JPH0240942Y2 - - Google Patents

Description

[Detailed Description of the Invention] Purpose of the Invention (Field of Industrial Application) This invention relates to a needle stop position control device for a sewing machine.

(Prior Art) Conventionally, there is a sewing machine that is equipped with a thread trimming mechanism, and when the needle reaches a predetermined position, the thread trimming mechanism is activated by the drive of the sewing machine main shaft to cut the thread.

(Problem that the invention aims to solve) However, in such a sewing machine, when the thread trimming mechanism ends, the load on the main shaft of the sewing machine is instantly released, causing the needle to overrun from its predetermined stopping position. There was a risk of it happening.

Structure of the invention (means for solving the problems) In order to solve the above problems, this invention has a needle that moves up and down as the main shaft of the sewing machine rotates, and a needle that can be rotated in forward and reverse directions to impart rotation to the main shaft of the sewing machine. a sewing machine motor, a braking means for applying a braking force to a motion system between the sewing machine motor and the needle so that the needle stops at a predetermined position, and outputting a detection signal when the needle reaches the predetermined position. a first detection means; a second detection means that outputs a detection signal when the needle overruns the predetermined position; and a brake force by the brake means is released based on the signal from the second detection means. and a brake means for controlling the sewing machine motor and a control means for controlling the sewing machine motor so that the sewing machine motor is reversely moved to cause the needle to move backward, and the sewing machine motor is stopped based on the signal from the first detection means. There is.

(Function) Therefore, when the needle overruns, the needle moves back to a predetermined position by reversing the sewing machine motor, and the needle can always be stopped at the predetermined position.

(Example) Hereinafter, an example that embodies this invention will be described based on the drawings.

As shown in FIG. 1, a sewing machine main body 2 is placed on a bed 1 of the sewing machine, and a needle 3 is supported on the head of the sewing machine main body 2 so as to be movable up and down.
The arm portion is provided with a main shaft 4, and rotation of the main shaft 4 causes the needle 3 to move up and down. A sewing machine pulley 5 is attached to the end of the main shaft 4, and encoders 6 as first and second detection means are attached to the sewing machine pulley 5. In addition to outputting a needle stop position signal, even when the needle 3 overruns from a predetermined stop position, a corresponding signal is also output.

Further, a sewing machine motor 7 which is a three-phase induction motor is provided below the bed portion 1, and its motor shaft 8
A motor pulley 9 is attached to the sewing machine pulley 5, and a belt 21 is hung between the sewing machine pulley 5 and the motor pulley 9. Further, as shown in FIG. 2, the motor shaft 8 is divided into two parts, and a clutch mechanism 10 is interposed in the divided part. The clutch mechanism 10 is coupled by energizing the clutch coil 12, and released by demagnetizing it. Furthermore, a brake mechanism (not shown) is arranged opposite to the pulley-side motor shaft 8a, and is operated by excitation of a brake coil 11 as a brake means.
Note that 14 indicates a rotor of the sewing machine motor M.

Next, the configuration of the electrical circuit of this sewing machine will be explained. As shown in FIG. 1, a central processing unit (hereinafter referred to as CPU) 22 as a control means has a read-only memory (hereinafter referred to as ROM) containing programs.
23 is connected to the clutch/brake control circuit 15 and sewing machine motor control circuit 16 via an input/output interface 24. A detection signal from the encoder 6 is inputted to the clutch/brake control circuit 15 and the sewing machine motor control circuit 16, thereby controlling the sewing machine motor 7, the clutch mechanism 10, and the brake mechanism. The sewing machine motor 7 is connected to four wires, three-phase power wires R, S, T and a ground wire E, and each power wire R, S, T has an electromagnetic contactor 1.
7, a switching contact 18A of the reversing relay 18, and a breaker 19 are connected. Further, a coil 17B of the electromagnetic contactor 17 and a normally open contact 20A of the power supply switching relay 20 are provided between the power supply wirings S and T.

As shown in FIG. 2, the sewing machine motor control circuit 15 has a transistor Tr1 that is switched by a power switch mechanism SG1, and the transistor Tr1 has a coil 20B of a power switch relay 20.
is connected, and a diode 25 is connected in parallel to the coil 20B. The coil 18 of the reversing relay 18 is connected to the transistor Tr2, which is switched by the reversing signal SG2, which is another signal of the sewing machine motor control circuit 15.
B is connected, and a diode 26 is connected in parallel to the coil 18B.

Now, the operation of the sewing machine constructed as described above will be explained based on the flowchart of FIG. This flowchart proceeds under the control of the CPU 22.

First, in step S1, the sewing machine motor control circuit 1
The drive signal SG1 is outputted from the transistor Tr6, and the transistor Tr1 becomes conductive. Therefore, the coil 20B of the power switch relay 20 is excited, and its contact 20A
closes. Then, by closing the contact 20A, the coil 17B of the electromagnetic contactor 17 is excited, the power switch 17A is turned on, and the motor power is turned on. Next, in step S2, a clutch signal is output from the clutch brake control circuit 15, the clutch coil 12 is energized, and the clutch mechanism 10 is energized.
becomes connected. Then, in step S3, the sewing machine motor 7 is driven in the normal rotation direction, and sewing is performed by the sewing machine.

In step S4, the CPU 22 waits for a stop signal to be output. This stop signal is output at the end of sewing. Then, the signal is output to step S.
5, a brake signal is output from the sewing machine motor control circuit 16, the brake coil 11 is energized, the brake is applied while the clutch mechanism 10 is in the engaged state, and the motor shaft 8 is stopped at the needle-up position. Then, just before this stop, the sewing machine main shaft 4
Thread cutting is performed using the rotation of the thread as a driving force.

Next, when the motor pulley 9 stops, the brake signal is turned off, and the process proceeds to step S6. In this step S6, it is determined whether or not the needle 3 is placed at the needle up stop position and the encoder 6 is outputting a needle stop signal. If it is being output, the process advances to END and the sewing ends. Further, when no output is being made, that is, when the needle 3 overruns the needle upper position and is located below it, the process advances to step S7. In this step S7, the sewing machine motor control circuit 1
6 is stopped, the coil 20B of the power switch relay 20 is demagnetized, and its contact 20A is opened. Then, by opening the contact point 20A, the coil 17B of the electromagnetic contactor 17 is demagnetized, and the power switch 17A is turned off. In the next step S7, the clutch/brake control circuit 16
The output of the clutch signal from the brake is stopped, and a brake signal is output to the brake, so that the clutch coil 12 is demagnetized and the brake coil 11 is energized. Therefore, the clutch is disengaged and a braking force is applied to the pulley-side motor shaft 8a. And the pulley side motor shaft 8a
When the vehicle stops, the brake signal is turned off.

In step S9, the sewing machine motor control circuit 15
The reverse rotation signal SG2 is output from the reverse rotation relay 18.
The coil 18B is excited, and its contact 18A is switched from the normal rotation terminal side to the reverse rotation terminal side. Therefore, two phases of the three-phase wiring are replaced by the reversing relay 18. In step S10, the drive signal SG is sent from the sewing machine motor control circuit 16.
1 is output, the motor power is turned on as in step S1, and three-phase power is supplied to reverse the motor. When the clutch signal is turned on in step S11, the clutch coil is excited and the clutch mechanism 10 is coupled.
Therefore, the motor 7 is reversely rotated, the sewing machine pulley 5 is reversely rotated, and the needle bar 3 is moved upward. At this time, the sewing machine motor 7 is driven at the lowest speed.

In step S12, the needle stop position signal from the encoder 6 is input, and the process proceeds to step S13 together with the output of the needle stop position signal. At this time, the needle bar 3 has reached the needle-up position. Then, in step S13, the clutch/brake control circuit 16 turns on the brake signal, and when the motor pulley 9 stops, the brake signal is turned off. In step S14, similarly to step S7, the electromagnetic contactor 17 is turned off to turn off the motor power, and the process proceeds to step S15.

In step S14, the same action as in step S8 is performed, and the motor rotor is stopped. Then, in step S16, the output of signal SG2 is stopped, and the operation opposite to step S9 is performed.
The reversal relay contact 18A is switched from the reverse rotation terminal side to the normal rotation terminal side. Therefore, the sewing machine motor 7 is driven in the normal rotation direction.

In this way, by using a three-phase induction motor and swapping the phases of the motor's power supply wiring,
The needle 3 can be returned to the predetermined needle up stop position.

In the above embodiment, the clutch is coupled by excitation of the clutch coil 12, but it may be conversely coupled by demagnetization.

Effects of the Invention As detailed above, this invention has an excellent effect in that when the needle overruns from a predetermined stop position, the needle can be moved back and always stopped at the predetermined position.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment embodying this invention, FIG. 2 is an electric circuit diagram, and FIG. 3 is a flowchart. In the figure, 3 is a needle, 4 is a sewing machine main shaft, 6 is a detector, 7 is a sewing machine motor, 11 is a brake means,
22 is a control means.

Claims (1)

[Claims for Utility Model Registration] A needle 3 that moves up and down as the sewing machine main shaft 4 rotates; a sewing machine motor 7 that can rotate in forward and reverse directions and that imparts rotation to the sewing machine main shaft 4; and a sewing machine motor 7 that rotates the needle 3 in a predetermined position. a brake means 11 that applies a braking force to the motion system between the sewing machine motor 7 and the needle 3 so as to stop the needle 3 at a stop; and a first detection means 6 that outputs a detection signal when the needle 3 reaches the predetermined position. and a second detection means 6 that outputs a detection signal when the needle 3 overruns the predetermined position, and releasing the braking force by the brake means 11 based on the signal from the second detection means 6. At the same time, a control means controls the brake means 11 and the sewing machine motor 7 so as to reverse the sewing machine motor 7 to move the needle 3 backward, and to stop the sewing machine motor 7 based on a signal from the first detection means 6. 22; A needle stop position control device for a sewing machine.