JP2019005502A - sewing machine - Google Patents

Abstract

Provided is a sewing machine that can smoothly control a rotation angle phase of an output shaft of a motor that adjusts a tension of a needle thread and that can stably rotate an output shaft of the motor. A sewing machine includes a thread tension motor and a thread tension plate. The thread tension disc is fixed to the output shaft of the thread tension motor. The operator winds the upper thread around the thread tension plate. As the thread tension motor is driven to rotate, the tension applied to the upper thread changes. The CPU of the sewing machine calculates and specifies the energization pattern for each of the plurality of coils of the thread tension motor by calculation control based on the detection result of the encoder (S53). The CPU energizes the plurality of coils of the thread tension motor with the specified conduction pattern (S55), and controls the drive of the thread tension motor. Every time the CPU calculates and specifies the energization pattern by calculation control (S53), the CPU energizes the plurality of coils (S55). Therefore, the value of the current flowing through the plurality of coils changes smoothly. [Selection diagram] FIG.

Description

  The present invention relates to a sewing machine.

  A sewing machine that controls the tension of the upper thread during sewing with a pulse motor is known. For example, the sewing machine disclosed in Patent Document 1 includes a thread tension plate, a pulse motor, an encoder, an operation panel, and a sewing machine motor. The pulse motor has an output shaft. The sewing machine controls driving of the pulse motor by inputting a driving pulse to the pulse motor driving unit. The thread tension plate is fixed to the output shaft. Upper thread is wound around the thread tension plate. The encoder detects the rotational position of the output shaft. The operator inputs the upper thread tension to the sewing machine via the operation panel. When the sewing machine motor is driven, the sewing machine executes a sewing operation. When the sewing machine motor is driven, the sewing machine drives and controls the pulse motor based on the detection result of the encoder so that the tension of the upper thread becomes the inputted tension.

JP 2009-89823 A

  In the sewing machine, since the control executed for the pulse motor is pulse control, the drive signal input to the pulse motor is a rectangular wave. Therefore, when the pulse motor is driven, the rotational position that is the target of the output shaft becomes discrete, and the sewing machine may not be able to smoothly control the rotational position of the output shaft of the pulse motor. In addition, when the sewing machine shortens the pulse signal transmission interval and shortens the width of the rectangular wave so that the rotational position of the output shaft can be controlled with high precision, the output shaft of the pulse motor can There is a possibility that it cannot follow the movement. That is, the output shaft of the pulse motor may not be able to rotate stably.

  An object of the present invention is to provide a sewing machine that can smoothly control the rotation angle phase of an output shaft of a motor that adjusts the tension of the upper thread and that can stably rotate the output shaft of the motor.

The sewing machine of the present invention has a needle bar that can move up and down to attach a sewing needle, and shows sewing means for sewing a cloth with the sewing needle, a thread tension plate around which an upper thread is wound, and tension applied to the upper thread. A motor having an input unit for inputting tension information, an output shaft connected to the thread tension plate, and a plurality of coils arranged along the rotation direction of the output shaft, and detecting a rotation angle phase of the output shaft An encoder that performs the control, and a control unit that drives and controls the sewing means and the motor.
A sewing control unit that drives and controls the sewing means to sew the cloth, before the sewing of the cloth by the sewing control unit, a tension acquisition unit that acquires the tension information input to the input unit, and the sewing control The tension applied to the upper thread by controlling the drive of the motor based on the tension information acquired by the tension acquisition unit and the detection result of the encoder at the time of sewing the cloth by the unit In the sewing machine including the motor drive control unit that makes the tension indicated by the motor drive control unit, the motor drive control unit sets an energization pattern for each of the plurality of coils in a cycle shorter than a cycle in which the needle bar moves up and down. A specific control unit that is calculated and specified by calculation control based on the detection result, and the energization specified by the specific control unit every time the specific control unit specifies the energization pattern Characterized in that it comprises a power supply controller for energizing the plurality of coils in turn.

  According to the above configuration, the specific control unit calculates and specifies the energization patterns for the plurality of coils by calculation control based on the detection result of the encoder. Each time the specific control unit specifies the energization pattern, the energization control unit energizes the plurality of coils with the energization pattern specified by the specific control unit. Since the current value flowing through the motor coil changes smoothly, the sewing machine can smoothly control the rotation angle phase of the motor output shaft, and the motor output shaft rotates stably following the sewing operation by the sewing controller. it can. Therefore, a sewing machine that can smoothly control the rotation angle phase of the output shaft of the motor for adjusting the tension of the upper thread and can stably rotate the output shaft of the motor is realized.

  In the sewing machine, the sewing means is provided with a cloth placement portion for placing the cloth, and an annular upper thread that is provided below the needle bar and is inserted into the sewing needle when the sewing needle penetrates the cloth. A rotary hook that captures and entangles the lower thread, and a sewing machine motor that drives the needle bar and the rotary hook, and the sewing control unit sews the cloth by driving and controlling the sewing machine motor, The control unit determines whether or not a sewing failure has occurred in which the amount of use of the upper thread at the time of sewing of the cloth by the sewing control unit deviates from a predetermined range based on the detection result of the encoder. A determination unit may be provided. Since the sewing failure determination unit can determine whether or not sewing failure has occurred, the sewing machine can stabilize the sewing operation.

  In the sewing machine, the sewing failure includes a stitch that the rotary hook fails to capture the upper thread, and the sewing failure determination unit is configured to perform the stitch skip in a specific sewing operation for forming a specific stitch on the cloth. A skip-jump determining unit that determines whether or not the hook has occurred, and the skip-jump determining unit includes a hook catching period in which the rotary hook catches the upper thread at the start of the hook catching period. It may be determined whether or not the skip has occurred by determining whether or not the rotation amount of the output shaft relative to the initial rotation angle phase of the output shaft is less than a specific value. The sewing machine can detect skipping.

  In the sewing machine, the sewing control unit may include a notification unit that notifies the occurrence of the stitch skip when the stitch skip determination unit determines that the stitch skip has occurred. The operator can recognize the occurrence of skipping.

  In the sewing machine, the sewing means includes a balance that moves up and down by driving of the sewing machine motor, and the rotary hook pulls up the upper thread that is entangled with the lower thread. The upper thread and the lower thread that form the seam when the upper thread and the lower thread are unbalanced, and the sewing failure determination unit includes a sewing operation that forms a specific seam on the cloth. A thread tightening failure determination unit that determines whether or not the thread tightening failure has occurred, wherein the thread tightening failure determination unit is based on an initial rotation angle phase of the output shaft at the start of the specific sewing operation; It may be determined whether or not the thread tightening failure has occurred by determining whether or not the rotation amount of the output shaft is outside a predetermined range. The sewing machine can detect a tightening defect in the sewing defect determination section.

  In the sewing machine, the sewing control unit may include a notification unit that notifies the thread tightening failure when the thread tightening failure determining unit determines that the thread tightening failure has occurred. The operator can recognize the occurrence of thread tightening failure.

  In the sewing machine, the sewing means includes a balance that moves up and down by driving of the sewing machine motor, and the rotary hook pulls up the upper thread entangled with the lower thread. The sewing failure determination unit includes a thread breakage determination unit that determines whether or not the thread breakage has occurred in a specific sewing operation for forming a specific stitch on the cloth. The rotation amount of the output shaft based on the initial rotation angle phase of the output shaft at the start of the hook catching period is a first predetermined value in the hook catching period in which the rotary hook catches the upper thread. And the amount of rotation of the output shaft based on the initial rotation angle phase of the output shaft at the start of the balance pulling period is a second amount in the balance pulling period, which is a period during which the balance pulls up the upper thread. Less than the specified value By determining whether there is, it may determine whether the thread breakage has occurred. The sewing machine can detect thread breakage at the sewing failure determination section.

  In the sewing machine, the control unit may include a stop control unit that stops the driving of the sewing means and the motor when the sewing failure determination unit determines that the sewing failure has occurred. The sewing machine stops sewing when a sewing failure occurs. Therefore, the sewing machine in which the sewing failure has occurred does not continue sewing.

The perspective view of the sewing machine 1. FIG. Sectional drawing of the thread tension control apparatus 60. FIG. The conceptual diagram of the output shaft 18 and the coil 33 of the thread tension motor 16. FIG. FIG. 2 is an electric block diagram of the sewing machine 1. Explanatory drawing which graphed the 1st relational expression and the 2nd relational expression. Explanatory drawing which shows the flow in which the rotary hook 39 catches the upper thread | yarn 6. FIG. Explanatory drawing which shows the movement curve of the needle bar 11, the balance 51, and the rotary hook 39. FIG. FIG. 3 is an explanatory diagram that graphs the relationship between the phase difference of the output shaft 18 and the torque generated by the thread tension motor 16. The flowchart of a sewing process. The flowchart of a thread tension motor drive process. The flowchart of a skipping determination process. Explanatory drawing which shows the flow which skips. The flowchart of a thread breakage determination process. The flowchart of a thread | tightening defect determination process.

  Embodiments of the present invention will be described below. In the following description, left, right, front, back, and top and bottom indicated by arrows in the figure are used. The sewing machine 1 shown in FIG. 1 is a tacking sewing machine that forms tacking stitches on the cloth 105.

  The schematic structure of the sewing machine 1 will be described with reference to FIGS. The sewing machine 1 includes a bed 2, a pedestal 3, and an arm 4. The bed 2 is a base of the sewing machine 1 and is installed on a work table extending horizontally. The bed portion 2 includes a bed main body portion 7 and a cylinder bed portion 8. The bed main body 7 is substantially box-shaped. The cylinder bed portion 8 extends forward from the bed main body portion 7. The inside of the bed main body portion 7 and the inside of the cylinder bed portion 8 communicate with each other. The cylinder bed portion 8 includes a needle plate 26 on the upper surface of the front end portion. The operator places the cloth 105 (see FIG. 6) on the needle plate 26. The needle plate 26 has a needle hole. The pedestal part 3 extends upward from the rear part of the bed main body part 7. The arm part 4 extends forward from the upper part of the columnar part 3 and faces the bed part 2. A front end portion of the arm portion 4 is a tip portion 5. The tip portion 5 includes a right wall portion 5A and a through hole 5B (see FIG. 2). The right wall portion 5 </ b> A is a wall portion on the right side of the tip portion 5. The through hole 5B penetrates the right wall portion 5A in the left-right direction.

  As shown in FIG. 4, the sewing machine 1 includes a control device 30, an operation unit 46, and a pedal 38. The control device 30 is fixed to the lower surface of the work table. The control device 30 controls the operation of the sewing machine 1. The operation unit 46 is fixed to the upper surface of the work table. The operation unit 46 includes a display unit 48 and operation buttons 47. The display unit 48 displays various information. The operation button 47 detects various information input by the operator. The operation button 47 includes a power button.

  As shown in FIG. 1, the sewing machine 1 includes a sewing mechanism 12. The sewing mechanism 12 includes a sewing machine motor 27 (see FIG. 4), an upper shaft 15, a linkage, a balance mechanism, a needle bar vertical movement mechanism, a shuttle driving mechanism, and a cloth feeding device 20. The sewing machine motor 27 is supported at the rear part of the arm part 4. The upper shaft 15 extends in the front-rear direction inside the arm portion 4. The rear end portion of the upper shaft 15 is connected to the drive shaft of the sewing machine motor 27 through a joint. The upper shaft 15 is rotated by driving the sewing machine motor 27. The front end portion and the rear end portion of the upper shaft 15 are coaxial with each other. The upper shaft 15 includes a crank portion in the vicinity of the rear end portion. The crank portion is a curved portion that curves at a position deviated from the axis of the front end portion and the rear end portion of the upper shaft 15. The linkage extends in the vertical direction inside the pedestal 3. The upper end portion of the linkage is connected to the crank portion so as to be rotatable.

  The balance mechanism and the needle bar up-and-down moving mechanism are supported by the tip 5. The balance mechanism includes a balance crank and a balance 51. The balance crank is connected to the front end portion of the upper shaft 15. The balance 51 is provided on the balance crank. As the balance crank rotates together with the upper shaft 15, the balance 51 moves up and down. The balance 51 has an upper thread insertion hole. The balance 51 holds the upper thread 6 inserted through the upper thread insertion hole. The upper thread 6 is unwound from an upper thread bobbin that is a thread supply source, and reaches the upper thread insertion hole of the balance 51 via a thread tension control device 60 described later.

  The needle bar vertical movement mechanism includes a needle bar crank rod, a needle bar 11 and the like. The needle bar crank rod is rotatably connected to the balance crank and extends in the vertical direction. The needle bar 11 extends in the vertical direction and is rotatably connected to the needle bar crank rod. A sewing needle 10 is attached to the lower end of the needle bar 11. The sewing needle 10 has an eye hole 10A at the lower end. The eye hole 10A inserts and holds the upper thread 6 via the upper thread insertion hole of the balance 51. The needle bar 11 moves up and down together with the sewing needle 10 as the needle bar crank rod reciprocates as the balance crank rotates.

  The shuttle driving mechanism is provided inside the bed 2. The shuttle driving mechanism includes a rotation shaft, an arm portion, a lower shaft, and a rotary shuttle 39. The rotation shaft is rotatably supported by the bed main body 7 and extends in the front-rear direction inside the bed main body 7. The arm portion is fixed to the rotation shaft and protrudes rightward from the rotation shaft. The tip of the arm is pivotably connected to the lower end of the linkage. As the linkage reciprocates as the upper shaft 15 rotates, the arm reciprocates around the rotation shaft. The lower shaft extends in the front-rear direction inside the bed main body portion 7 and the cylinder bed portion 8 and is rotatable. The lower shaft is below the upper shaft 15 and to the left of the rotation shaft. The lower shaft is connected to the rotating shaft via the connecting portion. The lower shaft reciprocates in conjunction with the rotation shaft.

  The rotary hook 39 is provided at the front end of the lower shaft and is below the needle hole. The rotary hook 39 is rotatable around the lower shaft. The rotary hook 39 includes a sword tip 36, a bobbin case 32, and a drawer 34 (see FIG. 6). The sword tip 36 is a part of the outer peripheral portion of the rotary hook 39 and projects toward the front view clockwise with the lower shaft as the center. The bobbin case 32 accommodates the bobbin around which the lower thread 9 is wound. The drawing portion 34 pulls the lower thread 9 fed out from the bobbin to the outside.

  The cloth feeding device 20 will be described. The cloth feeding device 20 includes a movable body 31, a swing shaft, a feed base 37, a swing motor 41 (see FIG. 4), a feed plate, a rack shaft 22, a moving motor 42 (see FIG. 4), a presser arm 23, and a presser foot. A motor 43 (see FIG. 4) is provided. The movable body 31 is provided so as to be movable back and forth within the bed main body portion 7. The swing shaft is a shaft that is fixed to the movable body 31 and extends in the vertical direction, and protrudes upward from the bed main body portion 7. The feed base 37 is connected to the movable body 31 inside the bed main body 7 and is provided on the swing shaft so as to be swingable. Therefore, the feed base 37 can move back and forth together with the movable body 31 and can swing in the left-right direction around the swing axis. The swing motor 41 is connected to the feed base 37. When the swing motor 41 is driven, the feed base 37 swings around the swing shaft. The feed plate is disposed on the upper surface of the bed portion 2. The feed plate supports the cloth 105. The feed plate moves back and forth integrally with the feed base 37 and swings. The feed plate has a hole at the front end. The sewing needle 10 that moves up and down passes through the hole in the feed plate and reaches the needle hole in the needle plate 26.

  The rack shaft 22 extends in the front-rear direction above the bed main body 7 and is movable back and forth. The front end portion of the rack shaft 22 is connected to the upper end portion of the swing shaft. The rear end portion of the rack shaft 22 is disposed inside the pedestal portion 3. The moving motor 42 is provided inside the pillar 3. The moving motor 42 moves back and forth on the rack shaft 22. At this time, the feed base 37, the feed plate, the swing shaft, and the movable body 31 move back and forth integrally with the rack shaft 22.

  The presser arm 23 extends upward from the feed base 37 and extends forward above the bed portion 2. The presser arm 23 is capable of moving back and forth and swinging integrally with the feed base 37. The presser arm 23 includes a presser foot 24, a shaft portion 29, and a lever portion 25. The presser foot 24 is provided at the front end of the presser arm 23 so as to be movable up and down. The presser foot 24 is disposed above the needle plate 26. The shaft portion 29 is provided at a substantially central portion in the front-rear direction of the presser arm 23 with the left-right direction as the axial direction. The lever portion 25 is provided on each of the left surface and the right surface of the presser arm 23 and is rotatable about the shaft portion 29. The front end portion of the lever portion 25 is connected to the presser foot 24. The presser foot motor 43 is provided inside the pedestal 3. The presser foot motor 43 is connected to the rear end portion of the lever portion 25 via a link mechanism provided inside the arm portion 4. The presser foot 24 moves up and down as the lever portion 25 rotates about the shaft portion 29 as the cloth presser motor 43 is driven. The presser foot 24 can press the cloth 105 with the feed plate.

  As shown in FIGS. 1 and 2, the sewing machine 1 includes a yarn tension control device 60 on the right wall portion 5 </ b> A of the distal end portion 5. The thread tension control device 60 includes a thread tension case 62, a thread tension base 63, a thread take-up spring 65, a thread tension motor 16, and a pair of thread tension plates 69. The thread tension case 62 is an annular member that is fixed inside the through hole 5B of the right wall portion 5A with a fastening member. The thread tension base 63 is an annular member that is fixed to the inside of the thread tension case 62 with the screw 14. The thread take-up spring 65 is fixed to the outer surface of the thread tension base 63 and wound between the thread tension base 63 and the thread tension case 62. One end of the thread take-up spring 65 is exposed to the right from the right wall 5A. When the thread tension base 63 rotates, the sewing machine 1 can adjust the spring pressure of the thread take-up spring 65. The thread tension motor 16 is fixed to the inside of the arm portion 4 with a bolt 17. An output shaft 18 (described later) of the thread tension motor 16 protrudes to the right of the right wall portion 5 </ b> A through the center hole of the thread tension base 63. The pair of thread tension plates 69 are fixed to the right end portion of the output shaft 18 with a screw 28. The upper thread 6 is wound around the thread tension plate 69 once or twice. The thread tension motor 16 includes an encoder 21 (see FIG. 4). The encoder 21 detects the rotational position of the output shaft 18.

  The thread tension motor 16 is a two-phase bipolar pulse motor. The thread tension motor 16 includes an output shaft 18 and a plurality of coils 33 (see FIG. 3). The output shaft 18 is rotatable with the left-right direction as the axial direction. The left end portion of the output shaft 18 fixes the disk of the encoder 21 inside the arm portion 4. The right end portion of the output shaft 18 supports a pair of thread tension plates 69 on the right side of the arm portion 4. In the present embodiment, the output shaft 18 is directly connected to the pair of thread tension plates 69. A plurality of coils 33 are arranged along the rotation direction of the output shaft 18. The number of coils in this embodiment is four. The sewing machine 1 can cause current to flow in each coil 33 in both directions. The sewing machine 1 controls the rotation angle phase of the output shaft 18 by electromagnetic force generated by the energized coils 33.

  The electrical configuration of the sewing machine 1 will be described with reference to FIG. The control device 30 of the sewing machine 1 includes a CPU 91. The CPU 91 controls the operation of the sewing machine 1. The CPU 91 is connected to the ROM 92, RAM 93, storage device 94, and I / O interface (hereinafter referred to as I / O) 45. The ROM 92 stores a program for executing various processes such as a sewing process (see FIG. 9) described later. The RAM 93 temporarily stores various values. The storage device 94 is nonvolatile. The storage device 94 stores sewing data for forming stitches on the cloth 105. The storage device 94 stores a hook catching period, a balance lifting period, and a sewing period. The hook catching period, the balance lifting period, and the sewing period will be described later. The storage device 94 includes a reference phase storage area and a phase storage area. The reference phase storage area stores the reference phase of the output shaft 18. The reference phase is a rotation angle phase of the output shaft 18 when current flows through the plurality of coils 33 in a specific energization pattern. The phase storage area stores the rotation angle phase of the output shaft 18 with respect to the reference phase.

  The I / O 45 is connected to the drive circuits 81-86. The drive circuit 81 is connected to the sewing machine motor 27. The sewing machine motor 27 is a DC brushless motor. The drive circuit 82 is connected to the swing motor 41. The drive circuit 83 is connected to the movement motor 42. The drive circuit 84 is connected to the presser foot motor 43. The swing motor 41, the movement motor 42, and the cloth presser motor 43 are pulse motors. The sewing machine motor 27, the swing motor 41, the movement motor 42, and the presser foot motor 43 include encoders 27A, 41A, 42A, and 43A, respectively. The encoders 27A, 41A, 42A, and 43A detect the rotational positions of the drive shafts of the sewing machine motor 27, the swing motor 41, the movement motor 42, and the presser foot motor 43, respectively, and output them to the CPU 91. CPU91 acquires the detection result of encoder 27A, 41A, 42A, 43A, and transmits a control signal to the drive circuits 81-84. Therefore, the CPU 91 drives and controls the sewing machine motor 27, the swing motor 41, the movement motor 42, and the presser foot motor 43. Hereinafter, when the sewing machine motor 27, the swinging motor 41, and the moving motor 42 are collectively referred to as a drive motor.

  The drive circuit 85 is connected to the thread tension motor 16. The encoder 21 of the thread tension motor 16 outputs the rotational position of the output shaft 18 of the thread tension motor 16 to the CPU 91 as a detection result. The CPU 91 controls the thread tension motor 16 by transmitting a control signal to the drive circuit 86. The control method executed by the CPU 91 for the thread tension motor 16 that is a pulse motor is not a pulse control method. In the present embodiment, the CPU 91 controls the thread tension motor 16 so that the phase difference of the output shaft 18 becomes a predetermined value. The phase difference of the output shaft 18 is a difference in the rotation angle phase of the output shaft 18 with respect to the reference phase. The outline of the control method executed by the CPU 91 for the thread tension motor 16 will be described later.

  The drive circuit 86 is connected to the display unit 48 of the operation unit 46. The CPU 91 displays various information on the display unit 48 by transmitting a control signal to the drive circuit 86. The operation button 47 of the operation unit 46 outputs various detected information to the CPU 91. The pedal 38 outputs the detection result to the CPU 91. The CPU 91 acquires the operation direction and the operation amount of the pedal 38 indicated by the detection result of the pedal 38.

  The storage device 94 stores a specific data table. The specific data table stores phase difference information and tension information in association with each other. The phase difference information indicates the phase difference of the output shaft 18. The tension information indicates the upper thread tension that is the tension of the upper thread 6. In the specific data table, the needle thread tension increases as the phase difference of the output shaft 18 increases.

A relational expression for driving and controlling the thread tension motor 16 stored in the storage device 94 will be described. Storage device 94 stores a first relational expression relating the I _A and theta, the second relational expression relating the theta and I _B. I _A is the current flowing in the A phase, which is one of the phases of the thread tension motor 16 is a two-phase motor, I _B is the current flowing in the B phase which is the other phase. θ is an electrical angle corresponding to the rotation angle phase of the output shaft 18 when in the reference phase. FIG. 5 is a graph showing the first relational expression and the second relational expression. The electrical angle of 360 ° in this embodiment corresponds to a mechanical angle of 7.2 °. The storage device 94 stores a first flag and a second flag in addition to the first relational expression and the second relational expression. Both the first flag and the second flag are switched to either 0 or 1.

  The operation outline of the sewing machine 1 will be described with reference to FIGS. The cloth 105 is placed on the feed plate and the needle plate 26. When the cloth presser motor 43 is driven, the presser foot 24 descends and presses the cloth 105 with the feed plate. The sewing machine motor 27, the moving motor 42, and the swing motor 41 are driven in synchronization with each other.

  The presser arm 23 and the feed plate move back and forth as the moving motor 42 is driven, and swing back and forth in the left-right direction as the swing motor 41 is driven. Therefore, the cloth feeding device 20 moves the cloth 105 back and forth and swings back and forth in the left-right direction. When the sewing machine motor 27 is driven synchronously with the moving motor 42 and the swing motor 41, the upper shaft 15 rotates. The needle bar vertical movement mechanism, the balance mechanism, and the rotary hook 39 are driven in conjunction with each other. The sewing needle 10 descending together with the needle bar 11 passes through the cloth 105 and passes through the needle hole. The upper thread 6 in the vicinity of the eye hole 10A lowered to the lower side of the needle hole becomes a loop shape (see FIG. 6A). When the rotary hook 39 rotates clockwise in front view, the sword tip 36 captures the loop-shaped upper thread 6 (see FIG. 6B). The sewing needle 10 moves upward toward the cloth 105, and the rotary hook 39 further rotates clockwise as viewed from the front. The sword tip 36 pulls the loop-shaped upper thread 6 in the rotating direction, and the loop-shaped upper thread 6 expands in diameter.

  When the rotary hook 39 passes through the looped upper thread 6 (see FIG. 6C), the upper thread 6 is entangled with the lower thread 9. The rotating direction of the rotary hook 39 is switched counterclockwise when viewed from the front, and the balance 51 pulls the upper thread 6 entangled with the lower thread 9 (FIG. 6D). The looped upper thread 6 is reduced in diameter, and the sewing machine 1 completes the sewing of the first stitch. In this embodiment, every time the upper shaft 15 rotates 360 °, the sewing machine 1 executes sewing for one stitch. The sewing machine 1 forms stitches on the cloth 105 by repeating the above operation.

  FIG. 7 is a graph showing the motion curves of the needle bar 11, the rotary hook 39, and the balance 51 when the sewing machine 1 repeats the sewing operation, with the rotation angle phase of the upper shaft 15 as the horizontal axis. Each of the movement curves of the needle bar 11, the rotary hook 39, and the balance 51 has one cycle corresponding to one rotation of the upper shaft 15. In the present embodiment, the period from when the balance 51 returns to the top dead center via the bottom dead center that is the lower end of the movable range is the sewing period for one stitch of the sewing machine 1. . That is, in the present embodiment, the rotation angle phase of the upper shaft 15 of 60 ° to 420 ° substantially coincides with the sewing period of the first stitch. The rotation angle phase of the upper shaft 15 is based on the detection result of the encoder 27A. There is a hook catching period in the sewing period of the sewing machine 1. The hook catching period is a period in which the rotary hook 39 catches the upper thread 6 with the sword tip 36. There is one hook catching period in one sewing period. In FIG. 7, the hook catching period in the sewing of the first stitch is indicated by L 1, and during this period, the upper thread 6 comes off from the rotary hook 39 from the “hook upper thread hook” where the sword tip 36 hooks the upper thread 6. This is the period until "upper thread loss".

  The sewing period of the sewing machine 1 includes a balance lifting period. The balance lifting period is a period in which the balance 51 pulls up the upper thread 6 from the time when the upper thread 6 is removed from the rotary hook 39. In FIG. 7, the lifting period of the balance in the sewing of the first stitch is indicated by L <b> 2, and this period is a period from “Upper thread removal from the hook” to “Upper dead center of the balance” which is the upper end of the movable range of the balance 51. It is.

  An outline of a control method executed by the CPU 91 for the thread tension motor 16 will be described with reference to FIGS. 1, 3 to 5, and 8. At the start of the sewing operation by the sewing machine 1, a specific pattern of current flows through the plurality of coils 33, and the thread tension motor 16 holds the output shaft 18 at a predetermined rotational angle phase (hereinafter referred to as initial rotational angle phase). ing. The initial rotation angle phase is a reference phase of the first output shaft 18. Therefore, when the sewing operation by the sewing machine 1 is started, the phase difference of the output shaft 18 is zero.

  When the balance 51 starts to pull up the upper thread 6 as the sewing operation of the sewing machine 1 proceeds, the sewing machine 1 consumes the upper thread 6. The upper thread 6 between the balance 51 and the pair of thread tension plates 69 extends, and the upper thread tension increases. Therefore, the upper thread 6 urges the output shaft 18 via the pair of thread tension motors 16, and the output shaft 18 gradually rotates against the holding force of the thread tension motor 16. The phase difference of the output shaft 18 that was 0 at the start of the sewing operation of the sewing machine 1 increases. As the upper thread tension increases, the phase difference of the output shaft 18 increases. Hereinafter, the value of the upper thread tension when the phase difference of the output shaft 18 with the initial rotation angle phase as the reference phase is a predetermined value is referred to as a predetermined tension. FIG. 8 shows the relationship between the phase difference of the output shaft 18 and the torque generated by the thread tension motor 16. The torque generated by the thread tension motor 16 increases as the phase difference of the output shaft 18 increases. Therefore, the needle thread tension and the torque generated by the thread tension motor 16 are correlated with each other.

When the phase difference of the output shaft 18 with the initial rotation angle phase as the reference phase exceeds a predetermined value, the CPU 91 switches the energization pattern for the plurality of coils 33. Specifically, the CPU 91 specifies the rotation angle phase (electrical angle) of the output shaft 18 that eliminates the increment with respect to the predetermined value. In other words, the CPU 91 specifies the rotation angle phase of the output shaft 18 that returns the upper thread tension exceeding the predetermined tension to the predetermined tension. The CPU 91 specifies I _A and I _B based on the first relational expression, the second relational expression, and the specified rotation angle phase. The CPU 91 supplies current to the plurality of coils 33 with the specified I _A and I _B. That is, the energization patterns of the plurality of coils 33 are switched, and the output shaft 18 rotates to the rotation angle phase specified by the CPU 91. The rotation angle phase of the output shaft 18 after rotation becomes a new reference phase. When the output shaft 18 is in a new reference phase, the upper thread tension returns to the predetermined tension.

The upper thread 6 is continuously pulled up by the balance 51, and the output shaft 18 is further rotated by the urging of the upper thread 6 from the switched reference phase. Therefore, the phase difference again exceeds the predetermined value, and the needle thread tension again exceeds the predetermined tension. The CPU 91 specifies the rotation angle phase of the output shaft 18 that eliminates the portion of the phase difference exceeding the predetermined value (that is, the rotation angle phase of the output shaft 18 that returns the upper thread tension to the predetermined tension). The CPU 91 identifies I _A and I _{B based} on the identified rotation angle phase of the output shaft 18, the first relational expression, and the second relational expression. The CPU 91 drives and controls the thread tension motor 16 by repeating the above process, and maintains the upper thread tension. In the present embodiment, the operator inputs a desired predetermined tension via the operation button 47. Therefore, the CPU 91 drives and controls the thread tension motor 16 so that a predetermined tension desired by the operator is generated.

  The sewing failure of the sewing machine 1 will be described. If the usage amount of the upper thread 6 at the time of sewing the sewing machine 1 is out of the predetermined range, poor sewing occurs. The sewing failure in this embodiment includes skipping, thread breakage, and thread tightening failure. The skipping is a problem that the rotary hook 39 fails to capture the upper thread 6 with the sword tip 36 (see FIG. 12). When skipping occurs, the usage amount of the upper thread 6 during the hook catching period is smaller than the predetermined amount A. The thread breakage is a problem that the upper thread 6 is cut on the upper thread supply path between the eye hole 10A and the upper thread bobbin. The thread break includes a thread break associated with a needle break at which the sewing needle 10 is broken. The sewing machine 1 detects a thread breakage during the hook catching period and a thread breakage during the balance lifting period in a sewing process described later. When thread breakage occurs, the amount of upper thread 6 used is less than the predetermined amount B. The thread tightening failure is a problem in which the balance between the upper thread 6 and the lower thread 9 forming the seam of the cloth 105 becomes poor when the upper thread 6 is pulled up by the balance 51. When the upper thread 6 is tightly entangled with the lower thread 9, the cloth 105 near the seam shrinks. At this time, the amount of the upper thread 6 used in the balance lifting period is smaller than the predetermined amount C. When the upper thread 6 is loosely entangled with the lower thread 9, the upper thread 6 forming the seam is separated from the cloth 105. At this time, the usage amount of the upper thread 6 in the balance lifting period is larger than the predetermined amount C.

  Even if any sewing failure such as stitch skipping, thread breakage, or thread tightening failure occurs, the usage amount of the upper thread 6 deviates from a predetermined amount. That is, when a sewing failure occurs, the rotation amount of the output shaft 18 of the thread tension motor 16 deviates from a predetermined amount. In the sewing process described later, the sewing machine 1 determines whether there is a sewing failure based on the rotational displacement amount of the thread tension motor 16. The predetermined amounts A, B, and C have a predetermined range, and can be determined by calculating the threshold value including 0 from the average value, the maximum value, the minimum value, the maximum value one stitch before, etc. Particularly in the case of yarn breakage, the threshold value 0 is not preferable.

  The sewing process will be described with reference to FIGS. The sewing process is a process in which the sewing machine 1 sews the cloth 105. For example, when the operator operates the operation button 47 to turn on the sewing machine 1, the CPU 91 reads a program from the ROM 92 and executes a sewing process.

  As shown in FIGS. 9 and 10, the CPU 91 executes an initialization process (S11). For example, the CPU 91 overwrites both the first flag and the second flag stored in the storage device 94 with 0. The CPU 91 acquires the rotation angle phase of the output shaft 18 of the thread tension motor 16 based on the detection result of the encoder 21 (S12). As will be described later, the rotation angle phase acquired in S12 is a reference phase. The CPU 91 stores the acquired rotation angle phase in the reference phase storage area of the storage device 94 (S12). CPU91 acquires tension information (S13). For example, the CPU 91 waits until the operation button 47 detects tension information. For example, when the operator inputs a specific numerical value to the operation button 47 as tension information, the CPU 91 acquires the tension information (S13). The CPU 91 acquires phase difference information of the output shaft 18 (S14). The CPU 91 refers to the specific information table stored in the storage device 94 and acquires phase difference information corresponding to the tension information acquired in S13. The CPU 91 stores the acquired phase difference information in the RAM 93 (S14).

  The CPU 91 determines whether or not a sewing start instruction that is an instruction to start the sewing operation of the sewing machine 1 has been detected (S15). The sewing start instruction is an instruction that the operator inputs by operating the operation button 47 or the pedal 38. The CPU 91 stands by until a sewing start instruction is detected (S15: NO). The operator places the cloth 105 on the needle plate 26 and the feed plate while the CPU 91 is on standby. When the operator inputs a sewing start instruction after placing the cloth 105 (S15: YES), the CPU 91 drives and controls the cloth presser motor 43 to lower the presser foot 24 (S16). The presser foot 24 sandwiches the cloth 105 with the feed plate.

CPU91 specifies the electricity supply pattern with respect to each of the some coil 33 (S17). The CPU 91 calculates I _A and I _B based on the rotation angle phase, the first relational expression, and the second relational expression acquired in S12 (S17). CPU91 performs electricity supply with respect to the some coil 33 by the electricity supply pattern specified by S17 (S18). A force that holds the output shaft 18 at the rotational angle phase acquired in S <b> 12 is generated in the thread tension motor 16. That is, the rotation angle phase acquired in S12 is the initial rotation angle phase that is the reference phase of the first output shaft 18. The CPU 91 controls the drive motor (S19). The needle bar 11, the rotary hook 39, and the feed base 37 operate in synchronization with each other. The CPU 91 executes a thread tension motor drive process (S21).

  The CPU 91 acquires the rotation angle phase of the output shaft 18 of the thread tension motor 16 based on the detection result of the encoder 21 (S51). The CPU 91 overwrites and stores the acquired rotation angle phase in the phase storage area of the storage device 94 (S51). The CPU 91 determines whether or not the actual phase difference of the output shaft 18 exceeds a predetermined value (S52). The actual phase difference is a value obtained by subtracting the rotation angle phase stored in the reference phase storage area from the rotation angle phase stored in the phase storage area of the storage device 94, and corresponds to the phase difference of the output shaft 18 in the actual machine. In the first thread tension motor driving process, the actual phase difference is a value obtained by subtracting the rotation angle phase acquired in S12 from the rotation angle phase acquired in S51. In the first thread tension motor driving process, the predetermined value is the phase difference indicated by the phase difference information acquired in S14. When the upper thread tension is equal to or less than the tension indicated by the tension information acquired in S13, the actual phase difference is smaller than the predetermined value (S52: NO), and the CPU 91 ends the thread tension motor drive process.

  The CPU 91 sequentially executes a skipping determination process (S23), a thread breakage determination process (S25), and a thread tightening failure determination process (S27). Details of S23, S25, and S27 will be described later. The CPU 91 determines whether or not the drive motor is stopped based on the detection results of the encoders 27A, 41A, and 42A (S29). CPU91 acquires each detection result of encoder 27A, 41A, 42A, for example twice. If at least one detection result of the encoders 27A, 41A, and 42A has changed, the CPU 91 determines that the drive motor has not stopped driving (S29: NO), and proceeds to S31. If none of the detection results of the encoders 27A, 41A, and 42A change, the CPU 91 determines that the drive motor is stopped (S29: YES), and moves the process to S35.

  When the drive motor is being driven (S29: NO), the CPU 91 determines whether or not a sewing end instruction, which is an instruction to end the sewing operation of the sewing machine 1, has been detected based on the detection result of the operation button 47 ( S31). The sewing end instruction is an instruction indicating that the operator has stopped operating the pedal 38 or has finished sewing based on the sewing data. If there is no instruction to end sewing (S31: NO), the CPU 91 proceeds to S21.

  The CPU 91 repeatedly executes S21 to S31. In the present embodiment, the cycle in which the CPU 91 repeats S21 to S31 is once every 10 μs to 10 ms, which is sufficiently shorter than the cycle in which the needle bar 11 moves up and down.

For example, in the tenth thread tension motor drive process after the start of the sewing process (S21), it is assumed that the actual phase difference exceeds a predetermined value (S52: YES). At this time, the upper thread tension of the actual machine exceeds the upper thread tension indicated by the tension information acquired in S13. CPU91 specifies the electricity supply pattern with respect to the some coil 33 (S53). In other words, CPU 91 identifies and calculates the _{I A} and _{I B} by a calculation control based on the detection result of the encoder 21 (S53). For example, the CPU 91 specifies an increment of the actual phase difference acquired in S52 with respect to a predetermined value. The CPU 91 acquires the rotation angle phase of the output shaft 18 that eliminates the specified increment as the reference phase, and overwrites the reference phase storage area of the storage device 94. The CPU 91 specifies a specific pattern based on the rotation angle phase acquired as the reference phase, the first relational expression, and the second relational expression (S53). CPU91 switches the electricity supply pattern currently performed with respect to the some coil 33 to the electricity supply pattern specified by S53 (S55). The output shaft 18 rotates to the rotation angle phase stored in the reference phase storage area of the storage device 94, and the upper thread tension of the actual machine returns to the upper thread tension indicated by the tension information acquired in S13. The CPU 91 ends the thread tension motor driving process. The actual phase difference in S52 of the eleventh thread tension motor drive process is determined from the rotation angle phase acquired in S51 of the eleventh thread tension motor drive process as the reference phase in S53 of the tenth thread tension motor drive process. The value obtained by subtracting the acquired rotation angle phase. The predetermined value is a value for maintaining the upper thread tension of the actual machine at the upper thread tension indicated by the tension information acquired in S13.

CPU91, every time for executing S53, identifies and calculates the _{I A} and _{I B} by a calculation control based on the detection result of the encoder 21 (S53), the energization pattern acquired energization pattern for a plurality of coils 33 in S53 (S55). As the CPU 91 repeatedly executes S21, the sewing machine 1 maintains the upper thread tension of the actual machine at the upper thread tension indicated by the tension information acquired in S13. Each time the CPU 91 repeats the thread tension motor driving process (S21), the CPU 91 updates the phase storage area of the storage device 94 by overwriting the stored rotation angle phase (S51).

  The skipping determination process (S23) will be described with reference to FIGS. The CPU 91 determines whether or not it is the shuttle capture period (S61). For example, the CPU 91 determines whether or not the rotation angle phase of the upper shaft 15 is within the hook capture period stored in the storage device 94 based on the detection result of the encoder 27A, thereby determining whether or not the hook capture period. to decide. In the first skip determination process after the start of the sewing process, the rotation angle phase of the upper shaft 15 is not within the hook capture period (S61: NO), and the CPU 91 overwrites the first flag stored in the storage device 94 with 0. (S63), the skipping determination process is terminated.

  The CPU 91 repeatedly executes S25 to S31 and S21. When the drive motor is driven, the upper shaft 15 rotates and enters the hook catching period (S61: YES). The CPU 91 determines whether or not the first flag stored in the storage device 94 is 1 (S65). When the first flag is 0 (S65: NO), the CPU 91 overwrites the first flag stored in the storage device 94 with 1 (S67). The CPU 91 stores the first initial rotation angle phase in the storage device 94 (S69). The first initial rotation angle phase is the rotation angle phase of the output shaft 18 when S69 is executed. The CPU 91 ends the skipping determination process.

  When the CPU 91 executes the next skip processing determination (S23), if the shuttle capture period continues (S61: YES), the first flag is 1 (S65: YES). The CPU 91 determines whether or not the first rotational displacement amount is less than a specific value (S71). The first rotational displacement amount is the rotation amount of the output shaft 18 with the first initial rotational angle phase as a reference. The specific value is a predetermined value, and is a value for determining the presence or absence of skipping. For example, the CPU 91 acquires the difference between the rotation angle phase of the output shaft 18 acquired based on the detection result of the encoder 21 and the first initial rotation angle phase. Therefore, the CPU 91 acquires the first rotational displacement amount. When the skip is not occurring, the first rotational displacement amount is equal to or greater than the specific value (S71: NO), and the CPU 91 ends the skip determination process.

  For example, if the rotary hook 39 catches the upper thread 6 with the sword tip 36 when the sewing machine 1 executes the first stitch sewing (see FIG. 6B), the first rotational displacement amount is specified during the hook catching period. It becomes more than a value (S71: NO). After the upper thread 6 has passed through the rotary hook 39 (see FIG. 6C), the balance 51 reaches the top dead center, and the sewing machine 1 finishes sewing the first stitch. When the upper thread 6 has passed through the rotary hook 39, it is not the hook catching period (S61: NO). The CPU 91 overwrites the first flag with 0 (S63). While the CPU 91 repeatedly executes S21 to S31, the sewing mechanism 12 executes the second and subsequent stitches. Therefore, CPU91 which performs S23 can judge the presence or absence of the skip in the hook capture period corresponding to each stitch number. In other words, the CPU 91 that executes S23 can determine the presence or absence of stitch skipping in the specific sewing operation for forming a specific stitch on the cloth 105.

  For example, when the rotary hook 39 fails to capture the upper thread 6 with the sword tip 36 when the sewing machine 1 performs the first stitch sewing (see FIGS. 12A and 12B), the upper thread 6 is not rotated by the rotary hook 39. Do not dive. At this time, since the upper thread 6 is not used, the used amount of the upper thread 6 is smaller than the predetermined amount A. Therefore, the first rotational displacement amount is less than the predetermined value (S71: YES), and the CPU 91 can detect the occurrence of skipping. The CPU 91 stops driving the drive motor (S73) and ends the skipping determination process. After executing S25 and S27, the CPU 91 determines that the drive motor has stopped driving (S29: YES), and proceeds to S35 described later.

  The thread breakage determination process (S25) will be described with reference to FIGS. The CPU 91 determines whether or not the drive motor has stopped driving (S81). S81 is the same as S29. For example, when the drive motor stops driving in the skipping determination process (S73), the CPU 91 determines that the drive motor stops driving (S81: YES). The CPU 91 ends the thread breakage determination process.

  When the drive motor has not stopped driving (S81: NO), the CPU 91 determines whether or not it is the shuttle catching period (S83). S83 is the same as S61 (see FIG. 11). The determination result of the CPU 91 in S83 matches the determination result of the CPU 91 in S61 executed immediately before.

  When the CPU 91 determines that it is not the shuttle catching period (S83: NO), it is determined whether it is the balance pulling period (S85). Based on the detection result of the encoder 27A, the CPU 91 determines whether or not the rotation angle phase of the upper shaft 15 is within the balance pull-up period stored in the storage device 94, thereby determining whether or not the balance pull-up period. to decide. For example, in the first thread breakage determination process after the start of the sewing process, the CPU 91 overwrites 0 in the second flag stored in the storage device 94 (S87) instead of the balance lifting period (S85: NO), and the thread The cut determination process ends. The CPU 91 repeatedly executes S27 to S31, S21, and S23.

  When the upper motor 15 is rotated by driving the drive motor and the hook catching period is reached (S83: YES), the CPU 91 determines whether or not the first rotational displacement amount is less than the first predetermined value (S89). ). The first rotational displacement amount is the same as the first rotational displacement amount acquired in the immediately preceding S71 (see FIG. 11). The first predetermined value is a predetermined value, and is a value for determining the presence or absence of yarn breakage during the hook catching period. For example, if the upper thread 6 does not break when the sewing machine 1 performs sewing, the upper thread 6 is used by diving through the rotary hook 39, and the amount of use of the upper thread 6 is within a predetermined amount B. It becomes. Therefore, the first rotational displacement amount is not less than the first predetermined value (S89: NO). At this time, the CPU 91 ends the thread breakage determination process.

  For example, if a thread breakage of the upper thread 6 occurs during the hook catching period in the sewing of the first stitch, the upper thread 6 is not used, and therefore the usage amount of the upper thread 6 is smaller than the predetermined amount B. Therefore, the first rotational displacement amount is less than the first predetermined value (S89: YES). Therefore, the CPU 91 detects the yarn breakage of the upper thread 6. The CPU 91 stops driving the drive motor (S99) and ends the thread breakage determination process.

  On the other hand, for example, after the hook catching period in the sewing of the first stitch is over (S83: NO), it becomes the balance lifting period corresponding to the sewing of the first stitch (S85: YES). The CPU 91 determines whether or not the second flag is 1 (S91). When the CPU 91 executes S91 for the first time during the sewing of the first stitch, the second flag is 0 (S91: NO). The CPU 91 overwrites the second flag stored in the storage device 94 with 1 (S93), and stores the second initial rotation angle phase in the storage device 94 (S95). The second initial rotation angle phase is the rotation angle phase of the output shaft 18 when S95 is executed. Immediately after the second flag is switched from 0 to 1 (S93), the CPU 91 stores the second initial rotation angle phase. Therefore, the second initial rotation angle phase is the rotation angle phase of the output shaft 18 at the start of the balance lifting period. The CPU 91 ends the thread breakage determination process. The CPU 91 repeatedly executes S27 to S31 and S21 to S25.

  In the first yarn breakage determination process after the CPU 91 stores the second initial rotation angle phase in the storage device 94, the storage device is not in the hook catching period (S83: NO) but during the balance pulling period (S85: YES). The second flag stored in 94 is 1 (S91: YES). The CPU 91 determines whether or not the second rotational displacement amount is less than a second predetermined value (S97). The second rotational displacement amount is a rotational angle phase of the output shaft 18 with reference to the second initial rotational angle phase. The second predetermined value is a predetermined value, and is a value for determining the presence or absence of yarn breakage in the lifting period. For example, the CPU 91 acquires the difference between the rotation angle phase of the output shaft 18 acquired based on the detection result of the encoder 21 and the second initial rotation angle phase. Therefore, the CPU 91 acquires the second rotational displacement amount. When the thread breakage does not occur during the lifting and pulling period, the upper thread 6 is used by the balance 51 pulling up the upper thread 6, so that the amount of the upper thread 6 used is within a predetermined amount B. . Therefore, the second rotational displacement amount becomes equal to or greater than the second predetermined value (S97: NO), and the CPU 91 ends the thread breakage determination process.

  In the thread breakage determination process immediately after the lifting of the balance in the first stitch (that is, immediately after starting the sewing of the second stitch), it is not the hook catching period (S83: NO) and is not the lifting period (S85). : NO). The CPU 91 overwrites the second flag stored in the storage device 94 with 0 (S87). While the CPU 91 repeatedly executes S21 to S31, the sewing mechanism 12 executes the second and subsequent stitches. Therefore, the CPU 91 can determine whether or not a thread break has occurred in the specific sewing operation by executing S25.

  On the other hand, when the thread breakage of the upper thread 6 occurs during the balance pulling period in the sewing of the first stitch, the balance 51 does not pull up the upper thread 6 and the upper thread 6 is not used. Less than a fixed amount B. Therefore, the second rotational displacement amount is less than the second predetermined value (S97: YES). Therefore, the CPU 91 detects the yarn breakage of the upper thread 6. The CPU 91 stops driving the drive motor (S99) and ends the thread breakage determination process.

  With reference to FIGS. 9 and 14, the thread tightening failure determination process will be described. The CPU 91 determines whether or not the drive motor is stopped (S101). S101 is the same as S29. For example, when the drive motor stops at S73 (see FIG. 11) or S99 (see FIG. 13) (S101: YES), the CPU 91 ends the thread tightening failure determination process.

  If the drive motor has not stopped driving (S101: NO), the CPU 91 determines whether or not sewing of the first stitch has been started based on the detection result of the encoder 27A (S102). The CPU 91 determines whether or not sewing of the first stitch has been started by determining whether or not the rotation angle phase of the upper shaft 15 is less than 60 °. Immediately after the start of the sewing process, the rotational angle phase of the upper shaft 15 is in the vicinity of 0 ° (S102: NO), and the CPU 91 ends the thread tightening failure determination process. The CPU 91 repeatedly executes S29, S31, and S21 to S25. When the rotation angle phase of the upper shaft 15 becomes 60 ° or more (S102: YES), the CPU 91 determines whether or not the number of stitches being sewn has been updated (S103). For example, the CPU 91 determines whether or not the number of stitches being sewn has been updated based on whether or not the rotation angle phase of the upper shaft 15 substantially matches 60 ° + 360 × N (N is an integer). When the rotation angle phase of the upper shaft 15 becomes 60 ° or more (S102: YES), the rotation angle phase of the upper shaft 15 is around 60 ° (S103: YES). The CPU 91 stores the third initial rotation angle phase in the storage device 94 (S105). The third initial rotation angle phase is the rotation angle phase of the output shaft 18 when S105 is executed. Each time the number of stitches is updated (S103: YES), the CPU 91 stores the third initial rotation angle phase. Therefore, the third rotation angle phase is the rotation angle phase of the output shaft 18 at the start of the specific sewing operation. After executing S105, the CPU 91 ends the thread tightening failure determination process. The CPU 91 repeatedly executes S29, S31, and S21 to S25.

  In the thread tightening failure determination process immediately after the CPU 91 stores the third initial rotation angle phase in the storage device 94, the rotation angle phase of the upper shaft 15 is not close to 60 ° (S102: YES, S103: NO). The CPU 91 determines whether or not the third rotational displacement amount is outside a predetermined range (S107). The third rotational displacement amount is a rotation amount of the output shaft 18 with reference to the third initial rotational angle phase. The predetermined range is a predetermined range and is a range for determining whether there is a thread tightening defect. For example, the CPU 91 acquires the difference between the rotation angle phase of the output shaft 18 acquired based on the detection result of the encoder 21 and the third initial rotation angle phase. Therefore, the CPU 91 acquires the third rotational displacement amount. When the thread tightening failure does not occur, the third rotational displacement amount falls within the predetermined range (S107: NO), and the CPU 91 ends the thread tightening failure determination process.

  For example, when the sewing machine 1 executes the first stitch, if the thread tightening is good, the amount of use of the upper thread 6 when the balance 51 pulls the upper thread 6 is within a predetermined amount C. Therefore, the third rotational displacement amount falls within a predetermined range (S107: NO). The CPU 91 repeatedly executes S29, S31, and S21 to S27, whereby the sewing mechanism 12 forms the first stitch on the cloth 105, and the sewing machine 1 starts sewing the second stitch. The rotation angle phase of the upper shaft 15 is close to 420 ° (S103: YES), and the CPU 91 overwrites and stores the third initial rotation angle phase in the storage device 94 (S105). In S103 immediately after the CPU 91 overwrites and stores the third initial rotation angle phase, the rotation angle phase of the upper shaft 15 is not near 420 ° (S103: NO). The CPU 91 determines whether there is a thread tightening defect by executing S107. While the CPU 91 repeatedly executes S21 to S31, the sewing mechanism 12 executes the second and subsequent stitches. Therefore, the CPU 91 can determine whether or not a thread tightening failure has occurred in the specific sewing operation by executing S27.

  If a thread tightening failure occurs when the sewing machine 1 executes the first stitch, the amount of use of the upper thread 6 when the balance 51 pulls up the upper thread 6 deviates from a predetermined amount C. Therefore, the third rotational displacement amount is outside the predetermined range (S107: YES). The CPU 91 detects a thread tightening failure. The CPU 91 stops driving the drive motor (S109) and ends the thread tightening failure determination process.

  As shown in FIG. 9, when the drive motor is stopped (S29: YES), the CPU 91 identifies a sewing failure (S35). The CPU 91 specifies the sewing failure by specifying the process in which the drive motor is stopped. For example, when the drive motor stops in S73 (see FIG. 11), the CPU 91 specifies that the sewing failure is skipped. When the drive motor stops in S99 (see FIG. 13), the CPU 91 specifies that the sewing failure is a thread break. When the drive motor stops in S109 (see FIG. 14), the CPU 91 specifies that the sewing failure is a thread tightening failure. The CPU 91 notifies the sewing failure specified in S35 (S37), and the process proceeds to S39. For example, the CPU 91 displays the sewing failure specified in S35 on the display unit 48 (S37). Therefore, the operator can recognize a specific sewing failure.

  When a sewing failure does not occur during the execution of the sewing process, the CPU 91 repeatedly executes S19 to S31, whereby a predetermined stitch is formed on the cloth 105. When there is a sewing end instruction (S31: YES), the CPU 91 stops driving the drive motor and the thread tension motor 16 (S33). The CPU 91 drives and controls the presser foot motor 43 to raise the presser foot 24 (S39), and then ends the sewing process. The cloth 105 can be taken out from the sewing machine 1.

  As described above, the CPU 91 calculates and specifies energization patterns for the plurality of coils 33 by calculation control based on the detection result of the encoder 21 (S53). Each time the CPU 91 executes the thread tension motor driving process (S21), the CPU 91 energizes the plurality of coils 33 with the energization pattern specified in S53. Since the current values flowing through the plurality of coils 33 change smoothly, the sewing machine 1 can smoothly control the rotation angle phase of the output shaft 18. Even when the sewing machine 1 executes the sewing operation at a high speed, the output shaft 18 of the thread tension motor 16 can rotate following the sewing operation of the sewing machine 1 stably. Therefore, the sewing machine 1 that can smoothly control the rotation angle phase of the output shaft 18 of the thread tension motor 16 that adjusts the needle thread tension and can rotate the output shaft 18 stably is realized.

  The CPU 91 determines whether there is any skipping by determining whether the first rotational displacement amount of the output shaft 18 is less than a specific value (S71). Therefore, the sewing machine 1 can detect skipping. The CPU 91 determines whether or not there is a thread tightening defect by detecting whether or not the third rotational displacement amount of the output shaft 18 is outside a predetermined range (S107). Therefore, the sewing machine 1 can detect a thread tightening failure. The CPU 91 determines whether or not there is a thread breakage during the hook catching period by determining whether or not the first rotational displacement amount of the output shaft 18 is less than the first predetermined value (S89). The CPU 91 determines whether or not there is a thread breakage during the lifting of the balance by determining whether or not the second rotational displacement amount of the output shaft 18 is less than the second predetermined value (S97). Therefore, the sewing machine 1 can detect thread breakage. The CPU 91 can determine whether there is a sewing failure by executing S71, S107, S89, and S97. Therefore, the sewing machine 1 can stabilize the sewing operation.

  When skipping occurs (S71: YES), the CPU 91 displays on the display unit 48 that skipping has occurred (S37). Therefore, the operator can recognize the occurrence of skipping. If a thread tightening failure has occurred (S89: YES, S97: YES), the CPU 91 displays on the display unit 48 that a thread tightening failure has occurred. Therefore, the operator can recognize the occurrence of thread tightening failure.

  When sewing failure occurs, the CPU 91 stops driving the drive motor and the thread tension motor 16 (S73, S99, S109). Therefore, the sewing machine 1 does not continue the sewing in the state where the sewing failure has occurred. Since the sewing needle 10 does not penetrate the cloth 105 unnecessarily, the sewing machine 1 can hardly cause the cloth 105 to be damaged.

  In the above description, the sewing mechanism 12 is an example of the sewing means of the present invention. The operation button 47 is an example of the input unit of the present invention. The thread tension motor 16 is an example of the motor of the present invention. The needle plate 26 is an example of the cloth placement portion of the present invention. CPU91 which performs S19 is an example of the sewing control part of the present invention. CPU91 which performs S13 is an example of the tension acquisition part of the present invention. CPU91 which performs S21 is an example of the motor drive control part of the present invention. The CPU 91 that executes S53 is an example of the specific control unit of the present invention. The CPU 91 that executes S55 is an example of an energization control unit of the present invention. The CPU 91 that executes S71, S97, and S107 is an example of the sewing failure determination unit of the present invention. The CPU 91 that executes S71 is an example of a skipping determination unit of the present invention. The CPU 91 that executes S107 is an example of a yarn tightening failure determination unit of the present invention. The CPU 91 that executes S71, S97, and S107 is an example of the sewing failure determination unit of the present invention. The CPU 91 that executes S37 is an example of a notification unit of the present invention. The CPU 91 that executes S97 is an example of the yarn breakage determination unit of the present invention. CPU91 which performs S73, S99, and S109 is a stop control part of the present invention.

  The present invention is not limited to the above invention. Instead of reciprocatingly swinging the cloth 105 in the left-right direction, the cloth feeding device 20 may reciprocate linearly in the left-right direction, for example. The sewing machine 1 may include a presser bar and a feed dog instead of including the cloth feeding device 20. The presser bar includes a presser member at the lower end. When the presser bar is lowered, the presser member sandwiches the cloth 105 with the feed dog. As the feed dog swings back and forth, the sewing machine 1 can feed the cloth 105 in a predetermined direction.

  The thread tension motor 16 may be a DC motor instead of a pulse motor. The output shaft 18 of the thread tension motor 16 may be indirectly connected to the pair of thread tension dishes 69 via gears or the like instead of being directly coupled to the pair of thread tension dishes 69, for example. The CPU 91 does not have to execute at least one of S23, S25, and S27. CPU91 may drive-control the thread tension motor 16 by control based on well-known dq conversion at the time of execution of S21. The CPU 91 may not execute the processes of S73 and S109. That is, when the sewing failure is other than thread breakage, the sewing machine 1 does not have to stop sewing.

DESCRIPTION OF SYMBOLS 1 Sewing machine 6 Upper thread 10 Sewing needle 11 Needle bar 12 Sewing mechanism 16 Thread tension motor 18 Output shaft 21 Encoder 26 Needle plate 27 Sewing motor 39 Rotary hook 47 Operation button 51 Scale 69 Thread tension plate 91 CPU
105 cloth

Claims (8)

A sewing means that has a needle bar that can be moved up and down to attach a sewing needle, and sews a cloth with the sewing needle;
A thread tension plate around which the upper thread is wound;
An input unit for inputting tension information indicating tension applied to the upper thread;
A motor having an output shaft connected to the thread tension plate, and a plurality of coils arranged along a rotation direction of the output shaft;
An encoder for detecting a rotation angle phase of the output shaft;
The sewing means and a control unit for driving and controlling the motor,
The controller is
A sewing control unit that drives and controls the sewing means to sew the cloth;
Before the sewing of the cloth by the sewing control unit, a tension acquisition unit that acquires the tension information input to the input unit;
At the time of sewing of the cloth by the sewing control unit, based on the tension information acquired by the tension acquisition unit and the detection result of the encoder, the tension applied to the upper thread is controlled by driving the motor. In a sewing machine comprising: a motor drive control unit that makes the tension indicated by the tension information;
The motor drive controller is
A specific control unit that calculates and specifies the energization pattern for each of the plurality of coils by calculation control based on the detection result of the encoder in a cycle shorter than the cycle in which the needle bar moves up and down;
A sewing machine comprising: an energization control unit configured to energize the plurality of coils with the energization pattern specified by the specific control unit each time the specific control unit specifies the energization pattern. The sewing means includes
A cloth placement section for placing the cloth;
A rotary hook provided below the needle bar, and when the sewing needle penetrates the cloth, the annular upper thread inserted through the sewing needle is captured and entangled with the lower thread;
A sewing machine motor that drives the needle bar and the rotary hook;
The sewing control unit sews the cloth by driving and controlling the sewing machine motor,
The control unit is configured to determine whether or not a sewing failure has occurred in which a use amount of the upper thread at the time of sewing of the cloth by the sewing control unit deviates from a predetermined range based on the detection result of the encoder. The sewing machine according to claim 1, further comprising a defect determination unit. The sewing failure includes a stitch that the rotary hook fails to capture the upper thread,
The sewing failure determination unit includes a stitch skip determination unit that determines whether or not the stitch skip has occurred in a specific sewing operation for forming a specific stitch on the cloth.
The skipping determination unit rotates the output shaft with reference to the initial rotation angle phase of the output shaft at the start of the hook catching period in the hook catching period in which the rotary hook catches the upper thread. 3. The sewing machine according to claim 2, wherein it is determined whether or not the skip has occurred by determining whether or not the amount is less than a specific value.   The sewing machine according to claim 3, wherein the sewing control unit includes a notifying unit that notifies the occurrence of the stitch skip when the stitch skip determination unit determines that the stitch skip has occurred. The sewing means includes
A balance that moves up and down by driving the sewing machine motor and pulls up the upper thread that the rotary hook is entangled with the lower thread;
The sewing failure includes a thread tightening failure that is an imbalance between the upper thread and the lower thread forming the seam when the balance pulls up the upper thread,
The sewing failure determination unit includes a thread tightening failure determination unit that determines whether or not the thread tightening failure has occurred in a specific sewing operation for forming a specific stitch on the cloth,
The thread tightening failure determination unit determines whether or not the rotation amount of the output shaft based on the initial rotation angle phase of the output shaft at the start of the specific sewing operation is outside a predetermined range. The sewing machine according to claim 2, wherein it is determined whether or not the thread tightening failure has occurred.   The sewing machine according to claim 5, wherein the sewing control unit includes a notification unit that notifies the thread tightening failure when the thread tightening failure determining unit determines that the thread tightening failure has occurred. The sewing means includes
A balance that moves up and down by driving the sewing machine motor and pulls up the upper thread that the rotary hook is entangled with the lower thread;
The poor sewing includes a thread breakage in which the upper thread is cut,
The sewing failure determination unit includes a thread breakage determination unit that determines whether or not the thread breakage has occurred in a specific sewing operation for forming a specific stitch on the cloth,
The yarn breakage determination unit rotates the output shaft based on the initial rotation angle phase of the output shaft at the start of the hook catching period in the hook catching period, which is a period in which the rotary hook catches the upper thread. The output shaft based on the initial rotation angle phase of the output shaft at the start of the balance pulling period in a balance pulling period in which the amount is less than a first predetermined value and the balance pulls the upper thread The sewing machine according to claim 2, wherein it is determined whether or not the yarn breakage has occurred by determining whether or not the rotation amount of the thread is less than a second predetermined value.   The said control part is provided with the stop control part which stops the drive of the said sewing means and the said motor, when the said sewing defect judgment part judges that the said sewing defect generate | occur | produced. 7. The sewing machine according to any one of 7 above.

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