JP2808812B2 - Thread catching mechanism drive of sewing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a needle bar on which a sewing needle carrying an upper thread is attached.
The needle bar driving motor reciprocates up and down, and the yarn catching mechanism that captures the yarn is rotated or rocked by the yarn catching mechanism driving motor to catch the yarn loop of the upper thread formed by the vertical movement of the needle bar. The present invention relates to a sewing machine that forms a seam on a work cloth by using a sewing machine.

[Prior Art] Conventionally, in a sewing machine of this type, a rotary position of a needle bar driving motor connected via a needle bar crank mechanism is detected by an encoder, and a signal from the encoder is used as a synchronization signal to drive the shuttle. What drives a motor is known. Therefore, the shuttle drive motor is rotated in synchronization with the rotation of the needle bar drive motor. The shuttle loaded with the bobbin bobbin is fixed on the motor shaft of the shuttle drive motor, and the shuttle is continuously rotated. The rotation speed of the shuttle at this time is set to twice the speed of the needle bar drive motor. When the rotation speed of the needle bar drive motor is changed, the rotation speed of the shuttle drive motor is also changed in response.

[Problems to be Solved by the Invention] However, since the shuttle is continuously rotated, the rotation of the needle bar drive motor is controlled by following the shuttle drive motor even when the sewing needle having the largest rotation fluctuation penetrates the work cloth. Therefore, the shuttle drive motor and its drive circuit must have good response characteristics, and there is a problem that the device becomes large and expensive. The rotation fluctuation of the needle bar drive motor increases as the thickness of the work cloth to be sewn increases and as the number of sewn sheets increases, and when the fluctuation width is large, the shuttle drive motor is driven synchronously. It is difficult.

Therefore, skipping may occur without synchronous driving of the shuttle.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a small and inexpensive sewing machine that can reduce the influence of rotation fluctuation of a needle bar drive motor and can prevent the occurrence of skipping. An object of the present invention is to provide a yarn catching mechanism driving device.

Means for Solving the Problems In order to achieve this object, a thread catching mechanism driving device for a sewing machine according to the present invention detects a predetermined position of a needle bar, and generates a detection signal thereof, And control means for controlling a thread catching mechanism drive motor so as to stop the thread catching mechanism after one rotation or one swing, in response to a detection signal from the needle position detector.

[Operation] In the present invention having the above configuration, the needle position detector detects a predetermined position of the needle bar reciprocated up and down by the needle bar drive motor, and generates a detection signal. The control means controls the thread catching mechanism drive motor so as to stop after turning the thread catching mechanism once or once in response to the detection signal from the needle position detector.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

 First, the configuration of the present embodiment will be described.

The needle bar drive motor 15 is a DC motor, and is driven at a constant speed by a drive circuit 46 in the control unit 41. The rotation speed of the needle bar drive motor 15 is kept constant by the phase signal of the encoder 18 provided on the output side of the motor 15 being fed back to the control unit 41 and the output of the drive circuit 46 being changed by the microcomputer 42. Kept at speed. The needle bar drive motor
The output shaft 15 is directly connected and fixed to an upper shaft 16, and the upper shaft 16 is connected to the needle bar crank mechanism 14. The rotational movement of the upper shaft 16 is
Needle bar to which sewing needle 11 is attached via needle bar crank mechanism
Converted into 13 reciprocating vertical motions. The encoder 18 serving as a needle position detector is a known one that includes a disk fixed to the upper shaft and having a number of slits formed thereon, and a photosensor that optically detects the slits. A code signal that changes sequentially according to the angle is generated. The encoder 18 is configured to change the code signal every time the rotation angle of the upper shaft 16 changes by one degree.

The shuttle drive motor 33 is a pulse motor, and its output shaft is directly connected to the shuttle shaft 34 to cause a rotary motion of the shuttle. The shuttle drive motor 33 is a microcomputer in the control unit 41.
It is connected to a drive circuit 47 controlled by the signal of 42 and rotates at twice the rotation speed of the needle bar drive motor 15. As shown in FIG. 4, when the hook 31 is stopped, the position of the sword tip 32 is -46 degrees, assuming that the point where the needle matches the sword tip of the hook (the point a where the needle and the sword meets) is 0 degree (FIG. 4). At position b). This occurs when the needle 11 rises from the lowermost point of the needle and the rotation phase of the upper shaft 16 becomes 203 degrees, that is, when the rotation angle of the upper shaft corresponding to the lowermost point of the needle is rotated 23 degrees from 180 degrees. This is because the tip of the kettle matches.

The control unit 41 includes a microcomputer 42 including a CPU 43, a ROM 44, and a RAM 45, and driving circuits 46 and 47.

The CPU 43 operates according to a program stored in the ROM 44. The CPU 43 checks the code signal from the encoder 18 and determines whether or not the code signal corresponds to the rotation angle of the upper shaft 16 of 180 degrees. At the time of the determination, a trigger pulse is output to the drive circuit 47 in a predetermined cycle with a predetermined number of pulses. As a result, the shuttle 33 is rotated one turn from the initial state in which the sword tip 32 is located at the position b in FIG. At this time, the cycle of the trigger pulse is set so that the speed becomes twice the rotation speed of the needle bar drive motor 15, and the rotation of the shuttle is stopped when the needle bar reaches the top dead center.

The needle bar 13 is supported by a needle bar holder 17 so as to be vertically movable, and the needle bar holder 17 is swingably supported by a pin 241 on a frame 24 and is connected to a known zigzag motor. I have. A presser bar 22 having a cloth presser foot 21 at the lower end is supported by a frame 24 so as to be able to move up and down, and is always spring-biased downward in FIG.

Next, the operation of the present embodiment having the above configuration will be described.

When the start of the sewing operation is instructed by a sewing start button (not shown), the microcomputer 42 in the control unit 41 sends a signal to the drive circuit 46 to drive the needle bar drive motor 15. The rotation of the needle bar drive motor 15 causes the needle bar 13 to start reciprocating up and down. The relationship between the needle point position and the rotation angle of the upper shaft 16 is shown in FIG. 3, where the needle is at the lowest point when the rotation angle is 180 degrees. Encoder mounted on upper shaft 16
18 outputs a code signal corresponding to the rotation angle of the upper shaft 16 to the microcomputer 42, which responds to the rotation angle (180 degrees) of the upper shaft 16 when the rotation of the shuttle 31 is started. Code signal (reference for rotation of hook)
Is compared with the code signal output from the encoder 18. As a result, when the detected code signal matches the shuttle rotation start reference, the microcomputer 42 sends a control signal to the drive circuit 47 to drive the shuttle drive motor 33.
Simultaneously with the start of rotation of the shuttle 31, the sewing needle 11 with the upper thread starts to rise, a thread loop is formed, and the thread loop is captured by the blade point 32 of the shuttle crossing the sewing needle 11. This capture position is the position where the upper shaft 16 has rotated 23 degrees and the shuttle drive motor 33 has rotated 46 degrees from the lowest point of the sewing needle. Thereafter, the rising of the sewing needle 11 and the rotation of the shuttle 31 continue, and the upper thread is pulled up by a balance (not shown) to form a final stitch. The shuttle 31 stops after being rotated 360 degrees by a signal from the microcomputer 42 to the drive circuit 47. By adding an operation of a feed mechanism (not shown) to this operation, a continuous seam can be formed.

The present invention is not limited to the embodiments described in detail above, and various changes can be made without departing from the gist of the present invention.

For example, in the present embodiment, the needle bar drive motor is directly connected to the upper shaft, but it may be connected to the upper shaft at a reduced speed by a gear or the like. The needle position detector may be other than an encoder. For example, a light emitting element and a light receiving element are arranged with a needle bar interposed therebetween, and light from the light emitting element is received only when the needle bar reaches the bottom dead center. The needle position detector may be configured such that the light receiving element outputs the detection signal after receiving the light. In this case, the configuration of the needle position detector is simplified, and the apparatus can be made inexpensive. Further, the hook rotation phase when the hook is stopped may be other than -46 degrees as long as the rotation start of the hook relative to the upper shaft rotation phase is changed. In addition to the rotary hook type, the hook type can also be a swinging hook type.

[Effects of the Invention] As is clear from the above description, according to the present invention, the needle position detector detects a predetermined position of the needle bar, generates a detection signal, and the control means controls the needle position detector. In response to the detection signal from the controller, the thread catching mechanism motor is controlled so as to stop after turning the thread catching mechanism once or once, and the thread catching mechanism motor repeats the rotation stop every one reciprocation of the sewing needle. Therefore, even if the rotation speed of the needle bar drive motor greatly changes when the sewing needle pierces the work cloth, the influence of the speed change of the needle bar drive motor on the thread catching mechanism motor is reduced. In addition, it is possible to prevent the occurrence of skipping and to achieve a unique effect that the size and cost can be reduced.

[Brief description of the drawings]

1 to 4 show an embodiment embodying the present invention. FIG. 1 is a schematic diagram showing an outline of the embodiment, FIG. 2 is a block diagram thereof, and FIG. FIG. 4 is a diagram showing a needle bar curve diagram showing a relationship with the shaft rotation angle, and FIG. 4 shows a meeting position a between the needle and the point of the blade and a standby position b of the blade when the shuttle stops. In the figure, 11 is a sewing needle, 13 is a needle bar, 15 is a needle bar drive motor, 18 is an encoder (needle position detector), 31 is a shuttle, 33 is a shuttle drive motor, and 41 is a control unit (control means).

Claims (1)

(57) [Claims] A needle bar (13) on which a sewing needle (11) carrying an upper thread is attached is reciprocated up and down by a needle bar drive motor (15), and a thread catching means (31) for catching the upper thread is provided. ) Is rotated or oscillated by a thread catching means driving motor (33) to catch the thread of the upper thread formed by the vertical movement of the needle bar, thereby forming a stitch on the work cloth. A needle position detector (18) for detecting a predetermined position of the rod and generating a detection signal, and responding to the detection signal from the needle position detector (18) to rotate the thread catching means once or once. And a control means (41) for controlling the thread catching means drive motor so as to stop after swinging.