JPH1033868A - Thread breakage detector for sewing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve sewing quality and operability by shortening an idle sewing distance without generating malfunctions in any stitch interval. SOLUTION: In the case of judging that bobbin thread is broken (Yes in S6) based on contact pressure generated when the bobbin thread is brought into contact with a bobbin thread tension sensor during the sewing of a sewing machine, a sewing distance Lc at the time is summed up and the drive of the sewing machine is stopped (S10) at the time of judging that the summed-up sewing distance becomes more than a thread breakage judgement distance Lb determined beforehand (Yes in S9.) On the other hand, in the case of judging that the bobbin thread is not broken (No in S6,) the sewing distance Lc summed up until then is cleared and judgement is prevented from being made as thread breakage in S9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sewing machine thread breakage detecting device for detecting a breakage of an upper thread or a lower thread in a sewing machine.

[0002]

2. Description of the Related Art Conventionally, a thread breakage detecting device of a sewing machine detects a thread payout amount for each stitch and detects a thread breakage when the thread payout amount of each needle becomes a predetermined value or less. The contact pressure with the needle is detected for each stitch using a swing of the spring or a pressure sensor, and when the amount of movement of the spring of each stitch or the contact pressure with the thread falls below a predetermined value, a thread may break. Was. These thread breakage detecting devices are difficult to detect when the stitch interval is small because the thread payout amount and the contact pressure with the thread are small. Therefore, even if the thread is not actually broken, it may be determined that the thread is broken, or conversely, it may not be determined that the thread is broken even though the thread is broken.

For this reason, the sewing machine is configured to stop when a predetermined number of stitches for thread breakage determination, for example, 10 stitches are determined to be continuously broken.

[0004]

However, when the stitch interval is large (for example, the stitch interval is 10 mm),
Until the sewing machine stops after a thread break occurs during continuous sewing, threadless sewing of a maximum of 10 mm * 10 stitches = 100 mm, that is, empty stitching, is performed. There was a problem that it was hurt and the quality of the sewn product deteriorated.

[0005] In addition, when the stitch interval is large, the moving distance of the work cloth is long, and when re-sewing after the sewing machine is stopped due to thread breakage, the needle hole deviated from the blank hole formed by the empty stitch is affected by the effect of the work cloth elongation. In many cases, stitches are formed, and there is a problem that the quality of a sewn product deteriorates.

Conversely, if the number of stitches for judging thread breakage is reduced to shorten the empty stitching distance, the thread payout amount and the contact pressure with the thread become small when the stitch interval is small, and there is a thread. Nevertheless, there was a case where a malfunction occurred in which the sewing machine was determined to be out of thread and stopped. For this reason, there is a problem that a time loss occurs due to the stop of the sewing machine due to a malfunction and the workability is significantly reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to improve the quality of sewn products and the workability by reducing the empty stitching distance without any malfunction at any stitch interval. An object of the present invention is to provide a sewing machine thread breakage detection device that can be improved.

[0008]

In order to achieve this object, a thread breakage detecting device of a sewing machine according to the present invention comprises a thread state detecting means for detecting a state of a thread being sewn, A first determining means for determining the presence or absence of a thread break or a slack of a thread based on the signal; and a sewing amount at that time when the first determining means determines that a thread break or a slack of the thread has occurred. When the first determining means determines that no thread breakage or thread slack has occurred, the sewing amount cumulative means for clearing the cumulative sewing amount and the sewing amount cumulative means are calculated by the sewing amount cumulative means. A second determining unit that determines that the thread has been cut when the sewing amount is equal to or greater than a predetermined reference sewing amount; and a sewing machine that stops driving of the sewing machine when the second determining unit determines that the thread is broken. Stop hand It is equipped with a door.

Therefore, when the state of the upper thread or the lower thread is broken or slackened during sewing of the sewing machine, the thread state detecting means detects the state, and based on the signal, the first judging means detects the upper thread or the lower thread. When it is determined that the bobbin thread has been cut or the thread has slackened, the sewing amount at that time is accumulated by the sewing amount accumulating means, and the accumulated sewing amount is determined by the second judging means to be equal to or more than a predetermined reference sewing amount. When it is determined that the operation has been completed, the sewing machine stopping means stops the driving of the sewing machine. On the other hand, if the first determining means determines that the upper thread or the lower thread is not in a state in which the thread is broken or the thread is slack, the sewing amount accumulated by the sewing amount accumulating means so far is cleared, The second determining means does not determine that the thread is broken.

In the sewing machine thread detecting device according to the present invention, the sewing amount is defined by a sewing distance.

Therefore, in the sewing amount accumulating means, when the first judging means judges that the thread is cut or the thread is slack, the sewing distance of the sewing is accumulated, and the accumulated sewing distance is calculated. When the second determining means determines that the distance has become equal to or greater than the predetermined reference sewing amount, the sewing machine is stopped by the sewing machine stopping means, so that the thread breakage is performed based on the actual sewing distance regardless of the sewing interval. Can be determined.

According to a third aspect of the present invention, in the sewing machine thread break detecting device, the sewing amount is constituted by the number of sewing needles, and the predetermined reference sewing amount is set to a plurality of reference sewing needles corresponding to sewing intervals. The second determining means determines that the thread has been cut when the number of sewing needles calculated by the sewing amount accumulating means is equal to or greater than a reference number of sewing needles corresponding to a predetermined sewing interval. I have to. Therefore, the sewing amount accumulating means accumulates the number of sewing needles sewn in a state where the thread is determined to be broken by the first determining means, and the accumulated number of sewing needles is set at a predetermined sewing interval. When it is determined by the second determination means that the number of sewing needles exceeds the corresponding reference number of sewing needles, the sewing machine is stopped by the sewing machine stopping means. Can be.

The thread state detecting means is constituted by a thread tension detecting section which comes into contact with the thread being sewn and detects the contact pressure, and the thread tension detecting section is provided between the needle plate and the bobbin. It is arranged so that it contacts. Therefore, the thread breakage detecting device can be housed in the sewing machine main body, and even when a lower thread breakage occurs, the sewing machine can be stopped with the lower thread remaining, thereby improving the quality of sewing products.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a sewing machine according to an embodiment of the present invention;

FIG. 1 is an external view of an embroidery sewing machine applied to a first embodiment in which the thread breakage detecting device of the present invention is implemented as a lower thread breakage detecting device, and FIG. 2 is an external view showing a lower thread path. FIG. 3 is a configuration diagram illustrating the sewing machine control device 50. In the first embodiment, the sewing distance is used as the sewing amount.

In FIG. 1, the sewing machine is roughly divided into a sewing machine arm 1 and a sewing machine bed 2.

The sewing machine arm 1 is mounted coaxially with the sewing machine spindle 10 and rotates a sewing machine spindle 10, a sewing needle 12 which moves up and down once by one rotation of the sewing machine spindle 10, and a sewing needle 12. And a spindle rotation sensor 13 for detecting the rotation angle of the sewing machine spindle 10 with the angle corresponding to the top dead center as 0 degree. Further, the upper thread 14 is passed through the sewing needle 12 from the thread spool 15 to the work cloth 16.
Supplied to

A work cloth 1 is provided on the upper surface of the sewing machine bed 2.
6 and a support frame 20 for holding X6 shown in FIG.
And an X motor 21 and a Y motor 22 that move in the Y direction, respectively.

As shown in FIG. 2, a lower part of the sewing machine bed 2 is provided with a needle plate 30 and an outer shuttle which rotates two rotations around one fixed axis line by one rotation of the main shaft 10 of the sewing machine below the needle plate 30. 31, an inner hook 32 rotatably supported with respect to the outer hook 31, and a bobbin 34 supported rotatably with respect to the inner hook 32 and wound with a lower thread 33 in the inner hook 32. Have been. Further, the bobbin 34 is fitted in the inner hook 32,
It is housed in a bobbin case 35 that cannot be rotated in the rotation direction. The lower thread 33 is supplied to the work cloth 16 through a needle hole 36 formed in the needle plate 30.

The outer hook 31 captures the upper thread 14 supplied by the sewing needle 12 through the needle hole 36, and
A thread catcher 37 for forming a seam on the work cloth 16 in cooperation with the sewing machine is provided.

Between the lower surface of the needle plate 30 and the outer hook 31, a bobbin thread tension sensor 40 as a cantilever-shaped thread tension detector having one end fixed to the sewing machine bed 2. Is installed. The lower thread tension sensor 40 includes a base parallel portion 41 and a tip parallel portion 42 having portions substantially parallel to the rotation surface of the outer shuttle 31, and a lower thread 33 with respect to the base parallel portion 41.
And a thread contact portion 43 that is inclined and bent in the direction of the path side of the lower thread 33 and is arranged to always contact the lower thread 33. A piezoelectric element 44 formed by laminating two pieces of piezoelectric ceramics is fixed to the side surface of the base end parallel portion 41 so that the polarization directions are opposite to each other.
As is well known, the piezoelectric element 44 generates a charge proportional to the applied strain. The bobbin thread tension sensor 40 functions as a thread state detecting unit that detects the state of the thread being sewn (the thread is broken, the thread is slack, etc.).

Therefore, the strain generated in the thread contact portion 43 due to the contact of the lower thread 33 is applied to the piezoelectric element 44 through the base parallel portion 41, and the contact pressure of the lower thread 33, that is, the lower thread 33 is applied to the piezoelectric element 44. An electric charge corresponding to the tension is generated.

A sewing machine control device 50 shown in FIG. 3 is installed below the sewing machine bed 2. The sewing machine control device 50 includes a well-known CPU (central processing unit) 51,
A RAM (read / write memory) 52, a ROM (read only memory) 53, a charge amplifier 54 for converting charges generated by the piezoelectric element 44 into a voltage, and a CPU 51 for converting an output voltage of the charge amplifier 54 into a digital signal and
And the X and Y of the embroidery frame 20 during embroidery sewing stored in the floppy disk.
A data input device 56 composed of a floppy disk drive for reading the movement amount data of each stitch in the direction,
A thread breakage determination distance input switch 57 for setting a thread breakage determination distance Lb as the reference sewing amount. Further, the CPU 51 transmits the sewing machine motor 11, the X motor 21, and the Y motor 22 through a drive circuit (not shown).
Is configured to be driven. Also, the spindle rotation sensor 1
The rotation angle of the sewing machine main shaft 10 output by 3 is input to the CPU 51.

The thread breakage determination distance input switch 57 is
The thread breakage determination distance Lb is constituted by a digital switch that can be set in units of mm, and is preferably set to be, for example, about 15 mm, which is smaller than the distance between the lower thread pull-out portion of the bobbin case 35 and the needle hole 36.

The threadless sewing distance L indicating the sewing distance in which the work cloth has been moved without the lower thread in the RAM 52.
A threadless sewing distance storage area 58 for storing c is provided, and a tension threshold Tth for determining the presence or absence of a lower thread based on the contact pressure of the lower thread 33 is stored in the ROM 53 in advance.

Next, the operation of the lower thread breakage detecting device constructed as described above according to the first embodiment will be described with reference to the flowchart shown in FIG. 4 and the waveform diagram in FIG. The following operation is performed by the CPU 51 reading out and executing a program stored in the ROM 53 in advance.

First, in step 1 of the flowchart shown in FIG. 4 (hereinafter, step is represented by S), the embroidery sewing data, that is, the amount of movement of the embroidery frame 20 of each stitch in the X and Y directions from the data input device 56 in advance. The data is read and stored in the RAM 52. Next, in S2, R
The threadless sewing distance Lc in the threadless sewing distance storage area 58 in the AM 52 is cleared to zero, and by driving a drive circuit (not shown) in S3, the sewing machine motor 11 is started to start sewing.

In S4, the X motor 21 is passed through a drive circuit (not shown) in synchronization with the rotation of the sewing machine spindle 10 based on the movement data in the X and Y directions stored in the RAM 52.
And the Y motor 22 are driven, and the support frame 20 and the support frame 2
The work cloth 16 supported at 0 is moved. With it
The contact pressure of the lower thread 33 and the upper thread 14 with respect to the thread contact portion 43 is detected by the piezoelectric element 44 and read via the charge amplifier 54 and the A / D converter 55, and is read from the RAM 5
2 is stored.

FIG. 5 shows the output voltage waveform of the charge amplifier 54 with respect to the rotation angle of the main shaft of the sewing machine. The voltage waveforms 60 and 61 generated at the rotation angle of 30 to 120 degrees of the main shaft of the sewing machine correspond to the movement of the work cloth 16. Generated by the pressure at which the lower thread 33 comes into contact with the thread contact portion 43 when the lower thread 33 is pulled out, the sewing machine main shaft rotation angle 240 degrees to 300 degrees
Voltage waveforms 62 and 63 generated in degrees are voltages generated by the pressure at which the upper thread 14 captured by the yarn catcher 37 comes into contact with the thread contact portion 43.

FIGS. 5A and 5B show the case where the stitch interval is 10 mm and 0.2 mm, respectively.
As shown in FIG. 5A, when the stitch interval is as large as 10 mm, the level of the voltage waveform 60 is larger than the tension threshold Tth because the lower thread 33 is drawn out longer.
It is easy to detect the breakage of the lower thread. However, when the stitch interval is extremely small, such as 0.2 mm, as shown in FIG. 5B, a stitch (a stitch area 65 to be described later) that is smaller than the tension threshold value Tth for one or more stitches occurs. Sometimes. That is, when the stitch interval is extremely small, the bobbin thread 33 is not drawn out from the bobbin 34 every needle, and the bobbin thread is consumed to some extent due to the influence of nonlinearity such as the elongation of the bobbin thread 33 and the friction of the bobbin 34 Until the lower thread tension is smaller than the tension threshold Tth. Then, the consumption of the lower thread gradually increases the lower thread tension, and a tension greater than the tension threshold Tth is generated. In FIG. 5B, the bobbin thread is fully extended at the seam (the seam 66 described later) in which the bobbin thread tension is larger than the tension threshold value Tth. This shows how many lower threads are being pulled out.

Next, in S5, of the contact pressures stored in the RAM 52 in S4, the maximum value Tmax at the sewing machine main shaft rotation angle of 30 to 120 degrees corresponding to the pull-out phase of the lower thread 33 is equal to the tension threshold value Tth. Be compared. As shown in the voltage waveform 60 of FIG. 5A in the case where the stitch interval is 10 mm, when the lower thread 33 is present, Tma is set in S6.
x ≧ Tth, and it is determined that there is a lower thread (No in S6),
The process proceeds to S7, where the threadless sewing distance Lc is cleared to zero, and returns to S4 to execute the next sewing again.
On the other hand, when the lower thread breakage occurs, the lower thread 3 in FIG.
The lower thread 33 is provided at the seam immediately after the bobbin case 35 has passed through the bobbin case 35.
Is free, so that the lower thread tension is zero, that is, Tmax is zero, as shown by the voltage waveform 64 in FIG.
Therefore, Tmax <Tth in S6 (Ye in S6).
s) It is determined that there is no bobbin thread, and the flow shifts to S8 to accumulate the current amount of movement in the X and Y directions in the threadless sewing distance Lc of the threadless sewing distance storage area 58, and then shifts to S9.

In S9, the threadless sewing distance storage area 58
Is compared with the thread breakage determination distance Lb set by the thread breakage determination distance input switch 57. In S9, Lc ≧ Lb, that is, the threadless sewing distance Lc indicating the total of the continuous stitch intervals in which the lower thread is continuous.
Is longer than the set yarn breakage determination distance Lb (S
9 (Yes), it is finally determined that the lower thread is broken, and the sewing machine motor 11 is stopped in S10.

On the other hand, when Lc <Lb (No in S9),
That is, when the total Lc of the continuous stitches without the lower thread does not reach Lb despite the absence of the lower thread, S
Returning to step 4, sewing of the next stitch is executed again.

For example, when Lb is set to 15 mm, as shown in FIG. 5A, when sewing is performed at a stitch interval of 10 mm and two stitches without a lower thread (Tmax <Tth) continue, Lc is set to 20 mm. 5B, it is determined that the bobbin thread is broken. On the other hand, there is no bobbin thread when the stitch interval is 0.2 mm as shown in FIG. 5B (Tmax <Tt).
When the stitch of h) continues for 75 stitches, Lc = 15 mm, it is determined that the lower thread is broken, and the sewing machine is stopped. Accordingly, as shown in the stitch area 65 where Tmax <Tth continues in FIG. Even if it is determined that there is no bobbin thread continuously, the bobbin thread tension increases as described above, and
Tmax ≧ T at the seam 66 pulled out from the fourth side
The voltage waveform 67 of the bobbin thread which becomes th is generated and it is determined that there is a bobbin thread in S6, and the threadless sewing distance Lc is cleared to zero in S8. Therefore, it is erroneously determined that there is no bobbin thread and the sewing machine is stopped. Nothing.

As described above, when the lower thread breakage occurs with respect to the distance of 30 mm between the lower thread pull-out portion of the bobbin case 35 and the needle hole 36, after detecting the absence of the lower thread 33,
Since the sewing machine is stopped at a threadless sewing distance of about 15 to 20 mm, the sewing machine can be stopped without performing empty sewing while leaving the lower thread 33 at 10 to 15 mm.

The processing step of S6 functions as a first determining means, the processing steps of S7 and S8 function as a sewing amount accumulating means, and the processing step of S9 functions as a second determining means. The processing step of S10 functions as sewing machine stopping means.

Next, a description will be given of an embroidery sewing machine according to a second embodiment in which the number of sewing needles is used as a sewing amount in the device for detecting thread breakage of the sewing machine according to the present invention.

The external view of the embroidery sewing machine of the second embodiment, the external configuration diagram showing the lower thread path, and the configuration diagram of the sewing machine control device are shown in FIGS. 1 and 2 of the embroidery sewing machine of the first embodiment, respectively.
Since the configuration is almost the same as that of FIG. 3 and FIG. 3, only the configuration of a different portion will be described.

The embroidery sewing machine according to the second embodiment differs from the embroidery sewing machine according to the first embodiment in that the number of threadless sewing needles shown in FIG. 6 is used instead of the threadless sewing distance storage area 58 shown in FIG. Only the stitch interval threshold value input switch 157 and the thread breakage stitch number input switch 158 shown in FIG. 6 are used instead of the threadless sewing stitch number storage area 158 for storing N and the thread breakage determination distance input switch 57 shown in FIG. Are configured as a sewing machine control device 150.

Here, the stitch interval threshold value input switch 157 is constituted by a digital switch capable of setting a stitch interval threshold value Po indicating a threshold value of the stitch interval, for example, Po = 0. It is set as 5 mm.

The thread breakage determination stitch number input switch 1
Numeral 58 indicates the number N of thread breakage determination stitches which indicates, when the value of the stitch interval P is equal to or more than Po and less than Po, when the number of stitches without bobbin thread is continued and the lower thread is finally determined to be broken.
When N1 <N2 is set to a value that satisfies N1 <N2 and the stitch interval threshold Po is 0.5 mm, for example,
N1 = 3 and N2 = 15 are set. Therefore, N
1, N2 are a plurality of reference sewing needle numbers corresponding to the sewing intervals.

Next, the operation of the embroidery sewing machine according to the second embodiment configured as described above will be described with reference to the flowchart shown in FIG. Here, S1, S3 to S in FIG.
6, the operations in S10 are the same as those in the flowchart of the embroidery sewing machine of the above-described first embodiment shown in FIG. 4, so the same reference numerals are given and the description thereof will be simplified.

In FIG. 7, after the embroidery sewing data is read in S1, the number N of threadless sewing needles in the RAM 52 is cleared to zero in S2. Next, in S3, the sewing machine motor 11
Is activated, the work cloth 16 is moved in S4, and the contact pressure between the lower thread 33 and the upper thread 14 is detected and read into the RAM 52. In subsequent S6, it is determined whether or not the lower thread 33 has broken. If it is determined in S6 that Tmax <Tth, that is, it is determined that the lower thread is not broken (Yes in S6),
The flow shifts to S18, where the number N of thread-free sewing needles is incremented, and the flow shifts to S19. On the other hand, in S6, Tmax ≧
Tth, that is, when it is determined that there is a lower thread (No in S6),
In S17, the number N of threadless sewing needles is cleared to zero.
4, the sewing of the next stitch is continued.

In S19, the immediately preceding stitch interval P is compared with the stitch interval threshold Po read by the stitch interval threshold value input switch 157, ie, 0.5 mm, and the immediately preceding stitch interval P is 0.5 mm. In the above case (S1
9), the process proceeds to S20, where the number N of thread-free sewing stitches is compared with the number N1 of thread breakage determination stitches read from the thread breakage stitch number input switch 158, that is, 3, and N ≧ 3, that is, there is a broken thread breakage. Is continued for three or more stitches (Yes in S20),
In S10, the sewing machine is stopped.

On the other hand, if the immediately preceding stitch interval P is less than 0.5 mm in S19 (No in S19), the flow shifts to S21, where the number N of threadless sewing stitches is read from the thread breakage stitching number input switch 158. Number N2 of thread breakage determination stitches, that is, 1
If N ≧ 15, that is, if there is no lower thread for 15 stitches or more (Yes in S21), the sewing machine is stopped in S10. In S20 and S21, N is N1,
If it is less than N2, the process returns to S4 as in S17, and the sewing of the next stitch is continued.

That is, when the stitch interval is large, for example,
If it is 0.5 mm or more, the sewing machine is stopped when the absence of three stitches is continuously detected. If the stitch interval is small, for example, if it is less than 0.5 mm, there is no continuous 15 stitches. The sewing machine stops when is detected.

The processing step of S6 functions as a first determining means, the processing steps of S17 and S18 function as a sewing amount accumulating means, and the processing steps of S19 to S21 function as a second determining means. Further, the processing step of S10 functions as a sewing machine stopping means.

The present invention is not limited to the above-described embodiment, but can be variously modified and used without departing from the gist thereof.

For example, the lower thread tension sensor 40 of the present embodiment
Is arranged at a position where the lower thread 33 always contacts the lower thread 33 between the needle plate 30 and the outer shuttle 31. However, this is not necessary. Thread 3
3 can be arranged at a position where it intermittently contacts, or can be installed at any part that can contact the lower thread 33, for example, the needle hole 36 or the hook stop.

In the present embodiment, the lower thread tension sensor 40
Is detected using the piezoelectric effect of the piezoelectric element 44, but the strain may be detected using a change in resistance of a strain gauge instead.

Further, in this embodiment, as shown in FIG.
Sewing machine main shaft rotation angle corresponding to contact of lower thread 33 30 degrees or more
Although the presence / absence of the lower thread 33 is configured to be detected using the generated voltage waveforms 60 and 61 of 120 degrees, the generated voltage waveform 62 of the main shaft rotation angle of 240 to 320 degrees corresponding to the contact of the upper thread 14, 63 may be used to detect the presence or absence of the upper thread 14.

Further, as in the present embodiment, the thread pressure detecting means detects the contact pressure of the lower thread 33, that is, the tension, and detects the presence or absence of the lower thread based on the magnitude of the tension. An encoder or a photocoupler for optically or magnetically detecting the rotation may be provided to detect whether or not the lower thread 33 is fed out and to detect the breakage of the lower thread.

Further, in the present embodiment, the needle plate 30 and the outer hook 31
The lower thread tension sensor 40 is installed between the thread winding 15 and the sewing needle 12 to detect the breakage of the lower thread.
The upper thread tension sensor detects the tension of the upper thread 14 in the path of the upper thread 14 to the upper thread 14, and detects the presence or absence of the tension of the upper thread 14, and an encoder or photo that optically or magnetically detects the amount of the upper thread unreeling. It is also possible to install a coupler or the like to detect whether or not the upper thread 14 is fed out, and to detect a break in the upper thread.

In this embodiment, the thread breakage determination distance Lb is set by the thread breakage determination distance input switch 57, the stitch interval threshold Po is set by the stitch interval threshold value input switch 157, and the thread breakage determination stitch number input switch 158 is set. , The numbers N1 and N2 of the thread breakage determination stitches are respectively input. Instead, the number of stitches N1 and N2 may be input from the outside using the data input device 56 in common.
3 may be stored.

Further, the work cloth 16 may be moved in the radius and rotation directions, or may be moved only in one dimension, instead of being movable in the X and Y directions as in the present embodiment. Such a configuration or a configuration in which the moving is performed using the power of the sewing machine motor 11 is also possible.

Further, the digital switch of the present embodiment may be constituted by an analog volume such as a variable resistor and a variable capacitor, and the value may be set in accordance with the resistance value, the capacitance value and the like. It is.

[0057]

As is apparent from the above description, the thread breakage detecting device for a sewing machine according to the first aspect of the present invention detects a state in which the upper thread or the lower thread breaks or the thread sags during sewing of the sewing machine. When the first determination means determines that the sewing machine is in the above-described state based on a signal from the detection means, the sewing amount at that time is accumulated by the sewing amount accumulation means, and the accumulated sewing amount is calculated by the second determination means. When it is determined that the sewing amount is equal to or larger than a predetermined reference sewing amount, the driving of the sewing machine is stopped by the sewing machine stopping means. On the other hand, when the first determining means determines that the upper thread or the lower thread is not broken or the thread is not slack, the sewing amount accumulated by the sewing amount accumulating means so far is cleared, and the first sewing amount is cleared. 2 Since the determination means does not determine that the thread is broken, even when the stitch interval is small, there is no time loss in which the sewing machine stops erroneously determining that there is no thread despite the presence of a thread, and the workability is remarkably improved. There is an effect of improving.

By setting the number of stitch-less stitches in the normal case to be small, the empty stitching distance can be shortened even when the stitch interval is large, and the fabric is damaged by unstitched needle holes. Without
This has the effect of improving the quality of sewn products.

According to a second aspect of the present invention, there is provided the sewing machine thread breakage detecting device, wherein the sewing amount accumulating means determines that the thread is broken or the thread is slackened by the first determining means. When the second determining means determines that the accumulated sewing distance is equal to or greater than a predetermined reference sewing amount, the driving of the sewing machine is stopped by the sewing machine stopping means. The thread breakage can be determined based on the actual sewing distance regardless of the sewing interval.

According to a third aspect of the present invention, there is provided a sewing machine with a thread breakage detecting device according to the first aspect of the present invention, wherein the sewing amount accumulating means performs sewing in a state where the first determining means determines that the thread has been cut or the thread has slackened. When the second determination means determines that the total number of sewing needles is equal to or greater than the reference number of sewing needles corresponding to a predetermined sewing interval, the sewing machine is driven. Since the sewing machine is stopped by the sewing machine stopping means, the presence or absence of thread breakage can be determined according to each sewing interval.

The thread breakage detecting device according to a fourth aspect of the present invention comprises a thread tension detecting section as the thread state detecting means which comes into contact with the thread being sewn and detects the contact pressure of the thread. Because it is arranged to contact the lower thread between
The thread breakage detecting device can be housed in the sewing machine main body, and even when a lower thread breakage occurs, the sewing machine can be stopped with the lower thread remaining to improve sewing quality.

[Brief description of the drawings]

FIG. 1 is an external view of an embroidery sewing machine according to an embodiment of the present invention.

FIG. 2 is an external configuration diagram showing a lower thread path.

FIG. 3 is a block diagram illustrating a configuration of a sewing machine control device according to the first embodiment.

FIG. 4 is a flowchart illustrating a lower thread breakage detecting operation according to the first embodiment;

5A and 5B are output voltage waveform diagrams of the charge amplifier 54 with respect to the rotation angle of the main shaft of the sewing machine. FIG.
m and (b) are voltage waveform diagrams when the sewing interval is 0.2 mm.

FIG. 6 is a block diagram illustrating a configuration of a sewing machine control device according to a second embodiment.

FIG. 7 is a flowchart illustrating a lower thread breakage detecting operation according to the second embodiment.

[Explanation of symbols]

 11 sewing machine motor 12 sewing needle 14 needle thread 30 needle plate 33 bobbin thread 40 bobbin thread tension sensor 50 sewing machine controller 57 thread breakage judgment distance input switch

Claims (4)

[Claims] 1. A thread state detecting means for detecting a state of a thread being sewn, a first determining means for determining whether or not a thread break or a slack has occurred based on a signal from the thread state detecting means; (1) When it is determined by the determining means that a thread break or a slack has occurred, the sewing amount at that time is accumulated, and it is determined by the first determining means that the thread break or the slack of the thread has not occurred. A sewing amount accumulating means for clearing the accumulated sewing amount, and a sewing amount judging that the thread has been cut when the sewing amount calculated by the sewing amount accumulating means is equal to or larger than a predetermined reference sewing amount. 2. A thread breakage detecting device for a sewing machine, comprising: a second determining unit; and a sewing machine stopping unit that stops driving of the sewing machine when the second determining unit determines that the thread is broken. 2. The thread breakage detecting device for a sewing machine according to claim 1, wherein the sewing amount is constituted by a sewing distance. 3. The sewing amount is constituted by the number of sewing needles; the predetermined reference sewing amount is constituted by a plurality of reference sewing needle numbers corresponding to a sewing interval; 2. The sewing machine according to claim 1, wherein when the number of sewing needles calculated by the amount accumulating means becomes equal to or greater than a reference number of sewing needles corresponding to a predetermined sewing interval, it is determined that the thread has broken. Yarn breakage detection device. 4. A thread tension detecting section comprising: a thread tension detecting section which comes into contact with a thread being sewn as a thread state detecting means and detects a contact pressure of the thread, wherein the thread tension detecting section comprises a bobbin thread between a needle plate and a bobbin. The thread breakage detecting device for a sewing machine according to claim 1, wherein the device is arranged so as to be in contact with the thread.