JP2023098053A - Sewing machine and bobbin thread determination means - Google Patents

Abstract

To provide a sewing machine and a bobbin thread determination method capable of detecting bobbin thread breakage and bobbin thread entanglement failure with better accuracy than before, irrespective of sewing conditions.SOLUTION: A sewing machine includes a needle bar, a needle bar vertical movement mechanism, a shuttle, a shuttle mechanism, a tensile force detector, a rotation detector, and a bobbin thread determination part. The needle bar mounts a sewing needle in which a needle thread is inserted. The needle bar vertical movement mechanism moves the needle bar vertically. The shuttle rotatably stores a bobbin which is provided below the needle bar, and around which a bobbin thread is wound. The shuttle mechanism rotates the shuttle synchronously with the vertical movement of the needle bar, and forms seams by capturing the annular needle thread which is inserted in the sewing needle and entangling it with the bobbin thread. The tensile force detector detects the tensile force of the needle thread or the bobbin thread. The rotation detector detects presence/absence of the rotation of the bobbin. The bobbin thread determination part determines presence/absence of the bobbin thread with respect to the seams, based on whether or not the tensile force detected by the tensile force detector is larger than a threshold value and the detection result of the rotation detector (S3-S7, S11-S19).SELECTED DRAWING: Figure 9

Description

The present invention relates to a sewing machine and a bobbin thread determination method.

The sewing machine disclosed in Patent Document 1 includes a bobbin thread tension sensor that detects the tension of the bobbin thread, and determines whether bobbin thread breakage has occurred based on the tension of the bobbin thread during sewing.

JP-A-10-33868

Depending on the sewing conditions, the above sewing machine may not be able to accurately detect bobbin thread breakage.

SUMMARY OF THE INVENTION An object of the present invention is to provide a sewing machine and a method for determining a bobbin thread that can detect a bobbin thread breakage and a bobbin thread entanglement failure more accurately than before, regardless of sewing conditions.

A sewing machine according to claim 1 comprises a needle bar on which a sewing needle through which an upper thread is passed, a needle bar vertical movement mechanism for vertically moving the needle bar, and a bobbin on which a bobbin thread is wound. A rotatably accommodated hook is rotated in synchronism with the up-and-down movement of the needle bar to catch the annular upper thread passing through the sewing needle and entwine it with the bobbin thread to perform stitching. a hook mechanism that forms a tension detector that detects the tension of the upper thread or the lower thread; an operation detector that detects the presence or absence of operation of the bobbin; and the tension detected by the tension detector is greater than a threshold. a bobbin thread judging section for judging presence or absence of the bobbin thread with respect to the stitch based on whether or not the needle thread is large and the detection result of the motion detector. The sewing machine of claim 1 determines whether or not the bobbin thread is present in the stitch based on whether or not the tension detected by the tension detector is greater than the threshold value and the detection result of the motion detector. The presence or absence of a bobbin thread for a stitch can be determined more accurately than a device that determines using a needle thread.

In the sewing machine according to claim 2, the bobbin thread determination unit detects that the bobbin does not move, and the tension detected by the tension detector is lower than a first threshold, which is the threshold. When it is large, it is determined that the bobbin thread is present with respect to the stitch, the motion detector detects that the bobbin does not move, and the tension detected by the tension detector is equal to or less than the first threshold. , it is determined that there is no bobbin thread for the stitch. According to the sewing machine of claim 2, even when it is detected that the bobbin does not move, if the tension detected by the tension detector is greater than the first threshold, it can be determined that the bobbin thread is present in the stitch. Although the operation of the bobbin is temporarily stopped, the sewing machine can avoid determining that there is no bobbin thread for the stitch in a situation where the bobbin thread is considered to be entangled with the needle thread.

The bobbin thread judging section of the sewing machine according to claim 3, wherein the tension detected by the tension detector is equal to or less than the second threshold, and the motion detector detects that the bobbin does not move. When the bobbin thread is detected, it is determined that the bobbin thread for the stitch is absent, the tension detected by the tension detector is equal to or less than the second threshold value, and the motion detector detects that the bobbin is in motion. is detected, it is determined that the bobbin thread for the stitch is present. According to the sewing machine of claim 3, even if the tension detected by the tension detector is equal to or less than the second threshold, it can be determined that the bobbin thread is present in the stitch when the bobbin is being operated. The sewing machine has a relatively small tension, but the bobbin continues to operate, and it is possible to avoid determining that there is no bobbin thread for a stitch in a situation where the bobbin thread is considered to be entangled with the needle thread.

The bobbin thread judging section of the sewing machine according to claim 4 uses different threshold values for a first sewing period from the start of sewing until a predetermined number of stitches are sewn, and a second sewing period following the first sewing period. judge. In the sewing machine according to claim 4, by changing the threshold value in the first sewing period and the second sewing period, the threshold value suitable for each of the first sewing period and the second sewing period is used to lower the stitches. The presence or absence of thread can be determined.

The bobbin thread judging section of the sewing machine according to claim 5 detects that the detection result of the tension detector is equal to or less than the threshold value continuously for a number of times equal to or more than the threshold value, and the motion detector detects that the bobbin does not move. If so, it is determined that the bobbin thread is broken. According to the sewing machine of claim 5, bobbin thread breakage can be determined based on the presence or absence of the bobbin thread with respect to the stitch.

In the sewing machine according to claim 6, the bobbin thread judging section is configured such that a ratio of the detection result of the tension detector to the number of sewn stitches that is equal to or lower than the threshold is equal to or higher than the ratio threshold, and the motion detector detects the bobbin. , it is determined that there is no bobbin thread for the stitch. According to the sixth aspect of the sewing machine, it is possible to avoid erroneous determination of the presence or absence of the bobbin thread on the stitch based on the singular value of the tension detector.

According to a seventh aspect of the present invention, there is provided a sewing machine further comprising a storage section for storing a combination of the number of stitches of the stitches and the threshold value, and the bobbin thread determining section determines the number of stitches based on the combination stored in the storage section. Determination is performed using the threshold value according to . According to the seventh aspect of the sewing machine, it is possible to determine whether or not the bobbin thread is present with respect to the stitch using a threshold value that takes into account the number of stitches.

The bobbin thread judging section of the sewing machine according to claim 8 uses the tension detected by the tension detector, which is obtained at a timing corresponding to the number of stitches in one cycle of the vertical movement of the needle bar. to make a decision. In the sewing machine according to claim 8, the influence of the stitches according to the number of stitches is greater than the case where the tension detected by the tension detector acquired at the same time regardless of the number of stitches is used to determine the presence or absence of the bobbin thread for the stitches. It is possible to determine the presence or absence of the bobbin thread with respect to the stitch by taking into consideration.

The bobbin thread judging section of the sewing machine according to claim 9 changes the frequency of timing at which the tension detector acquires the detection result for one cycle of vertical movement of the needle bar according to the number of stitches of the stitches. Then, the tension detected by the tension detector is used for determination. In the sewing machine according to claim 9, the influence of the stitches according to the number of stitches is greater than the case where the tension detected by the tension detector obtained at the same frequency regardless of the number of stitches is used to determine the presence or absence of the bobbin thread for the stitches. It is possible to determine the presence or absence of the bobbin thread with respect to the stitch by taking into consideration.

The sewing machine according to claim 10, further comprising a thread take-up lever for pulling up the needle thread entwined with the bobbin thread by the hook, the tension detector detecting the tension of the needle thread, and the bobbin thread judging section comprising: Whether or not the detection result of the tension detector is greater than the threshold value during any one of the take-up period during which the thread take-up pulls up the upper thread and the hook supplement period during which the hook captures the upper thread. Presence or absence of the bobbin thread for the stitch is determined based on the position and the detection result of the motion detector. According to the tenth aspect of the sewing machine, it is possible to determine the presence or absence of the bobbin thread for the stitch based on the tension of the needle thread detected during the take-up period or the period of supplementing the hook. Since the tension of the needle thread is greater during the take-up period or the supplementary period of the hook than during the period between the period of raising the thread take-up and the supplementary period of the hook, the bobbin thread judging section makes a judgment during the period in which the tension of the upper thread is relatively small. , it is possible to avoid erroneous determination.

The motion detector of the sewing machine according to claim 11 detects whether or not the bobbin is rotated. According to the eleventh aspect of the sewing machine, it is possible to detect the presence or absence of the bobbin operation based on the detection result of the rotation of the bobbin.

The motion detector of the sewing machine according to claim 12 detects whether or not the amount of the bobbin thread wound around the bobbin has changed. According to the sewing machine of claim 12, the presence or absence of bobbin operation can be detected based on the result of detecting the presence or absence of change in the amount of bobbin thread wound around the bobbin.

According to a thirteenth aspect of the present invention, there is provided a bobbin thread determining method comprising: a needle bar to which a sewing needle through which an upper thread is passed; a needle bar vertical movement mechanism for vertically moving the needle bar; a hook that rotatably accommodates a bobbin that has been sewn thereon; and a hook that rotates in synchronism with the vertical movement of the needle bar to catch the annular needle thread passing through the sewing needle and entangle it with the bobbin thread. A control unit of a sewing machine comprising a hook mechanism for forming stitches with a , a tension detector for detecting the tension of the needle thread or the bobbin thread, and an operation detector for detecting the presence or absence of operation of the bobbin. A bobbin thread determination method for determining the presence or absence of the bobbin thread for the stitch based on whether the tension detected by the tension detector is greater than a threshold value and the detection result of the motion detector. It includes a thread determination step. When the bobbin thread determination method of claim 13 is executed, the sewing machine determines the presence or absence of the bobbin thread for the stitch based on whether the tension detected by the tension detector is greater than a threshold value and the detection result of the motion detector. Therefore, it is possible to more accurately determine the presence or absence of the bobbin thread in the stitch compared to a device that uses only a tension detector.

1 is a perspective view of a sewing system 10 including a sewing machine 1 and an editing device 8; FIG. FIG. 4 is a partially enlarged view of the front end portion 7; 4 is a perspective view of the tension detector 18; FIG. FIG. 4 is a conceptual diagram showing how the hook 49 catches the upper thread 55; 3 is an electrical block diagram of the sewing machine 1 and the editing device 8; FIG. 4 is a flowchart of threshold setting processing; 4 is a conceptual diagram of sewing data 30 and stitches formed based on the sewing data 30. FIG. 4 is a chart showing the relationship between the tension D1 of the upper thread 55, the vertical position D2 of the needle tip, and the angle of the upper shaft. 4 is a flowchart of sewing processing; 9 is a graph showing the relationship between the number of stitches N at the first sewing time and the tension of the upper thread 55 in specific examples D3 and D4; (A) is a graph showing the relationship between the number of stitches N in the second sewing period and the number of revolutions of the upper shaft 22 in Specific Example D5, and (B) is a graph showing the number of stitches N in the second sewing period in Specific Example D5; FIG. 12C is a graph showing the relationship between the tension of the needle thread 55 detected during the hook supplement period, and (C) is the number of stitches N in the second sewing period in Concrete Example D5 and the tension of the needle thread 55 detected during the take-up take-up period; is a graph showing the relationship between (A) is a graph showing the relationship between the number of stitches N in the second sewing period and the number of revolutions of the upper shaft 22 in Specific Example D6; FIG. 12C is a graph showing the relationship between the tension of the needle thread 55 detected during the hook supplementary period, and (C) is the number of stitches N at the second sewing time in Concrete Example D6 and the tension of the needle thread 55 detected during the take-up take-up period; is a graph showing the relationship between FIG. 11 is a flowchart of sewing processing according to a modification; FIG.

Embodiments of the present invention will be described with reference to the drawings. In the following description, left and right, front and back, and up and down indicated by arrows in the drawings are used. A sewing system 10 will be described with reference to FIG. Sewing system 10 includes sewing machine 1 and editing device 8 . The editing device 8 is a portable terminal connected to the sewing machine 1 . The editing device 8 may be connected to a sewing machine other than the sewing machine 1, or may be connected to a plurality of sewing machines. The editing device 8 edits sewing data relating to stitches to be formed on a sewn product (for example, the cloth 69 in FIG. 4). The editing device 8 outputs sewing data to the sewing machine 1 . The sewing machine 1 performs pattern sewing for forming stitches on the cloth 69 based on the sewing data output from the editing device 8 .

A sewing machine 1 will be described with reference to FIGS. 1 to 4. FIG. A sewing machine 1 includes a bed portion 2 , a pedestal portion 3 and an arm portion 4 . The bed part 2 is placed on the table 50 . The bed portion 2 extends in the front-rear direction, and includes a hook 49 (see FIG. 4), a hook mechanism 48 (see FIG. 4), a rotation detector 141 (see FIG. 5), and the like. A hook 49 is provided below a needle bar 9, which will be described later, and rotatably accommodates a bobbin B around which a bobbin thread 67 is wound. The hook mechanism 48 rotates the hook 49 in synchronism with the vertical movement of the needle bar 9, catches the annular needle thread 55 passing through the sewing needle 11, and entangles it with the bobbin thread 67 to form stitches. The rotation detector 141 detects whether or not the bobbin B is rotated as whether or not the bobbin B is operated. The rotation detector 141 is, for example, a non-photoelectric proximity sensor (magnetic sensor). The bobbin B has a magnet installed in a part of the collar portion of the bobbin B, and the magnetic force around the rotation detector 141 changes as the bobbin B rotates. The rotation detector 141 can detect the presence or absence of rotation of the bobbin B by reading the change in the magnetic force. The pedestal part 3 extends vertically upward from the rear side of the bed part 2 . The pedestal part 3 includes a main motor 123 (see FIG. 5) and the like inside. The arm portion 4 extends forward from the upper end of the pedestal portion 3 to face the upper surface of the bed portion 2 and has a front end portion 7 . The arm portion 4 is internally provided with an upper shaft 22, a needle bar vertical movement mechanism 21, and the like. A needle bar 9 extends downward from the lower end of the front end portion 7 . A sewing needle 11 through which a needle thread 55 is inserted is attached to the needle bar 9 . Sewing needle 11 is detachably attached to the lower end of needle bar 9 and has an eyelet 111 at the lower end.

The sewing machine 1 has a workbench 5 and a transfer device 6 above the bed 2 . The workbench 5 has a needle plate 501 . A needle plate 501 has a needle hole 502 directly below the sewing needle 11 . The sewing needle 11 can be inserted through the needle hole 502 . The transfer device 6 includes an X-axis movement mechanism, a Y-axis movement mechanism, an arm portion 65 , a support portion 64 , an elevating portion 62 and a holder 60 . The X-axis moving mechanism is provided inside the bed portion 2 , and the Y-axis moving mechanism is provided inside the pedestal portion 3 . Arm 65 holds support 64 and connects to the Y-axis movement mechanism. The support portion 64 extends in the left-right direction and supports the lifting portion 62 and the holder 60 . The raising/lowering part 62 is provided on the support part 64 so that it can be raised and lowered. The holder 60 has a transfer plate 61 and a pressing plate 63 . The transfer plate 61 extends horizontally and has a rectangular opening in a plan view at its front end. Transfer plate 61 connects to support 64 . The pressing plate 63 extends horizontally and has a rectangular opening in plan view. The holding plate 63 is connected to the lower end of the lifting section 62 . The opening of the transfer plate 61 has substantially the same shape as the opening of the pressing plate 63 and corresponds to the position of the opening of the pressing plate 63 .

The X-axis movement mechanism uses an X-axis motor 124 (see FIG. 5) as a drive source, and moves the lifting section 62 and the holder 60 in the left-right direction (X-axis direction). The Y-axis moving mechanism uses a Y-axis motor 125 (see FIG. 5) as a driving source to move the arm portion 65 in the front-rear direction (Y-axis direction). The support portion 64 moves in the front-rear direction as the arm portion 65 moves in the front-rear direction. The lifting part 62 and the holder 60 move together with the support part 64 . The operator places the cloth 69 (see FIG. 4) on the transfer plate 61. As shown in FIG. When the lifting section 62 moves downward, the pressing plate 63 descends onto the transfer plate 61 . The holder 60 (pressing plate 63 and transfer plate 61) sandwiches the cloth 69 from above and below. The sewing machine 1 moves the holder 60 back and forth and left and right by the X-axis movement mechanism and the Y-axis movement mechanism, thereby moving the cloth 69 and the sewing needle 11 held by the holder 60 relative to each other.

As shown in FIG. 2, the front end 7 includes a guide mechanism 14, a needle bar 9, a presser bar 12, and the like. The guide mechanism 14 is provided on the right side of the front end portion 7 and guides the needle thread 55 . The guide mechanism 14 includes a sub tensioner 15 , a main tensioner 16 , a thread guide 17 , a tension detector 18 , a thread take-up 19 and a thread guide 20 . The needle thread 55 passes from the thread spool through the auxiliary thread tension device 15 , the main thread tension device 16 , the thread guide 17 , the tension detector 18 , the thread take-up 19 and the thread guide 20 , and is passed through the eye 111 of the sewing needle 11 . The thread take-up 19 pulls up the needle thread 55 entwined with the bobbin thread 67 by the hook 49 (see FIG. 4). The main tensioner 16 has a solenoid 128 (see FIG. 5). The main thread tension device 16 adjusts the thread tension by changing the tension applied to the needle thread 55 (hereinafter referred to as needle thread tension) in accordance with the operation of the solenoid 128 . The needle thread tension is set in consideration of the tension balance between the needle thread 55 and the bobbin thread 67 . A main motor 123 (see FIG. 5) drives the upper shaft 22 to rotate. The needle bar vertical motion mechanism 21 moves the needle bar 9 vertically as the upper shaft 22 rotates.

A presser bar 12 extends downward from the lower end of the front end portion 7 to the left of the needle bar 9 . The presser foot 13 is attached to the lower end of the presser bar 12 and has a lower end 131 . The lower end portion 131 has a vertically penetrating cylindrical shape through which the sewing needle 11 can pass. The presser foot driving mechanism vertically swings the presser bar 12 in synchronism with the vertical swing of the needle bar 9 caused by the rotation of the upper shaft 22 . The presser foot drive mechanism has a presser motor 129 (see FIG. 5). The presser foot driving mechanism can adjust the height from the upper surface of the needle plate 501 to the lower end of the presser foot 13 (hereinafter referred to as the presser foot height) as the presser foot motor 129 is driven. The presser foot 13 presses the cloth 69 against the throat plate 501 from above when the sewing needle 11 is pulled out of the cloth 69 , thereby preventing the cloth 69 from lifting from the throat plate 501 . The sewing needle 11 passes through the inside of the lower end 131 and pierces the cloth. Sewing needle 11 moves vertically through needle hole 502 .

As shown in FIGS. 2 and 3, the tension detector 18 is located on the right side of the front end portion 7 and on the path between the thread guide 17 and the thread take-up 19 at a vertical position between the sub thread tension device 15 and the main thread tension device 16. be. The tension detector 18 can detect needle thread tension. The tension detector 18 includes a mount 51 , a holder 52 , a magnetic sensor 53 , a plate 54 , guide members 77 and magnets 56 . The mounting base 51 includes a mounting portion 57 and a pedestal portion 59 . The mounting portion 57 and the base portion 59 are integrally formed with each other. The mounting portion 57 has an elongated hole 58 through which a screw is inserted. A screw inserted through the long hole 58 is fastened to a screw hole provided on the right side of the front end portion 7 . The pedestal portion 59 is on the left side of the mounting base 51 . The base portion 59 has a left protrusion 71 and a right protrusion 72 . Each of the left protrusion 71 and the right protrusion 72 has a rectangular parallelepiped shape extending in the front-rear direction.

The holding portion 52 is formed in a substantially rectangular parallelepiped shape and is attached to the pedestal portion 59 between the left protrusion 71 and the right protrusion 72 . The holding portion 52 is a non-magnetic material. The magnetic sensor 53 is held on the front surface of the holding portion 52 . The magnetic sensor 53 is a Hall element. The magnetic sensor 53 is located behind the front ends of the left projection 71 and the right projection 72, respectively.

The plate 54 has a plate shape having a thickness in the front-rear direction, and bridges the left protrusion 71 and the right protrusion 72 . The guide member 77 is attached to the left protrusion 71 and the right protrusion 72 . The guide member 77 sandwiches the left end of the plate 54 with the left protrusion 71 and sandwiches the right end of the plate 54 with the right protrusion 72 . The central portion of the plate 54 in the left-right direction has a gap between it and the front surface of the holding portion 52 . Therefore, the plate 54 bends in the front-rear direction with both ends in the left-right direction as fulcrums.

The magnet 56 is formed in a cylindrical shape extending in the front-rear direction. The magnet 56 is fixed to the rear surface of the plate 54 at the central portion in the left-right direction. When the plate 54 bends in the front-rear direction, the magnet 56 moves in the front-rear direction and the distance from the magnetic sensor 53 changes. The magnetic sensor 53 detects changes in magnetic flux density from the magnet 56 and outputs a voltage corresponding to the magnetic flux density.

The guide member 77 has an upper guide groove 74 and a lower guide groove 76 . The upper guide groove 74 and the lower guide groove 76 are vertically arranged with the plate 54 therebetween. The upper guide groove 74 and the lower guide groove 76 are opened in the vertical direction and formed in a hook shape when viewed from above. The upper guide groove 74 has an upper holding hole 73 and the lower guide groove 76 has a lower holding hole 75 . The upper holding hole 73 and the lower holding hole 75 are through holes that open vertically. The upper thread 55 is passed through the upper holding hole 73 and the lower holding hole 75, respectively. The upper thread 55 between the upper holding hole 73 and the lower holding hole 75 contacts the plate 54 from the front. As the needle thread tension increases, the needle thread 55 urges the plate 54 rearward. The magnetic sensor 53 outputs a voltage corresponding to the longitudinal position of the plate 54 which bends in the longitudinal direction due to the upper thread tension. The sewing machine 1 can acquire the needle thread tension based on the output voltage of the magnetic sensor 53 .

As shown in FIG. 1, the editing device 8 is arranged on a table 50 and has a display screen 86, a speaker 87 (see FIG. 5), an operation panel 88, selection keys 89, and the like. The display screen 86 displays various screens. A speaker 87 outputs various sounds. The operation panel 88 and selection keys 89 input various information and instructions to the editing device 8 . The operation panel 88 is a touch panel and is provided in front of the display screen 86 . Selection keys 89 are provided below the display screen 86 and include an up key 89A, a down key 89B, a left key 89C and a right key 89D. When inputting various information and instructions to the editing device 8, the operator operates the operation panel 88 or the selection key 89. FIG.

The electrical configuration of the sewing system 10 will be described with reference to FIG. The sewing machine 1 has a control section 100 . The control unit 100 includes a CPU 101, a ROM 102, a RAM 103, a storage device 104, an input/output interface (I/F) 106, and drive circuits 113-116. The input/output I/F 106 is connected to the CPU 101, ROM 102, RAM 103, storage device 104, drive circuits 113 to 116, footboard 126, power switch 127, rotation detector 141, tension detector 18, solenoid 128, and external connection I/F 130. do. A CPU 101 performs overall control of the operation of the sewing machine 1 . A ROM 102 stores various programs and the like. A RAM 103 temporarily stores various information. The storage device 104 is non-volatile and stores various information. The storage device 104 stores a combination of the number of stitches 35 (see FIG. 7) to be sewn according to the sewing data 30 (see FIG. 7) and a threshold value used in the main processing described later. The sewing data 30 is expressed in a sewing coordinate system that drives the X-axis motor 124 and the Y-axis motor 125 .

The drive circuit 113 connects with the main motor 123 . The CPU 101 controls the main motor 123 through the drive circuit 113 . For example, the CPU 101 controls the rotational speed (sewing speed) of the output shaft of the main motor 123 . The encoder 133 is provided on the output shaft of the main motor 123 and connected to the input/output I/F 106 . An encoder 133 detects the rotation speed and rotation position of the output shaft of the main motor 123 . The rotational position of the output shaft of the main motor 123 is called the upper shaft angle. Drive circuit 114 is connected to X-axis motor 124 . CPU 101 controls X-axis motor 124 through drive circuit 114 . The encoder 134 is provided on the output shaft of the X-axis motor 124 and connected to the input/output I/F 106 . The encoder 134 detects the rotation direction, rotation speed, and rotation position of the output shaft of the X-axis motor 124 . Drive circuit 115 is connected to Y-axis motor 125 . CPU 101 controls Y-axis motor 125 through drive circuit 115 . The encoder 135 is provided on the output shaft of the Y-axis motor 125 and connected to the input/output I/F 106 . The encoder 135 detects the rotation direction, rotation speed, and rotation position of the output shaft of the Y-axis motor 125 . Drive circuit 116 is connected to presser motor 129 . CPU 101 controls presser motor 129 through drive circuit 116 . The encoder 136 is provided on the output shaft of the presser motor 129 and connected to the input/output I/F 106 . An encoder 136 detects the rotation direction, rotation speed, and rotation position of the output shaft of the presser motor 129 .

The CPU 101 drives the main motor 123 to rotate the upper shaft 22, thereby controlling the vertical swing of the needle bar 9 and the presser bar 12 and the rotation of the vertical hook. Based on the sewing data, the CPU 101 drives the X-axis motor 124 and the Y-axis motor 125 at the same time as driving the main motor 123 to control the position of the holder 60 . The sewing machine 1 performs sewing on the cloth 69 under this control.

The footboard 126 inputs various instructions to the control unit 100 . For example, the operator steps on the treadle 126 when starting the sewing operation of the sewing machine 1 . A power switch 127 activates and terminates the sewing machine 1 . The rotation detector 141 inputs to the control unit 100 the detection result of whether or not the bobbin B attached to the hook 49 is rotated. The tension detector 18 outputs an output voltage corresponding to the needle thread tension to the control section 100 . The CPU 101 controls the operation of the solenoid 128 . The external connection I/F 130 connects to the external connection I/F 95 of the editing device 8 via the cable 70 .

The editing device 8 has a control section 80 . The control unit 80 includes a CPU 81 , a ROM 82 , a RAM 83 , a storage device 84 and an input/output I/F 85 . Input/output I/F 85 is connected to CPU 81 , ROM 82 , RAM 83 , storage device 84 , display screen 86 , speaker 87 , operation panel 88 , selection key 89 and external connection I/F 95 . The CPU 81 centrally controls the operation of the editing device 8 . A ROM 82 stores a program for performing main processing, which will be described later, a plurality of types of codes, and the like. The RAM 83 temporarily stores various information. The storage device 84 is non-volatile and stores various information such as sewing data. The CPU 81 performs display control of the display screen 86, sound output control of the speaker 87, and input control from the operation panel 88 and the selection key 89. FIG. External connection I/F 95 connects to external connection I/F 130 of sewing machine 1 via cable 70 .

An outline of the operation of the sewing machine 1 will be described with reference to FIGS. 1 to 5. FIG. The operator causes the holder 60 on the needle plate 501 to hold the cloth 69 . When the operator inputs sewing instructions, the sewing machine 1 drives the main motor 123, the X-axis motor 124, and the Y-axis motor 125 according to the sewing data. By driving the main motor 123, the upper shaft 22 rotates to move the needle bar 9 and the thread take-up 19 up and down. The hook 49 rotates in synchronism with the rotation of the upper shaft 22 .

The sewing needle 11 descending together with the needle bar 9 penetrates the cloth 69 and passes through a needle hole 502 (see FIG. 2) formed in the needle plate 501 . As shown in FIG. 4(a), the upper thread 55 near the eye 111 that has descended to the lower side of the needle eye 502 forms a loop. As shown in FIG. 4(b), the hook 49 rotates clockwise when viewed from the front, so that the blade point 46 catches the looped upper thread 55. As shown in FIG. Hereinafter, the period during which the blade tip 46 catches the looped needle thread 55 is referred to as the hook catching period. The sewing needle 11 rises upward toward the cloth 69, and the hook 49 further rotates clockwise when viewed from the front. The blade point 46 pulls the annular needle thread 55 in the rotating direction, and the annular needle thread 55 expands in diameter.

As shown in FIG. 4(c), when the circular needle thread 55 passes through the hook 49, the needle thread 55 is entangled with the bobbin thread 67. As shown in FIG. The rotational direction of the hook 49 is switched to counterclockwise when viewed from the front. As shown in FIG. 4(d), the thread take-up 19 pulls up the needle thread 55 entwined with the bobbin thread 67. As shown in FIG. Hereinafter, the period during which the thread take-up 19 pulls up the upper thread 55 is referred to as the take-up period. The annular needle thread 55 is reduced in diameter, and the sewing machine 1 completes sewing for one stitch. In this embodiment, the sewing machine 1 sews one stitch each time the upper shaft 22 rotates once. The sewing machine 1 forms a plurality of stitches 68 on the cloth 69 by repeating the above operation.

6 to 8, the threshold value setting process of the sewing machine 1 will be described using the specific example of FIG. After the operator turns on the sewing machine 1 and inputs a start instruction, the CPU 101 reads the program and sewing data from the ROM 102 and starts the threshold value setting process.

As shown in FIG. 6, the CPU 101 acquires sewing data 30 (S51). As shown in FIG. 7, the sewing data 30 of the specific example is data for forming a rectangular stitch 35 including needle drop points P1 to P70 according to a predetermined sewing order. The needle drop point is a position where the sewing needle 11 attached to the needle bar 9 is expected to pierce the cloth 69 . The needle drop point P1 is the first starting point in the sewing order, and the needle drop point P70 is the last ending point in the sewing order. The stitches based on the needle entry points P1 to P3 are formed in the direction indicated by the arrow J1, and the stitches based on the needle entry points P4 to P70 are formed counterclockwise from the needle entry point P3 in the directions of the arrows J2 to J6. It is formed. The editing device 8 can output the sewing data 30 to the sewing machine 1 . In sewing machine 1 , CPU 101 receives sewing data 30 output from editing device 8 . The CPU 101 sets a variable N to 1 for reading out the needle drop points P1 to P70 of the received sewing data 30 in the order from the start point P1 to the end point P70, and starts sewing based on the sewing data 30 acquired in S51. (S52). The sewing machine 1 drives the main motor 123 , the X-axis motor 124 and the Y-axis motor 125 according to the sewing data 30 . By driving the main motor 123, the upper shaft 22 rotates to move the needle bar 9 and the thread take-up 19 up and down. The hook 49 rotates in synchronism with the rotation of the upper shaft 22 .

The CPU 101 determines whether it is time to detect the needle thread tension (phase) from the upper shaft angle determined by the detection result of the encoder 133 (S53). As shown in FIG. 8, during sewing, the tension of the needle thread and the height of the lower end (needle tip) of the sewing needle 11 change periodically with the sewing period as a unit period, depending on the angle of the upper shaft. The sewing period is a period during which one stitch is sewn. The vertical axis on the right side of FIG. 8 indicates the height of the lower end of sewing needle 11 with the upper surface of needle plate 501 as a reference. When the upper shaft angles are H1 and H2, the lower end of sewing needle 11 is positioned at the same height as the upper surface of cloth 69 placed on the upper surface of throat plate 501 . That is, the period from H1 to H2 of the upper axis angle is the penetration period during which the sewing needle 11 penetrates the cloth 69 . The period in which the upper axis angle is less than H1 and the period in which the upper axis angle is greater than H2 are non-penetrating periods in which the sewing needle 11 is above the cloth 69. FIG. The sewing period includes a period for lifting the thread take-up and a period for capturing the hook. The needle thread tension has a peak during the period during which the thread take-up is lifted and the period during which the hook is caught. The CPU 101 of the present embodiment determines the needle thread tension determination timing (detection timing) from the upper shaft angle based on the detection result of the encoder 133 . The CPU 101 of this embodiment changes the determination timing between the first sewing period from the start of sewing until sewing of a predetermined number of stitches and the second sewing period following the first sewing period. The length of the first sewing period may be appropriately set, and in this embodiment, it is a period in which the number of stitches is less than 10 after the start of sewing. The CPU 101 uses the needle thread tension detected by the tension detector 18 during the hook catching period to determine whether or not the bobbin thread 67 is present in the stitches during the first sewing period. The CPU 101 uses the needle thread tension detected by the tension detector 18 during the thread take-up period to determine the presence or absence of the bobbin thread 67 for the stitches during the second sewing period. Based on the variable N, the CPU 101 determines whether it is the first sewing period or the second sewing period, and specifies the detection timing. When it is not the detection time (S53: NO), the CPU 101 waits until the detection time.

When it is time to detect (S53: YES), the CPU 101 stores the detection result output by the tension detector 18 as the tension corresponding to the variable N (S54). The CPU 101 determines whether the variable N is the last stitch number of the sewing data 30 acquired in S51 (S55). When the number of stitches is not the last (S55: NO), the CPU 101 adds 1 to the variable N (S56) and returns the process to S53. When the number of stitches is the last (S55: YES), the CPU 101 stops sewing based on the sewing data 30 (S57). The CPU 101 determines whether to continue processing (S58). The CPU 101 of the present embodiment executes the processes of S52 to S57 a plurality of times to acquire the correspondence between the number of stitches and the tension for a plurality of sets, and acquires the average value and the standard deviation of the tension for each number of stitches. do. The number of sets may be determined as appropriate, and may be anywhere from 5 to 20, for example. The operator of the sewing machine 1 changes the position of the cloth 69 with respect to the holder 60 and inputs a continuation instruction to execute the processes of S52 to S57. When the continuation instruction is detected (S58: YES), the CPU 101 returns the process to S52.

When the continuation instruction is not detected (S58: NO), the CPU 101 sets a threshold value for each stitch number based on the correspondence between a plurality of sets of stitch numbers and tension (S59). The CPU 101 sets a first threshold H1(N), which is the threshold for the number of stitches N in the first sewing period, according to the formula (1), and sets a second threshold H2(N), which is the threshold for the number of stitches N in the second sewing period. is set according to equation (2).
First threshold value H1 (N) = average value of tension (N) - C1 × standard deviation (N) Equation (1)
Second threshold H2 (N) = average tension (N) - C2 x standard deviation (N) Equation (2)
Here, the average value of tension (N) is the average value of tension corresponding to the number N of stitches, and the standard deviation (N) is the standard deviation of the tension corresponding to the number N of stitches. C1 and C2 are constants and may be the same or different. C1 and C2 may be set by the operator of the sewing machine 1, or may be automatically set by the CPU 101 according to sewing conditions. In this embodiment, as an example, C1 is 2 and C2 is 2 or 3. That is, C1 is a value less than or equal to C2. The CPU 101 associates the set threshold with the number of stitches N and stores them in the storage device 104 . The CPU 101 ends the threshold value setting process.

The sewing process of the sewing machine 1 will be described with reference to FIGS. 9 to 12. FIG. After the operator designates sewing data and inputs an instruction to start sewing, the CPU 101 reads a program from the ROM 102 and starts the sewing process shown in FIG. Specific examples D3 to D6 in FIGS. 10 to 12 are used as specific examples for determining the presence or absence of the bobbin thread 67 for the stitches when sewing according to the sewing data 30. FIG. Specific example D3 shows an example of the relationship between the needle thread tension and the number of stitches N when the bobbin thread 67 is present for the stitches over the first sewing period. Specific example D4 shows an example of the relationship between the needle thread tension and the number of stitches N when there is no bobbin thread 67 for the stitches at the start of sewing. In a specific example D5, the second threshold value H2 is set under the condition that C2 is 3, and the difference between the needle thread tension and the number of stitches N when the bobbin thread 67 for the stitch runs out (bobbin thread breakage) in the middle of the second sewing period. An example relationship is shown. A specific example D6 shows an example of the relationship between the needle thread tension and the number of stitches N when the second threshold value H2 is set under the condition that C2 is 2, and the pseudo sewing of multiple stitches is performed during the second sewing period. Pseudo stitching refers to defective stitching in which the needle thread 55 alone is used to form a stitch that looks like a stitch and the bobbin thread 67 is not entwined with the needle thread 55 . , and the pseudo-sewing of multiple stitches means a sewing example in which the pseudo-sewing occurs multiple times. In the case of pseudo sewing, the bobbin thread 67 is not sequentially supplied.

As shown in FIG. 9, the CPU 101 executes variable initialization processing (S1). The CPU 101 sets the counters E and F stored in the RAM 103 to 0 for counting the number of consecutive abnormalities detected, and sets the counter N to 1 for counting the number of stitches. The CPU 101 determines whether it is during the first sewing period based on the variable N (S2). When it is during the first sewing period (S2: YES), the CPU 101 determines whether the rotation of the bobbin B is detected based on the detection result of the rotation detector 141 (S3). In a specific example D3, rotation of the bobbin B is detected (S3: YES), the CPU 101 determines that the bobbin thread 67 is present in the stitch, and after setting the first sewing period counter E to 0 (S18 ), and the processing of S21, which will be described later, is performed. In the specific example D4, it is detected that the bobbin B does not rotate (S3: NO), and the needle thread tension detected by the tension detector 18 at a predetermined time within the first sewing period exceeds the first threshold value H1 ( N) is determined (S4). The CPU 101 uses the first threshold value H1(N) according to the number N of stitches based on the combination of the number N of stitches stored in the storage device 104 and the first threshold value H1. As shown in FIG. 10, when the number of stitches N is 1, the upper thread tension of the specific example D4 indicated by the white square is greater than the first threshold value H1 (1) indicated by the white circle (S4: YES), so the CPU 101 After it is determined that the bobbin thread 67 is present for the stitch and the counter E is set to 0 (S18), the process of S21, which will be described later, is performed. Thus, when the rotation detector 141 detects that the bobbin B does not rotate (S3: NO) and the tension detected by the tension detector 18 is greater than the first threshold value H1 (N) (S4: YES ), the CPU 101 determines that there is a bobbin thread 67 for the stitch. On the other hand, when the number of stitches N is any one of 3 to 6, the needle thread tension in the specific example D4 is equal to or less than the first threshold value H1 (N) (S4: NO), so the CPU 101 detects that the bobbin thread 67 is abnormal. 1 is added to the counter E for detecting (S5).

The CPU 101 determines whether the counter E is greater than the number threshold (S6). The number of times threshold may be set in advance to a value smaller than 9, which is the maximum number of stitches included in the first sewing period. The rotation threshold in this embodiment is three. When the variable N is 6, the counter E of the specific example D4 is 4, which is greater than the number threshold (S6: YES), so the CPU 101 determines that there is no bobbin thread 67 for the stitch (S17). The CPU 101 may output to the editing device 8 an instruction to display the determination result on the display screen 86 . If the sewing machine 1 is equipped with a notification unit such as an LED lamp, the CPU 101 may notify the notification unit of the determination result that the bobbin thread 67 is missing for the stitch. Thus, when the rotation detector 141 detects that the bobbin B does not rotate (S3: NO) and the tension detected by the tension detector 18 is equal to or less than the first threshold value H1 (N) (S4: YES), the CPU 101 determines that there is no bobbin thread 67 for the stitch (S17). In this embodiment, the amount of force detected by the tension detector 18 becomes equal to or less than the first threshold value H1 (N) continuously for the number of times threshold or more (S4: NO, S6: YES), and the rotation detector 141 detects the rotation of the bobbin B. If it is detected that there is no bobbin thread 67 (S3: NO), the CPU 101 determines that there is no bobbin thread 67 for the stitch (S17). The CPU 101 ends sewing based on the sewing data 30 in the middle of sewing (S23), and ends the sewing process. In the present embodiment, the absence of the bobbin thread 67 (for the stitch) means that the bobbin thread 67 has run out and the bobbin thread has been cut, or the bobbin thread 67 has run out when the cloth is fed during sewing. This means that the bobbin thread 67 is not entangled with the upper thread 55 because it has come off.

In the specific example D4, when the variable N is 5 or less, the counter E is equal to or less than the number of times threshold (S6: NO), so the CPU 101 determines that the bobbin thread 67 is present for the stitch (S7). is the last stitch number (S21). When the stitch number N is not the last stitch number (S21: NO), the CPU 101 adds 1 to the stitch number N (S22) and returns the process to S2. When the number of stitches N is the final number of stitches (S21: YES), the CPU 101 ends sewing (S23), and ends the sewing process.

When it is not the first sewing period (S2: NO), the CPU 101 determines that the needle thread tension detected by the tension detector 18 at a predetermined time within the second sewing period is higher than the second threshold value H2 (N) set in S59. It is judged whether it is larger (S11). The CPU 101 uses the second threshold value H2(N) according to the number N of stitches based on the combination of the number N of stitches stored in the storage device 104 and the second threshold value H2(N). As shown in FIG. 11C, in Example D5, when the number of stitches N is 10, the upper thread tension indicated by the black circle is greater than the second threshold value H2 (10) indicated by the white square (S11: YES). , the CPU 101 determines that the bobbin thread 67 is present for the stitch, sets the counter F for the second sewing period to 0 (S18), and then performs the above-described processing of S21. As shown in FIG. 12C, in specific example D6, when the number of stitches N is 10, the needle thread tension indicated by the black circle is equal to or lower than the second threshold value H2 (N) indicated by the white square (S11: NO). , the CPU 101 outputs to the editing device 8 an instruction to display on the display screen 86 that an abnormality has been detected (S12). If the sewing machine 1 is equipped with a notification unit such as an LED lamp, the CPU 101 may notify the notification unit that an abnormality has been detected. The CPU 101 adds 1 to the second sewing period counter F (S13). The CPU 101 determines whether the counter F is greater than the number threshold (S14). The number-of-times threshold for S14 may be the same as or different from the number-of-times threshold for S6. The number-of-times threshold in this embodiment is five, for example.

In specific example D6, when the number of stitches N is 10, the counter F is 1, which is equal to or less than the number of times threshold (S14: NO). It is determined whether or not the needle thread tension obtained is greater than the third threshold value (S15). The third threshold is less than the second threshold. The third threshold is a threshold for detecting a case where the bobbin thread 67 is not entangled in a stitch. In specific example D6, when the variable N is 10 and the needle thread tension is greater than the third threshold (S15: YES), the CPU 101 performs the process of S21. In specific example D3, when the number of stitches N is 11, the needle thread tension is greater than the second threshold value H2 (N) (S11: YES). After setting 0 (S18), the process of S21 described above is performed. Thus, in the specific example D6, the upper thread tension may become equal to or less than the second threshold value H2 (N). Therefore, it is determined that the bobbin thread 67 is present throughout the second sewing period. When the needle thread tension is equal to or less than the third threshold (S15: NO), the CPU 101 determines that there is no bobbin thread 67 for the stitch (S17), and finishes sewing based on the sewing data 30 ( S23), the sewing process ends. In other words, the CPU 101 detects that the bobbin thread 67 is not attached to the stitch when the needle thread tension becomes equal to or less than the third threshold even once.

On the other hand, in specific example D5, when the number of stitches N is 36, the counter F is 6, which is greater than the number threshold (S14: YES), so the CPU 101 determines whether the rotation detector 141 has detected the rotation of the bobbin B. (S16). When the detection result of the rotation detector 141 indicates that there is rotation (S16: YES), the CPU 101 determines that the bobbin thread 67 is present in the stitch (S19), and performs the processing of S21. Thus, when the tension detected by the tension detector 18 is equal to or less than the second threshold value H2 (N) and the rotation detector 141 detects that the bobbin B is rotating (S16: YES), the CPU 101 , it is determined that there is a bobbin thread 67 for the stitch.

When the detection result of the rotation detector 141 indicates no rotation (S16: NO), the CPU 101 determines that there is no bobbin thread 67 for the stitch (S17). Thus, when the tension detected by the tension detector 18 is equal to or less than the second threshold value H2 (N) (S11: NO) and the rotation detector 141 detects that the bobbin B does not rotate (S16: NO), the CPU 101 determines that there is no bobbin thread 67 for the stitch. In the present embodiment, the tension detected by the tension detector 18 continuously becomes equal to or less than the second threshold H2 (N) (S11: NO, S14: YES), and the rotation detector 141 detects the rotation of the bobbin B. When it is detected that there is no thread (S16: NO), the CPU 101 determines that the bobbin thread 67 has run out (bobbin thread breakage) (S17). The CPU 101 ends sewing based on the sewing data 30 in the middle of sewing (S23), and ends the sewing process.

The sewing process of the first modified example will be described with reference to FIG. 9 as in the above embodiment. After the operator designates the sewing data 30 and inputs an instruction to start sewing, the CPU 101 reads out the program from the ROM 102 and starts the sewing process of the first modification shown in FIG. The CPU 101 of the first modified example changes the determination frequency between the first sewing period from the start of sewing until the predetermined number of stitches are sewn and the second sewing period following the first sewing period. The CPU 101 determines the presence or absence of the bobbin thread 67 for the stitches in the first sewing period using the detection results of the tension detector 18 during the take-up take-up period and the hook catching period. The CPU 101 uses the detection result of the tension detector 18 during the take-up period to determine whether the bobbin thread 67 is present in the stitches during the second sewing period. That is, during the first sewing period, the CPU 101 detects the needle thread tension twice in one cycle of the vertical movement of the needle bar 9, and performs the determination of S4. The CPU 101 makes the determination of S4 using the first threshold value H1 (N) corresponding to the detection timing of the needle thread tension. During the second sewing period, the CPU 101 detects the needle thread tension once per cycle of the vertical movement of the needle bar 9, and makes the determination of S11. Other processes are the same as those in the above embodiment, so description thereof will be omitted.

Sewing processing of the second modification will be described with reference to FIG. In the sewing process of the second modified example, the CPU 101 determines whether or not the bobbin thread 67 is present in the stitch based on whether or not the ratio of detected abnormalities to the number of stitches N is greater than the ratio threshold. After the operator designates the sewing data 30 and inputs an instruction to start sewing, the CPU 101 reads the program from the ROM 102 and starts the sewing process shown in FIG. In FIG. 13, when the same processing as the sewing processing of FIG. 9 is performed, the same reference numerals are given. As shown in FIG. 13, the sewing process of the second modification differs from the sewing process of FIG. 9 in that S6 is replaced with S31, S14 is replaced with S32, and S18 is replaced with S33. S31 to S33, which are different from the sewing process shown in FIG. 9, will be described below, and description of the other processes will be omitted.

In S31, the CPU 101 determines whether the ratio obtained by dividing the counter E by the number of stitches N is greater than a ratio threshold value (S31). A value smaller than 1 may be set in advance as the ratio threshold. The percentage threshold is, for example, anywhere from 20% to 60%. When the ratio is greater than the ratio threshold (S31: YES), the CPU 101 determines that there is no bobbin thread 67 for the stitch (S17). When the ratio is equal to or less than the ratio threshold (S31: NO), the CPU 101 determines that there is the bobbin thread 67 for the stitch (S7).

In S32, the CPU 101 determines that the ratio obtained by dividing the counter F by the value obtained by subtracting 9, which is the maximum number of stitches in the first sewing period, from the number of stitches N (ie, the number of stitches in the second sewing period) is higher than the ratio threshold. It is determined whether it is larger (S32). A value smaller than 1 may be set in advance as the ratio threshold. The percentage threshold in S32 may be the same as or different from the percentage threshold in S31. The percentage threshold is, for example, anywhere from 5 to 10%. When the ratio is greater than the ratio threshold (S32: YES), the CPU 101 determines whether rotation of the bobbin B has been detected based on the detection result of the rotation detector 141 (S16). When the ratio is equal to or less than the ratio threshold (S31: NO), the CPU 101 determines whether the needle thread tension detected by the tension detector 18 at a predetermined time within the second sewing period is greater than the third threshold ( S15). In S33, the CPU 101 determines that the bobbin thread 67 is present without initializing the counters E and F (S33). In the modified example, when the ratio threshold is set to 0.1, in the case of the specific example D6 of FIG. (S16: NO), the CPU 101 can determine that there is no bobbin thread 67 for the stitch, especially that the stitch is pseudo sewing with multiple stitches.

In the above-described embodiment, first modification, and second modification, the sewing machine 1, the needle bar 9, the sewing needle 11, the tension detector 18, the needle bar vertical movement mechanism 21, the hook mechanism 48, the hook 49, the upper thread 55, the lower Thread 67, storage device 104, and rotation detector 141 are the sewing machine, needle bar, sewing needle, tension detector, needle bar vertical movement mechanism, hook mechanism, hook, needle thread, bobbin thread, storage device, and storage device, respectively. It is an example of a motion detector. The CPU 101 that executes the processes of S3 to S7 and S11 to S19 in FIG. 9 is an example of the lower thread determining section of the present invention. The processing of S3 to S7 and S11 to S19 in FIG. 9 is an example of the bobbin thread determination step of the present invention. The CPU 101 that executes the processes of S3 to S5, S7, S11 to S13, S15 to S17, S19, and S31 to S33 in FIG. 13 is an example of the lower thread determining section of the present invention. The processing of S3-S5, S7, S11-S13, S15-S17, S19, and S31-33 in FIG. 13 is an example of the bobbin thread determination step of the present invention.

The sewing machine 1 of the above-described embodiment, first modification, and second modification includes a needle bar 9, a needle bar vertical movement mechanism 21, a hook 49, a hook mechanism 48, a tension detector 18, a rotation detector 141, and a CPU 101. Prepare. A sewing needle 11 through which a needle thread 55 is inserted is attached to the needle bar 9 . A needle bar up-down movement mechanism 21 moves the needle bar 9 up and down. The hook 49 is provided below the needle bar 9 and rotatably accommodates the bobbin B around which the bobbin thread 67 is wound. The hook mechanism 48 rotates the hook 49 in synchronism with the vertical movement of the needle bar 9, catches the annular needle thread 55 passing through the sewing needle 11, and entangles it with the bobbin thread 67 to form stitches. A tension detector 18 detects the tension of the needle thread 55 or the bobbin thread 67 . A rotation detector 141 detects whether or not the bobbin B is rotated. The CPU 101 determines whether or not the bobbin thread 67 is attached to the stitch based on whether the tension detected by the tension detector 18 is greater than the threshold value and the detection result of the rotation detector 141 (S3 to S7, S11 to S19). ). The sewing machine 1 determines whether or not the bobbin thread 67 is attached to the stitch based on whether the tension detected by the tension detector 18 is greater than the threshold value and the detection result of the rotation detector 141. Therefore, only the tension detector 18 is used. The presence or absence of the bobbin thread 67 for the stitch can be accurately determined compared to a device that determines using .

The CPU 101 of the sewing machine 1 detects that the rotation detector 141 does not rotate the bobbin B (S3: NO), and the tension detected by the tension detector 18 is greater than the first threshold H1 (N). When (S4: YES), it is determined that the bobbin thread 67 is present for the stitch (S18, S33). When the rotation detector 141 detects that the bobbin B is not rotating (S3: NO) and the tension detected by the tension detector 18 is equal to or less than the first threshold value H1 (N) (S4: NO ), it is determined that there is no bobbin thread 67 for the stitch (S17). Even if it is detected that the bobbin B does not rotate, the sewing machine 1 can determine that the bobbin thread 67 is attached to the stitch when the tension detected by the tension detector 18 is greater than the first threshold value H1 (N). Although the rotation of the bobbin B is temporarily stopped, the sewing machine 1 can avoid determining that there is no bobbin thread 67 for the stitch in a situation where the bobbin thread 67 is considered to be entangled with the needle thread 55 .

The CPU 101 of the sewing machine 1 detects that the tension detected by the tension detector 18 is equal to or less than the second threshold value H2 (N) (S11: NO), and that the rotation detector 141 detects that the bobbin B does not rotate. If so (S16: NO), it is determined that there is no bobbin thread 67 for the stitch (S17). When the tension detected by the tension detector 18 is equal to or less than the second threshold value H2 (N) (S11: NO) and the rotation detector 141 detects that the bobbin B is rotating (S16: YES ), it is determined that the bobbin thread 67 is present for the stitch (S19). The sewing machine 1 can determine that the bobbin thread 67 is attached to the stitch when the bobbin B rotates, even if the tension detected by the tension detector 18 is equal to or less than the second threshold value H2 (N). In the sewing machine 1, the tension is relatively small, but the bobbin B continues to rotate, and in a situation where the bobbin thread 67 for the stitch is considered to be entwined with the needle thread 55, it is determined that the bobbin thread 67 for the stitch is absent. can be avoided.

The CPU 101 of the sewing machine 1 uses different thresholds to determine the first sewing period from the start of sewing until the predetermined number of stitches are sewn and the second sewing period following the first sewing period (S4, S11). The sewing machine 1 changes the threshold value for the first sewing period and the second sewing period, so that the sewing machine 1 uses the threshold value suitable for each of the first sewing period and the second sewing period to thread the bobbin thread 67 to the stitch. Presence or absence can be determined.

The CPU 101 of the sewing machine 1 of the above-described embodiment and the first modified example causes the tension detected by the tension detector 18 to become equal to or less than the threshold continuously for the number of times equal to or more than the threshold (S4: NO, S6: YES), and the rotation detector 141 If it is detected that the bobbin B does not rotate (S3: NO), it is determined that there is no bobbin thread 67 for the stitch (S17). The CPU 101 of the sewing machine 1 detects that the tension detected by the tension detector 18 has become equal to or less than the threshold continuously for the number of times greater than or equal to the threshold (S11: NO, S14: YES), and the rotation detector 141 has detected that the bobbin B has not rotated. If so (S16: NO), it is determined that there is no bobbin thread 67 for the stitch (S17). The sewing machine 1 can determine bobbin thread breakage based on the presence or absence of the bobbin thread 67 with respect to the stitch. As shown in FIG. 11(A), when the bobbin thread 67 runs out of the stitch partway through, no abnormality is seen in the rotation speed indicated by the black circle during sewing. When the bobbin thread 67 for the stitch runs out, the needle thread tension continuously becomes equal to or less than the second threshold value H2 (N). It can be detected that the thread 67 has run out. Furthermore, as shown in FIG. 11(C), the sewing machine 1 uses the tension detected by the tension detector 18 during the take-up period to determine the presence or absence of the bobbin thread 67 with respect to the stitch. ), the tension detected by the tension detector 18 acquired during the hook supplement period can be used to determine the presence or absence of the bobbin thread 67 for the stitch.

The CPU 101 of the sewing machine 1 of the second modification determines that the ratio of the tension detected by the tension detector 18 to the number of sewn stitches that is equal to or lower than the threshold is equal to or higher than the ratio threshold (S4: NO, S31: YES), and When the detector 141 detects that the bobbin B is not rotated (S3: NO), it is determined that the bobbin thread 67 is not attached to the stitch (S17). The CPU 101 determines that the ratio of the tension detected by the tension detector 18 to the number of sewn stitches being equal to or lower than the threshold is equal to or higher than the ratio threshold (S11: NO, S32: YES), and the rotation detector 141 determines that the rotation of the bobbin B If it is detected that there is no bobbin thread 67 (S16: NO), it is determined that there is no bobbin thread 67 for the stitch (S17). The sewing machine 1 can avoid erroneously determining the presence or absence of sewing defects involving the bobbin thread 67 based on the singular value of the tension detector 18 . As shown in FIG. 12(A), in the case of multi-needle pseudo sewing, no abnormalities were observed in the number of rotations indicated by black circles, and as shown in FIGS. Since there is no period of H2 (N) or less, it is difficult to detect pseudo sewing in the sewing process of the above embodiment. Pseudo-sewing can be appropriately detected based on whether the bobbin B is rotated.

The sewing machine 1 of the above-described embodiment, first modified example, and second modified example further includes a storage device 104 that stores a combination of the number of stitches and a threshold value. Based on this, a determination is made using a threshold corresponding to the number of stitches. The sewing machine 1 can determine the presence or absence of the bobbin thread 67 for the stitch using a threshold value that takes into account the number of stitches. Since the sewing machine 1 can form similar stitches on the same cloth 69 based on the sewing data 30, the stitches corresponding to the number of stitches in the sewing data are similar to each other. Therefore, when forming stitches on a similar cloth 69 according to the sewing data, the sewing machine 1 uses a threshold value set in consideration of the influence of the thickness of the cloth 69, whether it is curved or not, the feed amount, etc., to form stitches. The presence or absence of the bobbin thread 67 can be determined appropriately.

The CPU 101 makes a determination using the tension detected by the tension detector 18, which is obtained at a timing corresponding to the number of stitches in one period of vertical movement of the needle bar 9. FIG. The sewing machine 1 can reduce the influence of the stitches according to the number of stitches, compared to the case where the presence or absence of the bobbin thread 67 is determined using the tension detected by the tension detector 18 acquired at the same time regardless of the number of stitches. With this in mind, it is possible to determine the presence or absence of the bobbin thread 67 with respect to the stitch. In this embodiment, the CPU 101 uses the detection result of the tension detector 18 during the hook catching period to determine whether or not the bobbin thread 67 is present in the stitches during the first sewing period. By setting the detection timing of the tension detector 18 in this manner, the sewing machine 1 can suitably detect the absence of the bobbin thread 67 during the first sewing period. On the other hand, as shown in FIG. 11, the difference between the needle thread tension when the bobbin thread 67 runs out of the stitch and the second threshold value H2 is detected during the hook supplement period shown in FIG. 11(B). The detection result obtained while the balance was being pulled up shown in FIG. 11C is more remarkable than the result. Therefore, the sewing machine 1 determines the presence or absence of the bobbin thread 67 for the stitches during the second sewing period by using the detection result detected by the tension detector 18 during the take-up period. It is possible to suitably detect the case where there is no bobbin thread 67 with respect to.

The CPU 101 of the first modified example changes the frequency of timing at which the tension detector 18 acquires the detection result for one cycle of the vertical movement of the needle bar 9 according to the number of stitches, so that the tension detector 18 Determination is performed using the detected tension of The sewing machine 1 reduces the influence of the stitches according to the number of stitches, compared to the case where the presence or absence of the bobbin thread 67 for the stitches is determined using the tension detected by the tension detector 18, which is acquired at the same frequency regardless of the number of stitches. With this in mind, it is possible to determine the presence or absence of the bobbin thread 67 with respect to the stitch.

The sewing machine 1 further includes a thread take-up 19 for pulling up the upper thread 55 entwined with the bobbin thread 67 by the hook 49 , the tension detector 18 detects the tension of the upper thread, and the CPU 101 causes the thread take-up 19 to pull up the upper thread 55 . Whether or not the tension detected by the tension detector 18 is greater than the threshold during any of the period of raising the thread take-up and the period during which the hook 49 catches the needle thread 55, and the detection result of the rotation detector 141. Based on this, it is determined whether or not the bobbin thread 67 is attached to the stitch. The sewing machine 1 can determine the presence or absence of the bobbin thread 67 for the stitch based on the needle thread tension detected during the take-up period or the hook supplement period. Since the needle thread tension is greater during the take-up period or the supplementary period of the hook than in the period between the period of raising the thread take-up and the supplementary period of the hook, the CPU 101 makes the determination during the period when the upper thread tension is relatively small. , erroneous determination can be avoided.

The present invention can be modified in various ways in addition to the above embodiments. The configuration of the sewing machine 1 may be changed as appropriate, and for example, a sewing machine in which the holding body 60 does not sandwich the cloth 69 may be used. The configuration, arrangement, detection method, etc. of the tension detector 18 and the rotation detector 141 may be changed as appropriate. The sewing machine 1 may have the functions of the editing device 8 . Specifically, the tension detector 18 may be arranged between the secondary thread tension device 15 and the main thread tension device 16 on the path of the needle thread 55, or may be arranged downstream of the thread take-up 19 on the path of the needle thread 55. It may be arranged. The sewing machine 1 of the above-described embodiment is a single-needle sewing machine in which one sewing needle 11 is attached to the needle bar 9, but a two-needle sewing machine in which two sewing needles are attached to the needle bar 9 or three needles are attached to the needle bar 9. In the case of the sewing machine described above, a sewing machine in which a plurality of thread tension detection devices are arranged to detect the tension of each needle thread 55 may be used. Furthermore, in those cases, the sewing machine 1 may have a plurality of rotation detectors 141 to detect the rotation of the bobbins B of the plurality of hooks 49 . The tension detector 18 has a configuration using the magnetic sensor 53, but it may be one that receives the force of the yarn with an electrostrictive element and detects the tension based on the output.

A program for the sewing machine 1 to perform processing may be stored in the storage device 104 of the sewing machine 1 until the CPU 101 executes the program. Therefore, the program acquisition method, acquisition route, and device for storing the program may be changed as appropriate. A program executed by the CPU 101 may be received from another device via a cable or wireless communication and stored in a storage device such as a flash memory. Other devices include, for example, PCs and servers connected via a network.

Some or all of the processing performed by the sewing machine 1 may be performed by an electronic device (for example, an ASIC) other than the CPU 101 . The processing performed by the sewing machine 1 may be distributed among a plurality of electronic devices (for example, a plurality of CPUs). Each step of the processing performed by the sewing machine 1 can be changed in order, omitted, or added as necessary. The scope of the present invention also includes a mode in which an operating system (OS) or the like running on the sewing machine 1 performs part or all of each process according to commands from the CPU 101 . For example, the following modifications may be added to the above embodiment as appropriate.

In the sewing machine 1 of the above-described embodiment, when the detected needle thread tension is equal to or less than the second threshold (S11: NO), the abnormality detection counter is updated (S13). The presence or absence of rotation of bobbin B may be detected, and the counter may be updated only when rotation of bobbin B cannot be detected. In this case, the sewing machine 1 does not detect the rotation of the bobbin B in S16. (S17).

The processes of S11 to S16 may be executed during the first sewing period, and the processes of S3 to S7 may be executed during the second sewing period. Similar processing may be performed in the first sewing period and the second sewing period. The threshold may be the same between the first sewing period and the second sewing period. The CPU 101 may acquire the tension detected by the tension detector 18 at the same time during the first sewing period and the second sewing period. The CPU 101 does not have to determine the presence or absence of the bobbin thread 67 for each stitch. For example, the CPU 101 may determine the presence or absence of the bobbin thread 67 for each stitch for a predetermined number of stitches. The CPU 101 may acquire the tension detected by the tension detector 18 at the same frequency during the first sewing period and the second sewing period. The number of times threshold and the ratio threshold may be 0, and the CU 101 detects that the tension detected by the tension detector 18 is less than or equal to the threshold only once and the rotation detector 141 detects that the bobbin B does not rotate. It may be determined that there is no bobbin thread 67 for the stitch. Each of the first threshold value H1 and the second threshold value H2 does not have to be a value corresponding to the number of stitches N, and for example, a common value may be set for some or all of a plurality of stitch numbers. The tension detector 18 may detect the tension of the bobbin thread 67 . In the case where the sewing machine 1 forms stitches without sewing data, the sewing machine 1 can be adjusted according to conditions such as the material of the cloth 69 or thread, the thickness of the cloth 69, the type of stitches, the feed amount (stitch length), and the sewing speed. may change the threshold. The above modifications may be combined as appropriate within a consistent range.

In the sewing machine 1 of the above-described embodiment, the rotation detector 141 detects whether or not the bobbin B is rotating. A bobbin thread remaining amount detector for detecting whether or not the amount of thread 67 has changed may be used as an operation detector, and whether or not the bobbin B has been moved may be detected based on whether or not the bobbin thread amount has changed. Specifically, the sewing machine 1 has a side surface of a bobbin case that accommodates the bobbin B and a part of one flange of the bobbin B that is provided with a light-transmitting portion, and a reflective surface is formed on the inner walls of the other flanges. Equipped with an optical sensor that has an irradiating part that emits light from the light part and a light receiving part that receives the reflected light as a motion detector. can be Alternatively, in the sewing machine 1, a weight sensor for measuring the weight of the bobbin B may be added to the hook 49 as a motion detector, and a change in the bobbin thread remaining amount may be detected based on a change in the output of the weight sensor. When the bobbin B is operating normally during sewing, the amount of the bobbin thread 67 wound around the bobbin B decreases in accordance with the sewing amount. By detecting whether or not there is a change in the amount of the bobbin thread 67, it is possible to accurately detect whether or not the bobbin B is being operated.

1 : Sewing machine 9 : Needle bar 11 : Sewing needle 18 : Tension detector 21 : Needle bar vertical movement mechanism 48 : Hook mechanism 49 : Hook 55 : Needle thread 67 : Bobbin thread 101 : CPU
104: Storage Device 141: Rotation Detector B: Bobbin H1: First Threshold H2: Second Threshold

Claims (13)

a needle bar on which a sewing needle through which the needle thread is inserted;
a needle bar vertical movement mechanism for vertically moving the needle bar;
a hook provided below the needle bar for rotatably accommodating a bobbin wound with a bobbin thread;
a hook mechanism that rotates the hook in synchronism with the vertical movement of the needle bar, captures the annular upper thread passing through the sewing needle, and entangles it with the bobbin thread to form a stitch;
a tension detector that detects the tension of the needle thread or the bobbin thread;
a motion detector for detecting whether or not the bobbin is in motion;
a bobbin thread determination unit that determines whether or not the bobbin thread is present in the stitch based on whether the tension detected by the tension detector is greater than a threshold value and the detection result of the motion detector. Characteristic sewing machine. The bobbin thread determination unit
When the motion detector detects that there is no motion of the bobbin and the tension detected by the tension detector is greater than the first threshold value, it is determined that the bobbin thread is present on the stitch. judge,
When the motion detector detects that there is no motion of the bobbin and the tension detected by the tension detector is equal to or less than the first threshold value, it is determined that the bobbin thread is not attached to the stitch. The sewing machine according to claim 1, characterized in that: The bobbin thread determination unit
When the tension detected by the tension detector is equal to or less than the second threshold, and the motion detector detects that the bobbin does not move, there is no bobbin thread for the stitch. determined to be
When the tension detected by the tension detector is equal to or less than the second threshold and the motion detector detects that the bobbin is in motion, it is determined that the bobbin thread is attached to the stitch. The sewing machine according to claim 1 or 2, characterized in that: The bobbin thread determining unit uses different thresholds to determine a first sewing period from the start of sewing until a predetermined number of stitches are sewn and a second sewing period following the first sewing period. The sewing machine according to any one of claims 1 to 3. The bobbin thread judging section determines that the bobbin thread is broken when the detection result of the tension detector is equal to or less than the threshold value continuously for a number of times or more and the motion detector detects that the bobbin does not move. 5. The sewing machine according to any one of claims 1 to 4, wherein the determination is made. The bobbin thread judging section determines that a ratio of the detection result of the tension detector to the number of sewn stitches that is equal to or lower than the threshold is equal to or higher than a ratio threshold, and that the motion detector detects that the bobbin does not move. 5. The sewing machine according to any one of claims 1 to 4, characterized in that when it is detected, it is determined that the bobbin thread for the stitch is absent. a storage unit that stores a combination of the number of stitches and the threshold value;
The sewing machine according to any one of claims 1 to 6, wherein the bobbin thread determination unit performs determination using the threshold corresponding to the number of stitches based on the combination stored in the storage unit. The bobbin thread determination unit performs determination using the tension detected by the tension detector acquired at a timing corresponding to the number of stitches in one cycle of the vertical movement of the needle bar. The sewing machine according to any one of claims 1 to 7. The bobbin thread judging section changes the frequency of times at which the tension detector acquires the detection result for one period of vertical movement of the needle bar in accordance with the number of stitches of the stitches to detect the tension. The sewing machine according to any one of claims 1 to 7, wherein the tension detected by the machine is used for determination. The bobbin further comprises a balance for pulling up the needle thread entwined with the bobbin thread,
The tension detector detects the tension of the needle thread,
The bobbin thread judging section determines whether the detection result of the tension detector at any one of a take-up period during which the thread take-up pulls up the upper thread and a hook supplement period during which the hook captures the upper thread. 10. The sewing machine according to claim 8, wherein the presence or absence of the bobbin thread for the stitch is determined based on whether or not the value is greater than the threshold value and the detection result of the motion detector. The sewing machine according to any one of claims 1 to 10, wherein the motion detector detects whether or not the bobbin is rotated. The sewing machine according to any one of claims 1 to 10, wherein the motion detector detects whether or not the amount of the bobbin thread wound around the bobbin has changed. a needle bar on which a sewing needle through which the needle thread is inserted;
a needle bar vertical movement mechanism for vertically moving the needle bar;
a hook provided below the needle bar for rotatably accommodating a bobbin wound with a bobbin thread;
a hook mechanism that rotates the hook in synchronism with the vertical movement of the needle bar, captures the annular upper thread passing through the sewing needle, and entangles it with the bobbin thread to form a stitch;
a tension detector that detects the tension of the needle thread or the bobbin thread;
A bobbin thread determination method executed by a control unit of a sewing machine provided with a motion detector that detects whether the bobbin is in motion,
and a bobbin thread determination step of determining whether or not the bobbin thread is present in the stitch based on whether or not the tension detected by the tension detector is greater than a threshold value and the detection result of the motion detector. A bobbin thread judgment method.

Images