Electrically heated catalyst device

Abstract

The aim is to achieve both condensation control and flexibility in installation. [Solution] The catalyst device comprises a cylindrical base material 26, a first electrode, and a second electrode. The first electrode has a first electrode portion fixed to the surface of the base material 26, and a first connection portion 211c that extends in a direction away from the outer circumferential surface of the base material 26 and is connected to an external power source to supply power to the first electrode portion. The second electrode has a second electrode portion fixed to the surface of the base material 26 at a location spaced apart from the first electrode portion in the circumferential direction of the base material 26, and a second connection portion 212c that extends in a direction away from the outer circumferential surface of the base material 26 and is connected to an external power source to supply power to the second electrode portion. The first connection portion 211c and the second connection portion 212c are arranged side by side, spaced apart along the direction in which the central axis C of the base material 26 extends, and are positioned at the uppermost position of the base material 26 when mounted on a vehicle.

Description

Technical Field

[0001] The present invention relates to an electrically heated catalyst device.

Background Art

[0002] The electrically heated catalyst device described in Patent Document 1 includes a cylindrical substrate that supports a catalyst, and a first electrode and a second electrode provided on the outer peripheral surface of the substrate. In the vertical direction in the posture when installed in the exhaust pipe, the first electrode and the second electrode are located in a range above the central axis on the outer peripheral surface of the substrate. By having such a configuration, it is possible to suppress the condensed water generated inside the exhaust pipe in which the electrically heated catalyst device is disposed from reaching each electrode portion.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the electrically heated catalyst device described in Patent Document 1 above, the first electrode and the second electrode are arranged apart from each other in the circumferential direction of the substrate. Therefore, there are two power supply portions for supplying power to the first electrode and the second electrode. As a result, the degree of freedom of the mounting space is reduced.

Means for Solving the Problems

[0005] The electrically heated catalytic converter that solves the above problems is an electrically heated catalytic converter installed in the exhaust pipe of an internal combustion engine mounted on a vehicle. This catalytic converter comprises a cylindrical substrate that supports a catalyst, and a first electrode and a second electrode that supply current to the substrate. The first electrode has a first electrode portion fixed to the surface of the substrate, and a first connection portion that extends in a direction away from the outer circumferential surface of the substrate and is connected to an external power source to supply power to the first electrode portion. The second electrode has a second electrode portion fixed to the surface of the substrate at a location spaced apart from the first electrode portion in the circumferential direction of the substrate, and a second connection portion that extends in a direction away from the outer circumferential surface of the substrate and is connected to the external power source to supply power to the second electrode portion. The first connection portion and the second connection portion are arranged side by side spaced apart along the direction in which the central axis of the substrate extends, and are positioned at the uppermost position of the substrate when mounted on a vehicle. [Effects of the Invention]

[0006] This electrically heated catalytic converter can achieve both condensation control and flexibility in installation. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a radial cross-sectional view of a catalyst device according to one embodiment. [Figure 2] Figure 2 is a side view of the substrate and the first electrode of the catalyst device, along the direction in which the central axis of the substrate extends. [Figure 3] Figure 3 is a perspective view showing the substrate and its surrounding components. [Modes for carrying out the invention]

[0008] An embodiment of an electrically heated catalyst device will be described below with reference to Figures 1 to 3. <Regarding the configuration of the catalytic converter> This section describes an electrically heated catalytic converter 200 installed in the exhaust pipe of an internal combustion engine mounted on a vehicle. In the following, the upstream side in the direction of exhaust flow will be referred to as the "upstream side," and the downstream side in the direction of exhaust flow will be referred to as the "downstream side."

[0009] As shown in Figure 1, the catalytic converter 200 comprises a cylindrical substrate 26 on which a catalyst for purifying exhaust gas is supported. The substrate 26 has a honeycomb structure with multiple passages that extend in the direction of exhaust gas flow, and for example, a three-way catalyst is supported on it.

[0010] The base material 26 is housed in the case 20. The case 20 is a double cylinder made of metal, such as stainless steel, and consists of a cylindrical inner tube 24 that houses the base material 26 inside, and a cylindrical outer tube 23 that is spaced apart outside the inner tube 24.

[0011] A first mat 28 is interposed between the base material 26 and the inner tube 24. The first mat 28 is an insulator and is formed from inorganic fibers, for example, mainly composed of alumina. The first mat 28 is interposed between the base material 26 and the inner tube 24 in a compressed state. Therefore, the base material 26 is held inside the inner tube 24 by the restoring force of the compressed first mat 28.

[0012] A second mat 29 is interposed in the space between the outer tube 23 and the inner tube 24. The second mat 29 is an insulator and is formed from inorganic fibers, for example, mainly composed of alumina. The second mat 29 is interposed between the outer tube 23 and the inner tube 24 in a compressed state. Therefore, the inner tube 24 is held inside the outer tube 23 by the restoring force of the compressed second mat 29.

[0013] The base material 26 is formed of a material that generates heat when electricity is passed through it. For example, silicon carbide can be used as such a material. A pair of surface electrodes 30 are provided on the outer circumferential surface of the substrate 26, facing each other in the radial direction of the substrate 26. The surface electrodes 30 have a rectangular planar shape and extend in the axial direction of the substrate 26. The surface electrodes 30 are a porous film formed on the surface of the substrate 26 by thermal spraying, and are made of a metal material with excellent oxidation resistance at high temperatures, such as a NiCr alloy.

[0014] The catalyst device 200 includes a first electrode 211 and a second electrode 212 that supply current to the substrate 26. The first electrode 211 and the second electrode 212 are made of a metallic material such as stainless steel. The first electrode 211 is the positive electrode, and the second electrode 212 is the negative electrode. By applying a voltage from an external power source 400 between the first electrode 211 and the second electrode 212, current flows through the substrate 26. When current flows through the substrate 26, the substrate 26 is heated by generating heat due to its electrical resistance.

[0015] The first electrode 211 comprises a first electrode portion 211a, a first lead wire 211b, and a first connection portion 211c. The first electrode portion 211a is a comb-shaped thin plate and is fixed to the surface of one of the pair of surface electrodes 30.

[0016] The first lead wire 211b is a flat, thin plate that runs along the surface of the base material 26 and extends to the uppermost position in the vertical direction above the base material 26 in the circumferential direction, and is connected to the first electrode portion 211a. More specifically, the first lead wire 211b and the first electrode portion 211a are integrally formed.

[0017] The first connection portion 211c extends in a direction away from the outer surface of the base material 26 and is connected to the first lead wire 211b. More specifically, the end of the first lead wire 211b is bent in a direction away from the outer surface of the base material 26, and this portion of the first lead wire 211b that is bent in a direction away from the outer surface constitutes the first connection portion 211c. The end of this first connection portion 211c is connected to the positive electrode of the external power supply 400, thereby supplying power to the first electrode portion 211a.

[0018] The second electrode 212 includes a second electrode portion 212a, a second lead wire 212b, and a second connection portion 212c. The second electrode portion 212a also has the same shape as the first electrode portion 211a. That is, the second electrode portion 212a is also a comb-shaped thin plate and is fixed to the surface of the other surface electrode 30 of the pair of surface electrodes 30. Therefore, the second electrode portion 212a and the first electrode portion 211a are arranged to face each other in the radial direction of the base material 26.

[0019] The second lead wire 212b is a flat thin plate that extends along the surface of the base material 26 and reaches the uppermost position in the vertical direction above the base material 26 in the circumferential direction of the base material 26, and is connected to the second electrode portion 212a. More specifically, the second lead wire 212b and the second electrode portion 212a are integrally formed.

[0020] The second connection portion 212c extends in a direction away from the outer peripheral surface of the base material 26 and is connected to the second lead wire 212b. More specifically, the end portion of the second lead wire 212b is bent in a direction away from the outer peripheral surface of the base material 26, and the portion of the second lead wire 212b bent in the direction away from the outer peripheral surface is the second connection portion 212c. By connecting the end portion of this second connection portion 212c to the negative electrode of the external power 400, power is supplied to the second electrode portion 212a.

[0021] <M As shown in FIGS. 2 and 3, the first connection portion 211c and the second connection portion 212c are arranged side by side while being separated along the direction in which the central axis C of the base material 26 extends. In other words, when viewed in the direction in which the central axis C of the base material 26 extends, the first connection portion 211c and the second connection portion 212c are arranged to overlap.

[0022] As shown in Figure 2, the first connection portion 211c is positioned offset from the center point A of the base material 26 in the direction in which the central axis C extends, by a predetermined first offset amount OF1 toward the downstream end face 26D of the base material 26. The second connection portion 212c is positioned offset from the center point A by a predetermined second offset amount OF2 toward the upstream end face 26U of the base material 26. Therefore, the first connection portion 211c and the second connection portion 212c are spaced apart along the direction in which the central axis C of the base material 26 extends by the sum of the first offset amount OF1 and the second offset amount OF2. The sum of the first offset amount OF1 and the second offset amount OF2 is preferably, for example, the minimum distance required for insulation between the first connection portion 211c and the second connection portion 212c. In this embodiment, the first offset amount OF1 and the second offset amount OF2 are the same value, but they may be different.

[0023] As shown in Figure 1, the first connection part 211c and the second connection part 212c are positioned at the uppermost part of the base material 26 when the catalyst device 200 is mounted on the vehicle. As shown in Figure 3, a notch 28a is formed in the first mat 28. The notch 28a is formed to avoid the first electrode portion 211a, the first lead wire 211b, the first connection portion 211c, the second electrode portion 212a, the second lead wire 212b, and the second connection portion 212c.

[0024] As shown in Figure 1, in a state where a catalytic converter 200 is installed in the exhaust pipe of an internal combustion engine mounted on a vehicle, a hole 213 is formed in the vertically upper portion of the inner pipe 24. Similarly, in a state where a catalytic converter 200 is installed in the exhaust pipe of an internal combustion engine mounted on a vehicle, a hole 214 is formed in the vertically upper portion of the outer pipe 23. Hole 214 is located opposite hole 213. The first electrode 211 and the second electrode 212 pass through the holes 213 and 214 without contacting them.

[0025] The inner surface of the inner tube 24 is coated with an insulating material. The hole 214 is sealed by a metal electrode chamber 80. An electrode terminal 85, which is provided at the end of a power line that supplies power to the first electrode 211 and the second electrode 212, is inserted into this electrode chamber 80. The positive electrode of the electrode terminal 85 is connected to the first electrode 211. The negative electrode of the electrode terminal 85 is connected to the second electrode 212.

[0026] The catalyst device 200 is covered on its outer surface by an insulator 300. A notch 310 is formed in a part of the insulator 300, and the electrode chamber 80 protrudes from this notch 310.

[0027] <Operation and Effects of This Embodiment> (1) The first connection part 211c and the second connection part 212c, which are connected to the external power supply 400, are arranged to be spaced apart along the direction in which the central axis C of the base material 26 extends. As a result, the electrode chamber 80, which is a power supply unit that supplies power to the first electrode 211 and the second electrode 212, can be consolidated into one location. Therefore, compared to the case in which the electrode chamber 80 is divided into two locations in the circumferential direction of the base material 26, the degree of freedom in the mounting space of the catalyst device 200 can be increased.

[0028] On the other hand, if condensed water originating from moisture in the exhaust adheres to the first connection part 211c or the second connection part 212c housed in the electrode chamber 80, there is a risk that the electrode terminals 85 that supply power to the first connection part 211c or the second connection part 212c and the exhaust pipe may short-circuit via the condensed water.

[0029] In this embodiment, since the first connection portion 211c and the second connection portion 212c are positioned at the uppermost part of the base material 26 when mounted on a vehicle, condensed water is less likely to accumulate in the first connection portion 211c and the second connection portion 212c. Consequently, short circuits between the electrode terminals 85 that supply power to the first connection portion 211c and the second connection portion 212c and the exhaust pipe via condensed water are also suppressed. Thus, it is possible to achieve both measures against such condensed water and flexibility in mounting.

[0030] (2) Since condensed water is less likely to accumulate in the first connection part 211c and the second connection part 212c, corrosion resistance is improved. (3) Since the electrode terminals 85 are positioned at the uppermost position when mounted on the vehicle, the cooling effect of the electrode terminals 85 by the airflow while driving is enhanced. Therefore, for example, the durability of the electrode terminals 85 can be increased and material costs can be reduced.

[0031] (4) The electrode chambers 80 that supply power to the first electrode 211 and the second electrode 212 can be combined into one location. Therefore, the area of ​​the notch 310 provided in the insulator 300 can be reduced compared to the case where the electrode chambers 80 are divided into two locations. Therefore, the effect of the insulator 300 in suppressing heat damage to the surroundings can be enhanced.

[0032] (5) If the first mat 28 does not have the notch 28a, when the base material 26 and the first mat 28 are pressed into the inner tube 24, the first electrode portion 211a, the first lead wire 211b, the second electrode portion 212a, and the second lead wire 212b are pressed against the first mat 28. As a result, the first mat 28 may shift, and each component such as the first electrode portion 211a, the first lead wire 211b, the second electrode portion 212a, and the second lead wire 212b may be pulled. In addition, there is a risk that current may flow directly to the base material 26 through an unintended path without going through the first electrode portion 211a or the second electrode portion 212a. In this embodiment, however, since the first mat 28 is provided with the notch 28a, the occurrence of such problems is suppressed.

[0033] <Example of changes> The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0034] The first electrode portion 211a and the second electrode portion 212a were comb-shaped thin plates, but other shapes are also acceptable. The first electrode portion 211a and the second electrode portion 212a were fixed to the surface of the substrate 26 via the surface electrode 30, but they may also be fixed directly to the surface of the substrate 26.

[0035] The first connecting portion 211c and the second connecting portion 212c are provided at the center point A of the base material 26. Alternatively, the first connecting portion 211c and the second connecting portion 212c may be provided closer to the upstream end face 26U of the base material 26. Furthermore, the first connecting portion 211c and the second connecting portion 212c may be provided closer to the downstream end face 26D of the base material 26. [Explanation of symbols]

[0036] 20…Case 23…Outer tube 24…Inner tube 26…Base material 26D…Downstream end face 26U…Upstream end face 28…First mat 28a…Notch 29…Second mat 30…Surface electrode 80…Electrode chamber 85…Electrode terminal 200…Catalyst device 211…First electrode 211a…First electrode section 211b…First lead wire 211c…First connection section 212…Second electrode 212a…Second electrode section 212b…Second lead wire 212c…Second connection section 213…Hole 214…Hole 300…Insulator 310…Notch 400…External power

Claims

[Claim 1] An electrically heated catalytic converter installed in the exhaust pipe of an internal combustion engine mounted on a vehicle, A cylindrical substrate supporting a catalyst, It comprises a first electrode and a second electrode that conduct current on the substrate, The first electrode comprises a first electrode portion fixed to the surface of the substrate and a first connection portion extending in a direction away from the outer peripheral surface of the substrate and connected to an external power source to supply power to the first electrode portion. The second electrode has a second electrode portion fixed to the surface of the substrate at a location spaced apart from the first electrode portion in the circumferential direction of the substrate, and a second connection portion extending in a direction away from the outer surface of the substrate and connected to the external power supply to supply power to the second electrode portion. The first and second connecting portions are arranged side by side, spaced apart along the direction in which the central axis of the base material extends, and are positioned at the uppermost position of the base material when mounted on a vehicle. An electrically heated catalytic converter.

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