JPS5944075B2 - Control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control circuit, and particularly to a control circuit suitable for use in a control device for a sewing machine.

As seen in Japanese Patent Publication No. 47-17027 and U.S. Patent No. 3,487,438, the sewing machine control device is equipped with a solenoid for automatic thread trimming and thread removal, and there are also examples in which the drive stop mechanism is equipped with an electromagnetic clutch and a brake. many.

In conventional sequence control circuits that sequentially excite these solenoids, the electromagnetic energy of the coil including inductance is consumed as resistance heat, and the circuit structure is not necessarily such that it can be effectively recovered. An object of the present invention is to provide a control circuit that effectively utilizes the electromagnetic energy of these coils by devising the wiring configuration of the control circuit.

Another object of the present invention is to provide a control circuit with quick response.

Regarding control technology for sewing machines, in addition to the above-mentioned known examples, there is also the control technology of Japanese Patent Application Laid-Open No. 46-2454 and U.S. Patent No. 3,024,750 regarding fixing stitches to prevent fraying, and furthermore, the control technology of sewing machine speed change and drive stop by intermittent control of electromagnetic clutch brake. , U.S. Patent No. 3407910, Japanese Patent Publication No. 47-283
76, JP 47-22362, JP 47-9069
There are effective techniques that are widely known.

A typical example of operation of a sewing machine to which the control circuit of the present invention can be applied is shown in FIG. In FIG. 1, the horizontal axis shows time, and the vertical axis shows the sewing machine speed in the upper graph and the voltage of each control solenoid in the lower graph.

By operating a known sewing machine pedal (not shown), the time tl is
A voltage is applied to the clutch Cl, and the sewing machine is accelerated to speed N2. Thereafter, voltage is applied alternately to the brake Br and the clutch Cl, and the speed N2 is continued for a period of time 4.
In addition, the backtitch solenoid BT for time 2 and 3 is energized, and a known sewing machine cloth feed direction mechanism (not shown) feeds the fabric in the opposite direction to the time 1 to 2, and the backtitch is started. Then, from time 4 to time 5, the voltage of clutch Cl is applied and the sewing machine is operated at high speed sewing speed N3. When the operating force of the sewing machine pedal (not shown) is released at time 5 or applied in the opposite direction (reverse pedal), the brake Br is energized by known control technology, and the sewing machine decelerates from N3 to Ni. do. Time is 6, speed is N2
In this case, the clutch Cl and the brake Br are controlled alternately and intermittently, and for example, when the needle reaches the specified lower position, the time T
7, the speed increases again to N2, and the fixing stitch is performed at the speed N2 for a specified number of stitches, for example, from the specified position T, to the specified position, e.g., the next needle down position.
When the speed returns to N1 again, the thread trimming solenoid T
is excited and the thread cutting mechanism operates. And time Tl
When the needle is in the upper position at l, the excitation of the clutch CL and the excitation of the thread trimming solenoid T are completely de-energized, and the brake Br is energized. At the same time, after the thread removing solenoid W is energized for a short time, the presser foot lifting solenoid is energized at time Tl2. As in the sewing machine control described above, a circuit as shown in FIG. 2 has conventionally been used as a control circuit for sequentially exciting and releasing a plurality of solenoids.

That is, in the circuit shown in FIG. 2, the current from the commercial AC power supply 1 is stepped down by the transformer 2, and the diode 34 and smoothing capacitors 5 and 6 supply, for example, 48V DC to the line 23 and 24V DC to the line 24. bring. The clutch (or brake) coil 7 is an example in which 24 excitation is controlled by opening and closing the switch 8. When the switch 8 is opened, the energy stored in the inductance of the coil 7 } LI2 The closed circuit through the coil 7 dissipates resistance heat.

In addition, the brake (or clutch) coil 13 has 4
This is an example in which switching is possible using the switch 1, which has a contact 12 connected to the 8V line 23 and a contact 11 connected to the 24V line 24.In order to increase the speed of excitation, it is first connected to the contact 12, and after the solenoid is attracted by 48V, the contact is switched. 11 side and held at 24V, and then the switch 14 is opened. After the switch 14 is opened, the coil 13
The energy is consumed as resistance heat in the closed circuit of the diode 15 and the coil 13.

The example of the thread cutting coil 21 is configured so that the coil 21 is energized only for the time period during which the 48V energy stored in the capacitor 22 is discharged by switching the switch 18. In this manner, the sewing machine is controlled by energizing and releasing the plurality of coils in a predetermined order by a known sequence control circuit (not shown).

However, in the conventional circuit as shown in Fig. 2, the energy A-LI2 accumulated in the coil inductance is directly consumed as resistance heat, which goes against the energy saving and the current extinction time when the excitation is released, that is, the recovery time of the solenoid mechanism. The problem is that it takes a relatively long time. On the other hand, with coils like the coil 13, which are initially turned on at high pressure and high speed, and then held at low pressure,
It is cumbersome as it requires two low-voltage power supplies. The present invention seeks to overcome these conventional drawbacks.

The control circuit according to the present invention will be explained with reference to FIG.
The coil 25 is connected to the 4V power line 24', and the coil 2
A switch 26 is provided in series with 5.

Further, an energy transfer capacitor 28 is connected to the power supply line 24' via a diode 32 and a resistor 33.
A diode 27 is provided between the coil 25 and the capacitor 28. Furthermore, a series combination of a coil 29 and a switch 30 is provided in parallel with the capacitor 28. A diode 31 is connected in parallel to the coil 29. In such a configuration, first the switch 26 is closed and the coil 25 is energized, and then when the switch 26 is opened, the current in the coil 25 passes through the diode 27 and is photoelectrically transferred to the coil 24 via the diode 32 and the resistor 33. The energy stored in the inductance of the coil 25 is transferred to the capacitor 28 . Therefore, the potential of the capacitor 28 rises above the power supply 24V, but that voltage is maintained because of the diodes 27, 32 and the open switch 30. After that, when the switch 30 is closed, the coil 29 is initially connected to the capacitor 2.
8 high-voltage voltage, - then 24 lines 2
4 is maintained. In this way, in the circuit shown in FIG. 3 according to the present invention, the energy stored in the coil 25 is effectively utilized, and the attenuation of the current in the coil 25 takes the same time as the attenuation time when ordinary flywheel diodes are connected in parallel. It has the advantage that it decays in an even shorter time.

Another advantage is that the coil 29 is excited at high voltage only at the beginning with a simple circuit. According to theoretical calculations, the coil 25 has a self-inductance of 40mH and a resistance of 10Ω.
, the capacitance of capacitor 28 is 40PF, and the power supply voltage is 24V.
Then, the current decay time (time until the current becomes zero) is 144 mS when the switch 26 is first closed and opened.
, the voltage of the capacitor 28 becomes 70V. Further, the second time the switch 26 is closed/opened, the voltage is 1100 for 0.9 ms, and the voltage is 122 V for 0.76 mS the third time. The reason why the decay time of the current becomes shorter with each cycle and the rate of increase of the voltage of the capacitor 28 decreases is that the fixed coil storage energy +Ll2 is changed to the capacitor energy ±CE2 (C
is the capacitor capacity, and E is for shifting to the capacitor potential 7, which is caused by the fact that the potential E increases over time.

That is, ★L2 is due to the fact that Ei increases each time the number of times is increased when moving to the number of times. Since the time constant of the coil (time for the current to decay to 37%) is 4 ms, it can be seen that the decay time is greatly reduced.

Furthermore, it can be seen that a high voltage several times higher than that of the power source can be obtained by high-speed excitation of the coil 29. Furthermore, even if the switch 30 is closed at the same time as the switch 26 is opened, the energy in the coil 25 is initially shunted and transferred to the capacitor 28 and the coil 29, and as the capacitor 28 rises above the power supply voltage, the coil 29 is excited at a voltage higher than the power supply voltage.
Then, when the transfer energy decreases, capacitor 2
8 is discharged, and the coil 29 is continuously excited with a voltage. Finally, when the capacitor 28 becomes equal to the power supply voltage, the energy discharging of the coil 25 is completed and the coil 29 is held at the power supply voltage. It is clear that the above-mentioned advantages can also be achieved in this case.

When the circuit of FIG. 3 is applied to the control of a sewing machine, it is desirable that the coil 25 be a thread trimming solenoid and the coil 29 be a brake coil.

That is, the faster the response of the electromagnetic brake Br is, the more advantageous it is for stopping at a fixed position after thread trimming, but if the brake is kept strong all the time, the deceleration of the sewing machine becomes unstable. In the circuit shown in Figure 3, after releasing the thread trimming solenoid (coil 25),
Only when the switch 30 is closed can the braking operation be achieved by excitation of the coil 29 which has a particularly quick response. Another control circuit according to the invention is shown in FIG.

The left part of this figure shows the energy of one coil 35 as 2
A configuration is shown in which two capacitors 38 and 39 are used for high-voltage excitation of two coils 36 and 37. Also shown on the right is a configuration in which the energy of two coils 40 and 41 is collected in a capacitor 43 in order to be used for high-voltage excitation of one coil 42. Depending on the operation pattern of multiple coils to be forward excited in this way,
It is possible to distribute or concentrate the energy of the coil.

[Brief explanation of the drawing]

FIG. 1 is a time chart showing a typical example of the operation of a sewing machine. FIG. 2 is a diagram showing a conventional control circuit. FIG. 3 is a diagram showing a control circuit according to the present invention. FIG. 4 shows another control circuit according to the invention. Explanation of symbols, 1...
...AC power supply, 2...Transformer, 3, 4, 9
, 15, 16... Diode, 5, 6, 22...
... Capacitor, 7, 13, 21 ... Coil, 8, 10, 14, 18 ... Switch, 1
1, 12, 19, 20... Contact, 17...
...Resistance, 23...High voltage DC line, 24...
...Low voltage DC line, 24'...Power line, 25, 29, 35, 36, 37, 40, 41, 42
......Coil, 26,30...Switch, 2r,31,32...Diode, 28,3
8, 39, 43... Capacitor, 33...
··resistance.

Claims (1)

[Claims] 1 A control circuit comprising at least two coils to be sequentially excited, comprising two power supply lines, a first coil whose one end is connected to one of the power supply lines, and the first coil. a first switch means provided between the other end and the other power supply line; a first rectifier element whose one end is connected to the one power supply line; and the other end of the first rectifier element. an energy transfer capacitor provided between the other power supply line;
A second rectifier element provided between the other end of the first coil and the other end of the first rectifier element, a second coil provided in parallel to the capacitor, and a second coil that opens and closes. A control circuit characterized in that it includes a second switch means.