JP-7856068-B2 - Control device for internal combustion engines

Inventors

• 井手 宏二

Assignees

• トヨタ自動車株式会社

Dates

Publication Date

20260511

Application Date

20230815

Claims (1)

1. A control device for an internal combustion engine equipped with a catalyst in the exhaust passage, A control unit that performs rich control to control the air-fuel ratio in the internal combustion engine after fuel cut-off to a rich air-fuel ratio, A first estimation unit estimates the amount of oxygen that the catalyst can store from the time the rich control , which is performed after fuel cut, is initiated until the air-fuel ratio of the exhaust gas discharged from the catalyst becomes a rich air-fuel ratio. During the execution of the rich control performed after fuel cut , a second estimation unit estimates the oxygen storage amount of the catalyst, The system includes a stop unit that stops the rich control when the oxygen storage amount falls below a determination value smaller than the oxygen storage capacity , If the estimation of the oxygen storage capacity is not yet complete, the rich control is stopped when the air-fuel ratio of the exhaust gas discharged from the catalyst becomes a rich air-fuel ratio during the execution of the rich control. The first estimation unit estimates the oxygen storage capacity multiple times, and the learned value of the oxygen storage capacity is updated to the average value of the oxygen storage capacity when the number of times reaches the upper limit, thereby completing the estimation of the oxygen storage capacity. After the estimation of the oxygen storage capacity is completed, the stop unit stops the rich control when the oxygen storage capacity falls below the determination value, in a control device for an internal combustion engine.

Description

This invention relates to a control device for an internal combustion engine. There is a technique for estimating the oxygen storage capacity of a catalyst installed in the exhaust passage of an internal combustion engine. Specifically, during rich control after fuel cut-off, the oxygen storage capacity is estimated from the time rich control begins until the air-fuel ratio of the exhaust gas discharged from the catalyst becomes a rich air-fuel ratio (see Patent Document 1). Japanese Patent Application Publication No. 6-159048 This is a schematic diagram of an internal combustion engine.This is a flowchart illustrating OSC estimation control.This flowchart illustrates the control process for determining whether to continue or stop rich fuel mixture control after fuel cut-off.This timing chart illustrates OSC estimation control and the control for determining whether to continue or stop rich control after fuel cut. [Overall Configuration of an Internal Combustion Engine] Figure 1 is a schematic diagram of the internal combustion engine 1. The internal combustion engine 1 is installed in a vehicle, for example, but is not limited to that and may be installed in ships or other vessels. The internal combustion engine 1 has an engine body 10, an intake passage 20, and an exhaust passage 30. The engine body 10 is a multi-cylinder engine having multiple cylinders, and each cylinder is provided with a combustion chamber 11, a piston 12, a spark plug 16, etc. Inside the engine body 10 are a connecting rod 13 and a crankshaft 14. The piston 12 is connected to the crankshaft 14 by the connecting rod 13. The engine body 10 is provided with a rotational speed sensor 15, and an in-cylinder injection valve 17 is provided for each cylinder. The rotational speed sensor 15 detects the rotational speed of the engine body 10 by detecting the rotational speed of the crankshaft 14. The in-cylinder injection valve 17 directly injects fuel into the combustion chamber 11. Alternatively, instead of the in-cylinder injection valve 17, a port injection valve that injects fuel toward the intake port of the engine body 10 may be provided, or a port injection valve may be provided in addition to the in-cylinder injection valve 17. The spark plug 16 ignites the air-fuel mixture in the combustion chamber 11. The intake port and exhaust port of the engine body 10 are connected to an intake passage 20 and an exhaust passage 30, respectively. The intake valve 18a and exhaust valve 18b open and close the intake port and exhaust port of the engine body 10, respectively. The intake passage 20 is equipped with an air cleaner 21, an airflow meter 22, and a throttle valve 23, arranged in order from upstream to downstream. The air cleaner 21 removes dust and other particles from the air flowing in from the outside. The airflow meter 22 obtains the intake air volume Ga. The throttle valve 23 is driven by, for example, an actuator (not shown) to adjust the intake air volume Ga. When the intake valve 18a opens, air is introduced from the intake passage 20 into the combustion chamber 11. The fuel-air mixture injected from the in-cylinder injection valve 17 is compressed by the piston 12 and ignited by the spark plug 16. Ignition of the mixture causes the piston 12 to reciprocate up and down within the combustion chamber 11, rotating the crankshaft 14. The exhaust gases after combustion are discharged through the exhaust passage 30. The exhaust passage 30 is equipped with, in order from upstream to downstream, an upstream sensor 31a, a pre-catalyst 32a, a downstream sensor 31b, and a downstream catalyst 32b. The upstream sensor 31a and the downstream sensor 31b are air-fuel ratio sensors that detect the air-fuel ratio of the exhaust gas flowing through the exhaust passage 30, but are not limited to these. At least one of these sensors may be an oxygen concentration sensor capable of detecting the air-fuel ratio of the exhaust gas by detecting the oxygen concentration of the exhaust gas. The upstream sensor 31a detects the air-fuel ratio of the exhaust gas discharged from the engine body 10 and flowing into the pre-catalyst 32a. The downstream sensor 31b detects the air-fuel ratio of the exhaust gas discharged from the pre-catalyst 32a and flowing into the downstream catalyst 32b. The preceding catalyst 32a and the subsequent catalyst 32b contain catalytic metals such as platinum (Pt), palladium (Pd), and rhodium (Rh), and are three-way catalysts with oxygen storage capacity. Due to their catalytic action and oxygen storage capacity, the three-way catalysts purify NOx and HC depending on the oxygen storage amount (OSA). The ECU (Electric Control Unit) 100 is equipped with a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and memory devices such as flash memory, and performs various controls by executing programs stored in the ROM and memory devices. The ECU 100 controls the spark plug 16, in-cylinder injection valve 17,