thread breakage detection device for sewing machines.   The sewing machine according to any one of claims 1 to 7, wherein the permanent magnet member is composed of a plurality of permanent magnet pieces arranged annularly at equal intervals in the circumferential direction around the rotation axis of the rotary dish. Thread breakage detection device.