Exhaust heat recovery system

Abstract

An exhaust heat recovery system ( 18 ) includes first and second loop heat pipes ( 20 and 30 ). The first loop heat pipe ( 20 ) recovers exhaust heat downstream of a catalyst ( 5 ) in an exhaust passage ( 4 ) of an internal combustion engine ( 1 ) to exchange heat with the catalyst ( 5 ). The second loop heat pipe ( 30 ) recovers heat of the catalyst ( 5 ) to exchange heat with coolant that is once delivered from the internal combustion engine ( 1 ).

1 . An exhaust heat recovery system comprising:
 a first loop heat pipe that recovers exhaust heat downstream of a first catalyst in an exhaust passage of an internal combustion engine and that exchanges heat with the first catalyst; and   a second loop heat pipe that recovers heat of the first catalyst and that exchanges heat with coolant that is delivered from the internal combustion engine.   
     
     
         2 . The exhaust heat recovery system according to  claim 1 , wherein
 the first loop heat pipe includes   a first heat receiving unit that vaporizes working fluid, which is hermetically sealed and filled inside the first heat receiving unit, by exhaust heat downstream of the first catalyst in the exhaust passage,   a first heat radiating unit that is attached in an upstream region in the first catalyst and that causes heat exchange between working fluid, transferred from the first heat receiving unit, and the first catalyst to condense the working fluid,   a first transfer pipe that is used to transfer working fluid from the first heat receiving unit to the first heat radiating unit, and   a first return pipe that is used to return working fluid from the first heat radiating unit to the first heat receiving unit, and wherein   the second loop heat pipe includes   a second heat receiving unit that is attached in a downstream region in the first catalyst and that vaporizes working fluid, which is hermetically sealed and filled inside the second heat receiving unit, by heat of the first catalyst,   a second heat radiating unit that causes heat exchange between working fluid, transferred from the second heat receiving unit, and coolant, delivered from the internal combustion engine, to condense the working fluid,   a second transfer pipe that is used to transfer working fluid from the second heat receiving unit to the second heat radiating unit, and   a second return pipe that is used to return working fluid from the second heat radiating unit to the second heat receiving unit.   
     
     
         3 . The exhaust heat recovery system according to  claim 2 , wherein
 a first valve device is provided for the first return pipe or the first transfer pipe, and   a second valve device is provided for the second return pipe or the second transfer pipe.   
     
     
         4 . The exhaust heat recovery system according to  claim 3 , further comprising
 a communication passage connected to the first heat radiating unit and the second heat receiving unit, and wherein   a third valve device is provided in the communication passage.   
     
     
         5 . The exhaust heat recovery system according to  claim 4 , further comprising:
 a controller that controls the opening degrees of the first, second and third valve devices by actuators, wherein   when it is determined that it is necessary to activate the first catalyst, the controller opens the first valve device and closes the second and third valve devices, and   when it is determined that it is necessary to heat the coolant in a state where the first catalyst is activated, the controller closes the first valve device and opens the second and third valve devices.   
     
     
         6 . The exhaust heat recovery system according to  claim 5 , wherein
 when it is determined that the temperature of the first catalyst has not reached a first catalyst upper limit temperature in a state where the first catalyst is activated and when it is determined that the temperature of the coolant has not reached a coolant upper limit temperature in a state where the coolant has been warmed up, the controller closes the first valve device and opens the second and third valve devices, and   when it is determined that the temperature of the first catalyst has reached the first catalyst upper limit temperature and it is determined that the temperature of the coolant has reached the coolant upper limit temperature, the controller closes the first and second valve devices and opens the third valve device.   
     
     
         7 . The exhaust heat recovery system according to  claim 2 , wherein
 a first valve device is provided for the first return pipe or the first transfer pipe,   a bypass pipe that bypasses the second heat radiating unit is connected to the second transfer pipe and the second return pipe, and   a switching valve is provided at a portion at which the bypass pipe is connected to the second transfer pipe and is used to switch between a heat exchange route from the second transfer pipe toward the second heat radiating unit and a bypass route from the second transfer pipe toward the bypass pipe.   
     
     
         8 . The exhaust heat recovery system according to  claim 7 , further comprising:
 a controller that controls the opening degree of the first valve device by an actuator, wherein   the switching valve is a three-way valve,   the controller controls the switching valve by an actuator for switching,   when it is determined that it is necessary to activate the first catalyst, the controller opens the first valve device and secures the bypass route by the switching valve,   when it is determined that it is necessary to heat the coolant in a state where the first catalyst is activated, the controller closes the first valve device and secures the heat exchange route by the switching valve, and   when it is determined that the temperature of the coolant has reached a coolant upper limit temperature, the controller closes the first valve device and secures the bypass route by the switching valve.   
     
     
         9 . The exhaust heat recovery system according to  claim 7 , further comprising
 a communication passage connected to the first heat radiating unit and the second heat receiving unit, and wherein   a third valve device is provided in the communication passage.   
     
     
         10 . The exhaust heat recovery system according to  claim 9 , further comprising:
 a controller that controls the opening degrees of the first and third valve devices by actuators, wherein   the switching valve is a three-way valve,   the controller controls the switching valve by an actuator for switching,   when it is determined that it is necessary to activate the first catalyst, the controller opens the first valve device, closes the third valve device and secures the bypass route by the switching valve,   when it is determined that it is necessary to heat the coolant in a state where the first catalyst is activated, the controller closes the first valve device, opens the third valve device and secures the heat exchange route by the switching valve, and   when it is determined that the temperature of the coolant has reached a coolant upper limit temperature, the controller closes the first valve device, opens the third valve device and secures the bypass route by the switching valve.   
     
     
         11 . The exhaust heat recovery system according to  claim 3 , wherein
 the first valve device automatically controls its opening degree in accordance with a predetermined actuating condition, and the first valve device opens when a condition that it is necessary to activate the first catalyst is satisfied, while the first valve device closes when a condition that it is necessary to heat the coolant is satisfied in a state where the first catalyst is activated.   
     
     
         12 . The exhaust heat recovery system according to  claim 3 , wherein
 the second valve device automatically controls its opening degree in accordance with a predetermined actuating condition, and the second valve device closes when a condition that it is necessary to activate the first catalyst is satisfied, while the second valve device opens when a condition that the first catalyst is activated is satisfied.   
     
     
         13 . The exhaust heat recovery system according to  claim 3 , wherein
 the second valve device automatically controls its opening degree in accordance with a predetermined actuating condition, and the second valve device closes when a condition that it is necessary to activate the first catalyst is satisfied or when it is determined that the temperature of the coolant has reached a coolant upper limit temperature, while the second valve device opens when a condition that it is necessary to heat the coolant is satisfied in a state where the first catalyst is activated.   
     
     
         14 . The exhaust heat recovery system according to  claim 4 , wherein
 the third valve device automatically controls its opening degree in accordance with a predetermined actuating condition, and the third valve device closes when a condition that it is necessary to activate the first catalyst is satisfied, while the third valve device opens when a condition that it is necessary to heat the coolant is satisfied in a state where the first catalyst is activated or when a condition that the temperature of the coolant has reached a coolant upper limit temperature is satisfied.   
     
     
         15 . The exhaust heat recovery system according to  claim 4 , wherein
 the first heat radiating unit includes   a first hollow sleeve that is provided so as to surround an upstream region in the first catalyst and that has a first inner annular space, wherein the first transfer pipe and the first return pipe are connected to the first inner annular space and are in fluid communication with the first inner annular space, and   a radially outward-directed fin that is provided on an inner peripheral wall of the first hollow sleeve, wherein   the second heat receiving unit includes   a second hollow sleeve that is provided so as to surround a downstream region in the first catalyst and that has a second inner annular space, wherein the second transfer pipe and the second return pipe are connected to the second inner annular space and are in fluid communication with the second inner annular space, and   a radially outward-directed fin that is provided on an inner peripheral wall of the second hollow sleeve, and wherein   the first and second hollow sleeves are connected next to each other in an axial direction thereof at a connecting portion at which the communication passage is provided.   
     
     
         16 . The exhaust heat recovery system according to  claim 2 , wherein
 a vibration transmission damping portion is provided at a location adjacent to the internal combustion engine in the exhaust passage, and   the second heat radiating unit is attached in a region from the vibration transmission damping portion to the first catalyst.   
     
     
         17 . The exhaust heat recovery system according to  claim 2 , further comprising:
 a second catalyst provided downstream of the first catalyst in the exhaust passage,   wherein the first heat receiving unit is provided downstream of the second catalyst.   
     
     
         18 . The exhaust heat recovery system according to  claim 7 , wherein
 the first valve device automatically controls its opening degree in accordance with a predetermined actuating condition, and the first valve device opens when a condition that it is necessary to activate the first catalyst is satisfied, while the first valve device closes when a condition that it is necessary to heat the coolant is satisfied in a state where the first catalyst is activated.   
     
     
         19 . The exhaust heat recovery system according to  claim 9 , wherein
 the third valve device automatically controls its opening degree in accordance with a predetermined actuating condition, and the third valve device closes when a condition that it is necessary to activate the first catalyst is satisfied, while the third valve device opens when a condition that it is necessary to heat the coolant is satisfied in a state where the first catalyst is activated or when a condition that the temperature of the coolant has reached a coolant upper limit temperature is satisfied.   
     
     
         20 . The exhaust heat recovery system according to  claim 9 , wherein the first heat radiating unit includes
 a first hollow sleeve that is provided so as to surround an upstream region in the first catalyst and that has a first inner annular space, wherein the first transfer pipe and the first return pipe are connected to the first inner annular space and are in fluid communication with the first inner annular space, and   a radially outward-directed fin that is provided on an inner peripheral wall of the first hollow sleeve, wherein   the second heat receiving unit includes   a second hollow sleeve that is provided so as to surround a downstream region in the first catalyst and that has a second inner annular space, wherein the second transfer pipe and the second return pipe are connected to the second inner annular space and are in fluid communication with the second inner annular space, and   a radially outward-directed fin that is provided on an inner peripheral wall of the second hollow sleeve, and wherein   the first and second hollow sleeves are connected next to each other in an axial direction thereof at a connecting portion at which the communication passage is provided.