Exhaust heat recovery system

Abstract

An exhaust heat recovery system 25 provided with a plurality of heat pipes 60, 61 provided with heat recovery parts 60a, 61a and heat exchange parts 60b, 61b. The heat pipes recover heat from exhaust gas exhausted from an internal combustion engine at the heat recovery parts and transfer this recovered heat to an object to be heated at the heat exchange parts. The heat recovery part 60a of the first heat pipe 60 recovers heat from the exhaust gas at an exhaust purification catalyst 20′ provided in an engine exhaust passage or its upstream side. The heat recovery part 61b of the second heat pipe 61 recovers heat from the exhaust gas at the downstream side of the exhaust purification catalyst. Due to this, there is provided an exhaust heat recovery system which can recover at least a fixed amount of exhaust heat at all times while maintaining a warm-up performance of the exhaust purification catalyst.

Description

TECHNICAL FIELD[0001]The present invention relates to an exhaust heat recovery system.BACKGROUND ART[0002]The exhaust gas exhausted from an internal combustion engine in general is higher in temperature than the atmospheric temperature and therefore contains large heat energy. Therefore, an exhaust heat recovery system has been proposed which recovers the heat energy included in the exhaust gas and utilizes the recovered heat energy to raise the temperature of other systems of the internal combustion engine or converts the heat energy to electrical energy for storage in a battery.[0003]As such an exhaust heat recovery system, for example, it is known to attach a heat pipe to a component part of the exhaust system of an internal combustion engine and attach a thermoelectric conversion element to this heat pipe (for example, Japanese Patent Publication (A) No. 2005-264916). By using such a heat pipe, the heat of the exhaust system can be transferred to the thermoelectric conversion el...

AI Technical Summary

Benefits of technology

[0008]Therefore, an object of the present invention is to provide an exhaust heat recovery system able to recover at least a certain amount of exhaust heat at all times while maintaining the warm-up performance of an exhaust purification catalyst.

[0010]According to the above aspect, since the heat recovery part of the first heat transport device recovers heat from the exhaust gas at the exhaust purification catalyst or its upstream side, even at the time of the cold start of the internal combustion engine, it is possible to recover heat from the exhaust gas. On the other hand, since the heat recovery part of the second heat transport device recovers heat from the exhaust gas at the downstream side of the exhaust purification catalyst, it is possible to recover a large amount of heat from the exhaust gas after warm-up of the internal combustion engine.

[0018]According to the present invention, since the second heat transport device recovers the heat of the exhaust gas at the downstream side of the exhaust purification catalyst, it is possible to maintain the warm-up performance of the exhaust purification catalyst. Further, since the first heat transport device recovers the heat of the exhaust gas at the exhaust purification catalyst or its upstream side, even at the time of the cold start of the internal combustion engine, it is possible to recover a certain extent of heat. Therefore, according to the present invention, by suitably setting the heat transport capacities of the first heat transport device and second heat transport device, it is possible to recover at least a certain amount of exhaust heat while maintaining the warm-up performance of the exhaust purification catalyst.

Problems solved by technology

However, if setting the work start temperature of the heat pipe to a temperature higher than the activation temperature of the exhaust purification catalyst like in the exhaust heat recovery system described in Japanese Patent Publication (A) No. 2005-264916, when the temperature of the exhaust gas flowing into the exhaust purification catalyst is lower than the catalyst activation temperature, heat energy is not recovered by the heat pipe.

Therefore, during this time, it is not possible to raise the temperature of other systems of the internal combustion engine requiring a rise of temperature.

However, if using an exhaust heat recovery system such as described in the above-mentioned Japanese Patent Publication (A) No. 2005-264916, sometimes the temperature of the stock fuel flowing into the fuel separation system rises to the certain temperature or more and therefore the stock fuel cannot be efficiently separated.

If it is not possible to efficiently separate the stock fuel in this way, it is not possible to maintain the optimum combustion of the internal combustion engine.

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