CN111748915A

CN111748915A - Sewing machine

Info

Publication number: CN111748915A
Application number: CN202010106051.8A
Authority: CN
Inventors: 今村雄介; 近藤宏史
Original assignee: Brother Industries Ltd
Current assignee: Brother Industries Ltd
Priority date: 2019-03-28
Filing date: 2020-02-20
Publication date: 2020-10-09
Anticipated expiration: 2040-02-20
Also published as: CN111748915B; JP2020157007A

Abstract

The invention relates to a sewing machine which can easily set a detection standard of poor sewing and can easily execute detection processing of poor sewing. The sewing machine determines whether a sewing failure that a normal stitch is not formed in a sewing operation occurs in a sewing failure determination process based on a face thread tension that repeatedly varies in a unit cycle of a sewing period of one stitch. The sewing failure judgment processing comprises thread breakage judgment processing, stitch skipping judgment processing and thread take-up failure judgment processing, and whether sewing failure occurs or not is judged by comparing a comparison variable obtained according to the tension of the upper thread with the first threshold value to the fourth threshold value. The first to fourth threshold values set a comparison variable at the time of a normal sewing operation as a reference.

Description

Sewing machine

Technical Field

The present invention relates to a sewing machine.

Background

A sewing machine capable of detecting a sewing failure such as a broken thread is known. In a sewing device (sewing machine) disclosed in japanese patent laid-open No. 132188 of 1995, when tension change occurs in an upper thread, a thread take-up spring comes into contact with or separates from a regulation pin. In the sewing process, the upper thread generates periodic tension variation. The length of the cycle, i.e., the reference time, is determined according to sewing conditions such as a sewing pattern. When the thread breakage occurs, the periodic tension change of the upper thread according to the reference time is not generated. At this time, the thread take-up spring continues to contact the restricting pin. At this time, the sewing device stops driving and stops sewing.

In the sewing device, the reference time is determined according to the sewing condition. Therefore, the user needs to obtain the reference time by performing trial sewing in advance and set it before sewing.

Disclosure of Invention

The invention aims to provide a sewing machine which can easily set a detection standard of poor sewing and can easily execute detection processing of the poor sewing.

The sewing machine of claim 1 comprises: a needle bar to which a needle is fitted, the needle bar being capable of moving up and down; a shuttle having a tip capable of catching an upper thread passing through the needle, the upper thread caught by the tip being interlaced with a lower thread; a thread take-up lever that takes up the upper thread interwoven with the lower thread by the shuttle; an upper shaft which rotates to move the needle bar and the thread take-up lever up and down; a thread take-up mechanism which applies tension to the upper thread and has a thread take-up reel through which the upper thread passes at a position upstream of the thread take-up lever on a feed path of the upper thread to the needle; a thread tension detecting section for detecting a tension of the upper thread, i.e., a tension of the upper thread; an upper shaft angle detection unit that detects an upper shaft angle, which is a rotation angle phase of the upper shaft; a sewing control part for controlling the needle bar, the shuttle and the thread take-up lever to sew the cloth; a tension acquiring unit that acquires the upper thread tension that periodically varies with sewing by the sewing control unit based on a detection result of the thread tension detecting unit; an upper shaft angle acquisition unit that acquires the upper shaft angle detected by the upper shaft angle detection unit when the sewing control unit performs sewing; and a judging section that judges whether or not a sewing failure that does not form a normal stitch in a sewing operation performed by the sewing control section has occurred based on the upper thread tension acquired by the tension acquiring section and the upper shaft angle acquired by the upper shaft angle acquiring section, the sewing failure including at least a thread breakage, a stitch skipping, and a thread take-up failure, the judging section judging by comparing a difference between a first surface thread tension and a second surface thread tension acquired by the tension acquiring section at different timings and a threshold value set in correspondence with the sewing failure, respectively, the threshold value being set based on the upper thread tension within a predetermined range of the upper shaft angle when a normal sewing operation is performed.

The operator does not have to perform a preliminary operation for setting the threshold value. Therefore, the sewing machine can easily set the detection reference of the sewing failure.

In the sewing machine according to claim 2, the determination unit may include a thread breakage determination unit configured to determine whether or not the thread breakage has occurred, the thread breakage determination unit may set the upper thread tension as the first surface thread tension in a range of the upper axial angle corresponding to a period in which the thread take-up lever lifts the upper thread, set the upper thread tension as the second surface thread tension in a range of the upper axial angle corresponding to a period in which the upper thread is caught by the hook, and determine that the thread breakage has occurred when a difference between the first surface thread tension and the second surface thread tension is equal to or less than a first threshold value set for the thread breakage. During normal sewing operation, no upper thread tension is generated during the period when the upper thread is caught by the shuttle peak. The sewing machine sets the upper thread tension in the period as a reference. When the yarn breakage occurs, the first surface yarn tension decreases, and therefore, the difference obtained by subtracting the second surface yarn tension from the first surface yarn tension is equal to or less than the first threshold value. Therefore, the sewing machine can recognize whether the thread is broken or not.

In the sewing machine according to claim 3, the determination unit may include a skip stitch determination unit configured to determine whether or not the skip stitch has occurred, the skip stitch determination unit may set the upper thread tension as the first surface thread tension in a range of the upper axial angle corresponding to a period in which the shuttle interleaves the upper thread and the lower thread, set the upper thread tension as the second surface thread tension in a range of the upper axial angle corresponding to a period in which the shuttle hook captures the upper thread, and determine that the skip stitch has occurred when a difference between the first surface thread tension and the second surface thread tension is equal to or less than a second threshold value set for the skip stitch. During normal sewing operation, no upper thread tension is generated during the period when the upper thread is caught by the shuttle peak. The sewing machine sets the upper thread tension in the period as a reference. When the stitch skipping occurs, the first face line tension decreases, and therefore, the difference obtained by subtracting the second face line tension from the first face line tension is equal to or less than the second threshold value. Therefore, the sewing machine can recognize whether the skip stitch occurs.

The sewing machine according to claim 4 may further include a tension storage unit that stores the upper thread tension for each cycle of the upper thread tension that repeatedly varies with one vertical movement of the needle bar, that is, one needle as a cycle, wherein the determining unit may include a take-up failure determining unit that determines whether or not the take-up failure has occurred, wherein the take-up failure determining unit may set the upper thread tension as the first surface thread tension in a range of the upper axial angle corresponding to a period in which the thread take-up lever lifts the upper thread in an nth cycle, wherein N is a natural number of 2 or more, set the upper thread tension as the second surface thread tension in a range of the upper axial angle corresponding to a period in which the thread take-up lever lifts the upper thread in an N-1 th cycle, and set a condition that a difference between the first surface thread tension and the second surface thread tension is equal to or more than a third threshold value set for the take-up failure, a second condition is set to be a condition that a phase difference between the timing of generating the first surface line tension and the timing of generating the second surface line tension is equal to or greater than a fourth threshold value set for the wire rewinding failure, and it is determined that the wire rewinding failure has occurred when at least one of the first condition and the second condition is satisfied. When poor take-up occurs, the tension of the upper thread is changed in each period. The difference between the upper thread tension in the predetermined range of the upper shaft angle in the Nth period and the upper thread tension in the predetermined range of the upper shaft angle in the N-1 th period is more than or equal to a third threshold value. The poor take-up judging part can identify whether poor take-up occurs or not. When a poor take-up occurs, the difference between the timing of generating the face thread tension in the Nth cycle and the timing of generating the face thread tension in the N-1 th cycle is greater than or equal to a fourth threshold value. Therefore, the sewing machine can identify whether the poor take-up occurs or not.

The sewing machine according to claim 5 may further include: a sewing condition acquisition unit for acquiring a sewing condition of the sewing control unit; and a threshold value storage unit that stores a table in which the sewing conditions and the threshold values are associated with each other, the threshold values being set with reference to the table according to the sewing conditions acquired by the sewing condition acquisition unit. The operator does not have to perform a preliminary operation for setting the threshold value. Therefore, the sewing machine can easily set the detection reference of the sewing failure.

The sewing machine according to claim 6 may further include a threshold setting unit that sets the threshold based on the upper thread tension acquired by the tension acquiring unit, wherein the threshold setting unit may calculate and set the thresholds corresponding to the sewing defects based on a difference between the first surface thread tension and the second surface thread tension when the normal sewing operation is performed. The sewing machine updates the threshold value every time sewing is performed. The operator does not have to perform a preliminary operation for setting the threshold value. Therefore, the sewing machine can easily set the detection reference of the sewing failure.

The sewing machine according to claim 7 may further include a cloth thickness acquiring unit that acquires a cloth thickness that is a thickness of a cloth to be sewn, and the threshold value may be set based on the cloth thickness acquired by the cloth thickness acquiring unit. The operator does not have to perform a preliminary operation for setting the threshold value. Therefore, the sewing machine can easily set the detection reference of the sewing failure.

The sewing machine according to claim 8 may further include a cloth feed amount acquiring unit that acquires a cloth feed amount, which is a movement amount by which the cloth is moved in a horizontal direction during one vertical movement of the needle bar, i.e., one stitch, in the sewing operation by the sewing control unit, and the threshold value may be set based on the cloth feed amount acquired by the cloth feed amount acquiring unit. The operator does not have to perform a preliminary operation for setting the threshold value. Therefore, the sewing machine can easily set the detection reference of the sewing failure.

The sewing machine according to claim 9 may further include a speed acquiring unit that acquires a rotational speed of the upper shaft, and the threshold value may be set based on the rotational speed acquired by the speed acquiring unit. The operator does not have to perform a preliminary operation for setting the threshold value. Therefore, the sewing machine can easily set the detection reference of the sewing failure.

The sewing machine according to claim 10 may further include an operation stop unit that stops the sewing operation by the sewing control unit when the upper thread tension detected by the thread tension detection unit is equal to or greater than a predetermined value. The sewing machine stops sewing when the upper thread tension is more than a preset value which greatly exceeds a normal value. Therefore, the sewing machine can prevent the sewing from being continued in a state that the upper thread tension is excessive, and can prevent the thread tension detecting part from being broken down in advance.

Drawings

Fig. 1 is an overall perspective view of the sewing machine 1.

Fig. 2 is a partially enlarged view of the head 5.

Fig. 3 is a sectional view of the main wire gripper 60.

Fig. 4 is a perspective view of the wire tension detecting mechanism 130.

Fig. 5 is a perspective view of the presser bar 202 in a state where the cloth 300 is pressed by the presser foot 201.

Fig. 6 is an electrical block diagram of the sewing machine 1.

Fig. 7 is a conceptual diagram of the threshold value table 95.

Fig. 8 is a graph showing a varying tension when stitches are normally formed.

Fig. 9 is a graph showing a varying tension at the time of stitch skipping.

Fig. 10 is a graph showing a varying tension in the case of a take-up failure.

Fig. 11 is a flowchart of the sewing process.

Fig. 12 is a flowchart of the tension acquiring process.

Fig. 13 is a flowchart of the sewing failure determination process.

Fig. 14 is a flowchart of the disconnection determination process.

Fig. 15 is a flowchart of the skip stitch determination processing.

Fig. 16 is a flowchart of the wire rewinding failure determination process.

Detailed Description

A sewing machine 1 according to an embodiment of the present invention will be described. The following description uses the left and right, front and back, and up and down shown by arrows in the drawings.

Referring to fig. 1 and 2, the structure of the sewing machine 1 will be described. The sewing machine 1 has a base 2, a column 3, and an arm 4. The base unit 2 is fitted to an opening of the table and extends in the left-right direction. The housing part 2 is equipped with a needle plate 7 on the upper surface. The operator places the cloth 300 (see fig. 5) on the bed 2 and the needle plate 7. The needle plate 7 has a needle receiving hole 8 and a feed dog hole 14. The pin receiving hole 8 has a circular shape in plan view. The feed sprocket 14 has a long diameter in the front-rear direction, and the feed sprocket 14 is located at the left, rear, right, and front of the needle accommodating hole 8, respectively. The column part 3 extends upward from the right end of the seat part 2. The arm portion 4 extends leftward from the upper end of the column portion 3 and faces the upper surface of the base portion 2. The arm portion 4 has an input portion 24 and a display portion 25 at a substantially central portion in the left-right direction of the front surface. The input section 24 is three input buttons. The operator operates the input unit 24 while looking at the display unit 25 to input various instructions. The arm part 4 has a thread passing rod (Japanese vertical rod) 20 protruding upward on the left side of the upper surface. The thread take-up lever 20 is penetrated by the upper thread 6 drawn out from the thread spool.

The arm portion 4 includes an upper shaft 15 and a main motor 27 (see fig. 6) therein. The upper shaft 15 extends in the left-right direction and is connected to an output shaft of the main motor 27 via an upper shaft pulley. The upper shaft pulley is fixed to the right end of the upper shaft 15. The arm portion 4 has a head portion 5 at a left end portion. The head 5 protrudes downward from the arm 4 and faces the needle plate 7 from above. The head 5 supports the needle bar 11 so that the needle bar 11 can move up and down. The lower end of the needle bar 11 is fitted with a needle 10 and projects downward from the head 5. The needle bar 11 is connected to the upper shaft 15 by an up-and-down movement mechanism. The needle bar 11 is moved up and down by the up-down movement mechanism in accordance with the rotation of the upper shaft 15. The needle 10 moves up and down together with the needle bar 11 while holding the needle thread 6 passing through the needle eye. The needle 10 can be passed through the needle-receiving hole 8. The lower end of the movable range of the needle 10 is a bottom dead center.

The base unit 2 includes therein a shuttle, a thread cutting mechanism 17 (see fig. 6), and a cloth feeding mechanism. The shuttle is provided below the needle plate 7 and houses a bobbin around which a lower thread is wound. The shuttle has a tip, and can be rotated by power of the main motor 27, and catches the upper thread 6 passing through the eye of the needle 10 with the tip, and interweaves the upper thread 6 with the lower thread. The thread cutting mechanism 17 (see fig. 6) includes a fixed blade, a movable blade, and a thread cutting solenoid 17A. The movable blade is connected to the tangent line electromagnetic element 17A. The movable knife is moved relative to the fixed knife by driving the thread cutting solenoid 17A, and the thread cutting mechanism 17 cuts the surface thread 6 and the ground thread by cooperation of the movable knife and the fixed knife.

The cloth feeding mechanism includes upper and lower cloth feeding shafts, a cloth feeding table, cloth feeding teeth 13, a horizontal cloth feeding shaft, and a cloth feeding motor 123 (see fig. 6). The upper and lower cloth feed shafts extend in the right and left direction inside the machine base 2 and are connected to the upper shaft pulleys via belts. The cloth feeding table is arranged to be capable of swinging and is connected with the upper and lower cloth feeding shafts. When the up-down feed shaft is rotated by the driving force of the main motor 27, the feed table moves in the up-down direction. The feed dog 13 is supported on the feed table. The horizontal feed shaft extends in the left-right direction at a position forward of the upper and lower feed shafts, and connects the feed motor 123 and the feed table. When the horizontal cloth feeding shaft is rotated by the driving force of the cloth feeding motor 123, the cloth feeding table moves in the front-rear direction. The cloth feeding table swings as the main motor 27 and the cloth feeding motor 123 are driven, and the cloth feeding teeth 13 protrude from or retreat into the cloth feeding sprocket holes 14. The cloth feed dog 13 moves in the front-rear direction while protruding upward from the cloth feed dog hole 14, and feeds the cloth 300.

As shown in fig. 2, the head 5 includes a sub thread gripper 26, a main thread gripper 60, a thread guide 21, a thread tension detection mechanism 130, a thread take-up lever 23, a guide hook 29, and the like in this order from the thread spool to the upstream side of the feed path of the upper thread 6 of the needle 10.

The sub-chuck 26 is provided at the upper right portion of the front surface of the head 5. The main gripper 60 is provided below the sub gripper 26 and is a front surface of the head 5. The sub-gripper 26 and the main gripper 60 respectively give tension to the upper thread 6. The sub-gripper 26 applies tension to the surface thread 6, which is required when the surface thread 6 and the lower thread are cut by the thread cutting mechanism 17. The main thread tension device 60 adjusts the tension applied to the upper thread 6 in accordance with the sewing operation of the sewing machine 1. The wire guide 21 is provided on the left of the main wire gripper 60. The thread guide 21 folds back the upper thread 6 passing through the main thread gripper 60 toward the thread tension detecting mechanism 130 and the thread take-up lever 23. The wire tension detecting mechanism 130 is fixed to a recess 5A recessed rearward from the front surface of the head 5 by a screw 90, and is located at a vertical position between the sub wire gripper 26 and the main wire gripper 60. The thread tension detecting mechanism 130 can detect the tension acting on the upper thread 6. The thread take-up lever 23 is provided on the left side of the sub-gripper 26 and has a through hole 23A through which the upper thread 6 passes. The thread take-up lever 23 moves up and down in accordance with the driving of the main motor 27. The guide hook 29 is provided on the left of the wire tension detecting mechanism 130. The guide hook 29 guides the upper thread 6 passing through the through hole 23A of the thread take-up lever 23 toward the needle bar 11.

As shown in fig. 3, the main gripper 60 has a thread take-up drum 62, a thread take-up holder 63, a thread take-up spring 65, a thread take-up motor 16, and a thread take-up spool 69.

The wire clamping cylinder 62 is annular and is fixed to the inside of a through hole 5C formed in the front wall 5B of the head 5 by a fastening member. The wire holder 63 is annular and is fixed to the inside of the wire holding cylinder 62 by a screw 19. The thread take-up spring 65 is fixed on the outer side surface of the thread clamping seat 63 and is wound between the thread clamping seat 63 and the thread clamping barrel 62. One end portion of the thread take-up spring 65 is exposed from the front wall portion 5B. The sewing machine 1 can adjust the spring pressure of the thread take-up spring 65 by the rotation of the thread tension holder 63. The thread take-up motor 16 is fixed to the inside of the arm portion 4 by bolts. The output shaft 18 of the thread tension motor 16 protrudes forward of the front wall portion 5B through the center hole of the thread tension holder 63. The chuck plate 69 is fixed to the front end of the output shaft 18 by a screw 28. The upper thread 6 is wound around the thread take-up reel 69 by about one to two turns. The wire clamping disk 69 is rotated by the wire clamping motor 16. The thread tension motor 16 has an encoder 16A (see fig. 5). The encoder 16A detects the rotational position of the output shaft 18.

The clamp motor 16 is a pulse motor, and has an output shaft 18 and an encoder 16A (see fig. 6). The output shaft 18 is rotatable about an axis in the front-rear direction. The encoder 16A can detect the rotational position of the output shaft 18. The front end portion of the output shaft 18 supports a chuck plate 69 on the right side of the arm portion 4. The sewing machine 1 can control the rotational angle phase of the output shaft 18.

The thread tension detecting mechanism 130 shown in fig. 4 is provided between the thread take-up reel 69 and the thread take-up lever 23 on the feed path of the upper thread 6. The thread tension detecting means 130 detects the front and rear positions of the plate 50 which is deflected in the front and rear direction in accordance with the upper thread tension based on the output voltage of the magnetic sensor 105, and detects the tension of the upper thread 6, that is, the upper thread tension.

The wire tension detection mechanism 130 has a mount 140, a sensor holder 80, a magnetic sensor 105, a plate 50, a guide member 160, and a magnet 58.

The mount 140 has a mounting portion 42 and a pedestal portion 410. The mounting portion 42 and the pedestal portion 410 are integrally formed. The mounting portion 42 has an elongated hole 421 through which the screw 90 passes. The screw 90 inserted through the long hole 421 is fastened to a screw hole provided in the recess 5A (see fig. 2). Thus, the mount 140 is mounted to the head 5. The mount 410 is located to the left of the mount 140. The pedestal portion 410 has a right protrusion 410A and a left protrusion 410B. The right protrusion 410A and the left protrusion 410B are each rectangular parallelepiped-shaped extending in the front-rear direction.

The sensor holder 80 is a rectangular parallelepiped non-magnetic body, and is attached to the pedestal portion 410 between the right protrusion 410A and the left protrusion 410B. The magnetic sensor 105 is held on the front surface of the sensor holder 80. The magnetic sensor 105 includes a hall element. The magnetic sensor 105 is located more to the rear side than the front ends of the right protrusion 410A and the left protrusion 410B.

The plate 50 has a thickness in the front-rear direction and extends in the left-right direction. The guide member 160 is attached to the right protrusion 410A and the left protrusion 410B by the

screws

97 and 98. The guide member 160 sandwiches the right end portion of the plate 50 with the right protrusion 410A, and sandwiches the left end portion of the plate 50 with the left protrusion 410B. The left-right direction center portion of the plate 50 has a gap with the front surface of the sensor holder 80. Therefore, the plate 50 can be flexed in the front-rear direction with both ends in the left-right direction as fulcrums.

The magnet 58 is cylindrical with the front-rear direction as the axial direction, and is fixed to the rear surface of the left-right direction center portion of the plate 50 with an adhesive. Therefore, when the plate 50 is flexed in the front-rear direction, the magnet 58 moves forward and backward, and the distance from the magnetic sensor 105 changes. The magnetic sensor 105 detects a change in the magnetic flux density of the magnet 58.

The guide member 160 has an upper guide groove 182 and a lower guide groove 172. The upper guide groove 182 and the lower guide groove 172 are vertically aligned with the plate 50 interposed therebetween, and are formed in a hook shape that opens in the vertical direction. The upper guide groove 182 has an upper holding hole 181, and the lower guide groove 172 has a lower holding hole 171. The upper holding hole 181 and the lower holding hole 171 extend in the front-rear direction. The upper thread 6 penetrates the upper and lower holding

holes

181 and 171. The upper thread 6 positioned between the upper holding hole 181 and the lower holding hole 171 is in contact with the front surface of the plate 50 from the front. The more the tension of the needle thread increases, the more the needle thread 6 applies a force to the plate 50 in the rearward direction. Therefore, the sewing machine 1 can acquire the upper thread tension based on the output voltage of the magnetic sensor 105.

A mechanism for detecting the cloth thickness of the cloth 300 is explained with reference to fig. 5. The head 5 includes a pressing rod 202, a spring 203, a presser foot drive mechanism, and the like. The pressing rod 202 extends in the vertical direction and protrudes downward from the lower end of the head 5. The pressing lever 202 is located at the rear of the needle bar 11. A presser foot 201 is attached to the lower end of the pressing rod 202, and the pressing rod 202 is moved up and down by the driving of a presser foot driving mechanism provided inside the arm portion 4. The presser foot 201 faces the feed dog 13 (see fig. 2).

The press lever 202 has a press lever hoop 210 at the center in the vertical direction. The plunger 202 has a spring 203 on the upper side of the plunger hoop 210. The knob portion 204 is provided at the upper end of the arm portion 4 and abuts against the upper end of the spring 203. The spring 203 biases the plunger hoop 210 downward. The presser foot 201 descends to press the cloth 300 disposed on the needle plate 7 downward.

The left portion of the strut hoop 210 has a plate-shaped portion 211. The lower left portion of the plate-shaped portion 211 has a magnet 212. The head 5 has a base plate 221 opposed to the left surface of the plate-like portion 211. The base plate 221 is fixed to a mounting plate at the left end of the head 5. The substrate 221 is separated from the plate-shaped portion 211. The magnetic sensor 222 is provided on the right portion of the substrate 221.

The up-down position of the magnet 212 changes with the change in the up-down position of the plunger 202. The magnetic sensor 222 detects a change in the magnetic flux density of the magnet 212. Therefore, the sewing machine 1 can acquire the up-down position of the presser foot 201 based on the output voltage of the magnetic sensor 222. The sewing machine 1 detects the cloth thickness of the cloth 300 between the presser foot 201 and the needle plate 7 based on the vertical position of the presser foot 201.

An electrical structure of the sewing machine 1 is explained with reference to fig. 6. The control device 30 of the sewing machine 1 has a CPU 91. The CPU91 controls the operation of the sewing machine 1. 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. 11) described later. The RAM93 temporarily stores various values. The storage device 94 is a non-volatile storage device. The RAM93 stores a wire break flag, a jumper flag, and a wire take-up flag. The line break mark, the jumper mark and the line take-up mark are respectively switched to one of 0 and 1.

The I/O45 is connected to the drive circuits 81 to 83. The drive circuit 81 is connected to the main motor 27. The drive circuit 82 is connected to the cloth feed motor 123. The drive circuit 83 is connected to the clamp motor 16. The main motor 27, the cloth feeding motor 123, and the thread take-up motor 16 include an encoder 27A, an encoder 123A, and an encoder 16A, respectively. The encoder 27A detects the rotational position of the output shaft of the main motor 27. The detection result of the encoder 27A indicates the rotational angle phase of the upper shaft 15, i.e., the upper shaft angle. The encoder 123A detects the rotational position of the output shaft of the cloth feeding motor 123. The encoder 16A detects the rotational position of the output shaft 18 of the clamp motor 16. The CPU91 acquires the detection results of the

encoders

27A, 123A, and 16A, and sends control signals to the drive circuits 81 to 83. Therefore, the CPU91 controls the driving of the main motor 27, the cloth feeding motor 123, and the thread take-up motor 16. Hereinafter, the main motor 27, the cloth feeding motor 123, and the thread take-up motor 16 will be collectively referred to as a drive motor.

The I/O45 is connected to the drive circuit 84, the drive circuit 85, the input section 24, the pedal 38, the magnetic sensor 105, and the magnetic sensor 222. The drive circuit 84 is connected to the tangent electromagnetic element 17A. The driving circuit 85 is connected to the display unit 25. The CPU91 controls the tangent line solenoid 17A and the display unit 25 by sending control signals to the drive circuit 84 and the drive circuit 85. The input unit 24 outputs the input result input to the input unit 24 by the operator to the CPU 91. The pedal 38 outputs an operation direction and an operation amount of the pedal 38 operated by the operator to the CPU 91. The magnetic sensor 105 outputs an output voltage indicating the tension of the upper thread to the CPU 91. The magnetic sensor 222 outputs an output voltage indicating the cloth thickness of the cloth 300 to the CPU 91.

The storage device 94 stores the first threshold value, the second threshold value, the third threshold value, and the fourth threshold value. The first to fourth threshold values are values for determining the presence or absence of sewing failure, which will be described later. The first threshold value to the fourth threshold value vary according to sewing conditions. The sewing conditions in this example are the type of thread, the thread clamping setting, the type of cloth 300, the cloth thickness of the cloth 300, the cloth feed amount, and the upper shaft rotation speed. The yarn tension is set as a reference of the tension applied to the face yarn 6 by the main yarn tension device 60. The trapping setting is set in 10 stages of sequentially increasing 10 from 10 to 100. The upper shaft rotation speed is the rotation speed of the upper shaft 15. The CPU91 acquires the upper axis rotation speed based on the detection result of the encoder 27A. That is, the upper shaft rotation speed is the sewing speed.

As shown in fig. 7, the threshold value table 95 stored in the storage device 94 indicates the relationship between the first to fourth threshold values and the sewing conditions. In the sewing failure determination process (see fig. 13) described later, the CPU91 can acquire and change the first to fourth threshold values corresponding to the sewing conditions from the threshold value table 95.

With reference to fig. 1 to 3, an outline of the operation of the sewing machine 1 will be described. The operator places a cloth 300 (see fig. 5) on the needle plate 7. The upper shaft 15 moves the needle bar 11 and the thread take-up lever 23 up and down by driving of the driving motor, and the shuttle rotates. When the needle 10 has penetrated the fabric 300 and has moved up after it has moved down to the bottom dead center, the shuttle catches the endless upper thread 6 held by the eye of the needle 10 with the tip of the shuttle and weaves the upper thread 6 with the lower thread. The needle 10 is withdrawn upward from the cloth 300. At this time, the feed dog 13 is driven by the feed motor 123 and the main motor 27 to project upward from the feed dog hole 14 and swing rearward. Accordingly, the cloth 300 moves rearward. The thread take-up lever 23 lifts the upper thread 6 interlaced with the lower thread by the shuttle, thereby forming a stitch on the fabric 300. The cloth 300 is sewn by repeating the above operations by the upper shaft 15, the needle 10, the shuttle, the thread take-up lever 23, and the cloth feeding mechanism. One stitch is sewed into a cycle.

The sewing failure of the sewing machine 1 will be described. The sewing failure indicates that a normal stitch is not formed in the sewing operation. The sewing failure comprises poor winding, broken thread and stitch skipping. The poor take-up is a poor balance between the upper thread 6 and the lower thread which form a stitch on the fabric 300 when the upper thread 6 is lifted by the thread take-up lever 23. For example, when the face thread 6 is too strongly interwoven with the ground thread, the cloth 300 near the stitches shrinks. The thread breakage is a defect that the upper thread 6 is broken during sewing and a stitch is not formed on the fabric 300. The skip stitch is a failure in catching the needle thread 6 by the shuttle in sewing and is a failure in forming a normal stitch on the fabric 300.

In a sewing period of one stitch (one cycle) of the sewing machine 1, there are a convergence period, a shuttle catching period, and a take-up lever lifting period in this order. The convergence period is a period in which the needle 10 rises from the bottom dead center and reaches the vicinity of the needle-down position. The needle-down position is a height position of the needle 10 at which the shuttle captures the upper thread 6 with the shuttle tip. The shuttle catching period is a period in which the shuttle catches the upper thread 6 with the shuttle tip and the upper thread 6 passes through the shuttle. The thread take-up lever lifting period is a period during which the thread take-up lever 23 lifts the upper thread 6.

Fig. 8 is a graph in which the horizontal axis is an upper axis angle and the vertical axis is a variable tension. The variable tension is a face thread tension which periodically varies with sewing, and the sewing period of one stitch is set as a face thread tension which repeatedly varies in a unit period. The CPU91 stores the varying tension in the RAM93 for each cycle. Fig. 8 shows the variable tension in the third, fourth, and fifth cycles from the start of sewing.

The ranges of the upper shaft angle corresponding to the convergence period, the shuttle catching period, and the take-up lever lifting period are the first range D1, the second range D2, and the third range D3. In the period of the Nth period (N is a natural number), the convergence period is a period in which the upper thread tension is not generated, the shuttle catching period is a period in which the upper thread tension reaches the maximum for the first time, and the take-up lever lifting period is a period in which the upper thread tension reaches the maximum for the second time. Hereinafter, the cumulative value of the face line tension in units of the above axial angle in the first range D1 will be referred to as a first cumulative value. The first cumulative value is substantially 0. The cumulative value of the upper thread tension in units of the above axial angles of the second range D2 is referred to as a second cumulative value, and the cumulative value of the upper thread tension in units of the above axial angles of the third range D3 is referred to as a third cumulative value.

When thread breakage occurs, the upper thread tension is substantially 0 in one sewing cycle, and hardly varies. Therefore, the third accumulated value is extremely small as compared with the normal time. When the disconnection occurs, the first subtraction value T1, which is the difference obtained by subtracting the first accumulation value from the third accumulation value, is equal to or less than the first threshold value. The first threshold value is a threshold value for determining whether or not the CPU91 has broken the wire in the wire breakage determination process (see fig. 14). The first threshold value is set as a reference value of a first subtraction value T1 when the sewing machine 1 performs a normal sewing operation.

As shown in fig. 9, when the needle jump occurs, the upper thread tension fluctuates little during the shuttle catch. Therefore, the second accumulated value is extremely small as compared with the normal time. The third cumulative value is a value close to normal. When the skip stitch occurs, a second subtraction value T2, which is a difference obtained by subtracting the first accumulation value from the second accumulation value, is equal to or less than a second threshold value. The second threshold value is a threshold value for determining whether or not the skip stitch occurs in the skip stitch determination process (see fig. 15) by the CPU 91. The second threshold value is set as a reference value of the second subtraction value T2 when the sewing machine 1 performs a normal sewing operation.

As shown in fig. 10, when the take-up failure occurs, the upper thread tension shows a variable tension during the raising of the thread take-up lever different from that before one cycle. Therefore, the phase and the third accumulated value of the upper thread tension of the third range D3 are changed from the phase and the third accumulated value of the upper thread tension of the third range D3 under the reference variation tension, respectively. The reference fluctuating tension is a fluctuating tension serving as a reference in one cycle. The reference variable tension at the time of sewing in the Nth cycle is the variable tension in the Nth-1 th cycle. In this example, when N is 4 or more, the sewing machine 1 refers to the variable tension of the N-1 th cycle as the reference variable tension.

When a thread take-up failure occurs in the sewing of the Nth cycle, a third subtraction value T3, which is a difference obtained by subtracting the third cumulative value in the sewing of the Nth cycle from the third cumulative value in the sewing of the Nth cycle, is equal to or greater than a third threshold value. The timing difference P obtained by subtracting the generation timing of the facial thread tension of the third range D3 during the sewing of the Nth period from the generation timing of the facial thread tension of the third range D3 during the sewing of the Nth-1 period is more than or equal to a fourth threshold value. The third threshold value and the fourth threshold value are threshold values for the CPU91 to determine whether a wire rewinding failure has occurred in the wire rewinding failure determination process (see fig. 16). The third threshold value is set as a reference value of the third subtraction value T3 when the sewing machine 1 performs a normal sewing operation. The fourth threshold value sets the timing difference P when the sewing machine 1 performs a normal sewing operation as a reference. When either of the two conditions is satisfied, the CPU91 determines that the wire take-up is defective. Hereinafter, the first subtraction value T1, the second subtraction value T2, and the third subtraction value T3 are collectively referred to as a comparison variable when the time lag P is included.

The sewing process will be described with reference to fig. 11 to 16. When the operator turns on the power of the sewing machine 1, the CPU91 reads out the program from the ROM92 and starts the sewing process.

As shown in fig. 11, the CPU91 executes initialization processing (S10). The CPU91 sets the disconnection flag, the skip stitch flag, the line-up flag, and the stop flag stored in the RAM93 to 0. The CPU91 sets the variable N stored in the RAM93 to 1. The CPU91 sets the variable M stored in the RAM93 to 0. The variable M is a count value for counting a predetermined period from the time when the CPU91 determines that sewing is completed to the time when the upper thread 6 and the lower thread are cut, that is, the thread is cut. The predetermined period is stored in the storage device 94 in advance. The CPU91 removes the fluctuating tension stored in the RAM 93.

The CPU91 acquires the initial sewing conditions (S15). The initial sewing conditions in this example are the type of thread, the thread clamp setting, the type of cloth 300, and the feed amount. When setting the initial sewing condition, the operator operates the input unit 24. The input unit 24 inputs the initial sewing condition to the CPU 91.

The CPU91 determines whether to start the sewing operation of the sewing machine 1 based on the detection result of the pedal 38 (S20). When the operator does not depress pedal 38, pedal 38 outputs a shut-off signal. When the cut-off signal is received from the pedal 38, the CPU91 judges that the sewing operation is not started and stands by (S20: NO).

The operator places the cloth 300 on the needle plate 7 and presses the cloth 300 with the presser foot 201. When the operator depresses the pedal 38, the pedal 38 outputs an on signal. When the on signal is received from the pedal 38, the CPU91 determines that the sewing operation is started (S20: yes), and starts the process of updating the variable N (S22). That is, the CPU91 adds 1 to the variable N every time the needle bar 11 moves up and down based on the upper shaft angle based on the detection result of the encoder 27A during the sewing operation. The CPU91 starts driving the drive motor (S25) and starts the sewing operation for the cloth 300.

The CPU91 executes tension acquisition processing (S31). As shown in fig. 12, the CPU91 determines whether or not it is in the initial stage of sewing (S70). The initial stage of sewing is from the beginning of sewing to the predetermined number of needles. In the initial stage of sewing, the end of the upper thread 6 is close to a free state, and the tension of the upper thread is hard to be generated. The initial stage of sewing in this example is sewing from the start of sewing to the second needle (second cycle (N ═ 2)). When the variable N is 2 or less and the sewing is in the initial stage (S70: YES), the CPU91 ends the tension acquiring process and returns to the sewing process (FIG. 11).

As shown in fig. 11, the CPU91 determines whether the stop flag stored in the RAM93 is 1 (S33). When the stop flag is 1 (S33: yes), the CPU91 shifts the process to S58. When the stop flag is 0 (S33: No), the CPU91 judges whether or not to end the sewing operation based on the detection result of the pedal 38 (S35). As the operator continues to depress pedal 38, pedal 38 continues to output an on signal. When receiving the on signal from the pedal 38, the CPU91 determines not to end the sewing operation (S35: no), and shifts the process to the tension acquisition process (S31).

The CPU91 repeats the tension acquiring process (S31) while the operator is operating the pedal 38 (S35: no). The CPU91 judges whether or not the sewing is in the initial stage (S70). When the variable N is not less than 3 and the sewing is not in the initial stage (S70: NO), the CPU91 obtains the upper shaft rotation speed based on the detection result of the encoder 27A (S71). The CPU91 acquires the upper axis rotation speed by acquiring the detection result of the encoder 27A twice. The CPU91 stores the acquired upper axis rotation speed in the RAM 93.

The CPU91 acquires the needle thread tension based on the detection result of the magnetic sensor 105 and the upper axis angle based on the detection result of the encoder 27A (S73). The CPU91 associates the obtained needle thread tension with the upper axis angle and stores the resultant in the RAM93 as a varying tension.

The CPU91 determines whether the acquisition of the fluctuating tension for the nth cycle is completed based on the upper axis angle acquired in S73 (S75). If the upper shaft angle acquired in S73 immediately after the completion of the sewing period of the nth cycle is not the upper shaft angle corresponding to the completion of the sewing period, the CPU91 determines that the acquisition of the varying tension of the nth cycle is not completed (S75: no). At this time, the CPU91 shifts the process to S71. When the upper axis angle acquired in S73 immediately after the completion of the sewing period of the nth cycle is the upper axis angle corresponding thereto, the CPU91 determines that the acquisition of the varying tension of the nth cycle is completed (S75: yes). At this time, the CPU91 shifts the process to S76.

The CPU91 accumulates the needle thread tension and the upper axis angle as the varying tension every time S71 to S75 are repeated, and stores the accumulated tension in the RAM 93. The CPU91 calculates first to third integrated values from the fluctuating tension of the nth cycle stored in the RAM93 (S76). The CPU91 stores the calculated first to third accumulated values in the RAM 93. The CPU91 determines whether the calculated first to third accumulated values are less than a predetermined value (S77). The storage device 94 stores a predetermined value. The predetermined value is defined by the first to third cumulative values at the time of normal sewing, and is a value much larger than the first to third cumulative values at the time of normal sewing. When the calculated first to third integrated values are smaller than the predetermined value (S77: yes), the CPU91 shifts the process to S79. When the calculated first to third integrated values are equal to or greater than the predetermined value (S77: no), the CPU91 sets the stop flag to 1(S78) and shifts the process to S79. The CPU91 acquires the generation timing of the face line tension of the third range D3 according to the varied tension of the nth cycle (S79). The CPU91 stores the acquired generation timing of the upper thread tension of the third range D3 in the RAM 93. The CPU91 executes a sewing failure determination process (see fig. 13) (S80). The sewing failure judgment processing is processing for judging whether a thread break, a stitch skip and a thread take-up failure occur respectively. The CPU91 sets the thread breakage flag, the skip stitch flag, and the thread take-up flag to 1 in accordance with the sewing failure.

As shown in fig. 13, the CPU91 acquires the cloth thickness of the cloth 300 based on the detection result of the magnetic sensor 222 (S101). The CPU91 stores the acquired cloth thickness of the cloth 300 in the RAM 93. The CPU91 determines whether setting of the first to fourth thresholds is completed (S105). When the setting of the first to fourth thresholds is completed (yes in S105), the CPU91 shifts the process to S111. If the first to fourth threshold values are not set (S105: no), the CPU91 refers to the threshold value table 95 stored in the storage device 94, and sets the first to fourth threshold values based on the sewing conditions acquired in S15, S71, and S101 (S106). The CPU91 shifts the process to S111.

The CPU91 determines whether the upper shaft rotation speed has changed (S111). At this time, the CPU91 makes a determination based on the upper axis rotation speed at the time of the nth cycle sewing acquired in S71 and the upper axis rotation speed at the time of the nth-1 cycle sewing stored in the RAM 93. When the upper shaft rotation speed changes by a predetermined range or more, the CPU91 regards that the upper shaft rotation speed has changed.

When the upper shaft rotation speed is not changed (no in S111), the CPU91 determines whether the cloth thickness of the cloth 300 has changed (S112). At this time, the CPU91 makes a determination based on the cloth thickness of the cloth 300 at the time of sewing in the nth cycle acquired in S101 and the cloth thickness of the cloth 300 at the time of sewing in the N-1 th cycle stored in the RAM 93. When the cloth thickness of the cloth 300 changes by a predetermined amount or more, the CPU91 recognizes that the cloth thickness of the cloth 300 has changed. If the cloth thickness of cloth 300 has not changed (no in S112), CPU91 transfers the process to S121.

When the upper shaft rotation speed is changed (yes in S111) or the cloth thickness of the cloth 300 is changed (yes in S112), the CPU91 changes the threshold value set in S106 (S115). The upper shaft rotation speed, the cloth thickness of the cloth 300, and the cloth feed amount of the cloth 300 are sewing conditions that are variable during the sewing operation. When the sewing condition is changed, the CPU91 refers to the threshold table 95 and resets the first to fourth thresholds. The CPU91 shifts the process to S121.

The CPU91 executes disconnection determination processing (S121). As shown in fig. 14, the CPU91 determines whether the first subtraction value T1 is the first threshold value or less (S131). The CPU91 calculates a first subtraction value T1 based on the first accumulation value and the third accumulation value calculated in S76. When the first subtraction value T1 is greater than the first threshold value (S131: no), the CPU91 determines that thread breakage has not occurred, ends the thread breakage determination process, and returns to the sewing failure determination process (fig. 13). When the first subtraction value T1 is equal to or less than the first threshold value (S131: yes), the CPU91 determines that thread breakage has occurred during the nth cycle sewing and sets the thread breakage flag to 1 (S132). The CPU91 ends the thread breakage determination processing and returns to the sewing failure determination processing.

The CPU91 executes the skip stitch determination processing (S122). As shown in fig. 15, the CPU91 determines whether the second subtraction value T2 is the second threshold value or less (S141). The CPU91 calculates the second subtraction value T2 based on the first accumulation value and the second accumulation value calculated in S76. When the second subtraction value T2 is greater than the second threshold value (S141: no), the CPU91 determines that stitch skipping has not occurred, ends the stitch skipping determination process, and returns to the sewing failure determination process (fig. 13). When the second subtraction value T2 is equal to or less than the second threshold value (S141: yes), the CPU91 determines that a skip stitch has occurred during the sewing of the nth cycle and sets the skip stitch flag to 1 (S142). The CPU91 ends the stitch skipping determination processing and returns to the sewing failure determination processing.

The CPU91 executes a wire rewinding failure determination process (S123). As shown in fig. 16, the CPU91 determines whether N is 4 or more (S151). When N is less than 3 (S151: NO), the N-1 cycle is at the initial stage of sewing, and the variation tension is small and cannot be referred to as the reference variation tension. The CPU91 ends the poor take-up determination processing and returns to the poor sewing determination processing.

When N is 4 or more (S151: YES), the CPU91 acquires a third accumulated value at the time of sewing of the (N-1) th cycle stored in the RAM93 (S152). The CPU91 acquires the generation timing of the needle thread tension of the third range D3 at the time of sewing of the N-1 th cycle stored in the RAM93 (S153).

The CPU91 determines whether the third subtraction value T3 is equal to or greater than the third threshold value (S161). The CPU91 calculates a third subtraction value T3 based on the third accumulated value at the time of sewing of the nth cycle calculated in S76 and the third accumulated value at the time of sewing of the N-1 th cycle acquired in S152.

When the third subtraction value T3 is smaller than the third threshold value (S161: no), the CPU91 determines whether the time difference P is equal to or greater than the fourth threshold value (S162). The CPU91 calculates the timing difference P based on the generation timing of the upper thread tension in the third range D3 at the time of sewing in the nth cycle acquired in S79 and the generation timing of the upper thread tension in the third range D3 at the time of sewing in the N-1 th cycle acquired in S153. When the timing difference P is smaller than the fourth threshold (S162: no), the CPU91 determines that a poor thread take-up has not occurred, ends the poor thread take-up determination process, and returns to the poor sewing determination process.

When the third phase reduction value T3 is equal to or greater than the third threshold value (yes in S161) or when the timing difference P is equal to or greater than the fourth threshold value (yes in S162), the CPU91 determines that a wire-rewinding failure has occurred and sets the wire-rewinding flag to 1 (S164). The CPU91 ends the poor take-up determination processing and returns to the poor sewing determination processing.

As shown in fig. 13, after executing the thread breakage determination process (S121), the stitch skipping determination process (S122), and the thread take-up failure determination process (S123), the CPU91 ends the sewing failure determination process and returns to the tension acquisition process (fig. 12).

As shown in fig. 12, the CPU91 determines whether a sewing failure has occurred (S85). When the thread breakage flag, the stitch skipping flag, and the thread take-up flag are all 0, the CPU91 determines that a sewing failure has not occurred (S85: no). The CPU91 stores a comparison variable for normal sewing in the RAM 93. The CPU91 accumulates and stores the comparison variable in the RAM93 every time a sewing period of one stitch is repeated. The CPU91 calculates the average value of the accumulated comparison variables at the time of normal sewing. The CPU91 calculates the first to fourth threshold values based on the average value of the comparison variable. The CPU91 stores and updates the calculated first to fourth threshold values in the threshold value table 95 as new first to fourth threshold values (S86). In the normal sewing operation, the CPU91 repeatedly updates the first to fourth threshold values. The CPU91 ends the tension acquisition process and returns to the sewing process (fig. 11).

When the operator releases the pedal 38, the pedal 38 outputs a shut-off signal. As shown in FIG. 11, when the cut-off signal is received from the pedal 38, the CPU91 judges that sewing is finished (S35: YES). The CPU91 determines whether the variable M stored in the RAM93 has reached a predetermined period (S43). When the variable M does not reach the predetermined period (S43: NO), the CPU91 judges whether the variable M is 0 (S45). When the variable M is 0 (S45: YES), the CPU91 starts a process of updating the variable M (S46). Specifically, the CPU91 adds 1 to the variable M every time the needle 11 performs the up-down movement based on the upper axial angle based on the detection result of the encoder 27A. The CPU91 shifts the process to S51. When the variable M is not 0 (S45: no), the CPU91 shifts the process to S51.

The CPU91 executes tension acquisition processing (S51). The tension acquiring process of S51 is the same as the tension acquiring process of S31. The CPU91 determines whether the stop flag stored in the RAM93 is 1 after executing the tension acquisition process of S51 (S53). When the stop flag stored in the RAM93 is 1 (S53: yes), the CPU91 shifts the process to S58. When the stop flag stored in the RAM93 is 0 (S53: no), the CPU91 shifts the process to S43, and repeats the processes of S43 to S53 until the variable M reaches a predetermined cycle.

When the variable M reaches the predetermined period (S43: YES), the CPU91 controls the thread cutting solenoid 17A to perform thread cutting (S57). The CPU91 stops driving the drive motor (S58). The CPU91 stops the update of the variable N, M started in S22 and S46 (S59).

The CPU91 determines whether or not to cut off the power of the sewing machine 1 (S63). When the operator does not perform the operation of cutting off the power supply of the sewing machine 1 (S63: no), the CPU91 shifts the process to S10. During the standby of the CPU91 (S20: no), the operator places the unsewn cloth 300 on the needle plate 7 instead of the sewn cloth 300, and then depresses the pedal 38 (S20: yes).

As shown in fig. 12, when at least one of the thread breakage flag, the stitch skipping flag, and the thread take-up flag is 1, the CPU91 determines that a sewing failure has occurred (S85: yes), and the process proceeds to S88. The CPU91 determines the sewing failure (S88). The CPU91 determines the sewing failure by determining the 1 mark among the thread breakage mark, the stitch skipping mark, and the thread take-up mark. The CPU91 displays the determined sewing failure on the display unit 25 and notifies it (S89).

The CPU91 determines whether to stop driving the pinch motor 16 and the drive motor (S91). When the sewing failure is a broken thread or a stitch skipping, the CPU91 determines that the thread take-up motor 16 and the drive motor are stopped (S91: yes). At this time, the CPU91 sets the stop flag to 1(S92) and returns to the sewing process (fig. 11). When the sewing failure is a thread take-up failure, the CPU91 determines not to stop driving the thread take-up motor 16 and the drive motor (S91: no). At this time, the CPU91 ends the tension acquisition process and returns to the sewing process. When the thread take-up failure occurs before the sewing operation is completed, the operator may depress the pedal 38 (no in S35) or release the pedal 38 (yes in S35) after confirming the occurrence of the thread take-up failure on the display unit 25. When the thread take-up failure occurs before the variable M reaches the predetermined period after the sewing operation is finished, the CPU91 may continue the processing of S43 to S53 until the variable M reaches the predetermined period.

As shown in FIG. 11, when the operator turns off the power of the sewing machine 1 (S63: YES), the CPU91 ends the sewing process.

As described above, the CPU91 acquires the needle thread tension based on the detection result of the magnetic sensor 105 and the upper axis angle based on the detection result of the encoder 27A (S73). The CPU91 associates the obtained needle thread tension with the upper axis angle and stores the resultant in the RAM93 as a varying tension. The CPU91 executes a disconnection determination process (S121), a skip stitch determination process (S122), and a wire-rewinding failure determination process (S123). In each process, the CPU91 compares the plurality of comparison variables with the first to fourth thresholds to determine whether or not a sewing failure has occurred (S131, S141, S161, S162). The first threshold value is a threshold value corresponding to a broken wire, the second threshold value is a threshold value corresponding to a jumper pin, and the third threshold value and the fourth threshold value are threshold values corresponding to a poor take-up. The first threshold value to the fourth threshold value are set based on a comparison variable when the sewing machine 1 performs a normal sewing operation. Therefore, the operator does not have to perform a preliminary operation for setting the first to fourth threshold values. Therefore, the sewing machine 1 can easily set the first threshold value to the fourth threshold value as the detection reference of the sewing failure.

When the thread breakage occurs, the needle thread tension in the third range D3 is substantially 0. Therefore, the cumulative value of the face line tension in the third range D3, that is, the third cumulative value is extremely small as compared with the normal time. When the disconnection occurs, the first subtraction value T1, which is the difference obtained by subtracting the first accumulation value from the third accumulation value, is equal to or less than the first threshold value. When the first subtraction value T1 is equal to or less than the first threshold value (yes in S131), the CPU91 determines that disconnection has occurred and sets the disconnection flag to 1 (S132). The sewing machine 1 can determine whether or not a thread break occurs, and the sewing machine 1 can recognize the thread break as a sewing failure.

When the skip stitch occurs, the cumulative value of the needle thread tension in the second range D2, that is, the second cumulative value is extremely small as compared with the normal time. When the skip stitch occurs, a second subtraction value T2, which is a difference obtained by subtracting the first accumulation value from the second accumulation value, is equal to or less than a second threshold value. When the second subtraction value T2 is equal to or less than the second threshold value (S141: yes), the CPU91 determines that a skip stitch has occurred and sets the skip stitch flag to 1 (S142). The sewing machine 1 can determine whether or not a skip stitch occurs, and the sewing machine 1 can recognize the skip stitch as a sewing failure.

When a thread take-up failure occurs in the sewing of the Nth cycle, the phase and the third accumulated value of the upper thread tension in the third range D3 in the sewing of the Nth cycle are changed relative to the phase and the third accumulated value of the upper thread tension in the third range D3 in the sewing of the Nth-1 cycle, respectively. At this time, a third subtraction value T3, which is a difference obtained by subtracting the third cumulative value at the time of sewing in the (N-1) th cycle from the third cumulative value at the time of sewing in the (N) th cycle, is equal to or greater than a third threshold value (S161: YES). The timing difference P obtained by subtracting the generation timing of the face thread tension in the third range D3 in the Nth cycle of sewing from the generation timing of the face thread tension in the third range D3 in the N-1 th cycle of sewing is more than or equal to a fourth threshold value (S162: Yes). If any of the determinations in S161 and S162 match the above, the CPU91 determines that the wire is defective and sets the wire-rewinding flag to 1 (S164). The sewing machine 1 can determine whether or not a poor thread take-up occurs, and the sewing machine 1 can recognize the poor thread take-up as a poor thread take-up.

The storage device 94 stores a threshold table 95 in which sewing conditions are associated with first to fourth thresholds. The CPU91 acquires the first to fourth threshold values from the threshold value table 95, and can change the first to fourth threshold values according to the sewing conditions. The operator does not need to perform a preliminary operation for setting the first to fourth threshold values. Therefore, the sewing machine 1 can easily set a detection reference for a sewing failure.

The CPU91 accumulates and stores the comparison variable in the RAM93 every time the sewing machine 1 performs a normal sewing operation. The CPU91 calculates the average value of the accumulated comparison variables. The CPU91 calculates the first to fourth threshold values based on the average value of the comparison variables. The CPU91 stores and updates the calculated first to fourth threshold values in the threshold value table 95 as new first to fourth threshold values (S86). During the normal sewing operation of the sewing machine 1, the CPU91 repeatedly updates the first to fourth threshold values. The operator does not need to perform a preliminary operation for setting the first to fourth threshold values. Therefore, the sewing machine 1 can easily set a detection reference for a sewing failure.

The sewing machine 1 includes a magnetic sensor 222 capable of detecting the cloth thickness of the cloth 300. The CPU91 acquires the detection result of the magnetic sensor 222 (S101), and sets the first to fourth threshold values (S106). When the cloth thickness of the cloth 300 changes during the sewing operation (yes in S112), the CPU91 resets the first to fourth threshold values in accordance with the acquired cloth thickness of the cloth 300 (S115). The operator does not need to perform a preliminary operation for setting the first to fourth threshold values. Therefore, the sewing machine 1 can easily set a detection reference for a sewing failure.

When setting the cloth feed amount, the operator operates the input unit 24. The CPU91 acquires the feed amount information received from the input unit 24 (S15), and sets the first to fourth thresholds (S106). The operator does not need to perform a preliminary operation for setting the first to fourth threshold values. Therefore, the sewing machine 1 can easily set a detection reference for a sewing failure.

The sewing machine 1 has an encoder 27A. The CPU91 acquires the upper shaft rotation speed, which is the speed of sewing, from the detection result of the encoder 27A (S71), and sets first to fourth thresholds (S106). When the upper shaft rotation speed changes during the sewing operation (YES in S111), the CPU91 resets the first to fourth thresholds according to the acquired upper shaft rotation speed (S115). The operator does not need to perform a preliminary operation for setting the first to fourth threshold values. Therefore, the sewing machine 1 can easily set a detection reference for a sewing failure.

When the first to third cumulative values calculated in the tension acquisition process are equal to or greater than the predetermined value (S77: no), the CPU91 sets the stop flag to 1 (S78). At this time, the CPU91 stops the driving of the drive motor during the sewing process. The sewing machine 1 stops sewing when the upper thread tension is more than a predetermined value greatly exceeding a normal value. Therefore, the sewing machine 1 can prevent the sewing from being continued in a state where the upper thread tension is excessive, and can prevent the thread tension detecting section from malfunctioning in advance.

The main wire gripper 60 is an example of the wire gripping mechanism of the present invention. The magnetic sensor 105 is an example of the line tension detecting unit of the present invention. The encoder 27A is an example of the upper axis angle detecting unit of the present invention. The CPU91 when executing S25 and S58 is an example of the sewing control unit of the present invention. The CPU91 when executing S73 is an example of the tension acquiring section of the present invention. The CPU91 when S73 is executed is an example of the upper axis angle acquiring unit of the present invention. The CPU91 executing S80 is an example of the determination unit of the present invention. The CPU91 executing S121 is an example of the disconnection determining unit of the present invention. The CPU91 executing S122 is an example of the skip stitch determination unit of the present invention. The RAM93 is an example of the tension storing section of the present invention. The CPU91 when executing S123 is an example of the wire rewinding failure determination unit according to the present invention. The CPU91 in executing S15, S71, and S101 is an example of the sewing condition obtaining section of the present invention. Threshold value table 95 is an example of a table of the present invention. The storage device 94 is an example of a threshold storage unit of the present invention. The CPU91 executing S86 is an example of the threshold setting unit of the present invention. The CPU91 when executing S101 is an example of the cloth thickness obtaining section of the present invention. The CPU91 executing S15 is an example of the cloth feed amount acquiring unit of the present invention. The CPU91 when S71 is executed is an example of the speed acquisition section of the present invention.

The present invention is not limited to the above-described embodiments. The first, second, and third subtraction values T1, T2, and T3 may be calculated from the magnitudes of the respective maximum needle thread tensions in the first, second, and third ranges D1, D2, and D3. At this time, the size of the first range D1 at which the needle thread tension becomes maximum is substantially 0.

The threshold value table 95 may store correction values instead of the values of the first to fourth threshold values. At this time, the CPU91 refers to the correction value according to the sewing condition, and determines the first to fourth threshold values based on the comparison variable and the correction value in the normal sewing operation. An example of the correction value is a ratio to a comparison variable in a normal sewing operation. The process of S86 may be omitted. Threshold value table 95 may be omitted, or the first to fourth threshold values may be directly stored in storage device 94.

The timing difference P may be a timing to be compared between the sewing in the nth cycle and the sewing in the N-1 st cycle, which is a predetermined timing of the needle thread tension in the third range D3. For example, the compared timing may be a timing at which the needle thread tension in the third range D3 becomes maximum or a timing at which the needle thread tension ends. In this case, the CPU91 may determine whether or not the timing difference P obtained by subtracting the timing of generation of the face line tension in the third range D3 is equal to or greater than a fourth threshold, determine whether or not the timing difference P obtained by subtracting the timing of the maximum or end of the face line tension in the third range D3 is equal to or greater than a threshold, and determine that a take-up failure has occurred when either of the two determination results is satisfied.

The RAM93 need not store all of the varying tensions for the N cycles. It is sufficient that the variable tension of the nth cycle and the reference variable tension (the variable tension of the N-1 th cycle in the above embodiment) are present during the sewing operation. When the variable tension in the N-1 th cycle is set as the reference variable tension, the CPU91 may appropriately cancel the variable tension before the N-2 th cycle. The CPU91 may store the timing of generating the needle thread tension in the third range D3 of the reference variation tension in the storage device 94 as the timing of generating the needle thread tension in the third range D3 during normal sewing.

The initial sewing stage may be a stage from the start of sewing to the first cycle of sewing, or a stage to the third cycle of sewing. The predetermined number of stitches defining the initial stage of sewing may be different depending on the sewing failure. For example, when it is determined whether or not a thread break occurs, the stage up to the first cycle may be set as the initial stage of sewing, and when it is determined whether or not a stitch skip occurs, the stage up to the second cycle may be set as the initial stage of sewing. The initial stage of sewing may not be specified.

The CPU91 may acquire the first to third accumulated values for N cycles before acquiring the fluctuating tension for N cycles. For example, the CPU91 may acquire the first to third accumulated values at the acquisition timings of the needle thread tensions for the ranges of the upper axis angles of the first, second, and third ranges D1, D2, and D3 by acquiring the detection result of the encoder 27A. At this time, the CPU91 may also execute S80 before the sewing of the nth cycle is completed.

The magnetic sensor 105 may also include a magnetic impedance element, a magnetoresistance effect element, or the like instead of the hall element.

A microcomputer, an ASIC, or the like may also be used as the processor instead of the CPU 91. The sewing process or the like may be distributed by a plurality of processors.

The respective processes such as the sewing process and the first to fourth threshold values may be downloaded from a server connected to a network, not shown, and stored in the storage device 94. The first to fourth threshold values may be stored in a non-temporary storage medium such as a storage device included in the server.

Claims

1. A sewing machine, wherein,

the sewing machine has:

a needle bar (11) to which a needle (10) is fitted, the needle bar being capable of moving up and down;

a shuttle having a tip capable of catching an upper thread passing through the needle, the upper thread caught by the tip being interlaced with a lower thread;

a thread take-up lever (23) for taking up the upper thread interwoven with the lower thread by the shuttle;

an upper shaft (15) which rotates to move the needle bar and the thread take-up lever up and down;

a thread take-up mechanism (60) which applies tension to the upper thread and is provided with a thread take-up disk (69) through which the upper thread passes at a position on the upstream side of the take-up lever on a feeding path of the upper thread to the needle;

a thread tension detection unit (105) for detecting the tension of the upper thread, namely the tension of the upper thread;

an upper axis angle detection unit (27A) that detects an upper axis angle, which is a rotational angle phase of the upper axis;

a sewing control part (91) for controlling the needle bar, the shuttle and the thread take-up lever to sew the cloth;

a tension acquiring unit that acquires the upper thread tension that periodically varies with sewing by the sewing control unit based on a detection result of the thread tension detecting unit;

an upper shaft angle acquisition unit that acquires the upper shaft angle detected by the upper shaft angle detection unit when the sewing control unit performs sewing; and

a determination unit that determines whether or not a sewing failure in which a normal stitch is not formed in the sewing operation by the sewing control unit has occurred based on the upper thread tension acquired by the tension acquisition unit and the upper shaft angle acquired by the upper shaft angle acquisition unit,

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

the sewing failure at least comprises broken thread, skipping stitch and take-up failure,

the judging section judges by comparing a difference between the first surface thread tension and the second surface thread tension acquired at different timings by the tension acquiring section with thresholds set in correspondence with the sewing failures,

the threshold value is set based on the upper thread tension in a predetermined range of the upper shaft angle when the normal sewing operation is performed.

2. The sewing machine of claim 1,

the judging section has a disconnection judging section for judging whether or not the disconnection has occurred,

the wire breakage judging section

Setting the upper thread tension in the range of the upper shaft angle corresponding to the period of the thread take-up lever lifting the upper thread as the first surface thread tension,

setting the upper thread tension in the range of the upper shaft angle corresponding to the period of the upper thread being caught by the shuttle point as the second surface thread tension,

and determining that the wire breakage has occurred when a difference between the first surface wire tension and the second surface wire tension is equal to or less than a first threshold value set for the wire breakage.

3. Sewing machine as in claim 1 or 2,

the judging unit has a skip stitch judging unit for judging whether the skip stitch occurs,

the jumping pin judging part

Setting the upper thread tension in the range of the upper axis angle corresponding to a period in which the shuttle interleaves the upper thread and the lower thread as the first surface thread tension,

and determining that the skip stitch has occurred when a difference between the first surface line tension and the second surface line tension is equal to or less than a second threshold value set for the skip stitch.

4. Sewing machine as in any of claims 1 to 3,

the sewing machine further comprises a tension storage part (93) which stores the upper thread tension for each period for the upper thread tension repeatedly changing by one time of the vertical movement of the needle bar, namely one needle period,

the judging part is provided with a poor take-up judging part for judging whether the poor take-up occurs,

receive line bad judgement portion

Setting the upper thread tension as the first surface thread tension in a range of the upper shaft angle corresponding to a period in which the thread take-up lever lifts the upper thread in an Nth cycle, where N is a natural number of 2 or more,

setting the upper thread tension in the range of the upper shaft angle corresponding to the period of the N-1 th cycle during which the thread take-up lever lifts the upper thread as the second surface thread tension,

setting a condition that a difference between the first surface line tension and the second surface line tension is equal to or greater than a third threshold value set for the take-up failure as a first condition,

a second condition is set to be a condition that a phase difference between the timing of generating the first surface line tension and the timing of generating the second surface line tension is equal to or greater than a fourth threshold value set for the take-up failure,

and when at least one of the first condition and the second condition is met, judging that poor take-up occurs.

5. Sewing machine as in any of claims 1 to 4,

the sewing machine further has:

a sewing condition acquisition unit for acquiring a sewing condition of the sewing control unit; and

a threshold value storage unit (94) for storing a table in which the sewing conditions and the threshold values are associated with each other,

the threshold value is set by referring to the table according to the sewing condition acquired by the sewing condition acquisition unit.

6. Sewing machine as in any of claims 1 to 5,

the sewing machine further comprises a threshold value setting unit for setting the threshold value according to the upper thread tension acquired by the tension acquiring unit,

the threshold setting unit calculates and sets thresholds corresponding to the sewing failures based on a difference between the first surface thread tension and the second surface thread tension when the normal sewing operation is performed.

7. Sewing machine as in any of claims 1 to 6,

the sewing machine further comprises a cloth thickness obtaining part for obtaining the thickness of the cloth to be sewn, namely the cloth thickness,

the threshold value is set based on the cloth thickness acquired by the cloth thickness acquiring unit.

8. Sewing machine as in any of claims 1 to 7,

the sewing machine further comprises a cloth feeding amount acquiring part for acquiring a cloth feeding amount in the sewing operation by the sewing control part, wherein the cloth feeding amount is a moving amount for moving the cloth along the horizontal direction during one time of up and down movement of the needle bar, namely one time of sewing,

the threshold value is set based on the cloth feeding amount acquired by the cloth feeding amount acquisition unit.

9. The sewing machine according to any one of claims 1 to 8,

the sewing machine further has a speed obtaining part for obtaining the rotation speed of the upper shaft,

the threshold is set based on the rotation speed acquired by the speed acquisition unit.

10. The sewing machine according to any one of claims 1 to 9,

the sewing machine is provided with an action stopping part which stops the sewing action performed by the sewing control part when the upper thread tension detected by the thread tension detecting part is more than a preset value.