1. Field of the Invention
This invention relates to a control device for a multi-cylinder internal combustion engine in a vehicle, such as an automobile, or a stationary multi-cylinder internal combustion engine, and a signaling device capable of providing the control device with information. More specifically, the invention relates to the control device and the signaling device preferred for a multi-cylinder internal combustion engine which can perform a cylinder number control operation permitting some of the cylinders to rest without working.
2. Description of the Related Art
A vehicle, such as an automobile, is often compelled to stop transiently by traffic signals while running in an urban district. Even in such a case, the internal combustion engine (hereinafter referred to simply as an engine) installed on the vehicle continues idling, posing the problems of generating an exhaust gas and wasting fuel.
To resolve these problems, a proposal has been made to carry out an idle stop for bringing the engine to a halt manually or automatically when the vehicle makes a brief stop, thereby decreasing the exhaust gas or improving fuel economy (see Japanese Patent Application Laid-Open No. 2003-247439; hereinafter referred to as Patent Document 1). Even if the vehicle is at a stop without doubt, however, it may be inappropriate to perform an idle stop from the aspects of safety and functionality. Hence, it has been common practice to exercise idle stop control, namely, control such that many authorization conditions for authorizing an idle stop are set, and only when all of the authorization conditions for the idle stop have been satisfied, the idle stop is executed.
With the idle stop control as disclosed in Patent Document 1, however, the operation of all the cylinders is temporarily stopped. Thus, when the engine is restarted, the activity of posttreatment devices, such as DPF, NOx reduction catalyst, and oxidation catalyst, declines because of a fall in the exhaust gas temperature, thus aggravating exhaust emissions, and resulting in the increased frequency of driving a self-starting motor, which leads to the wear of this motor at an early stage. When the vehicle restarts, moreover, it is also indispensable to provide a check mechanism for a braking pressure, and detect the state of a transmission, for the purpose of preventing dangers. This presents the drawback that a control system becomes complicated, inducing cost increases.