JPS62120887A - Automatic yarn tension imparting apparatus of sewing machine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to an automatic thread tensioning device for a sewing machine.

(Conventional technology).

The key to completing a conventional automatic thread tension mechanism is how to detect material (fabric) information. For example, Japanese Patent Application Laid-Open No. 155285/1983 uses this information to detect the resistance that the needle receives when it penetrates the fabric. The signal is obtained by converting it into an electrical signal using a needle bar and a sensor inserted between the needles. Further, in Japanese Patent Application Laid-Open No. 59-141989, a signal is obtained from a sensor in a needle bar or a change in load current of a drive motor for a cloth penetrating saw of a needle.

(Problems to be Solved by the Invention) In the above-mentioned needle-bar built-in sensor, lead wires and the like for transmitting electrical signals must be placed inside the needle bar or along the needle bar. Not only is this complicated, but the sensor and other components move at high speeds along with the needle, making it difficult to maintain durability, making it particularly difficult to apply to industrial sewing machines that require high-speed operation.

In addition, especially during high-speed sewing, the needle often collides with the throat plate, etc., so the impact force on the needle bar that occurs at the end of this collision reaches several kilograms, and this load has a sensitivity of several tens to hundreds of nine. is large enough to destroy a sensor with a

On the other hand, in the type of drive motor that obtains a signal from fluctuations in the load current, the servo current value generated by the presence or absence of fabric is extremely small compared to normal servo motors, and requires a precise information transmission means. It was something that could not be done.

(Purpose of the invention) This invention solves the above problems and reduces the thickness of the fabric.

It is an object of the present invention to provide an automatic thread tension applying device that can obtain information on factors that affect thread tension during sewing, such as fabric quality and weave density.

(Means for Solving the Problems) In order to solve the above-mentioned problems, an automatic thread tension applying device for a sewing machine according to the present invention is provided in the bed of the sewing machine that automatically adjusts the upper thread tension. It is supported so as to be movable up and down in a throat plate in which a through hole is formed, and in the through hole of the throat plate, and its upper end surface is always located approximately on the same plane as the upper surface of the throat plate, and The fabric support has a needle hole formed therein, and a moving detection body detects the amount of vertical movement of the fabric support. The gist of this invention is that it is constructed so as not to apply an appropriate tension to the upper thread.

(Function) With the above configuration, when the needle that has moved downward during sewing passes through the workpiece cloth and passes through the needle hole of the cloth support, the resistance force exerted upon penetrating the cloth is applied to the cloth through the workpiece cloth. The fabric is propagated to the support and the cloth support moves downward. This support
The downward movement of the holder is detected by the IFffi detector, and appropriate tension is applied to the upper thread based on the detection signal.

(Embodiment) An embodiment embodying the present invention will be described below with reference to FIGS. 1 to 9.

The sewing machine frame 1 includes an arm portion 2 and a bed portion 3,
A needle 5 is attached to four rods 4 mounted in the head of the arm portion 2 so as to be movable up and down. An automatic thread tension device 6, which will be described later, is disposed on the upper part of the arm portion 2, and a well-known main thread tension device that can manually change the tension of the upper thread is provided on the #I surface of the arm portion 2. 7 is attached, and a plurality of thread guide bodies 8 are also attached.

Roughly speaking, a balance operated by a well-known balance mechanism is provided in the arm section 2, and its tip protrudes from the front surface of the arm section 2.

Therefore, the upper thread U supplied from the upper thread supply source is connected to the automatic light controller 4. Each thread guide 8. The raw silk HP device is supplied to the needle 5 via the 7° balance, and the needle 5 and the yarn ring catcher 9 provided in the bed section 3 work together to create a wood!
A seam is formed.

A sliding plate 10 and a throat plate 11 are disposed on the bed portion 3, and a through hole 12 is formed in the throat plate 11.

A base end of an elastic cantilever 13 is fixed to the lower surface of the throat plate 11, and a thread guide 14 as a fabric support is inserted into the through hole 12 so as to be able to move upward. It is fixed as one piece.

In order to make the needle 5 less susceptible to influences other than when passing through the work cloth, the similar path 14 is arranged so that its upper end surface is located at the same level or slightly below the upper surface of the needle plate 11. A through hole 14a passing through both the upper and lower ends is provided so that the needle 5 can pass through the hole 14a. A strain gauge 15 serving as a moving l detector is fixed to the base end 5 surface of the cantilever beam 13.

Kanki cantilever beam 13. A pressure sensor S is constituted by the yarn path 14 and the strain gauge 15. This pressure sensor S generates a resistance force when the needle 5 penetrates the work cloth N, but when the needle 5 moves further downward and penetrates the yarn path 14, the resistance force is applied to the yarn 1i14 through the work cloth N. is propagated, and the cognate path 14 moves downward. At this time, the force propagated to the thread path 14 is applied to the cantilever beam 13 as a bending moment! !
1, the cantilever beam 13 is moved down against its own elastic force.

Then, the strain gauge 15 outputs a detection signal due to a potential fluctuation occurring based on the amount of movement of the cantilever beam 13.

Next, the automatic thread tension device 6 will be explained in detail according to FIGS. 5 and 6. A sub-tension holder 16 is fixed to the upper front surface of the arm portion 2, and A large-diameter fitting hole 16a is drilled from the front, and a small-diameter female threaded hole 16b is transparently provided at the rear.

A cylindrical rotating shaft 18 constituting a rotary thread tension plate 17 is rotatably fitted into the fitting hole 16a, and a pair of discs 19 facing each other are provided on the front end surface of the rotating shaft 18. is fixed in one piece. The peripheral edges of both discs 19 are spaced apart from each other in opposite directions so that an upper thread can be wound thereon. The rotary thread tension disc 17 is rotatably inserted into the female threaded hole 16b by a thread guide copper rod 20 whose tip end is screwed into the thread guide rod 20 so as to be adjustable forward and backward.

A circumferential engagement groove 21 is formed on the outer periphery of the rear end of the rotating shaft 18, and a locking step 22 is formed on the outer periphery of the curved end of the rotating shaft 18. . A bifurcated thread guide plate 23 through which the rotating shaft 18 is inserted is fixed to the front surface of the sub-onesion holder 16.

Further, the thread guide copper rod 20 has its head 20a and the disk 19.
A spring 24 that acts when cutting thread is wound between the ends of the J! 1! The rotary light control j'[117 is biased toward the sub-tension holder 16 via a friction plate 25 made of a friction material.

A holder 26 is fixed to the upper surface of the arm portion 2, and a servo solenoid 27 is fixed to the upper part of one side of the holder 26 projecting upward by a hissing member. Further, an operating lever 2 is connected to a shaft 28 between the center portions of both side walls of the holder 26.
9 is rotatably supported by a shaft, and one end of the actuating lever 29 is linked to the lower end of the plunger 27a of the servo solenoid 27 via a link 30.

A spring 31 is wound around the shaft 33, one end of which is engaged with the holder 26, and the other end of the spring 31 is engaged with a engagement piece 29a formed on the upper part of the operating lever 29. , the front end of the operating lever 29 is always biased to rotate downward.

The rotary light control in the sub-tension holder 16? The upper part corresponding to the engagement groove 21 of lIn17 and the lower end of the lower wall of the holder 26 correspond to the engagement groove 2 of the rotating wheel 18.
A tension applying bottle 32 that abuts on the actuating lever 29 is inserted through the tension applying bottle 32 so as to be able to move up and down.

Therefore, this automatic thread tension device 6 is connected to the rotary thread tension disc 17.
When the upper thread U is moved in the supply direction with the upper thread tip wound around the peripheral edge of the disk 19, it rotates, and when the nervo solenoid 27 is excited and the plunger 27a is driven, the link 35 and The pressing force of the L tension applying bottle 32 against the engagement groove 21 is controlled via the operating lever 29.

By controlling the pressing force of the tension applying bottle 32 against the engagement groove 21, resistance is applied to the rotation of the rotary thread tension disc 17.
The tension of the upper thread U wound between the disks 19 is adjusted.

In addition, as shown in FIG. 7, this sewing machine has a pulley provided on the sewing machine main shaft (not shown) in the arm section 2.
Alternatively, a well-known main shaft rotation angle detector 33 is provided at a location where the motor drive shaft or the like is rotationally driven, and constantly detects the rotation angle of the sewing machine main shaft and outputs the detection signal to the calculation circuit 35. ing. Furthermore, a well-known sewing pitch detector 34 is provided at a location within the arm portion 2 that is linked to the cloth feeding mechanism, and is configured to detect the sewing pitch of the cloth feeding mechanism and output the detection signal to an arithmetic circuit 35. It has become.

The performance circuit 35 is a central processing unit (hereinafter referred to as CPLJ) 3
6, a read-only memory (hereinafter referred to as ROM) 37, and a read/write memory 38 (hereinafter referred to as RAM).

The input terminals of the CPU 36 are connected to the respective detectors 33.
34 and pressure sensor S are connected, and the servo solenoid 27 is connected to the output terminal.

The ROM 37 stores a control program for controlling the CPLJ 36, and also stores a plurality of functions fpn. That is, as shown in FIG. 8, the function fpn(T) is a function that expresses a certain relationship between the pressure data D based on the detection signal detected by the pressure sensor S and the required needle thread tension T, and is a function that represents the constant relationship between the needle thread tension T and the sewing pitch pn. (n=1.2.
3...) are available.

The trial sewing switch 39 is provided on the pillar portion of the arm g12, and its output terminal is connected to the CPU 36,
A trial sewing mode and a regular stitching mode are selected by turning on/off the trial sewing switch 39.

Next, the operation of the sewing machine constructed as described above will be explained with reference to the block circuit diagram shown in FIG. 7 and the flow chart shown in FIG. 9.

Now, when trial sewing is to be performed, the trial sewing switch 39 is turned on to set the trial sewing mode. Then, the main thread adjustment device 7
While adjusting as appropriate, test-sew the work cloth N. Then,
When the needle 5 that has penetrated the work cloth N moves downward and passes through the thread path 14, the resistance force generated when the needle 5 penetrates the work cloth N is equal to the work cloth N.
It is propagated to the thread path 14 through the medium, and the cognate 1114 moves downward.

This downward movement of the thread path 14 causes the cantilever beam 13 to move, and the strain gauge 15 detects the amount of movement and outputs a detection signal. Note that this trial sewing is preferably performed on a thin part or a coarsely woven part of the work cloth N (step 1).

Next, the CP (J36 determines whether the trial sewing switch 39 is turned on or not (step 2)), and when the trial sewing switch 39 is turned on, the CPLJ36 stores the pressure signal in the RAM 38 as initial data DO. do. Roughly speaking, the CPU 36 reads the detection signal detected from the sewing pitch detector 34 (step 3), and based on the detection signal, calculates the function fp corresponding to the current sewing pitch pn.
Select n(Ti and store it in the RAM 38 (Step 4)
).

For example, when the sewing pitch is p1, the CPU 36 selects the function fp1(T) shown in FIG.
2, the CPtJ36 selects the function f'p2(T).

At this time, the CPtJ36 calculates the required tension of the upper thread (0) based on the initial data DO and the selected function f pn (r), and outputs a control signal corresponding to the required tension (0) to the servo solenoid 27. do not.

That is, in the trial sewing mode, the operator
The raw silk tension device 7 is manually adjusted so that the tension TO is applied to the raw silk tension device 7.

Thereafter, when the trial sewing switch 39 is turned off and sewing is started in the regular sewing mode, the CPU 36 inputs data based on the pressure signal output from the pressure sensor S at that time (step 1).

Then, when the pressure sensor S detects that the right bank of the work cloth N has changed and the CPU 36 inputs data D1 based on the pressure signal output from the pressure sensor S, the CPU 36 calculates, for example, the function fp1(T). C when selected
The PU 36 calculates the necessary needle thread tension T1 from the same data D1 and the function rf)1(T), and further calculates ΔT=71−To (step 5). Also, for example, the function r p2 (
T), the CPU 36 outputs the same data D1.
The required needle thread tension T''1 is calculated from the function fl)2'(T), and ΔT-=Tl-T'O is calculated.

Then, the CPU 36 calculates the applied current to be applied to the servo solenoid 27 based on the calculation results (step 6), stores the calculation result in the RAM 38, and puts it in a standby state.

Next, the CPU 36 inputs the detection signal from the spindle rotation angle detector 33, and determines whether or not the spindle rotation angle data is within the range of 100° to 300° based on the detection signal (step 7). . Then, the CPU 36 has a spindle rotation angle of 1
When it is within the range of 00° to 300°, the standby state is canceled, the applied current data is read from the RAM 38, and the applied current is output to the servo solenoid 27 of the automatic light control T device 6.

On the other hand, when the spindle rotation angle is not within that range, when the spindle rotation angle reaches the range of 100' to 300 degrees, the standby state is canceled, the applied current data is read from the RAM 38, and the applied current is sent to the servo solenoid 27. The necessary upper thread tension is applied to the upper thread U (step 8).

In addition, when the pressure sensor S again detects a thin part of the padded cloth N in the same manner as the first time from the above state, the current applied to the servo solenoid 27 is reduced by following the same path, and the automatic thread tension device 6 Set the needle thread tension to the standard condition.

The pressure measurement by the pressure sensor S in the automatic thread tensioning device configured as described above was carried out when the sewing speed was 300O3, P, M.
The results obtained under the conditions of , are shown in FIG.

In the figure, α is when there is no work cloth N to be detected, β is when there is only one work cloth to be detected, γ is when there are two work cloths to be detected, and δ is when there are three work cloths to be detected. The case is shown below. In this way, this pressure sensor S can detect the thickness of the work cloth N with good accuracy.

Therefore, it is possible to apply tension to the needle thread with extremely high accuracy based on the detection signal from the pressure sensor S as described above.

In addition, since the change in resistance when the needle 5 penetrates the work cloth N is detected, it is possible to detect rough lightning due to differences in the weaving method of the work cloth N.
It can also be applied to two-tiered cloth sheets, and as mentioned above, it can also be applied to higher speeds. Also, in the unlikely event that needle 5 is set to thread path 1 during high-speed sewing,
4, the impact is transmitted to the strain gauge 15 via the cantilever beam 13, so that the pressure sensor S is less likely to be destroyed than when the pressure sensor is provided on the needle bar.

It should be noted that the present invention is not limited to the embodiments described above, and may be modified as desired without departing from the spirit of the invention.

Effects of the Invention As detailed above, the present invention is different from conventional needle bar built-in sensors in that it requires durability, can avoid troubles near the needle groove, and can be easily electrically connected to the sensor. Furthermore, since the condition of the work cloth can be identified with high accuracy, the thread tension to be applied to the needle thread can be adjusted with high precision. Since the sensor is provided on the throat plate, only a simple modification of the throat plate is required, and excellent effects are achieved in terms of accuracy, manufacturing cost, and wearability.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway front view of a sewing machine embodying the present invention, Fig. 2 is a plan view of the throat plate, Fig. 3 is a sectional view of the throat plate, and Fig. 4 is a bottom view of the throat plate. 5 is a front view of the automatic thread tension device, FIG. 6 is a side sectional view, FIG. 7 is an electric block circuit diagram, and FIG. 8 is a graph showing the relationship between pressure data and required needle thread tension. FIG. 9 is a flowchart 1-1, and FIG. 10 is a voltage oscilloscope of a detection signal showing measurement results by a pressure sensor. Needle 5, automatic thread tension device 6, raw thread tension device 7, rotary thread tension disc 17, thread guide auxiliary rod 20, tension adding bin 32, main shaft rotation angle detector 33, sewing pitch detector 34, arithmetic circuit 35
, central processing unit (CPLJ) 36, ROM 37, RAM
38, pressure sensor S. Needle thread U0 Patent applicant: Brother Industries, Ltd. Figure 5

Claims (1)

[Claims] 1. In a sewing machine that automatically adjusts needle thread tension by detecting resistance that occurs when a needle (5) that is moved up and down enters a work cloth (N), a needle plate (11) provided with a through hole (12) formed at the drop point of the needle (5), and supported vertically movably in the through hole (12) of the throat plate (11) Its upper end surface is always the needle plate (1
1) A cloth support (14) located substantially on the same plane as the upper surface and in which a needle hole (14a) for penetrating the needle is formed, and movement for detecting the amount of vertical movement of the cloth support (14). and a quantity detector (15), configured to detect the amount of downward movement of the work cloth (N) as the needle (5) descends and apply appropriate tension to the upper thread (U). An automatic thread tensioning device for a sewing machine, characterized by: