Exhaust gas purifying system

The present invention relates to an exhaust gas purifying system, and more particularly to a system for removing particulate matter from exhaust gas of a diesel engine.

In a conventional exhaust gas purifying system, a filter is provided in an exhaust pipe to collect particulate matter in exhaust gas of a diesel engine. In order to prevent particulate matter accumulation on the filter and thereby to prevent an increase in the flow resistance of the filter, particulate matter needs to be removed from the filter so that the filter is regenerated. In a known system, for example, disclosed in Japanese Unexamined Patent Application Publication No. 59-155523, hydrocarbon is supplied to a filter that contains oxidation catalysts. The hydrocarbons are oxidized or burned off on the filter, thereby removing particulate matter on the filter. The system has a fuel injection unit at an exhaust pipe disposed upstream of the filter with respect to the flow of exhaust gas. The fuel injection unit is connected through a fuel passage to a diesel fuel tank. The fuel passage has a reformer that contains reforming catalysts. The reformer produces hydrocarbons highly reactive with the oxidation catalysts of the filter by reforming diesel fuel. The reformer is connected to a bypass passage branching from the exhaust pipe. Exhaust gas flowing in the exhaust pipe is introduced through the branch passage into the reformer to preheat the reforming catalysts, thereby accelerating the reforming reaction of the diesel fuel in the reforming catalysts.

The system disclosed in the reference No. 59-155523, however, requires two catalytic reactions for removal of particulate matter on the filter. Specifically, the system requires reforming of diesel fuel in the reforming catalyst and oxidation of hydrocarbons in the oxidation catalysts of the filter, which prevents efficient removal of particulate matter from the filter.

The present invention is directed to an exhaust gas purifying system that efficiently removes particulate matter from a filter.

In accordance with an aspect of the present invention, an exhaust gas purifying system removes particulate matter from exhaust gas from an engine through an exhaust passage. The system includes a filter, a reforming catalyst, an injector, and a heat transfer member. The filter is provided in the exhaust passage and collects the particulate matter in the exhaust gas. The reforming catalyst is provided in the exhaust passage and generates the heat of reaction by reforming fuel. The injector supplies the fuel to the reforming catalyst. The heat transfer member is in directly contact with the filter and the reforming catalyst to transfer the heat therebetween.

In accordance with another aspect of the present invention, an exhaust gas purifying system removes particulate matter from exhaust gas from an engine through an exhaust passage. The system includes a filter, a reforming catalyst and an injector. The filter is provided in the exhaust passage and collects the particulate matter in the exhaust gas. The reforming catalyst is provided in the exhaust passage and is in directly contact with the filter. The reforming catalyst generates the heat of reaction by reforming fuel. The injector supplies the fuel to the reforming catalyst.

Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.