Catalytic converter

Abstract

To improve insulation quality of an insulation included in an electric heating type catalyst device.SOLUTION: A catalyst device 10 includes a case 20 storing a catalyst carrier 31 as a heat generator that is supplied with electric power to generate heat. The catalyst device 10 includes an introduction pipe 40 to introduce exhaust air into the case 20. The catalyst device 10 includes a connection pipe 50 connecting the introduction pipe 40 and the case 20. An end part 22 of the case 20 projects toward upstream in an exhaust direction from an end face of the catalyst carrier 31, which forms an insulation. As a temperature difference promotion structure for promoting a state where the connection pipe 50 is relatively lower than the end part 22 of the case 20 in temperature, a heat shield panel 100, which covers an outer peripheral surface of the connection pipe 50 and has an opening 110 formed partly on a part facing the outer peripheral surface of the connection pipe 50, and a stay 120, which connects an internal combustion engine and the outer peripheral surface of the connection pipe 50, are included.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a catalytic device having an electrically heated catalyst. [Background technology]

[0002] Electrically heated catalysts are known, in which the catalyst is heated by passing electricity through a heating element. The catalyst is attached in an electrically insulated state to the tubular case that houses the catalyst. In such electrically heated catalysts, if particulate matter contained in the exhaust adheres to the catalyst and causes an electrical short circuit between the catalyst and the case, electricity will also flow through the case. For this reason, the case must be insulating.

[0003] In order to ensure the insulation of such a case, for example, Patent Document 1 discloses a catalyst device having a labyrinth structure upstream of the catalyst in the exhaust flow direction. This catalytic converter includes a connecting pipe connected to an end of the case on the upstream side in the exhaust direction, and an introduction pipe connected to the end of the connecting pipe on the upstream side in the exhaust direction and having a diameter smaller than that of the case. The end of the case on the upstream side in the exhaust direction protrudes upstream in the exhaust direction further than the end of the heating element on the upstream side in the exhaust direction, and serves as an insulating part that provides electrical insulation. The connection portion between the connecting pipe and the case includes a joint portion where the connecting pipe is joined to the outer circumferential surface of the case, and a pipe structure in which the connecting pipe overlaps with the end of the case on the upstream side in the exhaust direction from the joint portion, and the connecting pipe and the case are separated in the radial direction. A labyrinth structure is formed at the connecting pipe, the end of the case, and the end of the introduction pipe.

[0004] In such catalytic converters, the end of the case is an insulating part, thereby ensuring the insulation of the case. If particulate matter contained in the exhaust gas accumulates on the insulating part, the insulating property of the case will be reduced because the particulate matter forms a conductive path connecting the end of the case and the connecting pipe. Therefore, this catalytic converter has the labyrinth structure described above, which prevents particulate matter from accumulating on the insulating part of the end of the case. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-137552 A Summary of the Invention [Problem to be solved by the invention]

[0006] Even in a catalytic converter such as that disclosed in Patent Document 1, there is a risk that particulate matter may accumulate in the insulating portion of the case end. Therefore, there is a demand for improving the insulation of the insulating portion of the case end by further suppressing the accumulation of particulate matter. [Means for solving the problem]

[0007] A catalytic converter for solving the above problem includes a catalyst for purifying exhaust gas, a heating element that generates heat by energizing to heat the catalyst, and a case that is a tube that houses the catalyst and the heating element, and is disposed in an exhaust passage of an internal combustion engine mounted on a vehicle. The catalytic converter includes a connecting pipe that is a tube connected to an end of the case on the upstream side of the exhaust direction, and an introduction pipe that is a tube connected to an end of the connecting pipe on the upstream side of the exhaust direction and has a diameter smaller than that of the case, with the direction in which exhaust gas flows through the exhaust passage being the exhaust direction. The end of the case on the upstream side of the exhaust direction protrudes upstream in the exhaust direction beyond the end of the heating element on the upstream side of the exhaust direction, and is an insulating part that provides electrical insulation. The connection portion between the connecting pipe and the case includes a joint portion where the connecting pipe is joined to the outer circumferential surface of the case, and a tube structure in which the connecting pipe overlaps with the end of the case on the upstream side of the exhaust direction so as to cover the end of the case, and the connecting pipe and the case are radially separated from each other upstream of the joint portion in the exhaust direction. The catalytic converter has a temperature difference promoting structure that promotes a state in which the temperature of the connecting pipe is relatively low compared to the temperature of the end of the case.

[0008] When the temperature of the connecting pipe becomes relatively low compared to the temperature of the end of the case, particulate matter (hereinafter referred to as PM) adhering to the end of the case moves to the inner circumferential surface of the connecting pipe by thermophoresis, and thus the accumulation of PM on the insulating part is suppressed. When the accumulation of PM on the insulating part is suppressed, the insulating property of the insulating part is improved.

[0009] Therefore, the present configuration has the above-mentioned temperature difference promotion structure, which promotes a state in which the temperature of the connecting pipe is relatively lower than the temperature of the end of the case, compared to a case in which the temperature difference promotion structure is not provided, thereby improving the insulation of the insulating part at the end of the case.

[0010] The temperature difference promotion structure may include a heat shield covering an outer circumferential surface of the connecting pipe and having an opening formed in a portion of the portion facing the outer circumferential surface of the connecting pipe. According to this configuration, the airflow from the vehicle passes through the opening and strikes the connecting pipe, lowering the temperature of the connecting pipe, thereby promoting a state in which the temperature of the connecting pipe is lowered relative to the temperature of the end of the case.

[0011] The temperature difference promoting structure may include a stay that connects a structure different from the catalytic converter to an outer circumferential surface of the connecting pipe. According to this configuration, since the stay is connected to the outer peripheral surface of the connecting pipe, the heat capacity of the connecting pipe is increased. When the heat capacity of the connecting pipe is increased, the temperature of the connecting pipe is less likely to increase. Therefore, it is possible to promote a state in which the temperature of the connecting pipe is relatively low compared to the temperature of the end of the case.

[0012] The temperature difference promotion structure may include a heat shield covering an outer circumferential surface of the connecting pipe, and a stay for fixing the heat shield to the outer circumferential surface of the connecting pipe. According to this configuration, the heat of the connecting pipe is transferred to the heat shield plate via the stay, so that the temperature of the connecting pipe is reduced, thereby promoting a state in which the temperature of the connecting pipe is relatively lower than the temperature of the end of the case.

[0013] The temperature difference promotion structure may include fins provided on an outer circumferential surface of the connecting pipe. According to this configuration, the heat of the connecting pipe is transferred to the outside air through the fins, thereby lowering the temperature of the connecting pipe, thereby promoting a state in which the temperature of the connecting pipe is relatively lower than the temperature of the end of the case.

[0014] The temperature difference promoting structure may include the connecting pipe formed of a casting. According to this configuration, since the connecting pipe is made of a casting, the heat capacity of the connecting pipe is increased compared to a case where the connecting pipe is made of a plate-shaped metal plate. When the heat capacity of the connecting pipe is increased, the temperature of the connecting pipe is less likely to rise. Therefore, it is possible to promote a state in which the temperature of the connecting pipe is relatively low compared to the temperature of the end of the case.

[0015] In addition, in the case where the connecting pipe is made of a casting, the connecting pipe may have a water jacket through which cooling water flows. According to this configuration, the connecting pipe is cooled by the cooling water, so the temperature of the connecting pipe is reduced, which can promote a state in which the temperature of the connecting pipe is relatively lower than the temperature of the end of the case.

[0016] As the temperature difference promotion structure, the end of the inlet pipe is arranged inside the case, the case and the inlet pipe are radially separated, the end of the case overlaps and covers the end of the inlet pipe, and the inlet pipe may have an enlarged diameter portion in which the diameter of the end of the inlet pipe becomes larger downstream in the exhaust direction.

[0017] According to this configuration, a part of the exhaust gas flowing from the introduction pipe toward the case flows along the enlarged diameter portion. Since the exhaust gas flowing along the enlarged diameter portion flows toward the end of the case, the temperature of the end of the case increases. Therefore, it is possible to promote a state in which the temperature of the connecting pipe is relatively low compared to the temperature of the end of the case. [Brief description of the drawings]

[0018] [Figure 1] 1 is a schematic diagram showing an internal combustion engine equipped with an embodiment of a catalytic device; [Diagram 2] FIG. 2 is a cross-sectional view of the catalytic converter according to the embodiment. [Diagram 3] FIG. 11 is a cross-sectional view showing a modified example of the catalytic converter. [Figure 4] FIG. 11 is a cross-sectional view showing another modified example of the catalytic converter. [Diagram 5] 5 is a diagram showing the structure of the catalytic converter as viewed from the direction of the arrow A shown in FIG. 4. [Figure 6] FIG. 11 is a cross-sectional view showing another modified example of the catalytic converter. [Figure 7] FIG. 11 is a cross-sectional view showing another modified example of the catalytic converter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] (First embodiment) Hereinafter, a first embodiment of a catalyst device will be described with reference to FIGS. <About internal combustion engines> FIG. 1 shows a catalytic converter 10 and an internal combustion engine 90 of a vehicle in which the catalytic converter 10 is mounted.

[0020] An example of the internal combustion engine 90 is a gasoline engine fueled by gasoline. The internal combustion engine 90 may also be a diesel engine fueled by diesel. The internal combustion engine 90 is equipped with an exhaust passage 91 through which exhaust gas discharged from a combustion chamber flows. In Fig. 1, the exhaust direction is indicated by an arrow as the direction of exhaust gas flow in which exhaust gas discharged from a combustion chamber passes through the exhaust passage 91 and is discharged to the outside from an exhaust port.

[0021] The catalytic converter 10 is disposed in the exhaust passage 91. The catalytic converter 10 is an electrically heated catalytic converter that includes a heating element that generates heat when electricity is applied thereto. The outer peripheral surface of the exhaust passage 91 and the outer peripheral surface of the catalytic converter 10 are covered with a thin heat shield plate 100 made of a metal material such as stainless steel.

[0022] <Structure of catalytic converter> In Fig. 2, an axis C1 is shown as a straight line along the central axis of the catalytic converter 10. The axis C1 coincides with a straight line along the central axis of the exhaust passage 91. The shape of the catalytic converter 10 is symmetrical with respect to the axis C1. Similarly to Fig. 1, an arrow indicating the exhaust direction is also shown in Fig. 2.

[0023] As shown in FIG. 2, the catalytic converter 10 includes a catalyst carrier 31 on which a catalyst for purifying exhaust gas is supported. The catalytic converter 10 includes a case 20, which is a tube that houses the catalyst carrier 31. The catalytic converter 10 includes a mat 32 that fixes the catalyst carrier 31 to the housing portion 21 in the case 20. The catalytic converter 10 includes a pair of electrodes 81 for applying electricity to the catalyst carrier 31. FIG. 2 illustrates one of the pair of electrodes 81. The catalytic converter 10 includes an introduction pipe 40, which is a tube that introduces exhaust gas flowing through the exhaust passage 91 into the case 20. The catalytic converter 10 includes a connection pipe 50 that connects the introduction pipe 40 and the case 20. The following describes the configuration of the upstream side in the exhaust direction of the catalytic converter 10. The configuration of the downstream side in the exhaust direction may be symmetrical to the configuration of the upstream side, or may be a single-pipe structure with the case 20 that houses the catalyst carrier 31.

[0024] The catalyst carrier 31 has an outer shape of a cylinder with the axis C1 as the central axis. The outline of the cross section of the catalyst carrier 31 in a plane perpendicular to the axis C1 is a circle. The outer shape of the catalyst carrier 31 may be a cylinder with an elliptical cross section, or a prismatic cross section with a polygonal cross section.

[0025] The catalyst carrier 31 is a porous body. As an example, the catalyst carrier 31 is a structure having a honeycomb structure in which a plurality of passages extending in the exhaust direction are defined. One example of a catalyst supported on the catalyst carrier 31 is a three-way catalyst. As the catalyst, an oxidation catalyst, a selective reduction catalyst, or the like can also be adopted.

[0026] As shown in FIG. 2, an electrode 81 is connected to the catalyst carrier 31. A current flows through the catalyst carrier 31 by applying a voltage between the pair of electrodes 81. When a current flows through the catalyst carrier 31, the catalyst carrier 31 generates heat due to the electrical resistance of the catalyst carrier 31. That is, the catalyst carrier 31 is a material that generates heat according to the electrical resistance when electricity is passed through it, and corresponds to a heating element that generates heat when electricity is passed through it. An example of the catalyst carrier 31 is ceramics made of silicon carbide. The heating element may be made of a different material from the catalyst carrier 31. For example, a configuration is possible in which the heating element to which the electrode 81 is connected is disposed in a portion upstream of the catalyst carrier 31 in the exhaust direction.

[0027] The mat 32 covers the surface of the catalyst carrier 31 that corresponds to the side surface of the cylinder. The mat 32 is an insulator with low electrical conductivity. An example of the mat 32 is inorganic fiber mainly composed of alumina. The mat 32 is sandwiched between the catalyst carrier 31 and the case 20. The outer diameter of the catalyst carrier 31 and the mat 32 in the state where the mat 32 is wrapped around the catalyst carrier 31 is larger than the inner diameter of the storage section 21 in the case 20. When the mat 32 is stored in the storage section 21, the mat 32 is compressed. The catalyst carrier 31 is fixed in the storage section 21 in the case 20 by the repulsion of the compressed mat 32. Since the catalyst carrier 31 is covered by the mat 32, electricity is prevented from flowing through the case 20 when electricity is applied to the catalyst carrier 31. Note that it is sufficient for the mat 32 to insulate the catalyst carrier 31 from the case 20. That is, the entire side surface of the catalyst carrier 31 does not necessarily need to be covered by the mat 32.

[0028] The case 20 is a tube made of a metal material such as stainless steel. The axis C1 coincides with a straight line along the central axis of the case 20. As shown in FIG. 2, the case 20 includes a housing portion 21 and an end portion 22 located upstream of the housing portion 21 in the exhaust direction. The upstream end surface of the catalyst carrier 31 housed in the case 20 in the exhaust direction is called the catalyst upstream end 31A. The upstream portion of the case 20, which is bounded by the catalyst upstream end 31A, is called the end portion 22, and the downstream portion is called the housing portion 21. The distance from the axis C1 to the inner peripheral surface of the housing portion 21 is called the inner diameter of the housing portion 21. The inner diameter of the housing portion 21 is constant from one end to the other end of the housing portion 21 in the direction in which the axis C1 extends. The end portion 22 of the case 20 protrudes upstream of the catalyst upstream end 31A in the exhaust direction. The surface of the end portion 22 of the case 20 is covered with an insulator. The insulator covering the entire surface of the end portion 22 forms an insulating layer at the end portion 22. In this manner, the end portion 22 of the case 20 serves as an insulating portion.

[0029] An electrode insertion hole 26 into which an electrode 81 is inserted is opened in the accommodation portion 21 of the case 20. The electrode 81 connected to the catalyst carrier 31 protrudes to the outside of the case 20 via the electrode insertion hole 26. The electrode insertion hole 26 is closed by an electrode holding portion 82. The electrode holding portion 82 fixes the electrode 81 inserted in the electrode insertion hole 26. The electrode holding portion 82 is an insulator with low electrical conductivity. The electrode holding portion 82 supports the electrode 81, thereby preventing electricity from flowing through the case 20.

[0030] The end 22 of the case 20 includes a reduced diameter section 24 located at the end of the case 20 upstream in the exhaust direction, and a constant diameter section 23 located between the reduced diameter section 24 and the storage section 21 and connecting the reduced diameter section 24 and the storage section 21. The distance from the axis C1 to the inner peripheral surface of the constant diameter section 23 is defined as the inner diameter of the constant diameter section 23. The inner diameter of the constant diameter section 23 is constant from one end to the other end of the constant diameter section 23 in the direction in which the axis C1 extends. The inner diameter of the constant diameter section 23 is equal to the inner diameter of the storage section 21.

[0031] 2, at reduced diameter section 24 of end 22 of case 20, the tube gradually narrows so that the distance to axis C1 becomes shorter the further upstream in the exhaust direction. That is, the inner diameter of reduced diameter section 24 becomes smaller the further upstream in the exhaust direction. In case 20, the inner diameter is smallest at the opening on the upstream side in the exhaust direction, i.e., case opening 25 located at the tip of reduced diameter section 24 on the upstream side in the exhaust direction.

[0032] In a cross section taken along the central axis of the catalytic converter 10 shown in Fig. 2, the inner circumferential surface of the reduced diameter section 24 is inclined with respect to the axis C1 so that the distance to the axis C1 becomes shorter the further upstream in the exhaust direction. Similarly, the outer circumferential surface of the reduced diameter section 24 is inclined with respect to the axis C1 so that the distance to the axis C1 becomes shorter the further upstream in the exhaust direction. Note that the reduced diameter section 24 may be curved so that the distance to the axis C1 becomes shorter the further upstream in the exhaust direction in the cross section shown in Fig. 2.

[0033] As shown in FIG. 2, the introduction pipe 40 is a pipe thinner than the case 20. The axis C1 coincides with a straight line along the central axis of the introduction pipe 40. The introduction pipe 40 is formed of a metal material such as stainless steel. The introduction pipe 40 is inserted into the case 20 from the case opening 25. More specifically, an introduction end 41, which is the end of the introduction pipe 40 on the downstream side in the exhaust direction, is inserted into the end 22 of the case 20. The central axis of the introduction pipe 40 overlaps with the central axis of the case 20.

[0034] The inlet end 41 of the inlet pipe 40 is provided with an expanded diameter section 42. The expanded diameter section 42 is gradually thickened so that the distance to the axis C1 becomes longer toward the downstream side in the exhaust direction. That is, the inner diameter of the expanded diameter section 42 becomes larger toward the downstream side 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, i.e., at the inlet port 43 located at the tip of the expanded diameter section 42 on the downstream side in the exhaust direction.

[0035] In a cross section taken along the central axis of the catalytic converter 10 shown in Fig. 2, the inner circumferential surface of the expanded diameter section 42 is inclined with respect to the axis C1 so that the distance to the axis C1 increases toward the downstream side in the exhaust direction. Similarly, the outer circumferential surface of the expanded diameter section 42 is inclined with respect to the axis C1 so that the distance to the axis C1 increases toward the downstream side in the exhaust direction. Note that the expanded diameter section 42 may be curved so that the distance to the axis C1 increases toward the downstream side in the exhaust direction in the cross section shown in Fig. 2.

[0036] An outer peripheral surface 40A of the introduction pipe 40 and an inner peripheral surface 22B at the end 22 of the case 20 are separated in the radial direction of the catalytic converter 10. Between the introduction pipe 40 and the case 20, there is a space through which exhaust gas can pass. Note that an arrow indicating the radial direction of the catalytic converter 10 is shown in Fig. 2. Hereinafter, the direction in which the distance to the axis C1 increases is sometimes referred to as the outward direction, and the direction in which the distance to the axis C1 decreases is sometimes referred to as the inward direction.

[0037] 2, in the catalytic converter 10, the expanded diameter portion 42 and the reduced diameter portion 24 of the case 20 overlap with each other so that the reduced diameter portion 24 of the case 20 is located outwardly of the expanded diameter portion 42 of the inlet pipe 40. The base end of the expanded diameter portion 42 of the inlet pipe 40 opposite the inlet port 43 in the direction in which the axis C1 extends is located downstream in the exhaust direction from the case opening 25 of the case 20. The outer diameter of the expanded diameter portion 42 at the point where the outer diameter is largest is smaller than the inner diameter of the reduced diameter portion 24 at the point where the inner diameter is smallest.

[0038] In the catalytic device 10, in a cross section taken along the central axis of the catalytic device 10 shown in Fig. 2, the outer peripheral surface of the expanded diameter portion 42 and the inner peripheral surface of the reduced diameter portion 24 are parallel. As long as the expanded diameter portion 42 and the reduced diameter portion 24 are spaced apart in the radial direction, the outer peripheral surface of the expanded diameter portion 42 does not necessarily have to be parallel to the inner peripheral surface of the reduced diameter portion 24. In other words, the angle at which the outer peripheral surface of the expanded diameter portion 42 is inclined relative to the axis C1 can be changed. The angle at which the inner peripheral surface of the reduced diameter portion 24 is inclined relative to the axis C1 can also be changed.

[0039] As shown in FIG. 2, the connecting pipe 50 is attached so as to cover the end 22 of the case 20 and the inlet end 41 of the inlet pipe 40. The axis C1 coincides with a straight line along the central axis of the connecting pipe 50. An upstream end 51 of the connecting pipe 50 located at the end on the upstream side in the exhaust direction is joined to the outer circumferential surface 40A of the inlet pipe 40. A portion where the upstream end 51 of the connecting pipe 50 and the inlet pipe 40 are joined in the catalytic converter 10 is called a first joint 12. A downstream end 55 of the connecting pipe 50 located at the end on the downstream side in the exhaust direction is joined to the outer circumferential surface 22A of the end 22 of the case 20. A portion where the downstream end 55 of the connecting pipe 50 and the case 20 are joined in the catalytic converter 10 is called a second joint 14. The connecting pipe 50 is joined to the inlet pipe 40 and the case 20, so that the space between the inlet pipe 40 and the case 20 is sealed.

[0040] The connecting pipe 50 is made of a metal material such as stainless steel. The connecting pipe 50 may be divided into a member including an upstream end 51 joined to the introduction pipe 40 and a member including a downstream end 55 joined to the case 20. In this case, the introduction pipe 40 and the case 20 can be connected by the connecting pipe 50 by joining the two divided bodies. The connecting pipe 50 may also be wound around the end 22 of the case 20 and the introduction end 41 of the introduction pipe 40 in the circumferential direction, and the two ends may be joined to each other at the portion where one end and the other end overlap, thereby connecting the introduction pipe 40 and the case 20.

[0041] The connecting pipe 50 has an inclined portion 52 whose distance to the axis C1 increases from the upstream end 51 toward the downstream side in the exhaust direction. The inner peripheral surface of the inclined portion 52 is separated from the outer peripheral surface of the introduction pipe 40 in the radial direction. The inner peripheral surface of the inclined portion 52 is positioned outwardly from the outer peripheral surface of the introduction pipe 40. A space is provided between the inclined portion 52 and the introduction pipe 40 through which the exhaust gas can flow. The inclined portion 52 is positioned outwardly from the case 20 on the same plane as the case opening 25.

[0042] The connecting pipe 50 has a terminal end 54 whose distance to the axis C1 increases toward the upstream side in the exhaust direction from a downstream end 55. The inner peripheral surface of the terminal end 54 is separated from the outer peripheral surface of the case 20 in the radial direction. The inner peripheral surface of the terminal end 54 is positioned outwardly from the outer peripheral surface of the case 20. There is a space between the terminal end 54 and the case 20 through which the exhaust gas can flow.

[0043] The connecting pipe 50 has an intermediate portion 53 located between the inclined portion 52 and the terminal portion 54 and connecting the inclined portion 52 and the terminal portion 54. The inner diameter of the intermediate portion 53 is constant from one end to the other end of the intermediate portion 53 in the direction in which the axis C1 extends. The inner circumferential surface of the intermediate portion 53 is separated from the outer circumferential surface of the case 20 in the radial direction. The inner circumferential surface of the intermediate portion 53 is shifted outward from the outer circumferential surface of the case 20. There is a space between the intermediate portion 53 and the case 20 through which exhaust gas can flow.

[0044] The boundary between the inclined portion 52 and the intermediate portion 53 in the connecting pipe 50 may be located downstream in the exhaust direction from the case opening 25. However, without being limited thereto, the boundary between the inclined portion 52 and the intermediate portion 53 may be located on the same plane as the case opening 25, or may be located upstream from the case opening 25 in the exhaust direction.

[0045] The boundary between the intermediate portion 53 and the terminal portion 54 of the connecting pipe 50 may be located downstream in the exhaust direction from the inlet 43. However, without being limited thereto, the boundary between the intermediate portion 53 and the terminal portion 54 may be located on the same plane as the inlet 43, or may be located upstream from the inlet 43 in the exhaust direction.

[0046] In a cross section taken along the central axis of the catalytic converter 10 shown in Fig. 2, the inner circumferential surface of the inclined portion 52 is inclined with respect to the axis C1 so that the distance to the axis C1 increases toward the downstream side in the exhaust direction. The inner circumferential surface of the terminal portion 54 is inclined with respect to the axis C1 so that the distance to the axis C1 increases toward the upstream side in the exhaust direction. The inner circumferential surface of the intermediate portion 53 is parallel to the axis C1.

[0047] In the catalytic converter 10, a portion of the connecting pipe 50 close to the upstream end 51 overlaps so as to cover the inlet pipe 40, thereby forming a double pipe structure D1. As shown in Fig. 2, the double pipe structure D1 is formed in the range from the first joint portion 12 to the case opening 25. The first joint portion 12 and the double pipe structure D1 form a first connection portion 11 which is the connection portion between the inlet pipe 40 and the connecting pipe 50.

[0048] In the catalytic converter 10, a portion of the connecting pipe 50 close to the downstream end 55 overlaps so as to cover the case 20, thereby forming a double pipe structure D2. As shown in Fig. 2, the double pipe structure D2 is formed in the range from the second joint 14 to the inlet 43. The second joint 14 and the double pipe structure D2 form a second connection part 13 which is the connection part between the case 20 and the connecting pipe 50.

[0049] Furthermore, in the catalytic converter 10, the connecting pipe 50 overlaps so as to cover the inlet end 41 and the end 22 of the case 20, thereby forming a triple pipe structure T1 in which the pipes are tripled. The triple pipe structure T1 is located between the first connecting part 11 and the second connecting part 13.

[0050] In the triple pipe structure T1, the case 20 and the connection pipe 50 are stacked in order outward from the introduction pipe 40. The space sandwiched between the introduction pipe 40 and the case 20 in the triple pipe structure T1 communicates with the inside of the case 20 on the downstream side in the exhaust direction. The space sandwiched between the introduction pipe 40 and the case 20 in the triple pipe structure T1 communicates with the space sandwiched between the connection pipe 50 and the introduction pipe 40 in the double pipe structure D1 on the upstream side in the exhaust direction. The space sandwiched between the case 20 and the connection pipe 50 in the triple pipe structure T1 communicates with the space sandwiched between the connection pipe 50 and the introduction pipe 40 in the double pipe structure D1 on the upstream side in the exhaust direction. The space sandwiched between the case 20 and the connection pipe 50 in the triple pipe structure T1 communicates with the space sandwiched between the connection pipe 50 and the introduction pipe 40 in the double pipe structure D2 on the downstream side in the exhaust direction.

[0051] The catalytic converter 10 includes a double pipe structure D1, a double pipe structure D2, and a triple pipe structure T1 in a portion upstream in the exhaust direction from the catalyst carrier 31. A labyrinth structure is formed by the double pipe structure D1, the double pipe structure D2, and the triple pipe structure T1.

[0052] <Temperature difference promotion structure> The catalytic converter 10 has a temperature difference promotion 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 case 20. As this temperature difference promotion structure, the catalytic converter 10 has a stay 120 that connects the internal combustion engine 90, which is a structural body, to the outer circumferential surface 50A of the connecting pipe 50, the heat shield 100 that covers the outer circumferential surface 50A of the connecting pipe 50, and the expanded diameter portion 42 of the lead-in pipe 40 described above.

[0053] The stay 120 is formed of a metal material such as stainless steel. One end of the stay 120 is fixed to the outer circumferential surface of the inclined portion 52 of the connecting pipe 50. The other end of the stay 120 is fixed to the outer wall of the internal combustion engine 90. Note that one end of the stay 120 may be fixed to the intermediate portion 53 or the terminal portion 54 of the connecting pipe 50.

[0054] The heat shield 100 covers the outer peripheral surface 50A of the connecting pipe 50, and has an opening 110 formed in a portion of the portion facing the outer peripheral surface 50A of the connecting pipe 50. This opening 110 is a notch that extends from the portion facing the outer peripheral surface 50A of the connecting pipe 50 to the end of the heat shield 100 on the upstream side in the exhaust direction.

[0055] <effect> The operation of this embodiment will be described. The flow of exhaust gas flowing from the inlet pipe 40 into the case 20 will be described with reference to FIG.

[0056] In the catalytic converter 10, a portion of the exhaust gas flowing from the inlet pipe 40 toward the case 20 flows along the expanded diameter portion 42 of the inlet pipe 40. Since the exhaust gas flowing along the expanded diameter portion 42 flows toward the inner circumferential surface 22B of the end portion 22 of the case 20, the temperature of the end portion 22 of the case 20 increases.

[0057] Furthermore, a portion of the exhaust gas flowing into the case 20 from the introduction pipe 40 collides with the catalyst upstream end 31A of the catalyst carrier 31 and changes its flow direction. When the exhaust gas that collides with the catalyst upstream end 31A flows outward, the exhaust gas flows back along the inner circumferential surface 22B at the end 22 of the case 20 toward the upstream side in the exhaust direction.

[0058] In the catalytic converter 10, the reduced diameter section 24 of the case 20 is disposed upstream of the catalyst upstream end 31A. Therefore, exhaust gas that collides with the catalyst upstream end 31A and flows back may hit the reduced diameter section 24. In addition, the expanded diameter section 42 of the lead-in pipe 40 is also disposed upstream of the catalyst upstream end 31A. Therefore, exhaust gas that collides with the catalyst upstream end 31A and flows back may hit the expanded diameter section 42. The exhaust gas collides with the reduced diameter section 24 or the expanded diameter section 42, thereby suppressing the exhaust gas from flowing back.

[0059] Furthermore, when the vehicle is moving, the wind from the vehicle impinges on the connecting pipe 50 through the openings 110 of the heat shield 100, causing the temperature of the connecting pipe 50 to decrease. In addition, the stay 120 is connected to the outer circumferential surface 50A of the connecting pipe 50. Therefore, the heat capacity of the connecting pipe 50 is increased compared to a case where the stay 120 is not connected.

[0060] <Effects> The effects of this embodiment will be described. (1) According to the catalytic converter 10, unless the direction of the exhaust gas flow that collides with the catalyst upstream end 31A is repeatedly reversed, the exhaust gas does not reach the portion between the case 20 and the connecting pipe 50 in the double pipe structure D2 of the second connecting portion 13. In other words, the exhaust gas is unlikely to reach the portion between the case 20 and the connecting pipe 50 in the second connecting portion 13. Therefore, PM is unlikely to accumulate in the portion between the case 20 and the connecting pipe 50. This makes it possible to suppress accumulation of PM on the outer peripheral surface 22A of the end portion 22 of the case 20.

[0061] Since the insulating layer formed on the end portion 22 can be prevented from being covered by PM, a path through which electricity flows can be prevented from being formed on the end portion 22. This can prevent a short circuit between the catalyst carrier 31, which is a heating element, and the case 20.

[0062] (2) When the temperature of the connecting pipe 50 becomes relatively low compared to the temperature of the end 22 of the case 20, PM adhering to the outer peripheral surface 22A of the end 22 of the case 20 moves by thermophoresis to the inner peripheral surface 50B of the connecting pipe 50, suppressing accumulation of PM on the insulating part, that is, the end 22. Suppressing accumulation of PM on the insulating part improves the insulation of the insulating part.

[0063] Therefore, the catalytic converter 10 has the above-mentioned temperature difference promotion 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 case 20. Therefore, compared to a case in which the temperature difference promotion structure is not provided, a state in which the temperature of the connecting pipe 50 is relatively lower than the temperature of the end 22 of the case 20 is promoted. Therefore, the insulation of the insulating part at the end 22 of the case 20 is improved.

[0064] (3) As the temperature difference promotion structure, the catalytic converter 10 has a heat shield 100 that covers the outer circumferential surface 50A of the connecting pipe 50 and has an opening 110 formed in a portion of the portion facing the outer circumferential surface 50A of the connecting pipe 50. As a result, the traveling wind passes through the opening 110 and hits the connecting pipe 50, lowering the temperature of the connecting pipe 50. This can promote a state in which the temperature of the connecting pipe 50 is relatively lower than the temperature of the end 22 of the case 20.

[0065] (4) As the temperature difference promotion structure, the catalytic converter 10 has a stay 120 that connects the internal combustion engine 90, which is a structure different from the catalytic converter 10, to the outer circumferential surface 50A of the connecting pipe 50. Since the stay 120 is connected to the outer circumferential surface 50A of the connecting pipe 50 in this manner, the heat capacity of the connecting pipe 50 increases. When the heat capacity of the connecting pipe 50 increases, the temperature of the connecting pipe 50 becomes less likely to increase. Therefore, it is possible to promote a state in which the temperature of the connecting pipe 50 is relatively low compared to the temperature of the end 22 of the case 20.

[0066] (5) As the temperature difference promotion structure, the introduction end 41 of the introduction pipe 40 is disposed inside the case 20. The case 20 and the introduction pipe 40 are radially separated from each other. The end 22 of the case 20 overlaps with the introduction end 41 of the introduction pipe 40 so as to cover it. The introduction pipe 40 has an expanded diameter portion 42 in which the diameter of the introduction end 41 becomes larger toward the downstream side in the exhaust direction. As a result, the exhaust gas flowing along the expanded diameter portion 42 flows toward the inner circumferential surface 22B of the end 22 of the case 20, so that the temperature of the end 22 of the case 20 increases. Therefore, this also promotes a state in which the temperature of the connection pipe 50 is relatively lower than the temperature of the end 22 of the case 20.

[0067] (6) In the insulating portion for providing electrical insulation between the catalyst carrier 31 and the case 20, the longer the length of the insulating portion in the direction in which the axis C1 extends, the less likely it is that a conductive path will be formed due to accumulation of PM. However, since the insulating portion is part of the case 20, there is a problem in that if the insulating portion is made longer, the overall length of the catalytic device 10 also increases.

[0068] In this regard, the catalytic converter 10 has the above-mentioned temperature difference promotion structure, which improves the insulation of the insulating portion at the end 22 of the case 20. Therefore, the insulation of the insulating portion can be improved without increasing the overall length of the catalytic converter 10.

[0069] Second embodiment Next, a second embodiment of the catalyst device will be described with reference to FIG. The catalyst device 10 of this embodiment has a temperature difference promotion structure different from that of Embodiment 1. The temperature difference promotion structure of the catalyst device 10 of this embodiment will be described below.

[0070] 3, the catalytic converter 10 of this embodiment also has the heat shield 100. The catalytic converter 10 is provided with a stay 130 for fixing the heat shield 100 to the outer circumferential surface 50A of the connecting pipe 50.

[0071] The stay 130 is formed of a metal material such as stainless steel. One end of the stay 130 is fixed to the outer circumferential surface of the middle portion 53 of the connecting pipe 50. The other end of the stay 130 is fixed to the heat shield 100. Note that one end of the stay 130 may be fixed to the inclined portion 52 or the terminal portion 54 of the connecting pipe 50. A plurality of stays 130 are provided in the circumferential direction of the outer circumferential surface 50A of the connecting pipe 50.

[0072] The function and effect of the temperature difference promotion structure of this embodiment will be described. According to the present embodiment, the heat of the connecting pipe 50 is transferred to the heat shield plate 100 via the stay 130, so that the temperature of the connecting pipe 50 is reduced. 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 portion 22 of the case 20.

[0073] Third embodiment Next, a third embodiment of the catalyst device will be described with reference to FIGS. The catalyst device 10 of this embodiment has a temperature difference promotion structure different from that of Embodiment 1. The temperature difference promotion structure of the catalyst device 10 of this embodiment will be described below.

[0074] As shown in FIG. 4, the catalytic converter 10 of this embodiment is provided with fins 140 on an outer circumferential surface 50A of the connecting pipe 50. As shown in FIG. The fins 140 are plate-shaped and made of a metal material such as stainless steel, etc. The fins 140 are provided from the inclined portion 52 of the connection pipe 50 to the terminal end 54.

[0075] 5, a plurality of fins 140 are provided at equal intervals in the circumferential direction of the outer circumferential surface 50A of the connection pipe 50. The number of fins 140 is arbitrary. The function and effect of the temperature difference promotion structure of this embodiment will be described.

[0076] According to this embodiment, the heat of the connecting pipe 50 is transferred to the outside air through the fins 140, so that the temperature of the connecting pipe 50 is reduced. 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 portion 22 of the case 20.

[0077] (Fourth embodiment) Next, a fourth embodiment of the catalyst device will be described with reference to FIG. The catalyst device 10 of this embodiment has a temperature difference promotion structure different from that of Embodiment 1. The temperature difference promotion structure of the catalyst device 10 of this embodiment will be described below.

[0078] As shown in Fig. 6, the connecting pipe 150 of the catalytic converter 10 of this embodiment is formed of a casting made of a metal material such as cast iron or an aluminum alloy, and in this respect it is different from the connecting pipe 50. The connecting pipe 150 has an upstream end 151, an inclined portion 152, an intermediate portion 153, an end portion 154, and a downstream end 155 similar to the upstream end 51, the inclined portion 52, the intermediate portion 53, the end portion 54, and the downstream end 55. Inside the connecting pipe 150, a water jacket 156 is formed in the circumferential direction, through which the cooling water W of the internal combustion engine 90 flows. The water jacket 156 is formed from the inclined portion 152 to the end portion 154 of the connecting pipe 150.

[0079] The function and effect of the temperature difference promotion structure of this embodiment will be described. In this embodiment, the connecting pipe 150 is formed of a casting, so the volume of the connecting pipe 150 is larger than when the connecting pipe is formed of a plate-shaped sheet metal. Therefore, the heat capacity of the connecting pipe 150 increases. When the heat capacity of the connecting pipe increases, the temperature of the connecting pipe becomes difficult to increase. On the other hand, the end 22 of the case 20 is exposed to exhaust gas, so the temperature is easily increased. In this way, the temperature of the end 22 of the case 20 is easily increased, but the temperature of the connecting pipe 150 is difficult to increase. Therefore, it is possible to promote a state in which the temperature of the connecting pipe 150 is relatively lower than the temperature of the end 22 of the case 20.

[0080] In addition, since the water jacket 156 is formed on the connecting pipe 150, the temperature of the connecting pipe 150 is lowered by being cooled by the cooling water W. This further promotes a state in which the temperature of the connecting pipe 150 is relatively lower than the temperature of the end 22 of the case 20.

[0081] <Example of change> The above-described embodiments can be modified as follows: Each embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0082] The opening 110 described in the first embodiment may be formed as a hole that opens only in the portion facing the outer circumferential surface 50A of the connection pipe 50, instead of a notch. The stay 120 described in the first embodiment may be fixed to a structure other than the internal combustion engine 90, for example, a transmission of a vehicle.

[0083] In the first embodiment, the stay 120 fixed to the outer circumferential surface 50A of the connection pipe 50 may be omitted. Even in this case, effects other than the above effect (4) can be obtained. The openings 110 described in the first embodiment may be provided in a plurality of positions in the circumferential direction of the heat shield 100. In this case, the amount of traveling air passing through the openings 110 and impinging on the connecting pipe 50 increases, so that the temperature of the connecting pipe 50 is further reduced. Therefore, the effect of (3) above can be further enhanced.

[0084] In the first embodiment, the introduction pipe 40 including the expanded diameter portion 42 is exemplified. The introduction pipe is not limited to one including an expanded diameter portion. For example, a pipe having a constant diameter in the direction in which the axis C1 extends may be used as the introduction pipe. Even in this case, effects other than the above (5) can be obtained.

[0085] One stay 130 described in the second embodiment may be provided in the circumferential direction of the outer circumferential surface 50A of the connecting pipe 50. In this case, for example, by fixing the stay 130 to a portion of the outer circumferential surface 50A of the connecting pipe 50 where the temperature is highest, the temperature of the connecting pipe 50 can be efficiently reduced.

[0086] The fins 140 described in the third embodiment may be provided on a portion of the outer circumferential surface of the connection pipe 50 between the inclined portion 52 and the terminal end portion 54 . The fins 140 described in the third embodiment may be concentrated in the area where the temperature is highest on the outer circumferential surface 50A of the connecting pipe 50. In this case, the temperature of the connecting pipe 50 can be efficiently reduced.

[0087] The water jacket 156 described in the fourth embodiment may be provided on a portion of the connecting pipe 150 between the inclined portion 152 and the terminal end 54. In this case, for example, by forming the water jacket 156 on the portion of the outer circumferential surface of the connecting pipe 150 where the temperature is highest, the temperature of the connecting pipe 150 can be efficiently reduced.

[0088] Cooling water other than the cooling water for the internal combustion engine 90 may be made to flow through the water jacket 156 described in the fourth embodiment. In the fourth embodiment, the water jacket 156 may be omitted. Even in this case, the above-mentioned functions and effects obtained by forming the connecting pipe 150 from a casting can be obtained.

[0089] The temperature difference promotion structures described in the first to fourth embodiments may be implemented in appropriate combination. The heat shield 100 may cover only the catalytic converter 10 .

[0090] In the first embodiment, the case 20 including the reduced diameter portion 24 is exemplified. The case 20 is not limited to having a reduced diameter portion. For example, the inner diameter of the end portion of the case 20 may be constant from one end to the other end in the direction in which the axis line along the central axis of the catalytic converter extends.

[0091] In the first embodiment, the case 20 including the constant diameter portion 23 is exemplified. The case 20 is not limited to having a constant diameter portion. In other words, the constant diameter portion may be omitted from the end portion 22 of the case 20, and the tube may be gradually tapered so that the distance to the central axis of the catalytic converter becomes shorter toward the upstream side in the exhaust direction.

[0092] In the first embodiment, the tip of the end 22 of the case 20 is located in the triple pipe structure T1. If the triple pipe structure is formed by the introduction pipe, the case, and the connection pipe, it is not essential that the tip of the case be located in the triple pipe structure. The tip of the end of the case may be bent into the case.

[0093] In the first embodiment, the introduction pipe 40 is disposed inside the case 20 so that the introduction port 43 of the introduction pipe 40 is located upstream of the second joint 14. Not limited to this, the introduction port 43 may be located downstream of the second joint 14. The introduction port 43 and the second joint 14 may be located on a plane perpendicular to the axis C1. In these configurations, a double pipe structure is formed in the range from the first joint 12 to the case opening 25. Furthermore, a triple pipe structure is formed in the range from the case opening 25 to the second joint 14. Even with such a configuration, it is possible to achieve the effect that exhaust gas is less likely to reach the portion between the case 20 and the connection pipe 50 in the second connection portion 13, as in the above embodiment.

[0094] In the first embodiment, the case 20 is made of a metal material, but the case 20 may be made of an insulating material. If the case itself is an insulating material, the end 22 of the case 20 does not need to be covered with an insulating layer.

[0095] In the first embodiment, the connecting pipe 50 is exemplified in which the inclined portion 52 and the terminal portion 54 are connected by the intermediate portion 53. The connecting pipe may be such that the intermediate portion 53 is omitted and the inclined portion 52 and the terminal portion 54 are connected to each other.

[0096] Although the catalytic converter 10 described in the first embodiment has a triple pipe structure, it is not essential to have such a triple pipe structure. An example of this modification is shown in FIG. As shown in Fig. 7, in this modified example, for example, the expanded diameter portion 42 of the inlet pipe 40 is omitted. However, it is not essential to omit this expanded diameter portion 42. And, the inlet pipe opening 44, which is the downstream open end of the inlet pipe 40, is disposed upstream of the case opening 25 of the case 20 in the exhaust direction. While this catalytic device 10 has the above-mentioned double pipe structures D1, D2, the triple pipe structure T1 is omitted. Even with a catalytic device 10 that does not have this triple pipe structure, by having the above-mentioned temperature difference promotion structure, the above-mentioned action and effect can be obtained. [Explanation of symbols]

[0097] 10...Catalyst device 11…First connection part 12…First joint part 13…Second connection part 14…Second joint part 20…Case 21…Storage section 22...End 22A…Outer surface 22B…Inner peripheral surface 24...Reduced diameter part 31...Catalyst carrier 31A...Catalyst upstream end 40...Introduction pipe 42…Expanded diameter part 50…Connecting pipe 52…Slope part 90…Internal combustion engine 91…Exhaust passage 100…Heat shield 110…Opening 120…Stay D1,D2…double tube structure T1…Triple tube structure

Claims

1. A catalytic converter device includes a catalyst for purifying exhaust gas, a heating element that generates heat by energizing the catalyst, and a case that is a tube that contains the catalyst and the heating element, the catalytic converter device being disposed in an exhaust passage of an internal combustion engine mounted on a vehicle, a connecting pipe that is a pipe connected to an end of the case on an upstream side of the exhaust direction, the direction in which exhaust gas flows through the exhaust passage being defined as an exhaust direction; and an introduction pipe that is connected to an end of the connection pipe on the upstream side in the exhaust direction and has a diameter smaller than a diameter of the case; an end portion of the case on the upstream side in the exhaust direction protrudes upstream in the exhaust direction further than an end portion of the heating element on the upstream side in the exhaust direction and serves as an insulating portion that provides electrical insulation; a connection portion between the connecting pipe and the case has a joint portion where the connecting pipe is joined to an outer peripheral surface of the case, and a pipe structure in which the connecting pipe overlaps with an end portion of the case on an upstream side of the joint portion in the exhaust direction so as to cover the end portion, and the connecting pipe and the case are separated from each other in a radial direction, 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 case; As the temperature difference promoting structure, A heat shield that covers the outer circumferential surface of the connecting pipe and has an opening formed in a portion of the portion facing the outer circumferential surface of the connecting pipe. Catalytic device.

2. A catalytic converter device includes a catalyst for purifying exhaust gas, a heating element that generates heat by energizing the catalyst, and a case that is a tube that contains the catalyst and the heating element, the catalytic converter device being disposed in an exhaust passage of an internal combustion engine mounted on a vehicle, a connecting pipe that is a pipe connected to an end of the case on an upstream side of the exhaust direction, the direction in which exhaust gas flows through the exhaust passage being defined as an exhaust direction; and an introduction pipe that is connected to an end of the connection pipe on the upstream side in the exhaust direction and has a diameter smaller than a diameter of the case; an end portion of the case on the upstream side in the exhaust direction protrudes upstream in the exhaust direction further than an end portion of the heating element on the upstream side in the exhaust direction and serves as an insulating portion that provides electrical insulation; a connection portion between the connecting pipe and the case has a joint portion where the connecting pipe is joined to an outer peripheral surface of the case, and a pipe structure in which the connecting pipe overlaps with an end portion of the case on an upstream side of the joint portion in the exhaust direction so as to cover the end portion, and the connecting pipe and the case are separated from each other in a radial direction, 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 case; As the temperature difference promoting structure, A stay is provided to connect a structure different from the catalytic converter and an outer circumferential surface of the connecting pipe. Catalytic device.

3. A catalytic converter device includes a catalyst for purifying exhaust gas, a heating element that generates heat by energizing the catalyst, and a case that is a tube that contains the catalyst and the heating element, the catalytic converter device being disposed in an exhaust passage of an internal combustion engine mounted on a vehicle, a connecting pipe that is a pipe connected to an end of the case on an upstream side of the exhaust direction, the direction in which exhaust gas flows through the exhaust passage being defined as an exhaust direction; and an introduction pipe that is connected to an end of the connection pipe on the upstream side in the exhaust direction and has a diameter smaller than a diameter of the case; an end portion of the case on the upstream side in the exhaust direction protrudes upstream in the exhaust direction further than an end portion of the heating element on the upstream side in the exhaust direction and serves as an insulating portion that provides electrical insulation; a connection portion between the connecting pipe and the case has a joint portion where the connecting pipe is joined to an outer peripheral surface of the case, and a pipe structure in which the connecting pipe overlaps with an end portion of the case on an upstream side of the joint portion in the exhaust direction so as to cover the end portion, and the connecting pipe and the case are separated from each other in a radial direction, 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 case; As the temperature difference promoting structure, A heat shield covering an outer circumferential surface of the connecting pipe; and a stay for fixing the heat shield to the outer circumferential surface of the connecting pipe. Catalytic device.

4. A catalytic converter device includes a catalyst for purifying exhaust gas, a heating element that generates heat by energizing the catalyst, and a case that is a tube that contains the catalyst and the heating element, the catalytic converter device being disposed in an exhaust passage of an internal combustion engine mounted on a vehicle, a connecting pipe that is a pipe connected to an end of the case on an upstream side of the exhaust direction, the direction in which exhaust gas flows through the exhaust passage being defined as an exhaust direction; and an introduction pipe that is connected to an end of the connection pipe on the upstream side in the exhaust direction and has a diameter smaller than a diameter of the case; an end portion of the case on the upstream side in the exhaust direction protrudes upstream in the exhaust direction further than an end portion of the heating element on the upstream side in the exhaust direction and serves as an insulating portion that provides electrical insulation; a connection portion between the connecting pipe and the case has a joint portion where the connecting pipe is joined to an outer peripheral surface of the case, and a pipe structure in which the connecting pipe overlaps with an end portion of the case on an upstream side of the joint portion in the exhaust direction so as to cover the end portion, and the connecting pipe and the case are separated from each other in a radial direction, 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 case; As the temperature difference promoting structure, The connecting pipe has fins provided on its outer circumferential surface. Catalytic device.

5. A catalytic converter device includes a catalyst for purifying exhaust gas, a heating element that generates heat by energizing the catalyst, and a case that is a tube that contains the catalyst and the heating element, the catalytic converter device being disposed in an exhaust passage of an internal combustion engine mounted on a vehicle, a connecting pipe that is a pipe connected to an end of the case on an upstream side of the exhaust direction, the direction in which exhaust gas flows through the exhaust passage being defined as an exhaust direction; and an introduction pipe that is connected to an end of the connection pipe on the upstream side in the exhaust direction and has a diameter smaller than a diameter of the case; an end portion of the case on the upstream side in the exhaust direction protrudes upstream in the exhaust direction further than an end portion of the heating element on the upstream side in the exhaust direction and serves as an insulating portion that provides electrical insulation; a connection portion between the connecting pipe and the case has a joint portion where the connecting pipe is joined to an outer peripheral surface of the case, and a pipe structure in which the connecting pipe overlaps with an end portion of the case on an upstream side of the joint portion in the exhaust direction so as to cover the end portion, and the connecting pipe and the case are separated from each other in a radial direction, 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 case; As the temperature difference promoting structure, The connecting pipe is formed by casting. Catalytic device.

6. The connecting pipe has a water jacket through which cooling water flows.

6. A catalytic converter as claimed in claim 5.

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