JP3671445B2 - Upper thread tension adjusting device for sewing machine - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an upper thread tension adjusting device for maintaining an upper thread tension of a sewing machine in a good state.
[0002]
[Prior art]
Conventionally, there has been an upper thread tension adjusting device for controlling the upper thread tension (hereinafter referred to as cloth tightening tension) to be constant at the time of cloth tightening with a balance in order to keep the upper thread tension always good. For example, an upper thread tension constant holding device of a sewing machine described in JP-A-57-185890 feeds back a difference between a maximum tension value detected by an upper thread tension detection device and a desired tension setting value. The upper thread tension adjusting device was controlled through a servo mechanism so that the value became zero.
[0003]
[Problems to be solved by the invention]
However, according to the above prior art, since the upper thread tension is adjusted at the next stitch based on the comparison result between the maximum tension value and the tension setting value, the upper thread tension is always delayed by one stitch. The cloth tightening tension could not be adjusted in real time for each needle. For this reason, if there is a transient or sudden change in the upper thread tension during the phase in which the upper thread tension occurs, especially when the upper thread tension suddenly increases, the upper thread is immediately It is impossible to control the tension to be equal to the set value, resulting in a problem that the stitches vary.
[0004]
In addition, it is necessary to use a maximum value holding device for holding the maximum tension value and an analog mechanism such as a servo mechanism, resulting in a problem that the manufacturing cost is increased.
The present invention has been made to solve the above-described problems. The purpose of the present invention is to adjust the upper thread tension in real time even if the cloth tightening tension fluctuates transiently and suddenly. An object of the present invention is to realize an upper thread tension adjusting device for a sewing machine that can form a beautiful seam.
[0005]
[Means and means for solving the problems]
In order to achieve the above object, an upper thread tension adjusting device of a sewing machine of the present invention is as described in claim 1.
It is arranged in the thread path from the upper thread supply source to the needle and grips the upper thread And release By switching and controlling the two states, An upper thread tension adjusting means capable of increasing or decreasing the upper thread tension;
An upper thread tension measuring means arranged in a yarn path from the upper thread tension adjusting means to the needle and capable of measuring the upper thread tension;
Cloth tightening tension setting means capable of setting the upper thread cloth tightening tension;
An upper thread tension comparing means for comparing a set value of the cloth tightening tension set by the cloth tightening tension setting means and a measured value of the cloth tightening tension measured by the upper thread tension measuring means;
The upper thread tension adjusting means always holds the upper thread, and when the measured value of the cloth tightening tension becomes larger than the set value of the cloth tightening tension, the upper thread tension adjusting means releases the upper thread. Grip release control means for performing control and
It is provided with.
[0006]
Here, as the upper thread tension adjusting means, the upper thread is actively gripped in accordance with an operation signal. And release The two states that have been switched from one to the other, this Therefore, any mechanism can be used as long as the upper thread tension can be increased or decreased. For example, the upper thread tension can be constituted by a laminated piezoelectric element or an electromagnetic solenoid. The upper thread tension measuring means may be any mechanism that can output a variable signal corresponding to the upper thread tension, and can be constituted by, for example, a strain gauge or a piezoelectric element that can output a signal corresponding to the upper thread tension. As the cloth tightening tension setting means, any mechanism can be used as long as the user can arbitrarily set the cloth tightening tension and can output a variable signal according to the set value, for example, a volume capable of arbitrarily setting the resistance value, An input device or the like having a numeric key capable of inputting a numerical value, a function key in which a predetermined set value is set in advance, or the like may be provided. The upper thread tension comparing means may be configured to compare the set value of the cloth tightening tension with the measured value and make a determination of the magnitude thereof. For example, the measurement signal and the target signal are input and the comparison result signal is input. Can be configured by a comparator or the like. The grip release control means only needs to be able to control the gripping / release of the upper thread by the upper thread tension adjusting means at an arbitrary timing. For example, the grip release control means can be configured by a flip-flop that can set / reset the operation signal with a predetermined timing signal. . The upper thread tension comparison means and the grip release control means may be configured by a logical operation circuit including a known CPU, ROM, RAM, etc., and each function may be realized by software processing.
[0007]
According to the upper thread tension adjusting device of the sewing machine of the present invention configured as described above, the set value of the cloth tightening tension set by the cloth tightening tension setting means and the cloth tightening tension measured by the upper thread tension measuring means. The measured value is compared with the upper thread tension comparing means, and when the measured value becomes larger than the set value, the grip release control means causes the upper thread tension adjusting means to release the upper thread, and the upper thread cloth tightening tension is Preventing it from becoming excessive.
[0008]
By the way, if the cloth is tightened with an appropriate tension, the upper thread tension adjusting means grips the upper thread again, but if the measured value becomes smaller than the set value, the upper thread is gripped immediately. The measured value becomes larger than the set value, and in some cases, the gripping / releasing control is frequently repeated, and the load applied to the upper thread tension adjusting means or the like may be increased.
[0009]
In order to prevent this, it is possible to provide release control continuation means for continuing the upper thread release control by the grip release control means for a while and to prevent the upper thread from being gripped immediately even if the measured value becomes smaller than the set value. More desirable. The release control continuation unit may be a re-grip instruction unit as long as it can control the timing of re-grip by the grip release control unit. As a specific example, when the grip release control means is configured by a flip-flop or the like, the output signal that is set when the measured value becomes larger than the set value may be reset at a timing that requires re-gripping. That's fine. When the grip release control means is constituted by a CPU or the like, re-grip can be performed at a necessary timing by software processing.
[0010]
Here, it is considered that various timings are required for re-gripping. However, if the upper thread release control is continued excessively by the release control continuation means, the upper thread may be fed out too much. It is conceivable that a sufficient upper thread tension cannot be obtained during the cloth tightening.
[0011]
Therefore, as described in claim 2,
A cloth tightening end detecting means capable of detecting a time when the phase in which the cloth tightening tension is generated ends;
Release control continuation means for continuing the upper thread release control by the grip release control means until the end of the phase in which the cloth tightening tension is detected is detected by the cloth tightening end detection means;
It is more desirable to have
[0012]
If configured in this manner, the upper thread is re-gripped at the timing when the phase in which the cloth tightening tension is generated is completed, so that the cloth tightening tension is not generated after re-gripping and the upper thread release control is continued excessively. There is nothing.
Alternatively, as described in claim 3,
A gripping tension setting means for setting an upper thread tension to cause the upper thread tension adjusting means to grip the upper thread;
Release control continuation means for continuing the upper thread release control by the grip release control means until the measured value of the cloth tightening tension becomes smaller than the set value set by the grip tension setting means;
It is also desirable to have
[0013]
With this configuration, the upper thread is re-gripped at the timing when the cloth tightening tension becomes smaller than the set value (gripping tension setting value) set by the gripping tension setting means. The gripping tension setting value is set to a small value that does not exceed the setting value (clothing tension setting value) in the cloth tightening tension setting means even if the upper thread tension fluctuates after re-gripping. As a result, an excessive cloth tightening tension is not regenerated after re-gripping, and the upper thread release control is not continued excessively.
[0014]
Incidentally, the upper thread tension may increase even in phases other than cloth tightening. If the set value in the cloth tightening tension setting means is larger than the needle thread tension value at this time, there is no particular problem, but if the set value in the cloth tightening tension setting means is small, or a phase other than cloth tightening When unexpectedly large abnormal tension may occur, unexpected upper thread release control may be performed in a phase other than cloth tightening.
[0015]
In order to prevent such an unexpected upper thread release control, as described in claim 4,
Cloth clamping phase detection means capable of detecting a cloth clamping phase in which the cloth clamping tension is generated;
A release prohibiting means for prohibiting the upper thread release control by the grip release control means in a phase other than the cloth tightening phase detected by the cloth tightening phase detecting means;
It is good to have.
[0016]
Alternatively, as described in claim 5,
An abnormal tension generation phase detecting means capable of detecting an abnormal tension generation phase in which an abnormal tension before the cloth fastening phase is generated;
In the abnormal tension generation phase detected by the abnormal tension generation phase detection means, a release prohibiting means for prohibiting the upper thread release control by the grip release control means;
May be provided.
[0017]
According to the upper thread tension adjusting device having the configuration described in claim 4, when the cloth tightening phase is not detected by the cloth tightening phase detecting means, the release prohibiting means performs the upper thread releasing control by the grip releasing control means. Since the prohibition is prohibited, the upper thread release control is not unexpectedly performed except in the cloth tightening phase. The cloth tightening phase detecting means can be constituted by various sensors capable of detecting the operation position, the rotation angle, and the like of a mechanism that operates in accordance with the operation of the sewing machine main shaft or the sewing machine main shaft. As the release prohibiting means, for example, when the grip release control means is constituted by a flip-flop or the like, the output signal is forcibly reset if the phase detected by the cloth tightening phase detecting means is not the cloth tightening phase. do it. When the grip release control means is constituted by a CPU or the like, release other than the cloth tightening phase can be prohibited by software processing. In addition, since the cloth tightening phase detection means can detect the start and end of the cloth tightening phase, when providing the cloth tightening end detection means according to claim 2, if there is only this cloth tightening phase detection means, It can also serve as a cloth tightening end detection means.
[0018]
Further, according to the needle thread tension adjusting device having the configuration described in claim 5, the abnormal tension generation phase is detected by the abnormal tension generation phase detecting means. The abnormal tension referred to here is usually referred to as hook hook pull-out tension and hook hook claw pull-out tension, and a phase in which these instantaneous strong tensions may appear is slightly before the cloth fastening phase. Therefore, in a state where the abnormal tension generation phase is detected, the release prohibiting means prohibits the upper thread release control by the grip release control means, thereby preventing unexpected upper thread release control due to the abnormal tension. The abnormal tension generation phase detecting means can be configured in the same manner as the cloth tightening phase detecting means by shifting the phase. As for the release prohibiting means, for example, when the grip release control means is constituted by a flip-flop or the like, the output signal is forcibly reset if the phase detected by the abnormal tension generation phase detection means is the abnormal tension generation phase. What is necessary is just to comprise. When the grip release control means is constituted by a CPU or the like, release at the abnormal tension generation phase can be prohibited by software processing. Note that there is an increase in tension called the hook overload tension in a phase further before the abnormal tension generation phase. Since the hook over tension is often much weaker than the abnormal tension, it is not a problem. However, the upper thread release control may be prohibited including the period in which the hook over tension occurs.
[0019]
【Example】
Next, an embodiment of the present invention will be described with reference to the drawings.
First, the first embodiment will be described.
As shown in FIG. 1, the sewing machine main body 10 includes a thread winding 12 as an upper thread supply source for feeding the upper thread 11, thread hooks 13, 14, and 15, and upper thread tension adjustment capable of gripping or releasing the upper thread 11. A thread gripper 16 as a means, an upper thread tension sensor 17 as an upper thread tension measuring means, a balance 19 that moves up and down in synchronization with the sewing machine spindle 18, a sewing needle 20, and a cloth tightening from the rotation angle of the sewing machine spindle 18. A cloth tightening phase detection sensor 21 serving as a cloth tightening phase detection means (also serving as a cloth tightening end detection means) for detecting the phase is installed, and the thread gripper 16, the upper thread tension sensor 17, and the cloth tightening phase detection sensor 21 are The upper thread tension control device 40 is connected.
[0020]
In the above configuration, the upper thread 11 supplied from the thread winding 12 is supplied to the sewing needle 20 through the thread hook 13, the thread gripper 16, the thread hook 14, the upper thread tension sensor 17, the thread hook 15, and the balance 19.
As shown in FIG. 2, the thread gripper 16 has L-shaped metal fittings 23 and hinge portions 24 integrally formed with the L-shaped metal fittings 23 at both ends in the expansion / contraction direction of the laminated piezoelectric element 22 that expands and contracts according to the applied voltage. The upper thread 11 can be gripped by a thread gripping plate 26 and a thread gripping opposing plate 27 formed at the end of the thread gripping arm 25 that is sandwiched and attached to the hinge portion 24. Based on the lever principle, the hinge portion 24 enlarges the amount of extension of the laminated piezoelectric element 22 and transmits it to the yarn gripping arm 25 to move the yarn gripping plate 26. Then, the position of the yarn gripping facing plate 27 is determined in relation to the moving distance. That is, the distance between the thread gripping plate 26 and the thread gripping counter plate 27 is set to be slightly larger than the thickness of the upper thread 11 so that the upper thread 11 can be completely released when the applied voltage to the laminated piezoelectric element 22 is 0 volts. In addition, when the applied voltage is 100 volts, the thickness is set to be smaller than the thickness of the upper thread 11 so that the upper thread 11 can be completely gripped.
[0021]
As shown in FIG. 3, the upper thread tension sensor 17 has a tension sensor thread hook 30 attached to the upper surface of one end of a rectangular metal plate 29 held in a cantilever shape by a tension sensor holding body 28. The strain gauge 31 is affixed on the lower surface of this. The upper thread 11 is hung on the tension sensor thread hook 30 between the thread hooks 14 and 15 (see FIG. 1), and the strain of the metal plate 29 caused by the tension of the upper thread 11 changes the resistance value of the strain gauge 31. Can be detected as
[0022]
As shown in FIG. 4, the cloth clamp phase detection sensor 21 has a notch 32 in a part thereof, a disk 33 attached coaxially with the sewing machine main shaft 18, and the notch 32 to detect the H level. It comprises a well-known photocoupler 34 that outputs. The notch 32 is formed at a position where the cloth fastening phase can be detected, and the photocoupler 34 outputs H level during the cloth fastening phase and L level during other phases. In the sewing machine of the present embodiment, the cloth tightening phase is in a range of about 30 to 66 degrees with the rotation angle of the sewing machine main shaft 18 at the needle top dead center being 0 degrees. Knotting and cloth tightening are performed.
[0023]
As shown in FIG. 1, the upper thread tension control device 40 includes resistors R <b> 1, R <b> 2, and R <b> 3, and a resistance bridge circuit 41 connected to the strain gauge 31 of the upper thread tension sensor 17 and the output of the bridge as a differential. A tension setting device as a cloth tightening tension setting means comprising a differential amplifier 42 that amplifies and outputs a positive voltage corresponding to the upper thread tension, and a tension setting volume that sets a voltage corresponding to a desired cloth tightening tension. 43, a well-known analog comparator 44 as an upper thread tension comparing means that compares the output voltage of the tension setting device 43 with the output voltage of the differential amplifier 42 and outputs an H level only when the latter is high, Of the photocoupler 34 of the cloth clamp phase detection sensor 21 that is set at the rising edge of the output waveform of the analog comparator 44. D flip-flop 45 as a grip release control means forcibly cleared at the L level of the force, and an amplifier that outputs 0 volt and 100 volt corresponding to the L level and H level of the inverted output value of the D flip flop 45, respectively. 46. The output of the amplifier 46 is connected to the laminated piezoelectric element 22 included in the yarn gripper 16. The D input of the D flip-flop 45 is fixed at the H level.
[0024]
Next, the operation of the upper thread tension adjusting device configured as described above will be described.
The waveform of each part in the upper thread tension control device 40 with respect to the rotation angle of the main spindle of the sewing machine when the needle top dead center is 0 degree is as shown in the graph of FIG.
First, when the sewing machine main shaft 18 is rotated and sewing is started, the resistance of the strain gauge 31 of the upper thread tension sensor 17 changes according to the tension of the upper thread 11, and the resistance from the differential amplifier 42 through the resistance bridge circuit 41. An upper thread tension signal 50 is output. On the other hand, in the tension setting device 43, a tension setting signal 51 corresponding to a desired set cloth tightening tension is set in advance by a user operation. The analog comparator 44 compares the upper thread tension signal 50 with the tension setting signal 51 and outputs an excessive tension detection signal 52 of H or L level.
[0025]
The cloth tightening phase output from the photocoupler 34 in the cloth tightening phase detection sensor 21 before entering the cloth tightening phase, that is, before the sewing machine main shaft rotation angle reaches 30 degrees during one rotation of the sewing machine main shaft 18. The signal 53 is an L level signal. For this reason, the D flip-flop 45 is forcibly cleared, and its inverted output signal 54 becomes H level. Then, 100 volts is output from the amplifier 46 and applied to the laminated piezoelectric element 22 of the thread gripper 16 so that the upper thread 11 is gripped by the thread gripper 16.
[0026]
When the sewing machine main shaft rotation angle exceeds 30 degrees and the cloth tightening phase is entered as the sewing machine main shaft 18 rotates, the cloth tightening phase signal 53 becomes H level and the forced clear signal for the D flip-flop 45 is released. Then, when the level of the needle thread tension signal 50 increases in accordance with the cloth tightening operation of the balance 19, and eventually becomes larger than the level of the tension setting signal 51, the excessive tension detection signal 52 changes from the L level to the H level. At this time, since the D input of the D flip-flop 45 is fixed at the H level, the D flip-flop 45 is set in response to the rising of the excessive tension detection signal 52, the inverted output signal 54 becomes the L level, and the amplifier 46 The output is 0 volts, and the thread gripper 16 releases the upper thread 11. Here, assuming that the upper thread 11 is not released, the upper thread tension signal 50 continues to increase beyond the level of the tension setting signal 51 as indicated by the dotted line, but in this embodiment, as described above. Since the upper thread 11 is released at the tension setting signal level, the upper thread tension quickly decreases and the level of the upper thread tension signal 50 decreases as shown by the solid line. That is, since the maximum value of the upper thread tension at the time of cloth fastening is limited by the level of the tension setting signal 51, the upper thread tension does not become excessive with respect to the set value. The cloth tension can be determined and adjusted.
[0027]
When the rotation angle of the main spindle of the sewing machine reaches 66 degrees, that is, when the upper dead center angle of the balance 19 where the feeding of the upper thread 11 and the end of the cloth tightening is reached, the cloth tightening phase signal 53 becomes L level again, and the D flip-flop 45 is The output signal 54 is forcibly cleared and the inverted output signal 54 becomes H level. Therefore, the output of the amplifier 46 becomes 100 volts, and the thread gripper 16 grips the upper thread 11 again.
[0028]
In FIG. 5, the pulse-like signal that appears in the needle thread tension signal 50 before entering the cloth tightening phase is an abnormal tension 55 that is transiently generated when the hook is pulled out and the hook supplementary claw is removed. The excessive tension detection signal 52 may become H level depending on the level of the abnormal tension 55. However, since the D flip-flop 45 is forcibly cleared in this phase, the inverted output signal 54 does not become L level. Absent.
[0029]
As described above, according to the upper thread tension adjusting device of the sewing machine of the first embodiment, the measured value of the cloth tightening tension measured by the upper thread tension sensor 17 is equal to the cloth tightening tension set by the tension setting unit 43. Since the upper thread is released by the thread gripper 16 when the set value becomes larger than the set value, the upper thread is not excessively tightened, and the upper thread is reliably re-gripped when the cloth tightening phase is completed. Therefore, the upper thread release control is not continued excessively, and the upper thread cloth tightening tension does not become too small. Therefore, the cloth tightening tension of each needle can be stabilized in an appropriate state against a transient and sudden change in the cloth tightening tension, and a uniform and beautiful stitch can be formed. Further, in the phases other than the cloth tightening phase, even if the abnormal tension 55 is generated, unexpected upper thread release control is not performed, and only the cloth tightening tension can be optimally adjusted.
[0030]
Next, a second embodiment will be described.
In the first embodiment, after the upper thread 11 is released due to an increase in the cloth tightening tension, the upper thread 11 is re-gripped when the sewing machine main shaft rotation angle reaches 66 degrees, whereas in the second embodiment, the upper thread 11 is re-gripped. After the upper thread 11 is released due to the increase in the tightening tension, the upper thread 11 is re-gripped according to the decrease in the tension of the upper thread 11. In addition, about the structure equivalent to 1st Example, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.
[0031]
The upper thread tension control device 140 provided in the upper thread tension adjusting device according to the second embodiment, as shown in FIG. 6, serves as a gripping tension setting means composed of a resistor that divides the output voltage of the tension setting unit 43. A drop tension setter 141 and an analog comparator 142 for comparing and outputting the voltage divided by the drop tension setter 141 and the output of the differential amplifier 42 are newly provided. The output of the analog comparator 142 is connected to the D flip-flop. Connected to the clear terminal. The drop tension setter 141 sets a set value of the upper thread tension at which the thread gripper 16 should re-hold the upper thread 11, and this set value depends on the ratio of the resistance values of the resistors R4 and R5. The needle thread tension is set to several tens% of the set value in conjunction with the set value set by the tension setting unit 43.
[0032]
Next, the operation of the needle thread tension adjusting device as the second embodiment will be described.
The waveform of each part in the upper thread tension control device 140 with respect to the rotation angle of the main spindle of the sewing machine with the needle top dead center being 0 degrees is as shown in the graph of FIG.
The upper thread tension signal 50 shown in FIG. 7 is given to the plus terminal of the analog comparator 142 shown in FIG. 6, while the tension setting signal 51 shown in FIG. A drop tension setting signal 150 divided by R5 is given, these signals are compared, a drop tension detection signal 151 is output, and applied to the D flip-flop 45 as a forced clear signal.
[0033]
Accordingly, the D flip-flop 45 and its inverted output signal 152 are set at the rise of the excessive tension detection signal 52 within the cloth tightening phase and output at the L level, and cleared at the L level of the drop tension detection signal 151 and at the H level. Is output. Therefore, when the upper thread tension increases with the cloth tightening operation and reaches the value set by the tension setting unit 43, the thread gripper 16 releases the upper thread 11, and the upper thread tension decreases as the upper thread is released. When the value becomes the value specified by the drop tension setter 141, the thread gripper 16 grips the upper thread 11 again.
[0034]
In the upper thread tension adjusting device of the sewing machine of the second embodiment described above, the measured value of the cloth tightening tension measured by the upper thread tension sensor 17 is larger than the set value of the cloth tightening tension set by the tension setting unit 43. When this happens, the upper thread is released by the thread gripper 16, so that the upper thread cloth tightening tension does not become excessive. In particular, since the upper thread is reliably re-gripped when the upper thread tension is lowered, excessive feeding of the thread when the upper thread is released can be accurately prevented, and the upper thread tightening tension becomes too low. Nor. Therefore, the cloth tightening tension of each needle can be stabilized in an appropriate state against a transient and sudden change in the cloth tightening tension, and a uniform and beautiful stitch can be formed.
[0035]
The configuration of the second embodiment assumes a sewing machine in which the level of the abnormal tension 55 described above is smaller than the cloth tightening tension set value by the tension setting device 43. Therefore, when the level of the abnormal tension 55 becomes larger than the set value by the tension setting unit 43, unexpected release control is performed by the large abnormal tension 55. In order to prevent such unexpected release control, the cloth clamp phase detection sensor 21 shown in the first embodiment is provided, and the cloth clamp phase signal 53 (see FIG. 5) is used in addition to the drop tension detection signal 151. In other than the cloth tightening phase, the D flip-flop 45 may be forcibly cleared.
[0036]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above embodiment, as the tension setting unit 43 and the drop tension setting unit 141, a voltage is generated using a resistor or a variable resistor, but an active element such as an operational amplifier may be used. Further, the setting value of the tension setting device 43 or the lowering tension setting device 141 may be set to be fixed or changed every needle.
[0037]
Furthermore, in the embodiment, a configuration is shown in which the D flip-flop 45 is forcibly cleared at a phase other than the cloth tightening phase. Usually, a large abnormal tension which is a problem is a tension called a hook catching tension and a hook supplementary catching tension. The phase in which these instantaneous strong tensions may appear is slightly before the cloth fastening phase. Therefore, instead of detecting the cloth tightening phase, an abnormal tension generation phase where the abnormal tension is generated may be detected, and the D flip-flop 45 may be forcibly cleared in the abnormal tension generation phase.
[0038]
The upper thread tension sensor 17 may be configured using a piezoelectric element, and the thread gripper 16 may be configured using an electromagnetic solenoid.
Further, the upper thread tension control devices 40 and 140 of the present embodiment are mainly constituted by so-called hardware such as an analog comparator, an operational amplifier, a digital IC, etc., but instead, a well-known CPU, ROM, RAM, By using an A / D converter or the like, it is possible to adopt a configuration in which each function is realized by software.
[0039]
【The invention's effect】
As described above, according to the upper thread tension adjusting device of claims 1 to 5 of the present invention, the upper thread is loosened immediately when the upper thread tension becomes excessive during the cloth tightening of each needle. Even if there is a transient and sudden increase in the tightening tension, the upper thread tension can be prevented from increasing in real time, and an excellent effect can be achieved in that uniform beautiful seams can be formed. Further, since the digital control is instructed to hold or release the needle thread tension adjusting means, the number of parts can be reduced and the configuration can be made at low cost.
[0040]
In particular, according to the upper thread tension adjusting device according to claim 2 or 3, since the upper thread can be re-gripped at an appropriate timing, the upper thread is unwound excessively or the tension of the upper thread becomes too low. There is no such problem, and it is possible to stabilize the cloth tightening tension of each needle in an appropriate state against transient and sudden fluctuations in the cloth tightening tension. Comparing the configuration according to claim 2 and the configuration according to claim 3, there is an advantage that the former can easily determine the timing of re-gripping, while the latter has a more optimal timing for re-gripping. There is an advantage of being able to make timing.
[0041]
Furthermore, according to the upper thread tension adjusting device of the fourth or fifth aspect, it is possible to optimally adjust only the cloth tightening tension while ignoring the increase in tension generated other than the cloth tightening. In addition, since the configuration according to claim 4 can be functionally shared with the configuration according to claim 2, the configuration according to claim 4 is more desirable when the configuration according to claim 2 is adopted.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an upper thread tension adjusting device of a sewing machine as a first embodiment.
FIG. 2 is a perspective view showing a thread gripper.
FIG. 3 is a perspective view showing an upper thread tension sensor.
FIG. 4 is a partially broken perspective view showing a cloth tightening phase detection sensor.
FIG. 5 is a graph showing waveforms of respective parts in the upper thread tension control device 40 in the first embodiment.
FIG. 6 is a schematic configuration diagram of a main part of an upper thread tension adjusting device of a sewing machine as a second embodiment.
FIG. 7 is a graph showing waveforms of respective parts in the upper thread tension control device 140 in the second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Sewing machine main body, 11 ... Upper thread, 12 ... Bobbin, 13, 14, 15 ... Yarn hook, 16 ... Yarn gripper, 17 ... Upper thread tension sensor, 18. ..Machine spindle, 19 ... balance, 20 ... sewing needle, 21 ... cloth clamping phase detection sensor, 22 ... multilayer piezoelectric element, 23 ... L-shaped bracket, 24 ... hinge part, 25 ... Thread gripping arm, 26 ... Thread gripping plate, 27 ... Thread gripping counter plate, 28 ... Tension sensor holder, 29 ... Metal plate, 30 ... Tension sensor thread hook, 31 ... strain gauge, 32 ... notch, 33 ... disk, 34 ... photocoupler, 40, 140 ... needle thread tension control device, 41 ... resistance bridge circuit, 42 ..Differential amplifier 43 ... Tension setting device 44,142 ... Analog comparator 45 ... D Flops, 46 ... amplifier, 141 ... reduced tension setter.

Claims (5)

An upper thread tension adjusting means that is arranged in a thread path from the upper thread supply source to the needle and is capable of adjusting the upper thread tension to be increased or decreased by switching between two states of gripping and releasing the upper thread;
An upper thread tension measuring means arranged in a yarn path from the upper thread tension adjusting means to the needle and capable of measuring the upper thread tension;
Cloth tightening tension setting means capable of setting the upper thread cloth tightening tension;
An upper thread tension comparing means for comparing a set value of the cloth tightening tension set by the cloth tightening tension setting means and a measured value of the cloth tightening tension measured by the upper thread tension measuring means;
The upper thread tension adjusting means always holds the upper thread, and when the measured value of the cloth tightening tension becomes larger than the set value of the cloth tightening tension, the upper thread tension adjusting means releases the upper thread. An upper thread tension adjusting device for a sewing machine comprising: a grip release control means for performing control. In the upper thread tension adjusting device of the sewing machine according to claim 1,
A cloth tightening end detecting means capable of detecting a time when the phase in which the cloth tightening tension is generated ends;
Release control continuation means for continuing upper thread release control by the grip release control means until the end of the phase in which the cloth tightening tension is detected is detected by the cloth tightening end detection means. Upper thread tension adjusting device for sewing machine. In the upper thread tension adjusting device of the sewing machine according to claim 1,
A gripping tension setting means for setting an upper thread tension to cause the upper thread tension adjusting means to grip the upper thread;
Release control continuation means for continuing the upper thread release control by the grip release control means until the measured value of the cloth tightening tension becomes smaller than the set value set by the grip tension setting means. The needle thread tension adjusting device of the sewing machine. In the upper thread tension adjusting device of the sewing machine according to any one of claims 1 to 3,
Cloth clamping phase detection means capable of detecting a cloth clamping phase in which the cloth clamping tension is generated;
The upper thread tension adjustment of the sewing machine, comprising: a release prohibiting means for prohibiting the upper thread release control by the grip release control means at a phase other than the cloth tightening phase detected by the cloth tightening phase detecting means. apparatus. In the upper thread tension adjusting device of the sewing machine according to any one of claims 1 to 3,
An abnormal tension generation phase detecting means capable of detecting an abnormal tension generation phase in which an abnormal tension before the cloth fastening phase is generated;
An upper thread tension adjusting device for a sewing machine, comprising: a release prohibiting means for prohibiting the upper thread release control by the grip release control means in the abnormal tension generation phase detected by the abnormal tension generation phase detecting means. .

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