Exhaust heat recovery apparatus

Abstract

An exhaust heat recovery apparatus includes: an exhaust heat recovery unit that produces motive power by recovering thermal energy from exhaust gas discharged from a heat engine; an electric generator that is driven by the exhaust heat recovery unit; a first power transmission-switching device that switches between connection and disconnection between the heat engine and the exhaust heat recovery unit; and a second power transmission-switching device that switches between connection and disconnection between the exhaust heat recovery unit and the electric generator, wherein the heat engine or the electric generator is selectively connected to the exhaust heat recovery unit, depending on the operational status of the heat engine. The exhaust heat recovery apparatus makes it possible to effectively use surplus motive power produced by an exhaust heat recovery unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The features, advantages thereof, and technical and industrial significance of this invention will be better understood by reading the following detailed description of preferred embodiments of the invention, when considered in connection with the accompanying drawings, in which:

FIG. 1 is a sectional view showing a Stirling engine, which functions as an exhaust heat recovery unit of a first embodiment;

FIG. 2 is a plan view showing a configuration of the exhaust heat recovery apparatus according to the first embodiment;

FIG. 3 is a schematic diagram showing a state in which the exhaust heat recovery apparatus according to the first embodiment is mounted on a vehicle;

FIG. 4 is a plan view showing the configuration of the exhaust heat recovery apparatus according to a modification of the first embodiment;

FIG. 5 is a schematic diagram showing the variation with time of the output from an internal combustion engine and the output from a Stirling engine when the vehicle on which the exhaust heat recovery apparatus according to the first embodiment is mounted runs and stops;

FIG. 6 is a flow chart showing an example of operation control of the exhaust heat recovery apparatus according to the first embodiment;

FIG. 7 is a flow chart showing operation control of an exhaust heat recovery apparatus according to another control example of the first embodiment; and

FIG. 8 is a sectional view showing a Stirling engine that an exhaust heat recovery apparatus according to a second embodiment includes.

Claims

1. An exhaust heat recovery apparatus, comprising: an exhaust heat recovery unit that produces motive power by recovering thermal energy from exhaust gas discharged from a heat engine;an electric generator that is driven by the exhaust heat recovery unit;a first power transmission-switching device that switches between connection and disconnection between the heat engine and the exhaust heat recovery unit; anda second power transmission-switching device that switches between connection and disconnection between the exhaust heat recovery unit and the electric generator,wherein the heat engine or the electric generator is selectively connected to the exhaust heat recovery unit, depending on operational status of the heat engine.

2. The exhaust heat recovery apparatus according to claim 1, wherein, when the heat engine is in a decelerating state or in a stopped state, the first power transmission-switching device is brought into a disconnected state, and the second power transmission-switching device is brought into a connected state.

3. The exhaust heat recovery apparatus according to claim 1, wherein, when the heat engine is neither in a decelerating state nor in a stopped state, and it is required to combine the motive power from the exhaust heat recovery unit and the motive power from the heat engine and output these motive powers together, the first power transmission-switching device is brought into a connected state, and the second power transmission-switching device is brought into a disconnected state.

4. The exhaust heat recovery apparatus according to claim 3, wherein, when the exhaust heat recovery unit does not apply a load to the heat engine, the first power transmission-switching device is brought into a connected state, and the second power transmission-switching device is brought into a disconnected state; on the other hand, when the exhaust heat recovery unit becomes a load to the heat engine, the first power transmission-switching device is brought into a disconnected state, and the second power transmission-switching device is brought into a connected state.

5. The exhaust heat recovery apparatus according to claim 4, wherein, when the heat engine is in steady operation, or when the heat engine is accelerating, if the increase in the rotation speed of the exhaust heat recovery unit follows the increase in the rotation speed of the heat engine, it is determined that the exhaust heat recovery unit does not apply a load to the heat engine, and therefore, the first and second power transmission-switching devices are brought into a connected state and a disconnected state, respectively.

6. The exhaust heat recovery apparatus according to claim 4, wherein, when the heat engine is in steady operation, or when the heat engine is accelerating, if the increase in the rotation speed of the exhaust heat recovery unit lags behind the increase in the rotation speed of the heat engine, it is determined that the exhaust heat recovery unit becomes a load to the heat engine, and therefore, the first and second power transmission-switching devices are brought into a disconnected state and a connected state, respectively.

7. The exhaust heat recovery apparatus according to claim 1, further comprising: a heat storage unit that stores heat obtained from exhaust gas of the heat engine, wherein,if there is no request to drive the heat engine, and a temperature of a heater that the exhaust heat recovery unit includes to recover thermal energy becomes lower than the temperature of the heat storage unit, heat is supplied from the heat storage unit to the heater to drive the exhaust heat recovery unit.

8. The exhaust heat recovery apparatus according to claim 7, further comprising: a heat pipe that is provided between the heat storage unit and the exhaust heat recovery unit, and transmits the thermal energy in the heat storage unit to the heater.