JPH06307628A - Combustion controller - Google Patents

Abstract

PURPOSE:To shorten impressing time of a monitoring voltage for an oxygen sensor during combustion and prevent the deterioration of the oxygen sensor by a method wherein the monitoring voltage of the oxygen sensor is impressed only when an oxygen concentration detecting information is required for correcting the output of a fan by a correcting means. CONSTITUTION:A correcting unit 12d corrects the output of a fan 4 only when it is decided that operation is in the optimum condition by a deciding unit 12e while a monitoring voltage control unit 12g impresses the monitoring voltage of an oxygen sensor 16 only when an oxygen concentration detecting information is requested in order to correct the output of a fan 4 by the correcting unit 12d. In this case, the monitoring voltage control unit 12g impresses the monitoring voltage of the oxygen sensor 16 only when it is decided by the deciding unit 12e that operation is in the optimum condition and when it is decided that the operation is not in the optimum condition, the impression of the monitoring voltage is stopped. According to this method, the impressing time of the monitoring voltage of the oxygen sensor 16 during combustion can be shortened and the deterioration of the oxygen sensor 16 can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to fan control means for adjusting the output of a fan for supplying combustion air according to the amount of fuel supply, and a limiting current type oxygen sensor for detecting the oxygen concentration in combustion exhaust gas. And a correction means for correcting the fan output by the fan control means based on the oxygen concentration detection information.

[0002]

2. Description of the Related Art Such a limiting current type oxygen sensor (hereinafter referred to as
(Oxygen sensor) uses the fact that when a DC voltage is applied between the electrodes provided on both sides of a disk-shaped stabilized zirconia, the current (limit current) that flows with oxygen ions as carriers changes depending on the oxygen concentration. To detect the oxygen concentration.

This current increases in proportion to the voltage when the voltage is low, but eventually a flat region is observed which does not increase even when the voltage becomes high (however, the oxygen concentration is constant).
This flat current is called a limiting current and has a current value proportional to the oxygen concentration. Therefore, if a voltage (hereinafter referred to as a monitoring voltage) is set in this flat region, the oxygen concentration can be detected from the current value. The limiting current is generated in a high temperature state. Therefore, a heater is integrally formed with the oxygen sensor so that the oxygen sensor is heated by energization.

In such a combustion control device, for example, as shown in Japanese Patent Application No. 4-319150 already proposed by the present applicant, a fuel supply amount and a fan output which are preset so as to obtain an appropriate air-fuel ratio. Based on the correlation, the fan output is adjusted according to the change in the fuel supply amount, and the variation in the device characteristics of each combustion device and the secular change of the device characteristics, or the ventilation in the air supply passage or the combustion exhaust gas passage The output of the oxygen sensor during combustion operation should be adjusted to prevent the air-fuel ratio from deviating from the optimum value due to changes in the relationship between the fan output and the actual air supply amount due to the occurrence of a failure, etc. Based on that, the fan output was corrected.
As described above, in the combustion control device that corrects the fan output based on the output of the oxygen sensor during the combustion operation, conventionally, the monitoring voltage is always applied to the oxygen sensor during the combustion operation to detect the oxygen concentration. Was there.

[0005]

However, when the combustion control is performed by using the oxygen sensor as described above, the monitoring voltage is always applied to the oxygen sensor during the combustion operation, so that the oxygen sensor always has the limiting current. Will flow.
For this reason, the deterioration of the oxygen sensor is promoted. Therefore, a detection circuit for automatically detecting the degree of deterioration of the oxygen sensor is added, or the oxygen sensor is regularly inspected to frequently There was a problem that it had to be exchanged. The present invention has been made in view of the above circumstances, and an object thereof is to provide a combustion control device that extends the life of an oxygen sensor as much as possible and that replaces the oxygen sensor with less maintenance.

[0006]

A combustion control device of the present invention is a fan control means for adjusting the output of a fan for supplying combustion air according to a fuel supply amount, and a limit for detecting an oxygen concentration in combustion exhaust gas. A current type oxygen sensor and a correction unit for correcting the fan output by the fan control unit based on the oxygen concentration detection information are provided. The first characteristic configuration of the oxygen sensor is the limiting current type oxygen sensor. Monitoring voltage control means for controlling the application of the monitoring voltage is provided, and the monitoring voltage control means applies the monitoring voltage only when the oxygen concentration detection information is required for the correction of the fan output by the correction means. It is a point that is configured. According to the second characteristic configuration, the correction unit is configured to execute the correction of the fan output only when the output of the fan and the fuel supply amount continue to be constant for a predetermined time or more,
The monitoring voltage control means is configured to apply the monitoring voltage only when the oxygen concentration detection information is required for the correction of the fan output by the correction means.

[0007]

According to the first characteristic construction of the present invention, the monitoring voltage of the oxygen sensor is applied only when the oxygen concentration detection information is required for the correction of the fan output by the correction means.
Based on the oxygen concentration detection information of the oxygen sensor at this time,
The fan output is corrected. By the way, in the above oxygen sensor, the deterioration of the oxygen sensor is promoted by applying the monitoring voltage to the oxygen sensor and causing the limiting current to flow.However, if the oxygen sensor is left without being applied with the monitoring voltage, it deteriorates. Does not occur. Therefore, when the oxygen concentration detection information is not requested, that is, when the fan output is not corrected, the monitoring voltage of the oxygen sensor is not applied to shorten the monitoring voltage application time of the oxygen sensor during combustion. Therefore, deterioration of the oxygen sensor can be prevented as much as possible. According to the second characteristic configuration, the monitoring voltage of the oxygen sensor is applied only when the fan output and the fuel supply amount are in a proper state in which the fan output and the fuel supply amount are kept constant for a predetermined time or longer, and based on the oxygen concentration detection information of the oxygen sensor at this time. Then, the fan output is corrected. In other words, as the fan output or fuel supply changes,
In the process where the combustion state changes transiently, due to its characteristics, a delay occurs in the measurement system, and there is no real-time consistency between the oxygen concentration in the exhaust gas and the detected value, causing a large error. In such a large error state (inappropriate state), the application of the monitoring voltage of the oxygen sensor can be stopped and the correction of the fan output can be stopped.

[0008]

According to the first characteristic configuration, the monitoring voltage application time of the oxygen sensor during combustion can be shortened as much as possible to prevent deterioration of the oxygen sensor as much as possible. Therefore, the life of the oxygen sensor can be extended. The maintenance of replacing the oxygen sensor can be reduced. According to the second characteristic configuration, the monitoring voltage of the oxygen sensor is applied only in the proper state, and the fan output is corrected only in the proper state, which is unnecessary. The application of the monitoring voltage and the correction of the fan output can be prevented, so that the deterioration of the oxygen sensor can be prevented as much as possible and the air-fuel ratio can be stably maintained.

[0009]

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 water heater, which includes 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 through the exhaust passage 3.

In the water supply path 5 to the heat exchanger 1, the water temperature ti is supplied.
A water temperature sensor 6 for detecting the water temperature 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. 10 in the figure
Is a fuel supply path for supplying the fuel gas g to the burner 2, 1
Reference numeral 1 denotes an electromagnetic proportional valve for intermittently supplying the fuel gas and adjusting the fuel gas supply amount Ip.

Further, in the figure, reference numeral 12 is a control device, and the control device 12 includes an ignition / extinguishing operation part 12a for starting and stopping combustion operation, and adjustment of the fuel gas supply amount Ip (that is, adjustment of the combustion amount). Hot water temperature adjusting unit 12 for adjusting the hot water supply temperature to by
b, and a fan controller 12c for adjusting the supply amount of the combustion air a by adjusting the output of the fan 4 (rotation speed adjustment in this example).

The ignition / extinguishing operation unit 12a detects the amount of water in the water amount sensor 7 when the hot water tap 13 is opened, and the proportional solenoid valve 1 is operated.
1, the ignition mechanism 14 is operated to start the combustion operation of the burner 2, and the solenoid 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 supply temperature ts 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 feedforward calculation according to the following equation. Required fuel gas supply amount Ipo 'is calculated, and required by feedback calculation based on deviation Δto between detected hot water supply temperature to and target hot water supply temperature ts, Ip ₀ ' = gW (ts-ti) (g is a coefficient) By calculating the correction value ΔIp and adding the necessary correction value ΔIp by the feedback calculation to the calculated fuel gas supply amount Ip ₀ ′ by the above feedforward calculation, the adjustment target value Ipo (= Ip ₀ of the fuel gas supply amount '+ ΔIp) is determined.

Then, the hot water temperature adjusting section 12b supplies the operating current value i for the electromagnetic proportional valve 11 to the fuel based on the setting function F1 of the fuel gas supply amount and the proportional valve current i (operating current value for the electromagnetic proportional valve 11). The value of the gas supply amount is adjusted to a value corresponding to the target value Ip ₀ , whereby the actual fuel gas supply amount to the burner 2 is adjusted to the target value Ip ₀ , and the hot water supply temperature to is adjusted to the target hot water supply temperature ts. maintain.

On the other hand, the fan control section 12c determines, based on the setting function F2 of the fuel gas supply amount Ip and the fan output N (fan rotation speed) that gives an air supply amount of an appropriate air-fuel ratio to each fuel gas supply amount Ip. The target value Ip of the fuel gas supply amount
_The fan output value corresponding to ₀ is determined as the adjustment target value of the fan output N, and the detected value matches the adjustment target value based on the deviation ΔN between the adjustment target value and the detection value detected by the rotation speed sensor 15. The fan output N is adjusted so that

Further, the relationship between the fan output N and the actual air supply amount Q changes due to variations in the device characteristics of each device, changes over time in the device characteristics, or the occurrence of ventilation obstacles in the air path or exhaust path 3. In order to prevent the air-fuel ratio from deviating from the optimum value due to it, the limiting current type oxygen sensor 16 for detecting the oxygen concentration x in the combustion exhaust gas eg is provided in the exhaust passage 3 in this water heater. At the same time, based on the detection information from the oxygen sensor 16, the controller 12 includes a correction unit 12d as a correction unit that corrects the adjustment of the fan output N by the fan control unit 12c.
Be prepared for.

The control device 12 is provided with a monitor voltage control section 12g as monitor voltage control means for controlling the application of the monitor voltage of the oxygen sensor 16, and the monitor voltage control section 12g is provided by the correction section 12d. The monitoring voltage is applied only when the oxygen concentration detection information is required to correct the fan output, that is, only when the correction of the fan output by the correction unit 12d is executed.

As shown in FIG. 3, the oxygen sensor 16 comprises 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 constructed by forming platinum electrodes 17b on both sides of a disk-shaped stabilized zirconia 17a and joining a cap 17d having a small hole 17c on one side thereof.
When a voltage (monitoring voltage) Vk is applied between both electrodes 17b,
A current with oxygen ions as carriers flows due to the pumping action.

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

The correction unit 12d calculates the fuel gas supply amount Ip,
Based on the setting function F3 with the oxygen concentration x in the combustion exhaust gas generated at the optimum air-fuel ratio at each fuel gas supply amount Ip, the concentration value corresponding to the above target value Ip ₀ of the fuel gas supply amount is adjusted to the adjustment target value of the oxygen concentration x. Then, according to 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,
When the detected value for the oxygen concentration x is smaller than the target value, the target value of the fan output N is corrected to the increasing side, and when the detected value for the oxygen concentration x is larger than the target value, the target value of the fan output N is set. Correct to the decreasing side).

As a concrete correction form, a correction form based on the following equation can be given as an example. N (correction value) ← N (decision value based on setting function F2) +
k '・ (Δx / x) (k' is a constant)

In connection with the above correction of the fan output N, the control unit 12 further includes a judging section 12e for judging whether or not the state of oxygen concentration detection by the oxygen sensor 16 is an appropriate state for accurate oxygen concentration detection. A storage unit 12f is provided for storing the deviation Δx between the detected value of the oxygen concentration x and the target value when the determination unit 12e recognizes the proper state as the oxygen concentration detection information in the proper state.

The determination unit 12e is configured to set the rising time Ta from the start of energization of the heater 17e (in this example, from the time when energization of the heater 17e is started with the start of combustion operation of the burner 2 to the oxygen sensor 16). Setting time T required for the temperature of T to rise to the stable temperature th (see FIG. 5)
After a), and when the fuel gas supply amount Ip or the fan output N is changed, the combustion state changes transiently with the change of the fuel gas supply amount Ip or the fan output N. A predetermined time Tb (3
After the elapse of 0 second), it is determined as an appropriate state (process (h) in the flowchart of FIG. 7).

As described above, the correction unit 12d is configured to correct the fan output N only when the determination unit 12e determines the proper state, and the monitoring voltage control unit 12g includes the correction unit. The monitoring voltage Vk is applied only when the oxygen concentration detection information is required to correct the fan output by 12d. That is, FIG.
As shown in the flowchart of FIG. 5, when the determination unit 12e determines that the state is appropriate (process (H)), the monitoring voltage control unit 12g applies a constant monitoring voltage Vk between the electrodes 17b (process (H)). (I)), and the correction unit 12d corrects the fan output N (fan correction control) based on the deviation Δx between the detected oxygen concentration x of the oxygen sensor 16 and the target value at that time (processing (le )). Therefore, the monitoring voltage controller 1
2g is configured to execute the application of the monitoring voltage Vk only when it is determined to be in the proper state by the determination unit 12e, and to stop the application of the monitoring voltage Vk when it is determined to be in the inappropriate state. Has been done.

At this time, the detected oxygen concentration x and the deviation Δx
Is stored in the storage unit 12f (process (nu)). That is, the storage unit 12f updates the stored information each time the determination of the determination unit 12e shifts from the improper state to the proper state, and detects the oxygen concentration x detected by the oxygen sensor 16 and the target value in the proper state after the shift. The deviation Δx of is stored by replacing it with the previously stored content.

Then, the correction unit 12d corrects the target value of the fan output N based on the stored information in the storage unit 12f, which is updated every time there is a change from the improper state to the proper state. The configuration is such that it is performed in a state, and further in an inappropriate state subsequent to the appropriate state (in other words, the target value correction of the fan output N is always performed according to the storage information of the storage unit 12f).

That is, the target value correction of the fan output N in the improper state is executed based on the stored information updated by the transition to the proper state after the previous proper state, so that the improper state is reduced. The erroneous correction caused by the erroneous detection of the oxygen concentration is avoided to maintain a good air-fuel ratio state.

It should be noted that the storage unit 12f has a format in which the stored information is retained even after the combustion operation of the burner 2 is stopped or during a stop period during a power failure. Information that is kept in the memory (initial value)
Based on the above, the target value of the fan output N is corrected (fan initial value control).

Next, the control by the control device 12 after the start of combustion is instructed will be described based on the flowchart of FIG. As the combustion start is commanded, that is, the 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 (process (a)).
The opening of the gas valve of the solenoid proportional valve 11 and the ignition of the burner 2 are also performed. However, in actuality, the opening of the gas valve and the ignition of the burner 2 are performed about 1 second later than the operation of the fan 5.

The time Ta until the oxygen sensor 16 (sensor element 17) is properly heated by the heater 11e, that is, the stable temperature (eg, 500 ° C.) is reached.
(About 1 minute) is required. Therefore, during this period, the fan control is performed with the target value corrected on the basis of the storage information stored in the storage unit 12f for the fan output N that is predetermined according to the fuel gas supply amount Ip to the burner 2. (Processing (b)). That is, the fan initial value control is performed until the oxygen sensor 10 becomes detectable (until the temperature of the oxygen sensor 10 reaches a stable temperature).

The controller 12 has an internal timer (not shown).
Manages the time for performing the fan initial value control. The internal timer is reset and starts counting with the start of combustion (start of energization of the heater 17e). Then, when the internal timer reaches the set rising time Ta (1 minute), the control of the fan 4 is shifted from the fan initial value control to the fan correction control (FIG. 7) described above (process (c)). Note that, as described above, the control of the fuel gas supply amount Ip by adjusting the opening degree of the solenoid proportional valve 11 is also 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 (d)). The fan 4 continues to operate at a predetermined output and performs a post-purge, that is, an exhaust operation after combustion is stopped for a predetermined time. When a predetermined time has passed, 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 (e)).

[Other Embodiments] Next, other embodiments will be listed. The fan output adjustment by the fan control unit 12c may be performed in the form of using the fan drive current or voltage as the adjustment index instead of the form of using the fan rotation speed as the adjustment index as in the above 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. It is also possible to adopt a mode in which the combustion air a is supplied to the burner 2 as the combustion exhaust gas eg is sucked and exhausted by the fan 4. In the above embodiment, the information stored in the storage means 12f is the deviation Δx between the detected oxygen concentration x and the target oxygen concentration,
Alternatively, it may be oxygen concentration detection information such as the detected oxygen concentration x itself, or may be information at the correction stage executed by the correction means 12d based on the oxygen concentration detection information in the proper state. In the above-described embodiment, the monitoring voltage Vk is always applied when the determination unit 12e determines that it is in the proper state, and the application of the monitoring voltage Vk is stopped when the determination unit 12e determines that it is in the inappropriate state, that is, In a proper state, the fan output is constantly corrected based on the oxygen concentration detection information of the oxygen sensor 16, but the monitoring voltage Vk is intermittently applied to detect the oxygen concentration of the oxygen sensor at that time. The fan output may be corrected intermittently based on the information. At this time, the fan output may be corrected with the oxygen concentration detection information obtained intermittently being in a proper state as an effective value. Further, the monitoring voltage Vk is applied only for a predetermined time (a time sufficient to detect the oxygen concentration) from the time when the inappropriate state is changed to the appropriate state, and based on the oxygen concentration detection information of the oxygen sensor 16 at that time. The fan output may be corrected by using the corrected fan output, and the fan may be driven by the corrected fan output until the next shift from the improper state to the proper state. By the above method, the time for applying the monitoring voltage Vk can be further reduced, and thus the deterioration of the oxygen sensor can be further prevented.

It should be noted that reference numerals are given in the claims for convenience of comparison with the drawings, but the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of 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: Rising characteristic diagram of oxygen sensor

FIG. 6 is a flowchart showing the control of the control means.

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

[Explanation of symbols]

 4 fan 12c fan control means 12d correction means 12g monitoring voltage control means 16 oxygen sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location G01N 27/41 (72) Inventor Hiroshi Kamiya 1-1-52 Minamiichioka, Minato-ku, Osaka-shi, Osaka Stocks Company Harman

Claims (2)

[Claims] 1. A fan control means (12) for adjusting an output of a fan (4) for supplying combustion air according to a fuel supply amount.
c), a limiting current type oxygen sensor (16) for detecting the oxygen concentration in the combustion exhaust gas, and a correction means (12d) for correcting the fan output by the fan control means (12c) based on the oxygen concentration detection information. And a monitoring voltage control means (12g) for controlling the application of the monitoring voltage of the limiting current type oxygen sensor (16), the monitoring voltage control means (12g) comprising: A combustion control device configured to apply the monitoring voltage only when the oxygen concentration detection information is required for the correction of the fan output by the correction means (12d). 2. The correction means (12d) is configured to execute the correction of the fan output only when the output of the fan (4) and the fuel supply amount are maintained in a constant state for a predetermined time or more, The monitoring voltage control means (12g) is configured to apply the monitoring voltage only when oxygen concentration detection information is required for correcting the fan output by the correction means (12d). Combustion control device.