Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1990-06-29
1992-03-31
Dolinar, Andrew M.
Internal-combustion engines
Charge forming device
Fuel injection system
F02D 4114
Patent
active
050998188
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to exhaust gas cleaning devices for internal combustion engines, and more particularly to exhaust gas cleaning devices which, by controlling the air-to-fuel ratio of the air-fuel mixture supplied to the engine to a predetermined level by means of a feedback from the air-to-fuel ratio sensor disposed in the exhaust system of the engine, optimizes the cleaning capacity of the catalytic converter disposed in the exhaust passage.
BACKGROUND ART
For the purpose of optimizing the efficiency of the catalytic converter (so-called three-way catalytic converter), which is effective for removing three noxious components (i.e., CO, HC, and NOx) contained in the exhaust gas of an internal combustion engine, it is necessary to maintain to or near the stoichiometric air-to-fuel ratio the air-to-fuel ratio of the exhaust gas supplied to the cylinders of the engine. Thus, irrespective of whether the fuel supply system of the engine employs a conventional caburetor or a fuel infector, the air-to-fuel ratio of the air-fuel mixture intake of the engine which utilizes the catalytic converter is controlled, in order to optimize the efficiency of the catalytic converter, by means of the feedback control upon the basis of the output of an air-to-fuel ratio sensor (so-called O.sub.2 (oxygen) sensor functioning upon the galvanic action due to the oxygen concentration) disposed, in the exhaust gas system of the engine.
Referring to FIGS. 1 and 2 of the drawings, let us briefly describe the conventional feedback control method of the air-to-fuel ratio utilizing an air-to-fuel ratio sensor; the method is disclosed, for example, in Japanese laid-open patent application No. 52-48738 or Japanese patent publication No. 62-12379. FIG. 1 shows the waveforms of the signals of the air-to-fuel ratio control system in the case where the rpm (revolution per minute) of the engine is relatively low; FIG. 2, on the other hand, shows the corresponding waveforms in the case where the rpm of the engine is relatively high. FIGS. 1(a) and 2(a) show the waveform of the output signal of the oxygen sensor which generates an output voltage corresponding to the O.sub.2 concentration of the exhaust gas; on the other hand, FIGS. 1(b) and 2(b) show the waveforms of the air-to-fuel ratio signals which are obtained by comparing the voltage signals of FIGS. 1(a) and 2(a), respectively, with a reference voltage of 0.5 V, and subjecting thereafter the resulting comparison signals to a waveform shaping; the air-to-fuel ratio is controlled by the proportional plus integral (PI) control method as indicated by the air-to-fuel control signals shown at FIGS. 1(c) and 2(c), which are obtained from the air-to-fuel ratio signals shown at FIGS. 1(b) and 2(b), respectively.
The air-to-fuel ratio of the engine is controlled by the feedback control method on the basis of the signals of FIGS. 1 and 2 as follows:
The air-to-fuel ratio sensor detects the O.sub.2 concentration contained within the exhaust gas of the engine; the output of the air-to-fuel sensor is utilized for the purpose of judging whether the air-to-fuel ratio of the air-fuel combustion mixture within the combustion chamber of the engine is smaller or greater than the stoichiometric air-to-fuel ratio, which is usually at about 14.7. (The state in which the air-to-fuel ratio is smaller than the stoichiometric ratio is referred to as the rich state, whereas that in which the air-to-fuel ratio is greater than the theoretical is referred to as the lean state.) The amount of fuel supplied to the engine, or the air-to-fuel ratio .lambda., is controlled upon the basis of the resulting comparison judgement signal, whose waveforms are shown in FIGS. 1(b) and 2(b); this feedback control of the air-to fuel ratio is effected as follows: First, referring to FIG. 1, let us consider the case where the rpm Ne of the engine is low. When the waveform of the comparison signal shown at FIG. 1(b) obtained from the output of the air-to-fuel ratio sensor shown at FIG. 1(a) is inverted from the l
REFERENCES:
patent: 4287865 (1981-09-01), Seitz
patent: 4402291 (1983-09-01), Aono
patent: 4512313 (1985-04-01), Tsuchida et al.
patent: 4628884 (1986-12-01), Geering et al.
Chino Masashi
Hashimoto Toru
Katashiba Hideaki
Miyake Mitsuhiro
Nishida Minoru
Dolinar Andrew M.
Mitsubishi Denki & Kabushiki Kaisha
Mitsubishi Jidosha Kogyo Kabushiki Kaisha
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