sewing machine

Abstract

To provide a sewing machine capable of determining the state of a needle thread.SOLUTION: In a sewing machine, a thread grip device includes a gripping part 44 extending in an X direction. At an end part on an X2 direction side of the gripping part 44, a hook 44A is formed. The thread grip device grips a needle thread 6 by the hook 44A. The thread grip device holds the needle thread 6 between the hook 44A and a pressure sensor 50 in a second state. The pressure sensor 50 detects a pressure by the needle thread 6 at a plurality of detection points R on the inside of a detection region 54. The sewing machine generates pressure distribution by the needle thread 6 based on the pressure by the needle thread 6 at each detection point R. The sewing machine determines the position of an end part 6A of the needle thread 6, the length and thickness of the needle thread 6 gripped by the thread grip device, as the state of the needle thread 6, based on the generated pressure distribution.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a sewing machine. [Background technology]

[0002] There are known conventional sewing machines that detect the presence or absence of an upper thread for normal sewing operation. The thread detection device for a sewing machine described in Patent Document 1 includes a piezoelectric tuning fork resonator, an oscillation circuit that drives the piezoelectric tuning fork resonator to oscillate, and a rectifying and amplifying circuit that rectifies and amplifies the output voltage of the oscillation circuit. The piezoelectric tuning fork resonator outputs an amplitude change signal whose magnitude fluctuates depending on whether or not an upper thread is threaded through the upper thread path. The amplitude change signal is rectified and amplified by the rectifying and amplifying circuit to output a thread detection signal. The thread detection device detects the presence or absence of an upper thread based on the thread detection signal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 1-129881 Summary of the Invention [Problem to be solved by the invention]

[0004] The sewing machine cannot adequately control the sewing operation based only on information about the presence or absence of the needle thread in the needle thread path.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to provide a sewing machine that is capable of determining the condition of the upper thread. [Means for solving the problem]

[0006] A sewing machine according to one aspect of the present invention is a sewing machine that sews with a sewing needle having an upper thread inserted therethrough, and is characterized by comprising a thread gripping unit that can grip and hold the upper thread, a detection unit that detects information about the upper thread held by the thread gripping unit at each of a plurality of predetermined positions, and a judgment unit that judges the state of the upper thread based on the information about the upper thread at the plurality of predetermined positions detected by the detection unit.

[0007] In the sewing machine, the detection unit detects information about the upper thread held by the thread gripping unit at a plurality of predetermined positions. Because the detection unit detects information about the upper thread at a plurality of predetermined positions, the sewing machine can determine the state of the upper thread (for example, the position, length, thickness, etc. of the upper thread held by the thread gripping unit) using the determination unit.

[0008] The sewing machine may include a defect prediction unit that predicts the occurrence of a defect during sewing based on the state of the upper thread determined by the determination unit, and a notification unit that notifies the operator that the defect has been predicted when the defect prediction unit predicts that the defect will occur. The sewing machine predicts the occurrence of a defect during sewing based on the state of the upper thread determined by the determination unit. When the sewing machine predicts the occurrence of a defect, the notification unit notifies the operator. Therefore, the sewing machine can prevent the occurrence of defects before they occur.

[0009] The detection unit may detect information about the upper thread at a predetermined time, and the determination unit may include a thread tangle determination unit that determines whether a thread tangle defect has occurred between the upper thread and the bobbin thread as the state of the upper thread based on a transition in the information about the upper thread detected by the detection unit. The sewing machine determines whether a thread tangle defect has occurred between the upper thread and the bobbin thread based on a transition in the information about the upper thread detected by the detection unit using the thread tangle defect determination unit. Thus, the sewing machine can suppress defects caused by thread tangle defects.

[0010] The detection unit may detect pressure of the upper thread held by the thread gripping unit at predetermined intervals in a predetermined direction, and the determination unit may determine the state of the upper thread based on the distribution of pressure of the upper thread detected by the detection unit. The detection unit detects pressure of the upper thread at predetermined intervals in a predetermined direction. The sewing machine can determine the state of the upper thread based on the pressure distribution of the upper thread in the predetermined direction.

[0011] The detection unit may further detect the pressure of the upper thread at a second predetermined interval in a second predetermined direction intersecting the first predetermined direction. The detection unit further detects the pressure of the upper thread at a second predetermined interval in the second intersecting direction. The sewing machine can determine the condition of the upper thread based on the two-dimensional pressure distribution of the upper thread in the first direction and the second predetermined direction.

[0012] The thread gripping unit may have a gripping portion capable of gripping the upper thread, and the gripping portion may be movable in the predetermined direction. Since the operating direction of the thread gripping unit and the pressure detection of the detection unit are aligned, the detection unit can more easily detect the state of the upper thread (for example, its position, length, etc.).

[0013] The determination unit may determine the position of the upper thread held by the thread gripping unit as the state of the upper thread based on the pressure distribution, and may include a position sewing control unit that controls the sewing operation based on the position of the upper thread determined by the determination unit. The sewing machine controls the sewing operation based on the position of the upper thread held by the thread gripping unit. Therefore, the sewing machine can suppress problems that occur when the position of the upper thread held by the thread gripping unit is not appropriate.

[0014] The determination unit may determine the length of the upper thread held by the thread gripping unit as the state of the upper thread based on the pressure distribution, and may include a length sewing control unit that controls the sewing operation based on the length of the upper thread determined by the determination unit. The sewing machine controls the sewing operation based on the length of the upper thread held by the thread gripping unit. Therefore, the sewing machine can prevent problems that occur when the length of the upper thread held by the thread gripping unit is not appropriate.

[0015] The determination unit may determine the thickness of the upper thread held by the thread gripping unit as the state of the upper thread based on the pressure distribution, and may include a thickness sewing control unit that controls the sewing operation based on the thickness of the upper thread determined by the determination unit. The sewing machine controls the sewing operation based on the thickness of the upper thread held by the thread gripping unit. Therefore, the sewing machine can prevent problems that occur when the thickness of the upper thread held by the thread gripping unit is inappropriate.

[0016] The thread gripping unit may have a first member formed of a light-transmitting portion at least partially transparent to light, and a second member that clamps the upper thread between the first member and the second member, and the detection unit may detect the upper thread clamped between the first member and the second member by scanning through the light-transmitting portion. The detection unit detects the upper thread by scanning through the light-transmitting portion of the first member. The sewing machine can determine the state of the upper thread detected by the detection unit scanning. [Brief explanation of the drawings]

[0017] [Figure 1] Front view of sewing machine 1. [Figure 2] FIG. 3 is a perspective view of the yarn clamping device 30 in a first state. [Figure 3] FIG. 3 is a front view of the yarn clamping device 30 in a first state. [Figure 4] FIG. 4 is a perspective view of the yarn clamping device 30 in a second state. [Figure 5] 4 is a diagram illustrating detection of the upper thread 6 by the pressure sensor 50. FIG. [Figure 6] Electrical block diagram for sewing machine 1. [Figure 7] Flow chart of pre-sewing processing. [Figure 8] Flow chart of the sewing start process. [Figure 9] 9 is a flow chart of the sewing start process, which is a continuation of FIG. 8. [Figure 10] FIG. 10 is a perspective view of the yarn clamping device 60 in a second state. [Figure 11] FIG. 10 is a front view of the thread clamping device 60 in a second state. [Figure 12] FIG. [Figure 13]10 is a flow chart of the second pre-sewing process. [Figure 14] 10 is a flow chart of the second stitching start process. [Figure 15] 15 is a flow chart of the second sewing start process, which is a continuation of FIG. 14. DETAILED DESCRIPTION OF THE INVENTION

[0018] A first embodiment of the present invention will be described with reference to Figures 1 to 9. In the following description, arrows in the figures will be used to indicate left and right, front and rear, and top and bottom.

[0019] The configuration of the sewing machine 1 will be described with reference to Figure 1. The sewing machine 1 comprises a bed 2, a pillar 3, an arm 4, a head 5, and a thread gripping device 30. The bed 2 has a needle plate 7 on the left side of its top surface, and is equipped internally with a shuttle mechanism, a lower shaft 22 (see Figure 6), a thread cutting mechanism 18 (see Figure 6), etc. The workpiece is placed on the top surface of the bed 2. The shuttle mechanism has a rotary shuttle below the needle plate 7, and the rotary shuttle accommodates a bobbin (not shown) around which a lower thread is wound.

[0020] The lower shaft 22 extends in the left-right direction. The lower shaft 22 rotates in synchronization with the main motor 24 (see Figure 6), which will be described later. The shuttle mechanism is driven by the rotation of the lower shaft 22, and captures the upper thread 6 held by the sewing needle 10 and entangles it with the bobbin thread. The thread cutting mechanism 18 (see Figure 6) comprises a fixed blade, a movable blade, and a thread cutting solenoid 19 (see Figure 6). The movable blade is connected to the thread cutting solenoid 19. When the thread cutting solenoid 19 is driven, the movable blade moves relative to the fixed blade, and the thread cutting mechanism 18 cuts the upper thread 6 and the bobbin thread with the cooperation of the movable blade and fixed blade. The pillar 3 extends upward from the right end of the bed 2.

[0021] The arm portion 4 extends leftward from the upper end of the pillar portion 3. The arm portion 4 is equipped with an operation unit 12, a thread tension unit 15, etc. on its front surface. The operation unit 12 is equipped with a display unit 13 and an input unit 14. The display unit 13 displays images. The input unit 14 is located to the right of the display unit 13. The input unit 14 is equipped with multiple switches and can input various instructions to the control unit 80 (see Figure 6). The thread tension unit 15 is located to the left of the operation unit 12. The thread tension unit 15 applies the tension required to the upper thread 6 when the upper thread 6 and bobbin thread are cut by the thread cutting mechanism 18, and optimizes the tension acting on the upper thread 6 as the sewing machine 1 sews.

[0022] The arm unit 4 has an upper shaft 21 (see Figure 6) and a main motor 24 inside. The upper shaft 21 extends in the left-right direction and is connected to the main motor 24 via an upper shaft pulley (not shown). The upper shaft pulley is fixed to the right end of the upper shaft 21. A lower shaft pulley (not shown) is fixed to the right end of the lower shaft 22. An endless belt (not shown) is stretched between the upper shaft pulley and the lower shaft pulley. When the upper shaft 21 is rotated by the drive of the main motor 24, the lower shaft 22 rotates in sync via the endless belt.

[0023] The head 5 is provided at the left end of the arm 4. The head 5 protrudes downward from the left end of the arm 4 and faces the needle plate 7 from above. The head 5 supports a needle bar 9 extending downward so that it can move up and down. The lower end of the needle bar 9 protrudes downward from the head 5. The needle bar 9 is connected to an upper shaft 21 via a vertical movement mechanism and moves up and down above the needle plate 7 as the upper shaft 21 rotates. A sewing needle 10 can be attached to the lower end of the needle bar 9. The sewing needle 10 holds an upper thread 6 inserted through an eye (not shown). The sewing needle 10 moves up and down together with the needle bar 9.

[0024] The head 5 is provided with a thread take-up lever 28 on its front side. The take-up lever 28 is provided downstream of the thread tensioning unit 15 in the path of the upper thread 6 that is unwound from a thread spool (not shown) (hereinafter referred to as the upper thread path). The take-up lever 28 moves up and down as the main motor 24 is driven. The head 5 is provided with a support plate 8 on its left rear end. The support plate 8 extends downward from the rear surface of the head 5. The support plate 8 supports a thread gripping device 30 on its front side.

[0025] The structure of the thread clamping device 30 will be described with reference to Figures 2 to 4. The thread clamping device 30 holds the upper thread 6 at the start of sewing to prevent the upper thread 6 from slipping out. Thread slippage will be described later. The start of sewing refers to the period from when the sewing machine 1 starts sewing until several dozen stitches have been sewn. The thread clamping device 30 is provided above and to the left of the sewing needle 10. For ease of explanation, the structure of the thread clamping device 30 will be described hereinafter using the X, Y, and Z directions indicated by arrows in Figure 2. The X direction is parallel to the extension direction of a clamping portion 44 (described later) and is inclined diagonally downward and leftward relative to the left-right direction of the sewing machine 1. The X direction includes the X1 direction and the X2 direction opposite to the X1 direction. The Y direction is parallel to the front-to-rear direction. The Y direction includes the Y1 direction and the Y2 direction opposite to the Y1 direction. The Z direction is perpendicular to the X and Y directions. The Z direction includes a Z1 direction and a Z2 direction opposite to the Z1 direction.

[0026] The yarn gripping device 30 includes bases 33, 36, 37, an air cylinder 31, a limit switch 40, a sliding portion 43, a gripping portion 44, a plate 46, and a pressure sensor 50. The base 33 is a plate-shaped member that extends in the Z2 direction. A portion of the base 33 bends and extends in the X2 direction from the lower end of the base 33 in the Z2 direction.

[0027] The air cylinder 31 and limit switch 40 are provided at the X1 end of the base 33. The air cylinder 31 has a rod 32 extending in the X direction. The rod 32 moves in the X direction relative to the base 33 when driven by the air cylinder 31. The limit switch 40 is provided on the Z1 side of the air cylinder 31. The limit switch 40 has a head portion 41. When the head portion 41 is pressed in the X1 direction, the limit switch 40 outputs an ON signal to the control unit 80. When the head portion 41 is not pressed in the X1 direction, the limit switch 40 outputs an OFF signal to the control unit 80.

[0028] The sliding part 43 is provided on the Z1 side of the base part 33. The sliding part 43 is a plate-shaped member that extends in the Z2 direction. A portion of the sliding part 43 bends and extends in the X2 direction from the Z2-direction lower end of the sliding part 43. The X1-direction end of the sliding part 43 is connected to the X2-direction end of the rod 32. The sliding part 43 slides in the X direction along the base part 33 by being driven by the air cylinder 31. When the rod 32 moves in the X1 direction, the sliding part 43 moves in the X1 direction together with the rod 32, pushing the head part 41 in the X1 direction. When the rod 32 moves in the X2 direction, the sliding part 43 moves in the X2 direction together with the rod 32, releasing the head part 41 from being pushed in the X1 direction.

[0029] The gripping portion 44 is provided at the X2-direction end of the sliding portion 43. The gripping portion 44 is movable in the X-direction integrally with the sliding portion 43. The gripping portion 44 is shaped like a plate extending in the X-direction. A hook 44A is formed at the X2-direction end of the gripping portion 44. When viewed from the Z1-direction side, the hook 44A has an inverted J-shape. An opening 45 is formed on the Y2-direction side of the hook 44A. The gripping portion 44 can grip the upper thread 6 with the hook 44A through the opening 45.

[0030] The base 36 is provided at the end of the base 33 in the X2 and Y2 directions. The base 36 is a plate-shaped member and extends in the Z1 direction. A portion of the base 36 is shaped like a rectangular parallelepiped that bends and extends in the X2 direction at the upper end of the base 36 in the Z1 direction. The plate 46 is provided at the end of the base 36 in the X2 direction. The plate 46 extends in the Y1 direction and then bends and extends in the X2 direction (see Figure 10). A groove 46A (see Figure 10) is formed at the end of the X2 direction on the Z1 side surface of the plate 46. The groove 46A extends in the X direction. The upper thread 6 can be inserted inside the groove 46A.

[0031] The base 37 is provided at the end of the base 36 in the X1 and Z1 directions. The base 37 has a rectangular parallelepiped shape extending in the Y1 direction. A fixing portion 38 is provided at the end of the base 37 in the Y1 direction. The fixing portion 38 fixes a plate 49 to the end in the Z2 direction. The plate 49 extends from the fixing portion 38 in the X2 direction. A pressure sensor 50 is provided at the end in the X2 direction of the plate 49. The pressure sensor 50 and the plate 46 face each other in the Z direction with the gripping portion 44 between them. The pressure sensor 50 has a rectangular parallelepiped shape extending in the X and Y directions. A signal line 59 is connected to the pressure sensor 50. A detailed description of the pressure sensor 50 will be given later.

[0032] The operation of the thread gripping device 30 will now be described. The thread gripping device 30 can be switched between a first state and a second state by driving the air cylinder 31. As shown in FIGS. 2 and 3, the thread gripping device 30 in the first state is a state in which the sliding part 43 is located at the end of the base part 33 on the X2 direction side. In the first state, the head part 41 is not pressed in the X1 direction by the sliding part 43. The hook 44A of the gripping part 44 is located on the X2 direction side of the pressure sensor 50 and the plate 46 in the X direction. Although not shown, the hook 44A is located behind the sewing needle 10 in the sewing machine 1.

[0033] As shown in Figure 4, the thread clamping device 30 in the second state is a state in which the slider 43 moves to the center of the base 33 in the X direction. In the second state, the head 41 is pressed in the X1 direction by the slider 43. The hook 44A is located between the pressure sensor 50 and the plate 46 in the Z direction. The hook 44A is located above and to the left of the sewing needle 10 in the sewing machine 1 (see Figure 1).

[0034] When the sewing machine 1 grips the upper thread 6 with the thread gripping device 30, the air cylinder 31 is actuated to switch from the second state to the first state. The hook 44A moves to the rear of the sewing needle 10 and grips the tip of the upper thread 6 inserted through the eye of the sewing needle 10 (see FIG. 2). In this state, the thread gripping device 30 switches from the first state to the second state. The hook 44A moves in the X1 direction together with the rod 32. In the second state, the upper thread 6 gripped by the hook 44A and located on the Z1 direction side is clamped between the hook 44A and the pressure sensor 50. The upper thread 6 gripped by the hook 44A and located on the Z2 direction side is released in the X2 direction via the groove 46A (see FIG. 10).

[0035] When the sewing machine 1 starts sewing, the drive of the air cylinder 31 is stopped. The rod 32 becomes movable in the X direction due to an external force. When the sewing start, tension is applied to the upper thread 6 when the thread take-up lever 28 pulls up the upper thread 6. The hook 44A gradually moves in the X2 direction due to the tension applied to the upper thread 6. When the hook 44A moves toward the X2 direction from the pressure sensor 50, the upper thread 6 is released from being clamped between the hook 44A and the pressure sensor 50. The limit switch 40 is released from pressing the head portion 41 in the X1 direction. The upper thread 6 comes out of the hook 44A, and the sewing start period ends.

[0036] The pressure sensor 50 will be described with reference to FIG. 5. A rectangular detection area 54 is provided on a surface 53 of the pressure sensor 50 facing the Z2 direction. The detection area 54 detects, at multiple detection points R, the pressure of the upper thread 6 held between the hook 44A and the pressure sensor 50 in the second state of the thread clamping device 30. The pressure sensor 50 has a structure in which, for example, a silicon diaphragm that deforms in response to external pressure and a piezoelectric element that detects the deformation of the silicon diaphragm are paired together and the paired pairs are arranged two-dimensionally. The pressure sensor 50 outputs the pressure of the upper thread 6 detected at each detection point R to the control unit 80 via a signal line 59.

[0037] The multiple detection points R are defined by multiple virtual lines P and multiple virtual lines Q. The virtual line P extends in the X direction inside the detection area 54. For example, the virtual line P passes through the centers of multiple pairs of diaphragms and piezoelectric elements arranged in the X direction. The multiple virtual lines P are arranged at equal intervals (0.1 mm in this embodiment) in the Y direction. The virtual line Q extends in the Y direction inside the detection area 54. The virtual line Q passes through the centers of multiple pairs of diaphragms and piezoelectric elements arranged in the Y direction. The multiple virtual lines Q are arranged at equal intervals (0.1 mm in this embodiment) in the X direction. The multiple detection points R are the intersections of the multiple virtual lines P and the multiple virtual lines Q. In other words, the multiple detection points R are arranged in a grid pattern in the X and Y directions inside the detection area 54.

[0038] The determination of the state of the upper thread 6 by the control unit 80 will be described. In this embodiment, the state of the upper thread 6 refers to whether or not the upper thread 6 is gripped by the hook 44A, the position of the end 6A of the upper thread 6 gripped by the hook 44A in the X1 direction, the length of the upper thread 6 gripped by the hook 44A, and the thickness of the upper thread 6. The control unit 80 generates a pressure distribution of the upper thread 6 inside the detection area 54 based on the pressure of the upper thread 6 at each detection point R detected by the pressure sensor 50. The control unit 80 determines the state of the upper thread 6 based on the pressure distribution of the upper thread 6 inside the detection area 54.

[0039] If pressure from the upper thread 6 is detected at at least one of the multiple detection points R, the control unit 80 determines that the upper thread 6 is gripped by the hook 44A, and if pressure from the upper thread 6 is not detected at any of the multiple detection points R, it determines that the upper thread 6 is not gripped by the hook 44A.

[0040] The control unit 80 determines the position of the end 6A of the upper thread 6 based on the position of the detection point R that detects the pressure of the upper thread 6 and is closest to the X1 direction among the detection points R arranged in the X direction.

[0041] The control unit 80 determines the length of the upper thread 6 gripped by the hook 44A based on the number of detection points R that detect the pressure of the upper thread 6 among the detection points R arranged in the X direction.

[0042] The control unit 80 determines the thickness of the upper thread 6 gripped by the hook 44A based on the number of detection points R that detect the pressure of the upper thread 6, among the detection points R arranged in the Y direction. In this embodiment, the thickness of the upper thread 6 is, for example, 0.5 mm.

[0043] The control unit 80 will now explain how it detects and predicts the occurrence of defects during sewing at the start of sewing. The control unit 80 detects the occurrence of defects during sewing based on the determined state of the upper thread 6 at the start of sewing. The control unit 80 detects the occurrence of a thread tangle defect as a defect during sewing. A thread tangle defect is a defect in which the thread becomes tangled between the upper thread 6 and the bobbin thread. If a thread tangle defect occurs at the start of sewing, the tension on the upper thread 6 held by the hook 44A is reduced, and the movement (amount of movement) of the hook 44A in the X2 direction is reduced.

[0044] The control unit 80 determines whether a thread entanglement problem has occurred between the upper thread 6 and the lower thread based on the change in the position of the end 6A of the upper thread 6 gripped by the hook 44A. The control unit 80 stores the previously determined position of the end 6A in the RAM 83. The control unit 80 derives the change in the position of the end 6A in the X2 direction from the difference between the currently determined position of the end 6A and the previously determined position of the end 6A. If the derived change in the position of the end 6A in the X2 direction is smaller than a predetermined threshold, the control unit 80 determines that a thread entanglement problem has occurred between the upper thread 6 and the lower thread.

[0045] The control unit 80 predicts the occurrence of defects during sewing based on the determined state of the upper thread 6 at the start of sewing. The control unit 80 predicts the occurrence of thread slippage and thread breakage as defects during sewing. Thread slippage is a defect in which the upper thread 6 comes out of the eye of the sewing needle 10. Thread breakage is a defect in which the upper thread 6 breaks during sewing.

[0046] If the hook 44A does not sufficiently grip the upper thread 6, the hook 44A will release its grip on the upper thread 6, which may result in thread slippage. The control unit 80 predicts the occurrence of thread slippage based on the length of the upper thread 6 gripped by the hook 44A. If the length of the upper thread 6 gripped by the hook 44A is less than a predetermined threshold, the control unit 80 determines that the hook 44A is not sufficiently gripping the upper thread 6 and predicts that thread slippage will occur.

[0047] If the thickness of the upper thread 6 is smaller than a preset thickness of the upper thread 6, there is a possibility that thread breakage will occur during sewing. The control unit 80 predicts the occurrence of thread breakage based on the thickness of the upper thread 6 gripped by the hook 44A. The memory device 84 stores the thickness of the upper thread 6 used for sewing. If the thickness of the upper thread 6 gripped by the hook 44A is smaller than a predetermined threshold value with respect to the thickness of the upper thread 6 stored in the memory device 84, the control unit 80 predicts that thread breakage will occur.

[0048] The electrical configuration of the sewing machine 1 will be described with reference to Figure 6. The control unit 80 of the sewing machine 1 includes a CPU 81. The CPU 81 controls the operation of the sewing machine 1. The CPU 81 is connected to a ROM 82, a RAM 83, a storage device 84, and an I / O interface (hereinafter referred to as I / O) 85. The ROM 82 stores programs for executing various processes, such as pre-sewing processing (see Figure 7), which will be described later. The RAM 83 temporarily stores various values. The storage device 84 is non-volatile. The storage device 84 stores the thickness of the upper thread 6, various settings of the sewing machine 1, etc.

[0049] I / O 85 is connected to drive circuits 91 to 95. Drive circuit 91 is connected to the main motor 24. Drive circuit 92 is connected to the thread tension solenoid 16. Drive circuit 93 is connected to the thread cutter solenoid 19. Drive circuit 94 is connected to the air cylinder 31. Drive circuit 95 is connected to the display unit 13. The main motor 24 is equipped with an encoder 25. The encoder 25 detects the rotational position of the output shaft of the main motor 24.

[0050] The CPU 81 acquires the detection result of the encoder 25 and sends a control signal to the drive circuit 91. The CPU 81 drives and controls the upper shaft 21 and the lower shaft 22 by sending a control signal to the drive circuit 91. The CPU 81 drives and controls the thread tensioning unit 15 by sending a control signal to the drive circuit 92. The CPU 81 drives and controls the thread cutting mechanism 18 by sending a control signal to the drive circuit 93. The CPU 81 drives and controls the air cylinder 31 by sending a control signal to the drive circuit 94. The CPU 81 drives and controls the display unit 13 by sending a control signal to the drive circuit 95.

[0051] The I / O 85 is connected to the input unit 14, the limit switch 40, and the pressure sensor 50. The input unit 14 outputs various instructions to the CPU 81. The limit switch 40 outputs either an ON signal or an OFF signal to the control unit 80 depending on the state of the head unit 41. The pressure sensor 50 outputs the pressure of the upper thread 6 detected at each detection point R (see FIG. 5) to the control unit 80 via a signal line 59 (see FIG. 2).

[0052] The pre-sewing process will be described with reference to Figure 7. The pre-sewing process is a process for gripping the upper thread 6 with the thread gripping device 30 before the start of sewing by the sewing machine 1. When the pre-sewing process starts, the sewing machine 1 stops sewing and the thread gripping device 30 is in the second state.

[0053] The variables used in the pre-sewing process will be explained. The RAM 83 stores a variable N. The variable N is the number of times that the thread clamping device 30 has attempted to grip the upper thread 6. At the start of the pre-sewing process, the value of the variable N is 0. Before the start of the pre-sewing process, the operator stores in the memory device 84 the thickness and type of the upper thread 6 to be used for sewing.

[0054] When the operator issues an instruction to start the sewing pre-processing via the input unit 14, the CPU 81 starts the sewing pre-processing by reading out a program from the ROM 82. When the sewing pre-processing is started, the CPU 81 sets the value of the variable N to 1 and stores it in the RAM 83 (S1).

[0055] The CPU 81 drives the air cylinder 31 to switch the thread clamping device 30 from the second state to the first state, thereby starting the operation of clamping the upper thread 6 by the thread clamping device 30 (S2). In S2, the hook 44A moves in the X2 direction relative to the pressure sensor 50, and the head portion 41 is released from being pressed in the X1 direction. The hook 44A clamps the tip of the upper thread 6 behind the sewing needle 10.

[0056] The CPU 81 drives the air cylinder 31 to switch the thread clamping device 30 from the first state to the second state, thereby ending the operation of clamping the upper thread 6 by the thread clamping device 30 (S3). In S3, the hook 44A moves in the X1 direction, and the head portion 41 is pushed in the X1 direction. The hook 44A is positioned between the pressure sensor 50 and the plate 46 in the Z direction. The tip end of the upper thread 6 is clamped between the hook 44A and the pressure sensor 50.

[0057] The CPU 81 acquires the pressure due to the upper thread 6 at each detection point R detected by the pressure sensor 50 (S4). Based on the pressure due to the upper thread 6 acquired in S4, the CPU 81 generates a pressure distribution due to the upper thread 6 inside the detection area 54 (S5).

[0058] The CPU 81 determines whether the pressure distribution caused by the upper thread 6 generated in S5 is normal (S6). The ROM 82 stores information about the pressure distribution caused by the upper thread 6 when the hook 44A normally grips the upper thread 6, by thread thickness and type. In S6, the CPU 81 reads out from the ROM 82 information about the pressure distribution caused by the upper thread 6 when the hook 44A corresponding to the upper thread 6 used for sewing normally grips the upper thread 6, and compares it with the pressure distribution generated in S5. The determination of whether the needle thread 6 is normal may be made by determining, from the pressure distribution generated in S5, whether the needle thread 6 is gripped by the hook 44A, the position of the end 6A of the needle thread 6 gripped by the hook 44A in the X1 direction, the length of the needle thread 6 gripped by the hook 44A, and the thickness of the needle thread 6, as described above, and comparing the values ​​of the position of the end 6A of the needle thread 6, the length of the needle thread 6, and the thickness of the needle thread 6 in the information on the normal pressure distribution of the needle thread 6 used for sewing in the ROM 82, and determining that the pressure distribution is normal if it is within a predetermined range, for example, a range of ±10%. Alternatively, the normal pressure distribution of the needle thread 6 used for sewing may be stored in the ROM 82, and the corresponding normal pressure distribution may be read out and compared with the pressure distribution generated in S5, and the matching between the two pressure distributions may be determined to be normal if the degree of agreement exceeds a predetermined threshold, for example, 90%, and abnormal if it is below that threshold.

[0059] If the CPU 81 determines that the pressure distribution generated in S5 is normal with respect to the pressure distribution when the hook 44A normally grips the upper thread 6 (S6: YES), the CPU 81 stores the pressure distribution generated in S5 in the RAM 83 (S7). The CPU 81 issues a notification that sewing is possible (S8). In S8, the CPU 81 drives the display unit 13 and notifies the user that the hook 44A has normally gripped the upper thread 6 and sewing can begin. The CPU 81 ends the pre-sewing process.

[0060] When the CPU 81 determines that the pressure distribution generated in S5 is not normal with respect to the pressure distribution when the hook 44A normally grips the upper thread 6 (S6: NO), the CPU 81 determines whether the value of the variable N is at its upper limit (S9). The ROM 82 stores the upper limit value of the variable N.

[0061] When the CPU 81 determines that the value of the variable N is smaller than the upper limit and is not the upper limit (S9: NO), it adds 1 to the value of the variable N and stores it in the RAM 83 (S10). The CPU 81 returns the process to S2. The CPU 81 starts gripping the upper thread 6 by the thread gripping device 30 again (S2).

[0062] When the CPU 81 determines that the value of the variable N is equal to the upper limit value and is the upper limit (S9: YES), it issues a pre-sewing warning (S11). In S11, the CPU 81 drives the display unit 13 to warn that the hook 44A cannot properly grip the upper thread 6. The CPU 81 then ends the pre-sewing process.

[0063] The sewing start process will be described with reference to Figures 8 and 9. In the sewing start process, a determination is made as to whether sewing is being performed normally by the sewing machine 1 at the start of sewing, based on the state of the upper thread 6 in the thread clamping device 30. Before the sewing start process begins, the thickness of the upper thread 6 to be used for sewing is stored in the memory device 84. When the sewing start process begins, the sewing machine 1 stops sewing, the air cylinder 31 is driven, and the thread clamping device 30 is in the second state.

[0064] The variables used in the sewing start process will be explained. The RAM 83 stores variables L and M. Variable L is the number of times that the condition of the upper thread 6 in the thread clamping device 30 has been determined to be abnormal. Variable M is the number of times that the needle bar 9 has moved up and down, and is the number of times that sewing for one stitch has been repeated. At the start of the sewing start process, the values ​​of variables L and M are 0.

[0065] When the operator issues an instruction to start the sewing start process via the input unit 14, the CPU 81 reads out a program from the ROM 82 and starts the sewing start process. As shown in Fig. 8, when the sewing start process starts, the CPU 81 obtains the thickness of the upper thread 6 from the storage device 84 (S21). The CPU 81 stops driving the air cylinder 31 (S22). The rod 32 becomes movable in the X direction by an external force.

[0066] The CPU 81 drives the main motor 24 and the thread tension solenoid 16 to start sewing (S23). The main motor 24 is driven at the sewing speed. The CPU 81 starts counting the variable M (S24). Thereafter, the CPU 81 adds 1 to the value of the variable M each time sewing of one stitch is repeated.

[0067] The CPU 81 determines whether the value of the variable M has reached a predetermined number (S31). The ROM 82 stores the predetermined number, which is a natural number. If the CPU 81 determines that the value of the variable M has not reached the predetermined number (S31: NO), the process returns to S31.

[0068] When the CPU 81 determines that the value of the variable M has reached a predetermined number (S31: YES), it acquires the pressure of the upper thread 6 at each detection point R detected by the pressure sensor 50 (S32). Based on the pressure of the upper thread 6 acquired in S32, the CPU 81 generates a pressure distribution of the upper thread 6 inside the detection area 54 (S33).

[0069] The CPU 81 acquires the previous pressure distribution (S34). The previous pressure distribution is the pressure distribution generated before the current execution of S33. The RAM 83 stores the previous pressure distribution. If the CPU 81 is immediately after starting sewing, it acquires the pressure distribution stored in S7 (see FIG. 7) as the previous pressure distribution. As will be described in detail later, the CPU 81 stores the pressure distribution generated in S33 in the RAM 83 as the previous pressure distribution each time it determines the state of the upper thread 6 in the thread clamping device 30. In this case, the CPU 81 acquires the pressure distribution generated in the current execution of S33 and stored in the RAM 83 in the next execution of S34.

[0070] The CPU 81 determines the position of the end 6A of the upper thread 6 gripped by the thread gripping device 30 (S35). In S35, the CPU 81 estimates the position of the end 6A from the position of the detection point R that detects the pressure of the upper thread 6, among the detection points R arranged in the X direction, which is closest to the X1 direction, based on the pressure distribution generated in S33.

[0071] The CPU 81 determines the length of the upper thread 6 gripped by the thread gripping device 30 (S36). In S36, the CPU 81 counts the number of detection points R that detect the pressure of the upper thread 6 among the detection points R arranged in the X direction based on the pressure distribution generated in S33, and determines the length of the upper thread 6 gripped by the hook 44A.

[0072] The CPU 81 determines the thickness of the upper thread 6 gripped by the thread gripping device 30 (S37). In S37, the CPU 81 counts the number of detection points R arranged in the Y direction that detect the pressure of the upper thread 6, based on the pressure distribution generated in S33, and determines the thickness of the upper thread 6 gripped by the thread gripping device 30. The CPU 81 shifts the process to S31 (see FIG. 9).

[0073] 9, the CPU 81 determines whether a thread tangling problem has occurred between the upper thread 6 and the lower thread (S41). In S41, the CPU 81 determines whether a thread tangling problem has occurred based on the change in the position of the end portion 6A in the X2 direction. The CPU 81 derives the change in the position of the end portion 6A in the X2 direction from the difference between the position of the end portion 6A determined in S35 (see FIG. 8) and the position of the end portion 6A in the previous pressure distribution acquired in S34 (see FIG. 8).

[0074] If the change in the position of the end 6A in the X2 direction is smaller than a predetermined threshold, the CPU 81 determines that a line tangling defect has occurred (S41: YES) and shifts the process to S46. If the change in the position of the end 6A in the X2 direction is equal to or larger than a predetermined threshold, the CPU 81 determines that a line tangling defect has not occurred (S41: NO) and shifts the process to S42.

[0075] The CPU 81 determines whether or not the occurrence of thread slippage of the upper thread 6 has been predicted (S42). The ROM 82 stores the relationship between the total number of needle points since the start of sewing and the length of the upper thread 6 gripped by the thread gripping device 30. In S42, the CPU 81 compares the length of the upper thread 6 determined in S36 (see FIG. 8) with the length of the upper thread 6 based on the total number of needle points stored in the ROM 82.

[0076] If the length of the upper thread 6 determined in S36 is smaller than a predetermined threshold value relative to the length of the upper thread 6 based on the total number of needle points stored in the ROM 82, the CPU 81 determines that the occurrence of thread slippage has been predicted (S42: YES) and proceeds to S46.

[0077] If the length of the upper thread 6 determined in S36 is equal to or greater than a predetermined threshold value relative to the length of the upper thread 6 based on the total number of needle points stored in the ROM 82, the CPU 81 determines that the occurrence of thread coming off has not been predicted (S42: NO). In this case, it determines whether the occurrence of thread breakage has been predicted (S43). In S43, the CPU 81 compares the thickness of the upper thread 6 determined in S37 (see FIG. 8) with the thickness of the upper thread 6 acquired in S22 (see FIG. 8).

[0078] If the thickness of the upper thread 6 determined in S37 is smaller than a predetermined threshold value for the thickness of the upper thread 6 acquired in S22, the CPU 81 determines that thread breakage has been predicted (S43: YES) and proceeds to S46. If the thickness of the upper thread 6 determined in S37 is equal to or greater than a predetermined threshold value for the thickness of the upper thread 6 acquired in S22, the CPU 81 determines that thread breakage has not been predicted (S43: NO) and proceeds to S52.

[0079] When the CPU 81 predicts that a thread tangle defect will occur as a sewing defect (S41: YES), when it predicts that a thread slippage will occur (S42: NO), or when it determines that a thread breakage will occur (S43: NO), it adds 1 to the value of the variable L and stores it in the RAM 83 (S46).

[0080] The CPU 81 reduces the sewing speed of the main motor 24 (S48). The CPU 81 issues a sewing start warning (S49). At S49, the CPU 81 drives the display unit 13 to warn that the state of the upper thread 6 in the thread clamping device 30 is not normal and that the occurrence of poor sewing has been detected and predicted. The CPU 81 determines whether the value of the variable L is at its upper limit (S50). The ROM 82 stores the upper limit value of the variable L.

[0081] If the CPU 81 determines that the value of variable L is smaller than the upper limit and is not the upper limit (S50: NO), the CPU 81 proceeds to S54. If the CPU 81 determines that the value of variable L is equal to the upper limit and is the upper limit (S50: YES), the CPU 81 stops driving the main motor 24 and the thread tension solenoid 16, and ends the sewing that started in S23 (see FIG. 8) (S51). The CPU 81 ends the sewing start process.

[0082] The CPU 81 determines whether a sewing start warning is being issued via the display unit 13 (S52). If a sewing start warning is being issued in S49 (S52: YES), the CPU 81 stops driving the display unit 13 and stops the sewing start warning (S53). The CPU 81 proceeds to S54. If a sewing start warning is not being issued (S52: NO), the CPU 81 proceeds to S54.

[0083] The CPU 81 stores the pressure distribution generated by the upper thread 6 in S33 (see FIG. 8) as the previous pressure distribution in the RAM 83 (S54). Based on the pressure distribution generated by the upper thread 6 in S33, the CPU 81 determines whether the upper thread 6 is gripped by the hook 44A (S55).

[0084] When the pressure of the upper thread 6 is detected at at least one of the detection points R in the detection area 54, the CPU 81 determines that the upper thread 6 is gripped by the hook 44A (S55: NO). The CPU 81 sets the value of the variable M to 0, stores this in the RAM 83 (S56), and returns the process to S31 (see FIG. 8). The CPU 81 repeats the processes of S31 to S56 until it determines that the upper thread 6 is not gripped by the hook 44A.

[0085] If the pressure of the upper thread 6 is not detected at any of the detection points R due to the upper thread 6 coming off the hook 44A, the CPU 81 determines that the upper thread 6 is not gripped by the hook 44A (S55: YES). The CPU 81 then ends the sewing start process.

[0086] As described above, in the sewing machine 1 of the first embodiment, the thread clamping device 30 clamps the upper thread 6 with the hook 44A. In the second state, the thread clamping device 30 clamps the upper thread 6 between the hook 44A and the pressure sensor 50. The pressure sensor 50 detects the pressure of the upper thread 6 at multiple detection points R inside the detection area 54 (S32). Based on the pressure of the upper thread 6 at each detection point R, the CPU 81 determines the state of the upper thread 6, including the position of the end 6A of the upper thread 6 (S35), the length (S36) and the thickness (S37) of the upper thread 6 clamped by the thread clamping device 30. The pressure sensor 50 detects the pressure of the upper thread 6 at multiple detection points R. Therefore, the sewing machine 1 can determine not only whether the upper thread 6 is clamped by the thread clamping device 30, but also the position, length, thickness, etc. of the upper thread 6 clamped by the thread clamping device 30.

[0087] The CPU 81 predicts the occurrence of thread slippage (S42) and thread breakage (S43) as defects that may occur during sewing, based on the state of the upper thread 6. If the CPU 81 predicts the occurrence of a defect during sewing, it drives the display unit 13 and issues a warning before starting sewing (S49). The sewing machine 1 predicts the occurrence of thread slippage and thread breakage based on the length and thickness of the upper thread 6 gripped by the hook 44A. The sewing machine 1 notifies the operator via the display unit 13 that a sewing defect has been predicted. Therefore, the sewing machine 1 can prevent defects from occurring.

[0088] Each time the variable M reaches a predetermined number, the CPU 81 determines the position of the end 6A based on the current pressure distribution of the upper thread 6 (S35). The CPU 81 derives the transition of the position of the end 6A from the difference between the position of the end 6A based on the current pressure distribution of the upper thread 6 and the position of the end 6A based on the previous pressure distribution. Based on the transition of the position of the end 6A, the CPU 81 determines whether a thread tangling defect has occurred as the state of the upper thread 6 (S41). By detecting the occurrence of a thread tangling defect, the sewing machine 1 can prevent problems caused by the thread tangling defect.

[0089] The pressure sensor 50 detects the pressure of the upper thread 6 at a plurality of detection points R inside the detection area 54. The plurality of detection points R are arranged in the X direction. The CPU 81 generates a pressure distribution of the upper thread 6 inside the detection area 54 based on the pressure of the upper thread 6 at each detection point R detected by the pressure sensor 50 (S33). Based on the generated pressure distribution, the CPU 81 determines the position of the end 6A of the upper thread 6 (S35) and the length of the upper thread 6 gripped by the thread gripping device 30 (S36). In this way, the sewing machine 1 can determine the state of the upper thread 6 from the pressure distribution of the upper thread 6.

[0090] In the pressure sensor 50, a plurality of detection points R are arranged in a grid pattern in the X and Y directions. The CPU 81 generates a two-dimensional pressure distribution due to the upper thread 6 based on the pressure due to the upper thread 6 at each detection point R detected by the pressure sensor 50 (S33). Based on the pressure distribution due to the upper thread 6, the CPU 81 determines the position (S35) of the end 6A of the upper thread 6, and the length (S36) and thickness (S37) of the upper thread 6 gripped by the thread gripping device 30. In this way, the sewing machine 1 can determine the state of the upper thread 6 from the two-dimensional pressure distribution due to the upper thread 6.

[0091] The thread gripping device 30 grips the upper thread 6 with a hook 44A of the gripping portion 44. The gripping portion 44 is movable in the X direction by driving the air cylinder 31. Furthermore, the multiple detection points R are arranged in the X direction. Because the direction in which the gripping portion 44 moves and the arrangement of the multiple detection points R that detect the pressure of the upper thread 6 are aligned, the sewing machine 1 can easily detect the state of the upper thread 6 with the pressure sensor 50.

[0092] The CPU 81 determines the position of the end 6A of the upper thread 6 as the state of the upper thread 6 based on the pressure distribution of the upper thread 6 (S35). When the CPU 81 determines that a thread tangle problem has occurred based on the position of the end 6A (S41: YES), it slows down the sewing speed of the main motor 24 (S48). Therefore, the sewing machine 1 can prevent problems that occur when the position of the end 6A is not appropriate.

[0093] The CPU 81 determines the length of the upper thread 6 gripped by the hook 44A as the state of the upper thread 6 based on the pressure distribution of the upper thread 6 (S36). When the CPU 81 determines that thread slippage is predicted based on the length of the upper thread 6 (S42: YES), it slows down the sewing speed of the main motor 24 (S48). Therefore, the sewing machine 1 can prevent problems that occur when the length of the upper thread 6 gripped by the hook 44A is not appropriate.

[0094] The CPU 81 determines the thickness of the upper thread 6 gripped by the hook 44A as the state of the upper thread 6 based on the pressure distribution of the upper thread 6 (S37). When the CPU 81 determines that thread breakage has been predicted based on the thickness of the upper thread 6 (S43: YES), it slows down the sewing speed of the main motor 24 (S48). Therefore, the sewing machine 1 can prevent problems that occur when the thickness of the upper thread 6 gripped by the hook 44A is inappropriate.

[0095] A second embodiment of the present invention will be described with reference to Figures 10 to 14. In Figures 10 and 11, the same components as those in the sewing machine 1 of the first embodiment are denoted by the same reference numerals. The sewing machine 1 of the second embodiment includes a thread clamping device 60 instead of the thread clamping device 30. As shown in Figures 10 and 11, the thread clamping device 60 differs from the thread clamping device 30 in that it includes a scanner 70 instead of the pressure sensor 50.

[0096] As shown in FIG. 12 , the scanner 70 includes a base 62, frame portions 64 and 69, a scanning unit 68, and a light-transmitting member 74. The base 62 has a rectangular parallelepiped shape extending in the X and Y directions. A plate 49 is fixed to the surface of the base 62 facing in the Z2 direction. The frame portion 64 is provided at the end of the base 62 facing in the X2 direction and on the Z1 direction side. The frame portion 64 has a plate shape extending in the X and Y directions. The frame portion 69 is provided at the end of the base 62 facing in the X2 direction and on the Z2 direction side. The frame portion 69 is fixed to the end of the frame portion 64 facing in the Z2 direction. The frame portion 69 has a rectangular cylindrical shape extending in the X and Y directions. A through hole penetrating the frame portion 69 in the Z direction is formed in the frame portion 69. The scanning unit 68 is provided at the end of the frame portion 64 facing in the Z2 direction and inside the through hole of the frame portion 69. The light-transmitting member 74 is provided at the end of the scanning unit 68 in the Z2 direction and inside the through-hole of the frame unit 69. The light-transmitting member 74 has light-transmitting properties.

[0097] In the thread gripping device 60 in the second state, the frame 69 and the light-transmitting member 74 clamp the upper thread 6 between themselves and the hook 44A (see FIG. 10 ). The scanning unit 68 scans in the X and Y directions to capture image information of the upper thread 6 through the light-transmitting member 74. The scanner 70 outputs the image information captured by the scanning unit 68 to the control unit 80. The CPU 81 of the control unit 80 acquires the image information output by the scanner 70 and generates an image. The CPU 81 performs image analysis based on the generated image to determine information about the upper thread 6, such as whether the hook 44A is gripping the upper thread 6, the position of the end 6A of the upper thread 6, and the length and thickness of the upper thread 6 gripped by the hook 44A.

[0098] The second pre-sewing processing executed by the CPU 81 of the second embodiment will be described with reference to Fig. 13. In Figs. 13 to 15, the same processes as those in the first embodiment are denoted by the same reference numerals. The second pre-sewing processing differs from the pre-sewing processing in that the processes of S64 to S66 are executed instead of the processes of S4 to S6. The following description of the second pre-sewing processing will focus on the differences from the pre-sewing processing.

[0099] When the thread gripping device 60 finishes gripping the upper thread 6 (S3), the tip of the upper thread 6 is clamped between the hook 44A and the scanner 70. The CPU 81 scans the scanning unit 68 and captures image information into the scanner 70 via the light-transmitting member 74 (S64). The CPU 81 obtains the image information from the scanner 70 and generates an image (S65).

[0100] The CPU 81 performs image analysis to determine whether the image generated in S65 includes the upper thread 6 (S66). If the image generated in S65 includes the upper thread 6 (S66: YES), the CPU 81 stores the image generated in S65 in the RAM 83 (S67).

[0101] The second sewing start processing executed by the CPU 81 of the second embodiment will be described with reference to Figures 14 and 15. The second sewing start processing differs from the sewing start processing in that the processing of S72 to S83, S84, and S85 is executed instead of the processing of S32 to S43, S54, and S55. The second sewing start processing will be described below, focusing on the differences from the sewing start processing.

[0102] As shown in FIG. 14, when the CPU 81 determines that the value of the variable M has reached a predetermined number (S31: YES), the CPU 81 scans the scanning unit 68 and captures image information into the scanner 70 via the light-transmitting member 74 (S72). The CPU 81 acquires the image information from the scanner 70 and generates an image (S73). The CPU 81 acquires a previous image (S74). The previous image is an image generated before the current execution of S73. The RAM 83 stores the previous image. If the CPU 81 is immediately after the start of sewing, it acquires the image stored in S67 (see FIG. 14) as the previous image. In the subsequent processing of S74, the CPU 81 acquires the previous image stored in the RAM 83 in S84, which will be described later.

[0103] The CPU 81 determines the position of the end 6A of the upper thread 6 (S75), and the length (S76) and thickness (S77) of the upper thread 6 gripped by the hook 44A as the state of the upper thread 6. The processing of S75 to S77 differs from S35 to S37 in that the determination is made by performing image analysis based on the image generated in S73 instead of the pressure distribution of the upper thread 6.

[0104] 15, the CPU 81 determines whether a thread tangling problem has occurred (S81), whether a thread slippage has been predicted (S82), and whether a thread breakage has been predicted (S83). The processes of S81 to S83 differ from S41 to S43 in that the determination is made based on the state of the upper thread 6 determined in S75 to S77 and the previous image acquired in S74, instead of the state of the upper thread 6 determined in S35 to S37 and the previous pressure distribution acquired in S34.

[0105] The CPU 81 stores the image generated in S73 (see FIG. 14) as a previous image in the RAM 83 (S94). The CPU 81 performs image analysis based on the image generated in S73 to determine whether the upper thread 6 is not gripped by the hook 44A (S95).

[0106] As described above, in the sewing machine 1 of the second embodiment, the thread clamping device 60 clamps the upper thread 6 between the hook 44A and the scanner 70 in the second state. The CPU 81 scans the scanning unit 68 in the X and Y directions to capture image information of the upper thread 6 through the light-transmitting member 74 (S72). The CPU 81 acquires the image information from the scanner 70 and generates image information (S73). The CPU 81 performs image analysis based on the generated image to determine the position (S75) of the end 6A of the upper thread 6, and the length (S76) and thickness (S77) of the upper thread 6 gripped by the thread clamping device 30. In this way, the sewing machine 1 can determine the state of the upper thread 6 by scanning with the scanning unit 68 of the scanner 70.

[0107] In the above embodiment, the thread clamping devices 30 and 60 are examples of the thread clamping unit of the present invention. The pressure sensor 50 and the scanner 70 are examples of the detection unit of the present invention. The CPU 81 that executes the processes of S35 to S37 and S75 to S77 is an example of the determination unit of the present invention. The CPU 81 that executes the processes of S42, S43, S82, and S83 is an example of the defect prediction unit of the present invention. The display unit 13 is an example of the notification unit of the present invention. The CPU 81 that executes the processes of S41 and S81 is an example of the thread tangle defect determination unit of the present invention. The X direction is an example of the predetermined direction of the present invention. The Y direction is an example of the second predetermined direction of the present invention. The CPU 81 that executes the process of S48 is an example of the position sewing control unit, length sewing control unit, and thickness sewing control unit of the present invention. The light-transmitting member 74 is an example of the first member of the present invention. The hook 44A is an example of the second member of the present invention.

[0108] The present invention can be modified in various ways from the first and second embodiments. The various modifications described below can be combined with each other as long as no contradictions arise. For example, the thread clamping devices 30 and 60 may be provided below the needle plate 7.

[0109] The thread clamping devices 30, 60 may be equipped with a tension detection unit instead of the pressure sensor 50 and the scanner 70. The tension detection unit detects the tension of the upper thread 6 at a plurality of predetermined positions. In this case, the CPU 81 acquires the tension of the upper thread 6 at a plurality of predetermined positions from the tension detection unit as information about the upper thread 6, and determines the state of the upper thread 6. The thread clamping devices 30, 60 may be equipped with the pressure sensor 50 and the scanner 70. In this case, the CPU 81 may determine the state of the upper thread 6 by combining the pressure of the upper thread 6 output by the pressure sensor 50 and the image information output by the scanner 70.

[0110] In the thread clamping devices 30 and 60, the method of holding the upper thread 6 is not limited to the method of clamping with the hook 44A. For example, in the thread clamping devices 30 and 60, a clamp may clamp the upper thread 6 instead of the hook 44A. The thread clamping devices 30 and 60 may be driven by a drive source other than the air cylinder 31. For example, the thread clamping devices 30 and 60 may be driven by the power of a motor.

[0111] The sewing machine 1 may be equipped with a speaker. In this case, the CPU 81 may notify the user by outputting sound from the speaker in steps S8, S11, S48, and S49.

[0112] In the first embodiment, the pressure sensor 50 detects the pressure of the upper thread 6 two-dimensionally using multiple detection points R arranged in a grid pattern in the X and Y directions. Alternatively, the pressure sensor 50 may detect the pressure of the upper thread 6 one-dimensionally along either a virtual line P arranged in the X direction or a virtual line Q arranged in the Y direction. When the pressure sensor 50 detects the pressure of the upper thread 6 one-dimensionally along a virtual line P arranged in the X direction, the CPU 81 determines the position of the end 6A of the upper thread 6 based on the position of the virtual line P arranged in the X direction that is closest to the X1 direction and detects the pressure of the upper thread 6. When the pressure sensor 50 detects the pressure of the upper thread 6 one-dimensionally along virtual lines Q arranged in the Y direction, the CPU 81 determines the thickness of the upper thread 6 gripped by the hook 44A based on the number of virtual lines Q arranged in the Y direction and that detect the pressure of the upper thread 6. The spacing between the multiple virtual lines P in the X direction may be changed as appropriate. The spacing between the multiple virtual lines Q in the Y direction may be changed as appropriate. The spacing between the multiple virtual lines P in the X direction and the spacing between the multiple virtual lines Q in the Y direction may be different. Furthermore, the pressure distribution acquired by the pressure sensor 50 may be such that not only the positions and number of detection points R at which pressure is detected, but also the strength of pressure at each detection point R can be detected at multiple levels, and the resulting pressure distribution, including the strength of pressure, may be compared with an appropriate pressure distribution stored in the ROM 82 or a previous pressure distribution stored in the RAM 83 to detect or predict the occurrence of sewing defects. Furthermore, appropriate values ​​(e.g., upper and lower limit thresholds) of pressure to be detected at the detection points R may be set for each thickness and type of needle thread 6 used for sewing, and the length, thickness, end position, etc. of the needle thread 6 may be detected only from detection points R that detect pressure within the appropriate range. Furthermore, sewing defects may be detected or predicted based on the number of detection points R that detect pressure values ​​outside the appropriate range.

[0113] In the second embodiment, it is sufficient that at least a portion of the light-transmitting member 74 is light-transmitting. The scanning unit 68 may perform scanning by moving the hook 44A relative to the scanner 70 in the X and Y directions.

[0114] In the pre-sewing processing, the CPU 81 may determine the state of the upper thread 6 based on the pressure distribution of the upper thread 6 generated in S5. In the second pre-sewing processing, the CPU 81 may determine the state of the upper thread 6 by performing image analysis based on the image generated in S65. The CPU 81 may execute the pre-sewing processing and the second pre-sewing processing when sewing by the sewing machine 1 is completed.

[0115] In the sewing start processing, the CPU 81 may omit some of the processing from S35 to S37. The CPU 81 may omit the processing from S41. The CPU 81 may omit some or all of the processing from S42 and S43. In the second sewing start processing, the CPU 81 may omit some of the processing from S75 to S77. The CPU 81 may omit the processing from S81. The CPU 81 may omit some or all of the processing from S82 and S83.

[0116] In the sewing start process and the second sewing start process, if it is determined that a thread tangle defect has occurred, if thread slippage is predicted, or if thread breakage is predicted, the sewing speed of the main motor 24 is reduced and a sewing start warning is issued. On the other hand, if the CPU 81 detects or predicts the occurrence of a sewing defect, it may perform control according to the respective sewing defect. For example, if the CPU 81 predicts the occurrence of thread slippage, it may control the thread tension solenoid 16 to reduce the tension of the upper thread 6 applied by the thread tension unit 15.

[0117] In the sewing start process and the second sewing start process, the CPU 81 may change the sewing conditions based on the determined state of the upper thread 6. For example, suitable sewing conditions according to the thickness of the upper thread 6 are preset in the ROM 82, and the CPU 81 may read the corresponding sewing conditions from the ROM 82 based on the thickness of the upper thread 6 gripped by the hook 44A, and change the sewing speed of the main motor 24, the tension of the upper thread 6 applied by the thread tension unit 15, and the movement amount of the movable blade of the thread cutting mechanism 18.

[0118] 7 to 9 and 13 to 15 may be stored in a storage device of the sewing machine 1 before the CPU 81 executes the program. Therefore, the program acquisition method, acquisition path, and program storage device may each be changed as appropriate. The program executed by the CPU 81 may be received from another device via a cable or wireless communication and stored in the storage device 84, etc. The other device may include, for example, a PC or a server connected to the sewing machine 1 via a network.

[0119] The steps of the processes in Figures 7 to 9 and 13 to 15 are not limited to those executed by the CPU 81, and may be executed in part or in whole by another electronic device (for example, an ASIC). Multiple electronic devices (for example, multiple CPUs) may perform distributed processing of the steps of the processes in Figures 7 to 9 and 13 to 15. The order of the steps of the processes in Figures 7 to 9 and 13 to 15 may be changed, steps may be omitted, or steps may be added as appropriate. An operating system (OS) or the like running on the sewing machine 1 may perform some or all of the processes in Figures 7 to 9 and 13 to 15 in response to instructions from the CPU 81. The various numerical values ​​given in the embodiments are merely examples and may be changed as appropriate. [Explanation of symbols]

[0120] 1 sewing machine 30, 60 Yarn gripping device 44A Hook 50 Pressure Sensor 70 Scanner 81 CPU

Claims

1. In a sewing machine that sews with a needle threaded through it, a thread gripping portion capable of gripping and holding the upper thread; a detection unit that detects information about the upper thread held by the thread gripping unit at each of a plurality of predetermined positions; a determining unit that determines a state of the upper thread based on information about the upper thread at the plurality of predetermined positions detected by the detecting unit.

2. a defect prediction unit that predicts the occurrence of a defect during sewing based on the state of the upper thread determined by the determination unit; 2. The sewing machine according to claim 1, further comprising a notification unit that notifies the user that the defect is predicted to occur when the defect prediction unit predicts that the defect will occur.

3. the detection unit detects information about the upper thread when the upper thread is held by the thread gripping unit, or each time the needle bar moves up and down a predetermined number of times while the upper thread is held by the thread gripping unit; The sewing machine according to claim 1 or 2, characterized in that the judgment unit is provided with a thread tangling fault judgment unit that judges whether a thread tangling fault has occurred between the upper thread and the bobbin thread as the state of the upper thread based on the transition of the information of the upper thread detected by the detection unit.

4. the detection unit detects pressure of the upper thread held by the thread gripping unit at predetermined intervals in a predetermined direction; 4. The sewing machine according to claim 1, wherein the determining unit determines the state of the upper thread based on the distribution of pressure on the upper thread detected by the detecting unit.

5. 5. The sewing machine according to claim 4, wherein the detection unit further detects the pressure of the upper thread at second predetermined intervals in a second predetermined direction intersecting the first predetermined direction.

6. 6. The sewing machine according to claim 4, wherein the thread gripping section has a gripping portion capable of gripping the upper thread, and the gripping portion is movable in the predetermined direction.

7. the determining unit determines the position of the upper thread held by the thread gripping unit as the state of the upper thread based on the pressure distribution; 7. The sewing machine according to claim 4, further comprising a position sewing control unit that controls a sewing operation based on the position of the needle thread determined by the determination unit.

8. the determining unit determines the length of the upper thread held by the thread gripping unit as the state of the upper thread based on the pressure distribution; 8. The sewing machine according to claim 4, further comprising a length sewing control unit that controls a sewing operation based on the length of the needle thread determined by the determination unit.

9. the determining unit determines the thickness of the upper thread held by the thread gripping unit as the state of the upper thread based on the pressure distribution; 9. The sewing machine according to claim 4, further comprising a thickness sewing control unit that controls a sewing operation based on the thickness of the needle thread determined by the determination unit.

10. The thread gripping portion has a first member formed of a light-transmitting portion at least partially having light transmittance, and a second member that grips the upper thread between the first member and the second member, The sewing machine according to claim 1 , wherein the detection unit detects the upper thread held between the first member and the second member by scanning through the light-transmitting portion.

Images