JP3343007B2 - 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 combustion device that controls an amount of air supplied from a fan motor to a combustor to perform ideal combustion.

[0002]

2. Description of the Related Art FIG. 8 is a block diagram showing a conventional combustion control apparatus. In the figure, reference numeral 1 denotes a burner as a combustor, 1a
Is a combustion chamber, 1b is an outlet of the combustion chamber 1a, 1c is an igniter for igniting a burner (combustor) 1, and 2a is a fan motor for controlling the amount of air supplied to the burner 1 in accordance with the rotation speed.

An air flow sensor 3 detects the amount of air supplied to the burner 1. 5 is burner 1
Is a shutoff valve provided upstream of the proportional valve 5.

[0004] Further, a control unit 8 controls the fuel by the proportional valve 5 in accordance with the target combustion amount, and controls the fan motor 2a.
Of the fan motor 2 so that the air amount detected by the air flow sensor 3 is constant.
This is an arithmetic unit as a combustion control circuit for controlling the number of revolutions of the motor.

Next, the operation will be described. FIG. 9 is a characteristic diagram showing the relationship between the amount of air supplied to the burner 1 and the output of the air flow sensor 3. The characteristic equation in the initial state is y = ax.
And FIG. 10 is a characteristic diagram showing the relationship between the amount of air supplied to the burner 1 and the number of rotations of the fan motor 2a. The characteristic equation in the initial state is r = bx.

In this case, since the exhaust gas from the combustion chamber 1a is discharged outside, if the wind is received at the exhaust port 1b, the rotational speed of the fan motor 2a does not need to be increased to obtain the same amount of air as when there is no wind. Not be. Therefore, in this case, FIG.
R = b ₂ x.

Next, a procedure for correcting an error due to aging of the air flow sensor 3 will be described. First, when the ignition of the burner 1 performs an ignition operation after a certain amount of air x ₀ determined in advance.

The output of the air flow sensor 3 corresponding to the amount of air at the time of ignition and the rotation speed of the fan motor 2a when there is no influence of wind on the exhaust port 1b are stored in the computing unit 8 in advance as initial values. Keep it.

That is, assuming that the air amount at the time of ignition is x ₀ , the sensor output y _{0 of the} air flow sensor 3 is shown in FIG.
From FIG. 10, the rotational speed r ₀ of the fan motor 2 a is stored in the arithmetic unit 8.

Subsequently, at the start of the ignition operation of the burner 1,
First, the rotation speed of the fan motor 2a is controlled so that the air amount becomes x ₀ , that is, the output of the air flow sensor 3 becomes the initial value y _0.
The number of revolutions performed the ignition operation after the storage to the combustion control circuit 8 as r _01.

However, as shown in FIG. 10, the difference | r ₀₂ -r ₀ | between the rotation speed r ₀₂ of the fan motor 2a and the initial rotation speed r ₀ at this time is larger than a predetermined Δr _0. time, it is determined that there is the influence of the wind to the exhaust port 1b, it does not store the rotational speed r ₀₂ at this time.

[0012] Thus, the rotational speed at the start of the next ignition operation and r _02. On the other hand, when | r ₀₂ −r ₀ | is larger than r _max , it is determined that the air flow sensor 3 is abnormal, and the ignition operation is stopped.

Thereafter, every time the ignition operation is performed, the number of revolutions of the fan motor 2a at each ignition time is changed to r ₁ , r ₂ , r ₃ ,.
successively stores and r _n. Then, when the number of stored rotation number data becomes n, an average value r _av of the n number of rotation number data is obtained.

Then, the stored initial value r _{0 of} the fan motor 2a and the average value r _av are compared, and when there is a difference | r ₀ −r _av | ≧ μ over a certain value μ, the air speed is reduced. It is determined that the flow sensor 3 has an error due to aging.

Then, based on the initial value r ₀ and the average value r _{av of the} number of revolutions of the fan motor 2a, the characteristic equation between the air amount and the output of the air flow sensor 3 shown in FIG. , The initial value y ₀ of the output of the air flow sensor 3 is updated.

As described above, conventionally, the output of the air flow sensor 3 at a certain point and the fan motor 2a
The rotational speed of the air flow sensor 3 is stored in advance as an initial value, and the aging of the air flow sensor 3 is detected and corrected based on the difference from the subsequent rotational speed.

When the burner 1 has been used for a long time, dust adheres to the intake port and soot adheres to the exhaust path, so that the intake / exhaust path from the intake port to the exhaust port 1b gradually increases. The air permeability becomes worse (hereinafter, this is called clogging).

As described above, in order to obtain the same amount of air as that of a new product in a clogged state, the fan motor 2
It is necessary to increase the capacity of the fan 9, and therefore, control is performed so as to increase the rotation speed of the fan motor 29.

[0019]

Since the conventional combustion control device is constructed as described above, even if the air flow sensor 3 does not change over time, the characteristic of the rotation speed of the fan motor 29 with respect to the air amount is obtained. Has the same characteristics as when the drift shown in FIG. 10 occurs in the air flow sensor 3, the drift cannot be distinguished from the above-described clogging, and the clogging is erroneously determined as the drift. There were problems such as making corrections.

Since such correction works in the direction of reducing the amount of air, the burner 1 is in the direction of generating carbon monoxide, which is extremely dangerous.

Further, since the degree of the clogging cannot be easily confirmed by eyes, there is a problem that even if the clogging is severe, the clogging is used as it is, and the above danger cannot be avoided.

The present invention has been made in order to solve the above-described problems. Even if dust adheres to an intake port or soot adheres to an exhaust passage, clogging occurs.
An object of the present invention is to provide a combustion control device that can realize ideal air-fuel ratio control of a burner by performing correction in consideration of the clogging, thereby enabling safe combustion control.

[0023]

According to a first aspect of the present invention, there is provided a combustion control apparatus for detecting a flow rate and rotation of air detected by a flow rate detector when a blower is operated without performing feedback control for a predetermined period. A combustion control circuit is provided for detecting a change in the characteristics of the flow rate detector and a change in the number of rotations of the blower by comparing the number of rotations of the blower detected by the number detector with a set value.

According to a second aspect of the present invention, there is provided a combustion control apparatus wherein the detected flow rate is corrected by a combustion control circuit so as to eliminate a change in the characteristic of the flow rate detector and a change in the rotation speed of the blower.

According to a third aspect of the present invention, there is provided a combustion control apparatus in which a blower is controlled at a constant current or a constant voltage for a predetermined period.

According to a fourth aspect of the present invention, there is provided a combustion control apparatus wherein a predetermined period is provided before starting combustion or after stopping combustion in the combustor.

According to a fifth aspect of the present invention, there is provided a combustion control apparatus, wherein a predetermined period is provided at a predetermined number of times of ignition or at a predetermined time.

According to a sixth aspect of the present invention, the constant current value or the constant voltage value controlled by the constant current control or the constant voltage control is set to a value in the vicinity of the maximum combustion air amount. Things.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. In FIG. 1, reference numeral 11 denotes a case of a combustion device main body having a box shape as a whole, and an intake port 12 for taking in outside air is provided at a lower left portion of the case 11.

Reference numeral 13 denotes the intake port 1 in the case 11.
2 Fan motors as blowers arranged in the vicinity, 14
Is an air passage for guiding air sent from the fan motor 13 into the combustion chamber 15 installed in the case 11.

The combustion chamber 15 has an exhaust port 16 on the upper right side, and the exhaust port 16 projects out of the case 11 through a through hole 17 provided on the upper right side of the main body 11 of the combustion device.

The fan motor 13 is provided with a rotation speed detecting means 18. As the rotation speed detecting means 18, for example, a device in which a magnet is provided on the rotor side of the fan motor 13, a Hall IC is provided on the stator side, and a pulse signal corresponding to the rotation speed of the rotor is detected is used.

Reference numeral 19 denotes an air flow sensor which is disposed in the middle of the air passage 14 and serves as an air flow rate detector.
Is a burner as a combustor provided in the combustion chamber 15, and fuel can be supplied to the burner 20 through a fuel passage 21. Reference numeral 22 denotes a proportional valve provided in the middle of the fuel passage 21.

Numeral 23 denotes a combustion control circuit as a combustion control means by hardware or software. The combustion control circuit 23 adjusts the opening of the proportional valve 22 in accordance with a combustion amount setting signal supplied from the outside to control the amount of fuel sent to the burner 20. In addition to the control, the control of the amount of air supplied to the burner 20 is optimally performed according to the respective detection outputs of the rotation speed detecting means 18 and the air flow sensor 19.

Next, the operation will be described. First, on the fuel side, the amount of fuel supplied to the burner 20 is varied as described above in accordance with a signal supplied from the combustion control circuit 23 to the proportional valve 22, and the burner 20 can obtain an arbitrary amount of combustion. For example,
In the water heater, a certain amount of combustion is determined by a feedforward calculation by a set temperature, an input water temperature sensor, and a sensor of a tap water flow rate, and the combustion amount is finely adjusted by a feedback signal from the tap water temperature sensor.

On the other hand, on the combustion air side, the air taken into the case 11 from the air supply port 12 is supplied to the fan motor 13.
Is forced into the combustion chamber 15 through the air passage 14 and the air flow sensor 19.

At this time, the amount of air flowing into the combustion chamber 15 is detected by the air flow sensor 19, and the detection signal is fed back to the combustion control circuit 23, and the electric power supplied to the fan motor 13 in accordance with the detection signal. Is controlled, an arbitrary amount of air can be sent to the combustion chamber 15.

The combustion control circuit 23 uses the previously stored air amount control characteristic as shown in FIG.
The supply of the air amount at which an ideal combustion amount is obtained in the burner 20 is performed by controlling the electric power to the fan motor 13 based on a feedback signal from the air flow sensor 19.

On the other hand, the output signal of the air flow sensor 19 with respect to the amount of air is as shown in FIG. 3. First, the power supplied to the fan motor 13 is controlled based on the initial characteristics so that the desired amount of air is obtained. I just need.

However, when the air flow sensor 19 changes over time, this output signal drifts as shown by the dotted line in FIG. 3 and changes in the vertical direction of the initial characteristic. If so, the desired amount of air cannot be obtained, and as a result, the burner 20 cannot continue ideal combustion.

The fan motor 13 is normally subjected to feedback control using a signal from the air flow sensor 19, but the fan motor 13 is temporarily driven with a constant current for drift detection. By doing so, the output signal of the air flow sensor 19 is changed due to the drift.
The characteristics are as shown in FIG.

As shown in FIG. 4, the fan motor 13
Is driven by the fan drive current a (A), the sensor output of the initial characteristics that does not change over time becomes bo (V), but due to the drift, the sensor output becomes b ′.
(V) or b ″ (V), which causes a deviation from the initial characteristics, so that drift detection can be performed.

However, when clogging occurs in the intake and exhaust passages of the combustion equipment as described above, or when the fan motor is deteriorated and its performance is reduced, the drift similar to the negative (-) side drift in FIG. Since it will be output, it is necessary to identify the contents of the shift.

When the sensor output drifts to the plus (+) side, it can be immediately determined that the drift has occurred. Therefore, the drift in a dangerous direction that reduces the amount of air and generates carbon monoxide can be easily detected.

Therefore, the fan rotation speed when the fan motor 13 is driven at a constant current in the same manner as described above is obtained to obtain a rotation speed characteristic as shown in FIG. According to this, when the fan motor 13 is driven by, for example, a (A), the fan rotation speed when there is no clogging or a decrease in the performance of the fan motor 13 is C ₀ (rpm).

However, when clogging occurs, the fan speed increases to C ′ (rp · m). On the other hand, when the performance of the fan motor 13 decreases, C ″ (rp · m) and the fan speed increases. Therefore, it is possible to determine the distinction between the clogging and the reduction in the performance of the fan motor 13 (that is, the difference in the cause of the decrease in the sensor output with respect to the fan drive current).

FIG. 6 shows that the fan motor 13
7A is a graph showing the state of the sensor output of the airflow sensor 19 when the number of rotations is increased or decreased by intentionally causing the clogging or the decrease in the performance of the fan motor 13 by driving in FIG. It is.

Now, the fan motor 13 is set to a constant current a.
The number of rotations and the initial number of rotations C ₀ (r ·
p · m), the output of the air flow sensor 19 at this time is represented by the deviation Δ of the sensor output shown in FIG.
Add d. By doing so, even if the clogging or the deterioration of the performance of the fan motor 13 occurs, the influence on the output of the air flow sensor 19 can be canceled.

As a result, if the output value obtained by adding the deviation Δd is compared with the initial value b ₀ (V) of the output of the air flow sensor 19 shown in FIG. 4, the air flow as shown in FIG. Only the drift Δb of the sensor 19 can be obtained.

Accordingly, the initial value b _{0 of the} drift Δb.
By correcting the initial characteristic of FIG. 3 by this ratio, and then using the corrected characteristic to perform feedback control of the fan motor 13 as before,
Even if the airflow sensor 19 drifts,
By correcting this, ideal combustion can be continued.

However, the drift Δb is a certain value Δb
_If the sensor output is larger than _{max and} it is difficult to correct the sensor output, it is determined that the sensor is abnormal, and the user is notified of the abnormality by issuing an alarm signal or the like, so that subsequent combustion is not performed.

The drift detection operation may be performed temporarily during the combustion in the burner 20, but if it is performed during the pre-purge before the start of the combustion or during the post-purge after the end of the combustion, the fuel side stops. As a result, the air-fuel ratio does not temporarily deteriorate.

Further, the fan drive current a (A) during the drift detection operation is obtained in advance by obtaining a current value that is approximately the maximum air amount used for combustion (air amount at the time of maximum combustion).
It is better to perform the drift detection operation with this current value. The reason for this is that the larger the amount of air discharged from the exhaust port, the smaller the effect of the outdoor wind on the sensor output and the number of rotations of the fan (this is a correction error).

Since the drift and clogging of the air flow sensor 19 and the deterioration of the performance of the fan motor 13 do not occur suddenly, it is not necessary to perform the above-described correction processing in one drift detection operation.

Accordingly, the drift detection operation is performed once every combustion operation or every certain fixed time, and the average value of the output deviation of the air flow sensor 19 when this operation is performed several tens to several hundreds of times is performed. And fan motor 1
By performing the correction with the average value of the deviation of the number of rotations of 3, the reliability of the drift correction can be further improved.

If correction of the rotation speed of the fan motor 13 becomes difficult due to the clogging or the deterioration of the performance of the fan motor 13, it becomes difficult to perform correction by outputting an alarm signal. To inform the user of the maintenance request for the combustion equipment.

FIG. 7 is a flowchart showing a procedure for switching the control of the fan motor 13 from the feedback control to the constant current control during the post-purge after the end of the combustion and performing the drift detection and the correction.

First, the combustion control circuit 23 determines whether or not a combustion start request has been made (step ST1). If a combustion start request has been made, the fan motor 13 is operated and the air flow is started. The air amount control based on the feedback based on the output of the sensor 19 is performed to start the combustion (step ST2).

As a result, steady combustion is executed, and the steady combustion is continued by feedback control until there is a request to stop combustion (step ST3).

On the other hand, it is monitored whether or not a combustion stop request has been made (step ST4). If so, the combustion is stopped, the fan motor 13 is switched to constant current (or constant voltage) control, and post-purge is performed. (Step ST
5).

Subsequently, the post-purge is started, and when the rotation speed C _n (r · p · m) of the fan motor 13 is stabilized, the previously stored initial rotation speed C ₀ (r · p · m) is stored.
m) (step ST6).

That is, C _n is C ₀ ± (ΔC _max + α)
If not, the subsequent calculations are not performed, and after the post-purge time has elapsed, the fan motor 13 is stopped, and the processing of step ST1 and subsequent steps is executed again. Here, α is a constant value for determining whether there is an influence of the wind or not.

However, if C _n is within C ₀ ± (ΔC _max + α), the output level of the air flow sensor 19 and the rotation speed of the fan motor 13 at this time are stored (step ST7).

The storage operation is repeated (n =
n + 1) (step ST8), and the number of storage times is n
_It is determined whether or not _max has been reached (step ST9).

When the number of storages reaches n _max ,
The stored average value BA of the output level of the airflow sensor 19 and the average value CA of the rotation speed of the fan motor 13 are calculated (step ST10), and the average value CA is C ₀ ± Δ.
It is determined whether it is within _Cmax (step ST1).
1) If not, worsening of clogging or fan motor 1
Then, it is determined that the performance is reduced in No. 3 and the process proceeds to the maintenance request.

However, if the average value CA is within C ₀ ± ΔC _max , the decrease in the output of the air flow sensor 19 due to clogging or a decrease in the performance of the fan motor 13 is canceled, and the drift value of the air flow sensor 19 itself is reduced. Calculation is performed (step ST12).

If the drift value is larger than Δb _max , it is determined that the sensor is abnormal, and the process proceeds to a maintenance request (step ST13). If it is smaller than Δb _max , the characteristic of the air flow sensor 19 is corrected (step ST14).

Then, it is finally determined whether or not the post-purge has been completed (step ST15). If the post-purge has been completed, the fan motor 13 is stopped (step ST16), and the re-processing after step ST1 is executed. In preparation, if the post-purge is not completed, the post-purge is sufficiently continued until a given time (step ST17).

After that, by performing the air amount control by the feedback with the corrected characteristics, the ideal air-fuel ratio control without the influence of the drift of the air flow sensor 19 can be realized.

[0070]

As described above, according to the first aspect of the present invention, when the blower is operated without performing the feedback control for a predetermined period, the detected flow rate and the rotation number of the air detected by the flow rate detector are detected. By comparing the rotational speed of the blower with a set value, a combustion control circuit for detecting a change in the characteristic of the flow detector and a change in the rotational speed of the blower is provided. Thus, it is possible to reliably detect clogging, which is a deterioration in air permeability of intake and exhaust, and a decrease in the capacity of the blower. If the drift or clogging of the flow detector becomes significant,
There is an effect that the following combustion operation can be stopped or a warning can be issued. Particularly, a drift on the positive (+) side in the direction of reducing the amount of air may generate carbon monoxide, which can be easily detected.

According to the second aspect of the present invention, since the detected flow rate is corrected by the combustion control circuit so as to eliminate the change in the characteristics of the flow rate detector and the change in the rotation speed of the blower, the clogging of the intake and exhaust passages is reduced. Even if it occurs, the influence of the clogging on the output of the flow detector can be canceled and only the drift of the flow detector can be detected. Therefore, the ratio between the drift and the initial value is used as a correction value, and the subsequent feedback control is performed. By performing the above, there is an effect that an object capable of realizing ideal burner combustion control can be obtained.

According to the third aspect of the present invention, the blower is configured to perform constant current control or constant voltage control during a fixed period, so that the flow rate detector and the blower can be controlled based on their own input / output characteristics. The clogging between the intake and exhaust passages, the degree of reduction in the capacity of the blower, and the drift of the flow rate detector can be detected with high accuracy, thereby providing an effect that ideal combustion control data of the burner can be obtained.

According to the fourth aspect of the present invention, the predetermined period is provided before the start of combustion or after the stop of combustion in the combustor, so that the air-fuel ratio control can be realized without changing the combustion control pattern on the way. In addition, there is an effect that it is possible to prevent the air-fuel ratio from being temporarily deteriorated even when the combustion side is stopped.

According to the fifth aspect of the present invention, the predetermined period is provided at a predetermined number of times of ignition or at a predetermined time, so that the average value of the deviation of the output of the flow rate detector and the deviation of the rotation speed of the blower is calculated. Based on this, there is an effect that a more reliable determination of drift of the flow rate detector, clogging of the intake and exhaust passages, and reduction of the capacity of the blower can be obtained.

According to the sixth aspect of the present invention, the constant current value or the constant voltage value controlled by the constant current control or the constant voltage control is set to a value in the vicinity of obtaining the air amount during the maximum combustion. Therefore, the influence of the sensor output and the fan rotation speed due to the outdoor wind, which is an error of the above, can be suppressed to a small degree, whereby there is an effect that a drift can be detected with high accuracy.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a combustion control device according to an embodiment of the present invention.

FIG. 2 is an air amount-fuel amount characteristic diagram showing an air amount characteristic according to the present invention.

FIG. 3 is a sensor output-air amount characteristic diagram showing output characteristics of the air flow sensor according to the present invention.

FIG. 4 is a sensor output-fan drive current characteristic diagram showing an output characteristic of the air flow sensor according to the present invention.

FIG. 5 is a fan motor rotation speed-fan drive current characteristic diagram showing the rotation speed characteristics of the fan motor according to the present invention.

FIG. 6 is a sensor output-fan speed characteristic diagram showing output characteristics of the air flow sensor according to the present invention.

FIG. 7 is a flowchart showing a procedure of drift detection and output characteristic correction of an airflow sensor according to the present invention.

FIG. 8 is a configuration diagram showing a conventional combustion control device.

9 is a sensor output-air amount characteristic diagram showing a sensor output characteristic of a computing unit in FIG. 8;

FIG. 10 is a fan speed-air amount characteristic diagram showing the speed characteristics of the fan motor of the arithmetic unit in FIG. 8;

[Explanation of symbols]

 Reference Signs List 13 fan motor (blower) 18 rotation speed detecting means 19 air flow sensor (flow rate detector) 20 burner (combustor) 23 combustion control circuit

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F23N 3/08 F23N 5/18 F23N 5/24

Claims (6)

(57) [Claims] 1. A blower for supplying air to a combustor, a rotation speed detecting means for detecting a rotation speed of the blower, and a flow detector for detecting a flow rate of air supplied to the combustor by the blower, In the combustion control device that performs feedback control of the blower based on the detected flow rate of the flow rate detector, the detected flow rate and the rotation speed that are detected when the blower is operated without performing the feedback control for a predetermined period are set. A combustion control device comprising: a combustion control circuit that detects a change in the characteristic of the flow rate detector and a change in the rotation speed of the blower by comparing the value with a value. 2. The combustion control device according to claim 1, wherein the combustion control circuit corrects the detected flow rate so as to eliminate a change in the characteristic of the flow rate detector and a change in the rotation speed of the blower. 3. The combustion control device according to claim 1, wherein the combustion control circuit performs constant current control or constant voltage control of the blower during a predetermined period. 4. The combustion control device according to claim 1, wherein a predetermined period is provided before starting combustion or after stopping combustion in the combustor. 5. The combustion control device according to claim 1, wherein a predetermined period is provided for a predetermined number of ignitions or for a predetermined time. 6. The combustion control device according to claim 3, wherein the constant current value or the constant voltage value controlled by the constant current control or the constant voltage control is set to a value in the vicinity of obtaining the air amount at the time of the maximum combustion.