vehicle

Abstract

To provide a vehicle capable of suppressing deterioration of insulation performance of an EHC.SOLUTION: A vehicle 1 includes: an EHC 10 that is provided in an exhaust passage 3 of an internal combustion engine 2 and of which temperature can be raised through electric conduction; a cylindrical first case 5 that accommodates the EHC 10; and an insulation coat 12 surrounding the outer periphery of the EHC 10 and disposed between an inner wall of the first case 5 and the outer periphery of the EHC 10; a diameter contraction part 5C provided at an end part on the downstream side in an exhaust gas flowing direction of the first case 5 and formed by contracting an inner diameter of the first case 5 in the flowing direction; and an EGR passage 7 connected to the diameter contraction part 5C.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to vehicles. [Background technology]

[0002] Patent Document 1 discloses a configuration in an exhaust system of a vehicle's internal combustion engine that includes an EHC (Electrically Heated Catalyst: a catalyst that can be heated by passing electricity through it) and an EGR (Exhaust Gas Recirculation) outlet downstream of an oxidation catalyst. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-202607 Summary of the Invention [Problem to be solved by the invention]

[0004] To ensure insulation between the electrodes and substrate of the EHC and the case in which the EHC is housed, it is conceivable to apply an insulating coating to the outer periphery of the EHC. However, there is a risk that insulation will be reduced due to the accumulation of soot on the insulating coating, and there is room for improvement in EGR-equipped vehicles such as those described in Patent Document 1.

[0005] The present disclosure aims to provide a vehicle that can suppress deterioration of the insulation properties of an EHC. [Means for solving the problem]

[0006] A vehicle according to one aspect of an embodiment of the present invention comprises an exhaust purification catalyst that is provided in an exhaust passage of an internal combustion engine and can be heated by passing current through it; a cylindrical case that houses the exhaust purification catalyst; an insulating coat that surrounds the outer periphery of the exhaust purification catalyst and is arranged between the inner wall of the case and the outer periphery of the exhaust purification catalyst; a reduced diameter portion that is provided at the end of the case that is downstream in the flow direction of the exhaust gas and that reduces the inner diameter of the case along the flow direction; and an EGR passage that is connected to the reduced diameter portion. [Effects of the Invention]

[0007] According to the present disclosure, a vehicle can be provided that can suppress deterioration of the insulation properties of the EHC. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a configuration of an exhaust passage of a vehicle in the vicinity of an EHC according to an embodiment; [Figure 2] A diagram explaining the effect of a configuration in which an EGR passage is connected to a reduced diameter portion. [Figure 3] FIG. 1 shows a modified example of a catalytic converter. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments will be described with reference to the accompanying drawings. To facilitate understanding of the description, the same components in the drawings will be denoted by the same reference numerals as much as possible, and duplicated descriptions will be omitted.

[0010] FIG. 1 is a diagram showing the configuration of an exhaust passage 3 of a vehicle 1 according to an embodiment, in the vicinity of an EHC 10. As shown in FIG.

[0011] The vehicle 1 is equipped with an internal combustion engine 2 as a driving source for traveling. The internal combustion engine 2 draws air into the engine body through an intake passage (not shown), and burns a mixture of fuel and intake air in the engine body to generate driving force. The internal combustion engine 2 discharges exhaust gases after combustion through an exhaust passage 3.

[0012] As shown in Figure 1, a catalytic converter 4 for purifying exhaust gas is provided in the exhaust passage 3. In Figure 1, the left side of the drawing is the upstream side in the exhaust flow direction, and the right side is the downstream side. In Figure 1, the main flow of exhaust gas in the exhaust passage 3 is shown by arrows G1, G2, and G3.

[0013] In the example of Figure 1, the catalytic converter 4 has a first case 5 arranged upstream in the exhaust gas flow direction, and a second case 6 arranged downstream of the first case 5. The first case 5 is cylindrical and houses an exhaust gas purification catalyst that can be heated by applying electricity, i.e., an EHC (Electrically Heated Catalyst) 10, and a rear catalyst 20 arranged downstream in the exhaust gas flow direction from the EHC 10. The EHC 10 and rear catalyst 20 are, for example, three-way catalysts that simultaneously remove three substances in the exhaust gas - hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) - through oxidation-reduction reactions.

[0014] The second case 6 is also cylindrical and houses a particulate filter 30 therein that captures particulate matter in the exhaust gas. The particulate filter 30 is, for example, a GPF (Gasoline Particulate Filter) when the internal combustion engine 2 is a gasoline engine, or a DPF (Diesel Particulate Filter) when the internal combustion engine 2 is a diesel engine.

[0015] The first case 5 has a double-tube structure having an outer tube 5A and an inner tube 5B disposed inside the outer tube 5A. The EHC 10 and rear catalyst 20 are housed inside the inner tube 5B. The EHC 10 is a structure including a substrate carrying a catalyst that generates heat when energized, electrodes for energization, etc., and is held within the inner tube 5B by a mat 11 disposed between the outer peripheral surface of this structure and the inner peripheral surface of the inner tube 5B. Similarly, the rear catalyst 20 is held within the inner tube 5B by a mat 21 disposed between the outer peripheral surface of the rear catalyst 20 and the inner peripheral surface of the inner tube 5B.

[0016] The particulate filter 30 is held in the second case 6 by a mat 31 that is arranged between the inner peripheral surface of the second case 6 and the outer peripheral surface of the particulate filter 30 .

[0017] Exhaust gas G1 flowing through the exhaust passage 3 enters the first case 5 and passes through the EHC 10 and the rear catalyst 20, from which harmful substances have been removed, and exits the first case 5 as exhaust gas G2. Thereafter, the exhaust gas G2 enters the second case 6 and passes through the particulate filter 30, from which particulate matter has been further removed, and is then discharged to the outside as exhaust gas G3.

[0018] Since the EHC 10 heats the catalyst using electrical energy from a power source, insulation is ensured by applying an insulating coating 12 between the electrodes or substrate and the case. In the example of Fig. 1, the insulating coating 12 is formed on the inner peripheral surface of the inner cylinder 5B so as to cover the entire EHC 10 along the flow direction of the exhaust gas, and also to cover a portion of the rear catalyst 20 on the upstream side in the flow direction. Furthermore, the insulating coating 12 is formed on the upper end side of the inner cylinder 5B in the flow direction so as to cover the upper end and also to cover a portion of the upper end side of the outer peripheral surface of the inner cylinder 5B.

[0019] As a result, the insulating coating 12 surrounds the outer periphery of the EHC 10 and is disposed between the inner wall of the first case (the inner peripheral surface of the outer cylinder 5A) and the outer periphery of the EHC 10. The insulating coating 12 is also formed so as to surround the outer periphery of the EHC 10 and extend to at least a portion of the upstream side in the flow direction of the rear catalyst 20. Note that the insulating coating 12 may also be provided on the entire inner peripheral surface of the inner cylinder 5B, so as to cover the entire rear catalyst 20 in the flow direction.

[0020] Furthermore, a reduced diameter section 5C is provided at the end of the first case 5 that is downstream in the flow direction of exhaust gas. As shown in FIG. 1, for example, the reduced diameter section 5C is formed integrally with the outer cylinder 5A of the first case 5, and is formed so as to reduce the inner diameter of the outer cylinder 5A of the first case 5 along the flow direction. The inner diameters of the first case 5 and the second case 6 are larger than the inner diameters of the other parts of the exhaust passage 3. The inner diameter of the downstream end of the reduced diameter section 5C is formed to be the same size as the other parts of the exhaust passage 3, thereby returning the inner diameter of the exhaust passage 3 downstream of the first case 5 to its original size.

[0021] In the internal combustion engine 2 according to this embodiment, the exhaust passage 3 and the intake passage are connected by an EGR (Exhaust Gas Recirculation) passage 7. Exhaust gas is guided from the exhaust passage 3 to the intake passage via the EGR passage 7.

[0022] In particular, in this embodiment, the EGR passage 7 is connected to the exhaust passage 3 at the reduced diameter portion 5C of the first case 5. That is, in the exhaust passage 3, a portion ΔG2 of the exhaust gas G2 after passing through the EHC 10 and the rear catalyst 20 is introduced into the EGR passage 7.

[0023] 2A and 2B are diagrams illustrating the effect of a configuration in which the EGR passage 7 is connected to the reduced diameter portion 5C. Fig. 2A shows, as a comparative example, the flow of exhaust gas within the first case 5 in a configuration in which the EGR passage 7 is not connected downstream of the first case 5, i.e., to the reduced diameter portion 5C. On the other hand, Fig. 2B shows the flow of exhaust gas within the first case 5 in the configuration of this embodiment, i.e., the configuration in which the EGR passage 7 is connected to the reduced diameter portion 5C.

[0024] As mentioned above, the EHC 10 heats the catalyst using electrical energy from the power source, and therefore insulation is ensured by applying an insulating coating 12 between the electrodes, substrate, and case. However, conventional EHCs have a problem in that soot generated during cold engine start-up gradually accumulates on the insulating coating, reducing insulation performance. To address this problem, the upstream side of the EHC has traditionally been designed with a labyrinth shape that makes it difficult for soot to adhere. However, because the same measures cannot be taken on the downstream side, there is room for improvement in suppressing soot adhesion.

[0025] Here, in order to suppress soot adhesion downstream of the EHC 10, it is desirable that the high-temperature exhaust gas G2 that has been heated by the EHC 10 and passed through the rear catalyst 20 can enter the gap between the outer cylinder 5A and inner cylinder 5B of the first case 5 and the gap between the inner cylinder 5B and the rear catalyst 20. However, in the comparative example shown in Fig. 2(A), a vortex V1 of the exhaust gas G2 is generated near the end face on the downstream side of the rear catalyst 20, and this vortex V1 obstructs the exhaust gas G2 from entering the gap.

[0026] In response to such a conventional problem, in this embodiment, the EGR passage 7 is connected to the reduced diameter portion 5C. As a result, as shown in FIG. 2(B), a portion ΔG2 of the exhaust gas G2 flows into the EGR passage 7, and the flow of the exhaust gas G2 differs from that in the comparative example.

[0027] The exhaust gas ΔG2 mainly flows radially outward from the first case 5. When this type of exhaust gas ΔG2 is generated, a portion of the exhaust gas G2 flowing downstream must change direction, for example by hitting the inner wall of the EGR passage 7. For this reason, a vortex V2 flowing upstream is thought to be generated at the connection between the reduced diameter portion 5C and the EGR passage 7. This vortex V2 is larger than the vortex V1 shown in FIG. 2(A).

[0028] 2(B), this vortex V2 is thought to generate a gas flow V3 toward the upstream side near the outer radial edge of the first case 5. Because this flow V3 is larger than the vortex V1 generated near the downstream end face of the rear catalyst 20, it can enter the gap between the outer cylinder 5A and inner cylinder 5B of the first case 5 and the gap between the inner cylinder 5B and the rear catalyst 20 without being obstructed by the vortex V1. This allows the high-temperature exhaust gas to flow all the way to the insulating coat 12 around the rear catalyst 20, actively reducing soot and restoring insulation performance.

[0029] The vehicle 1 of this embodiment includes an EHC 10 that is provided in an exhaust passage 3 of an internal combustion engine 2 and that can be heated by energizing it, a cylindrical first case 5 that houses the EHC 10, an insulating coating 12 that surrounds the outer periphery of the EHC 10 and is arranged between the inner wall of the first case 5 and the outer periphery of the EHC 10, a reduced diameter portion 5C that is provided at the end of the first case 5 that is downstream in the exhaust flow direction and that reduces the inner diameter of the first case 5 along the exhaust flow direction, and an EGR passage 7 that is connected to the reduced diameter portion 5C. The vehicle 1 also includes a rear catalyst 20 that is housed in the first case 5 and is arranged downstream of the EHC 10 in the exhaust flow direction, and the insulating coating 12 surrounds the outer periphery of the EHC 10 and extends to at least a portion of the rear catalyst 20 in the exhaust flow direction.

[0030] This configuration allows exhaust gas to flow into the gap between the first case 5 and the insulating coating 12, and into the gaps between the insulating coating 12 and the EHC 10 and rear catalyst 20, thereby reducing soot near the insulating coating 12 due to high-temperature exhaust gas. This prevents a decrease in the insulation properties of the EHC 10. Furthermore, by placing the rear catalyst 20 near the EHC 10, warming up of the rear catalyst 20 can be promoted and the installation space can be reduced.

[0031] 1 and 2, the EGR passage 7 is preferably arranged so that the direction of the axis C2 at the connection portion with the reduced diameter portion 5C is perpendicular to the direction of the axis C1 of the first case 5 (exhaust passage 3). This configuration makes it easier for the exhaust gas G2 flowing downstream to impinge on the inner wall of the EGR passage 7, making it easier to generate a vortex V2 and an upstream flow V3.

[0032] However, the direction of the axis C2 of the EGR passage 7 does not necessarily have to be perpendicular to the direction of the axis C1 of the exhaust passage 3. The direction of the axis C2 of the EGR passage 7 only needs to allow the exhaust gas G2 flowing downstream to strike the inner wall of the EGR passage 7, and may be a direction other than perpendicular, such as a direction inclined toward the upstream side (left side of the figures) of the axis C2 shown in Figures 1 and 2.

[0033] Fig. 3 is a diagram showing a modified example of a catalytic converter. As shown in Fig. 3, a catalytic converter 4A may have only a single first case 5, and an EHC 10, a rear catalyst 20, and a particulate filter 30 may be arranged inside the first case 5 in this order from the upstream side in the exhaust gas flow direction.

[0034] 3, the reduced diameter portion 5C of the first case 5 is disposed downstream of the particulate filter 30. That is, the exhaust gas G1 flows through the exhaust passage 3 and into the first case 5, and after passing through the EHC 10, the rear catalyst 20, and the particulate filter 30, a portion ΔG3 of the exhaust gas G3 is introduced into the EGR passage 7 at the reduced diameter portion 5C.

[0035] In this configuration, similar to the action shown in FIG. 2(B), a vortex V2 generated at the connection between the reduced diameter portion 5C and the EGR passage 7 generates an upstream gas flow V3 near the radial outer edge of the first case 5. This flow V3 can enter the gap between the outer cylinder 5A and inner cylinder 5B of the first case 5 and the gap between the inner cylinder 5B and the particulate filter 30. This allows high-temperature exhaust gas to flow all the way to the insulating coating 12 around the particulate filter 30, actively reducing soot and restoring insulation performance. This prevents a deterioration in the insulation performance of the EHC 10. Furthermore, because the EHC 10, rear catalyst 20, and particulate filter 30 are housed together inside the single first case 5, the catalytic converter 4A can be made more compact than the configuration having the first case 5 and second case 6 illustrated in FIGS. 1 and 2.

[0036] 1 and 2 illustrate a configuration in which the EHC 10 and the rear catalyst 20 are housed inside the first case 5, and the example in FIG. 3 illustrates a configuration in which the EHC 10, the rear catalyst 20, and the particulate filter 30 are housed inside the first case 5, but a configuration in which only the EHC 10 is housed inside the first case 5 may also be used. In this case, the rear catalyst 20 and the particulate filter 30 are housed in a separate case that is located downstream of the first case 5 in the exhaust flow direction. In this configuration, the reduced diameter portion 5C of the first case 5 is located downstream of the EHC 10. In other words, a portion of the exhaust gas G1 that flows through the exhaust passage 3 and into the first case 5 and then passes through the EHC 10 is introduced into the EGR passage 7 at the reduced diameter portion 5C.

[0037] In this configuration, the EGR passage 7 is connected to the reduced diameter portion 5C of the first case 5, which is the same as the configuration example shown in Figures 1 to 3. Therefore, as in the above configuration example, soot can be actively reduced in the insulating coating 12, and the insulating performance can be restored, thereby suppressing a decrease in the insulating properties of the EHC 10.

[0038] The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Design modifications to these specific examples made by a person skilled in the art as appropriate are also included within the scope of the present disclosure as long as they comprise the features of the present disclosure. The elements of the above-described specific examples, as well as their arrangement, conditions, shape, etc., are not limited to those exemplified and can be modified as appropriate. The elements of the above-described specific examples can be combined in various ways as appropriate, as long as no technical contradictions arise. [Explanation of symbols]

[0039] 1 vehicle 2. Internal combustion engine 3 Exhaust passage 5. Case 1 5C Reduced diameter part 7 EGR passage 10 EHC (exhaust gas purification catalyst) 12 Insulation Coat 20 Rear catalyst 30 Particulate filter

Claims

1. an exhaust purification catalyst provided in an exhaust passage of the internal combustion engine and capable of being heated by energization; a cylindrical case that houses the exhaust purification catalyst; an insulating coat that surrounds the outer periphery of the exhaust purification catalyst and is arranged between the inner wall of the case and the outer periphery of the exhaust purification catalyst; a reduced diameter portion provided at a downstream end of the case in the exhaust gas flow direction, the reduced diameter portion reducing an inner diameter of the case along the exhaust gas flow direction; an EGR passage connected to the reduced diameter portion; A vehicle equipped with:

2. a rear catalyst housed in the case and arranged downstream of the exhaust purification catalyst in the flow direction; The insulating coat surrounds the outer periphery of the exhaust purification catalyst and extends to at least a part of the rear catalyst in the flow direction. The vehicle of claim 1 .

3. a particulate filter housed in the case and disposed downstream of the rear catalyst in the flow direction; the insulating coat surrounds the outer peripheries of the exhaust purification catalyst and the rear catalyst and extends to at least a part of the particulate filter in the flow direction.

3. The vehicle of claim 2.

4. The EGR passage is disposed so that an axial direction of a connection portion between the EGR passage and the reduced diameter portion is perpendicular to an axial direction of the case. A vehicle according to any one of claims 1 to 3.

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