JPH0120526Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a combustion control device for oil fan heaters and the like.

2. Description of the Related Art Structure of Conventional Example and Its Problems A conventional combustion appliance, for example, an oil fan heater, has an oil tank 3 and a burner unit 4 inside an exterior 1 and a base 2, as shown in FIG.
Combustion gas A burned in the burner is blown out as warm air C from the front louver 7 along with room air B by a fan 6 attached to a blower motor 5, and is used for heating the room. FIG. 2 is a schematic diagram of the burner. Kerosene is vaporized and mixed with air for optimal combustion. A mixed gas is ejected from a mesh 9 in the upper part of a vaporization chamber 8 and ignited by an ignition electrode 10 to form a combustion flame A. A voltage is applied between the flame rod 11 set in the flame A and the burner case 12, and the state of the flame A is checked using the rectification phenomenon of the flame A. A circuit as shown in FIG. 3 is provided between the flame rod 11 and the burner case 12. That is, AC power supply 13, resistors 14, 15
and point c of the circuit consisting of the capacitor 16 and the frame rod 11, the DC power supply 17, and the resistors 18 and 19.
The operational amplifier 20 compares the potential with the point a of the circuit consisting of the frame rotor 11.
A current due to the flame rectification phenomenon between the burner case 12 and the burner case 12 is charged in the capacitor 16, and the potential at point c changes. In this circuit, when the combustion condition is good, the charge in the capacitor 16 increases, so that point c becomes higher than point a, and the output point d of the operational amplifier 20 becomes high. When the combustion condition deteriorates, point c becomes lower than point a, and the output of the operational amplifier 20 at point d also becomes lower. Such a combustion detected signal enters the entire control circuit 21, which is connected to a vaporization heater 23 operated by a main power supply 22, a burner motor 24, a blower motor 5, an electromagnetic pump 25,
Each load such as the igniter 26 is controlled. In this case, when the outside temperature changes, the density of the air sent by the burner motor 24 changes and it changes greatly, but the amount of kerosene supplied by the electromagnetic pump 25 does not change much, so the flame A As the temperature decreases, the amount of air increases,
The rectified current will decrease. Therefore, the voltage charged in the capacitor 16 becomes low, but since the reference voltage at point a does not change at all, the operational amplifier 20 considers it to be a misfire and sends a low signal to the control circuit 21.
In other words, it has the disadvantage that even though combustion is normal, if the outside temperature drops, a false signal is sent indicating a misfire.

Purpose of the invention The present invention was developed in view of the above problems, and its purpose is to eliminate the influence of outside temperature and always perform stable control.

Structure of the Invention In order to achieve the above object, the present invention uses a thermistor to change the reference potential according to the room temperature.

DESCRIPTION OF EMBODIMENTS The embodiment will be described below with reference to FIGS. 4 and 5. FIG. 4 is a control circuit diagram, in which AC power 13 is applied to a circuit consisting of burner case 12, flame rod 11, resistors 14, 15, and capacitor 16, as in the conventional example, and point c is output. On the other hand, the connection of the DC power supply 17 and resistors 18 and 19 to the reference potential side is the same as in the conventional example, but a thermistor 27 for detecting room temperature, resistors 28 and 29, and a diode 30 are newly connected as shown in the figure. do. and c,
Output d of operational amplifier 20 with positive and negative inputs at point a
The point is connected to the overall control circuit 21, and the main power supply 2
2 and their loads are completely the same circuits as in the conventional example.

In such a circuit configuration, if the room temperature is high and the resistance value of the thermistor 27 is small, the temperature will be higher than point b than point a.
Since the potential is higher at the point, the circuit including the thermistor 27 and resistors 28 and 29 has no influence due to the diode 30. When the temperature is low, the resistance value of the thermistor 27 is large, so the potential at point b becomes lower than that at point a, and the potential at point a also becomes lower.
This situation is shown in FIG. If we take the potential at point a on the vertical axis and the ambient temperature on the horizontal axis, the potential at point a in Figure 4 is determined by the resistors 18 and 19, so it is parallel to a ₀ in Figure 5 and has no relation to the ambient temperature, but the thermistor When 27 circuits are connected, the characteristics change as shown by a ₁ and a ₂ .
In other words, the temperature at which the temperature starts to drop is determined by the selection of the values of the resistors 28 and 29. In the case of characteristic a ₁ , the temperature starts to drop when the ambient temperature is around 0°C or lower, and in the case of characteristic a ₂ , the temperature starts to drop from around 10°C or lower. , thermistor 27
The resistors 28 and 29 and the resistors 18 and 19 can be freely designed by changing their values. On the other hand, the characteristics at point c determined by the state of flame A are as shown in characteristic C in Figure 5.
The constant of characteristic a can be determined by considering how much margin should be given to the difference from characteristic a. However, in the event of an abnormality such as a misfire, it is of course necessary to select a point that is always lower than characteristic a.

Effects of the invention As is clear from the above explanation, when the structure of the invention is used, while the indoor air is not yet sufficiently warmed,
Although the reference potential is low, it becomes a constant reference voltage when the temperature reaches a certain level, making it easy and reliable to detect ignition and misfire.It is also a method that does not change the air volume or oil volume, so it is a design-friendly method. It is simple and requires fewer parts. Furthermore, since the temperature, which is affected by the ambient temperature, can be determined simply by selecting the resistance value, the burner configuration is also simplified.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the combustion appliance, Figure 2 is a sectional view of the same burner, Figure 3 is a conventional combustion control circuit diagram, and Figure 4 is a sectional view of the burner.
The figure shows a combustion control circuit diagram in an embodiment of the present invention.
FIG. 5 is an explanatory diagram of the same characteristics. 11... Flame rod, 12... Burner case, 14, 15... First and second resistors, 16...
Capacitor, 27...Thermistor, 29...3rd
resistance, 30...diode.

Claims (1)

[Scope of utility model registration request] A voltage is applied between the burner and the flame rod, and a capacitor voltage obtained by accumulating the current flowing through the combustion flame in the capacitor and a constant DC voltage are connected to the connection point a of the first and second resistors. In a circuit that monitors the combustion state of the burner by comparing a reference voltage obtained by dividing, a thermistor whose resistance value changes depending on the temperature and a third resistor are connected in series, and the connection part is b. A combustion control device characterized in that a diode is connected between the point B and the point A, and the point A is an anode and the point B is a cathode.