Sewing machine and bobbin thread judging method

Abstract

The present invention provides a sewing machine and a bobbin thread judging method capable of accurately detecting that the bobbin thread is used up or that the bobbin thread is entangled with the thread even under any sewing conditions. The sewing machine includes a needle bar, a needle bar up-and-down movement mechanism, a bobbin, a bobbin mechanism, a tension detector, a rotation detector, and a bobbin thread judging section. The needle bar is equipped with a needle through which a thread is inserted. The needle bar up-and-down movement mechanism moves the needle bar up and down. The bobbin is provided below the needle bar and houses a bobbin spindle on which a bobbin thread is wound in a rotatable manner. The bobbin mechanism rotates the bobbin in synchronization with the up-and-down movement of the needle bar, catches a loop-shaped thread inserted through the needle, and entangles the thread with the bobbin thread to form a stitch. The tension detector detects the tension of the thread or the bobbin thread. The rotation detector detects whether the bobbin spindle is rotating. The bobbin thread judging section judges the presence or absence of the bobbin thread with respect to the stitch based on whether the tension detected by the tension detector is greater than a threshold value and the detection result of the rotation detector (S3-S7, S11-S19).

Description

Technical Field

[0001] This invention relates to sewing machines and methods for determining the bottom thread. Background Technology

[0002] The sewing machine of Patent Document 1 has a bottom thread tension sensor that detects the tension of the bottom thread and determines whether the bottom thread has run out based on the tension of the bottom thread during the sewing process.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 10-33868 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] Depending on the sewing conditions, the aforementioned sewing machines sometimes cannot accurately detect when the bobbin thread is used up.

[0008] The purpose of this invention is to provide a sewing machine and a method for judging the thread count that can accurately detect when the thread is used up or when the thread is poorly interlaced, regardless of the sewing conditions, compared to the past.

[0009] Solution for solving the problem

[0010] Technical solution 1 provides a sewing machine, comprising: a needle bar fitted with a needle through which a top thread is inserted; a needle bar up-and-down movement mechanism that causes the needle bar to move up and down; a shuttle disposed below the needle bar, the shuttle rotatably housing a bobbin wound with a bottom thread; a shuttle mechanism that rotates the shuttle synchronously with the up-and-down movement of the needle bar, capturing the looped top thread inserted into the needle and interweaving the top thread with the bottom thread to form a stitch; a tension detector that detects the tension of the top thread or the bottom thread; a motion detector that detects the presence or absence of motion of the bobbin; and a bottom thread determination unit that determines the presence or absence of the bottom thread relative to the stitch based on whether the tension detected by the tension detector is greater than a threshold and the detection result of the motion detector. The sewing machine of technical solution 1 determines the presence or absence of the bottom line relative to the stitch based on whether the tension detected by the tension detector is greater than a threshold and the detection result of the motion detector. Therefore, compared with the device that only uses the tension detector for judgment, it can accurately determine the presence or absence of the bottom line relative to the stitch.

[0011] In the sewing machine of technical solution 2, when the motion detector detects an action without the bobbin and the tension detected by the tension detector is greater than a first threshold (which is the threshold value), the thread bottom determination unit determines that a thread bottom is present relative to the stitch. When the motion detector detects an action without the bobbin and the tension detected by the tension detector is below the first threshold value, the thread bottom determination unit determines that a thread bottom is present relative to the stitch. In the sewing machine of technical solution 2, even when an action without the bobbin is detected, a thread bottom is present relative to the stitch if the tension detected by the tension detector is greater than the first threshold value. In this sewing machine, even when the bobbin action is temporarily stopped, but the thread bottom and top thread are considered to be intertwined, the determination that a thread bottom is present relative to the stitch can be avoided.

[0012] In the sewing machine of technical solution 3, when the tension detected by the tension detector is below a second threshold (which is the threshold value) and the motion detector detects no bobbin movement, the thread bottom determination unit determines that there is no thread bottom relative to the stitch. Conversely, when the tension detected by the tension detector is below the second threshold and the motion detector detects bobbin movement, the thread bottom determination unit determines that there is thread bottom relative to the stitch. In the sewing machine of technical solution 3, even if the tension detected by the tension detector is below the second threshold, it is possible to determine that there is thread bottom relative to the stitch when bobbin movement is present. In the sewing machine, even when the tension is relatively low, but the bobbin continues to move, and the thread bottom and top thread are considered to be intertwined, it is possible to avoid determining that there is no thread bottom relative to the stitch.

[0013] In the sewing machine of technical solution 4, the bottom thread determination unit uses different threshold values ​​between the first sewing period (from the start of sewing until a predetermined number of stitches are sewn) and the second sewing period (continuing with the first sewing period). By changing the threshold values ​​between the first and second sewing periods, the sewing machine of technical solution 4 can determine the presence or absence of the bottom thread relative to the stitch using threshold values ​​that are adaptive to both the first and second sewing periods.

[0014] In the sewing machine of technical solution 5, if the number of consecutive occurrences of the detection result of the tension detector being below the threshold exceeds a threshold and the motion detector detects no bobbin movement, the bobbin thread determination unit determines that the bobbin thread is used up. The sewing machine of technical solution 5 can determine that the bobbin thread is used up based on the presence or absence of bobbin thread relative to the stitch.

[0015] In the sewing machine of technical solution 6, when the proportion of the detection result of the tension detector below the threshold relative to the number of stitches sewn is above the threshold and the motion detector detects that there is no bobbin motion, the bottom thread determination unit determines that there is no bottom thread relative to the stitch. The sewing machine of technical solution 6 can avoid making incorrect judgments about the presence or absence of bottom thread relative to the stitch based on the singular value of the tension detector.

[0016] The sewing machine of technical solution 7 further includes a storage unit that stores a combination of the stitch count and the threshold. The bottom thread determination unit makes a determination based on the combination stored in the storage unit, using the threshold corresponding to the stitch count. The sewing machine of technical solution 7 is capable of determining the presence or absence of a bottom thread relative to the stitch count using a threshold that takes into account the stitch count.

[0017] The bottom thread detection unit of the sewing machine in technical solution 8 uses the tension detected by the tension detector, which is acquired at a time corresponding to the number of stitches in the stitch within one cycle of the up-and-down movement of the needle bar, to make a determination. In the sewing machine of technical solution 8, compared to the case where the presence or absence of the bottom thread is determined by using the tension detected by the tension detector, which is acquired at the same time regardless of the number of stitches, the influence of the stitch corresponding to the number of stitches can be taken into account to determine the presence or absence of the bottom thread.

[0018] In the sewing machine of technical solution 9, the bottom thread determination unit changes the frequency at which the tension detector acquires the detection result relative to one cycle of the needle bar's up-and-down movement, in accordance with the number of stitches in the stitch, and uses the tension detected by the tension detector to make the determination. In the sewing machine of technical solution 9, compared to the case where the presence or absence of the bottom thread is determined by using the tension detected by the tension detector, which is acquired at the same frequency regardless of the number of stitches, the influence of the stitches corresponding to the number of stitches can be considered when determining the presence or absence of the bottom thread.

[0019] The sewing machine of technical solution 10 further includes a take-up lever that lifts the top thread, which is interwoven with the bottom thread by the shuttle. A tension detector detects the tension of the top thread. The bottom thread determination unit determines the presence or absence of the bottom thread relative to the stitch based on whether the detection result of the tension detector is greater than a threshold and the detection result of the motion detector during either the take-up lever lifting the top thread or the shuttle capturing the top thread. The sewing machine of technical solution 10 can determine the presence or absence of the bottom thread relative to the stitch based on the top thread tension detected during the take-up lever lifting or the shuttle capturing period. Since the top thread tension during the take-up lever lifting or the shuttle capturing period is greater than the top thread tension during the period between the take-up lever lifting and the shuttle capturing period, incorrect judgments can be avoided compared to using the bottom thread determination unit to make a judgment during a period of relatively low top thread tension.

[0020] The sewing machine of technical solution 11 uses a motion detector to detect whether the bobbin is rotating. The sewing machine of technical solution 11 can detect the presence or absence of bobbin motion based on the detection result of the presence or absence of bobbin rotation.

[0021] The motion detector of the sewing machine in technical solution 12 detects whether there is a change in the amount of thread wound around the bobbin. The sewing machine in technical solution 12 can detect the presence or absence of bobbin motion based on the detection result of whether there is a change in the amount of thread wound around the bobbin.

[0022] Technical solution 13 provides a bottom thread determination method executed by the control unit of a sewing machine. The sewing machine includes: a needle bar fitted with a needle through which the top thread passes; a needle bar up-and-down movement mechanism that moves the needle bar up and down; a shuttle located below the needle bar, which rotatably holds a bobbin wound with the bottom thread; a shuttle mechanism that rotates the shuttle synchronously with the up-and-down movement of the needle bar, capturing the looped top thread passing through the needle and interweaving the top thread with the bottom thread to form a stitch; a tension detector that detects the tension of the top thread or the bottom thread; and a motion detector that detects the presence or absence of motion of the bobbin. The bottom thread determination method includes a bottom thread determination step, in which the presence or absence of the bottom thread relative to the stitch is determined based on whether the tension detected by the tension detector is greater than a threshold and the detection result of the motion detector. When the bottom line determination method of technical solution 13 is implemented, the sewing machine determines the presence or absence of the bottom line relative to the stitch based on whether the tension detected by the tension detector is greater than the threshold and the detection result of the motion detector. Therefore, compared with the determination device that only uses the tension detector, it can accurately determine the presence or absence of the bottom line relative to the stitch. Attached Figure Description

[0023] Figure 1 It is a perspective view of a sewing system 10 including a sewing machine 1 and an editing device 8.

[0024] Figure 2 This is a magnified view of a portion of the front end 7.

[0025] Figure 3 This is a three-dimensional view of the tension detector 18.

[0026] Figure 4 This is a schematic diagram illustrating the process of shuttle 49 capturing surface line 55.

[0027] Figure 5 This is an electrical block diagram of the sewing machine 1 and the editing device 8.

[0028] Figure 6 This is a flowchart of the threshold setting process.

[0029] Figure 7 It is a schematic diagram of sewing data 30 and the stitches formed based on sewing data 30.

[0030] Figure 8 It is a graph showing the relationship between the tension D1 of the facet 55, the vertical position D2 of the needle tip, and the upper axis angle.

[0031] Figure 9 This is a flowchart of the sewing process.

[0032] Figure 10 It is a graph showing the relationship between the number of stitches and the tension of the top thread 55 in the first sewing period of specific examples D3 and D4.

[0033] Figure 11 (A) is a graph showing the relationship between the number of stitches in the second sewing period and the rotation speed of the upper shaft 22 in specific example D5. Figure 11 (B) is a graph showing the relationship between the number of stitches in the second sewing period in specific example D5 and the tension of the face thread 55 detected during the shuttle capture period. Figure 11 (C) is a graph showing the relationship between the number of stitches in the second sewing period in specific example D5 and the tension of the top thread 55 detected during the lifting of the take-up lever.

[0034] Figure 12 (A) is a graph showing the relationship between the number of stitches in the second sewing period and the rotation speed of the upper shaft 22 in specific example D6. Figure 12 (B) is a graph showing the relationship between the number of stitches in the second sewing period in specific example D6 and the tension of the face thread 55 detected during the shuttle capture period. Figure 12(C) is a graph showing the relationship between the number of stitches in the second sewing period in specific example D6 and the tension of the top thread 55 detected during the lifting of the take-up lever.

[0035] Figure 13 This is a flowchart of the sewing process for the modified example.

[0036] Explanation of reference numerals in the attached figures

[0037] 1. Sewing machine; 9. Needle bar; 11. Needle; 18. Tension detector; 21. Needle bar up-and-down movement mechanism; 48. Shuttle mechanism; 49. Shuttle; 55. Top thread; 67. Bottom thread; 101. CPU; 104. Storage device; 141. Rotation detector; B. Bobbin; H1. First threshold; H2. Second threshold. Detailed Implementation

[0038] Referring to the accompanying drawings, embodiments of the present invention will be described. In the following description, left and right, front and back, and up and down, as indicated by arrows in the drawings, are used. (Refer to...) Figure 1 The sewing system 10 is described below. The sewing system 10 includes a sewing machine 1 and an editing device 8. The editing device 8 is a portable terminal and is connected to the sewing machine 1. The editing device 8 can also be connected to other sewing machines besides the sewing machine 1, or to multiple sewing machines. The editing device 8 edits and forms on the sewing object (e.g., ...). Figure 4 The editing device 8 outputs the sewing data related to the stitches of the fabric 69 to the sewing machine 1. The sewing machine 1 sews a pattern of stitches on the fabric 69 based on the sewing data output by the editing device 8.

[0039] Reference Figures 1-4 And describe sewing machine 1. Sewing machine 1 has a base section 2, a support section 3, and a machine arm section 4. The base section 2 is placed on a platform 50. The base section 2 extends in the front-to-back direction and has a shuttle 49 inside (see reference). Figure 4 ), shuttle mechanism 48 (refer to) Figure 4 ) and rotation detector 141 (refer to Figure 5The shuttle 49 is located below the needle bar 9 (described later) and houses the bobbin B, with the bobbin thread 67 wound around it, in a rotatable manner. The shuttle mechanism 48 rotates the shuttle 49 synchronously with the up-and-down movement of the needle bar 9, capturing the annular face thread 55 that passes through the needle 11 and interweaving the face thread 55 with the bobbin thread 67 to form a stitch. The rotation detector 141 detects the presence or absence of rotation of the bobbin B as the presence or absence of bobbin B's movement. The rotation detector 141 is, for example, a non-photoelectric proximity sensor (magnetic sensor). The bobbin B has a magnet on a portion of its flange, and the magnetic force around the rotation detector 141 changes accordingly with the rotation of the bobbin B. The rotation detector 141 can detect the presence or absence of bobbin B's rotation by reading the change in this magnetic force. The support section 3 extends vertically upward from the rear side of the base section 2. The support section 3 has a main motor 123 inside (see reference). Figure 5 The machine arm 4 extends forward from the upper end of the support section 3, opposite to the upper surface of the machine base 2, and has a front end portion 7. The machine arm 4 internally includes an upper shaft 22 and a needle bar up-and-down movement mechanism 21, etc. The needle bar 9 extends downward from the lower end of the front end portion 7. The needle bar 9 is fitted with a needle 11 through which the thread 55 is inserted. The needle 11 is detachably mounted at the lower end of the needle bar 9, and the needle 11 has a needle eye 111 at its lower end.

[0040] The sewing machine 1 has a worktable 5 and a transfer device 6 above the base 2. The worktable 5 has a needle plate 501. The needle plate 501 has a needle-receiving hole 502 directly below the needle 11. The needle-receiving hole 502 allows the needle 11 to pass through. The transfer device 6 has an X-axis moving mechanism, a Y-axis moving mechanism, an arm 65, a support 64, a lifting part 62, and a retainer 60. The X-axis moving mechanism is located inside the base 2, and the Y-axis moving mechanism is located inside the support 3. The arm 65 holds the support 64 and is connected to the Y-axis moving mechanism. The support 64 extends in the left-right direction and supports the lifting part 62 and the retainer 60. The lifting part 62 is provided on the support 64 in a way that allows it to be raised and lowered. The retainer 60 has a transfer plate 61 and a pressure plate 63. The transfer plate 61 extends in the horizontal direction and has an opening at its front end that is rectangular in shape when viewed from above. The transfer plate 61 is connected to the support 64. The pressure plate 63 extends horizontally and has an opening that is rectangular in shape when viewed from above. The pressure plate 63 is connected to the lower end of the lifting part 62. The opening of the transfer plate 61 is approximately the same shape as the opening of the pressure plate 63, and the position of the opening of the transfer plate 61 corresponds to the position of the opening of the pressure plate 63.

[0041] The X-axis movement mechanism uses X-axis motor 124 (see reference). Figure 5 The lifting unit 62 and the holding body 60 are driven by a Y-axis motor 125, which moves the lifting unit 62 and the holding body 60 in the left-right direction (X-axis direction). The Y-axis moving mechanism is driven by a Y-axis motor 125 (see reference). Figure 5) serves as the driving source and moves the arm 65 in the front-rear direction (Y-axis direction). Along with the movement of the arm 65 in the front-rear direction, the support portion 64 moves in the front-rear direction. The lifting portion 62 and the holding body 60 move together with the support portion 64. The operator places the fabric 69 (refer to Figure 4 ) on the transfer plate 61. When the lifting portion 62 moves downward, the pressing plate 63 descends onto the transfer plate 61. The holding body 60 (the pressing plate 63 and the transfer plate 61) clamps the fabric 69 from above and below. The sewing machine 1 moves the holding body 60 in the front, rear, left, and right directions by using the X-axis movement mechanism and the Y-axis movement mechanism, so that the sewing needle 11 and the fabric 69 clamped by the holding body 60 move relative to each other.

[0042] As Figure 2 shown, the front end portion 7 has a guide mechanism 14, a needle bar 9, a presser bar 12, etc. The guide mechanism 14 is provided on the right side surface of the front end portion 7 to guide the upper thread 55. The guide mechanism 14 includes a sub-thread clamp 15, a main thread clamp 16, a thread lead 17, a tension detector 18, a thread take-up lever 19, and a thread lead 20. The upper thread 55 passes through the eye 111 of the sewing needle 11 from the bobbin through the sub-thread clamp 15, the main thread clamp 16, the thread lead 17, the tension detector 18, the thread take-up lever 19, and the thread lead 20. The thread take-up lever 19 lifts the upper thread 5� that is intertwined with the bobbin thread 67 by the shuttle 49 (refer to Figure 4 ). The main thread clamp 16 has an electromagnetic element 128 (refer to Figure 5 ). The main thread clamp 16 changes the tension applied to the upper thread 55 (hereinafter referred to as the upper thread tension) along with the operation of the electromagnetic element 128, thereby adjusting the thread clamping degree (Japanese: 糸調子). The upper thread tension is set in consideration of the tension balance between the upper thread 55 and the bobbin thread 67. The main motor 123 (refer to Figure 5 ) rotationally drives the main shaft 22. The needle bar vertical movement mechanism 21 moves the needle bar 9 up and down along with the rotational drive of the main shaft 22.

[0043] The 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 assembled to the lower end portion of the presser bar 12, and the presser foot 13 has a lower end portion 131. The lower end portion 131 is a cylindrical shape that penetrates in the up-down direction and can allow the sewing needle 11 to pass through. The presser foot drive mechanism swings the presser bar 12 in the up-down direction synchronously with the up-down swing of the needle bar 9 that is carried out along with the rotational drive of the main shaft 22. The presser foot drive mechanism has a presser foot motor 129 (refer to Figure 5The presser foot drive mechanism, driven by the presser foot motor 129, adjusts the height (hereinafter referred to as presser foot height) from the upper surface of the needle plate 501 to the lower end of the presser foot 13. When the needle 11 disengages from the fabric 69, the presser foot 13 presses the fabric 69 against the needle plate 501 from above, thereby preventing the fabric 69 from lifting off the needle plate 501. The needle 11 penetrates the fabric through the inner side of its lower end 131. The needle 11 passes through the needle receiving hole 502 and moves vertically.

[0044] like Figure 2 , Figure 3 Thus, the tension detector 18 is located on the right surface of the front end 7, in a vertical position between the auxiliary wire clamp 15 and the main wire clamp 16, on the path between the wire guide 17 and the take-up lever 19. The tension detector 18 is capable of detecting the tension of the surface thread. The tension detection mechanism 18 has a mounting base 51, a holding part 52, a magnetic sensor 53, a plate 54, a guide member 77, and a magnet 56. The mounting base 51 has a mounting part 57 and a seat part 59. The mounting part 57 and the seat part 59 are integrally formed with each other. The mounting part 57 has an elongated hole 58 for a screw to pass through. The screw inserted into the elongated hole 58 is fastened to a threaded hole provided on the right surface of the front end 7. The seat part 59 is located on the left side of the mounting base 51. The seat part 59 has a left protrusion 71 and a right protrusion 72. The left protrusion 71 and the right protrusion 72 are each cuboids extending in the front-rear direction.

[0045] The retaining part 52 is generally rectangular in shape and is mounted on the base 59 between the left protrusion 71 and the right protrusion 72. The retaining part 52 is non-magnetic. The magnetic sensor 53 is held on the front surface of the retaining part 52. The magnetic sensor 53 is a Hall element. The magnetic sensor 53 is located rearward from the front ends of the left protrusion 71 and the right protrusion 72.

[0046] Plate 54 is a plate-shaped material with thickness in the front-rear direction, and it is mounted on the left protrusion 71 and the right protrusion 72. Guide member 77 is installed on the left protrusion 71 and the right protrusion 72. Guide member 77 clamps the left end of plate 54 between itself and the left protrusion 71, and clamps the right end of plate 54 between itself and the right protrusion 72. There is a gap between the central portion of plate 54 in the left-right direction and the front surface of the retaining portion 52. Therefore, plate 54 flexes in the front-rear direction using its two ends in the left-right direction as fulcrums.

[0047] The magnet 56 is formed into a cylindrical shape extending in the front-to-back direction. The magnet 56 is fixed to the rear surface of the central portion of the plate 54 in the left-to-right direction. When the plate 54 flexes in the front-to-back direction, the magnet 56 moves back and forth, changing the distance between the magnet 56 and the magnetic sensor 53. The magnetic sensor 53 detects the change in magnetic flux density from the magnet 56 and outputs a voltage corresponding to the magnetic flux density.

[0048] 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 vertically in such a way that the plate 54 is placed between them. The upper guide groove 74 and the lower guide groove 76 are open in the vertical direction and form a hook shape when viewed from above. The upper guide groove 74 has an upper retaining hole 73, and the lower guide groove 76 has a lower retaining hole 75. The upper retaining hole 73 and the lower retaining hole 75 are through holes that open in the vertical direction. The face thread 55 is inserted through the upper retaining hole 73 and the lower retaining hole 75, respectively. The face thread 55 located between the upper retaining hole 73 and the lower retaining hole 75 contacts the plate 54 from the front. As the tension of the face thread increases, the face thread 55 exerts a rearward force on the plate 54. The magnetic sensor 53 outputs a voltage corresponding to the front-rear position of the plate 54, which is bent in the front-rear direction due to the tension of the face thread. The sewing machine 1 can obtain the tension of the face thread based on the output voltage of the magnetic sensor 53.

[0049] like Figure 1 Thus, the editing device 8 is mounted on the platform 50 and includes a display screen 86 and a speaker 87 (see reference). Figure 5 The device includes an operation panel 88, selection keys 89, etc. A display screen 86 shows various images. A speaker 87 outputs various sounds. Various information and instructions can be input to the editing device 8 via the operation panel 88 and selection keys 89. The operation panel 88 is a touch panel located on the front surface of the display screen 86. The selection keys 89 are located 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 keys 89.

[0050] Reference Figure 5 The electrical structure of the sewing system 10 is described below. The sewing machine 1 has a control unit 100. The control unit 100 includes a CPU 101, ROM 102, RAM 103, storage device 104, input / output interface (I / F) 106, and drive circuits 113 to 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, pedal 126, power switch 127, rotation detector 141, tension detector 18, electromagnetic element 128, and external connection I / F 130. The CPU 101 comprehensively controls the operation of the sewing machine 1. The ROM 102 stores various programs, etc. The RAM 103 temporarily stores various information. The storage device 104 is non-volatile and stores various information. The storage device 104 stores the sewing data 30 (see reference). Figure 7 Stitch 35 when sewing is performed (refer to) Figure 7 The stitch count is a combination of the number of stitches and the threshold used in the main processing described later. The sewing data 30 is represented in a sewing coordinate system that drives the X-axis motor 124 and the Y-axis motor 125.

[0051] Drive circuit 113 is connected to main motor 123. CPU 101 controls main motor 123 via drive circuit 113. For example, CPU 101 controls the rotational speed (sewing speed) of the output shaft of main motor 123. Encoder 133 is located on the output shaft of main motor 123 and connected to input / output I / F 106. Encoder 133 detects the rotational speed and position of the output shaft of main motor 123. The rotational position of the output shaft of 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 via drive circuit 114. Encoder 134 is located on the output shaft of X-axis motor 124 and connected to input / output I / F 106. Encoder 134 detects the rotational direction, rotational speed, and rotational position of the output shaft of X-axis motor 124. Drive circuit 115 is connected to Y-axis motor 125. CPU 101 controls Y-axis motor 125 via drive circuit 115. Encoder 135 is located on the output shaft of Y-axis motor 125 and connected to input / output I / F 106. Encoder 135 detects the rotation direction, rotation speed, and rotation position of the output shaft of Y-axis motor 125. Drive circuit 116 is connected to presser foot motor 129. CPU 101 controls presser foot motor 129 via drive circuit 116. Encoder 136 is located on the output shaft of presser foot motor 129 and connected to input / output I / F 106. Encoder 136 detects the rotation direction, rotation speed, and rotation position of the output shaft of presser foot motor 129.

[0052] CPU 101 drives main motor 123 to rotate upper shaft 22, thereby controlling the vertical oscillation of needle bar 9 and pressure bar 12 and the rotation of vertical shuttle. While driving main motor 123 based on sewing data, CPU 101 also drives X-axis motor 124 and Y-axis motor 125, and controls the position of holding body 60. Under this control, sewing machine 1 sews fabric 69.

[0053] The pedal 126 inputs various instructions to the control unit 100. For example, the operator presses the pedal 126 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 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 thread tension to the control unit 100. The CPU 101 controls the operation of the electromagnetic element 128. The external connection I / F 130 is connected to the external connection I / F 95 of the editing device 8 via cable 70.

[0054] The editing device 8 has a control unit 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. The input / output I / F 85 is connected to the CPU 81, ROM 82, RAM 83, storage device 84, display screen 86, speaker 87, operation panel 88, selection keys 89, and external connection I / F 95. The CPU 81 comprehensively controls the operation of the editing device 8. The ROM 82 stores the main processing program (described later), various symbols, etc. 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 on the display screen 86, sound output control on the speaker 87, and input control from the operation panel 88 and selection keys 89. The external connection I / F 95 is connected to the external connection I / F 130 of the sewing machine 1 via a cable 70.

[0055] Reference Figures 1-5 Here is a summary of the operation of the sewing machine 1. The operator holds the fabric 69 on the holder 60 on the needle plate 501. By inputting sewing instructions by the operator, 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. Driven by the main motor 123, the upper shaft 22 rotates, causing the needle bar 9 and the take-up lever 19 to move up and down. The shuttle 49 rotates synchronously with the rotation of the upper shaft 22.

[0056] The needle 11, descending together with the needle bar 9, penetrates the fabric 69 and passes through the needle-receiving hole 502 formed in the needle plate 501 (see reference). Figure 2 ).like Figure 4 As in (a), the surface line 55 descends to the vicinity of the needle eye 111 below the needle hole 502 in a ring shape. Figure 4 As in (b), the shuttle 49 rotates clockwise around the main view, thereby the shuttle tip 46 captures the annular thread 55. The period during which the shuttle tip 46 captures the annular thread 55 will be referred to as the shuttle capture period. The needle 11 rises above the fabric 69, and the shuttle 49 continues to rotate clockwise around the main view. The shuttle tip 46 pulls the annular thread 55 in the direction of rotation, thus expanding the diameter of the annular thread 55.

[0057] like Figure 4 As in (c), when the shuttle 49 passes through the looped facet 55, the facet 55 interweaves with the bottom line 67. The rotation direction of the shuttle 49 switches to the counterclockwise direction in the main view. Figure 4As in (d), the take-up lever 19 lifts the top thread 55 interlaced with the bottom thread 67. The period during which the take-up lever 19 lifts the top thread 55 is referred to as the take-up lever lifting period. The looped top thread 55 narrows, and the sewing machine 1 completes one stitch. In this embodiment, the sewing machine 1 performs one stitch for each rotation of the upper shaft 22. The sewing machine 1 forms multiple stitches 68 on the fabric 69 by repeating the above actions.

[0058] Reference Figures 6-8 ,use Figure 7 To illustrate the threshold setting process of sewing machine 1 with a specific example: When the operator turns on the power of sewing machine 1 and inputs the start instruction, CPU 101 reads the program and sewing data 30 from ROM 102 and begins the threshold setting process.

[0059] like Figure 6 In that case, CPU 101 acquires sewing data 30 (S51). For example... Figure 7 In this specific example, the sewing data 30 includes data for forming rectangular stitches 35 based on needle points P1 to P70 according to a predetermined sewing sequence. The needle point is a predetermined position where the needle 11, mounted on the needle bar 9, pierces the fabric 69. Needle point P1 is the initial start point of the sewing sequence, and needle point P70 is the final end point. The stitches based on needle points P1 to P3 are formed in the direction indicated by arrow J1, and the stitches based on needle points P4 to P70 are formed counterclockwise from needle point P3 in the direction indicated by arrows J2 to J6. The editing device 8 can output the sewing data 30 to the sewing machine 1. In the sewing machine 1, the CPU 101 receives the sewing data 30 output by the editing device 8. CPU 101 sets the count N for the needle drop points P1 to P70 of the received sewing data 30, which is read in order 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 according to the sewing data 30. Driven by the main motor 123, the upper shaft 22 rotates, causing the needle bar 9 and the take-up lever 19 to move up and down. The shuttle 49 rotates synchronously with the rotation of the upper shaft 22.

[0060] CPU101 determines whether the detection timing (phase) for surface tension is based on the upper shaft angle obtained from the detection result of encoder 133 (S53). For example... Figure 8 In this way, during sewing, the tension of the thread and the height of the lower end (needle tip) of the needle 11, along with the upper shaft angle, change periodically with the sewing period as the unit cycle. The sewing period is the time during which one stitch is made. Figure 8The right-hand vertical axis represents the height of the lower end of the needle 11 relative to the upper surface of the needle plate 501. When the upper axis angle is H1 or H2, the lower end of the needle 11 is at the same height as the upper surface of the fabric 69 placed on the upper surface of the needle plate 501. That is, the period from upper axis angle H1 to H2 is the penetration period of the needle 11 into the fabric 69. The periods when the upper axis angle is less than H1 and greater than H2 are the non-penetration periods when the needle 11 is above the fabric 69. The sewing period includes the take-up lever lifting period and the shuttle capture period. The thread tension has peaks during the take-up lever lifting period and the shuttle capture period within the sewing period. In this embodiment, the CPU 101 determines the thread tension based on the upper axis angle obtained from the encoder 133 (the determination timing). In this embodiment, the CPU 101 alternates between a first sewing period, from the start of sewing until a predetermined number of stitches are sewn, and a second sewing period that follows the first sewing period, to determine the timing of the detection. The length of the first sewing period can be set appropriately; in this embodiment, it is the period after the start of sewing when the number of stitches is less than 10. The CPU 101 uses the thread tension detected by the tension detector 18 during the shuttle capture period to determine the presence or absence of the bottom thread 67 relative to the stitch during the first sewing period. The CPU 101 uses the thread tension detected by the tension detector 18 during the take-up lever lifting period to determine the presence or absence of the bottom thread 67 relative to the stitch during the second sewing period. The CPU 101 determines whether it is in the first sewing period or the second sewing period based on a count N to determine the detection timing. If it is not a detection timing (S53: No), the CPU 101 remains in standby mode until the detection timing is reached.

[0061] When the detection timing is right (S53: Yes), the CPU 101 stores the detection result output by the tension detector 18 as the tension corresponding to the count N (S54). The CPU 101 determines whether the count N is the last stitch count of the sewing data 30 acquired in S51 (S55). If it is not the last stitch count (S55: No), the CPU 101 increments the count N by 1 (S56) and returns the processing to S53. If it is the last stitch count (S55: Yes), the CPU 101 stops sewing based on the sewing data 30 (S57). The CPU 101 determines whether to continue processing (S58). In this embodiment, the CPU 101 acquires multiple sets of data corresponding to the stitch count and tension by executing the processes of S52 to S57 multiple times, and acquires the average value and standard deviation of the tension for each stitch count. The number of sets can be appropriately determined, for example, any of 5 to 20. The operator of sewing machine 1 changes the position of fabric 69 relative to the holder 60 and inputs a continuation instruction to perform the processing in S52 to S57. When the continuation instruction is detected (S58: Yes), CPU 101 returns the processing to S52.

[0062] If no continuation instruction is detected (S58: No), the CPU101 sets a threshold for each stitch based on the corresponding data of multiple sets of stitch counts and tension (S59). The CPU101 sets the threshold of the stitch count (N) during the first sewing period, i.e., the first threshold H1 (N), according to equation (1), and sets the threshold of the stitch count (N) during the second sewing period, i.e., the second threshold H2 (N), according to equation (2).

[0063] First threshold H1(N) = Average tension (N) - C1 × Standard deviation (N) ... Equation (1)

[0064] Second threshold H2(N) = Average tension (N) - C2 × Standard deviation (N) ... Equation (2)

[0065] Here, the average tension (N) is the average tension corresponding to the number of stitches (N), and the standard deviation (N) is the standard deviation of the tension corresponding to the number of stitches (N). C1 and C2 are constants, which can be the same or different from each other. C1 and C2 can be set by the operator of the sewing machine 1, or they can be automatically set by the CPU 101 according to the sewing conditions. As an example in this embodiment, 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 it in the storage device 104. The CPU 101 completes the threshold setting process through the above steps.

[0066] Reference Figures 9-12 The text then describes the sewing process of sewing machine 1. When the operator specifies the sewing data and inputs the start instruction, CPU 101 reads the program from ROM 102 and begins sewing. Figure 9 The sewing process. As a specific example of determining the presence or absence of the bottom line 67 of the stitch when sewing according to sewing data 30, using... Figures 10-12Specific examples D3 to D6 are provided. Example D3 illustrates the relationship between top thread tension and stitch count (N) when the bottom thread 67 is present throughout the first sewing period. Example D4 illustrates the relationship between top thread tension and stitch count (N) when the bottom thread 67 is absent at the start of sewing. Example D5 illustrates the relationship between top thread tension and stitch count (N) when the second threshold H2 is set to C2 of 3, and the bottom thread 67 disappears (bottom thread is used up) midway through the second sewing period. Example D6 illustrates the relationship between top thread tension and stitch count (N) when the second threshold H2 is set to C2 of 2, and multiple-needle simulated sewing is performed during the second sewing period. Furthermore, simulated sewing refers to a poor sewing condition where only the top thread 55 forms a stitch-like mark, appearing as if a stitch has been formed, but the bottom thread 67 is not interwoven with the top thread 55. Multiple-needle simulated sewing refers to a sewing example in which this simulated sewing is performed multiple times. In the case of simulated sewing, the bottom line 67 is not supplied sequentially.

[0067] like Figure 9 In this case, CPU 101 performs a count initialization process (S1). CPU 101 sets the counts E and F, which are stored in RAM 103 to count the number of consecutively detected anomalies, to 0, and sets the count N, which is used to count the number of stitches, to 1. CPU 101 determines whether it is within the first sewing period based on the count N (S2). If it is within the first sewing period (S2: Yes), CPU 101 determines whether the rotation of the bobbin B is detected based on the detection result of the rotation detector 141 (S3). In specific example D3, the rotation of the bobbin B is detected (S3: Yes), CPU 101 determines that there is a bottom line 67 relative to the stitch, sets the count E for the first sewing period to 0 (S18), and then performs the process described later in S21. In specific example D4, if the detection indicates no rotation of the bobbin B (S3: No), the CPU 101 determines whether the thread tension detected by the tension detector 18 at a predetermined time during the first sewing period is greater than the first threshold H1(N) set in S59 (S4). The CPU 101 uses the first threshold H1(N) corresponding to the count N based on the combination of the number of stitches (N) stored in the storage device 104 and the first threshold H1(N). Figure 10Thus, when the count N is 1, the tension of the thread in specific example D4, represented by the white quadrilateral, is greater than the first threshold H1 (1) represented by the white circle (S4: Yes). Therefore, the CPU 101 determines that there is a bottom line 67 relative to the stitch and sets the count E to 0 (S18). Then, the processing described in S21 (described later) is performed. Thus, 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 CPU 101 determines that there is a bottom line 67 relative to the stitch. On the other hand, when the count N is any one of 3 to 6, the tension of the thread in specific example D4 is less than or equal to the first threshold H1 (N) (S4: No). Therefore, the CPU 101 increments the count E for detecting the abnormality of the bottom line 67 by 1 (S5).

[0068] CPU 101 determines whether the count E is greater than the count threshold (S6). The count threshold can be preset to a value smaller than 9, which is the maximum number of stitches included in the first sewing period. In this embodiment, the count threshold is 3. When the count N is 6, the count E in specific example D4 is 4, which is greater than the count threshold (S6: Yes). Therefore, CPU 101 determines that there is no bottom thread 67 relative to the stitch (S17). CPU 101 may also output an instruction to the editing device 8 to display the determination result on the display screen 86. If the sewing machine 1 has a notification unit such as an LED light, CPU 101 may also have the notification unit notify the determination result that there is no bottom thread 67 relative to the stitch. Thus, 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 below the first threshold H1 (N) (S4: Yes), CPU 101 determines that there is no bottom thread 67 relative to the stitch (S17). In this embodiment, if the tension detected by the tension detector 18 is below the first threshold H1(N) for more than a certain number of consecutive occurrences (S4: No, S6: Yes) and the rotation detector 141 detects no rotation of the bobbin B (S3: No), the CPU 101 determines that there is no bobbin thread 67 relative to the stitch (S17). The CPU 101 terminates the sewing based on the sewing data 30 midway through the sewing process (S23), thus ending the sewing process. In addition, in this embodiment, the absence of bobbin thread 67 (relative to the stitch) means that the bobbin thread 67 has been used up, resulting in a state where the bobbin thread is exhausted, or that the bobbin thread 67 has detached during fabric feeding and is not interwoven with the top thread 55.

[0069] In specific example D4, when the count N is below 5, the count E is below the count threshold (S6: No). Therefore, CPU 101 determines that there is a bottom line 67 relative to the stitch (S7) and determines whether the count N is the last stitch (S21). When the count N is not the last stitch (S21: No), CPU 101 increments the count N by 1 (S22), causing the process to return to S2. When the count N is the last stitch (S21: Yes), CPU 101 ends the sewing (S23), thus ending the sewing process.

[0070] When it is not the first sewing period (S2: No), CPU 101 determines whether the thread tension detected by tension detector 18 at a predetermined time during the second sewing period is greater than the second threshold H2(N) set in S59 (S11). CPU 101 uses the second threshold H2(N) corresponding to the count N based on the combination of the number of stitches (N) stored in storage device 104 and the second threshold H2(N). Figure 11 As in (C), in specific example D5, when the count N is 10, the tension of the thread represented by the black circle is greater than the second threshold H2 (10) represented by the white quadrilateral (S11: Yes). Therefore, CPU101 determines that there is a bottom line 67 relative to the stitch, sets the count F during the second sewing period to 0 (S18), and then performs the aforementioned processing S21. Figure 12 As in example (C), in specific example D6, when the count N is 10, the thread tension represented by the black circle is below the second threshold H2(N) represented by the white quadrilateral (S11: No). Therefore, the CPU 101 outputs an instruction to the editing device 8 to display an abnormality detected on the display screen 86 (S12). If the sewing machine 1 has a notification unit such as an LED light, the CPU 101 can also cause the notification unit to notify that an abnormality has been detected. The CPU 101 increments the count F during the second sewing period by 1 (S13). The CPU 101 determines whether the count F is greater than the number of times threshold (S14). The number of times threshold in S14 can be the same as or different from the number of times threshold in S6. The number of times threshold in this embodiment is, for example, 5.

[0071] In specific example D6, when the count N is 10, the count F is 1, which is below the count threshold (S14: No). Therefore, the CPU 101 determines whether the thread tension detected by the tension detector 18 at a predetermined time during the second sewing period is greater than the third threshold (S15). The third threshold is less than the second threshold. The third threshold is a threshold for detecting cases where there is no bottom thread 67 interlacing at the stitch. In specific example D6, when the count N is 10 and the thread tension is greater than the third threshold (S15: Yes), the CPU 101 performs the process S21. In specific example D6, when the count N is 11 and the thread tension is greater than the second threshold H2(N) (S11: Yes), the CPU 101 determines that there is bottom thread 67, sets the count F to 0 (S18), and then performs the aforementioned process S21. Thus, in specific example D6, there is a situation where the thread tension is below the second threshold H2(N). However, since there is no period during which the number of consecutive occurrences of the thread tension being below the second threshold H2(N) exceeds a threshold, it is determined that a bottom thread 67 exists throughout the entire second sewing period. When the thread tension is below the third threshold (S15: No), the CPU 101 determines that there is no bottom thread 67 relative to the stitch (S17) and ends the sewing based on the sewing data 30 (S23), thereby ending the sewing process. That is, the CPU 101 detects that there is no bottom thread 67 relative to the stitch when the thread tension is below the third threshold at least once (S17).

[0072] On the other hand, in specific example D5, when the count N is 36, the count F is 6, which is greater than the count threshold (S14: Yes). Therefore, the CPU 101 determines whether the rotation detector 141 has detected the rotation of the bobbin B (S16). When the rotation detector 141 detects that rotation exists (S16: Yes), the CPU 101 determines that there is a bottom line 67 relative to the stitch (S19) and performs the processing in S21. Thus, when the tension detected by the tension detector 18 is below the second threshold H2 (N) and the rotation detector 141 detects that the bobbin B has rotated (S16: Yes), the CPU 101 determines that there is a bottom line 67 relative to the stitch (S19).

[0073] When the rotation detector 141 detects no rotation (S16: No), the CPU 101 determines that there is no bottom thread 67 relative to the stitch (S17). Similarly, when the tension detected by the tension detector 18 is below the second threshold H2(N) (S11: No) and the rotation detector 141 detects no rotation of the bobbin B (S16: No), the CPU 101 determines that there is no bottom thread 67 relative to the stitch (S17). In this embodiment, if the tension detected by the tension detector 18 is below the second threshold H2(N) for more than a certain number of consecutive occurrences (S11: No, S14: Yes) and the rotation detector 141 detects no rotation of the bobbin B (S16: No), the CPU 101 determines that the bottom thread 67 is exhausted (bottom thread used up) (S17). The CPU 101 terminates the sewing based on the sewing data 30 midway through the sewing process (S23), thus ending the sewing process.

[0074] Refer to the same implementation method as described above. Figure 9 The sewing process of the first modified example is explained. When the operator inputs the instruction to start sewing after specifying the sewing data 30, the CPU 101 reads the program from the ROM 102 and begins sewing. Figure 9 The sewing process of the first modified example. In the first modified example, the CPU 101 changes the judgment frequency between a first sewing period (from the start of sewing until a predetermined number of stitches are sewn) and a second sewing period (continuing after the first sewing period). The CPU 101 uses the detection results detected by the tension detector 18 during the thread take-up period and the shuttle capture period to determine the presence or absence of the bottom line 67 relative to the stitch during the first sewing period. The CPU 101 uses the detection results detected by the tension detector 18 during the thread take-up period to determine the presence or absence of the bottom line 67 relative to the stitch during the second sewing period. That is, the CPU 101 detects the top thread tension twice during one cycle of the up-and-down movement of the needle bar 9 in the first sewing period and performs judgment S4. The CPU 101 uses a first threshold H1(N) corresponding to the timing of the top thread tension detection to perform judgment S4. The CPU 101 detects the top thread tension once during one cycle of the up-and-down movement of the needle bar 9 in the second sewing period and performs judgment S11. Other processes are the same as in the above embodiment, so descriptions are omitted.

[0075] Reference Figure 13 The sewing process of the second variation is explained. In the sewing process of the second variation, the CPU 101 determines the presence or absence of the bottom line 67 of the stitch based on whether the proportion of detected anomalies relative to the count N is greater than a proportion threshold. When the operator inputs the sewing start instruction after specifying the sewing data 30, the CPU 101 reads the program from the ROM 102 and begins sewing. Figure 13 The sewing process. In Figure 13China and Figure 9 When the sewing process is the same, the same reference numerals should be used. For example... Figure 13 Therefore, in the sewing process of the second variation, S31 is used to replace S6, S32 is used to replace S14, and S33 is used to replace S18. This is consistent with... Figure 9 The sewing processes differ from each other. Below, we will discuss the differences between them. Figure 9 The different sewing processes S31 to S33 will be explained, while the explanation of other processes will be omitted.

[0076] In S31, CPU101 determines whether the ratio obtained by dividing count E by count N is greater than a ratio threshold (S31). The ratio threshold only needs to be preset to a value less than 1. For example, the ratio threshold is any value between 20% and 60%. When the ratio is greater than the ratio threshold (S31: Yes), CPU101 determines that there is no bottom line 67 relative to the line (S17). When the ratio is less than the ratio threshold (S31: No), CPU101 determines that there is a bottom line 67 relative to the line (S7).

[0077] In S32, CPU 101 determines whether the ratio obtained by dividing count F by the value obtained by subtracting 9 (the maximum number of stitches in the first sewing period) from count N (i.e., the number of stitches in the second sewing period) is greater than a ratio threshold (S32). The ratio threshold only needs to be preset to a value less than 1. The ratio threshold of S32 can be the same as or different from the ratio threshold of S31. The ratio threshold is, for example, any value between 5% and 10%. When the ratio is greater than the ratio threshold (S32: Yes), CPU 101 determines whether the rotation of bobbin B is detected based on the detection result of rotation detector 141 (S16). When the ratio is less than the ratio threshold (S31: No), CPU 101 determines whether the tension of the top thread detected by tension detector 18 at a predetermined time in the second sewing period is greater than a third threshold (S15). In S33, CPU 101 does not initialize counts E and F and determines that a bottom line 67 exists (S33). In the second variation, when the ratio threshold is set to 0.1, Figure 12 In the specific case of D6, if the ratio is greater than the ratio threshold (S32: Yes) and the rotation detector 141 detects that there is no rotation of the bobbin B (S16: No), the CPU 101 can determine that there is no bottom line 67 relative to the stitch, and in particular, it can determine that it is a multi-needle simulated sewing (S17).

[0078] In the above-described embodiments, the first modification, and the second modification, the sewing machine 1, needle bar 9, needle 11, tension detector 18, needle bar up-and-down movement mechanism 21, shuttle mechanism 48, shuttle 49, top thread 55, bottom thread 67, storage device 104, and rotation detector 141 are respectively examples of the sewing machine, needle bar, needle, tension detector, needle bar up-and-down movement mechanism, shuttle mechanism, shuttle, top thread, bottom thread, storage device, and motion detector of the present invention. Figure 9 The CPU 101 during the processing of S3 to S7 and S11 to S19 is an example of the bottom line determination unit of the present invention. Figure 9 The processes S3-S7 and S11-S19 are an example of the bottom-line judgment process of this invention. (Execution) Figure 13 The CPU 101 during the processing of S3~S5, S7, S11~S13, S15~S17, S19, and S31~33 is an example of the bottom line determination unit of the present invention. Figure 13 The processing of S3-S5, S7, S11-S13, S15-S17, S19, and S31-33 is an example of the bottom line judgment process of the present invention.

[0079] The sewing machine 1 of the above-described embodiments, the first modification, and the second modification includes a needle bar 9, a needle bar up-and-down movement mechanism 21, a shuttle 49, a shuttle mechanism 48, a tension detector 18, a rotation detector 141, and a CPU 101. The needle bar 9 is fitted with a needle 11 through which the top 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 located below the needle bar 9 and houses the bobbin B, which is wound with the bottom thread 67, in a rotatable manner. The shuttle mechanism 48 rotates the shuttle 49 synchronously with the up-and-down movement of the needle bar 9, capturing the looped top thread 55 inserted into the needle 11 and interweaving the top thread 55 with the bottom thread 67 to form a stitch. The tension detector 18 detects the tension of the top thread 55 or the bottom thread 67. The rotation detector 141 detects whether the bobbin B is rotating. The CPU 101 determines the presence or absence of the bottom thread 67 relative to the stitch based on whether the tension detected by the tension detector 18 is greater than a threshold and the detection result of the rotation detector 141 (S3-S7, S11-S19). Since the sewing machine 1 determines the presence or absence of the bottom thread 67 relative to the stitch based on whether the tension detected by the tension detector 18 is greater than a threshold and the detection result of the rotation detector 141, it can more accurately determine the presence or absence of the bottom thread 67 relative to the stitch compared to a device that only uses the tension detector 18 for judgment.

[0080] When the rotation detector 141 detects 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 CPU 101 of sewing machine 1 determines that a bottom thread 67 exists relative to the stitch (S18, S33). When the rotation detector 141 detects no rotation of the bobbin B (S3: No) and the tension detected by the tension detector 18 is below the first threshold H1(N) (S4: No), the CPU 101 determines that a bottom thread 67 exists relative to the stitch (S17). In sewing machine 1, even when no rotation of the bobbin B is detected, the presence of a bottom thread 67 relative to the stitch can be determined when the tension detected by the tension detector 18 is greater than the first threshold H1(N). In sewing machine 1, even when the rotation of the bobbin B temporarily stops, but it is assumed that the bottom thread 67 is intertwined with the top thread 55, the determination that a bottom thread 67 does not exist relative to the stitch can be avoided.

[0081] When the tension detected by the tension detector 18 is below the second threshold H2(N) (S11: No) and the rotation detector 141 detects no rotation of the bobbin B (S16: No), the CPU 101 of sewing machine 1 determines that there is no bottom thread 67 relative to the stitch (S17). When the tension detected by the tension detector 18 is below the second threshold H2(N) (S11: No) and the rotation detector 141 detects rotation of the bobbin B (S16: Yes), the CPU 101 determines that there is a bottom thread 67 relative to the stitch (S19). In sewing machine 1, even if the tension detected by the tension detector 18 is below the second threshold H2(N), it can still determine that there is a bottom thread 67 relative to the stitch when there is rotation of the bobbin B. In sewing machine 1, when the tension is relatively small, but the bobbin B continues to rotate, and it is assumed that the bottom thread 67 relative to the stitch is intertwined with the top thread 55, it can avoid determining that there is no bottom thread 67 relative to the stitch.

[0082] Between the first sewing period, from the start of sewing until a predetermined number of stitches are made, and the second sewing period, which follows the first sewing period, the CPU 101 of sewing machine 1 uses different thresholds for each period (S4, S11). By changing the threshold between the first and second sewing periods, sewing machine 1 can use thresholds that are adapted to both the first and second sewing periods to determine the presence or absence of the bottom line 67 of the stitch.

[0083] In the above-described embodiment and the first variation of the sewing machine 1, if the tension detected by the tension detector 18 is below a threshold value for a number of consecutive occurrences exceeding a threshold value (S4: No, S6: Yes) and the rotation detector 141 detects no rotation of the bobbin B (S3: No), it determines that there is no bottom line 67 relative to the stitch (S17). If the tension detected by the tension detector 18 is below a threshold value for a number of consecutive occurrences exceeding a threshold value (S11: No, S14: Yes) and the rotation detector 141 detects no rotation of the bobbin B (S3: No), it determines that there is no bottom line 67 relative to the stitch.

[0084] If the rotation detector 141 detects that there is no rotation of the bobbin B (S16: No), it determines that there is no bottom thread 67 relative to the stitch (S17). The sewing machine 1 can determine the presence or absence of the bottom thread 67 relative to the stitch based on its position.

[0085] To determine when the baseline has been used up. For example Figure 11 As in (A), when the bottom line 67 of the stitch disappears midway, although no abnormality is observed in the rotation speed indicated by the black circle during sewing, but as Figure 11 (B) Figure 11 As in (C), taking the disappearance of the bottom line 67 relative to the trace as an opportunity, the tension of the surface line continues.

[0086] Since the second threshold H2(N) continues to fall below, the sewing process described above allows for early detection of the disappearance of the bottom line 67 relative to the stitch. Furthermore, in the sewing machine 1, as...

[0087] Figure 11 As in (C), the presence or absence of the bottom thread 67 relative to the stitch is determined by using the tension detected by the tension detector 18 during the lifting of the thread take-up lever, thus enabling the sewing machine 1 to determine the presence or absence of the bottom thread 67 earlier than the thread take-up lever 1. Figure 11 (B) uses the tension detected by tension detector 18 during shuttle capture to...

[0088] Determine the presence or absence of the bottom line 67 relative to the line trace, and accurately detect the disappearance of the bottom line 675 relative to the line trace.

[0089] In the second variation, the CPU 101 of the sewing machine 1 has a ratio of tension below a threshold relative to the number of stitches already sewn, as detected by the tension detector 18, that is above a threshold (S4: No, S31:).

[0090] If (S1) the rotation detector 141 detects no rotation of the spindle B (S2) and determines that...

[0091] There is no bottom line 67 relative to the stitch (S17). The CPU101 detects tension below the threshold value when the tension detected by the tension detector 18 is 0 relative to the number of stitches already sewn, which is above the threshold value (S11:

[0092] No, S32: Yes) and the rotation detector 141 detects that there is no rotation of the spindle B (S16:

[0093] If no), it is determined that there is no bottom line 67 relative to the stitch (S17). In the sewing machine 1, it is possible to avoid making incorrect judgments about the presence or absence of sewing defects associated with the bottom line 67 based on the singular value of the tension detector 18.

[0094] like Figure 12 As in (A), under the case of multi-needle simulated sewing, the rotation speed 5, represented by the black circle, showed no abnormalities, such as Figure 12 (B) Figure 12 As in (C), due to the absence of continuous surface tension...

[0095] During the period below the second threshold H2(N), it is difficult to detect simulated sewing in the sewing process of the above embodiment. However, by performing the sewing process of the second variation, it is possible to appropriately detect simulated sewing based on the tension of the surface thread of multiple stitches and the presence or absence of the rotation of the bobbin B.

[0096] The sewing machine 1 in the above-described embodiments, the first modification, and the second modification further includes a storage device 104 that stores a combination of stitch count and threshold values. The CPU 101 uses a threshold value corresponding to the stitch count to make a judgment based on the combination stored in the storage device 104. The sewing machine 1 can use a threshold value that takes into account the stitch count to determine the presence or absence of the bottom thread 67 relative to the stitch. Since the sewing machine 1 can form the same stitch on the same fabric 69 based on the sewing data 30, the stitches corresponding to the stitch count in the sewing data become similar to each other. Therefore, in the sewing machine 1, when stitches are formed on the same fabric 69 according to the sewing data, the presence or absence of the bottom thread 67 relative to the stitch can be appropriately determined using a threshold value that takes into account the thickness of the fabric 69, whether it is curved, the feed rate, etc.

[0097] The CPU 101 uses the tension detected by the tension detector 18, acquired at a time corresponding to the number of stitches within one cycle of the up-and-down movement of the needle bar 9, to make a judgment. In the sewing machine 1, compared to using the tension detected by the tension detector 18, acquired at the same time regardless of the number of stitches, to determine the presence or absence of the bottom thread 67 relative to the stitch, it is possible to consider the influence of the stitch corresponding to the number of stitches when determining the presence or absence of the bottom thread 67 relative to the stitch. In this embodiment, the CPU 101 uses the detection result detected by the tension detector 18 during the shuttle capture period to determine the presence or absence of the bottom thread 67 relative to the stitch during the first sewing period. By setting the detection timing of the tension detector 18 in this way, the sewing machine 1 can better detect the absence of the bottom thread 67 during the first sewing period. On the other hand, as Figure 11 As shown, regarding the deviation of the surface tension from the second threshold H2 when the bottom line 67 of the trace disappears midway, compared to... Figure 11 (B) shows the detection results acquired during the shuttle capture period. Figure 11 The detection results obtained during the take-up lever lifting period shown in (C) are quite significant. Therefore, by using the detection results detected by the tension detector 18 during the take-up lever lifting period to determine the presence or absence of the bottom line 67 relative to the stitch during the second sewing period, the sewing machine 1 can better detect the absence of the bottom line 67 relative to the stitch during the second sewing period.

[0098] In the first modified example, the CPU 101 changes the frequency at which the tension detector 18 acquires detection results relative to one cycle of the up-and-down movement of the needle bar 9, according to the number of stitches in the stitch, and uses the tension detected by the tension detector 18 to make a judgment. In the sewing machine 1, compared to the case where the presence or absence of the bottom thread 67 is determined by using the tension detected by the tension detector 18, which is acquired at the same frequency regardless of the number of stitches, the presence or absence of the bottom thread 67 can be determined by taking into account the influence of the stitches corresponding to the number of stitches.

[0099] The sewing machine 1 also includes a take-up lever 19 that lifts the top thread 55, which is interwoven with the bobbin thread 67 by the shuttle 49. A tension detector 18 detects the tension of the top thread. The CPU 101 determines the presence or absence of the bobbin thread 67 relative to the stitch based on whether the tension detected by the tension detector 18 is greater than a threshold and the detection result of the rotation detector 141 during either the take-up lever lift-up period or the shuttle capture period. The sewing machine 1 can determine the presence or absence of the bobbin thread 67 relative to the stitch based on the top thread tension detected during the take-up lever lift-up period or the shuttle capture period. Since the top thread tension during the take-up lever lift-up period or the shuttle capture period is greater than the top thread tension during the period between the take-up lever lift-up period and the shuttle capture period, incorrect judgments can be avoided compared to the case where the CPU 101 makes a judgment during a period with relatively low top thread tension.

[0100] In addition to the embodiments described above, the present invention can be modified in various ways. The structure of the sewing machine 1 can also be modified appropriately; for example, it can be a sewing machine that does not use the holding body 60 to hold the fabric 69. The structure, configuration, and detection method of the tension detector 18 and the rotation detector 141 can be modified appropriately. The sewing machine 1 can also have the function of the editing device 8. Specifically, the tension detector 18 can be configured between the auxiliary thread clamp 15 and the main thread clamp 16 on the path of the top thread 55, or it can be configured on the path of the top thread 55 at a position downstream of the take-up lever 19. In addition, the sewing machine 1 of the above embodiment is a single-needle sewing machine with one needle 11 mounted on the needle bar 9, but it can also be a double-needle sewing machine with two needles mounted on the needle bar 9, or a sewing machine with three or more needles, in which multiple thread tension detection devices are configured to detect the tension of each top thread 55. Furthermore, in these cases, multiple rotation detectors 141 may be configured in the sewing machine 1 to detect the rotation of the bobbin B of each of the multiple shuttles 49. The tension detector 18 has a structure that uses a magnetic sensor 53, but it may also be that the force of the thread 55 is received by an electrostrictive element and the tension is detected based on its output.

[0101] The program used to process the sewing machine 1 only needs to be stored in the storage device 104 of the sewing machine 1 before the CPU 101 executes the program. Therefore, the method of obtaining the program, the acquisition path, and the device for storing the program can all be appropriately changed. Alternatively, the program executed by the CPU 101 can be received from other devices via cable or wireless communication and stored in a storage device such as flash memory. Other devices include, for example, a PC and a server connected via a network.

[0102] Some or all of the processing performed by the sewing machine 1 can also be performed by other electronic devices (e.g., ASICs) different from the CPU 101. The processing performed by the sewing machine 1 can also be distributed by multiple electronic devices (e.g., multiple CPUs). The order of the steps in the processing performed by the sewing machine 1 can be changed, steps can be omitted, or additional steps can be added as needed. The scope of the invention also includes the following method: the operating system (OS) running on the sewing machine 1 performs some or all of the processing using instructions from the CPU 101. For example, the following modifications can be appropriately applied to the above embodiments.

[0103] In the sewing machine 1 of the above embodiment, when the detected thread tension is below the second threshold (S11: No), the count of detected abnormalities is directly updated (S13). However, it is also possible to detect the presence or absence of bobbin B rotation before updating the count, and update the count only when bobbin B rotation cannot be detected. In this case, in the sewing machine 1, it is also possible not to perform the detection of bobbin B rotation in S16, and directly determine that there is no bottom line 67 relative to the stitch if the count exceeds the number threshold (S14: Yes) or the proportion exceeds the proportion threshold (S32: Yes) (S17).

[0104] Processes S11 to S16 can be performed during the first sewing period, and processes S3 to S7 can be performed during the second sewing period. The same process can also be performed between the first and second sewing periods. The threshold values ​​can be the same between the first and second sewing periods. The CPU 101 can also acquire the tension detected by the tension detector 18 at the same time between the first and second sewing periods. The CPU 101 can determine the presence or absence of the bottom line 67 relative to the stitch not for each stitch, but for example, it can determine the presence or absence of the bottom line 67 relative to the stitch for each predetermined number of stitches. The CPU 101 can also acquire the tension detected by the tension detector 18 at the same frequency between the first and second sewing periods. The number threshold and the proportion threshold can be 0. The CPU 101 can also determine that there is no bottom line 67 relative to the stitch if the tension detected by the tension detector 18 is below the threshold once and the rotation detector 141 detects no rotation of the bobbin B. The first threshold H1 and the second threshold H2 may not each correspond to the count N. For example, a shared value can be set for a portion or all of the multiple stitch counts. The tension detector 18 can also detect the tension of the bobbin thread 67. When the sewing machine 1 does not form a stitch based on sewing data, the thresholds can be changed accordingly based on conditions such as the material of the fabric 69, the top thread 55 or the bobbin thread 67, the thickness of the fabric 69, the type of stitch, the feed rate (stitch length), and the sewing speed. The above variations can be appropriately combined within a range without contradiction.

[0105] In the sewing machine 1 described above, the detection result of the presence or absence of rotation of the bobbin B based on the rotation detector 141 is used as the detection result of the presence or absence of bobbin B's movement. However, instead of the rotation detector 141, a bobbin thread balance detector that detects the change in the amount of bobbin thread 67 wound around the bobbin B can be used as the movement detector, and the presence or absence of change in bobbin thread balance can be used as the detection result of the presence or absence of bobbin B's movement. Specifically, the sewing machine 1 can also have an optical sensor as the movement detector, which detects the change in bobbin thread balance based on the change in the reflected light output by the optical sensor. This optical sensor has a light-transmitting part on the side of the bobbin sleeve that houses the bobbin B and a part of the flange of one of the bobbin B, and a reflective surface is formed on the inner wall of the plurality of flanges. It has an irradiation part that irradiates light from the light-transmitting part and a light-receiving part that receives the reflected light. Alternatively, in the sewing machine 1, a weight sensor that measures the weight of the bobbin B can be added to the shuttle 49 as the movement detector, and the presence or absence of change in bobbin thread balance can be detected based on the change in the output of the weight sensor. During the sewing process, when the bobbin B moves normally, the amount of bobbin thread 67 wound around the bobbin B will decrease accordingly with the sewing amount. Therefore, in the sewing machine 1 of this modified example, by detecting whether there is a change in the amount of bobbin thread 67 wound around the bobbin B, the presence or absence of bobbin B movement can be accurately detected.

Claims

1. A sewing machine characterized by comprising: a needle bar that mounts a needle through which a thread is threaded; a needle bar up-and-down movement mechanism that moves said needle bar up and down; a shuttle that is provided below said needle bar, the shuttle housing a bobbin on which a bobbin thread is wound in a rotatable manner; a shuttle mechanism that rotates said shuttle in synchronization with the up-and-down movement of said needle bar, catches said thread that is threaded in a loop shape by said needle and interweaves the thread with said bobbin thread, thereby forming a stitch; a tension detector that detects a tension of said thread or said bobbin thread; a motion detector that detects the presence or absence of a motion of said bobbin; a bobbin thread judging section that judges the presence or absence of said bobbin thread with respect to said stitch based on whether said tension detected by said tension detector is greater than a threshold value and the detection result of said motion detector.

2. The sewing machine according to claim 1, characterized in that: said bobbin thread judging section judges that said bobbin thread is present with respect to said stitch when said motion detector detects that said motion of said bobbin is not present and said tension detected by said tension detector is greater than a first threshold value as said threshold value, said bobbin thread judging section judges that said bobbin thread is not present with respect to said stitch when said motion detector detects that said motion of said bobbin is not present and said tension detected by said tension detector is equal to or less than said first threshold value.

3. The sewing machine according to claim 1 or 2, characterized in that: said bobbin thread judging section judges that said bobbin thread is not present with respect to said stitch when said tension detected by said tension detector is equal to or less than a second threshold value as said threshold value and said motion detector detects that said motion of said bobbin is not present, said bobbin thread judging section judges that said bobbin thread is present with respect to said stitch when said tension detected by said tension detector is equal to or less than said second threshold value and said motion detector detects that said motion of said bobbin is present.

4. The sewing machine according to claim 1 or 2, characterized in that: said bobbin thread judging section judges using different threshold values from each other during a first sewing period from the start of sewing until sewing of a predetermined number of stitches is performed and during a second sewing period that is consecutive to said first sewing period.

5. The sewing machine according to claim 1 or 2, characterized in that: said bobbin thread judging section judges that a bobbin thread is used up when the number of times that said detection result of said tension detector is equal to or less than said threshold value consecutively appears is equal to or greater than a threshold value and said motion detector detects that said motion of said bobbin is not present.

6. The sewing machine according to claim 1 or 2, characterized in that: said bobbin thread judging section judges that said bobbin thread is not present with respect to said stitch when the proportion that said detection result of said tension detector is equal to or less than said threshold value with respect to the number of stitches that have been sewn is equal to or greater than a threshold value and said motion detector detects that said motion of said bobbin is not present.

7. The sewing machine according to claim 1 or 2, characterized in that: ​ ​ The sewing machine further has a storage section that stores a combination of the number of stitches and the threshold value, The bobbin thread judging section judges using the threshold value corresponding to the number of stitches based on the combination stored in the storage section.

8. The sewing machine according to claim 1 or 2, characterized in that The bobbin thread judging section judges using the tension detected by the tension detector acquired at a timing corresponding to the number of stitches within one cycle of the up-and-down movement of the needle bar.

9. The sewing machine according to claim 1 or 2, characterized in that 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 corresponding to the number of stitches, and judges using the tension detected by the tension detector.

10. The sewing machine according to claim 8, characterized in that The sewing machine further has a thread take-up lever that lifts the face thread interwoven with the bobbin thread by the shuttle, The tension detector detects the tension of the face thread, The bobbin thread judging section judges the presence or absence of the bobbin thread with respect to the stitch based on whether the detection result of the tension detector at the timing during either the thread take-up lever lift period in which the thread take-up lever lifts the face thread or the shuttle capture period in which the shuttle captures the face thread is greater than the threshold value and the detection result of the action detector.

11. The sewing machine according to claim 1 or 2, characterized in that The action detector detects the presence or absence of rotation of the bobbin.

12. The sewing machine according to claim 1 or 2, characterized in that The action detector detects the presence or absence of a change in the amount of the bobbin thread wound around the bobbin.

13. A bobbin thread judging method executed by a control section of a sewing machine having a needle bar that fits a needle into which a face thread is threaded, a needle bar up-and-down movement mechanism that moves the needle bar up and down, a shuttle provided below the needle bar that houses a bobbin core on which a bobbin thread is wound in a rotatable manner, a shuttle mechanism that rotates the shuttle in synchronization with the up-and-down movement of the needle bar, captures the loop-like face thread threaded into the needle and interweaves the face thread with the bobbin thread, thereby forming a stitch, a tension detector that detects the tension of the face thread or the bobbin thread, and an action detector that detects the presence or absence of an action of the bobbin core, the bobbin thread judging method comprising a bobbin thread judging process in which the presence or absence of the bobbin thread with respect to the stitch is judged based on whether the tension detected by the tension detector is greater than a threshold value and the detection result of the action detector. ​

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