JP2825213B2 - Combustion equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel adjusting means for adjusting a fuel supply amount to a burner, a ventilation means for supplying combustion air to a combustion portion, and an air supply amount to the combustion portion by the ventilation means. Detecting the amount of air, controlling the fuel adjusting means according to the combustion load, and maintaining the detection value of the air amount detecting means at a target value determined according to the fuel supply amount. And a control means for controlling the ventilation means.

[0002]

2. Description of the Related Art There is a combustion apparatus which adjusts the amount of air supplied to a combustion section using a ventilation means (for example, an electric fan) so that an appropriate amount of air is supplied according to the amount of fuel supplied to a burner. (For example, JP-A-63-2040).
No. 17).

In this type of combustion apparatus, air amount detecting means for detecting the amount of air supplied to the combustion section is provided, and the detected value is determined by the amount of fuel supplied to the burner adjusted by the fuel adjusting means. The blowing capacity of the ventilation means is controlled so as to be maintained at a target value determined accordingly. As a result, even if the blowing capacity is reduced due to, for example, dust adhesion, the driving amount of the ventilation means (for example, the rotation speed of the electric fan) is increased and the required air supply amount is secured.

[0004] However, when the ventilation means reaches the upper limit of the blowing capacity, a necessary air supply amount cannot be secured. In such a case, incomplete combustion occurs, so it is necessary to perform a process such as immediately stopping the combustion. Therefore, conventionally, when it is determined that the ventilation capacity of the ventilation means is in a limit state based on the detection value of the air amount detection means and the like, the fuel supply to the burner is stopped.

[0005]

However, even if the incomplete combustion is avoided as described above, if the combustion is suddenly stopped, it is inconvenient for the user. The present invention has been made in view of such circumstances, and its purpose is to always stop the combustion when the air supply amount shortage occurs due to the limit of the ventilation capacity of the ventilation means as described above. Rather, in some cases, it is another way to avoid incomplete combustion.

[0006]

According to the present invention, there is provided a combustion apparatus comprising: a fuel adjusting means for adjusting an amount of fuel supplied to a burner; a ventilation means for supplying combustion air to a combustion part; Air amount detecting means for detecting an air supply amount to the fuel control means according to a combustion load, and a detection value of the air amount detecting means is set to a target value determined according to the fuel supply amount. Control means for controlling the ventilation means so as to be maintained, wherein a first characteristic configuration is such that the operation amount given to the fuel adjustment means by the control means is a maximum value on the fuel supply amount increasing side. In addition, when the operation amount given to the ventilation means reaches a maximum value on the side of increasing the air supply amount, the operation amount given to the fuel adjustment means is reduced by a predetermined amount.

A second characteristic configuration is that the operation amount given to the fuel adjustment means by the control means is a maximum value on the fuel supply amount increasing side, and the operation amount given to the ventilation means is the air supply amount increasing side. When the detected value of the air amount detecting means does not reach the target value even when it reaches the maximum value, the operation amount given to the fuel adjusting means is reduced by a predetermined amount.

[0008]

In general, the decrease in the ventilation capacity of the ventilation means due to dust clogging or the like gradually progresses, and it is rare that a large decrease in the capacity suddenly occurs from a certain time. Therefore, according to the first characteristic configuration, the control means is configured such that the operation amount given to the fuel adjustment means to the burner is the maximum value on the fuel supply amount increasing side, and the operation amount given to the ventilation means is the air supply amount increasing side. Is detected, the operation amount given to the fuel adjusting means is reduced by a predetermined amount.

Here, the operation amount given to the ventilation means means, for example, the applied voltage when the ventilation means is an electric fan and the number of rotations (blowing amount) is changed by changing the applied voltage. Similarly, the operation amount given to the fuel adjustment means refers to, for example, the current when the fuel adjustment means is a proportional solenoid valve and the opening (fuel supply amount) is changed by changing the current. However, not only the case where the control means can directly recognize the operation amount inside the control means, but also the case where the operation amount (state quantity) of the applied voltage or the like is detected through the external detection means is included.

Therefore, when the ventilation means is in the upper limit state of the ventilation capacity and the fuel supply amount is the maximum, the shortage state of the air supply amount is released by reducing the fuel supply amount by a predetermined amount, and incomplete combustion is performed. Will be avoided. That is, although the combustion capacity is reduced by a predetermined amount, the usability is much better than when the combustion is stopped. Then, for example, the maintenance lamp is turned on to request maintenance. If maintenance such as removal of dust is properly performed, the ventilation means will restore the initial blowing ability.

The condition for performing the above-mentioned control not only that the ventilation means is in the upper limit state of the blowing capacity but also that the fuel supply amount is the maximum is determined when the blowing capacity is gradually reduced. The upper limit of the ventilation capacity of the ventilation means
This is because the fuel supply occurs first in the maximum state.
That is, the greater the fuel supply amount, the more the supply of combustion air is required.

Therefore, when the processing for reducing the fuel supply amount by a predetermined amount is performed once when both of the above conditions are satisfied, and the upper limit state of the blowing capacity is still not released, that is, when the operation amount given to the ventilation means is air, When the maximum value on the supply amount increasing side is maintained, the control is not performed by the above-described feature configuration. In this case, for example, processing such as stopping the combustion is performed as usual.

The operation according to the second characteristic configuration is substantially the same as the operation according to the first characteristic configuration, except for the air supply amount of the two conditions for performing the process of reducing the fuel supply amount by a predetermined amount. The difference is that the condition is that the detection value of the air amount detection means does not reach the target value even if the operation amount given to the ventilation means reaches the maximum value on the side of increasing the air supply amount.
Therefore, when the operation amount given to the ventilation means by the predetermined control reaches the maximum value on the side of increasing the air supply amount, it is excluded.

[0014]

As described above, according to the combustion apparatus of the present invention, when the air supply becomes insufficient due to the limit of the ventilation capacity of the ventilation means, the combustion is not always stopped, but the ventilation capacity is gradually increased. When the air supply amount is insufficient due to the decrease, the combustion is continued by decreasing the combustion capacity by a predetermined amount, so that the usability is improved.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a water heater will be described below with reference to the drawings. The water heater of the present embodiment is configured as shown in FIG. A fin tube type heat exchanger 4 for heating water by a high-temperature exhaust gas from a combustion section 3 having a burner 2 is provided in a cylindrical case 1. The lower end of the cylindrical case 1 is connected to the discharge side of a fan 5 as ventilation means for supplying combustion air to the combustion section 3, and the upper end of the cylindrical case 1 is connected to an exhaust passage 6.

The fuel supply path 7 to the burner 2 is provided with a gas proportional valve 8 as a fuel adjusting means for adjusting the fuel supply amount. The opening of the gas proportional valve 8 is controlled by a combustion controller 9 as control means. The combustion controller 9 controls the fuel supply amount via the gas proportional valve 8 so as to reduce the deviation between the set hot water temperature set by the setting means R and the hot water temperature detected by the hot water detecting means S.

That is, the proportional valve driving circuit 9a in the combustion controller 9 drives the gas proportional valve 8 with an exciting current determined based on the deviation between the set hot water temperature and the detected hot water temperature. Therefore, this exciting current corresponds to the operation amount given to the gas proportional valve 8.

In order to control the hot water temperature, it is necessary to appropriately control not only the amount of fuel supplied to the burner 2 but also the amount of combustion air supplied to the combustion section 3. Therefore, the combustion controller 9 also controls the amount of air blown by the fan 5, that is, the number of revolutions. Further, a ceramic oxygen sensor 10 for detecting the oxygen concentration in the exhaust gas is provided in the exhaust passage 6 as an air supply amount detecting means for detecting an air supply amount to the combustion unit 3.

The ceramic oxygen sensor (hereinafter simply referred to as oxygen sensor) 10 indirectly detects the amount of air supplied to the combustion section by detecting the oxygen concentration in the exhaust gas after combustion. That is, if the amount of air supplied to the combustion section is excessive, the oxygen concentration (remaining amount) in the exhaust gas is large. Conversely, if the air supply amount is insufficient, the oxygen concentration (remaining amount) in the exhaust gas is large.
Is smaller.

The oxygen sensor 10 detects that when a predetermined voltage is applied between the electrodes provided on both sides of the disk-shaped stabilized zirconia, the current (limit current) flowing with oxygen ions as a carrier changes according to the oxygen concentration. Utilization is used to detect oxygen concentration. The detection value (current value) of the oxygen sensor 10 is input to the combustion controller 9, and the combustion controller 9 controls the fan 5 so that the detection value is maintained at a target value determined according to the amount of fuel supplied to the burner 2.
The number of revolutions is controlled to regulate the supply of combustion air. The target value of the oxygen concentration is an appropriate value obtained by an experiment, and changes according to the fuel supply amount (gas proportional valve current) as shown in FIG.

The rotation speed of the fan 5 is controlled by changing the voltage applied to the fan motor (DC motor). That is, the fan drive circuit 9 in the combustion controller 9
b drives the fan 5 with a voltage determined based on the deviation between the value detected by the oxygen sensor 10 and the target value. Therefore, this voltage corresponds to the operation amount of the fan 5.

As described above, the voltage applied to the fan 5 (hereinafter referred to as
The fan voltage is determined based on the deviation between the value detected by the oxygen sensor 10 and its target value.
As shown in (2), the higher the fuel supply amount (gas proportional valve current), the higher the voltage. This is because a larger amount of fuel supply requires more combustion air.

In FIG. 4, the initial characteristics of the solid line L0 are as follows.
At the maximum value Imax of the gas proportional valve current, the fan voltage has a margin Vs with respect to the maximum value Vmax. However, when the blowing capacity of the fan 5 is reduced due to the attachment of dust or the like, the fan voltage for obtaining the same air supply amount is increased, and the characteristics as shown by the one-dot chain line L1 or the broken line L2 are obtained.

In the characteristics of the dashed line L1, the fan voltage is equal to the maximum value Vmax at the maximum value Imax of the gas proportional valve current.
max and there is no room at all. When the air blowing performance decreases to the characteristic indicated by the broken line L2, the fan voltage saturates to the maximum value Vmax when the gas proportional valve current is equal to or higher than Ir. As a result, as shown by the broken line in FIG. 3, the detection value of the oxygen sensor 10 greatly decreases when the gas proportional valve current is equal to or higher than Ir, and the target oxygen concentration cannot be secured. This means that incomplete combustion occurs, and it is necessary to avoid such a condition.

Therefore, in the water heater of the present embodiment, the combustion controller 9 sets the gas proportional valve current to the maximum value Imax.
In addition, when the fan voltage reaches the maximum value Vmax, control is performed such that the gas proportional valve current is reduced by a predetermined amount (for example, 10%). Thus, for example, if the gas proportional valve current Ir is 90% of Imax,
Combustion can be continued without saturation of the fan voltage up to the characteristic indicated by the broken line L2. Specifically, the control as shown in the flowchart of FIG. 2 is performed.

FIG. 2 shows an outline of the processing of the combustion controller 9 from the start of combustion at the start of hot water supply to the stop of combustion at the stop of hot water supply. Start of hot water supply and stop of hot water supply are detected by an on / off signal of a water flow switch 15 provided in the water supply passage. After the drive of the fan 5 (prepurge), the opening of the gas proportional valve 8 and the like, and the ignition, the control of the gas proportional valve 8 and the fan 5 is performed as described above (process (A)). at the same time,
The maximum values of the fan voltage and the gas proportional valve current are checked (process (b)). The maximum value check of the fan voltage is valid when the maximum value continues for a predetermined time (for example, 5 seconds) in order to prevent erroneous determination.

As a result of the check, if the fan voltage and the gas proportional valve current are both maximum values, the gas proportional valve current is reduced by a predetermined amount (for example, 10%), and the maintenance lamp 16 provided in the setting means R is turned on. After that, the combustion control is continued. The maintenance lamp 16 is reset after predetermined maintenance such as replacement of the fan 5 and removal of dust is performed.

If the fan voltage is at the maximum value and the gas proportional valve current is not at the maximum value, the maintenance lamp 16 is turned on as abnormal and then combustion is stopped. Therefore,
If the state in which the fan voltage is at the maximum value is not released even after executing the processing for reducing the gas proportional valve current by a predetermined amount (for example, 10%), the processing for stopping the combustion is performed. Note that the combustion stop process is also performed when the water flow switch 15 is turned off. The combustion stop process includes closing the gas proportional valve and the like, stopping the fan 5 after the post-purge, and the like.

Another embodiment will be described below. In the above embodiment, the gas proportional valve current is reduced by a predetermined amount if the two conditions of the fan voltage being the maximum value and the gas proportional valve current being the maximum are configured. The condition may be that “the detected value of the oxygen sensor does not reach the target value even if the fan voltage reaches the maximum value”. In this case, when the fan voltage reaches the maximum value (special case) by the predetermined control, the condition is excluded from the condition.

In the above-described embodiment, the combustion controller 9 is configured to be capable of monitoring the current value, which is the operation amount applied to the gas proportional valve 8, and the applied voltage, which is the operation amount applied to the fan 5 ( In practice, the digital output values corresponding to them are checked.) However, for example, the PID using the OP
When the operation amount cannot be directly checked as in the case of a control circuit, a means for detecting the gas proportional valve current or the fan voltage may be provided, and the detected value may be fed back to the combustion controller 9.

The operation amount is not limited to the gas proportional valve current or the fan voltage, and may be, for example, the rotation speed of a fan. The ventilation means is not limited to the blower fan, but may be a suction fan provided on the exhaust side.

Incidentally, reference numerals are written in the claims for convenience of comparison with the drawings, but the present invention is not limited to the configuration of the attached drawings by the entry.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a water heater according to an embodiment of the present invention.

FIG. 2 is a flowchart showing processing of a control means (combustion controller).

FIG. 3 is a graph showing a relationship between a fuel supply amount (gas proportional valve current) and an oxygen concentration target value.

FIG. 4 is a graph showing a relationship between a fuel supply amount (gas proportional valve current) and a fan voltage (operating amount of a blowing unit).

[Explanation of symbols]

 2 Burner 3 Burning part 5 Ventilation means 8 Fuel adjustment means 9 Control means 10 Air amount detection means

Claims (2)

(57) [Claims] 1. A fuel adjusting means (8) for adjusting a fuel supply amount to a burner (2), a ventilation means (5) for supplying combustion air to a combustion part (3), and the ventilation means (5). Means for detecting the amount of air supplied to the combustion section (3) by the air conditioner, and means for controlling the fuel adjusting means (8) according to the combustion load, and the means for detecting the amount of air (10) And a control means (9) for controlling the ventilation means (5) such that the detected value is maintained at a target value determined in accordance with the fuel supply amount, wherein the control means (9) The amount of operation given to the fuel adjusting means (8) is the maximum value on the fuel supply amount increasing side, and the ventilation means (5)
A combustion device configured to reduce the operation amount applied to the fuel adjusting means (8) by a predetermined amount when the operation amount applied to the fuel supply unit reaches the maximum value on the air supply amount increasing side. 2. A fuel adjusting means (8) for adjusting a fuel supply amount to a burner (2), a ventilation means (5) for supplying combustion air to a combustion part (3), and the ventilation means (5). Means for detecting the amount of air supplied to the combustion section (3) by the air conditioner, and means for controlling the fuel adjusting means (8) according to the combustion load, and the means for detecting the amount of air (10) And a control means (9) for controlling the ventilation means (5) such that the detected value is maintained at a target value determined according to the fuel supply amount, wherein the control means (9) comprises: The amount of operation given to the fuel adjusting means (8) is the maximum value on the fuel supply amount increasing side, and the ventilation means (5)
When the detected value of the air amount detecting means (10) does not reach the target value even if the operating amount given to the fuel supply amount reaches the maximum value on the air supply amount increasing side, the operating amount given to the fuel adjusting means (8) is determined. A combustion device configured to reduce by a fixed amount.