JPH02611B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a combustion control device for oil hot air blowers and the like.

Conventional configuration and its problems Due to the nature of the product, combustion equipment such as oil hot air blowers require sufficient attention to prevent fires, oil leaks, and other abnormalities.In particular, the combustion control circuit that controls and manages combustion,
Care must be taken to prevent abnormal operations such as malfunctions and runaways. Recently, due to improvements in combustion technology, microcomputers (hereinafter referred to as microcomputers) are often used for control circuits in response to complicated combustion control methods to satisfy such demands as variable combustion and reduction in carbon monoxide. Microcontrollers are composed of complex logic that operates on weak signals, and even if sufficient noise countermeasures are taken in the peripheral circuits, it is difficult to say that there will be no malfunction or runaway, and there is also the risk of partial destruction of the microcontroller due to static electricity. It is difficult to predict what the output state will be in the unlikely event that the microcontroller loses its control ability due to malfunction or runaway. Therefore, there is a risk of fire, oil leakage, etc. Conventionally, in order to prevent unsafe operation when a microcomputer runs out of control, a hardware method has been used to stop the product safely when the microcomputer program enters an infinite loop and stops taking normal steps.

FIG. 1 explains the above-mentioned conventional example, and shows a control circuit for an oil hot air fan using a microcomputer. 1st
Figure A shows a high voltage circuit, Figure B shows a low voltage circuit, and 1 is connected to a commercial power source through a power plug. 2 is a current fuse, and 3 is a temperature limit switch, which opens when the temperature inside the oil hot air blower becomes abnormally high.The power transformer 4, burner motor 5, pump circuit 6, and carburetor cylinder heater 7 necessary for maintaining combustion are By cutting off the power supply to the fuel, combustion is stopped. On the other hand, the relay contact 8a has its primary side connected to the current fuse 2, its secondary side connected to the burner motor 5, one end of the blower motor 9, and the relay contact 10a.
is connected to the normally open contact side of the relay contact 8a.
When it closes, the burner motor 5 that supplies combustion air and the blower motor 9 that converts combustion heat into warm air and sends it into the room are started. On the common terminal side, that is, on the load side of the relay 10a, there is an igniter 11 that operates for a certain period of time after energization and ignites the petroleum liquefied gas, and a solenoid 12 that changes the amount of combustion air sent from the burner motor 5 when switching the combustion amount.
Through the normally closed contact of 3a, the diode bridge 14
connected after being full-wave rectified. Furthermore, a pump circuit 6 that drives a pump 15 that supplies kerosene as fuel is also connected to the common terminal side of the relay 10a.

On the other hand, in FIG. 1B, the diode bridge 16 and the smoothing capacitor 17 rectify and smooth the AC power source to obtain DC. A is a DC bus line that is tangential to the positive electrode side of the diode bridge 16. Furthermore, it is connected to one end of the coils of the relays 8 and 13, to the emitter terminal side of the PNP transistor 19, and to the input side of the stabilized power supply 20. A room temperature thermistor 22 for detecting the room temperature is a burner thermistor for detecting the temperature of the vaporizing cylinder that vaporizes kerosene and changes it into a state suitable for combustion.A flame rod 23 is for detecting the combustion state. Signals obtained from the thermistor 22 and flame rod 23 are processed as combustion information within the microcomputer 24. 25 is a driving switch. Reference numeral 26 denotes an F/V conversion circuit for converting frequency into voltage, whose input is connected to the microcomputer 24 and whose output is connected to the base of the transistor 19 via a transistor 27. A relay 10 and one end of a coil of a relay 18 that turns ON/OFF the heater 7 that heats the vaporizing cylinder are connected to the bus line RO connected to the collector of the transistor 19. Above relay 8, 13, 1
The other ends of the coils 0 and 18 are connected to the output terminal of the microcomputer 24 via a relay drive circuit 28.

In the above configuration, normally relay contacts 8a, 18
a and 10a are open and combustion has stopped. When the microcomputer 24 detects that the operation switch 25 is closed, the signal line 29 is set to "H", the coil of the relay 18 is energized, and the relay contact 13a is closed. Then, energization is started to the heater of the vaporization cylinder, and the temperature of the vaporization cylinder rises until the burner thermistor 22 detects that the temperature has reached the appropriate temperature. When the temperature of the vaporizing cylinder reaches an appropriate value, the contact 18a opens, and instead the signal line 30 becomes "H", the contact 8a closes, and the burner motor 5 operates. After a certain period of time after the contact 8a closes, the signal line 31 also becomes "H", the contact 10a closes, and at the same time as the igniter 11 starts operating, the pump circuit 6 is also energized and combustion starts. The flame rod 23 monitors whether the ignition is ignited and combustion is being maintained reliably, and if it is normal, the combustion state will continue to be maintained.

The above ~ is the combustion processing routine, which is 32 in the flowchart shown in FIG. In FIG. 2, the pulse output 34 is a safety processing routine for outputting a synchronous pulse signal of about 2 to 10 ms from the signal line 33, and the microcomputer 24 is operating normally regardless of whether the operation switch 25 is ON or OFF. It is a routine that always goes through. When a predetermined pulse signal is output from the safety processing routine to the signal line 33, the pulse frequency is converted to voltage in the F/V conversion circuit 26, turning on the transistor 27, which eventually turns on the transistor 19 and turns the bus line RO on. Power is supplied to DC bus A.

In the above conventional example, a countermeasure against runaway or malfunction of the microcomputer 24 is taken by providing an F/V conversion circuit 26, but static electricity etc.
If a short circuit occurs in the signal line 29 or 31, resulting in a constant "H" signal, there is a risk that the combustion will not be able to be stopped, or the carburetor cylinder will melt, resulting in an unsafe situation. Microcomputer 2
4 had the problem that even if an abnormality could be detected, it could not be processed at all.

Purpose of the Invention The present invention was made in view of the above-mentioned problems, and aims to prevent the microcomputer from becoming unsafe even when it is partially destroyed, malfunctioning, or running out of control due to static electricity, etc. .

Structure of the Invention In order to achieve the above object, the present invention provides a high-level or low-level signal when the microcomputer 24 detects an abnormality.
The pulse signal supplied to the input of the V/F conversion circuit 26 is fixed at "H" or "L" using a terminal for outputting a signal and an abnormality processing routine.

DESCRIPTION OF EMBODIMENTS One embodiment will be described below with reference to FIG.
In Figure 3, parts and symbols with the same number have the same name,
It is something that has an effect.

P ₁ is the signal line 29, P ₂ is the signal line 31, P ₃ is the signal line 34 that drives the relay 13, P ₄ is the signal line 30
is the name of the output port of the microcomputer 24 connected to each. _P0 is a signal line that sends an "H" signal when the microcomputer 24 detects some abnormal condition, such as the temperature of the carburetor cylinder becoming abnormally high or an ignition signal being input from the flame rod 23 even though it is not the sequence that should be used for combustion. 35 is connected to the base of a transistor 37 via a resistor 36. On the other hand, inside the F/V conversion circuit 26 in this embodiment, the signal line 33 is connected to a resistor 38, and the other end of the resistor 38 is connected to a capacitor 39.
and the collector of the transistor 37.

FIG. 4 shows a schematic flowchart of a program processed inside the microcomputer 24 in this embodiment, and is a routine that normally checks whether the operation switch 25 is open or closed to determine whether or not combustion is to be performed. Based on the judgment of "operation switch ON" 40, the closed loop of 41 is activated when the operation is OFF, and the closed loop of 42 is activated when the operation is OFF.
is running in a closed loop. A routine "abnormality detection" 43 for detecting system abnormalities is incorporated in a closed loop that is processed before "operation switch ON" 40, and when an abnormality is detected, it branches to a loop 44 and executes processing 45 and processing 46. do.

In the above configuration, under normal conditions, the P ₀ port outputs “L”, the P ₁ port to the P ₄ port are in an output state according to a series of sequences, and a constant pulse is output to the signal line 33. It is being output. Now, if the microcomputer 24 is partially destroyed while the _P1 port is fixed at "H" due to some reason such as static electricity, the coil of the relay 18 will be energized and the contact 18a will be
is closed, and the heater 7 remains energized.

When the vaporizing cylinder temperature rises abnormally and is on the verge of melting, the burner thermistor 22 detects an abnormality, and the "abnormality detection" routine 43 changes to a loop 44. Then, in process 45, a signal is first issued to set ports _P1 to _P4 to "L", and then in process 46,
Set _P0 port to “H”. Signal line 35 is “H”
When this happens, the transistor 37 is turned on, the potential at the connection point between the capacitor 39 and the resistor 38 is fixed at Ov, and the F/V conversion circuit 26 is stopped, so the transistor 27 is also turned off, and the transistor 19 is also turned off.
As a result, power supply to bus line RO is stopped. After that,
No matter how high the signal line 29 is, the current to the coil of the relay 18 is stopped, so the contact 18
a is opened and power supply to the heater 7 is also stopped.

In the above embodiment, the necessary minimum number of relays 10 and 18 are connected to bus line RO, but all loads may be connected. Also, when an abnormality is detected, the _P0 port is set to “H” and the transistor 3
Although the F/V conversion circuit 26 is stopped through the circuit 7, it is also possible to use a logic gate element.
The F/V conversion circuit 26 may be any circuit as long as it has the function of a hardware final safety circuit that operates independently of the operation of the microcomputer 24 when the microcomputer 24 goes out of control.

Effects of the Invention As described above, according to the present invention, microcomputer runaway and
It can protect the entire system from stopping in an unsafe direction even in the event of malfunction, combustion, system abnormality, or partial failure of the microcomputer itself, and the final safety circuit in the event of a microcomputer runaway, such as an F/V conversion circuit. By configuring it so that it always stops even when a simple abnormality is detected, it is possible to check the operation of the F/V conversion circuit without having to do troublesome work such as intentionally causing the microcomputer to run out of control during circuit inspection. .

[Brief explanation of drawings]

Figures 1A and B are control circuit diagrams showing conventional examples;
The figure is a flowchart of a program showing the operation of a conventional microcomputer, FIGS. 3A and 3B are control circuit diagrams showing an embodiment of the present invention, and FIG. 4 is a flowchart of a program showing the operation of the microcomputer. 10a...Relay contact for pump, 18a...Relay contact for heater, 19...Transistor, 2
4...Microcomputer, 25...Operation switch, 26...
...F/V conversion circuit, 34...Pulse output routine, 43...Abnormality detection routine, P〓~ _P4 ...Microcomputer output port.

Claims (1)

[Claims] 1 When the device is operating normally according to the prescribed procedure, it outputs a pulse signal that repeats “H” and “L”.
Output is “H” or “L” in case of runaway or malfunction.
It is equipped with a microcomputer equipped with a safety processing routine that outputs the signal as it is, and a final safety circuit that shuts off peripheral circuits when the pulse signal from the microcomputer's safety processing routine becomes "H" or "L". In addition to the safety processing routine, the microcomputer is provided with an abnormality processing routine that outputs an "H" or "L" signal when a combustion abnormality or system abnormality is detected,
The combustion control device is configured to OR or AND the output from the abnormality processing routine with the output from the safety processing routine and output the result to the final safety circuit to operate the final safety circuit.