JPS58163025A - Temperature controller - Google Patents

Abstract

PURPOSE:To increase the lifetime of a relay contact, by latching the coil of a latch relay connected to a heater with the signal which is supplied via a Schmitt circuit and a hysteresis means by the temperature of detection and therefore reducing the opening/closing times of the relay contact. CONSTITUTION:Transistors TR27 and TR26 are turned on and off when the temperature of a heater 2 is lower than that set by a volume 25 with a high level of resistance of a thermistor 31. At the same time, a temperature detecting means A is set at an H output, and TR15 and TR14 of a Schmitt circuit B are turned off and on respectively with TR4 and TR11 turned on. Thus an inverting means D has an L output, and a TR8 is turned off. Then a charging current flows instantaneously to a capacitor 6 to close and latch a contact 3A. When the heater 2 conducts to raise up the temperature, the state of each part is inverted. Then the capacitor 6 is discharged to release the latching state. In this case, the temperature of the thermistor 31 drops, and the TR15 is turned on. Thus the base potential of the TR26 is set at a high level owing to a diode 22 and a resistance 21, and the temperature of the thermistor 31 is lowered less than the level obtained when the heater 2 is turned off. Then the thermistor 31 is finally turned on to draw a hysteresis.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control device that controls the energization of a heater such as a heating device using a latch relay, and is compatible with a temperature detection means including a heat-sensitive element and an output signal of the temperature detection means. A switching circuit that operates as a switching circuit, hysteresis means for the switching circuit, means for inverting the output of the switching circuit, and a latch relay driving means for controlling a latch relay in response to the output of the switching circuit and the output of the inverting means. A temperature control device is provided.

The details will be explained below with reference to the drawings.

Fig. 1 is an electric circuit diagram showing one embodiment of the temperature control device according to the present invention.6 In Fig. 1, 1 is an AC power supply, 2 is a heater, 3 is a latch relay (8A is a latch relay). Contact, 3B is coil),
4 is npn) run lister, 5 is resistor, 6 is capacitor,
7 is a resistor, 8 is an npn transistor, 9 and 10 are resistors,
11 is an npn) run lister, 12.13 is a resistor, 14.
15 is pnp) Ranlister, + 6, + 7.18.
19, 20.21 is a resistor, 22 is a diode, 23.2
4 is a resistor, 25 is a variable resistor for temperature setting (adjustment) (hereinafter referred to as a volume), 26.27 is a npn) run lister,
2g, 29° and 30 are resistors, and 31 is a heat sensitive element such as a thermistor (hereinafter referred to as thermistor).

(A) is a temperature detection means consisting of a resistor bridge and a differential amplifier; (a) is a switching circuit consisting of a Schmitt circuit; (0 is a hysteresis means; ]) is the latch relay drive circuit, -1-vcc is the high side of the DC power supply, and GND is the low side of the DC power supply.

and AC power supply] to heater 2 and latch relay contact 3.
A is connected to form the main circuit.

A capacitor 6 is connected in series to the latch relay coil 3B, and the series circuit is connected to a DC power source via a resistor 5 and a transistor 4. A transistor 8 is connected in parallel to the series circuit of the coil 3B and the capacitor 6 through a resistor 7, and the base of the transistor 8 is connected to the connecting end of resistors 9 and 10 connected to a DC power source. . Further, a transistor 11 is connected to the connection end and the low side (GND) of the DC power supply. Also transistor 4
The base of the resistor 12.13 is connected to the collector of the transistor 14, the resistor 12.13 is connected between the connecting end and the low side of the DC power supply, and the connecting end of the resistor 12.13 is connected to the base of the transistor 11. Further, the emitter of the transistor 14 is connected to the emitter of the transistor 15, and the connecting end is connected to the high side (+Vcc) of the DC power supply via the resistor 18, and the high side (+Vcc) of the DC power supply and the transistor 15 are connected to each other.
A resistor 16.17 is connected between the collectors of the resistor 16.
．． The connection end of 17 is connected to the base of transistor 14 . A connection end between the transistor 15 and the resistor 17 is connected to the low side (GND) of the DC power supply via the resistor 19. The base of the transistor 15 is connected to the collector of a transistor 26 via a resistor 20, and the collector of the transistor 15 is connected to the base of the transistor 26 via a series circuit of a diode 22 and a resistor 21.

A resistor 28, 24, a potentiometer 25, a resistor 30, and a thermistor 31 are connected to the DC power supply to form a resistor bridge, and the outputs of the resistor bridge are respectively connected to the bases of transistors 26, 27 of the differential amplifier. . The emitters of transistors 26 and 27 of the differential amplifier are shorted together and connected to the low side (GNP) of the DC power supply.
The collector of the transistor 27 is connected to the high side of the DC power supply, and the collector of the transistor 26 is connected to the high side (10 Vcc) of the DC power supply via the resistor 28.

In the temperature control device configured as described above, when the temperature of the heating device is lower than the temperature set by the regulator 25 and the resistance value of the thermistor 31 is high, the output of the resistance bridge is higher than the base potential of the transistor 27. The base potential of No. 26 is lower. Therefore, transistor 27 is ON
, since the transistor 26 is in the OFF state, the output of the differential amplifier (collector potential of the transistor 26) is ■.

Therefore, since the output of the temperature detection means is -, the base current of the transistor 15 of the switch notching circuit (B) does not flow and is OFF, so the transistor I4 is ON.

Therefore, base current is supplied to transistor 4 and transistor 11, and transistors 4 and 11 are in an ON state.

Since the transistor 11 is ON, the output of the inverting means is ■, the base of the transistor 8 is shorted, and the transistor 8 is OFF.
It is F. Therefore, when the transistor 4 is turned on, the charging current of the capacitor 6 flows instantaneously to the coil 3B of the U-nochi relay via the resistor 5. Then, the latch relay 3 is moved and the contact 3A is closed. (Latched (held) until this close or the next time reverse power is applied to the latch relay coil 3B.
be done. ) Then, the heater 2 is energized and the temperature of the heating device rises, and the temperature of the thermistor 3I also rises, and its resistance value decreases. And the output of the resistor bridge is inverted,
The base potential of transistor 27 is lower, and the base potential of transistor 26 is higher. Then, the transistor 26 is turned on and the transistor 27 is turned off, so that the collector potential of the transistor 26, that is, the output of the differential amplifier becomes ■, and when the output of the temperature detection means (A) becomes 0 in this way, the switching circuit (B) Transistor 15 is O
It becomes N. Therefore, transistor 14 is turned off. Then, transistor 4 and transistor 11 are turned off. Then, the output of the inverting means becomes ■, and the transistor 8
turns on. Then, the charge stored in capacitor 6 is transferred to capacitor 6, latch relay coil 3B, resistor 7,
In order to discharge in a closed circuit consisting of the transistor 8 and capacitor 6, reverse power is instantaneously applied to the latch relay coil 3B, the latch (holding) of the latch relay 3 is released, the latch relay contact 3A is opened, and the heater 2 is no longer energized. will be stopped.

The temperature of the heating device and thermistor 31 then decreases. However, at this time, when the transistor 15 is turned on, a current flows to the base of the transistor 26 via the diode 22 and the resistor 21, and the base potential of the transistor 26 is slightly higher (compared to when the transistor 15 is turned off). Then, unless the temperature of the thermistor 31 falls below the temperature when the heater 2 is turned off, the heater 2 will not be turned on next time. That is, a so-called hysteresis is applied in which the temperature when the heater 2 is turned on is different from the temperature when it is turned off.

By providing a range of temperature during ON and OFF in this way, the number of opening and closing times of the contacts of the latch relay can be reduced, so the reliability and life of the contacts can be improved.

By repeating the above operations, the temperature of the heating device can be maintained constant.

-As mentioned above, according to the present invention, since control is performed by a latch relay, the circuit current is relatively small, and the self-temperature rise of the latch relay is also small, making the temperature control device highly reliable and safe. is obtained.

[Brief explanation of drawings]

FIG. 1 is an electrical circuit diagram showing an embodiment of a temperature control device according to the present invention. (b); Temperature detection means; (B); Schmitt circuit; (C)
: Hysteresis means, (D); Reversing means, (E); Latch relay driving means.

Claims (1)

[Claims] 1. Temperature detection means including a heat-sensitive element, a switching circuit that operates in response to an output signal of the temperature detection means, hysteresis means for the switching circuit, further means for inverting the output of the switching circuit, and a means for inverting the output of the switching circuit and the inversion means. A temperature control device comprising a latch relay drive means for controlling a latch relay in response to an output.