JPS6115816Y2 - - Google Patents

Description

[Detailed description of the invention] This invention uses separate needles that move up and down to supply needle thread, and a needle thread catcher that captures loops formed by the needle thread with hooks to form stitches. The present invention relates to a control device that allows a hook to reliably catch a loop of upper thread in an electric sewing machine driven by a motor.

In conventional sewing machines, the upper shaft, which is driven to rotate to move the needle up and down, and the lower shaft, which rotates to drive the upper thread catching device, are connected by gears or belts, and both shafts are driven to rotate by a single motor. Was. However, with this type of drive method, it is difficult to control the encounter between the needle and the hook of the upper thread catching device, and this can lead to skipped stitches, especially in sewing machines that operate at high speeds.
This was causing the thread tension to become unstable. Also,
High processing precision is required for the upper shaft, lower shaft, and support means for both shafts, and even higher precision is required especially for sewing machines that operate at high speeds or industrial sewing machines with relatively long arms, as well as vibration prevention. Various measures have been taken to achieve this, which has caused an increase in manufacturing costs. Furthermore, since power transmission means such as gears and belts are used, these are a cause of noise generation.

This invention was made to eliminate these drawbacks, and will be explained in detail below with reference to the drawings.

In FIG. 1, the upper end of a needle bar support frame 1 is pivotally connected to an arm 2 of a sewing machine by a short shaft 3, so that it can swing from side to side. A needle bar 4 is mounted on the support frame 1 so as to be movable up and down, a horizontal shaft 5 is fixed to the middle part of the needle bar 4, and a needle 6 is fixed to the lower end part.

Reference numeral 7 denotes a needle drive motor mounted within the arm 2, and a crank 9 is fixed to the end of the motor shaft 8. A small crank 11 is pivotally attached to the crank pin 10 of the crank 9, and the other end of the small crank 11 is connected to the horizontal shaft 5, and the rotational movement of the crank pin 10 accompanying the rotation of the motor shaft 8 is transferred to the needle bar 4. is converted into vertical motion.

A base end of a balance 13 is pivotally connected to the rack crank pin 10 via a link 12, and an intermediate portion of the balance 13 is connected to a link 15 pivotally connected to a shaft 14 fixed to the arm 2. As a result, the rotational movement of the crank pin 10 and the vertical swinging movement of the links 12 and 15 are applied to the thread hole 16 of the thread take-up 13 through which the upper thread (not shown) is inserted.

A needle position detection device 17 is connected to the needle drive motor 7, and the needle drive motor 7 and the needle position detection device 17 are connected to each other.
is electrically connected to the motor control circuit 18.

Reference numeral 19 denotes an upper thread catching device disposed within the sewing machine frame 20, and a hook 2 for catching the upper thread.
1 is formed, and this rotary hook 22 is fixed to one end of a lower shaft 23 rotatably supported by the sewing machine frame 20. Lower shaft 23
A bevel gear 24 is fixed to the other end, and the bevel gear 24 meshes with a bevel gear 27 fixed to one end of a motor shaft 26 of a lower shaft drive motor 25.

The lower shaft drive motor 25 is equipped with a hook position detection device 2.
8 are connected, and the lower shaft drive motor 25 and the hook position detection device 28 are electrically connected to the motor control circuit 18.

29 is a needle swing motor using a linear motor, and its armature 30 is connected to the needle bar support frame 1 via a link 31. Needle swing motor 29
A needle swing position detection device 32 that detects the swing position of the needle 6, that is, the amount of movement of the armature 30 from the reference position is connected to the needle swing position detection device 32. The needle swing motor 29 and the needle swing position detection device 32 are electrically connected to the motor control circuit 18.

The operation of such a configuration will be explained using FIG. 2.

The motor control circuit 18 has a speed command device 35. This speed command device 35 includes a start/stop function for the sewing machine, and allows the operator to arbitrarily set the machining speed. The speed command signal from the speed command device 35 is supplied to the driver circuit 37 via the adder 36 at a voltage level proportional to the command speed, and rotates the needle drive motor 7 at a predetermined speed. The rotation of the needle drive motor 7 is transmitted to the needle bar 4 via a crank 9 and a small crank 11, and each rotation of the motor 7 causes the needle 6 to move up and down once.
Further, the rotation of the needle drive motor 7 is converted into a swinging motion of the balance 13 via the link 12,
3 performs thread tightening operation after stitch formation.

Needle position detection device 1 connected to needle drive motor 7
A potentiometer 7 outputs a position signal corresponding to the rotational position of the needle drive motor 7. As shown in FIG. 3, the phase of this position signal is advanced while the needle drive motor 7 rotates from the needle down position to the needle up position, and the phase is delayed while it rotates from the needle up position to the needle down position. Ru. This position signal is F
Negative feedback is sent to the adder 36 through the -V converter 38 so that the needle drive motor 7 rotates at the commanded speed.

The position signal output of the needle position detection device 17 is supplied to the adder 39 of the motor control circuit 18 as a speed command signal of the lower shaft drive motor 25, and the driver circuit 40
The lower shaft drive motor 25 is driven through the lower shaft drive motor 25. The lower shaft drive motor 25 is synchronized with the needle drive motor 7 so that the timing of the encounter between the hook 21 of the upper thread catching device 19 and the needle 6 is optimal. Hook position detection device 2 connected to lower shaft drive motor 25
8 is constituted by a potentiometer, the output signal of which is negatively fed back to an adder 39, and the needle drive motor 7 and the lower shaft drive motor 25
and rotate synchronously.

When sewing a zigzag pattern, motor control circuit 1
A needle vibration command signal is output from the needle vibration command device 41 of No. 8, and the needle swing motor 29 is driven via an adder 42 and a driver circuit 43. The output signal of the needle swing position detection device 32 connected to the needle swing motor 29 is negatively fed back to the adder 42 to adjust the swing position of the needle 6 to the command value.
The output signal is also fed back to the adder 39 of the feedback circuit of the lower shaft drive motor 25, so that the hook 21 of the upper thread catching device 19 meets the needle 6 optimally according to the swinging position of the needle 6. It is controlled as follows.

Since the output signal of the needle position detection device 17 is partially out of phase as shown in FIG. The threaded needle 6 passes through the workpiece fabric (not shown) and moves at high speed from the time it reaches the needle-down position until it completely comes out of the workpiece fabric. The rotation of the lower shaft 23 becomes slow while the lower shaft 23 reaches this position and descends again to the needle lower position. During this rapid rotation of the lower shaft 23, a loop is formed by the upper thread on the lower surface of the workpiece cloth, so the hook 21 of the upper thread catching device 19 can reliably catch the loop. As the upper thread loop slips out of the hook 21, a stitch is formed between it and the lower thread, and at the same time, the upper thread is pulled up by the lifting of the thread take-up 13, thereby tightening the thread.

As detailed above, the device of this invention uses two motors, one to drive the needle and the other to drive the needle thread catcher, so the speed of each motor can be controlled by the control device. can. Therefore, when the needle rises a little above the lowest point and a loop is formed by the upper thread, it is necessary to rotate the lower shaft quickly to ensure that the loop is caught by the hook and to prevent skipped stitches. It is possible. Also,
As a relative phenomenon, it is possible to lengthen the time from when the upper thread comes off the hook until the needle falls to the lowest point again, so that the thread tightness of the stitch can be stabilized. Furthermore, since the needle and needle thread catcher are driven by separate motors, sewing machines with long arms can be manufactured easily, and the use of gears, belts, cams, etc. as power transmission means can be reduced. This makes it possible to operate at high speed and reduce noise.

In this embodiment, a potentiometer was used as the needle position detection device, and a part of its output signal was shifted in phase to be used as the speed command signal for the lower shaft drive motor. It is also possible to give the output signal a desired waveform by using an encoder and changing the spacing of its slits.

[Brief explanation of the drawing]

Figure 1 is a front view of the main parts of an electric sewing machine implementing this invention, Figure 2 is a block circuit diagram, Figure 3 is a diagram showing the output signal of the needle position detection device, and Figure 4 is a diagram showing the rotation speed of the lower shaft. FIG. In the figure, 6 is a needle, 7 is a needle drive motor, 18 is a motor control circuit, 19 is an upper thread catching device, 21 is a hook, and 25 is a lower shaft drive motor.

Claims (1)

[Scope of utility model registration request] a needle drive motor that moves up and down a needle that supplies needle thread; a needle thread catching device that catches a loop formed by the needle thread with a hook to form a stitch; and the needle thread catching device is connected to the needle drive motor. a lower shaft drive motor that rotates synchronously; the lower shaft drive motor rotates faster than the rotation of the needle drive motor while the hook captures the loop of the upper thread; and after the loop is captured, the lower shaft drive motor rotates faster; 1. A control device for an electric sewing machine, comprising: a motor control circuit that controls both the motors so as to slow the rotation of the motors.