JPH0577440B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a needle thread amount adjusting device for a sewing machine.

[Prior art] Conventionally, this type of device assumes sewing conditions such as stitch pitch, thread elasticity, and fabric thickness in advance, and uses control data that is predetermined in accordance with each sewing condition. There is one that changes the stroke of the thread take-up based on control data of commanded sewing conditions to change the amount of needle thread supplied.

[Problems to be Solved by the Invention] In this device, the user selects and commands the sewing conditions closest to the sewing conditions of the actual sewing operation from among the assumed sewing conditions, and controls the needle thread supply. Since the sewing work starts after determining the amount, if the actual sewing conditions are not included in the assumed sewing conditions or if the sewing conditions commanded by the user are incorrect, the stitches may not be properly sewn. The stitches were not formed by tightening the threads, resulting in seam wrinkles and the like, making it difficult to obtain good stitches.

[Object of the Invention] The present invention has been made in order to eliminate the drawbacks of the prior art, and its purpose is to provide a needle thread amount for a sewing machine in which the amount of needle thread supplied is automatically adjusted regardless of the sewing conditions. The purpose of the present invention is to provide a regulating device.

[Means for Solving the Problems] The present invention includes a thread take-up that is supported to be movable up and down relative to the machine frame, and a thread take-up that engages the needle thread that is under tension due to the rise of the thread to change its path. a yarn amount adjusting member displaceably installed with respect to the machine frame;
a driving means for displacing the thread amount adjusting member; a detecting means provided on the upper thread path of the machine frame for detecting release of tension in the upper thread and generating a detection signal;
a determining means for determining whether or not the detection signal is generated within a predetermined period from when the needle reaches the work cloth from the top dead center; and when the detection signal is not generated within the predetermined period, the driving and control means for activating the means so that the detection signal is always generated within the predetermined period.

[Function] In the present invention, the upper thread is tensioned by raising the thread take-up, the thread amount adjusting member engages with the upper thread to determine the supply amount of the upper thread, and the tension of the upper thread is released by lowering the thread take-up. , a detection means detects this and generates a detection signal. Further, the determining means determines whether or not a detection signal is generated during a predetermined period from when the needle reaches the work cloth from the top dead center, and when the detection signal is not generated during the predetermined period, the control means controls the driving means. is operated to displace the thread amount adjusting member and change the upper thread supply amount, thereby controlling the detection signal to be generated at a predetermined period of time.

[Example] The details will be described below with reference to an example embodying the present invention.

In the figure, a thread take-up 2 is connected to a main shaft (not shown) on a machine frame 1 of the sewing machine, and is supported in a groove 19 formed in the machine frame 1 to make a known rocking motion. At the tip of the thread take-up lever 2, a bifurcated part 22 is formed, which is fixed and has a through hole 21 for the upper thread 3 formed therein.
A thread amount adjusting member 4 is rotatably supported on the machine frame 1 by a shaft 5 parallel to the main shaft, and its free end 41 protrudes from the groove 19 of the machine frame 1 and connects to the bifurcated portion 22 of the thread take-up 2. located inside. An upper thread engaging surface 42 is formed on the free end 41 of the thread amount adjusting member 4, and the upper thread engaging surface 42 engages the upper thread 3 inserted into the forked portion 22 when the thread take-up lever 2 is raised. and bend it.

A vertical hanging part 11 is formed protruding from the upper part of the machine frame 1, and a pulse motor 6 as a driving reference is connected to a screw 7 on the side of the vertical hanging part 11 on the side of the yarn amount adjusting member 4.
Fixed by The drive shaft 61 of this pulse motor 6 is parallel to the main shaft of the yarn amount adjusting member 4.
An engaging member 8 is fixed by a screw 12 adjacent to the thread amount adjusting member 4 .

This engaging member 8 is formed with an engaging groove 81 extending in the radial direction of the drive shaft 61, and is rotatable together with the drive shaft 61.

Here, an engagement pin 9 is provided on the thread amount adjusting member 4 so as to protrude toward the engagement member 8 side, and this engagement pin 9 is inserted into the engagement groove 8 of the engagement member 8.
1 is engaged. Therefore, the pulse motor 6
The thread amount adjusting member 4 is rotated in conjunction with the engaging member 8, which is rotated by the operation of the thread amount adjusting member 4.

Thread guides 15, 16, and 17 are attached to the machine frame 1, respectively.
17 guides the needle thread 3 from a needle thread supply source (not shown) through the thread take-up 2 to a needle 18 which is moved up and down.

A detection switch 23 as a detection means is installed on the upper thread path between the thread guides 15 and 16 of the machine frame 1. When the tension is released by lowering the balance 2, it is turned off and a one-pulse detection signal is generated.

On the other hand, inside the machine frame 1 is a spindle rotation angle detector 2.
4 is installed, and this spindle rotation angle detector 2
4 has a counter (not shown) and is configured to generate a count signal N having a value proportional to the rotation angle of the main shaft. The main shaft rotation angle detector 24 generates a count signal N that increases as the needle 18 descends from the top dead center.

Further, a controller 25 formed by a central processing unit is installed in the machine frame 1, and the detection switch 23 and the spindle rotation angle detector 24 are connected to its input terminal, respectively, and the output terminal A pulse motor 6 is connected to. This controller 25 is composed of a determining means 26 and a controlling means 27.

The determining means 26 stores first comparison data D1 and second comparison data D2 having a larger value, and when the detection signal is generated, the count signal of the spindle rotation angle detector 24 is N is detected and compared with both data D1 and D2, respectively, and the results are output to the control means 27 as a normality determination signal, an insufficient yarn amount signal, and an excessive yarn amount signal. Incidentally, both the data D1 and D2
is the count signal N generated many times until the needle 18 descends from the top dead center and reaches the work cloth.
It defines the time when the tension on the needle thread 3 should be released by the descent of the thread take-up 2. That is, the count signal N when the detection signal is generated is the first
When the count signal N is smaller than the second comparison data D1, it is determined that a good stitch cannot be formed due to excess needle thread supply, and an excess thread amount signal is output. When the count signal N is larger than the second comparison data D2, the needle thread It is determined that good stitches cannot be formed due to insufficient supply, and an insufficient thread amount signal is output, and when the count signal N is greater than the first comparison data D1, the second comparison data D is determined.
When it is smaller than 2, it is determined that a good stitch has been formed with an appropriate upper thread supply amount, and a normal signal is output.

When the excessive thread amount signal is output by the determining means 26, the control means 27 rotates the pulse motor 6 by a predetermined amount in a direction to reduce the amount of bending of the upper thread by the thread amount adjusting member 4, and rotates the pulse motor 6 to that position. hold,
When the yarn amount shortage signal is output, the pulse motor 6 is rotated by a predetermined amount in the direction of increasing the amount of bending and held at that position, and when the normality determination signal is output, the pulse motor 6 is not rotated and remains as it is. It is configured to be held in position.

Next, its operation will be explained with reference to FIG.

The user first passes the upper thread 3 through the thread guide 15, then passes it through each insertion hole 21 of the thread take-up 2, passes the upper thread 3 through the thread guides 15, 16, and 17, and inserts the upper thread 3 into the needle 18.
be carried.

When the sewing machine is then started, the counter starts counting as the main shaft rotates, the balance 2 starts swinging up and down, and the controller 25 performs the following operations.

In step 30, the determining means 26 determines whether or not a detection signal is generated. If not, this step 30 is repeated. Eventually, the thread take-up 2 is moved up and down by the rotation of the main shaft, and the tension on the needle thread 3 is released. When detected, the detection switch 23 generates a detection signal,
Proceed to step 31.

At step 31, the determining means 26 detects the count signal N of the counter and proceeds to step 32.

In step 32, the determining means 26 compares the count signal N and the first comparison data D1, and when the count signal N is smaller than the first comparison data D1, outputs an excessive yarn amount signal to the control means 27 and executes the step. Proceed to step 33, otherwise proceed to step 34.

In step 33, when the excessive thread amount signal is output, the control means 27 rotates the pulse motor 6 by a predetermined amount in the direction of decreasing the upper thread supply amount, and then in step 30
Proceed to.

In step 34, the determining means 26 compares the count signal N and the second comparison data D2, and when the count signal N is larger than the second comparison data D2, outputs a yarn amount insufficient signal to the control means 27 and executes the step. The process proceeds to step 35, and if not, a normality determination signal is output to the control means 27 and the process proceeds to step 36.

In step 35, when the thread amount shortage signal is output, the control means 27 rotates the pulse motor 6 by a predetermined amount in a direction that increases the amount of upper thread supplied, and the process proceeds to step 30.

At step 36, when the normality determination signal is output, the control means 27 proceeds to step 30 without rotating the pulse motor 6.

The controller 25 performs the above control every time one stitch is formed, and the needle thread supply amount is automatically adjusted to the optimum value for the sewing conditions, so that a good stitch is formed. be done.

[Effects of the Invention] According to the present invention, the determining means determines whether or not the release of tension in the upper thread detected by the detecting means has occurred within a predetermined period, and the controlling means adjusts the upper thread supply amount. Since the needle thread tension is released during this predetermined period, the amount of needle thread supplied is automatically adjusted during the sewing operation to ensure good sewing regardless of the sewing conditions. Eyes can be formed.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment embodying the present invention,
2 is a front view of the sewing machine, FIG. 3 is a partially cutaway side view of the sewing machine, and FIG. 4 is a flowchart of the controller. 1 is a machine frame, 2 is a thread take-up, 3 is an upper thread, 4 is a thread amount adjustment member, 6 is a pulse motor (drive means), 18 is a needle,
23 is a detection switch (detection means), 26 is a discrimination means, and 27 is a control means.

Claims (1)

[Scope of Claims] 1. A thread take-up that is supported to be movable up and down with respect to the machine frame and carries an upper thread; a thread amount adjusting member that engages with the thread amount adjusting member and changes the upper thread supply amount by changing its path; a driving means that operates to displace the thread amount adjusting member; a detection means for detecting the release of tension in the needle thread caused by the lowering of the thread take-up and generating a detection signal; a determining means for determining whether or not a signal has been generated; and based on the determination result of the determining means, when the detection signal is not generated within the predetermined period, the driving means is actuated, so that the detection signal is always What is claimed is: 1. A needle thread amount adjusting device for a sewing machine, comprising a control means for controlling the needle thread amount to be generated within a predetermined period of time.