JP2005194962A - Exhaust pipe and exhaust device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve emission control efficiency by maintaining exhaust gas temperature in appropriate temperature in an exhaust pipe of an internal combustion engine. <P>SOLUTION: A double exhaust pipe 29 having an outer pipe 33 provided outside of an inner pipe 31 via a space part 32 is provided between an exhaust manifold 28 and an emission control catalyst device 30. A heat conduction member 34 made of shape memory alloy is attached on an inner circumference surface of the outer pipe 33. The heat conduction member 34 deforms according to temperature of the outer pipe 33 correlating to temperature of exhaust gas and the inner pipe 31 and the outer pipe 33 can be switched in a connection condition and a disconnection condition. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exhaust pipe and an exhaust device that process exhaust gas burned in an internal combustion engine.

  An exhaust system of an internal combustion engine is provided with a catalyst for treating exhaust gas discharged after combustion. For example, a three-way catalyst includes nitrogen carbide (HC) and carbon monoxide (CO) contained in exhaust gas. In addition, harmful substances such as nitrogen oxides (NOx) can be purified. However, this three-way catalyst needs to be maintained at a predetermined activation temperature in order to efficiently treat these harmful substances. Particularly, at the time of cold start of the internal combustion engine, each component of the internal combustion engine Since the temperature of the exhaust gas is low, the heat of the exhaust gas is deprived and the temperature of the three-way catalyst cannot be increased by the exhaust gas.

  Therefore, in order to suppress the temperature drop of the exhaust gas, the exhaust pipe is a double pipe, and even during the cold start of the internal combustion engine, by introducing a high temperature exhaust gas into the three-way catalyst and raising the temperature, Techniques that enable early activation have been proposed. However, during high-speed operation of the internal combustion engine, the exhaust gas temperature becomes high, and the exhaust gas purification process area is out of place and the harmful substances cannot be properly purified, or the three-way catalyst is heated by the hot exhaust gas. There is a problem of deterioration.

  As an solution to this problem, there is an “exhaust device” described in Patent Document 1 below. The one described in Patent Document 1 constitutes an exhaust pipe from an inner pipe and an outer pipe, and the inner pipe is located at a position separated from the outer pipe at a low temperature. It is in close contact with the outer tube. Therefore, the high-temperature exhaust gas passing through the inside of the inner pipe can radiate heat through the outer pipe, and the temperature of the exhaust gas can be lowered to prevent thermal degradation of the three-way catalyst.

JP 2000-027638 A

  In the above-described conventional “exhaust device”, the inner pipe of the exhaust pipe is made of a shape memory alloy, and when the exhaust gas reaches a predetermined temperature or more, the inner pipe is deformed and brought into close contact with the outer pipe. The gas is dissipating heat. However, the exhaust pipe has a predetermined length, and manufacturing using an expensive shape memory alloy over the entire length leads to an increase in material cost. In general, it is technically difficult to mold the inner pipe of the exhaust pipe having a cylindrical shape into an irregular cross-sectional shape such as a cross-sectional wave shape at a low temperature, and the manufacturing cost increases.

  The present invention is intended to solve such problems, and provides an exhaust pipe and an exhaust device for an internal combustion engine that improve exhaust purification efficiency by maintaining the exhaust gas temperature at an appropriate temperature. Objective.

  In order to solve the above-described problems and achieve the object, an exhaust pipe of an internal combustion engine of the present invention is provided with an inner pipe having an exhaust passage through which exhaust gas flows and a space portion outside the inner pipe. In the exhaust pipe of an internal combustion engine having an outer pipe, a heat transfer member capable of switching the inner pipe and the outer pipe to a connected state or a non-connected state in accordance with the temperature of the exhaust gas is provided in the space portion. It is characterized by.

  In the exhaust pipe of the internal combustion engine of the present invention, one end of the heat transfer member is attached to the inner peripheral surface of the outer pipe, and the other end is deformed when the temperature of the exhaust gas exceeds a predetermined temperature. Is in contact with the outer peripheral surface of the inner tube.

  In the exhaust pipe of the internal combustion engine of the present invention, the heat transfer member is deformed when the temperature of the outer pipe exceeds a preset predetermined temperature, and the other end contacts the outer peripheral surface of the inner pipe. It is said.

  In the exhaust pipe of the internal combustion engine of the present invention, the heat transfer member is a shape memory alloy that deforms according to the temperature of the exhaust gas or the temperature of the outer pipe.

  In the exhaust pipe of the internal combustion engine according to the present invention, a plurality of the heat transfer members are provided along the longitudinal direction of the exhaust pipe, and each of the heat transfer members corresponds to the temperature of the different exhaust gas. Are switched to a connected state or a disconnected state.

  An exhaust system for an internal combustion engine according to the present invention is provided with the exhaust pipe according to claim 1 on the upstream side of a catalyst, and the heat transfer member is configured so that the exhaust gas temperature exceeds the preset catalyst purification temperature region. The inner tube and the outer tube are connected to each other.

  In the exhaust system for an internal combustion engine according to the present invention, a three-way catalyst and a NOx catalyst are arranged in series in an exhaust passage of the internal combustion engine, and the first exhaust pipe according to claim 1 is provided upstream of the three-way catalyst. In addition, the second exhaust pipe according to claim 1 is provided between the three-way catalyst and the NOx catalyst, and the heat transfer member of the first exhaust pipe is a three-way catalyst purification in which an exhaust gas temperature is preset. When the temperature range is exceeded, the inner pipe and the outer pipe are connected, and the heat transfer member of the second exhaust pipe has the exhaust gas temperature when the exhaust gas temperature exceeds a preset NOx catalyst purification temperature range. The inner tube and the outer tube are connected to each other.

  An exhaust system for an internal combustion engine according to the present invention includes a turbocharger turbine and a catalyst arranged in series in an exhaust passage of the internal combustion engine, and the exhaust pipe according to claim 1 is provided between the turbine and the catalyst. The heat transfer member of the exhaust pipe is characterized in that the inner pipe and the outer pipe are connected when the exhaust gas temperature exceeds a preset catalyst purification temperature region.

  According to the exhaust pipe and exhaust system of the internal combustion engine of the present invention, the inner pipe and the outer pipe can be switched between a connected state and a non-connected state in the space between the inner pipe and the outer pipe depending on the temperature of the exhaust gas. Since the heat transfer member is provided, when the exhaust gas is at a low temperature, the inner tube and the outer tube are disconnected from each other, and the temperature drop of the exhaust gas flowing inside the inner tube can be suppressed. Sometimes the inner tube and the outer tube are connected via the heat transfer member, and the heat of the exhaust gas flowing inside the inner tube is released from the inner tube to the outer tube through the heat transfer member, thereby suppressing the temperature rise. As a result, by maintaining the exhaust gas temperature at an appropriate temperature, it is possible to improve the exhaust purification efficiency of the catalyst.

  Embodiments of an exhaust pipe and an exhaust device for an internal combustion engine according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  1 is a cross-sectional view of an essential part showing an exhaust pipe of an internal combustion engine according to a first embodiment of the present invention, FIG. 2-1 is a schematic diagram showing an exhaust pipe of the first embodiment, and FIG. FIG. 3 is a schematic configuration diagram of an internal combustion engine to which the exhaust pipe of the first embodiment is applied.

  In the internal combustion engine to which the exhaust pipe of the first embodiment is applied, as shown in FIG. 3, the engine 11 is a spark ignition engine. In the engine 11, a cylinder head 13 is fastened on a cylinder block 12, and pistons 15 are respectively fitted to a plurality of cylinder bores 14 formed in the cylinder block 12 so as to be vertically movable. A crankshaft (not shown) is rotatably supported at the lower portion of the cylinder block 12, and each piston 15 is connected to the crankshaft via a connecting rod 16. In the following description, only one cylinder will be described.

  The combustion chamber 17 includes a cylinder block 12, a cylinder head 13, and a piston 15, and an intake port 18 and an exhaust port 19 are formed facing the upper portion of the combustion chamber 17, that is, the lower surface of the cylinder head 12. The lower ends of the intake valve 20 and the exhaust valve 21 are located with respect to the intake port 18 and the exhaust port 19. Accordingly, when the intake valve 20 and the exhaust valve 21 move up and down at a predetermined timing, the intake port 18 and the exhaust port 19 are opened and closed, and the intake port 18 and the combustion chamber 17, and the combustion chamber 17 and the exhaust port 19 are respectively opened and closed. You can communicate.

  An intake pipe 23 is connected to the intake port 18 via an intake manifold 22. An air cleaner 24 is attached to an air intake port of the intake pipe 23, and a throttle valve 25 is provided downstream of the air cleaner 24. Is provided. The intake manifold 22 is provided with an injector 26 for injecting fuel (gasoline) into each intake port 18, and the cylinder head 13 is positioned above the combustion chamber 17 to ignite the air-fuel mixture. 27 is attached.

  On the other hand, an exhaust pipe 29 is connected to the exhaust port 19 via an exhaust manifold 28, and an exhaust purification catalyst device (for example, a three-way catalyst) 30 is attached to the exhaust pipe 29.

  The electronic control unit can control the fuel injection timing of the injector 26, the ignition timing of the spark plug 27, and the like. The detected intake air amount, throttle opening (or accelerator opening), engine speed, etc. The fuel injection amount, injection timing, ignition timing, etc. are determined based on the engine operating state.

  By the way, the exhaust purification catalyst device 30 provided in the exhaust pipe 29 of the engine 11 can purify harmful substances such as HC, CO, NOx contained in the exhaust gas, but at the time of cold start of the engine 11. If the temperature is lower than a predetermined activation temperature, the harmful substances cannot be efficiently purified. If the temperature is higher than a predetermined temperature such as when the engine 11 is operated at high speed, the exhaust heat may cause thermal deterioration. is there.

  Therefore, in this embodiment, the exhaust pipe 29 is a double pipe in order to suppress the temperature drop of the exhaust gas due to the outside air (cold air), and the thermal purification of the exhaust purification catalyst device 30 due to the high temperature exhaust gas is prevented. A movable heat transfer member is provided between the inner tube and the outer tube. Thereby, when the engine 11 is in a cold state, the temperature reduction of the exhaust gas passing through the inner pipe is suppressed, while when the engine 11 is operating at high speed, the hot exhaust gas passing through the inner pipe is passed through the heat transfer member through the outer pipe. The exhaust gas is radiated and the temperature of the exhaust gas is appropriately controlled so that the purification ability of the exhaust purification catalyst device 30 can always be secured.

  That is, as shown in FIGS. 1 and 2-1, the exhaust pipe 29 according to the first embodiment is arranged with an inner pipe 31 having an exhaust passage through which exhaust gas flows and a space portion 32 outside the inner pipe 31. The outer tube 33 is provided. The inner tube 31 and the outer tube 33 have a cylindrical shape, each end portion in the longitudinal direction is joined so as to close the space portion 32, and one end portion (upstream end portion) is the downstream end portion of the exhaust manifold 28. The other end (downstream end) is connected to the exhaust purification catalyst device 30. That is, a double-pipe exhaust pipe 29 is provided between the exhaust manifold 28 and the exhaust purification catalyst device 30, and the exhaust gas is guided from the exhaust manifold 28 to the exhaust purification catalyst device 30 through the inner pipe 31 of the exhaust pipe 29. It becomes.

  The space portion 32 maintains the outer peripheral surface of the inner tube 31 and the inner peripheral surface of the outer tube 33 in a non-contact state and contributes as a heat insulating layer, and is filled with air or an inert gas, or It is good also as a vacuum state.

  The base end portion of the heat transfer member 34 is fixed to the inner peripheral surface of the outer pipe 33 of the exhaust pipe 29 so that the distal end portion can be freely deformed to contact the outer peripheral surface of the inner pipe 31. Furthermore, it is in a free state that is not restrained. The heat transfer member 34 is formed in a plate shape by a shape memory alloy (for example, an alloy of titanium and nickel) that deforms in accordance with a predetermined temperature set in advance, and a base end portion is welded 35 to the inner periphery of the outer tube 33. It is fixed to the surface. Therefore, when the exhaust gas flowing through the exhaust pipe 29 is at a low temperature, the heat transfer member 34 is not deformed and the inner pipe 31 and the outer pipe 33 are maintained in a disconnected state, and the exhaust gas flowing through the exhaust pipe 29 is maintained. When the gas is at a high temperature, the heat transfer member 34 is bent and deformed to contact the inner tube 31, and the inner tube 31 and the outer tube 33 are connected.

  In the case of the present embodiment, the heat transfer member 34 is fixed to the outer tube 33 and is configured to be deformed according to the temperature of the outer tube 33 that is correlated with the temperature of the exhaust gas. For example, the exhaust purification catalyst 30 has a purification temperature region in which harmful substances can be purified. If the exhaust purification catalyst 30 exceeds this purification temperature region, there is a risk of thermal degradation. Therefore, when the upper limit value of the purification temperature region of the exhaust purification catalyst 30, that is, the heat deterioration temperature is 800 ° C., the temperature of the exhaust gas passing through the inner pipe 31 is 800 ° C. based on experiments in advance. The temperature of the outer pipe 33 at that time is obtained, and this temperature is set as the thermal deterioration determination temperature of the exhaust purification catalyst 30. Then, the temperature at which the heat transfer member 34 is deformed is configured to be the heat deterioration determination temperature. Although the temperature difference between the inner tube 31 and the outer tube 33 widens during sudden acceleration, the temperature of the outer tube 33 is lower by 200 ° C. to 300 ° C. than the temperature of the inner tube 31 in a general operating state.

  Therefore, when the temperature of the outer tube 33 is lower than the thermal deterioration determination temperature, the heat transfer member 34 remains flat without being deformed as shown in FIG. The inner tube 31 and the outer tube 33 are maintained in a non-connected state without contacting the surface. On the other hand, when the temperature of the outer tube 33 is higher than the thermal deterioration determination temperature, the heat transfer member 34 is bent and deformed as shown in FIG. The tube 31 and the outer tube 33 are connected.

  A plurality of heat transfer members 34 are provided at predetermined positions in the exhaust pipe 29, that is, in the circumferential direction of the outer pipe 33, and at a predetermined interval in the longitudinal direction. In this embodiment, the double exhaust pipe 29 and the exhaust purification catalyst device 30 constitute an exhaust device.

  In the exhaust pipe of the internal combustion engine of the present embodiment configured as described above, when the ignition switch is turned on by the driver when the engine 11 is cold-started, a predetermined amount of air at the time of idling is drawn from the intake pipe 23 to the intake port. 18 and the amount of fuel commensurate with the amount of air is injected. This mixture of air and fuel is sucked into the combustion chamber 17 when the intake valve 20 is opened and closed, and after being compressed, is ignited and burned by the spark plug 27, and the combustion gas is exhausted as an exhaust gas when the exhaust valve 21 is opened and closed. Through the exhaust manifold 28. Thereafter, the exhaust gas is introduced into the exhaust purification catalyst device 30 through the exhaust pipe 29, where harmful substances such as HC, CO, and NOx in the exhaust gas are purified.

  When the engine 11 is cold-started, the temperature of the outer tube 33 is lower than the heat deterioration determination temperature, and the temperature of the exhaust purification catalyst 30 is in the purification temperature region, so that the heat transfer member 34 is not deformed and the inner tube 31 is not deformed. The outer tube 33 is not connected. Therefore, although the engine 11 is at a low temperature, the outer pipe 31 of the exhaust pipe 29 is covered with a space (heat insulating layer) 32 and an outer pipe 33, and the exhaust gas flowing through the inner pipe 31 is kept warm. Thus, the temperature drop is suppressed. Therefore, the exhaust gas can be introduced into the exhaust purification catalyst device 30 at a high temperature, and the exhaust purification catalyst device 30 can be heated and activated at an early stage, and the exhaust purification efficiency can be improved.

  If the high speed operation continues after the engine 11 is started, the temperature of the exhaust gas becomes high, and the temperature of the outer tube 33 rises due to the heat of the exhaust gas. When the temperature of the outer tube 33 becomes higher than the heat deterioration determination temperature and the temperature of the exhaust purification catalyst 30 exceeds the purification temperature region, the heat transfer member 34 becomes substantially the same temperature, and is bent and deformed, and the tip portion is in the inner tube. The inner tube 31 and the outer tube 33 are in a connected state in contact with the outer peripheral surface of the tube 31. Therefore, the heat of the exhaust gas flowing inside the inner pipe 31 is transmitted to the outer pipe 33 through the heat transfer member 34 and is released from the outer pipe 33 to the outside air, and the temperature rise of the inner pipe 31 and the exhaust gas. Can be suppressed. Accordingly, the exhaust gas purification catalyst device 30 can be introduced while suppressing an increase in the temperature of the exhaust gas, the thermal purification of the exhaust gas purification catalyst device 30 can be prevented, and high exhaust purification efficiency is continuously ensured. Can do.

  When the driver stops the engine 11 or when the exhaust temperature is lowered due to low-speed operation, the temperature of the outer tube 33 becomes lower than the thermal deterioration determination temperature, and the heat transfer member 34 in the deformed state is the original. The inner pipe 31 and the outer pipe 33 are disconnected from each other.

  As described above, the exhaust pipe of the internal combustion engine according to the first embodiment is configured by providing the outer pipe 33 between the exhaust manifold 28 and the exhaust purification catalyst device 30 outside the inner pipe 31 via the space portion 32. A double exhaust pipe 29 is provided, and a heat transfer member 34 made of a shape memory alloy is mounted on the inner peripheral surface of the outer pipe 33. Then, the heat transfer member 34 is deformed according to the temperature of the outer tube 33 that is correlated with the temperature of the exhaust gas, and the inner tube 31 and the outer tube 33 can be switched between a connected state and a non-connected state.

  Therefore, when the exhaust gas is at a low temperature, the outer tube 33 is lower than a predetermined temperature (thermal deterioration determination temperature), so the inner tube 31 and the outer tube 33 are disconnected from each other, and the space portion 32 functions as a heat insulating layer. It is possible to suppress the temperature drop of the exhaust gas flowing through 31 and to activate the exhaust purification catalyst device 30 at an early stage. On the other hand, when the exhaust gas is at a high temperature, the outer tube 33 and the heat transfer member 34 are higher than a predetermined temperature (thermal deterioration determination temperature), so the inner tube 31 and the outer tube 33 are connected via the heat transfer member 34, The heat of the exhaust gas flowing through the pipe 31 is released from the inner pipe 31 to the outer pipe 33 through the heat transfer member 34, and the temperature rise of the exhaust gas can be suppressed and thermal deterioration of the exhaust purification catalyst device 30 can be prevented. As a result, the exhaust gas purification efficiency of the exhaust gas purification catalyst device 30 can be improved by maintaining the exhaust gas temperature at an appropriate temperature regardless of the operating state of the engine 11.

  Further, the heat transfer member 34 is mounted on the inner peripheral surface of the outer tube 33, and is deformed according to the temperature of the outer tube 33 so as to come into contact with the inner tube 31. In this case, when the heat transfer member 34 is mounted on the outer peripheral surface of the inner tube 31, the inner tube 31 becomes hot due to the exhaust gas, and the heat transfer member 34 is deformed to contact the outer tube 33, and the heat of the exhaust gas is transferred to the outer tube. However, the temperature of the heat transfer member 34 that immediately contacts the outer tube 33 is lowered and the deformation is restored, so that the heat of the exhaust gas cannot be lowered sufficiently. On the other hand, when the heat transfer member 34 is mounted on the inner peripheral surface of the outer tube 33, the outer tube 33 becomes hot due to the exhaust gas, the heat transfer member 34 is deformed and contacts the inner tube 31, and the heat of the exhaust gas is removed. 33 through. At this time, since the inner tube 31 is hotter than the outer tube 33, the temperature of the heat transfer member 34 contacting the inner tube 31 does not decrease immediately, and the heat of the exhaust gas is sufficiently decreased. Can do.

  FIG. 4 is a schematic configuration diagram of an internal combustion engine to which the exhaust pipe of the internal combustion engine according to the second embodiment of the present invention is applied. In addition, the same code | symbol is attached | subjected to the member which has the same function as what was demonstrated in the Example mentioned above, and the overlapping description is abbreviate | omitted.

  In the exhaust pipe of the internal combustion engine of the second embodiment, as shown in FIG. 4, the engine 41 is a cylinder ignition type spark ignition engine. In this engine 41, the combustion chamber 17 is composed of a cylinder block 12, a cylinder head 13, and a piston 15, and an intake port 18 and an exhaust port 19 communicate with each other, and the intake port 18 and the exhaust port 19 are connected to an intake valve 20. The exhaust valve 21 can be opened and closed. The cylinder head 12 is equipped with an injector 26 that directly injects fuel (gasoline) into the combustion chamber 17, and a spark plug 27 is mounted above the combustion chamber 17.

  On the other hand, a three-way catalyst 43 is connected to the exhaust port 19 via the exhaust manifold 28 via the first exhaust pipe 42 and a NOx occlusion reduction type catalyst 45 is connected via the second exhaust pipe 44. Yes. This three-way catalyst 43 simultaneously purifies HC, CO, and NOx contained in the exhaust gas by an oxidation-reduction reaction. The NOx occlusion reduction type catalyst 45 temporarily stores NOx contained in the exhaust gas at the time of stratified combustion, and stores NOx occluded by using HC and CO contained in the exhaust gas as a reducing agent when in the rich combustion region or stoichiometric combustion region. It is reduced and purified.

  By the way, the three-way catalyst 43 and the NOx occlusion reduction type catalyst 45 may be thermally deteriorated by the exhaust heat when the exhaust gas becomes a predetermined temperature or higher, such as when the engine 61 is operated at high speed. The three-way catalyst 43 and the NOx occlusion reduction catalyst 45 have different temperature limits for thermal degradation.

  Therefore, in this embodiment, the first and second exhaust pipes 42 and 44 are double pipes, and in order to prevent thermal degradation of the respective catalysts 43 and 45 due to high-temperature exhaust gas, the inner pipe and the outer pipe are connected. A movable heat transfer member is provided between them so that they can move at different temperatures. As a result, during high-speed operation of the engine 61, high-temperature exhaust gas passing through the inner pipe is radiated by the outer pipe through each heat transfer member, and the temperature of the exhaust gas is appropriately controlled for each catalyst 43, 45 for purification. The ability is always secured.

  That is, the first exhaust pipe 42 provided between the exhaust manifold 28 and the three-way catalyst 43 is composed of an inner pipe 46 and an outer pipe 48 provided with a space 47 outside the inner pipe 46. Has been. And the base end part of the several heat-transfer member 49 formed of the shape memory alloy is being fixed to the internal peripheral surface of the outer tube | pipe 48, and when the exhaust gas, ie, the outer tube | pipe 48, becomes high temperature, the heat-transfer member 49 The tip is bent and deformed to come into contact with the inner tube 46 at the same temperature, and the inner tube 46 and the outer tube 47 are connected. In this embodiment, when the heat deterioration temperature of the three-way catalyst 43 is 800 ° C., the temperature of the outer tube 48 at this time is obtained in advance based on experiments, and this temperature is determined by the three-way catalyst 43. The heat deterioration determination temperature is set to a temperature at which the heat transfer member 49 is deformed.

  The second exhaust pipe 44 provided between the three-way catalyst 43 and the NOx occlusion reduction type catalyst 45 includes an inner pipe 50 and an outer pipe 52 provided with a space 51 on the outside of the inner pipe 50. It consists of and. And the base end part of the several heat-transfer member 53 formed with the shape memory alloy is being fixed to the internal peripheral surface of the outer tube | pipe 52, and when the exhaust gas, ie, the outer tube | pipe 52, becomes high temperature, the heat-transfer member 53 The tip portion is bent and deformed to come into contact with the inner tube 50 to bring the inner tube 50 and the outer tube 52 into a connected state. In this embodiment, when the thermal deterioration temperature of the NOx occlusion reduction catalyst 45 is 500 ° C., the temperature of the outer tube 52 at this time is obtained in advance based on experiments, and this temperature is used as the NOx occlusion reduction. It is set as a temperature at which the heat transfer member 53 is deformed as the heat deterioration determination temperature of the mold catalyst 45.

  Accordingly, when the engine 41 is cold-started, the temperatures of the outer pipes 48 and 52 are lower than the thermal deterioration determination temperature of the catalysts 43 and 45, so that the heat transfer members 49 and 53 are not deformed and the inner pipes 46 and 53 are not deformed. 50 and the outer tubes 48 and 52 are not connected. In this case, although the engine 41 is at a low temperature, the inner pipes 46 and 50 are covered with the outer space (heat insulating layers) 47 and 51 and the outer pipes 48 and 52 so that the exhaust gas is kept warm and the temperature is lowered. Is suppressed. Therefore, the exhaust gas is introduced into the three-way catalyst 43 and the NOx occlusion reduction type catalyst 45 at a high temperature, and each catalyst 43, 45 can be heated up and activated at an early stage.

  On the other hand, when the engine 41 is operated at high speed, the temperature of the exhaust gas becomes high, the temperature of the exhaust pipes 42 and 44 rises, and the temperature of the outer pipe 52 of the second exhaust pipe 44 is the heat of the NOx storage reduction catalyst 45. When the temperature is higher than the deterioration determination temperature, the heat transfer member 53 is also bent and deformed at substantially the same temperature, the tip portion comes into contact with the outer peripheral surface of the inner tube 50, and the inner tube 50 and the outer tube 52 are connected. . In this case, the exhaust gas flowing inside the inner pipe 50 is transmitted to the outer pipe 52 through the heat transfer member 53 and released to the outside air, thereby suppressing the temperature rise of the inner pipe 50 and the exhaust gas. be able to. Therefore, the exhaust gas is introduced into the NOx storage reduction catalyst 45 with the temperature rise suppressed, and thermal degradation of the NOx storage reduction catalyst 45 can be prevented.

  Further, when the temperature of the exhaust gas becomes higher and the temperature of the outer pipe 46 of the first exhaust pipe 42 becomes higher than the thermal deterioration determination temperature of the three-way catalyst 43, the heat transfer member 49 is bent at substantially the same temperature. As a result, the distal end portion contacts the outer peripheral surface of the inner tube 46, and the inner tube 46 and the outer tube 48 are connected. In this case, the exhaust gas flowing inside the inner pipe 46 is transmitted to the outer pipe 48 through the heat transfer member 49 and released to the outside air, thereby suppressing the temperature rise of the inner pipe 46 and the exhaust gas. be able to. For this reason, the exhaust gas is introduced into the three-way catalyst 43 with the temperature rise suppressed, and thermal deterioration of the three-way catalyst 43 can be prevented.

  Thus, in the exhaust pipe of the internal combustion engine of the second embodiment, the engine 61 is in-cylinder injection type, the three-way catalyst 43 and the NOx occlusion reduction type catalyst 45 are provided in the exhaust system, and the exhaust manifold 28 and the three-way catalyst 43 are provided. A double first exhaust pipe 42 composed of an inner pipe 46, an outer pipe 48 and a heat transfer member 49 is provided between the inner pipe 50 and the outer pipe between the three-way catalyst 43 and the NOx occlusion reduction type catalyst 45. A double second exhaust pipe 44 comprising 52 and a heat transfer member 53 is provided, and the heat transfer members 49 and 53 are deformed at different temperatures, and the inner pipes 46 and 50 and the outer pipes 48 and 52 are connected. Alternatively, it can be switched to a disconnected state.

  Accordingly, the heat transfer member 53 of the second exhaust pipe 44 is deformed when the temperature of the exhaust gas exceeds the thermal deterioration determination temperature of the NOx storage reduction catalyst 45, and the inner pipe 50 and the outer pipe 52 are connected. The heat transfer member 49 of the first exhaust pipe is deformed when the temperature of the exhaust gas exceeds the thermal deterioration determination temperature of the three-way catalyst 43 to bring the inner pipe 46 and the outer pipe 48 into a connected state. Therefore, the exhaust gas is suppressed to a temperature suitable for the purification characteristics of the catalysts 43 and 45, the thermal deterioration of the three-way catalyst 43 and the NOx storage reduction catalyst 45 can be prevented, and the operation of the engine 41 is performed. Regardless of the state, by maintaining the exhaust gas temperature at an appropriate temperature, the exhaust purification efficiency of each of the catalysts 43 and 45 can be improved.

  In the second embodiment, the internal combustion engine is an in-cylinder spark ignition engine. However, a port injection engine may be used. Further, the NOx occlusion reduction type catalyst 45 is connected via the second exhaust pipe 44, but any NOx catalyst may be used, and a selective reduction type NOx catalyst may be used in place of the NOx occlusion reduction type catalyst 45.

  FIG. 5 is a schematic configuration diagram of an internal combustion engine to which an exhaust pipe of an internal combustion engine according to Embodiment 3 of the present invention is applied. In addition, the same code | symbol is attached | subjected to the member which has the same function as what was demonstrated in the Example mentioned above, and the overlapping description is abbreviate | omitted.

  In the exhaust pipe of the internal combustion engine of the third embodiment, as shown in FIG. 5, the engine 61 is a diesel engine. In the engine 61, an intake pipe 23 is connected to the intake manifold 22, and an air cleaner 24 is attached to an air intake port of the intake pipe 23. On the other hand, an exhaust purification catalyst device (for example, a diesel particulate filter carrying an oxidation catalyst) 64 is attached to the exhaust manifold 28 via a first exhaust pipe 62 and a second exhaust pipe 63.

  The engine 61 is provided with a supercharger (turbocharger) 65. The supercharger 65 is configured by coaxially connecting a compressor 66 provided in the intake pipe 23 and a turbine 67 provided in the exhaust pipes 62 and 63. The intake pipe 23 is provided with an intercooler 68 located downstream of the compressor 66. Further, an EGR passage 69 that recirculates exhaust gas is provided between the exhaust manifold 28 and the downstream portion of the intake pipe 23, and the EGR amount can be adjusted by opening and closing the EGR control valve 70.

  In the present embodiment, the second exhaust pipe 63 provided between the turbine 67 of the supercharger 65 and the exhaust purification catalyst device 64 is a double pipe, and the inner pipe is used to prevent thermal deterioration due to high-temperature exhaust gas. A movable heat transfer member is provided between the outer tube and the outer tube. Thus, without reducing the efficiency of the supercharger 65, the high-temperature exhaust gas flowing through the exhaust purification catalyst device 64 is radiated by the outer pipe via the heat transfer member during high-speed operation of the engine 61, and the temperature of the exhaust gas Is appropriately controlled so that the purification ability of the exhaust purification catalyst device 64 can be always secured.

  That is, the second exhaust pipe 63 includes an inner pipe 71 and an outer pipe 73 disposed with a space portion 72 outside the inner pipe 71. And the base end part of the several heat-transfer member 74 formed with the shape memory alloy is being fixed to the internal peripheral surface of the outer tube | pipe 73, and when the exhaust gas, ie, the outer tube | pipe 73, becomes high temperature, the heat-transfer member 74 is carried out. The tip portion is bent and deformed to come into contact with the inner tube 71 to bring the inner tube 71 and the outer tube 73 into a connected state. In this embodiment, when the heat deterioration temperature of the exhaust purification catalyst device 64 is 500 ° C., the temperature of the outer pipe 73 at this time is obtained in advance based on experiments, and this temperature is used as the exhaust purification catalyst device. It is set as the temperature at which the heat transfer member 74 is deformed.

  Accordingly, during the high-speed operation of the engine 71, the high-temperature exhaust gas discharged from the engine 61 drives the turbine 67 of the supercharger 65 with almost no temperature drop from the exhaust manifold 28 through the first exhaust pipe 62, Thereafter, the exhaust gas is introduced into the exhaust purification catalyst device 64 through the second exhaust pipe 63, where the harmful substances are purified. At this time, when the temperature of the second exhaust pipe 63 rises due to the high-temperature exhaust gas and the temperature of the outer pipe 73 becomes higher than the thermal deterioration determination temperature of the exhaust purification catalyst device 64, the heat transfer member 74 also has substantially the same temperature. As a result, the distal end portion comes into contact with the outer peripheral surface of the inner tube 71, and the inner tube 71 and the outer tube 73 are connected. In this case, the exhaust gas flowing inside the inner pipe 71 has its heat transferred to the outer pipe 73 through the heat transfer member 74 and released to the outside air, thereby suppressing the temperature rise of the inner pipe 71 and the exhaust gas. be able to. Therefore, the exhaust gas is introduced into the exhaust purification catalyst device 64 with the temperature rise suppressed, and thermal deterioration of the exhaust purification catalyst device 64 can be prevented.

  Thus, in the exhaust pipe of the internal combustion engine of the third embodiment, the turbocharger 65 is mounted on the diesel engine 61, and the inner pipe 71 and the exhaust purification catalyst device 64 are connected between the turbine 67 of the supercharger 65 and the exhaust purification catalyst device 64. A double second exhaust pipe 63 composed of an outer pipe 73 and a heat transfer member 74 is provided, and deforms when the heat transfer member 74 exceeds the thermal degradation determination temperature of the exhaust purification catalyst device 64, and the inner pipe 71 and the outer pipe 73 Can be switched to the connected state.

  Therefore, the high-temperature exhaust gas discharged from the engine 61 drives the turbine 67 of the supercharger 65 with little temperature drop through the first exhaust pipe 62, and a predetermined supercharging efficiency can be ensured. Then, the exhaust gas that has driven the turbine 67 flows into the second exhaust pipe 63 to raise the temperature of the outer pipe 73, and the temperatures of the outer pipe 73 and the heat transfer member 74 become the heat deterioration determination temperature of the exhaust purification catalyst device 64. When exceeded, the heat transfer member 74 is deformed to bring the inner tube 71 and the outer tube 73 into a connected state. Therefore, the exhaust gas is suppressed to a temperature suitable for the purification characteristics of the exhaust purification catalyst device 64, and thermal degradation can be prevented and exhaust purification efficiency can be improved.

  In the third embodiment, only the second exhaust pipe 63 is a double pipe, but the first exhaust pipe 62 is a double pipe, and the heat transfer member is deformed when the exhaust gas exceeds 1000 ° C. By connecting the inner pipe and the outer pipe, excessive heating of the exhaust manifold 28 and the supercharger 65 may be prevented. It is also possible to provide an exhaust gas purification device (for example, a diesel particulate filter) that does not have a catalytic function in the exhaust pipe 63 and keep the exhaust gas purification device below the heat deterioration determination temperature. Further, although the internal combustion engine is a diesel engine, it may be a spark ignition engine.

  Moreover, in each Example mentioned above, although the thermal degradation determination temperature of each catalyst 30,43,45,64 was set as 800 degreeC, 500 degreeC, etc., this temperature changes according to the form of a catalyst, An appropriate temperature may be set according to the type of the catalyst, and it is desirable to set the temperature lower in consideration of safety. And the number of the heat transfer members 34, 49, 53, 74 may be appropriately set according to the length of the exhaust pipe, and the deformation temperature is set to 300 ° C, 500 ° C, 800 ° C, etc. Different ones may be provided.

  Further, in each of the above-described embodiments, the heat transfer members 34, 49, 53, 74 are fixed to the inner peripheral surface of the outer pipe so as to come into contact with the inner pipe when the temperature of the exhaust gas rises. It may be fixed to the surface and contact the outer tube when the temperature of the exhaust gas rises. Further, although the heat transfer members 34, 49, 53, and 74 are formed of a shape memory alloy and are deformed according to the temperature of the outer tube 33, the present invention is not limited to this configuration. For example, the heat transfer member is configured to be actuated by an actuator or the like, and a temperature sensor is provided for measuring the temperature of exhaust gas (or outer pipe or inner pipe) flowing in the exhaust pipe. Based on this, the heat transfer member may be actuated by an actuator to switch the connection state and non-connection state between the inner tube and the outer tube.

  Further, the present invention changes the heat transfer member according to the temperature of the exhaust gas and switches the inner tube and the outer tube to a connected state or a non-connected state. In each embodiment, the purification temperature of the exhaust purification catalyst The upper limit value of the region is set to the heat deterioration determination temperature, and when the exhaust gas temperature exceeds the heat deterioration determination temperature, the heat transfer member is deformed to connect the inner tube and the outer tube. It is not limited to.

FIG. 6 is a graph showing the purification rate with respect to the exhaust purification catalyst device temperature. As shown in the graph of FIG. 6, the purification rate of harmful substances in the exhaust purification catalyst device is lower as the temperature of the exhaust purification catalyst device is lower or too high, and the appropriate purification region is set at that temperature. Set. The appropriate purification region varies depending on the form of the exhaust purification catalyst device, but the upper limit value T ₁ of the appropriate purification region is the maximum purification temperature, and the high temperature T ₂ is the above-described heat deterioration temperature. Then, the maximum purification temperature T ₁ in the appropriate purification region in the exhaust purification catalyst is set as the purification determination temperature, and when the exhaust gas temperature exceeds the purification determination temperature, the heat transfer member is deformed and the inner pipe and the outer pipe are connected. You may make it do. Therefore, the temperature of the exhaust purification catalyst device can be maintained in the appropriate purification temperature region, and a high purification rate can be maintained at all times.

  As described above, the exhaust pipe and the exhaust device of the internal combustion engine according to the present invention connect the inner pipe and the outer pipe according to the temperature of the exhaust gas by the heat transfer member provided between the exhaust pipe as a double structure. It can be switched to a state or a disconnected state, and is useful for an exhaust pipe of an internal combustion engine provided with a catalyst device on the downstream side.

It is principal part sectional drawing showing the exhaust pipe of the internal combustion engine which concerns on Example 1 of this invention. 2 is a schematic diagram illustrating an exhaust pipe of Example 1. FIG. FIG. 3 is a schematic diagram illustrating the operation of the exhaust pipe of the first embodiment. 1 is a schematic configuration diagram of an internal combustion engine to which an exhaust pipe of Example 1 is applied. It is a schematic block diagram of the internal combustion engine to which the exhaust pipe of the internal combustion engine which concerns on Example 2 of this invention was applied. It is a schematic block diagram of the internal combustion engine to which the exhaust pipe of the internal combustion engine which concerns on Example 3 of this invention was applied. It is a graph showing the purification rate with respect to exhaust purification catalyst apparatus temperature.

Explanation of symbols

11, 41, 61 Engine 17 Combustion chamber 19 Exhaust port 28 Exhaust manifold 29 Exhaust pipe 30, 64 Exhaust purification catalyst device 31, 46, 50, 71 Inner pipe 32, 47, 51, 72 Space 33, 48, 52, 73 Outer pipes 34, 49, 53, 74 Heat transfer members 42, 62 First exhaust pipe 43 Three-way catalyst 44, 63 Second exhaust pipe 45 NOx occlusion reduction type catalyst 65 Supercharger 67 Turbine

Claims (8)

  In an exhaust pipe of an internal combustion engine having an inner pipe having an exhaust passage through which exhaust gas flows and an outer pipe disposed outside the inner pipe with a space portion, the space portion has a temperature corresponding to the temperature of the exhaust gas. An exhaust pipe for an internal combustion engine, comprising a heat transfer member capable of switching the inner pipe and the outer pipe to a connected state or a non-connected state.   2. The exhaust pipe of the internal combustion engine according to claim 1, wherein the heat transfer member has one end attached to an inner peripheral surface of the outer pipe and is deformed when the temperature of the exhaust gas exceeds a predetermined temperature set in advance. An exhaust pipe of an internal combustion engine, characterized in that an end portion contacts an outer peripheral surface of the inner pipe.   3. The exhaust pipe of an internal combustion engine according to claim 2, wherein the heat transfer member is deformed when the temperature of the outer pipe exceeds a predetermined temperature set in advance, and the other end contacts the outer peripheral surface of the inner pipe. An exhaust pipe for an internal combustion engine.   4. The exhaust pipe of an internal combustion engine according to claim 1, wherein the heat transfer member is a shape memory alloy that deforms according to a temperature of exhaust gas or a temperature of the outer pipe. An exhaust pipe of an internal combustion engine.   The exhaust pipe of the internal combustion engine according to any one of claims 1 to 4, wherein a plurality of the heat transfer members are provided along a longitudinal direction of the exhaust pipe, and each of the heat transfer members has a different exhaust gas temperature. Accordingly, the exhaust pipe for an internal combustion engine is characterized in that the inner pipe and the outer pipe are switched between a connected state and a disconnected state.   The exhaust pipe according to claim 1 is provided upstream of the catalyst, and the heat transfer member is connected to the inner pipe and the outer pipe when the exhaust gas temperature exceeds a preset catalyst purification temperature region. An exhaust system for an internal combustion engine, characterized in that   A three-way catalyst and a NOx catalyst are arranged in series in an exhaust passage of an internal combustion engine, the first exhaust pipe according to claim 1 is provided upstream of the three-way catalyst, and the three-way catalyst and the NOx catalyst. The second exhaust pipe according to claim 1 is provided between the inner pipe and the heat transfer member of the first exhaust pipe when the exhaust gas temperature exceeds a preset three-way catalyst purification temperature region. And the outer pipe are connected, and the heat transfer member of the second exhaust pipe is connected to the inner pipe and the outer pipe when the exhaust gas temperature exceeds a preset NOx catalyst purification temperature region. An exhaust system for an internal combustion engine, characterized in that   A turbocharger turbine and a catalyst are arranged in series in an exhaust passage of the internal combustion engine, the exhaust pipe according to claim 1 is provided between the turbine and the catalyst, and a heat transfer member of the exhaust pipe includes: An exhaust system for an internal combustion engine, wherein the inner pipe and the outer pipe are connected when the exhaust gas temperature exceeds a preset catalyst purification temperature region.

Images