JP2013180007A - sewing machine - Google Patents

Abstract

To provide a sewing machine capable of preventing an upper thread from being wound around a rotary balance without damaging a sewing product when a thread breakage of the upper thread occurs.
A thread hook 18 for guiding an upper thread 10 hung on a rotary balance 9 to a needle bar 3 and a thread hook for guiding an upper thread 10 provided on the needle bar 3 and guided by the thread hook 18 to a sewing needle 2. 19 is provided between the yarn hooking portion 18 and the yarn hooking portion 19, and a sensor 40 is provided that receives the reflected light of the light projected toward the upper yarn 10 and outputs a light receiving signal corresponding to the amount of light received. It was. Further, when the sensor 40 outputs a light reception signal when there is no upper thread 10 at a predetermined timing, it is determined that the upper thread is broken.
[Selection] Figure 2

Description

  The present invention relates to a sewing machine including a rotary balance, and more particularly to a sewing machine that can detect thread breakage of an upper thread.

  Conventionally, a rotary balance used in a staggered sewing machine or the like protrudes outward from a face plate at an end of an arm portion and can rotate in conjunction with a sewing machine main shaft. An upper thread to be supplied from the upper thread supply source to the sewing needle is hung on the rotary balance. When the upper thread breaks during sewing, the upper thread is wound around the rotating rotary balance.

  The sewing machine disclosed in Patent Document 1 includes a rotary balance guard cover that covers the rotary balance from the outside of the face plate. The rotary balance guard cover includes an annular balance guard that is fixed to the outer surface of the face plate at the end of the arm portion and protrudes outward from the outer surface of the face plate, and a cover member that is provided on the end face of the balance guard and rotates in a vertical plane.

  The cover member can cover the outer circumference of the rotary balance between the cover guard and the balance guard by covering the opposite side of the face plate of the balance guard by turning. If the upper thread breaks during sewing and the upper thread is wound around the rotary balance, the cover member is rotated to open the side opposite the face plate of the balance guard, and the upper thread wound around the rotary scale is removed. be able to.

JP 2001-145794 A

  However, in the sewing machine described in Patent Document 1, when the upper thread breaks during sewing and the upper thread is wound around the rotary balance, the upper thread does not exist on the sewing needle. Since the sewing machine does not perform stop control even if the upper thread breaks, the sewing product will not be able to form a stitch when the sewing needle that does not pass the upper thread passes through the sewing object, resulting in damage to the sewing product. was there. Further, the upper thread is wound around the rotary balance by the amount of rotation of the rotary balance after the upper thread is broken. Therefore, the trouble of removing the wound upper thread is increased, and there is a problem that production time is lost.

  An object of the present invention is to provide a sewing machine that can prevent an upper thread from being wound around a rotary balance without damaging the sewing product when the upper thread breaks.

  In order to achieve the above object, a first aspect of the present invention is a motor that rotationally drives a main shaft, a rotary balance that is connected to the main shaft and rotates in conjunction with the main shaft by the driving of the motor, and a hung on the rotary balance. In a sewing machine comprising a needle bar that fixes a sewing needle that passes the passed upper thread and swings in a horizontal direction, a first thread guide portion that guides the upper thread that is passed over the rotary balance to the needle bar, and A second thread guide section that is provided on a needle bar and guides the upper thread guided by the first thread guide section to the sewing needle, and is disposed between the first thread guide section and the second thread guide section; A sensor that receives reflected light or transmitted light of light projected toward the upper thread and outputs a light reception signal corresponding to the amount of light received, and the light reception signal when the sensor does not have the upper thread at a predetermined timing Means for determining that the upper thread is broken. , When the determining unit determines that yarn breakage of the upper thread, characterized in that it comprises a stop means for stopping the driving of the motor.

  In the first invention of the present application, a first thread guide part that guides an upper thread that is below the rotary balance and is wound on the rotary scale to the needle bar, and an upper thread that is provided on the needle bar and guided by the first thread guide part. A sensor is disposed between the second thread guide portion that guides the needle to the sewing needle. Based on the light reception signal output from the sensor, the determination means determines that a thread breakage of the upper thread has occurred when a light reception signal when there is no upper thread is output at a predetermined timing. When it is determined that the upper thread breakage has occurred, the sewing machine controls to stop driving the motor. Therefore, the sewing machine can prevent the sewing product from being damaged because the sewing needle is stuck in the sewing product after the thread breakage of the upper thread, and the stitches cannot be formed. The sewing machine can eliminate the trouble of removing the upper thread after the thread breakage of the upper thread is not excessively wound on the rotary balance, thereby avoiding production time loss.

  According to a second invention, in the first invention, the first yarn guide portion is provided below the rotary balance and at a lower end of an arm portion of a sewing machine, and the sensor is provided at the lower end of the arm portion and the first yarn guide portion. The light is projected toward the upper thread passing through the lower end.

  In the sewing machine of the second invention of the present application, the first thread guide portion is provided below the rotary balance and at the lower end of the arm portion of the sewing machine. The sensor projects light toward the upper thread that is provided at the lower end of the arm part and passes through the lower end of the first thread guide part. The upper yarn immediately after passing through the first yarn guide portion is restricted from moving in the front-rear direction and the left-right direction by the first yarn guide portion. The upper thread has the least movement (swaying and flickering) around the first thread guide part provided below the rotary balance and at the lower end of the arm part of the sewing machine. Accordingly, since the sewing machine is provided with a sensor at a position where the upper thread can be detected immediately after passing through the first thread guide portion, the presence or absence of the upper thread can be reliably detected.

  According to a third invention, in the first or second invention, the predetermined timing is a period during which the rotary balance rotates at least 360 ° or more.

  The sewing machine according to the third aspect of the present invention detects in a period during which the rotary balance rotates at least once. Therefore, even if the sewing machine does not always have a constant upper thread behavior on the rotary balance due to the sewing conditions (sewing needle swing width and sewing speed), the needle thread breaks due to a signal output erroneously by the sensor. Can be prevented.

  According to a fourth invention, in the first or second invention, the predetermined timing is a period during which the rotary balance tightens the upper thread.

  The sewing machine according to the fourth aspect of the present invention detects in a period in which the rotary balance with the minimum movement (runout / flapping) of the upper thread during sewing tightens the upper thread. Therefore, the sewing machine can easily detect the thread breakage of the upper thread without continuously detecting it by the sensor during one rotation of the rotary balance.

  ADVANTAGE OF THE INVENTION According to this invention, when the thread breakage of an upper thread | yarn occurs, the sewing machine which does not damage a to-be-sewn material and prevents an upper thread | yarn from being wound around a rotary balance can be provided.

It is a principal part perspective view of a staggered sewing machine. It is a left view of a staggered sewing machine. FIG. 3 is a partially enlarged view of FIG. 2. It is a partial front view of a staggered sewing machine. It is an enlarged view of a sensor front-end | tip part. It is a block diagram of a control system of a staggered sewing machine. It is a flowchart which shows a thread break detection process. It is a figure explaining the state in which the upper thread moves greatly from front to back and from side to side. It is a thread quantity curve diagram of a staggered sewing machine. It is a flowchart which shows the change form of a thread breakage detection process. It is a time chart which shows the relationship between an upper shaft rotation speed and the number of needles.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The configuration of the staggered sewing machine M will be described with reference to FIGS. Note that the lower right side, upper left side, lower left side, upper right side, upper side, and lower side in FIG. 1 are the front side, rear side, left side, right side, upper side, and lower side of the staggered sewing machine M, respectively.

  As shown in FIGS. 1 to 4, the staggered sewing machine M includes an arm portion 1. The arm part 1 holds the needle bar 3 inside the left end part. The needle bar 3 has the sewing needle 2 attached to the lower end. The arm portion 1 is provided with a presser foot 4 that presses a work cloth against a needle plate (not shown) below the left end portion. The arm portion 1 is provided with an adjusting screw 5 for adjusting the pressing force of the presser foot 4 on the upper left end portion. The arm unit 1 includes an upper shaft (main shaft, not shown) that rotates by driving an upper shaft motor 75 (see FIG. 6), and a needle bar vertical drive mechanism (not shown) that drives the needle bar 3 up and down by rotating the upper shaft. And a needle bar swing drive mechanism (not shown) that drives the needle bar 3 to swing left and right. The upper shaft extends in the left-right direction within the arm portion 1. Since the needle bar up / down drive mechanism and the needle bar swing drive mechanism are well-known techniques, detailed description thereof is omitted. The arm unit 1 includes an operation panel 6 on the front side. The operator operates the operation panel 6 to select a stitch shape to be used for sewing, set a stitch size, and the like.

  The arm portion 1 is provided with a face plate 7 at the left end portion. The face plate 7 has a circular hole (not shown) communicating with the inside of the arm portion 1. The upper shaft has a rotating plate 8 connected to the left end portion so as to be interlocked with the upper shaft. The rotating plate 8 is positioned loosely in a circular hole in the face plate 7. The rotary balance 9 is fixed to the left end surface of the rotating plate 8. The rotary balance 9 includes a rotating arm portion 9a and an upper thread holding portion 9b. The rotating arm portion 9 a is fixed to the rotating plate 8 and rotates together with the rotating plate 8. The rotating arm portion 9a protrudes leftward from the face plate 7 and rotates about the same rotation axis a as the upper shaft. The upper thread holding portion 9b extends from the left end portion of the rotating arm portion 9a in a substantially arc shape in the rotating direction of the rotating arm portion 9a.

  The face plate 7 includes a thread hook 18 and a bracket 41 at the lower end. The thread hook 18 is located below the circular hole of the face plate 7. The bracket 41 is provided behind the thread hook 18 and is fixed to the face plate 7 with a plurality of screws. The bracket 41 holds a sensor 40 described later. The yarn hooking portion 18 corresponds to the first yarn guide portion of the present invention.

  The upper thread 10 is pulled out from a thread supply section (not shown) such as a thread spool, and the thread hook sections 11 and 12 of the arm section 1, the thread tension mechanism 13, the thread tension section 14, the thread tension mechanism 15, the thread tension section 16, 17, it is hung from the front side on the rotary balance 9 at the upper rear of the yarn hooking portion 17. The upper thread 10 hung on the rotary balance 9 is guided to the thread hook 18. The upper thread 10 guided by the thread hook 18 is guided to the eye hole of the sewing needle 2 via the thread hook 19 provided on the needle bar 3. The upper thread 10 from the thread hook 17 to the rotary balance 9 and the upper thread 10 from the rotary balance 9 to the thread hook 18 pass through a gap between the face plate 7 and a balance guard 21 (described later) fixed to the face plate 7. . The yarn hooking portion 19 corresponds to the second yarn guide portion of the present invention.

  The rotary balance guard cover 20 includes a balance guard 21 and a cover member 30. The rotary balance guard cover 20 covers the rotary balance 9 from the left side. The balance guard 21 is a substantially annular member that protrudes to the left from the outer surface of the face plate 7. The balance guard 21 is fixed to the face plate 7 with a predetermined gap. The cover member 30 is a substantially disk-shaped member provided on the left end surface of the balance guard 21. The cover member 30 is made of a resin whose center in the radial direction is transparent, and the rotary balance 9 is visible. The cover member 30 is attached to the balance guard 21 so as to be rotatable by a pivot shaft 50. The cover member 30 can be switched between a state of covering the periphery of the rotary balance 9 and a state of opening the left side of the rotary balance 9 by rotating around the pivot shaft 50. The operator can remove the upper thread 10 wound around the rotary balance 9 with the left side of the rotary balance 9 opened.

  The sensor 40 will be described. The sensor 40 is held by the bracket 41 described above. The front end of the sensor 40 is located directly below the lower end of the yarn hooking portion 18 and faces the upper yarn path between the yarn hooking portion 18 and the yarn hooking portion 19. The sensor 40 is a known photoelectric sensor, and includes a light projector (for example, a light emitting diode), a light receiver (for example, a phototransistor), a light emitting drive circuit, an amplifier that amplifies a light reception signal, a circuit that shapes a signal, and a yarn break signal. A comparison circuit or the like is provided. The sensor 40 receives the reflected light of the light projected from behind the upper yarn 10 passing between the yarn hooking portion 18 and the yarn hooking portion 19 and generates a light receiving signal of a level corresponding to the amount of light received.

  That is, the sensor 40 receives a large amount of light when the upper thread 10 is about several millimeters in front of the tip (see also FIG. 5), and decreases when there is no upper thread 10. Generate a signal. The sensor 40 amplifies the light reception signal and shapes the waveform, and then compares the signal with a threshold value set in advance by a comparison circuit. On the other hand, the sensor 40 outputs a yarn break signal when the light reception signal is lower than the threshold value. The sensor 40 is connected to a control device 70 described later.

  As shown in FIG. 2, the rotary balance 9 rotates as the needle bar 3 moves up and down, so that the upper thread 10 that spans the rotary balance 9 swings in the front-rear direction. As shown in FIG. 4, the needle bar 3 swings in the left-right direction by the needle bar swing drive mechanism, so that the upper thread 10 passed through the sewing needle 2 swings in the left-right direction. However, the upper thread 10 is guided by the thread hooking portion 18 after being passed over the rotary balance 9, and is guided to the sewing needle 2 through the thread hooking portion 19 of the needle bar 3. Therefore, the movement of the upper yarn 10 immediately after passing through the yarn hooking portion 18 in the front-rear direction and the left-right direction is restricted by the yarn hooking portion 18. Accordingly, since the sensor 40 is provided at a position where the upper thread 10 immediately after passing through the yarn hooking portion 18 can be detected, the presence or absence of the upper thread 10 can be reliably detected. As shown in FIG. 5, the tip of the sensor 40 is formed in a cylindrical shape having a diameter sufficiently larger than the thickness of the upper thread 10. The sensor 40 is a coaxial type in which a projector is provided in the center and a light receiver is provided around the projector.

  The electrical configuration of the control system of the staggered sewing machine M will be described with reference to FIG. The control device 70 of the staggered sewing machine M includes a CPU 71, a memory 72, drive circuits 73 and 74, and the like. The CPU 71, the memory 72, and the drive circuits 73 and 74 are electrically connected via a data bus or the like. The control device 70 electrically connects the sensor 40, the foot pedal 60, the operation panel 6, and the like. The control device 70 electrically connects the upper shaft motor 75, the main shaft encoder 76, the needle swing motor 77, and the needle swing encoder 78 via drive circuits 73 and 74, respectively. The CPU 71 controls the staggered sewing machine M and executes processing according to various programs stored in the memory 72.

  The memory 72 includes a control program for sewing control including drive control of various drive mechanisms and various display controls, sewing data for various pattern stitches, and output timing data of a thread break signal for detecting thread breakage. Etc. are stored in advance.

  The sensor 40 is electrically connected to the control device 70 and outputs a yarn break signal to the control device 70. The control device 70 detects the yarn breakage of the upper yarn 10 when the sensor 40 outputs a yarn breakage signal at a predetermined timing set in advance. When the yarn breakage of the upper thread 10 is detected, the control device 70 controls the upper shaft motor 75 to stop.

  The upper shaft encoder 76 provided in the upper shaft motor 75 outputs a detection result of the rotation angle of the main shaft, the needle upper position and the needle lower position of the sewing needle 2 to the control device 70. A needle swing encoder 78 provided in the needle swing motor 77 outputs a detection result of the needle left stop position and the needle right stop position to the control device 70.

  With reference to FIG. 7, the thread breakage detection process of the upper thread of the staggered sewing machine M will be described. The process of FIG. 7 is a process of determining that the thread is broken when the sensor 40 does not detect the upper thread 10 while the upper shaft interlocked with the rotary balance 9 rotates once (360 degrees).

  The thread breakage detection process of the upper thread starts when the power of the staggered sewing machine M is turned on. The CPU 71 determines whether or not the start switch is turned on (step S702). The start switch is turned ON / OFF by the operator operating the foot pedal 60. If the start switch is not turned on (step S702 / No), the CPU 71 repeats the determination in step S702. When the start switch is turned on (step S702 / Yes), the CPU 71 drives the upper shaft motor 75 to start sewing and sets the upper thread presence flag F1 and the upper thread absence flag F2 stored in the memory 72 to “0”. (Step S703).

  The CPU 71 determines whether or not the position of the sewing needle 2 is the needle upper position by the upper shaft encoder 76 (step S704).

  When the position of the sewing needle 2 is not the needle up position (step S704 / No), the CPU 71 determines whether or not the sensor 40 has turned on (outputs) a thread break signal of the upper thread 10 (step S705). If the thread break signal is not ON (step S705 / No), the CPU 71 stores the upper thread presence flag F1 = 1 in the memory 72 (step S706), and returns the process to step S704. When the thread break signal is turned on (step S705 / Yes), the CPU 71 stores the no upper thread flag F2 = 1 in the memory 72 (step S707), and returns the process to step S704.

  When the position of the sewing needle 2 is the needle up position (step S704 / Yes), the CPU 71 determines whether or not the flag stored in the memory 72 is the needle thread present flag F1 = 0 and the needle thread absent flag F2 = 1. (Step S708). When the upper thread presence flag F1 = 0 and the upper thread absence flag F2 = 1 are not satisfied (step S708 / No), the CPU 71 sets the upper thread presence flag F1 and the upper thread absence flag F2 stored in the memory 72 to “0” (step S708). S713), the process returns to step S704. On the other hand, when the upper thread presence flag F1 = 0 and the upper thread absence flag F2 = 1 (step S708 / Yes), the CPU 71 stops the upper shaft motor 75 (step S709). The CPU 71 displays a thread break error display on a predetermined display portion of the operation panel 6 (step S710).

  The CPU 71 determines whether or not the reset switch of the operation panel 6 has been turned on (step S711). When the reset switch is not ON (step S711 / No), the CPU 71 repeats the determination in step S711. On the other hand, when the reset switch is turned on (step S711 / Yes), the CPU 71 cancels the thread break error display on the predetermined display section of the operation panel 6 (step S712), and returns the process to step S702. The thread breakage detection process of the upper thread ends when the power of the staggered sewing machine M is turned off.

  As described above, when the sewing needle 2 is in the needle upper position, the CPU 71 determines that the upper thread is broken from the state of the upper thread presence flag F1 and the upper thread absence flag F2. That is, the CPU 71 has not detected the upper thread 10 once while the upper shaft rotates once (360 degrees) until the position of the sewing needle 2 reaches the next upper needle position. When the thread breakage signal ON is continuously output, it is determined that the thread breakage of the upper thread has occurred.

  As described above, the sensor 40 is arranged at a position where the movement (swing / flutter) of the upper thread 10 is small. However, the behavior of the upper thread 10 that is passed over the rotary balance 9 is not necessarily constant depending on the sewing conditions (sewing needle swinging width and sewing speed). Therefore, as shown in FIG. 8, when the upper thread 10 is in a position where the light projected from the tip of the sensor 40 does not hit, the sensor 40 cannot detect the upper thread 10 and outputs a thread break signal. . In this case, the movement of the upper thread 10 when the upper thread 10 is released from the tightening and releasing of the upper thread 10 due to the change in the thread amount of the upper thread 10 fed from the rotary balance 9 in the thread amount curve shown in FIG. It happens more. Therefore, the sensor 40 detects a yarn break while the rotary balance 9 makes one rotation as a predetermined timing. Therefore, the staggered sewing machine M determines that the upper thread is broken when the upper thread 10 is not detected at any position other than the rotational position of the rotary balance 9 in which the behavior of the upper thread 10 that is passed over the rotary balance 9 is unstable. Therefore, the staggered sewing machine M can be prevented from erroneously determining that the upper thread is broken.

  With reference to FIG. 10, a modified form of the upper thread breakage detection process of the staggered sewing machine M will be described. Hereinafter, the description of the same processing as that of FIG. 7 will be simplified.

  The process of FIG. 10 starts when the power of the staggered sewing machine M is turned on. The CPU 71 determines whether or not the start switch is turned on (step S1002). When the start switch is not turned on (step S1002 / No), the CPU 71 repeats the determination in step S1002. When the start switch is turned on (step S1002 / Yes), the CPU 71 drives the upper shaft motor 75 to start sewing, and also has an upper thread flag F1 and an upper thread flag F2 stored in the memory 72, and the number of start stitches. The counter C1 and the thread breakage needle number counter C2 are each set to “0” (step S1003). The start stitch number counter C1 counts when a needle up position signal (needle up signal) is output among the needle position signals output by the upper shaft encoder 76. In the thread breakage needle number counter C2, while the upper shaft encoder 76 outputs a needle up signal and the upper shaft rotates once (360 degrees), the sensor 40 has not detected the upper thread 10 (yarn). It counts when the cut signal ON is continuously output).

  The CPU 71 determines whether the position of the sewing needle 2 is the needle upper position by the upper shaft encoder 76 (step S1004).

  When the position of the sewing needle 2 is not the needle up position (step S1004 / No), the CPU 71 determines whether or not the sensor 40 has turned on the thread break signal of the upper thread 10 (step S1005). If the thread break signal is not ON (step S1005 / No), the CPU 71 stores the upper thread presence flag F1 = 1 in the memory 72 (step S1006), and returns the process to step S1004. When the thread break signal is turned on (step S1005 / Yes), the CPU 71 stores the upper thread absence flag F2 = 1 in the memory 72 (step S1007), and returns the process to step S1004.

  When the position of the sewing needle 2 is the needle upper position (step S1004 / Yes), the CPU 71 determines whether or not C1 <N1 is satisfied (step S1008). N1 is a comparison parameter for invalidating a predetermined number of stitches in detecting thread breakage during acceleration of the upper shaft motor 75 at the start of sewing. When the upper shaft motor 75 is accelerated, the movement of the upper thread is likely to increase, and the sensor 40 may erroneously output a thread break signal. Since the staggered sewing machine M disables the detection of thread breakage by a predetermined number of stitches from the start of sewing, it can be prevented that the sensor 40 determines that the upper thread breakage is caused by a thread breakage signal output by mistake. N1 is desirably set to a sufficiently large value.

  If C1 <N1 is satisfied (step S1008 / Yes), the CPU 71 increments the value of C1 by 1 (step S1009) and determines whether C1 ≧ N1 is satisfied (step S1010). When C1 ≧ N1 is not satisfied (step S1010 / No), the CPU 71 clears the counter and sets C2 = 0 (step S1011). The CPU 71 initializes the upper thread presence flag F1 and the upper thread absence flag F2 stored in the memory 72 to “0” (step S1012), and returns the process to step S1002.

  When C1 ≧ N1 is satisfied (step S1010 / Yes), or when C1 <N1 is not satisfied (step S1008 / No), the CPU 71 stores the flag with the upper thread flag F1 = 0 and the upper thread without flag. It is determined whether or not F2 = 1 (step S1013). When the upper thread presence flag F1 = 0 and the upper thread absence flag F2 = 1 are not satisfied (step S1013 / No), the CPU 71 clears the counter and sets C2 = 0 (step S1011). The CPU 71 initializes the upper thread presence flag F1 and the upper thread absence flag F2 stored in the memory 72 to “0” (step S1012), and returns the process to step S1002.

  When the upper thread presence flag F1 = 0 and the upper thread absence flag F2 = 1 (step S1013 / Yes), the CPU 71 determines whether or not C2 <N2 is satisfied (step S1014). N2 is a comparison parameter for enabling the yarn break signal output from the sensor 40 when the predetermined number of stitches is continued. The zigzag stitching machine M validates the thread breakage detection when the sensor 40 outputs only the thread breakage signal continuously for a predetermined number of stitches, so that it is determined that the upper thread breakage is based on the thread breakage signal erroneously output by the sensor 40. Can be prevented. N2 is desirably set to a sufficiently large value.

  When C2 <N2 is satisfied (step S1014 / Yes), the CPU 71 increments the value of C2 by 1 (step S1015), and determines whether or not C2 ≧ N2 is satisfied (step S1016). When C2 ≧ N2 is not satisfied (step S1016 / No), the CPU 71 initializes the upper thread presence flag F1 and the upper thread absence flag F2 stored in the memory 72 to “0” (step S1012), and the process proceeds to step S1002. Return to.

  When C2 ≧ N2 is satisfied (step S1016 / Yes), or when C2 <N2 is not satisfied (step S1014 / No), the CPU 71 stops the upper shaft motor 75 (step S1017). The CPU 71 displays a thread break error display on a predetermined display portion of the operation panel 6 (step S1018).

  The CPU 71 determines whether or not the reset switch of the operation panel 6 has been turned on (step S1019). When the reset switch is not ON (step S1019 / No), the CPU 71 repeats the determination in step S1019. When the reset switch is turned on (step S1019 / Yes), the CPU 71 cancels the yarn break error display on the predetermined display section of the operation panel 6 (step S1020), and returns to step S1002. The thread breakage detection process of the upper thread ends when the power of the staggered sewing machine M is turned off.

  With reference to FIG. 11, a specific example of the process of FIG. 10 will be described with reference to a graph showing the relationship between the upper shaft rotation speed and the needle number. In the following description, it is assumed that N1 = 4 (needle) and N2 = 2 (needle) are set.

  The vertical axis of the graph in FIG. 11 is the sewing machine rotation speed (upper shaft rotation speed) from the top, the needle up signal based on the detection of the needle upper position of the sewing needle 2 by the upper shaft encoder 76, and the thread breakage signal from the sensor 40. Is time.

  In the staggered sewing machine M, the number of stitches that disable thread breakage detection at the start of sewing is N1 = 4. Therefore, the sensor 40 turns the thread breakage signal ON ( Even if “H: No thread” is output, thread breakage detection is disabled. The zigzag stitching machine M has N2 = 2 as the number of stitches that enable the thread breakage detection when the thread breakage signal ON output from the sensor 40 is continued, so the needle up signal (for each stitch) is output from the output of the thread breakage signal ON. When the output of the thread break signal ON is continued until it is turned ON twice, the thread break detection is enabled.

  Specifically, the thread break signals a and b are invalid because the sensor 40 outputs the thread break signal ON before the needle up signal (for each stitch) is turned ON four times from the start of sewing, and C1 <N1. (It is not determined that the upper thread is broken). Regarding the thread breakage signals c to e, the sensor 40 outputs the thread breakage signal ON after the needle up signal (for each stitch) is turned ON four times from the start of sewing, and C1 ≧ N1. However, the thread break signals c and d are invalid because the thread break signal ON is not continued until the needle up signal (for each stitch) is turned ON twice from the output of the thread break signal ON, and C2 <N2. is there.

  The thread break signal e continues to be output from the output of the thread break signal ON until the needle up signal (for each stitch) is turned ON twice, and is valid because C2 ≧ N2. Therefore, the staggered sewing machine M determines that the upper thread is broken.

  As described above, the staggered sewing machine M of the present embodiment includes the thread hook 18 that guides the upper thread 10 that is passed over the rotary balance 9 to the needle bar 3, and the upper thread 10 that is guided by the thread hook 18. A sensor 40 is provided between the thread hooking portion 19 guided to the sewing needle 2. When the sewing needle 2 is in the needle up position, the staggered sewing machine M determines the thread breakage of the upper thread from the state of the upper thread presence flag F1 and the upper thread absence flag F2. That is, the CPU 71 detects that the sensor 40 is once threaded while the rotary balance 9 interlocking with the upper shaft is rotated once (360 degrees) until the position of the sewing needle 2 reaches the next needle upper position. When 10 is not detected (yarn break signal ON is continuously output), it is determined that the thread breakage of the upper thread has occurred. When it is determined that the upper thread breakage has occurred, the staggered sewing machine M controls the upper shaft motor 75 to stop. Therefore, the staggered sewing machine M can prevent the sewing product from being damaged because the sewing needle 2 is stuck in the sewing product after the needle thread breakage, and the stitches cannot be formed. The staggered sewing machine M can eliminate the need to remove the upper thread 10 from the rotary balance 9 after the upper thread breakage occurs, thereby eliminating the time for removal and avoiding loss of production time.

  In the present embodiment, the staggered sewing machine M holds the sensor 40 on the bracket 41 provided at the lower end of the face plate 7 of the arm portion 1, and the tip end portion is positioned directly below the lower end of the thread hook portion 18. The sensor 40 projects light toward the upper yarn 10 that passes through the lower end of the yarn hooking portion 18. The upper yarn 10 immediately after passing through the yarn hooking portion 18 is restricted from moving in the front-rear direction and the left-right direction by the yarn hooking portion 18. Accordingly, since the sensor 40 is provided at a position where the upper thread 10 immediately after passing through the yarn hooking portion 18 can be detected, the presence or absence of the upper thread 10 can be reliably detected.

  In the present embodiment, the staggered sewing machine M, even when the sewing machine starts, even if the sensor 40 outputs a thread break signal ON (H: no thread) before the number of stitches N1 that invalidates the thread break detection when starting sewing. Disable cut detection and do not enable it. The staggered sewing machine M validates the thread breakage detection when it continues to output the thread breakage signal ON up to the number N2 of stitches that enable the thread breakage detection when the thread breakage signal ON output from the sensor 40 is continued. Therefore, the staggered sewing machine M can prevent the upper thread from being judged to be broken based on the yarn break signal output by the sensor 40 in error.

  In the present embodiment, when the staggered sewing machine M detects a thread breakage of the upper thread, it performs stop control of the upper shaft motor 75 and displays a thread breakage error display on a predetermined display portion of the operation panel 6. Therefore, the operator can easily visually recognize that the zigzag sewing machine M has been stopped due to the thread breakage of the upper thread.

  In the present embodiment, the upper shaft motor 75 corresponds to the “motor” of the present invention. The CPU 71 that performs the processing of S708 in FIG. 7 and S1013 in FIG. 10 corresponds to the “determination unit” of the present invention. The CPU 71 that performs the processing of S709 of FIG. 7 and S1017 of FIG. 10 corresponds to the “stop unit” of the present invention.

  The present invention can be variously modified in addition to the above-described embodiment. In the sensor 40, the light projector and the light receiver may be arranged to face each other at a position where the upper thread 10 between the yarn hooking portion 18 and the yarn hooking portion 19 is sandwiched from the front and rear.

  In the present invention, while the rotary balance 9 interlocking with the upper shaft until the position of the sewing needle 2 becomes the next needle upper position from the needle upper position is rotated once (360 degrees), the sensor 40 performs the upper thread 10 once. Is not detected (the yarn break signal ON is continuously output), it is determined that the upper thread has been broken, but the present invention is not limited to this. For example, it may be a period during which the rotary balance 9 tightens the upper thread 10 instead of one rotation of the rotary balance 9. The movement (swing / flapping) of the upper thread 10 during sewing is suppressed and minimized during a period in which the rotary balance 9 tightens the upper thread 10 (tension application). In the yarn amount curve shown in FIG. 9, the period during which the upper thread 10 is tightened (tension applied) refers to a period in which the upper shaft rotation angle exceeds 330 to 360 degrees and is 30 degrees, for example. In this case, the staggered sewing machine can easily detect the thread breakage of the upper thread without continuously detecting by the sensor 40 while the rotary balance 9 rotates once.

  According to the present invention, it is not necessary to detect thread breakage until the sewing needle 2 is positioned from the upper needle position to the next upper needle position. For example, the yarn breakage may be detected at a predetermined rotation angle of the upper shaft. The number and shape of the sensor and the yarn hooking portion are not limited, and various types can be applied.

M Staggered sewing machine 1 Arm 2 Sewing needle 3 Needle bar 9 Rotary balance 10 Upper thread 18 Thread hook 19 Thread hook 40 Sensor 70 Control device 75 Upper shaft motor

Claims (4)

A motor that rotates the spindle,
A rotary balance connected to the main shaft and rotating in conjunction with the main shaft by driving the motor;
In a sewing machine that includes a needle bar that fixes a sewing needle that passes an upper thread that is stretched over the rotary balance and swings in a horizontal direction.
A first thread guide for guiding the upper thread that has been wound around the rotary balance to the needle bar;
A second thread guide part that is provided on the needle bar and guides the upper thread guided by the first thread guide part to the sewing needle;
It is arranged between the first yarn guide portion and the second yarn guide portion, receives the reflected light or transmitted light of the light projected toward the upper yarn, and outputs a received light signal corresponding to the received light amount. A sensor,
When the sensor outputs the light reception signal when the upper thread is not present at a predetermined timing, a determination unit that determines that the upper thread is broken,
A sewing machine comprising: a stopping unit that stops driving the motor when the determining unit determines that the upper thread is broken. The first thread guide portion is provided below the rotary balance and at the lower end of the arm portion of the sewing machine,
The sewing machine according to claim 1, wherein the sensor projects the light toward the upper thread that is provided at the lower end of the arm part and passes through the lower end of the first thread guide part.   The sewing machine according to claim 1 or 2, wherein the predetermined timing is a period during which the rotary balance rotates at least 360 ° or more. The sewing machine according to claim 1 or 2, wherein the predetermined timing is a period during which the rotary balance tightens the upper thread.

Images