JPH0571846B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a combustion control device that includes a control circuit for controlling the supply amount of air, fuel, and supply amount in a forced air 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, the amount of air supplied is estimated based on the operating state of the blower, such as the voltage applied to the blower and the rotational speed of the fan, so the apparent amount of air supplied and the actual amount of air supplied are different. There is a difference in the amount of supply. That is,
In forced air combustion devices, the flow rate of the mixture of air and fuel is limited by the small nozzles of the burner plate installed in the combustion chamber, so if the fluid resistance of the small nozzles changes, the supply amount will change. 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 rotational 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 During this period, the desired air-fuel ratio cannot be obtained. Therefore, when the blower and proportional control valve of the combustion device are controlled to obtain a desired air-fuel ratio, the amount of air supplied is a proportion greater than the desired air-fuel ratio compared to the amount of fuel supplied. It will be supplied by

As a result, the air-fuel ratio of the air-fuel mixture increases, causing a problem in that the flame propagation speed decreases and ignition becomes difficult.

An object of the present invention is to provide a combustion control device that can smoothly perform ignition in a combustion apparatus equipped with a control circuit that controls the amount of fuel supplied according to the amount of air supplied to obtain a desired air-fuel ratio. purpose.

[Means for solving the problem] The present invention disposes a burner in a combustion case, supplies combustion air from a blower upstream of the burner, and supplies fuel gas through a proportional control valve, and starts combustion downstream of the burner. The combustion device is operated by a user, and includes an air flow rate detection device that detects the amount of air supplied by the blower based on the rotation speed of the blower, and a combustion temperature sensor that detects the combustion temperature of the burner. The blower is controlled in accordance with the combustion amount set by the combustion amount setting means, and the optimum air-fuel ratio of the proportional control valve is obtained based on the detection signal of the airflow amount detection device and the detection signal of the combustion temperature sensor. In a combustion control device that controls the current value to be applied to the proportional control valve to set the valve opening, after ignition, until the combustion temperature reaches a predetermined temperature, the valve opening is set to the optimum valve opening. The technical means is to energize the proportional control valve with a current value obtained by adding a fixed current value set regardless of the detection signal of the air flow rate detection device and the detection signal of the combustion temperature sensor to the current value.

[Operation] In the present invention, when the combustion device starts operating, the blower is controlled according to the combustion amount set by the combustion amount setting means. On the other hand, the proportional control valve has a current value that is a current value that provides a desired air-fuel ratio based on the air flow rate detected by the rotation speed of the fan and the combustion temperature detected by the combustion temperature sensor, and a fixed current value. is energized.

As a result, the temperature of the burner, etc. has not risen sufficiently before ignition, so the actual air flow rate is higher than the air flow rate detected from the fan rotation speed by the air flow rate detection device. , the current value to the proportional control valve, which is determined only from the rotation speed of the blower and the detection signal of the combustion temperature sensor, is fixed even if the amount of fuel supplied is smaller than the amount of combustion air supplied. By increasing the value,
As the valve opening increases and the amount of fuel supplied increases,
It is possible to approach the desired air-fuel ratio.

Therefore, ignitability is improved and ignition is ensured.

In addition, even after ignition, until the combustion temperature rises to a predetermined temperature, the amount of fuel supplied increases in proportion to the actual amount of air blown, which is greater than the amount of air blown detected from the rotation speed, so it is stable. This results in a fuel condition that is as follows.

Here, when the number of revolutions of the fan is high, there is little difference in the actual amount of air blown between the initial stage of ignition and during steady combustion, but when the number of revolutions of the fan is small, the amount of air blown is larger at the beginning of ignition. easy to become,
There is a large difference between the initial stage of ignition and steady combustion.

Therefore, by applying a fixed current value and energizing the proportional control valve regardless of the set combustion amount, it is possible to approach the predetermined air-fuel ratio from small to large combustion amounts.

When the predetermined temperature is reached, a current value that provides a desired air-fuel ratio is appropriately determined based on the detection signal of the air flow rate detection device and the detection signal of the combustion temperature sensor, resulting in a stable combustion state.

[Effects of the Invention] As described above, in the present invention, after ignition, until the combustion temperature reaches a predetermined temperature, the proportional control valve is energized so that the opening is larger than the optimum valve opening during steady combustion. .

For a while after this ignition, the fluid resistance of the combustion device is decreasing, so the amount of air actually supplied by the blower is greater 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. Therefore, ignition can be performed smoothly.

[Example] Next, the present invention will be described based on an example 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 type water heater has water heater case 10.
, a combustion box 20 , an all-primary forced air type gas combustion device 30 that performs complete combustion using only primary air, a fuel supply path 40 , and a control circuit 50 .

The outside of the water heater case 10 is provided with a temperature setting means 11, which is the combustion amount setting means of the present invention and is used by the user to set the temperature, and an ignition switch 12, which also serves as a power switch for the control circuit 50. for,
A combustion box 20 and a gas combustion device 30 are housed. 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 an exhaust port 21 is provided at the upper end of the combustion box 20.
An exhaust pipe 22 provided in communication with the outside of the water heater case 10 is connected. At the upper part of the combustion box 20, there is a heat exchanger 2 welded to both walls of the combustion box 20.
3 is arranged, and this heat exchanger 23 is equipped with a plate fin group 24 that promotes heat exchange. On the other hand, the lower end is open, and the gas combustion device 30
is provided so as to close the opening, and a refractory frame 25 made of ceramic is provided inside the combustion box 20 near this gas combustion device 30. Further, in the lower part of the combustion box 20, there are provided an ignition device 26 for igniting the gas combustion device 30, an operation detection device 27 for detecting the operating state of the ignition device 26, and a combustion temperature sensor consisting of a thermocouple. 35 are provided.

The gas combustion device 30 includes a mixing box 31 that mixes fuel and air, and a burner plate 33 that is provided on a flange 32 formed at the upper end of the mixing box 31 and burns the air-fuel mixture.

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.

A blower 36 for supplying air is provided below the mixing box 31, and the high speed blower 36 is equipped with an air flow rate detection device 37 that infers the amount of air supplied based on the rotation speed of the blower 36.

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

The fuel supply path 40 is a gas pipe 42 that guides gas from a fuel supply source (not shown) to the injection port 41, and a solenoid valve 4 is connected to the gas pipe 42 from the upstream side where the fuel supply source is located.
3 and a proportional control valve 44 are provided. When the electromagnetic valve 43 is energized, the fuel supply path 40
The fuel supply path 40 is brought into an open state, and the fuel supply path 40 is brought into a closed state when the power is not energized. Further, the proportional control valve 44 controls the fuel in the fuel supply passage 40 according to the energization state, but since it does not have a sealing property, it cannot completely close the fuel supply passage 40 even when the electricity is not energized. I can't.

The control circuit 50 inputs the signal from the operation detection device 27 and energizes the solenoid valve 43 . In addition, the signal from the temperature setting means 11 is inputted to control the energization of the blower 36, and the temperature setting means 11 and the combustion temperature sensor 3 are controlled.
5. Input the signal from the air flow rate detection device 37,
The proportional control valve 44 is energized and controlled to obtain a desired air-fuel ratio. 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 in accordance with the signal from the air flow rate detection device 37. The current value I applied to the proportional control valve 44 at
A current value greater than [A] by a certain amount: [A] is energized.

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 the signal from the air flow rate detection device 37, a current value i[A] larger than the current value I[A] for obtaining the desired air-fuel ratio is supplied to the proportional control valve 44.

On the other hand, when the operation detection device 27 detects the operation of the ignition device 26, the solenoid valve 43 is energized and the gas pipe 42 is activated.
The gas inside passes through the solenoid valve 43 and flows into the proportional control valve 44. At this time, the proportional control valve 44 is energized with a current value that is i[A] larger than the current value I[A] for obtaining the desired air-fuel ratio. Therefore, until the combustion temperature sensor 35 is sufficiently heated, the supplied gas is supplied in an amount larger than that required to obtain the desired air-fuel ratio according to the signal from the air flow rate detection device 37. be done. 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 reduced 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 since the air-fuel ratio is close to the desired air-fuel ratio, ignition can be performed smoothly.

After the combustion device is ignited, when the combustion temperature sensor 35 is sufficiently heated, the proportional control valve 44, which had been energized with a current value i [A] larger by the control circuit 50, receives a current value that obtains the desired air-fuel ratio. I[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 becomes close to the desired air-fuel ratio even though the current is energized at a current value larger than A] will be described below with reference to FIG.

The air-fuel ratio is determined to be a stoichiometric air-fuel ratio depending on the type of fuel, and in a gaseous combustion apparatus such as the present invention, it is generally set to an air-fuel ratio with a high proportion of fuel. In the present invention, the blower 36 supplies air according to the setting of the temperature setting means 11, and the proportional control valve 44 is controlled by a signal from the air flow rate detection device 37 to obtain a desired air-fuel ratio.

The control circuit 5 is now set to the desired air-fuel ratio.
0, the relationship between the rotational speed N of the blower 36 and the current I to the proportional control valve 44 during steady combustion has a linear characteristic, as shown by the solid line A in FIG. The air-fuel ratio 〓 is represented by the slope of the solid line A. Here, the proportional control valve 4 for the rotation speed N ₁ of the blower 36 when the set temperature is low.
The point a indicates the current I ₁ to 4, and the proportional control valve 4 corresponds to the rotation speed N ₂ of the blower 36 when the set temperature is high.
Let b be the point indicating the current I ₂ to 4.

In a combustion device with the above relationship, after ignition,
The relationship between the rotational speed N of the blower 36 and the current I to the proportional control valve 44 when the temperature of the combustion box 20 is still low is as follows, since the current I to the proportional control valve 44 increases by i by the control circuit 50. As shown by the broken line B in FIG. 3, the solid line A is translated in parallel. Then, the point c indicating the current I to the proportional control valve 44 with respect to the rotation speed N ₁ of the blower 36 is the current value I ₁ +i, and the point d indicating the current I to the proportional control valve 44 with respect to the rotation speed N ₂ is the current value I ₂ +i respectively.

Here, if we calculate the current I to the proportional control valve 44 at the rotation speed N ₁ when the supply air is small, based on the apparent air-fuel ratio 〓' by the control circuit 50 at the rotation speed N ₂ when the supply air is large. , the current value at point e is I′ ₁ according to the chain line C, and the control circuit 50
is smaller than the current value I ₁ +i obtained by

However, if the amount of combustion is large, that is, the blower 36
When the rotational speed N of When the rotation speed N of the blower 36 is low, the amount of air blown into the combustion box 20 is small, so the flame heats the vicinity of the burner plate 33, 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 rotation speed N of the blower 36 is high, the current value to the proportional control valve 44 is increased by i [A],
Similarly, increasing the current value to the proportional control valve 44 by i [A] even when the rotational speed N is low allows the desired air-fuel ratio to be obtained even when the rotational speed N of the blower 36 is low. Therefore, a desired air-fuel ratio can be obtained over the entire range set by the temperature setting means 11, 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 I to the proportional control valve with respect to the rotation speed N; In the figure, 35... Combustion temperature sensor, 36... Air blower, 37... Air flow rate detection device, 44... Proportional control valve, 50... Control circuit.

Claims (1)

[Claims] 1. A combustion device in which a burner is disposed in a combustion case, combustion air is supplied by a blower from upstream of the burner, fuel gas is supplied via a proportional control valve, and combustion is performed downstream of the burner. , a combustion amount setting means operated by a user, comprising an air blowing amount detection device that detects the amount of air supplied by the blower based on the rotational speed of the blower, and a combustion temperature sensor that detects the combustion temperature of the burner. In order to control the blower according to the combustion amount and to set the proportional control valve to the optimum valve opening degree to obtain a desired air-fuel ratio based on the detection signal of the air blowing amount detection device and the detection signal of the combustion temperature sensor. In the combustion control device, the current value is controlled to be energized to the proportional control valve, and after ignition, until the combustion temperature reaches a predetermined temperature, the current value for setting the optimum valve opening is set to the current value. A combustion control device characterized in that the proportional control valve is energized with a current value obtained by adding a fixed current value that is set regardless of the detection signal of the airflow detection device and the detection signal of the combustion temperature sensor. 2. The combustion control device according to claim 1, wherein the predetermined temperature is a temperature reached after a time limit set by a timer has elapsed.