JPH0727333A - Combustion control device - Google Patents

Abstract

PURPOSE:To prevent a premature blow off in the detection of oxygen deficiency in air fuel ratio control action by changing combustion amount according to the output of a flame rod. CONSTITUTION:The target air fuel ratio setting value of a target air fuel ratio setting part 14 is corrected based on an output from a self-correcting part 22 for correcting sensor output by the combustion amount output from a combustion control part 24 and the characteristic deterioration, etc., of an oxygen sensor 9. In this manner, while an air fuel ratio control is being effected to adjust the balance of combustion amount and combustion air amount so as to keep constant the oxygen concentration in exhaust gases by the oxygen sensor 9, the combustion condition is detected by a frame rod 26, a lowering condition of indoor oxygen concentration is judged by the changing combustion condition and the combustion amount in the air fuel ratio control is changed to enable the supply amount of air to be reduced. Therefore, a premature blow off in the condition of oxygen deficiency at the time of the air fuel ratio control can be eliminated. The burning condition in each combustion amount can be controlled to the optimum extent and a highly accurate combustion control can also be effected despite a change of the oxygen sensor 9 with the passage of time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control device for petroleum burning appliances and the like.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 8, a combustion control device of this type energizes a heater 64 at the start of operation, and when a vaporization cylinder 54 reaches a set temperature, a burner fan 52 is driven and a fuel pump 53 is driven. It is energized, an ignition operation is performed by the ignition device, and the process proceeds to combustion. When combustion is started, the sensor control unit 66 receives the output from the oxygen sensor 65, detects the oxygen concentration in the exhaust gas, and controls the air-fuel ratio by comparing it with the air-fuel ratio preset by the air-fuel ratio setting unit 67. The part 68 corrects the operation of the burner motor 51 or the fuel pump 53 to expand the variable range of the combustion amount by optimal air amount setting and combustion amount setting and reduce the influence on combustion due to various factors to realize stable combustion. is doing.

[0003]

However, in the above-described conventional combustion control device, when the oxygen depletion state is present, the burner motor 5 tries to match the optimum air-fuel ratio when the oxygen concentration of the supply air is low.
Since the rotation speed of 1 is corrected, the amount of air supplied becomes larger than the normal optimum air-fuel ratio, which causes a phenomenon in which the flame blows off. In other words, it is a premature disconnection phenomenon in which the combustion is blown out in a state where the oxygen concentration does not decrease so much.

When an oxygen deficiency state occurs, it is desirable to detect the oxygen deficiency state as soon as possible to stop combustion. However, in the present situation where the oxygen deficiency detection method is detected by the combustion state, that is, the output change of the flame rod. It is difficult to set the oxygen deficiency detection level with high accuracy. Considering safety, if you set the oxygen deficiency level without securing a large difference from normal combustion, the oxygen deficiency detection will be activated immediately due to slight fluctuations in the combustion state, component variations, and changes in the operating environment, and combustion will stop. It is very inconvenient to do. Therefore, generally, the oxygen deficiency level is set to about 17% in consideration of the influence on the human body, the allowable combustion variation range, the variation of parts, the variation range of the use environment, and the like. However, in the conventional combustion control method, even if the oxygen concentration becomes thin, the air-fuel ratio is corrected to the rotational speed of the burner motor with the preset target value of the air-fuel ratio, so the air amount at the set air-fuel ratio at normal times becomes much larger. However, the phenomenon that the flame blows off occurs, and the combustion stops at about 19% at which the oxygen concentration does not drop so much.

The present invention solves the above-mentioned problems, and prevents the oxygen deficiency detection from prematurely being cut off by changing the combustion amount in the air-fuel ratio control operation according to the output of the frame rod, and ensures a predetermined oxygen deficiency detection level. Thus, a safe and convenient combustion control device is provided.

[0006]

In order to solve the above-mentioned conventional problems, the present invention firstly discloses a burner, an oxygen sensor provided in the exhaust passage of the burner, and a combustion control section for controlling the combustion amount of the burner. The output from the oxygen sensor is compared with the air-fuel ratio target value of the air-fuel ratio target setting unit to output the control output of at least one of the combustion air amount and the fuel amount, and the combustion state of the burner. A combustion detection unit for detecting the combustion state by detecting with a flame rod, and an oxygen deficiency correction unit for changing the combustion amount set by the combustion control unit based on the output from the combustion detection unit are provided, and Furthermore, the air-fuel ratio target value of the air-fuel ratio target setting unit is corrected based on the combustion amount output from the combustion control unit and the output from the self-correction unit that corrects the sensor output due to the characteristic deterioration of the oxygen sensor. It is configured to.

[0007]

According to the present invention, according to the above structure, the oxygen sensor is arranged in the combustion flame while performing the air-fuel ratio control for adjusting the balance between the fuel amount and the combustion air amount so as to keep the oxygen concentration in the exhaust gas constant. The combustion state is detected by the flame rod, the decrease of the indoor oxygen concentration is judged by the change state of the flame rod output, and the combustion amount in the air-fuel ratio control can be changed to reduce the supply air amount. It is possible to eliminate premature disconnection in the oxygen deficient state during control, and since the air-fuel ratio target value is corrected according to the combustion amount, it is possible to optimally control the combustion state at each combustion amount. Since the self-correction operation for correcting the air-fuel ratio target value is performed according to the output state of the sensor, highly accurate combustion control can be performed even if the oxygen sensor changes over time.

[0008]

Embodiments of the present invention will be described below with reference to FIGS. First, the configuration will be described with reference to FIG.
Is a burner fan that supplies combustion air, and includes a motor 1A and a fan 2. Reference numeral 3 is a burner. In this embodiment, a burner of a system that vaporizes fuel and mixes it with combustion air to burn is used, and a heater 3A is provided in a vaporizing cylinder for vaporizing fuel.
In addition, the temperature detection sensor 8 is embedded. 5 is a fuel pump for supplying fuel into the vaporizing cylinder of the burner 3, 6
Is a blower motor for exchanging heat of the combustion gas, and 7 is an exhaust path for discharging the heat-exchanged combustion gas.

Reference numeral 9 denotes a limiting current type oxygen sensor, which is attached to the exhaust passage 7 to measure the oxygen concentration in the combustion gas. Reference numeral 10 denotes a heater power source for the oxygen sensor 9 for heating the heater incorporated in the oxygen sensor 9. 10A is a voltage switching unit for switching the heater applied voltage based on a predetermined sequence, and 11 is a power source for the sensor, which is a power source for generating a limiting current according to the oxygen concentration. Reference numeral 12 is an adjusting resistor for adjusting the output of the oxygen sensor 9. Reference numeral 13 is an amplifier that amplifies the output of the oxygen sensor 9 for input to the control unit.

Reference numeral 14 is an air-fuel ratio (m value) target setting section, and 15
Is a correction calculation unit that compares the output of the oxygen sensor 9 with the air-fuel ratio target value to calculate a correction value. Reference numeral 16 is a burner motor rotation speed correction unit, which determines the output value of the burner motor rotation speed based on the calculation result of the correction calculation unit 15.
The target setting unit 16 constitutes a control output unit 16A. A limiter 17 stops when the output value of the burner motor rotation number deviates from a predetermined range.
Reference numeral 18 is a burner motor drive circuit.

Reference numeral 20 is a K value correction unit for correcting the target value of the air-fuel ratio based on the combustion amount output from the combustion control unit, which will be described later. Reference numeral 21 is a limiter, which is a portion for limiting the target value correction result of the air-fuel ratio. If it goes out of range, stop it. Two
2 is a self-correction unit that detects the initial characteristics of the oxygen sensor,
A correction output of the air-fuel ratio target value is output according to the characteristic. 23
Is an electromagnetic pump drive circuit.

Reference numeral 24 is a combustion control unit for setting the combustion amount based on the room temperature from the room temperature detecting unit and the set temperature from the room temperature setting unit. The combustion amount is set through the combustion coefficient setting unit 29 to the burner motor drive circuit 18 And electromagnetic pump drive circuit 23
It is designed to output to. Reference numeral 25 is an air-fuel ratio control unit composed of the above-mentioned elements.

Reference numeral 26 is a frame rod, which is attached to a location facing the burner head and exposed to the combustion flame. Two
Reference numeral 7 denotes a combustion detection unit that converts the flame current generated by the flare rod into a combustion control signal. Reference numeral 28 denotes an oxygen deficiency correction unit, which outputs a combustion amount correction output to the combustion control unit 18 in response to a combustion control signal from the combustion detection unit. In other words, if the flame rod output decreases despite the air-fuel ratio control, it is determined that the oxygen deficiency condition exists, and the combustion amount is corrected according to the flame rod output to eliminate the air-fuel ratio imbalance. Fix it.

The operation of the combustion control device having the above construction will be described with reference to the flow charts of FIGS. 2, 3 and 4. First, when the indoor environment is normal, the air-fuel ratio target value is initialized by starting operation, and at the same time, a predetermined voltage is applied to the sensor heater and the sensor. The power source of the sensor heater switches the voltage level by the power source switching unit 10A when a predetermined time has elapsed. This is done to improve the initial response of the sensor.

In that state, wait for the stability of the sensor output,
After a lapse of a predetermined time, the sensor output is read, and compared with the standard output characteristic, self-correction is performed to the initial value of the air-fuel ratio target,
If it is within the limiter range, the air-fuel ratio target value is updated.
If it is out of the limiter range, stop it. That is, it is performed for the purpose of correcting the deviation of the output characteristic due to deterioration and the like, and as shown in FIG. 5, the initial value D of the air-fuel ratio is corrected from the slope D / C of the standard characteristic and the sensor reading value E,
The air-fuel ratio target value F point is calculated. Without this self-correction operation, the oxygen concentration in the combustion exhaust gas controlled at the air-fuel ratio D point becomes large with the output characteristics deviated. In other words, combustion with a low carbon dioxide setting tends to be lifted. Therefore, by correcting the air-fuel ratio to point F, combustion is performed at a regular oxygen concentration.

Next, the combustion control unit 24 starts the combustion operation in a predetermined combustion sequence, and thereafter, performs the combustion under predetermined conditions until the combustion becomes stable. When a predetermined time elapses and the K value control operation for controlling the combustion amount by the difference between the set temperature and the room temperature is entered, the air-fuel ratio target value is further corrected to a value suitable for the combustion amount and set as the air-fuel ratio target value. . At the same time, the sensor output is read and compared with the air-fuel ratio target value to perform a correction operation.
The correction operation will be described with reference to FIG. 3. The correction is performed within a predetermined width (comparison amount X) with respect to the air-fuel ratio target value. Is set to + Y% (2%), conversely, in the case of the air-fuel ratio target value + comparison amount X, -Y% (2%) is set as the correction amount, and the read value of the sensor output is within the comparison amount range. In the case of, the correction amount is set to 0%. This cycle of setting the correction amount is repeated for a predetermined time (400 ms),
Further, when a predetermined time (2 seconds) has elapsed, the correction amount is determined. Further, the correction amount calculation in the correction amount setting cycle is performed by an integration method, and the combustion state for 2 seconds is averaged to perform the correction.

Next, when the correction amount is determined, the limiter 17
Checks whether the correction amount is within the preset allowable range. If the correction amount is within the allowable range, the output is sent to the drive circuit, the motor or the electromagnetic pump is controlled, and adjustment is made so that combustion is performed at the set air-fuel ratio. If it is out of the allowable range, it is regarded as an abnormal use state and stopped. When the series of correction operations are completed, the sensor output is read again and the same correction operation is repeated.

By repeating the above operation, the change in the sensor characteristics is corrected, the optimum air-fuel ratio is set according to the combustion amount, the variable range of the combustion amount is expanded, and the influence of each factor on combustion is corrected. The combustion state at each combustion amount can be optimally controlled.

FIG. 6 shows the relationship between sensor characteristics and carbon dioxide characteristics. By controlling the air-fuel ratio by the target value ± comparative amount X, it is possible to control carbon dioxide within a specified set range in any combustion condition fluctuation.

Next, when the oxygen concentration in the room decreases and the oxygen deficiency state occurs, the burner motor speed is corrected upward by the air-fuel ratio control operation described above, and the air amount is increased to increase the set air-fuel ratio. However, when the oxygen concentration of the supply air is low, the correction amount becomes larger than the correction at the normal oxygen concentration, so the burner motor speed also increases and the supply air amount also increases. Will be done. In other words, if the air amount is reduced due to clogging of the air supply path and correction is applied, the supply air amount at the set air-fuel ratio does not change even if the burner motor speed increases, so the combustion state is normal combustion at the set air-fuel ratio. To maintain. However, during the air-fuel ratio control in the oxygen-deficient state, as described above, the amount of supplied air increases, so that the combustion balance is not deteriorated, but the combustion flame blows off to cause a misfire. In other words, carbon dioxide is a phenomenon in which it misfires while being maintained in the set state.

Therefore, in the present invention, in addition to the confirmation of the combustion state by the oxygen sensor 9, the confirmation of the combustion state by the frame rod 26 and the combustion detection unit 27 is also performed, and the oxygen deficiency correction unit 28 is detected by the combustion detection signal from the frame rod 26. Through,
The air-fuel ratio target value of the air-fuel ratio control unit 25 is corrected. This specific operation will be described with reference to FIGS. 4, 7 and 8.

When the indoor oxygen concentration decreases, the flame rod output gradually decreases from the initial value FR1 in the air-fuel ratio control region, and after a certain point, it begins to decrease extremely. If it is left as it is, it will be blown out, but here the frame rod output is the predetermined level FR2.
When the predetermined time elapses, the combustion coefficient that becomes the combustion amount output is changed to A0, that is, the combustion amount is decreased, that is, the correction amount of the motor rotation speed is decreased and the air amount is decreased. As a result, the blowout state of the combustion flame is eliminated and the normal flame is restored. Therefore, the frame rod output also changes in a stable or increasing direction. When the flame rod output is between the predetermined levels FR2 and FR1, the combustion coefficient is A0.
Then, the flame rod output is restored to FR1, and when that state has passed for a predetermined time or longer, the combustion coefficient is set to the original value again.

However, even if the combustion coefficient is changed to A0, the flame rod output does not recover, and the flame rod output becomes FR.
When it falls below 3 and the predetermined time has elapsed, the combustion coefficient is further changed to FF with a low combustion amount. When the flame rod output recovers to FR3 or more by this correction operation, the combustion coefficient is changed to A0 and the change in the flame rod output is observed. When the flame rod output is further recovered and becomes FR1 or more, the combustion coefficient is corrected to the original value. On the contrary, if the flame rod output does not recover even if the combustion coefficient is changed to FF and it drops below FR4, it is regarded as oxygen deficiency detection and the operation is stopped.

By correcting the combustion coefficient, that is, the combustion amount in the state of the flame rod output as described above, the premature disconnection phenomenon due to the decrease in the oxygen concentration in the room is eliminated, the combustion is stopped at a predetermined oxygen deficiency level, and the optimum empty space is obtained. By controlling the combustion with the fuel ratio, the variable range of the combustion amount can be expanded, and the combustion state with each combustion amount can be kept optimal.

It should be noted that the above-mentioned embodiments are merely examples in which the present invention is effectively embodied. For example, the oxygen sensor and burner configurations are not limited to those of the embodiments, and the combustion air is used. Instead of controlling the amount, the fuel amount or both may be controlled, and any configuration may be adopted as long as the object of the present invention is achieved.

[0026]

As described above, the combustion control device of the present invention performs the air-fuel ratio control for adjusting the balance between the fuel amount and the combustion air amount by the oxygen sensor so as to keep the oxygen concentration in the exhaust gas constant. At the same time, the combustion state is detected by the flame rod placed in the combustion flame, and if the decrease in the indoor oxygen concentration is judged by the change state of the flame rod output, and if there is a lack of oxygen, the combustion amount setting is changed and controlled. Therefore, there is no possibility of premature disconnection in the oxygen deficient state due to the large amount of supply air during air-fuel ratio control,
It is possible to provide a highly safe and easy-to-use combustor by reducing combustion troubles due to changes in operating environment conditions and aging factors.

Further, by correcting the air-fuel ratio target value according to the combustion amount, the combustion state at each combustion amount can be optimally controlled, and the variable range of the combustion amount can be greatly expanded.

Further, since the self-correction operation for correcting the air-fuel ratio target value is performed according to the output state of the oxygen sensor, highly accurate combustion control can be performed even if the oxygen sensor changes with time.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing the operation of the device.

FIG. 3 is a flowchart showing the operation of the device.

FIG. 4 is a flowchart showing an oxygen deficiency control operation of the apparatus.

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

FIG. 6 is a characteristic diagram showing a relationship between a sensor output and carbon dioxide by the device.

FIG. 7 is a characteristic diagram showing the relationship among indoor oxygen concentration, combustion count (combustion amount), and flame rod output by the same device.

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

[Explanation of symbols]

 1 Burner fan 3 Burner 5 Electromagnetic pump 7 Exhaust path 9 Oxygen sensor 14 Air-fuel ratio target setting unit 16A Control output unit 20 K value correction unit 21 Self-correction unit 26 Frame rod 27 Combustion detection unit 28 Oxygen deficiency correction unit

Claims (2)

[Claims] 1. A burner, an oxygen sensor provided in an exhaust path of the burner, a combustion control unit for controlling a combustion amount of the burner, and an output from the oxygen sensor as an air-fuel ratio target value of an air-fuel ratio target setting unit. A control output unit that outputs a control output for at least one of the combustion air amount and the fuel amount, and a combustion detection unit that detects the combustion state of the burner with a frame rod and confirms the combustion state. A combustion control device comprising: an oxygen deficiency correction unit that changes a combustion amount set by the combustion control unit based on an output from a combustion detection unit. 2. A burner having a vaporization tube for vaporizing fuel, which burns vaporized gas from the vaporization tube, an electromagnetic pump for supplying fuel to the vaporization tube, and a burner fan for supplying combustion air to the vaporization tube. And a combustion control unit that controls the combustion amount by driving the electromagnetic pump and the burner fan, a flame rod provided in the combustion flame, and a combustion that detects the flame current generated by the flame rod and confirms the combustion state. A detection unit, a limiting current type oxygen sensor provided in the exhaust path of the burner, a self-correction unit that corrects deterioration of sensor characteristics of the oxygen sensor, and an air-fuel ratio target based on the combustion amount control output from the combustion control unit. K-value correction unit for correcting the value, an air-fuel ratio target setting unit for setting an air-fuel ratio target value based on the outputs from the self-correction unit and the K-value correction unit, output from the oxygen sensor and air-fuel ratio target setting A control output unit that outputs an output for control of at least one of combustion air amount and fuel amount by comparing the output from the unit, and a combustion amount set in the combustion control unit based on the output from the combustion detection unit. A combustion control device including an oxygen deficiency correction unit that changes