JP2003164686A - Device and method for controlling seam of sewing machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce tension applied to a sewing thread of a sewing machine by combining supply of compulsively drawn thread and bobbin thread of a tension according to the kinds of a winding pattern rotating balance and enable zigzag stitch, embroidering, and straight stitch with uniform shrinkage and tightness even if a thin or soft fabric is sewn at a high speed. <P>SOLUTION: A device and a method of controlling needle thread supply for the sewing machine which is of winding pattern rotating balance form, in which a needle thread holding means and a friction drawing out type needle thread supplying roller with a constant speed drive encoder are placed in the upper stream and the down stream within a needle thread supplying path, respectively. The holding means holds the needle thread at a shuttle passing signal of the needle thread, liberates it at a cloth fastening ending signal, measures the encoder, moves up and holds the needle thread even at a signal in which a measured value is in accord with a specified one, the bobbin thread establishes supply tension according to the kinds of a non rotary shuttle bobbin and sewing room operation cloth, and tension applied to sewing thread is reduced. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stitch forming control device and method in a sewing machine, which adopts a set amount forced feeding system for supplying upper thread, and adjusts the tension generated in the lower thread to the physical properties of the sewing cloth. Sewing control of the sewing machine, which is adjusted to the minimum necessary and enables not only sewing of medium-thickness and heavy-weight materials, but also extremely thin materials, light-weight materials, and other favorable sewing conditions under all sewing conditions. An apparatus and a method.

[0002]

2. Description of the Related Art In a conventional sewing machine, in order to allow adjustment of the upper thread tension by a tension plate, the amount of the upper thread consumed for the first stitch by the upper thread picking action of a link balance is fed out from the tension plate.
The bobbin thread is required by the interaction between the needle thread pick-up tension after being entangled with the needle thread loop by the reciprocating motion of the needle and the action of the shuttle, and the bobbin thread tension given by the adjusting spring of the bobbin bobbin case. The bobbin thread consumption is fed to form a seam.

As described above, in the conventional sewing method in which the amount of the upper thread consumed for forming the first stitch is controlled by adjusting and adjusting the tension of the sewing thread, only the magnitude of the tension applied to the sewing thread is adjusted after all. Since the required thread amount is regulated, the compatibility with the characteristics of the sewing cloth, the sewing conditions, etc. may be lost.

FIG. 5 shows low-speed sewing (for household use, 500 stitches /
Min) standard conditions (two pieces of cotton broad cloth, threads of Tetoron spun thread # 60) are allowed, and a correlation diagram of upper and lower thread tensions at a balanced sewing point is shown. For example, in FIG. The correlation of the tension applied to the upper and lower threads when the link balance is adopted in is the link balance curve in the chart.
It is shown by a folding type rotary balance, a blade type rotary balance curve, and a winding type rotary balance curve.

When a known link balance is adopted as the upper thread take-up means, the upper thread is unnecessarily supplied to the thread take-up device side when an abnormal tension is generated in the upper thread at the time of pulling out the hook during one cycle of sewing. In order to prevent this, it was general to adjust the needle thread supply tension by the tension disc to a large degree.
In order to form a balanced seam, it is necessary to set the size of the lower thread tension so as to match the adjusted upper thread tension (see FIG. 5). As a result, the magnitude of the tension applied to the sewing thread is increased. Cannot be reduced [Prof. Kamada's Proceedings, The Textile Machinery Society of Japan, Vol. 6, No. 6 (1998)].

If the tension generated in the sewing thread during the sewing operation is large, the thread is untwisted and the thread strength is reduced, or the sewing thread (made of synthetic resin fiber, spandex fiber, wool, etc.) which is easily stretched is used. Is difficult, and especially in the case of sewing ultra-thin material or thin material cloth, there is a disadvantage that shrinkage or tightness of the sewing occurs. The abnormal tension generated in this type of needle thread is small at low speeds but increases as the speed increases, so it was difficult to sew a thin material well with a high-speed sewing machine such as an industrial sewing machine. .

Therefore, the upper thread tension is adapted to the lower thread tension to control the sewing amount of the upper thread which is consumed for the first stitch, instead of the so-called conventional needle thread feeding method based on tension adjustment. A device or method for controlling the upper thread supply amount of a sewing machine, in which the amount of upper thread consumed for each stitch at first stitch is calculated and set in advance and forcibly fed out, and the minimum tension required for sewing is applied. However, prior to the filing of the present application, for example, JP-A-61-279283, "Method for controlling the sewing tone of a pattern sewing machine", JP-A-61-279294, "Needle thread supply control device", and JP-A-1-265995. Technical developments have been made such as "a needle thread supply control method" or Japanese Patent Laid-Open No. 2001-178976, "a complete stitch formation control device in a sewing machine", but due to various circumstances, it has been widely used. Tena .

[0008]

SUMMARY OF THE INVENTION The present invention relates to an improved technique of the above-mentioned conventional device and method adopting the upper yarn supply amount forced feeding system. The present invention relates to a winding type rotary balance as a needle thread pick-up means (Japanese Patent Publication No. 35-13442).
JP-B-43-26074 or JP-B-43-260
No. 75 publication), the upper thread designated amount forced-feeding system is assembled, and the lower thread bobbin is provided with a lower thread tension reducing means such as a lightweight material, a bobbinless bobbin, a non-rotating bobbin, and Set the bobbin thread supply tension according to the physical properties of the sewing cloth,

In the sewing operation, the untwisting of the sewing thread can be reduced to enable the use of a stretchable sewing thread, and in particular, the zigzag stitch and the unevenness of the knotting point of the sewing thread which tends to occur in the embroidery sewing are improved.
Needless to say, sewing of materials such as medium-weight materials, heavy materials, and extra-thick materials,
In particular, it enables the formation of good stitches and proper cloth tightening conditions even for sewing under all sewing conditions, such as balanced stitching for ultra-thin materials and thin materials, prevention and removal of unevenness in sewing tightness, etc. An object of the present invention is to provide a stitch forming control device and method for a sewing machine.

[0010]

The present invention is configured by combining the following requirements in order to solve the above problems and objects. (1) Upper thread gripping means provided on the upstream side in the upper thread supply path that connects the upper thread supply side and the upper thread pick-up device, and the upper thread is gripped based on the signal obtained by measuring the rotational phase of the upper shaft of the sewing machine. And the needle thread gripping means for repeating the release, a means for measuring the supply of a designated amount of the upper thread to be fed, and advancing the needle thread gripping time of the needle thread gripping means, the needle thread supply path A constant speed driven friction feeding type upper thread supply roller provided on the downstream side of the upper thread gripping means, and the upper thread that supplies the upper thread to the upper thread pick-up device side only during the release period of the upper thread gripping means. A pair of pins having different distances from the center are planted on the inner and outer surfaces of the disc, respectively, and the central angle at which each pin surrounds the center of the disc is set to a predetermined angle. , The phase of the pins implanted on each surface is shifted by a predetermined angle between the inner and outer surfaces. Boss was rotating disc, travels through the periphery thereof in proximity to the outer periphery of the rotating disk, the rotation direction of the rotary disk,
The upper thread supply side guide provided on the sewing machine face plate side, the thread reversing guide and the needle side guide, and the upper thread supplied from the upper thread amount compulsory supply means side in order at substantially equal intervals. To the needle side guide through the outer peripheral side of the pin arranged in the disc inner path, the thread inversion guide, the outer peripheral side of the pin arranged in the outer disc outer path, and the direction opposite to the rotating direction of the rotating disc. The upper thread take-up means consisting of a winding type rotary balance passed through the needle hole side, the lower thread bobbin formed by a material with a small specific gravity, the bobbinless bobbin or the non-rotating bobbin, etc. to match the type of sewing cloth. A stitch forming control device for a sewing machine, wherein a bobbin case provided with a bobbin thread tension adjusting spring for setting a supply tension is inserted and combined, and the hook is provided.

(2) For supplying the lower thread, a method of setting the supply tension according to the type of sewing cloth is used, and for supplying the upper thread, the upper thread consumption amount required for each stitch is preset and forced. A stitch forming control method for a sewing machine, which employs a winding method and a winding-type rotary balance method as upper thread picking-up means, respectively, which are combined in the order of steps.

(3) The needle thread consumption required for each stitch is
The stitch formation control method according to the above item (2) of the sewing machine, in which the length is set to a length calculated based on the following equation, and the stitch is forcibly extended for each stitch. D x (1-sewing tightening rate according to the type of sewing cloth) + PP = sewing pitch D = cloth thickness of sewing cloth

(3) The needle thread consumption required for each stitch is
The stitch formation control method according to item (2) of the zigzag stitch or embroidery stitch sewing machine in which the stitch length is calculated based on the following formula and forcedly feeds out for each stitch. D x (1-sewing tightening rate according to the type of sewing cloth) + √
(P ² + W ² ) P = sewing pitch W = stitch width of zigzag stitch D = thickness of sewing cloth

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is a cloth tightening condition which is consumed for forming a balanced stitch for each stitch (pitch and swing width of a needle) and which is suitable for the kind (thickness and elasticity) of the sewing cloth. The amount of needle thread consumption required to form the yarn is calculated and specified in advance, and forced supply is performed. During sewing, the upper thread amount forced supply system is adopted in which the upper thread gripping means releases the upper thread gripping means only during the period in which the upper thread of the above-specified length (quantity) is fed out. By adopting the winding type rotary balance as the upper thread take-up means, the magnitude of the tension applied to the upper thread during one sewing cycle is greatly reduced. The bobbin thread bobbin is made of lightweight material, or bobbinless bobbin or non-rotating bobbin is used to reduce or reduce the bobbin thread tension even if the sewing speed is increased. By adjusting the bobbin thread tension adjusting spring provided, set according to the type of sewing cloth.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram schematically showing a preferred example of a needle thread feed control device and method of the present invention applied to a single-needle lockstitch sewing machine including a zigzag stitch sewing machine. The method is generally configured by combining the members described below.

Starting from the side of the sewing needle 1 toward the upper thread bobbin 13, along the path of the upper thread 17, a pair of sewing needle 1, needle side thread guide 2, and a pair of inner and outer surfaces of the rotary disc S are respectively planted. An upper thread pick-up means (apparatus) B including a winding rotary balance having pins 3 and 5, a reverse thread guide 4, a supply side thread guide 6, a thread take-up spring 7 and a guide 8 and a friction feeding type constant speed drive with an encoder. Thread supply rollers 9 and 10, electromagnetic needle thread gripping means (hereinafter referred to as "needle thread gripper" or "gripping machine") 1
1. A combination of an upper thread amount compulsory supply means (upper thread supply amount control device) A including a base tension tray 12 and an upper thread bobbin 13. The pulley 1 is provided on the sewing machine body (frame) side.
4 and an upper shaft 15 to which a rotary encoder 16 made of a disk provided with slits equally divided on the peripheral edge is attached.

A shuttle C equipped with a bobbin thread bobbin is arranged in the space of the lower plate corresponding to the reciprocating direction of the sewing needle 1, and the sewing cloth 18 is sewn by an inner shuttle which rotates in synchronization with the reciprocating operation of the sewing needle 1. A sword tip is hooked on the loop of the upper thread that is pierced and fed, the inner hook that accommodates the lower thread bobbin passes through, and the lower thread 19 that is fed from the bobbin is entangled to sew the sewing cloth 18 and form stitches. To do. The base tension tray 12 is provided in order to apply a tension to the needle thread at the time of supply so that the needle thread 17 connecting between the tray and the needle thread pick-up device B is not loosened.

The structure of the upper thread supply amount control device A will be described. A driven roller 10 axially supported in parallel with the rotation axis of a motor driven upper thread supply roller (supply roller) 9 is provided, and both roller peripheral surfaces are brought into contact with each other. , The upper thread 17 is sandwiched between them and passed. That is, the driven roller 10 is provided on the frame of the upper thread supply amount control device A, and the upper thread supply roller 9
Lever with one end bearing on a support shaft provided in parallel with the rotating shaft of
0b is supported in parallel with the rotating shaft of the supply roller 9, and torque is applied to the lever 10b so that the peripheral surface of the driven roller is constantly in pressure contact with the peripheral surface of the supply roller 9.

Gears 9a and 10a are concentrically fixed to the end surfaces of the needle thread supplying roller 9 and the driven roller 10, respectively, and when the peripheral surfaces of the rollers 9 and 10 are in contact with each other and pressed. The supply rollers 9 and 10 are meshed with each other so that the peripheral surfaces of the supply rollers 9 and 10 always move in the same direction at the same speed. In addition, the meshing of the gears 9a and 10a is performed by the both rollers 9, 1
It does not come off even if the 0th surface is slightly separated. Therefore, even if the thickness (count) of the upper thread sandwiched between the supply rollers 9 and 10 may slightly change, the rollers 9 and 10
The press contact force and the needle thread feeding operation do not change. By providing this structure, the feeding action of the upper yarn 18 sandwiched between the peripheral surfaces of the supply rollers 9 and 10 is surely performed without slipping if necessary.

The force by which the above-mentioned rollers convey the upper thread is equal to the amount of rotation of the rollers 9 and 10 due to the friction between the peripheral surface of the supply roller and the upper thread 17, and the base tension tray 12 is provided.
The size is set to be large enough to reliably feed the upper thread 17 to the upper thread pick-up device B side against the supply tension of the upper thread 17 applied in step 1. However, when the upper thread is gripped by the upper thread gripper 11 arranged on the upstream side, both rollers 9, 10
A slip occurs between the peripheral surface and the upper thread 17, and the upper thread supply is stopped. At this time, the pressing force of both rollers must be large enough not to damage the strength and characteristics of the upper thread 17 in a short time. Further, the upper thread gripping force by the gripper 11 is such that the upper thread is not fed out to the upper thread pick-up device B side even when the upper thread 17 is subjected to sewing tension (the magnitude of the gripping force). ≫ It is also the size of (tightening tension).

Since the upper thread supply roller 9 is constantly rotating, there is no change in inertia in the upper thread delivery operation, and when the upper thread grasper 11 releases the upper thread, the predetermined upper thread delivery amount is immediately reached. Can be fed to the upper thread pick-up device B side, and the feeding operation can be performed precisely and reliably. Gripper 11
At the same time when the upper thread is released from gripping, the encoder 9b provided on the upper thread supply roller 9 starts measuring the upper thread delivery length (closing the measurement circuit), and the supply rollers 9 and 10 rotate to deliver the first thread. Needle thread consumed for each sewing 1
A signal when the measured signal value reaches the set length by comparing the signal for measuring the length (quantity) of 7 with the supply length of the needle thread calculated and set (programmed) for each stitch in advance. Thus, the upper thread gripper 11 is lifted up to grip the upper thread 17, and then the feeding of the upper thread is stopped.

In the upper thread supply amount control device A, the length (amount) of feeding the upper thread is essential. In short, the upper thread grasper 11 operates the upper thread grasper 11 to operate the upper thread grasper 11 to grasp the upper thread 17. The length is such that the supply rollers 9 and 10 can deliver the upper thread 17 within the period until the start.

As an example of the structure of the upper thread gripper 11, a movable iron piece type electromagnetic coil is used to dispose an upper thread supply path between the movable iron piece and the winding frame of the coil, and to the coil (from the rotary encoder 16). (Based on the signal of (1)), the upper thread 17 is sandwiched between the iron piece and the coil winding frame to hold the upper thread, or the movable iron piece is always urged by a spring to keep the iron piece The upper thread is sandwiched between the coil winding frame and the upper thread 17, and the upper thread 17 is gripped, but the gap between the iron piece and the coil winding is opened to release the upper thread grip only during the time when the current is applied to the coil. There is a means of. In the above description, the gripper 11
The movable iron piece type electromagnetic coil was mentioned as an example of the configuration of
The use of a movable iron core type electromagnetic coil or a movable coil type electromagnetic device as the upper thread gripper 11 is not excluded.

Next, the setting of the feeding length (amount) of the upper thread, which is designated in advance for each stitch, will be described. FIG. 2 shows the stitch structure for each pitch P.
(B) shows the case where there is an entanglement point of the upper thread and the lower thread at the intermediate position of the cloth thickness D to be sewn (balance stitch, complete stitch that meets the sewing condition). Regarding Fig. 2, "Analysis of seam structure and tightness in lockstitch sewing machine" Toru Matsubara Vol. 40, No. 10 (1984) and JIS Industrial Sewing Machine Thread Tightness Test Method B905
6 (1986). In order to sew the sewing cloth together, it is necessary to apply an appropriate tightening tension to the sewing thread, and the stitch configuration at that time is more or less, from the standard stitch (rectangular model) shown in FIG. 2 (a) to FIG. 2 (b). It is common to transform into the actual stitches (elliptical stitch model) in the complete sewing of. This applies to any of straight stitch, zigzag stitch or embroidery stitch.

FIG. 2C shows the supply (consumption) length of the upper and lower stitching threads corresponding to the standard stitch in FIG. 2A. In this case, the length of the upper thread required for the first stitch = P + 2d ₁ However, D = 2d ₁ Fig. 2 (d) shows the supply (consumption) length of the upper and lower sewing threads corresponding to the actual stitch in Fig. (B), and the length of the upper thread required for the first stitch at that time. = P + 2d ₂ = P + (D-
d ₃ ) However, D = 2d ₂ + d ₃ , and d ₃ obtained by subtracting 2d ₂ from the cloth thickness D is the tightening margin of the cloth. The above is a condition of balanced sewing,
In practice, the upper thread tightening margin (rate) and the lower thread tightening margin (rate) are often not the same.

As a matter of course, if the tension ratio of the upper and lower sewing threads is broken, the entanglement point of the upper thread and the lower thread may be displaced from the middle position of the sewing cloth thickness. It is difficult to maintain the entanglement point of the sewing thread at the middle position of the cloth thickness of sewing cloth when sewing thin and flexible cloth such as ultra-thin material or thin material cloth. Limited to things. In this case, the effect of this embodiment is particularly expected.

Regarding the tightening margin (tightening ratio) d ₃ ,
In the change diagram of the balanced sewing point and the tightening rate (one example) in FIG. 3, the cloth thickness corresponding to the x axis, the type of the sewing cloth, the tightening rate d _3, and the magnitude of the tension applied to the bobbin thread according to the sewing cloth (g ), In the lower figure, the y-axis is the cloth thickness D = 1 and d ₂ , and the cloth tightness ratio d ₃
In the y-axis direction, which is a line symmetry with respect to a straight line extending in the x-axis direction passing through the middle position of the cloth thickness D, that is, 0.5 in the y-axis and extending in the vertical direction. Also, the tightness ratio d of the cloth according to each sewing cloth type
₃ is represented. There, d ₂ = (1-d ₃ ) / 2
This is shown in the case of balanced sewing in which the upper and lower thread tightening ratios are equal.

From the above material, the pay-out length of the upper thread amount consumed per stitch = P + 2d ₂ = P + (D-d ₃ ) is derived. Also, the magnitude of the lower thread supply tension and the tightening rate d
₃ is, for example, an extremely thin type of sewing cloth and has a lower thread tension of 3 to
In the case of 5 g, d ₃ is about 0.05 to 0.1. In the case of a thin product, when the bobbin thread tension is 7 g, the tightness ratio d ₃ is 0.
Numerical values such as 2, ... are illustrated (see FIG. 3).

Further, in calculating and setting the needle thread feeding length (consumption amount) (in the case of zigzag stitching and embroidery stitching)
Not only the pitch P but also the swing width W of the needle needs to be included in the condition. In that case, M = √ (P
² + W ² ) is substituted. That is, the upper thread feeding length = 2d
₂ + √ (P ² + W ² ) = D × (1-d ₃ ) + M In the above setting of D, cloth thickness measuring means is attached to the cloth retainer, and D is automatically detected and input. , JP-A-61-1
The inventions described in JP-A-159989, JP-A-61-279283 or JP-A-61-290493 have also been proposed as an example.

Further, in calculating and setting the length (consumption amount) of the upper thread feeding, the inertial force acts as the rotation speed of the sewing machine increases, and the feed pitch of the actual sewing cloth tends to be longer than the set pitch P. Must be taken into account. For example, there is a document that the feed pitch of the sewing cloth is extended by about 5% from the set pitch P every time the sewing speed of the sewing machine is increased by 1000 stitches / minute. If the pitch of the cloth feed substantially increases after setting the upper thread feeding length (consumption amount), the tightening margin d ₃ naturally increases, so that the phenomenon of tightening and shrinking of the stitches may occur with thin material. is there. In addition to the above conditions, it is necessary to include an element of sewing speed of the sewing machine in the setting program of the needle thread feeding length (consumption amount) for one stitch pitch (Japanese Patent Laid-Open No. 2001-1).
78976).

On the other hand, the lower thread consumption amount (length) is shown in FIG.
Referring to (b) and (d), the magnitude of the lower thread supply tension set according to the type of sewing cloth is directly related. In this embodiment, after the needle thread supply length per stitch is determined,
Whether or not the sewing tightness is good depends on the magnitude of the lower thread supply tension, and by using the lower thread supply method described later,
It becomes easy to freely set the lower thread supply tension according to the type of sewing cloth shown in FIG. The balanced stitch of this embodiment is
It is premised that the setting is made as described in the section [0028] (see FIG. 3) in order to optimize the lower thread supply tension (an example) according to the type of sewing cloth.

Since the magnitude of the above-mentioned bobbin thread supply tension is sufficient for the kind of sewing cloth, the tension applied to the upper thread is also small accordingly (see FIG. 5, winding-type rotary balance curve, etc.). As a result, it is possible to prevent untwisting of the sewing thread, and it is possible to use sewing thread that stretches easily.In addition, the capacity of the needle thread gripping means is reduced, and the linearity of the stitch marks is maintained even at the time of high-speed sewing. To improve, or sew ultra-thin or thin materials,
A special effect such as the formation of good stitches without tightness or shrinkage of stitches can be obtained.

FIG. 4 is a chart showing a needle thread feed-out amount diagram, a needle thread tension change curve, an upper thread gripping period, a current value at the time of grasping the upper thread, and an operation curve chart of the balance in each sewing cycle. Is the upper axis phase (rotation angle) θ, the upper thread feeding (feed) length (amount), the upper thread tension, the upper thread gripping force (current value), and the operation curve of the balance on the y axis. In the figure,
The speed of sewing of the sewing machine is represented by expansion and contraction of one cycle of sewing on the x-axis. That is, the scale in the x-axis direction is represented narrower as the sewing speed of the sewing machine increases. For example, the diagram in FIG.
If the case of 0 stitches / minute is shown, FIG. 4C shows a diagram of the same model for about 1200 stitches / minute.

FIGS. 4 (b) and 4 (c) show the charts when the sewing speed is different.
, Sewing speed 5000 stitches / minute, 1 cycle time = 12
The following is an explanation using a chart targeting ms / needle as an example. FIG. 4 (b) shows a schematic view of the material measured over a plurality of cycles in units of one sewing cycle (one stitch pitch), and the upper side with the x-axis as a boundary,
The upper thread tension change curve, the upper thread gripping period, the current value when grasping the upper thread, the lower side is a table showing an example of the operation curve of the balance,
The x-axis in the figure is the upper shaft phase, specifically, the upper shaft 15 or the pulley 1.
4, the upper thread tension, the upper thread gripping force (current value), and the operation curve of the balance are plotted on the rotation angle θ and the y axis of FIG. In the figure, (a) is shown in the x-axis direction along the operation curve of the lower balance with the x-axis as the boundary, (b) is the time when the cloth tension is generated in the sewing thread, and (b) is the balance Death (highest)
Point ((c)) is the point at which the tension of cloth tightening disappears, which is about the time θ ₁
Overlap with. (D) shows the dead point (bottom) under the balance.

The above chart will be described in comparison with the schematic diagram of the sewing machine configuration shown in FIG. The upper thread tension change curve of the upper side of the x-axis will be described. Regarding the tension curve generated in the upper thread during one cycle of the sewing operation, the tension required for sewing the sewing cloth is applied to the upper thread, and the sewing is completed. When the upper thread is counted from θ ₁ , the upper thread 17 is abnormally tensioned at the time of pulling out the hook from the hook after passing θ ₂ just before the needle is passed over the hook and pulling out from the hook with the operation of picking the upper thread. Thereafter, as the balance approaches the top dead center, the tension required for sewing the sewing cloth is applied to the upper thread, and the sewing is completed, and one cycle is completed.

The upper thread tension other than the above-mentioned sewing tightening tension is such that the upper thread 17 turns around the outside of the hook (over the hook) during sewing, and a locking piece that stops the inner hook against the rotational torque of the outer hook. Abnormal tension applied when pushing and opening between the inner hook and the inner hook, which is unavoidably generated due to the mechanism of the sewing machine.In particular, the hook stop pull-out tension causes the inner hook to move as the sewing speed of the sewing machine increases. Since the force applied to the locking portion to be stopped (relative to the rotation of the outer hook) is increased, the abnormal tension generated in the upper thread tends to be increased. The operation of the electromagnetic type upper thread gripper 11 shuts off the abnormal tension and the sewing tightening tension generated in the upper thread to the upper thread supply side, and the upper thread 17 calculates the feeding length (quantity) calculated and set in advance. Since the upper thread 17 is constrained with respect to the thread supply side so as not to be pulled out beyond the thread pick-up means B side,
The capacity of the needle thread gripper 11 cannot be reduced below a certain level.

From the above description, the operation period (upper thread grasping) of the electromagnetic type upper thread gripper 11 is at least the timing θ ₂ before the upper thread is pulled out of the hook and immediately before the upper thread is tensioned. It is understood that the starting point is, and the end of θ ₁ at the end of the sewing tension applied to the needle thread is released.

In the charts of FIGS. 4 (b) and 4 (c), the gripping period of the electromagnetic needle thread gripping device 11 is a region shown by a rough hatching to the lower right, and the strength of the gripping force is As mentioned above, the height of the upper thread sewing tension curve and the maximum abnormal tension curve must be exceeded (since the abnormal tension magnitude is not constant). Although the strength of the grasping force of the upper thread grasper 11 is determined based on the current value supplied to the upper thread grasper, the magnitude of the tension applied to the sewing thread is adjusted to the sewing material in comparison with the conventional method. In this embodiment, which can be set small, the magnitude of the current value for gripping the needle thread or the capacity of the gripper 11 can be made smaller as described above. Further, this forcible supply method of the upper thread amount can employ the simplest and cheapest device including the upper thread holding means of one magnet.

The operation of the upper thread gripper 11 is controlled mainly based on the angle signal of the rotary encoder 16 attached to the upper shaft 15. That is, passing the needle thread 17 over the hook,
Immediately before the rotary encoder 16 passes over the hook, since there is a one-to-one correspondence between the timing when the hook is pulled out and when the sewing is tightened and the rotation angle (phase) of the pulley 14 and the rotary encoder 16 attached to the upper shaft 15 of the sewing machine is maintained. Angle θ ₂
A gripping current is applied to the upper thread gripper 11 based on the signal,
The gripping current is interrupted and the needle thread grip is released by the angle θ ₁ signal corresponding to the time when the sewing tension of the rotary encoder 16 disappears.

FIG. 4 (a) shows a needle thread amount forced supply length diagram when operating under the same conditions as the chart of FIG. 4 (b), and in FIG. a point y axis gripper 11 fit timing theta ₁ which tension is lost is through the time of releasing the gripping of the upper thread (iii) crosses the x-axis as a base point 0, extending upward to the right (upper thread supply) linear The upper y coordinate is
It shows the amount of needle thread fed out per stitch at the sewing machine. The above straight line intersects with the y-axis (d) passing through the time point θ ₂ immediately before the needle thread passes over the shuttle (as shown at the left end of FIG. 4B), that is, the gripper 11 grips the needle thread. By the time
It is growing.

Since it is as described above, the maximum length L of the upper thread that can be fed out per one stitch (1 pitch) is extended within the period in which the gripper 11 releases the upper thread. It is understood that this corresponds to the length L of the upper thread [Fig. 4 (a)].
Left side reference] (see JP-A-62-290492).

In FIGS. 4 (a) and 4 (b), the maximum length L of the upper thread that can be fed out (the upper thread supply amount when the upper thread grip release period is the longest at the maximum sewing speed) is given by the supply roller. Number of readings of encoder 9b attached to 9 and 10 m
Correspondingly displayed. However, as will be described later, the upper thread delivery maximum length (amount) L is not always used, and the upper thread delivery length designated in advance is extremely shorter than the maximum length L (m >> m ₁ , m ₂ , m ₃ ,
...), and usually the gripper 11 is operated based on this.

Next, when the rotation speed of the sewing machine becomes slower, the time required for one stitch sewing becomes relatively longer, and one cycle of sewing is expressed as a whole extending in the x-axis direction. As shown in c), the time when the gripper 11 releases the upper thread grip, that is, the time from the timing θ ₁ to the timing θ ₂ , becomes longer, and the upper limit of the length of the upper thread that can be fed per stitch is extended. looks like.

However, since the upper thread supply rollers 9 and 10 rotate at a constant speed, the upper thread supply speed is constant regardless of the rotation speed of the sewing machine, and the upper thread can be supplied at a fixed maximum speed. The maximum length L (the number of readings by the corresponding encoder is m) is set so as not to change even when the rotation speed of the sewing machine is reduced. In short, even when the rotation speed of the sewing machine is reduced, the time during which the upper thread gripper 11 releases the upper thread is not changed. In FIG. 4 (c), when the area hatched to the lower left is the maximum speed, when the rotation speed of the sewing machine is decreased from the time when the needle thread gripper should be operated [y-axis (d)]. It shows a period in which a current is applied to the gripper by connecting a gap time until the operation timing θ ₂ of the needle thread gripper 11.

In FIGS. 4 (a) and 4 (b), the measured value of the upper thread forced feed amount (length) for each stitch of the sewing machine is
Setting values m ₁ , m ₂ , m ₃ , of the program described above (created by specifying the number of readings by the supply roller-attached encoder 9b for each stitch based on the sewing conditions)
The number of readings by the encoder 9b for each stitch is determined by comparing with the upper thread feeding length m ₁ specified in the program.
When m ₂ , m ₃ , ... is reached, if the upper thread grasper 11 is operated to be advanced before the timing θ ₂ to grasp the upper thread, the upper thread feeding operation after that point is stopped and designated. According to the program described above, it is possible to control the feeding lengths L ₁ , L ₂ , L ₃ ... Of the upper thread on the y axis [see FIG. 4 (a)] (see Japanese Patent No. 2592633).

The above control is shown in FIGS. 4 (b) and 4 (c).
At least the set value m₁, M_Two, M _Three,… And encoder
When the number read on 9b matches, the needle thread gripper 11
Circuit for raising operation and relevant operation of needle thread gripper 11
Signal from the rotary encoder 16 to grasp the upper thread 17
Timing to start holding θ_TwoAdd means to continue until
Achieved by and. In the figure above,
The period indicated by the time when the needle thread gripper 11 is moved up
This is the place that shows the distance. Also, in FIG. 4 (c), the lower left
The rough hatched area connects the gap times.
At the timing θ_TwoPeriod to continue until
Is shown.

As described above, the needle thread feeding lengths L ₁ , L ₂ , L ₃ , ... (≦ L) for each stitch are provided for each pitch regardless of the sewing speed of the sewing machine. It will be appreciated that this can be controlled by setting the number of encoder readings m ₁ , m ₂ , m ₃ , ... (≦ m) in the program. However, due to the mechanism, the upper limit of the number of readings for each pitch of the stitch set in the program cannot be set to be equal to or more than the set value m corresponding to the upper thread length L that can be paid out at the maximum sewing speed of the sewing machine.

Next, the upper thread feeding lengths L ₁ , L ₂ ,
The following is a description of L ₃ , ... (≦ L). Explaining the needle thread feeding length L _{1 by} taking the case of straight advance sewing as an example, L ₁ (the needle thread feeding length per stitch)
In general, the requirements that compose the above include P, D, and d ₃ (see the [0025] column). Therefore, even if the stitch pitch and the thickness of the sewing cloth are the decisive factors for specifying the needle thread let-up length, the type of sewing cloth shows the upper thread let-up in the form of the sewing tightening rate. It will be appreciated that it affects length.

If one or more conditions among the above P, D and d ₃ are changed, the needle thread let-out length L ₁ becomes L ₂ or L ₃ accordingly. In addition, it must be remembered that the rotation speed of the sewing machine also affects the upper thread feeding length setting as described above. In FIGS. 4 (a) and 4 (b), the upper thread feeding length is continuously changed as L ₁ , L ₂ , L ₃ , ... For each stitch, but it is displayed straight. If the sewing conditions do not change during sewing, it is natural that if the upper thread take-up length is set to L ₁ as an initial condition, then the pay-out length becomes L ₁ after that.

In the case of zigzag stitching or embroidery stitching, unlike the above, √ (P ² +
W ² ) is included (see column [0029]). Therefore, if any one or more requirements of P, W, D and d ₃ are changed, the needle thread feeding length L is changed accordingly.
Changes to ₁ , L ₂ or changes to L ₃ . In the case of zigzag stitching and embroidery stitching, it is general that both P and W continuously change. Other conditions are the same as in the case of straight advance sewing.

If P or / and W change every stitch,
Along with that, the needle feed length is L ₁ , L for each stitch.
_{, 2} , L ₃ , ..., Therefore, the set value specified in advance must be m ₁ , m ₂ , m ₃ , ... (See the column [0045]). The variation of the upper thread supply length schematically shown in FIGS. 4A and 4B represents the case of the embroidery sewing.

In this embodiment (actual stitch), it is premised that the lower thread supply tension is set according to the kind of sewing cloth and then the sewing is performed. That is, as an example is shown in the lower part of FIG. 3, the size of the lower thread supply tension corresponding to the type of sewing cloth is set. At this time, referring to the upper and lower thread tension correlation diagram (FIG. 5) at the knitting point of the sewing thread under the standard sewing conditions, the upper thread when each balance mechanism is adopted according to the magnitude of the lower thread supply tension. It can be estimated how large the tension will be.

For example, assuming that the sewing cloth is a medium-weight material, in the case of the winding type rotary balance, when the corresponding lower thread supply tension is approximately 10 g, the sewing tension applied to the upper thread is slightly higher than this. It becomes the size. When the link balance is adopted, the sewing tension applied to the upper thread is about 60 g. The effect when the tension applied to the sewing thread at the time of sewing is reduced as described above is very convenient as described above, particularly when high-speed sewing of ultra-thin material and thin material cloth is performed.

Further, in the case of the conventional upper thread supply system by adjusting the tension using a tension plate, it is impossible to eliminate the thread passage clearance on the back side of the cloth retainer, so that the sewing shrinkage of the cloth and the upper thread Although the uneven tightening could not be resolved, the upper thread can be forcibly pulled up by using the above-mentioned upper thread amount forced supply method (installation of upper thread gripping means), and the needle hole on the back of the cloth retainer Since it is possible to eliminate the thread passage relief of the part and make it a flat surface so that the cloth can be pressed completely, the cloth shrinkage on the left and right of the satin stitch of the zigzag stitch and the good effect on the balanced stitching of the upper and lower threads of the left and right seams are achieved. It became so.

Next, the structure and operation of the needle thread pick-up device B will be described. The main part of the needle thread pick-up device B is a winding type rotary balance schematically shown in FIGS. 1, 6 and 7, and the configuration of the winding type rotary balance is as described below. That is, the center 0 is fixed to the upper shaft 15 of the sewing machine, and the needle thread contact pins 3a (5a) are separated from the inner and outer surfaces of the disk S that rotates clockwise in positions near the rotation center 0 measured in the radial direction. Similarly, contact pins 3b (5b) are planted in the same place, and contact pins (hereinafter referred to as "pins") 3a (5)
a), 3b (5b) is stretched with respect to the center 0 (measured in the clockwise direction, the same applies hereinafter), the angle (center angle) is 100 ° to 1
The angle is 40 °, and the ratio of the radial distance between the center 0 and the pin 3a (5a) and the radial distance between the center 0 and the pin 3b (5b) is set to about 0.6: 1.0. Further, the angle (center angle) formed by the pins 3a and 5a on both side surfaces of the disk S with respect to the center 0 point is approximately 130 °.

Further, the supply side thread guide 6 which is guided along the supply path of the upper thread 17 through the guide 8 and the thread take-up spring 7 to the inner path of the disk S is brought close to the outer circumference of the disk S (in the figure). The reverse thread guide 4 which is fixed to the sewing machine face plate diagonally above and to the left of the disk and guides the upper thread 17 from the inner path to the outer path is provided on the side opposite to the supply side thread guide 6 with the rotation center 0 of the disk S interposed therebetween. A needle side guide 2 that is close to the outer periphery of the plate S and is fixed to the sewing machine face plate on the right side of the plate S, and guides it from the outer path of the disc S to the thread hole of the needle 1 passes through the rotation center 0 of the disc S vertically. It is fixed to the sewing machine face plate, which is close to the lower peripheral edge of the disc S on the line.

The upper thread 17 is guided to the thread take-up spring 7 through the guide 8, and then is guided to the inner path side of the disk S through the supply side thread guide 6 and is rotated in the direction opposite to the rotational direction of the disk, so that the pin 5
It guides to the reverse thread guide 4 through the outside of b and 5a, and from there,
It extends toward the outer thread path side in the direction opposite to the direction of rotation of the disc, and wraps around the outside of the pins 3b and 3a, guides it from the pin 3a to the needle side guide 2, and passes it through the needle hole of the needle 1. As described above, the upper thread 17 is wound around the disk S in the direction opposite to the rotation direction of the disk S by using the three guides, the inner and outer thread paths and the pins, and is supplied from the supply source to the needle side. . Of the above, the same effect can be obtained by reversing the order of drawing the upper thread on the inner path side and the outer path side of the disc S.

The upper thread pick-up (apparatus) means having the above structure is referred to as a winding type rotary balance in this embodiment, and the operation and effect of the balance will be described with reference to FIGS. 1, 6 and 7. . FIG. 7 is a diagram showing the relationship between the upper thread supply amount curve α and the upper thread absorption amount curve β in one cycle of sewing machine sewing (upper shaft, one rotation) by the thread take-up device, in the x-axis (rotation angle) direction. Along the line a, at the top dead center of the needle, b at the start of lowering the needle hole below the needle plate, c at the bottom dead center of the needle, d at the start of hooking the upper thread of the hook, and e at the bottom of the balance. At dead point, f is f '
Indicates a needle bar top dead center when the upper thread separates from and passes through the hook and the hook stopper, and h indicates a timing at which the upper thread moves up from the hook to the needle plate.

6 (a), (b), (d), (e),
(F) and (h) are circles corresponding to timings (angles) a, b, d, e, f, h in one sewing cycle shown in the upper thread supply amount curve and the upper thread absorption amount curve of FIG. 7, respectively. The phase diagram of the disk S is shown, and the phase diagram of the disk corresponding to the c timing of the curve shown in FIG. 7 is as shown in FIG. Less than,
The action and effect exerted by the clockwise rotating disc S and the pins 3a, 3b and 5a, 5b which are planted away from the disc center 0 are described in JP-B-35-13442 and JP-B-43-26.
It is clear with reference to the contents and drawings of the specification described in Japanese Patent Publication No. 074 or Japanese Examined Patent Publication No. S43-26075.

As described above, each pair of pins and three needle thread guides arranged on the winding-type rotary balance and the three upper thread guides are wound around the winding balance in such a manner that the upper thread is wound in a direction opposite to the rotation direction of the rotary balance. In addition to the gradual needle thread supply slackening and the rapid pick-up and tightening for forming the stitches necessary for the needle thread only with the mold rotary balance, the cloth tightening direction is adjusted toward the thread supply side over the entire period of one cycle of the sewing operation. Tension and ironing are applied to ensure the formation of a secure seam by ensuring the upper thread catch of the hook and passing between the hook and the rotation stopper of the hook without vibrating the needle thread and needle at all.

FIG. 5 shows standard conditions (sewing speed: 500 stitches /
Min, cloth is 2 cotton broad, thread is Tetron spun thread # 6
0) shows an example of a correlation diagram of the upper and lower thread tensions at the equilibrium sewing point (entanglement point) in 0), where the tension applied to the lower thread in the x-axis direction (unit: g) and the tension applied to the upper thread in the y-axis direction ( g), the correlation curve of the upper and lower thread tensions at the respective equilibrium sewing points in the case of the known link balance mechanism, folding type rotary balance or blade type rotary balance, and the winding type rotary balance adopted in this embodiment. It is shown.

When a link balance is adopted as the upper thread take-up device and the upper thread is supplied by the tension adjusting method, the upper thread does not come out due to the tension applied to the upper thread when the hook is pulled out by hitting at high speed. Thus, the supply tension had to be set to a considerably large value, and the bobbin thread tension had to be set to a large value (see FIG. 5, link balance curve). However, if the upper thread amount compulsory supply means in which the above-mentioned upper thread gripping means 11 is installed on the upstream side of the upper thread supply path is adopted, the abnormal tension when the hook is pulled out of the upper thread is interrupted to the supply side. The above inconvenience is eliminated. From this, it will be understood that the object of the present invention can be achieved to some extent by combining the upper thread amount forced supply means and the like, regardless of which mechanism is selected as the upper thread pickup means.

The winding type rotary balance is characterized in that the needle thread tension can be made extremely small as compared with other needle thread pick-up means.
In the range of ultra-thin sewing, slightly larger than the bobbin thread tension,
Although it is possible to form a complete stitch by setting the same degree, the magnitude of the tension generated in the upper thread is very sensitive to changes in the sewing speed, and adjustment is made correspondingly with the conventional tone plate adjustment method. There are difficult characteristics.

Conventionally, it was difficult to adapt to the characteristics of the winding type rotary balance because it was a yarn feeding system using only mechanical means, but in the present embodiment, the yarn feeding (feeding) system is made electronic, By using an electromagnetic actuator,
We were able to eliminate the above difficulties. By combining the winding-type rotary balance and the upper thread amount forced supply method, the cloth tightening becomes positive, and by eliminating the escape of the presser, especially in the satin sewing of embroidery sewing, Most effective for balanced stitching of the upper and lower threads of the seam.

Next, the structure of the hook C related to the upper thread bobbin case will be described. In the seam shown in FIG. 2B, even when the specified amount compulsory supply system is adopted for the upper thread supply, the lower thread supply amount is controlled by setting the lower thread supply tension. Conventionally, the magnitude of the bobbin thread tension fed from the bobbin thread bobbin is not only adjusted by the bobbin thread adjusting spring, but also the bobbin rotates as the sewing speed increases, and the tension tension is piled up based on the rotation moment generated from the stopping operation. , It changed according to the sewing speed of the sewing machine and was gradually increasing.

As shown in FIG. 5 (in the case of balanced sewing), if the magnitude of the bobbin thread tension fluctuates, it is necessary to set the magnitude of the upper thread tension to match it, and the sewing thread as a whole is It becomes difficult to reduce the tension applied to. Therefore, first, the specific gravity of the material of the bobbin thread bobbin is made extremely small, for example, a bobbin made of synthetic resin is used to reduce the rotation moment of the bobbin, a bobbinless bobbin is used, or a non-rotating bobbin is mounted. And again
Even when the sewing speed of the sewing machine is increased by, for example, using synthetic resin as the material of the inner hook to facilitate thread removal, a means is adopted in which the bobbin thread feeding tension does not fluctuate substantially.

In the case of this embodiment, the bobbin thread supply tension by adjusting the bobbin thread adjusting spring is set to the tension corresponding to the kind of sewing cloth with reference to FIG. A winding-type rotary balance is adopted as the upper thread pick-up means, and a supply amount forced feeding method is used for the upper thread.
By combining the bobbin thread with a bobbin thread amount tension supply system (consisting of a supply tension adjusted to be extremely small according to the type of sewing cloth), various effects are guaranteed by making the sewing thread tension as small as possible. Ultra-thin material for high-speed sewing,
Zigzag stitching, embroidery stitching on various kinds of sewing cloth such as thin cloth,
The straight stitches and the like are sewn tightly, and good stitches without shrinkage are formed so that they can be efficiently performed.

The following two setting methods are presented for the forced supply of the designated upper thread amount. (1) A fully automatic method in which the cloth thickness is detected by the cloth presser, the sewing pitch and the swing width are set by the dial, the lower thread supply tension is adjusted as described above, and the upper thread supply amount is calculated by the microcomputer. See Japanese Patent Publication No. 61-159987 (2) Know the cloth thickness by visually checking the sewing test result without detecting the cloth thickness, and set the sewing pitch and the swing width with a dial.
A simple semi-automatic system in which the lower thread supply tension is adjusted as described above and the upper thread supply amount is determined by a microcomputer. Or, use a fully automatic method. See Japanese Patent Publication No. 61-159989, Japanese Patent Publication No. 61-279283, or Japanese Patent Publication No. 62-29090493.

[0069]

As described above, according to the present invention, the predetermined upper thread supply length consumed for forming stitches is forcibly fed out and the lower thread supply tension is adjusted according to the type of sewing cloth. In addition, by adopting a winding rotary balance as the upper thread take-up means, the tension of the sewing thread is reduced as much as possible, the twisting back of the thread is prevented, the range of use of the easy-to-extend sewing thread is expanded, and the thread breakage prevention, especially, the very thin object, Economical needle thread supply control device and method for sewing machine that enables efficient seam formation such as good seam formation under various sewing conditions such as sewing thin materials, tightening, and prevention of sewing shrinkage. To provide.

[Brief description of drawings]

FIG. 1 is an embodiment diagram showing a schematic configuration of a needle thread supply control device of a sewing machine of the present invention.

FIG. 2 shows a stitch configuration for each stitch pitch P.

FIG. 3 is an example of a bobbin thread tension suitable for the physical properties of a sewing cloth and a stitching ratio table for each stitch.

FIG. 4 shows an example of a tension curve, an upper thread gripping operation diagram, and an upper thread supply amount diagram, which are generated in the upper thread by the upper thread take-up device of the sewing machine during one sewing cycle.

FIG. 5 is an example of a correlation diagram of needle thread tension and bobbin thread tension at a balanced stitch point under a standard condition of low-speed stitching.

FIG. 6 is a state diagram of the winding rotary balance at each phase of disk rotation.

FIG. 7 is an explanatory diagram showing an upper thread supply amount curve and an absorption amount curve during one sewing cycle.

[Explanation of symbols]

1 Sewing needle 2 Needle side thread guide 3, 5 Pin 4 Reverse thread guide 6 Supply side thread guide 7 Upper thread tension spring 8 Guide 9, 10 Friction feed type upper thread supply roller with encoder 11 Electromagnetic upper thread gripper 12 Base tension Plate 13 Upper thread bobbin 14 Pulley 15 Upper shaft 16 Rotary encoder 17 Upper thread 18 Sewing cloth 19 Lower thread 20 Lower plate

Claims (4)

[Claims] 1. A needle thread gripping means provided upstream in a needle thread supply path connecting the needle thread supply side and the needle thread pick-up device, and an upper thread based on a signal obtained by measuring a rotation phase of a sewing machine upper shaft. The upper thread gripping means for gripping and releasing the upper thread, means for advancing the upper thread gripping timing of the upper thread gripping means by measuring the supply of the specified upper thread payout amount, the upper thread A constant speed driven friction feeding type upper thread supply roller provided on the downstream side of the upper thread gripping means in the supply path, and supplying the upper thread to the upper thread pick-up device side only during a release period of the upper thread gripping means. Upper thread amount compulsory supplying means composed of an upper thread supplying roller, and a pair of pins having different distances from the center are planted on the inner and outer surfaces of the disk, respectively, and a predetermined central angle at which each pin surrounds the center of the disk The angle of the pins that are planted on each of the above-mentioned surfaces is the specified angle between the inner and outer surfaces. Rotating discs that are set to be shifted, around the outer periphery of the rotating disc, and around the periphery of the rotating disc. Guide, needle side guide, needle thread supplied from the needle thread amount compulsory supply means side in order, the needle thread supply side guide, the outer peripheral side of the pin arranged in the inner path of the rotating disc, the thread reversing guide, the rotating circle An upper thread pick-up consisting of a winding-type rotary balance which is routed in the direction opposite to the rotation direction of the rotary disc to the needle side guide through the outer peripheral side of the pin arranged in the plate outer side path and passes through the needle hole side. Means, bobbin bobbin formed of material with small specific gravity, bobbin less bobbin or non-rotating bobbin, etc. is incorporated, and bobbin case equipped with bobbin thread tension adjusting spring for setting supply tension according to the kind of sewing cloth is inserted and combined. That the hook is connected Stitch forming control device of the sewing machine to symptoms. 2. A method of setting a supply tension according to the kind of sewing cloth for supplying the lower thread, and a predetermined amount of upper thread consumption required for each stitch is preset for supplying the upper thread. The method for controlling the stitch formation of the sewing machine comprises adopting a winding rotary balance method as the upper thread picking-up means, and combining these in the order of the steps. 3. A sewing machine according to claim 2, wherein the needle thread consumption amount required for each stitch is set to a length substantially calculated according to the following formula, and forcible feeding is performed for each stitch. Seam formation control method. D x (1-sewing tightening rate according to the type of sewing cloth) + PP = sewing pitch D = cloth thickness of sewing cloth 4. A zigzag stitch or an embroidery stitch sewing machine in which the upper thread consumption amount required for each stitch is set to a length calculated based on the following formula, and forcible feeding is performed for each stitch. The stitch formation control method according to claim 2. D x (1-sewing tightening rate according to the type of sewing cloth) + √
(P ² + W ² ) P = sewing pitch W = stitch width of zigzag stitch D = thickness of sewing cloth