JP-7855944-B2 - Method and apparatus for controlling the warm-up of a three-way catalytic converter

Inventors

• 羽野 祐史

Assignees

• 日産自動車株式会社

Dates

Publication Date

20260511

Application Date

20220630

Claims (5)

1. A method for warming up a three-way catalytic converter, comprising a three-way catalytic converter in the exhaust passage of an internal combustion engine, wherein during the warm-up of the three-way catalytic converter, perturbation control is performed by periodically repeating a rich combustion period with a large equivalent ratio and a lean combustion period with a small equivalent ratio so that the exhaust air-fuel ratio of the exhaust gas flowing into the three-way catalytic converter fluctuates between rich and lean, The rich combustion period and the lean combustion period each consist of M rich and lean combustion cycles performed consecutively in multiple cylinders according to the combustion sequence, where the number of these consecutive rich or lean combustion cycles M is equal to or greater than the number of cylinders N in the internal combustion engine, and the number of rich and lean combustion cycles are equal to each other. The range of change in the equivalence ratio for rich combustion and the range of change in the equivalence ratio for lean combustion are equal, with an equivalence ratio of 1 as the baseline. A method for controlling the warm-up of a three-way catalytic converter.
2. During the transition from the rich combustion period to the lean combustion period and during the transition from the lean combustion period to the rich combustion period, stoichiometric combustion with an equivalent ratio of 1 is performed in at least one cylinder. A method for controlling the warm-up of a three-way catalytic converter as described in claim 1.
3. It has multiple repeating patterns in which the rich/lean period of perturbation control differs, Select one of the repeating patterns depending on the operating conditions of the internal combustion engine during warm-up. A method for controlling the warm-up of a three-way catalytic converter as described in claim 1.
4. The internal combustion engine is a 3-cylinder internal combustion engine, and the number M mentioned above is 3. A method for controlling the warm-up of a three-way catalytic converter as described in claim 1.
5. A warm-up control device for a three-way catalytic converter, which is equipped with a three-way catalytic converter in the exhaust passage of an internal combustion engine, and which performs perturbation control during the warm-up of the three-way catalytic converter, which periodically repeats a rich combustion period with a large equivalent ratio and a lean combustion period with a small equivalent ratio so that the exhaust air-fuel ratio of the exhaust gas flowing into the three-way catalytic converter fluctuates between rich and lean, The rich combustion period and the lean combustion period each consist of M rich and lean combustion cycles performed consecutively in multiple cylinders according to the combustion sequence, where the number of these consecutive rich or lean combustion cycles M is equal to or greater than the number of cylinders N in the internal combustion engine, and the number of rich and lean combustion cycles are equal to each other. The range of change in the equivalence ratio for rich combustion and the range of change in the equivalence ratio for lean combustion are equal, with an equivalence ratio of 1 as the baseline. A three-way catalytic converter warm-up control system.

Description

This invention relates to a warm-up control method and apparatus for an internal combustion engine, which promotes the warm-up of a three-way catalytic converter by periodically varying the exhaust air-fuel ratio of the exhaust gas flowing into the three-way catalytic converter between rich and lean. To quickly warm up the three-way catalytic converter installed in the exhaust passage of an internal combustion engine to near its activation temperature, a control method that periodically alternates between rich and lean combustion has been proposed. For example, Patent Document 1 discloses a catalytic converter warm-up control called irregular injection dithering control for an in-line four-cylinder internal combustion engine, which repeats a pattern of rich combustion in one cylinder followed by lean combustion in multiple cylinders according to the combustion sequence. In one embodiment, the pattern is to perform rich combustion in one cylinder, then lean combustion in two cylinders, then rich combustion in the next cylinder, and then lean combustion in the next two cylinders. Japanese Patent Publication No. 2004-353552 A diagram illustrating the configuration of an internal combustion engine in one embodiment to which this invention is applied.A time chart showing several examples of repeating patterns.An explanatory diagram showing the distribution of exhaust gas from one cylinder in a cross-section of a three-way catalytic converter.A diagram illustrating the periodic change in rich/lean conditions in a cross-section of a three-way catalyst. The following describes in detail an embodiment of this invention based on the drawings. Figure 1 is an explanatory diagram showing the schematic configuration of an internal combustion engine 1 in one embodiment to which this invention is applied. The internal combustion engine 1 in this embodiment is a 3-cylinder, 4-stroke, spark-ignition internal combustion engine (a so-called gasoline engine), in which a pair of intake valves 2 and a pair of exhaust valves 3 are provided in the combustion chamber 5 of each cylinder, and a spark plug 4 is positioned in the center of the combustion chamber 5. In the illustrated example, as a direct injection engine, a fuel injection valve 6 that injects fuel into the cylinder is positioned, for example, on the intake valve 2 side. In this invention, a port injection configuration in which fuel is injected towards the intake port 7 of each cylinder is also possible. An electronically controlled throttle valve 10, whose opening degree is controlled by a control signal from the engine controller 9, is interposed upstream of the collector portion 8a of the intake passage 8 connected to the intake port 7 of each cylinder. The exhaust ports 12 of each cylinder are connected to the branch sections of the exhaust manifold 13, and these are combined into a single exhaust passage by the exhaust manifold 13. A three-way catalytic converter 15 for exhaust purification is provided at the outlet of the exhaust manifold 13. The three-way catalytic converter 15 is a so-called monolithic ceramic catalyst, for example, a monolithic ceramic body with fine passages formed therein, coated with a catalytic layer containing a catalytic metal. In addition to the three-way catalytic converter 15 located at the outlet of the exhaust manifold 13, the three-way catalytic converter may also include another three-way catalytic converter (for example, an underfloor catalytic converter) arranged in series downstream. An air-fuel ratio sensor 16 for detecting the exhaust air-fuel ratio is positioned upstream of the three-way catalytic converter 15 in the exhaust passage 14. This air-fuel ratio sensor 16 is a so-called wide-range air-fuel ratio sensor that provides an output corresponding to the exhaust air-fuel ratio. Furthermore, a downstream air-fuel ratio sensor, such as an O2 sensor that responds to the composition of the exhaust gas that has passed through the three-way catalytic converter 15, may be additionally provided downstream of the three-way catalytic converter 15 for purposes such as calibrating the air-fuel ratio feedback control system including the air-fuel ratio sensor 16 and diagnosing the deterioration of the three-way catalytic converter 15. The detection signal from the air-fuel ratio sensor 16 is input to the engine controller 9. Furthermore, the engine controller 9 receives detection signals from numerous sensors, including an air flow meter 20 for detecting the intake air volume upstream of the throttle valve 10, a crank angle sensor 21 for detecting engine rotational speed and crank angle position, a water temperature sensor 22 for detecting coolant temperature, and an accelerator pedal position sensor 23 for detecting the amount of accelerator pedal depression by the driver. Based on these input signals, the engine controller 9 optimally controls the fuel injection amount and timing by the fuel injector 6, the ignition timing by the spa