JPH0793997B2 - Sewing machine with thread trimming mechanism - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a sewing machine with a thread trimming mechanism, and in particular, via a needle thread end holding mechanism that holds the end of the needle thread that is automatically cut at the end of sewing. And the upper thread end is left short on the back side of the fabric.

[Prior art]

Conventionally, for example, as described in JP-A-56-139793,
A sewing machine equipped with a thread cutting mechanism that automatically engages a movable blade with a fixed blade via a lower shaft between a needle plate and a hook at the end of sewing to automatically cut an upper thread and a lower thread is already known. Has been.

In this sewing machine with a thread trimming mechanism, if the amount of thread from the eyelet of the sewing needle to the thread end of the upper thread is short, the thread end of the upper thread will come off from the eyelet of the sewing needle at the first stitch at the start of sewing. In order to prevent this, the yarn is cut while leaving a large amount of yarn from the eyelet to the yarn end.

However, when sewing with this sewing machine with a thread trimming mechanism, it is possible to prevent the upper thread from slipping out of the eye hole, but since the thread amount from the eye hole to the thread end is long, the upper thread remains on the back side of the fabric for a long time,
There is a problem in that the quality of the sewn product is extremely deteriorated by being entangled with the bobbin thread after the second stitch and entangled in a bird's nest shape as shown in FIG.

Therefore, in Japanese Utility Model Laid-Open No. 61-157487, the thread end of the upper thread is prevented from slipping out of the eye hole at the first stitch at the start of sewing, and the upper thread and the lower thread on the back side of the cloth are bird's nest. In order to prevent entanglement, the end of the upper thread cut by the thread cutting mechanism after the end of sewing is caught by the thread catching member above the needle plate, and the upper thread end is formed as a thread holding member and a thread catching member. Has proposed a sewing machine provided with a thread holding device which holds the sewing machine at a position considerably distant from the sewing needle.

[Problems to be Solved by the Invention]

In the sewing machine provided with the thread holding device of the latter publication, the upper thread and the lower thread do not get entangled in a bird's nest shape on the back side of the work cloth at the start of sewing, but from the eye hole to the thread end of the upper thread. Since the upper thread end is cut at a position that is considerably distant from the eyelet while cutting with the thread length left long, as shown in FIG.
A long needle thread will remain on the front side of the fabric. Therefore, it is necessary to manually perform a thread picking operation for cutting the end portion of the upper thread, an excessive amount of the upper thread for the thread picking is consumed, and the upper thread remains uncut even if the thread picking operation is performed. Remains on the surface of the fabric.

An object of the present invention is to provide a sewing machine with a thread cutting mechanism in which the end of the upper thread remains short on the back side of the fabric without being entangled with the lower thread.

[Means for Solving the Problems]

A sewing machine with a thread trimming mechanism according to the present invention is a sewing machine driven by a sewing machine motor and vertically reciprocally driven through a needle hole of a needle plate of a bed, and a balance driven in synchronization with vertical movement of the sewing needle. A shuttle arranged below the needle plate for interlacing the upper thread and the lower thread in cooperation with the sewing needle, and a thread cutting mechanism for cutting the upper thread and the lower thread between the needle plate and the shuttle, A sewing machine including a thread tension mechanism that applies resistance to the upper thread between the thread supply source and the balance, and a thread loosening mechanism that releases the resistance applied to the upper thread by the thread tension mechanism. A thread holding member that is movable in the vicinity of the lower side of the sewing needle located in the position, a thread holding position in the vicinity of the side of the sewing needle located in the uppermost position, and an open position in which the held upper thread is released. A holding force applying member for holding the end of the upper thread in cooperation with the thread holding member in the thread holding position. An upper thread end holding mechanism, and a thread holding driving means operatively connected to the thread holding member of the upper thread end holding mechanism for selectively switching the thread holding member to the three positions, and a thread trimmer. After the thread cutting operation by the mechanism is completed, the thread holding driving means is controlled so that the thread holding member moves from the open position to the thread holding position through the thread catching position, and when the sewing machine motor start signal is received, the start thereof is started. Thread holding for controlling the thread holding driving means so that the thread holding member moves to the open position after a first predetermined period corresponding to the period until the entanglement of the upper and lower threads of the first rear needle is formed When receiving the control means and the sewing machine motor start-up signal, the sewing needle is moved from the uppermost position to the second predetermined period within the first predetermined period from the start of the sewing machine motor in order to loosen the upper thread in the thread tension mechanism at the start of sewing. Down to the lower position Is provided with a the thread tension releasing control means on actuating between thread loosening mechanism of the second predetermined period corresponding to a period in which the upper thread loop is formed through the pot.

[Action]

In the sewing machine with the thread cutting mechanism according to the present invention, the thread holding control means is arranged such that, after the driving of the sewing machine motor is completed and the thread cutting operation by the thread cutting mechanism is completed, the thread holding member is moved from the open position to the uppermost position via the thread capturing position. Since the thread holding driving means is controlled so as to move to the thread holding position in the vicinity of the side of the sewing needle located at, the thread holding member catches the end of the upper thread extending from the eyelet hole of the sewing needle at the thread catching position. Move to the thread holding position,
The upper thread end is held by the cooperation of the thread holding member and the holding force imparting member.

Further, the yarn holding control means receives the sewing machine motor start signal, and after the sewing machine motor is started, a first predetermined period of time elapses.
For example, for holding the thread so that the thread holding member moves to the release position after the lapse of a period in which the sewing needle descends from the uppermost position to form a loop of the upper thread and the entanglement (knot) of the upper thread and the lower thread is formed. Control the drive means. When the needle thread loosening control means receives the sewing machine motor start signal, the first thread loosening control means starts the sewing machine motor from the start to loosen the needle thread in the thread tension mechanism at the start of sewing.
During a second predetermined period within the predetermined period, for example, during a period in which the needle descends from its uppermost position to its lowermost position and an upper thread loop is formed by the shuttle, the thread loosening mechanism is operated. Therefore, the tension associated with the vertical movement of the balance and the formation of the upper thread loop hardly acts on the upper thread, and the upper thread end does not come off from the thread holding mechanism.

〔The invention's effect〕

According to the sewing machine with the thread trimming mechanism according to the present invention, as described above, by providing the upper thread end holding mechanism, the thread holding drive means, the thread holding control means, and the upper thread loosening control means, the sewing start Immediately after that, during the second predetermined period immediately after the start of sewing, the sewing needle descends from the uppermost position to the lowermost position, and the needle thread loop is formed through the shuttle. Since the thread is loosened and the tension caused by the vertical movement of the balance is hardly acted on the upper thread, the upper thread end does not come off from the upper thread end holding mechanism. Then, the upper thread end holding mechanism holds the upper thread end until the first predetermined period corresponding to the period from the start of sewing until the entanglement of the upper thread and the lower thread of the first stitch is formed. Therefore, skipping does not occur and the thread end of the needle thread does not slip out of the eyelet of the sewing needle.

Here, the upper thread end holding mechanism holds the upper thread end at a position near the side of the sewing needle located at the uppermost position, so that the thread amount from the eyelet of the sewing needle to the upper thread end is The thread can be cut through the thread cutting mechanism so that it becomes shorter.

Therefore, since the thread amount can be set short, the end of the upper thread moves to the back side of the fabric and does not remain on the front side by the sewing operation after the second stitch, and the end of the upper thread and the nest of the lower thread and the bird's nest are formed. There is no need to do thread picking work,
The quality of the sewn product at the start of each sewing can be significantly improved.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.
In this embodiment, the present invention is applied to a sewing machine having a thread cutting mechanism and a thread loosening mechanism.

First, the thread tension mechanism 1 for applying a resistance force to the upper thread N _S fed from the thread spool (not shown) and the thread loosening mechanism 2 for removing this resistance force will be described.

As shown in FIGS. 1 and 2, at the head portion 8 of the arm portion 6 of the sewing machine M, the thread tension shaft is movably attached to the machine frame 5 in the front-rear direction.
The thread tension shaft 10 is supported by a fixed thread tension disc 11, a movable thread tension disc 12 and a compression spring 13. The front end of the thread tension shaft 10 has a resistance force applied to the upper thread N _S. Adjustment knob to adjust
14 is screwed, and by rotating the adjusting knob 14 clockwise or counterclockwise, the spring force of the spring 13 changes and the upper thread N _S sandwiched between the pair of thread tension discs 11 and 12 is rotated. The resistance acting on is adjusted. The movable thread tension disc 12 is engaged with the step portion of the thread tension shaft 10 from the front side, and when the thread tension shaft 10 is moved forward against the spring force of the spring 13, the movable thread tension disc 12 is fixed. The resistance force applied to the upper thread N _S , which is separated from the thread tension disc 11, is released.

On the rear side of the thread tension shaft 10, a thread loosening shaft 15 is supported by the machine frame 5 so as to be able to move back and forth. The front end of the thread loosening shaft 15 contacts the rear end of the thread tension shaft 10 and the rear end thereof is a thread loosening plate. It is in contact with the cam portion 17 of 16. The cam portion 17 has an operating portion that pushes the yarn loosening shaft 15 forward and a step-down portion that is stepped down from the operating portion. The drive unit 18 of the thread loosening plate 16 is connected to a plunger 21 of a thread loosening solenoid 20 via a connecting rod 19. The thread loosening solenoid 20 is fixed to the machine frame 5 by a bracket 22, and the plunger 21 is constantly urged to the left in FIG. 1 by a compression spring 23. Therefore, when the thread loosening solenoid 20 is not energized, the thread loosening shaft 15 does not contact the stepped-down portion of the cam portion 17 and does not push the thread tension shaft 10 forward.
Adjusted resistance is added to N _S. However, when the thread loosening solenoid 20 is energized, the connecting rod 19 moves to the right in FIG. 1, the thread loosening plate 16 is rotated clockwise, and the thread loosening shaft 15
Is pushed by the operating portion of the cam portion 17 and pushes the thread tension shaft 10 forward, the movable thread tension disc 12 is separated from the fixed thread tension disc 11 and the resistance force applied to the upper thread N _S is released. To be done.

Next, the thread cutting mechanism 3 for cutting the upper thread N _S and the lower thread B _S will be described. Since this is the same as that described in JP-A-56-139793, it will be briefly described.

As shown in FIGS. 3 and 4, a needle plate 27 having a needle hole (not shown) through which the sewing needle 24 is inserted is attached to the bed portion 7,
A lower shaft 28 is rotatably supported by the machine frame 5 below the needle plate 27, and a sword tip 29, an outer hook 30, and an inner hook 31 are provided at a left end portion of the lower shaft 28.
In the state in which a full-rotation type thread ring catcher 32, which is generally called a hook, is disposed, and a bobbin case 33 for accommodating a bobbin (not shown) is attached, the upper thread is operated in cooperation with the vertical movement of the sewing needle 24. N _S and by entangling the lower thread B _S so as to form a stitch on the work cloth W.

A fixed blade 34 is fixed to the machine frame 5 on the front side of the thread catcher 32 with screws at substantially the front half thereof, and the latter half of this fixed blade 34 is the thread catcher.
Along the 32, it extends in an arc shape to the vicinity of the needle hole of the needle plate 27, and a blade portion 35 is formed at the tip thereof. Incidentally, reference numeral 36 is the inner hook.
Reference numeral 37 is a bobbin stopper which restrains the rotation of 31 and a fixed blade 34 is provided when the needle thread B _S detached from the sword tip 29 is pulled up during sewing.
It is a shield plate that prevents it from being entangled with.

A movable blade holder 38 is rotatably supported on the machine frame 5 on the rear side of the thread catcher 32 so as to be capable of reciprocatingly rotating about the same axis as the lower shaft 28. Movable blade 40 in the mounting part 39
Is screwed. A thread separating portion 41, a thread catching groove portion 42, and a shoulder portion 43 are formed on an arcuate left end portion of the movable blade 40. On the other hand, in order to rotate the movable blade 40, a swing arm 45 is fixed to a swing shaft 44 that is rotated by a cam drive mechanism (not shown), and the swing arm 45 is movable via a connecting lever 46. The connecting portion 47 of the blade holder 38 is connected. Further, in order to drive the cam drive mechanism by the rotation of the lower shaft 28, the cam drive mechanism is connected to the drive shaft of the thread cutting solenoid 48 (see FIG. 9). Reference numeral 49 is a winding spring for biasing the swing arm 45 to rotate counterclockwise in FIG. 3 so as to hold the movable blade 40 in the non-cutting position shown in FIG. Therefore, as will be described later, the thread trimming solenoid is
When 48 is energized, the cam drive mechanism is driven by the rotation of the lower shaft 28 to rotate the swing shaft 44 in the direction of the arrow, so that the swing arm 45
The movable blade holder 38 is rotated clockwise in FIG. 3 via the connecting lever 46, and the movable blade 40 is also rotated clockwise in FIG.
The movable blade 40 catches the upper thread N _S and the lower thread B _S which are continuous with the work cloth W at the timing when the thread ring of the upper thread N _S is detached from the sword tip 29 of the outer hook 30 and is pulled up at the same time, and the blade portion of the fixed blade 34. Engage with 35 and disconnect. Here, the length of the cut upper thread N _{S from} the eyelet 25 of the sewing needle 24 to the thread end (hereinafter referred to as the upper thread end length) is proportional to the length of the thread catching groove portion 42. Thread catching groove
By shortening the length of 42, the needle thread end length can be shortened.

Next, the upper thread end holding mechanism 51 and the thread holding drive mechanism 52 that hold the upper thread end of the upper thread N _S that has been cut after the end of sewing will be described.

As shown in FIGS. 5 to 8, a mounting plate 53 is screwed to the rear side of the head portion 8 of the sewing machine M, and a second solenoid (bistable latching solenoid) 54 is arranged vertically.
Is fixed to a substantially left half portion of the mounting plate 53 by a bracket 58, and a first solenoid 59 arranged vertically is fixed to a substantially right half portion of the mounting plate 53 by a bracket 61. The second solenoid 54 is provided with an upper solenoid 55 and a lower solenoid 56 (see FIG. 12), and when the upper solenoid 55 is driven, the plunger 57 moves upward as shown in FIG. (In the direction of arrow U)
When the lower solenoid 56 is driven, the plunger 57 moves downward (in the direction of arrow D) and is held at the lower position. Immediately above the second solenoid 54 (28) The first side is substantially U-shaped
The output link 62 is rotatably supported on the mounting plate 53 by a pin 65 oriented in the front-rear direction, and a second output link 66 having a substantially U-shape in a side view is provided immediately below the pin 69 oriented in the front-rear direction. Is rotatably supported by a mounting plate 53.

The drive arm portion 63 of the first output link 62 is rotatably pivotally attached to the connecting member 70 fixed to the upper end portion of the plunger 57 of the second solenoid 54, and the swing arm portion 64 of the first output link 62 is the same. Long hole
A pin 74 fixed to the first arm 72 of the substantially L-shaped first link 71 is fitted to 64a and is connected to the first link 71. This first link 71 is pivotally supported at its base end by a stepped screw 76 in the front-rear direction via a spacer 75 so as to be rotatable on the mounting plate 53, and the lower end of the second arm 73 of the first link 71 is Stepped screw
77 is rotatably connected to the right end of the second link 78. The left end of the second link 78 is rotatably connected to the lower end of the third link 80 by a pin 79 and rotatably connected to the upper end of the fourth link 81, and the lower end of the fourth link 81 is threaded. A pin 85 is rotatably connected to the right end portion of the drive arm portion 83 of the knob link member 82.

On the other hand, the drive arm portion 67 of the second output link 66 is connected to the connecting member 86 by fitting the pin 87 fixed to the connecting member 86 fixed to the lower end portion of the plunger 57 of the second solenoid 54 into the long hole 67a. The right end of the swing arm 68 of the second output link 66 is a pin 88.
Is rotatably connected to the upper end of the fifth link 89, and the lower end of the fifth phosphorus 89 is pin 90 to the first arm 92 of the thread holding link 91.
Are linked to.

A boss portion 53a in the front-rear direction is fixed to the lower end of the mounting plate 53, and a pivot shaft 94 in the front-rear direction is rotatably supported by inserting the boss portion 53a and the mounting plate 53. A holder mounting plate 95 is fixed to the front end of 94, a thread holding holder 96 is screwed to the holder mounting plate 95, and a holding force imparting member 97 made of a spring member is screwed to the thread holding holder 96. ing. A tip portion of the holding force imparting member 97 is formed in a downwardly convex curved yarn pressing portion 98 (elastic contact portion).

A thread holding link 91 having a boss 99 having a step is fixed to the rear end of the pivot 94. Therefore, the fifth
By moving the link 89 upward or downward, the thread holding link 91
Rotates counterclockwise or clockwise, and a holding force imparting member is provided via the pivot shaft 94, the holder mounting plate 95, and the thread holding holder 96.
97 rotates counterclockwise or clockwise in synchronization with the thread holding link 91.

On the other hand, the drive arm portion of the thread grasping link member 82 having a substantially oblique U-shaped plane
A pivot shaft 94 is inserted through the base end portion of 83 and the base end portion of the swing arm portion 84, respectively, and the thread gripping link member 82 is rotatably supported by the pivot shaft 94, and is supported by the swing arm portion 84. The thread holding member 100 is screwed. Reference numeral 102 is a spacer. This thread holding member 1
The front end portion of 00 is formed in an arc shape around the pivot 94, and the hook portion 101 for catching the needle thread N _S extending downward through the eye hole 25 of the sewing needle 24 is formed at the left end portion of the arc shape portion. (Thread catching portion) is formed, and the thread pressing portion 98 of the holding force imparting member 97 elastically abuts on the concave portion of the upper surface of the hook portion 101 and cooperates with the hook member 101 to end the upper thread N _S. Is able to hold. Therefore, the yarn gripping link member 82 rotates counterclockwise or clockwise by the upward or downward movement of the fourth link 81, and the yarn holding member 100 rotates counterclockwise or clockwise. A pivot 94 between the swing arm 84 and the mounting plate 53
One end of the winding spring 103, which is installed on the outside, has a thread gripping link member 8
The second end of the thread holding link 91 is locked to the base end of the second
The thread holding link member 82 is locked by the pin 104 fixed to the arm 93 and is always urged to rotate counterclockwise in FIG. 7 with respect to the thread holding link 91, and the thread holding link 91 is fixed to the thread holding link 91. Since it is always urged clockwise with respect to the member 82,
The thread pressing portion 98 can surely come into contact with the hook portion 101. The drive arm portion 83 and the swing arm portion 84 of the thread gripping link member 82 have an opening angle of about 30 degrees.

A pin 105 oriented in the front-rear direction is fixed to the lower end portion of the plunger 60 of the first solenoid 59, and a third output link 106 having a substantially U-shaped side view is fixed to the lower end portion of the bracket 61. The third output link 106 is rotatably supported at 109 so that the contact portion 107 of the third output link 106 always contacts the pin 105 from below. Is urged to rotate in the clockwise direction. The swing arm 108 of the third output link 106 is the third link 80.
Is rotatably connected to the upper end of the pin by a pin 111. still,
Reference numeral 26 is a needle bar, reference numeral 112 is a presser bar, and reference numeral 113 is a presser foot.

Next, the operation of the needle thread end holding mechanism 51 and the thread holding drive mechanism 52 will be described with reference to FIGS. 7, 12, 13 (a) to 13 (c).

When the up solenoid 55 is driven, the plunger 57 moves up to the up position shown in FIG. 12, and the first output link 62, the first link 71, and the second link via the connecting member 70. 78,
The fourth link 81, the thread gripping link member 82, and the thread holding member 100 respectively move to the solid line positions. The position of the thread holding member 100 at this time is referred to as a retracted position. On the other hand, as the plunger 57 moves to the upper moving position, the fifth link 89, the thread holding link 91, the holder mounting plate 95, the thread holding holder 96, and the holding force imparting member 97 are respectively connected via the connecting member 86. Move to the solid line position. The position of the holding force imparting member 97 at this time is set to the retracted position (first
(See FIG. 13 (a)). At this retracted position, the thread holding member 100
Rotates largely in the counterclockwise direction, and the hook portion 101 thereof is located at a position far above the needle plate 27.

Next, when the lower solenoid 56 is driven, the plunger
57 moves down to the down position shown in Fig. 12, and the connecting member
Through the 70, the first output link 62, the first link 71, the second link 78, the fourth link 81, the thread gripping link member 82, and the thread holding member.
100 moves to the one-dot chain line position, respectively. The position of the thread holding member 100 at this time is referred to as a thread holding position. At this thread holding position, the hook portion 101 of the thread holding member 100 is the sewing needle at the uppermost position.
It will be near the right side of 24. On the other hand, with the downward movement of the plunger 57, the second output link 66, the fifth link 89, the thread holding link 91, the holder mounting plate 95, the thread holding holder 96, and the holding force imparting member 97 are connected via the connecting member 86. Each moves to the position indicated by the alternate long and short dash line in FIG. 12 (see FIG. 13 (c)). At this time, the thread pressing portion 98 of the holding force imparting member 97 engages with the recess of the hook portion 101 and can hold the upper thread N _S.

When the first solenoid 59 is driven in this state, the plunger 60 moves downward and the third output link 10 is moved through the pin 105.
6, third link 80, fourth link 81, thread grip link member 8
2. The thread holding member 100 moves to the position of the chain double-dashed line in FIG. At this time, the hook portion 101 of the thread holding member 100 is positioned near the uppermost position of the sewing needle 24 and catches the end portion of the upper thread N _S extending downward from the eyelet 25 of the sewing needle 24. The position of the yarn holding member 100 at this time is referred to as a yarn catching position. When the drive of the first solenoid 59 is stopped, the spring force of the winding spring 110 causes the third output link 106, the third link 80, and the fourth link 8
1. Since the thread gripping link members 82 are respectively returned to the positions indicated by alternate long and short dash lines in FIG. 12, the thread holding member 100 is returned to the thread holding position with its hook portion 101 capturing the upper thread end, and the holding force is increased. The upper thread end portion is held in cooperation with the thread pressing portion 98 of the applying member 97 (see FIG. 13 (c)).

Further, when the upper solenoid 55 is driven, the thread holding member 10
0 and the holding force applying member 97 move to the retracted position respectively,
Since the second link 78, the third link 80, and the fourth link 81 form a four-bar link, immediately after the start of the movement to the retracted position, the moving speed of the yarn holding member 100 is the holding force imparting member 97. 13b, the thread pressing portion 98 of the holding force imparting member 97 is disengaged from the hook portion 101, and the upper thread end portion is released, as shown in FIG. 13 (b). Thread holding member at this time
The 100 position is the release position.

Next, the overall configuration of the control system of the sewing machine M will be described based on the block diagram of FIG. Thread trimmer solenoid 48, thread loosening solenoid 20, upper solenoid 55, lower solenoid
56, the first solenoid 59 and the sewing machine motor 115 are connected to the drive circuits 116 to 121, respectively.
Are connected to the input / output interface 130 of the controller C, respectively.

The operation panel 122 releases a thread end portion of the upper thread N _S from the start of sewing or a loosening time setting key for setting a loosening time (second predetermined period) of the upper thread N _S by the thread loosening mechanism 2 immediately after the start of sewing. The release time setting key for setting the release time (first predetermined time) and when the needle 24 is replaced or when the needle thread N _S is passed through the needle 24, the thread holding member 100 and the holding force imparting member 97 are forced. Equipped with a retreat movement command key for moving the retreat position to the retreat position, and outputs the setting data and the command signal set by each key operation to the input / output interface 130.

The foot pedal 123 has three positions of a front step position, a horizontal neutral position, and a rear step position. When the foot step pedal 123 is in the front step position by the operator's step position, a sewing machine start command signal (“H” level) is sent. A sewing machine stop command signal (“L” level) is output to the input / output interface 130 at the neutral position, and a thread trimming signal is output to the input / output interface 130 at the rearward step position.

The on-needle signal generator 124 is a proximity switch that switches the rotational position of a metallic disk member formed by forming a small opening at a predetermined circumferential position provided on a sewing machine main shaft (not shown) driven by a sewing machine motor 115. Detected and the needle up signal is output to the input / output interface 130 when the sewing needle 24 is at the uppermost position. The needle down signal generator 125 is also configured similarly to the needle up signal generator 124, and outputs the needle down signal to the input / output interface 130 when the sewing needle 24 is at the uppermost position.

The control device C includes a CPU 132 and an input / output interface 130 connected to the CPU 132 via a bus 131 such as a data bus.
It is composed of a ROM 133 and a RAM 140.

The ROM 133 stores a control program for the upper thread processing control including the upper thread holding control and the thread loosening control. RAM140 has
Thread loosening set time data memory 141 that stores the set thread loosening time data, needle thread release setting time data memory 142 that stores the set thread release time data of needle thread N _S , and foot pedal 123 goes backward after passing the neutral position. Thread trimming flag memory 14 that stores the thread trimming flag that is set when the pedal is depressed and is reset when the pedal is not depressed to the rear
3, a needle drop signal counter that counts the needle drop signal input from the needle drop signal generator 125 (its content is I) 144, C
Various memories are provided for temporarily storing the results calculated by the PU 132.

Next, the upper thread processing control routine executed by the controller C of the sewing machine M will be described with reference to the flowchart of FIG.
This will be described with reference to FIGS. 11, 12 and 13 (a) to 13 (c). However, for easy understanding of the explanation, the stepping pedal 123 will be stepped to the front stepped position, S1 to S11 will be executed, and the sewing will be described from the stage in which sewing is being executed. During the execution of sewing, the thread holding member 100 and the holding force imparting member 97 are moved to the retracted position shown in FIG. 13 (a). In the figure
Si (i = 1, 2, 3, ...) Indicates each step, and T1 to T7 in FIG. 11 indicate timings.

When the foot pedal 123 is operated to move from the neutral position to the rear step position at the time of T1 during execution of sewing (the step signal is at the “L” level), the thread trim flag of the thread trim flag memory 143 is set ( S12), needle down signal generator 125-2
T2 when two needle down signals are input and the counter I becomes "2"
(S13 to S15), the thread trimming solenoid 48 and the thread loosening solenoid 20 are respectively driven, and the upper thread N _S and the lower thread B _S are cut while the resistance force acting on the upper thread N _S is released. (S1
6). Thereafter, when the needle up signal is input from the needle up signal generator 124 (S17), the driving of the thread trimming solenoid 48 and the thread loosening solenoid 20 is stopped (S18), and the sewing machine motor 115
Of the sewing machine motor 115 when the drive of the sewing machine is stopped and the brake in the sewing machine motor 115 is activated by the brake signal.
15 surely stops (S19).

At T3 when the sewing machine motor 115 is stopped, the lower solenoid 56 is driven for a predetermined time (for example, 60 msec) (S2
0). Therefore, as described above, the thread gripping link member 82 and the thread holding link 91 move from the solid line position in FIG. 12 to the alternate long and short dash line position, so that the thread holding member 100 and the holding force imparting member 97 are shown in FIG. 13 (c). Move to the indicated thread holding position. Then, the first solenoid 59 is driven for a predetermined time (for example, 60 msec). (S21). Therefore, only the thread holding member 100 moves to the thread catching position and moves back to the thread holding position again while holding the thread end of the needle thread N _S extending from the eye hole 25 of the sewing needle 24 by the hook portion 101 and holding it. The upper thread end portion is held in cooperation with the thread pressing portion 98 of the force applying member 97.

Next, when the foot pedal 123 is operated to start sewing and is depressed to the front step position (the step signal is "H").
Level) is (S2), a predetermined time t1 (for example, 100 msec) is stored in the first timer M1 provided in the control device C, and counting is started (S3). At this time (S4), when the sewing machine motor 115 is driven by the sewing machine motor drive signal, the thread loosening set time data memory 141
Setting data t2 of the upper thread release setting time data memory and setting data t3 of the needle thread release setting time data memory 142 are stored in the second timer M2 and the third timer M3 in the control device C, respectively (S6). Until the time reaches
The thread loosening solenoid 20 during the period in which the needle thread descends from the uppermost position to the lowermost position and the needle thread looper 32 forms an upper thread loop.
Are driven (S7, S8), and after T6 when the second timer M2 has timed up and after T7 when the third timer M3 has timed up, for example, the sewing needle 24 descends from the uppermost position and a loop of the upper thread N _S is formed. After the lapse of the period in which the upper thread N _S and the lower thread B _S are entangled (knot) (S9, S10), the upper solenoid 55 is driven for a predetermined time (for example, 60 msec) (S11). At this time, the release position of the thread holding member 100 (the first position immediately after the start of movement of the thread holding member 100 and the holding force imparting member 97 from the thread holding position shown in FIG. 13C to the retracted position of FIG. 13A). 13 (b)), the upper thread end is released. After that, sewing is continuously executed, and the control after S11 is executed.

As described above, since the upper thread N _S is loosened by the thread loosening mechanism 2 during the thread loosening period t2 immediately after the start of sewing, the tension due to the vertical movement of the balance hardly acts on the upper thread N _S , and the upper thread end Part holding mechanism
The upper thread end does not come off from 51 without permission. Further, since the upper thread end holding mechanism 51 holds the upper thread end portion from the start of sewing until the entanglement of the upper thread N _S and the lower thread B _{S of} the first stitch is formed,
There is no stitch skipping and the thread end of the upper thread N _S does not come off from the eyelet hole 25 of the sewing needle 24.

Further, the needle thread end holding mechanism 51 is provided with the sewing needle 24 located at the uppermost position.
Since the upper thread end is held at a position near the side of the upper thread, the upper thread N _S can be cut by the thread cutting mechanism 3 so that the length of the upper thread end is shortened. Therefore, since the length of the upper thread end can be shortened, the end of the upper thread N _S moves to the back side of the cloth W and does not remain on the front side by the sewing operation after the second stitch as shown in FIG. Since the thread end does not entangle with the bobbin thread B _S in a bird's nest shape, there is no need to perform thread picking work, and the quality of the sewn product at each sewing start portion can be significantly improved.

Incidentally, the thread tension mechanism 1, the thread loosening mechanism 2 in the above embodiment,
The thread trimming mechanism 3 is merely an example, and it is needless to say that various known structures can be used in place of these, and the thread holding drive mechanism 52 and the upper thread end portion holding mechanism 51 are used.
It is needless to say that the present invention can be used not only as an example but also as various existing ones, as well as variously modified or modified ones according to the present embodiment.

[Brief description of drawings]

1 to 14 show an embodiment of the present invention.
The figure is a front view of the arm part of the sewing machine with a part cut away,
2 is a partial side view of the sewing machine, FIG. 3 is a side view of a longitudinal section of a main portion of the bed, FIG. 4 is a partial perspective view of a thread catcher and a thread cutting device, and FIG. 5 is a thread holding drive mechanism. Partial side view of
6 is a side view of the thread holding drive mechanism and the upper thread end holding mechanism, FIG. 7 is a sectional view taken along line VII-VII of FIG. 6, and FIG. 8 is FIG.
VIII-VIII sectional view, FIG. 9 is a block diagram of the control system of the sewing machine, FIG. 10 is a schematic flowchart of a needle thread processing control routine including needle thread holding control and thread loosening control, and FIG. 11 is various signal times. A chart, FIG. 12 is a mechanical view of an upper thread end holding mechanism and a thread holding drive mechanism, FIGS. 13 (a) to 13 (c) are partial front views showing respective states of the thread holding mechanism, and FIG. FIG. 15 and FIG. 16 are enlarged cross-sectional views of the fabric showing the thread end portion of the upper thread of the sewing start portion, and FIGS. M: sewing machine, 1 ... thread tension mechanism, 3 ... thread trimming mechanism,
11 …… Fixed thread tension tray, 12 …… Movable thread tension tray, 15 …… Thread loosening shaft, 20 …… Thread loosening solenoid, 24 …… Sewing needle, 27 …… Stitch plate, 30 …… Outer hook, 31 …… Inner hook, 34 ... Fixed blade, 40 ... Movable blade, 48 ... Thread trimming solenoid, 51 ... Upper thread end holding mechanism, 52 ... Thread holding drive mechanism, 54 ... Second solenoid,
55 …… Upward solenoid, 56 …… Downward solenoid, 59 ……
1st solenoid, 71 ... 1st link, 78 ... 2nd link, 80 ... 3rd link, 100 ... Thread holding member, 101 ... Hook part.

Claims (1)

[Claims] 1. A sewing needle driven by a sewing machine motor to reciprocate up and down through a needle hole of a needle plate of a bed, a balance driven in synchronization with vertical movement of the sewing needle, and a needle needle arranged below the needle plate. A hook provided for interlacing the upper thread and the lower thread in cooperation with the sewing needle, a thread cutting mechanism for cutting the upper thread and the lower thread between the needle plate and the hook, a thread supply source, and a balance. In the sewing machine equipped with a thread tension mechanism that applies resistance to the upper thread between the upper thread and a thread loosening mechanism that releases the resistance applied to the upper thread by the thread tension mechanism, A thread holding member that is movable near a thread catching position near the lower side, a thread holding position near the side of the sewing needle located at the uppermost position, and a releasing position that releases the held upper thread, and a thread at the thread holding position. A needle thread end holding mechanism having a holding force imparting member that holds the end portion of the needle thread in cooperation with the holding member; A thread holding driving means operatively connected to the thread holding member of the upper thread end holding mechanism for selectively switching the thread holding member to the three positions, and after the thread cutting operation by the thread cutting mechanism is completed, The yarn holding driving means is controlled so that the yarn holding member moves from the released position to the yarn holding position via the yarn catching position, and when the sewing machine motor start start signal is received, the upper and lower threads of the first stitch after the start A thread holding control means for controlling the thread holding driving means so that the thread holding member moves to the release position after the lapse of the first predetermined period corresponding to the period until the entanglement with the thread is formed, and the sewing machine motor start start signal. When the sewing machine receives the needle, the sewing needle is lowered from the uppermost position to the lowermost position within the second predetermined period within the first predetermined period from the start of the sewing machine motor in order to loosen the upper thread in the thread tension mechanism at the start of sewing, and the needle is lowered through the hook. Upper thread loop Thread cutting mechanism with a sewing machine, characterized in that between thread loosening mechanism of the second predetermined time period is provided a thread tension releasing control means on actuating corresponding to a period is formed.