CN116356505A

CN116356505A - Sewing machine and bobbin thread judging method

Info

Publication number: CN116356505A
Application number: CN202211667011.6A
Authority: CN
Inventors: 中野元就; 夏原优弥
Original assignee: Brother Industries Ltd
Current assignee: Brother Industries Ltd
Priority date: 2021-12-28
Filing date: 2022-12-22
Publication date: 2023-06-30
Also published as: JP2023098053A

Abstract

The invention provides a sewing machine and a bobbin thread judging method which can accurately detect the bobbin thread run out and the bobbin thread interweaving failure regardless of sewing conditions. The sewing machine comprises a needle bar, a needle bar up-and-down motion mechanism, a shuttle mechanism, a tension detector, a rotation detector and a bottom thread judging part. The needle bar is provided with a needle for inserting the upper thread. The needle bar up-and-down movement mechanism moves the needle bar up and down. The shuttle is provided below the needle bar, and rotatably houses a bobbin around which the bobbin thread is wound. The shuttle mechanism rotates the shuttle in synchronization with the up-and-down movement of the needle bar, captures an endless upper thread inserted in the needle, and weaves the upper thread with a lower thread, thereby forming a stitch. The tension detector detects tension of the upper thread or the lower thread. The rotation detector detects the presence or absence of the rotation of the bobbin. The bobbin thread judging section judges whether or not a bobbin thread is present with respect to the stitch based on whether or not the tension detected by the tension detector is greater than a threshold value and a detection result of the rotation detector (S3 to S7, S11 to S19).

Description

Sewing machine and bobbin thread judging method

Technical Field

The invention relates to a sewing machine and a bottom thread judging method.

Background

The sewing machine of patent document 1 has a bobbin thread tension sensor for detecting a tension of a bobbin thread, and determines whether or not the bobbin thread runs out based on the tension of the bobbin thread during sewing.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 10-33868

Disclosure of Invention

Problems to be solved by the invention

Depending on the sewing conditions, the sewing machine may not detect the end of the bottom thread with good accuracy.

The purpose of the present invention is to provide a sewing machine and a bobbin thread judging method capable of accurately detecting a bobbin thread run out and a bobbin thread interweaving defect regardless of sewing conditions, compared with the prior art.

Solution for solving the problem

The invention according to claim 1 provides a sewing machine, wherein the sewing machine comprises: a needle bar for assembling a needle into which the upper thread is inserted; a needle bar up-and-down movement mechanism that moves the needle bar up and down; a shuttle provided below the needle bar, the shuttle rotatably accommodating a bobbin around which a bobbin thread is wound; a shuttle mechanism that rotates the shuttle in synchronization with the up-and-down movement of the needle bar, captures the endless upper thread inserted in the needle, and interweaves the upper thread with the lower thread to form a stitch; a tension detector that detects tension of the upper thread or the lower thread; an operation detector that detects the presence or absence of an operation of the bobbin; and a bobbin thread judging section that judges whether or not the bobbin thread is present with respect to the stitch based on whether or not the tension detected by the tension detector is greater than a threshold value and a detection result of the motion detector. Since the sewing machine according to claim 1 determines whether or not the bobbin thread is present with respect to 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 operation detector, the sewing machine can accurately determine whether or not the bobbin thread is present with respect to the stitch as compared with a device that uses only the tension detector for determination.

In the sewing machine according to claim 2, the bobbin thread determination unit determines that the bobbin thread is present with respect to the stitch when the motion detector detects that the motion of the bobbin is absent and the tension detected by the tension detector is greater than a first threshold value which is the threshold value, and determines that the bobbin thread is absent with respect to the stitch when the motion detector detects that the motion of the bobbin is absent and the tension detected by the tension detector is not greater than the first threshold value. In the sewing machine according to claim 2, even when the absence of the bobbin operation is detected, it can be determined that the bobbin thread is present with respect to the stitch when the tension detected by the tension detector is greater than the first threshold value. In the sewing machine, the operation of the bobbin is temporarily stopped, but it is considered that the bobbin thread is interlaced with the upper thread, and it is possible to avoid judging that the bobbin thread corresponding to the stitch is not present.

In the sewing machine according to claim 3, the bobbin thread determination unit determines that the bobbin thread is not present with respect to the stitch when the tension detected by the tension detector is equal to or less than a second threshold value which is the threshold value and the motion detector detects that the motion of the bobbin thread is absent, and determines that the bobbin thread is present with respect to the stitch when the tension detected by the tension detector is equal to or less than the second threshold value and the motion detector detects that the motion of the bobbin thread is present. In the sewing machine according to claim 3, even if the tension detected by the tension detector is equal to or less than the second threshold value, it can be determined that the bobbin thread is present when there is an operation of the bobbin. In the sewing machine, under the condition that the tension is relatively small but the bobbin continues to operate, under the condition that the bottom thread and the upper thread are interweaved, the judgment that the bottom thread relative to the stitch is not existed can be avoided.

In the sewing machine according to claim 4, the bobbin thread judging section judges using the threshold values different from each other between a first sewing period from the start of sewing to the execution of sewing of a predetermined number of stitches and a second sewing period subsequent to the first sewing period. The sewing machine according to claim 4 can determine the presence or absence of a base thread with respect to the stitch by changing the threshold value between the first sewing period and the second sewing period, and using the threshold value that is suitable for each of the first sewing period and the second sewing period.

In the sewing machine according to claim 5, the bobbin thread judging section judges that the bobbin thread is running out when the detection result of the tension detector is equal to or less than the threshold value, the number of consecutive occurrences is equal to or greater than a threshold value, and the action detector detects that the action of the bobbin thread is absent. The sewing machine according to claim 5 can determine that the base thread is used up based on the presence or absence of the base thread with respect to the stitch.

In the sewing machine according to claim 6, the bobbin thread judging section judges that the bobbin thread is not present with respect to the stitch when the ratio of the detection result of the tension detector to the number of sewn stitches is equal to or smaller than the threshold value is equal to or greater than the ratio threshold value and the motion detector detects that the motion of the bobbin thread is not present. The sewing machine according to claim 6 can avoid erroneous determination of presence or absence of a base thread with respect to a stitch based on a singular value of the tension detector.

The sewing machine according to claim 7 further includes a storage unit that stores a combination of the number of stitches and the threshold value, and the bobbin thread determination unit determines using the threshold value corresponding to the number of stitches based on the combination stored in the storage unit. The sewing machine according to claim 7 is capable of determining the presence or absence of a base thread with respect to a stitch using a threshold value in consideration of the number of stitches.

The bobbin thread determining section of the sewing machine according to claim 8 determines the bobbin thread using the tension detected by the tension detector, the tension being acquired at a timing corresponding to the number of stitches in one cycle of the up-and-down movement of the needle bar. In the sewing machine according to claim 8, compared with a case where the presence or absence of the base thread with respect to the stitch is determined using the tension detected by the tension detector acquired at the same timing regardless of the number of stitches, the presence or absence of the base thread with respect to the stitch can be determined in consideration of the influence of the stitch corresponding to the number of stitches.

In the sewing machine according to claim 9, the bobbin thread judging section changes the frequency of the timing at which the tension detector acquires the detection result with respect to one cycle of the up-and-down movement of the needle bar in accordance with the number of stitches, and judges using the tension detected by the tension detector. In the sewing machine according to claim 9, compared with a case where the presence or absence of the base thread with respect to the stitch is determined using the tension detected by the tension detector acquired at the same frequency regardless of the number of stitches, the presence or absence of the base thread with respect to the stitch can be determined in consideration of the influence of the stitch corresponding to the number of stitches.

The sewing machine according to claim 10 further includes a thread take-up lever that lifts the upper thread intersecting the lower thread by the shuttle, wherein the tension detector detects the tension of the upper thread, and wherein the lower thread judging unit judges whether or not the lower thread is present with respect to the thread based on whether or not the detection result of the tension detector at the timing during any one of a thread take-up period during which the thread take-up lever lifts the upper thread and a shuttle capturing period during which the shuttle captures the upper thread is greater than the threshold value and the detection result of the motion detector. The sewing machine according to claim 10 can determine whether or not a bobbin thread is present with respect to the stitch based on the upper thread tension detected during the lifting of the take-up lever or the catching of the shuttle. Since the upper thread tension in the take-up period or the shuttle capturing period is larger than the upper thread tension in the period between the take-up period and the shuttle capturing period, erroneous judgment can be avoided as compared with the case where judgment is made by the lower thread judgment section in the period in which the upper thread tension is relatively small.

The motion detector of the sewing machine according to claim 11 detects the presence or absence of rotation of the bobbin. The sewing machine according to claim 11 can detect the presence or absence of the bobbin operation based on the detection result of the presence or absence 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 is changed. The sewing machine according to claim 12 can detect the presence or absence of bobbin operations based on a detection result of the presence or absence of a change in the amount of bobbin thread wound around the bobbin.

The invention 13 provides a bobbin thread determination method executed by a control unit of a sewing machine having: a needle bar for assembling a needle into which the upper thread is inserted; a needle bar up-and-down movement mechanism that moves the needle bar up and down; a shuttle provided below the needle bar, the shuttle rotatably accommodating a bobbin around which a bobbin thread is wound; a shuttle mechanism that rotates the shuttle in synchronization with the up-and-down movement of the needle bar, captures the endless upper thread inserted in the needle, and interweaves the upper thread with the lower thread to form a stitch; a tension detector that detects tension of the upper thread or the lower thread; and a motion detector that detects the presence or absence of motion of the bobbin, wherein the bobbin thread determination method includes a bobbin thread determination step of determining the presence or absence of the bobbin thread with respect to the stitch based on whether or not the tension detected by the tension detector is greater than a threshold value and a detection result of the motion detector. In the case where the bobbin thread determining method according to claim 13 is executed, the sewing machine determines whether or not the bobbin thread is present with respect to 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 operation detector, and therefore, it is possible to accurately determine whether or not the bobbin thread is present with respect to the stitch as compared with the case where the determining device is used only with the tension detector.

Drawings

Fig. 1 is a perspective view of a sewing system 10 including a sewing machine 1 and an editing device 8.

Fig. 2 is a partial enlarged view of the distal end portion 7.

Fig. 3 is a perspective view of the tension detector 18.

Fig. 4 is a schematic view showing a flow of capturing the upper thread 55 by the shuttle 49.

Fig. 5 is an electrical block diagram of the sewing machine 1 and the editing apparatus 8.

Fig. 6 is a flowchart of the threshold setting process.

Fig. 7 is a schematic view of the stitching data 30 and stitch formed based on the stitching data 30.

Fig. 8 is a graph showing the relationship among the tension D1 of the needle thread 55, the vertical direction position D2 of the needle tip, and the upper shaft angle.

Fig. 9 is a flowchart of the sewing process.

Fig. 10 is a graph showing a relationship between the number of stitches at the first sewing time and the tension of the upper thread 55 in specific examples D3 and D4.

Fig. 11 (a) is a graph showing a relationship between the number of needles at the second sewing time and the rotational speed of the upper shaft 22 in the specific example D5, fig. 11 (B) is a graph showing a relationship between the number of needles at the second sewing time and the tension of the upper thread 55 detected during the shuttle capturing period in the specific example D5, and fig. 11 (C) is a graph showing a relationship between the number of needles at the second sewing time and the tension of the upper thread 55 detected during the take-up period in the specific example D5.

Fig. 12 (a) is a graph showing a relationship between the number of needles at the second sewing time and the rotational speed of the upper shaft 22 in the specific example D6, fig. 12 (B) is a graph showing a relationship between the number of needles at the second sewing time and the tension of the upper thread 55 detected during the shuttle capturing period in the specific example D6, and fig. 12 (C) is a graph showing a relationship between the number of needles at the second sewing time and the tension of the upper thread 55 detected during the take-up period in the specific example D6.

Fig. 13 is a flowchart of a sewing process according to a modification.

Description of the reference numerals

1. A sewing machine; 9. a needle bar; 11. a needle; 18. a tension detector; 21. a needle bar up-and-down movement mechanism; 48. a shuttle mechanism; 49. a shuttle; 55. an upper thread; 67. a bottom line; 101. a CPU; 104. a storage device; 141. a rotation detector; B. a bobbin; h1, a first threshold value; h2, a second threshold.

Detailed Description

Embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the right and left, front and back, up and down, and the arrows in the figures are used. With reference to FIG. 1, a sewing system 10 is illustrated. The sewing system 10 includes a sewing machine 1 and an editing device 8. The editing apparatus 8 is a portable terminal, and is connected to the sewing machine 1. The editing apparatus 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 related to a stitch formed on a sewing object (for example, a cloth 69 of 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 outputted from the editing apparatus 8.

The sewing machine 1 is described with reference to fig. 1 to 4. The sewing machine 1 has a seat portion 2, a pillar portion 3, and a arm portion 4. The seat 2 is mounted on the platform 50. The seat portion 2 extends in the front-rear direction, and includes a shuttle 49 (see fig. 4), a shuttle mechanism 48 (see fig. 4), a rotation detector 141 (see fig. 5), and the like therein. The shuttle 49 is provided below a needle bar 9 described later, and rotatably houses a bobbin B around which a bobbin thread 67 is wound. The shuttle mechanism 48 rotates the shuttle 49 in synchronization with the up-and-down movement of the needle bar 9, captures the endless upper thread 55 inserted in the needle 11, and weaves the upper thread 55 with the lower thread 67, thereby forming a stitch. The rotation detector 141 detects the presence or absence of the rotation of the bobbin B as the presence or absence of the operation of the bobbin B. The rotation detector 141 is, for example, a non-photoelectric proximity sensor (magnetic sensor). The bobbin B is provided with a magnet in a part of the flange portion of the bobbin B, and the magnetic force around the rotation detector 141 changes in accordance with the rotation of the bobbin B. The rotation detector 141 can detect the presence or absence of the rotation of the bobbin B by reading the change in the magnetic force. The pillar portion 3 extends vertically upward from the rear side of the seat portion 2. The pillar portion 3 includes a main motor 123 (see fig. 5) and the like therein. The arm portion 4 extends forward from the upper end of the pillar portion 3 to face the upper surface of the base portion 2, and the arm portion 4 has a distal end portion 7. The arm portion 4 has an upper shaft 22, a needle bar up-down movement mechanism 21, and the like inside. The needle bar 9 extends downward from the lower end of the distal end portion 7. The needle bar 9 is fitted with a needle 11 into which the upper thread 55 is inserted. The needle 11 is detachably provided at the lower end of the needle bar 9, and the needle 11 has an eye 111 at the lower end.

The sewing machine 1 has a table 5 and a transfer device 6 above the bed 2. The table 5 has a needle plate 501. The needle plate 501 has a needle accommodating hole 502 directly below the needle 11. The needle accommodating hole 502 can be penetrated by the needle 11. The transfer device 6 includes an X-axis movement mechanism, a Y-axis movement mechanism, an arm 65, a support 64, a lifting unit 62, and a holder 60. The X-axis moving mechanism is provided inside the base 2, and the Y-axis moving mechanism is provided inside the column 3. The arm 65 holds the support 64 and is connected to the Y-axis moving mechanism. The support portion 64 extends in the left-right direction and supports the lifting portion 62 and the holder 60. The lifting portion 62 is provided in the support portion 64 so as to be capable of lifting. The holder 60 has a transfer plate 61 and a pressing plate 63. The transfer plate 61 extends in the horizontal direction and has a rectangular opening at the front end in plan view. The transfer plate 61 is connected to the support portion 64. The pressing plate 63 extends in the horizontal direction and has an opening having a rectangular shape in plan view. The pressing plate 63 is connected to the lower end of the lifting/lowering portion 62. The opening of the transfer plate 61 and the opening of the platen 63 are substantially the same shape, and the position of the opening of the transfer plate 61 corresponds to the position of the opening of the platen 63.

The X-axis moving mechanism uses an X-axis motor 124 (see fig. 5) as a driving source, and moves the lifting unit 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, and moves the arm 65 in the front-rear direction (Y-axis direction). The support portion 64 moves in the front-rear direction along with the movement of the arm portion 65 in the front-rear direction. The lifting portion 62 and the holding body 60 move together with the supporting portion 64. The worker places a cloth 69 (see fig. 4) on the transfer plate 61. When the lifting/lowering portion 62 moves downward, the pressing plate 63 moves up and down toward the transfer plate 61. The holding body 60 (the pressing plate 63 and the transfer plate 61) holds the cloth 69 from above and below. The sewing machine 1 moves the holder 60 in the front-rear direction and the left-right direction by the X-axis moving mechanism and the Y-axis moving mechanism, thereby moving the needle 11 and the cloth 69 held by the holder 60 relative to each other.

As shown in fig. 2, the tip portion 7 has a guide mechanism 14, a needle bar 9, a plunger 12, and the like. The guide mechanism 14 is provided on the right side surface of the distal end portion 7, and guides the needle thread 55. The guide mechanism 14 includes a sub-gripper 15, a main gripper 16, a thread guide 17, a tension detector 18, a take-up lever 19, and a thread guide 20. The upper thread 55 is inserted from the bobbin through the sub-thread clamp 15, the main thread clamp 16, the thread guide 17, the tension detector 18, the take-up lever 19 and the thread guide 20 into the eye 111 of the needle 11. The thread take-up lever 19 lifts the upper thread 55 which is intersected with the lower thread 67 by the shuttle 49 (see fig. 4). The main wire holder 16 has an electromagnetic element 128 (see fig. 5). The main thread clamp 16 changes the tension applied to the upper thread 55 (hereinafter referred to as upper thread tension) in response to the operation of the solenoid 128, thereby adjusting the thread clamping degree (nude prescription). The upper thread tension is set in consideration of the tension balance of the upper thread 55 and the lower thread 67. The main motor 123 (see fig. 5) rotationally drives the upper shaft 22. The needle bar up-and-down movement mechanism 21 moves the needle bar 9 up and down with the rotational drive of the upper shaft 22.

The presser bar 12 extends downward from the lower end of the front end portion 7 in the left direction of the needle bar 9. The presser foot 13 is fitted to the lower end portion of the presser bar 12, and the presser foot 13 has a lower end portion 131. The lower end 131 is cylindrical and penetrates in the vertical direction, and can be penetrated by the needle 11. The presser foot drive mechanism swings the presser bar 12 in the up-down direction in synchronization with the swing in the up-down direction of the needle bar 9 performed with the rotational drive of the upper shaft 22. The presser foot driving mechanism includes a presser foot motor 129 (see fig. 5). The presser foot driving mechanism can adjust the height (hereinafter referred to as the presser foot height) from the upper surface of the needle plate 501 to the lower end of the presser foot 13 in association with the driving of the presser foot motor 129. The presser foot 13 presses the cloth 69 against the needle plate 501 from above when the needle 11 is disengaged from the cloth 69, thereby preventing the cloth 69 from tilting from the needle plate 501. The needle 11 penetrates the inside of the lower end 131 to penetrate the cloth. The needle 11 passes through the needle accommodating hole 502 and moves in the up-down direction.

As shown in fig. 2 and 3, the tension detector 18 is located on the right surface of the distal end portion 7 and on the path between the thread guide 17 and the take-up lever 19 at a position in the up-down direction between the sub-thread guide 15 and the main thread guide 16. The tension detector 18 can detect the upper thread tension. The tension detecting mechanism 18 has a mount 51, a holding portion 52, a magnetic sensor 53, a plate 54, a guide member 77, and a magnet 56. The mount 51 has a mount 57 and a seat 59. The mounting portion 57 and the seat portion 59 are integrally formed with each other. The mounting portion 57 has a long hole 58 into which a screw is inserted. The screw inserted into the long hole 58 is fastened to a screw hole provided in the right surface of the distal end portion 7. The seat 59 is on the left side of the mount 51. The seat 59 has a left protruding portion 71 and a right protruding portion 72. The left protruding portion 71 and the right protruding portion 72 each have a rectangular parallelepiped shape extending in the front-rear direction.

The holding portion 52 is formed in a substantially rectangular parallelepiped shape, and the holding portion 52 is attached to the seat portion 59 between the left protruding portion 71 and the right protruding portion 72. The holding portion 52 is a nonmagnetic body. 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 at a position on the rear side of the front ends of the left projecting portion 71 and the right projecting portion 72, respectively.

The plate 54 is plate-shaped having a thickness in the front-rear direction, and is provided to stand on the left protruding portion 71 and the right protruding portion 72. The guide member 77 is mounted to the left and right protruding

portions

71 and 72. The guide member 77 sandwiches the left end portion of the plate 54 between it and the left protruding portion 71, and sandwiches the right end portion of the plate 54 between it and the right protruding portion 72. A gap is provided between the left-right direction center portion of the plate 54 and the front surface of the holding portion 52. Accordingly, the plate 54 is deflected in the front-rear direction with both end portions in the left-right direction thereof 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 left-right direction central portion of the plate 54. When the plate 54 is flexed in the front-rear direction, the magnet 56 moves back and forth, and the distance between the magnet 56 and the magnetic sensor 53 changes. The magnetic sensor 53 detects a change 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 arranged in the up-down direction in such a manner that the plate 54 is interposed therebetween. The upper guide groove 74 and the lower guide groove 76 are open in the up-down direction, and are formed in a hook shape in a plan view. 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 in the up-down direction. The upper thread 55 is inserted into 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 upper thread tension increases, the upper thread 55 biases the plate 54 rearward. The magnetic sensor 53 outputs a voltage corresponding to the position of the plate 54 in the front-rear direction, which is deflected in the front-rear direction by the tension of the upper thread. The sewing machine 1 can acquire the upper thread tension based on the output voltage of the magnetic sensor 53.

As shown in fig. 1, the editing apparatus 8 is disposed on the platform 50, and includes a display screen 86, a speaker 87 (see fig. 5), an operation panel 88, a selection key 89, and the like. The display screen 86 displays various screens. The speaker 87 outputs various sounds. Various information and instructions can be input to the editing apparatus 8 through the operation panel 88 and the selection keys 89. The operation panel 88 is a touch panel, and is provided on the front surface of the display screen 86. The 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 apparatus 8, the operator operates the operation panel 88 or the selection key 89.

The electrical structure of the sewing system 10 is described with reference to fig. 5. The sewing machine 1 has a control unit 100. The control unit 100 includes a CPU101, a ROM102, a RAM103, a storage device 104, an input/output interface (I/F) 106, and drive circuits 113 to 116. The input/output I/F106 is connected to the CPU101, ROM102, RAM103, storage device 104, drive circuits 113 to 116, pedal 126, power switch 127, rotation detector 141, tension detector 18, electromagnetic element 128, and external connection I/F130. The CPU101 comprehensively controls the operation of the sewing machine 1. The ROM102 stores various programs and the like. The RAM103 temporarily stores various information. The storage 104 is nonvolatile and stores various information. The storage device 104 stores a combination of the number of stitches of the stitch 35 (see fig. 7) and a threshold value used in a main process described later when sewing is performed in accordance with the sewing data 30 (see fig. 7). The sewing data 30 is represented by a sewing coordinate system that drives the X-axis motor 124 and the Y-axis motor 125.

The driving circuit 113 is connected to the main motor 123. The CPU101 controls the main motor 123 via the drive circuit 113. For example, the CPU101 controls the rotational speed (sewing speed) of the output shaft of the main motor 123. The encoder 133 is provided at the output shaft of the main motor 123 and connected to the input/output I/F106. The encoder 133 detects the rotational speed and rotational position of the output shaft of the main motor 123. The rotational position of the output shaft of the main motor 123 is referred to as an upper shaft angle. The drive circuit 114 is connected to an X-axis motor 124. The CPU101 controls the X-axis motor 124 via the drive circuit 114. The encoder 134 is provided at the output shaft of the X-axis motor 124 and is connected to the input/output I/F106. The encoder 134 detects the rotational direction, rotational speed, and rotational position of the output shaft of the X-axis motor 124. The drive circuit 115 is connected to a Y-axis motor 125. The CPU101 controls the Y-axis motor 125 via the drive circuit 115. The encoder 135 is provided at the output shaft of the Y-axis motor 125 and connected to the input/output I/F106. The encoder 135 detects the rotational direction, rotational speed, and rotational position of the output shaft of the Y-axis motor 125. The drive circuit 116 is connected to a presser foot motor 129. The CPU101 controls the presser foot motor 129 via the drive circuit 116. The encoder 136 is provided at the output shaft of the presser foot motor 129 and is connected to the input/output I/F106. The encoder 136 detects the rotational direction, rotational speed, and rotational position of the output shaft of the presser foot motor 129.

The CPU101 drives the main motor 123 to rotationally drive 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 shuttle. The CPU101 drives the main motor 123 based on the sewing data, drives the X-axis motor 124 and the Y-axis motor 125, and controls the position of the holder 60. The sewing machine 1 sews the cloth 69 under this control.

The pedal 126 inputs various instructions to the control unit 100. The operator depresses the pedal 126, for example, when starting the sewing operation of the sewing machine 1. The power switch 127 is used to start and stop the sewing machine 1. The rotation detector 141 inputs the detection result of the presence or absence of the rotation of the bobbin B mounted on the shuttle 49 to the control unit 100. The tension detector 18 outputs an output voltage corresponding to the tension of the upper thread to the control unit 100. The CPU101 controls the operation of the solenoid 128. The external connection I/F130 is connected to the external connection I/F95 of the editing apparatus 8 by means of the cable 70.

The editing apparatus 8 has a control unit 80. The control section 80 has a CPU81, a ROM82, a RAM83, a storage 84, and an input/output I/F85. The input/output I/F85 is connected to the CPU81, ROM82, RAM83, storage 84, display screen 86, speaker 87, operation panel 88, selection key 89, and external connection I/F95. The CPU81 comprehensively controls the operation of the editing apparatus 8. The ROM82 stores programs, a plurality of symbols, and the like for performing main processing described later. The RAM83 temporarily stores various information. The storage device 84 is nonvolatile and stores various information such as sewing data. The CPU81 performs display control of the display screen 86, audio output control of the speaker 87, input control from the operation panel 88 and the selection key 89. The external connection I/F95 is connected to the external connection I/F130 of the sewing machine 1 by means of the cable 70.

An outline of the operation of the sewing machine 1 will be described with reference to fig. 1 to 5. The worker holds the cloth 69 on the holding body 60 of the needle plate 501. By inputting a sewing instruction by the operator, the sewing machine 1 drives the main motor 123, the X-axis motor 124, and the Y-axis motor 125 in accordance with the sewing data. The upper shaft 22 rotates according to the driving of the main motor 123, thereby moving the needle bar 9 and the take-up lever 19 up and down. The shuttle 49 rotates in synchronization with the rotation of the upper shaft 22.

The needle 11, which descends together with the needle bar 9, passes through the cloth 69 and then passes through the needle accommodating hole 502 (see fig. 2) formed in the needle plate 501. As shown in fig. 4 (a), the upper thread 55 which descends to the vicinity of the needle hole 111 below the needle accommodating hole 502 is in a loop shape. As shown in fig. 4 (b), the shuttle needle 46 captures the loop-shaped upper thread 55 by rotating the shuttle 49 clockwise in the main view. Hereinafter, a period during which the loop-shaped upper thread 55 is caught by the shuttle tip 46 is referred to as a shuttle catching period. The needle 11 is lifted upward above the cloth 69, and the shuttle 49 continues to rotate clockwise in the main view. The shuttle tip 46 pulls the annular needle thread 55 in the rotational direction, and expands the diameter of the annular needle thread 55.

As shown in fig. 4 (c), when the shuttle 49 drills out from the endless upper thread 55, the upper thread 55 is interlaced with the lower thread 67. The rotational direction of the shuttle 49 is switched to the counterclockwise direction when viewed from the front. As shown in fig. 4 (d), the thread take-up lever 19 lifts the upper thread 55 interwoven with the lower thread 67. Hereinafter, the period during which the take-up lever 19 lifts up the upper thread 55 is referred to as a take-up lever lifting period. The loop-shaped upper thread 55 is reduced in diameter, and the sewing machine 1 performs one-needle-amount sewing. In the present embodiment, the sewing machine 1 performs sewing with one needle amount every time the upper shaft 22 rotates one turn. The sewing machine 1 repeats the above operation to form a plurality of stitches 68 on the cloth 69.

The threshold setting process of the sewing machine 1 will be described with reference to fig. 6 to 8 by using the specific example of fig. 7. When the worker inputs a start instruction after turning on the power supply of the sewing machine 1, the CPU101 reads out the program and the sewing data 30 from the ROM102 and starts the threshold setting process.

As shown in fig. 6, the CPU101 acquires the sewing data 30 (S51). As shown in fig. 7, the specific example sewing data 30 includes stitch 35 for forming a rectangular shape based on needle falling points P1 to P70 in a predetermined sewing order. The needle drop point is a predetermined position where the needle 11 mounted on the needle bar 9 pierces the cloth 69. The needle drop point P1 is a start point at which the sewing sequence is first, and the needle drop point P70 is an end point at which the sewing sequence is last. The stitch based on the needle falling points P1 to P3 is formed in the direction indicated by the arrow J1, and the stitch based on the needle falling points P4 to P70 is formed in the counterclockwise direction from the needle falling point P3 in the direction indicated by the arrow J2 to J6. The editing apparatus 8 can output the sewing data 30 to the sewing machine 1. In the sewing machine 1, the CPU101 receives the sewing data 30 output from the editing apparatus 8. The CPU101 sets the count N of the needle drop points P1 to P70 for reading out the received sewing data 30 in the order of arrangement from the start point P1 to the end point P70 to 1, 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 in accordance with the sewing data 30. The upper shaft 22 rotates according to the driving of the main motor 123, thereby moving the needle bar 9 and the take-up lever 19 up and down. The shuttle 49 rotates in synchronization with the rotation of the upper shaft 22.

The CPU101 determines whether or not the timing (phase) of the detection of the upper thread tension is based on the upper shaft angle obtained based on the detection result of the encoder 133 (S53). As shown in fig. 8, during sewing, the upper thread tension and the height of the lower end (needle tip) of the needle 11 are periodically changed in a unit period of the sewing period in accordance with the upper shaft angle. The sewing period is a period during which sewing of one needle amount is performed. The vertical axis on the right in fig. 8 indicates the height of the lower end of the needle 11 with respect to the upper surface of the needle plate 501. When the upper shaft angles are H1 and H2, the lower end of the needle 11 is positioned at the same height as the upper surface of the cloth 69 placed on the upper surface of the needle plate 501. That is, the period in which the upper shaft angle is H1 to H2 is a penetration period in which the needle 11 penetrates the cloth 69. The period in which the upper shaft angle is smaller than H1 and the period in which the upper shaft angle is larger than H2 are non-penetration periods in which the needle 11 is located above the cloth 69. The sewing period includes a thread take-up period and a shuttle capturing period. The upper thread tension has peaks during the take-up of the take-up lever and during the catching of the shuttle during sewing. The CPU101 of the present embodiment determines the determination timing (detection timing) of the line tension based on the upper axis angle obtained based on the detection result of the encoder 133. The CPU101 of the present embodiment changes the determination timing between a first sewing period from the start of sewing to the execution of sewing with a predetermined number of stitches and a second sewing period subsequent to the first sewing period. The length of the first sewing period may be appropriately set, and in the present embodiment, the length is a period in which the number of stitches after the start of sewing is less than 10. The CPU101 uses the upper thread tension detected by the tension detector 18 during the shuttle capturing to determine whether or not the lower thread 67 with respect to the stitch is present during the first sewing. The CPU101 uses the upper thread tension detected by the tension detector 18 during the lifting of the take-up lever to determine whether or not the bobbin thread 67 with respect to the stitch is present during the second sewing. The CPU101 determines whether it is in the first sewing period or the second sewing period based on the count N to determine the detection timing. When the detection timing is not present (S53: no), the CPU101 stands by until the detection timing is reached.

When the detection timing is the detection timing (S53: yes), the CPU101 stores the detection result outputted from the tension detector 18 as the tension corresponding to the count N (S54). The CPU101 determines whether the count N is the last needle count of the sewing data 30 acquired in S51 (S55). If the count is not the last needle count (S55: NO), the CPU101 increments the count N by 1 (S56), and returns the process to S53. When the last stitch number is the last (S55: yes), the CPU101 stops the sewing based on the sewing data 30 (S57). The CPU101 determines whether to continue the processing (S58). The CPU101 of the present embodiment acquires the corresponding data of the plurality of sets of the needle count and the tension by executing the processing of S52 to S57 a plurality of times, and acquires the average value and the standard deviation of the tension for each needle count. The number of groups may be appropriately determined, and is, for example, any one of 5 to 20. 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 for executing the processing of S52 to S57. When the continuation instruction is detected (S58: yes), the CPU101 returns the process to S52.

When the continuation instruction is not detected (S58: NO), the CPU101 sets a threshold value for each needle count based on the correspondence data of the plural sets of needle counts and the tension (S59). The CPU101 sets a first threshold H1 (N) which is a threshold value of the number of stitches (N) during the first sewing period according to the formula (1), and sets a second threshold H2 (N) which is a threshold value of the number of stitches (N) during the second sewing period according to the formula (2).

First threshold H1 (N) =average of tension (N) -c1×standard deviation (N) … (1)

Second threshold H2 (N) =average of tension (N) -c2×standard deviation (N) … (2)

The average value (N) of the tension is an average value of the tension corresponding to the number of stitches (N), and the standard deviation (N) is a standard deviation of the tension corresponding to the number of stitches (N). C1 and C2 are constants and may be the same or different from each other. C1 and C2 may be set by an operator of the sewing machine 1 or may be automatically set by the CPU101 in accordance with sewing conditions. As an example in this embodiment, C1 is 2, and C2 is 2 or 3. That is, C1 is a value of C2 or less. The CPU101 associates the set threshold value with the number of pins (N) and stores the threshold value in the storage device 104. The CPU101 completes the threshold setting process through the above steps.

The sewing process of the sewing machine 1 will be described with reference to fig. 9 to 12. When the worker inputs an instruction to start sewing after designating the sewing data, the CPU101 reads out a program from the ROM102 and starts the sewing process of fig. 9. Specific examples D3 to D6 of fig. 10 to 12 are used as specific examples for determining whether or not the bobbin thread 67 is present with respect to the stitch when sewing is performed according to the sewing data 30. Specific example D3 shows an example of the relationship between the needle count (N) and the upper thread tension when the lower thread 67 is present in the stitch in the whole first sewing period. Specific example D4 shows an example of the relationship between the needle count (N) and the upper thread tension in the case where the lower thread 67 with respect to the stitch is not present at the start of sewing. Specific example D5 shows an example of the relationship between the needle thread tension and the number of stitches (N) when the second threshold H2 is set under the condition that C2 is 3 and the bobbin thread 67 of the stitch disappears (the bobbin thread runs out) in the middle of the second sewing period. Specific example D6 shows an example of the relationship between the needle count (N) and the upper thread tension in the case of the multi-needle simulated sewing in the second sewing period, in which the second threshold H2 is set under the condition that C2 is 2. The simulated sewing is a bad sewing in which only the upper thread 55 forms a trace in the shape of a stitch, which looks like a stitch is formed, and the bottom thread 67 is not interwoven with the upper thread 55, and the multi-needle simulated sewing is a sewing example in which the simulated sewing is performed a plurality of times. In the case of the simulated sewing, the bobbin thread 67 is not sequentially supplied.

As shown in fig. 9, the CPU101 executes count initialization processing (S1). The CPU101 sets a count E, F stored in the RAM103 and counting the number of times an abnormality is continuously detected to 0 and sets a count N counting the number of pins to 1. The CPU101 determines whether or not it is within the first sewing period based on the count N (S2). When the first sewing period is in (S2: yes), the CPU101 judges whether or not the rotation of the bobbin B is detected based on the detection result of the rotation detector 141 (S3). In specific example D3, the presence of the rotation of the bobbin B is detected (S3: yes), the CPU101 judges that the bobbin thread 67 corresponding to the stitch is present, sets the count E of the first sewing period to 0 (S18), and then carries out the processing of S21 described later. In specific example D4, it is detected that there is no rotation of the bobbin B (S3: NO), the CPU101 judges whether or not the tension of the upper thread detected by the tension detector 18 at a predetermined timing within the first sewing period is greater than the first threshold value H1 (N) set in S59 (S4). The CPU101 uses the first threshold H1 (N) corresponding to the count N based on a combination of the number of pins (N) stored in the storage 104 and the first threshold H1 (N). As shown in fig. 10, when the count N is 1, the upper thread tension of the specific example D4 indicated by the white quadrangle is larger than the first threshold H1 (1) indicated by the white circle (yes in S4), and therefore, the CPU101 determines that the bottom line 67 with respect to the stitch is present, sets the count E to 0 (S18), and thereafter, performs the processing of S21 described later. In this way, when the rotation detector 141 detects that there is no rotation of the bobbin B (S3: no) and the tension detected by the tension detector 18 is greater than the first threshold H1 (N) (S4: yes), the CPU101 determines that the bobbin thread 67 with respect to the stitch exists. On the other hand, when the count N is any one of 3 to 6, the upper thread tension of the specific example D4 is equal to or less than the first threshold H1 (N) (S4: no), and therefore, the CPU101 adds 1 to the count E at which the abnormality of the lower thread 67 is detected (S5).

The CPU101 determines whether the count E is greater than the count threshold (S6). The number of times threshold may be set to a value smaller than 9, which is the maximum number of stitches included in the first sewing period. The number of times threshold of this embodiment is 3. When the count N is 6, the count E of the specific example D4 is 4 and is larger than the count threshold (S6: yes), and therefore, the CPU101 determines that the under thread 67 with respect to the stitch does not exist (S17). The CPU101 may output an instruction to cause the display screen 86 to display the determination result to the editing apparatus 8. In the case where the sewing machine 1 includes a notification unit such as an LED lamp, the CPU101 may cause the notification unit to notify that the judgment result of the bobbin thread 67 with respect to the stitch is not present. In this way, when the rotation detector 141 detects that there is no rotation of the bobbin B (S3: no) and the tension detected by the tension detector 18 is equal to or less than the first threshold H1 (N) (S4: yes), the CPU101 determines that there is no bobbin thread 67 with respect to the stitch (S17). In the present embodiment, when the tension detected by the tension detector 18 is equal to or less than the first threshold H1 (N), the number of consecutive occurrences is equal to or greater than the threshold (S4: no, S6: yes), and the rotation detector 141 detects that the bobbin B is not rotating (S3: no), the CPU101 determines that the bobbin 67 is not present with respect to the stitch (S17). The CPU101 ends the sewing based on the sewing data 30 in the middle of the sewing (S23), and ends the sewing process. In the present embodiment, the absence of the bobbin thread 67 (relative to the stitch) means that the bobbin thread 67 runs out, or that the bobbin thread 67 is separated from the upper thread 55 when the cloth is fed during sewing, and the like, and the bobbin thread 67 is not interwoven with the upper thread 55.

In specific example D4, when the count N is 5 or less, the count E is the number of times or less threshold (S6: NO), and therefore, the CPU101 judges whether or not the bottom line 67 with respect to the stitch exists (S7), and judges whether or not the count N is the last needle count (S21). When the count N is not the last needle count (S21: no), the CPU101 adds 1 to the count N (S22), and returns the process to S2. When the count N is the last stitch number (yes in S21), the CPU101 ends the sewing (S23), and ends the sewing process.

When not during the first sewing (S2: NO), the CPU101 judges whether or not the upper thread tension detected by the tension detector 18 at a predetermined timing in the second sewing period is greater than the second threshold H2 (N) set in S59 (S11). The CPU101 uses the second threshold H2 (N) corresponding to the count N based on a combination of the needle count (N) stored in the storage 104 and the second threshold H2 (N). As shown in fig. 11C, in the specific example D5, when the count N is 10, the upper thread tension indicated by the black circle is larger than the second threshold H2 (10) indicated by the white quadrangle (yes in S11), and therefore, the CPU101 determines that the bobbin thread 67 for the stitch is present, sets the count F during the second sewing period to 0 (S18), and then performs the processing in S21 described above. As shown in fig. 12C, in the specific example D6, when the count N is 10, the upper thread tension indicated by the black circle is equal to or less than the second threshold H2 (N) indicated by the white quadrangle (S11: no), and therefore, the CPU101 outputs an instruction to cause the display screen 86 to display that abnormality is detected to the editing apparatus 8 (S12). In the case where the sewing machine 1 includes a notification unit such as an LED lamp, the CPU101 may notify the notification unit of the detection of the abnormality. The CPU101 adds 1 to the count F during the second sewing (S13). The CPU101 determines whether the count F is greater than the count threshold (S14). The number of times threshold of S14 may be the same as or different from the number of times threshold of S6. The number of times threshold in this embodiment is, for example, 5.

In the specific example D6, when the count N is 10, the count F is 1 and is equal to or less than the threshold number of times (S14: NO), and therefore, the CPU101 judges whether or not the upper thread tension detected by the tension detector 18 at a predetermined timing in the second sewing period is greater than the third threshold value (S15). The third threshold is less than the second threshold. The third threshold is a threshold at which detection is made of the absence of the bobbin thread 67 interleaving at the thread. In specific example D6, when the count N is 10 and the upper thread tension is greater than the third threshold value (S15: yes), the CPU101 performs the processing of S21. In specific example D6, when the count N is 11, the upper thread tension is greater than the second threshold H2 (N) (yes in S11), and therefore, the CPU101 determines that the lower thread 67 is present, sets the count F to 0 (S18), and then performs the processing in S21 described above. In this way, in specific example D6, the upper thread tension is equal to or lower than the second threshold H2 (N), but since there is no period in which the upper thread tension is equal to or lower than the second threshold H2 (N) and the number of times of occurrence is equal to or greater than the threshold, it is determined that the bobbin thread 67 is present throughout the second sewing period. When the upper thread tension is equal to or lower than the third threshold value (S15: NO), the CPU101 determines that the bottom thread 67 corresponding to the stitch is not present (S17), and ends the sewing based on the sewing data 30 (S23), and ends the sewing process. That is, when the upper thread tension becomes the third threshold value or less at least once, the CPU101 detects that the bobbin thread 67 with respect to the stitch is not present (S17).

On the other hand, in specific example D5, when the count N is 36, the count F is 6 and is greater than the count threshold (yes in S14), and therefore, the CPU101 determines whether the rotation detector 141 detects the rotation of the bobbin B (S16). When the rotation detector 141 detects that there is a rotation (yes in S16), the CPU101 determines that there is a bobbin thread 67 for the stitch (S19), and performs the processing in S21. In this way, when the tension detected by the tension detector 18 is equal to or less than the second threshold H2 (N) and the rotation detector 141 detects that there is rotation of the bobbin B (yes in S16), the CPU101 determines that there is the bobbin thread 67 with respect to the stitch (S19).

When the detection result of the rotation detector 141 is no rotation (S16: NO), the CPU101 determines that the bobbin thread 67 with respect to the stitch does not exist (S17). In this way, when the tension detected by the tension detector 18 is equal to or less than the second threshold H2 (N) (S11: no) and the rotation detector 141 detects that there is no rotation of the bobbin B (S16: no), the CPU101 determines that there is no bobbin 67 with respect to the stitch (S17). In the present embodiment, when the tension detected by the tension detector 18 is equal to or less than the second threshold H2 (N) and the rotation detector 141 detects that the bobbin B is not rotating (S16: no), the CPU101 determines that the bobbin 67 is in a state of being used up (bobbin run out) (S17). The CPU101 ends the sewing based on the sewing data 30 in the middle of the sewing (S23), and ends the sewing process.

The sewing process of the first modification will be described with reference to fig. 9 as in the above embodiment. When the worker inputs an instruction to start sewing after designating the sewing data 30, the CPU101 reads out a program from the ROM102 and starts the sewing process of the first modification of fig. 9. The CPU101 of the first modification changes the judgment frequency between a first sewing period from the start of sewing to the execution of sewing of a predetermined number of stitches and a second sewing period subsequent to the first sewing period. The CPU101 uses the detection results detected by the tension detector 18 during the thread take-up and the shuttle capturing to determine whether or not the bobbin thread 67 is present with respect to the stitch during the first sewing. The CPU101 uses the detection result detected by the tension detector 18 during the lifting of the thread take-up lever to determine whether or not the bobbin thread 67 with respect to the stitch is present during the second sewing. That is, the CPU101 detects the upper thread tension twice with respect to one cycle of the up-and-down movement of the needle bar 9 during the first sewing period, and determines S4. The CPU101 makes a judgment of S4 using the first threshold H1 (N) corresponding to the timing of detecting the upper thread tension. The CPU101 detects the upper thread tension once with respect to one cycle of the up-and-down movement of the needle bar 9 during the second sewing period, and determines S11. Other processes are the same as those of the above embodiment, and therefore, the description thereof is omitted.

The sewing process of the second modification will be described with reference to fig. 13. In the sewing process of the second modification, the CPU101 determines whether or not the bobbin thread 67 is present with respect to the stitch based on whether or not the proportion of the detected abnormality with respect to the count N is greater than a proportion threshold. When the worker inputs an instruction to start sewing after designating the sewing data 30, the CPU101 reads out a program from the ROM102 and starts the sewing process of fig. 13. In fig. 13, the same reference numerals are given to the same processes as those of fig. 9. As shown in fig. 13, the sewing process of the second modification differs from the sewing process of fig. 9 in that S31 is performed instead of S6, S32 is performed instead of S14, and S33 is performed instead of S18. Hereinafter, S31 to S33 different from the sewing process of fig. 9 will be described, and the description of other processes will be omitted.

In S31, the CPU101 determines whether the ratio obtained by dividing the count E by the count N is greater than a ratio threshold (S31). The ratio threshold value may be set to a value smaller than 1 in advance. The ratio threshold is, for example, any of 20% to 60%. When the ratio is greater than the ratio threshold (S31: yes), the CPU101 determines that there is no under-yarn 67 with respect to the stitch (S17). When the ratio is equal to or less than the ratio threshold (S31: NO), the CPU101 determines that the under-yarn 67 with respect to the stitch exists (S7).

In S32, the CPU101 determines whether the ratio obtained by dividing the count F by the value obtained by subtracting 9, which is the maximum number of stitches during the first sewing period (i.e., the number of stitches during the second sewing period), from the count N is greater than the ratio threshold (S32). The ratio threshold value may be set to a value smaller than 1 in advance. The ratio threshold value of S32 may be the same as or different from the ratio threshold value of S31. The ratio threshold is, for example, any one of 5% to 10%. When the ratio is greater than the ratio threshold (S32: yes), the CPU101 determines whether the rotation of the bobbin B is 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 CPU101 judges whether or not the upper thread tension detected by the tension detector 18 at a predetermined timing in the second sewing period is greater than a third threshold (S15). In S33, the CPU101 does not initialize the count E, F, and determines that the bottom line 67 is present (S33). In the second modification, when the ratio threshold is set to 0.1, in the case of the specific example D6 of fig. 12, if the ratio is larger than the ratio threshold (S32: yes) and if the rotation detector 141 detects that there is no rotation of the bobbin B (S16: no), the CPU101 can determine that there is no bobbin thread 67 with respect to the stitch, and particularly can determine that the multi-needle simulated sewing (S17).

In the above embodiment, the first modification and the second modification, the sewing machine 1, the needle bar 9, the needle 11, the tension detector 18, the needle bar up-and-down movement mechanism 21, the shuttle mechanism 48, the shuttle 49, the upper thread 55, the lower thread 67, the storage 104 and the rotation detector 141 are examples of the sewing machine, the needle bar, the needle, the tension detector, the needle bar up-and-down movement mechanism, the shuttle, the upper thread, the lower thread, the storage and the motion detector of the present invention, respectively. The CPU101 in executing the processing of S3 to S7 and S11 to S19 in fig. 9 is an example of the floor line judgment unit of the present invention. The processing of S3 to S7 and S11 to S19 in fig. 9 is an example of the ground line determination step of the present invention. The CPU101 in executing the processing of S3 to S5, S7, S11 to S13, S15 to S17, S19, and S31 to 33 in fig. 13 is an example of the floor line judgment section of the present invention. The processing of S3 to S5, S7, S11 to S13, S15 to S17, S19, and S31 to 33 in fig. 13 is an example of the ground line determination process of the present invention.

The sewing machine 1 of the above embodiment, the first modification, and the second modification includes the needle bar 9, the needle bar up-and-down movement mechanism 21, the shuttle 49, the shuttle mechanism 48, the tension detector 18, the rotation detector 141, and the CPU101. The needle bar 9 is fitted with a needle 11 into which the upper thread 55 is inserted. The needle bar up-and-down movement mechanism 21 moves the needle bar 9 up and down. The shuttle 49 is provided below the needle bar 9, and rotatably houses the bobbin B around which the bobbin thread 67 is wound. The shuttle mechanism 48 rotates the shuttle 49 in synchronization with the up-and-down movement of the needle bar 9, captures the endless upper thread 55 inserted in the needle 11, and weaves the upper thread 55 with the lower thread 67, thereby forming a stitch. The tension detector 18 detects the tension of the upper thread 55 or the lower thread 67. The rotation detector 141 detects the presence or absence of rotation of the bobbin B. The CPU101 determines whether or not the bobbin thread 67 is present with respect to the stitch based on whether or not 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). Since the sewing machine 1 determines whether or not the bobbin thread 67 is present with respect to the stitch based on whether or not the tension detected by the tension detector 18 is greater than the threshold value and the detection result of the rotation detector 141, it is possible to accurately determine whether or not the bobbin thread 67 is present with respect to the stitch, as compared with a device that uses only the tension detector 18 for determination.

When the rotation detector 141 detects that there is no rotation of the bobbin B (S3: no) and the tension detected by the tension detector 18 is greater than a first threshold H1 (N) which is a threshold (S4: yes), the CPU101 of the sewing machine 1 determines that the bobbin 67 with respect to the stitch is present (S18, S33). When the rotation detector 141 detects that there is no rotation of the bobbin B (no in S3) and the tension detected by the tension detector 18 is equal to or less than the first threshold H1 (N) (no in S4), the CPU101 determines that there is no bobbin thread 67 with respect to the stitch (S17). In the sewing machine 1, even when the absence of the rotation of the bobbin B is detected, it can be determined that the under thread 67 with respect to the stitch exists when the tension detected by the tension detector 18 is greater than the first threshold H1 (N). In the sewing machine 1, the rotation of the bobbin B is temporarily stopped, but in a case where the under thread 67 is considered to be interlaced with the upper thread 55, it is possible to avoid determining that there is no under thread 67 with respect to the stitch.

When the tension detected by the tension detector 18 is equal to or less than a second threshold value H2 (N) which is a threshold value (S11: NO), and the rotation detector 141 detects that the bobbin B is not rotating (S16: NO), the CPU101 of the sewing machine 1 determines that the under thread 67 with respect to the stitch is not present (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 there is rotation of the bobbin B (S16: yes), the CPU101 determines that there is the bobbin thread 67 with respect to the stitch (S19). In the sewing machine 1, even if the tension detected by the tension detector 18 is equal to or less than the second threshold H2 (N), the presence of the bobbin 67 with respect to the stitch can be determined when there is rotation of the bobbin B. In the sewing machine 1, when the bobbin B continues to rotate while the tension is relatively small, and the under thread 67 with respect to the stitch is considered to be interwoven with the upper thread 55, it is possible to avoid determining that the under thread 67 with respect to the stitch is not present.

The CPU101 of the sewing machine 1 determines that the threshold values are different from each other between a first sewing period from the start of sewing to the start of sewing by a predetermined number of stitches and a second sewing period subsequent to the first sewing period (S4, S11). By changing the threshold between the first sewing period and the second sewing period, the sewing machine 1 can determine the presence or absence of the bobbin thread 67 with respect to the stitch using the threshold adapted to each of the first sewing period and the second sewing period.

The CPU101 of the sewing machine 1 according to the above embodiment and the first modification determines that the bobbin 67 is not present with respect to the stitch when the tension detected by the tension detector 18 is equal to or less than the threshold value of the number of consecutive occurrences (S4: no, S6: yes) and the rotation detector 141 detects that the rotation of the bobbin B is not present (S3: no). The CPU101 of the sewing machine 1 rotates at a time of continuously appearing times above a threshold value (S11: NO, S14: yes) when the tension detected by the tension detector 18 is below the threshold value

When the rotation detector 141 detects that there is no rotation of the bobbin B (S16: no), it determines that there is no bobbin 67 with respect to the stitch 5 (S17). The sewing machine 1 can be based on the presence or absence of the bobbin thread 67 with respect to the stitch

To judge that the bottom line is used up. When the bottom line 67 with respect to the stitch is disappeared in the middle of the sewing as shown in fig. 11 (a), although the rotation speed indicated by the black circle is not abnormal in the middle of the sewing, the upper thread tension is connected with the bottom line 67 with respect to the stitch disappearing as shown in fig. 11 (B) and 11 (C)

Since the second threshold H2 (N) or less is continuously set, the absence of the bobbin thread 67 with respect to the stitch can be detected in advance by 0 using the sewing process according to the above embodiment. And, in the sewing machine 1, as

As shown in fig. 11 (C), the presence or absence of the bobbin thread 67 with respect to the stitch is determined by using the tension detected by the tension detector 18 acquired during the lifting of the thread take-up lever, and thus, as shown in fig. 11 (B), the tension detected by the tension detector 18 acquired during the capturing of the shuttle can be used earlier than in the sewing machine 1

Whether or not the under-yarn 67 is present with respect to the stitch is determined, and disappearance of the under-yarn 675 with respect to the stitch is accurately detected.

The CPU101 of the sewing machine 1 of the second modification is configured to set the ratio of the tension detected by the tension detector 18 to the number of sewn stitches to the threshold value or less to the ratio threshold value or more (S4: no, S31:

Yes), and the rotation detector 141 detects that there is no rotation of the bobbin B (S3: no), judge

A ground line 67 with respect to the stitch is not present (S17). The CPU101 sets the ratio of 0 relative to the number of sewn stitches to the ratio of tension detected by the tension detector 18 to be equal to or smaller than the threshold value to be equal to or larger than the ratio threshold value (S11:

no, S32: yes), and the rotation detector 141 detects that there is no rotation of the bobbin B (S16:

no), it is determined that the ground wire 67 with respect to the stitch does not exist (S17). In the sewing machine 1, it is possible to avoid making an erroneous judgment of the presence or absence of a defective sewing associated with the bobbin thread 67 based on the singular value of the tension detector 18.

In the case of the multi-needle simulated sewing as shown in fig. 12 (a), the rotation speed 5 indicated by the black circle is not abnormal, and as shown in fig. 12 (B) and 12 (C), the upper thread tension is not present, and the sewing is continued

Since the period of time equal to or less than the second threshold H2 (N) is set, it is difficult to detect the simulated sewing in the sewing process of the above embodiment, but by performing the sewing process of the second modification, it is possible to appropriately detect the simulated sewing based on the presence or absence of the upper thread tension of the plural stitches and the rotation of the bobbin B.

The sewing machine 1 of the above embodiment, the first modification, and the second modification further includes a storage device 104 that stores a combination of the needle count of the stitch and a threshold value, and the cpu101 uses the threshold value corresponding to the needle count to determine based on the combination stored in the storage device 104. The sewing machine 1 can determine the presence or absence of the bobbin thread 67 with respect to the stitch using a threshold value in consideration of the number of stitches. The sewing machine 1 can form the same stitch on the same cloth 69 based on the sewing data 30, and therefore, stitches corresponding to the number of stitches of the sewing data become stitches similar to each other. Therefore, in the sewing machine 1, when forming stitches on the same cloth 69 according to the sewing data, the presence or absence of the bobbin thread 67 with respect to the stitches can be appropriately determined using the threshold value set in consideration of the influence of the thickness of the cloth 69, whether or not it is a curve, the feed amount, and the like.

The CPU101 makes a judgment using the tension detected by the tension detector 18 acquired at a timing corresponding to the number of stitches in one cycle of the up-and-down movement of the needle bar 9. In the sewing machine 1, compared with a case where the presence or absence of the base thread 67 with respect to the stitch is determined using the tension detected by the tension detector 18 acquired at the same timing regardless of the number of stitches, the presence or absence of the base thread 67 with respect to the stitch can be determined in consideration of the influence of the stitch corresponding to the number of stitches. In the present embodiment, the CPU101 uses the detection result detected by the tension detector 18 during the shuttle capturing to determine whether or not the bobbin thread 67 with respect to the stitch is present during the first sewing. By thus setting the detection timing of the tension detector 18, the sewing machine 1 can preferably detect the absence of the bobbin thread 67 during the first sewing period. On the other hand, as shown in fig. 11, the deviation of the upper thread tension from the second threshold H2 when the lower thread 67 with respect to the stitch is disappeared halfway is more remarkable than the detection result obtained during the shuttle capturing period shown in fig. 11 (B), which is obtained during the take-up of the take-up lever shown in fig. 11 (C). Accordingly, the sewing machine 1 can preferably detect that the under-thread 67 with respect to the stitch is not present during the second sewing period by judging whether the under-thread 67 with respect to the stitch is present during the second sewing period by using the detection result detected by the tension detector 18 during the lifting of the thread take-up lever.

The CPU101 of the first modification changes the frequency of timing at which the tension detector 18 acquires the detection result with respect to one cycle of the up-and-down movement of the needle bar 9 in accordance with the number of stitches, and determines using the tension detected by the tension detector 18. In the sewing machine 1, compared with a case where the presence or absence of the base thread 67 with respect to the stitch is determined using the tension detected by the tension detector 18 acquired at the same frequency regardless of the number of stitches, the presence or absence of the base thread 67 with respect to the stitch can be determined in consideration of the influence of the stitch corresponding to the number of stitches.

The sewing machine 1 further includes a thread take-up lever 19, the thread take-up lever 19 lifts the upper thread 55 intersecting the lower thread 67 by the shuttle 49, the tension detector 18 detects the tension of the upper thread, and the CPU101 determines whether or not the lower thread 67 with respect to the thread trace is present based on whether or not the tension detected by the tension detector 18 is greater than a threshold value and a detection result of the rotation detector 141 at a timing in any one of a take-up lever lifting period in which the thread take-up lever 19 lifts the upper thread 55 and a shuttle catching period in which the shuttle 49 catches the upper thread 55. The sewing machine 1 can determine the presence or absence of the bobbin thread 67 with respect to the stitch based on the upper thread tension detected during the take-up of the take-up lever or the shuttle catching. Since the upper thread tension in the take-up period or the shuttle capturing period is larger than the upper thread tension in the period between the take-up period and the shuttle capturing period, erroneous judgment can be avoided as compared with the case where judgment is made by the CPU101 in the period in which the upper thread tension is relatively small.

The present invention can be variously modified in addition to the above-described embodiments. The structure of the sewing machine 1 may be changed as appropriate, and for example, the sewing machine may be configured such that the cloth 69 is not held by the holder 60. The structures, arrangements, detection methods, and the like of the tension detector 18 and the rotation detector 141 may be changed as appropriate. The sewing machine 1 may also have the function of the editing device 8. Specifically, the tension detector 18 may be disposed between the sub-thread clamp 15 and the main thread clamp 16 on the path of the upper thread 55, or may be disposed on the downstream side of the take-up lever 19 on the path of the upper thread 55. The sewing machine 1 of the above embodiment is a single-needle sewing machine in which one needle 11 is attached to the needle bar 9, but may be a double-needle sewing machine in which two needles are attached to the needle bar 9, or a sewing machine in which three or more needles are provided, and a plurality of thread tension detecting devices are provided for detecting the tension of the respective upper threads 55. In these cases, the sewing machine 1 may be provided with a plurality of rotation detectors 141 for detecting rotations of the bobbin B of the respective shuttles 49. The tension detector 18 has a structure using the magnetic sensor 53, but may be configured to receive the force of the upper thread 55 by the electrostrictive element and detect the tension based on the output thereof.

The program for causing the sewing machine 1 to perform the processing may be stored in the memory device 104 of the sewing machine 1 before the CPU101 executes the program. Thus, the program acquisition method, the acquisition path, and the device storing the program can be changed as appropriate. The program executed by the CPU101 may be received from another device through 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 another electronic device (for example, ASIC) other than the CPU 101. The processing performed by the sewing machine 1 may be distributed processing by a plurality of electronic devices (e.g., a plurality of CPUs). The steps of the processing performed by the sewing machine 1 can be changed in order, omitted, and added as needed. The scope of the invention also includes the following ways: part or all of the respective processes are performed by an Operating System (OS) or the like operating on the sewing machine 1 by instructions of the CPU 101. For example, the following modifications may be appropriately applied to the above-described embodiment.

In the sewing machine 1 of the above embodiment, the count at which the abnormality is detected is updated directly (S13) when the detected upper thread tension is equal to or lower than the second threshold (S11: no), but the count may be updated only when the rotation of the bobbin B cannot be detected, by detecting the presence or absence of the rotation of the bobbin B before updating the count. In this case, in the sewing machine 1, it may be determined directly that the bobbin B is not rotated in S16, and that the bobbin B is not rotated in the case where the count exceeds the count threshold (yes in S14) or the ratio exceeds the ratio threshold (yes in S32), respectively (S17).

The processes S11 to S16 may be performed during the first sewing period, or the processes S3 to S7 may be performed during the second sewing period. The same process may also be performed between the first sewing period and the second sewing period. The threshold values may be the same as each other between the first sewing period and the second sewing period. The CPU101 may acquire the tension detected by the tension detector 18 at the same timing between the first sewing period and the second sewing period. The CPU101 may not determine the presence or absence of the under-yarn 67 for the stitch for each needle, and may determine the presence or absence of the under-yarn 67 for the stitch for each predetermined number of needles, for example. The CPU101 may also acquire the tension detected by the tension detector 18 at the same frequency between the first sewing period and the second sewing period. The number of times threshold value and the ratio threshold value may be 0, and cpu101 may determine that there is no bobbin 67 with respect to the stitch when the tension detected by tension detector 18 is equal to or less than the threshold value and rotation detector 141 detects that there is no rotation of bobbin B. The first threshold H1 and the second threshold H2 may not be values corresponding to the count N, and for example, a common value may be set for a part of or all of the plurality of needle counts. Tension detector 18 may also detect the tension of bobbin thread 67. In the case where the sewing machine 1 does not form stitches based on sewing data, the threshold value may be changed in accordance with conditions such as the material of the cloth 69, the upper thread 55, or the lower thread 67, the thickness of the cloth 69, the type of stitch, the feed amount (length of stitch), and the sewing speed. The above modifications may be appropriately combined within a range where there is no contradiction.

In the sewing machine 1 of the above embodiment, the detection result of the presence or absence of the rotation of the bobbin B by the rotation detector 141 is used as the detection result of the presence or absence of the operation of the bobbin B, but instead of the rotation detector 141, a bobbin thread remaining amount detector that detects the presence or absence of a change in the amount of the bobbin thread 67 wound around the bobbin B may be used as the operation detector, and the presence or absence of a change in the bobbin thread remaining amount may be used as the detection result of the presence or absence of the operation of the bobbin B. Specifically, the sewing machine 1 may include an optical sensor as the operation detector, and the optical sensor may be provided with a light transmitting portion in a part of the flange portion of one of the side surface of the bobbin case accommodating the bobbin B and the bobbin B, and a reflecting surface formed on the inner wall of the plurality of flange portions, and may include an irradiation portion for irradiating light from the light transmitting portion and a light receiving portion for receiving the reflected light. Alternatively, in the sewing machine 1, a weight sensor for measuring the weight of the bobbin B may be added to the shuttle 49 as an operation detector, and the presence or absence of the bobbin thread margin change may be detected based on a change in the output of the weight sensor. Since the amount of the bobbin thread 67 wound around the bobbin B decreases in accordance with the amount of sewing during normal operation of the bobbin B, in the sewing machine 1 of this modification, the presence or absence of the operation of the bobbin B can be accurately detected by detecting the presence or absence of a change in the amount of the bobbin thread 67 wound around the bobbin B.

Claims

1. A sewing machine is characterized in that,

the sewing machine comprises:

a needle bar for assembling a needle into which the upper thread is inserted;

a needle bar up-and-down movement mechanism that moves the needle bar up and down;

a shuttle provided below the needle bar, the shuttle rotatably accommodating a bobbin around which a bobbin thread is wound;

a shuttle mechanism that rotates the shuttle in synchronization with the up-and-down movement of the needle bar, captures the endless upper thread inserted in the needle, and interweaves the upper thread with the lower thread to form a stitch;

a tension detector that detects tension of the upper thread or the lower thread;

an operation detector that detects the presence or absence of an operation of the bobbin; and

and a bobbin thread judging section for judging whether or not the bobbin thread is present with respect to the stitch based on whether or not the tension detected by the tension detector is greater than a threshold value and a detection result of the motion detector.

2. The sewing machine of claim 1, wherein the sewing machine is configured to perform the sewing operation,

when the motion detector detects that the motion of the bobbin does not exist and the tension detected by the tension detector is larger than a first threshold value which is the threshold value, the bobbin thread judging section judges that the bobbin thread relative to the stitch exists,

When the motion detector detects that the motion of the bobbin does not exist and the tension detected by the tension detector is equal to or less than the first threshold value, the bobbin thread judging section judges that the bobbin thread with respect to the stitch does not exist.

3. A sewing machine as defined in claim 1 or 2, wherein,

when the tension detected by the tension detector is equal to or less than a second threshold which is the threshold and the motion detector detects that the motion of the bobbin does not exist, the bobbin thread judging section judges that the bobbin thread corresponding to the stitch does not exist,

the bobbin thread judging section judges that the bobbin thread is present with respect to the stitch when the tension detected by the tension detector is equal to or less than the second threshold value and the motion detector detects the presence of the motion of the bobbin thread.

4. A sewing machine as defined in any one of claims 1-3, wherein the sewing machine comprises a frame,

the bobbin thread judging section judges using the threshold values different from each other between a first sewing period from the start of sewing to the sewing of a predetermined number of stitches and a second sewing period subsequent to the first sewing period.

5. The sewing machine of any of claims 1-4, wherein the sewing machine of any of claims 1-4,

the bobbin thread judging section judges that the bobbin thread is used up when the detection result of the tension detector is equal to or less than the threshold value, the number of consecutive occurrences is equal to or greater than a threshold value, and the action detector detects that the action of the bobbin thread is absent.

6. The sewing machine of any of claims 1-4, wherein the sewing machine of any of claims 1-4,

when the ratio of the detection result of the tension detector to the number of sewn stitches is equal to or smaller than the threshold value, which is equal to or larger than a ratio threshold value, and the motion detector detects that the motion of the bobbin is absent, the bobbin thread judging section judges that the bobbin thread with respect to the stitch is absent.

7. The sewing machine of any of claims 1-6, wherein the sewing machine of any of the claims,

the sewing machine further has a storage section that stores a combination of the stitch count and the threshold value,

the bottom line judgment unit uses the threshold value corresponding to the number of needles to judge based on the combination stored in the storage unit.

8. The sewing machine of any of claims 1-7, wherein the sewing machine of any of the claims,

The bobbin thread judging section judges using the tension detected by the tension detector acquired at a timing corresponding to the number of stitches in one cycle of the up-and-down movement of the needle bar.

9. The sewing machine of any of claims 1-7, wherein the sewing machine of any of the claims,

the bobbin thread judging section changes the frequency of the timing at which the tension detector acquires the detection result with respect to one cycle of the up-and-down movement of the needle bar in accordance with the number of stitches, and judges using the tension detected by the tension detector.

10. The sewing machine of claim 8 or 9, wherein the sewing machine comprises a frame,

the sewing machine further has a thread take-up lever that lifts the upper thread that is intersected with the lower thread by the shuttle,

the tension detector detects the tension of the upper thread,

the bobbin thread judging section judges whether or not the bobbin thread is present with respect to the thread based on whether or not the detection result of the tension detector at the timing in any one of a thread take-up period in which the thread take-up lever lifts the upper thread and a shuttle capturing period in which the shuttle captures the upper thread is greater than the threshold value and the detection result of the motion detector.

11. The sewing machine of any of claims 1-10, wherein the sewing machine of any of the claims,

the motion detector detects the presence or absence of rotation of the bobbin.

12. The sewing machine of any of claims 1-10, wherein the sewing machine of any of the claims,

the motion detector detects whether or not the amount of the bobbin thread wound around the bobbin is changed.

13. A bottom thread judging method is executed by a control part of a sewing machine, the sewing machine comprises: a needle bar for assembling a needle into which the upper thread is inserted; a needle bar up-and-down movement mechanism that moves the needle bar up and down; a shuttle provided below the needle bar, the shuttle rotatably accommodating a bobbin around which a bobbin thread is wound; a shuttle mechanism that rotates the shuttle in synchronization with the up-and-down movement of the needle bar, captures the endless upper thread inserted in the needle, and interweaves the upper thread with the lower thread to form a stitch; a tension detector that detects tension of the upper thread or the lower thread; and an operation detector for detecting the presence or absence of an operation of the bobbin, wherein,

the bobbin thread determination method includes a bobbin thread determination step of determining whether or not the bobbin thread is present with respect to the stitch based on whether or not the tension detected by the tension detector is greater than a threshold value and a detection result of the motion detector.