JP2612891B2 - Engine air-fuel ratio measurement method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for measuring an air-fuel ratio of an engine for a vehicle such as an automobile.

(Prior Art) Generally, in order to grasp the combustion efficiency and the like of an engine for a vehicle such as an automobile, it is necessary to accurately and quickly measure an air-fuel ratio. As a method for measuring the air-fuel ratio, for example, as disclosed in Japanese Utility Model Application Laid-Open No. 58-26660, a sample gas discharged from an engine is introduced into an inlet pipe having an oxidation catalyst heated to 300 ° C. or higher. After the CO and various HCs in the sample gas are completely oxidized, the concentration of the oxidized CO ₂ is analyzed by a quadrupole mass spectrometer, and the air-fuel ratio is calculated based on the analysis value. Is conventionally known.

However, in this method, it takes a considerable time to completely oxidize the CO and various HCs, so that the response is poor.In addition, since a heating device for heating the oxidation catalyst to a high temperature is required, the structure of the analyzer is reduced. There was a problem that it became complicated. Further, since the combustion efficiency of the engine is affected by whether the fuel constituting the air-fuel mixture is in a vaporized state or a liquid state (particle state), there is a problem that the air-fuel ratio cannot be accurately measured. .

Therefore, the mixture of the engine is introduced into the quadrupole mass spectrometer, and the amount of HC ions contained in the fuel constituting the mixture and the amount of O ₂ ions contained in the air constituting the mixture are determined. measured, then by to measure the air-fuel ratio of the engine based on the correlation between the air amount calculated from the HC ion amount fuel amount calculated from the O ₂ ion amount,
A method for accurately and quickly measuring the air-fuel ratio has been proposed (see Japanese Patent Application No. 62-99476 and drawings).

(Problems to be Solved by the Invention) However, in the method according to the above proposal, when the degree of vacuum in the chamber of the quadrupole mass spectrometer decreases to around 5 × 10 ⁻⁵ Torr, as shown in FIG. In addition, since the amount of O ₂ ions represented by the solid line suddenly changes (increases sharply) as compared with the total amount of HC ions represented by the broken line, the measured air-fuel ratio leans to the rich side from the actual air-fuel ratio. Therefore, a situation occurs in which the air-fuel ratio cannot always be measured accurately.

The present invention has been made in view of such a point, and an object of the present invention is to measure a specific ion among various ions contained in air constituting an air-fuel mixture of an engine by a quadrupole mass analyzer. By doing so, even if the degree of vacuum in the chamber of the quadrupole mass spectrometer is reduced, the amount of the specified ions does not suddenly change (abruptly increase) compared to the total ion amount of various HC ions. Accordingly, an object of the present invention is to always accurately measure the air-fuel ratio without being affected by the degree of vacuum in the chamber.

(Means for Solving the Problems) In order to achieve the above object, a solution of the present invention is that a mixture of an engine is introduced into a quadrupole mass spectrometer and is contained in a fuel constituting the mixture. The amount of HC ions and the amount of Ar ions contained in the air constituting the mixture are measured. Next, the air-fuel ratio of the engine is measured based on the correlation between the fuel amount calculated from the HC ion amount and the air amount calculated from the Ar ion amount.

(Operation) With the above configuration, according to the method of the present invention, the air-fuel mixture of the engine is introduced into the quadrupole mass analyzer and contained in the fuel.
The amount of HC ions and the amount of Ar ions contained in the air are measured, and the air-fuel ratio of the engine is determined based on the correlation between the amount of fuel calculated from the amount of HC ions and the amount of air calculated from the amount of Ar ions. Measured. Ar ions applied to this quadrupole mass spectrometer have the property of being hardly affected by the degree of vacuum. From this, even if the degree of vacuum in the chamber of the quadrupole mass spectrometer decreases, the amount of Ar ions does not change suddenly, and thus the air-fuel ratio is always independent of the degree of vacuum in the chamber. It will be measured accurately.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic configuration of an analyzer used for implementing an engine air-fuel ratio measuring method according to an embodiment of the present invention. In order to explain the procedure for measuring the air-fuel ratio of the engine by the analyzer, first, an air-fuel mixture of the engine is introduced from the introduction passage 1 into the first vacuum chamber 3 evacuated by the operation of the rotary vacuum pump 2.

Next, the air-fuel mixture introduced into the first vacuum chamber 3 is introduced into the second vacuum chamber 5 through the orifice 4 while regulating the flow rate, and the inside of the second vacuum chamber 5 is supplied with a turbo molecular pump 6 and a rotary Vacuum is drawn by the operation of the vacuum pump 7 to maintain a predetermined degree of vacuum.

Thereafter, the mixture in the second vacuum chamber 5 is introduced into the quadrupole mass spectrometer 8, and HC contained in the fuel constituting the mixture is used.
The amount of ions and the amount of Ar ions contained in the air constituting the mixture are measured. Specifically, as shown in FIG. 2, each component in the air-fuel mixture is ionized by applying an electron impact to the components in the air-fuel mixture at the ion source unit 9, and the ionized components are converged by the lens system 10. To form an ion beam. Next, ions passing through the lens system 10 are introduced between the four rods constituting the electrode unit 11, and vibration is applied to pass only ions having a specific charge ratio. That is, in the present embodiment, by adjusting the voltage value applied to the electrode section 11, various HCs can be converted into ions having a specific charge ratio.
The amounts of ions and Ar ions are selectively detected.
After that, various HC ions and Ar
By introducing the ions into the secondary electron multiplier 12, the amount of each ion is detected as an ion current. As described above, Ar ions among the ions in the air that constitute the air-fuel mixture were measured because Ar ions were reduced by 5 × 10 ^{Even at} around ^-5 Torr, as shown in FIG. 4, the amount of Ar ions shown by the solid line is smaller than the total amount of HC ions shown by the broken line, as in the case of O ₂ ions (see FIG. 5). Is stable without abrupt change and has a property of being hardly affected by the degree of vacuum.

Thereafter, the measured values of the various HC ion amounts measured as described above are input to the computer 13 as a fuel amount detection signal to calculate the fuel amount, and the measured value of the Ar ion amount is used as the air amount detection signal by the computer. 13 to calculate the amount of air, and calculate the amount of fuel and Ar
The amount of air calculated from the amount of ions is
The air-fuel ratio of the engine is measured based on the correlation between the mass fragment of the reference mixture stored in advance and the mass fragment of the reference mixture. Incidentally, a specific example of the above-mentioned mass fragment is, for example, as shown in FIG. 3, and N ₂ ²⁺ (charge ratio
14), O ₂ ²⁺ (charge ratio 16), Ar ²⁺ (charge ratio 20), N ₂ ⁺ (charge ratio 28), O ₂ ⁺ (charge ratio 32), Ar ⁺ (charge ratio 40), C ₄ H ₈ ⁺
(Charge ratio 56), C ₆ H ₆ ⁺ (charge ratio 78), C ₇ H ₇ ⁺ (charge ratio 91)
And the corresponding relationship between each ion amount such as C ₈ H ₉ ⁺ (charge ratio 105) and each component amount is obtained in the manner described above. In FIG. 1, valves 14 and 15 are for introducing and discharging the mixture.

As described above, in the present embodiment, of the ions contained in the air of the engine mixture, the Ar ions that are not easily affected by the degree of vacuum were measured by the quadrupole mass spectrometer 8, so that the quadrupole mass spectrometer 8 was used. Even if the degree of vacuum in the chamber of the analyzer 8 decreases,
The amount of the Ar ions does not change suddenly, so that the air-fuel ratio can always be accurately measured without being affected by the degree of vacuum in the chamber.

(Effects of the Invention) As described above, according to the method of the present invention, the mixture of the engine is introduced into the quadrupole mass spectrometer, and the amount of HC ions contained in the fuel constituting the mixture, The amount of Ar ions contained in the air constituting the mixture is measured, and then the air-fuel ratio of the engine is determined based on the correlation between the amount of fuel calculated from the amount of HC ions and the amount of air calculated from the amount of Ar ions. Therefore, the air-fuel ratio can always be accurately measured without being affected by the degree of vacuum in the chamber of the quadrupole mass analyzer.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an analyzer used for implementing an engine air-fuel ratio measuring method according to an embodiment of the present invention.
The figure is a schematic diagram showing the internal structure of the quadrupole mass spectrometer, FIG. 3 is a diagram showing mass fragments of each component contained in the gas mixture, and FIG. 4 is a graph showing the total amount of HC ions and Ar ions. FIG. 5 is a diagram showing the relationship between the change and the degree of vacuum, and FIG. 5 is a diagram showing the relationship between the change in the amount of ions of total HC ions and O ₂ ions and the degree of vacuum. 8. Quadrupole mass spectrometer.

Claims (1)

(57) [Claims] An air-fuel mixture of an engine is introduced into a quadrupole mass spectrometer to determine the amount of HC ions contained in fuel constituting the air-fuel mixture and the amount of Ar ions contained in air constituting the air-fuel mixture. And then measuring the air-fuel ratio of the engine based on the correlation between the amount of fuel calculated from the amount of HC ions and the amount of air calculated from the amount of Ar ions. Method.