Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1990-02-26
1991-01-15
Wolfe, Willis R.
Internal-combustion engines
Charge forming device
Fuel injection system
F02D 4114, G01N 2750, G05D 1100
Patent
active
049845519
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method and a device for lambda control in an internal combustion engine with at least two lambda probes.
BACKGROUND OF THE INVENTION
A plurality of lambda probes on an internal combustion engine are used in two fundamentally different arrangements. In one arrangement, the plurality of probes is located in the exhaust-gas channel of the internal combustion engine at successive locations. In the other arrangement, the lambda probes are each mounted in an identical position in different component channels of the exhaust-gas channel system. The invention relates to an arrangement of the last-mentioned type.
An arrangement of this type is provided, for example, for the methods and devices according to U.S. Pat. No. 4,231,334 and published German application DE-Al-2,255,879 corresponding to U.S. Pat. application Ser. No. 401,195 and filed on 9-27-73. In each case, a lambda probe is arranged in the exhaust-gas component channel of each half of a V-type engine in front of the particular point before the two component channels are combined to form a manifold, in which a catalyst is arranged. In the method according to DE-Al-2,255,874, the signals of the two probes serve for supplying actual values for two separate control circuits, each of which is assigned to one half of the engine. In the method according to DE-Al-2,7l3,988, the signals of the two probes serve as actual values for a single control circuit. In accordance with the nature of the signals from the two probes, a decision is made as to whether the controller increases or decreases the regulating value or leaves it unchanged. Furthermore, the regulating value is wobbled as a function of a summed control deviation in such a way that, on top of the conventional oscillation of the two-position controller, the mixture alternates between rich and lean rapidly and continuously.
The known methods and devices serve for supplying air/fuel mixtures which result in exhaust gas of such a kind that harmful substances still present in the exhaust gas can be converted as efficiently as possible by means of a catalyst.
The object on which the invention is based is to provide a method for lambda control in an internal combustion engine with at least two lambda probes in an identical position, which allows an even better conversion of harmful substances than previous methods. A further object of the invention is to providing a device for carrying out such a process.
SUMMARY OF THE INVENTION
The method according to the invention is characterized in that at least two different air/fuel mixtures for different cylinders are put under two-position control in different control circuits and desired phase shifts are set between the control oscillations. The device according to the invention has at least one means for the two-position control, one means for determining the actual phase shift and one means for setting the desired phase shift between each two control circuits.
The invention makes use of the following consideration. In a two-position lambda control, the lambda value continuously executes oscillations between rich and lean. The larger the amplitude of these oscillations, the lower the relative conversion of harmful substances by the catalyst. Now if two control circuits are used instead of a single control circuit, it must be possible to match the oscillations in the two circuits to one another in such a way that the mixture in one control circuit oscillates in the rich direction exactly when the mixture in the other control circuit oscillates in the lean direction. The exhaust gases of the rich mixture and of the lean mixture come together in the manifold in front of the catalyst and there result in exhaust gas of approximately the lambda value 1. The lambda value of the exhaust gas will undergo hardly any oscillation if the phase shift amounts to approximately half an oscillation period. If it is more or less, there is still an oscillation of the lambda value, but with a considerably lower amplitude than witho
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Ottesen Walter
Robert & Bosch GmbH
Wolfe Willis R.
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