JPH0473091A - Controller for tension of needle thread in sewing machine - Google Patents

Abstract

PURPOSE:To successively control the tension of a needle thread in accord with the movement of a mechanism by providing a needle thread clamping means for clamping the needle thread in a thread guide between a thread take-up lever and a needle thread supply source and interlocking the command value of clamping force applied to the needle thread clamping means with the operation of the thread take-up lever. CONSTITUTION:The phase of a thread take-up lever 3 is detected as voltage by a potentiometer 9. A phase detecting signal is A/D converted and input to a one-chip microcomputer 31. In a memory of the one-chip microcomputer 31, one cycle of feature data of a clamping force pattern representing a relation between the phase of the thread take-up lever 3 during a sewing operation and an optimum needle thread clamping force is stored. Namely, the current phase of the thread take-up lever 3 is calculated from a voltage value input from the potentiometer 9. The needle thread clamping force corresponding to the phase is obtained from the clamping force pattern. Then, a current value necessary for generating desired needle thread clamping force in an electromagnet constituting a needle thread clamping means 7 is obtained from calculation and output to a servo amplifier 32. In accordance with the input current command, the servo amplifier 32 applies the desired current to a coil 21 of the needle thread clamping means 7.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for controlling the needle thread tension of a sewing machine, which enables stable sewing regardless of changes in sewing speed or sewing conditions by controlling the needle thread tension of the sewing machine. This relates to a control device.

[Conventional technology]

In conventional sewing machines, the tension of the upper thread during sewing was adjusted by the force of the preset thread tension plate, and remained constant regardless of the sewing operation, making high-speed sewing difficult. .

To solve this problem, as shown in Japanese Unexamined Patent Application Publication No. 159987/1987, stable sewing at high speed is possible by configuring the upper thread unwinding device and the cloth tightening device using a thread take-up separately. There have been proposals to do so.

FIG. 9 is a block diagram showing the configuration of the automatic sewing tension control device of the sewing machine disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 61-159987. In the figure, 1 is a sewing cloth, 2 is a sewing needle, and 3
4 is a thread take-up spring, 5.6 is a guide, 17 is an electromagnetic needle thread gripper for tightening the cloth by the thread take-up lever 3, 13 is a thread pulling roller with a built-in encoder, 14 is a presser roller, and 15 is a needle thread paying-out control. 16 is a paste tension plate, 18 is a needle thread, and 8 is a needle thread bobbin as a supply source of the needle thread 18. Note that the symbol A indicates a cloth tightening device portion using the thread take-up lever 3, and the symbol B indicates a needle thread pay-out device portion.

Next, the operation will be explained.

The upper thread 18 from the upper thread bobbin 8 is attached to the past tension disc 1.
6 gives tension to the extent that the thread is not disturbed, passes through the electromagnetic upper thread gripper 15 for controlling upper thread reeling out, which is in an inactive state, and is held between the thread reeling roller 13 with a built-in encoder and the presser roller 14, and then moved to the thread take-up lever 3. It is rolled out to the side. The feeding amount control is carried out by stopping the running of the needle thread 18 by gripping the needle thread by the electromagnetic needle thread gripper 15 for controlling needle thread feeding, and then moving the needle thread 18 between the encoder built-in thread feeding roller 13 and the needle thread 1.
This is performed by an upper thread unwinding control device that causes a sliding action with respect to the upper thread 8, so that the encoder-incorporated yarn unwinding roller 13 continues to rotate, but the supply of the upper thread 18 is stopped.

The needle thread 18 that has been fed out to the thread take-up lever 3 in this way passes through the electromagnetic needle thread gripper 17 for cloth tightening, which is in an inoperative state, the guide 6°5, and the thread take-up spring 4, and then passes through the electromagnetic needle thread gripper 17 for cloth tightening, which is in an inoperative state, the guide 6°5, and the thread take-up spring 4. Due to the cloth tightening action of the thread take-up 3 at the time when the upper thread is gripped by the gripper 17, the sewing needle 2 is used to form the first stitch of the sewing cloth 1.

[Problem to be solved by the invention]

The sewing tension control device of a conventional sewing machine is configured as described above, and by actively letting out the upper thread 18, the upper thread 18 is adjusted to be suitable for supplying the upper thread 18 and for tightening the cloth.
However, the tension of the upper thread 18 is obtained by the ON10 F F of the electromagnetic upper thread gripper 15 for controlling upper thread payout and the electromagnetic upper thread gripper 17 for tightening the cloth. The tension of the upper thread 18 is determined only by the intermittent supply of the upper thread 18 and the movement of other mechanisms of the sewing machine, and it is impossible to directly control the tension accurately and continuously. Another problem was that the number of parts increased, making the structure of the sewing machine complex.

This invention was made to solve the above-mentioned problems, and it is possible to directly and continuously control the tension of the needle thread, and to create a sewing machine that can achieve this with a simple mechanism. The purpose is to obtain a thread tension control device.

[Means for Solving the Problems] A needle thread tension control device for a sewing machine according to the present invention includes a needle thread gripping device for gripping the needle thread in a thread path between a thread take-up thread take-up and a needle thread supply source, and a gripping force control device that controls the gripping force with which the thread gripping device grips the upper thread; a phase detector that detects the phase of the balance; and the gripping force control device controls based on a phase detection signal of the phase detector. A gripping force calculation device for calculating the gripping force to be used is provided.

[Function] The upper thread tension control device of the sewing machine according to the present invention changes the command value of the gripping force given to the gripping force control device in conjunction with the operation of the thread take-up, so that the tension of the upper thread can be adjusted in accordance with the movement of the mechanism. continuously controlled.

〔Example〕

A first embodiment of the present invention will be described below with reference to the drawings.

In Figure 1, 1 is a suture cloth, 2 is a sewing needle, 3 is a balance,
4 is a thread take-up spring, 5.6 is a guide, 7 is an electromagnetic needle thread gripping device, 8 is a needle thread bobbin, and 18 is a needle thread. Further, 9 is a phase detector for detecting the phase of the balance 3, and a potentiometer 9 is used in this embodiment. Reference numeral 10 indicates a gripping force calculation device that calculates a desired upper thread gripping force based on the phase detection signal of the phase detector 9; This is a gripping force control device that generates force.

FIG. 2 is a diagram showing the detailed structure of the upper thread gripping device 7. Reference numeral 21 shows a coil, 22 an armature that moves when the coil 21 is energized, and 23 a armature that moves when the coil 21 is energized. The fixed side iron cores 24a and 24b forming a magnetic circuit between them are attached to the armature 22 and the fixed side iron core 23, respectively, and the upper thread 18
A pair of thread tension disks 25 holding the thread conductor (conducting wire) conduct current to the coil 21.

Further, FIG. 3 shows a configuration in which the grip force calculation device 10 and the grip force control device 11 are realized by a microcomputer and other electric circuits, and 31 indicates the phase detection signal of the potentiometer 9. A
/D-converted signal is added to one-chip microcontroller, 3
Reference numeral 2 denotes a servo amplifier that controls the needle thread gripping device 7 in accordance with a command value calculated by the one-chip microcomputer 31 and converted from D/A.

In addition, FIGS. 4(A) and 4(B) show the one-chip microcomputer 3.
1 is a flowchart showing the contents of processing carried out inside the device 1 and characteristic data necessary for the processing.

Next, the operation will be explained.

Similarly to the conventional sewing machine, in the sewing machine according to the present invention, the needle thread 18 is supplied from the needle thread bobbin 8 to the sewing needle 2 after passing through the needle thread gripping device 7, the guide 6.5, the thread take-up spring 4, and the thread take-up lever 3. . In conventional sewing machines, the part corresponding to the needle thread gripping device 7 of the present invention is the thread tension disc 16 shown in FIG. 9, and the preset needle thread gripping force cannot be changed.

In addition, in conventional sewing machines, the two operations of tightening the cloth and letting out the upper thread 18 are realized by the movements of the thread take-up lever 3 and the thread take-up spring 4, and the balance between these two operations is adjusted by the thread tension disc 16. Was.

Since this balance changes as the sewing speed increases, it has been difficult for conventional sewing machines to perform sewing with good quality at both low and high speeds.

In contrast, in the present invention, the above two operations are performed by the upper thread gripping device 7, which can actively change the gripping force in synchronization with the phase of the thread take-up 3. Stable sewing can be achieved without being affected by changes in balance.

In this first embodiment, the phase of the balance 3 is detected as a voltage by the potentiometer 9, and the phase detection signal is A/D converted and input to the one-chip microcomputer 31. As shown in Figure 4 (B), one-chip microcomputer 3
The memory in the sewing machine 1 stores one cycle's worth of gripping cover turn characteristic data indicating the relationship between the phase of the thread take-up 3 associated with the sewing operation and the optimum needle thread gripping force. In FIG. 4(A), the one-chip microcomputer 31 calculates the current phase of the thread take-up lever 3 from the voltage value input from the potentiometer 9 in step STI, and calculates the upper thread gripping force corresponding to the phase in step ST2. Obtained from the grip cover turn. Next, in step ST3, a current value necessary to generate a desired needle thread gripping force in the electromagnet constituting the needle thread gripping device 7 is calculated, and a current command corresponding to the current value is given to the servo amplifier in step ST4. Output to 32. According to the input current command, the servo amplifier 32 applies a desired current to the coil 21 of the needle thread gripping device 7. Note that steps STI and ST2 are performed by the gripping force calculation device 10, and steps ST3. ST4 is performed by the gripping force control device 11.

This upper thread gripping device 7 constitutes an electromagnet that generates a magnetic circuit between the armature 22 and the fixed side iron core 23 when the coil 21 is energized. The armature 22 is attracted to the fixed side iron core 23 by the action of the magnetic circuit due to the energization,
As a result, a gripping force is generated between the pair of thread tension discs 24a and 24b attached to the armature 22 and the fixed side iron core 23, respectively, and a restraining force due to friction is generated on the needle thread 18 passing between them. . It is known that the attractive force generated by an electromagnet changes depending on the width of the gap in its magnetic circuit, but in this needle thread gripping device 7, the distance between the armature 22 and the fixed side iron core 23 is approximately constant. Therefore, the suction force can be easily calculated.

FIG. 5 shows the relationship between the needle thread gripping force value for one cycle stored in the memory of the one-chip microcomputer 31, the movement of the thread take-up lever 3, and the changes in needle thread tension. In FIG. 5, section A is a section in which the upper thread 18 is not paid out;
Section B is a section in which the feeding operation of the upper thread 18 by the thread take-up 3 and the cloth tightening operation are performed in parallel. Since the upper thread 18 is not paid out in section A, the upper thread gripping device 7 grips the upper thread 18 with a weak force, and in section B, the upper thread 18 is initially
In order to make it easier to draw out the balance 8, the gripping force is gradually increased while being gripped with a weak force, and the gripping force is increased towards the end, so that the balance 3 is tightened to be easily operated. This allows the needle thread 18 to be fed out and the cloth tightening operation to be performed stably.

FIG. 6 is a diagram showing the configuration of the second embodiment. In the figure, 12 is a tension detector that detects the tension of the upper thread 18, and the output of this tension detector 12 is sent to the gripping force control device 11. It has been entered.

The gripping force calculation device 10 and the gripping force control device 11 in FIG. 6 are composed of the one-chip microcomputer 31 as in the first embodiment, and the internal processing thereof is shown in FIG. 7(A)CB). This is shown in a flowchart and characteristic data.

FIG. 8 shows the tension detector 12 used in this second embodiment.
41 is a diagram showing the structure of the needle thread guide (
42 is a support spring that is deformed by the tension of the needle thread acting on the guide 41; 43 is a strain gauge that is attached to the support spring 42 to detect its deformation; 44 is a strain gauge 4;
This is a strain gauge amplifier that amplifies and outputs the weak signal from 3.

Next, the operation will be explained.

In this embodiment as well, the phase of the balance 3 is converted into voltage by the potentiometer 9, and the one-chip microcomputer 31
is input. In addition, in this embodiment, the memory of the one-chip microcomputer 31 stores the characteristics of the needle thread tension cover pattern indicating the relationship between the phase of the thread take-up 3 and the optimum needle thread tension accompanying the sewing operation, as shown in FIG. 7(B). Data is stored for one cycle. In FIG. 7(A), in step STI,
The current phase of the thread take-up lever 3 is calculated from the voltage value input from the potentiometer 9, and in step ST2, the needle thread tension command value corresponding to the phase is determined from the needle thread tension cover turn. Next, in step ST3, the current of the electromagnet according to the tension command value is calculated.

Next, in step ST4, the tension currently occurring in the needle thread 18 is determined from the signal output from the tension detector 12, and this is compared with the needle thread tension command value previously determined in step ST2 in step ST5. do.

When the current tension is smaller than the command value, the current command is made larger than the current value in step ST6, and when the current tension is larger than the command value, the current command is made smaller than the current value in step ST7, and the current The command is output to the servo amplifier 32 in step ST8. As a result, the gripping force generated by the electromagnet is controlled so that the actual tension of the needle thread 18 follows the desired needle thread tension command value.

According to the above, in the second embodiment, the needle thread tension can be controlled more accurately than in the first embodiment, and stable high-speed sewing is possible. Note that steps STI and ST2
is performed by the gripping force calculation device 10, and steps STI to ST
8 is performed by the gripping force control device 11.

In each of the embodiments described above, an electromagnet is used for the upper thread gripping device 7, but the same effect can be obtained even if a voice coil type drive device is used.

Further, in each of the above embodiments, various signal processing is performed by the one-chip microcomputer 31, but this portion may be performed only by an electric circuit without using a microcomputer.

Furthermore, by controlling the tension more accurately, it is also possible to omit the thread take-up spring 4.

[Effect of the invention] As described above, according to the present invention, an upper thread gripping device for gripping the upper thread is provided in the thread path between the thread take-up lever and the upper thread supply source, and the upper thread gripping device is provided with the upper thread gripping device. Since the gripping force command value is configured to change in conjunction with the movement of the thread take-up, the tension of the needle thread can be continuously controlled in accordance with the movement of the mechanism, and compared to conventional mechanisms, Since there is no need for an electromagnetic upper thread gripper for tightening the cloth or a thread pay-out roller, the above functions can be achieved with a simpler mechanism, which allows for high-quality sewing regardless of speed. The effect of this can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the needle thread tension control device of a sewing machine according to the first embodiment of the present invention, FIG. 2 is a block diagram showing the structure of the needle thread gripping device in the first embodiment, and FIG. FIG. 4 is a block diagram showing the specific configuration of the grip force calculation device and the grip force control device in the first embodiment, and FIG. 5 is a diagram showing the behavior of the needle thread and thread take-up in the operation of the first embodiment. FIG. 6 is a configuration diagram showing the needle thread tension control device of the sewing machine according to the second embodiment. The figure is a flowchart showing the internal processing of the gripping force calculation device and the gripping force control device in the embodiment of FIG. 2, and a characteristic diagram used for the internal processing, and FIG. FIG. 9 is a block diagram showing a conventional automatic sewing tension control device. 3 is a balance, 7 is an upper thread gripping device, 8 is an upper thread bobbin, 9 is a potentiometer, 10 is a gripping force calculation device, 11 is a gripping force control device, and 18 is an upper thread. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] an upper thread gripping device that is provided in a thread path between a thread take-up lever and an upper thread supply source and grips the upper thread; a gripping force control device that controls the gripping force with which the upper thread gripping device grips the upper thread; Needle thread tension control device for a sewing machine, comprising: a phase detector that detects the phase of a balance; and a gripping force calculation device that calculates a gripping force controlled by the gripping force control device based on a phase detection signal of the phase detector. .