Method and arrangement for cooling an exhaust system

Abstract

The present invention relates to an arrangement for cooling an exhaust system of a vehicle having an internal combustion engine. The arrangement includes a controller for detecting an elevated temperature condition of the exhaust system, such as a so called hot soak condition, as well as detecting a predetermined engine operating status, such as either of an engine shutdown, a stopped or an idling status. A secondary air injection system may then be actuated to inject ambient air into the exhaust system thereby cooling said exhaust system.

Description

TECHNICAL FIELD[0001]The present invention relates to an arrangement for cooling an exhaust system of a vehicle having an internal combustion engine, and more particularly to a secondary air injection system comprising such an arrangement.BACKGROUND AND SUMMARY OF THE INVENTION[0002]In the field of motor vehicles which are operated by means of internal combustion engines it is a general requirement that the concentration of certain regulated substances in the engine's exhaust gas should be as low as possible. These substances are mainly present in the form of unburnt residues of hydrocarbons (HC), oxides of nitrogen (NOx) and carbon monoxide (CO). In today's motor vehicles equipped with gasoline engines, a purification of the exhaust gas is normally carried out by means of a catalytic converter, or catalyst, arranged in the exhaust system. In the contemporary so-called three-way catalyst, the major part of the above-mentioned substances is eliminated by means of various well-known c...

AI Technical Summary

Benefits of technology

[0007]The present invention is directed to providing an improved arrangement for cooling an exhaust system of a vehicle having an internal combustion engine, which has limited space requirements and is potentially less costly and complex to manufacture and has improved efficiency and operating characteristics and eliminates or at least reduces the effects of the above discussed problems as well as contributes to reducing evaporative emissions.

[0009]Therefore, quick and efficient cooling of an exhaust system of a vehicle having an internal combustion engine can be achieved through this injection of air into the exhaust system of the vehicle in response to a detected elevated temperature condition during a detected predetermined engine status.

[0012]Detection of this so-called hot soak condition after heavy load operation of said engine as a requisite for injecting the cooling airflow will contribute in counteracting the negative effects normally associated with the so-called hot soak condition as well as to component protection, especially of components arranged at or close to the exhaust system, and the reduction of evaporative emissions.

Problems solved by technology

In addition, evaporative emissions occur when, for example, on hot days gasoline heats up and evaporates from both the gasoline tank and wherever fuel may be present throughout the engine.

After the car is turned off, the engine still remains hot for a period of time, and gas vaporizes then, as well, even when the car is parked.

Furthermore, pressure may build in the fuel system.

If any of the fuel injectors drip, excess gas is likely to build up in the engine, making it hard to start.

Still further, components arranged at or close to the exhaust system of the engine may suffer negative effects due to overheating thereof during the conditions described above.

A technical problem encountered with utilization of the air stream from an engine cooling fan as described above is that, although the above-mentioned arrangement results in a cooling of the exhaust system, it is not satisfactory either because of the space requirements of the ducting required to convey the air stream from the fan back to the engine exhaust or, conversely, to convey the engine exhaust forward to the air stream from the fan.

Furthermore, the cooling fan will, in the prior art apparatus above, have to be run for a rather long period of time in order to provide for sufficient cooling during a hot soak condition.

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