JPH08187382A - Upper thread tension controller for sewing machine - Google Patents

Abstract

PURPOSE: To stably form uniform stitches by calculating a control value for controlling an upper thread tension control means so that the detected value of an upper thread tension detecting means can become a target value, and controlling the upper thread tension control means based on the calculated control value. CONSTITUTION: Concerning the upper thread tension controller for sewing machine, an error calculating means calculates a tension error to be generated for each stitch based on the detected value of the upper thread tension detecting means and the previously set target value at the timing to generate the cloth fastening tension of a sewing machine, and an error accumulating means calculates a cumulative value based on the tension errors calculated by the error calculating means. Based on the cumulative value calculated by the error accumulating means, a control value calculating means calculates the control value for controlling the upper thread tension control means so that the value of upper thread tension detected by the upper thread tension detecting means can become the target value and, based on this calculated value, the upper thread tension control means controls the upper thread tension by controlling the upper thread tension control means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a needle thread tension adjusting device for keeping the needle thread tension of a sewing machine in a good condition.

[0002]

2. Description of the Related Art Conventionally, as an apparatus of this type, for example, JP-A-54-131448 and JP-A-54-1.
No. 23353, Japanese Patent Publication No. 60-20029 and the like are provided with a tension detector for detecting the upper thread tension and a tension adjuster for adjusting the upper thread tension by gripping / releasing the upper thread.
Tension adjustment according to the difference between the needle thread tension (hereinafter referred to as cloth fastening tension) and the preset target value of cloth fastening tension (hereinafter referred to as deviation) when the cloth is tightened by the balance detected by the tension detector A needle thread tension adjusting device is disclosed that is configured to feedback control a winder.

Further, Japanese Laid-Open Patent Publication No. 57-185890 also includes a tension detector and a tension adjuster, and holds the maximum value of the needle thread tension detected by the tension detector in one needle. , The control value for the next stitch is calculated from the difference between the maximum value of the held upper thread tension and the target value of the cloth tightening tension,
A needle thread tension adjusting device that controls a tension adjusting device based on this control value is disclosed.

[0004]

However, in the case of the former,
Based only on the deviation and the feedback gain determined by the characteristics of the amplifier that constitutes the feedback loop,
Since the needle thread tension is adjusted by controlling the tension adjuster, there is a problem that suitable control can be realized only in an extremely limited range and stable and uniform stitches cannot be formed.

That is, in these devices, the tension adjuster has, for example, a holding member that holds the upper thread from both sides,
Since the upper thread tension is adjusted by changing the distance between the sandwiching members according to the control amount input to the tension adjuster, the control characteristics of the tension adjuster according to the thickness of the thread used, etc. (The change amount of the needle thread tension with respect to the control amount) changes. And the feedback gain is usually
It is preset so that optimum control can be performed under a predetermined use condition, that is, when the control characteristic of the tension regulator is in a certain state. For this reason, when the thickness of the thread used is changed and the control characteristics of the tension adjuster change, the change amount of the needle thread tension with respect to the deviation (that is, the feedback gain) may become too large. In this case, since hunting is likely to occur and the needle thread tension fluctuates, stable needle thread tension cannot be generated, and eventually stable and uniform stitches cannot be formed.

On the other hand, in the latter case, the maximum value of the cloth tightening tension is held, and the needle thread tension at the next needle is controlled based on the result of comparison between this maximum value and the target value. If there is a sudden change in tension due to such a cause, the needle thread tension on the next one needle will be completely affected by the sudden change, and as in the former case, it will be stable. There was a problem that it was not possible to form uniform seams.

In order to solve the above problems, the present invention provides
An object of the present invention is to provide a needle thread tension adjusting device for a sewing machine capable of forming stable and uniform stitches.

[0008]

The invention according to claim 1 made in order to achieve the above object is arranged in a yarn path from an upper yarn supply source to a needle, as illustrated by a solid line in FIG. An upper thread tension adjusting means for adjusting the upper thread tension of the upper thread supplied from the upper thread supply source; an upper thread tension detecting section arranged in the thread path for detecting the upper thread tension; Error calculating means for calculating a tension error generated for each stitch based on the upper thread tension detected by the upper thread tension detecting means at the cloth tightening tension generation time and a preset target value, and the error calculating means. Error accumulation means for calculating the cumulative value of the tension error based on the tension error calculated by the means, and the detected value of the upper thread tension detection means based on the cumulative value calculated by the error accumulation means. Control for controlling the needle thread tension adjusting means to obtain a value And a control value calculating means for calculating the upper thread tension controlling means for controlling the upper thread tension adjusting means based on the control value calculated by the control value calculating means. The tension adjusting device is the gist.

The invention described in claim 2 is the same as claim 1.
In the needle thread tension adjusting device of the sewing machine described in (3), the control value calculating means calculates the control value for each stitch. Next, the invention according to claim 3 is the needle thread tension adjusting device according to claim 1 or 2, as shown by the dotted line in FIG. The deviation calculating means has a deviation calculating means for calculating a deviation between the upper thread tension detected by the detecting means and the target value a predetermined number of times during the cloth tightening tension generation period, and the deviation calculating means is calculated during the period. It is characterized in that the average of a predetermined number of deviations is used as the tension error.

Next, the invention described in claim 4 is as follows.
In the needle thread tension adjusting device of the sewing machine according to claim 3, the control value calculating means, based on the deviation every time the deviation calculating means calculates the deviation,
It is characterized by having a control value correcting means for correcting the control value.

[0011]

In the needle thread tension adjusting device according to the first aspect of the present invention configured as described above, the error calculating means uses the upper thread tension detecting means at the time when the cloth tightening tension of the sewing machine is generated. The tension error generated for each stitch is calculated based on the detected upper thread tension detected value and the preset target value, and the error accumulating unit calculates the accumulated value based on the tension error calculated by the error calculating unit. Based on the accumulated value calculated by the error accumulating means, the control value calculating means controls the upper thread tension adjusting means so that the detected value of the upper thread tension by the upper thread tension detecting means becomes the target value. A control value for performing is calculated, and based on this control value, the upper thread tension control means controls the upper thread tension adjusting means to adjust the upper thread tension.

Therefore, according to the present invention, the needle thread tension is controlled on the basis of the cumulative value calculated based on the tension error generated for each stitch, so that the needle thread tension is transiently or suddenly changed. The effect of is suppressed to be small, and as a result, a stable upper thread tension can be generated, and a stable seam can be formed.

The tension error calculated by the error calculating means may be a value obtained by integrating the deviation between the detected value of the needle thread tension and the target value during the cloth tightening tension generation time, or the integrated value of this deviation. May be averaged according to the period. Alternatively, it may be calculated based on the needle thread tension detected at any one point during the cloth tightening tension generation period.

Further, the accumulated value calculated by the error accumulating means may be simply added by adding the tension error or may be accumulated by adding the tension error multiplied by an appropriate magnification. Alternatively, the average of the added values of the tension error may be calculated for each predetermined number of stitches, and this may be sequentially added and accumulated.

Next, the control value calculating means may calculate the control value for each predetermined number of stitches. In the sewing machine needle thread tension adjusting device according to the second aspect, the control value is controlled for each stitch. Calculate the value. Therefore, according to the present invention, it is possible to cope with a change in the condition for each stitch, and it is possible to control the needle thread tension according to the present condition.

Next, in the needle thread tension adjusting device according to the third aspect of the invention, the error calculating means has a deviation calculating means, and the deviation calculating means is detected by the needle thread tension detecting means. In addition, the deviation between the needle thread tension and the target value is calculated a predetermined number of times during the cloth tightening tension generation period, and the error calculating means sets the average of a predetermined number of deviations calculated during the period as the tension error.

Therefore, according to the present invention, even if a transient or sudden fluctuation of the needle thread tension occurs during the cloth tightening tension generation period, the influence of this fluctuation is averaged.
The influence on the subsequent calculation of the control value can be suppressed to be small, and more stable control can be realized.

Further, in the needle thread tension adjusting device according to a fourth aspect of the present invention, the control value calculating means has a control value correcting means, and the control value correcting means functions as the deviation calculating means. Each time the deviation is calculated, the control value calculated based on the accumulated value based on the deviation is corrected.

Therefore, according to the present invention, when a transient or sudden fluctuation of the needle thread tension occurs during the cloth tightening tension generation period within one needle, it is possible to follow up with it. It is possible to realize control that is more in line with the current situation. According to the present invention, the needle thread tension is controlled based on the accumulated value, that is, the average needle thread tension across a plurality of needles is controlled so as to match the target value. As a result, the needle thread tension is
Since the target value is displaced so as to be approximately the average, the correction of the control value by the control value correction means may be comparatively small. Therefore, since the feedback gain of the deviation calculated by the deviation calculation means can be made small, the needle thread tension can be reduced. There is no fluttering.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is an explanatory diagram showing a schematic configuration of a sewing machine to which the needle thread tension adjusting device of this embodiment is applied.

As shown in FIG. 2, the sewing machine main body 10 includes
A bobbin 12 as an upper thread supply source for feeding the upper thread 11;
Thread hooks 13, 14 provided along the path of the upper thread 11,
15, an upper thread tension adjuster 16 as an upper thread tension adjusting means capable of gripping or releasing the upper thread 11, an upper thread tension sensor 17 as an upper thread tension detecting means, and a vertical movement in synchronization with a sewing machine main shaft 18. The balance 19 and the sewing needle 20, and the sewing machine spindle 1
The main shaft rotation sensor 21 that outputs various timing signals according to the rotation phase of 8, the foot switch 34 (see FIG. 3) for the user to input the start / end of sewing, and the main body rotation sensor 21 are provided in the sewing machine main body 10. A control device 40 for executing various control processes is provided, and the needle thread tension adjuster 16, the needle thread tension sensor 17, the spindle rotation sensor 21, and the footboard switch 3 are provided.
4 is connected to the control device 40. In addition, spool 1
The needle thread 11 supplied from 2 is thread hook 13, needle thread tension adjuster 16, thread hook 14, needle thread tension sensor 17, thread hook 1
5, it is supplied to the sewing needle 20 through the balance 19.

Here, as shown in FIG. 3, the control device 40 comprises a CPU 41 for executing various control processes, a ROM 42 for storing control programs and the like, and a RAM 43 for temporarily storing data etc. necessary for the processes. A well-known microcomputer is mainly configured, and further, an interface circuit 44 for inputting a signal from the needle thread tension sensor 17, and an A / D conversion for converting an analog signal output from the interface circuit 44 into a digital value The machine 45, a driver 48 as a needle thread tension control means for applying a drive voltage to the needle thread tension adjuster 16, and a sewing machine motor driver 51 for operating a sewing machine motor 50 for driving the sewing machine spindle 18.

Then, the CPU 41 controls the spindle rotation sensor 2
1 output various timing signals, needle thread tension sensor 17
Is detected by the A / D converter 45 and the upper thread tension detection signal converted into a digital value by the A / D converter 45, a status signal indicating the ON / OFF state of the footboard switch, etc. A tension adjustment signal for driving, a motor drive signal for driving the sewing machine motor 50, and the like are output to the sewing machine motor driver 51.

Here, the spindle rotation sensor 21 rotates with the sewing machine spindle 18 and includes a light transmitting portion formed with a large number of slits for transmitting light, and a light detecting portion for detecting light passing through the light transmitting portion. The optical encoder is provided. Then, as shown in FIG. 4, the main spindle rotation sensor 21 sets the rotation angle at which the sewing needle 20 is at the needle top dead center to 0 ° as a timing signal, from 358.5 ° to 1.5 °.
The needle up signal Su that becomes High level only during the period, High level from 0 ° to 1.5 °, and Lo from 1.5 ° to 3 °
A phase signal Sp, which generates one pulse each time the main shaft of the sewing machine rotates by 3 °, such as w level, is output. The phase signal Sp is input to the interrupt signal input terminal of the CPU 41, and the phase signal interrupt process described later is started at the rising timing thereof.

Next, as shown in FIG. 5, the needle thread tension adjuster 16 causes the laminated piezoelectric element 22 to expand and contract according to the applied voltage.
An L-shaped metal fitting 23 fixed to the sewing machine main body 10, a hinge portion 24 integrally molded with the L-shaped metal fitting 23, and holding the L-shaped metal fitting 23 at both ends in the expansion and contraction direction of the laminated piezoelectric element 22, and the hinge portion 24 at one end Attached to the thread gripping plate 26 at the other end
And a thread gripping counter plate 27 disposed at a position facing the thread gripping plate 26 so as to grip the upper thread 11 together with the thread gripping plate 26.

When a voltage is applied to the laminated piezoelectric element 22 to cause it to expand and contract, the hinge portion 24 operates according to the lever principle.
The expansion and contraction amount of the laminated piezoelectric element 22 is expanded and transmitted to the thread gripping arm 25, and as a result, the thread gripping plate 26 moves in a direction of approaching / isolating from the thread gripping counter plate 27. The distance between the thread gripping plate 26 and the thread gripping opposing plate 27 is such that when the voltage Vc applied to the laminated piezoelectric element 22 is 0 V (release voltage).
When the upper thread 11 is set to be a little thicker than the thickness of the upper thread 11 passing between the thread holding plate 27 and the thread gripping counter plate 27 and the applied voltage Vc is 100 V (complete gripping voltage Vmax), It is set to be smaller than the thickness of the thread 11 so that the upper thread 11 can be completely grasped.

Next, as shown in FIG. 6, the needle thread tension sensor 17 includes a rectangular metal plate 29 fixed to the sewing machine body 10 in a cantilever shape by a tension sensor holder 28, and a metal plate 29. The tension sensor thread hook 30 is disposed on the upper surface of the open end side, and the strain gauge 31 is attached to the lower surface of the metal plate 29 and has a resistance value that changes according to the strain of the metal plate 29. The upper thread 11 is hung on the tension sensor thread hook 30 between the thread hooks 14 and 15 (see FIG. 2), and the metal plate 29 is distorted in accordance with the tension of the upper thread 11 to cause the strain gauge 31. The resistance value of changes.

Further, the interface circuit 44 connected to the needle thread tension sensor 17 is composed of four resistors including a strain gauge and outputs a voltage value corresponding to a change in the resistance value of the strain gauge. The outputs of the circuit 44a and the resistance bridge circuit 44a are differentially amplified, and the needle thread tension sensor 1
And a known differential amplifier circuit 44b that outputs a positive voltage corresponding to the needle thread tension detected at 7.

Here, the operation of the needle thread tension adjusting device of this embodiment will be described along with the main processing and the phase signal interruption processing for realizing the needle thread tension adjusting control executed by the CPU 41. First, a main process of detecting the start of sewing, initializing various parameters, and permitting the start of the needle thread tension adjustment control will be described.

As shown in FIG. 7, when this process is started, first, in S110, it is determined whether or not the footboard switch 34 is on, and if not, S110 is repeatedly executed. On the other hand, if the footboard switch 34 is on, it is determined that sewing has started, and the process proceeds to S120.

In S120 to S140, various parameters used in the phase signal interrupt processing described later, that is, the control start flag C, the average tension error accumulation register for storing the average tension error accumulation value Tac, and the tension error accumulation are stored. The tension error accumulation registers for storing the value Tc are each cleared to 0, and in the subsequent S150, the interruption by the phase signal Sp is permitted, and the execution of the phase signal interruption processing is permitted.

In the following S160, it is determined whether or not the footboard switch 34 is off, and if it is not off, S160 is repeatedly executed. On the other hand, if the tread switch 34 is off, it is determined that the sewing has been completed and S170
Proceeding to step S11, the interrupt by the phase signal Sp is prohibited, and the execution of the phase signal interrupt processing is prohibited.
The processing of 0 to S170 is repeatedly executed.

Next, the phase signal interruption process for performing the needle thread tension adjustment control will be described with reference to the flow chart shown in FIG. It should be noted that this processing is executed every time an interrupt due to the phase signal Sp occurs, that is, every time the sewing machine main shaft 18 rotates 3 °. As shown in FIG. 8, when this process is started, it is first determined in S210 whether the control start flag C is set (= 1), and if not set, the process proceeds to S220.

In S220, the needle up signal Su of the spindle rotation sensor 21 is read, and it is determined whether or not the needle up signal Su read in S230 is at a high level. Then, if the needle up signal Su is not at the high level, this processing is ended as it is, and if the needle up signal Su is at the high level, S
After shifting to 240 and setting the control start flag C, S
Proceed to 270.

On the other hand, if it is determined in S210 that the control start flag C is set, the process proceeds to S250, in which the needle up signal Su is read as in S220, and in S260 that follows. It is determined whether or not the needle up signal Su is at the high level. If the needle up signal Su is at the high level, the process proceeds to S270, the rotation angle register for calculating the spindle rotation angle θ is cleared to 0, and then the process proceeds to S290, while at S260, the needle up signal Su is obtained. If it is determined that is not at the High level, the process proceeds to S280, 3 ° is added to the value of the spindle rotation angle θ stored in the rotation angle register, and then the process proceeds to S290.

That is, S220 to S240 are processes executed from the start of sewing until the first detection of the needle suture signal Su, and the needle top dead center phase (θ) serving as the control reference. = 0 °) for phase matching. When this is detected, the control start flag C
Is set and the actual control is started.

Further, S250 to S280 are processes for calculating the spindle rotation angle θ. Every time this process is started, the contents of the rotation angle register are updated by 3 ° and the sewing machine spindle 18
Is rotated once to detect the needle up signal Su, the contents of the rotation angle register are cleared and the phase is adjusted.

In the following S290, it is determined whether or not the spindle rotation angle θ is in the cloth tightening phase (30 ° ≦ θ ≦ 90 °), and if it is the cloth tightening phase, the process proceeds to S300. In S300,
From the upper thread tension sensor 17 to the interface circuit 44 and A
The needle thread tension T is read via the / D converter 45, and then S
At 310, the applied voltage Vc of the needle thread tension adjuster 16 is calculated based on the equation (1), and the calculated value is output to the driver 48.

Vc = −a × (T−Tref) −b × Tac + Vmax / 2 (1) where a and b are preset constants for converting the tension value into a voltage value at a predetermined ratio. . Tref is a target value of the needle thread tension (cloth tightening tension) in the cloth tightening phase,
It is set automatically / manually according to the thickness of the cloth.

Then, the first item (-a * (T-T
ref)) is the target value Tr of the currently detected needle thread tension T.
The correction voltage is calculated according to the deviation from ef. The second item (-b * Tac) on the right side is for calculating an offset voltage that is constantly applied during one stitch from an average tension accumulation value described later. Next, the third item (Vmax / 2) on the right side is the applied voltage V at the start of control.
The initial value of c is given, and is set to 1/2 of the maximum gripping voltage Vmax which is the maximum value of the applied voltage so that the calculated value of the applied voltage Vc converges to a substantially constant value at a relatively early time. .

The driver 48, to which the applied voltage Vc calculated in this way is input, receives the calculated applied voltage Vc.
By c / D converting c, a voltage corresponding to the applied voltage Vc is actually generated and applied to the needle thread tension adjuster 16. In subsequent S320, it is determined whether or not the spindle rotation angle θ is the tension error cumulative phase (39 ° ≦ θ ≦ 66 °), and if it is not the tension error cumulative phase, this processing is ended as it is, and the tension error cumulative phase is set. If there is, the process proceeds to S330.

In S330, S30 is calculated according to the equation (2).
Needle thread tension T read at 0 and target value T of cloth tightening tension
After the deviation from ref is calculated and added to the tension error cumulative value Tc stored in the tension error cumulative register, this processing ends. Tc = Tc + (T-Tref) (2) That is, in S300 to S330, the upper thread tension T is actually detected in the cloth tightening phase, and the applied voltage Vc to the upper thread tension adjuster 16 is calculated and output. Adjust the needle thread tension,
Further, in the tension error accumulated phase, the tension error accumulated value Tc is obtained based on the error between the needle thread tension T and the target value Tref. During the tension error cumulative phase, this process
Since the process is executed once, the error for 10 times is accumulated.

On the other hand, if it is determined in S290 that the spindle rotation angle θ is not in the cloth tightening phase, the process proceeds to S340, the applied voltage Vc is set to the complete gripping voltage Vmax, and the subsequent S350 is performed. , It is determined whether or not the spindle rotation angle θ is 93 °, that is, immediately after the cloth fastening phase. Then, if the spindle rotation angle θ is not 93 °, this processing is ended as it is, and if it is 93 °, the process proceeds to S360.

In step S360, the average (average tension error) of the errors detected during the tension error accumulation phase is calculated based on the tension error accumulation value Tc stored in the tension error accumulation register according to the equation (3), and the average is calculated. It is added to the average tension error accumulated value Tac stored in the tension error accumulated register.

Tac = Tac + Tc / 10 (3) In the subsequent S370, the tension error accumulation register is cleared (=
0) and then this processing is terminated. That is, S340 to S3
In 70, when the sewing machine main shaft 18 is in a phase other than the cloth tightening phase, the applied voltage Vc is held at the perfect grip voltage Vmax to completely grip the upper thread, and immediately after the cloth tightening phase ends, The average tension error in the cloth tightening phase is calculated and sequentially accumulated.

The value of the average tension accumulation register Tac becomes an offset value for calculating the applied voltage Vc in S310 in the next cloth tightening phase. That is, FIG.
, The spindle rotation angle θ is the cloth tightening phase (30 ° ≦ θ
≦ 90 °), the applied voltage Vc corresponding to the detected upper thread tension T and the average tension cumulative value Tac in S310.
Is calculated, and in the other phases, the applied voltage Vc is held at the complete gripping voltage Vmax. When the spindle rotation angle θ is in the tension error accumulated phase (39 ° ≦ θ ≦ 66 °), the error between the needle thread tension T and the target value Tref is calculated and accumulated, and the tension error accumulated value Tc (shaded line in the figure). Part) is calculated. Then, the average value (Tc / 1
The voltage corresponding to 0) is added and controlled as an offset value in the calculation of the applied voltage Vc in the next cloth fastening phase.

Incidentally, S330 corresponds to the error calculating means of the present invention, S360 corresponds to the error accumulating means, and S310 corresponds to the control value calculating means and the control value correcting means. As described in detail above, in the needle thread tension adjusting device of the present embodiment, the needle thread tension T and the target value Tref in the tension accumulation phase for each stitch.
The average tension error (Tc / 10), which is the average value of the errors with, is calculated, and in the next cloth tightening phase, the applied voltage V to the needle thread tension adjuster 16 is calculated based on the cumulative value Tac of the mean tension errors.
c is calculated and the needle thread tension T is controlled. That is, the average error cumulative value Tac is fed back to control so that the tension error cumulative value Tc (and by extension, the average tension error) becomes zero.

Therefore, according to this embodiment, the needle thread tension T
In the cumulative tension error phase, the target value Tref is displaced so as to be a substantially average value and does not deviate largely from the target value Tref. Therefore, stable needle thread tension T can be generated, and In addition, stable seams can be formed.

The average tension error Tac accumulated for calculating the applied voltage Vc is the average tension error, that is, the needle thread tension T and the target value Tref in the tension accumulation phase within one needle.
It is obtained by accumulating the average values of the errors between and. Therefore, according to the present embodiment, even if the needle thread tension T suddenly fluctuates greatly in the tension accumulation phase, the influence thereof is averaged and dispersed, so that it has a great influence in the subsequent calculation of the applied voltage Vc. Stable control can be realized without affecting.

Further, in this embodiment, the applied voltage Vc calculated based on the accumulated value Tac of the average tension errors is corrected based on the deviation between the needle thread tension T and the target value Tref. That is, the deviation between the needle thread tension T and the target value Tref is also fed back in order to calculate the applied voltage Vc.

Therefore, it is possible to sufficiently follow a transient or sudden change in tension within one needle, and it is possible to realize control according to the current situation. In this embodiment,
As described above, by feeding back the average tension cumulative value Tac, the needle thread tension T is controlled so as to change with the target value Tref as a substantially average value.
The gain of the deviation (constant a) can be made smaller as compared to the case where the control value is calculated only based on the deviation between the target value Tref and the target value Tref, and as a result, hunting or the like is prevented from occurring.
The needle thread tension T does not flutter, and a stable seam can be formed.

Although one embodiment of the present invention has been described above, the present invention is not limited to this and can be implemented in various modes without departing from the scope of the present invention. For example, in the above embodiment, the needle thread tension adjuster 16
Adjusts the tension by grasping and releasing the upper thread from both sides. However, using a mechanism of a tone tray that has been conventionally used in sewing machines, the tone tray is raised according to the calculated applied voltage Vc. The needle thread tension may be adjusted by changing the pressure for pinching the thread.

Further, in the above embodiment, the cumulative value is obtained only based on the error detected in the tension accumulation phase within the cloth fastening phase, but the entire range of the cloth fastening phase may be used as the tension cumulative phase. , This may be obtained at only one arbitrary point within the cloth tightening phase. In the case of obtaining it at any one point, it may be performed, for example, when the spindle rotation angle θ corresponding to the balance top dead center is 66 °.

In the above embodiment, the average tension error Tac used when calculating the applied voltage Vc is updated for each stitch, but it may be updated for every plural stitches, for example, every two stitches. Good. In this case, the tension error cumulative value Tc may be continuously accumulated over a plurality of stitches and the average thereof may be calculated, or the average value of a plurality of stitches of the values calculated for each stitch may be calculated and averaged. The tension error Tac may be accumulated.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of the present invention.

FIG. 2 is a schematic configuration diagram of a sewing machine to which the needle thread tension adjusting device of the embodiment is applied.

FIG. 3 is a block diagram showing a schematic configuration of a control device.

FIG. 4 is an explanatory diagram showing a timing signal output from a spindle rotation sensor.

FIG. 5 is a perspective view showing a needle thread tension adjuster.

FIG. 6 is a perspective view of a needle thread tension sensor and a circuit diagram of an interface circuit connected to the sensor.

FIG. 7 is a flowchart showing main processing executed by a CPU.

FIG. 8 is a flowchart showing a phase signal interrupt process executed by a CPU.

FIG. 9 is an explanatory diagram showing the relationship between the upper thread tension detected by the upper thread tension sensor and the applied voltage for operating the upper thread tension adjuster.

[Explanation of symbols]

10 ... Sewing machine main body 11 ... Upper thread 16 ... Upper thread tension adjuster 17 ... Upper thread tension sensor 18 ... Sewing machine spindle 19 ...
Balance 20 ... Sewing needle 21 ... Spindle rotation sensor 22 ... Multilayer piezoelectric element 23
... L-shaped metal fitting 24 ... Hinge part 25 ... Thread gripping arm 26 ... Thread gripping plate 27 ... Thread gripping counter plate 28 ... Tension sensor holder 29 ... Metal plate 31 ... Gauge 34 ... Footboard switch 40 ... Control device 41 ... C
PU 42 ... ROM 43 ... RAM 44 ... Interface circuit 45 ...
A / D converter 48 ... Driver 50 ... Sewing machine motor 51 ... Sewing machine driver

Claims (4)

[Claims] 1. An upper thread tension adjusting means for adjusting the upper thread tension of the upper thread supplied from the upper thread supply source, the upper thread tension adjusting means being arranged in the thread path from the upper thread supply source to the needle. Based on the upper thread tension detecting means arranged to detect the upper thread tension, the upper thread tension detected by the upper thread tension detecting means at the time when the sewing tension of the sewing machine is generated, and a preset target value, An error calculating means for calculating a tension error generated for each stitch, an error accumulating means for calculating a cumulative value of the tension error based on the tension error calculated by the error calculating means, and an error accumulating means. And a control value calculating means for calculating a control value for controlling the upper thread tension adjusting means so that the detection value of the upper thread tension detecting means becomes the target value. The upper thread tension adjusting means is controlled based on the calculated control value. Thread tension adjusting device of a sewing machine, characterized in that it comprises a needle thread tension control means, the for. 2. The needle thread tension adjusting device according to claim 1, wherein the control value calculation means calculates the control value for each stitch. 3. The error calculating means calculates a deviation between the upper thread tension detected by the upper thread tension detecting means and the target value,
2. A deviation calculation means for calculating a predetermined number of times during the cloth tightening tension generation period, wherein the deviation calculation means uses a mean of a predetermined number of deviations calculated during the period as a tension error. Alternatively, the needle thread tension adjusting device according to claim 2. 4. The needle thread tension adjusting device according to claim 3, wherein the control value calculating means corrects the control value based on the deviation every time the deviation calculating means calculates the deviation. A needle thread tension adjusting device for a sewing machine having a control value correcting means.