JPH0712333A - Combustion control device - Google Patents

Abstract

PURPOSE:To expand a variable margin of the amount of combustion by setting an optimum air fuel ratio in conformity with the amount of combustion. CONSTITUTION:This combustion control device comprises an oxygen sensor 9 installed to an exhaust passage of a burner, a K value correction unit 20 which outputs a correction value of an air fuel ratio based on the combustion output from a combustion controller 24, an air fuel ratio target value setting unit 14 which sets an air fuel ratio based on the output from the K value correction unit and a control output unit 16A which outputs either the amount of combustion air or the amount of fuel based on the output from the air fuel target value setting unit and the output from the above oxygen sensor. The target value of the air fuel ratio is corrected in conformity with the amount of combustion so as to attain the setting air fuel ratio under control. This construction makes it possible to secure an optimum combustion state in each amount of combustion and prevent the oxygen sensor from malfunctioning by changes with time or the like and perform highly accurate control as well.

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 various combustion appliances.

[0002]

2. Description of the Related Art Conventionally, for example, as shown in FIG. 5, in a combustion control device for an oil burning appliance, a heater 51 is energized at the start of operation, and when a vaporization cylinder 52 reaches a set temperature, a burner fan 54 is driven to drive a fuel. The pump 55 is energized, an ignition operation is performed by the ignition device, and the combustion proceeds. When the combustion is started, the combustion control unit 5 adjusts the air-fuel ratio to a preset value.
7 controls the burner motor 56 and the fuel pump 55 to perform combustion.

[0003]

However, in the combustion control of the above-mentioned configuration, considering the combustion efficiency, thermal problems, and characteristic balance such as NOx emission amount, etc., in the entire range of the variable combustion amount, the variable range of the combustion amount. There was a problem that could not be taken too large.

That is, generally, the combustion state is determined by the air-fuel ratio, that is, the amount of primary air, and if the air-fuel ratio is set near 1 in order to improve the thermal efficiency, the flame temperature becomes high,
There is a problem with flashback and heat resistance of parts, and dew condensation occurs due to a decrease in exhaust temperature in a region where the amount of combustion is small. Also N
The amount of Ox discharged becomes extremely large. On the other hand, if the air-fuel ratio is set to about 1.6 in order to lower the flame temperature, the NOx emission amount will also decrease and the thermal problem will be reduced, but this will lead to a decrease in combustion efficiency and blow in a region where the combustion amount is small. The problem of disappearing occurs.

Therefore, in the above-mentioned conventional configuration, the air-fuel ratio is set to an intermediate value of about 1.4, and the variable width of the combustion amount is set within the combustion range where the above problems do not occur. It corresponds. Therefore, the variable range of the combustion amount was extremely small. In addition, the air-fuel ratio is a fixed value even when the combustion air amount fluctuates due to fluctuations in the electromagnetic pump flow rate, motor rotation speed, fan variations, and clogging of the air supply path, which are factors that affect the combustion state. Proper combustion can be secured only within the allowable range of burner capacity,
If the amount of fluctuation exceeds that, abnormal combustion occurs.

The present invention is intended to solve the above problems, and has as its first object to expand the variable range of the combustion amount by setting the optimum air-fuel ratio according to the combustion amount, and to improve the control accuracy. The second purpose is to further improve safety
The purpose of.

[0007]

In order to achieve the above object, the present invention provides a burner, an oxygen sensor provided in the exhaust passage of the burner, a combustion control unit for controlling the combustion amount of the burner, and the combustion control. Value correction unit that outputs a corrected output of the air-fuel ratio based on the combustion amount output from the unit, an air-fuel ratio target value setting unit that sets the air-fuel ratio based on the output from this K-value correction unit, and the air-fuel ratio target There is provided a control output unit that outputs a control output for at least one of the combustion air amount and the fuel amount based on the output from the value setting unit and the output from the oxygen sensor. A self-correction unit that corrects the sensor output due to deterioration of the characteristics of the oxygen sensor is provided, and the air-fuel ratio target value setting unit sets the air-fuel ratio based on the outputs from the self-correction unit and the K value correction unit. It is configured to control at least one of the combustion air amount and the fuel amount based on the output from the air-fuel ratio target value setting unit and the output from the oxygen sensor, and A limiter that outputs a combustion stop output is provided when the control output from the control output unit that outputs at least one of the air amount and the fuel amount is out of a predetermined output range.

[0008]

According to the present invention, according to the above configuration, the air-fuel ratio target value is corrected according to the combustion amount, and the control for correcting the combustion air amount or the fuel amount by the output of the oxygen sensor so that the set air-fuel ratio is achieved. As a result, the optimum combustion state can be secured for each combustion amount. In other words, the amount of air or the amount of fuel is automatically changed according to the combustion state to adjust the combustion state, so that variations in parts, effects due to changes in operating environment conditions, and changes in combustion conditions due to changes over time are covered within a predetermined range. Therefore, it is possible to expand the variable range of the combustion amount.

Further, since the target value of the air-fuel ratio can be corrected according to the change of the output characteristic of the oxygen sensor, it is possible to prevent the malfunction of the oxygen sensor due to the change with time and the like, and it is possible to perform the highly accurate control.

If the output for controlling the combustion air amount or the fuel amount from the control output unit is out of a predetermined output range, the control output unit is provided with a limiter that outputs a combustion stop output so that the normal combustion range is controlled. If it is not possible, combustion will be stopped and safety will be improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment 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, 2 is a motor, and constitutes a burner fan that supplies combustion air together with the fan 2A. Reference numeral 3 denotes a vaporization cylinder for vaporizing the fuel and mixing it with combustion air. A heater 4 and a temperature detection sensor 8 are embedded in the vaporization cylinder. 5 is an electromagnetic pump for supplying fuel into the vaporization cylinder 3,
6 is a heat exchanger for exchanging heat with the combustion gas, and 7 is an exhaust path for discharging the heat-exchanged combustion gas.

A limiting current type oxygen sensor 9 is attached to the exhaust passage 7 to measure the oxygen concentration in the combustion gas. Reference numeral 10 is a power source for the heater of the oxygen sensor, which heats the heater incorporated in the oxygen sensor. 1
Reference numeral 0A 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. 13 is an amplifier, which is the oxygen sensor 9
Is amplified to be input to the air-fuel ratio control unit.

Reference numeral 14 is an air-fuel ratio target value setting unit, and 15 is a correction calculation unit, which compares the output of the oxygen sensor 9 with the air-fuel ratio target value to calculate a correction value. Reference numeral 16 denotes 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, and the correction calculation unit 15 constitutes a control output unit 16A. 1
A limiter 7 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, 19 is a vaporization tube temperature setting unit, 20
Is a K value correction unit that corrects the target value of the air-fuel ratio, and corrects and calculates the target value of the air-fuel ratio based on the combustion amount output from the combustion control unit 24. A self-correction unit 21 detects the initial output characteristic of the oxygen sensor and outputs a correction value for the target value of the air-fuel ratio according to the characteristic. Reference numeral 22 is a limiter, which is a part that limits the target value correction result of the air-fuel ratio, and is stopped when it goes out of a predetermined range. Reference numeral 23 is an electromagnetic pump drive circuit, 24 is a combustion control unit, and 25 is an air-fuel ratio control unit composed of the above-mentioned elements.

The operation of the combustion control device having the above structure will be described with reference to the flow charts of FIGS. First, 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 oxygen sensor 9. The sensor heater power source 10 switches the voltage level by the power source switching unit 10A when a predetermined time elapses. This is done to improve the initial response of the oxygen sensor 9.

Next, in that state, the stability of the sensor output is waited, the sensor output is read after a lapse of a predetermined time, and the sensor output is compared with a predetermined standard output characteristic of the oxygen sensor 9 and self-corrected to the initial value of the air-fuel ratio target. If it is within the limiter range, the target value setting unit 14 updates the air-fuel ratio target value. If it is out of the limiter range, the driving operation is stopped. That is, the deviation of the output characteristics due to the deterioration of the oxygen sensor 9 is corrected. As shown in FIG. 4, the air-fuel ratio initial value D is corrected based on the slope D / C of the standard characteristic and the sensor read value E to obtain the air-fuel ratio target value F point. 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 the operation to control the combustion amount by the difference between the set temperature and the room temperature (hereinafter referred to as K value control operation) is started after a predetermined time has elapsed, the air-fuel ratio target value is further corrected to a value suitable for the combustion amount and Set as the fuel ratio target value. That is,
The K value correction unit 2 based on the combustion amount output from the combustion control unit 24.
0 calculates the air-fuel ratio according to the combustion amount, and the target value setting unit 14 receives the corrected output thereof and sets the air-fuel ratio target value. Then, the sensor output is read and compared with the target value of the air-fuel ratio, and in this embodiment, the correction operation of the combustion air amount is performed.

The correction operation will be described with reference to FIG. 3. The correction is performed within a predetermined range (comparison amount X) with respect to the air-fuel ratio target value. Sets + Y% (2%) as the correction amount. Conversely, in the case of the air-fuel ratio target value + the comparison amount X, the correction amount is −
Y% (2%) is set, and if the read value of the sensor output is within the comparison amount range, the correction amount is set to 0%. This correction amount setting cycle is repeated for a predetermined time (400 ms), and when the 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 of the combustion air amount is determined, the limiter 17 checks whether or not the correction amount is within a preset allowable range, and if it is within the allowable range, the output is sent to the burner motor drive circuit 18. , The motor 1 is controlled and adjusted to burn at the set air-fuel ratio. If it is out of the allowable range, it is regarded as an abnormal use state and stopped. Then, 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 optimum air-fuel ratio is set according to the combustion amount, the variable range of the combustion amount is expanded, the influence of each factor on the combustion is corrected, and the change in the sensor characteristic is corrected. Thus, the combustion state at each combustion amount can be accurately and optimally controlled.

The relationship between the sensor characteristics and carbon dioxide is shown in FIG. 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.

It should be noted that the above-mentioned embodiments are merely examples in which the present invention is effectively embodied. For example, the forms of the oxygen sensor and the burner 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.

[0022]

As described above, the combustion control device of the present invention can optimally control the combustion state at each combustion amount by correcting the output of the oxygen sensor according to the combustion amount. The variable width can be greatly expanded, and combustion troubles due to variations in the combustion amount and the combustion air amount due to various factors, variations in parts, changes in operating environment conditions, etc. can be reduced.

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.

Further, when the normal combustion range cannot be controlled, the combustion is stopped, so that the safety is improved.

[Brief description of drawings]

FIG. 1 is a configuration 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 a combustion air amount correction operation by the device.

FIG. 4 is a characteristic diagram of an oxygen sensor using the same device.

FIG. 5 is a characteristic diagram showing a control situation by the device.

FIG. 6 is a configuration diagram of a conventional combustion control device.

[Explanation of symbols]

 1 Burner 7 Exhaust Path 9 Oxygen Sensor 10 Heater Power Supply Section 10A Power Supply Switching Section 11 Sensor Power Supply Section 14 Air-Fuel Ratio Target Value Setting Section 16A Control Output Section 17 Limiter 20 K Value Correction Section 21 Self-Correction Section 24 Combustion Control Section

Claims (4)

[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 a correction output of an air-fuel ratio based on a combustion amount output from the combustion control unit. The K-value correction unit that outputs the value, the air-fuel ratio target value setting unit that sets the air-fuel ratio based on the output from the K-value correction unit, the output from the air-fuel ratio target value setting unit, and the output from the oxygen sensor. A combustion control device comprising: a control output unit that outputs a control output for at least one of a combustion air amount and a fuel amount based on the control output unit. 2. 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 a correction output of an air-fuel ratio based on a combustion amount output from the combustion control unit. A K value correction unit that outputs a value, a self-correction unit that corrects the sensor output due to deterioration of the characteristics of the oxygen sensor, and an air-fuel ratio target that sets an air-fuel ratio based on the outputs from the self-correction unit and the K value correction unit. Combustion consisting of a value setting unit and a control output unit that outputs a control output for at least one of the combustion air amount and the fuel amount based on the output from the air-fuel ratio target value setting unit and the output from the oxygen sensor Control device. 3. The oxygen sensor is a limiting current type oxygen sensor, and is equipped with a power source unit for a heater for heating a sensor, a power source switching unit for switching a heater voltage in a predetermined sequence, and a sensor power source unit for generating a limiting current, The self-correction unit for correcting deterioration of sensor characteristics is configured to perform output correction by comparing a sensor output obtained before the start of combustion of the burner with a preset sensor output.
The combustion control device described. 4. A burner, an oxygen sensor provided in the exhaust path of the burner, a combustion control unit for controlling the combustion amount of the burner, and a correction output of the air-fuel ratio based on the combustion amount output from the combustion control unit. The K-value correction unit that outputs the value, the air-fuel ratio target value setting unit that sets the air-fuel ratio based on the output from the K-value correction unit, the output from the air-fuel ratio target value setting unit, and the output from the oxygen sensor. A control output unit that outputs a control output for at least one of combustion air amount and fuel amount based on the above, and a combustion stop output when the control output from the control output unit is outside a predetermined output range Combustion control device consisting of a limiter.