JP2006230465A - Buttonholing machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To finely change a needle thread tension when a needle is located in an inside needle position and in an outside needle position by a thread tension regulator provided in a needle thread supply route from a needle thread supply source to a needle thread and to improve the quick response of the finely regulating operation of the needle thread tension. <P>SOLUTION: An eyelet buttonholing machine which has a needle bar-swinging mechanism swinging a needle bar between the inside needle position and the outside needle position in a buttonhole, a looper and the like is provided with the thread tension regulator 20 regulating a tensile to be applied to the needle thread in the thread supply route from a bobbin, or the needle thread supply source, to the needle thread in the upper face of an arm part 3. The machine instantaneously changes a driving voltage to be fed to a laminated piezoelectric actuator 34 provided in the thread tension regulator 20 to control the thread tension regulator 20 that the needle thread tension when the needle is located in the inside needle position becomes larger than the needle thread tension when the needle is located in the outside needle position. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a bobbin sewing machine, and in particular, when forming a bouncing seam around a button hole, it is possible to eliminate skipping of an upper thread and thread breakage.

  Conventionally, in a boring machine that sews various bouncing seams around a button hole, a sewing mechanism that synchronizes and drives a needle bar and a looper facing the needle bar, and a looper base provided with a looper A rotation mechanism that rotates the needle bar around the vertical axis is provided, and a feed mechanism that moves the feed base on which the work cloth is placed in the X direction and the Y direction is provided. Various hole stitches are formed by driving and controlling the sewing mechanism, the feed mechanism, and the rotation mechanism based on the stitch data.

  By the way, in this kind of hole sewing machine, the upper thread from the thread spool is supplied to the needle of the needle bar through a predetermined thread supply path. Various yarn tension adjusting devices for applying tension are provided.

  For example, a buttonhole sewing machine described in Patent Document 1 is provided with a voice coil motor and an electromagnetic brake (hysteresis brake) in a path of a needle thread introduced from a thread supply source to a needle bar. By pressing with a pair of thread tension plates attached to the output shaft of the coil motor or electromagnetic brake, and supplying a control current to the moving coil incorporated in the voice coil motor or the excitation coil incorporated in the electromagnetic brake, The thread tightening is adjusted.

  In this type of buttonhole sewing machine, the thread tension adjusting device such as a voice coil motor or electromagnetic brake provided in the thread supply path in this way has the type of needle thread and the thickness of the thread used to form the hole stitch. The upper thread tension can be adjusted as necessary according to the need or according to the type of fabric used for sewing.

  By the way, in general, when sewing buttonhole stitches or eyelet stitches, it is better to set the upper thread tension slightly larger than the lower thread tension and the thread tightness is better and the seam feel is better. There are many cases. However, there is a problem that stitch skipping and thread breakage often occur when sewing at a high speed using an upper thread of poor quality.

  Therefore, the inventors of the present application have determined the upper thread tension when the needle is dropped at the inner needle position and the upper thread tension when the needle is dropped at the outer needle position so that such skipping and thread breakage are eliminated. An experiment was carried out to sew the eyelet stitches while changing the needle thread tension so that the needle thread was different.

  In other words, the needle thread tension when the needle is dropped to the inner needle position is gradually set larger (smaller value) than the needle thread tension (small value: 0.7 N) when the needle is dropped to the outer needle position, and vice versa. In addition, the case where the upper thread tension when the needle is dropped at the outer needle position is gradually set larger (larger value) than the upper thread tension when the needle is dropped at the inner needle position (small value: 0.7 N) is tested. Went. As a result, the probability of skipping was obtained as shown in FIG. 12, and the probability of occurrence of yarn breakage was obtained as shown in FIG.

  On the other hand, when the needle thread tension when dropping the needle to the inner needle position is gradually set larger (smaller value) than the needle thread tension (small value: 0.5N) when dropping the needle to the outer needle position, and vice versa. In addition, the experiment was conducted for the case where the needle thread tension when the needle is dropped to the outer needle position is gradually set larger (small value) than the needle thread tension (small value: 0.5 N) when the needle is dropped to the inner needle position. Went. As a result, the probability of occurrence of skipping was obtained as shown in FIG. 14, and the probability of occurrence of yarn breakage was obtained as shown in FIG.

Comprehensively inferring these results, the needle thread tension when dropping the needle to the inner needle position is set larger than the needle thread tension (0.5N, 0.7N) when dropping the needle to the outer needle position. The stitch skip ratio is lower than when the upper thread tension when dropping the needle to the outer needle position is set larger than the upper thread tension (0.5N, 0.7N) when dropping the needle to the inner needle position. However, the thread breakage rate is lower when the upper thread tension when the needle is dropped at the inner needle position is set within the range of 0.8N to 1.0N.
JP 2001-170385 A (pages 6 to 8, FIGS. 4 and 5)

  In this way, the upper thread tension when the needle is dropped to the inner needle position and the upper thread tension when the needle is dropped to the outer needle position are instantaneously switched, and the upper thread tension when the needle is dropped to the inner needle position is instantaneously switched. It has been found that the stitch skip rate and the thread breakage rate can be lowered by setting the needle thread tension higher than the needle thread tension when the needle is dropped into the position.

  In this case, when the sewing speed is high, for example, 2200 rpm, the inner stitch formation period by the inner needle position and the outer stitch formation period by the outer needle position are about 28 ms, which are very short. However, as described above, in the buttonhole overlock sewing machine described in Patent Document 1, a voice coil motor or electromagnetic brake is used as a solenoid actuator as a thread tension adjusting device, and control is performed using a movable coil or an excitation coil. By supplying current, the needle thread tension is adjusted by the suction force (thrust) of the output shaft proportional to the current, so even if the magnitude of the control current is changed instantaneously, Since the responsiveness reflected in the magnitude of the thread tension is inferior, it is impossible to switch the needle thread tension every minute time.

  Furthermore, even when the control current is finely adjusted, the responsiveness of the output shaft due to the change in the magnetic field generated by the movable coil or exciting coil is poor, so fine adjustment of the needle thread tension is impossible. Even if the thread tension can be finely adjusted, there is a problem that the upper thread tension becomes unstable.

  The boring machine according to claim 1 is a needle bar to which a sewing needle is attached, an upper thread supply source for supplying upper thread to the sewing needle, and the needle bar is swung over the inner needle position and the outer needle position in the button hole. In a perforated sewing machine having a needle bar swinging mechanism, a looper driven in synchronization with the vertical movement of the needle bar, and a lower thread supply source for supplying lower thread to the looper, from the upper thread supply source to the sewing needle The thread tension adjustment device that can adjust the tension applied to the upper thread in the thread supply path, and the upper thread tension when the needle is dropped at the inner needle position and the upper thread tension when the needle is dropped at the outer needle position are different. And a yarn tension control means for controlling the yarn tension adjusting device.

  In the thread supply path from the upper thread supply source to the sewing needle, the tension applied to the upper thread is adjusted by the thread tension adjusting device. Therefore, the thread tension adjusting device controls the thread tension adjusting device so that the upper thread tension when the needle is dropped at the inner needle position and the upper thread tension when the needle is dropped at the outer needle position are different.

  If the needle thread tension when the needle is dropped to the inner needle position is greater than the needle thread tension when the needle is dropped to the outer needle position, the details are not clarified, but the direction of the stitches and the spreader In relation to the movement direction with respect to the looper and the cloth feed direction before the sewing needle comes out of the fabric, not only can the stitches and thread breakage be prevented at the inner needle position, the loop diameter is the same, and the sewing hardness is increased. It becomes soft.

  On the other hand, if the needle thread tension when dropping the needle to the outer needle position is greater than the needle thread tension when dropping the needle to the inner needle position, details are not elucidated, but the direction of the eye of the sewing needle and In relation to the movement direction of the spreader with respect to the looper and the cloth feed direction before the sewing needle comes out of the fabric, not only can the stitches and thread breakage be prevented at the outer needle position, the loop diameter is the same, and the sewing width is growing.

  The boring machine according to claim 2 is a needle bar to which a sewing needle is attached, an upper thread supply source for supplying upper thread to the sewing needle, and the needle bar is swung over the inner needle position and the outer needle position in the button hole. In a perforated sewing machine having a needle bar swinging mechanism, a looper driven in synchronization with the vertical movement of the needle bar, and a lower thread supply source for supplying lower thread to the looper, from the upper thread supply source to the sewing needle A thread tension adjusting device capable of adjusting the tension applied to the upper thread in the thread supply path, and the upper thread tension when the needle is dropped at the inner needle position is larger than the upper thread tension when the needle is dropped at the outer needle position. Thus, a yarn tension control means for controlling the yarn tension adjusting device is provided.

  In the thread supply path from the upper thread supply source to the sewing needle, the tension applied to the upper thread is adjusted by the thread tension adjusting device. Therefore, the thread tension adjusting device controls the thread tension adjusting device so that the upper thread tension when the needle is dropped at the inner needle position is larger than the upper thread tension when the needle is dropped at the outer needle position.

  If the needle thread tension when the needle is dropped to the inner needle position is greater than the needle thread tension when the needle is dropped to the outer needle position, the details are not clarified, but the direction of the stitches and the spreader In relation to the movement direction with respect to the looper and the cloth feed direction before the sewing needle comes out of the fabric, not only can the stitches and thread breakage be prevented at the inner needle position, the loop diameter is the same, and the sewing hardness is increased. It becomes soft.

  According to a third aspect of the present invention, the sewing machine according to the second aspect is characterized in that, in the second aspect, the thread tension control means causes the needle thread drop to the outer needle position at the inner stitch formation period in which the needle drop to the inner needle position occurs in each sewing cycle. The thread tension adjusting device is controlled to be larger than the upper thread tension in the outer stitch formation period.

  According to a fourth aspect of the present invention, the thread sewing machine according to the second or third aspect is such that the thread tension adjusting device has a piezo actuator for adjusting the needle thread tension.

  According to a fifth aspect of the present invention, there is provided a boring machine according to the fourth aspect, wherein the yarn tension adjusting device includes a rotating body that engages with the upper thread and a tension adjusting mechanism that generates a rotational load on the rotating body. Is a layered piezo actuator that applies a rotational braking force to a rotating body to impart a thread tension to the upper thread.

  According to the first aspect of the present invention, the needle bar to which the sewing needle is attached, the upper thread supply source for supplying the upper thread to the sewing needle, and the needle bar is swung over the inner needle position and the outer needle position in the button hole. In a bobbin sewing machine having a needle bar swinging mechanism, a looper driven in synchronism with the vertical movement of the needle bar, and a lower thread supply source for supplying lower thread to the looper, a thread tension adjusting device, a thread Tension control means, and the needle thread tension when the needle is dropped at the inner needle position and the needle thread tension when the needle is dropped at the outer needle position are different. It is possible to suppress the occurrence rate of thread breakage and to express the texture of the seams in various ways.

  According to the invention of claim 2, the needle bar to which the sewing needle is attached, the upper thread supply source for supplying the upper thread to the sewing needle, and the needle bar is swung over the inner needle position and the outer needle position in the button hole. In a bobbin sewing machine having a needle bar swinging mechanism, a looper driven in synchronism with the vertical movement of the needle bar, and a lower thread supply source for supplying lower thread to the looper, a thread tension adjusting device, a thread A tension control means is provided so that the upper thread tension when the needle is dropped at the inner needle position is greater than the upper thread tension when the needle is dropped at the outer needle position. The occurrence rate of the seam can be suppressed and the texture of the seam can be expressed.

  According to the invention of claim 3, the thread tension control means forms an outer stitch that causes the needle thread drop to the outer needle position during the inner stitch formation period in which the needle is dropped to the inner needle position in each sewing cycle. Since the thread tension adjusting device is controlled so as to be larger than the upper thread tension in the period, a large upper thread tension is continuously maintained in the inner stitch formation period, and a stable large upper thread tension is maintained. Can be granted. Other effects similar to those of claim 2 can be achieved.

  According to the invention of claim 4, since the yarn tension adjusting device has a piezo actuator for adjusting the needle thread tension, it is small and lightweight, quick response, microscopic change in elongation, etc., which are characteristics of the piezo actuator. Can be used to quickly change the needle thread tension and achieve quick response. Other effects similar to those of the second or third aspect are achieved.

  According to the invention of claim 5, the yarn tension adjusting device has a rotating body that engages with the upper thread and a tension adjusting mechanism that generates a rotational load on the rotating body, and the tension adjusting mechanism is a laminated piezoelectric actuator. The rotational braking force is applied to the rotating body to apply the thread tension to the upper thread, so the number of stacked piezo elements can be set arbitrarily, so the degree of freedom in manufacturing the stacked piezo actuator can be greatly increased, In addition, the magnitude of the rotational braking force can be set as necessary. Other effects similar to those of the fourth aspect are achieved.

  The electronic eyelet hole sewing machine of this embodiment is provided with a thread tension adjusting device adopting a laminated piezo actuator in the upper thread supply path, and the upper thread tension in the inner stitch formation period in which the sewing needle drops to the inner needle position, The upper thread tension during the outer stitch formation period during which the needle is dropped to the outer needle position is set to prevent stitch skipping and thread breakage.

  As shown in FIGS. 1 and 2, the electronic eyelet sewing machine 1 integrally has an arm portion 3 that continuously extends forward from an upper portion of a rear portion thereof to a bed portion 2 having a substantially rectangular box shape. And is placed on the sewing machine table 4.

  The sewing machine table 4 has a needle bar 6 in addition to a thread spool base 8 on which a plurality of thread spools 7 can be mounted simultaneously and an operation panel 9 that selectively selects from a plurality of types of eyelet stitches. The sewing machine motor 55 and the foot-operated start / stop switch 50 (see FIG. 8), which are the drive sources of the sewing mechanism that synchronously drives the vertical movement and swing of the sewing machine and the looper mechanism (not shown), and the operation of each mechanism are controlled. A control device 40 comprising a microcomputer is provided.

  A needle bar 6 having a sewing needle 5 attached to the lower end thereof is provided at the distal end of the arm 3 so as to be movable up and down by a needle bar vertical movement mechanism (not shown). Further, the needle bar 6 has a needle swinging mechanism (not shown). ) To the left and right swing positions (inner needle position) and right swing position (outer needle position) by a predetermined width. In this case, one rotation of the main shaft 10 causes the needle bar 6 to move up and down twice between the inner needle position and the outer needle position.

  As shown in FIG. 2, the bed portion 2 is provided with a looper base 11 having a looper mechanism having a pair of left and right loopers (not shown) so as to face the needle bar 6, and this looper base 11 is illustrated. It can be rotated around the vertical axis by an external rotating mechanism. These two loopers are driven to swing in synchronism with the vertical movement of the needle bar 6 by the rotation of the main shaft 10 via a link mechanism or cam mechanism provided on the looper base 11.

  Here, an upper thread 7a supplied from a thread spool 7, which is a thread supply source, is inserted into the sewing needle 5, and a lower thread (not shown) is inserted into the tip of the left looper. The right looper is an upper thread. While the loop is knitted, the lower thread is entangled to form a loop coupling portion. Further, the needle bar 6 and the looper base 11 are integrally rotated around the vertical axis in the horizontal plane by a rotation mechanism comprising a θ-direction drive motor 57 (see FIG. 8) and a gear mechanism provided in the bed portion 2, respectively. It is like that.

  As shown in FIG. 2, the bed 2 further includes a knife 12 which is fixedly disposed on the rear side of the looper base 11 to form a eyelet hole portion, and is attached to a mounting base (not shown) with bolts. A punching hammer 13 that can be attached to the knife 12 from above is provided in the arm portion 3 so as to be swingable up and down.

  A hammer body 14 is detachably attached to the tip of the punching hammer 13 and is driven by a hammer drive mechanism (not shown) including an air cylinder 61 (see FIG. 8) provided in the bed 2. By the cooperation of the hammer main body 14 and the knife 12, an eyelet hole portion comprising a substantially circular eyelet portion and a linear foot portion connected to the eyelet portion is punched in the work cloth.

  As shown in FIGS. 2 and 3, the bed portion 2 is provided with a feed base 15 on which a work cloth used for eyelet stitching is set. The feed base 15 has a thin rectangular box shape as a whole, and a portion facing the looper base 11 and the knife 12 is open. Further, although not shown in the figure, a pair of left and right cross plates (not shown) made of metal are provided on the upper surface of the feed base 15, respectively.

  In the bed portion 2, an X-direction moving mechanism (not shown) for feeding and moving the feed table 15 in the X direction (left and right direction) by driving an X direction drive motor 62 (see FIG. 8) comprising stepping, and a stepping A Y-direction moving mechanism (not shown) is provided that feeds and moves in the Y direction (front-rear direction) by driving a Y-direction drive motor 64 (see FIG. 8) that is a motor.

  Next, the thread tension adjusting device 20 capable of adjusting the tension applied to the upper thread 7a in the thread supply path from the thread spool 7 to the sewing needle 5 will be described with reference to FIGS.

  An auxiliary thread tensioner 19 and a thread tension adjusting device 20 are provided on the vertical mounting wall 3 a on the upper surface of the arm 3. The secondary thread tensioner 19 preliminarily applies a small thread tension to the upper thread 7a, and the thread tension adjusting device 20 applies a large thread tension to the upper thread 7a.

  As shown in FIG. 4, the yarn tension adjusting device 20 includes a pair of left and right rotating plates 21 (which correspond to a rotating body) to which the upper thread 7 a is wound once to be engaged, and the pair of rotating plates. And a tension adjusting mechanism 22 that applies a rotational braking force, which is a rotational load, to the upper thread 7a.

  The pair of rotating plates 21 is fixed to the left end portion of the rotating shaft 23 while being pressed against each other, and the upper thread 7a from the thread spool 7 first passes through the secondary thread tensioner 19 and then adjusts the tension. It is wound only once between the rotating plates 21 of the mechanism 22, and then supplied to the sewing needle 5 through the balance 16 and the hollow inside of the needle bar 6.

  The tension adjusting mechanism 22 has a pair of left and right cylindrical cases 23 and 24 fixed together as an assembly to the mounting wall portion 3a by a plurality of fixing bolts 26, and a rear end portion (right end portion) of the right cylindrical case 24. ), The adjusting screw 25 is screwed. The right end portion of the rotating shaft 23 passes through the pivotal support hole 3b of the mounting wall 3a and is located inside the cylindrical case 23, and a circular inner bearing disc 27 is fixed thereto. However, the rotary shaft 23 is pivotally supported by the mounting wall 3a by a bear rig 28, and thrust bearings 29 and 30 are interposed on both the left and right sides of the inner bearing disc 27, respectively.

  On the right side of the right thrust bearing 30, a circular outer bearing disk 32 is incorporated inside the cylindrical case 23 so as to be movable in the left-right direction. A pressurizing ball 33 is arranged on the right side of the outer bearing disk 32 so as to abut on it, and a laminated piezo actuator 34 in which a plurality of piezo elements are stacked in a line is provided between the pressing ball 33 and the adjusting screw 25. The laminated piezoelectric actuator 34 is supplied with a drive voltage from a control device 40 which will be described later. Further, a compression spring 35 is mounted between the outer bearing disk 32 and the adjustment screw 25.

  Even when no driving voltage is supplied to the piezo actuator 34, the outer bearing disk 32 is always pressed to the left by the spring force of the compression spring 35. Therefore, the inner bearing disk 27 has thrust bearings 29 and 30 on both sides thereof. However, since it is pressed against the mounting wall 3a, a rotational load acts on the inner bearing disk 27, a slight rotational braking force acts on the rotating tray 21, and a weak tension is applied to the upper thread 7a. Has been granted.

  By the way, when a driving voltage of, for example, 100 V is supplied to the piezo actuator 34, the extension amount reaches about 10 to 12 μm. As a result, as shown in FIG. 5, the inner bearing disk 27 receives a pressing force corresponding to the extension amount of the piezo actuator 34, so that a large rotational braking force acts on the rotating plate 21 integral with the inner bearing disk 27, A large upper thread tension is applied to the upper thread 7a. However, the upper thread tension in this case is a hysteresis curve in which the drive voltage V indicated by the straight line is different from the increase state indicated by the alternate long and short dash line.

  By the way, the inventors, when sewing the eyelet stitch seam DN shown in FIG. 11, respectively adjust the upper thread tension and the lower thread tension when the needle is dropped to the outer needle position ON as shown in FIG. When the needle thread tension is set to 0.5 N (Newton) and needle drop at the inner needle position IN is changed to 0.6 N, 0.8 N, 1.0 N, 1.2 N, 1.5 N, 2.0 N Each was determined experimentally.

  Further, as shown in FIG. 7, the inventors set the upper thread tension and the lower thread tension when the needle is dropped to the outer needle position ON to 0.5 N (Newton), respectively, and the needle at the inner needle position IN. The thread breakage rate when the upper thread tension when dropping was changed to 0.6 N, 0.8 N, 1.0 N, 1.2 N, 1.5 N, and 2.0 N was experimentally determined.

  As a result, the inventors set “0.5 N” as the upper thread tension and the lower thread thread tension when the needle is dropped to the outer needle position ON where both the stitch skip ratio and the thread breakage ratio are relatively small. It was decided to set “0.8 N” as the needle thread tension when dropping the needle to the needle position IN.

  Next, an outline of the control system of the electronic eyebrowsing sewing machine 1 will be described based on the block diagram of FIG.

  The control device 40 of the electronic eyelet hole sewing machine 1 includes a microcomputer including a CPU 41, a ROM 42, a RAM 43, a nonvolatile memory 44 and the like, an input interface 46 connected to the microcomputer via a common bus 45 such as a data bus, and an output. It consists of an interface 47 and the like.

  The input interface 46 includes a start / stop switch 50, a presser foot switch 51 connected to the presser foot, a needle up sensor 52 that outputs a needle up signal when the needle bar 6 is on the needle, and the needle bar 6. Signals from a needle down sensor 53 that outputs a needle down signal when the needle is down, a timing signal generator 54, and the operation panel 9 are supplied.

  From the output interface 47, a drive circuit 56 for the sewing machine motor 55, a drive circuit 58 for the θ-direction drive motor 57, and an electromagnetic switching valve 59 connected to the air cylinder 61 that drives the hammer 13 for punching. In addition to the drive circuit 60, the drive circuit 63 for the X-direction drive motor 62 that moves and drives the feed base 15, and the drive circuit 65 for the Y-direction drive motor 64, each of the operation panels 9 has a drive signal and control. A signal is supplied.

  Here, the needle up sensor 52, the needle down sensor 53, and the timing signal generator 54 are provided in association with the main shaft 10 of the electronic eyelet sewing machine 1. The timing signal generator 54 detects the rotational phase of the main shaft 10 by an encoder provided on the main shaft 10 and outputs various phase signals when performing eyelet stitching.

  The ROM 42 generates stitch data of a bouncing seam or eyelet seam DN having a plurality of types of tack seams and an upper thread tension “0.5 N” when the needle is dropped to the outer needle position ON. Based on the piezo actuator drive voltage Vo for this purpose, the piezo actuator drive voltage Vi for generating the needle thread tension “0.8 N” when the needle drops at the inner needle position IN, and the stitch data, the motors 55, 57, In addition to a drive control program for driving the sewing mechanisms such as the feed base 15 and the rotation mechanism by driving and controlling the 62, 64 and the electromagnetic switching valve 59, a display control program for displaying various images on the operation panel 9 will be described later. A control program for yarn tension adjustment control unique to the present application is stored.

  The RAM 43 is provided with various work memories, buffers, pointers, and the like as necessary.

  Next, a routine of thread tension adjustment control executed by the control device 40 of the electronic eyelet sewing machine 1 will be described based on the flowchart of FIG. However, in the figure, reference sign Si (i = 11, 12, 13,...) Represents each step. Here, in order to sew the hole stitch DN, the needle bar 6 is always dropped into the inner needle position IN and then dropped into the outer needle position ON in one sewing cycle.

  In this case, the needle drop timing to the inner needle position IN (inner stitch formation start timing) and the needle drop timing to the outer needle position ON (outer stitch formation start timing) are the needle up signal from the needle upper sensor 52, It is determined by calculation based on a needle down signal from the needle down sensor 53, an encoder signal from the timing signal generator 54, and the like.

  By the way, the inner stitch formation period is a period from the inner stitch formation start time at which the sewing needle 5 drops to the inner needle position IN to the outer stitch formation start timing at which the needle 5 drops to the outer needle position ON. The stitch formation period is a period from the outer stitch formation start time at which the sewing needle 5 drops to the outer needle position ON to the inner stitch formation start timing at which the needle 5 drops to the inner needle position IN.

  This control is started when the electronic eyelet hole sewing machine 1 is turned on. First, it is determined whether or not the start / stop switch 50 is operated, that is, whether or not sewing of the hole stitch DN is started. Even when the sewing is started (S11: Yes), if it is not the inner stitch formation start time, the process waits until the inner stitch formation start timing is reached (S12: No).

  When it is time to start the inner stitch formation (S12: Yes), the inner needle position IN drive voltage Vi is applied to the laminated piezoelectric actuator 34 until the inner stitch formation period ends (S14: No). (S13). Then, when it is time to finish the inner stitch formation period (S14: Yes), the process waits until the outer stitch formation start time is reached (S15: No). When the outer stitch formation start time is reached (S15: Yes), the outer needle position ON drive voltage Vo is applied to the stacked piezoelectric actuator 34 until the outer stitch formation period ends (S17: No). Applied (S16).

  When it is time to finish the outer stitch formation period (S17: Yes), if the sewing process of the eyelet stitching DN is not completed (S18: No), S12 and subsequent steps are repeated. The On the other hand, when the sewing process for the eyelet stitch stitch DN is completed (S18: Yes), the highest drive voltage Vmax that can be set to the piezo actuator 34 is applied for the thread presser (S19). When the operation is finished (S20: Yes), the drive voltage V applied to the piezo actuator 34 is set to "0" (S21), and this control is finished. However, the inner needle position IN drive voltage Vi is set higher by a predetermined voltage than the outer needle position ON drive voltage Vo. Here, the control device 40 constitutes a yarn tension control means.

  Next, the action of the electronic eyelet hole sewing machine 1 configured as described above will be described with reference to FIG.

  When the sewing process is started, the upper thread 7a and the lower thread are crossed by the vertical movement of the needle bar 6 and the cooperation of the left looper and the right looper, and a stitch is formed. The eyelet stitch hole DN shown in FIG. 11 is formed by the turning mechanism. Incidentally, as shown in FIG. 10, in each sewing cycle, in the inner stitch formation period corresponding to the first half portion, the piezoelectric actuator 34 has a relatively large driving voltage Vi for the inner needle position IN (for example, as shown in FIG. 5). Therefore, the upper thread tension by the thread tension adjusting device 20 is set to about 0.8N.

  On the other hand, in each sewing cycle, a relatively small driving voltage Vo for the inner needle position IN (for example, about 18 V as shown in FIG. 5) is applied to the piezo actuator 34 during the outer stitch formation period corresponding to the latter half. Therefore, the upper thread tension by the thread tension adjusting device 20 is set to about 0.5N.

  Here, in FIG. 10, the start of the inner stitch formation period is when the left spreader corresponding to the left looper indicated by reference numeral “1” opens, and is the optimal time for switching with a small change in upper thread tension. The start of the outer stitch formation period is when the right spreader corresponding to the right looper indicated by reference numeral “4” opens, and is the optimal time for switching with a small change in upper thread tension.

  In FIG. 10, as another time when the needle thread tension changes more than the change indicated by the signs “1” and “4”, the sign “2” is the needle drop timing at the inner needle position IN of the sewing needle 5. “3” is the right looper swallowing time, “5” is the needle drop time at the outer needle position ON of the sewing needle 5, and “6” is the left looper swallowing time.

  In this way, the needle bar 6 to which the sewing needle 5 is attached, the thread piece 7 for supplying the upper thread 7a to the sewing needle 5, and the needle bar 6 are swung over the inner needle position IN and the outer needle position ON in the button hole. In an electronic eyelet hole sewing machine 1 having a needle bar swinging mechanism to be moved, a looper driven in synchronization with the vertical movement of the needle bar 6, and a lower thread supply source for supplying lower thread to the looper, thread tension When the adjusting device 20 is provided and the laminated piezo actuator 34 included in the yarn tension adjusting device 20 is controlled by the control device 40, the needle thread tension during the inner stitch formation period during which the needle is dropped to the inner needle position IN in each sewing cycle. Is made larger than the upper thread tension during the outer stitch formation period in which the needle is dropped to the outer needle position ON, so that the rate of occurrence of skipping and thread breakage at the inner needle position IN can be suppressed, and the stitches can be suppressed. It is possible to variously express the texture, it is possible to have stable needle thread tension in the inner stitch forming period upper thread 7a.

  Further, since the yarn tension adjusting device 20 includes the piezo actuator 34 for adjusting the upper yarn tension, the upper and lower yarns are utilized by taking advantage of the characteristics of the piezo actuator 34, such as small size and light weight, quick response, and minute change in elongation. Rapid tension change and quick response can be realized.

  Further, the yarn tension adjusting device 20 has a rotating tray 21 that engages with the upper thread 7a and a tension adjusting mechanism 22 that generates a rotational load on the rotating tray 21. The tension adjusting mechanism 22 is a laminated piezo actuator 34. Since a rotational braking force is applied to the rotating plate 21 to apply a thread tension to the upper thread 7a, the number of stacked piezoelectric elements can be arbitrarily set, so that the degree of freedom in manufacturing the stacked piezoelectric actuator 34 can be greatly increased. In addition, the magnitude of the rotational braking force can be appropriately set as necessary.

  Next, a modified embodiment in which the above embodiment is partially modified will be described.

  1] Although a laminated type is adopted as the piezo actuator 34, a bimorph type piezo actuator may be used.

  2] In FIG. 10, the inner stitch formation start timing may be earlier or later than the timing indicated by “1”, and the outer stitch formation start timing is also greater than the timing indicated by “4”. It may be early or late.

  3] Basically, the upper thread tension is set to a reference value of about 0.5 N, and the upper thread tension is temporarily set to a large value only at the inner stitch formation start timing when the needle is dropped to the inner needle position IN. In this manner, the upper thread tension may be temporarily set to be small only at the outer stitch formation start timing when the needle is dropped to the outer needle position ON.

  4] In the thread tension adjustment control shown in FIG. 9, the upper thread tension in the outer stitch formation period is set larger than the upper thread tension in the inner stitch formation period as a drive voltage applied to the laminated piezoelectric actuator 34. May be.

  5] Although the case where the present invention is applied to an electronic eyelet hole sewing machine has been described, the present invention can be applied to various hole sewing machines equipped with a needle bar vertical movement mechanism and a needle swinging mechanism.

  6) The present invention is not limited to the embodiment described above, and those skilled in the art can implement the present invention by adding various modifications without departing from the spirit of the present invention. The present invention includes such modifications.

1 is a perspective view of an electronic eyelet hole sewing machine according to an embodiment of the present invention. 1 is a side view of an electronic eyelet hole sewing machine according to an embodiment of the present invention. FIG. 3 is an enlarged perspective view of an electronic eyelet hole sewing machine. It is a principal part vertical front view of a yarn tension adjusting device. It is a diagram which shows the relationship between the drive voltage of a piezoelectric actuator, and the needle thread tension. It is a figure which shows the stitch skipping rate when the needle thread tension in an inner needle position is changed. It is a figure which shows the thread breakage rate when the upper thread | yarn tension | tensile_strength in an inner needle position is changed. It is a block diagram of a control system of an electronic eyelet hole sewing machine. It is a flowchart of thread tension adjustment control. It is a time chart of thread tension and various signals in a sewing cycle. It is a top view of an eyelet stitching stitch. FIG. 7 is a view corresponding to FIG. 6 when the upper thread tension at the outer needle position is set to 0.7 N according to the conventional technique. FIG. 8 is a view corresponding to FIG. 7 when the upper thread tension at the outer needle position is set to 0.7 N according to the conventional technique. FIG. 7 is a view corresponding to FIG. 6 when the upper thread tension at the outer needle position is set to 0.5 N according to the conventional technique. FIG. 8 is a view corresponding to FIG. 7 when the upper thread tension at the outer needle position is set to 0.5 N according to the conventional technique.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electronic eyelet sewing machine 5 Sewing needle 6 Needle bar 7 Thread piece 20 Thread tension adjusting device 21 Rotating tray 22 Tension adjusting mechanism 34 Stack type piezo actuator IN Inner needle position ON Outer needle position

Claims (5)

A needle bar to which a sewing needle is attached; an upper thread supply source that supplies upper thread to the sewing needle; and a needle bar swing mechanism that swings the needle bar over the inner needle position and the outer needle position in the button hole. In a boring machine having a looper driven in synchronism with the vertical movement of the needle bar and a lower thread supply source for supplying lower thread to the looper,
A thread tension adjusting device capable of adjusting the tension applied to the upper thread in the thread supply path from the upper thread supply source to the sewing needle;
Thread tension control means for controlling the thread tension adjusting device so that the upper thread tension when the needle is dropped at the inner needle position and the upper thread tension when the needle is dropped at the outer needle position are different;
A boring machine characterized by comprising A needle bar to which a sewing needle is attached; an upper thread supply source that supplies upper thread to the sewing needle; and a needle bar swing mechanism that swings the needle bar over the inner needle position and the outer needle position in the button hole. In a boring machine having a looper driven in synchronism with the vertical movement of the needle bar and a lower thread supply source for supplying lower thread to the looper,
A thread tension adjusting device capable of adjusting the tension applied to the upper thread in the thread supply path from the upper thread supply source to the sewing needle;
Thread tension control means for controlling the thread tension adjusting device so that the upper thread tension when the needle is dropped at the inner needle position is larger than the upper thread tension when the needle is dropped at the outer needle position;
A boring machine characterized by comprising   In each sewing cycle, the thread tension control means has an upper thread tension in an inner stitch formation period in which a needle is dropped to the inner needle position more than an upper thread tension in an outer stitch formation period in which a needle is dropped to the outer needle position. 3. The boring machine according to claim 2, wherein the thread tension adjusting device is controlled so as to be increased.   The bobbin sewing machine according to claim 2 or 3, wherein the yarn tension adjusting device includes a piezo actuator for adjusting an upper thread tension. The yarn tension adjusting device includes a rotating body that engages with the upper thread and a tension adjusting mechanism that generates a rotational load on the rotating body, and the tension adjusting mechanism is a laminated piezo actuator and a rotational braking force applied to the rotating body. 5. The boring machine according to claim 4, wherein a thread tension is applied to the upper thread by acting on the upper thread.