JPS58142411A - Safety device for electric heater - Google Patents

Abstract

PURPOSE:To prevent the danger due to continuous power application to a heater, by controlling the power to the heater based on a detected output of a thermister and stopping the power application of the heater forcibly through the periodic detection of open wire. CONSTITUTION:In closing a power switch 29, a power supply is given to a DC side. Since an output signal of an outpu generating circuit 12 starts at a time T1, a transistor (TR)13 is set off, a TR20 is turned on, a stop relay 28 is excited and the power application to an AC switching circuit 10 and a heater 11 is made possible. Further, when a detection pulse is outputted from the circuit 1 for a time T2, the TR13 is turned on, a relay 14 is excited and a thermister 5 is connected to a positive input of a comparator 18. In this case, if the thermister 5 is opened, an L level is outputted from the comparator 18, a TR19 is turned off, and a TR20 is also turned off. After a delay time depending on a resistor 25 and a capacitor 26, a TR32 is turned on and a fuse 21 is blown.

Description

[Detailed description of the invention]

The present invention relates to an electric heating device such as an open cooker, a fryer, or a griddle that uses a heater as a heating source, and relates to an electric heating device in which energization of the heater is controlled based on the output C of a temperature detection device using a thermistor as a temperature sensing element. Conventionally, when energizing a heater using a thermistor as a temperature sensing element, the thermistor that is generally widely used has a negative temperature coefficient, so
It is possible to distinguish between Iff line and low humidity.
In the case of liI, the heater tends to be continuously energized, which is very dangerous. In view of these points, the present invention is a thermistor! The output of the temperature detection circuit connected to the thermosensing element (second crystal) controls the energization of the heater, and at the same time provides a safety device that periodically detects disconnection of the thermistor and forcibly stops the energization of the heater. 42 One embodiment of the present invention will be explained based on the drawings.
: is connected to a temperature detection circuit (4) via a rectifier (3). The detection circuit (41) is formed by connecting a negative characteristic thermistor (5) to one side of the bridge. A series of control circuits with a load t-ms are constructed on the output side of the temperature detection circuit (4). The control circuit is a bridge l of the temperature detection circuit (4): an amplifier (6) that amplifies the resulting non-balanced voltage. The output of the amplifier (6) is compared with the voltage set by the ff1lf setting resistor (7). A first comparator (8) that outputs a light emitting element (9A) that blinks based on
A photocoupler +91 consisting of a pair of light-receiving elements (9B) is connected to the current switching circuit 'dII (lift=
It consists of Thus, the switching circuit lI@■ and the heater a1 are connected in series to the AC power supply (1), and the energization of the heater n11 is controlled according to the state of the switching circuit αG. On the other hand, through the rectifier (3), the output generation port FIIIt
Connect the Uri. Output generation port W! 103 is a short detection pulse at a long time (T1) interval as shown in Figure 2.

[T! ]
Output. On the output side of the output generation port @OSI, there is a first transistor 03 that turns on when a detection pulse is output.
Nine switching devices, ie, switching relays 041, are connected in series with the switch. The relay 041 connects the thermistor 151 at time T1.
vii [f detection circuit (41 (: between the normally closed contact (14m) connected to TzW!C: thermistor (5) v normally open contact (14b) connected to the disconnection detection circuit described later The disconnection detection circuit is connected via a rectifier (3), and a detection pulse is output from the output generation circuit Q2.
The thermistor (
5) and resistor 09 as a positive input, and resistor 061
A second comparator 081 whose connection point between and resistor 0η is negative human power, a second transistor 09 that responds to the output of this comparator 08, and the output generation port w! Output I of Ia'a:
It consists of a third transistor that responds, a fourth transistor that forms a fuse C2uOJ blowout circuit, etc., and to describe the specific connection of each element, the collector line of the transistor α9 of 1i2 is a fuse that operates a stop device that will be described later. C! Connected to the 1st resistor connected in series with υ and %3rd
Similarly to the second transistor 09, the collector line of the transistor 09 is connected to the protection resistor, and the IJI3
The base line of the transistor ■ is the diode 1241
V via the stop relay ■ and the first transistor I3
j′( is connected between the collectors of
°□ Base line to 2nd and II3 transistor 0
9 and (2) in parallel with C2 mapped resistor 4 and capacitor 1
) ■ m#! The collector line of the fourth transistor (2) bypasses the protection resistor 0V and connects to the fuse &11 via the resistive surface. Further, the stop device is a stop relay (2) connected between the above-mentioned heat shield υ and the protective resistor G, and the above-mentioned AC switching l! ! It has a first normally open contact (28tll) for cutting off the power supply to the L path (2), and a second normally open contact (28bffi) for cutting off the power supply 13a to the DC side. The container is $22 above.
This is an automatic reset type power switch connected in parallel with a normally open connection (28bffi). Next, the operation will be explained based on the above circuit configuration. When the power switch @ is closed, power is first supplied to the DC side. Since the output signal of the output generation port 1@03 starts from the T1 period, the voltage at the A point is Ov, and the first transistor 03 is in the off state! I3 transistor ω
is turned on, the stop relay ■ is energized, and the first and W42
The normally open contacts (28b 1 ) and (28, bffi) are closed. This C: allows the AC switching circuit Q (I and heater 01) to be energized. By the way, during the Ts time, since the first transistor 03 is off, the switching relay 04 is not energized and the relay contact is in the normally closed contact (14a)C position. Therefore, the thermistor (5) acts directly to control the heater out', and the control path (a) controls the energization of the heater O1l based on the output of the warm detection circuit (4). On the other hand, during T1 time, the normally open contact (14b) of the switching relay ■
) is released, the relationship between the connection point electron (Vt) which becomes a positive input of the second comparator 081 and the connection point voltage +BCvt which becomes a negative input is vl (vl, and the output of the comparator Nishiki is The transistor n9 of '442 is in the off state, but since the third transistor ■ is on at this time, the collector current of the third transistor ■ is sufficiently limited by the protective resistor (2). This prevents fuse C2υ from blowing out.Next, after time T1 has elapsed, a detection pulse is output from output generation circuit 03 at time Tt.Then, the voltage at point A rises and transistor 0 of Wil 127 is turned on, and the 127 switching relay a4 is energized.As a result, the relay peak point is switched from the normally closed aneurysm A (14 &) to the normally open single point (14b), and thermistor (5)'%: second comparator Connect to the positive input terminal of Nishiki and perform °C1 disconnection detection. First, operation 1 when the thermistor (5) is not disconnected.
Explain. At this time, the input level is determined so that the relationship of V t ) V 1 is established. Then, the output of the second comparator Oa is rHJ, and the transistor 09 of %lI2 is turned on. As a result, similar to the on-state of the third transistor (3) described above, the second transistor f1g
The collector current of Q11 is sufficiently limited by the protective resistor (2) to prevent the fuse Q11 from blowing out. When the detection pulse is output and the first transistor RO 3 is turned on, the transistor 1wl3 turns from the on state to the IF 17M t: off, but the second transistor 09 changes from the off state after the switching relay 041 operates. To turn on I:, second and third transistors a9 and ■
The conditions for the partner to opt for instant confrontation are established. At this time, in order to prevent the fourth transistor forming the fusing circuit from turning on, the fourth transistor is delayed by the resistor (■) and the capacitor (■), and the operation is slower than the normal operation of the switching relay 041, and for 72 hours. To prevent malfunction, transistors 1 and 4 are turned on at the same time. As mentioned above, if the disconnection of the thermistor (5) is not detected at the time Tm when the detection pulse is output from the output generation amount [03, the output generation amount sea will be °r! Stop time output +1:. Then, the first transistor 1 (is turned off and the switching relay I is de-energized, and its contact is normally connected to the N4 contact (15
b) to a normally closed contact (15a). Therefore, the thermistor (5) is connected again to the temperature/darkness detection circuit so as to control the energization of the heater ON. If it is detected that the wire mister (5) is not disconnected, the T light time C: returns again and the energization of the heater 09 is controlled.
j.Next, the operation when the team resistor (5) is disconnected will be explained. T1 hour! When a detection pulse is output from the output generation circuit Roku after a while, the first transistor 03 is turned on and the switching relay Oa is excited. As a result, the relay contact changes from normally closed contact (14m) to normally @ contact (14t).
l), the thermistor (5) is connected to the positive input of the second comparator. This and the most important thing - Mr. (5)
Since the wire is disconnected, the input level of the comparison ``an'' at t:$2 is V1(V), and the output of the comparator a is ``L''.
When the output is completed, the second transistor 01 is turned off. On the other hand, since the transistor ① of 41'Is5 is also off, the transistor 011 of 2nd and IJ3) and the G of
The off state of the other is codified. Then, after the delay time caused by the resistor 1 and the capacitor has elapsed, the fourth transistor 2 is turned on, forming the MY circuit. In other words, the frequency C of the fourth transistor Ω becomes larger than the fusing current of the fuse 1:
Since the resistance @7 is defined, C Nihiez Zll is fused. As a result, the stop relay example becomes de-energized and the first and
I! II2 normally closed contact (28b1) and (2$bffi
) and open ii! Flow printing and power supply to the AC side!
Shut off the power and bring the heater aD to a completely stopped state. Then, I replaced the fuse Chi11' and turned on the power switch @
If the power is turned on, the above operation will resume. In the g% upper example, the fuse cIυ is blown when the thermistor (5) is disconnected, but the fuse C! υ no Bewa January; Current breaker C breaker) J for l, 1 Moyo I, 1
゜ Also, during the TR period, the temperature control traces of heater 01):
Regarding this, the condition is the same as when the thermistor (5) is disconnected, and the heater AL is forcibly energized, but T! Since the very short time of 2 to 3 seconds is sufficient, there will be no adverse effect on the equipment, but if there is a problem, the normally closed contact of the switching relay a should be connected to the light emitting element (9) of the photocoupler (9). Person) side C: Connect in series and detect disconnection. For the time period, the signal to the AC switching times %QQ may be cut off to temporarily stop the energization of the heater 01 (4==4). (=, 'l' and T! Waiting time used Equipment C: Determined experimentally, taking into consideration the thermal inertia of the corresponding heating section. T! Waiting time of 2 to 3 seconds is sufficient. The present invention is based on the above-mentioned electrical heating equipment based on the output of the temperature detection circuit that is connected to the thermosensor element and the temperature sensing element. In order to maintain the temperature and humidity at the set humidity, the heater is energized at' and the heater is energized for a very short period of time without any trouble.
The thermistor is connected to the disconnection detection circuit C: the thermistor is connected to detect the disconnection of the thermistor, and only when the thermistor is disconnected, a stop circuit is activated to forcibly stop the energization of the heater. Safety g: Demonstrates excellent effects. #, -2% I- When the mister is disconnected, the power to the DC power supply is also cut off, so the control circuit, disconnection detection circuit, and timer circuit do not operate unnecessarily. will not continue

[Brief explanation of drawings]

FIG. 1 is an electric circuit diagram of an electric heating device equipped with the safety equipment of the present invention, and FIG. 2 is an output pulse waveform diagram of a timer circuit. (5)...Thermistor, On...Heater,
Q3...Output generation circuit% Oa...Switching relay,
舖...Second comparator, aS-...Second transistor, □□□...Third transistor% ■...
Fourth transistor % G...stop relay.

Claims (1)

[Claims] t A temperature detection circuit using a thermistor as a temperature sensing element, and am
#f Heater energization t-11 based on the output of the detection circuit
There was an electric heating machine 5cX equipped with a control circuit TGV, and the thermistor was disconnected! A disconnection detection circuit that detects a disconnection, an output generation circuit that outputs a short detection signal at long time intervals,
While the detection signal is being output from the output generation circuit,
The thermistor is separated from the ijA degree detection circuit and 1M1i! is connected to the disconnection detection circuit. l! a switching device to
A safety device for electric heating equipment, characterized in that a stop date @Y is provided for stopping energization of the heater when the disconnection detection circuit detects a disconnection of the thermistor.