JP2018150915A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance an effect of maintaining a catalyst in an appropriate temperature range.SOLUTION: An exhaust emission control device 12 includes: an auxiliary flow passage 24 branched from an exhaust pipe 14 on the upstream side of a catalyst carrier 16, passing trough the circumference of the catalyst carrier 16 and merging with the exhaust pipe 14; a heat storage member 40 provided at a position around the catalyst carrier 16 in the auxiliary flow passage 24; a selector valve 30 for switching a flow of exhaust gas in the exhaust pipe 14 to the auxiliary flow passage 24; and a control device 36 for controlling the selector valve 30.SELECTED DRAWING: Figure 1

Description

  The present application relates to an exhaust emission control device.

  Patent Document 1 discloses an exhaust gas of an engine provided with a heat storage material composed of a substance having a melting point and a freezing point in the vicinity of a set temperature in the active temperature region of the catalyst upstream of the catalyst in the exhaust passage of the engine. A purification device is described.

  Patent Document 2 discloses a catalyst case device having a catalyst case that houses a catalyst for purifying exhaust gas, and an exhaust heat recovery unit that recovers heat of exhaust gas that passes through the catalyst and transfers heat between the catalyst and the catalyst. Is described.

  In Patent Document 3, in an exhaust gas purification apparatus having a catalyst structure comprising a catalyst for purifying exhaust gas and a catalyst carrier for supporting the catalyst, the exhaust gas purification apparatus has a catalyst activation temperature region within the activation temperature region. A configuration in which a heat storage body made of a metal material having a melting point is provided is described.

JP 60-212608 A JP 2000-179338 A JP 2000-204936 A

  In the technique described in Patent Document 1, the heat quantity of the exhaust gas is temporarily stored with a heat storage material. That is, since the exhaust gas flows into the catalyst after passing through the heat storage material, it may be difficult to maintain the temperature of the catalyst within a predetermined range because heat is radiated from the exhaust gas to the pipe between the heat storage material and the catalyst.

  In the technique described in the cited document 2, heat transfer to the exhaust heat recovery unit is not performed directly from the exhaust, and heat transfer from the catalyst case is dominant in the exhaust heat recovery of the exhaust heat recovery unit. When the thermal conductivity of the catalyst case is low, it takes time to transfer the heat to the exhaust heat recovery unit, so it is difficult to maintain the temperature of the catalyst in the effective temperature range.

  In the technique described in Patent Document 3, since the catalyst carrier is integrated including the heat storage body, the substantial heat capacity of the catalyst carrier is larger than that of the structure in which the heat storage material is not integrated. For this reason, it is difficult to raise the temperature of the catalyst carrier in a short time.

  Thus, the techniques described in any of the patent documents have room for improvement in maintaining the catalyst in an appropriate temperature range.

  In view of the above facts, the present invention aims to increase the effect of maintaining the catalyst in an appropriate temperature range.

  In the first aspect, a catalyst carrier that is provided in the exhaust pipe and carries a catalyst that purifies exhaust gas, and a branching part from the exhaust pipe at a branch portion upstream of the exhaust gas from the catalyst carrier, the catalyst carrier A sub-flow path that merges with the exhaust pipe at a junction between the flow-dividing part and the catalyst carrier, and a heat storage member that is provided in the sub-flow path at a position around the catalyst carrier, A switching member that switches the flow of the exhaust gas in the exhaust pipe to the sub-flow path; and a control device that controls the switching member.

  In this exhaust purification device, the exhaust gas flowing through the exhaust pipe is purified by the catalyst carried by the catalyst carrier.

  The sub-flow path branches off at the branch portion upstream of the catalyst carrier. By switching the switching member by the control device, the exhaust gas can be flowed into the sub-flow path. Since the heat storage member is provided in the sub-flow path, the temperature of the exhaust gas can be lowered by storing a part of the heat of the exhaust gas in the heat storage member. For example, the deterioration of the catalyst can be suppressed and the catalyst can be protected by reducing the exhaust temperature to such an extent that it does not reach the temperature at which the catalyst is deteriorated.

  The sub-flow path is provided so as to pass around the catalyst carrier. And in this subchannel, the heat storage member is provided in the position around a catalyst carrier. Since the temperature of the catalyst carrier is kept around the catalyst carrier, it is possible to suppress a decrease in the temperature of the catalyst even when the engine is stopped. Even when the temperature of the exhaust gas is low, such as immediately after starting the engine, a high exhaust gas purification performance can be obtained by maintaining the catalyst at the active temperature (or raising the temperature to the active temperature in a short time).

  According to a second aspect, in the first aspect, there is provided a downstream opening / closing member that is controlled by the control device and opens / closes the exhaust pipe downstream of the exhaust with respect to the catalyst carrier.

  By opening the downstream opening / closing member, it is possible to realize a state in which exhaust flows through the exhaust pipe. By setting the downstream opening / closing member in the closed state, it is possible to suppress the air from the downstream side from reaching the catalyst and to suppress the temperature decrease of the catalyst.

  According to a third aspect, in the second aspect, there is provided an upstream opening / closing member that is controlled by the control device and opens / closes the exhaust pipe upstream of the flow dividing portion.

  By opening the upstream opening / closing member, it is possible to realize a state in which exhaust flows through the exhaust pipe. By closing the upstream opening / closing member, the gas from the upstream side can be prevented from reaching the catalyst, and the temperature drop of the catalyst can be suppressed.

  According to a fourth aspect, in the third aspect, there is provided an engine operation sensor that detects operation and stop of the engine and transmits the detected operation to the control device, and the control device has the downstream opening and closing member and the upstream opening and closing member when the engine is stopped. Is closed, and the downstream opening and closing member and the upstream opening and closing member are opened when the engine is operating.

  When the engine is operating, the downstream opening / closing member and the upstream opening / closing member are opened, so that exhaust from the engine flows through the exhaust pipe. Since the downstream opening / closing member and the upstream opening / closing member are closed when the engine is stopped, it is possible to suppress the air from the downstream side and the upstream side from reaching the catalyst.

  In a fifth aspect, in any one of the first to fourth aspects, an exhaust temperature sensor that detects a temperature of the exhaust gas flowing in the exhaust pipe, a heat storage member temperature sensor that detects a temperature of the heat storage member, and A catalyst carrier temperature sensor for detecting a temperature of the catalyst carrier, and the control device controls the switching member based on the temperature of the exhaust, the temperature of the heat storage member, and the temperature of the catalyst carrier. To do.

  The switching member is controlled based on the temperature of the exhaust, the temperature of the heat storage member, and the temperature of the catalyst carrier, so that heat is transferred from the exhaust to the heat storage member or the catalyst carrier (catalyst), or the heat storage member and the catalyst. The transfer of heat to the support (catalyst) can be appropriately controlled.

  According to a sixth aspect, in any one of the first to fifth aspects, the heat storage member includes a storage member in which the heat storage material is stored, and a fin extending from the storage member. is there.

  Since the heat storage member includes the heat storage material housed in the housing member, heat storage and heat dissipation can be reliably performed by transferring heat to the heat storage material. Since the heat storage material is housed in the housing member, it does not leak out.

  Since the fin is extended from the housing member and the substantial surface area of the housing member is widened, heat can be efficiently transferred to the heat storage material.

  Since this invention was set as the said structure, the effect of maintaining a catalyst in a suitable temperature range is high.

FIG. 1 is a cross-sectional view showing an exhaust emission control device according to the first embodiment. 2 is a cross-sectional view taken along line 2-2 of FIG. 1 showing the exhaust emission control device of the first embodiment. FIG. 3 is a partially enlarged cross-sectional view of the exhaust emission control device of the first embodiment. FIG. 4 is a cross-sectional view showing the exhaust emission control device of the second embodiment. FIG. 5 is a cross-sectional view showing the exhaust emission control device of the third embodiment. FIG. 6 is a cross-sectional view showing the exhaust gas purification apparatus of the first modification in the same cross section as FIG. FIG. 7 is a cross-sectional view showing the exhaust gas purification apparatus of the second modification in the same cross section as FIG.

  Hereinafter, the exhaust emission control device 12 of the first embodiment will be described with reference to the drawings.

  As shown in FIGS. 1 and 2, the exhaust purification device 12 has a catalyst carrier 16 attached to the inside of the exhaust pipe 14. In the present embodiment, the exhaust pipe 14 has a substantially cylindrical shape, but a part in the longitudinal direction is a large-diameter pipe 14B having a larger diameter than the other part. The catalyst carrier 16 is disposed in the large diameter pipe 14B.

  Hereinafter, the terms “upstream side” and “downstream side” simply refer to the upstream side and the downstream side in the exhaust flow direction (in the direction of arrow F1) in the exhaust pipe 14, respectively.

  In the exhaust pipe 14, a portion upstream of the large-diameter pipe 14B is the upstream pipe 14A, and a downstream portion is the downstream pipe 14C. A portion from the upstream pipe 14A to the downstream pipe 14C through the large diameter pipe 14B is a main flow path 22 through which exhaust from the engine flows. The large-diameter pipe 14B and the downstream pipe 14C are continuous by a tapered pipe 14D whose diameter gradually changes. However, the large-diameter pipe 14B and the upstream pipe 14A are discontinuous, and a later-described branching section 26 and A junction 28 is provided.

  The catalyst carrier 16 has a structure in which the surface area is increased by making the thin plate into a wave shape or a honeycomb shape, for example, and the catalyst is supported on the surface. The catalyst has an action of purifying substances (hydrocarbons, etc.) in the exhaust gas flowing in the exhaust pipe 14. Examples of the catalyst having such an action include platinum, palladium, rhodium and the like. The structure for increasing the surface area of the catalyst carrier 16 is not limited to the above-described wave shape or honeycomb shape.

  The catalyst carrier 16 is formed in a columnar shape or a cylindrical shape as a whole so as to be accommodated in the exhaust pipe 14.

  A predetermined range including the large-diameter pipe 14B of the exhaust pipe 14 and the upstream side and the downstream side of the large-diameter pipe 14B is covered with an outer cylinder 18 having a larger diameter than that of the large-diameter pipe. As shown in FIG. 2, the outer cylinder 18 of the first embodiment has a cylindrical shape that surrounds the large-diameter pipe 14B in the circumferential direction.

  The upstream end portion 18A of the outer cylinder 18 is connected to the upstream pipe 14A by an upstream tapered portion 18B whose diameter gradually decreases toward the upstream side, and the downstream end portion 18E is downstream by a downstream tapered portion 18D whose diameter gradually decreases toward the downstream side. It is connected to the pipe 14C.

  An intermediate cylinder 20 is disposed between the large diameter pipe 14 </ b> B and the outer cylinder 18. The intermediate cylinder 20, the large diameter pipe 14B, and the outer cylinder 18 are separated from each other. On the upstream side of the intermediate cylinder 20, the diameter gradually decreases toward the upstream side by the upstream taper portion 20 </ b> B. The upstream end 20A of the intermediate cylinder 20 is not in contact with the exhaust pipe 14 and the outer cylinder 18. On the other hand, a portion where the diameter gradually decreases is not formed on the downstream side of the intermediate cylinder 20, and the downstream end portion 20 </ b> C is not in contact with the exhaust pipe 14 and the outer cylinder 18.

  By providing the outer cylinder 18 and the intermediate cylinder 20 as described above, the upstream side of the catalyst carrier 16 is branched from the main flow path 22 by the diverter 26, and around the catalyst carrier 16 outside the main flow path 22. As a result, a sub-flow path 24 that merges with the main flow path 22 is formed by the merge portion 28. Specifically, the auxiliary flow path 24 branches from the main flow path 22 at a flow dividing portion 26 between the upstream tapered portion 18B of the outer cylinder 18 and the upstream tapered portion 20B of the intermediate cylinder 20. Then, the space between the outer cylinder 18 and the intermediate cylinder 20 reaches the downstream side, and is turned back at the downstream end 20C of the intermediate cylinder 20 to reach the upstream side between the intermediate cylinder 20 and the large-diameter pipe 14B. Furthermore, it joins to the main flow path 22 from the junction 28 between the upstream tapered portion 20B of the intermediate cylinder 20 and the upstream end of the large diameter pipe 14B.

  A switching valve 30 is provided at the upstream end 20 </ b> A of the intermediate cylinder 20. The switching valve 30 is an example of a switching member.

  The switching valve 30 of the present embodiment includes a valve body 34 that can rotate around an axis 32 that is orthogonal to the flow direction of the exhaust gas. The rotation angle of the valve body 34 is controlled by the control device 36. And the switching valve 30 can take the closed state HS shown with a continuous line in FIG. 1, and the open state KS shown with a dashed-two dotted line by the rotation angle of the valve body 34. FIG.

  An engine operation sensor 38 that detects operation and stop of the engine is connected to the control device 36. The control device 36 may be configured to be able to control the state of the engine. In this case, the control device also serves as an engine operation sensor.

  When the switching valve 30 is in the open state KS, the exhaust gas that has flowed through the upstream pipe 14A can flow into both the large-diameter pipe 14B and the sub-flow path 24. However, since the flow resistance of the main flow path 22 is smaller than that of the sub flow path 24, most of the exhaust flows directly to the large diameter pipe 14B without passing through the sub flow path 24. On the other hand, when the switching valve 30 is in the closed state HS, the exhaust gas that has flowed through the upstream pipe 14A does not flow directly into the large-diameter pipe 14B, and therefore flows through the auxiliary flow path 24. Then, after the exhaust gas flows through the sub-flow channel 24, it flows through the merging portion 28 to the large-diameter pipe 14B.

  A heat storage member 40 is disposed in the sub flow path 24. As shown in detail in FIG. 3, the heat storage member 40 includes a housing member 42 disposed in contact with the inner peripheral surface of the outer cylinder 18, the outer peripheral surface and inner peripheral surface of the intermediate cylinder 20, and the outer peripheral surface of the large-diameter pipe 14 </ b> B. doing. The housing member 42 is hollow, and a heat storage material is housed therein. Heat exchange is performed between the exhaust gas flowing through the sub-channel 24 and the heat storage material in the housing member 42. For example, when the exhaust gas flowing through the auxiliary flow path 24 is hotter than the heat storage material in the housing member 42, the heat of the exhaust gas moves to the heat storage material and is stored in the heat storage material, and the temperature of the exhaust gas decreases. On the contrary, when the exhaust gas flowing through the sub flow path 24 is at a lower temperature than the heat storage material in the housing member 42, the heat of the heat storage material moves to the exhaust gas, and the temperature of the exhaust gas rises.

  A plurality of fins 44 extend from the housing member 42 toward the sub-flow path 24. The substantial surface area of the housing member 42 is increased by the fins 44. That is, the heat storage member 40 includes a housing member 42 and fins 44 and is a heat exchanger that performs heat exchange with the outside for the internal heat storage material.

  Next, the operation of this embodiment will be described.

  In the exhaust gas purification device 12 of the first embodiment, when the switching valve 30 is in the open state KS (indicated by a two-dot chain line in FIG. 1), most of the exhaust gas flowing through the upstream pipe 14A has a large diameter instead of the sub flow path 24. It flows directly to the pipe 14B, that is, to the main flow path 22. Further, the exhaust gas that has flowed to the sub-flow channel 24 also merges from the merge portion 28 to the main flow channel 22. Then, the exhaust gas is purified by the catalyst supported on the catalyst carrier 16, and the purified exhaust gas flows further downstream from the downstream pipe 14C.

  When the switching valve 30 is in the open state KS, most of the exhaust gas is directly introduced into the catalyst carrier 16, so that, for example, the heat of the exhaust gas is reduced as compared with a structure in which most of the exhaust gas flows through the auxiliary flow path 24. It is possible to increase the temperature in a short time (improving the temperature increase rate) by acting on the catalyst.

  In contrast, when the switching valve 30 is in the closed state HS (shown by a solid line in FIG. 1), the exhaust gas flowing through the upstream pipe 14A is directly introduced into the large diameter pipe 14B, that is, the catalyst carrier 16. Instead, it flows through the auxiliary flow path 24. Since the heat storage member 40 is disposed in the sub-channel 24, a part of the heat of the exhaust moves to the heat storage member 40, particularly the heat storage material, and is stored. Then, the exhaust gas with the temperature lowered joins the large diameter pipe 14 </ b> B (main flow path 22) from the junction 28 and is introduced into the catalyst carrier 16. Since the temperature of the exhaust gas is lowered, the heat of the high-temperature exhaust gas does not act on the catalyst supported on the catalyst carrier 16 and the deterioration of the catalyst can be suppressed.

  The sub flow path 24 is provided so as to pass around the catalyst carrier 16, and the heat storage member 40 is disposed in the sub flow path 24. The heat storage member 40 stores heat that has acted from the exhaust. That is, the heat storage member 40 in a state of storing heat is disposed around the catalyst carrier 16. Therefore, for example, even when the engine is stopped and the exhaust gas is not introduced into the catalyst carrier 16, the temperature of the catalyst supported on the catalyst carrier 16 can be maintained, and the temperature drop of the catalyst can be suppressed. In particular, the heat carrying member is, for example, compared with the structure arranged in the upstream pipe 14A, due to heat conduction from the heat accumulating member 40, natural convection of the gas moved from the heat accumulating member 40 through the sub-flow path 24, etc. The heat of the heat storage member 40 can be effectively applied to 16.

  Further, when the engine is started in a state where heat is stored in the heat storage member 40, the exhaust is introduced into the catalyst carrier 16 via the sub-flow path 24 if the switching valve 30 is closed. Although it is assumed that the temperature of the exhaust gas is not sufficiently increased immediately after the engine is started, even in such a case, the exhaust gas flowing through the auxiliary flow path 24 is heated by receiving heat from the heat storage member 40. The heated exhaust gas is introduced into the catalyst carrier 16, so that this heat can be applied to the catalyst carried on the catalyst carrier 16. Thereby, the temperature of a catalyst can be raised toward a desired temperature in a short time.

  In the first embodiment, as a criterion for determining the open / closed state of the switching valve 30, for example, the temperature of the catalyst carrier 16 can be detected by a temperature sensor and can be performed based on the detected temperature. Furthermore, the opening / closing of the switching valve 30 may be controlled according to the time from the start of the engine. Specifically, since the temperature of the exhaust gas is low for a predetermined time from the start of the engine, the switching valve 30 is set to the open state KS. Then, after a predetermined time has elapsed from the start of the engine, the temperature of the exhaust gas becomes high. Therefore, the switching valve 30 is closed to prevent the heat of the high-temperature exhaust gas from directly acting on the catalyst, and the heat storage member What is necessary is just to make the heat of exhaust act on 40.

  Next, a second embodiment will be described. In the second embodiment, elements, members, and the like that are the same as in the first embodiment are assigned the same reference numerals, and detailed descriptions thereof are omitted.

  As shown in FIG. 4, in the exhaust purification device 62 of the second embodiment, an upstream on-off valve 64 is provided in the upstream pipe 14A, and a downstream on-off valve 66 is provided in the downstream pipe 14C. The upstream opening / closing valve 64 and the downstream opening / closing valve 66 are controlled by the control device 36.

  The upstream opening / closing valve 64 is a valve that opens and closes the exhaust pipe 14 (main flow path 22) at a position upstream of the flow dividing section 26, and is an example of an upstream opening / closing member. The downstream opening / closing valve 66 is a member that opens and closes the exhaust pipe 14 (main flow path 22) at a position downstream of the catalyst carrier 16, and is an example of a downstream opening / closing member.

  The exhaust purification device 62 of the second embodiment configured as described above has the same operational effects as the exhaust purification device 12 of the first embodiment, but further has the following operational effects.

  That is, in the exhaust purification device 62 of the second embodiment, for example, when the engine is stopped, the control device 36 closes the upstream on-off valve 64 and the downstream on-off valve 66.

  The gas existing on the upstream side of the upstream opening / closing valve 64 may be at a lower temperature than the gas in the vicinity of the catalyst carrier 16. Therefore, if the upstream opening / closing valve 64 is not closed, gas movement (convection) between the upstream side and the downstream side of the upstream opening / closing valve 64 occurs, and the temperature of the air in the vicinity of the catalyst carrier 16 may decrease. . However, in this embodiment, since the upstream on-off valve 64 is closed, gas movement between the upstream side and the downstream side of the upstream on-off valve 64 is prevented. For this reason, the low temperature gas on the upstream side of the upstream opening / closing valve 64 does not flow into the catalyst carrier 16. Further, the air in the vicinity of the catalyst carrier 16 does not move to the upstream side of the upstream opening / closing valve 64. That is, the temperature drop of the catalyst carrier 16 can be suppressed.

  Further, the gas present on the downstream side of the downstream on-off valve 66 may be at a lower temperature than the gas in the vicinity of the catalyst carrier 16. Therefore, if the downstream on-off valve 66 is not closed, gas movement between the upstream side and the downstream side of the downstream on-off valve 66 occurs, and the temperature of the air in the vicinity of the catalyst carrier 16 may decrease. However, in this embodiment, since the downstream on-off valve 66 is closed, gas movement between the upstream side and the downstream side of the downstream on-off valve 66 is prevented. For this reason, the low temperature gas on the downstream side of the downstream opening / closing valve 66 does not flow into the catalyst carrier 16. Further, the air in the vicinity of the catalyst carrier 16 does not move to the downstream side of the downstream on-off valve 66. That is, the temperature drop of the catalyst carrier 16 can be suppressed.

  Then, by closing the upstream opening / closing valve 64 and the downstream opening / closing valve 66, the catalyst carrier 16 and the heat storage member 40 are positioned in a sealed space between the upstream opening / closing valve 64 and the downstream opening / closing valve 66. . Gas convection occurs due to a temperature difference between the catalyst carrier 16 and the heat storage member 40. This convection suppresses escape of high-temperature gas inside the sealed space into the upstream pipe 14A and the downstream pipe 14C, and thus the catalyst. Heat exchange between the carrier 16 and the heat storage member 40 can be promoted.

  For example, when the distance from the engine to the catalyst carrier 16 (substantially the length of the upstream pipe 14A) is short and there is little heat radiation from the upstream pipe 14A, the upstream on-off valve 64 is omitted. Also good. Even if the upstream opening / closing valve 64 is omitted, the gas transfer between the upstream side and the downstream side of the switching valve 30 can be prevented by closing the switching valve 30. In this case, the switching valve 30 has a structure also serving as an upstream opening / closing member.

  Next, a third embodiment will be described. In 3rd embodiment, the same code | symbol is attached | subjected about the same element, member, etc. as 1st embodiment or 2nd embodiment, and detailed description is abbreviate | omitted.

  As shown in FIG. 5, the exhaust purification device 72 of the third embodiment has an exhaust temperature sensor 74, a heat storage member temperature sensor 76, and a catalyst carrier temperature sensor 78.

  The exhaust temperature sensor 74 is provided in the upstream pipe 14 </ b> A, detects the temperature of the exhaust, and transmits it to the control device 36.

  The heat storage member temperature sensor 76 is disposed in contact with the heat storage member 40, detects the temperature of the heat storage member 40, and transmits it to the control device 36.

  The catalyst carrier temperature sensor 78 is disposed in contact with the catalyst carrier 16, detects the temperature of the catalyst carrier 16, and transmits it to the control device 36. Since the temperature of the catalyst carrier is substantially equal to the temperature of the catalyst, hereinafter, the temperature detected by the catalyst carrier temperature sensor 78 is simply referred to as the catalyst temperature.

  The control device 36 controls the switching valve 30, the upstream on-off valve 64, and the downstream on-off valve 66 based on the exhaust temperature, the heat storage member temperature, and the catalyst temperature in addition to the operation of the engine.

  Below, an example of control of the switching valve 30, the upstream on-off valve 64, and the downstream on-off valve 66 in 3rd embodiment is explained in full detail.

  In this control, threshold temperatures are set for the exhaust gas temperature, the heat storage member temperature, and the catalyst temperature, and the opening and closing of each valve is controlled in relation to these threshold temperatures. In Table 1, for each of the exhaust temperature, the heat storage member temperature, and the catalyst temperature, a state that is higher than the set threshold temperature is “high”, and a state that is lower is “low”. This threshold temperature is the catalyst activation temperature. If the temperature is higher than this threshold temperature, the catalyst exhibits a high ability to purify the exhaust gas.

  Condition (1) in Table 1 is a state where the engine is stopped. In this case, the switching valve 30, the upstream on-off valve 64, and the downstream on-off valve 66 are all closed. Inflow of low-temperature air in the upstream pipe 14A and the downstream pipe 14C is suppressed, and convection between the heat storage member 40 and the catalyst carrier 16 is also suppressed. Then, the heat stored in the heat storage member 40 is dissipated and acts on the catalyst carrier 16, so that the temperature drop of the catalyst carrier 16 is suppressed.

  Conditions (2) to (9) are when the engine is operating, and the upstream on-off valve 64 and the downstream on-off valve 66 are both open.

  Condition (2) is when the engine is operating and all of the exhaust temperature, the catalyst temperature, and the heat storage member temperature are lower than the respective threshold temperatures. In this case, if the exhaust gas temperature is higher than the heat storage member temperature, the switching valve 30 is opened, and the exhaust gas is introduced into the catalyst carrier 16, so that the catalyst carrier 16 can be raised in a short time. However, when the exhaust temperature is lower than the heat storage member temperature, the switching valve 30 is closed. As a result, the exhaust gas is not directly introduced into the catalyst carrier 16, but is heated in the sub-flow path 24 by receiving heat from the heat storage member 40. Since the heated exhaust gas is introduced into the catalyst carrier 16, the catalyst carrier 16 can be heated. That is, if the exhaust gas is hotter than the heat storage member 40, the exhaust gas is directly introduced into the catalyst carrier 16. If the heat storage member 40 is hotter than the exhaust gas, the exhaust gas is heated by the heat storage member 40. It is introduced into the catalyst carrier 16.

  Condition (3) is when the exhaust temperature and the catalyst temperature are each lower than the threshold temperature, and the heat storage member temperature is higher than the threshold temperature. In this case, the switching valve 30 is opened, and the exhaust gas flows into the sub flow path 24. The exhaust gas is heated by the heat storage member 40, and the heated exhaust gas is introduced into the catalyst carrier 16, so that the catalyst carrier 16 can be heated in a short time. It is possible to suppress a decrease in the temperature of the catalyst due to the low temperature exhaust gas being directly introduced into the catalyst carrier 16.

  Condition (4) is when the exhaust gas temperature and the heat storage member temperature are lower than the temperature threshold and the catalyst temperature is higher than the threshold temperature. In this case, if the exhaust gas temperature is higher than the heat storage member temperature, the switching valve 30 is opened and the exhaust gas is directly introduced into the catalyst carrier 16. The exhaust gas having a temperature higher than that of the heat storage member 40 is introduced into the catalyst carrier 16 without being lowered in temperature by the heat storage member 40, so that the temperature drop of the catalyst can be suppressed. On the other hand, when the exhaust temperature is lower than the heat storage member temperature, the switching valve 30 is closed. The exhaust gas is not directly introduced into the catalyst carrier 16, but is heated in the sub-flow path 24 by receiving heat from the heat storage member 40. Since the exhaust gas whose temperature has been raised is introduced into the catalyst carrier 16, the temperature drop of the catalyst carrier 16 can be suppressed as compared with the case where the exhaust gas is not heated by the heat storage member 40.

  Condition (5) is when the exhaust gas temperature is lower than the threshold temperature, and the catalyst temperature and the heat storage member temperature are higher than the threshold temperature. In this case, if the catalyst temperature is higher than the heat storage member temperature, the switching valve 30 is opened, and the exhaust gas is directly introduced into the catalyst carrier 16, so that excessive temperature rise of the catalyst can be suppressed. On the other hand, when the catalyst temperature is lower than the heat storage member temperature, the switching valve 30 is closed. Since the exhaust gas whose temperature has been raised by the heat storage member 40 is introduced into the catalyst carrier 16 in the sub-channel 24, the temperature of the catalyst carrier 16 can be raised.

  Condition (6) is when the exhaust temperature, the catalyst temperature, and the heat storage member temperature are all higher than the threshold temperature. In this case, if the catalyst temperature is higher than the exhaust temperature and the exhaust temperature is higher than the heat storage member temperature, the switching valve 30 is closed, so that the exhaust gas whose temperature has been lowered by the heat storage member 40 is introduced into the catalyst carrier 16 and the catalyst Excessive temperature rise can be suppressed. If the catalyst temperature is higher than the heat storage member temperature and the heat storage member temperature is higher than the exhaust temperature, the switching valve 30 is opened, so that excessive temperature rise of the catalyst can be suppressed by exhaust. When the exhaust gas temperature is higher than the heat storage member temperature and the heat storage member temperature is higher than the catalyst temperature, the switching valve 30 is opened, and the exhaust gas can be directly introduced into the catalyst carrier 16 to raise the temperature of the catalyst. If the exhaust gas temperature is higher than the catalyst temperature and the catalyst temperature is higher than the heat storage member temperature, the switching valve 30 is closed, and the exhaust gas heated by the heat storage member 40 is introduced into the catalyst carrier 16 so that the catalyst is The temperature can be raised.

  Condition (7) is when the exhaust gas temperature is higher than the threshold temperature, and the catalyst temperature and the heat storage member temperature are lower than the threshold temperature. In this case, the temperature of the catalyst can be raised by opening the switching valve 30 and introducing exhaust directly into the catalyst carrier 16.

  Condition (8) is when the exhaust gas temperature and the heat storage member temperature are higher than the threshold temperature and the catalyst temperature is lower than the threshold temperature. In this case, when the exhaust gas temperature is lower than the heat storage member temperature, the switching valve 30 is closed. The exhaust gas is not directly introduced into the catalyst carrier 16, but is heated in the sub-flow path 24 by receiving heat from the heat storage member 40. Since the exhaust gas whose temperature has been raised is introduced into the catalyst carrier 16, the temperature drop of the catalyst carrier 16 can be suppressed as compared with the case where the exhaust gas is not heated by the heat storage member 40. On the other hand, if the exhaust gas temperature is higher than the heat storage member temperature, the switching valve 30 is opened and the exhaust gas is directly introduced into the catalyst carrier 16. The exhaust gas having a temperature higher than that of the heat storage member 40 is introduced into the catalyst carrier 16 without being lowered in temperature by the heat storage member 40, so that the temperature drop of the catalyst can be suppressed.

  Condition (9) is when the exhaust gas temperature and the catalyst temperature are higher than the threshold temperature, and the heat storage member temperature is lower than the threshold temperature. In this case, since the switching valve 30 is closed, the exhaust gas whose temperature has been lowered by the heat storage member 40 is introduced into the catalyst carrier 16, and excessive temperature rise of the catalyst can be suppressed.

  As described above, in the exhaust purification device 72 of the third embodiment, in addition to the operation of the engine, the switching valve 30, the upstream on-off valve 64, and the downstream on-off valve 66 are provided based on the exhaust temperature, the heat storage member temperature, and the catalyst temperature. By controlling, the temperature of the catalyst can be appropriately controlled.

  In 1st-3rd embodiment, the structure of the subchannel 24 is not limited to what was mentioned above, The structure of the 1st modification shown in FIG. 6 and the 2nd modification shown in FIG. 7 can be taken.

  In the exhaust emission control device 82 of the first modification shown in FIG. 6, the outer cylinder 84 has a pair of parallel flat portions 86. The interval between the flat portions 86 is equal to the outer diameter of the large-diameter pipe 14B, and the flat portions 86 are in contact with the large-diameter pipe 14B at the center in the width direction (arrow W1 direction). The intermediate cylinder 88 is also formed in two left and right arc shapes in cross section so as to be positioned between the flat portions 86.

  In the first modification, the height of the outer cylinder 84 is lower than the height of the outer cylinder 18 of the first embodiment. Therefore, in the first modified example, the exhaust purification device 82 can be arranged avoiding interference with the surrounding members, and the degree of freedom of arrangement is high.

  In the exhaust emission control device 92 of the second modified example shown in FIG. 7, the outer cylinder 94 has a pair of parallel flat plate portions 96 in addition to the flat portion 86, and the outer cylinder 94 has a flow direction. It is rectangular when viewed in a cross section perpendicular to it. The intermediate cylinder 98 also has a flat portion 100 parallel to the flat plate portion 96 of the outer cylinder 94. Further, a partition wall 102 parallel to the flat portion 100 is formed between the intermediate cylinder 98 and the large diameter pipe 14B.

  In the second modification example, the outer cylinder 94 is thus rectangular when viewed in a cross section perpendicular to the flow direction, and there is no curved surface portion. Also. The intermediate cylinder 98 also has no curved portion. Therefore, the outer cylinder 94 and the intermediate cylinder 98 can be easily molded, and the exhaust purification device 92 can be manufactured at a low cost.

  In the exhaust purification apparatus of each of the above-described embodiments and modifications, the heat storage material is not particularly limited as long as it can store heat by receiving heat from high-temperature exhaust and can radiate heat to low-temperature exhaust. For example, a molten salt having a melting point in the range of 100 ° C. or higher and 600 ° C. or lower can be used. A molten salt is a substance obtained by melting a salt or oxide that is solid at room temperature into a liquid by heating, and is composed of cations and anions. And enthalpy changes with phase change (melting, primary transition, or secondary transition), and heat storage and heat dissipation are carried out.

  As can be seen from Table 2 above, the phase change when actually storing and radiating heat in each of the above embodiments may be melting accompanied by a phase transition between the solid phase and the liquid phase. Stores and dissipates heat as latent heat. On the other hand, heat storage and heat dissipation may be performed by a phase change that does not involve a phase transition between the solid phase and the liquid phase.

  Among these molten salts, in particular, a molten salt having a phase change temperature in the range of 100 ° C. or more and 600 ° C. or less can efficiently perform heat exchange with the exhaust gas, and is preferable for the exhaust purification apparatus of each embodiment and modification. Applicable.

  Depending on the type of molten salt, there is also a molten salt whose volume changes due to a phase change. In the case of using a molten salt whose volume changes, a sufficient volume may be secured in the housing member 42 so that the volume change of the molten salt can be absorbed.

12 Exhaust purification device 14 Exhaust pipe 16 Catalyst carrier 18 Outer cylinder 20 Intermediate cylinder 22 Main flow path 24 Sub-flow path 26 Splitting section 28 Junction section 30 Switching valve 36 Controller 38 Engine operation sensor 40 Heat storage member 42 Housing member 44 Fin 62 Exhaust Purification device 64 Upstream on-off valve 66 Downstream on-off valve 72 Exhaust purification device 74 Exhaust temperature sensor 76 Heat storage member temperature sensor 78 Catalyst carrier temperature sensor 82 Exhaust purification device 92 Exhaust purification device

Claims (6)

A catalyst carrier provided in the exhaust pipe and carrying a catalyst for purifying exhaust;
Branches from the exhaust pipe at a branch portion upstream of the exhaust from the catalyst carrier, passes through the periphery of the catalyst carrier, and joins the exhaust pipe at a junction between the branch portion and the catalyst carrier. A secondary flow path
A heat storage member provided in the sub-flow path at a position around the catalyst carrier;
A switching member for switching the flow of the exhaust gas in the exhaust pipe to the sub-flow channel;
A control device for controlling the switching member;
Exhaust gas purification apparatus.   The exhaust emission control device according to claim 1, further comprising a downstream opening / closing member that is controlled by the control device and opens / closes the exhaust pipe on a downstream side of the exhaust with respect to the catalyst carrier.   The exhaust emission control device according to claim 2, further comprising an upstream opening / closing member that is controlled by the control device and opens / closes the exhaust pipe upstream of the flow dividing section. An engine operation sensor that detects operation and stop of the engine and transmits the detected operation to the control device;
The exhaust emission control device according to claim 3, wherein the control device closes the downstream opening / closing member and the upstream opening / closing member when the engine is stopped, and opens the downstream opening / closing member and the upstream opening / closing member when the engine is operating. An exhaust temperature sensor for detecting the temperature of the exhaust flowing in the exhaust pipe;
A heat storage member temperature sensor for detecting the temperature of the heat storage member;
A catalyst carrier temperature sensor for detecting the temperature of the catalyst carrier;
Have
The exhaust control device according to any one of claims 1 to 4, wherein the control device controls the switching member based on a temperature of the exhaust gas, a temperature of the heat storage member, and a temperature of the catalyst carrier. . The heat storage member is
A housing member for housing the heat storage material;
A fin extending from the housing member;
The exhaust gas purification device according to any one of claims 1 to 5, wherein the exhaust gas purification device is a heat exchanger having a heat exchanger.