JPS59196454A - Combustion state detecting method - Google Patents

Abstract

PURPOSE:To effectively remove factors except for A/F ratio determining the combustion state by a method wherein the air/fuel ratio is detected from electric resistance of a metal oxide semiconductor with the combustor in exhaust gas and the exhaust gas temperature. CONSTITUTION:Upon receiving signals indicative of temperature and electric resistance from a metal oxide semiconductor gas sensor 10 mounted in an exhaust pipe 20 of an automobile engine, a data processor 30 sends a signal to a fuel injection amount controller 40. From the relationship curves between the electric resistance from the gas sensor and the exhaust gas temperature which are measured by operating an engine in ranges of 1,500-3,000rpm, 20-40 deg. ignition angle, 1/4- full load and 13-16.5 air/fuel ratio, which substantially satisfy the normal operation state of the automobile, it will be clearly observed that the A/F ratio can be determined with high accuracy independent of rpm, load and ignition angle.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention detects the combustion state of a combustor such as a gas or oil stove, or a car engine, which burns a fuel mainly composed of hydrocarbons mixed with the atmosphere. Regarding how to.

(Conventional structure and its problems) Generally, SnOr ZnO+ Tie2+ Fe2O3
+ It is widely known that the electrical resistance value of metal oxide semiconductors such as Coo changes depending on the gas composition in the atmosphere, and this phenomenon has been used to detect the combustion state of internal combustion engines, burners, etc. ing. In other words, it attempts to save fuel by detecting increases and decreases in the concentration of specific components in exhaust gas, mostly oxygen or oxidizing gases such as NOx, and controlling the air-fuel ratio (hereinafter referred to as A/'F). It is something.

However, the exhaust gas component composition cannot always be obtained in a form that corresponds to the combustion state. Taking an automobile engine as an example, even if the -p, /F value is the same, the engine speed, ignition timing, load, etc. As the exhaust gas composition changes greatly when the
Controlling the combustion state using only the ideal air-fuel ratio (A/F'' = 14.7) where the exhaust gas composition changes drastically, even though it is necessary to control the A/F at a point where it becomes greater than 4.7. There was a drawback that could only be done.

(Objective of the Invention) The present invention eliminates these conventional drawbacks and provides a combustion state detection method for controlling the A/F not only at the ideal air-fuel ratio but also at the A4 value over a wide range. purpose.

(Structure of the Invention) The present invention attempts to detect the combustion state by simultaneously detecting the change in electrical resistance of the metal oxide in the exhaust gas and the temperature of the exhaust gas.

That is, exhaust gas is discharged from the combustor at high temperature, and the gas components of this exhaust gas include components that cause chemical reactions with each other at high temperatures (for example, 300 to 600 degrees Celsius). , Co, 02゜■20, etc., and the concentrations of these gas components are determined by their respective concentrations and exhaust gas temperature.The ratio between NO, NO2, and H2O2 is 3NO2 + H2O-+.
They are intricately entangled with each other like 2HNO3 + NO, and K l + K'2 + K3 is the equilibrium constant of each reaction and is mainly determined by temperature, so the exhaust gas temperature depends on the component composition in the exhaust gas. It can be seen that this is an important factor determining the On the other hand, if we take an automobile engine as a typical combustor, the exhaust gas temperature generally increases as the load and engine speed increase; It is known that it is not dependent on sweetness (variation of approximately ±20°C between A7F = 14 and 19).

The present invention was devised by focusing on the inherent characteristics of the combustor as described above, and is designed to compensate for fluctuations in the exhaust gas state due to factors that define the combustion state other than the air-fuel ratio, such as rotation speed and load. , can be effectively removed by simultaneously detecting the exhaust gas temperature, and by combining this with detecting changes in the electrical resistance of metal oxide semiconductors, it is possible to control 8A even at non-ideal air-fuel ratios, resulting in savings. This is an effective method for turning it into fuel.

(Description of Examples) FIG. 1 is a diagram showing the appearance of a gas detector using a metal oxide semiconductor as a gas sensitive material, which was used to examine the effects of the present invention.
FIG. 2 is a partially enlarged view of the gas detector 10 shown in FIG. Sa 50
00X tin oxide (5nO2) metal oxide semiconductor film. Reference numeral 13 denotes an electrode for extracting a change in electrical resistance of the gas sensitive body 2 obtained by printing and baking a conductive platinum base as an external signal. 14 has a diameter of 9φ and a thickness of 0
．． 5 is an alumina substrate, and 15 is a thermocouple made of a CA wire (chromel-alumel wire) for detecting the exhaust gas temperature.

Next, a case where the present invention is applied to an automobile engine will be described. In FIG. 3, 30 is a data processing device that receives electrical resistance and temperature signals from the aforementioned gas detector 10 attached to the exhaust pipe 20 of the automobile engine and sends the signals to the fuel injection amount control device 40. be.

The specifications of the automobile engine used are as follows.

Type: Water-cooled single-cylinder 4-stroke gasoline engine Bore x stroke near 4.0 x 750 deaf exhaust
Volume: 322.6cc Compression ratio = 871 Maximum shaft output 12.1 / 5500 ps/ rp
m maximum shaft torque: 2.1/2000 kg・m/rp
m Maximum average effective pressure: 8.0/2000 kg/c
m2/rpm The engine has a rotational speed of 1500 rpm to 3000 rpm, which almost satisfies the driving conditions of a normal car.
The relationship between the electrical resistance of the gas detector and the exhaust gas temperature when operating at an ignition angle of 20° to 40°, a load of 1/4 to full load, and an air-fuel ratio of 13 to 16.5. This is shown in Figure 4. As is clear from this figure, by simultaneously detecting the electrical resistance of the gas detector and the exhaust gas temperature according to the present invention, regardless of the rotational speed or load/ignition angle, the combustion state can be determined uniquely and accurately. It can be seen that the detection can be performed effectively.

For comparison, Figure 5 shows the change in the electrical resistance of the gas detector compared to the A/F, but the A/F value can be determined accurately and uniquely by the electrical resistance of the gas detector alone. I understand difficult things.

From this, it will be understood how superior the detection method of the present invention is.

In the embodiments of the present invention, an automobile ennon was used as an example of a combustor, but the effects of the present invention can be effectively applied to other combustors, such as gas stoves and kerosene stoves. Although tin oxide is mentioned as an example of the metal oxide semiconductor, metal oxide semiconductors other than tin oxide, such as T', O, ZnO, Fe2O3
It is no secret that the effects of the present invention can be effectively obtained even if CoO is used.

(Effects of the Invention) As explained above, the present invention detects the air-fuel ratio of the combustor from the electrical resistance of the metal oxide semiconductor in the exhaust gas of the combustor and the severity of the exhaust gas of the combustor. Therefore, A/F
It is possible to effectively eliminate factors that determine the combustion state other than the above. Therefore, according to the combustion state detection method of the present invention, it is possible to control the A/F value not only at the ideal air-fuel ratio but also over a wide range.

[Brief explanation of the drawing]

Figure 1 is an external view of the gas detector used in the present invention, Figure 2 is an external view of the gas detector used in the present invention.
Figure (A) is a partially enlarged plan view of the gas detector shown in Figure 1, Figure 2 (B) is a partially enlarged sectional view, and Figure 3 is an explanatory diagram when the present invention is applied to an automobile engine. Fig. 4 is a diagram showing the relationship between exhaust gas temperature, electrical resistance of a gas detector, and air-fuel ratio for detailed explanation of the present invention, and Fig. 5 is a diagram showing the relationship between electrical resistance of a gas detector and air-fuel ratio. FIG. io...Gas detector, 1 Gas detection unit, 12 Gas sensitive body, 13 Electrode, 14...Kumeda →, 20...Exhaust pipe, 30...Data processing device, 40... Fuel injection amount control device. Fig. 1 Fig. 2 (81 2 b Fig. 3 Fig. 4 200 300 400 500
600 琲 Fusuma 5 Power゛Mata return (6C)

Claims (1)

[Claims] A combustion state detection method comprising detecting an air-fuel ratio of a combustor from the electrical resistance of a metal oxide semiconductor in the exhaust gas of the combustor and the temperature of the exhaust gas of the combustor.