1. Field of the Invention
The present invention relates to an internal combustion engine having a combustion heater.
2. Description of the Prior Art
At a cold time, it is required that a warm-up of an internal combustion engine be speeded up, and it is desirable to have a high performance of a car room heater of a vehicle mounted with the internal combustion engine.
For achieving such object, for example, Japanese Patent Application Laid-Open Publication No.62-75069, discloses an art of speeding up the warm-up and enhancing the performance of the car room heater, by providing an intake system with a combustion heater separately from the internal combustion engine body, introducing into the intake system a combustion gas emitted from the combustion heater (which gas is hereinafter referred to as "the combustion gas" unless otherwise specified), raising a temperature of engine cooling water contained in the internal combustion engine body by utilizing combustion heat of the combustion heater and thereby attaining the above object.
On the other hand, as well known, an EGR device primarily aims at reducing a generation of NOx, and secondary aims at enhancing the performance of the car room heater as well as speeding up the warm-up. The letters "EGR" of the EGR device are an abbreviation of Exhaust Gas Recirculation, and the term EGR literally means that a part of the exhaust gas from the internal combustion engine is returned to the intake system from an exhaust system and reintroduced into cylinders. Therefore, the EGR device includes at least an exhaust gas recirculation passageway, which is a pipe for connecting in bypass a discharge passageway and an intake passageway of the internal combustion engine to cylinders thereof, for recirculating the exhaust gas between the discharge passageway and the intake passageway by flowing a part of the exhaust gas back to the intake passageway from the discharge passageway, and an exhaust gas recirculation quantity control valve, disposed in the exhaust gas recirculation passageway, for controlling a quantity of the exhaust gas returned to the intake passageway.
When the EGR device is combined with the internal combustion engine having the combustion heater which introduces the combustion gas into the intake system, the intake system is supplied with both of the combustion gas of the combustion heater and a part (an EGR gas) of the exhaust gas of the internal combustion engine which is recirculated by the EGR device. Each of the combustion gas and the EGR gas is the exhaust gas after being once used. Accordingly, the reuse of such exhaust gas implies that a fresh air quantity to an intake air quantity of the internal combustion engine decreases, while a quantity of carbon dioxide increases. Consequently, there is a possibility that the air/fuel ratio in the cylinders of the internal combustion engine becomes rich enough to produce the smoke.
Further, a concentration of the carbon dioxide contained in the exhaust gas of the combustion heater differs from a concentration of the carbon dioxide contained in the EGR gas of the EGR device. Hence, if mixed, an intake air composed of a mixture of those gases, each having the different concentration of the carbon dioxide, and the fresh air to be used as the intake air of the intake passageway, is used without any adjustment as the intake air of the internal combustion engine, an adverse effect might be exerted upon the combustion in the internal combustion engine. In this case, it is difficult to attain reductions of both NOx and minute powders which are so-called particulate matters (hereinafter referred to as a "PM reduction") contained in the smoke.
Thus, it is desired to provide an art which is capable of reducing NOx and the smokes, especially, the PM, simply and easily.