JP3072200B2 - 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 control apparatus, and more particularly, to a fan control means for adjusting an output of a fan for supplying combustion air in accordance with a fuel supply amount, and detecting an oxygen concentration in combustion exhaust gas. The present invention relates to a combustion control device provided with a detection unit and a correction unit that corrects a fan output adjustment by the fan control unit based on the oxygen concentration detection information.

[0002]

2. Description of the Related Art Conventionally, in a combustion control apparatus as described above, a fan control means 12c is provided with a fuel supply amount Ip and an output of a combustion air supply fan 4 which are preset so as to obtain an appropriate air-fuel ratio, as shown in FIG. Based on the correlation F2 with N
The fan output N is adjusted according to the change of the fuel supply amount Ip, and the variation of the device characteristics of the combustion device, the aging of the device characteristics, or the occurrence of a ventilation failure in the air supply passage or the combustion exhaust gas passage 3 are performed. As a result, the relationship between the fan output N and the actual air supply amount changes, which causes the air-fuel ratio to deviate from the optimum value.
During the combustion operation, the detecting means 16 constantly monitors the oxygen concentration x in the combustion exhaust gas, and the correcting means 12d calculates the oxygen concentration target value at each time point and the oxygen concentration target value giving the optimum air-fuel ratio. The correction of the fan output adjustment by the fan control means 12c is successively made so that the oxygen concentration x becomes the target value.

[0003]

However, when the detecting means 16 for detecting the oxygen concentration x starts its operation, the combustion state is transient with respect to a rising period until the detected value is stabilized or a change in the fuel supply amount Ip. Due to its characteristics, a large error occurs between the actual oxygen concentration in the combustion exhaust gas and the detected value during the process period that changes periodically, etc. It is handled without distinction from the appropriate oxygen concentration detection information, and the correction of the fan output is made based on the oxygen concentration detection information. There has been a problem that it greatly deviates and temporarily causes poor combustion.

[0004] An object of the present invention is to solve the above problem by correcting the fan output adjustment based on the oxygen concentration detection information in a rational manner.

[0005]

A first characteristic configuration of the combustion control device according to the present invention is a fan control means for adjusting an output of a fan for supplying combustion air in accordance with a fuel supply amount,
In a configuration in which detection means for detecting the oxygen concentration in the combustion exhaust gas and correction means for correcting the fan output adjustment by the fan control means based on the oxygen concentration detection information are provided, the state of the oxygen concentration detection by the detection means Determining means for determining whether or not an appropriate situation that satisfies the setting condition;
Storage means for storing information of the oxygen concentration detection information when the appropriate state is recognized by the determination means, or information of the correction executed by the correction means for the oxygen concentration detection information at that time, The present invention is characterized in that, when the determination by the determination means is in an inappropriate state, the correction of the fan output adjustment is executed in accordance with the information stored in the storage means.

In a second characteristic configuration according to the present invention, the determination means may be configured to set a stable value after a lapse of a set rising time from the start of operation of the detection means and from a time when a fuel supply amount is changed. After the elapse of the activation time.

[0007]

In other words, in the above-mentioned first characteristic configuration, it is determined whether or not the detection condition of the oxygen concentration satisfies the set condition.
A determination is made as to whether the detection means is in a proper state in which the actual oxygen concentration can be accurately detected, or whether the detection means is in an inappropriate state in which a detection error larger than an allowable range with respect to the actual oxygen concentration occurs.

Then, in an appropriate situation where the actual oxygen concentration can be accurately detected, the oxygen concentration detection information at that time or correction information executed by the correction means for the fan output adjustment based on the oxygen concentration detection information at that time ( That is, correct oxygen concentration detection information that matches the actual oxygen concentration, or appropriate correction information that is executed based on the correct oxygen concentration detection information) is stored, and then the actual oxygen concentration is accurately calculated. When an unsuitable situation that cannot be detected occurs, the correction of the fan output by the fan control means is executed in accordance with the stored correct oxygen concentration detection information or the stored correct correction information.

In the second characteristic configuration, after the detection means operates, the rise time required for the detection value to match the actual oxygen concentration and stabilize, and the change in the fuel supply amount (that is, the combustion amount) ), A stabilization time required for the combustion state to stabilize through a transient change is set.

Then, after the set rising time elapses from the start of the operation of the detecting means and after the set stabilization time elapses from the time when the operation of changing the fuel supply amount is performed, an accurate value is obtained. By making the determination as an appropriate state in which the oxygen concentration can be detected, the first characteristic configuration can avoid inappropriate fan output correction caused by an oxygen concentration detection error in a rising process or a transient change process of a combustion state. .

[0011]

In other words, according to the present invention, it is possible to prevent the air-fuel ratio from temporarily deteriorating in a conventional device in an inappropriate situation where the detecting means cannot accurately detect the oxygen concentration in the combustion exhaust gas, and to reduce the air-fuel ratio. It becomes possible to continuously maintain an appropriate value and stably, and the combustion operation performance can be greatly improved as compared with the related art.

[0012]

FIG. 1 shows a hot water supply apparatus, which is a water tube type heat exchanger 1, a burner 2 for heating the heat exchanger 1, and a supply of combustion air a to the burner 2 and after passing through the heat exchanger. A fan 4 for exhausting the combustion exhaust gas eg through the exhaust path 3 to the outside is provided.

The feed water path 5 to the heat exchanger 1 has a feed water temperature ti.
A water temperature sensor 6 for detecting the water supply amount W and a water amount sensor 7 for detecting the water supply amount W are provided, and a hot water temperature sensor 9 for detecting the hot water supply temperature to is provided in the hot water supply passage 8 from the heat exchanger 1.

Reference numeral 10 denotes a fuel supply passage 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.

Reference numeral 12 denotes a control device.
The ignition / extinguishing operation unit 12a that starts and stops the combustion operation, the hot water temperature adjustment unit 12b that adjusts the hot water supply temperature to by adjusting the fuel supply amount Ip (that is, the adjustment of the combustion amount), and the output adjustment of the fan 4 The fan control unit 12c and the like for adjusting the supply amount of the combustion air a by (rotational speed adjustment in this example) are provided.

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 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 (see FIG. 2) obtains the target hot water temperature ts by feedforward calculation using the following equation from the detected hot water temperature ti, the detected hot water amount W, and the set target hot water temperature ts. The required fuel supply amount Ip 'is calculated, and the necessary correction value ΔIp is calculated by a feedback calculation based on a deviation Δto between the detected hot water supply temperature to and the target hot water supply temperature ts. Ip ′ = kW · (ts−ti) , The required correction value ΔI obtained by the feedback calculation with respect to the fuel supply amount Ip ′ calculated by the feedforward calculation described above.
By adding p, the adjustment target value of the fuel supply amount Ip (=
Ip ′ + ΔIp) is determined.

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 supply amount Ip and the proportional valve current i (the operating current value for the electromagnetic proportional valve 11). The supply amount Ip is adjusted to a value corresponding to the target value, whereby the actual fuel supply amount Ip to the burner 2 is adjusted to the target value, and the hot water temperature to is adjusted and maintained at the target hot water temperature ts.

On the other hand, the fan control unit 12c determines the fuel supply amount by a setting function F2 of a fuel supply amount Ip and a fan output N (fan rotation speed) for providing an air supply amount having an appropriate air-fuel ratio for each fuel supply amount Ip. Determining a fan output value corresponding to the target value of the amount Ip as an adjustment target value of the fan output N; and adjusting the fan output N (rotation speed) with the adjustment target value and the detection value detected by the rotation speed sensor 15. Is adjusted based on the deviation ΔN of the fan output N so that the detected value matches the adjustment target value.

Also, the relationship between the fan output N and the actual air supply amount Q changes due to variations in the device characteristics of the devices, aging of the device characteristics, or occurrence of a ventilation failure in the air path or the exhaust path 3. In order to prevent the air-fuel ratio from deviating from the optimum value due to the occurrence of the air-fuel ratio, in this hot water supply device, an oxygen sensor 16 for detecting the oxygen concentration x in the combustion exhaust gas eg is provided in the exhaust path 3 and the oxygen sensor The fan control unit 1 based on the detection information of the sensor 16
The control unit 12 is provided with a correction unit 12d for correcting the adjustment of the fan output N by 2c.

The correction unit 12d calculates the fuel supply amount Ip,
A concentration value corresponding to the target value of the fuel supply amount Ip is set as an adjustment target value of the oxygen concentration x based on a setting function F3 with the oxygen concentration x in the combustion exhaust gas generated at the optimum air-fuel ratio at each fuel supply amount Ip; In accordance with the deviation Δx between the target value of the oxygen concentration x and the value detected by the oxygen sensor 16, the target value of the fan output N in the fan control unit 12c is corrected to the side that eliminates the concentration deviation Δx (ie, If the detected value of the oxygen concentration x is smaller than the target value, the fan output N
Is corrected to the increasing side, and when the detected value of the oxygen concentration x is larger than the target value, the target value of the fan output N is corrected to the decreasing side.

As a specific correction mode, a correction mode based on the following equation can be given as an example.

N (correction value) ← N (determined value based on setting function F2) + k · Δx (k constant)

In connection with the correction of the fan output N, the control unit 12 further includes a determination unit 12e for determining whether the state of oxygen concentration detection by the oxygen sensor 16 is an appropriate state in which accurate oxygen concentration detection can be performed, and The storage unit 12f is provided for storing a deviation Δx between the detected value of the oxygen concentration x and the target value when the determination unit 12e recognizes the appropriate situation as the oxygen concentration detection information in the appropriate situation.

The determination section 12e determines the set rise time Ta from the start of operation of the oxygen sensor 16 (in this embodiment, the energization of the temperature compensation heater 16a in the oxygen sensor 16 is started with the start of combustion operation of the burner 2). When the set time Ta) required until the temperature of the heater 16a rises to the stable temperature th (see FIG. 3) from the time point has elapsed and the fuel supply amount Ip has changed, the fuel supply amount After the set stabilization time Tb required for the combustion state to stabilize through a transient change with respect to the change of the time elapses, it is determined as an appropriate situation.

Each time the judgment by the judgment unit 12e shifts from an inappropriate situation to an appropriate situation, the storage unit 12f updates the stored information as a detection value and a target value of the oxygen concentration x in the appropriate situation after the transition. Is replaced with the previous stored content and stored.

The judgment by these judgment units 12e
In addition, the correction by the correction unit 1
2d, when there is a transition from the inappropriate situation to the proper situation, the target value correction of the fan output N based on the updated storage density deviation Δx of the storage unit 12f is changed to the proper situation after the transition, and further to the proper situation. The configuration is such that the target value of the fan output N is always corrected in accordance with the stored density deviation Δx of the storage unit 12f in the following inappropriate situation.

That is, the correction of the target value of the fan output N in the unsuitable state is executed in accordance with the stored density deviation Δx updated in the transition to the appropriate state following the previous appropriate state. Thus, an erroneous correction caused by an erroneous detection of the oxygen concentration is avoided, and a good air-fuel ratio state is maintained.

The storage section 12f retains the stored concentration deviation Δx even after the burn operation of the burner 2 is stopped or during a stop period at the time of a power failure. The target value of the fan output N is corrected based on the stored density deviation Δx during the period.

[Another Embodiment] Next, another embodiment will be described.

(1) The adjustment of the fan output by the fan control means 12c uses a fan drive current or voltage as an adjustment index instead of the embodiment using the fan rotation speed as an adjustment index as in the above-described embodiment. It may be.

(2) 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. A configuration in which the fan 4 is provided in the exhaust path 3 and the combustion air a is supplied to the burner 2 with the suction and exhaust of the combustion exhaust gas eg by the fan 4 may be adopted.

(3) The condition for judging the appropriate situation in the judging means 12e may be appropriately determined according to the detection method of the detecting means 16 for detecting the oxygen concentration x in the combustion exhaust gas.

(4) The information stored in the storage means 12f may be oxygen concentration detection information such as a deviation Δx between the detected oxygen concentration x and the target oxygen concentration or the detected oxygen concentration x itself. The information may be information on a correction stage executed by the correction unit 12d based on the oxygen concentration detection information in the situation.

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.

FIG. 2 is a control block diagram.

FIG. 3 is a graph showing a rising characteristic of the oxygen sensor.

FIG. 4 is a control block diagram showing a conventional example.

[Explanation of symbols]

 Reference Signs List 4 fan 12c fan control means 12d correction means 12e determination means 12f storage means 16 detection means a combustion air eg combustion exhaust gas Ip fuel supply amount N fan output x oxygen concentration

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroshi Kamiya 1-152 Oka, Minami-shi, Minato-ku, Osaka-shi, Osaka (56) References JP-A-61-96322 (JP, A) JP-A Sho 58-168814 (JP, A) JP-A-3-199815 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F23N 1/02 101 F23N 3/08 F23N 5/00

Claims (2)

(57) [Claims] 1. A fan control means (12c) for adjusting an output (N) of a fan (4) for supplying combustion air (a) according to a fuel supply amount (Ip), and a combustion exhaust gas (eg).
Detection means (16) for detecting the oxygen concentration (x) in the air; and the fan control means (1) based on the oxygen concentration detection information.
Correction means (12) for correcting the fan output adjustment according to 2c).
d) determining means for determining whether or not the state of oxygen concentration detection by said detecting means (16) is in an appropriate state satisfying a set condition; and Storage means (12f) for storing oxygen concentration detection information at the time when it is recognized as proper by (12e), or correction information executed by said correction means (12d) for the oxygen concentration detection information at that time. And the correction means (12d) is provided with the judgment means (12d).
A combustion control device configured to execute correction of fan output adjustment in accordance with the information stored in the storage means (12f) when the determination status according to e) is an inappropriate status. 2. The method according to claim 1, wherein the determining means (12e) sets a set rise time (T
2. The configuration according to claim 1, wherein the appropriate state is determined after elapse of a) and after elapse of a set stabilization time (Tb) from a point in time when a change operation of the fuel supply amount (Ip) is performed. Combustion control device.