JPH0356754B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a thread tension device that is located on the needle thread path between the needle thread (needle thread) supply source and the needle and applies tension to the needle thread. The present invention relates to a needle thread tension adjustment device for a sewing machine, and particularly relates to a device that automatically sets tension according to the type of thread.

[Conventional technology and its disadvantages] For example, in a lockstitch sewing machine, in order to form a seam with good thread tightness on cloth, the tension of the upper and lower threads must be set to a predetermined strength. As is well known from Japanese Utility Model Publication No. 45-2870 or Japanese Utility Model Publication No. 49-25635, etc., the pressing force of the leaf spring of the bobbin thread bobbin case is adjusted with a screw to apply a predetermined tension to the lower thread. A predetermined tension corresponding to the bobbin thread tension is applied to the upper thread (needle thread) using a thread tension device as is well known from the above publication. However, since the stitches have to be actually formed, the worker must operate the thread tension device while looking at the stitches, and make adjustments based on intuition, making the work complicated and requiring advanced techniques, which significantly reduces work efficiency. This resulted in a disadvantage.

Also, normally the same type of thread is used for the upper and lower threads, but the slippage (frictional resistance) of the threads varies depending on the type of thread.
For this reason, even if the leaf spring setting is constant, the actual bobbin thread tension will vary depending on the type of bobbin thread due to the frictional resistance it receives when passing between the leaf springs of the bobbin case. different. Therefore, when changing the type of upper and lower threads, the same complicated work as above is required to readjust the tension of the upper and lower threads, resulting in a drawback that work efficiency is significantly reduced. remove the defects of things,
The purpose is to improve work efficiency by automatically setting needle thread tension.

[Example] Embodiments of this invention will be described with reference to the drawings.

A thread spool 33 is removably arranged on a spool pin 32 on a sewing machine head (not shown), and a thread spool 33 is placed on the path of the upper thread (needle thread) 1 between the thread spool 33 and a needle (not shown). , the auxiliary thread tension device 2 is placed on the front side of the path, and the main thread tension device 3 is placed on the back side of the path.

In FIG. 1, the main thread tension device 3 supports a shaft 5 so as to be movable in the axial direction with respect to the machine frame 4, and one plate 6a fixed to the shaft 5 is loosely fitted onto the shaft 5 and attached to the machine frame 4. The spring 7 expands and contracts in relation to the rotational position of the operating dial 8, which is always pressed against the other fixed plate 6b by the force of the spring 7 and supported on the machine frame so as to be rotatable about the shaft 5. It has a well-known structure that allows the pressure contact force to be adjusted. A gear 9 of approximately the same diameter is coaxially fixed to the operation dial 8, and a gear 12 is screwed to the drive shaft 11 of a four-phase stepping motor 10 fixed to the machine frame. to be fixed.

In FIG. 2, the auxiliary thread tension device 2 has a pair of plates 13a and 13b, and is approximately equal to the pressing force of the leaf spring (not shown) of the lower thread bobbin case, which is extremely small compared to the spring 7 of the main thread tension device 3. Pressed together by elastic force.

A thread tension detection means is arranged on the thread path between the main thread tension device 3 and the auxiliary thread tension device 2. A support shaft 14 having an axis perpendicular to the axial direction of the shaft 5 is fixed to a machine frame, and a movable body 15 is supported with respect to the support shaft 14 so as to be movable in the axial direction. A pulley 16 that is rotatable around an axis parallel to the shaft 5 and around which the needle thread 1 is wrapped between the auxiliary thread tension device 2 and the main thread tension device 3.
is supported at the upper end of the movable body 15, and an operating shaft 17 is fixedly supported at the lower end of the movable body 15 in parallel to the support shaft 14. (left side in Figure 2) is subjected to an elastic force. The operating shaft 17 is arranged in relation to a potentiometer 19 fixed to the machine frame, and the potentiometer 1
Reference numeral 9 relates to the movement of the operating shaft 17 with the moving body 15, and generates different voltage outputs corresponding to the movement position.

In this thread tension detection means, the upper thread 1, which is passed around the auxiliary thread tension device 2, the pulley 16, and the main thread tension device 3, is pulled and drawn out toward the needle each time a stitch is formed by driving the sewing machine. At this time, the pulley 16 receives a force acting in the other axial direction of the support shaft 14 (to the right in FIG. 2) in approximately proportion to the tension of the auxiliary thread tension device 2, and the movable body 15 receives the action of the coil spring 18 due to this force. It moves against the force and stops when the tension of the auxiliary thread tension device 2 and the elastic force of the coiled spring 18 are balanced. That is, when the force 2T that the pulley 16 receives from the needle thread 1 and the elastic force F of the coiled spring 18 are balanced, 2T=F(kx), and this equation becomes x=2T/k, so that depending on the change in T, the elastic force F of the coiled spring 18 becomes 2T=F(kx). The amount of elongation, that is, the amount of displacement of the moving body 15 can be determined. As mentioned above, the auxiliary thread tension device 2
Since T has a very small elastic force against the spring 7 of the main thread tension device 3, which is almost equal to the pressing force by the leaf spring of the bobbin thread bobbin case, T is a tension almost equal to the bobbin thread tension, and this tension is determined as described above. The expansion and contraction (displacement amount x) of the coiled spring 18 is determined by the type of yarn. Therefore, the moving body 15
The movement position corresponds to the yarn type.

In FIG. 7, a thread spool detector 24 placed inside the sewing machine frame has a switch 24a protruding from a hole 34 provided in the machine frame, and the switch 24a is activated when the thread spool 33 is attached to the thread spool pin 32. It is pressed down to close and generates an H level signal with a predetermined pulse width.

Next, the electric circuit shown in FIG. 3 will be explained. G
1, G2, G4 are or gates, G3, G5, G6
is an and gate. W1 and W2 are well-known one-shot circuits, and the one-shot circuit W1 is triggered by the startup detection signal generated from the sewing machine startup circuit LS, and generates an H level output while the sewing machine is sewing 5 or 6 stitches at low speed. W2 is triggered by the rise of the output of the one shot circuit W1, and generates an H level output for a predetermined time. 20 is an A/D converter that converts the analog output of the potentiometer 19 into digital;
Reference numeral 21 is a latch circuit that reads the output of the converter 20 when the output of the one-shot circuit W1 falls, outputs it, and holds it.

The ROM is a memory circuit that stores thread tension data in advance, and based on the experimentally obtained graph in Fig. 6, the upper thread tension for a plurality of predetermined bobbin thread tensions is determined to be three (high, medium, and weak) for each thread type. The thread tension data is read out in accordance with the output contents of the latch circuit 21, and a 6-bit output is generated. The graph in FIG. 6 was obtained through experiments by the applicant. For example, when initially setting the pressure on the bobbin leaf spring to set the bobbin thread tension to 15 g,
If type A thread is used as the upper and lower threads, the lower thread tension will be 15 g, and the optimal needle thread tension will be approximately 180 g. If you change it to , the actual bobbin thread tension will be, for example, 10, because the slippage and elongation are different from thread I.
g, and the optimum needle thread tension is, for example, about 130 g. Similarly, if thread of type E is used, the actual bobbin thread tension is 19 g, and the optimum needle thread tension is about 200 g.
g. Therefore, the optimum upper thread tension for each type of thread relative to the lower thread tension can be determined based on this graph. 2
2 is an initial setting circuit, which connects the plate 6 of the main thread tension regulator 3.
It outputs data (6 bits) for controlling the stepping motor 10 so as to apply a predetermined pressing force to a and 6b, that is, to apply a predetermined tension to the upper thread 1, and the setting position can be input from the outside. be adjustable. 23 is a well-known multiplexer, which selects the ROM data and the output data of the initial setting circuit 22, reads one of them, and outputs it;
When the H level is input to the select input S from the terminal of the flip-flop circuit F1, the data from the initial setting circuit 22 is input, and when the L level is input, the data is input from the initial setting circuit 22.
Select each ROM data. Reference numeral 25 is a reset circuit, which resets H with a predetermined pulse width when the power is turned on.
Generates a level signal.

CT1 and CT2 are binary up-down counters that use the clock pulse of the oscillator 26 as a clock input. The counter CT1 is reset by the H level output of the gate G1, and adds the clock pulse when the gate G5 is at the H level and subtracts it when it is at the L level to generate a two-bit output to a comparator 29 and a decoder 27, which will be described later. One pulse is generated in the counter CT2 every time four clock pulses are calculated. Counter CT2 is gate G
When the A terminal of the comparator 29 is at the H level output, the output of the counter CT1 synchronized with the clock pulse is added, and when the A terminal is at the L level, it is subtracted, and the 4-bit output is sent to the comparator 29. Occur. Therefore, the outputs of counters CT1 and CT2 input to the comparator 29 are as follows: the output of counter CT1 is the lower two digits, and the output of counter CT2 is the lower two digits.
The output is the first four-digit signal.

The decoder 27 converts the 2-bit output of the counter CT1 into a 4-bit output corresponding to each phase of ABCD of the stepping motor 10, and sequentially outputs the output from the drive circuit 28 so that one terminal becomes an H level output.
Output to. The drive circuit 28 sequentially supplies an energizing current to each phase of ABCD based on the output of the decoder 27 so as to step drive the stepping motor 10.

The comparator 29 compares the 6-bit output data of the multiplexer 23 with the 6-bit output data of the counters CT1 and CT2, and outputs the data from the multiplexer 23.
When the content (numeric value) of the output data of counters CT1 and CT2 is smaller than the output of counter 3, the A and B output terminals are set to H and L levels, and in the opposite case, set to L and L levels, and when both match, they are set to L levels. , H level.
F1 to F3 are J-K type flip-flops, and F1 is reset by the H level output of the gate G1 to set the terminal to the H level, and is preset by the H output of the B terminal of the comparator 29 to set the Q terminal to the L output. do. F2 is reset by the H output of gate G4, making the terminal H level,
The H output opens the gate G3 and makes the drive circuit 28 inactive, and the B of the comparator 29
It is preset by the H output of the terminal and the terminal is set to L.
level, closes the gate G3, and activates the delay circuit 30. The delay circuit 30 activates the drive circuit 28 after a predetermined period of time has elapsed since its activation. F3
is reset when the gate G6 becomes H level due to the output from the A terminal of the decoder 27 and the origin detector 31, the terminal is set to the H level, the Q terminal is set to the L level, and the H output of the terminal opens the gate G5. In addition, it is preset by the H output of gate G1 to set the terminal to L level and the Q terminal to H level.
The gate G5 is closed by the L output of the terminal. The origin detector 31 is arranged in relation to the stepping motor 10, and generates an H level detection signal when the stepping motor 10 is located at the origin.

The present invention has the above-mentioned structure, and its operation will be explained next when a thread of type A is used as the upper and lower threads and is replaced with a thread of type C.

The main thread tension device 3 and the leaf spring of the bobbin case are set so that the upper thread has an appropriate tension of 180 g and the lower thread has an appropriate tension of 15 g for thread type A (see Fig. 6).

When the bobbin thread bobbin in the bobbin case is replaced with one of the thread type A and pulled out via the leaf spring, the tension of the bobbin thread becomes 10 g, as is clear from FIG. 6, despite the above settings. When a new thread spool 33 is attached to the thread spool pin 32 in order to replace the upper thread, an H level signal with a predetermined pulse width is generated from the thread spool detector 24.
Through gate G1, counter CT1 and flip-flop F1 are reset and flip-flop F3 is preset, and through gate G4, flip-flop F2 is reset. Multiplexer 2 is reset by resetting flip-flop F1.
3 reads data from the initial setting circuit 22, for example, data corresponding to needle thread tension of 180 g and outputs it. Further, by resetting flip-flop F2, the driving circuit is activated and data G3 is opened. By presetting the flip-flop F3, the counter CT2 is reset via the gate G2, and the gate G5 is set to the L level.
Set CT1 to subtraction state.

The counter CT1 inputs and subtracts the clock pulse of the oscillator 2, and its two-bit output drives the stepping motor 10 toward the origin via the decoder 27 and the drive circuit 28, and a detection signal is generated from the origin detection circuit 31. The output from the A terminal of the decoder 27 after that causes the gate G6 to go to the H level, the flip-flop F3 is reset, and the reset of the counter CT2 is canceled via the gate G2, and the counter CT1 is brought into the addition state. Counter CT2
When CT1 is in the reset state, only the input of counter CT1 changes among the counter side inputs of comparator 29, and does not match the output of multiplexer 23.

The counter CT1 enters the addition state of adding clock pulses, and generates one pulse to the counter CT2 every time four clock pulses are added.The counter CT2 adds the pulses of the counter CT1 in synchronization with the clock pulses, and the drive circuit 28 drives the stepping motor 10 stepwise in the direction opposite to the origin. Comparator 29 is this counter CT
1. When the output of CT2 matches the output of multiplexer 23 (data of initial setting circuit 22),
That is, the main thread tension device 3 is controlled by the stepping motor 10.
When the needle thread tension is set to 180 g according to the data of the initial setting circuit 22, the B terminal is set to H level. This B terminal output causes flip-flop F
1, F2 is preset, and the multiplexer 23 is
The ROM data is read and output, gate G3 is opened, and delay circuit 30 is activated.

When the sewing machine is driven at low speed in this state, the needle thread 1 is pulled toward the needle each time a stitch is knotted in cooperation with the bobbin thread, but at this time, the auxiliary tension device 2 and the main tension device 3
The movable body 15 having the pulley 16 on which the needle thread 1 is applied moves on the support shaft 14 in the other axial direction (to the right in FIG. 2) to a position corresponding to the needle thread 1.

As a result, the potentiometer 19 generates an analog output corresponding to its movement position, which is converted into a digital code by the A/D converter 20. One-shot W1W2 is triggered by a start-up detection signal generated from the start-up circuit 32 when the sewing machine is started, and after five or six stitches are sewn after the sewing machine starts, the output of this one-shot W1 falls, and this causes the latch circuit to close. 21 holds the output of the converter 20 and outputs it to the ROM, and also triggers the one shot W2. Therefore, the ROM outputs the needle thread tension data corresponding to the sewing thread C, that is, the needle thread tension data of 130 g, to the multiplexer 23. Due to the H output of the one shot W2 for a predetermined time, the gate circuit G4 becomes an H output and resets the flip-flop F2, which opens the gate circuit _G8 and starts the counter.
Clock pulses are input to CT ₁ and CT ₂ . At this time, since the output data of the multiplexer 23 is smaller than the outputs of the counters CT ₁ and CT ₂ , the comparator 29 outputs the A and B terminals L and L, and both counters
CT ₁ and CT ₂ are in a subtraction state, and the output of counter CT ₁ drives the stepping motor 10 in the direction of the origin, and when the outputs of counters CT ₁ and CT ₂ and the multiplexer 23 match, the comparator 29
The A and B terminals of the flip-flop become L and H.
Preset F ₂ and connect gate circuit G ₃ in the same way as above.
When the stepping motor 10 is closed, the stepping motor 10 is closed.
It is stopped at the step angle set by the ROM data. Therefore, the needle thread tension applied by the main thread tension device 3 is 10 g which the bobbin thread receives from the leaf spring of the bobbin case.
The tension is 130g, which corresponds to the tension shown in Figure 6.

Furthermore, when using the sewing thread E, the output data (200g) of the ROM read out in accordance with the output of the potentiometer ₁₉ , that is, the output data of the multiplexer ₂₃ , is read out in accordance with the output of the potentiometer 19, rather than the output data of the initial setting circuit 22, that is, the outputs of the counters CT1 and CT2. Since the output is larger,
The A and B terminals of the comparator 29 become H and L outputs, the counters CT ₁ and CT ₂ become in an addition state, and the output of the counter CT ₁ drives the stepping motor 10 stepwise in the direction opposite to the origin.
When CT ₁ and CT ₂ match the output data of the multiplexer 23, the stepping motor 10
It is stopped at the step angle set by the ROM output data. Therefore, the needle thread tension applied by the main thread tension device 3 is received by the bobbin thread from the leaf spring of the bobbin case.
The result is 200g, which corresponds to a tension of 19g (Figure 6).

Next, a second embodiment controlled by a microcomputer will be described.

The mechanical configuration is the same as the present embodiment and will be omitted.

In the electric circuit (FIG. 4), parts that overlap with those in this embodiment are designated by the same numbers and explanations thereof will be omitted.

NP is a needle position detection means that is arranged in relation to the main shaft of the sewing machine and generates a rotation signal at a predetermined rotation angle for each revolution, and MC is a microcomputer (microcomputer). A program is described that stores data on the corresponding needle thread tension and sets the needle thread tension based on the flow shown in FIG.

Next, the operation of this second embodiment will be explained according to the flowchart of FIG.

When the power is turned on, the sewing machine motor and thread tension flags are reset to 0, and at this time it is judged whether or not there is an output from the potentiometer 19, and when the power is off, the thread tension flag is reset to 0. Next, the thread tension flag is "judged" and when it is 1, the state of the potentiometer 19 is "judged" again, and when it is 0, the stepping motor 10 is turned on to return to the home position, and the home position is reached. At that time, the stepping motor 10 is operated to reach the setting value of the initial setting circuit 22. Next, the sewing machine motor flag is judged, and when it is 1, it is "judged" whether the sewing machine main shaft has rotated six times, and when the sewing machine main shaft has rotated six times, the output of the potentiometer 19 is read, and the setting value is high.
The stepping motor 10 is operated so that the tension value is either medium or low, then the power to the stepping motor 10 is turned off, the thread tension flag is set to 1, and the output of the potentiometer 19 is set to ``1'' again. Return to “Judgment.”

In the second embodiment, "judgment" of the output of the potentiometer was included, but as shown in FIG. It's okay.

Further, in the first and second embodiments, a tone disc was used as the auxiliary tone device 2, but other means such as a leaf spring may be used.

Further, in the first and second embodiments, a stepping motor is used, but a servo motor, an electromagnet, etc. may also be used.

Furthermore, in the first and second embodiments, a potentiometer was used as the sewing thread detection means, but a strain gauge was placed on the sewing thread path between the main tension device and the auxiliary tension device so that the output of the strain gauge could be monitored. It's okay.

Furthermore, although the first and second embodiments are shown for a lockstitch sewing machine that uses top and bottom threads, similar results can be obtained for a chainstitch sewing machine that uses top and bottom threads or a chainstitch sewing machine that uses only needle threads. The tension to be applied to the needle thread based on experimental data may be stored in the ROM as data, and read out using a detection signal from the detection means 19 to control the needle thread tension.

Furthermore, in the first and second embodiments, the sewing thread detection means was arranged in the needle thread path, but as shown in FIG.
For example, a strain gauge 4 is attached to the lower end surface of the needle hole 39a of the throat plate 39 during the path of the bobbin thread 38 between
It is also possible to fix the value to 0 and read data from the ROM based on its output.

[Effect] As described above, according to the present invention, it is possible to apply the optimum needle thread tension to the thread actually used, so that the seam can always be formed with the appropriate tension and the seam can be neatly formed. In addition, when changing the thread, the operator does not need to operate a dial to set the thread tension, and can apply the desired tension by simply moving the sewing machine, which significantly improves work efficiency. is obtained.

[Brief explanation of drawings]

Figure 1 is a side view of the main thread tension device of this embodiment;
The figure is a perspective view of the sewing thread detection means, FIG. 3 is an electric circuit,
FIG. 4 shows the electric circuit of the second embodiment, FIG. 5 shows the flow of the tension setting program of the second embodiment, and FIG.
The figure is a graph showing an example of the relationship between the tension of upper and lower threads corresponding to the type of sewing thread, FIG. 7 is a thread spool detection means, and FIG. 8 is a side view showing an embodiment in which a sewing thread detection means is arranged in the bobbin thread path. It is.

Claims (1)

[Scope of Claims] 1. A thread tension device 3 disposed on the needle thread path between the needle thread supply source and the needle and capable of adjusting the tension applied to the needle thread; A driving body 10 is arranged in relation to the thread tension device so as to change the needle thread tension by the thread tension device in accordance with the amount of displacement, and a drive body 10 is arranged in relation to the thread tension device so as to change the needle thread tension by the thread tension device in accordance with the amount of displacement, and a drive body 10 that corresponds to the actual thread tension for each type of thread when a specific acting force is applied. Memory means (ROM) that stores data regarding appropriate needle thread tension for each type of thread
and detection means 2 and 1 arranged on the bobbin thread or needle thread path to detect the thread tension in a state where the specific acting force is applied and generate a detection signal corresponding to the thread tension.
9, reading means 23 for reading data of the corresponding appropriate needle thread tension from the storage means in relation to the detection signal;
24, F1, a drive means 28 for displacing the drive body, and control means 26 to 31, CT1, for controlling the drive means so that the drive body applies the needle thread tension according to the read data.
A sewing machine needle thread tension adjustment device equipped with CT2, F2, F3, G2, G3, G5, G6.