Operation control device and operation control method for multi-cylinder internal combustion engine

Abstract

When the cut-off cylinder operation execution condition of a multi-cylinder internal combustion engine is fulfilled, the temperature of the catalytic converter provided in the exhaust passage linked to the cylinders that are made inoperative during the cut-off cylinder operation is estimated, and when this temperature is less than the predetermined preliminary heating requiring temperature, a catalyst preliminary heating operation is executed by which the ignition timing of the cylinders is delayed and the temperature of the catalytic converter is raised. Then, the cut-off cylinder operation is started after the temperature of the catalytic converter becomes equal to or higher than the preliminary heating requiring temperature.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The invention relates to an operation control device and an operation control method for a multi-cylinder internal combustion engine. More specifically, the invention relates to the improvement designed to extend the continuation time of a cut-off cylinder operation in a multi-cylinder internal combustion engine in which the cut-off cylinder operation can be executed by which some of the cylinders are made inoperative in response to a load of the internal combustion engine.[0003]2. Description of the Related Art[0004]A multi-cylinder engine is available in which a cut-off cylinder operation can be executed in which some of the cylinders are made inoperative and fuel consumption ratio is improved when no load is applied to the engine, as disclosed for example, in Japanese Patent Application Publication No. 2005-351134 (JP-A-2005-351134), Japanese Patent Application Publication No. 2001-227369 (JP-A-2001-227369), and Japa...

AI Technical Summary

Benefits of technology

The invention relates to a multi-cylinder internal combustion engine that can execute a cut-off cylinder operation to improve fuel efficiency and reduce fuel consumption. The invention provides an operation control device and method that can maintain the temperature of the inoperative cylinder's catalyst high during the cut-off cylinder operation, extending the duration of the cut-off operation. The invention recognizes that the temperature of the first catalyst decreases during the cut-off operation and proposes a solution to extend the duration of the cut-off operation. The invention also includes a catalyst preliminary heating operation that raises the temperature of the first catalyst to a required temperature for the cut-off operation, ensuring effective participation of the catalyst in the temperature increase and reducing fuel consumption.

Problems solved by technology

Therefore, the intake-exhaust loss increases and combustion efficiency can drop.

However, the following problem can arise in an engine in which the cut-off cylinder operation can be executed when the engine is so configured that the catalyst of the exhaust system that is connected to a cylinder (inoperative cylinder) that is in an inoperative state during the cut-off cylinder operation (this catalyst will be referred to hereinbelow as an inoperative cylinder catalyst) and the catalyst of the exhaust system connected to a cylinder (operative cylinder) that continues operating (this catalyst will be referred to hereinbelow as an operative cylinder catalyst) are independent from each other, as disclosed in JP-A-2005-351134 and JP-A-2001-227369.

As a result, the decrease in the catalyst temperature per unit time is easily increased and the above-described problem is aggravated.

In such cases the continuation time of the cut-off cylinder operation becomes extremely short and merits of the engine system in which the cut-off cylinder operation can be executed are difficult to use to a full extent.

As a result, it is possible that the effect of improving the fuel consumption ratio and the effect of reducing the fuel consumption amount will not be fully demonstrated.

In other words, in the configuration described in JP-A-2005-351134, the catalyst temperature is raised by delaying the ignition timing after a transition has been made from the cut-off cylinder operation to the full-cylinder operation, and such a technique cannot extend the continuation period of the cut-off cylinder operation by extending the period in which the temperature of the inoperative cylinder catalyst in the cut-off cylinder operation is maintained at the activation temperature.

In the configuration disclosed in JP-A-2001-227369, the cut-off cylinder operation is prohibited when the catalyst temperature becomes lower than the predetermined temperature, and this technique also fails to extend the interval in which the temperature of the inoperative cylinder catalyst in the cut-off cylinder operation is maintained at the activation temperature.

As a result, the above-described problem of the temperature of some of the catalysts decreasing in the execution of the cut-off cylinder operation is not encountered.

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