JP2917098B2 - Microcomputer controlled heating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device such as a stove or a stove, and more particularly to a heating device controlled by a microcomputer. The microcomputer is reset by an abnormal signal or noise of a watchdog circuit. In this case, the heat generation operation is stopped so that a safe state can be ensured.

[0002]

2. Description of the Related Art As a heating device such as a stove for controlling the heat generation operation of a heat source by a microcomputer, a heat source, a control circuit incorporating a microcomputer for controlling the heat source, and a heat generation state of the heat source are described. And an operation switch for applying a power supply voltage to the microcomputer to start the microcomputer.

In this device, when the operation switch is turned on, a power supply voltage is applied to the microcomputer, and the microcomputer starts to generate heat from the heat source simultaneously with the application of the power supply voltage. When the abnormality detection circuit detects an abnormal operation or the like of the heat source, the heat operation is forcibly stopped and a safe state is ensured. However, in the case of the above, when the microcomputer operates abnormally and is reset, especially when the device is reset when the appliance is abnormally stopped, the heat generation operation is suddenly restarted and the safe state is secured. There was a problem that it could not be done.

[0004] The above problem will be described in more detail. The microcomputer has a built-in watchdog circuit that manages its own operation, and the output of the circuit is output from a specific output terminal of the microcomputer. In a general device controlled by a microcomputer, a reset circuit for applying a reset signal to a reset input terminal when the watchdog circuit outputs an abnormal signal is externally provided. Therefore, if the microcomputer is reset by noise or an abnormal signal from the watchdog circuit while the microcomputer is maintaining the appliance in the forced stop state due to the occurrence of an abnormal state, the program counter becomes "0". The microcomputer is restarted. Then, the microcomputer re-executes the command to cause the heat source to generate heat, and the instrument that has been forcibly stopped is heated and cannot secure a safe state. [Invention of claim 1] The invention of claim 1 has been made in view of the above points, and has a function of inputting a start signal for starting heat generation of a heat source to a microcomputer and having an operation force. In a microcomputer-controlled heating device provided with an operation switch that does not lose the start signal even when it is released, when the microcomputer receives a reset signal, the heat source is maintained in the heat generation stopped state. Accordingly, it is an object of the present invention to avoid a risk that a heat source is left in a heat generating state even when a microcomputer performs a reset operation at abnormal stop.

[0005]

The technical means of the present invention for solving the above-mentioned problem is that "a safety judgment capacitor charged when a power plug is connected and a charge amount of the safety judgment capacitor are judged. If this is below the reference level, a judgment circuit for issuing a heat generation stop signal and a discharge circuit for discharging the above-mentioned safety judgment capacitor are provided. Even if a start signal is output from the operation switch when the microcomputer is reset, the judgment circuit is provided. If the heat generation stop signal is output from the CPU, the heat source is maintained in the heat generation stop state, and if the heat generation stop signal is not output when the output of the determination circuit is determined, the discharge circuit is maintained in the operation state. And the discharge circuit is stopped when the operation switch is turned off. "

[0006]

The above technical means operates as follows. When the power supply voltage is applied to the heating device by connecting the power plug to the outlet, charging of the safety determination capacitor starts, and when the charging continues and the charged amount reaches the reference level, a signal indicating this state is output. It is output from the determination circuit. Note that the signal output from the determination circuit when the charge amount of the safety determination capacitor is equal to or less than the reference level is the heat generation stop signal described in the section of the technical means, and after the safety determination capacitor is charged to the reference level. Indicates that the heat generation stop signal from the determination circuit has disappeared.

[0007] When the start signal is output from the operation switch and the microcomputer starts heating the heat source while the charge amount of the safety determination capacitor is equal to or less than the reference level, a heat generation stop signal is output from the determination circuit at this time. In this case, the heating operation is continued by causing the heat source to continuously generate heat in the same manner as in the conventional case. On the other hand, according to the above technical means, when the output of the determination circuit is determined and the heat generation stop signal is not output, the discharge circuit is maintained in the operating state. Therefore, thereafter, the determination circuit that monitors the output of the safety determination capacitor continuously outputs a heat generation stop signal (a signal indicating that the safety determination consensor is in a discharging state).

When a reset signal is input to the reset input terminal due to abnormal operation of the microcomputer or noise in the state where the heat generation stop signal is output from the safety determination circuit, the program counter of the microcomputer is reset to " This is reset to "0", and this causes the control program to be executed again from the beginning. However, at this time, since the safety determination capacitor has already been discharged and the determination circuit has output the heat generation stop signal, when the microcomputer is started again, the heat source is maintained in the heat generation stop state.

[0009]

The invention of claim 1 has the following unique effects. When a reset signal is input to the microcomputer, the heat source is maintained in the heat generation stop state. Therefore, even if the microcomputer performs a reset operation at abnormal stop, the danger that the heat source is left in the heat generation state can be avoided.

[0010]

Next, an embodiment in which the present invention is applied to a stove will be described. As shown in FIG. 1, a gas valve (11) is inserted in a gas circuit (10) to a gas burner (1) as a heat source, and a gas valve (11) is provided near the gas burner (1) to ignite the gas. The igniter (2) and the flame detector (21) are arranged.

The gas valve (11) is a microcomputer
It is controlled by a control circuit (3) incorporating (6), and the control circuit (3) is connected to a power supply circuit (32) through a seesaw type operation switch (31) whose contacts do not automatically return. Electricity is supplied. That is, the operation switch (31)
When the power supply is turned on, the power supply voltage is supplied to the microcomputer (6) and other circuits incorporated in the control circuit (3), and these start to operate. Also, the above control circuit (3)
The output of the safety circuit (4) is applied to the
(4) is a safety judgment capacitor (34) charged by the connection of the power plug (33), the safety judgment capacitor (34)
A discharge resistor (35) inserted into a circuit connected from the high potential side to the ground, a reference voltage setting circuit (36) for setting a reference voltage to be compared with the output of the safety determination capacitor (34),
The reference voltage setting circuit (36) and the safety judgment capacitor (3
A comparator (37) for comparing the output of (4) and a power supply capacitor (38) for applying a voltage to the comparator (37) and the like. In this embodiment, a set of the reference voltage setting circuit (36), the comparator (37) and the power supply capacitor (38) corresponds to the determination circuit described in the section of the technical means described above. Further, a combustion lamp (41) which is supplied with electricity from a power supply circuit (32) is connected to a specific output port (39) of a microcomputer (6) constituting the control circuit (3), and is connected to the output port (39). Three
The circuit between 9) and the combustion lamp (41) is connected to the output of the safety judgment capacitor (34) by a short circuit (43).

In the microcomputer (6), FIG.
The operation of the stove of the illustrated embodiment will be described below with reference to FIG. When the power plug (33) is connected to an outlet (not shown), charging of the safety judgment capacitor (34) starts, and when a predetermined charging time (about 1 second) has elapsed since the connection of the power plug (33), the safety judgment is performed. The output voltage of the capacitor (34) becomes higher than the output of the reference voltage setting circuit (36), and "H" is output from the comparator (37).

When the operation switch (31) is turned on while the comparator (37) is outputting the "H" signal, the power supply voltage is applied to the microcomputer (6) and the microcomputer (6) starts to operate. The microcomputer (6) is shown in FIG.
Step (80) is performed. That is, the output of the comparator (37) is checked, and this outputs an "H" signal.
If it is determined that it is immediately after
(81) is executed to drive the igniter (2) and open the gas valve (11) to start combustion of the gas burner (1).
Next, in step (82), it is checked whether or not the gas burner (1) has ignited by checking the output of the flame detector (21). Then, if the gas burner (1) is maintained in the combustion state, step (8)
In 3), the igniter (2) is kept in the OFF state and an "L" signal is output to the output port (39). Then, the power circuit
(32) → Combustion lamp (41) → Current flows through the output port (39) to turn on the combustion lamp (41), which causes the gas burner (1)
Is displayed to be maintained in a combustion state. Also, when the output port (39) is in the "L" state, a current flows through the safety determination capacitor (34) → short circuit (43) → output port (39) and the safety determination capacitor (34) is discharged. As a result, an "L" signal as a heat generation stop signal is output from the comparator (37). In this embodiment, the capacitor (34)
→ The short circuit (43) → the circuit connected to the output port (39) corresponds to the discharge circuit described in the section of the technical means described above.

Next, when the gas burner (1) blows out and the like during the continuation of combustion and the flame detector (21) detects abnormal combustion, this is judged in step (84). Then, by closing the gas valve (11), the gas burner (1) is maintained in a fire extinguishing state,
Further, the combustion lamp (41) is caused to blink (step (8)
Five)). That is, the "H" signal and the "L" signal are alternately output to the output port (39) of the microcomputer (6) to make the combustion lamp (41) blink. At the time of this blinking, the time width of the "L" signal is set to be larger than that of the "H" signal.
The output of (34) is prevented from rising to the reference level (the output of the reference voltage setting circuit (36)).

When the gas burner (1) is in an extinguishing state while maintaining the fire extinguishing state, a reset IC (61) for monitoring the output of the watchdog terminal (63) is activated by noise or the like, and the microcomputer (6) is operated. When a reset signal is input to the reset terminal (64), the control operation returns to step (80). However, as described above, at the time of abnormal stop, since the safety determination capacitor (34) is maintained in a discharge state in conjunction with the blinking of the combustion lamp (41), the heat generation stop signal "L" is output from the comparator (7). Signal is continuously output.
Therefore, in this case, the control operation is shifted from step (80) to step (85), the gas valve (11) is maintained in the closed state, and the combustion lamp (41) is maintained in the blinking state. A safe state is ensured. Thereafter, when a reset signal is input to the reset terminal (64) of the microcomputer (6), each time the steps (80) and (85) are repeated, the gas burner (1)
Are maintained in a fire extinguishing state.

Next, in the stove of the above embodiment, when the power failure generated during the combustion is restored, the gas burner (1) can be maintained in a fire extinguishing state. That is, if a power failure occurs during the combustion of the gas burner (1), if a charge remains in the safety judgment capacitor (34), this is the discharge resistance (3).
It is completely discharged to the earth side via 5). When the power failure recovers in this state, the operation switch (3
1) Restart the power supply from the microcomputer
(6) operates immediately, but the microcomputer (6)
Since the safety determination capacitor (34) is in the middle of charging during the operation of, the output does not rise to the reference voltage of the reference voltage setting circuit (36). Therefore, in such a case, when the microcomputer (6) operates and executes the step (80), the "L" signal as the heat generation stop signal is still output from the comparator (37). In this case, step (85) is executed to execute control for maintaining the gas valve (11) in the closed state. That is, the gas burner (1) is maintained in the fire extinguishing state after the power failure recovery, thereby avoiding the danger of the gas burner (1) suddenly starting to burn after the power failure recovery.

In the above embodiment, the gas burner (1) is used as the heat source, but it goes without saying that an electric heater can be used instead. Further, in the above-described embodiment, the case where the present invention is applied to a stove has been exemplarily described, but the present invention can also be applied to a heating device such as a stove or a water heater. Furthermore, in the above-described embodiment, a non-return type switch in which the contact does not automatically return is employed as the operation switch. However, if a holding circuit for maintaining a state where the start signal is output is provided, a return type switch is used. May be. This is because even if the operating force applied to the reset type switch is released, the state where the start signal is output by the holding circuit is maintained. [About the invention of claim 2] The invention of claim 2 is claim 1
The present invention solves the same problem as the invention.

[0018]

Technical means according to a second aspect of the present invention is that the charging is started after the operation switch is turned ON and the OF is turned on.
A safety judgment capacitor discharged when the F operation is performed;
A judgment circuit for judging a charge amount of the safety judgment capacitor and outputting a heat generation stop signal when this is equal to or higher than a reference level, and a charging circuit for charging the safety judgment capacitor are provided.
Even when a start signal is output from the operation switch when the microcomputer is reset, if the heat generation stop signal is output from the determination circuit, the heat source is maintained in the heat generation stop state and the output of the determination circuit is determined. In this case, if the heat generation stop signal is not output, the charging circuit is maintained in the operating state. "

[0019]

[Operation and effect] The above technical means operates as follows.
When the power plug is connected to the outlet and the operation switch is turned on, the microcomputer starts controlling the heat source. Then, the capacitor for safety determination starts to be charged, but has not been charged to the reference level, and the determination circuit does not output the heat generation stop signal. Therefore, in such a case, the heat source is not maintained in the heat generation stop state, and the heating operation is started in the same manner as in the related art.

On the other hand, according to the above technical means, when the output of the determination circuit is determined, if the heat generation stop signal is not output, the charging circuit operates to continuously charge the safety determination capacitor. Thus, the judgment circuit for monitoring the output of the safety judgment capacitor keeps outputting the heat generation stop signal. If the microcomputer is reset in this state due to malfunction or the like in this state, when the microcomputer (6) is restarted, the capacitor for safety judgment is charged and the heat generation stop signal is output from the judgment circuit. In this case, the heat source is maintained in the heat generation stopped state, and the safe state is ensured.

[0021]

Next, a second embodiment of the present invention will be described with reference to FIGS. This device charges the safety judgment capacitor (34) when the microcomputer (6) operates, and discharges the safety judgment capacitor (34) when the operation switch (31) is turned off,
The same parts as those in FIG. 1 described above are described using the same reference numerals.

In this device, the circuits below the power supply capacitor (38) and the comparator (37) are supplied with electricity via the charging transistor (30). A discharge switch (311) that mechanically interlocks with the operation switch (31) and opens and closes in the opposite direction is inserted in the circuit that connects the output section of (34) and the ground. Next, the operation of the stove of the embodiment will be described with reference to the flowchart of FIG.

Even if the power plug (33) is connected to the outlet, before the operation switch (31) is turned on, the charging transistor
(30) is maintained in the OFF state, whereby the safety determining capacitor (34) maintains the discharged state. When the operation switch (31) is turned on, the discharge switch (311) is maintained in the OFF state in conjunction with the operation switch (31), and the microcomputer (6) starts the control operation of FIG. The output of the comparator (37) is confirmed. Then, when the safety determining capacitor (34) is not charged to the reference level and the comparator (37) outputs an "L" signal (it is determined that the operation switch (31) has just been turned on). Case)
In step (91), the igniter (2) is driven and the gas valve (11) is opened to start combustion of the gas burner (1), and the charging transistor (30) is maintained in the ON state. Then, electricity is supplied to the safety determination capacitor (34) and the power supply capacitor (38) to be charged. In this embodiment, a circuit connected from the charging transistor (30) to the safety determination capacitor (34) corresponds to the charging circuit described in the section of the technical means described above.

Next, in steps (92) and (93), it is determined whether or not the gas burner (1) has ignited based on the signal of the flame detector (21). ) Is turned on to maintain the combustion state. If the gas burner (1) goes into an abnormal state due to abnormal fire extinguishing, etc. in step (94), step (95) is executed to close the gas valve (11) and to set the combustion lamp
(41) is kept blinking. Further, the charging transistor (30) is turned on. In this state, when the reset IC (61) is operated and the microcomputer (6) is reset, the microcomputer (6) executes step (90) again. However, at this time, the safety judgment capacitor (34) is in a charged state and the comparator (37)
From the "H" signal (this embodiment becomes a heat generation stop signal)
Is output, and in this case, step (95) is repeatedly executed, whereby the gas burner (1) is maintained in the fire extinguishing state.

It should be noted that an electric heater can be used as a heat source, that the present invention can be applied to a heating device such as a stove or a water heater, and that a return-type switch can be used as an operation switch. Same as the example.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating an embodiment of the present invention;

FIG. 2 is a flowchart illustrating a control operation according to the first embodiment of the present invention;

FIG. 3 is a circuit diagram for explaining an embodiment of the invention according to claim 2;

FIG. 4 is a flowchart for explaining a control operation according to the invention of claim 2;

[Explanation of symbols]

 (6) ・ ・ ・ Microcomputer (31) ・ ・ ・ Operation switch (33) ・ ・ ・ Power plug (34) ・ ・ ・ Capacitor for safety judgment

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-28801 (JP, A) JP-A-3-71301 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G05B 9/02 F24C 3/12 G05B 15/02 G05D 23/19

Claims (2)

(57) [Claims] 1. A microcomputer control having a function of inputting a start signal for starting heat generation of a heat source to a microcomputer and having an operation switch of such a type that the start signal does not disappear even when the operating force is released. In a heating device of the type, a safety judgment capacitor charged when a power plug is connected, a judgment circuit for judging a charge amount of the safety judgment capacitor and outputting a heat generation stop signal when this is below a reference level, Discharge circuit for discharging the above-mentioned safety judgment capacitor is provided, and when the microcomputer is reset, even if the start signal is output from the operation switch and the heat generation stop signal is output from the judgment circuit, the heat source is stopped. If the heat generation stop signal is not output when the output of the determination circuit is determined, the discharge circuit And a microcomputer-controlled heating device for stopping the discharge circuit when the operation switch is turned off. 2. A microcomputer control having a function of inputting a start signal for starting heat generation of a heat source to a microcomputer and having an operation switch of such a type that the start signal does not disappear even when the operating force is released. In a heating device of the type, charging is started after the operation switch is turned ON, and the safety determination capacitor discharged when the operation switch is turned OFF, and the charge amount of the safety determination capacitor are determined. In the above case, a determination circuit that outputs a heat generation stop signal and a charging circuit that charges the capacitor for safety determination are provided, and when the microcomputer is reset, even if a start signal is output from the operation switch, the determination circuit stops heating. When the signal is output, the heat source is maintained in the heat generation stop state, and the output of the determination circuit is determined. And a microcomputer-controlled heating device for maintaining the charging circuit in an operating state when no heat generation stop signal is output.