JPH0144967B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field of the Invention> The present invention relates to a combustion control device for a hot air heater or the like.

<Prior art> In a combustion control device such as a hot air heater, when the fuel such as gas is continuously changed, ideally the amount of air is also continuously changed in order to obtain a nearly constant air-fuel ratio. , it is necessary to make changes in very finely divided steps. However, in the case of AC100V single-phase motors used in general home hot-air heaters, it is extremely difficult to control the air volume as described above without using an extremely expensive inverter. Therefore, it deviates significantly from market needs.

However, from the perspective of human comfort, controlling the amount of fuel proportionally generally does not have a strong effect on improving comfort, and a sudden change in the amount of hot air causes discomfort.

Therefore, if the combustion amount can be controlled in several stages, the amount of hot air will not change suddenly, and the above-mentioned discomfort can be avoided.

Incidentally, in order to control the fuel amount in stages, it is conceivable to arrange a large number of solenoid valves at appropriate locations in a fuel passage branched into a plurality of channels, and to control the amount by controlling the open/closed states of these solenoid valves. As the number of stages increases, the number of electromagnetic valves increases, resulting in a complicated fuel supply passage and an increase in cost.

<Summary of the Invention> The present invention has been made in view of the above circumstances, and it is possible to control the control current of the proportional control valve interposed in the fuel supply passage by
By performing stepwise control with a value that substantially matches the characteristics of the proportional control valve depending on the positive or negative slope of the current, and at the same time appropriately selecting the capacity switching terminal of the blower according to the stepwise control, The purpose of this invention is to eliminate the above-mentioned conventional inconveniences.

<Embodiment of the Invention> An embodiment of the present invention will be described below based on FIGS. 1 to 4.

In the figure, 1 is a combustion tube such as a hot air heater, 2 is a mixing chamber, 3 is an air duct, and 4 is a blower for supplying combustion air and convection.
It has four capacity switching terminals so that MH>ML>L can be obtained. 5 is a spark plug; 6 is a fuel injection nozzle whose tip opening faces a throat 7 communicating with the mixing chamber 2; 8 is an incomplete combustion prevention sensor using a semiconductor whose resistance value changes in response to oxygen partial pressure; 9 1 is a proportional control valve that adjusts the injection pressure P of the fuel injection nozzle 6, 10 is a dual solenoid valve that is interposed in the fuel supply passage upstream of the proportional control valve 9, 11 is a thermistor that detects the indoor temperature, and 12 is a heater. Start switch, 13
is a control circuit such as a microcomputer that controls the operation of the spark plug 5, the blower 4, the proportional control valve 9, and the dual solenoid valve 10 based on signals from the heating start switch 12, the incomplete combustion prevention sensor 8, and the thermistor 11; A positive/negative detection means detects whether the slope of the control current of the proportional control valve 9 is positive or negative, and a control current that approximately matches the hysteresis characteristic curve of the proportional control valve 9 is gradually adjusted depending on whether the slope of the control current by the positive/negative detection means is positive or negative. It also has the function of a combustion amount adjusting means for selecting the capacity switching terminal of the blower 4 according to the control current.

Next, the effect will be explained.

When the heating start switch 12 is operated, this operation signal is input to the control circuit 13, and the dual solenoid valve 10 is activated.
When the valve is opened, the blower 4 is operated, the spark plug 5 is ignited, and hot air is discharged into the room. Then, as the indoor temperature rises, the indoor temperature T detected by the thermistor 11 rises, and the difference ΔT from the set temperature To increases.
is within a predetermined value, the control circuit 13 determines the control current I _-1 to the proportional control valve 9, and switches the air flow rate Q _-1 of the blower 4 from H to MH to keep the air-fuel ratio approximately constant. Reduce combustion while maintaining

The method _{for determining} the control current _{I -1} is, for example, as shown in _{FIG .} The minimum value I _nio and the maximum value of the control current, respectively, with ₊₂ as the dividing point.
Divide I _nax into N parts. For example, if N=15,
I _-2 , I ₊₂ , I _-1 , I ₊₁ are 2, 3, and 3, respectively, in Figure 2.
Since the 6th and 7th division points correspond, I _-1 = I _nio + 6 x (I _nax - I _nio )/15.

Then, when the detected room temperature T rises further and the difference ΔT from the set temperature To becomes smaller, the control circuit 13 adjusts the control current I _-2 by I _-2 = I _nio + 2 x (I _nax - I _nio )/15. At the same time, set the air flow rate Q ₂ of blower 4 to MH
→Switch to ML and lower the combustion amount while keeping the air-fuel ratio constant.

Furthermore, the detection room temperature T rises and the set temperature To
When the difference ΔT _between the
Switch to Even in this minimum combustion amount state, the detected indoor temperature T further increases, and when the difference ΔT from the set temperature To becomes zero, combustion is stopped.

On the other hand, if the detected indoor temperature T falls due to the above-mentioned combustion stop and a slight difference ΔT from the set temperature To occurs,
Switches to the lowest combustion state.

Then, as the detected indoor temperature T falls further, the difference ΔT from the set temperature To becomes even larger, so the control circuit 13 controls the control current I ₊₂ to be I ₊₂ = I _nio + 3 x (I _nax − I _nio )/ 15, and at the same time, change the blowing amount Q ₊₂ from L to ML to increase the combustion amount while keeping the air-fuel ratio constant.

Then, when the detected indoor temperature T further decreases and the difference ΔT from the set temperature To further increases, the control circuit 13 changes the control current I ₊₁ to I ₊₁ = I _nio + 7 x (I _nax − I _nio )/ 15, and switch the blowing amount Q ₊₁ from ML to MH to further increase the combustion amount while keeping the air-fuel ratio constant.

Furthermore, the detected indoor temperature T decreases and the set temperature To
When the difference ΔT _from
Switches combustion to the maximum combustion amount state while maintaining a constant air-fuel ratio.

Since the fuel amount and air amount are controlled stepwise in accordance with the hysteresis characteristic of the proportional control valve 9 in this manner, the combustion amount can be varied at a constant air-fuel ratio with an inexpensive configuration.

<Effects of the Invention> As explained above, in the present invention, the control current of the proportional control valve interposed in the fuel supply passage is set to a value that approximately matches the characteristics of the proportional control valve depending on the sign of the slope of the current. Since the configuration is such that the control is performed in stages and at the same time the capacity switching terminal of the blower is appropriately selected in accordance with the stepwise control, the combustion amount can be controlled at a constant air-fuel ratio with an inexpensive configuration.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the main parts of a hot air heater which is an embodiment of the present invention, Fig. 2 is a characteristic diagram of the proportional control valve shown above, and Fig. 3 shows the interaction between the proportional control valve and the blower. The related characteristic diagram, FIG. 4, is a flowchart of the same control circuit. DESCRIPTION OF SYMBOLS 1... Combustion tube, 4... Blower, 6... Fuel injection nozzle, 9... Proportional control valve, 11... Thermistor, 13...
control circuit.

Claims (1)

[Claims] 1. In a combustion control device including a proportional control valve interposed in a fuel supply passage and a blower for supplying combustion air having a plurality of capacity switching terminals, detecting whether the slope of the control current of the proportional control valve is positive or negative. outputting a control current that substantially matches the characteristics of the proportional control valve to the proportional control valve in stages according to the positive or negative slope of the control current detected by the positive/negative detection means; A combustion control device comprising: combustion amount adjusting means for selecting a capacity switching terminal of the blower accordingly.