JPH0520653B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION (Industrial Field of Application) The present invention relates to a safety circuit for floor heating systems such as electric carpets.

(Prior Art) For example, in an electric carpet, a heater is provided in the carpet body, and a relay is provided on the heater, and the relay is energized and controlled by a microcomputer to heat a desired area. There is a function that does this. Some microcomputers for electric carpets have a function of storing a program for a heating area switching pattern for switching each heater to a desired heating area, and a function of storing current time.

In such electric carpets, the microcomputer is energized even when the heater is turned off, so even when the heater is turned off, the microcomputer can detect welding of the relay contacts. I'm starting to do it.

Therefore, even if the relay contacts connected in series to the heater close due to welding, the microcomputer detects the welding and blows the temperature fuse to forcibly cut off the power to the heater. ing.

By the way, as disclosed in Japanese Patent Publication No. 59-21061, the runaway behavior of microcomputers is
Normal routines are not performed and the processing time varies. In other words, runaway refers to a phenomenon in which the processing order of a main routine or subroutine is skipped, or the processing is fixed in a stagnant state.

Therefore, the synchronization signal that is synchronized with the processing routine of the microcomputer has a cycle that becomes longer or shorter, or is fixed at "H" or "L".

In this way, when the microcomputer goes out of control, the normal processing described above is not performed.

Here, if the relay contacts are welded and the microcomputer goes out of control, the welding of the relay contacts cannot be detected in the normal state as described above, and the heater will overheat abnormally. As a result, the heat-sensitive layer of the heater softens and comes into contact with the short-circuit detection wire attached to the heater, resulting in a short-circuit condition, which finally causes the temperature fuse to blow out.

In other words, the last safety measure was to soften the heat-sensitive layer of the heater and cause a short circuit, which was a low safety measure.

(Problem to be Solved by the Invention) As described above, in the case of a double failure where the relay contacts are welded and the microcomputer goes out of control, the power to the heater cannot be cut off until the heater is heated up. Therefore, the safety was low.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a safety circuit for a floor heating system that has improved safety and can blow out the temperature fuse without overheating the main body of the floor heating system even if the relay contacts are welded and the microcomputer goes out of control. shall be.

[Structure of the invention]

(Means for Solving the Problems) Therefore, the present invention connects a relay contact to a heater disposed in a heating device main body, and connects this relay contact to a microcomputer to which power is supplied even when power to the heater is cut off. In a safety circuit of a floor heating system that opens and closes to control energization of the heater, there is a temperature fuse connected between the heater and the power supply, and a temperature fuse connected in parallel to the power supply for blowing the temperature fuse. an indirect heat resistance, a relay contact that opens and closes by controlling a relay coil, a detection unit that is provided inside the microcomputer and is connected to one end of the relay contact to detect the open and closed state of the relay contact, and the operation of the microcomputer. a synchronous signal detection circuit that detects a synchronous signal continuously transmitted from the microcomputer in synchronization with the
A switch means that turns on when a change occurs in the synchronization signal detected by the synchronization signal detection circuit, and a power control means that is connected in series with the indirect heat resistance and the switch means and conducts when the relay contact is closed. This is a safety circuit for the floor heating system that should be installed.

(Function) With the provision of such a means, if the relay contacts are welded and the microcomputer goes out of control, the synchronizing signal detection circuit detects a change in the synchronizing signal that is synchronized with the processing operation output from the microcomputer, and the switch is activated. Turn on the means. At this time, the relay contacts are in a closed state due to welding, so the power control means is in a conductive state, and current flows through the indirect heating resistors connected in series, generating heat. Then, the temperature fuse connected between the heater and the power source is blown, and the power supply to the heater is stopped.

(Example) An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram in which the safety circuit of a floor heating system is applied to an electric carpet. Each heater 4 , 5 , 6 is connected to the power plug 1 via a power switch 2 and a temperature fuse 3 . These heaters 4,
5 and 6 are arranged in respective areas 8, 9 and 10 divided in the electric carpet body 7, as shown in FIG. In addition, the power plug 1 is connected to the power circuit 1 via a power switch 2 and a temperature fuse 3.
1 is connected. This power supply circuit 11 creates each voltage of +V and -V, and the voltage +V is connected to a microcomputer 12 and a relay drive circuit 13.
At the same time, a voltage -V is applied to one end of the relay power switch 14. Each relay coil 15, 16, 17 corresponding to each heater 4, 5, 6 is connected to the relay drive circuit 13,
Furthermore, these relay coils 15, 16, and 17 are commonly connected and connected to the other end of the relay power switch 14. These relay coils 15,1
Relay contacts 6 and 17 are such that the relay contact 15a of the relay coil 15 is connected in series to the heater 4, the relay contact 16a of the relay coil 16 is connected in series to the heater 5, and the relay contact 1 of the relay coil 17 is connected in series to the heater 5.
7a is connected to the heater 6 in series. The microcomputer 12 has a relay control signal output port P.
A relay control signal is sent from 1, P2, and P3 to the relay drive circuit 13, and each relay coil 15, 16,
17 has a function of energizing control. Specifically, a heating region changeover switch 18 consisting of region selection switches 18a, 18b, and 18c for selecting each region 8, 9, and 10 is connected, and for example, when the region selection switch 18a is pressed, a relay control signal is sent out. It has a function of energizing the relay coil 15. The microcomputer 12 also has a built-in program for heating patterns, such as heating with heaters 4 and 5, switching to heater 6 after a predetermined period of time, and heating with heater 6.
It has functions such as storing in RAM (random access memory) and clock function. Note that the heating pattern can be changed to a desired pattern. Although not shown, each heater 4,
5 and 6 are also equipped with short-circuit detection wires, and if heaters 4, 5, and 6 become overheated and their temperature-sensitive layers soften and come into contact with the short-circuit detection wires, resulting in a short circuit, the microcomputer Reference numeral 12 has a function of detecting this short-circuit condition and sending out a fusing signal to blow out the temperature fuse 3.

Now, 20 is a fusing circuit, and this fusing circuit 20 detects the energization of the heaters 4, 5, and 6 regardless of whether the relay power switch 14 is opened or closed, and each of the relay control signal output ports P1, P2 ,P
3 and the control output, and if they are not in the same state, the temperature fuse 3 is blown. Specifically, a power switch 2 is connected to a power plug 1, an indirect heat resistor 21 for blowing out the temperature fuse via a temperature fuse 3, and a thyristor (SCR) as a power control means.
22 and a series circuit between the emitter and the collector of a transistor 23 serving as a switch means is connected. The base of this transistor 23 is connected to the synchronizing signal detection circuit 24 via a voltage regulating resistor R1, and further connected to the microcomputer 12.
It is connected to the synchronization signal output port D of. On the other hand, a Noah gate 25 is provided, and this Noah gate 25
Each contact of each heater 4, 5, 6 and each relay contact 15a, 16a, 17a is connected to each input terminal of . The output end of this NOR gate 25 is connected to a thyristor drive circuit (hereinafter referred to as an SCR drive circuit) 26. The input terminals of the NOR gate 25 are connected to the NOR gates 15b and 16.
Each relay contact 15a, 16 via b, 17b
It is connected to detection units S1, S2, and S3 of a microcomputer that detects the open/closed states of a and 17a. Note that G is an input port for detecting the open/closed state of the relay power switch.

Next, the operation of the circuit configured as described above will be explained.

When the power switch 2 is closed and power is being supplied from the power supply circuit 11 to the microcomputer 12, the relay power switch 14 is closed and, for example, the area selection switches 18a, 18b are
When pressed, the microcomputer 12
sends out a heater control signal from each heater control signal output port P1, P2. This energizes each relay coil 15, 16 and closes each corresponding relay contact 15a, 16a. As a result, each heater 4, 5 is energized and each region 8,
9 heating is performed. Further, when the microcomputer 12 receives an instruction from a key (not shown) to perform a heating operation according to a heating pattern, the microcomputer 12 sends each heater control signal to each heater over time according to the heating pattern program stored in the RAM. The control signal is sent from output ports P1, P2, and P3.

By the way, during the above operation, each relay control signal output port P1, P of the microcomputer 12
2. Control signal from P3 and each relay contact 15a,
By comparing the open states from 16a and 17a, a synchronization signal of a constant period synchronized with the processing of the microcomputer 12 is continuously sent from the synchronization signal output port D to the synchronization signal detection circuit 24.

Now, if heating is not to be performed and the heating pattern is to be maintained as is, the relay power switch 14 is released. In this state, power is supplied from the power supply circuit 11 to the microcomputer 12, and the power supply to each relay coil 15, 16, 17 can be cut off.

By the way, if, for example, the relay contact 15a is welded when using a carpet, the Noah gate 25 should be
An “L” signal is input to the SCR drive circuit 26, and a drive pulse to the SCR 22 is output.
This SCR 22 becomes conductive. Furthermore, when the microcomputer 12 determines that an output different from the signal output from the relay control signal output port P1 has been input to the detection unit S1 of the microcomputer 12, the synchronization signal of the synchronization signal output port D is inputted to the detection unit S1 of the microcomputer 12.
For example, a constant "L" output is set, and the synchronization signal detection circuit 24 detects this and turns on the transistor 23.

Thus, a current flows through the indirect heating resistor 21, generates heat, and blows out the temperature fuse. As a result, heater 4
Not only that, the power supply to the other heaters 5 and 6 is forcibly cut off.

Furthermore, even if a double failure occurs in which the relay contact 15a is welded and the microcomputer 12 goes out of control, the microcomputer 1
The output synchronized with the processing of the microcomputer 12 from the synchronization signal output port D of No. 2 becomes, for example, constant at "H" or "L". That is, when the microcomputer does not perform normal processing and the synchronization signal changes, the transistor 23 becomes conductive. On the other hand, relay contact 15a is in a conductive state.
Since the SCR 22 is also in a conductive state due to the SCR drive circuit 26, the temperature fuse 3 is blown.

Therefore, regardless of whether the relay power switch 14 is opened or closed, if the power supply to each heater 4, 5, 6 is abnormal, the power supply to each heater 4, 5, 6 is forcibly cut off. .

Note that the above explanation has been given for the case where the relay contact 15a is welded, but other relay contacts 16
a, 17a or two or more relay contacts 15 at the same time
When a, 16a, and 17a are welded together, the temperature fuse 3 is blown out in the same manner as described above.

In this way, in the embodiment, at least one of the heaters 4, 5, 6 is supplied with power regardless of whether the relay power switch 14 for supplying power to the relay coils 15, 16, 17 is opened or closed. Since the temperature fuse 3 is fused when abnormal energization is detected, the relay contacts 15a and 16
Even if the microcomputer 12 goes out of control and the heaters 4, 5, 6 are welded together,
The temperature fuse 3 can be fused immediately when the current is applied to the temperature fuse 3. Therefore, each heater 4, 5, 6 can be reliably fused without overheating, and safety can be improved without relying on the final safety measure.

In addition, not only the welding of the relay contacts 15a, 16a, 17a but also the failure of each heater 4, 5, 6 due to other causes.
Even if the temperature fuse 3 is energized, the temperature fuse 3 can be blown out as an abnormal operation.

Furthermore, even if only the microcomputer 12 goes out of control, the synchronization signal detection circuit 24 detects a change in the synchronization signal of the microcomputer 12, and the relay contacts 15a, 16a,
Since the temperature fuse 3 is blown when 17a is on, it is extremely safe.

〔Effect of the invention〕

As described in detail above, according to the present invention, even if the relay contacts are welded and the microcomputer goes out of control, the safety circuit of the floor heating system has improved safety by being able to blow out the temperature fuse without overheating the main body of the floor heating system. can be provided.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the safety circuit of a floor heating system according to the present invention applied to an electric carpet, and FIG. 2 is a diagram showing each area of the electric carpet. 3...Temperature fuse, 4,5,6...Heater,
7... Carpet body, 11... Power supply circuit, 12
...Microcomputer, S1, S2, S3...
...Detection unit, 14...Relay power switch, 20
... Fusing circuit, 24 ... Synchronous signal detection circuit, P
1, P2, P3...Relay control signal output ports.

Claims (1)

[Claims] 1 A relay contact is connected to a heater provided in the main body of the heating device, and the relay contact is opened and closed by a microcomputer to which power is supplied even when power is cut off to the heater, thereby controlling energization to the heater. In the safety circuit of a floor heating system, a temperature fuse connected between the heater and a power source, an indirect heating resistor connected in parallel to the power source to melt the temperature fuse, and a relay coil are controlled to open and close. A relay contact, a detection unit provided inside the microcomputer and connected to one end of the relay contact to detect the open/closed state of the relay contact, and a synchronization unit that is continuously transmitted from the microcomputer in synchronization with the operation of the microcomputer. a synchronous signal detection circuit for detecting a signal; a switch means that is turned on when a change occurs in the synchronous signal detected by the synchronous signal detection circuit; A safety circuit for a floor heating system, characterized in that it is equipped with a power control means that conducts when