Catalyst device

Abstract

A catalyst device is provided. The catalyst device includes a housing that houses a catalyst carrier that is a heating body that generates heat by electric conduction. The catalyst device includes an introduction pipe that introduces exhaust gas into the housing. The catalyst device includes a connection pipe that connects the introduction pipe and the housing. An end portion of the housing protrudes toward an upstream side in an exhaust gas direction from an end surface of the catalyst carrier, and is an insulating portion. As a temperature difference promoting structure that promotes a state in which a temperature of the connection pipe relatively decreases with respect to a temperature of the end portion of the housing, a heat shield that covers an outer peripheral surface of the connection pipe and in which an opening portion is formed in a portion facing the outer peripheral surface of the connection pipe, and a strut that connects an internal combustion engine and the outer peripheral surface of the connection pipe are provided.

Description

Technical Field

[0001] This invention relates to catalyst devices. Background Technology

[0002] There are known electrically heated catalysts, which heat the catalyst by energizing a heating element. The catalyst is mounted in an electrically insulated manner relative to the tubular shell housing the catalyst. In such electrically heated catalysts, if an electrical short circuit occurs between the catalyst and the shell due to particulate matter contained in the exhaust gas adhering to it, electricity will also flow to the shell. Therefore, the shell must be insulated.

[0003] To ensure the insulation of such a housing, for example, Japanese Patent Application Publication No. 2015-137552 discloses a catalyst device having a labyrinth structure on the upstream side of the catalyst in the direction of exhaust flow.

[0004] The catalyst device includes a connecting pipe connected to the end of the housing on the upstream side in the exhaust direction, and an inlet pipe connected to the end of the connecting pipe on the upstream side in the exhaust direction, with a diameter smaller than the diameter of the housing. Furthermore, the end of the housing on the upstream side in the exhaust direction protrudes upstream of the end of the heating element on the upstream side in the exhaust direction and serves as an insulating portion for electrical insulation. Additionally, the connection portion between the connecting pipe and the housing has a joint where the connecting pipe engages with the outer peripheral surface of the housing, and a pipe structure where, on the upstream side in the exhaust direction, the connecting pipe overlaps with the end of the housing in a manner that covers the joint, and the connecting pipe and the housing are radially separated. Furthermore, a labyrinth structure is formed at the ends of the connecting pipe, the housing, and the inlet pipe.

[0005] In such a catalyst device, the insulation of the housing is ensured by having an insulating section at the end of the housing. Here, particulate matter contained in the exhaust gas can sometimes accumulate at the insulating section at the end of the housing. As a result, the particulate matter forms a conductive path connecting the end of the housing and the connecting pipe, reducing the insulation of the housing. Therefore, this catalyst device uses the aforementioned labyrinth structure to suppress the accumulation of particulate matter at the insulating section at the end of the housing.

[0006] In the catalyst device disclosed in Japanese Patent Application Publication No. 2015-137552, particulate matter may also accumulate on the insulating portion at the end of the shell. Therefore, it is required to improve the insulation at the insulating portion at the end of the shell by further suppressing the accumulation of particulate matter. Summary of the Invention

[0007] To address the aforementioned issues, according to a first aspect of the present invention, a catalyst device is provided disposed in the exhaust passage of an internal combustion engine mounted in a vehicle. The catalyst device includes: a catalyst for purifying exhaust gas; a heating element for heating the catalyst by means of electricity; and a housing, a tube that houses the catalyst and the heating element. Furthermore, the catalyst device includes: a connecting pipe, which connects to an upstream end of the housing in the exhaust direction, with the direction of exhaust gas flow in the exhaust passage as the exhaust direction; and an inlet pipe, which connects to the upstream end of the connecting pipe in the exhaust direction and has a diameter smaller than the diameter of the housing. The upstream end of the housing in the exhaust direction protrudes upstream of the heating element in the exhaust direction and is an electrically insulating portion. The connection portion between the connecting pipe and the housing includes: a joint portion, where the connecting pipe engages with the outer peripheral surface of the housing; and a pipe structure, where the connecting pipe overlaps the end of the housing at a point upstream of the housing in the exhaust direction beyond the joint portion, and the connecting pipe is radially separated from the housing. The catalyst device also has a temperature difference promoting structure that promotes a state in which the temperature of the connecting pipe is relatively lower than the temperature of the end of the housing. Attached Figure Description

[0008] Figure 1 This is a schematic diagram showing one embodiment of an internal combustion engine equipped with a catalyst device.

[0009] Figure 2 This is a cross-sectional view showing the catalyst device involved in this embodiment.

[0010] Figure 3 This is a cross-sectional view showing a modified example of the catalyst unit.

[0011] Figure 4 This is a cross-sectional view showing other variations of the catalyst unit.

[0012] Figure 5 It shows from Figure 4 A diagram showing the structure of the catalyst device when viewed in the direction of arrow A.

[0013] Figure 6 This is a cross-sectional view showing another variation of the catalyst unit.

[0014] Figure 7 This is a cross-sectional view showing another variation of the catalyst unit. Detailed Implementation

[0015] (First Implementation)

[0016] The following is for reference Figure 1 and Figure 2The first embodiment of the catalyst device will now be described.

[0017] <About Internal Combustion Engines>

[0018] Figure 1 The catalyst device 10 and the internal combustion engine 90 of the vehicle equipped with the catalyst device 10 are shown.

[0019] One example of internal combustion engine 90 is a gasoline engine that uses gasoline as fuel. Internal combustion engine 90 can also be a diesel engine that uses light oil as fuel.

[0020] The internal combustion engine 90 has an exhaust passage 91 for the flow of exhaust gas from the combustion chamber. Figure 1 In the diagram, the direction of exhaust flow, which is the direction in which exhaust gas passes through exhaust passage 91 and is discharged to the outside from the exhaust port, is shown by an arrow.

[0021] Catalyst device 10 is disposed in exhaust passage 91. Catalyst device 10 is an electrically heated catalyst device having a heating element that heats up when energized.

[0022] The outer periphery of the exhaust passage 91 and the outer periphery of the catalyst device 10 are covered by a heat insulation plate 100 made of a thin sheet of metal material such as stainless steel.

[0023] <Structure of a Catalyst Unit>

[0024] exist Figure 2 In this diagram, axis C1 is represented as a straight line along the central axis of the catalyst device 10. Axis C1 coincides with the straight line along the central axis of the exhaust passage 91. The shape of the catalyst device 10 is symmetrical with respect to axis C1. Furthermore, in... Figure 2 Nakaya and Figure 1 Similarly, arrows indicating the direction of exhaust are shown.

[0025] like Figure 2 As shown, the catalyst device 10 includes a catalyst carrier 31 supporting a catalyst for purifying exhaust gas. The catalyst device 10 includes a tube, i.e., a housing 20, that houses the catalyst carrier 31. The catalyst device 10 includes a pad 32 that secures the catalyst carrier 31 to the housing portion 21 of the housing 20. The catalyst device 10 includes a pair of electrodes 81 for energizing the catalyst carrier 31. Figure 2 The diagram shows one of a pair of electrodes 81. The catalyst device 10 includes an inlet pipe 40 that guides the exhaust gas flowing in the exhaust passage 91 into the housing 20. The catalyst device 10 also includes a connecting pipe 50 that connects the inlet pipe 40 to the housing 20. Hereinafter, the structure of the upstream side of the catalyst device 10 in the exhaust direction will be described. The structure of the downstream side in the exhaust direction can be symmetrical to the upstream side structure, or it can be a single-tube structure formed by the housing 20 that houses the catalyst carrier 31.

[0026] The catalyst support 31 has a cylindrical shape with axis C1 as its central axis. The cross-sectional outline of the catalyst support 31 in a plane orthogonal to axis C1 is circular. The shape of the catalyst support 31 can be a cylindrical shape with an elliptical cross-section, or it can be a prism shape with a polygonal cross-section.

[0027] The catalyst support 31 is a porous material. For example, the catalyst support 31 is a structure having a honeycomb structure with multiple pathways extending in the exhaust direction. An example of a catalyst supported on the catalyst support 31 is a three-way catalyst. As the catalyst, an oxidation catalyst or a selective reduction catalyst can be used.

[0028] Electrodes 81 are connected to the catalyst support 31. A voltage is applied between the pair of electrodes 81, causing current to flow into the catalyst support 31. As current flows into the catalyst support 31, the catalyst support 31 heats up due to its resistance. That is, the catalyst support 31 is a material that heats up due to resistance when energized, equivalent to a heating element that heats up when energized. One example of the catalyst support 31 is a ceramic made of silicon carbide. It should be noted that the heating element can also be composed of components different from the catalyst support 31. For example, a structure in which the heating element connected to the electrodes 81 is positioned upstream of the catalyst support 31 in the exhaust direction is conceivable.

[0029] The pad 32 covers the cylindrical side surface of the catalyst carrier 31. The pad 32 is an insulator with low conductivity. An example of the pad 32 is an inorganic fiber primarily composed of alumina. The pad 32 is sandwiched between the catalyst carrier 31 and the housing 20. With the pad 32 wound around the catalyst carrier 31, the outer diameter of both the catalyst carrier 31 and the pad 32 is larger than the inner diameter of the receiving portion 21 of the housing 20. Therefore, when the pad 32 is received into the receiving portion 21, it is compressed by the inner circumferential surface of the receiving portion 21. Through the rebound of the compressed pad 32, the catalyst carrier 31 is fixed within the receiving portion 21 of the housing 20. By covering the catalyst carrier 31 with the pad 32, even when electricity is applied to the catalyst carrier 31, electricity does not flow to the housing 20. It should be noted that the pad 32 only needs to insulate the catalyst carrier 31 from the housing 20. That is, the entire side surface of the catalyst carrier 31 does not necessarily need to be covered by the pad 32.

[0030] The housing 20 is a tube made of a metal material such as stainless steel. The axis C1 is aligned with a straight line along the central axis of the housing 20. The housing 20 has a receiving portion 21 and an end portion 22 located upstream of the receiving portion 21 in the exhaust direction. The upstream end face in the exhaust direction of the catalyst carrier 31 housed in the housing 20 is called the upstream end 31A of the catalyst. The portion of the housing 20 upstream of the upstream end 31A of the catalyst is the end portion 22, and the portion downstream of the upstream end 31A of the catalyst is the receiving portion 21. The inner diameter of the receiving portion 21 is defined as twice the distance from the axis C1 to the inner circumferential surface of the receiving portion 21. The inner diameter of the receiving portion 21 is constant from one end to the other in the direction extending from the axis C1. The end portion 22 of the housing 20 protrudes upstream of the upstream end 31A of the catalyst in the exhaust direction. The surface of the end portion 22 of the housing 20 is covered by an insulator. An insulating layer is formed at the end portion 22 by covering the entire surface of the end portion 22 with an insulator. Thus, the end 22 of the housing 20 is an insulating part.

[0031] An electrode insertion hole 26 is provided in the receiving portion 21 of the housing 20 for inserting an electrode 81. The electrode 81, connected to the catalyst carrier 31, protrudes out of the housing 20 through the electrode insertion hole 26. The electrode insertion hole 26 is blocked by an electrode holding portion 82. The electrode holding portion 82 fixes the electrode 81 inserted into the electrode insertion hole 26. The electrode holding portion 82 is an insulator with low conductivity. The electrode holding portion 82 supports the electrode 81 to prevent electricity from flowing into the housing 20.

[0032] The end 22 of the housing 20 has a reduced-diameter portion 24 located upstream in the exhaust direction within the housing 20, and a constant-diameter portion 23 located between the reduced-diameter portion 24 and the receiving portion 21, connecting the reduced-diameter portion 24 and the receiving portion 21. The inner diameter of the constant-diameter portion 23 is defined as twice the distance from the axis C1 to the inner circumferential surface of the constant-diameter portion 23. The inner diameter of the constant-diameter portion 23 is constant from one end to the other in the direction extending from the axis C1. The inner diameter of the constant-diameter portion 23 is equal to the inner diameter of the receiving portion 21.

[0033] At the reduced diameter section 24 in the end 22 of the housing 20, the tube gradually tapers in such a way that the distance from the inner circumferential surface of the reduced diameter section 24 to the axis C1 decreases as it moves upstream in the exhaust direction. That is, the inner diameter of the reduced diameter section 24 decreases as it moves upstream in the exhaust direction. In the housing 20, the inner diameter is smallest at the opening on the upstream side in the exhaust direction, that is, at the housing opening 25 located at the upstream end of the reduced diameter section 24 in the exhaust direction.

[0034] exist Figure 2In the cross-section shown along the central axis of the catalyst device 10, the inner circumferential surface of the reduced diameter portion 24 is inclined relative to the axis C1 such that the distance from the inner circumferential surface of the reduced diameter portion 24 to the axis C1 decreases as it approaches the exhaust direction upstream. Similarly, the outer circumferential surface of the reduced diameter portion 24 is inclined relative to the axis C1 such that the distance from the outer circumferential surface of the reduced diameter portion 24 to the axis C1 decreases as it approaches the exhaust direction upstream. It should be noted that the reduced diameter portion 24 may also be... Figure 2 The cross-section shown bends in such a way that the distance from the inner or outer circumferential surface of the reduced diameter portion 24 to the axis C1 is smaller the upstream side of the exhaust direction.

[0035] The inlet tube 40 is a tube thinner than the housing 20. The axis C1 is aligned with a straight line along the central axis of the inlet tube 40. The inlet tube 40 is made of a metallic material such as stainless steel. The inlet tube 40 is inserted into the housing 20 through the housing opening 25. More specifically, the downstream end of the inlet tube 40 in the exhaust direction, i.e., the inlet end 41, is inserted into the end 22 of the housing 20. The central axis of the inlet tube 40 overlaps with the central axis of the housing 20.

[0036] The inlet end 41 of the inlet pipe 40 has an enlarged diameter portion 42. The enlarged diameter portion 42 gradually widens in such a way that the distance from the inner circumferential surface of the enlarged diameter portion 42 to the axis C1 increases as it moves downstream in the exhaust direction. That is, the inner diameter of the enlarged diameter portion 42 is larger as it moves downstream in the exhaust direction. In the inlet pipe 40, the inner diameter is largest at the opening on the downstream side in the exhaust direction, that is, at the inlet port 43 located at the downstream front end of the enlarged diameter portion 42 in the exhaust direction.

[0037] exist Figure 2 In the cross-section shown along the central axis of the catalyst device 10, the inner circumferential surface of the expansion section 42 is inclined relative to the axis C1 such that the distance from the inner circumferential surface of the expansion section 42 to the axis C1 increases as it moves downstream in the exhaust direction. Similarly, the outer circumferential surface of the expansion section 42 is inclined relative to the axis C1 such that the distance from the outer circumferential surface of the expansion section 42 to the axis C1 increases as it moves downstream in the exhaust direction. It should be noted that the expansion section 42 can also be... Figure 2 The cross-section shown bends in such a way that the distance from the inner or outer circumferential surface of the enlarged diameter portion 42 to the axis C1 is greater the downstream side in the exhaust direction.

[0038] The outer peripheral surface 40A of the inlet pipe 40 and the inner peripheral surface 22B at the end 22 of the housing 20 are separated radially from each other in the catalyst device 10. There is a space between the inlet pipe 40 and the housing 20 through which exhaust gas can pass. It should be noted that... Figure 2 The image shows a radial arrow indicating the catalyst device 10. Hereinafter, the direction away from axis C1 will sometimes be referred to as the outward direction, and the direction approaching axis C1 will be referred to as the inward direction.

[0039] In the catalyst device 10, the expanding section 42 and the narrowing section 24 overlap in such a way that the narrowing section 24 of the housing 20 is located outward relative to the expanding section 42 of the inlet pipe 40. The base end 43A of the expanding section 42, on the side opposite to the inlet port 43, is positioned downstream in the exhaust direction from the housing opening 25 of the housing 20. The outer diameter of the expanding section 42 at its largest outer diameter is smaller than the inner diameter of the narrowing section 24 at its smallest inner diameter.

[0040] In catalyst device 10, Figure 2 In the cross-section shown along the central axis of the catalyst device 10, the outer peripheral surface of the expanding portion 42 is parallel to the inner peripheral surface of the constricted portion 24. As long as the expanding portion 42 and the constricted portion 24 are separated radially, the outer peripheral surface of the expanding portion 42 does not necessarily have to be parallel to the inner peripheral surface of the constricted portion 24. That is, the angle at which the outer peripheral surface of the expanding portion 42 is inclined relative to the axis C1 can be changed. The angle at which the inner peripheral surface of the constricted portion 24 is inclined relative to the axis C1 can also be changed.

[0041] The connecting pipe 50 is installed such that it covers the end 22 of the housing 20 and the inlet end 41 of the inlet pipe 40. The axis C1 is aligned with a straight line along the central axis of the connecting pipe 50. The upstream end 51 of the connecting pipe 50, located on the upstream side in the exhaust direction, is engaged with the outer peripheral surface 40A of the inlet pipe 40. The portion in the catalyst device 10 where the upstream end 51 of the connecting pipe 50 engages with the inlet pipe 40 is referred to as the first engagement 12. The downstream end 55 of the connecting pipe 50, located on the downstream side in the exhaust direction, is engaged with the outer peripheral surface 22A of the end 22 of the housing 20. The portion in the catalyst device 10 where the downstream end 55 of the connecting pipe 50 engages with the housing 20 is referred to as the second engagement 14. The connecting pipe 50 is engaged with the inlet pipe 40 and the housing 20, and the space between the inlet pipe 40 and the housing 20 is sealed.

[0042] The connecting tube 50 is formed of a metal material such as stainless steel. The connecting tube 50 can also be divided into a component including an upstream end 51 that engages with the inlet tube 40 and a component including a downstream end 55 that engages with the housing 20. In this case, the inlet tube 40 and the housing 20 can be connected using the connecting tube 50 by joining the two segments. Alternatively, the connecting tube 50 can be wound circumferentially relative to the end 22 of the housing 20 and the inlet end 41 of the inlet tube 40, and the inlet tube 40 and the housing 20 can be connected by joining the two ends together at the overlapping portion.

[0043] The connecting pipe 50 has an inclined portion 52, with the upstream end 51 as a base point, the distance from the inner circumferential surface of the connecting pipe 50 to the axis C1 increasing as it moves downstream in the exhaust direction. The inner circumferential surface of the inclined portion 52 is radially separated from the outer circumferential surface of the inlet pipe 40. The inner circumferential surface of the inclined portion 52 is located at a position offset outward from the outer circumferential surface of the inlet pipe 40. There is a space between the inclined portion 52 and the inlet pipe 40 where exhaust can flow. The inclined portion 52 is located at a position offset outward from the housing 20 on the same plane as the housing opening 25.

[0044] The connecting pipe 50 has an end portion 54, which, with the downstream end 55 as a base point, has a greater distance from the inner circumferential surface of the connecting pipe 50 to the axis C1 as it moves upstream in the exhaust direction. The inner circumferential surface of the end portion 54 is radially separated from the outer circumferential surface of the housing 20. The inner circumferential surface of the end portion 54 is located at a position offset outward from the outer circumferential surface of the housing 20. There is a space between the end portion 54 and the housing 20 where exhaust can flow.

[0045] The connecting pipe 50 includes a middle portion 53 located between the inclined portion 52 and the end portion 54, connecting the inclined portion 52 and the end portion 54. The inner diameter of the middle portion 53 is constant from one end to the other in the direction extending from the axis C1. The inner circumferential surface of the middle portion 53 is radially separated from the outer circumferential surface of the housing 20. The inner circumferential surface of the middle portion 53 is located at a position offset outward from the outer circumferential surface of the housing 20. There is a space between the middle portion 53 and the housing 20 where exhaust can flow.

[0046] The junction of the inclined portion 52 and the intermediate portion 53 in the connecting pipe 50 can be located downstream of the housing opening 25 in the exhaust direction. However, it is not limited to this; the junction of the inclined portion 52 and the intermediate portion 53 can also be located on the same plane as the housing opening 25, or upstream of the housing opening 25 in the exhaust direction.

[0047] The junction of the middle portion 53 and the end portion 54 in the connecting pipe 50 can be located downstream of the inlet 43 in the exhaust direction. However, it is not limited to this; the junction of the middle portion 53 and the end portion 54 can also be located on the same plane as the inlet 43, or it can be located upstream of the inlet 43 in the exhaust direction.

[0048] exist Figure 2 In the cross-section shown along the central axis of the catalyst device 10, the inner circumferential surface of the inclined portion 52 is inclined relative to the axis C1 such that the distance from the inner circumferential surface of the inclined portion 52 to the axis C1 increases as it moves downstream in the exhaust direction. The inner circumferential surface of the end portion 54 is inclined relative to the axis C1 such that the distance from the inner circumferential surface of the end portion 54 to the axis C1 increases as it moves upstream in the exhaust direction. The inner circumferential surface of the middle portion 53 is parallel to the axis C1.

[0049] In the catalyst device 10, a double-tube structure D1 is formed by overlapping the portion of the connecting pipe 50 near the upstream end 51 to cover the inlet pipe 40. The double-tube structure D1 is formed from the first joint 12 to the housing opening 25. The first joint 12 and the double-tube structure D1 constitute the connection portion, namely the first connection portion 11, between the inlet pipe 40 and the connecting pipe 50.

[0050] In the catalyst device 10, the portion of the connecting pipe 50 near the downstream end 55 overlaps with the housing 20 to form a double-tube structure D2. The double-tube structure D2 is formed from the second joint 14 to the inlet 43. The second joint 14 and the double-tube structure D2 constitute the connection portion between the housing 20 and the connecting pipe 50, namely the second connection portion 13.

[0051] Furthermore, in the catalyst device 10, the connecting pipes 50 overlap to cover the inlet end 41 and the end 22 of the housing 20, forming a triple-tube structure T1. The triple-tube structure T1 is located between the first connecting part 11 and the second connecting part 13.

[0052] In the triple-tube structure T1, the housing 20 and the connecting pipe 50 overlap sequentially at a position further outward than the inlet pipe 40. The space between the inlet pipe 40 and the housing 20 in the triple-tube structure T1 communicates with the interior of the housing 20 on its downstream side in the exhaust direction. The space between the inlet pipe 40 and the housing 20 in the triple-tube structure T1 communicates with the space between the connecting pipe 50 and the inlet pipe 40 in the double-tube structure D1 on its upstream side in the exhaust direction. The space between the housing 20 and the connecting pipe 50 in the triple-tube structure T1 communicates with the space between the connecting pipe 50 and the inlet pipe 40 in the double-tube structure D1 on its upstream side in the exhaust direction. The space between the housing 20 and the connecting pipe 50 in the triple-tube structure T1 communicates with the space between the connecting pipe 50 and the housing 20 in the double-tube structure D2 on its downstream side in the exhaust direction.

[0053] The catalyst device 10 has a double-pipe structure D1, a double-pipe structure D2, and a triple-pipe structure T1 on the upstream side of the catalyst carrier 31 in the exhaust direction. The double-pipe structure D1, the double-pipe structure D2, and the triple-pipe structure T1 form a labyrinth structure.

[0054] <Regarding temperature difference-induced structural features>

[0055] The catalyst device 10 has a temperature difference promoting structure that promotes a state in which the temperature of the connecting pipe 50 is relatively lower than the temperature of the end 22 of the housing 20. As this temperature difference promoting structure, the catalyst device 10 has a support rod 120 that connects the internal combustion engine 90, which is a structural body, and the outer peripheral surface 50A of the connecting pipe 50, the aforementioned heat insulation plate 100 that covers the outer peripheral surface 50A of the connecting pipe 50, and the aforementioned enlarged diameter portion 42 of the aforementioned inlet pipe 40.

[0056] The support rod 120 is made of stainless steel or other metal materials. One end of the support rod 120 is fixed to the outer peripheral surface of the inclined portion 52 of the connecting pipe 50. The other end of the support rod 120 is fixed to the outer wall of the internal combustion engine 90. It should be noted that one end of the support rod 120 can also be fixed to the middle portion 53 or the end portion 54 of the connecting pipe 50.

[0057] The heat insulation plate 100 covers the outer peripheral surface 50A of the connecting pipe 50, and an opening 110 is formed in a portion of the portion facing the outer peripheral surface 50A of the connecting pipe 50. The opening 110 is a cut extending from the portion facing the outer peripheral surface 50A of the connecting pipe 50 to the upstream end of the heat insulation plate 100 in the exhaust direction.

[0058] <Function>

[0059] The function of this embodiment will be explained.

[0060] use Figure 2 The flow of exhaust gas flowing from the inlet pipe 40 into the housing 20 will be explained.

[0061] In the catalyst device 10, a portion of the exhaust gas flowing from the inlet pipe 40 toward the housing 20 flows along the expansion section 42 of the inlet pipe 40. The exhaust gas flowing along the expansion section 42 flows toward the inner circumferential surface 22B at the end 22 of the housing 20, thus causing the temperature of the end 22 of the housing 20 to rise.

[0062] Additionally, a portion of the exhaust gas flowing from the inlet pipe 40 into the housing 20 collides with the upstream end 31A of the catalyst carrier 31, changing its flow direction. If the exhaust gas after colliding with the upstream end 31A of the catalyst flows outward, the exhaust gas flows in reverse along the inner circumferential surface 22B at the end 22 of the housing 20 towards the upstream side in the exhaust direction.

[0063] In the catalyst unit 10, a narrowed section 24 of the housing 20 is disposed upstream of the catalyst upstream end 31A. Therefore, exhaust gas flowing backwards due to collision with the catalyst upstream end 31A sometimes encounters the narrowed section 24. Additionally, an expanded section 42 of the inlet pipe 40 is also disposed upstream of the catalyst upstream end 31A. Therefore, exhaust gas flowing backwards due to collision with the catalyst upstream end 31A sometimes also encounters the expanded section 42. By the exhaust gas colliding with the narrowed section 24 or the expanded section 42, the backward flow of exhaust gas is suppressed.

[0064] In addition, when the vehicle is in motion, the airflow will come into contact with the connecting pipe 50 through the opening 110 of the heat insulation plate 100, thus causing the temperature of the connecting pipe 50 to drop.

[0065] In addition, a support rod 120 is connected to the outer peripheral surface 50A of the connecting pipe 50. Therefore, compared with the case where the support rod 120 is not connected, the heat capacity of the connecting pipe 50 is increased.

[0066] <Effect>

[0067] The effects of this implementation method will be explained.

[0068] (1) According to the catalyst device 10, as long as the flow direction of the exhaust gas after colliding with the upstream end 31A of the catalyst is not repeatedly reversed, the exhaust gas will not reach the portion between the housing 20 and the connecting pipe 50 in the double-pipe structure D2 of the second connecting part 13. That is, the exhaust gas is unlikely to reach the portion between the housing 20 and the connecting pipe 50 in the second connecting part 13. Therefore, PM is unlikely to accumulate in the portion between the housing 20 and the connecting pipe 50. As a result, the accumulation of PM on the outer peripheral surface 22A in the end 22 of the housing 20 can be suppressed.

[0069] Since the insulating layer formed at end 22 can be prevented from being covered by PM, the formation of a path for power flow at end 22 can be suppressed. Thus, a short circuit between the catalyst support 31, which serves as a heating element, and the housing 20 can be suppressed.

[0070] (2) If the temperature of the connecting pipe 50 is relatively lower than the temperature of the end 22 of the housing 20, the PM adhering to the outer peripheral surface 22A of the end 22 of the housing 20 will move to the inner peripheral surface 50B of the connecting pipe 50 through thermophoresis, thus suppressing the accumulation of PM at the end 22, which is an insulating part. If the accumulation of PM at the insulating part is suppressed, the insulation of the insulating part is improved.

[0071] Therefore, the catalyst device 10 has the aforementioned temperature difference promoting structure, which promotes a state where the temperature of the connecting pipe 50 is relatively lower than the temperature of the end 22 of the housing 20. Thus, compared to the case without the temperature difference promoting structure, the state where the temperature of the connecting pipe 50 is relatively lower than the temperature of the end 22 of the housing 20 is promoted. Therefore, the insulation of the insulating portion at the end 22 of the housing 20 is improved.

[0072] (3) As described above, the catalyst device 10 has a heat insulation plate 100 that covers the outer peripheral surface 50A of the connecting pipe 50 and has an opening 110 formed in a portion of the part facing the outer peripheral surface 50A of the connecting pipe 50. Therefore, the driving air will come into contact with the connecting pipe 50 through the opening 110, and thus the temperature of the connecting pipe 50 will drop. Therefore, it is possible to promote a state in which the temperature of the connecting pipe 50 is relatively lower than the temperature of the end 22 of the housing 20.

[0073] (4) As a temperature difference promoting structure described above, the catalyst device 10 has a support rod 120 connecting the outer peripheral surface 50A of the connecting pipe 50, which is a different structure from the catalyst device 10. Because the support rod 120 is connected to the outer peripheral surface 50A of the connecting pipe 50 in this way, the heat capacity of the connecting pipe 50 is increased. If the heat capacity of the connecting pipe 50 is increased, the temperature of the connecting pipe 50 is less likely to rise. Therefore, it is possible to promote a state in which the temperature of the connecting pipe 50 is relatively lower than the temperature of the end 22 of the housing 20.

[0074] (5) As a temperature difference promoting structure as described above, the inlet end 41 of the inlet pipe 40 is disposed inside the housing 20. Furthermore, the housing 20 and the inlet pipe 40 are radially separated. Additionally, the end 22 of the housing 20 overlaps with the inlet end 41 of the inlet pipe 40. Moreover, the inlet pipe 40 has an enlarged diameter portion 42, the diameter of which increases towards the downstream side in the exhaust direction. As a result, exhaust flowing along the enlarged diameter portion 42 flows toward the inner circumferential surface 22B of the end 22 of the housing 20, thus increasing the temperature of the end 22 of the housing 20. Therefore, this also promotes a state where the temperature of the connecting pipe 50 is relatively lower than the temperature of the end 22 of the housing 20.

[0075] (6) At the insulating part used to electrically insulate the catalyst support 31 from the housing 20, the longer the length of the insulating part in the direction of the axis C1, the less likely it is to form a conductive path based on PM accumulation. However, since the insulating part is part of the housing 20, there is a problem that if the insulating part is lengthened, the overall length of the catalyst device 10 will also increase.

[0076] In this regard, in the catalyst device 10, the insulation of the insulating portion at the end 22 of the housing 20 is improved by having the temperature difference promoting structure described above. Therefore, the insulation of the insulating portion can be improved without increasing the overall length of the catalyst device 10.

[0077] (Second Implementation)

[0078] Next, refer to Figure 3 The second embodiment of the catalyst device will now be described.

[0079] The catalyst device 10 of this embodiment has a temperature difference promoting structure different from that of the first embodiment. Hereinafter, the temperature difference promoting structure of the catalyst device 10 of this embodiment will be described.

[0080] like Figure 3 As shown, the catalyst device 10 of this embodiment also includes the aforementioned heat insulation plate 100. Furthermore, it includes a support rod 130 for fixing the heat insulation plate 100 to the outer peripheral surface 50A of the connecting pipe 50.

[0081] The support rod 130 is made of stainless steel or other metal materials. One end of the support rod 130 is fixed to the outer peripheral surface of the middle portion 53 of the connecting pipe 50. The other end of the support rod 120 is fixed to the heat insulation plate 100. It should be noted that one end of the support rod 130 can also be fixed to the inclined portion 52 or the end portion 54 of the connecting pipe 50. Multiple support rods 130 are provided circumferentially on the outer peripheral surface 50A of the connecting pipe 50.

[0082] This describes the role and effect of the temperature difference-promoting structure in this embodiment.

[0083] According to this embodiment, the heat from the connecting pipe 50 moves to the heat insulation plate 100 via the support rod 130, thus lowering the temperature of the connecting pipe 50. Therefore, it is possible to promote a state where the temperature of the connecting pipe 50 is relatively lower than the temperature of the end 22 of the housing 20.

[0084] (Third Implementation)

[0085] Next, refer to Figure 4 and Figure 5 The third embodiment of the catalyst device will now be described.

[0086] The catalyst device 10 of this embodiment has a temperature difference promoting structure different from that of the first embodiment. Hereinafter, the temperature difference promoting structure of the catalyst device 10 of this embodiment will be described.

[0087] like Figure 4 As shown, the catalyst device 10 of this embodiment has fins 140 on the outer peripheral surface 50A of the connecting pipe 50.

[0088] The fin 140 is plate-shaped and formed of metal materials such as stainless steel. The fin 140 is provided from the inclined portion 52 of the connecting pipe 50 to the end portion 54.

[0089] like Figure 5 As shown, multiple fins 140 are evenly spaced along the circumferential direction of the outer peripheral surface 50A of the connecting pipe 50. It should be noted that the number of fins 140 is arbitrary.

[0090] This describes the role and effect of the temperature difference-promoting structure in this embodiment.

[0091] According to this embodiment, the heat from the connecting pipe 50 moves to the outside air via the fins 140, thus lowering the temperature of the connecting pipe 50. Therefore, it is possible to promote a state where the temperature of the connecting pipe 50 is relatively lower than the temperature of the end 22 of the housing 20.

[0092] (Fourth Implementation)

[0093] Next, refer to Figure 6 The fourth embodiment of the catalyst device will now be described.

[0094] The catalyst device 10 of this embodiment has a temperature difference promoting structure different from that of the first embodiment. Hereinafter, the temperature difference promoting structure of the catalyst device 10 of this embodiment will be described.

[0095] like Figure 6 As shown, the connecting pipe 150 of the catalyst device 10 in this embodiment is formed by casting, which is made of a metal material such as cast iron or aluminum alloy, unlike the connecting pipe 50 described above. The connecting pipe 150 has the same upstream end 151, inclined portion 152, intermediate portion 153, end portion 154, and downstream end 155 as the upstream end 51, inclined portion 52, intermediate portion 53, end portion 54, and downstream end 55 described above. Furthermore, a water jacket 156 for the flow of cooling water W from the internal combustion engine 90 is formed circumferentially inside the connecting pipe 150. The water jacket 156 extends from the inclined portion 152 of the connecting pipe 150 to the end portion 154.

[0096] This describes the role and effect of the temperature difference-promoting structure in this embodiment.

[0097] In this embodiment, since the connecting pipe 150 is formed from a casting, its volume is larger compared to the case where the connecting pipe is formed using a plate-shaped metal sheet. Therefore, the heat capacity of the connecting pipe 150 is increased. If the heat capacity of the connecting pipe is increased, its temperature is less likely to rise. On the other hand, the end 22 of the housing 20 is exposed to exhaust gas, and therefore its temperature rises easily. Thus, while the temperature of the end 22 of the housing 20 easily rises, the temperature of the connecting pipe 150 does not easily rise. Therefore, it is possible to promote a state where the temperature of the connecting pipe 150 is relatively lower than the temperature of the end 22 of the housing 20.

[0098] Furthermore, since a water jacket 156 is formed in the connecting pipe 150, the connecting pipe 150 is cooled by the cooling water W, resulting in a temperature decrease. Therefore, it is possible to further promote a state where the temperature of the connecting pipe 150 is relatively lower than the temperature of the end 22 of the housing 20.

[0099] <Example of Change>

[0100] The above embodiments can be implemented by modification as follows. The embodiments and the following modifications can be combined with each other within the scope of technical non-contradiction.

[0101] Alternatively, the opening 110 described in the first embodiment may not be formed as a cut, but rather as a hole that opens only at the portion facing the outer peripheral surface 50A of the connecting tube 50.

[0102] • The strut 120 described in the first embodiment can also be fixed to a structure other than the internal combustion engine 90, such as the vehicle's transmission.

[0103] • In the first embodiment, the support rod 120 fixed to the outer peripheral surface 50A of the connecting pipe 50 may also be omitted. Even in this case, effects other than those described in (4) can still be obtained.

[0104] • Alternatively, multiple openings 110 as described in the first embodiment can be provided circumferentially on the heat insulation plate 100. In this case, the amount of airflow that comes into contact with the connecting pipe 50 through the openings 110 increases, and therefore the temperature of the connecting pipe 50 decreases further. Thus, the effect described above (3) can be further improved.

[0105] • In the first embodiment, an inlet pipe 40 having an enlarged diameter portion 42 is shown. The inlet pipe is not limited to having an enlarged diameter portion. For example, a pipe with a constant diameter in the direction extending along the axis C1 can also be used as the inlet pipe. Even in this case, effects other than those described above (5) can be obtained.

[0106] Alternatively, one support rod 130 as described in the second embodiment can be provided circumferentially on the outer peripheral surface 50A of the connecting pipe 50. It should be noted that, in this case, by fixing the support rod 130 at, for example, the location with the highest temperature on the outer peripheral surface 50A of the connecting pipe 50, the temperature of the connecting pipe 50 can be reduced efficiently.

[0107] • Alternatively, the fins 140 described in the third embodiment may be provided on a portion of the outer peripheral surface between the inclined portion 52 and the end portion 54 of the connecting tube 50.

[0108] Alternatively, the fins 140 described in the third embodiment can be concentrated at the highest temperature location on the outer peripheral surface 50A of the connecting pipe 50. In this case, the temperature of the connecting pipe 50 can be reduced efficiently.

[0109] Alternatively, the water jacket 156 described in the fourth embodiment may be provided in a portion between the inclined portion 152 and the end portion 54 of the connecting pipe 150. It should be noted that, in this case, by forming the water jacket 156 at, for example, the portion of the outer peripheral surface of the connecting pipe 150 where the temperature is highest, the temperature of the connecting pipe 150 can be reduced efficiently.

[0110] • It is also possible to allow cooling water other than the cooling water of the internal combustion engine 90 to flow into the water jacket 156 described in the fourth embodiment.

[0111] • In the fourth embodiment, the water jacket 156 may also be omitted. Even in this case, the aforementioned function and effect of forming the connecting pipe 150 using a casting can still be obtained.

[0112] • The temperature difference promoting structures described in the first to fourth embodiments can also be appropriately combined and implemented.

[0113] • The heat insulation plate 100 may also cover only the catalyst device 10.

[0114] • In the first embodiment, a housing 20 having a reduced diameter portion 24 is shown. However, the housing 20 is not limited to having a reduced diameter portion. For example, the inner diameter of the end of the housing 20 may be constant from one end to the other in a direction extending along the axis of the central axis of the catalyst device.

[0115] • In the first embodiment, a housing 20 having a constant diameter portion 23 is shown. The housing 20 is not limited to having a constant diameter portion. That is, the constant diameter portion may be omitted as the end 22 of the housing 20, or the tube may be tapered in such a way that the distance from the inner circumferential surface of the housing 20 to the central axis of the catalyst device is smaller as it moves upstream in the exhaust direction.

[0116] In the first embodiment, the front end of the end 22 of the housing 20 is located at the portion of the triple tube structure T1. As long as the triple tube structure is formed by the inlet tube, the housing, and the connecting tube, the front end of the housing being located at the portion of the triple tube structure is not a necessary structure. The front end of the end of the housing may also be bent inwards into the housing.

[0117] In the first embodiment, the inlet 40 is disposed inside the housing 20 such that its inlet 43 is located upstream of the second joint 14. However, it is not limited to this; the inlet 43 may also be located downstream of the second joint 14. Alternatively, the inlet 43 and the second joint 14 may be located on a plane orthogonal to the axis C1. In these structures, a double-tube configuration is formed from the first joint 12 to the housing opening 25. Furthermore, a triple-tube configuration is formed from the housing opening 25 to the second joint 14. Even with such a configuration, the same effect as in the above embodiment is achieved, making it difficult for exhaust gas to reach the portion between the housing 20 and the connecting pipe 50 in the second connecting portion 13.

[0118] • In the first embodiment, a housing 20 made of metal is shown, but the housing 20 may also be formed of an insulator. If the housing itself is an insulator, the ends 22 of the housing 20 may not need to be covered with an insulating layer.

[0119] • In the first embodiment, a connecting pipe 50 is shown that connects the inclined portion 52 and the end portion 54 via the middle portion 53. As a connecting pipe, the middle portion 53 may be omitted and the inclined portion 52 and the end portion 54 may be connected.

[0120] The catalyst device 10 described in the first embodiment has a triple-tube structure, but it is not mandatory to have such a triple-tube structure. Figure 7 The image shows an example of this change.

[0121] like Figure 7 As shown, in this modified example, for example, the enlarged diameter section 42 of the inlet pipe 40 is omitted. It should be noted that the omission of the enlarged diameter section 42 is not necessary. Furthermore, the downstream opening end of the inlet pipe 40, i.e., the inlet pipe opening 44, is located upstream in the exhaust direction than the housing opening 25 of the housing 20. In such a catalyst device 10, the above-described dual-pipe structures D1 and D2 are present, but the above-described triple-pipe structure T1 is omitted. Even with this catalyst device 10 that does not have a triple-pipe structure, the above-described effects and functions can be obtained by having the above-described temperature difference promoting structure.

Claims

1. A catalyst device configured in an exhaust passage of an internal combustion engine mounted on a vehicle, the catalyst device comprising: a catalyst that purifies exhaust gas; a heating element that heats the catalyst by generating heat through electric conduction; a housing that is a pipe that houses the catalyst and the heating element; a connection pipe that is a pipe connected to an end portion of the housing on an upstream side in an exhaust gas direction, the exhaust gas direction being a direction in which exhaust gas flows in the exhaust passage; an introduction pipe that is a pipe connected to an end portion of the connection pipe on the upstream side in the exhaust gas direction and has a smaller diameter than the housing; an end portion of the housing on the upstream side in the exhaust gas direction protruding more to the upstream side in the exhaust gas direction than an end portion of the heating element on the upstream side in the exhaust gas direction and being an insulating portion that is electrically insulated; a connection portion between the connection pipe and the housing having a joint portion at which the connection pipe is joined to an outer peripheral surface of the housing and a pipe structure in which the connection pipe overlaps the housing to cover the end portion of the housing on the upstream side in the exhaust gas direction than the joint portion, the connection pipe and the housing being separated in a radial direction; the catalyst device having a heat shield, an outer peripheral surface of the exhaust passage and an outer peripheral surface of the catalyst device being covered by the heat shield; an opening portion being formed in a portion of the heat shield facing an outer peripheral surface of the connection pipe; and a temperature of the connection pipe being relatively lowered with respect to a temperature of the end portion of the housing by running wind colliding with the connection pipe through the opening portion, whereby particulate matter adhering to the outer peripheral surface of the end portion of the housing moves to an inner peripheral surface of the connection pipe by thermophoresis to suppress accumulation of the particulate matter to the outer peripheral surface in the end portion of the housing.

2. The catalyst device according to claim 1, wherein the catalyst device has a stay that connects an outer peripheral surface of the connection pipe and a structure different from the catalyst device. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Images