JPH0218875B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sewing machine that allows automatic adjustment of sewing tension.

Currently, including household sewing machines and industrial sewing machines,
A problem that has become the subject of technological innovation is the possibility of automatic seam adjustment. Although it is possible to control the sewing tension by changing the thread tension, etc., it has been studied and researched by many people, but it is still not possible to detect the quality of sewing or detect subtle changes in sewing. It's not on. Therefore, the challenge is to develop sensors that accurately respond to these conditions. but,
This type of product has not yet been found to be suitable for practical use.

Conventionally, the needle thread tension was adjusted by increasing or decreasing the tension of the needle thread by changing the pressure on the tension disc, but now the tension of the needle thread is adjusted by increasing or decreasing the tension of the needle thread by changing the pressure of the tension disc. Because of this, it lacked stability and required delicate adjustment of pressure changes.

The present invention is based on the idea that a state between the underhang stitch and the underhang stitch of the sewing tension is a good sewing condition, which is a different point of view from the idea that has been researched up to now.
It detects the intertwining timing of the upper thread and bobbin thread in the suspended sewing state, and also detects the intertwining timing of the upper thread and bobbin thread in the suspended sewing state, and the necessary amount of upper thread is paid out by the thread take-up from the intermediate point. It's something you're trying to get done.

This will be explained below with reference to the drawings.

FIG. 1 is an explanatory diagram showing the relationship between the upper thread and the bobbin thread when fabrics are sewn together, and A shows a top hanging stitch, B shows a bottom hanging stitch, and C shows a good stitch.

By the way, if we consider the case of hanging stitching,
The needle thread is entangled with the bobbin thread and pulled, increasing the needle thread tension (the needle thread tension changes as shown in the diagram in Figure 2 when viewed on an oscillograph), so the detection of the interlacing time _t1 is as follows: It can be done easily. In addition, the interlacing timing _t3 of the upper thread and lower thread in the upper hanging sewing state is clear from Figure 1A, when upper hanging sewing occurs when the upper thread is fed by the fabric feed amount, that is, one stitch P. Therefore, the needle thread take-up curve of the thread take-up shown in Fig. 3,
In particular, as shown in the enlarged view in Figure B, the time t ₃ can be found in the figure. This is, of course, a counter that is normally provided in an electronic computer circuit as a computer for controlling the needle thread payout amount built into a sewing machine.
It can be easily calculated using registers, arithmetic circuits, and a CPU. If the needle thread take-up is started at time t ₂ intermediate between t ₁ and t ₃ , the amount of needle thread taken out by the thread take-up will bring about a good sewing condition.

To explain this in detail, Fig. 3A is a diagram showing the needle thread take-up curve of the thread take-up and the corresponding tension change due to the entanglement of the needle thread and bobbin thread. This is a fixed value specific to that sewing machine. On the other hand, the tension change due to the intertwining of the upper thread and lower thread is
The moment when the upper thread intertwines with the lower thread and tries to pull it into the sewing fabric, that is, the time when the upper thread and lower thread are intertwined in Figure 1B, and the amount of thread taken up by the thread take-up reaches its maximum. , that is, it reaches its maximum at the top dead center of the balance t ₀ ,
It then decreases. Therefore, if the start time t ₁ of the increase in needle thread tension is detected, the time when the needle thread and bobbin thread are intertwined in the form of hanging stitch state can be detected. Next, the time when the upper thread and lower thread intertwine in the form of hanging stitch state.
To find t ₃ , in order to perform top-hung stitching, as you can see from Figure 1 A, when sewing the first stitch with the upper thread, move the thread take-up by a length corresponding to one fabric feed amount determined by the fabric feed adjustment device. Therefore, in the needle thread take-up characteristic curve of the thread take-up peculiar to the sewing machine, the maximum point of the needle thread take-up curve of the thread take-up is set by the cloth feed amount P, as shown in Fig. 3 (b). A lower point in time, ie _t3 , is sought. therefore,
In order to obtain good stitching, the thread take-up should be used at the intermediate time between t ₁ and t ₃ .
This means that it is sufficient to perform a thread unwinding action from _t2 .

FIG. 4 is an explanatory diagram showing an embodiment in which the present invention is applied to a sewing machine.The sewing machine head 1 is provided with a thread take-up lever 2 and upper thread guides 3, 4 as in a general sewing machine. In place of the tension disc, a needle thread gripping disc opening/closing magnet (needle thread gripping device) 5 for gripping and releasing the needle thread is provided, and a strain gauge 6 is provided in the needle thread guide portion that guides the needle thread thread take-up. In addition, upper thread guide 3
also acts as a base tension device. Furthermore, the sewing machine 1 stores the thread take-up characteristics of the needle thread take-up and the sewing machine cloth feed amount, and the data detected by the strain meter (needle thread tension detection device) 6 indicates when the needle thread tension increases due to the entanglement of the needle thread and the bobbin thread. is added to calculate the upper thread grip release timing required for good sewing, and based on the data, the opening/closing magnet 5 is controlled to open and close the upper thread gripping discs 7 and 8 that grip the upper thread. It is configured. In addition, the reference numeral 9 in the figure is a display that shows the level of the stitches when a device is installed that can perform top-hung stitching and bottom-hung stitching as needed. ), 10 is a spool. In addition, in the above description, it is also possible to grip the upper thread using a pulse motor and a feed roller as the upper thread gripping device.

As described above, according to the present invention, the amount of upper thread necessary for good sewing is determined by detecting the intertwining timing of the upper thread and lower thread and adding the needle thread take-up characteristics of the thread take-up and the cloth feed amount. Appropriate control of the needle thread gripping member is performed by calculating the opening/closing timing of the needle thread gripping member for taking in the needle thread with the thread take-up, making use of changes in needle thread tension that can be easily and accurately detected. Therefore, it is possible to always perform good sewing.

FIG. 5 is a diagram illustrating the outline of a computer circuit used in the present invention, in which the strain meter 6 detects the time t ₁ at which the needle thread tension starts to increase due to the entanglement of the needle thread and bobbin thread during sewing work, and The needle thread take-up timing t ₃ is determined based on the material feed amount P, the needle thread take-up characteristics of the thread take-up stored in the calculator, and the thread take-up required to obtain a top hanging sewing state.
The upper thread gripping _{plates 7 and} 8
This is to control the opening/closing magnet (needle thread gripping device) 5 to release the upper thread grip by the needle thread gripper.

As explained above, according to the present invention, the sewing tension can be automatically adjusted, which has been considered extremely difficult in the past, and it is now possible to always perform the best sewing work without the need for the operator to make any adjustments. Summer.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the sewing state by the sewing machine.
A shows upper hanging stitching, B shows lower hanging stitching, C shows good sewing condition, Figure 2 is a diagram showing changes in needle thread tension, and Figure 3 shows
Figure A is a diagram showing the relationship between the needle thread take-up characteristic curve and needle thread tension change by the thread take-up, Figure 3B is an enlarged partial view of the same part, Figure 4 is a diagram showing an embodiment of the present invention, and Figure 5 The figure is an explanatory diagram showing one example of a computer circuit used in the present invention. 1... Sewing machine, 2... Balance, 5... Needle thread gripping device, 6... Strain meter (needer thread tension detection device), P... Fabric feed amount of sewing machine (1 sewing stitch), t ₁ ... Intertwining time of upper thread and lower thread, t ₂ ... Intermediate time between t ₁ and t ₃ , t ₃ ...
... Timing of intertwining of the upper thread and lower thread in the suspended sewing state (timing to release the upper thread grip in order to feed the upper thread by the amount of cloth feed).

Claims (1)

[Claims] 1. In a needle thread supply device of a sewing machine, which is equipped with a needle thread payout device equipped with a needle thread gripping device, a needle thread tension detection device, a balance, and a computer for controlling needle thread payout amount, The calculator has a memory means that stores the thread take-up characteristics of the thread take-up, and a needle thread position corresponding to a position one fabric feed pitch before the top dead center of the thread take-up, in accordance with the fabric feed amount input from the fabric feed adjustment device. a counting means for outputting the pick-up time from the storage means in which the thread take-up characteristic is stored; and an intermediate time between the output needle thread pick-up time and the start time of increasing the tension of the needle thread tension detecting device. 1. A sewing machine with automatic stitch tension adjustment, comprising: a calculation means for calculating , and an upper thread gripping device is released at an intermediate time outputted from the calculation means.