JPH0312911B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a system in which a needle thread of a length necessary for forming each stitch is drawn out in advance from a needle thread supply source each time a stitch is formed by a feeding means that is linked to a stepping motor, and This invention relates to a needle thread supply device for a sewing machine.

This type of sewing machine uses a signal generated every time the main shaft rotates by a predetermined angle, which is linked to the stitch forming mechanism and cloth feed mechanism of the sewing machine, to rotate the stepping motor for feeding the needle thread at a speed that also corresponds to the cloth feed pitch. The yarn feeding device converts the above-mentioned signal generated at a frequency corresponding to the rotational speed of the main shaft into a voltage corresponding to that frequency, attenuates it at a ratio corresponding to the conversion operation of the cloth feed pitch, and then converts that voltage again. This converts the pulse signal into a pulse signal with a frequency corresponding to the level and inputs it to the stepping motor. However, when converting a pulse signal of a predetermined frequency into a voltage, as the frequency of the pulse signal becomes smaller, that is, as the sewing machine is rotated more slowly by hand, etc., the voltage fluctuation becomes larger, and the ripple center voltage becomes lower than that of the above-mentioned pulse signal. It no longer corresponds to the frequency of the signal, and as a result, it becomes impossible to supply the necessary amount of upper thread in just the right amount, resulting in a disadvantage that the thread tightness of the stitches becomes poor. In particular, this invention uses a stepping motor to rotate continuously during the entire operating period of the thread take-up when the sewing machine is operating at normal speed, and also during the non-thread-tightening period of the thread take-up when a low speed signal occurs. The object of the present invention is to eliminate the above-mentioned drawbacks by rotating only the rotor.

Embodiments of the present invention will be described below with reference to the drawings.
1 is a needle bar on which a needle 2 with an upper thread T is fixed at the lower end;
It moves up and down in conjunction with the main shaft (not shown) of the sewing machine. Reference numeral 3 denotes a well-known thread take-up, which supports the needle thread T between the needle thread spool 4 and the needle 2 as a needle thread supply source, rises to pull up the needle thread loop above the throat plate, and descends to take up the needle thread loop. It moves up and down between two predetermined positions in conjunction with the main shaft and in synchronization with the up and down movement of the needle bar 1 so as to allow the upper and lower threads to be captured by the needle bar 1 and fall out of the hook. The thread tightening period corresponds to the rotation angle of the main shaft from when the thread reaches the lower surface of the fabric until the entangled portion is drawn into the fabric. 5 is an outer frame (machine frame) of the sewing machine, a thread hook 6 is fixed to the front wall 5a thereof, and a thread guide groove 7 is formed in the upper wall 5b so as to penetrate into the machine frame.

On the front wall 5a, a drive roller 9 fixed to the output shaft of a stepping motor (hereinafter referred to as motor) 8 is disposed on one side of the path of the upper thread T passing through the thread guide groove 7, and on the other side. A driven roller 10 is disposed at , and both rollers 9 and 10 constitute a feeding means. The driven roller 10 is rotatably supported at the free end of an arm 11 whose base end is rotatably supported on the machine frame, and is attached to an elastic body (see FIG. The outer periphery is always pressed against the outer periphery of the drive roller 9 by the acting force (not shown). In the machine frame 5, a pair of clamping plates 12 and 13 are disposed facing each other across the path of the upper thread T between the rollers 9 and 10 and the bobbin 4, and one clamping plate 12 is connected to an electromagnetic solenoid (hereinafter referred to as a solenoid). The needle thread T is fixed to a movable element 14, and the upper thread T is gripped and released by the clamping plates 12 and 13 by energizing and de-energizing the solenoid 14. The solenoid 14 is energized when the rotation angle position of the main shaft corresponding to the thread tightening period is detected by the balance 3 by a detector not shown, and the main shaft corresponding to the non-thread tightening period is energized. The demagnetization is performed in connection with the detection of the rotational angular position of the needle thread gripping device.

Note that 15 is a known base tension disposed at the rear of the thread guide groove 7, and always provides a constant resistance to the upper thread T that is weaker than the tension of the lower thread.

Next, the electric circuit of this invention will be explained with reference to FIG.

G1 to G4 are NAND gate circuits (hereinafter referred to as gates), and I1 and I2 are inverters.

Reference numeral 20 denotes a main shaft pulse generator, which consists of a disk fixed to the main shaft and having a plurality of slits arranged at equal intervals on the same circle, and a sensor placed opposite to the rotation path of the slits, and which generates pulses every time the main shaft rotates by a predetermined angle. A signal is generated in connection with the detection of the slit. A first conversion circuit 21 converts an input signal into a signal with a voltage value corresponding to the frequency and outputs the signal. A second conversion circuit 22 converts an input signal into a signal with a frequency corresponding to the voltage value and outputs the signal. Reference numeral 23 denotes a variable resistor as a first attenuator, and the resistance value is determined in relation to the setting conditions of the setting means that allows setting different sewing conditions by manual operation or based on information recorded electrically or mechanically in advance. change. For example, it may be mechanically linked to the mode of manual operation of any one or all of a manual device for setting the fabric feed pitch, a manual device for setting the swing width of the needle bar 1, and a manual device for setting the fabric thickness. , or related to the information read out from the storage means electrically related to aspects of these manual devices, or one stitch previously recorded in the recording device electrically (ROM) or mechanically (cam) The resistance value changes in relation to each information.

Reference numeral 24 denotes an upper position detector, which consists of a disc fixed to the main shaft and having a cutout corresponding to the rotation angle corresponding to the tension of the upper thread T by the thread take-up lever 8, and a sensor placed opposite to the circuit path of the cutout. During the tension period, a low level signal (hereinafter referred to as L) is output, and during the relaxation period, a high level signal (hereinafter referred to as H) is output. 25 is a pulse edge generating circuit which captures the rising edge of the input and instantaneously generates an H signal. 2
6 is a counter which is reset by receiving an H signal at its B terminal. A second attenuator 27 is linked to the first attenuator 28. Reference numeral 28 denotes an analog/digital conversion means as a third conversion circuit, which converts the input signal into a binary code corresponding to the voltage value and outputs the binary code. The second attenuator 27 and the third conversion circuit 28 constitute a reference signal generation circuit. 29
is a matching circuit which generates an L signal when the output of the counter 26 and the output of the third conversion circuit 28 match. Note that VA is a voltage that is adjusted appropriately through a resistor to the power supply voltage, and can be changed.

80 detects whether the rotational speed of the spindle is above or below a certain speed, and opens/closes gates G2 and G3 so that if the speed is above the certain speed, gate G2 is opened, and in the following cases, gate G3 is opened. This is a judgment circuit that controls the circuit, and consists of multiple elements as shown below. That is,
31 and 32 are comparator circuits, and when the input voltage of the negative terminal is higher than the input voltage of the positive terminal,
generates a signal. 33 is an RS type flip-flop (hereinafter referred to as FF), which outputs an H signal from the Q terminal when an L signal is input to the S terminal, and outputs an H signal from the Q terminal when an L signal is input to the R terminal. Output a signal. Vcc is a power supply voltage, and R1 to R3 are resistors.

The present invention has the above configuration, and its operation will be explained next. When the sewing machine is driven, the iron rod 1 and the balance 3 move up and down in conjunction with the rotation of the main shaft while maintaining a slight phase shift. Furthermore, a signal is output from the main shaft pulse generator 20 every time the main shaft rotates by a predetermined angle, and a signal of L is output from the upper position detector 24 during the tensioning period of the upper thread T by the thread take-up 3.

Therefore, for example, when the sewing machine is driven at a certain speed or lower, that is, when the output voltage of the first conversion circuit 21 is lower than the voltage level of the P1 point, the FF 33 outputs an L signal to the R terminal. Since the signal is input, an L signal (low speed signal) is output from the Q terminal. This closes the gate G2 and cuts off the output of the second conversion circuit 22. On the other hand, since gates G3 and G1 open at the same time as gate G2 closes, motor 8 is driven clockwise in FIG. Rotate to. To describe this in more detail, the counter 26 is connected to the pulse edge generating circuit 2.
Until it is set by the signal No. 5, the gate G is controlled by the signal output from the main shaft pulse generator 20.
As the motor 8 rotates via G4, G3, and G1, the signal is counted by the counter 26, and when the counted value matches the output code of the third conversion circuit 28, the output of the matching circuit 29 is output. The gate G4 is closed and the motor 8 is stopped. Therefore, for example, assuming that the number of signals oscillated from the spindle pulse generator 20 during one reciprocating movement of the balance 8 is 100 pulses, the condition for matching the outputs of the counter 26 and the third conversion circuit 28 is as follows. The closing condition for the gate G4 is that the value of the counter 26 can be set to a maximum of 100 and any value below it by setting the second attenuator 27.
For example, if the value is set to 20, the motor 8 rotates for 20 pulses from the start of relaxing the needle thread T by the thread take-up lever 3 and then stops, and this process is repeated every time the sewing machine forms one stitch.

Therefore, the feeding of the upper thread (rotation of the stepping motor) is continuous if the number of pulses set by the second attenuator 27 is 100 in the case of the above embodiment, and is intermittent if it is less than 100.

Contrary to the above, when the sewing machine is being driven at a specific speed or higher, that is, when the output voltage of the first conversion circuit 21 is higher than the voltage level at point P2,
Since an L signal is input to the S terminal of the FF33, an H signal (high speed signal) is output from the Q terminal. As a result, the gate G2 is opened at the same time as the gate G3 is closed, so that the motor 8 rotates clockwise in FIG. 1 via the amplifier circuit 23 at a speed corresponding to the driving speed of the sewing machine. If the number of pulses output from the spindle pulse generator 20 during one rotation of the spindle is 100, and the attenuation rate of the first attenuator 23 is 1/2, then the second conversion circuit 22 The number of pulses output from is 50, and motor 8 outputs these 50 pulses during one rotation of the main shaft.
It rotates in response to the pulses. Therefore, the amount of yarn let out in this case is 1/ of the maximum amount that can be let out with this feeding device.
It becomes 2. Further, if the attenuation rate of the first attenuator 23 is 1/4, the number of pulses output from the second conversion circuit 22 will be 25, and the yarn payout amount will be further 1/2 of the above. In this way, even if the sewing machine is driven at the same speed, if the sewing conditions such as cloth feed pitch, needle amplitude, and cloth thickness are different, the amplification factor of the amplifier circuit 23 will be different, so the rotational speed of the motor 8 will also be different. It becomes ivy.

When the motor 8 rotates in this manner, the roller 9
rotates in the clockwise direction in FIG.
With the cooperation of the above, the needle thread T is continuously paid out from the bobbin 4 toward the thread take-up 3 at a speed corresponding to its rotational speed.

Note that during the thread tightening period by the thread take-up lever 3, the electromagnetic solenoid 14 is energized and the upper thread T is held by the set of clamp plates 12 and 13 and is prevented from being fed out from the bobbin winder 4. Microscopically, the upper thread T between the rollers 9, 10 and the pair of clamping plates 12, 13 is stretched slightly, but this thread tightening period is only a small amount when converted to the rotation angle of the main shaft. However, since it only lasts for a moment, it has no effect on sewing.

As described above, the present invention includes a pulse generator that is interlocked with the spindle and generates a pulse signal every time the spindle rotates by a predetermined angle during the entire rotation period of the spindle, and a first conversion circuit that generates a voltage proportional to the frequency of the pulse signal output. and a setting means that can set different sewing conditions based on manual operation or information recorded electrically and mechanically in advance; and a setting means for changing the output voltage of the first conversion circuit in relation to the setting conditions of the setting means. A first attenuator that outputs, a second conversion circuit that generates a pulsed drive signal at a frequency proportional to the output voltage value of the first attenuator, and a rotation of the main shaft based on the frequency of the pulse signal output from the pulse generator. a determination circuit that determines the magnitude of speed based on a specific speed and generates different signals;
a reference signal generation circuit that encodes and outputs a numerical value corresponding to the needle thread length required to form one stitch in relation to the sewing conditions set by the setting means;
When the sewing machine is operating at a speed higher than a specific speed, the number of pulses obtained by multiplying the number of pulses from the pulse generator by the ratio is applied to the stepping motor in synchronization with the rotation of the main shaft, and When the sewing machine is operating at a speed slower than the specified speed, the stepping motor receives the output from the reference signal generating circuit and applies the coded number of pulses to the stepping motor during the thread loosening operation period of the thread take-up. Therefore, even when the sewing machine is running at low speed, with a large ripple during frequency/voltage conversion in the first conversion circuit, the signal is transmitted via the reference signal generation circuit to the current operating speed, cloth feed pitch, etc. Since the number of pulses corresponding to the appropriate needle thread length can be input to the stepping motor each time one stitch is formed, the required amount of needle thread can be applied to the stepping motor every time one stitch is formed, regardless of the operating conditions of the sewing machine. This has the effect of ensuring that there is no shortage of supplies.

In addition, since the stepping motor is rotated at a speed corresponding to the output frequency of the pulse generator and the upper thread is continuously fed out during the entire operating period of the thread take-up, it is possible to use a stepping motor with poor response characteristics. Since it is possible to sufficiently follow the high-speed operation of the sewing machine, it is also possible to obtain the effect of increasing the operating speed of the sewing machine and improving sewing efficiency.

Note that FIG. 3 shows another embodiment of the first conversion circuit 21 in this embodiment, and the same elements as in this embodiment are given the same numbers. FIG. 4 is a time chart of FIG. 3. That is, regarding the configuration, 4
0 is a first pulse edge generating circuit that captures changes in the signal of the main shaft pulse generator 20 and instantaneously generates an H signal. A second pulse edge generating circuit 41 catches the falling edge of the signal from the generating circuit 40 and instantaneously generates an H signal. 42 is a reference pulse generator that always generates a signal at a constant frequency. 4
3 is a counter which clears its contents upon receiving an H signal at its R terminal. 44 is a latch circuit, and H is connected to the R terminal.
It receives the signal and outputs the input state at that time. 4
5 is a digital/analog converter, input (numeric value)
generates a voltage at a level corresponding to G5~G7
is a gate, and I5 is an inverter.

As shown in FIG. 3, when the sewing machine is driven, a signal is generated from the main shaft pulse generator every time the main shaft rotates by a predetermined angle. On the other hand, during the period from the rising edge to the falling edge of the signal or from the falling edge to the rising edge of the signal, the output signal of the reference pulse generator 42 is counted by the counter 48 via the gate G6 and the inder I5. The latch circuit 44 is latched by the signal from the generating circuit 41 related to the change, and the voltage is at a level corresponding to the count value of the counter 43 at that time (when the count value is large, the voltage is at a lower level than when it is small). ) is output from the converter 45.

Further, FIGS. 5 and 6 show separate other embodiments corresponding to FIG. 1, and the same elements as in this embodiment are given the same numbers. That is, FIG. 5 shows the solenoid 14 and the clamping plate 1 as the upper thread gripping device.
2 and 13 are rollers 9 and 1 as feeding means.
0 in the direction in which the upper thread T is fed out, and when the upper thread T is tensioned by the thread take-up 3, the clamping plate 1
2 and 13 grip the upper and lower T, thereby preventing a large load from being applied to the motor 8 when tightening the stitches, and preventing the needle thread T from being unwound excessively.

Furthermore, in this embodiment, if the pressing force of the rollers 9 and 10 is strengthened and the motor 8 with a large torque is used to prevent the needle thread T from being excessively paid out when the thread take-up thread is tightened by the thread take-up lever 3, it is possible to 12,13
And the solenoid 14 may be omitted.

Further, in this embodiment, the stepping motor 8 is used as the drive source for the feeding means, but a servo motor may also be used. In this case, the second conversion circuit 22 in the embodiment of FIG. 2 is not required, and the output of the attenuator 23 is input to the servo motor via a comparison circuit (not shown), and the position of the servo motor is detected. The configuration may be such that the output of the potentiometer is fed back to the comparison circuit for control.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of the main parts, Fig. 2 is a block diagram of the electric circuit, Fig. 3 is another embodiment of the first conversion circuit,
Figure 4 is the time chart of Figure 3, Figure 5 is the time chart of Figure 1.
This is another example corresponding to the figure. 3 is a balance, 8 is a stepping motor, 9, 10
is a roller as a feeding means, 20 is (main shaft)
A pulse generator, 21 a first conversion circuit, 22 a second conversion circuit, 23 a first attenuator, 24 a detector, 2
6 is a counter, 27 and 28 are a second attenuator and a third conversion circuit that constitute a reference signal generation circuit, 30 is a determination circuit, G4 is a first gate circuit, G2 is a second gate circuit, and G3 is a third gate circuit. It is.

Claims (1)

[Claims] 1. A stepping motor 8 that rotates in response to a pulse signal, a thread take-up 3 and a needle thread supply source 4 that operate in synchronization with the main shaft to tighten or loosen the needle thread. A sewing machine in which a required amount of thread is paid out from an upper thread supply source and supplied to a thread take-up by means of unwinding means 9 and 10 rotatably supported on a machine frame in conjunction with a stepping motor disposed on an upper thread path. The needle thread supply device includes a pulse generator 20 that is linked to the main shaft and generates a pulse signal every time the main shaft rotates by a predetermined angle during its entire rotation period, and a first conversion circuit 21 that generates a voltage proportional to the frequency of the pulse signal output. and a setting means capable of setting different sewing conditions based on manual operation or information recorded electrically and mechanically in advance; and a setting means for changing the output voltage of the first conversion circuit in relation to the setting conditions of the setting means. A first attenuator 23 that outputs, and a second conversion circuit 22 that generates a pulsed drive signal at a frequency proportional to the output voltage value of the first attenuator.
, a detector 24 that generates a signal in connection with the end of said upper thread tightening of the thread take-up, and a detector 24 that counts the signal of the pulse generator, encodes and outputs the counted value, and resets in relation to the signal of the detector. a counter 26, which has a second attenuator linked to the first attenuator, and which encodes and outputs a numerical value corresponding to the needle thread length required to form one stitch; A matching circuit 29 that compares both outputs from the generator circuit and generates a matching signal when both match, and a first gate circuit that is normally open so that the pulse generator signal can be input to the counter and closed upon receiving the matching signal. G4, a determination circuit 30 that detects the output voltage of the first conversion circuit and generates a high-speed signal or a low-speed signal in relation to the voltage becoming above or below a specific level; and a low-speed signal of the decision circuit. a second gate circuit G2 that is closed in connection with the high speed signal and opened in connection with the high speed signal to allow the signal of the second conversion circuit to pass; A third gate circuit G3 is provided which is open to allow the signal from the gate circuit to pass through, and the stepping motor is rotated continuously during the entire operating period of the thread take-up when a high-speed signal is generated, and during the non-thread tightening period of the thread take-up when a low-speed signal is generated. An upper thread supply device for a sewing machine, characterized in that the needle thread supply device rotates only the upper thread.