JP3291428B2 - Electric iron - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric iron having a power supply circuit for a relay.

[0002]

2. Description of the Related Art An electric iron of this type is disclosed, for example, in Japanese Patent Application Laid-Open No. Hei 4-90797, and FIG.
The description will be given according to the electric circuit diagram of FIG. In FIG. 3, a heating means 41 for heating a base (not shown), a temperature detecting means 42 for detecting a temperature of the base, a temperature setting means 43, and a control means 44 connected to both means 42, 43 , A relay 45, a switching element 46, and a relay contact 47. The relay power supply circuit 5 includes a capacitor 48, a Zener diode 49, a resistor 50, and a diode 51.
2 are provided.

[0003]

As described above, when the supply voltage from the AC power supply 53 is a positive potential, the relay power supply circuit 52 performs half-wave rectification by the diode 51 and applies a constant voltage to the relay 45 by the zener diode 49. Supplying.
When the supply voltage from the AC power supply 53 is a negative potential, the capacitor 48 connected in parallel with the Zener diode 49
A substantially constant voltage is supplied to the relay 45 by the discharge voltage. In this manner, a substantially constant DC voltage is applied to the relay 45.

However, if the capacitor 48 fails and becomes open, the voltage applied to the relay 45 becomes zero when the AC voltage is negative, and the relay contact 47 is opened. When the AC voltage has a positive potential, the relay contact 47 is closed. In this way, the relay contact 47 is repeatedly opened and closed every half cycle of the AC power supply, and arcs are discharged at both contacts of the relay contact 47 so that both contacts are welded. As a result, there is a first disadvantage that the heating means 41 continues to be energized and the base temperature rises abnormally, damaging the ironing cloth. Further, since the temperature fuse 54 is set to a temperature much higher than the normal temperature (prevention of premature disconnection), the cloth is significantly damaged before the temperature fuse 54 melts.

For this reason, the relay power supply circuit 52 is configured by a transformer to perform full-wave rectification. However, the provision of the transformer has a second disadvantage that the iron becomes large and heavy. Therefore, the present invention has been made in consideration of such conventional drawbacks, and aims to provide a small-sized electric iron that prevents abnormal temperature rise of a base when a capacitor is opened.

[0006]

In order to solve the above-mentioned problems, the present invention provides a heating means for heating a base, a temperature detecting means for detecting a temperature of the base, a temperature setting means, and an output of the temperature detecting means. Control means for comparing the output of the temperature setting means with the base and controlling the temperature of the base, a relay for controlling the energization of the heating means, a switching element for driving the relay, a power supply circuit for a relay comprising a rectifying diode and a capacitor, Contact detection means for detecting the opening and closing of the relay contact within a predetermined time considering the operation delay time of the relay from the zero cross point of the AC power supply, wherein an ON signal is output to the switching element, and When the signal indicates the opening of the contact, the control means stops driving of the switching element.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An electric iron according to an embodiment of the present invention will be described below with reference to the electric circuit diagram of FIG. FIG.
Here, a base (not shown) is made of metal or the like, and has a built-in heating means 1. The heating means 1 comprises, for example, an electric heater. The temperature sensor 2 includes a thermistor or the like, and is disposed on a base. The temperature detecting means 3 converts the temperature information of the temperature sensor 2 into an electric signal (voltage) and detects the temperature of the base.

The temperature setting means 4 sets a base temperature (off, low temperature, medium temperature, high temperature, etc.) desired by the user.
The control means 5 comprises, for example, a microcomputer or the like,
Terminals P1 and P2 are connected to temperature detecting means 3 and temperature setting means 4, respectively.
It is connected to the. The control means 5 compares the output of the temperature detection means 3 with the output of the temperature setting means 4, and outputs an ON signal to the terminal P3 when the former output is lower than the latter output, and outputs an OFF signal to the terminal P3 when the former output is lower than the latter. Temperature control.

The relay 6 opens and closes a relay contact 7 connected in series to the heating means 1 and controls the power supply to the heating means 1. The switching element 8 drives the relay 6, and is composed of, for example, a transistor. The emitter of the switching element 8 is connected to one side of the AC power supply 9 via the first lead wire 10. The base of the switching element (transistor) 8 is connected to the terminal P3 of the control means 5 via the resistor 11, and the collector is connected to one side of the relay 6.

The other side of the relay 6 is connected to a second lead wire 12 and includes a smoothing capacitor 13 and a Zener diode 14.
Are connected between the first lead wire 10 and the second lead wire 12. A connection point between the second lead wire 12 and one side of the Zener diode 14 is connected in series to the step-down resistor 15 and the rectifier diode 16, and is connected to the other side of the AC power supply 9 via the third lead wire 17. . The capacitor 13, the Zener diode 14, the step-down resistor 15, and the rectifier diode 16 constitute a power supply circuit 18 for a relay (half-wave rectification).

A resistor 19, a resistor 20, and a diode 21 are connected in series, and a series circuit is connected between the first lead 10 and the third lead 17. Transistor 22
Is connected to the first lead wire 10, the base is connected to the junction between the resistors 19 and 20, and the collector is connected to the fourth
It is connected to a terminal P4 of the control means 5 via a lead wire 23. The potential of the first lead wire 10 is V1, the potential of the third lead wire 17 is V2, and the AC voltage supplied by the AC power supply 9 is V = V2-V1. The resistors 19 and 20, the diode 21, and the transistor 22 constitute a synchronizing signal generator 24.

FIG. 2A shows the waveform of the AC voltage V, and FIG. 2B shows the waveform of the synchronizing signal A generated from the synchronizing signal generating means 24. In these figures, when the AC voltage V is a half cycle of the positive potential, the diode 19 causes the resistors 19, 2
The current does not flow to 0, the base current of the transistor 22 does not flow, the transistor 22 is turned off, and the synchronization signal A has a “Lo” waveform. Further, when the AC voltage V is a half cycle of the negative potential, a current flows through the resistors 19 and 20 by the diode 21, the transistor 22 is turned on, and the synchronization signal A shows a “Hi” waveform.

Referring again to FIG. 1, the relay contact 7 comprises a first fixed contact 7a, a second fixed contact 7b, and a movable contact 7c, and the first fixed contact 7a is connected to the first lead wire 10. The resistor 25, the resistor 26, and the diode 27 are connected in series, one side of this series circuit is connected to the first lead wire 10, and the other side of the series circuit is connected to the junction between the second fixed contact 7a and the heating means 1. ing. Transistor 2
The emitter of 8 is connected to the first lead 10, the base is connected to the junction of the resistors 25 and 26, and the collector is connected to the terminal P5 of the control means 5 via the fifth lead 29. The resistors 25 and 26, the diode 27, and the transistor 28 constitute a contact detection unit 30. As described above, the contact detecting means 30 is connected to the fifth lead wire 29.
And outputs a contact detection signal B to the control means 5 via the control circuit 5. The electric iron 31 is constituted by these components.

Next, the operation when the electric iron 31 is operating normally will be described with reference to FIG. AC voltage V = V
2- If V1 is a negative potential, the potential V1 is higher than V2, and if a voltage equal to or higher than the Zener voltage is applied, the rectifier diode 16 rectifies the first lead wire 10, the Zener diode 14, the resistor 15, the rectifier diode 16 And a current flows through the third lead wire 17. At this time, the capacitor 1
3 is charged. If the output of the temperature detecting means 3 is smaller than the output of the temperature setting means 4, the control means 5 outputs an ON signal to the base of the switching element 8, the switching element 8 is turned on, the relay 6 is energized, and the relay contact 7 Is closed, and the heating means 1 is energized.

When the AC voltage V has a positive potential, the potential V2
Is higher than V1, the Zener diode 14 and the resistor 1
No current flows through the rectifier diode 5 and the rectifier diode 16, and charging of the capacitor 13 is stopped and discharging is started. The discharge voltage of the capacitor 13 is supplied to the switching element 8 and the relay 6, and the relay contact 7 keeps closing.

The waveform of the contact detection signal B in the normal state shown by the broken line in FIG. 2D keeps "Lo". At this time, the contact detection signal B from the contact detection means 30 is synchronized with the synchronization signal A by the control means 5 for a predetermined time, for example, 3.9 ms from the zero-cross point C of the AC power supply. Is determined. As a result, the control means 5 determines that the relay contact 7 is closed, determines that the operation of the capacitor 13 is normal, continues to output an ON signal to the switching element 8, and continues energizing the heating means 1.

If the output of the temperature detecting means 3 is larger than the output of the temperature setting means 4, the control means 5 outputs an OFF signal to the switching element 8, and the energization of the relay 6 is stopped.
The relay contact 7 is opened, and the energization of the heating means 1 is stopped.
The potential V1 becomes V by the rectifying action of the diode 27.
When the value is larger than 2, that is, when the AC voltage V has a negative potential, the contact detection signal B outputs a “Hi” signal. However, the control device 5 determines the contact detection signal B only when the ON signal is output to the switching element 8, so that in the above case, the control means 5 determines that the operation of the capacitor 13 is normal.

Next, an operation when the electric iron 31 is in an abnormal operation (the capacitor 13 is open) will be described with reference to FIGS. 1, 2C and 2D. FIG. 2C shows the waveform of the voltage applied to the first fixed contact 7a and the second fixed contact 7b during the abnormal operation, and FIG. 2D shows the waveform of the contact detection signal during the abnormal operation. In these figures, the AC power supply 9
For example, in 1 Hz, 1/4 period = 1/60 × 1 /
4 × 1000 = 4.17 ms.

The relay 6 is composed of a coil and has an impedance of wL (w is the frequency, and L is the inductance of the coil). As a result, the relay 6 has an operation delay time, for example, about 4 ms from the start of energizing the relay 6 until the relay contact 7 is closed, and about 4 ms from the stop of energizing the relay 6 to the opening of the relay contact 7. Occurs.

First, during the period E in FIG. 2C, when the AC power supply V is at a negative potential before that, the potential V1> V2, and the rectifying action of the rectifying diode 16 causes the relay 6 to be energized, so that about 4 ms The relay contact 7 is closed due to the delay. Therefore, during the period E in FIG. 2C, the voltage V3 between the first fixed contact 7a and the second fixed contact 7b becomes substantially zero.

Next, when the AC voltage V becomes a positive potential as shown by F, V2> V1, the energization of the relay 6 is stopped by the rectifier diode 16, and the relay contact 7 is opened with a delay of about 4 ms. An arc is generated between the first fixed contact 7a and the second fixed contact, and the voltage V3 changes irregularly during the G period.

Next, when the AC voltage V becomes a negative potential like H, V2 <V1 and the energization of the relay 6 by the rectifier diode 16 is started, but due to the operation delay of the relay 6, up to about 4 ms (period I). In ()), since the relay contact 7 is open, the voltage V3 becomes substantially the same as the waveform of H. Then, after the period I, the relay contact 7 is closed, and the voltage V3 becomes substantially zero (period J).

Next, when the AC voltage V becomes a positive potential again like K, the voltage V3 becomes substantially zero in the L period as described above, and the voltage V3 shows an irregular change in the M period. .
As described above, the voltage V3 repeats a series of changes in the E, G, I, and J periods.

Next, as shown in FIG. 2D, the contact detecting means 30 synchronizes with the synchronization signal A, and within a predetermined time (D period) from the zero cross point C of the AC power supply 9, for example, 3.9 ms,
The control means 5 outputs a contact detection signal N indicating that the relay contact 7 is open.
To the terminal P5. At this time, if the control unit 5 outputs an ON signal from the terminal P3 to the switching element 8, after determining the output of the contact detection signal N,
An off signal is output to the switching element 8 so that the driving of the switching element 8 is stopped.

As described above, the control means 5 determines that the capacitor 13 has opened and has failed, and determines that the switching element 8 has failed.
, The power supply to the relay 6 is stopped, the relay contact 7 is opened, and the power supply to the heating means 1 is stopped. As a result, the base temperature of the electric iron 31 is prevented from rising abnormally, and the cloth being ironed is not damaged. Also, each component in the electric iron 31 is not damaged. Furthermore, the electric iron 31 uses a half-wave rectifying power supply circuit for a relay composed of a rectifying diode and a capacitor, instead of the conventional full-wave rectification having a transformer, so that the size and cost are reduced.

As described with reference to FIGS. 2C and 2D, immediately before the zero-cross point C, a reverse voltage is applied to the rectifier diode 16 connected to the relay 6, and
Is stopped and the relay contact 7 is open. Immediately after the zero-cross point C, a forward voltage is applied to the rectifier diode connected to the relay 6 and the relay 6 starts to be energized. However, the relay contact 7 opens due to the operation delay of the relay 6 (period D). Operation delay time of relay 6 (about 4 ms)
Later, the relay contact 7 closes. Thus, the capacitor 13
Is open and has failed, the contact detection signal N indicating the opening of the relay contact 7 during the period D outputs a "Hi" signal.

During the period D, the relay 6
Should be shorter than the operation delay time (e.g., about 4 ms).
It is better to specify 2.5 ms as the period D1. By designating the period D1 in this way, if the capacitor 13 is open, the contact detection signal P always becomes "H" in the period D1.
i "signal. In order to specify the period D1 (1 to 2.5 ms from the zero-cross point C) in this way, the contact detection signal P output to the control means 5 is synchronized with the zero-cross point C in the control means 5, and the control is performed. 1 to 5
The period D1 is specified by measuring 2.5 ms.
Is determined whether the contact detection signal P is "Hi" or "Lo". Since the operation delay time of the relay 6 varies between 4 and 5 ms, as described above, the period D1 is specified between 1 and 2.5 ms from the zero cross point C to cover this variation.

If the control means 5 outputs an ON signal to the switching element 8 as described above and the control means 5 outputs a contact detection signal N or P indicating that the relay contact 7 is open, A display (not displayed) connected to the control means 5 may be displayed to indicate that an abnormality has occurred. Further, at the time of the above-described abnormality, an abnormal sound may be generated in the sounding body connected to the control means 5. By doing so, the user is clearly notified that the capacitor 13 has opened and has failed.

[0029]

As described above, according to the present invention, when a capacitor fails and becomes open, the contact detecting means opens the contact of the relay within a predetermined time (shorter than the operation delay time of the relay) from the zero cross point. Output to the control means. The control means determines that the contact detection signal is “Hi” when outputting the ON signal to the switching element. As a result, the control unit outputs an off signal to the switching element, stops the relay, and stops energizing the heating unit. Therefore, abnormal temperature rise of the base is prevented, and damage to the cloth is prevented.

Further, according to the present invention, since the relay power supply circuit is a half-wave rectification power supply circuit comprising a rectifying diode and a capacitor, a compact and lightweight electric iron can be obtained without the need for a transformer or the like as in the prior art.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of an electric iron according to an embodiment of the present invention.

2A shows a waveform of an AC voltage V supplied to the electric iron, and FIG. 2B shows a waveform of a synchronization signal A used for the iron. FIG. 2C shows the voltage V between the relay contacts when the capacitor is opened.
FIG. 2D shows the waveform of the contact detection signal of the iron in the above state.

FIG. 3 is an electric circuit diagram of a conventional electric iron.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating means 3 Temperature detecting means 4 Temperature setting means 5 Control means 6 Relay 8 Switching element 13 Capacitor 16 Rectifier diode 18 Power supply circuit 24 Synchronous signal generating means 30 Contact detecting means

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yuji Saito 3-201 Minamiyoshikata, Tottori City, Tottori Pref. Tottori Sanyo Electric Co., Ltd. 5-307992 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) D06F 75/26 G05B 9/02 G05D 23/19

Claims (1)

(57) [Claims] 1. A heating means for heating a base, a temperature detecting means for detecting a temperature of the base, a temperature setting means,
Control means for comparing the output of the temperature detection means and the output of the temperature setting means to control the temperature of the base, a relay for controlling the energization of the heating means, a switching element for driving the relay, and a rectifying diode And a relay power supply circuit comprising a capacitor, and contact detection means for detecting the opening and closing of the relay contact within a predetermined time considering the operation delay time of the relay from the zero-cross point of the AC power supply, and an ON signal to the switching element. Is output, and when the signal from the contact detecting means indicates the opening of the contact, the control means stops driving the switching element.