JP2017096229A - Catalyst temperature control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively maintain a catalyst temperature in an activation temperature range even when an exhaust gas temperature exceeds an activation upper limit temperature of a catalyst.SOLUTION: A catalyst temperature control device includes: an aftertreatment device 16 having a catalyst 18 provided in an exhaust pipe 12 of an engine 10 to purify exhaust gas; and a heat pipe 20 having a heat reception section 23 and a heat radiation section 24 provided on one end side and the other end side of a cylindrical pipe 21 in which working fluid is included, respectively. The heat reception section 23 is disposed upstream of the aftertreatment device 16 in the exhaust pipe 12, and the heat radiation section 24 is disposed outside the exhaust pipe 12. When a temperature of exhaust gas for heating the heat reception section 23 is raised to a catalyst activation upper limit temperature, the working fluid is moved from the heat reception section 23 to the heat radiation section 24 for heat exchange with outside air, so as to cool the exhaust gas flowing into the catalyst 18.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a catalyst temperature control device, and more particularly to a technique for maintaining a catalyst temperature in an active temperature range at a high exhaust temperature.

  Conventionally, a selective reduction type NOx catalyst (SCR catalyst), an occlusion reduction type NOx catalyst (LNT catalyst), and the like are known as catalysts for reducing and purifying nitrogen compounds (hereinafter referred to as NOx) contained in exhaust gas.

  In order for these NOx catalysts to exhibit good purification performance, it is preferable to maintain the catalyst temperature in a catalyst activation temperature range (for example, a range of about 200 to about 600 ° C.). For this reason, for example, when the exhaust gas temperature is low, such as during cold start, the intake air amount is reduced, the opening timing of the exhaust valve is advanced, or the oxidation reaction heat of the oxidation catalyst by post injection is used. Various so-called temperature raising controls for raising the catalyst temperature to the activation temperature at an early stage by raising the exhaust gas temperature have been proposed.

JP 2006-152841 A JP 2001-263050 A

  By the way, as described above, it is possible to activate the catalyst at an early stage by performing the temperature rise control at a low exhaust temperature such as at the time of cold start. However, there is no effective means for lowering the catalyst temperature to the active temperature range when the NOx catalyst is heated to a temperature higher than the activation upper limit temperature by high-temperature exhaust gas during high load operation or forced filter regeneration. There is a problem of deteriorating the purification performance.

  The disclosed technique aims to effectively maintain the catalyst temperature in the activation temperature range even when the exhaust gas temperature exceeds the activation upper limit temperature of the catalyst.

  The disclosed technology includes a post-processing device including a catalyst for purifying exhaust gas provided in an exhaust pipe of an engine, a heat receiving portion on one end side of a cylindrical tube in which a working fluid is sealed, and a heat radiating portion on the other end side. And a heat pipe in which the heat receiving portion is disposed upstream of the post-processing device in the exhaust pipe and the heat radiating portion is disposed outside the exhaust pipe, and exhausts that heat the heat receiving portion When the temperature of the gas rises to the upper limit temperature of activation of the catalyst, the working fluid moves from the heat receiving portion to the heat radiating portion to exchange heat with outside air, thereby cooling the exhaust gas flowing into the catalyst. And

  The internal pressure of the cylindrical tube may be set to an internal pressure value that vaporizes the working fluid when the temperature of the heat receiving portion rises to the activation upper limit temperature.

  A closed body provided between the heat receiving portion and the heat radiating portion in the cylindrical tube and capable of blocking or opening a flow path in the cylindrical tube is further provided, and the temperature of the exhaust gas that heats the heat receiving portion is the activity. When the temperature rises to the upper limit temperature, the closing body may start the movement of the working fluid from the heat receiving portion to the heat radiating portion by switching the flow path from closed to open.

  The closing body may be formed of an elastic member that can be expanded and contracted, and may be expanded when a viscous liquid is supplied as a pressure medium to close the flow path.

  A fin may be provided on an outer periphery of at least one of the heat receiving unit or the heat radiating unit.

  When the temperature of the exhaust gas that heats the heat receiving part rises to the activation upper limit temperature, a cooling fan that blows cooling air to the heat radiating part may be further provided.

  According to the disclosed technology, the catalyst temperature can be effectively maintained in the activation temperature range even when the exhaust gas temperature exceeds the activation upper limit temperature of the catalyst.

1 is a schematic overall configuration diagram showing an intake / exhaust system of an engine to which a catalyst temperature control device according to a first embodiment of the present invention is applied. It is typical sectional drawing which shows the heat pipe which concerns on 1st embodiment of this invention. In the heat pipe which concerns on 2nd embodiment of this invention, it is typical sectional drawing which shows the state which the obstruction body obstruct | occluded the flow path in a cylindrical tube. In the heat pipe which concerns on 2nd embodiment of this invention, it is typical sectional drawing which shows the state which the obstruction body open | released the flow path in a cylindrical tube. It is typical sectional drawing which shows the heat pipe which concerns on other embodiment of this invention. It is typical sectional drawing which shows the heat pipe which concerns on other embodiment of this invention.

  Hereinafter, a catalyst temperature control apparatus according to each embodiment of the present invention will be described with reference to the accompanying drawings. The same parts are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

[First embodiment]
FIG. 1 is a schematic overall configuration diagram showing an intake / exhaust system of an engine to which a catalyst temperature control device according to a first embodiment is applied. An intake pipe 11 is connected to the intake manifold 10A of the engine 10, and an exhaust pipe 12 is connected to the exhaust manifold 10B.

  The intake pipe 11 is provided with an air filter 13, a supercharger compressor 14 </ b> A, an intercooler 15, and the like in order from the intake upstream side. The exhaust pipe 12 is provided with a turbocharger turbine 14B, a heat pipe 20, an exhaust aftertreatment device 16 and the like in order from the exhaust upstream side. A NOx catalyst 18 for reducing and purifying NOx contained in the exhaust gas is housed in the case 17 of the exhaust aftertreatment device 16.

  Next, based on FIG. 2, the detail of the heat pipe 20 which concerns on this embodiment is demonstrated. The heat pipe 20 is provided with a cylindrical tube 21 filled with a working fluid such as water, a wick 22 lined on the inner wall of the cylindrical tube 21, and provided on one end side of the cylindrical tube 21 and inserted into the exhaust pipe 12. A heat receiving part 23 heated by the exhaust gas, a heat dissipating part 24 provided on the other end side of the cylindrical tube 21 and arranged outside the exhaust pipe 12 for exchanging heat with the working air, and an outer periphery of the heat receiving part 23 A plurality of heat receiving fins 25 provided to expand the heat receiving area and a plurality of heat dissipating fins 26 provided on the outer periphery of the heat radiating portion 24 to expand the heat radiating area are provided.

  The cylindrical tube 21 is formed to be bent in a substantially L shape, the tube axis direction of the heat receiving portion 23 is substantially parallel to the flow direction of the exhaust gas, and the front end side of the heat receiving portion 23 is the exhaust aftertreatment device 16. It is fixed to the exhaust pipe 12 so as to be disposed adjacent to the upstream side (catalyst inlet).

  In the present embodiment, the internal pressure of the cylindrical tube 21 is an internal pressure value that vaporizes (evaporates) the working fluid in the cylindrical tube 21 when the temperature of the heat receiving portion 23 rises to the activation upper limit temperature (for example, about 600 ° C.) of the NOx catalyst 18. Is set in That is, when the heat receiving unit 23 is heated to the catalyst activation upper limit temperature by the high-temperature exhaust gas, the working fluid is vaporized and moved to the heat radiating unit 24, and is cooled by heat exchange with the outside air. The release to is promoted. As described above, when the exhaust gas temperature is higher than the upper limit temperature of the catalyst activation by the heat receiving unit 23, the exhaust gas is promoted to cool by the heat transfer of the heat pipe 20, so that the exhaust gas downstream of the heat pipe 20 is exhausted. The gas temperature (catalyst inlet temperature) can be kept lower than the catalyst activation upper limit temperature.

  As described above in detail, in the catalyst temperature control device of the present embodiment, when the temperature of the heat receiving portion 23 heated by the high temperature exhaust gas rises to the upper limit temperature of the catalyst activity, the working fluid in the cylindrical tube 21 is vaporized to dissipate heat. By moving to the unit 24 and releasing the exhaust heat to the outside air, the cooling of the high temperature exhaust gas is promoted. That is, when the NOx catalyst 18 enters a high exhaust temperature state in which the temperature is raised above the catalyst activity upper limit temperature, the cooling of the high temperature exhaust gas is promoted by the heat transfer of the heat pipe 20, so that the catalyst inlet temperature becomes the activity upper limit. The temperature becomes lower than the temperature. As a result, the catalyst temperature can be effectively maintained in the activation temperature range even at a high exhaust temperature, and deterioration of exhaust emission due to a decrease in purification performance can be prevented.

[Second Embodiment]
Next, based on FIG.3, 4, the detail of the heat pipe of the catalyst temperature control apparatus which concerns on 2nd embodiment is demonstrated.

  The heat pipe 20 of the second embodiment has a closed body 27 provided between the heat receiving part 23 and the heat radiating part 24 in the cylindrical tube 21, and the closed body 27 has a lower vapor pressure than water such as grease or oil. A pressure medium supply / discharge mechanism 30 for supplying or discharging a viscous liquid (low boiling point) as a pressure medium is further provided.

  The closing body 27 is formed of an elastic material such as rubber having elasticity and heat resistance. When the pressure medium is supplied from the pressure medium supply / discharge mechanism 30, the closing body 27 expands in the radial direction to the inner wall of the cylindrical tube 21. Closely. As described above, when the closing body 27 is in close contact with the inner wall of the cylindrical tube 21, the flow path in the cylindrical tube 21 is blocked, and the flow of steam from the heat receiving portion 23 to the heat radiating portion 24 is blocked. . On the other hand, when the pressure medium is discharged from the closing body 27, the closing body 27 is reduced to the state shown in FIG. 4, and the flow path in the cylindrical tube 21 is opened.

  The pressure medium supply / discharge mechanism 30 controls the storage unit 31 that stores viscous liquid such as grease and oil, the electric pump 33 that is normally or reversely driven by an electric motor 32 such as a DC motor, and the drive of the electric pump 33. A control unit 34, a first supply / exhaust pipe 35 that allows the electric pump 33 and the storage unit 31 to communicate, and a second supply / exhaust pipe 36 that allows the electric pump 33 and the closing body 27 to communicate through the cylindrical pipe 21. And a temperature sensor 37 for detecting the exhaust gas temperature upstream of the heat pipe 20. The second supply / exhaust pipe 36 is fixed to the cylindrical pipe 21 by welding or the like so that the degree of vacuum in the cylindrical pipe 21 does not decrease.

  The electric pump 33 is driven to rotate forward when the movement of the steam (working fluid) in the cylindrical tube 21 is interrupted. More specifically, when the electric pump 33 is driven to rotate forward, the pressure medium in the reservoir 31 is supplied from the first supply / exhaust pipe 35 to the closing body 27 via the second supply / exhaust pipe 36, and the blocking body 27 causes the cylindrical pipe to be supplied. Since the flow path in 21 is blocked, the flow of steam (working fluid) from the heat receiving portion 23 to the heat radiating portion 24 is blocked.

  On the other hand, the electric pump 33 is reversely driven when the movement of the steam (working fluid) in the cylindrical tube 21 is allowed. When the electric pump 33 is driven in reverse, the pressure medium in the closing body 27 is discharged from the second supply / discharge pipe 36 to the storage portion 31 via the first supply / discharge pipe 35, and the closing body 27 is contracted, so that the cylindrical pipe The flow path in 21 is opened.

  In the present embodiment, the electric pump 33 is driven to rotate forward when the exhaust gas temperature detected by the temperature sensor 37 is lower than the activation upper limit temperature of the NOx catalyst 18, and the exhaust gas temperature detected by the temperature sensor 37 is the activation upper limit. When it exceeds the temperature, it is driven in reverse. That is, when the temperature of the exhaust gas that heats the heat receiving unit 23 becomes equal to or higher than the activation upper limit temperature, the pressure medium is discharged from the closed body 27 by the reverse drive of the electric pump 33, and the closed body 27 is reduced and the inside of the cylindrical tube 21 is reduced. By opening the flow path, cooling of the high-temperature exhaust gas by heat transfer of the heat pipe 20 is started.

  As described above in detail, according to the catalyst temperature control apparatus of the second embodiment, when the temperature of the exhaust gas that heats the heat receiving portion 23 rises to the activation upper limit temperature or more, the closure body 27 is reduced and the inside of the cylindrical tube 21 is reduced. By starting the movement of the working fluid and promoting the cooling of the high temperature exhaust gas by the heat pipe 20, the catalyst inlet temperature can be kept lower than the activation upper limit temperature as in the first embodiment. As a result, the catalyst temperature can be effectively maintained in the activation temperature range even at a high exhaust temperature, and deterioration of exhaust emission due to a decrease in purification performance can be prevented.

  The present invention is not limited to the above-described embodiments, and can be appropriately modified and implemented without departing from the spirit of the present invention.

  For example, as shown in FIG. 5, when the air cooling fan 28 is provided adjacent to the heat radiating portion 24 of the cylindrical tube 21 and the exhaust gas temperature detected by the temperature sensor 37 becomes equal to or higher than the upper limit temperature of activation of the NOx catalyst 18, the air cooling fan 28. May be configured to be driven. Thus, by forcibly cooling the heat radiating part 24 with the air cooling fan 28, the cooling of the high-temperature exhaust gas by the heat pipe 20 is effectively promoted, and the catalyst temperature is reliably maintained in the active temperature range. can do.

  Further, the cylindrical tube 21 is not limited to the one bent in a substantially L shape, and a straight tube may be used as shown in FIG. In this case, the wick 22 can be omitted if the heat dissipating part 24 is arranged above the heat receiving part 23 and the working fluid liquefied by the heat dissipating part 24 is recirculated to the heat receiving part 23 by gravity. Good.

DESCRIPTION OF SYMBOLS 10 Engine 12 Exhaust pipe 16 Exhaust after-treatment apparatus 18 NOx catalyst 20 Heat pipe 21 Cylindrical pipe 22 Wick 23 Heat receiving part 24 Heat radiating part 25 Heat receiving fin 26 Heat radiating fin

Claims (6)

An aftertreatment device including a catalyst that is provided in an exhaust pipe of an engine and purifies exhaust gas;
A heat receiving portion is provided on one end side of the cylindrical tube filled with the working fluid, and a heat radiating portion is provided on the other end side, and the heat receiving portion is disposed on the upstream side of the aftertreatment device in the exhaust pipe, and the heat radiating portion A heat pipe disposed outside the exhaust pipe,
When the temperature of the exhaust gas that heats the heat receiving part rises to the upper limit temperature of the catalyst, the working fluid moves from the heat receiving part to the heat radiating part and exchanges heat with the outside air, so that the exhaust flowing into the catalyst A catalyst temperature control device characterized by cooling a gas. The catalyst temperature control device according to claim 1, wherein the internal pressure of the cylindrical tube is set to an internal pressure value that vaporizes the working fluid when the temperature of the heat receiving portion rises to the upper limit of activation temperature. Further comprising a closing body provided between the heat receiving portion and the heat radiating portion in the cylindrical tube and capable of blocking or opening the flow path in the cylindrical tube;
When the temperature of the exhaust gas that heats the heat receiving part rises to the upper limit temperature of the activation, the closing body switches the flow path from the closed state to the open state, thereby moving the working fluid from the heat receiving part to the heat radiating part. The catalyst temperature control device according to claim 1. The catalyst temperature control device according to claim 3, wherein the closing body is formed of an elastic member that can expand and contract, and expands when the viscous liquid is supplied as a pressure medium to block the flow path. The catalyst temperature control device according to any one of claims 1 to 4, wherein a fin is provided on an outer periphery of at least one of the heat receiving unit or the heat radiating unit. The catalyst temperature control device according to any one of claims 1 to 5, further comprising a cooling fan that blows cooling air to the heat radiating portion when the temperature of the exhaust gas that heats the heat receiving portion rises to the activation upper limit temperature. .

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