Catalytic converter

Abstract

To provide a catalytic converter capable of improving sensitivity of a sensor for detecting fluid while suppressing deterioration in purification efficiency of the fluid.SOLUTION: A catalytic converter includes a first catalyst case for storing a catalyst for purifying fluid, a second catalyst case for storing a catalyst for purifying the fluid on the downstream side of the first catalyst case, and a connection part to which a sensor for detecting the fluid is attached, which is connected between the first catalyst case and the second catalyst case. The cross-sectional area of a first flow passage of the fluid in the connection part is smaller than the cross-sectional area of a second flow passage of the fluid in the first catalyst case. The first flow passage is provided so that the deviation width on a sensor attaching position side with respect to the second flow passage is larger than the deviation width on an opposite side facing the attaching position.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a catalytic converter.

Background Art

[0002] For example, Patent Document 1 describes a catalytic converter including two accommodating portions that accommodate a catalyst carrier carrying a catalyst for purifying exhaust gas, and a reduced-diameter portion that connects between the accommodating portions and has a mounting seat for an oxygen concentration sensor.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The sensitivity of the oxygen concentration sensor varies depending on the flow rate of the exhaust gas hitting the detection portion at the tip thereof. Depending on the shape of the reduced-diameter portion, there is a possibility that the exhaust gas hits the detection portion at the tip of the oxygen concentration sensor at a low flow rate, resulting in insufficient sensitivity of the oxygen concentration sensor. On the other hand, if the detection portion is extended toward the region with a high flow rate inside the reduced-diameter portion, the gas flow rate hitting the detection portion can be increased to improve the sensitivity. However, there is a possibility that the purification efficiency of the exhaust gas decreases on the downstream side because the detection portion blocks the flow of the exhaust gas.

[0005] Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide a catalytic converter capable of improving the sensitivity of a sensor for detecting a fluid while suppressing a decrease in the purification efficiency of the fluid.

Means for Solving the Problems

[0006] The catalyst converter of the present invention includes a first catalyst case that houses a catalyst for purifying a fluid, a second catalyst case that houses a catalyst for purifying the fluid on the downstream side of the first catalyst case, and a sensor for detecting the fluid is attached, and a connecting portion connected between the first catalyst case and the second catalyst case. The cross-sectional area of the first flow path of the fluid in the connecting portion is smaller than the cross-sectional area of the second flow path of the fluid in the first catalyst case. The first flow path is provided such that the deviation width on the side of the attachment position of the sensor with respect to the second flow path is larger than the deviation width on the opposite side facing the attachment position. In the cross-section of the first flow path, the dimension in the first direction in which the sensor protrudes into the first flow path is larger than the dimension in the second direction that is substantially orthogonal to the first direction. 。

[0008] In the above catalyst converter, in the second direction, the dimension of the first flow path may be smaller than the dimension of the second flow path.

[0009] In the above catalyst converter, the second flow path may be inclined with respect to the third flow path of the fluid in the second catalyst case.

[0010] In the above catalyst converter, the connecting portion includes a first press-worked part having a cone shape with a first opening end defining the first flow path at the apex, and a second press-worked part and a third press-worked part having a cone shape with a second opening end defining the first flow path at the apex and divided into two along the flow direction of the fluid. The first press-worked part, the second press-worked part, and the third press-worked part are assembled such that the first opening end and the second opening end are connected to each other. One of the first press-worked part and the second press-worked part may be provided with an attachment portion for attaching the sensor.

Advantages of the Invention

[0011] According to the present invention, it is possible to improve the sensitivity of a sensor for detecting a fluid while suppressing a decrease in the purification efficiency of the fluid in the catalyst converter.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

DETAILED DESCRIPTION OF THE INVENTION

[0013] FIG. 1 is a plan view showing an example of a catalytic converter 1 in side view and top view. The catalytic converter 1 is provided in an exhaust system of an internal combustion engine such as a gasoline engine, for example. The catalytic converter 1 has an upstream catalytic case 10, a downstream catalytic case 11, and a connecting part 12.

[0014] The upstream catalytic case 10 and the downstream catalytic case 11 are, for example, cylindrical metal members, and are connected in series via the connecting part 12. The upstream catalytic case 10 and the downstream catalytic case 11 each have exhaust gas flow paths 90 and 91 discharged from an exhaust manifold of the internal combustion engine. The flow paths 90 and 91 extend along the central axes of the cylindrical shapes of the upstream catalytic case 10 and the downstream catalytic case 11, respectively. In the flow of the exhaust gas in the catalytic converter 1, the upstream catalytic case 10 is provided upstream of the downstream catalytic case 11. Note that the exhaust gas is an example of a fluid. Also, the flow path 90 is an example of a second flow path, and the flow path 91 is an example of a third flow path.

[0015] The upstream catalyst case 10 houses the catalyst carrier 100, and the downstream catalyst case 11 houses the catalyst carrier 110. The catalyst carriers 100 and 110 are respectively arranged in the flow paths 90 and 91 and carry a catalyst (such as palladium) for purifying the exhaust gas. Note that the upstream catalyst case 10 is an example of the first catalyst case, and the downstream catalyst case 11 is an example of the second catalyst case.

[0016] The connection part 12 has the air-fuel ratio sensor 2 attached thereto and is connected between the upstream catalyst case 10 and the downstream catalyst case 11. The connection part 12 has a reduced-diameter part 120, a flow path part 122, and an enlarged-diameter part 121. The reduced-diameter part 120 is provided upstream of the flow path part 122, and the enlarged-diameter part 121 is provided downstream of the flow path part 122. The reduced-diameter part 120 and the enlarged-diameter part 121 have a cone shape with the apex facing the flow path part 122 side, and the flow path part 122 has a substantially cylindrical shape. Note that an oxygen concentration sensor may be attached to the connection part 12 instead of the air-fuel ratio sensor 2.

[0017] The exhaust gas flow path 920 in the reduced-diameter part 120 narrows from the exhaust gas flow path 90 in the upstream catalyst case 10 toward the exhaust gas flow path 92 in the reduced-diameter part 120. The exhaust gas flow path 921 in the enlarged-diameter part 121 expands from the exhaust gas flow path 92 in the reduced-diameter part 120 toward the exhaust gas flow path 91 in the downstream catalyst case 11. The cross-sectional area of the flow path 92 in the flow path part 122 is substantially constant along the flow of the exhaust gas. Note that the flow path 92 is an example of the first flow path.

[0018] On the upper surface of the reduced-diameter part 120, a mounting seat 123 for mounting the air-fuel ratio sensor 2 is provided. The air-fuel ratio sensor 2 has a substantially cylindrical shape and is inserted into the central hole of the mounting seat 123. When inserted, the detection part 2a at the tip of the air-fuel ratio sensor 2 is exposed to the flow path 92 in the flow path part 122. Note that the mounting seat 123 is an example of a mounting part for mounting the air-fuel ratio sensor 2.

[0019] The air-fuel ratio sensor 2 is an example of a sensor that detects exhaust gas. Specifically, the air-fuel ratio sensor 2 detects the air-fuel ratio of the internal combustion engine from the exhaust gas hitting the detection unit 2a. The air-fuel ratio sensor 2 transmits a detection signal of the air-fuel ratio to a control device (not shown), and the control device performs feedback control on the internal combustion engine based on the detection signal. Therefore, if the sensitivity of the air-fuel ratio sensor 2 is low, the detection of the air-fuel ratio may be delayed and there is a risk that the control accuracy may decrease because it cannot keep up with the speed of the feedback control.

[0020] On the other hand, in order to increase the sensitivity of the air-fuel ratio sensor 2, the flow path 92 in the connecting portion 12 is provided so that the mounting seat 123 side is more displaced than the opposite side of the mounting seat 123 with respect to the flow path 90 in the upstream catalyst case 10. For this reason, in a side view of the catalytic converter 1, the difference Va in the height direction between the upper surface of the flow path portion 122 where the mounting seat 123 of the air-fuel ratio sensor 2 is provided and the upper surface of the upstream catalyst case 10 is larger than the difference Vb in the height direction between the lower surface of the flow path portion 122 and the lower surface of the upstream catalyst case 10.

[0021] FIG. 2 is a cross-sectional view of the catalytic converter 1 taken along line A-A of FIG. 1. FIG. 2 shows the flow path 92 in the connecting portion 12 and the flow path 90 in the upstream catalyst case 10 in a front view facing the direction in which the exhaust gas flows. The air-fuel ratio sensor 2 protrudes into the flow path 92 in the connecting portion 12, and the detection unit 2a at its tip is exposed to the flow path 92. Here, the protruding direction of the air-fuel ratio sensor 2 is taken as the height direction of the flow path 92, and the direction orthogonal to the height direction is taken as the width direction of the flow path 92. The height direction is an example of the first direction, and the width direction is an example of the second direction.

[0022] The cross-sectional area of the flow path 92 in the connecting portion 12 is smaller than that of the flow path 90 in the upstream catalyst case 10. Also, the flow path 92 in the connecting portion 12 is provided such that the displacement width T of the mounting seat 123 side of the air-fuel ratio sensor 2 with respect to the flow path 90 in the upstream catalyst case 10 is larger than the displacement width B of the opposite position 124 side facing the mounting seat 123.

[0023] Therefore, as shown in FIG. 1, in a side view of the catalytic converter 1, the flow Fa of the exhaust gas on the upper side in the flow path 90 of the upstream catalytic case 10 hits the detection part 2a of the air-fuel ratio sensor 2 concentratedly. Specifically, the exhaust gas on the upper side flows along the flow path 90 in the upstream catalytic case 10, changes its direction downward along the flow path 920 in the reduced-diameter part 120, and flows into the flow path 92 in the flow path part 122 and hits the detection part 2a concentratedly. Thereby, compared with the case where the displacement width T on the mounting seat 123 side is the same as the displacement width B on the opposite position 124 side, the flow velocity of the exhaust gas in the detection part 2a of the air-fuel ratio sensor 2 increases.

[0024] On the other hand, in a side view of the catalytic converter 1, the flow Fb of the exhaust gas on the lower side in the flow path 90 of the upstream catalytic case 10 has less change in the flowing direction compared with the flow Fa of the exhaust gas on the upper side, flows substantially linearly, flows into the flow path 92 in the flow path part 122, and flows into the flow path 91 in the downstream catalytic case 11 without hitting the detection part 2a. For this reason, the flow Fb of the exhaust gas on the lower side is less likely to be blocked by the detection part 2a compared with the flow Fa of the exhaust gas on the upper side, and the pressure loss can be suppressed.

[0025] Therefore, the catalytic converter 1 can improve the sensitivity of the air-fuel ratio sensor 2 while suppressing a decrease in the purification efficiency of the exhaust gas.

[0026] Further, as shown in FIG. 2, in the cross section of the flow path 92, the dimension H in the height direction is larger than the dimension W in the width direction. In this example, the dimension H in the height direction is the distance from the root of the exposed area of the detection part 2a in the flow path 92 to the opposite position 124 facing the mounting seat 123. For this reason, compared with the case where the dimension H in the height direction is equal to or less than the dimension W in the width direction, the exhaust gas is less likely to diffuse left and right in the width direction of the flow path 92 and is likely to concentrate on the detection part 2a of the air-fuel ratio sensor 2. For this reason, the flow velocity of the exhaust gas in the detection part 2a of the air-fuel ratio sensor 2 increases, and the sensitivity of the air-fuel ratio sensor 2 is further improved. Note that, different from this example, in the case of the flow path 92 having a cross-sectional shape in which the dimension W in the width direction varies according to the position in the height direction, for example, by setting the dimension H in the height direction to be larger than the maximum value of the dimension W in the width direction, the above effects can be obtained.

[0027] Further, since the cross-section of the flow path 92 is oval-shaped, the resistance to stress is improved. For example, if the cross-section of the flow path 92 is a shape with a small radius of curvature at the bent portion, such as a polygonal shape or a teardrop shape, when the connecting portion 12 expands due to the heat of the exhaust gas and stress is generated, or when stress is generated due to vibration, there is a risk that stress will concentrate on the bent portion and cause deformation. Therefore, by using a shape with a large radius of curvature at the bent portion like the oval shape, stress concentration can be suppressed and the strength can be improved.

[0028] Also, in a top view of the catalytic converter 1, the positions of the left and right side surfaces of the flow path portion 122 are shifted toward the center by a difference Vs from the positions of the left and right side surfaces of the upstream catalytic case 10. Specifically, as shown in FIG. 2, in the width direction, the dimension W of the flow path 92 is smaller than the dimension Wu of the flow path 90 in the upstream catalytic case 10. Note that the shift width L of the left side surface of the flow path portion 122 with respect to the left side surface of the upstream catalytic case 10 and the shift width R of the right side surface of the flow path portion 122 with respect to the right side surface of the upstream catalytic case 10 may be the same or different.

[0029] Therefore, in a top view of the catalytic converter 1 shown in FIG. 1, the flow Fc of the exhaust gas on the left and right sides in the flow path 90 of the upstream catalytic case 10 concentrates and hits the detection portion 2a of the air-fuel ratio sensor 2. Specifically, the exhaust gas on the left and right sides flows along the flow path 90 in the upstream catalytic case 10, changes its direction toward the center along the flow path 920 in the reduced-diameter portion 120, and flows into the flow path 92 in the flow path portion 122 and hits the detection portion 2a so as to concentrate. Therefore, the flow velocity of the exhaust gas at the detection portion 2a of the air-fuel ratio sensor 2 increases, and the sensitivity of the air-fuel ratio sensor 2 is further improved.

[0030] FIG. 3 is a side view showing another example of the catalytic converter 1a. The catalytic converter 1a is different from the above-described catalytic converter 1 in that the angles of the flow path 90 in the upstream catalytic case 10 and the flow path 91 in the downstream catalytic case 11 are different.

[0031] The catalytic converter 1a has a connecting portion 12a corresponding to the upstream catalytic case 10 and the downstream catalytic case 11 with different angles instead of the connecting portion 12. The connecting portion 12a has a reduced-diameter portion 120a, a flow path portion 122, and an enlarged-diameter portion 121a. The reduced-diameter portion 120a is formed in a shape corresponding to the positional relationship between the flow path portion 122 and the upstream catalytic case 10, and the enlarged-diameter portion 121a is formed in a shape corresponding to the positional relationship between the flow path portion 122 and the downstream catalytic case 11. For example, since the inlet of the flow path 91 of the downstream catalytic case 11 is above the outlet, the region on the upper surface side of the enlarged-diameter portion 121a is formed wider than the region on the lower surface side.

[0032] Also, in this example too, the flow path 92 in the flow path portion 122 is provided so that the mounting seat 123 side is more displaced from the opposite side of the mounting seat 123 than the flow path 90 in the upstream catalytic case 10. The upper surface of the flow path portion 122 near the mounting seat 123 is displaced by a difference Vc (>0) from the upper surface of the upstream catalytic case 10. On the other hand, the lower surface of the flow path portion 122 near the position facing the mounting seat 123 is substantially at the same position as the lower surface of the upstream catalytic case 10. Therefore, the same effect as the above-described catalytic converter 1 can be obtained even with the catalytic converter 1a in this example.

[0033] When the flow path 90 in the upstream catalytic case 10 and the flow path 91 in the downstream catalytic case 11 are arranged substantially in parallel as in the above-described catalytic converter 1, it may be difficult to mount the catalytic converter 1 depending on the shape of the internal combustion engine. On the other hand, in the catalytic converter 1a, since the flow path 90 in the upstream catalytic case 10 is inclined with respect to the flow path 91 in the downstream catalytic case 11, it becomes easy to mount the catalytic converter 1a in the above-described case.

[0034] Also, as described below, when the connecting portions 12, 12a are formed of press-worked parts, it is easy to form the reduced-diameter portions 120, 120a and the enlarged-diameter portions 121, 121a according to the positional relationship with the upstream catalytic case 10 and the downstream catalytic case 11.

[0035] FIG. 4 is a plan view showing an example of the press-worked part 12A of the connecting part 12, and FIG. 5 is a plan view showing examples of the other two press-worked parts 12B and 12C of the connecting part 12. The connecting part 12 includes, as an example, three press-worked parts 12A to 12C. In this example, the press-worked parts 12A to 12C of the connecting part 12 shown in FIG. 1 are cited, but the connecting part 12a shown in FIG. 3 is also formed from the press-worked parts of the connecting part 12.

[0036] FIG. 4 shows the press-worked part 12A including a part of the reduced-diameter portion 120 and the flow path portion 122 in front view, top view, and side view, respectively. The press-worked part 12A is an example of the first press-worked part. The press-worked part 12A has a cone shape with an open top and bottom. The press-worked part 12A is provided with an open end 122a that defines the flow path 92 in the flow path portion 122 at the apex. Also, the end portion 120E on the side opposite to the open end 122a is joined to the upstream catalyst case 10. For this reason, an opening is formed at the end portion 120E with a substantially constant diameter. Note that the open end 122a is an example of the first open end.

[0037] The press-worked part 12A is formed by pressing a metal plate into a cone shape. Here, the open end 122a is formed by, for example, burring. The open end 122a is fitted to the open ends of the other press-worked parts 12B and 12C described later.

[0038] FIG. 5 shows the press-worked parts 12B and 12C including a part of the enlarged-diameter portion 121 and the flow path portion 122 in front view, top view, and side view, respectively. The press-worked parts 12B and 12C are shown in a state of being fitted to each other.

[0039] The press - formed parts 12B and 12C each have a cone shape similar to the press - formed part 12A, which is divided into two along the direction of the exhaust gas flow. In the cone shape, an opening end 122bc that defines the flow path 92 in the flow path portion 122 is provided at the apex. Also, an end portion 121E on the side opposite to the opening end 122bc is joined to the downstream catalyst case 11. For this reason, an opening is formed at the end portion 121E with a substantially constant diameter. The opening end 122bc is fitted into the opening end 122a of the press - formed parts 12B and 12C.

[0040] The press - formed parts 12B and 12C divide the cross - section of the flow path 92 into two across the diagonal line L. The diagonal line L extends obliquely with respect to the height direction and the width direction so as not to cross the mounting seat 123. Specifically, the diagonal line L divides the oval - shaped cross - section of the flow path 92 into two substantially symmetric regions.

[0041] The press - formed parts 12B and 12C have a portion 121b and 121c obtained by dividing the diameter - expanded portion 121 into two, and a portion 122b and 122c obtained by dividing the opening end 122bc into two. The opening end 122bc is formed by welding the end faces of the portions 122b and 122c of each press - formed part 12B and 12C in a state where they are in contact with each other, as indicated by the symbol C. The area of the opening portion of the opening end 122bc is larger than the opening end 122a so as to partially overlap and fit with the opening end 122a. The diameter - expanded portion 121 is formed by overlapping and welding the bent portions Ea and Eb, which are obtained by bending both end edges of the portion 121c of the press - formed part 12C in a stepped shape, to both end edges of the portion 121b of the other press - formed part 12B. Also, the press - formed part 12B has a mounting seat 123. Note that the opening end 122bc is an example of a second opening end.

[0042] The press - formed parts 12B and 12C are formed by press - working a metal plate. For example, the press - formed parts 12B and 12C are processed from a common metal plate with the portions 121b and 121c obtained by dividing the diameter - expanded portion 121 facing each other. For this reason, the production efficiency is improved compared to the case where the press - formed parts 12B and 12C are processed from separate metal plates.

[0043] Further, the press - formed parts 12B and 12C have a shape in which a cone shape is divided into two parts, and a mounting seat 123 is formed by drilling in one of the press - formed parts 12B. Therefore, when comparing with the case where the diameter - expanding part 121 and the flow - path part 122 are formed as one part like the other press - formed part 12A, it is easy to arbitrarily process the length and shape of the opening end 122bc, and it is also easy to form the mounting seat 123 on the opening end 122bc.

[0044] FIG. 6 is a diagram showing an example of the assembling method of the press - formed parts 12A to 12C. In FIG. 6, the same reference numerals are given to the components common to FIGS. 4 and 5, and the description thereof is omitted.

[0045] Reference symbol Ga shows a front view showing the assembly of the press - formed parts 12B and 12C. By overlapping the bent portions Ea and Eb of the portion 121c of the press - formed part 12C with the respective edges of the portion 121b of the press - formed part 12B, the press - formed parts 12B and 12C are fitted together (see the arrow). At this time, the end faces of the portions 122b and 122c of the respective press - formed parts 12B and 12C are in contact with each other so that the opening end 122bc is formed. Thereby, a cone - shaped member including a part of the diameter - expanding part 121 and the flow - path part 122 is completed.

[0046] Reference symbol Gb shows a side view of the assembly of the combined press - formed parts 12B and 12C and the press - formed part 12A. The tip portion of the opening end 122a of the press - formed part 12A overlaps the tip of the opening end 122bc of the press - formed parts 12B and 12C, so that the opening ends 122a and 122bc are fitted to each other (see the arrow). Thereby, the connecting portion 12 is completed. In this example, among the connecting portion 12, the member on the diameter - expanding part 121 side is constituted by two press - formed parts 12B and 12C, and the member on the reduced - diameter part 120 side is constituted by one press - formed part 12A. Conversely, the member on the diameter - expanding part 121 side may be constituted by one press - formed part A, and the member on the reduced - diameter part 120 side may be constituted by two press - formed parts 12B and 12C.

Explanation of reference symbols

[0047] 1,1a catalytic converter 2 air-fuel ratio sensor (sensor) 10 upstream catalyst case (first catalyst case) 11 downstream catalyst case (second catalyst case) 12 connecting part 12A~12C press-worked parts 90~92 flow path 122 flow path part 122a,122bc opening ends (first opening end and second opening end) 123 mounting seat (mounting part)

Claims

1. A first catalyst case that houses a catalyst for purifying a fluid, A second catalyst case that houses a catalyst for purifying the fluid on the downstream side of the first catalyst case, It has a sensor for detecting the fluid attached thereto and a connecting portion connected between the first catalyst case and the second catalyst case, The cross-sectional area of the first flow path of the fluid in the connecting portion is smaller than the cross-sectional area of the second flow path of the fluid in the first catalyst case, The first flow path is provided such that the displacement width on the side of the mounting position of the sensor with respect to the second flow path is larger than the displacement width on the opposite side facing the mounting position, In the cross-section of the first flow path, the dimension in the first direction in which the sensor protrudes into the first flow path is larger than the dimension in the second direction that is substantially orthogonal to the first direction, A catalytic converter.

2. In the second direction, the dimension of the first flow path is smaller than the dimension of the second flow path, The catalytic converter according to claim 1.

3. The second flow path is inclined with respect to the third flow path of the fluid in the second catalyst case, The catalytic converter according to claim 1 or 2.

4. The connecting portion A first press-worked part having a conical shape with a first opening end that defines the first flow path provided at the apex, It includes a second press-worked part and a third press-worked part having a conical shape with a second opening end that defines the first flow path provided at the apex and divided into two along the direction of fluid flow, The first press-worked part, the second press-worked part, and the third press-worked part are assembled such that the first opening end and the second opening end are connected to each other, One of the first press-worked part and the second press-worked part is provided with a mounting portion for mounting the sensor, The catalytic converter according to claim 1 or 2.

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