JP3312052B2 - Combustion control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fan control means for adjusting an output of a fan for supplying combustion air in accordance with a fuel supply amount, an oxygen concentration detecting means for detecting an oxygen concentration in combustion exhaust gas, Oxygen concentration setting means for setting an appropriate oxygen concentration corresponding to the supply amount, and the output of the fan so that the detected oxygen concentration of the oxygen concentration detecting means becomes the appropriate oxygen concentration set by the oxygen concentration setting means. The present invention relates to a combustion control device provided with a correction means for correcting.

[0002]

2. Description of the Related Art Conventionally, in such a combustion control device, a fan output is changed according to a change in fuel supply amount based on a predetermined correlation between the fuel supply amount and the fan output so as to obtain an appropriate air-fuel ratio. And the relationship between the fan output and the actual air supply amount due to variations in the device characteristics of the combustion device, aging of the device characteristics, or occurrence of ventilation problems in the air supply path or combustion exhaust gas path. The oxygen concentration in the combustion exhaust gas is detected by the oxygen concentration detecting means, and the fan output is determined based on the detected value. Was corrected. That is, conventionally, for example, as shown in Japanese Patent Application No. 4-319150 already proposed by the present applicant, in the entire fuel supply amount, an appropriate oxygen concentration preset for each fuel supply amount and the measured oxygen concentration are determined. The fan output was directly corrected based on the deviation from the density.

[0003]

However, in a normal combustion device (for example, a gas water heater), in a region where the fuel supply amount is low, as shown in FIG. 9, dew condensation and incomplete combustion in the heat exchanger are performed. In general, combustion is performed at a high excess air ratio in order to prevent the above problem. As a result, in a region where the fuel supply amount is low, the oxygen concentration increases as the fuel supply amount decreases. The excess air ratio at this time indicates the ratio between the actual amount of air and the theoretical amount of air required for complete combustion, and the excess air ratio (proper value) in FIG. 9 is obtained experimentally. Things. However, since the relationship between the oxygen concentration and the excess air ratio changes as shown in FIG. 8, when the excess air ratio is high, the change in the oxygen concentration is small with respect to the change in the excess air ratio. In other words, in the high excess air ratio region, the oxygen concentration changes only slightly even when the excess air ratio is increased by increasing the fan output and increasing the supply air amount.

Accordingly, as in the prior art, the fan output is corrected based on the difference between the proper oxygen concentration set in advance corresponding to the fuel supply amount and the actually measured oxygen concentration to correct the excess air ratio appropriately. However, there is a problem that the excess air ratio cannot be corrected more accurately in a region where the excess air ratio is high (that is, in a region where the fuel supply amount is low) than in a region where the excess air ratio is low. In other words, considering the detection error and detection accuracy of the oxygen concentration detection means and its detection circuit, etc.,
In the high excess air ratio region, the actual excess air ratio cannot be detected based on the detected oxygen concentration value of the oxygen concentration detecting means, so that the fan output cannot be properly corrected. By the way, in the region where the excess air ratio is high, in order to accurately detect the excess air ratio based on the detected oxygen concentration value, it is necessary to make the oxygen concentration detecting means and its detection circuit extremely accurate. As a result, there is a problem that the cost of the combustion control device becomes expensive. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a low-cost combustion control device capable of obtaining an appropriate excess air ratio.

[0005]

SUMMARY OF THE INVENTION A combustion control apparatus according to the present invention includes a fan control means for adjusting an output of a fan for supplying combustion air in accordance with a fuel supply amount, and an oxygen control means for detecting an oxygen concentration in combustion exhaust gas. Concentration detecting means, an oxygen concentration setting means for setting an appropriate oxygen concentration corresponding to the fuel supply amount, and an oxygen concentration detecting means for setting the detected oxygen concentration of the oxygen concentration detecting means to the appropriate oxygen concentration set by the oxygen concentration setting means. , A correction means for correcting the output of the fan, wherein the first characteristic configuration is such that when the correction means has a fuel supply amount estimated to be less than a set value,
The output of the fan is corrected based on the oxygen concentration detected by the oxygen concentration detecting means. When the fuel supply amount is estimated to be equal to or higher than the set value, the oxygen concentration is determined to be lower than the set value. The point is that the correction value is obtained based on the correction information at the time of the estimated fuel supply amount, and the output of the fan is corrected. The second characteristic configuration is such that the oxygen concentration setting means is configured to set a lower limit value and an upper limit value of an appropriate oxygen concentration corresponding to each fuel supply amount, and the correction means is provided to the oxygen concentration detection means. When the detected oxygen concentration falls below the lower limit, the fan output is increased by a predetermined value, and when the oxygen concentration exceeds the upper limit, the fan output is decreased by a predetermined value. . A third characteristic configuration is that the oxygen concentration detecting means is a limiting current type oxygen sensor, and the monitoring voltage control means for controlling the application of the monitoring voltage of the oxygen sensor is estimated that the oxygen concentration becomes less than the set value. The configuration is such that the monitoring voltage of the limiting current type oxygen sensor is applied only when the fuel supply amount is constant.

[0006]

According to the first characteristic configuration of the present invention, when the fuel supply amount is estimated to be less than the set value, the fan output is corrected based on the oxygen concentration detected by the oxygen concentration detecting means, and When the fuel supply amount is estimated to be equal to or higher than the set value, a correction value is obtained based on the correction information when the oxygen concentration is estimated to be lower than the set value, and the fan output is reduced. Will be corrected. That is, as described above, the region where the excess air ratio is high (the region of the fuel supply amount where the oxygen concentration is estimated to be equal to or higher than the set value).
In this case, since the fan output cannot be properly corrected, the fan in a region with a low excess air ratio (a region of the fuel supply amount in which the oxygen concentration is estimated to be less than the set value) in which the fan output can be properly corrected. From the output correction information, it is possible to accurately estimate the correction amount of the fan output in a region where the excess air ratio is high. According to the second feature configuration,
When the oxygen concentration detected by the oxygen concentration detection means falls below the lower limit of the appropriate oxygen concentration, the fan output is increased by a predetermined value, and when the oxygen concentration exceeds the upper limit of the appropriate oxygen concentration, the fan output is increased by a predetermined value. Decrease. That is, as shown in FIG. 10, the lower limit value to a proper oxygen concentration value X ₀ X _L and upper limit value X
Set _H, when the lower limit value X _L, or the upper limit value X
Only when the value exceeds _H , that is, when a deviation exceeding a predetermined value occurs, the fan output is changed. According to the third characteristic configuration, the monitoring voltage application of the limiting current type oxygen sensor is performed only when the oxygen supply amount is the fuel supply amount estimated to be less than the set value. The application time can be shortened, so that the deterioration of the oxygen sensor can be prevented as much as possible. still,
The limiting current type oxygen sensor will be described in more detail. Such a limiting current type oxygen sensor (hereinafter simply referred to as an oxygen sensor) is obtained by applying a DC voltage between electrodes provided on both surfaces of a disk-shaped stabilized zirconia. In addition, the oxygen concentration is detected by utilizing the fact that the current (limit current) flowing using oxygen ions as a carrier varies depending on the oxygen concentration. For this reason, if a monitoring voltage is always applied to the oxygen sensor, a limiting current always flows through the oxygen sensor, and therefore, the deterioration of the oxygen sensor is promoted.

[0007]

According to the first characteristic configuration, it is possible to accurately estimate the correction amount of the fan output in the region where the excess air ratio is high, so that special oxygen concentration detecting means and its detecting circuit are provided. Thus, a combustion control device capable of obtaining an appropriate excess air ratio with a low-cost device has been provided. According to the second feature configuration, the fan output is changed only when a predetermined deviation occurs. Therefore, even if the air amount fluctuates slightly due to disturbance, for example, the fan output is changed one by one for the fluctuation. It is possible to avoid performing unnecessary control, such as ending up, and it is not necessary to change the fan output one by one, so that the control can be further simplified. According to the third characteristic configuration, the monitoring voltage application time of the oxygen sensor during combustion can be shortened, and deterioration of the oxygen sensor can be prevented as much as possible. Therefore, the life of the oxygen sensor is extended, and the oxygen sensor is replaced. Maintenance can be reduced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the combustion control device of the present invention is applied to a hot water supply device will be described below with reference to the drawings. FIG. 1 shows a hot water supply apparatus, a water pipe type heat exchanger 1, a burner 2 for heating the heat exchanger 1, and combustion air a for the burner 2.
And a fan 4 for discharging the combustion exhaust gas eg after passing through the heat exchanger to the outside via the exhaust path 3.

A water supply passage 5 to the heat exchanger 1 has a water supply temperature ti.
Is provided with a water temperature sensor 6 for detecting the temperature and a water amount sensor 7 for detecting the water supply amount W. In the hot water supply path 8 from the heat exchanger 1,
A hot water temperature sensor 9 for detecting hot water supply temperature to is provided.
The exhaust passage 3 is provided with a limiting current type oxygen sensor (hereinafter simply referred to as an oxygen sensor) 16 as an oxygen concentration detecting means for detecting the oxygen concentration X in the combustion exhaust gas eg. In the drawing, reference numeral 10 denotes a fuel supply path for supplying the fuel gas g to the burner 2, and reference numeral 11 denotes an electromagnetic proportional valve for intermittently supplying the fuel gas and adjusting the fuel gas supply amount Ip.

In the figure, reference numeral 12 denotes a control device. The control device 12 includes an ignition / extinguishing operation section 12a for starting and stopping the combustion operation, and adjusting the fuel gas supply amount Ip (ie, adjusting the combustion amount). Hot water temperature adjusting unit 12 for adjusting hot water temperature to
b, a fan control unit 12c for adjusting the supply amount of the combustion air a by adjusting the output of the fan 4 (in this example, adjusting the rotation speed), and an adjustment target value N as an appropriate oxygen concentration corresponding to the fuel gas supply amount Ip. Concentration setting section (oxygen concentration setting means) 12d for setting the temperature, a correction section (correction means) 12e for correcting the output of the fan 4 by changing the adjustment target value N of the oxygen concentration setting section 12d, and the oxygen sensor 16 A monitoring voltage control unit (monitoring voltage control means) 12f for controlling the application of the monitoring voltage V _K is provided.

As shown in FIG. 3, the oxygen sensor 16 includes a sensor element 17, a terminal 18, a terminal block 19, and a mesh cover 20. As shown in FIG. 4, the sensor element 17 is formed by forming platinum electrodes 17b on both sides of a disk-shaped stabilized zirconia 17a and joining a cap 17d provided with a small hole 17c on one side thereof.
When a voltage (monitoring voltage) Vk is applied between both electrodes 17b,
A current using oxygen ions as carriers flows by the pumping action.

The inflow of air into the cap 17d is caused by the small holes 1
7c, the current becomes substantially constant (limit current) in a predetermined voltage range. Since this limit current changes in proportion to the oxygen concentration in the air, a constant monitoring voltage Vk is applied between both electrodes 17b, and the oxygen concentration can be detected from the current value at that time. Since the pumping action occurs at a high temperature (about 500 ° C.), a heater 17e is integrally formed above the cap 17d, and the sensor element 17 is heated by energizing the heater 17e.

The ignition / extinguishing operation unit 12a detects the amount of water by the water amount sensor 7 when the hot water tap 13 is opened and detects the electromagnetic proportional valve 1
1, the ignition mechanism 14 is operated to start the combustion operation of the burner 2, and the electromagnetic proportional valve 11 is closed by the non-detection of the water amount by the water amount sensor 7 when the hot water tap 13 is closed. The combustion operation of No. 2 is stopped.

The hot water temperature adjusting unit 12b calculates a target hot water supply temperature t from the detected hot water supply temperature ti, the detected hot water supply amount W, and the set target hot water supply temperature ts by a feedforward calculation using the following equation (1).
The fuel gas supply amount Ip ₀ ′ necessary to obtain s is calculated.

Ip ₀ ′ = q · W · (ts−ti) where q is a predetermined constant. Further, the hot water temperature adjusting unit 12
b is a deviation Δto between the detected hot water supply temperature to and the target hot water supply temperature ts.
The required correction value ΔIp is calculated by the feedback calculation based on the above, and the required correction value ΔIp by the feedback calculation is added to the fuel gas supply amount Ip ₀ ′ calculated by the feedforward calculation, thereby adjusting the fuel gas supply amount. Determine the value Ip ₀ (= Ip ₀ ′ + ΔIp).

The hot water temperature adjusting section 12b determines the operating current value i for the electromagnetic proportional valve 11 based on the setting function F1 of the fuel gas supply amount Ip and the proportional valve current i (the operating current value for the electromagnetic proportional valve 11). The target value Ip of the fuel gas supply amount
Adjusted to a value corresponding to _0, thereby, to adjust the actual fuel gas supply amount to the burner 2 to the target value Ip _0, adjust and maintain the hot water temperature to the target hot-water supply temperature ts.

The fan control unit 12c includes an oxygen concentration setting unit 1
The fan output is adjusted based on the deviation ΔN between the adjustment target value N set in 2d and the detection value detected by the rotation speed sensor 15 so that the detected value matches the adjustment target value N.

The oxygen concentration setting section 12d determines the fuel gas supply amount.
Ip and the initial set output value N of the fan 4 ₀Setting function F2
Initial setting output corresponding to each fuel gas supply amount Ip based on
Force value N₀Is set, and the initial setting output value N₀And correction unit 1
2e, based on a correction coefficient k set as described later.
Then, the adjustment target value N is set by the following equation (2).

[Number 2] N = k · N ₀

The correction unit 12e supplies a fuel gas supply amount (in this embodiment, 22%) in which the oxygen concentration is estimated to be less than the set value.
000 kcal or more), the output of the fan 4 is corrected based on the oxygen concentration X detected by the oxygen sensor 16, and the fuel gas supply amount (less than 22000 kcal) is estimated to be higher than the set value. The output of the fan 4 is corrected by obtaining a correction value based on the correction information when the oxygen gas concentration is estimated to be less than the set value.

That is, the correction unit 12e determines whether the fan output N and the actual air supply amount Q are due to variations in the device characteristics of the devices, aging of the device characteristics, or the occurrence of a ventilation failure in the air path or the exhaust path 3. To prevent the air-fuel ratio from deviating from the optimum value due to the change, the oxygen concentration is corrected by correcting the value of the correction coefficient k based on the detection information of the oxygen sensor 16. Setting unit 1
The fan output is corrected by changing the adjustment target value N of 2d. However, since the relationship between the oxygen concentration and the excess air ratio changes as shown in FIG. 8, a high excess air ratio (fuel gas supply amount I
If p is less than 22000 kcal), the fan output cannot be accurately controlled based on the detection information of the oxygen sensor 16 so as to obtain an appropriate excess air ratio.
Therefore, when the fuel gas supply amount Ip is less than 22000 kcal, as described later, the fuel gas supply amount Ip becomes 22000 kcal.
The correction value is obtained based on the correction information at the time of kcal or more, that is, the fan output is corrected using the correction coefficient k at the time of 22000 kcal or more.

The optimum excess air ratio Z ₀ for each fuel gas supply amount Ip is experimentally determined by a function F4 of the fuel gas supply amount Ip and the excess air ratio Z shown in FIG.
Since the excess air ratio Z and the oxygen concentration X have a correlation as shown in FIG. 8, the relationship between the fuel gas supply amount Ip and the excess air ratio Z in FIG. When this is replaced with the relationship shown in FIG.
That, F3 shows the proper oxygen concentration value X ₀ for the fuel gas supply amount Ip.

The oxygen concentration setting unit 12d, as shown in FIG. 10, which is configured to set the lower limit X _L and the upper limit value X _H of the proper oxygen concentration value X ₀ corresponding to the fuel gas supply amount Ip . In the present embodiment, it is set to ± 5% relative lower limit X _L and the upper limit value X _H of the proper oxygen concentration value X _0. In FIG. 9, Z _L, compared optimal excess air ratio Z _0, represents the lower limit corresponding to -5%, Z _H, the optimum air to excess ratio Z _0, + 5% corresponding to the upper limit value Is shown.

The correcting unit 12e, the oxygen concentration X, which is detected by the oxygen sensor 16 is below the lower limit value X _L, and 1.05 times the correction factor k increases the fan output N by a predetermined value, Beyond the upper limit X _H, the correction coefficient k 1 / 1.05
The fan output N is reduced by a predetermined value.

The monitoring voltage control unit 12f determines the fuel gas supply amount (22) estimated that the oxygen concentration X becomes less than the set value.
000 kcal or more), the monitoring voltage V _K of the oxygen sensor is applied.

Hereinafter, a control (fan correction control) in which the correction unit 12e corrects the value of the correction coefficient k to change the adjustment target value N of the oxygen concentration setting unit 12d and correct the fan output (fan correction control) will be described with reference to FIG. This will be described with reference to a flowchart. The correction unit 12e determines that the fuel gas supply amount Ip is 22000 kca
1 is determined (processing (a)).
kcal or more, the monitor voltage V _{K of the} oxygen sensor 16
Is applied to measure the oxygen concentration by the oxygen sensor 16, and if it is less than 22000 kcal, the monitor voltage V _K
Is stopped, and the measurement of the oxygen concentration by the oxygen sensor 16 is stopped. In the hot water supply apparatus of this embodiment, the maximum gas supply amount maxIp of the fuel gas supply amount Ip is 30,000.
kcal, and the fan output N is up to 440
It is specified at 0 rpm.

The fuel gas supply amount Ip is 22000 kcal
In this case, after the fuel gas supply amount Ip is changed and the fan output target value N is changed, a waiting time of 30 seconds is provided until the atmosphere environment of the oxygen sensor 16 is stabilized (processing ( B)) Then, the measurement operation of the oxygen sensor 16 is started. The output X of the oxygen sensor 16 is first once / second at 10 times measured by calculating the average value X ₁ (1-th set), then again it measured 10 times at one time / 1 second average value X ₂ Is calculated (the second set). Then, the error ΔX between the two sets of measurement results X ₁ and X ₂ before and after is calculated by the following equation 3, and the error ΔX
The measurement by the oxygen sensor 16 is repeatedly performed until X becomes within 1% (process (c)).

ΔX = (| X ₁ −X ₂ | / X ₂ ) × 100 (%)

The error ΔX between the front and rear two sets is within 1%
And the average value X_TwoTo the lower limit X_LAnd upper limit X_HCompare with
And the average value X_TwoIs the lower limit X_LIf so, the correction coefficient k
1.05 times the fan output by 1.05 times
And the average value X_TwoIs the upper limit X _HIf less than, the correction coefficient
By multiplying k by 1 / 1.05, the fan output is reduced by 1 /
It is increased to 1.05 times (processing (d)). Therefore, the fan output
N is one step from k = 1.0 as shown in FIG.
Will be changed. Further, the correction coefficient k is supplemented as described above.
Check whether the fuel gas supply amount Ip is constantly changed
It is checked whether or not the fuel gas supply amount Ip is changed.
For example, it is configured to return to the process (a) again.
Further, the correction coefficient k may be such that the power supply of the apparatus is stopped.
E^TwoPROM (non-volatile memory)
Has been updated.

During the above control, the value of the correction coefficient k is constantly monitored, and in a state where the maximum gas supply amount maxIp is not limited (maxIp = 30000 kcal), when k ≧ 1.22, the maximum gas supply amount maxIp
Is limited to 26000 kcal (87% output at maximum) (gas amount limitation), an abnormal lamp (not shown) is turned on, and the above control is executed again ((processing (e)). This is because the fan capacity is limited (440)
0 rpm) to prevent the device from running out of air volume and causing incomplete combustion, and to prevent the device from suddenly stopping and causing inconvenience to the user.

After the gas amount is restricted, when the correction coefficient returns to k ≦ 1.16, the gas amount restriction is released and the abnormal lamp is turned off ((processing (f)). This is to prevent the control from continuing unnecessarily while the gas amount is small when the gas amount is limited as described above due to a temporary decrease in the air amount such as the reverse wind pressure.

As described above, if k ≧ 1.28 despite the gas amount restriction, the combustion is determined to be abnormal, and the combustion is stopped ((processing (g)). During the above control, the fuel gas supply amount Ip is constantly monitored, and the fuel gas supply amount Ip is 22,000 kc.
If the value is equal to or more than al, the change of the correction coefficient k is executed at any time as described above. However, if the value is less than 22000 kcal, the change of the correction coefficient k is stopped (process (h)), and the value of the correction coefficient k before that is changed. Is controlled based on the fan output.

The correction coefficient k by the correction unit 12e described above
Is changed from the set rise time Ta from the start of energization to the heater 17e (in this example, the temperature of the oxygen sensor 16 is changed to the stable temperature th from the start of energization to the heater 17e along with the start of combustion operation of the burner 2). (See FIG. 5) after the elapse of a set time Ta).

Next, control by the controller 12 after the start of combustion is commanded will be described with reference to the flowchart of FIG. As the start of combustion is instructed, that is, hot water tap 1
3 is opened and the water amount sensor 7 for detecting the water supply amount W is turned on, the energization of the heater 17e of the oxygen sensor 16 and the operation of the fan 5 are started (processing (nu)), and the electromagnetic proportional valve The gas valve 11 is opened and the burner 2 is ignited. However, actually, the opening of the gas valve and the ignition of the burner 2 are performed about one second later than the operation of the fan 5.

The time Ta until the oxygen sensor 16 (sensor element 17) is heated to an appropriate state by the heater 11e, that is, until the oxygen sensor 16 reaches a stable temperature (for example, 500 ° C.).
(About 1 minute). So, during this time, k
= 1.0 fan initial value control is executed (process (l)). That is, until the detection of the oxygen sensor 10 becomes possible (until the temperature of the oxygen sensor 10 reaches a stable temperature).
Control.

The control device 12 has an internal timer (not shown)
The time during which the fan initial value control is performed is managed. The internal timer is reset at the start of combustion (start of energization of the heater 17e) and starts counting. Then, when the internal timer reaches the set rise time Ta (1 minute), the control of the fan 4 is shifted from the fan initial value control to the above-described fan correction control (FIG. 7) (process (e)). As described above, the control of the fuel supply amount by adjusting the opening of the electromagnetic proportional valve 11 is performed at the same time.

When the hot water tap 13 is closed and the water amount sensor 7 is turned off, the electromagnetic proportional valve 11 is closed and the combustion is stopped (process (W)). The fan 4 continues to operate at a predetermined output, and performs a post-purge, that is, an exhaust operation after the combustion is stopped for a predetermined time. When the predetermined time has elapsed, the fan 4 is stopped, the energization of the oxygen sensor 16 (the energization of the heater 11e and the application of the monitoring voltage) is stopped, and the operation is terminated (process (f)).

[Another embodiment] Next, another embodiment will be described. The fan output adjustment by the fan control unit 12c may be performed by using a fan drive current or voltage as an adjustment index instead of using the fan rotation speed as an adjustment index as in the above-described embodiment. In the above embodiment, the fan 4 is provided on the side of the supply path of the combustion air a, and the fan 4 supplies the combustion air a to the burner 2 under pressure. To supply the combustion air a to the burner 2 with the suction and exhaust of the combustion exhaust gas eg by the fan 4. In the above embodiment, the correction coefficient k is reset to the initial value 1 every time the combustion is stopped. However, the correction coefficient k is stored and stored in the storage device, and is stored and stored when the combustion is restarted. The fan output may be controlled using the correction coefficient k. In the above embodiment, the oxygen concentration X, which is detected by the oxygen sensor 16 is below the lower limit value X _L, increases the fan output by a predetermined value, if the value exceeds the upper limit X _H, the fan output predetermined value The fan output N may be directly corrected based on the difference between the oxygen concentration X detected by the oxygen sensor 16 and the appropriate oxygen concentration X ₀ . In the above embodiment, the example in which the combustion control device of the present invention is applied to a hot water supply device is described. However, the present invention is not limited to the hot water supply device, and can be applied to other combustion devices. Further, the oxygen concentration detecting means in the above embodiment is not limited to the limiting current type oxygen sensor 16 and can be variously changed.

In the claims, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the configuration shown in the attached drawings.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a water heater.

FIG. 2 is a control block diagram.

FIG. 3 is a sectional view of an oxygen sensor.

FIG. 4 is a sectional view of a sensor unit.

FIG. 5 is a rise characteristic diagram of the oxygen sensor.

FIG. 6 is a flowchart showing control by a control unit.

FIG. 7 is a flowchart showing the control of the control means.

FIG. 8 is a graph showing the relationship between the excess air ratio and the oxygen concentration.

FIG. 9 is a graph showing a relationship between a fuel supply amount and an excess air ratio.

FIG. 10 is a graph showing a relationship between a fuel supply amount and an oxygen concentration.

FIG. 11 is a graph showing a relationship between a fuel supply amount and a fan output.

[Explanation of symbols]

 Reference Signs List 4 fan 12c fan control means 12d oxygen concentration setting means 12e correction means 12f monitoring voltage control means 16 oxygen concentration detection means

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Kamiya 1-52-1, Oka, Minami-shi, Minato-ku, Osaka, Osaka Prefecture Herman Co., Ltd. (72) Yoshikatsu Ishikawa 1-1-1, Oka, Minami-shi, Minato-ku, Osaka, Osaka No. 52 Harman Co., Ltd. (56) References JP-A-60-228819 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F23N 1/02 101 F23N 3/08 F23N 5 / 24 107 G01N 27/41

Claims (3)

(57) [Claims] A fan control means (12) for adjusting an output of a fan (4) for supplying combustion air in accordance with a fuel supply amount.
c), oxygen concentration detecting means (16) for detecting the oxygen concentration in the combustion exhaust gas, oxygen concentration setting means (12d) for setting an appropriate oxygen concentration corresponding to the fuel supply amount, and the oxygen concentration detecting means (16). The correction means (12) for correcting the output of the fan (4) so that the detected oxygen concentration of (2) becomes the appropriate oxygen concentration set by the oxygen concentration setting means (12d).
e) wherein the correction means (12e) detects the detected oxygen by the oxygen concentration detection means (16) when the fuel supply amount is estimated to be less than the set value. The output of the fan (4) is corrected based on the concentration, and when the oxygen concentration is the fuel supply amount estimated to be equal to or higher than the set value, the fuel supply is estimated to be lower than the set value. A combustion control device configured to calculate a correction value based on correction information in the case of an amount and to correct the output of the fan (4). 2. The oxygen concentration setting means (12d) is configured to set a lower limit value and an upper limit value of an appropriate oxygen concentration corresponding to each fuel supply amount, and the correction means (12e) includes: When the oxygen concentration detected by the oxygen concentration detecting means (16) falls below the lower limit, the fan output is increased by a predetermined value, and when it exceeds the upper limit, the fan output is decreased by a predetermined value. The combustion control device according to claim 1, wherein the combustion control device is configured as follows. 3. The oxygen concentration detection means (16) is a limiting current type oxygen sensor, and a monitoring voltage control means (12f) for controlling the application of a monitoring voltage of the oxygen sensor includes: 3. The combustion control device according to claim 1, wherein the monitoring voltage of the limiting current type oxygen sensor is applied only when the fuel supply amount is estimated to be less than the fuel supply amount.