JPS63251720A - Combustion control device - Google Patents

Abstract

PURPOSE:To smoothly carry out the ignition of a burner by setting a proportional control valve to an initial valve opening degree which is greater than the optimum valve opening degree at the normal combustion by a detection signal from a blast quantity detector and a detection signal from a combustion temperature sensor, in a period from the ignition of the burner to a time the temperature reaches a predetermined value. CONSTITUTION:A control circuit 50 is supplied with a signal from an operation detector 27 and supplies power to a solenoid valve 43. Further, the control circuit 50 is supplied with a signal from temperature setting means 11 to control the power supply to a blower 36, and further is supplied with signals from temperature setting means 11, combustion temperature sensor 35, and a blast quantity detector 37, and to control the power supply to a proportional control valve 44 so as to obtain a desired air-to-fuel ratio. In a period from the ignition of the burner to a time a predetermined temperature, at which the combustion temperature sensor 35 is amply heated, is reached, power is supplied to the burner in a current value which is greater by a predetermined quantity (i) than the current value I of power supplied to the proportional control valve 44 so as to obtain a desired air-to-fuel ratio in accordance with a signal from the blast quantity detector 37, and a gas is supplied to the burner in a large quantity. However, since a burner plate 33 within a combustion box 20 is not sufficiently heated, the fluid resistance of the gas becomes small, and the quantity of air supplied is substantially large. Hence, the air-to-fuel ratio becomes close to the desired air-fuel ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a combustion control device including a control circuit for controlling the amount of air supplied and the amount of fuel supplied in an all-primary air type combustion device.

[Prior Art] In a conventional combustion control device, a control circuit detects the combustion temperature using a combustion temperature sensor such as a thermocouple installed in the combustion chamber, and adjusts the amount of fuel according to the amount of air blown by a blower that supplies air. The desired air-fuel ratio was obtained by controlling the proportional control valve that supplies the fuel to an optimal valve opening.

[Problems to be solved by the invention] However, since the amount of air supplied can be estimated based on the operating state of the blower, such as the voltage applied to the blower and the rotational speed of the fan, the amount of air supplied in There is a difference in the actual supply amount. In other words, in an all-air combustion type combustion device, the flow rate of the mixture of air and fuel is limited by the small nozzles of the burner plate provided in the combustion chamber, so the fluid resistance of the small nozzles is When the amount changes, the amount supplied also changes. The fluid resistance of this group of small craters increases as the temperature of the burner plate itself and the temperature of the fluid passing through it increase. In other words, the amount of air-fuel mixture supplied to the combustion chamber changes as the temperature changes even if the blower has the same applied voltage and rotation speed.

However, since the control circuit is controlled to obtain the desired air-fuel ratio in a steady state when the combustion chamber temperature is sufficiently high, the Therefore, if the blower and proportional control valve of the combustion device are controlled to obtain the desired air-fuel ratio, the amount of air supplied is equal to the amount of fuel supplied. Compared to this, the air-fuel ratio is supplied at more than the desired air-fuel ratio.

As a result, the air-fuel ratio of the mixture increases, so the flame method 1, 5
There is a problem that the speed decreases and it becomes difficult to ignite.

The present invention provides a combustion control device that can smoothly perform ignition in a combustion device equipped with a control circuit that controls the fuel supply 41j according to the air supply and armpit to obtain a desired air-fuel ratio. and the purpose.

[Means for solving the problem] The present invention disposes a burner in a combustion case, supplies combustion air through a feeder 1 from upstream thereof, and supplies fuel gas through a proportional control valve, and supplies combustion air through a proportional control valve downstream of the burner. An all-primary air type combustion device for combustion, comprising an air flow rate detection device that detects the amount of air supplied by the blower based on the rotation speed of the blower, a control circuit that controls the proportional control valve, and a combustion temperature sensor. In the combustion control device, the control circuit controls the proportional control valve to an optimum valve opening for obtaining a desired air-fuel ratio based on the detection signal of the air flow rate detection device and the detection signal of the combustion temperature sensor. After ignition, until the combustion temperature reaches a predetermined temperature, the proportional control valve is set to an initial valve opening larger than the optimum valve opening for steady combustion based on the detection signal of the air flow rate detection device and the detection signal of the combustion temperature sensor. The technical means was to control the temperature so that the

[Function] With the above configuration, in the present invention, when the power is turned on, the blower operates and air is supplied. Then, the air supply amount is detected by the air blowing amount detection device. Based on the detection signal from the air flow rate detection device, the control circuit energizes the proportional control valve so that the initial valve opening is larger than the optimum valve opening for steady combustion. The fuel supplied by the proportional control valve is ignited. After ignition, when the combustion temperature reaches a predetermined temperature, the control circuit uses the detection signal from the combustion temperature sensor to adjust the proportional control valve to the optimum valve opening to obtain the desired air-fuel ratio. The control valve is energized and fuel is supplied according to the amount of air supplied.

[Effects of the Invention] As described above, the present invention allows the proportional control valve to open so that the opening is larger than the j1i appropriate valve opening during steady combustion until the combustion temperature reaches a predetermined temperature after ignition. +”1j
be done.

For a while after this ignition, because the fluid resistance of the combustion device is small, the air actually supplied by the blower (jQ) becomes larger than the apparent supply amount detected by the air flow rate detection device. Therefore, even if the proportional control valve is opened larger than the optimum valve opening and more fuel is supplied, the actual air-fuel ratio is close to the desired air-fuel ratio.This allows for smooth ignition. It can be carried out.

[Embodiments] Next, the present invention will be explained based on embodiments shown in the drawings. FIG. 1 shows a gas combustion type water heater incorporating the combustion control device of the present invention.

This gas combustion water heater includes a water heater case 10, a combustion box 20, an all-primary forced air type gas combustion device 30 that performs complete combustion only with primary air, a fuel supply path 40, and a control circuit 5.
It consists of 0.

The outside of the water heater case 10 is provided with a temperature setting means 11 for the user to set the temperature, and an ignition switch 12 that also serves as a power switch for the control circuit 50, and inside the water heater case 10 is provided with a combustion box 20 and a gas combustion device. 30 are stored. Further, an outside air inlet 13 is provided at the lower part of the side wall of the water heater case 10.

The combustion box 20 forms a combustion chamber, and -1=Elf
is provided with an exhaust port 21, and an exhaust pipe 22 provided in communication with the outside of the water heater case 10 is connected to the exhaust port 21. In the upper part of the combustion box 20, the combustion box 20
A heat exchanger 23 welded to both walls of the
is provided. On the other hand, the lower end is open, and a gas combustion device 30 is provided to close the opening, and a ceramic refractory frame 25 is provided in the combustion box 20 near the gas combustion device 30. Further, in the lower part of the combustion box 20, an ignition device 26 for igniting the gas combustion device 30 and an operation detection device 27 for detecting the operating state of the ignition device 26 are provided, and a combustion temperature sensor consisting of a thermocouple is provided. 35 are provided.

The gas combustion device 30 includes a mixing box 3 that mixes fuel and air.
1 and a flange 32 formed at the upper end of this mixing box 31.
A burner plate 3 provided on the top of the burner plate 3 for partially combusting the mixture.
It consists of 3.

The burner plate 33 includes a group of small nozzles 34, which have different diameters from each other in order to reduce noise during combustion.

Below the mixing box 31 is a blower 3 for supplying air.
6, and this blower 36 is equipped with an air flow rate detection device 37 that estimates the amount of air supplied based on the rotation speed of the blower 36.

Further, below the mixing box 31, a fuel supply passage 40 and an injection port 41 that is the end of the fuel supply passage 40 are provided.

The fuel supply path 40 connects a fuel supply source (not shown) to the injection port 4.
A solenoid valve 43 and a proportional control valve 4 are connected to the gas pipe 42 from the upstream side where the fuel supply source is located.
4 are provided. The electromagnetic valve 43 opens the fuel supply path 40 when energized, and closes the fuel supply path 40 when not energized.

Further, the proportional control valve 44 controls the fuel supply path 4 depending on the energization state.
However, since there is no airtightness, the fuel supply path 40 cannot be completely opened even when the power is not supplied.

The control circuit 50 inputs the signal from the operation detection device 27 and energizes the solenoid valve 43 . Further, the signal from the temperature setting means 11 is inputted to control the energization of the blower 36, and the signals from the temperature setting means 11, the combustion temperature sensor 35, and the air flow rate detection device 37 are inputted to obtain a desired air-fuel ratio. The proportional control valve 44 is energized and controlled.

Furthermore, in this embodiment, after the combustion device is ignited, until the combustion temperature sensor 35 reaches a predetermined temperature at which it is sufficiently heated, the desired air-fuel ratio is obtained according to the signal from the air flow rate detection device 31. The current value I applied to the proportional control valve 44 at
A current value greater than [A] by a certain amount i [A] is applied.

Next, the operation of the combustion control device of the present invention having the above configuration will be explained with reference to FIG.

When the user sets the temperature using the temperature setting means 11 and turns on a water flow switch (not shown), the ignition switch 12 is turned on, and the control circuit 50 is turned on together with the ignition device 26. Then, the ignition device 26 is activated, and the blower 36 supplies air according to the setting of the temperature setting means 11.

Then, in response to a signal from the air flow rate detection device 31, a current value that is i [A] larger than a current value I [A] for obtaining a desired air-fuel ratio is supplied to the proportional control valve 44.

On the other hand, when the operation detection device 21 detects the operation of the ignition device 26, the electromagnetic valve 43 is energized and the gas in the gas pipe 42 passes through the electromagnetic valve 43 and flows into the proportional control valve 44. At this time, the proportional control valve 44 has a current value I [A
] A current value that is i [A] larger than that is applied. Therefore, until the combustion temperature sensor 35 is sufficiently heated, the amount of gas to be supplied is larger than that required to obtain the desired air-fuel ratio according to the signal from the air flow rate detection device 37. Ru. However, at this time, since the burner plate 33 in the combustion box 20 is not sufficiently heated, the fluid resistance of the gas is small and the amount of air supplied is substantially increased. Therefore, even though the control circuit 50 provides more current to the proportional control valve 44, the actual air-fuel ratio can be close to the desired air-fuel ratio.

The air-fuel mixture that has flowed into the combustion box 20 is ignited by the ignition device 26 that is already in operation, and smooth ignition can be performed to achieve a desired air-fuel ratio.

After the combustion device is ignited, when the combustion temperature sensor 35 is sufficiently heated, the proportional control valve 44, which had been energized by the control circuit 50 with a current value larger than i[Δ], receives a current value that obtains the desired air-fuel ratio. 1 [A] is energized, and the combustion device continues combustion under control to obtain a desired air-fuel ratio.

In this embodiment, depending on the setting of the temperature setting means 11, the combustion amount may be large or small, but in order to make the air-fuel ratio lower than the desired air-fuel ratio, the current value of the proportional control valve 44 is simply set to i [ The reason why the actual air-fuel ratio is close to the desired air-fuel ratio even though the current is energized by A] is as follows.
The following is explained based on Figure 3.

The air-fuel ratio is determined by the stoichiometric air-fuel ratio depending on the type of fuel, and in a gas combustion apparatus such as the present invention, the air-fuel ratio is generally set to λ, which has a large proportion of fuel.9 In the present invention, the blower 36 is Air is supplied according to the settings of the temperature setting means 11, and the proportional control valve 44 is controlled by the signal from the air blower 1 [detection device 31 to obtain a desired air-fuel ratio λ.

Now, in the combustion apparatus with the control circuit 50 set to the desired air-fuel ratio λ, the rotation speed N of the blower 36 during steady combustion is set to the desired air-fuel ratio λ.
The relationship between the current (2) and the current (2) to the proportional control valve 44 has a linear characteristic, as shown by the solid line A in FIG. The air-fuel ratio λ is represented by the slope of the solid line A. Here, point a indicates the current ■1 to the proportional control valve 44 for the rotation speed N1 of the blower 36 when the set temperature is low, and point a indicates the current to the proportional control valve 44 for the rotation speed N2 of the blower 36 when the set temperature is high. Let b be the point showing the current ■2.

In the combustion apparatus having the above relationship, the relationship between the rotation speed N of the blower 3G and the current I to the proportional control valve 44 when the temperature of the combustion box 20 is still low after ignition is determined by the control circuit 50. Since the current I to increases by i, the third
As shown by the broken line B in the figure, the solid line A is translated in parallel. Then, point C indicating the current ■ to the proportional control valve 44 relative to the rotation speed N1 of the blower 36 is the current value I, +i, and point d indicating the current ■ to the proportional control valve 44 relative to the rotation speed N2 is the current value l2) -H. are required respectively.

Here, the proportional control valve 44 at the rotation speed N□ when the supply air is small is based on the apparent air-fuel ratio λ゛ by the control circuit 50 at the rotation speed N2 when the supply air is large.
When calculating the current I to , the current value rl at point e according to the chain line C
, and the current value I, +i obtained by the control circuit 50
become smaller.

However, when the amount of combustion is large, that is, when the rotation speed N of the blower 36 is high, the amount of air blown inside the combustion box 20 is large, so the temperature near the burner plate 33 does not change much between the steady state and the ignition. On the other hand, when the combustion amount is small, that is, when the rotation speed N of the blower 36 is low, the combustion box 2
Due to the small amount of air flow in the
3 and the temperature of the burner plate 33 gradually increases. Therefore, the difference in the actual amount of air blown between ignition and steady combustion becomes larger than when the rotation speed N of the blower 36 is high.

For the above reasons, in order to obtain the desired air-fuel ratio when the rotational speed N of the blower 36 is high, the current value to the proportional control valve 44 is increased by i [A], and similarly the rotational speed N
Even when the current value to the proportional control valve 44 is low, i
Increasing [A] works to obtain the desired air-fuel ratio even when the rotational speed N of the blower 36 is low. can be obtained, and ignition can be performed smoothly.

[Brief explanation of the drawing]

Fig. 1 is a schematic cross-sectional view of a gas combustion type water heater showing an embodiment of the present invention, Fig. 2 is a block diagram showing a signal path of this embodiment, and Fig. 3 is a diagram showing a blower used to explain the operation of the present invention. FIG. 3 is a characteristic diagram of the control circuit showing the current value (■) to the proportional control valve with respect to the rotational speed N;

Claims (1)

[Claims] 1) All-primary air type in which a burner is arranged in a combustion case, combustion air is supplied from a blower upstream of the burner, and fuel gas is supplied via a proportional control valve, which is then combusted downstream. The combustion device includes: an air flow rate detection device that detects the amount of air supplied by the blower based on the rotational speed of the blower; a control circuit that controls the proportional control valve; and a combustion temperature sensor; A combustion control device that controls the proportional control valve to an optimum valve opening for obtaining a desired air-fuel ratio based on a detection signal of the device and a detection signal of the combustion temperature sensor, wherein the control circuit controls the combustion temperature after ignition. until the temperature reaches a predetermined temperature, the proportional control valve is controlled to have an initial valve opening larger than the optimum valve opening in steady combustion based on the detection signal of the air flow rate detection device and the detection signal of the combustion temperature sensor. A combustion control device characterized by: 2) The combustion control device according to claim 1, wherein the predetermined temperature is a temperature that is reached after a time limit set by a timer has elapsed.