JPH0626640A - Combustion apparatus - Google Patents

Abstract

PURPOSE:To provide a highly reliable combustion apparatus capable of carrying out combustion in an optimum air/fuel ratio at all times by gradually varying the supply rate of fuel. CONSTITUTION:The feed rate of air is controlled by a control unit 8 on the basis of an oxygen concentration signal released from a limiting current type oxygen sensor 4 disposed in an exhaust gas flow passage 5. A fuel supplying means 1 has: a fuel supply rate detecting means 9; a fuel supply rate instructing means 10 for newly instructing the supply rate of fuel; and a fuel supply rate varying means 11 for gradually varying the supply rate of fuel according to differences between the supply rate of fuel newly instructed and the supply rate of fuel detected by the fuel supply rate detecting means 9, all these means being provided additionally to the fuel supplying means 1 and electrically connected thereto. Variations in the supply rate of fuel is gradually effected according to differences between the supply rate of fuel newly instructed by the fuel supply rate instructing means 10 and the supply rate of fuel detected by the fuel supply rate detecting means 9. As a result, favorable combustion characteristics can be obtained at all times without generating a large amount of carbon monoxide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion device for performing combustion while controlling a fuel supply amount or an air supply amount using a limiting current type oxygen sensor.

[0002]

2. Description of the Related Art In conventional combustion equipment, the ratio of the air supply amount to the fuel supply amount (hereinafter referred to as the air-fuel ratio) is calculated in advance so that complete combustion can be obtained, and the air supply amount based on the calculation. Alternatively, it was burned with the fuel supply amount. However, when the combustion equipment is used in various environments, the air-fuel ratio fluctuates from the initially calculated value due to fluctuations in outside air temperature and atmospheric pressure, and fluctuations in the durability of the fuel supply means and air supply means. Incomplete combustion may occur if the air-fuel ratio is used as it was originally calculated on a flat land in a high altitude of oxygen-diluted environment of m.

As a means to solve this, focusing on the fact that the air-fuel ratio correlates with the oxygen concentration in the combustion exhaust gas, a limiting current type oxygen sensor for measuring the oxygen concentration was developed, and this sensor was used in the combustion exhaust gas passage. Attempts have been made to develop combustion equipment that is placed in the air conditioner to control the optimum air-fuel ratio.

FIG. 4 shows an example of conventional combustion equipment. In this combustion apparatus, the fuel is supplied by the fuel supply means 41, the air is supplied by the air supply means 42, the fuel is burned in the combustion section 43, and the combustion exhaust gas is exhaust gas passage 45 in which the limiting current type oxygen sensor 44 is arranged. It is configured to exhaust through. On the other hand, the limiting current type oxygen sensor 44 is connected to the DC voltage source 46 in series.
And the limiting current detecting means 47 are connected to form a closed circuit, and the output side of the limiting current detecting means 47 is connected to the microcomputer 48 to detect the oxygen concentration signal from the limiting current type oxygen sensor 44 by the microcomputer 48. In addition, the microcomputer 48 is electrically connected to the air supply means 42 and the fuel supply means 41, and the supplied air amount or supplied fuel amount is controlled by the microcomputer 48 based on the oxygen concentration signal from the limiting current type oxygen sensor 44. It is configured to do.

In FIG. 5, reference numeral 49 is ZrO ₂ .Y ₂ O ₃ which is an oxygen ion conductive solid electrolyte plate, and a pair of platinum electrode films is formed on both sides in pairs. A spiral spacer 51 made of glass, which surrounds a cathode-side electrode film 50 made of a platinum electrode film and is arranged so that its start end and end end are spaced apart from each other, is arranged above one side of the solid electrolyte plate 49. . A seal plate 52 is arranged on the upper part of the spiral spacer 51, and a heating part 53 is arranged on the upper part of the seal plate 52 to form a sensor element. The diffusion-controlling body is composed of a spiral spacer 51 and a seal plate 52, and the oxygen diffusion passage 54 is a spiral space surrounded by the opposing partition walls of the spiral spacer 51, the solid electrolyte plate 49, and the seal plate 52. It is formed. Oxygen diffuses into the cathode-side electrode film 50 via the oxygen diffusion passage 54 and exhibits limiting current characteristics. The operating temperature of the sensor is 450 ° C.

[0006]

However, in the configuration in which the air-fuel ratio control is performed by using the limiting current type oxygen sensor, if the limiting current type oxygen sensor operating at 450 ° C. is used, the response is slow and good combustion is achieved. There is a problem that a large amount of carbon monoxide is generated by incomplete combustion until the characteristics are not obtained and the oxygen concentration stabilizes up to the set concentration (set air-fuel ratio value). Therefore, the operating temperature of the limiting current type oxygen sensor needs to be raised to 700 ° C. in order to speed up the response, but the operating temperature is high, so that the life is short and the sensor needs to be replaced periodically.

The present invention solves the above-mentioned problems of the prior art. Even if the sensor has a slow response, incomplete combustion does not occur.
It is an object of the present invention to provide a highly reliable combustion device that always burns at an optimum air-fuel ratio.

[0008]

In order to solve the above-mentioned problems, the combustion equipment of the present invention is an air supply system for supplying air to a combustion section based on an oxygen concentration signal from a limiting current type oxygen sensor arranged in an exhaust gas passage. In the combustion device that controls the supply unit by the control unit, the fuel supply unit that supplies the fuel to the combustion unit,
Fuel supply amount detecting means for detecting the fuel supply amount in the fuel supply means, fuel supply amount command means for newly instructing the fuel supply amount in the fuel supply means, and fuel supply amount detected in the fuel supply amount detecting means A fuel supply amount changing means for gradually changing the fuel supply amount according to the difference in the newly supplied fuel supply amount, and the fuel supply amount change means newly instructing the fuel supply amount change means. It is configured to be gradually performed based on the amount.

[0009]

With the above structure, the combustion device gradually changes the fuel supply amount based on the newly commanded fuel supply amount. Therefore, even if a limiting current type oxygen sensor having a slow response is used, the air supply amount is accordingly changed. Since it changes gradually, good combustion characteristics can always be obtained without generating a large amount of carbon monoxide due to incomplete combustion.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, the combustion equipment supplies fuel by a fuel supply means 1 and burns fuel in a combustion part 3 while supplying air by an air supply means 2 to generate a combustion exhaust gas by a limiting current type oxygen sensor 4. The exhaust gas is arranged to be exhausted through the arranged exhaust gas passage 5. On the other hand, the limiting current type oxygen sensor 4 is connected in series with a DC voltage source 6 and a limiting current detecting means 7 to form a closed circuit, and the output side of the limiting current detecting means 7 is connected to a control section 8.
The oxygen concentration signal from the limiting current type oxygen sensor 4 is detected by the control unit 8 by being connected to. Further, the control unit 8 is electrically connected to the fuel supply unit 1 and the air supply unit 2, and the supply amount of air is controlled by the control unit 8 based on the oxygen concentration signal from the limiting current type oxygen sensor 4.

On the other hand, the fuel supply means 1 includes a fuel supply amount detection means 9 for detecting the fuel supply amount in the fuel supply means 1.
Depending on the fuel supply amount command means 10 for newly instructing the fuel supply amount in the fuel supply means 1, and the difference between the newly commanded fuel supply amount and the fuel supply amount detected by the fuel supply amount detecting means 9. A fuel supply amount changing means 11 for gradually changing the fuel supply amount is provided side by side and electrically connected. Therefore, the change in the fuel supply amount is gradually performed according to the difference between the fuel supply amount newly instructed by the fuel supply amount commanding means 10 and the fuel supply amount detected by the fuel supply amount detecting means 9.

FIG. 2 is a flow chart of the control of the combustion equipment which is an embodiment of the present invention. In FIG. 2, when the start button is pressed, the RAM of the microcomputer is cleared and new data can be written. When the combustion is started, the fuel supply amount Qn is detected. Next, the newly commanded fuel supply amount Q is called, and Qn
By comparing Q and Q, the fuel supply amount is set to gradually change according to the difference. On the other hand, the oxygen concentration in the combustion exhaust gas is read as Bn. Then, the preset value B stored in advance is called, and the oxygen concentration Bn in the combustion exhaust gas is compared with the preset value B stored in advance. When the oxygen concentration Bn in the combustion exhaust gas is larger than the set value B, the supply air amount is reduced, and the oxygen concentration in the combustion exhaust gas becomes B again.
read as n. On the other hand, when the oxygen concentration Bn in the combustion exhaust gas is smaller than the set value B, the supply air amount is increased and the oxygen concentration in the combustion exhaust gas is read again as Bn. Hereinafter, the control to the optimum oxygen concentration B is performed by repeating this.

On the other hand, regarding the comparison between the detected fuel supply amount Qn and the newly commanded fuel supply amount Q, the comparison is always performed separately from this control flow. When the newly commanded fuel supply amount Q is generated, the fuel supply amount is set to gradually change according to the difference by comparing Q, and it is detected that the newly commanded fuel supply amount Q does not occur. Fuel of the fuel supply amount Qn is supplied.

The effect of the present invention was evaluated using the limiting current type oxygen sensor of FIG. 5 and the combustion equipment of FIG. In the combustion device of FIG. 1, the slowest response is the limiting current type oxygen sensor, which has a 90% response for 20 seconds. Other means respond in less than 1 second.

In FIG. 3, the limiting current value generated from the limiting current type oxygen sensor and the carbon monoxide concentration in the combustion exhaust gas when the oxygen concentration, that is, the air-fuel ratio is changed in the combustion equipment, are measured in a stable combustion state. It is a thing. The limiting current value generated from the limiting current type oxygen sensor shows a characteristic approximately proportional to the oxygen concentration and further a characteristic substantially proportional to the air-fuel ratio. On the other hand, carbon monoxide in the combustion exhaust gas has an air-fuel ratio of 1.2.
In the case of up to 2.0, the least characteristic is shown.

800g / hr of kerosene and 13.68 in combustion equipment
After supplying air of Nm ³ to start combustion, the fuel supply amount to be newly supplied was commanded to be 400 g / hour. Based on this new supply amount command of 400 g / hour, the current supply amount of 800
In order to gradually change the fuel supply rate according to the difference of 400 g / hour from g / hour, a control mode is set to change the fuel supply rate at a rate of 100 g / hour every 10 seconds, and a new supply rate command is issued after 40 seconds. It was set to 400 g / hour. On the other hand, in the air-fuel ratio control by the limiting current type oxygen sensor, the combustion target is the oxygen concentration 7.0% region where the generation amount of carbon monoxide is small, and the limiting current value generated by the limiting current type oxygen sensor at that time is 37 μA. Thus, the control unit 8 controls the air supply means 2 based on the oxygen concentration signal. As a result, the oxygen concentration always maintained the 7.0% region even after the fuel supply amount changed from 800 g / hour to 400 g / hour for about 40 seconds and thereafter. This is because the fuel supply amount does not change slightly or the air supply amount does not change slightly, and if the change is small, a limiting current type oxygen sensor having a slow response can sufficiently cope with the change. Therefore, as can be seen from FIG. 3, the air-fuel ratio control of good combustion in which the air-fuel ratio is always present in the region where the amount of carbon monoxide generated is small was achieved. On the other hand, in the case of performing air-fuel ratio control with only the limiting current type oxygen sensor with a slow response in the combustion equipment, if the combustion amount is immediately changed to 400 g / hour of the newly supplied fuel amount, the supply air amount will be delayed to the optimum value. However, there is a problem that the air-fuel ratio shifts and a large amount of carbon monoxide is generated for about 20 seconds until the supply air amount reaches the optimum value.

[0018]

As described above, according to the present invention, the control section controls the air supply means for supplying the air to the combustion section based on the oxygen concentration signal from the limiting current type oxygen sensor arranged in the exhaust gas passage. A fuel supply amount detecting means for detecting the fuel supply amount of the fuel supply means, and a fuel supply amount command means for newly instructing the fuel supply amount of the fuel supply means And the fuel supply amount changing means for gradually changing the fuel supply amount according to the difference between the fuel supply amount detected by the fuel supply amount detecting means and the newly commanded fuel supply amount, are jointly provided side by side. The fuel supply amount command means gradually changes the fuel amount in accordance with the difference from the fuel supply amount newly commanded. Therefore, since the fuel supply amount is gradually changed based on the newly commanded fuel supply amount, the air supply amount is gradually changed with the use of the limiting current type oxygen sensor having a slow response, and incomplete combustion occurs. Therefore, good combustion characteristics are always obtained without generating a large amount of carbon monoxide.

[Brief description of drawings]

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

FIG. 2 is a flowchart of the control flow.

FIG. 3 is a characteristic diagram of the sensor and the combustion device.

FIG. 4 is a block diagram of a conventional combustion device.

FIG. 5 is a sectional perspective view of the same limiting current type oxygen sensor.

[Explanation of symbols]

 1 Fuel Supply Means 2 Air Supply Means 3 Combustion Section 4 Limiting Current Oxygen Sensor 5 Exhaust Gas Flow Path 6 DC Voltage Source 7 Limiting Current Detecting Means 8 Control Section 9 Fuel Supply Quantity Detecting Means 10 Fuel Supply Quantity Command Means 11 Fuel Supply Quantity Change means

Claims (1)

[Claims] 1. A fuel supply device supplies fuel, and an air supply device supplies air to burn the fuel in a combusting section, exhaust combustion exhaust gas through an exhaust gas passage, and a limiting current type in the exhaust gas passage. An oxygen sensor is arranged, a direct current voltage source and a limiting current detecting means are connected in series to the limiting current type oxygen sensor to form a closed circuit, and the output side of the limiting current detecting means is further connected to a control unit, and The oxygen concentration signal from the limiting current type oxygen sensor is detected by the control unit, and the control unit and the air supply unit and the fuel supply unit are electrically connected to each other to obtain the oxygen concentration from the limiting current type oxygen sensor. In a combustion device in which the control unit controls the air supply unit based on a signal, a fuel supply unit for supplying fuel to the combustion unit detects a fuel supply amount of the fuel supply unit. An amount detection means, a fuel supply amount command means for newly instructing the fuel supply amount in the fuel supply means, and a difference between the fuel supply amount detected by the fuel supply amount detection means and the newly instructed fuel supply amount. A fuel supply amount changing means for gradually changing the fuel supply amount is connected to the fuel supply amount changing means, and the fuel supply amount is changed according to the difference from the fuel supply amount newly instructed by the fuel supply amount instruction means. Combustion equipment that gradually changes.