JP2537782B2 - Combustion device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion apparatus for supplying hot water or heating by burning a fuel such as gas or petroleum with a small throttle ratio.

2. Description of the Related Art A conventional water heater using this type of combustion device is shown in FIG. In the figure, 1 is a burner and 2 is a nozzle. 3 is a heat exchanger, 4 is a combustion fan that sends combustion air to the burner 1, 5
Is a gas proportional valve, 6 is an air flow sensor, 7 is a temperature sensor, and 8 is a control circuit.

The gas proportional valve 5 is controlled by the control circuit 8 so as to eliminate the difference between the hot water temperature of the hot water supplied from the heat exchanger 3 measured by the temperature sensor 7 and the set temperature.
A proportional signal is output from the control circuit 8 to the combustion fan 4 so that the air flow rate becomes a predetermined air flow rate with respect to the gas flow rate from (1) to control the air flow rate. At this time, the amount of gas can be set to almost the desired amount because the supply pressure of the gas is constant by the burner (not shown), but the amount of air can be set according to the supply / exhaust conditions such as the presence or absence of a chimney and the variation of equipment Because of a large change, the air flow rate measured by the air flow rate sensor 6 is fed back to the control circuit 8, and the air flow rate measured by the air flow rate sensor 6 and the air flow rate set by the proportional signal from the control circuit 8 Feedback control is performed to eliminate the difference. In this way, the burner 1 burns and the heat exchanger 3 heats the water with a predetermined amount of gas supplied from the nozzle 2 and a predetermined amount of air supplied from the combustion fan 4.

Problems to be Solved by the Invention However, with the above-mentioned configuration, the gas amount,
Both the air amount and the throttle ratio (The throttle ratio at the maximum combustion is set to 1, and the throttle ratio that is smaller than this throttle ratio 1 is defined as 1/2 when the maximum combustion is combusted.) There is only about 1/3, and combustion often stopped when the combustion was low, such as when hot water was supplied to the kitchen. Further, in order to reduce the throttle ratio, when the nozzles are switched, the distribution ratio of the passing air between the burner that is burning and the burner that is not burning is different from that when all the burners are burning. Therefore, even if the total air amount (the amount of air passing through all the burners) is managed by the air flow rate sensor 6, combustion failure may occur.

The present invention solves such a conventional problem, and an object thereof is to extremely reduce the throttle ratio, and to realize it, an air flow rate sensor is arranged at a predetermined position to prevent combustion failure. To do.

Means for Solving the Problems In order to solve the above problems, the combustion apparatus of the present invention is
Multiple nozzles, multiple burners corresponding to each nozzle, a combustion fan that supplies combustion air, a control circuit that controls the gas flow rate to the burner and the amount of combustion air, and control as the gas flow rate decreases A switching valve that switches to supply gas to the nozzles that are sequentially closed by a signal from the circuit, and a primary air intake of the burner that detects the primary air amount of the burner corresponding to the nozzle that is open at the time of minimum combustion. And an air flow rate sensor arranged so as to surround the nozzle on the upstream side of the mouth, and the control circuit is provided with the air flow rate sensor even when the air volume is detected by the air flow rate sensor. The combustion fan is controlled so that a predetermined primary air amount with respect to the gas amount of the nozzle is obtained.

Action The air flow rate sensor, which is arranged to detect the primary air amount of the burner corresponding to the nozzle that is open at the time of minimum combustion, is the amount of gas flowing to the nozzle that is open at the time of minimum combustion regardless of whether the nozzle is switched or not. Accordingly, the primary air amount of the burner corresponding to the nozzle is fed back to the control circuit to set the total air amount. That is, since the total air amount is related to the resistance ratio of the primary air system path and the secondary air system path and the relationship with the primary air amount can be uniquely determined, the control circuit can easily determine the total air amount by feeding back the primary air. Can be set.

By the above control, the required amount of air can be accurately supplied to the open nozzles even when the nozzles are fully opened or when the nozzles are switched.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an embodiment when the present invention is applied to a water heater,
In the figure, the same members as those in FIG. 3 are designated by the same reference numerals. In Fig. 1, 2a is a nozzle opened at the time of minimum combustion, 1a
Is a burner corresponding to the nozzle 2a, and 9 is a switching valve provided in the gas supply passage of the nozzle 2. Further, a gas proportional valve 5 is disposed at the base, and is divided into a gas supply passage in which a switching valve 9 and a nozzle 2 are provided ahead of it, and a gas supply system passage in which a nozzle 2a is directly provided. Then, the burner 1a surrounds the nozzle 2a.
Air flow sensor 6 to set the required primary air volume for
Are arranged. A combustion fan 4 for sending combustion air is arranged upstream of the burners 1 and 1a, and a heat exchanger 3 is arranged downstream thereof. A temperature sensor 7 is provided on the outlet side of the heat exchanger 3.

In the above embodiment, the gas proportional valve 5 is controlled by the control circuit 8 so as to eliminate the difference between the hot water temperature measured by the temperature sensor 7 and the set temperature, and the gas amount is set. At this time, when the gas amount is large, all the switching valves 9 are opened, but when the gas amount is small and the throttle ratio becomes 1/3 or less, the switching valves 9 are sequentially closed, and only the nozzle 2a is opened at the time of minimum combustion. Is supplied with gas. That is, when the nozzles 2 and 2a are open, the control circuit 8 sets the gas amount by the gas proportional valve 5, and the air flow rate sensor 6 sets the air amount of the combustion fan 4 so as to supply the required primary air amount to the burner 1a. To set. Here, the air flow rate sensor 6 is provided inside and detects the amount of air per unit time by capturing a temperature change that changes according to the flow rate by a detection element such as a heat wire or a thermocouple. When the combustion amount becomes smaller and the throttle ratio becomes smaller than 1/3, the sequential switching valve 9
Is closed, and finally only the nozzle 2a is opened.

Here, the excess air ratio m regarding only the burner 1a corresponding to the nozzle 2a will be described with reference to FIG. When the load of the combustion device is set to be large, that is, when the temperature is set to a high temperature or the flow rate is set to a large amount, the switching valve 9 is fully opened and the nozzle
Gas is ejected from all of 2,2a. As long as the switching valve 9 is fully open, if the gas amount decreases, the air amount correspondingly decreases, and the excess air ratio m is kept substantially constant as shown by A1 in FIG.

However, when the load is small (in the case of low temperature setting or small flow rate setting) and the throttle ratio gradually decreases to 1/3, 1/4, etc., an air flow rate sensor is installed at the discharge port of the fuel fan 4 etc. as in the prior art. When the total amount of air is controlled by switching the switching valve 9 and the gas is not ejected from the nozzle 2 but is ejected only from the nozzle 2a, the gas is ejected from all the nozzles. Control the amount of air. As a result, the excess air ratio m in this case does not become the control target value B1 but becomes a value lower than this, as shown by the broken line of B2.

In this way, when the excess air ratio m does not reach the control target value, especially when the excess air ratio m becomes 1 or less as shown in B2, incomplete combustion occurs and carbon monoxide CO is generated. Become.

On the other hand, in the present invention, since the air flow rate sensor 6 is arranged on the upstream side of the primary air intake port of the burner and so as to surround the nozzle, the excess air ratio m is shown by B1 in FIG. It is controlled to the control target value, and problems such as the generation of harmful gases such as carbon monoxide CO do not occur.

Therefore, the air flow rate sensor 6 having the above-described arrangement configuration
Detects the primary air amount required to burn the burner 1a, and at this time controls the control circuit 8 so that a predetermined air amount corresponding to the gas amount is obtained. However, as shown by the solid line in FIG. 2, the excess air ratio m
Can be controlled so as to reach the target value.

Effects of the Invention As described above, according to the combustion apparatus of the present invention, the following effects are obtained.

(1) Since the air amount of the burner corresponding to the nozzle that is open at the time of minimum combustion is controlled, combustion failure does not occur even if the throttle ratio is reduced by the switching valve.

(2) By increasing the number of switching valves, it is possible to correspondingly reduce the throttling ratio without causing defective combustion, and thus to meet all demands.

(3) Since the amount of combustion is reduced by the switching valve, a combustion device that is strong against wind can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a water heater adopting an embodiment of the present invention,
FIG. 2 is a graph showing the relationship between the excess air ratio and the combustion amount, and FIG. 3 is a configuration diagram of a conventional water heater. 1 ... Burner, 2 ... Nozzle, 4 ... Combustion fan, 6 ...
... Air flow sensor, 8 ... Control circuit, 9 ... Switching valve.

Claims (1)

(57) [Claims] 1. A plurality of nozzles, a plurality of burners corresponding to each nozzle, a combustion fan for sending combustion air to the burner, a control circuit for controlling a gas flow rate to the burner and an amount of combustion air, and the gas. A switching valve that switches to supply gas to the nozzle that is sequentially closed by a signal from the control circuit as the flow rate decreases, and a primary air amount of the burner corresponding to the nozzle that is opened at the time of minimum combustion. In order to detect, the control circuit comprises an air flow rate sensor disposed upstream of the primary air intake port of the burner and surrounding the nozzle, and the control circuit controls whether the air flow rate detected by the air flow rate sensor is the nozzle switching mode. A combustion apparatus that controls the combustion fan so that a predetermined primary air amount with respect to a gas amount of a nozzle provided with the air flow rate sensor is set even at a time.