JPH0325020Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a combustion control device using a thermocouple.

(Prior art) As a conventional device of this type, a thermocouple is placed on the combustion surface of a burner having a large number of flame ports, and the ratio of gas and air supplied to the burner is controlled by the output from the thermocouple. , a burner that allows normal combustion is known (see Japanese Patent Laid-Open No. 16218/1983).

(Problem to be solved by the invention) As with the conventional hot air heater mentioned above, if the change in the gas supply amount to the burner is relatively small, for example, 4000 to 6000 kcal/h, even if the gas supply amount is changed. However, the thermocouple provides an output proportional to the amount of gas supplied, which controls, for example, the rotational speed of a fan that supplies combustion air, making it possible to accurately control the ratio of gas and air supplied to the burner. This allows the burner to burn normally. However, when there are large changes in water temperature and water volume, such as in water heaters that supply water to multiple locations, and the change in the amount of gas supplied to the burner is relatively large, e.g. 7,000 to 30,000 kcal/h, the thermocouple If you try to control the ratio of gas and air supplied to the burner using output, if the gas supply amount changes significantly, the positional relationship between the thermocouple and the combustion flame will change, and the output from the thermocouple will be proportional to the gas supply amount. For example, if you control the rotation speed of a fan that supplies combustion air to a water heater, you will not be able to accurately control the ratio of gas and air supplied to the burner, resulting in the inconvenience of not being able to achieve normal combustion in the burner. arise.

(Means for solving the problem) The present invention aims to provide a device that can always obtain accurate output from a thermocouple regardless of changes in the amount of gas supplied to the burner. A thermocouple faces the combustion surface having a large number of flame ports of a variable capacity burner, and the ratio of gas and air supplied to the burner is controlled by the output from the thermocouple. It is characterized in that the portion facing the thermocouple is formed without a flame port.

(Function) The present invention has the above configuration, and according to this, the amount of gas supplied to the burner is, for example, 14000 kcal/
Even if it becomes larger than h, there is no flame port on the part of the combustion surface facing the thermocouple, so the gas supply to the thermocouple is as small as less than 14000kcal/h.
The combustion heat of the burner from the surroundings, which does not affect the change in the position of the combustion flame, comes into contact with it, and the thermocouple produces an output proportional to the amount of gas supplied. By controlling the rotational speed of the fan that supplies the burner, the ratio of gas and air supplied to the burner can be accurately controlled, and as a result, the burner can be maintained in a normal combustion state.

(Embodiment) Next, an embodiment in which the present invention is applied to a water heater in which the change in the amount of gas supplied to the burner is relatively large, for example, from 7000 to 30000 kcal/h will be described based on the drawings.

In FIGS. 1 and 2, reference numeral 1 indicates a water heater main body having an exhaust port 2 at the upper front surface, and inside the main body 1, a heat exchanger 3 and a capacity switching type burner 4 for heating the heat exchanger 3 are installed in the middle of the main body 1. A combustion case 7 is provided with a fan 5 for supplying combustion air to the burner 4 in the lower part of the interior, a space 6 for concentrating combustion exhaust in the upper part of the interior, and a water supply pipe 8 on the upstream side of the heat exchanger 3. The water sent from the heat exchanger 3 is heated in the heat exchanger 3 so that hot water at a desired temperature can be obtained from the hot water supply pipe 9 downstream of the heat exchanger 3, and the combustion that collects in the space 6 in the combustion case 7 The exhaust gas is discharged to the outside from the exhaust port 2.

Gas is supplied to the burner 4 through a nozzle 10a at the tip of the gas supply path 10 at the air suction port of the fan 5.
The gas ejected from the nozzle 10a is sucked in from the air suction port by the rotation of the fan 5 and sent to the combustion surface 11 of the burner 4, which has a large number of flame ports 11a. The supply amount is controlled to increase or decrease according to the hot water temperature set by an electromagnetic proportional valve 12 interposed in the gas supply path 10, and when the hot water temperature falls below the set temperature, the gas is The amount of heat generated by the burner 4 was increased by increasing the supply amount.

Here, when increasing or decreasing the amount of gas supplied to the burner 4 according to the set hot water temperature, if the rotation speed of the fan 5 is kept constant, the burner 4 will suffer from poor combustion, so the amount of gas supplied must be increased or decreased. At the same time, it is necessary to increase/decrease the rotation speed of the fan 5 and control the ratio of the gas supplied to the burner 4 and the combustion air to achieve normal combustion in the burner.

This increase/decrease control of the rotation speed of the fan 5 is performed by the combustion surface 11.
Generally, this is carried out using the output from the thermocouple 13 placed above. Specifically, when a combustion flame is formed on the combustion surface 12 by the combustion operation of the burner 4, the thermocouple 13 is activated by the hot combustion air. In this case, as the amount of gas supplied to the burner 4 increases and the amount of heat generated increases, the temperature of the hot combustion air tends to increase in proportion to this, so the output from the thermocouple 13 is proportional to the amount of gas supplied. The fan 5 changes according to this output.
By controlling the rotation speed to increase or decrease, the amount of combustion air supplied is automatically adjusted to a value corresponding to the actual calorific value of the burner 4, and normal combustion of the burner 4 can be achieved.

However, if the amount of gas supplied to burner 4 is
When the amount increases to 14,000 kcal/h or more, the positional relationship between the thermocouple 13 and the combustion flame changes, and as a result, the thermocouple 13 is exposed to unburned gas and is cooled.
For example, as shown by the dotted line in FIG. 4, the thermocouple 13 no longer provides an output proportional to the amount of gas supplied, and if the rotational speed of the fan 5 is controlled to increase or decrease based on this output, normal combustion in the burner 4 cannot be obtained.

Therefore, in the present invention, the part of the combustion surface 11 facing the thermocouple 13 is formed in a part without the flame port 11a. Specifically, the part of the combustion surface 11 facing the thermocouple 13 is formed as shown in FIG. Block the flame port 11a of
Alternatively, when manufacturing the combustion plate 11, the flame port 11a is not formed in the part facing the thermocouple 13. According to this, when the amount of gas supplied to the burner 4 is, for example, 14,000 kcal/h or more, In this case, the positional relationship between the thermocouple 13 and the combustion flame changes, resulting in defective combustion in the burner 4. However, in the present invention, as mentioned above, the thermocouple 13 is heated by the surrounding hot combustion air, so its output is As shown by the solid line in the figure, it changes in proportion to the gas supply amount. Therefore, if the rotational speed of the fan 5 is controlled to increase or decrease based on this output, normal combustion of the burner can be obtained.

In the figure, 14 indicates a sound deadening material made of a porous member,
15 indicates a rotation speed control circuit.

In the above embodiment, the output of the thermocouple 13 is used to change the amount of combustion air supplied to control the ratio of gas and air supplied to the burner 4. The ratio of gas and air supplied to the burner 4 may be controlled by changing both gases.

(Effects of the invention) As described above, according to the invention, the part of the combustion surface facing the thermocouple is formed without a flame port, so even if the amount of gas supplied to the burner changes greatly from small to large. The thermocouple now provides an output proportional to the amount of gas supplied, and using this output has the effect of always accurately controlling the ratio of gas and air supplied to the burner.

[Brief explanation of drawings]

Fig. 1 is a cutaway front view showing an embodiment in which the present invention is applied to a large-capacity water heater, Fig. 2 is a cutaway side view thereof, Fig. 3 is a plan view of the main parts, and Fig. 4 is a gas FIG. 3 is an explanatory diagram illustrating the relationship between the supply amount and the output of a thermocouple. 4...burner, 11... combustion plate, 11a... flame port, 13... thermocouple.

Claims (1)

[Scope of utility model registration request] A thermocouple faces the combustion surface having a large number of flame ports of a variable capacity burner, and the ratio of gas and air supplied to the burner is controlled by the output from the thermocouple. A combustion control device characterized in that a portion facing the thermocouple is formed without a flame port.