CN110295463B - Sewing machine - Google Patents

Abstract

The invention relates to a sewing machine, which can make the upper thread tension to be the required tension compared with the prior art. The sewing machine has a sewing portion, a thread clamping mechanism, a driving portion and a control portion. The sewing part is provided with: a needle bar which is equipped with a needle and which can move up and down; and a thread take-up lever which moves up and down in synchronization with the up-and-down movement of the needle bar and can lift up the upper thread, and the sewing part can form a stitch on the fabric by using the machine needle. The thread tension mechanism can apply tension to the upper thread. The driving part is used for driving the wire clamping mechanism. The control part is used for controlling the driving of the sewing part and the driving part. The control part forms a stitch on the cloth by controlling the driving of the sewing part. The control part controls the drive of the drive part to control the supply of the upper thread and make the upper thread move towards the withdrawing direction opposite to the supply direction in the process of controlling the drive of the sewing part and in the period from the time when the needle bar is positioned at the bottom dead point of the vertical movement range to the time when the take-up lever is positioned at the top dead point of the vertical movement range.

Description

Sewing machine

Technical Field

The present invention relates to a sewing machine.

Background

A sewing machine capable of controlling the tension of an upper thread at the time of sewing by a pulse motor is known, and a sewing machine disclosed in japanese patent laid-open No. 2009 89823 includes a pulse motor, a thread tension disk, an encoder, an operation panel, and a sewing machine motor. The pulse motor has an output shaft. The sewing machine controls the driving of the pulse motor by inputting a driving pulse to the pulse motor driving part. The wire clamping disc is fixed on the output shaft. The thread clamping disc is wound with an upper thread. The encoder detects a rotational position of the output shaft. An operator inputs the upper thread tension to the sewing machine by means of the operation panel. When the sewing machine motor is driven, the sewing machine moves the needle bar up and down to perform sewing. When the sewing machine motor is driven, the sewing machine controls the driving of the pulse motor based on the detection result of the encoder, so that the upper thread tension reaches the input tension.

Due to the material of the fabric to be sewn, the operator may wish to change the needle thread tension at a predetermined timing in the vertical movement cycle of the needle bar. In the sewing machine, when the sewing machine motor is driven, the driving of the pulse motor is controlled so that the upper thread tension is maintained at the inputted tension. Therefore, in the case of the sewing machine, the upper thread tension may not reach the required tension, and the stitch may become unstable, resulting in poor sewing.

Disclosure of Invention

The invention aims to provide a sewing machine which can make the upper thread tension to be required tension compared with the prior art.

The sewing machine of claim 1 comprises: a sewing part having a needle bar equipped with a machine needle and capable of moving up and down, and a thread take-up lever that moves up and down in synchronization with the up and down movement of the needle bar and is capable of lifting up a needle thread, the sewing part being capable of forming a stitch on a fabric by means of the machine needle; a thread tension mechanism capable of applying tension to the upper thread; a driving section for driving the wire clamping mechanism; and a control part for controlling the drive of the sewing part and the drive part, the sewing machine is characterized in that the control part functions as a sewing control part and a thread clamping control part, the sewing control part is used for controlling the drive of the sewing part, and the stitch is formed on the cloth; the thread clamping control part is used for controlling the driving of the driving part to move the surface to a withdrawing direction opposite to the supplying direction in the process of controlling the driving of the sewing part by the sewing control part and in the period from the time when the needle rod is positioned at the bottom dead point of the vertical movement range to the time when the thread take-up lever is positioned at the top dead point of the vertical movement range. The sewing machine can control the drive of the drive part to control the supply of the upper thread during the sewing process, thereby leading the upper thread supplied to the side of the take-up lever than the thread clamping mechanism to move reversely to the supply direction. The sewing machine can provide proper tension to the upper thread when the take-up lever lifts the upper thread by moving the upper thread, thereby providing required tension to the upper thread more reliably than the existing sewing machine. Therefore, compared with the existing sewing machine, the sewing machine can stabilize the stitch during sewing, thereby inhibiting poor sewing.

The sewing machine according to claim 2 may further include a thread tension disk around which the upper thread is wound, wherein the drive unit is a motor having an output shaft that supports the thread tension disk in a rotatable manner, and an encoder that detects a rotation angle of the output shaft, and wherein the thread tension control unit controls the drive of the motor to rotate the thread tension disk in a direction opposite to a rotation direction in which the upper thread is supplied, in a process in which the sewing control unit controls the drive of the sewing unit. The sewing machine can make the thread clamping disc rotate reversely to the supplying direction of the upper thread by controlling the driving of the motor, thereby making the upper thread supplied to the side of the thread taking-up lever than the thread clamping disc move to the withdrawing direction.

The sewing machine according to claim 3 may include a shuttle mechanism having a shuttle tip and capable of catching a loop of the upper thread inserted through the needle by the shuttle tip, the shuttle mechanism rotating the shuttle in conjunction with a vertical movement of the needle, wherein the thread tension control unit controls the driving of the motor when the shuttle mechanism rotates the shuttle and during a shuttle release period from when the loop of the upper thread caught by the shuttle tip is released from the shuttle to when the upper thread is pulled up by the thread take-up lever to apply tension to the upper thread. The sewing machine can control the driving of the motor during the period of separating from the shuttle, so that the upper thread moves towards the withdrawing direction. The sewing machine can provide proper tension to the upper thread when the take-up lever lifts the upper thread by moving the upper thread excessively supplied between the thread clamping disc and the stitch in the withdrawing direction, thereby preventing poor sewing caused by insufficient tension of the upper thread during sewing.

The sewing machine according to claim 4 may further include a first input unit that enables the first movement amount by which the thread tension control unit moves the upper thread in the retraction direction during the shuttle disengagement period to be input, wherein the control unit may further function as a first acquisition unit that acquires a first rotation amount by which the drive of the motor is controlled to rotate the thread tension disc in the reverse direction based on the first movement amount input by the first input unit, and wherein the thread tension control unit controls the drive of the motor to rotate the thread tension disc in the reverse direction during the shuttle disengagement period to rotate the thread tension disc in the first rotation amount. The sewing machine can digitalize the variable (first rotation amount) for adjusting the surface thread tension when adjusting the surface thread tension. Therefore, compared with the existing sewing machine, the sewing machine can improve the repeatability of adjusting the tension of the upper thread in the period of separating from the shuttle, and the operator can simply adjust the tension of the upper thread in the period of separating from the shuttle compared with the prior art.

The thread tension control unit of the sewing machine according to claim 5 may control the driving of the motor to rotate the thread tension disk in the reverse direction when the shuttle mechanism rotates the shuttle, and may control the driving of the motor to rotate the thread tension disk in a shuttle catching period from when the hook tip meets the loop of the upper thread to catch the loop of the upper thread until the loop of the upper thread caught by the hook tip is released from the shuttle. The sewing machine is capable of imparting a desired tension to the thread during shuttle capture.

The sewing machine according to claim 6 may further include a detection unit capable of outputting an output value corresponding to a supply amount of the upper thread, which is a supply amount of the upper thread, to the control unit, wherein the control unit further functions as an output value acquisition unit for controlling driving of the motor to rotate the thread tension disc in the reverse direction during the hook capture period, and then acquiring the output value corresponding to the supply amount of the upper thread during a period before the loop of the upper thread captured by the hook tip is released from the hook, and a determination unit for determining whether or not a skip stitch of the loop of the upper thread captured by the hook is generated in accordance with the output value acquired by the output value acquisition unit. Compared with the existing sewing machine, the sewing machine can accurately judge whether the needle skipping occurs in the period before the loop of the upper thread captured by the shuttle tip is separated from the shuttle.

The sewing machine according to claim 7 may further include a second input unit that enables a second movement amount, which is an amount by which the needle thread is moved in the retraction direction by the needle thread tension control unit during the shuttle catch period, to be input by the second input unit, wherein the control unit may further function as a second acquisition unit that acquires a second rotation amount, which is a value for controlling the driving of the motor to rotate the needle thread tension disk in the reverse direction, based on the second movement amount input by the second input unit, and the needle thread tension control unit may control the driving of the motor to rotate the needle thread tension disk in the reverse direction during the shuttle catch period. The sewing machine can digitalize the variable (second rotation amount) for adjusting the surface thread tension when adjusting the surface thread tension. Therefore, compared with the existing sewing machine, the sewing machine can improve the repeatability of adjusting the tension of the upper thread in the catching period of the shuttle, and the operator can simply adjust the tension of the upper thread in the catching period of the shuttle compared with the prior art.

Drawings

Fig. 1 is a perspective view of the sewing machine 1.

Fig. 2 is a sectional view of the thread tension mechanism 60.

Fig. 3 is a schematic view of the output shaft 18 and the coil 33 of the clamp motor 16.

Fig. 4 is a block diagram of an electrical structure of the sewing machine 1.

Fig. 5 is a graph showing the first relational expression and the second relational expression.

Fig. 6A to 6D are explanatory diagrams showing a flow of capturing the upper thread 6 by the rotating hook 39.

Fig. 7 is an explanatory diagram showing a needle bar movement curve of the needle bar 11, a thread take-up lever thread amount curve of the thread take-up lever 51, a shuttle thread amount curve of the rotating hook 39, and a supply amount of the upper thread 6.

Fig. 8 is a flowchart of the sewing process.

Fig. 9 is a flowchart of a normal process.

Detailed Description

Embodiments of the present invention will be described. The following description uses the left and right, front and back, and up and down indicated by arrows in the drawings. The sewing machine 1 shown in fig. 1 is a knotter for forming knotted stitches on a cloth 99.

Referring to fig. 1 to 6A, a general structure of the sewing machine 1 will be described. The sewing machine 1 has a bed 2, a column 3, and a arm 4. The bed 2 is a base of the sewing machine 1, and is provided on a table extending horizontally. The base unit 2 includes a base main body 7 and a cylindrical base unit 8. The base main body portion 7 has a substantially box shape. The cylindrical housing part 8 extends forward from the housing main body part 7. The inside of the housing main body 7 and the inside of the cylindrical housing 8 communicate with each other. The tubular bed portion 8 has a needle plate 26 on the upper surface of the front end portion. The operator places the cloth 99 on the needle plate 26. Needle plate 26 has needle receiving holes. The pillar 3 extends upward from the rear portion of the base body 7. The arm portion 4 extends forward from an upper portion of the column portion 3 and faces the base portion 2. The front end of the arm 4 is a tip 5. The distal end portion 5 has a right wall portion 5A and a through hole 5B (see fig. 2). The right wall portion 5A is a wall portion of the tip portion 5 located on the right side. The through hole 5B penetrates the right wall portion 5A in the left-right direction.

As shown in fig. 4, the sewing machine 1 has a control device 30, an operation portion 46, and a pedal 38. The control device 30 is fixed to the lower surface of the table. The control device 30 controls the operation of the sewing machine 1. The operation portion 46 is fixed to the upper surface of the table. The operation unit 46 includes a display unit 48 and an operation knob 47. The display unit 48 can display various information. The operation knob 47 can detect various information input by the operator. The operation knob 47 includes a power knob.

As shown in fig. 1, the sewing machine 1 has a sewing mechanism 12. The sewing mechanism 12 has a needle bar 11, the needle bar 11 is equipped with a needle 10, and the needle bar 11 can move up and down, and the sewing mechanism can form a stitch 98 (see fig. 6A) on a fabric 99 by the needle 10. The sewing mechanism 12 includes a main motor 27 (see fig. 4), an upper shaft 15, a link, a thread take-up mechanism, a needle bar up-down movement mechanism, a shuttle mechanism 40, and a cloth feeding device 20. The main motor 27 is supported at the rear of the arm portion 4. The upper shaft 15 extends in the front-rear direction inside the arm portion 4. The rear end of the upper shaft 15 is coupled to an output shaft of the main motor 27 via a coupling. The upper shaft 15 can be rotated by the main motor 27. The front end and the rear end of the upper shaft 15 are coaxial with each other. The upper shaft 15 has a crank portion near the rear end portion. The crank portion is eccentric with respect to the axes of the front and rear ends of the upper shaft 15. The link extends in the vertical direction inside the column portion 3. The upper end portion of the connecting rod is connected to the crank portion so that the connecting rod can rotate relative to the crank portion. The connecting rod can reciprocate along with the rotation of the upper shaft 15.

The thread take-up mechanism and the needle bar up-and-down movement mechanism are supported by the tip end portion 5. The thread take-up mechanism has a thread take-up crank and a thread take-up lever 51. The thread take-up crank is connected to the front end of the upper shaft 15. The thread take-up lever 51 is provided to the thread take-up crank. The thread take-up lever 51 moves up and down in conjunction with the up-and-down movement of the needle bar 11 by the rotation of the thread take-up crank together with the upper shaft 15. The thread take-up lever 51 has an upper thread through hole. The thread take-up lever 51 holds the upper thread 6 inserted in the upper thread passing hole. The needle thread 6 (see fig. 6A) is fed from the needle thread supply source and is fed to the needle thread punch of the thread take-up lever 51 via a thread take-up mechanism 60 described later.

The needle bar up-and-down motion mechanism is provided with a needle bar crank connecting rod, a needle bar 11 and the like. The needle bar crank connecting rod is connected with the thread take-up crank in a rotatable mode and extends along the vertical direction. The needle bar 11 extends in the vertical direction and is connected to the needle bar crank link. The lower end of the shank 11 is fitted with a needle 10. The needle 10 has an eye 10A at a lower end (see fig. 6A). The upper thread 6 perforated by the upper thread of the thread take-up lever 51 can be inserted into the eye 10A of the needle 10, so that the needle 10 holds the upper thread 6. The needle bar 11 moves up and down together with the needle 10 by the reciprocating movement of the needle bar crank link by the rotation of the thread take-up crank.

The shuttle mechanism 40 is provided inside the housing unit 2, and has a lower shaft and a rotating shuttle 39. The lower shaft extends in the front-rear direction inside the housing main body 7 and inside the cylindrical housing part 8, and is rotatable. The lower shaft is connected to the link via a connecting portion, and the lower shaft is capable of reciprocating rotation in conjunction with the reciprocating motion of the link.

As shown in fig. 6A, the rotary hook 39 is provided at the front end of the lower shaft and below the needle receiving hole. The rotary hook 39 can rotate about a lower shaft. The rotary hook 39 has a hook tip 36 (see fig. 6A). The hook tip 36 is a part of the outer peripheral portion of the rotary hook 39, and protrudes toward the clockwise direction in the front view with the lower axis as the center. The bobbin case 32 can be fitted into the rotary hook 39. The bobbin case 32 accommodates a bobbin around which the lower thread 9 is wound. The bobbin case 32 has a lead-out portion 34. The bobbin thread 9 fed out from the bobbin can be guided to the outside by the lead-out portion 34.

As shown in fig. 1 and 4, the cloth feeding device 20 includes a movable body 31, a swing shaft, a cloth feeding table 37, a swing motor 41, a cloth feeding plate, a rack shaft 22, a moving motor 42, a pressing arm 23, and a cloth pressing motor 43. The movable body 31 is provided inside the base main body 7 so as to be movable forward and backward. The swing shaft is a shaft fixed to the movable body 31 and extending in the vertical direction, and protrudes upward from the base main body 7. The cloth feeding table 37 is connected to the movable body 31 inside the base body 7, and is provided on a swing shaft so as to be swingable. Therefore, the cloth feeding table 37 can move forward and backward together with the movable body 31 and can swing in the left-right direction about the swing axis. The swing motor 41 is connected to the cloth feeding table 37. The cloth feeding table 37 is driven by the swing motor 41 to swing about a swing axis. The cloth feeding plate is disposed on the upper surface of the base unit 2. The cloth feed plate supports the cloth 99. The cloth feeding plate is movable back and forth integrally with the cloth feeding table 37 and is swingable integrally with the cloth feeding table 37. The cloth feeding plate has a hole at the front end. The needles 10 moving up and down pass through the holes in the feed plate to the needle receiving holes in the needle plate 26.

The rack shaft 22 extends in the front-rear direction above the housing main body 7 and is movable forward and backward. The front end of the rack shaft 22 is coupled to the upper end of the swing shaft, and the rear end of the rack shaft 22 is located inside the column part 3. The movement motor 42 is provided inside the column part 3. The moving motor 42 can move the rack shaft 22 back and forth. In this case, the cloth feeding table 37, the cloth feeding plate, the swing shaft, and the movable body 31 move back and forth integrally with the rack shaft 22.

The pressing arm 23 extends upward from the cloth feeding table 37 and forward above the bed unit 2. The pressing arm 23 is movable back and forth integrally with the cloth feed table 37 and is swingable integrally with the cloth feed table 37. The presser arm 23 has a presser foot 24, a shaft portion 29, and a lever portion 25. The presser foot 24 is provided above the needle plate 26 so as to be movable up and down and is provided at the front end of the presser arm 23. The shaft portion 29 is provided at a substantially central portion in the front-rear direction of the pressure arm 23, with the left-right direction being an axial direction. The lever portions 25 are provided on the left and right surfaces of the pressing arm 23, respectively, and are rotatable about the shaft portion 29. The front end of the lever 25 is connected to the presser foot 24. The cloth pressing motor 43 is provided inside the column part 3. The cloth pressing motor 43 is connected to the rear end of the lever 25 via a link mechanism provided inside the arm 4. The presser foot 24 moves up and down by the lever portion 25 rotating about the shaft portion 29 in accordance with the driving of the presser motor 43. The presser foot 24 can press the cloth 99 between the presser foot 24 and the cloth feeding plate.

As shown in fig. 1 and 2, the sewing machine 1 includes a thread clamping mechanism 60 on a right wall portion 5A of the tip end portion 5. The thread tension mechanism 60 includes a thread tension cylinder 62, a thread tension holder 63, a thread take-up spring 65, a thread tension motor 16, a thread tension disc 69, and an encoder 21 (see fig. 4). The thread clamping mechanism 60 is capable of feeding the thread between the thread clamping disc 69 and the stitch 98 by the power of the thread clamping motor 16. The wire clamping tube 62 is an annular member fixed to the inside of the through hole 5B of the right wall portion 5A by a fastening member. The wire holder 63 is a ring-shaped member fixed to the inside of the wire-clamping cylinder 62 by the screw 14. The thread take-up spring 65 is fixed to the outer side surface of the thread clamping base 63 and wound between the thread clamping base 63 and the thread clamping cylinder 62. One end portion of the thread take-up spring 65 is exposed rightward from the right wall portion 5A. The wire clamping motor 16 is fixed to the inside of the arm part 4 by bolts. The clamp motor 16 has an output shaft 18, and the output shaft 18 penetrates a center hole of the clamp base 63 and protrudes to the right of the right wall portion 5A. The output shaft 18 is rotatable in the left-right direction as an axial direction, and a right end portion thereof rotatably supports the chuck 69 on the right side of the arm portion 4. In the present embodiment, the output shaft 18 is directly coupled to the chuck 69. The chuck plate 69 is fixed to the right end portion of the output shaft 18 by the screw 28. The needle thread 6 is wound around the thread take-up reel 69 by one to two turns.

The thread tension motor 16 applies tension to the thread 6 by rotating the thread tension disk 69 via the output shaft 18. The clamp motor 16 is a two-phase bipolar pulse motor. The clamp motor 16 includes a plurality of coils 33 (see fig. 3). The plurality of coils 33 are arranged along the rotational direction of the output shaft 18. The number of coils 33 in the present embodiment is four. The sewing machine 1 can supply current to each coil 33 bidirectionally. The sewing machine 1 controls a rotation angle (rotation position) of the output shaft 18 by an electromagnetic force generated by the plurality of electrically energized coils 33. The encoder 21 detects the rotation angle of the output shaft 18. A code wheel of an encoder 21 is fixed to a left end portion of the output shaft 18 and inside the arm portion 4.

Referring to fig. 4, an electrical structure of the sewing machine 1 is explained. The control device 30 of the sewing machine 1 has a CPU 91. The CPU91 can control the operation of the sewing machine 1 including the sewing mechanism 12 and the thread tension motor 16. The CPU91 is connected to a ROM92, a RAM93, a storage device 94, and an I/O interface (hereinafter referred to as I/O) 45. The ROM92 stores programs and the like for executing various processes such as a sewing process (see fig. 8) described later. The RAM93 is used to temporarily store various values. Storage device 94 is non-volatile. The storage device 94 stores sewing data for forming a stitch 98 on a cloth 99. The storage device 94 stores a first relational expression and a second relational expression, which will be described later.

The sewing period is a period in which the sewing machine 1 sews a stitch, that is, a period in which the upper shaft 15 rotates one turn. As shown in fig. 7, the period during which the sewing machine 1 sews a stitch is a period from the take-up lever top dead center, which is the upper end of the movable range, to the take-up lever bottom dead center, which is the lower end of the movable range, and then to the take-up lever top dead center, and this period substantially coincides with a period corresponding to the range of 60 degrees to 420 degrees of the rotation angle of the upper shaft 15. The off-shuttle period T1 is a period from when the upper thread 6 is taken off the shuttle after passing around the rotating shuttle 39, that is, "upper thread off-shuttle", until the thread take-up lever 51 lifts the upper thread 6 and applies tension to the upper thread 6. The shuttle catching period T2 is a period during which the hook tip 36 catches the upper thread 6. The shuttle catching period T2 is a period from "the hook of the upper thread on the shuttle" indicating the hook of the upper thread 6 by the hook of the upper thread 36 with the hook of the lower thread 6 by the meeting of the lower thread 36 and the needle 10 to "the upper thread is released from the shuttle". The convergence of the hook 36 and the needle 10 is a timing at which the hook 36 catches the loop of the upper thread 6 near the eye 10A. The detection period H is a period for monitoring whether or not a skip occurs. The skipping stitch refers to the following unfavorable condition: the hook tip 36 of the rotary hook 39 fails to catch the loop of the upper thread 6, and the stitch 98 cannot be formed on the cloth 99. The skip stitch is an example of poor sewing. The detection period H is set immediately before the hook 39 releases the loop of the upper thread 6. The detection period H in this example is a period from "the hook hooks the upper thread" to the needle bar top dead center, and includes the take-up lever bottom dead center and "the upper thread is disengaged from the hook". The CPU91 determines the shuttle off timing (first timing) set in the shuttle off period T1, the shuttle capturing timing (second timing) set in the shuttle capturing period T2, and the detection period H based on the rotation angle of the upper shaft 15 based on the detection result of the encoder 27A. The timing of the shuttle catching in this example is in the period T3 on the side of the "shuttle hook upper line" with respect to the detection period H.

The first relational expression and the second relational expression are used when controlling the driving of the clamp motor 16. The first relational expression is an expression that relates the electric angle to the a-phase current flowing to the a-phase that is one phase in the clamp motor 16. The second relational expression is an expression that relates the phase B current flowing to the phase B, which is another phase in the clamp motor 16, to the electrical angle. As shown in fig. 5, two sinusoids having phases shifted from each other by 90 degrees are shown in the graph representing the a-phase current and the B-phase current. The electrical angle of 360 degrees in the present embodiment corresponds to the mechanical angle of 7.2 degrees. The CPU91 controls the driving of the clamp motor 16 so that the phase difference of the output shaft 18 reaches a target value. The phase difference of the output shaft 18 is an absolute value of a difference between a reference phase as a reference of the output shaft 18 and a rotational angle phase of the output shaft 18. The sewing machine 1 maintains the upper thread tension at a predetermined tension by maintaining the phase difference of the output shaft 18 at a predetermined target value.

The I/O45 is connected to the drive circuits 81 to 86. The drive circuit 81 is connected to the main motor 27. The drive circuit 82 is connected to the swing motor 41. The drive circuit 83 is connected to the moving motor 42. The drive circuit 84 is connected to the cloth pressing motor 43. The swing motor 41, the traveling motor 42, and the cloth pressing motor 43 are pulse motors. An encoder 27A is provided on an output shaft of the main motor 27, an encoder 41A is provided on an output shaft of the swing motor 41, an encoder 42A is provided on an output shaft of the traveling motor 42, and an encoder 43A is provided on an output shaft of the cloth pressing motor 43. The encoder 27A detects the rotational position of the output shaft of the main motor 27 and outputs the detected rotational position to the CPU91 via the I/O45, the encoder 41A detects the rotational position of the output shaft of the swing motor 41 and outputs the detected rotational position to the CPU91 via the I/O45, the encoder 42A detects the rotational position of the output shaft of the shift motor 42 and outputs the detected rotational position to the CPU91 via the I/O45, and the encoder 43A detects the rotational position of the output shaft of the cloth pressing motor 43 and outputs the detected rotational position to the CPU91 via the I/O45. The CPU91 acquires the detection result of the encoder 27A and sends a control signal to the drive circuit 81, the CPU91 acquires the detection result of the encoder 41A and sends a control signal to the drive circuit 82, the CPU91 acquires the detection result of the encoder 42A and sends a control signal to the drive circuit 83, and the CPU91 acquires the detection result of the encoder 43A and sends a control signal to the drive circuit 84. Therefore, the CPU91 can control the driving of the main motor 27, the swing motor 41, the traveling motor 42, and the cloth pressing motor 43. In the following, the main motor 27, the swing motor 41, and the travel motor 42 will be collectively referred to as a drive motor.

The drive circuit 85 is connected to the clamp motor 16. The encoder 21 outputs the rotational position of the output shaft 18 of the thread tension motor 16 as a detection result to the CPU 91. The CPU91 controls the clamp motor 16 by sending a control signal to the drive circuit 85. The control method of the thread tension motor 16 will be described later.

The drive circuit 86 is connected to the display unit 48 in the operation unit 46. The CPU91 sends a control signal to the drive circuit 86 to display various information on the display unit 48. The operation knob 47 in the operation section 46 outputs the detected various information to the CPU91 via the I/O45. The pedal 38 outputs the detection result to the CPU91 via the I/O45. The CPU91 acquires the operation direction and the operation amount for the pedal 38 indicated by the detection result of the pedal 38.

With reference to fig. 6A to 6D, an outline of the operation of the sewing machine 1 will be described. The cloth 99 is placed on the cloth feeding plate and the needle plate 26, and the cloth 99 is pressed between the presser foot 24 and the cloth feeding plate by the presser foot 24. The main motor 27, the traveling motor 42, and the swing motor 41 are driven in synchronization with each other. The press arm 23 and the cloth feeding plate move back and forth with the driving of the moving motor 42, and oscillate back and forth in the left-right direction with the driving of the oscillating motor 41. Therefore, the cloth feeding device 20 moves the cloth 99 back and forth, and swings the cloth 99 back and forth in the right and left direction. When the main motor 27 is driven in synchronization with the moving motor 42 and the swing motor 41, the upper shaft 15 rotates. The needle bar up-and-down movement mechanism, the thread take-up mechanism and the rotary shuttle 39 are driven in conjunction with each other. The needle 10, which descends together with the shank 11, penetrates the cloth 99 and passes through the needle receiving hole. The upper thread 6 which has been lowered to the vicinity of the needle eye 10A below the needle receiving hole is in a ring shape (fig. 6A). The hook 36 catches the upper thread 6 in a loop shape by rotating the hook 39 clockwise in the main view. The needle 10 ascends to be separated from the cloth 99 upward, and the rotary hook 39 continues to rotate clockwise in the main view. The hook 36 pulls the endless upper thread 6 in the rotation direction to expand the diameter of the endless upper thread 6 (fig. 6B). When the upper thread 6 in a loop shape passes around the rotary hook 39 and is separated from the rotary hook 39 (fig. 6C), the upper thread 6 is interwoven with the lower thread 9. The rotating direction of the rotary hook 39 is switched to the counterclockwise direction in the main view, and the thread take-up lever 51 lifts the upper thread 6 interlaced with the lower thread 9 (fig. 6D). The upper thread 6 in a ring shape is reduced in diameter, so that the sewing machine 1 finishes sewing one needle. The sewing machine 1 performs one stitch sewing every time the upper shaft 15 rotates 360 degrees. The sewing machine 1 repeats the above operations to form a stitch 98 on the fabric 99.

The sewing process will be described with reference to fig. 8. The sewing process is a process in which the sewing machine 1 sews the fabric 99. When the operator operates the operation knob 47 to start power supply to the sewing machine 1, the CPU91 reads out a program from the ROM92 to the RAM93 to execute sewing processing.

The CPU91 executes initialization processing (S1). The CPU91 reads various setting values from the storage device 94 into the RAM 93. The CPU91 acquires the rotation angle of the output shaft 18 of the thread tension motor 16 based on the detection result of the encoder 21 (S2). This rotational angle is the reference phase of the output shaft 18 in the initial state, and is stored in the RAM 93. The CPU91 acquires the first and second movement amounts input with the operation knob 47 (S3). The first movement amount is an amount for moving the upper thread 6 supplied to the thread take-up lever 51 side of the thread take-up mechanism 60 in the retracting direction. The retracting direction is a direction closer to the needle thread supply source (e.g., bobbin) than the thread tension mechanism 60. At the timing of the removal from the shuttle (first timing), the thread tension disk 69 rotates in the reverse direction of the rotation direction at the time of feeding the upper thread 6 (counterclockwise direction in right view), and the upper thread 6 is moved by a first movement amount. The second movement amount is an amount for moving the upper thread 6 supplied to the thread take-up lever 51 side of the thread take-up mechanism 60 in the retracting direction. At the shuttle catching timing (second timing), the thread take-up reel 69 rotates in the reverse direction to move the upper thread 6 by the second movement amount. The first and second shift amounts may be absolute amounts indicating a length of the face line 6 shifted in the retracting direction, or relative amounts indicating the length. When the operator inputs a specific numerical value as the first movement amount by operating the operation knob 47, the CPU91 acquires the input first movement amount. When the operator inputs a specific numerical value as the second movement amount by operating the operation knob 47, the CPU91 acquires the input second movement amount. The CPU91 may acquire predetermined values as the first movement amount and the second movement amount. The values of the first rotation amount and the second rotation amount may be the same or different.

The CPU91 acquires a target value corresponding to the prescribed tension (S4). The upper thread tension has a correlation with the torque generated by the thread tension motor 16. The target value is the phase difference of the output shaft 18 when the value of the face line tension calculated based on the correlation stored in the storage device 94 reaches a predetermined tension. The predetermined tension may be a value input by an operator or a predetermined value. The CPU91 calculates the first and second rotation amounts from the first and second movement amounts acquired in S3 according to the correlation between the movement amount of the upper thread 6 and the rotation amount of the output shaft 18 of the thread take-up motor 16 (S5). The first amount of rotation is the amount of rotation the output shaft 18 would have to rotate in the reverse direction when disengaged from the shuttle. The second amount of rotation is the amount of rotation that the output shaft 18 would like to rotate in the reverse direction when the shuttle is captured.

The CPU91 determines whether or not a sewing start instruction of the sewing machine 1 is detected (S6). The operator inputs a sewing start instruction by operating the operation knob 47 or the pedal 38. The CPU91 is in a standby state before detecting the sewing start instruction (S6: NO). During standby, the operator places the cloth 99 on the needle plate 26 and the cloth feeding plate. When the sewing start instruction is input by the operator after the cloth 99 is placed (S6: yes), the CPU91 controls the drive of the cloth pressing motor 43 to lower the presser foot 24 (S7). The presser foot 24 sandwiches the cloth 99 between the presser foot 24 and the cloth feed plate. The CPU91 determines the energization types corresponding to the respective coils 33 and energizes them (S8). The energization types include a phase-a current and a phase-B current. The CPU91 determines the energization type based on the first relational expression, the second relational expression, the rotation angle of the output shaft 18 acquired in S2, and the target value calculated in S4.

CPU91 controls the driving of the driving motor to form stitch 98 on fabric 99 (S10). The needle bar 11, the rotary hook 39 and the cloth feeding table 37 are operated in synchronization with each other. The CPU91 determines whether or not it is the first timing based on the output value of the encoder 27A (S11). When the CPU91 determines that it is the first timing (yes in S11), the CPU91 controls the drive circuit 85 to rotate the output shaft 18 of the thread tension motor 16 in the reverse direction (counterclockwise in the right view) by the first rotation amount calculated in S5 (S12). The CPU91 controls the driving of the clamp motor 16 until the rotation amount of the output shaft 18 of the clamp motor 16 in the reverse rotation reaches the first rotation amount. When the CPU91 determines that it is not the first timing (S11: no), the CPU91 determines whether it is the second timing based on the output value of the encoder 27A (S13). When the CPU91 determines that it is the second timing (yes in S13), the CPU91 controls the drive circuit 85 to rotate the output shaft 18 of the pinch motor 16 in the reverse direction by the second rotation amount calculated in S5 (S14). The CPU91 controls the driving of the clamp motor 16 until the rotation amount of the output shaft 18 of the clamp motor 16 in the reverse rotation reaches the second rotation amount. After S12 or S14, the CPU91 performs S22 described later.

When the CPU91 determines that it is not the second timing (S13: no), the CPU91 executes normal processing (S15). The normal process is a process of controlling the tension of the face thread to a predetermined tension. As shown in fig. 9, the CPU91 acquires the rotation angle of the output shaft 18 of the pinch motor 16 (S31). The CPU91 determines whether the comparison value is greater than the threshold value (S32). The comparison value is obtained by subtracting the target value from the phase difference of the output shaft 18. The CPU91 calculates a comparison value using the rotation angle of the output shaft 18 acquired in S31, the target value acquired in S4, and the reference phase stored in the RAM 93. The threshold value is determined according to the target value and is a value greater than 0. When the sewing machine 1 starts the sewing operation, the phase difference is theoretically 0 (S32: No). In this case, the CPU91 ends the normal processing and returns the processing to the sewing processing in fig. 8.

After a predetermined number of times of normal processing (S15) from the sewing processing, the comparison value becomes greater than the threshold value (S32: YES). In this case, the needle thread tension is greater than the prescribed tension corresponding to the target value acquired in S4. The CPU91 determines the energization types corresponding to the respective plurality of coils 33 (S33). The CPU91 determines an energization type capable of eliminating the difference between the phase difference of the output shaft 18 and the target value, based on the first relational expression, the second relational expression, and the rotation angle of the output shaft 18 acquired in S31 (S33). The CPU91 switches the energization type being performed for the plurality of coils 33 to the energization type determined in S33 (S34). The output shaft 18 rotates, and the upper thread tension is returned to the prescribed tension corresponding to the target value acquired in S4. At this time, the CPU91 rewrites the RAM93 with the rotational angle of the output shaft 18 after rotation as a reference phase. The CPU91 ends the normal processing. The CPU91 determines the energization type based on the output value of the encoder 21 every time S33 is executed (S33), and switches the energization types of the plurality of coils 33 (S34). S15 is repeatedly executed by the CPU91, whereby the sewing machine 1 maintains the upper thread tension at the prescribed tension corresponding to the target value acquired in S4.

The CPU91 determines whether or not the detection period H is present, based on the output value of the encoder 27A (S16). When the CPU91 determines that the detection period H is not present (S16: no), the CPU91 performs S22 described later. When the CPU91 determines that it is the detection period H (S16: yes), the CPU91 acquires the output value of the encoder 21 as an output value according to the amount by which the shuttle pulls the upper thread 6 (S17). The amount by which the upper thread 6 is pulled by the rotating hook 39 is an amount by which the upper thread 6 is moved in the feeding direction. The CPU91 determines whether a stitch jump has occurred based on the output value acquired in S17 (S18). The detection period H includes a period in which the upper thread 6 is moved in the feeding direction by the hook 39 pulling the upper thread 6. The thread take-up reel 69 rotates in accordance with the amount by which the shuttle pulls the upper thread 6. The CPU91 detects whether or not a needle jump has occurred based on the amount by which the shuttle pulls the upper thread based on the output value of the encoder 21 in the detection period H. As shown in a lower legend V4 in fig. 7, when the rotary hook 39 is not pulled to the upper thread 6, the upper thread supply amount is not changed during the detection period H. Therefore, the CPU91 detects that the skip stitch has occurred based on the output value of the encoder 21 (S18: YES). In this case, the CPU91 notifies that an error has occurred (S19). The CPU91 controls the drive circuit 86 to display the content "the skip stitch is detected" on the display unit 48, for example. The CPU91 determines whether or not to stop the driving of the drive motor (S20). The CPU91 makes this determination in accordance with the setting content stored in advance in the storage device 94. When the CPU91 determines that the drive of the drive motor is not to be stopped (S20: no), the CPU91 performs S22 described later. When the CPU91 determines that the drive of the drive motor is to be stopped (yes in S20), the CPU91 stops the drive of the drive motor (S21) and ends the sewing process.

As shown in a lower legend V3 of fig. 7, when the CPU91 determines that the upper thread 6 is supplied during the detection period H, the CPU91 detects that the stitch skipping has not occurred (S18: no). In this case, the CPU91 determines whether or not a sewing end instruction of the sewing machine 1 is detected based on the detection result of the operation knob 47 (S22). The sewing end instruction indicates that the operation of the pedal 38 by the operator is stopped or the sewing is ended based on the sewing data. When the CPU91 does not detect the sewing end instruction, the CPU91 continues the sewing operation (S22: NO). When the CPU91 detects the sewing end instruction (S22: yes), the CPU91 stops driving of the drive motor (S23). The needle bar 11, the rotating shuttle 39, and the cloth feeding table 37 stop operating. The CPU91 controls the driving of the cloth pressing motor 43 to raise the presser foot 24 (S24), and then ends the sewing process. The cloth 99 can be taken off from the sewing machine 1.

In the above embodiment, the sewing mechanism 12 is an example of a sewing portion of the present invention, the thread tension motor 16 is an example of a driving portion (motor) of the present invention, the rotary hook 39 is an example of a shuttle of the present invention, the encoder 21 is an example of a detecting portion of the present invention, and the control device 30 is an example of a control portion of the present invention. The operation knob 47 is an example of the first input unit and the second input unit of the present invention. The CPU91 executing S10 is an example of the sewing control unit of the present invention. The CPU91 when executing S12 and S14 is an example of the pinch control unit of the present invention. The CPU91 when executing S3 and S5 is an example of the first acquisition unit of the present invention. The CPU91 executing S17 exemplifies the output value acquisition unit of the present invention. The CPU91 executing S18 exemplifies the determination unit of the present invention. The CPU91 when executing S3 and S5 is an example of the second acquisition unit of the present invention.

The sewing machine 1 of the above embodiment can control the drive of the thread tension motor 16 to control the supply of the upper thread 6 during sewing, so that the upper thread 6 supplied to the side of the thread take-up lever 51 relative to the thread tension mechanism 60 moves in the reverse direction of the supply direction (S12, S14). The sewing machine 1 can apply an appropriate tension to the upper thread 6 when the thread take-up lever 51 lifts the upper thread 6 by moving the upper thread 6, and can reliably apply a desired tension to the upper thread 6 as compared with a conventional sewing machine. Therefore, the sewing machine 1 can stabilize the stitch during sewing as compared with the conventional sewing machine, and can suppress defective sewing.

The output shaft 18 of the clamp motor 16 rotatably supports the clamp plate 69. The CPU91 controls the driving of the thread tension motor 16 to rotate the thread tension disk 69 in the reverse direction in the process of controlling the driving of the sewing mechanism 12 (S12, S14). The sewing machine 1 can move the upper thread 6 supplied to the thread take-up lever 51 side of the thread take-up reel 69 in the direction of the upper thread supply source side of the thread take-up reel 69 by controlling the driving of the thread take-up motor 16 to rotate the thread take-up reel 69 in the reverse direction.

The sewing machine 1 controls the driving of the thread tension motor 16 during the off-shuttle period T1 (S12). More specifically, the sewing machine 1 controls the driving of the thread tension motor 16 at the shuttle off timing set in the shuttle off period T1 to move the upper thread 6 in the retracting direction. The sewing machine 1 moves the upper thread 6 excessively supplied between the thread take-up reel 69 and the stitch 98 in the retracting direction during the off-shuttle period T1. Therefore, the sewing machine 1 can apply an appropriate tension to the upper thread 6 when the thread take-up lever 51 lifts the upper thread 6, and can suppress a sewing failure caused by insufficient tension of the upper thread at the time of sewing.

The CPU91 acquires a first rotation amount according to the first movement amount input with the operation knob 47 (S3, S5). The CPU91 controls the driving of the thread tension motor 16 during the shuttle off period T1 to rotate the thread tension disk 69 in the reverse direction by the first rotation amount calculated in S5 (S12). In the case of the existing sewing machine, when the tension of the surface thread is adjusted, an operator adjusts the thread take-up spring intuitively. In the case of the sewing machine 1, when the surface thread tension is adjusted, the variable (first rotation amount) for adjusting the surface thread tension can be digitalized. Therefore, the sewing machine 1 can improve the repeatability of adjusting the upper thread tension during the period T1 when the needle thread is disengaged from the shuttle compared with the conventional sewing machine, and can easily adjust the upper thread tension for the operator compared with the conventional one.

The sewing machine 1 controls the driving of the thread take-up motor 16 to rotate the thread take-up disk 69 in the reverse direction during a shuttle catch period T2 from when the hook 36 meets the loop of the upper thread 6 with the loop of the upper thread 6 to catch the loop of the upper thread 6 until the loop of the upper thread 6 caught by the hook 36 is released from the hook 39. The sewing machine 1 is capable of imparting a desired tension to the thread 6 during the shuttle catching period T2.

The sewing machine 1 has an encoder 21. The encoder 21 can output an output value corresponding to the needle thread supply amount, which is the amount of movement of the needle thread 6 in the supply direction, to the control device 30. The CPU91 controls the driving of the thread tension motor 16 during the shuttle catching period T2 to rotate the thread tension disk 69 in the reverse direction, and thereafter acquires an output value corresponding to the amount of thread supplied during the detection period H (S17). The detection period H is set before the loop of the upper thread 6 caught by the hook tip 36 is released from the rotating hook 39. The CPU91 determines whether or not a skip occurs in accordance with the output value acquired in S17 (S18). Compared with the existing sewing machine, the sewing machine 1 can accurately judge whether the skip stitch occurs in the detection period H. In the case of the conventional sewing machine, the drive of the thread tension motor 16 is not controlled to rotate the thread tension disk 69 in the reverse direction during the shuttle catching period T2. Therefore, the upper thread supply amount in the normal case is, for example, a legend V1 shown in the lower part of fig. 7, and the upper thread supply amount when the skip stitch occurs is a legend V2 shown in the lower part of fig. 7. The difference of the upper thread supply amount in the detection period H of the legend V3 and the legend V4 of the sewing machine 1 is larger than the difference of the upper thread supply amount in the detection period H of the legend V1 and the legend V2. Therefore, the sewing machine 1 can accurately judge whether the skip stitch occurs based on the upper thread supply amount in the detection period H, compared with the conventional sewing machine.

The sewing machine 1 has an operation knob 47. The second movement amount, which is the amount of movement of the upper thread 6 in the retracting direction during the shuttle catching period T2, can be input by the operation knob 47. The CPU91 acquires a second rotation amount according to the second movement amount input with the operation knob 47 (S3, S5). The CPU91 controls the driving of the thread tension motor 16 during the shuttle catching period T2 to rotate the thread tension disk 69 in the reverse direction by the second rotation amount (S14). In the case of the existing sewing machine, when the tension of the surface thread is adjusted, an operator adjusts the thread take-up spring intuitively. In the case of the sewing machine 1, when the surface thread tension is adjusted, the variable (second rotation amount) for adjusting the surface thread tension can be digitalized. Therefore, the sewing machine 1 can improve the repeatability of adjusting the upper thread tension during the shuttle catching period T2 compared with the conventional sewing machine, and can easily adjust the upper thread tension for the operator compared with the conventional one.

The present invention is not limited to the above-described embodiments. The sewing machine may be a sewing machine for a flat seam, a buttonhole sewing machine, or the like, or a home sewing machine or an embroidery sewing machine. The sewing machine may be a circular sewing machine or the like without a shuttle mechanism. The thread tension mechanism may be a mechanism capable of sequentially releasing the upper thread. This mechanism may be a known mechanism that can control the tension when the upper thread is fed out one by one, for example. The retracting direction may be changed according to the structure of the wire clamping mechanism. The driving unit is a single-phase motor, a three-phase or more motor, various electric motors such as a DC (direct current) motor and a coreless motor, an electromagnetic valve, a cylinder, and the like, depending on the structure of the wire clamping mechanism. The sewing machine can omit the first input part and the second input part. The first input unit and the second input unit may have other configurations such as a dial input unit and a touch panel. The sewing machine may further include a detection unit capable of outputting an output value corresponding to the upper thread supply amount to the control unit, in addition to the encoder capable of detecting the rotation angle of the output shaft of the thread tension motor.

The program for executing the sewing process in fig. 8 may be stored in a storage device of the sewing machine before the sewing machine executes the program. The program acquisition method, the acquisition path, and the device for storing the program may be appropriately changed, respectively. Alternatively, the sewing machine may receive a program to be executed by the processor from another device by wire or wireless communication, and store the program in the storage device. Other devices include, for example, computers and servers connected via a network. The storage device of the sewing machine may be a storage device such as an HDD or an SSD.

The steps in the sewing process in fig. 8 are not limited to the example executed by the CPU91, and some or all of the processes may be executed by another electronic device (for example, ASIC). Each step in the above-described processing may be distributed processing by a plurality of electronic devices (for example, a plurality of CPUs). The order of the steps in the sewing process of the above embodiment can be changed as necessary, and the steps can be omitted or added. The present invention may be embodied as follows: the functions of the above embodiments are realized by executing a part or all of the actual processing by an OS or the like operating on the position specifying device in accordance with an instruction from the control unit of the sewing machine.

The sewing machine may not perform a general process but adjust the upper thread tension directly using the thread take-up spring. The sewing machine may omit S17, S18. The detection period of S16 may be changed as appropriate. When detecting the occurrence of a stitch skipping (S18: YES), the sewing machine may continue driving the drive motor. The notification method at S19 may be by audio output or the like, depending on the configuration of the notification unit. The sewing machine may be configured such that the drive of the drive unit is controlled to control the supply of the upper thread and the upper thread is moved in the retracting direction during at least one of the shuttle catching period and the shuttle disengaging period. The sewing machine may control the drive of the drive unit to control the supply of the upper thread and move the upper thread in the retracting direction at two or more timings during at least one of the shuttle catching period and the shuttle disengaging period.

Claims (7)

1. A sewing machine (1) has:

a sewing part (12) having a needle bar (11) to which a needle (10) is attached and which can move up and down, and a thread take-up lever (51) which moves up and down in synchronization with the up and down movement of the needle bar and which can lift up an upper thread (6), the sewing part being capable of forming a stitch (98) on a fabric (99) by means of the needle;

a thread tension mechanism (60) capable of applying tension to the upper thread;

a driving section for driving the wire clamping mechanism; and

a control part (30) for controlling the driving of the sewing part and the driving part,

the sewing machine is characterized in that the sewing machine is provided with a sewing machine,

the control part functions as a sewing control part and a thread clamping control part,

the sewing control part is used for controlling the driving of the sewing part and forming the stitch on the cloth,

the thread clamping control part is used for controlling the driving of the driving part to move the surface to a withdrawing direction opposite to the supplying direction in the process of controlling the driving of the sewing part by the sewing control part and in the period from the time when the needle rod is positioned at the bottom dead point of the vertical movement range to the time when the thread take-up lever is positioned at the top dead point of the vertical movement range.

2. The sewing machine of claim 1,

the sewing machine has a thread take-up reel (69) around which the upper thread is wound,

the drive unit is a motor (16) having an output shaft (18) that rotatably supports the wire clamping plate,

the sewing machine further has an encoder (21) capable of detecting a rotation angle of the output shaft,

the thread clamping control part controls the driving of the motor in the process that the sewing control part controls the driving of the sewing part, so that the thread clamping disc rotates reversely to the rotating direction of the upper thread.

3. The sewing machine of claim 2,

the sewing machine comprises a shuttle mechanism (40) having a shuttle (39) having a shuttle tip (36) for catching a loop of the upper thread passing through the needle, the shuttle mechanism rotating the shuttle in conjunction with the vertical movement of the needle,

the thread tension control unit controls the driving of the motor when the shuttle mechanism rotates the shuttle and during a shuttle release period from when the loop of the upper thread caught by the shuttle tip is released from the shuttle to when the upper thread is lifted by the thread take-up lever to apply tension to the upper thread.

4. The sewing machine of claim 3,

the sewing machine further comprises a first input unit (47) for inputting a first movement amount by which the upper thread is moved in the retracting direction by the thread tension control unit during the shuttle disengaging period,

the control unit further functions as a first acquisition unit that acquires a first rotation amount for controlling the driving of the motor to rotate the wire chuck in the reverse direction based on the first movement amount input by the first input unit,

the thread tension control unit controls the driving of the motor to rotate the thread tension disc in the reverse direction by the first rotation amount during the shuttle release period.

5. Sewing machine as in claim 3 or 4,

the thread tension control unit controls the driving of the motor to rotate the thread tension disk in the reverse direction when the shuttle mechanism rotates the shuttle, and during a shuttle catching period from when the shuttle peak meets the loop of the upper thread to catch the loop of the upper thread until the loop of the upper thread caught by the shuttle peak is separated from the shuttle.

6. Sewing machine as in claim 5,

the sewing machine further comprises a detection part (21) which can output an output value corresponding to the upper thread supply amount which is the supply amount of the upper thread in the supply direction to the control part,

the control unit also functions as an output value acquisition unit and a determination unit,

the thread tension control unit controls the driving of the motor to rotate the thread tension disc in the reverse direction during the shuttle catching period, and then the output value acquiring unit acquires the output value corresponding to the thread feeding amount during a period until the loop of the upper thread caught by the shuttle tip is released from the shuttle,

the determination unit determines whether or not a skip stitch of a loop in which the upper thread is not caught by the shuttle occurs, in accordance with the output value acquired by the output value acquisition unit.

7. The sewing machine of claim 6,

the sewing machine further comprises a second input part (47) which can be used for inputting a second movement amount, wherein the second movement amount is the amount of the upper thread moving towards the withdrawing direction in the shuttle catching period by the thread clamping control part,

the control unit further functions as a second acquisition unit that acquires a second rotation amount for controlling the driving of the motor to rotate the wire chuck in the reverse direction based on the second movement amount input by the second input unit,

the thread tension control unit controls the driving of the motor to rotate the thread tension disc in the reverse direction by the second rotation amount during the shuttle catching period.

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