JP6601446B2 - Exhaust pipe - Google Patents

Description

  The present application relates to an exhaust pipe.

  In Patent Document 1, two external fitting members that form a gap between the inner tube portion are connected in an airtight manner using a joint with a suction port, the vacuum valve of the joint with a suction port is opened, and the suction port is opened. A double pipe structure is described in which air in the gap is sucked and exhausted by a vacuum pump.

  Patent Document 2 includes a vacuum space portion that blocks heat transfer to the outer cylinder that covers the exhaust purification catalyst, and if the detected value of the vacuum space detected by the pressure detection means is greater than a predetermined determination reference value, the exhaust purification is performed. A technique for determining that a device has failed is described.

  In Patent Document 3, a gap is formed between an inner cylinder and an outer cylinder, and a plurality of slits of the outer cylinder are insulated by a heat-sensitive bimetal when it is cold to insulate the gap and open at a high temperature. An exhaust pipe is described in which part of the heat of the exhaust gas is taken to the outside directly through the outside.

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

  In the technique described in Patent Document 1, an attempt is made to maintain a stable heat insulating effect by setting the gap to a desired reduced pressure state, but it is difficult to increase the heat dissipation from the exhaust pipe.

  In the technique described in Patent Document 2, heat transfer from the exhaust purification catalyst to the outer cylinder is blocked by the vacuum space, but it is difficult to increase the heat dissipation from the exhaust pipe.

  In the technique described in the cited document 3, the heat dissipation from the exhaust pipe can be improved by opening the slit. However, in order to introduce the outside air into the gap between the inner cylinder and the outer cylinder, the outside air more than the flow resistance of the gap. Introduction pressure is required. Since the outside air introduction pressure is affected by the running state and environment of the vehicle, it is difficult to stably improve the heat dissipation from the exhaust pipe.

  If the heat of the exhaust gas is appropriately applied to the catalyst carried on the catalyst carrier in the exhaust pipe and the temperature of the catalyst is maintained within a predetermined temperature range, the catalyst deterioration can be suppressed and the exhaust gas can be purified. Highly effective.

  However, the techniques described in any of the patent documents have room for improvement in terms of adjusting the temperature of the exhaust gas by reliably increasing the heat insulation and heat dissipation in the exhaust pipe.

  This invention considers the said fact and makes it a subject to adjust the heat insulation and heat dissipation in an exhaust pipe appropriately, and to raise the effect of maintaining a catalyst in a suitable temperature range.

  In the first aspect, an inner pipe through which exhaust from the engine flows, a catalyst carrier provided inside the inner pipe for carrying a catalyst for purifying the exhaust, and disposed at an outer peripheral side of the inner pipe at least from the engine And an outer tube that forms a sealed space between the catalyst carrier and the inner tube, and a pressure adjusting member that pressurizes and depressurizes the sealed space.

  In this exhaust pipe, exhaust from the engine flows inside the inner pipe. The exhaust gas is purified by the catalyst supported by the catalyst carrier.

  An outer tube is disposed on the outer peripheral side of the inner tube. A sealed space is formed between the outer tube and the inner tube.

  The sealed space is formed from the engine to at least a portion of the catalyst carrier. The sealed space can be pressurized and depressurized by the pressure adjusting member. By pressurizing the sealed space, it is possible to increase the number density of gas molecules in the sealed space and increase heat dissipation (lower heat insulation). When the heat dissipation of the sealed space is increased, the heat dissipation of the exhaust pipe is also increased. On the contrary, by reducing the pressure in the sealed space, the number density of gas molecules in the sealed space can be lowered and the heat insulation can be increased (the heat dissipation can be lowered). When the heat insulating property of the sealed space increases, the heat insulating property of the exhaust pipe also increases.

  Thus, by appropriately adjusting the heat insulation and heat dissipation in the exhaust pipe, it is possible to introduce the exhaust gas adjusted in temperature into the catalyst carrier and maintain the catalyst in an appropriate temperature range. For example, when the exhaust temperature is high enough to degrade the catalyst, the exhaust temperature can be lowered to suppress catalyst degradation and protect the catalyst. In addition, when the exhaust temperature is in a temperature range (activation temperature) where the catalyst can effectively exhibit the exhaust purification effect, the catalyst is maintained at the activation temperature (or for a short time) by suppressing heat release from the exhaust. It is possible to increase the exhaust gas purification performance by raising the temperature to the activation temperature.

  According to a second aspect, in the first aspect, the pressure adjusting member includes an intake / exhaust port provided in the outer pipe, a pump connected to the intake / exhaust port, and a control device that controls the pump. Have.

  By sucking and exhausting the sealed space through the intake / exhaust port by driving the pump, the sealed space can be reliably pressurized and depressurized. Since the pump is controlled by the control device, the pressure adjustment in the sealed space is easy.

  In a third aspect, in the second aspect, a plurality of the catalyst carriers are arranged along the flow direction of the exhaust gas, and the sealed space is divided for each of the plurality of catalyst carriers.

  For each of the plurality of catalyst carriers, the corresponding sealed space can be pressurized or depressurized. In other words, it is possible to cause the heat of exhaust at an appropriate temperature to act on each catalyst supported on the catalyst support. For example, an exhaust gas whose temperature is kept high can be introduced into the catalyst carrier located upstream of the exhaust flow by reducing the pressure of the corresponding sealed space to enhance the heat insulation. On the other hand, exhaust with reduced temperature can be introduced into the catalyst carrier located on the downstream side by pressurizing the corresponding sealed space to enhance heat dissipation.

  In a fourth aspect, in the third aspect, one or more intake / exhaust ports are provided for each of the plurality of sealed spaces.

  Since there are one or more intake / exhaust ports for each of the plurality of sealed spaces, each of the sealed spaces can be appropriately pressurized and depressurized. In addition, in a structure in which a plurality of intake / exhaust ports are provided in a sealed space, gas is sucked into the sealed space through some of the intake / exhaust ports, and gas is exhausted from the sealed space through other intake / exhaust ports. It is also possible to generate a gas flow.

  In a 5th aspect, it has the on-off valve controlled by the said control apparatus in the 3rd or 4th aspect, and opens and closes the intake / exhaust piping between the said pump and the said intake / exhaust port.

  By opening and closing the on-off valve, the sealed space can be appropriately pressurized and depressurized.

  In a sixth aspect, in the fifth aspect, the on-off valve is provided for each of the plurality of intake / exhaust ports.

  Since the on-off valve is opened / closed for each of the plurality of intake / exhaust ports, the desired sealed space can be pressurized and depressurized by a pump.

  In the seventh aspect, in any one of the third to sixth aspects, the pump is shared by a plurality of the sealed spaces.

  Since pumps are shared by a plurality of sealed spaces, the number of pumps can be reduced as compared with a structure in which a pump is provided for each sealed space.

  According to an eighth aspect, in any one of the second to seventh aspects, an engine operation sensor that detects operation and stop of the engine and transmits the detected operation to the control device is provided, and the pressure adjusting member is in an engine stop state. The pressure in the sealed space is reduced and the pressure is maintained until the next engine start.

  Since the sealed space is decompressed when the engine is stopped and this state is maintained until the next engine start, the heat insulation of the exhaust pipe is maintained. Thereby, it is possible to suppress the heat radiation of the exhaust gas flowing through the exhaust pipe at the next engine start.

  In a ninth aspect, in any one of the first to eighth aspects, the pressure adjusting member introduces gas into the sealed space when the catalyst carrier is warmed up.

  In a state where the catalyst carrier is warmed up, the gas is introduced into the sealed space, so that the sealed space is pressurized (or a gas flow is generated), so that the heat dissipation of the exhaust pipe is improved, An excessive temperature rise of the catalyst carrier can be suppressed.

  Here, “warm-up” refers to a state in which the catalyst carried on the catalyst carrier is at a temperature at which the exhaust gas purifying ability can be sufficiently exerted.

  In a tenth aspect, in any one of the first to ninth aspects, a thermal radiation suppressing member that suppresses thermal radiation is disposed in the sealed space.

  The heat radiation suppressing member suppresses heat radiation in the sealed space and enhances the heat insulating property of the sealed space, thereby improving the heat insulating property of the exhaust pipe.

  In an eleventh aspect, in any one of the first to tenth aspects, a hole member having a plurality of holes is arranged in contact with at least one of the inner tube and the outer tube in the sealed space. Has been.

  In the inner tube or the outer tube in contact with the hole member, the hole member increases the substantial surface area in the sealed space. For this reason, the heat radiation of the exhaust pipe can be enhanced by promoting the heat radiation in the sealed space and enhancing the heat radiation of the sealed space.

  According to a twelfth aspect, in the eleventh aspect, the hole member is in contact with both the inner tube and the outer tube.

  Since the hole member is disposed in contact with both the inner tube and the outer tube, the substantial surface area in the sealed space is increased in both the inner tube and the outer tube, and the heat dissipation of the sealed space can be further improved. it can.

  According to a thirteenth aspect, in any one of the first to twelfth aspects, the heat recovery device is provided inside the inner pipe and recovers the heat of the exhaust and acts on a heat medium, An outer tube forms the sealed space from the engine to the heat recovery unit.

  The heat of the exhaust gas can be effectively utilized by recovering the heat of the exhaust gas and causing it to act on the heat medium.

  Since the outer tube is formed with a sealed space from the engine to the site of the heat recovery unit, the exhaust having an appropriate temperature can be introduced into the heat exchanger.

  In a fourteenth aspect, in any one of the first to thirteenth aspects, the sealed space is divided between the engine and the catalyst carrier that is upstream in the flow direction of the exhaust gas. .

  The sealed space on the upstream side of the divided portion is located further on the upstream side than the most upstream catalyst carrier. That is, by pressurizing and depressurizing the sealed space further upstream than the most upstream catalyst carrier, the temperature of the exhaust gas can be adjusted in a stage until the exhaust reaches the site of the most upstream catalyst carrier.

  Since this invention was set as the said structure, the heat insulation and heat dissipation in an exhaust pipe can be adjusted appropriately, and the effect of maintaining a catalyst in a suitable temperature range can be heightened.

FIG. 1 is a cross-sectional view showing the exhaust pipe of the first embodiment in a cross section along the longitudinal direction of the exhaust pipe. 2 is a cross-sectional view taken along line 2-2 of FIG. 1 showing the exhaust pipe of the first embodiment. FIG. 3 is a cross-sectional view showing the exhaust pipe of the second embodiment in a cross section along the longitudinal direction of the exhaust pipe. FIG. 4 is a cross-sectional view showing the exhaust pipe of the third embodiment in a cross section along the longitudinal direction of the exhaust pipe. FIG. 5 is a partially enlarged cross-sectional view of the exhaust pipe of the third embodiment. FIG. 6 is a sectional view showing the exhaust pipe of the third embodiment partially enlarged. FIG. 7 is a cross-sectional view showing a partially enlarged exhaust pipe of the third embodiment. FIG. 8 is a cross-sectional view showing the exhaust pipe of the first modification in the same cross section as FIG. FIG. 9 is a cross-sectional view showing the exhaust pipe of the second modified example in the same cross section as FIG. FIG. 10 is a cross-sectional view showing the exhaust pipe of the third modified example in the same cross section as FIG. FIG. 11 is a cross-sectional view showing the exhaust pipe of the fourth modification in a cross section along the longitudinal direction of the exhaust pipe.

  Hereinafter, the exhaust pipe 24 of the first embodiment will be described with reference to the drawings.

  FIG. 1 shows the exhaust pipe 24 of the first embodiment connected to the engine 20.

  The engine 20 mixes air and fuel sucked through the intake pipe 22 and burns them in the combustion chamber. Then, the exhaust is discharged to the outside through the exhaust pipe 24. Hereinafter, the terms “upstream side” and “downstream side” simply refer to the upstream side and the downstream side in the exhaust flow direction (arrow F1 direction) in the exhaust pipe 24, respectively.

  The exhaust pipe 24 has an exhaust collecting pipe 26 connected to the engine 20. The exhaust collecting pipe 26 has the same number of branch portions 26A as the exhaust ports of the engine 20, and the plurality of branch portions 26A are aggregated to form one aggregate portion 26B. The exhaust collecting pipe 26 is located at the uppermost stream in the flow direction in the entire exhaust pipe 24, and is also the first connecting pipe 24A.

  The exhaust pipe 24 is further arranged in order from the exhaust collecting pipe 26 (first connection pipe 24A) to the downstream side, and is connected to the second connection pipe 24B, the third connection pipe 24C, and the fourth connection pipe 24D connected by the connection portion 28. Have.

  An upstream catalyst carrier 30 is arranged inside the second connection pipe 24B, and a downstream catalyst carrier 32 is arranged inside the third connection pipe 24C. In this embodiment, a plurality of (two) catalyst carriers are provided, and the upstream catalyst carrier 30 is the most upstream catalyst carrier in the exhaust flow direction.

  Each of the upstream catalyst support 30 and the downstream catalyst support 32 has a structure in which the surface area is increased by making the thin plate into a corrugated shape or a honeycomb shape, for example, and the upstream catalyst and the downstream catalyst are respectively supported on the surface. ing. These catalysts have a function of purifying exhaust gas by removing substances (hydrocarbons and the like) in the exhaust gas flowing in the exhaust pipe 24. Examples of the catalyst having such an action include platinum, palladium, rhodium and the like. The structure for increasing the surface areas of the upstream catalyst support 30 and the downstream catalyst support 32 is not limited to the wave shape or the honeycomb shape described above.

  The exhaust gas flowing through the exhaust pipe 24 is purified by the upstream catalyst carried on the upstream catalyst carrier 30 and further purified by the downstream catalyst carried on the downstream catalyst carrier 32. The upstream catalyst and the downstream catalyst may be different types (purification performance) of the catalyst, but may be the same type of catalyst.

  The upstream catalyst carrier 30 and the downstream catalyst carrier 32 are formed in a columnar shape or a cylindrical shape as a whole so as to be accommodated in the exhaust pipe 24.

  A heat recovery unit 34 is disposed inside the fourth connection pipe 24D. A heat medium pipe (not shown) is connected to the heat recovery unit 34, and the heat of the exhaust gas is recovered and applied to the heat flowing through the heat medium pipe. The heat of the heat medium whose temperature has been increased by heating can be used, for example, for warming up or heating each part of the vehicle.

  The exhaust collecting pipe 26 (first connecting pipe 24A), the second connecting pipe 24B, the third connecting pipe 24C, and the fourth connecting pipe 24D all have a double pipe structure having an inner pipe 36 and an outer pipe 38. In the present embodiment, the inner tube 36 and the outer tube 38 are both formed in a cylindrical shape and arranged concentrically. The inner diameter of the outer tube 38 is larger than the outer diameter of the inner tube 36, and a sealed space 40 is formed between the inner tube 36 and the outer tube 38. Hereinafter, the sealed space 40 may be appropriately distinguished from the first sealed space 40A, the second sealed space 40B, the third sealed space 40C, and the fourth sealed space 40D from the upstream side.

  The sealed space 40 is formed from the engine 20 to the position of the fourth connecting pipe 24D. That is, in the structure having a plurality of catalyst carriers, at least the downstream catalyst carrier 32 is formed. In the present embodiment, the sealed space 40 is further formed up to the portion of the heat recovery device 34 that is downstream of the downstream catalyst carrier 32.

  As described above, the upstream catalyst carrier 30 is the most upstream catalyst carrier in the exhaust flow direction. The first sealed space 40A is a sealed space located further upstream than the upstream catalyst carrier 30.

  The exhaust pipe 24 has a pressure adjusting member 42, and the sealed space 40 can be pressurized and depressurized by the pressure adjusting member 42. In the first embodiment, the pressure adjusting member 42 has an intake / exhaust port 44 and a pump 46.

  The intake / exhaust port 44 has intake / exhaust ports 44 </ b> A, 44 </ b> B, 44 </ b> C, 44 </ b> D corresponding to the outer tubes 38 of the sealed space 40. The pump 46 is connected to the intake / exhaust ports 44A, 44B, 44C, 44D. In the first embodiment, one pump 46 is provided for a plurality of (four) intake / exhaust ports 44A, 44B, 44C, 44D, and the gas supply / exhaust pipe 52 extending from the pump 46 is branched into four. Are connected to the intake / exhaust ports 44A, 44B, 44C, 44D. The pump 46 is controlled by a control device 48 and can perform pressurization by supplying gas and depressurization by discharging gas to the sealed space 40.

  An engine drive sensor 50 that detects the drive state of the engine 20 is connected to the control device 48. The control device 48 can control the pump 46 based on the driving state of the engine 20.

  Next, the operation of this embodiment will be described.

  In the exhaust pipe 24 of the first embodiment, the exhaust from the engine 20 passes through the exhaust collecting pipe 26 (first connecting pipe 24A), the second connecting pipe 24B, the third connecting pipe 24C, and the fourth connecting pipe 24D to the outside. Discharged. The exhaust gas is purified by the first catalyst carried on the upstream catalyst carrier 30 and the second catalyst carried on the downstream catalyst carrier 32. Further, the heat of the exhaust is recovered by the heat recovery unit 34 and acts on the heat medium. The heat of the heat medium can be used for warming up or heating each part of the vehicle.

  In the exhaust pipe 24, a sealed space 40 is formed between the inner pipe 36 and the outer pipe 38. When the control device 48 drives the pump 46, the sealed space 40 can be pressurized and depressurized.

  When the sealed space 40 is pressurized, the number density of gas molecules in the sealed space 40 is increased, and the heat conductivity is increased. When the exhaust gas flowing inside the exhaust pipe 24 is hotter than the outside air, if the sealed space 40 is set to a high pressure in this way, the heat dissipation performance when heat is radiated from the exhaust through the exhaust pipe 24 is enhanced. For example, even when the temperature of the exhaust gas immediately after being discharged from the engine 20 is high, the exhaust gas temperature can be lowered by sufficiently dissipating heat from the exhaust gas. And deterioration of a catalyst can be suppressed by making the heat of high temperature exhaust gas not act on an upstream catalyst or a downstream catalyst (or make an effect | action small).

  On the other hand, when the sealed space 40 is depressurized, the number density of gas molecules in the sealed space 40 is lowered, and the heat insulation is increased. For example, when the temperature of the exhaust gas is in a temperature range in which the action of purifying the exhaust gas is high in the upstream catalyst and the downstream catalyst, the heat of the exhaust gas is suppressed from being radiated by the exhaust pipe 24, and the heat of the exhaust gas is reduced to the first. It is possible to effectively act on the catalyst and the second catalyst.

  In addition, when the engine 20 is in a stopped state, heat release from the exhaust pipe 24 can be suppressed at the position of the upstream catalyst carrier 30 by reducing the pressure in the second sealed space 40B, and the temperature drop of the upstream catalyst can be suppressed. Similarly, when the engine 20 is stopped, heat release from the exhaust pipe 24 can be suppressed at the position of the downstream catalyst carrier 32 by reducing the pressure in the third sealed space 40C, and the temperature drop of the downstream catalyst can be suppressed.

  When the upstream catalyst carrier 30 is in a warmed-up state, the heat release from the exhaust pipe 24 can be suppressed at the position of the upstream catalyst carrier 30 by reducing the pressure of the second sealed space 40B, and the temperature of the upstream catalyst is excessively increased. Can be suppressed. Similarly, when the downstream catalyst carrier 32 is in a warm-up state, heat release from the exhaust pipe 24 can be suppressed at the position of the downstream catalyst carrier 32 by reducing the pressure in the third sealed space 40C, and excessive temperature of the downstream catalyst is increased. The rise can be suppressed.

  Note that whether or not the upstream catalyst carrier 30 and the downstream catalyst carrier 32 are in a warm-up state can be determined based on various determination indexes. For example, if a temperature sensor is provided in the upstream catalyst carrier 30 and the downstream catalyst carrier 32, whether or not the upstream catalyst carrier 30 and the downstream catalyst carrier 32 are in a warm-up state based on the temperature detected by the temperature sensor. I can judge. Further, the temperature of the upstream catalyst carrier 30 and the downstream catalyst carrier 32 is estimated from the outside air temperature and the exhaust temperature (or engine temperature), the engine drive time, etc., and at this estimated temperature, the upstream catalyst carrier 30 and the downstream catalyst It can be determined whether the carrier 32 is in a warm-up state. These determinations can be performed by the control device 48.

  The first sealed space 40 </ b> A is a sealed space positioned further upstream than the upstream catalyst carrier 30. By pressurizing and depressurizing the first sealed space 40A, before the exhaust reaches the upstream catalyst carrier 30 which is the most upstream catalyst carrier, the heat dissipation and heat insulation properties of the exhaust pipe 24 are adjusted, It is possible to adjust the temperature of the exhaust.

  Thus, in this embodiment, the heat insulation of sealed space can be adjusted by pressurizing and pressure-reducing the sealed space 40. FIG. Since the exhaust gas adjusted in temperature can be introduced into the upstream catalyst carrier 30 and the downstream catalyst carrier 32, the upstream catalyst and the downstream catalyst can be maintained in appropriate temperature ranges, and the exhaust gas purification performance of the catalyst can be exhibited highly.

  Moreover, the sealed space 40 is formed from the engine 20 at a site including the catalyst carrier (upstream catalyst carrier 30 and downstream catalyst carrier 32). Therefore, all the catalysts (upstream catalyst and downstream catalyst) supported on the catalyst support can be maintained in an appropriate temperature range, and the exhaust gas purification performance of the catalyst can be exhibited highly.

  In the present embodiment, a heat recovery device 34 is provided in the exhaust pipe 24. For example, if the heat insulation is improved by reducing the pressure in all the sealed spaces 40, the temperature drop until the exhaust reaches the heat recovery unit 34 can be suppressed. Therefore, a large amount of heat that can be recovered by the heat recovery unit 34 can be secured, and the heat recovery The rate can be improved.

  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.

  In the exhaust pipe 54 of the second embodiment, the pressure adjusting member 56 has an opening / closing valve 58 in addition to the pump 46 and the intake / exhaust ports 44A, 44B, 44C, 44D. The on-off valve 58 is provided in each of the intake / exhaust ports 44A, 44B, 44C, 44D. Opening and closing of the on-off valve 58 is controlled by the control device 48.

  Therefore, in the second embodiment, it is possible to pressurize or depressurize only a specific sealed space 40 among the plurality of sealed spaces 40. For example, the first sealed space 40A can be pressurized more than the second sealed space 40B, the third sealed space 40C, and the fourth sealed space 40D to enhance heat dissipation. As a result, heat can be efficiently radiated from the exhaust immediately after being discharged from the engine 20. Since the second sealed space 40B, the third sealed space 40C, and the fourth sealed space 40D are not pressurized, the energy of the pump 46 required for pressurization is small.

  Further, for example, when the heat resistance temperature of the downstream catalyst supported on the downstream catalyst carrier 32 is lower than the heat resistance temperature of the upstream catalyst supported on the upstream catalyst carrier 30, the second catalyst corresponding to the downstream catalyst carrier 32 is used. The three sealed spaces 40C may be pressurized to improve heat dissipation.

  In the second embodiment, the example in which the open / close valves 58 are provided in all the intake / exhaust ports 44A, 44B, 44C, 44D has been described. However, the open / close valves 58 are provided only in some of the intake / exhaust ports 44. May be provided. In this case, intake or exhaust by the pump 46 directly acts on the sealed space 40 corresponding to the intake / exhaust port 44 in which the on-off valve 58 is not provided. On the other hand, in the sealed space 40 corresponding to the intake / exhaust port 44 provided with the opening / closing valve 58, it is possible to prevent intake or exhaust by the pump 46 by closing the opening / closing valve 58. .

  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.

  In the exhaust pipe 64 of the third embodiment, as shown in FIGS. 4 and 5, a pressure adjusting member 66 is provided in one-to-one correspondence with each of the sealed spaces 40. Although the plurality of pressure adjusting members 66 have the same configuration, FIGS. 5 to 7 illustrate the pressure adjusting member 66 provided in the first sealed space 40A.

  The outer pipe 38 is provided with two intake / exhaust ports (a first intake / exhaust port 68P and a second intake / exhaust port 68Q). The gas supply / exhaust pipe 60P that connects the first intake / exhaust port 68P and the pump 46 is provided with a first on-off valve 70P, and the gas supply / exhaust pipe 60Q that connects the second intake / exhaust port 68Q and the pump 46 has A second on-off valve 70Q is provided.

  In the gas supply / exhaust pipe 60P, a first atmospheric valve 72S is provided between the first intake / exhaust port 68P and the first on-off valve 70P, and a second atmospheric valve 72T is provided between the first on-off valve 70P and the pump 46. Is provided. In the gas supply / exhaust pipe 60Q, a third atmospheric valve 72U is provided between the pump 46 and the second on-off valve 70Q. In the third embodiment, the opening / closing of the first opening / closing valve 70P, the second opening / closing valve 70Q, the first atmospheric valve 72S, the second atmospheric valve 72T, and the third atmospheric valve 72U is controlled by the control device 48 (see FIG. 4). The

  In the third embodiment, the pump 46 is a pump that generates a gas flow only in the direction of the arrow F2 by driving.

  In the third embodiment, when the sealed space 40 is decompressed, as shown in FIG. 5, the first on-off valve 70P and the third atmospheric valve 72U are opened, and the second on-off valve 70Q, the first atmospheric valve 72S and The second atmospheric valve 72T is closed. When the pump 46 is driven in this state, the gas in the sealed space 40 can be exhausted from the first intake / exhaust port 68P and the first on-off valve 70P through the third atmospheric valve 72U, and the sealed space 40 can be decompressed. And if the 1st on-off valve 70P is closed in the state where the sealed space 40 became the desired pressure, the sealed space 40 can be maintained at the desired pressure.

  In the third embodiment, when pressurizing the sealed space 40, as shown in FIG. 6, the second on-off valve 70Q and the second atmospheric valve 72T are opened, and the first on-off valve 70P, the first atmospheric valve 72S, and The third atmospheric valve 72U is closed. By driving the pump 46 in this state, the atmosphere can be taken in from the second atmosphere valve 72T and supplied to the sealed space 40 via the second on-off valve 70Q and the second intake / exhaust port 68Q, and the sealed space 40 can be pressurized. .

  In the third embodiment, the inside of the sealed space 40 is scavenged, that is, the gas in the sealed space 40 is discharged while the gas is supplied from the outside into the sealed space 40, and a gas flow is generated in the sealed space 40. It is also possible. In this case, as shown in FIG. 7, the first atmospheric valve 72S, the second atmospheric valve 72T, and the second on-off valve 70Q are opened, and the first on-off valve 70P and the third atmospheric valve 72U are closed. In this state, by driving the pump 46, the atmosphere is taken in from the second atmospheric valve 72T, supplied to the sealed space 40 through the second on-off valve 70Q, and gas is supplied from the sealed space 40 to the outside through the first atmospheric valve 72S. Can be discharged. Thus, by scavenging the inside of the sealed space 40, the exhaust pipe 64 can be cooled and the temperature of the exhaust can be lowered. For example, when the upstream catalyst carrier 30 and the downstream catalyst carrier 32 are in a warm-up state, the temperature of the exhaust is lowered by scavenging the inside of the sealed space 40, and the upstream catalyst carrier 30 and the downstream catalyst carrier 32. Excessive temperature rise can be suppressed.

  In addition, when scavenging in the sealed space 40 is not performed, the first atmospheric valve 72S may be omitted. In other words, the first intake / exhaust port 68P and the first on-off valve 70P may not be communicated with the atmosphere.

  In the third embodiment, as in the second embodiment, it is possible to pressurize or depressurize only a specific sealed space among the plurality of sealed spaces 40. Furthermore, it is easy to pressurize some of the sealed spaces 40 and depressurize other sealed spaces.

  In the pressure control device of each of the above embodiments, since the pump 46 is controlled by the control device 48, the pressure of the sealed space 40 can be easily adjusted. The intake and exhaust of the sealed space 40 by the pump 46 can be reliably performed through the intake and exhaust ports, and the sealed space 40 can be pressurized and depressurized.

  In particular, in a structure having a plurality of sealed spaces 40, each of the sealed spaces 40 is provided with an intake / exhaust port, so that pressurization and decompression of each sealed space 40 can be appropriately performed.

  As the internal structure of the sealed space 40, the following first to third modified structures may be employed.

  In the first modification shown in FIG. 8, the thermal radiation suppressing member 74 is disposed in the sealed space 40. In the example shown in FIG. 8, the thermal radiation suppressing member 74 is disposed in contact with the outer peripheral surface of the inner tube 36.

  The second modification shown in FIG. 9 has the same heat radiation suppressing member 74 as that of the first modification, but this heat radiation suppressing member 74 is provided on the outer peripheral surface of the inner tube 36 and the inner tube 38. It arrange | positions without contact with respect to a surrounding surface.

  The heat radiation suppressing member 74 is a member that suppresses heat radiation in the sealed space 40, thereby suppressing (preferably blocking) heat transfer due to heat radiation and improving the heat insulation of the exhaust pipe 24. Specific examples of the thermal radiation suppressing member 74 include a metal sheet such as copper and aluminum, a porous body (aerogel, etc.), and a powder heat insulating material (perlite, etc.).

  Thus, in the first modification and the second modification, since the heat insulation of the exhaust pipe 24 is high, the effect of maintaining the temperature of the exhaust flowing inside the exhaust pipe 24 is high. In particular, when the inside of the sealed space 40 is at a low pressure, the heat conduction in the sealed space 40 is dominated by the amount of heat transferred by heat radiation. By suppressing the heat radiation in the sealed space 40, the heat insulation of the exhaust pipe 24 can be effectively enhanced.

  In the first modification and the second modification, a plurality of thermal radiation suppressing members 74 may be arranged in layers in the sealed space 40.

  In the third modification shown in FIG. 10, the hole member 76 is disposed in contact with at least one of the outer peripheral surface of the inner tube 36 and the inner peripheral surface of the outer tube 38 in the sealed space 40. In particular, in the example of FIG. 10, the hole member 76 is filled in the sealed space 40 and is in contact with both the outer peripheral surface of the inner tube 36 and the inner peripheral surface of the outer tube 38.

  The hole member 76 is a member having a plurality of holes therein, and a gas exists in the hole part. Further, on the outer peripheral surface of the inner tube 36 and the inner peripheral surface of the outer tube 38 with which the hole member 76 is in contact, the area (surface area) in which the gas contacts substantially in the sealed space 40 is widened. . That is, the hole member 76 is a member that improves the heat dissipation of the exhaust pipe 24.

  The gas can enter and exit from the outside of the hole member 76 to the inside (inside the hole), and the air flow inside the hole member 76 is not hindered. Specific examples of such a hole member 76 include a porous body through which a gas can pass, a fiber of woven fabric or non-woven fabric, and the like.

  As described above, in the third modified example, since the heat dissipation performance of the exhaust pipe 24 is high, the effect of radiating heat from the exhaust flowing inside the exhaust pipe 24 is high. In particular, when the sealed space 40 is in a high pressure state or when the sealed space 40 is scavenged, the heat dissipation of the exhaust pipe 24 can be effectively enhanced by promoting the heat dissipation to the gas in the sealed space 40. .

  In the third modification, the hole member 76 may be in contact with only one of the outer peripheral surface of the inner tube 36 and the inner peripheral surface of the outer tube 38. That is, in the inner tube 36 or the outer tube 38 with which the hole member 76 is in contact, the substantial surface area in the sealed space 40 is increased, and the heat dissipation is increased. As shown in FIG. 10, when the hole member 76 is in contact with both the outer peripheral surface of the inner tube 36 and the inner peripheral surface of the outer tube 38, it can be compared with a structure in which only one of them is in contact. Furthermore, high heat dissipation is obtained.

  As can be seen from the above description, the heat radiation suppressing member 74 of the first modified example is a member that suppresses heat radiation in a state where the sealed space 40 is at a low pressure and improves the heat insulation of the exhaust pipe 24. On the other hand, the hole member 76 of the third modified example promotes heat transfer to the gas in the sealed space 40 when the sealed space 40 is in a high pressure state or scavenging, and improves the heat dissipation of the exhaust pipe 24. It is a member. For example, the porous body can also be used as a member serving as both the heat radiation suppressing member 74 and the hole member 76.

  As the pump 46 in each of the above embodiments, for example, a pump (electric pump) that is driven by receiving power supply and pressurizes or depressurizes the target can be used. Further, a Knudsen pump can be used as the pump 46. A Knudsen pump is a pump that uses two gas chambers connected by a narrow tube with a diameter smaller than the mean free path of gas molecules, and gas moves from the low temperature side to the high temperature side when a temperature difference occurs in the gas in the air chamber. It is. In the Knudsen pump, for example, engine cooling water or the like can be used as a heat source that generates the above-described temperature difference, and electric power for driving is unnecessary. Therefore, the sealed space 40 can be efficiently pressurized and depressurized.

  The pressure adjusting member is not limited to a structure having a pump. For example, the structure of the fourth modification shown in FIG. 11 can be used.

  The exhaust pipe 84 of the fourth modified example has a compressor 86. The compressor 86 is driven by the control device 48. The compressor 86 is connected to each sealed space 40 by a compression pipe 88.

  Therefore, the sealed space 40 can be pressurized by driving the compressor 86. Moreover, the sealed space 40 can be decompressed by reversely driving the compressor 86.

20 Engine 24 Exhaust pipe 30 Upstream catalyst carrier 32 Downstream catalyst carrier 34 Heat recovery unit 36 Inner pipe 38 Outer pipe 40 Sealed space 42 Pressure adjusting member 44 Intake / exhaust port 46 Pump 48 Controller 50 Engine drive sensor 54 Exhaust pipe 56 Pressure Adjustment member 58 On-off valve 64 Exhaust pipe 66 Pressure adjustment member 68P First intake / exhaust port 68Q Second intake / exhaust port 70P First on-off valve 70Q Second on-off valve 72S First atmosphere valve 72T Second atmosphere valve 72U Third atmosphere valve 74 Thermal radiation suppressing member 76 Hole member

Claims (13)

An inner pipe through which exhaust from the engine flows,
A catalyst carrier provided inside the inner pipe and carrying a catalyst for purifying exhaust; and
An outer tube which is disposed on the outer peripheral side of the inner tube and forms a sealed space with the inner tube from the engine to at least a portion of the catalyst carrier;
A pressure adjusting member that pressurizes and depressurizes the sealed space;
Have
A plurality of the catalyst carriers are arranged along the flow direction of the exhaust,
The sealed space is divided for each of the plurality of catalyst carriers,
Exhaust pipe. The pressure adjusting member is
Intake and exhaust ports provided in the outer pipe;
A pump connected to the intake and exhaust ports;
A control device for controlling the pump;
The exhaust pipe according to claim 1. The exhaust pipe according to claim 2 , wherein at least one intake / exhaust port is provided for each of the plurality of sealed spaces. The exhaust pipe according to claim 2 or 3 , further comprising an on-off valve controlled by the control device and configured to open and close an intake / exhaust pipe between at least one of the pump and the intake / exhaust port. The exhaust pipe according to claim 4 , wherein the on-off valve is provided for each of the plurality of intake / exhaust ports. The exhaust pipe according to any one of claims 2 to 5 , wherein the pump is shared by a plurality of the sealed spaces. An engine operation sensor that detects operation and stop of the engine and transmits the detected operation to the control device;
The exhaust pipe according to any one of claims 2 to 6 , wherein the pressure adjusting member depressurizes the sealed space while the engine is stopped and maintains the depressurization until the next engine start. The exhaust pipe according to any one of claims 1 to 7 , wherein the pressure adjusting member introduces gas into the sealed space when the catalyst carrier is warmed up. The exhaust pipe according to any one of claims 1 to 8 , wherein a heat radiation suppressing member that suppresses heat radiation is disposed in the sealed space. The exhaust pipe according to any one of claims 1 to 9 , wherein a hole member having a plurality of holes is arranged in contact with at least one of the inner pipe and the outer pipe in the sealed space. . The exhaust pipe according to claim 10 , wherein the hole member is in contact with both the inner pipe and the outer pipe. A heat recovery unit provided inside the inner pipe for recovering heat of the exhaust and acting on a heat medium;
The exhaust pipe according to any one of claims 1 to 11 , wherein the outer pipe forms the sealed space from the engine to a portion of the heat recovery unit. The exhaust pipe according to any one of claims 1 to 12 , wherein the sealed space is divided from the engine to the catalyst carrier located upstream in the flow direction of the exhaust gas.