JPH02213381A - Needle thread-controlling device for sewing machine - Google Patents

Abstract

PURPOSE:To make it possible to automatically balance the stitch and tense the thread in any speed of sewing by providing a timing-deciding device by which work-feeding is partially done while a needle thread is released by both of contact members after outputs from a speed-detecting device and phase-detecting device for an arm shaft are received, and the faster a rotary speed of the arm shaft is, the later the starting timing of a period of the needle thread being released is made. CONSTITUTION:A timing-deciding device is operated by a speed signal from a speed- detecting device and a phase signal from a phase-detecting device, and work-feeding is partially done while a needle thread is released by a pair of contact members. The starting timing of a period of the needle thread being released is also so decided that the faster a rotary speed of an arm shaft is, the later the release of the needle thread is made. A controlling device controls a contact member-driving device so that the needle thread can be released by the starting timing, and the needle thread is released after both of the contact parts are relatively shifted from an access position to a separate position. As a result of it, the needle thread is fully tightened by being operated together with a feeding movement and the thread take-up movement of its lever, while restricted, and is fed to the take-up lever from a thread-spooling piece, which is necessary for forming the next stitch.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a sewing machine equipped with a feeding mechanism directly driven by a stepping motor, a pair of engaging bodies for restraining and releasing an upper thread, and engaging body driving means. The present invention relates to a needle thread control device for use in the industry, and particularly relates to a needle thread control device that changes the needle thread release timing based on the rotational speed of the upper shaft.

[Prior art]

Previously, a sewing machine was proposed in which the forward and backward movement mechanism of the feed dog that feeds the cloth was directly driven by a stepping motor, so that in addition to straight stitches and zigzag stitches, it was possible to stitch many patterns including alphabets and numbers. has been done.

For example, in Japanese Unexamined Patent Publication No. 139694/1983, the applicant of the present application has constructed a structure in which the vertical movement mechanism of the feed dog is driven by a sewing machine motor, and the forward and backward movement mechanism of the feed dog is driven by a feeding stepping motor. As shown in the figure, we have proposed a fabric feeding device for a sewing machine that drives the feeding stepping motor to feed the fabric at a timing slightly earlier than the 0 degree rotation phase of the upper shaft when the sewing needle reaches its uppermost position.

Furthermore, the applicant of the present application proposed in Japanese Patent Application Laid-open No. 63-125285 a fabric feeding device for a sewing machine in which a plurality of rollers are rotated by a feeding stepping motor instead of feeding teeth to feed the fabric.

Furthermore, in order to enable automatic thread tension of the upper thread, the applicant of the present application has disclosed, for example, in Japanese Patent Application Laid-Open No. 63-105790,
A pair of engaging bodies that restrain and release the upper thread from the thread spool to the thread holding part of the thread take-up at a predetermined timing (see Fig. 10) in synchronization with the rotation of the upper shaft, and their approach and separation. We have proposed a sewing machine that is equipped with a thread passage control device that controls thread passage. The forward and backward movement mechanism and vertical movement mechanism of the feed dog of this sewing machine are driven by the sewing machine motor via the upper shaft.
The cloth feeding operation is timed to any rotational speed of the upper shaft from a phase near the 0 degree rotational phase of the upper shaft when the sewing needle reaches the uppermost position to a phase approximately in the middle during the release period of the upper thread. and executed.

[Problem to be solved by the invention]

In order to realize a sewing machine that is capable of automatic thread tension of the upper thread and that is capable of sewing a large number of patterns, a cloth feeding device of the sewing machine,
When a pair of engaging bodies and a thread passage control device are combined, the vertical movement of the thread take-up and sewing needle, the timing of restraint and release of the upper thread, and the timing of starting cloth feeding are controlled by the upper shaft at any rotational speed of the upper shaft. are executed at predetermined rotational phases in synchronization with the rotations of the respective rotations. The feeding stepping motor is driven by pulses having a constant pulse frequency.

Therefore, when the cloth is fed by a predetermined amount, as shown in FIG. 10, the timing at which cloth feeding ends becomes slower as the rotational speed of the upper shaft increases.

Therefore, the rotation speed of the upper shaft is medium speed or higher (for example, about 45
Orpm or above), part of the cloth feeding operation is performed during the upper thread release period, so the upper thread is sufficiently tightened in conjunction with the feeding operation and the raising operation of the thread take-up while being restrained by the engaging body. After the needle thread is released by the engaging body, the amount of thread necessary for forming the next stitch is let out from the thread spool, so that the thread tension is improved.

On the other hand, when the rotational speed of the upper shaft is lower than medium speed, the fabric feeding operation ends with the upper thread being restricted, which causes the upper thread to be tightened too much and the quality of the seams to deteriorate dramatically. There's a problem. Furthermore, even when the feed amount is small, there is a problem in that the quality of the stitches deteriorates at any rotational speed of the upper shaft, as described above.

SUMMARY OF THE INVENTION An object of the present invention is to provide a needle thread control device for a sewing machine that is equipped with a pair of engaging bodies, engaging body driving means, and a feeding mechanism directly driven by a stepping motor. The object of the present invention is to provide a possible upper thread control device.

[Means to solve the problem]

As shown in the functional block diagram of FIG. 1, the needle thread control device for a sewing machine according to the present invention has a needle bar that is equipped with a sewing needle and is reciprocally driven by a sewing machine motor via an upper shaft, and a needle thread control device that is synchronized with the needle bar. The thread take-up is driven reciprocally up and down by the sewing machine motor, and is provided upstream of the thread thread path from the thread supply source through the thread thread take-up to the sewing needle. a pair of engaging bodies that are movable relative to each other; and engaging body driving means that drives the engaging bodies between an approaching position and a separating position;
a feed mechanism that transports the workpiece cloth with a feed dog in synchronization with the needle bar;
In a sewing machine equipped with a feeding stepping motor that drives a feeding mechanism and a feeding control means that controls the feeding stepping motor, a speed detection means that detects the rotational speed of the upper shaft and a phase detection means that detects the rotational phase of the upper shaft. In response to outputs from the speed detecting means and the phase detecting means, part of the work cloth transfer is performed during the upper thread release period by both engaging bodies, and the higher the rotational speed of the upper shaft, the longer the upper thread release period becomes. and a control means for controlling the engaging body driving means to release the upper thread at the start timing determined by the timing determining means. be.

[Effect]

The operation of the needle thread control device of the sewing machine according to the present invention will be explained.

The needle bar and the thread take-up are each reciprocated by a sewing machine motor via the upper shaft, and the feed control means starts driving the stepping motor for feeding at a predetermined timing of the upper shaft, and transports the work cloth using the feed teeth of the feed mechanism. .

On the other hand, the timing determining means determines, based on the speed signal from the speed detecting means and the phase signal from the phase detecting means, that part of the work cloth transfer is executed during the needle thread release period by the pair of engaging bodies and that the upper shaft is The start timing of the needle thread release period is determined so that the needle thread is released at a later time as the rotational speed increases.

Since the control means controls the engaging body driving means to release the upper thread at the start timing, both engaging bodies move relatively from the close position to the separated position and the upper thread is released.

As a result, the upper thread is sufficiently tightened in conjunction with the feeding operation and the thread take-up operation of the thread take-up during the upper thread restraint period, and is tightened sufficiently in conjunction with the feeding operation during the upper thread release period to obtain the necessary thread for forming the next stitch. The amount of thread is supplied from the thread spool to the thread take-up. This ensures stable thread tension at any rotational speed of the upper shaft.
A beautiful seam is formed.

〔Effect of the invention〕

According to the needle thread control device of the sewing machine according to the present invention, [Function]
As explained in the above section, the start timing of the needle thread release period is delayed according to the increase in the rotational speed of the upper shaft, and at any rotational speed of the upper shaft, the cloth feeding operation changes from before the needle thread is released to after the needle thread is released. Since the process is executed continuously, stable thread tension can be obtained regardless of the sewing speed, and beautiful stitches can be formed.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

This embodiment is a case in which the present invention is applied to an electronically controlled zigzag sewing machine equipped with a cloth feeding mechanism that moves a feed dog back and forth using a feeding stepping motor, and a thread passage regulating device that regulates the passage of upper thread. .

As shown in FIGS. 2 to 4, in the lockstitch sewing machine M, a pedestal section 4 is erected at the right end of the bed section 2, and an arm section 6 extending leftward from the upper end of the pedestal section 4 is provided. A head part 8 is provided at the left end of the arm part 6, and a needle bar 10 is provided on the head part 8.
and presser rods 18 are arranged in the vertical direction.

A sewing needle 12 is attached to the lower end of this needle bar 10.
0 is attached to a needle bar support 24 so as to be vertically movable, and the upper end of the needle bar support 24 is pivotally attached to the machine frame via a pin 26. As a result, the needle bar 10 is able to swing left and right about the pin 26 together with the needle bar support 24, and the needle bar 10 is attached to the sewing machine main shaft 28 disposed within the arm portion 6 and the end of the sewing machine main shaft 28. It is designed to be driven up and down by a needle bar crank 30. Further, a needle bar 10 and a needle bar support 2
4 is driven to swing in the left-right direction by a stepping motor 17 for swinging the needle bar via a connecting rod 13, a sector gear 15, and a drive gear 16.

A presser foot 20 is removably attached to the lower end of the presser bar 18, and this presser foot 18 is connected to an operating body 21 (see FIG. 3).
The position is switched between the raised position and the lowered position by the operation of .

Next, the balance mechanism will be explained with reference to FIGS. 2 to 4.

The sewing machine main shaft 28 is rotatably mounted on the machine frame via a bushing metal 32, etc., and a pivot shaft 34 is disposed diagonally above and behind the main shaft 28 in parallel with the main shaft 28. It is rotatably attached to the machine frame. One end of a swing lever 36 is rotatably connected to this pivot shaft 34, and this swing lever 36 extends from the pivot shaft 34 to the left end side of a balance crank 38 fixed to the main shaft 28, The crank pin 40 of 38 extends through the elongated cam hole 42 of the swing lever 36, and a connecting plate 44 is fixed to the left end of the crank pin 40 on the left side of the swing lever 36. A needle bar crank 30 is rotatably connected to a pivot pin 46 extending to
The lower end portion of the needle bar 10 is connected to the middle portion of the needle bar 10.

A crank-shaped lever 48 extending upward is integrally formed at the upper end of the front portion of the swing lever 36, and a thread holding portion 48a is formed at the upper end of the lever 48.

The cam hole 42 of the swing lever 36 allows the crank pin 40, which is located near the uppermost position and has the same radius as the rotation locus of the crank pin 40, to rotate approximately 74 degrees as shown in FIGS. 2 and 3. It is formed of an arcuate hole 42a and a short straight hole 42b extending straight from both ends of the arcuate hole 42a, and the outer periphery of this cam hole 42 is reinforced with a reinforcing portion 36a.

With the crank pin 40 inserted into the cam hole 42 of the swing lever 36, the balance crank 38 and the crank pin 40
When the lever rotates around the main shaft 28, the swing lever 36 moves from the top position (maximum system pickup position) shown in solid line in FIG. 3 to the top position shown in phantom line in FIG. It is driven to reciprocate up and down between the lower position (maximum system relaxation position). At this time, the needle bar 10 is reciprocated up and down via the needle bar crank 30 and crank pin 40 in synchronization with the rotational movement of the sewing machine main shaft 28.

Since the circular arc hole 42a as described above is formed in a part of the cam hole 42 of the swing lever 36, the movement of the balance 48 using the rotational phase angle of the main shaft 28 as a parameter is as shown by the curve MA in FIG. The movement of the sewing needle 12 attached to the lower end of the needle bar 10 is as shown by the curve MB in FIG.

The thread take-up 48 is held at the uppermost position from when the main shaft 28 of the sewing machine is at about 40 degrees until the eye of the sewing needle 12 reaches the upper surface of the throat plate 22. quantity is secured.

Next, the cloth feeding mechanism 41 that moves the feeding dog 23 up and down and back and forth will be explained based on FIG. 2.

A feed stand 43 is disposed in the bed portion 2 below the presser foot 20 in the front-rear direction, and this feed stand 43 supports the feed dog 23, and the bifurcated portion at the front end of the feed stand 43 supports the upper and lower feed arms 45.
The vertical feed arm 45 is fitted with the upper shaft portion, and the vertical feed arm 45 is connected to the vertical feed shaft 4.
It is fixed to 7.

A cam 49 that fits into the bifurcated portion of the vertical feed shaft 47 is fixed to a swinging body 51, and the swinging body 51 and the crank portion 28a of the main shaft 28 of the sewing machine are connected via a crank rod 53.

On the other hand, the rear i portion of the feed table 43 is rotatably supported by a pair of arms protruding from the horizontal feed shaft 55.
is supported on the machine frame so that it can swing about its own axis. A sector gear 5 is attached to the right end of this horizontal feed shaft 55.
7 is fixed, and its gear portion meshes with a drive gear 61 fixed to the output shaft of the stepping motor 59 for feeding. Therefore, as the swinging body 51 swings and rotates via the crank rod 53 due to the rotation of the sewing machine main shaft 28, the feed dog 23 is vertically driven via the cam 49, the vertical feed shaft 47, and the vertical feed arm 45. Since the feeding stepping motor 59 is driven in synchronization with the vertical movement of the feed dog,
The feed dog 23 is moved back and forth in its raised and lowered positions.

Next, a pair of engaging bodies that restrain and release the upper thread 14 and an engaging body driving mechanism 7 that drives them to the approaching position and the separating position.
The yarn passage regulating device 54 and the like equipped with 0 will be explained with reference to FIGS. 2 to 5.

Immediately to the left of the needle bar crank 30 at the left end of the main shaft 28, a plate member 50, which is a part of the machine frame, is provided perpendicularly to the main shaft 28. As shown in FIGS. 2 and 3, a needle thread 14 is attached to the left side of the plate member 50 at a position slightly forward of the main shaft 28.
A britension device 52 that can provide passage resistance is provided as necessary.

This britension device 52 allows the upper thread to pass between a pair of thread tension discs 52a, and by rotating a dial, the spring force can be adjusted to adjust the thread passing resistance. This britension device 52 may be omitted.

Furthermore, the needle thread 14 from the thread spool to the thread holding part 48a of the thread take-up lever 48 is restrained and Thread path regulating plates 56 as a pair of engaging bodies can be released.
The yarn passage regulating device 54 is provided as follows, and includes a movable plate 58 having a movable ring 64 and an engaging body drive mechanism 70 for driving these to an approach position and a separation position.

A yarn path regulating plate 56 (engaging body) is fixed to the left side of the plate member 50 at a position below the britension device 52, and a movable plate 5 is disposed near the left side of the yarn path regulating plate 56.
8 and the lower end of the support plate 60 are connected to the plate member 50 with stepped screws 62.
The upper end of the support plate 60 is rotatably connected to the plate member 5.
It is fixed to 0 with a screw. The movable ring 64 of the movable plate 58 (
The engaging body) is arranged so as to come into contact with the regulating part 56a of the thread path regulating plate 56 from below to clamp and restrain the upper thread 14 between the regulating part 56a and the movable ring 64, and the movable plate 58 The movable plate 58 is elastically biased by a tension spring 66 whose one end is fixed to the machine frame so that the ring 64 is pressed against the regulating portion 56a.
A contact shaft 68 is rotatably attached to the arm portion 58a.

As shown in FIG. 2, FIG. 3, and FIG. The restricting portion 56a is formed in an inverted U shape when viewed from the side so as to be engaged with the groove 64a from above, and the restricting portion 56a is formed in a convexly curved surface having a U-shaped cross section.

The needle thread 14 that has passed through the britension device 52 is bent into a U-shape at the regulating portion 56a of the thread path regulating plate 56, and extends to the sewing needle 12 via the thread holding portion 48a of the thread take-up lever 48.

The needle thread 14 bent by the regulating part 56a is held between the regulating part 56a and the groove 64a at two points and is strongly restrained. In particular, the movable ring 6 moves in a direction parallel to the plane including the thread supply path of the needle thread 14 bent at the regulating portion 56a.
4 is driven and clamps and restrains the upper thread 14 in a transverse manner.
The surface pressure that clamps the needle thread 14 becomes extremely large. In other words, even when the force pressing the movable ring 64 is small, the needle thread 14 can be strongly restrained.

In order to release and restrain the needle thread 14 by driving the movable ring 64 of the movable plate 5 up and down, the needle thread 14 is moved to the right from the position where it contacts the contact shaft 68, as shown in FIGS. 2 and 4. An actuating plate 72 extending to
5, and a solenoid 73 is connected to the right end of the operating plate 72.

The above pair of engaging bodies 56 and 64 and the engaging body drive mechanism 70
In the thread passage regulating device 54 equipped with a solenoid 73
When the actuating plate 72 is driven, the actuating plate 72 rotates counterclockwise about the shaft 75 in a plan view. As a result, the actuating plate 72
When the contact shaft 68 is pushed forward at the left end of the movable plate 5
8 rotates against the spring force, and the movable wheel 64 rotates against the thread path regulating plate 5.
6, and the upper thread 14 is released from the restrained state. Further, when the drive of the solenoid 73 is stopped and the left end of the actuating plate 72 moves rearward, the movable plate 58 is rotated by the elastic force of the spring 660, the movable ring 64 comes into contact with the regulating part 56a, and the upper thread 14 is regulated. It is clamped and restrained between the portion 56a and the movable ring 64. In this way, the release and restraint of the upper thread 14 are performed by the solenoid 73.

Next, to explain the detector etc., the sewing machine main shaft 2
8 is rotationally driven by a sewing machine motor 67 via a timing belt 63 and a boot U 65.

A disk in which a large number of slits are formed radially at predetermined intervals is fixed to the main shaft 28 of the sewing machine, and a speed detection device is composed of this disk and a photo ink club that detects these slits and outputs a speed signal (pulse signal). A container 69 is provided. Furthermore, a disk with one slit is fixed to the sewing machine main shaft 28, and when the rotational phase between this disk and the sewing machine main shaft 28 is about 330 degrees, this slit is detected and a reference signal (pulse signal) for releasing the upper thread is generated. A reference signal generator 71 for releasing the upper thread is provided, which is a photo ink converter that outputs a reference signal generator 71 for releasing the upper thread.

Next, the overall configuration of the control system of the sewing machine M will be explained based on the block diagram shown in FIG.

The following switches, volume, etc. are connected to the input/output interface 90 of the control device C as input signals.

A pattern selection switch 77 that selects a desired pattern, a start/stop switch 78 that is connected to a start/stop button and outputs a start signal and a stop signal, and a speed detector 6 that outputs a speed signal.
9. A feed amount adjustment volume 79 connected to the feed amount adjustment knob and outputting a feed amount adjustment signal; an A/D converter 80 that converts the signal into A/D; connected to the needle swing amount adjustment knob and outputting a needle swing amount adjustment signal; A needle oscillation I adjustment volume 81 that outputs the signal, and an A/D converter 82 that converts the signal to A/l).
, a speed volume 83 connected to the speed adjustment knob and outputting a set speed signal, an A/D converter 84 converting the signal into A/D, a clock pulse generator 85 generating clock pulses of approximately IK) IZ, and an upper thread. A needle thread release reference signal generator 71 that outputs a release reference signal is composed of a disk attached to the sewing machine main shaft 28 and a photo ink club, and adjusts the cloth speed at predetermined timings in synchronization with the rotation of the sewing machine main shaft 28. The fabric speed timing signal generator 76 outputs a timing signal (pulse signal), and consists of a disk and a photo ink club attached to the sewing machine main shaft 28, and the sewing machine main shaft 28 synchronizes with the rotation of the sewing machine main shaft 28 to generate a needle at a predetermined timing. A needle swing timing signal generator 86 outputs a swing timing signal (pulse signal), the solenoid 73 is driven via a drive circuit 74, the sewing machine motor 67 is driven via a drive circuit 87, and the feeding stepping motor 59 is driven. circuit 88
The stepping motors 17 for swinging the needle bar are connected to input/output interfaces 90 via drive circuits 89, respectively.

The control device C includes a CPU (central processing unit) 92 and its C
An input/output interface 90, ROM 93, and RA connected to the PU 92 via a bus 9 such as a data bus.
It is composed of M94.

The following data and programs are stored in the ROM 93 in advance.

(1) Pattern data in which needle position data for each weaving operation is stored in correspondence with pattern numbers for each of a large number of patterns such as letters, symbols, marks, etc. (2) Set speed signal output from speed volume 83 and activation - A control program that controls the driving of the sewing machine motor 67 based on the start signal and stop signal output from the stop switch 78 (3) The stepping motor for swinging the needle bar at the needle swing timing based on the selected pattern data. control 17,
Feeding stepping motor 5 at cloth speed timing
(4) A control program for upper thread release start control that determines the start timing of the upper thread release period based on pattern data and a speed signal The upper thread release start control program includes the following data. and subroutines are stored in advance.

(i) Calculation subroutine for calculating the rotational speed of the sewing machine main shaft 28 based on the number of pulses of the input speed signal (ii) Number of clock pulses from the time of input of the reference signal for needle thread release to the timing of starting needle thread release A subroutine that determines the upper thread release start timing by calculating S using the formula: S=C/V + Am×V. However, C is a predetermined constant, and ■ is the rotation speed (rpm) of the sewing machine main shaft 28.
, coefficient A1 is 0~0.5mm, 0.6~1.0mm
, . . . For each cloth speed amount of 5.6 to 6.0 mm, the table is stored in advance so that the feed amount increases as the feed amount increases.

(iii) The number of clock pulses P from the time when the reference signal for releasing the upper thread is input to the phase of approximately 105 degrees at which the upper thread 14 starts to be restrained is calculated using the formula P-C, /V, and the upper thread is restrained. A subroutine that determines when to start. However, CI is a predetermined constant, and ■ is the rotational speed of the sewing machine main shaft 28 (
rpm) RAM94 contains the following information. A counter and memory are provided.

(1) First pulse counter 95 (2) that counts clock pulses input from the clock pulse generator 85
A second pulse counter 96 that counts the number of clock pulses (3) A solenoid flag memory 97 that stores the solenoid flag F that is set when the solenoid 73 is driven (4) Temporarily stores the results of arithmetic processing by the CPU 92 Various memories Next, a routine for controlling the start of needle thread release performed by the control device C of the sewing machine M will be described with reference to the flowchart shown in FIG. In addition, St (i=1.2.3...
・) is each step.

When the start/stop switch 78 is operated and a start signal is input, this control is started and initial settings are executed (S
l). At the same time, the activation signal causes the above (
Based on the program 2), the sewing machine motor 67 is driven to rotate the sewing machine main shaft 28, and it is determined whether the CPU 92 has detected the needle thread release reference signal (S2). As shown in FIG. 6, when the rotational phase of the sewing machine main shaft 28 is about 330 degrees, when the needle thread release reference signal is input from the needle thread release reference signal generator 71, it is determined as Yes at 82, and the needle thread release reference signal is input from the needle thread release reference signal generator 71. The count value M of the 1-pulse counter 95, the count value N of the 2nd pulse counter 96, and the solenoid flag memory 9
7 solenoid flags F are each cleared (S3).

Next, the speed signal (pulse signal) input from the speed detector 69 is read for a predetermined time (S4), and the ROM 93
Based on the subroutine (i), the rotational speed (2) of the main shaft 28 of the sewing machine is calculated (S5). Next, the feed amount adjustment signal from the feed amount adjustment volume 79 and the pattern selection switch 77
The next feed amount data is read based on the feed amount data of the pattern data selected in (S6). Next, using the rotational speed V of the sewing machine main shaft 28 and the feed amount data, the number of pulses S and the number of pulses P are respectively determined by the above calculation formula (
S7).

Next, this pulse number S is stored as the count value M of the first pulse counter 95, and the second pulse counter 95
The number of pulses P is stored as the number P of the number 6 (S
8). Next, when a clock pulse is input from the clock pulse generator 85 (39), the solenoid flag F
is reset (S10), the count value M and the count value N are each decremented by one (Sll
), and when this count value M is not "0", (312
), 39 to S12 are repeated. Then, when the count value M reaches "0", that is, at the timing to start releasing the upper thread based on the rotational speed ■ and the feed amount, the solenoid 73 is driven (S13), and the solenoid flag F is set (314). ). As a result, the actuating plate 72 rotates counterclockwise in plan view, and the needle thread 14 is released from the restrained state. Next, every time a clock pulse is input (S9
), the SIO determines Yes, the count value N is decremented by one (S15), and this plant value N becomes "0".
If not, I am (S16), S9~S10・315~S
16 is repeated. Then, when the count value N reaches rQJ, that is, at a predetermined upper thread restraint timing, the driving of the solenoid 73 is stopped (S17), and the process returns to S2.

As explained above, the larger the feed amount and the rotational speed (2) of the main shaft 28 of the sewing machine, the later the start timing of releasing the upper thread becomes. To explain the case where the feed amount is constant, as shown in FIG. 6, as the sewing speed increases, the needle thread release starts at a later timing. Furthermore, as shown in FIG. 9, when the rotational speed of the sewing machine main shaft 28 is constant (for example, about 40 rpm), the larger the feed amount, the later the start timing of needle thread release becomes. That is, in the first half of any cloth feeding operation, the upper thread 14 touches the thread path regulating plate 56.
and the movable ring 64, the feed dog 23
The upper thread 14 is reliably tightened in conjunction with the feeding operation and the raising operation of the thread take-up lever 48, and the second half of the cloth feeding operation is executed during the release period in which the upper thread 14 is released from the constraint. In conjunction with the feeding operation, the amount of thread necessary for forming the next stitch is supplied from the thread spool to the thread take-up 48. Moreover, by the time the sewing needle 12 reaches the throat plate 22, the upper thread 14 is again restrained, and the sewing operation is performed with the upper thread 14 restrained. Therefore, stable thread tension can be obtained at any sewing speed and feed amount, and beautiful stitches can be formed.

In the upper thread release start control program, the number of pulses S for the upper thread release start timing may be stored as a map using the feed amount and the rotational speed V of the sewing machine main shaft 28 as parameters.

The upper thread release reference signal generator 71 is configured to output a plurality of pulse signals from the rotation phase of 330 degrees, and these pulse signals are counted in steps 89 to S11 of the upper thread release start control. You can.

It goes without saying that the present invention can be similarly applied to a case where the pair of engaging bodies is configured to be driven by an electric actuator other than a solenoid.

Further, in the sewing machine of the present invention, the thread passage regulating device 54
While releasing the needle thread 14, the thread take-up 48 is held at the uppermost position to ensure the maximum system take-up amount.
The maximum system take-up amount may be ensured while the upper thread 14 is being released by using the mechanisms described in Japanese Patent Application No. 63-296787 and the like.

Furthermore, although the sewing machine of the present invention is configured to directly detect the speed of the main shaft 28 by the speed detector 69, the speed of the sewing machine main shaft 28 is indirectly detected by the set speed signal generated by the speed volume 830. You can do it like this.

[Brief explanation of the drawing]

Figure 1 is a functional block diagram showing the configuration of the present invention, Figures 2-
9 shows an embodiment of the present invention, FIG. 2 is a perspective view showing the internal mechanism of the sewing machine, FIG. 3 is a side view of the internal mechanism, FIG. 4 is a front view of the internal mechanism, and FIG. Figure 5 is Figure 3 V
-■ Line sectional view, Figure 6 is a time chart showing the operation of each mechanism of the sewing machine, Figure 7 is a block diagram of the control system of the sewing machine,
FIG. 8 is a schematic flowchart of the upper thread release start control routine, FIG. 9 is a diagram illustrating the upper thread release start timing based on various cloth feed amounts at a specific rotational speed of the main shaft of the sewing machine, and FIG. 10 is a conventional technique. FIG. 3 is a diagram illustrating the relationship between the cloth feeding operation and the upper thread release period. M... Sewing machine, 10... Needle bar, 12... Sewing needle, 14
・・Needle thread, 28・・Sewing machine main shaft, 34・・Pivot shaft,
36... Swing lever 41... Cloth feed mechanism, 43... Feed stand, 47... Vertical feed shaft, 48... Balance, 53...
Crank rod, 54... Thread passage regulating device, 55...
・Horizontal feed shaft, 56.. Thread path regulation plate, 59.. Stepping motor for feeding, 60.. Support plate, 64.. Movable wheel, 69.. Speed detector, 71.. Operating plate for upper thread release. Ya・Clock Pulse 93・・ROM. - First pulse counter, 67... Sewing machine motor, 70... Engaging body drive mechanism, reference signal generator, 72... 73... Solenoid, 85 Generator, 92... CPU. 94: RAM, 95: C: Control device. Figure 1

Claims (1)

[Claims] (1) A needle bar that is equipped with a sewing needle and is reciprocated up and down by the sewing machine motor via an upper shaft, a thread take-up that is synchronized with the needle bar and driven back and forth by the sewing machine motor, and a sewing needle that flows from the thread supply source through the thread take-up. It is installed upstream of the thread take-up in the thread path leading to the thread take-up.
a pair of engaging bodies that are movable relative to each other between an approach position where the needle thread is restrained and a remote position where the upper thread is not restrained; an engaging body driving means that drives the engaging bodies between the approach position and the remote position; and the needle bar. A sewing machine comprising: a feeding mechanism that transports a work cloth using a feed dog in synchronization with a feeding mechanism; a feeding stepping motor that drives the feeding mechanism; and a feeding control means that controls the feeding stepping motor. speed detection means for detecting the rotational speed of the upper shaft; and phase detection means for detecting the rotational phase of the upper shaft; a timing determining means for determining the start timing of the upper thread release period so that the start timing of the upper thread release period is delayed as a part of the transfer is executed and the rotational speed of the upper shaft increases; and at the start timing determined by the timing determining means. 1. A needle thread control device for a sewing machine, comprising: control means for controlling an engaging body drive means to release the needle thread.