JP4501971B2 - Exhaust purification device - Google Patents

Description

  The present invention relates to an exhaust gas purification device in which a protective cover is mounted on a shell of an exhaust gas purification unit with a space layer therebetween, and more particularly to an exhaust gas purification device that is suitable when it is difficult to clamp the end of the protective cover.

  Recently, in vehicles such as automobiles equipped with an internal combustion engine, a high level of exhaust gas purification performance is required. Therefore, a catalyst for detoxifying harmful substances in the exhaust in the exhaust path of the internal combustion engine and particulates in the exhaust An exhaust emission control device is provided in which a filter for collecting substances is housed in a cylindrical shell. Further, since the exhaust purification catalyst has insufficient exhaust purification performance until it reaches the activation temperature region, it is necessary to raise the temperature of the catalyst to the activation temperature region early when the internal combustion engine is started. In many cases, it is arranged immediately after the exhaust manifold near the exhaust port to enhance the warming effect, or the shell of the exhaust purification unit is covered with a protective cover to enhance the heat shielding effect such as heat insulation and heat retention.

  As this type of exhaust emission control device, for example, a catalyst unit shell and a protective cover are used as inner and outer cylindrical shells, and a heat insulating space is formed between the inner and outer cylindrical shells (for example, Patent Documents). 1).

In addition, the inner cylindrical shell of the inner and outer cylindrical shells is thickened to shield the radiant heat from the catalyst, and the end of the outer cylindrical shell is reduced in diameter by spinning. Thus, it is known that the outer cylindrical shell is not required to have a so-called mid-alignment structure (see, for example, Patent Document 2). In this case, the one end side straight portion of the outer cylindrical shell is supported by the one end side straight portion of the inner cylindrical shell via the cylindrical metal mesh.
Japanese Patent Laid-Open No. 11-36851 JP 2002-227640 A

  In the conventional exhaust purification apparatus as described above, both ends of the protective cover are absorbed by the catalyst unit while absorbing the difference in expansion and contraction due to heat between the shell of the catalyst unit and the outer cylindrical shell serving as the protective cover. If it was not securely clamped to both ends of the shell or the exhaust pipe, abnormal noise was likely to occur due to contact between the protective cover and the shell when the vehicle was running. For this reason, a straight portion is usually provided at each end of the protective cover and the end of the catalyst unit, the end of the catalyst unit has a double tube structure, and the straight portion is clamped with a clamp member. .

  However, as the recent demand for exhaust purification performance increases, it is sometimes necessary to place the exhaust purification device closer to the exhaust port side of the engine, and thus the straightness of the protective cover may not be ensured. In that case, the edge of the protective cover is cut at the frustum-shaped part of the shell of the catalyst unit, and a gap is formed between the edge of the protective cover and the shell, so that foreign matter such as dead grass is mixed in the protective cover. There was a problem that it was easy to do.

  On the other hand, it is conceivable to reduce the gap between the shell only at the extreme end of the protective cover, but it requires dimensional accuracy of parts and high level of assembly accuracy, which not only increases costs. When the protective cover comes into contact with the frustum-shaped portion of the catalyst unit shell, the above-described abnormal noise is generated.

  Further, if the end of the outer cylindrical shell is fixed to the inner cylindrical shell, not only the above-described difference in expansion / contraction due to heat between the inner and outer cylindrical shells can be absorbed, but also when the catalyst unit is overheated. There is a problem in that the heat dissipation is poor and the catalyst unit is likely to deteriorate early.

  The present invention has been made to solve the above-described conventional problems, and does not cause noise due to contact between the protective cover and the shell of the exhaust purification unit such as the catalyst unit, and overheats the exhaust purification unit. It is an object of the present invention to provide a low-cost exhaust purification device with excellent exhaust purification performance that can ensure heat dissipation at the time, and can reliably prevent foreign matter from entering the space layer. To do.

In order to achieve the above object, an exhaust emission control apparatus according to the present invention includes: (1) an exhaust purification unit positioned in an exhaust path of an internal combustion engine; and a cylindrical shape that houses the exhaust purification unit; a shell having a shaped portion, and a protective cover mounted with a space layer on the outer peripheral side of the shell, an exhaust gas purification device having at least one end portion of the protective cover to the frustum-shaped portion of the shell On the other hand, the porous member is opposed to the space layer and has air permeability and flexibility so as to partition the inside and outside of the protective cover between at least one end of the protective cover and the frustum-shaped portion of the shell. Is provided.

With this configuration, a breathable and flexible porous member is disposed between at least one end of the protective cover and the frustum-shaped portion of the shell . Therefore, there is no noise due to interference between the protective cover and the shell of the catalyst unit, and the porous member can not only ensure heat dissipation when the exhaust purification unit is overheated, but also foreign matter can enter the space layer. Can be reliably prevented.

In the exhaust emission control device according to (1), preferably, (2) the porous member has a hollow cross section, and the space layer on the inner surface side of the protective cover is air circulated to the outside of the protective cover. Communication is possible. (3) The porous member is formed in a string shape extending in the circumferential direction of the frustum-shaped portion of the shell, and at least one end portion of the protective cover and the frustum-shaped portion of the shell. The gap between them is blocked.

With this configuration, the porous member is not specially molded to follow the periphery of the frustum-shaped portion of the shell, and the gap between the end of the protective cover and the frustum-shaped portion of the shell of the exhaust gas purification unit is eliminated. The gap can be reliably closed by the porous member so as to allow ventilation, and the porous member can be easily attached to the frustum-shaped portion of the shell. Here, the string-like shape is a dimension in which the thickness of the porous member in the shell radial direction and the width of the porous member in the shell length direction are close to each other, and the end of the protective cover and the cone of the shell of the exhaust purification unit. When placed between the trapezoidal part, the elongated shape of a circular cross-section or polygonal or other irregular cross-section that makes a line contact or surface contact in an annular shape with a width of, for example, about the thickness of the heat shield space layer with respect to both it is a meaning with.

In the exhaust emission control device according to the above (2) or (3) , (4) it is preferable that the porous member is made of a cylindrical metal mesh.

  In this case, it is only necessary to place the metal mesh knitted along the periphery of the frustum-shaped portion of the shell of the exhaust purification unit, and it is very easy to install and has good adhesion, and also has excellent heat resistance, so it can be Heat dissipation can be secured.

In the exhaust emission control device according to the above (1) to (4) , (5) a retaining portion for preventing the porous member from slipping out from the inside of the protective cover is provided at one end of the protective cover; The porous member is preferably held between the retaining portion and the frustum-shaped portion of the shell. (6) The protective cover has a plurality of concave and convex ribs spaced at least in the circumferential direction, and the porous member is between the retaining portion, the plurality of ribs, and the frustum-shaped portion of the shell. It is more preferable that it is held at the surface.

In this case, the position of the porous member with respect to the protective cover is accurately held by the retaining portion at the optimum position in the length direction of the exhaust purification device, and the overheated state is between the protective cover and the shell of the exhaust purification unit. A gap suitable for heat dissipation can be easily set.

Moreover, in the exhaust emission control device according to the above (1) to (6) , (7) the protective cover includes a pair of cover members each having a concave shape on the inner surface facing the shell, and the porous member includes It is preferable to have a portion fixed to at least one of the pair of cover members.

  With this configuration, the porous member can be handled integrally with the cover member, the assembly can be facilitated, and the assembly position can be stably assembled. In addition, a part of the arc-shaped porous member is fixed to each of the pair of cover members, and at the same time the pair of cover members are mounted on the shell of the exhaust purification unit, the porous member is exhausted with the cover member. It can also be mounted between the shell of the unit.

According to the present invention, the air-permeable and flexible porous member is provided between at least one end portion of the protective cover on the outer peripheral side of the shell and the frustum-shaped portion of the shell. Low noise that does not cause noise due to interference with the shell, can ensure heat dissipation when the exhaust purification unit is overheated by the porous member , and can reliably prevent foreign matter from entering the space layer It is possible to provide an exhaust purification device that is excellent in exhaust purification performance at a low cost.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is an external perspective view of an exhaust purification apparatus according to an embodiment of the present invention, and FIG. 2 is a perspective view showing a state where an upper half portion of a protective cover of the exhaust purification apparatus according to the embodiment is removed. FIG. 3 is a partial cross-sectional view showing the main configuration of one end of the protective cover of the exhaust emission control device according to the embodiment. FIG. 4 is a cross-sectional view showing a mounting portion of the porous member to the protective cover in the exhaust gas purification apparatus according to the embodiment. FIG. 4A is an aspect in which the porous member is formed as a single product in an annular shape. (B) shows another embodiment in which the porous member is divided into two arc-shaped members.

As shown in FIGS. 1 and 2, the exhaust purification apparatus of this embodiment includes a known exhaust purification unit 11 inserted into an exhaust path 10 from an internal combustion engine (not shown) and a shell that houses the exhaust purification unit 11. 12 and a protective cover 14 mounted around the shell 12 (outer peripheral side) with a heat shield space layer 13 (space layer) therebetween.

  The exhaust purification unit 11 is a known unit having a shell 12 containing a catalyst for detoxifying harmful substances in the exhaust in the exhaust path of the internal combustion engine, a filter for collecting particulate substances in the exhaust, and the like. It incorporates a three-way catalyst used in cars, an oxidation catalyst and a reduction catalyst used in diesel cars, or a DPF (diesel particulate filter). Further, the shell 12 has a cylindrical shape in the middle in the longitudinal direction, and has heat-resistant structures having frustum-shaped portions 12a and 12b connected to the front and rear exhaust pipes 10a and 10b at least at one end, for example, both ends. A container, for example, a stainless steel container.

  At least one end portion of the protective cover 14, for example, both end portions 14 a and 14 b are opposed to the frustum-shaped portions 12 a and 12 b of the shell 12 in the radial direction of the shell 12 with the heat shield space layer 13 interposed therebetween. Further, between the both end portions 14a and 14b of the protective cover 14 and the frustum-shaped portions 12a and 12b of the shell 12, a string shape having flexibility and heat resistance so as to partition and separate the inside and outside of the protective cover 14, respectively. An annular porous member 21 is provided. The flexibility here means that when the frustum-shaped portions 12a and 12b of the shell 12 and the both ends 14a and 14b of the protective cover 14 are compressed from both sides, they are elastically deformed following them. It means that it can be bent (compressibility), or in addition, it can be bent at the time of assembly, and heat resistance means heat resistance equivalent to or higher than that of the protective cover 14.

The porous member 21 is formed in a string shape having a hollow cross section extending in the circumferential direction of the frustum-shaped portions 12a and 12b of the shell 12, and the protective cover 14 and the shell are formed at both ends 14a and 14b of the protective cover 14. The gap between the twelve frustum-shaped portions 12a and 12b is closed and substantially constant. Here, the string shape means a dimension in which the thickness of the porous member in the radial direction of the shell 12 and the width of the porous member in the length direction of the shell 12 are close to each other, for example, the ratio of the thickness t and the width w shown in FIG. It means an elongated shape set so that t / w is larger than 1/2 and smaller than 2, and may be not only a circular cross section but also a polygonal or other irregular cross section .

  When the string-like porous member 21 is disposed between the end portions 14 a and 14 b of the protective cover 14 and the frustum-shaped portions 12 a and 12 b of the shell 12 of the exhaust purification unit 11, For example, the end portions 14a and 14b and the frustum-shaped portions 12a and 12b of the shell 12 of the exhaust purification unit 11 are annularly line-contacted or surface-contacted with a width equal to or less than the thickness of the heat shield space layer 13, for example. Long and flexible.

Specifically, the porous member 21 in the present embodiment is made of a metal mesh made of, for example, a stainless steel wire knitted into a cylindrical shape. This metal mesh is about a fraction of the density of ordinary stainless steel (g / cm ³ ), and its wire diameter is smaller than a fraction of the plate pressure of the protective cover, When the protective cover 14 is attached to the shell 12 of the exhaust purification unit 11, it is sufficient to closely contact the end portions 14 a and 14 b of the protective cover 14 and the frustum-shaped portions 12 a and 12 b of the shell 12 of the exhaust purification unit 11. It has excellent flexibility, heat resistance and corrosion resistance, and filter characteristics and air permeability that prevent foreign matter from entering the heat shielding space layer 13.

Of course, the porous member 21 is not limited to a tubular metal mesh as long as it has these characteristics, and if it is hollow, for example, it seems that a thin metal wire is wound spirally. The metal fiber may be a non-woven fabric or a low-density string, or a thin metal plate wound with a large number of small-diameter punch holes or narrow slits. In short, the porous member 21 only needs to be capable of forming a large number of air passages (porous) that allow air to pass through the inside and outside of the protective cover 14 with a size that can prevent entry of foreign matter such as dead grass. .

  On the other hand, both end portions 14a and 14b of the protective cover 14 are provided with a retaining portion 14c that prevents the porous member 21 from coming out of the inside of the protective cover 14, and this retaining portion 14c has a cylindrical shape. The porous member 21 made of a metal mesh is smaller than the outer diameter of the porous member 21 when arranged in a winding shape extending around the ends of the frustum-shaped portions 12a, 12b of the shell 12 of the exhaust purification unit 11. It has an inner diameter.

  More specifically, as shown in FIG. 3, the retaining portions 14 c provided at both end portions 14 a and 14 b of the protective cover 14 are formed on the frustum-shaped portions 12 a and 12 b of the shell 12 of the exhaust purification unit 11, for example. A diameter-reduced portion which is provided continuously with the cone portion 14f facing each other with a certain gap and which is reduced in diameter along the outer periphery of the porous member 21 from the end portion of the cone portion 14f to the vicinity of the center diameter of the porous member 21. 14s. In the present embodiment, an annular opening that is further reduced in diameter to an inner diameter that forms a gap g that is suitable for heat dissipation when the exhaust purification unit 11 is overheated with the exhaust pipe 10 continuously from the reduced diameter portion 14s. It has an edge 14t. Here, the portion of the gap g on the left side of the porous member 21 in FIG. 3 is partitioned outside the protective cover 14 by the porous member 21, and the space in the protective cover 14 on the right side of the porous member 21 in FIG. That is, the portion of the heat shield space layer 13 is partitioned in the protective cover 14 by the porous member 21.

  The porous member 21 is restricted from moving leftward in the figure by the retaining portion 14c between the retaining portion 14c of the protective cover 14 and the frustum-shaped portions 12a and 12b of the shell 12 of the exhaust purification unit 11. At the same time, the movement to the right in the figure is restricted by the frustum-shaped portions 12a and 12b of the shell 12, and is held between the two.

  As shown in FIGS. 1 and 4, the protective cover 14 includes a pair of cover members 31 and 32 each having a concave shape on the inner surface facing the shell 12, and the porous member 21 includes a pair of cover members 31 and 32. For example, it is fixed to at least one of 32 by spot welding. The protective cover 14 is pressed into an uneven shape so as to have a plurality of ribs R1 and R2 that are spaced apart in the circumferential direction and the longitudinal direction, respectively, and the retaining portion 14c is one of the annular ribs R2 that are spaced apart in the longitudinal direction. An annular groove is formed inwardly so as to function as a part.

  For example, as shown in FIG. 4A, the porous member 21 may be formed as a single product in an annular shape, but as shown in FIG. 4B, the porous member 21 is composed of a pair of arcuate parts 21a and 21b. Alternatively, the pair of arcuate parts 21a and 21b may be spot-welded to the cover members 31 and 32 at a plurality of locations, respectively. In the latter case, when the pair of cover members 31 and 32 are mounted on the shell 12 of the exhaust purification unit 11 to constitute the protective cover 14, the porous member 21 is opposed or abutted with both ends thereof facing each other. 14 and the shell 12 of the exhaust purification unit 11 are mounted in a ring shape. Further, the cover members 31 and 32 have a plurality of fastening holes 31c and 31d formed in the longitudinal intermediate portions of the flange portions 31a, 31b, 32a and 32b on both sides in the short direction (the fastening of the flange portion 31a in FIG. 1). Only the holes are shown and the other parts are not shown) and are fastened together by bolts (not shown). Thereby, the cover member 14 can be attached to and detached from the shell 12. Note that the outer edge portions of the flange portions 31a, 31b, 32a, and 32b on both sides in the short direction of the cover members 31 and 32 are bent from one side to the other side of the pair facing each other.

  Next, the operation will be described.

  In the exhaust purification apparatus of the present embodiment configured as described above, in the operating state of the internal combustion engine in which the exhaust gas passes through the exhaust purification unit 11, heat from the exhaust gas is applied to the exhaust purification apparatus, and the exhaust purification unit 11 A difference in expansion and contraction due to heat occurs between the shell 12 and the protective cover 14, and this difference in expansion and contraction is absorbed by the porous member 21 having flexibility and compressibility.

  The exhaust purification apparatus of this embodiment is subjected to vibrations associated with the operation of the internal combustion engine or the vehicle, but the porous member 21 has the end portions 14a and 14b of the protective cover 14 and the frustum-shaped portions 12a and 12b of the shell 12. Since both ends 14a and 14b of the protective cover 14 are elastically supported moderately with respect to both ends 12a and 12b of the shell 12 through the porous member 21, the exhaust pipes 10a and 10b are disposed in close contact with each other. And no contact with the shell 12. Therefore, no abnormal noise is generated due to contact / interference between the protective cover 14 and the shell 12 of the exhaust purification unit 11. In addition, the porous member 21 having sufficient air flowability (breathability) is disposed at the end of the heat shield space layer 13 to reliably prevent foreign matters from entering the heat shield space layer 13. In addition, it is possible to ensure heat dissipation when the exhaust purification unit 11 is overheated.

  Moreover, in this embodiment, since the porous member 21 is a flexible string shape, special shaping | molding (molding) is carried out to the porous member 21 in order to follow the circumference of the frustum shape part 12a, 12b of the shell 12. ) Is not necessary. In addition, the gap between the end portions 14 a and 14 b of the protective cover 14 and the frustum-shaped portions 12 a and 12 b of the shell 12 of the exhaust purification unit 11 can be stably held while being reliably closed by the porous member 21. In this case, since the retaining portion 14c of the protective cover 14 that prevents the porous member 21 from falling off also functions as a rib of the end portions 14a and 14b of the protective cover 14, the end portions 14a and 14b of the protective cover 14 are clamp materials. Even without the clamp by, the stable holding can be performed more reliably.

  Further, since the metal mesh porous member 21 knitted into a circular cross section only has to be provided around the frustum-shaped portions 12a and 12b of the shell 12 of the exhaust purification unit 11, the attachment is very easy. is there. In addition, the moderate flexibility and flexibility of the porous member 21 provides good adhesion to the shell 12 and the protective cover 14, and the metal member porous member 21 has sufficient air flow and heat resistance during overheating. The heat dissipation of can be secured more sufficiently.

  In addition, the position of the porous member 21 relative to the protective cover 14 is accurately held at the optimum position in the longitudinal direction of the exhaust purification device by the retaining portion 14c of the protective cover 14, and the opening of the retaining portion 14c. By appropriately setting the inner diameter of the edge portion 14t, it is possible to easily set a gap g suitable for heat dissipation during overheating between the end portions 14a, 14b of the protective cover 14 and the shell 12 of the exhaust purification unit 11. it can.

  In addition, the arc-shaped parts 21a and 21b of the porous member 21 are spot welded to the cover members 31 and 32 constituting the protective cover 14, respectively, so that the protective cover 14 and the porous member 21 can be handled integrally. As a result, the assembly can be facilitated, and the assembly operation of the assembly position of the porous member 21 can be performed stably.

  Thus, in the exhaust emission control device of the present embodiment, the flexible porous member 21 is brought into close contact between at least one end portions 14a, 14b of the protective cover 14 and the frustum-shaped portions 12a, 12b of the shell 12. Since it can be arranged, noise due to contact / interference between the protective cover 14 and the shell 12 of the exhaust purification unit 11 does not occur, and the porous member 21 radiates heat when the exhaust purification unit 11 is overheated. Therefore, it is possible to provide an exhaust gas purification device that can secure the performance and is excellent in exhaust gas purification performance at low cost.

  The porous member referred to in the present invention is preferably made of a metal mesh having a cross-sectional shape with a thickness to width ratio close to 1 as described above. An irregular cross-sectional shape such as a shape, an oval shape, or a diamond shape may be used. Furthermore, it is not limited to metal mesh as long as it has flexibility and flexibility, heat resistance and corrosion resistance, filter characteristics to prevent entry of foreign matter and air permeability substantially equivalent to those made of metal mesh. It is as follows. Further, it is possible to provide a porous structure in which the porous member is provided only on one end side of the exhaust purification unit 11 and the other end side has a conventional straight portion. Further, the size of the gap that becomes the end of the heat shield space layer 13 may be different between the one end side and the other end side of the exhaust purification unit 11, and the porous members having different shapes and required characteristics from each other. May be provided. In the above example, the frustum-shaped portions 12a and 12b on both ends of the shell 12 are each of a truncated cone shape. However, the frustum-shaped portion referred to in the present invention is the central portion in the axial direction of the shell of the exhaust purification unit. As long as the end has a shape with a reduced diameter, the cross section may be any non-circular shape, and the vertical cross section is curved (corresponding to the curved outer peripheral surface of the frustum). It may be a substantially trapezoidal shape or the like.

As described above, the exhaust gas purification apparatus of the present invention, provided with a porous member of breathability and flexibility at least between the one end and the frustum-shaped portion of the shell of the protective cover on the outer peripheral side of the shell As a result, noise from contact and interference between the protective cover and the shell of the exhaust purification unit is not generated, heat dissipation when the exhaust purification unit is overheated can be secured , and foreign matter is mixed in the space layer. It is possible to provide an exhaust purification device that can reliably prevent exhaust gas at low cost and has excellent exhaust purification performance, and a protective cover is provided with a heat shield space layer on the shell of the exhaust purification unit. It is useful for exhaust gas purification devices for vehicles.

1 is an external perspective view of an exhaust emission control device according to an embodiment of the present invention. It is a perspective view which shows the state which removed the upper half part of the protective cover of the exhaust gas purification apparatus which concerns on one Embodiment. It is a fragmentary sectional view which shows the principal part structure in the one end side of the protective cover of the exhaust gas purification apparatus which concerns on one Embodiment. It is sectional drawing which shows the mounting part to the protective cover of the porous member in the exhaust gas purification apparatus which concerns on one Embodiment, (a) is the one aspect | mode in which the porous member was cyclic | annularly formed, (b) The other aspects by which the porous member was divided | segmented into two circular-arc-shaped components are each shown.

Explanation of symbols

10 Exhaust pipe (exhaust path)
DESCRIPTION OF SYMBOLS 11 Exhaust gas purification unit 12 Shell 12a, 12b Frustum shape part 13 Thermal insulation space layer (space layer)
14 Protective cover 14a End (one end)
14b end (other end)
14c Detachment part 14f Cone part 14s Reduced diameter part 14t Opening edge part 21 Porous member 21a, 21b Arc-shaped part 31, 32 Cover member
R1, R2 ribs (multiple ribs)

Claims (7)

Separating the exhaust gas purifying unit located in the exhaust path of an internal combustion engine, the shell having a frustum-shaped portion on at least one end with forming a cylindrical housing the exhaust gas purifying unit, a space layer on the outer peripheral side of the shell An exhaust purification device having a protective cover mounted thereon,
At least one end of the protective cover is opposed to the frustum-shaped portion of the shell across the space layer, and between the at least one end of the protective cover and the frustum-shaped portion of the shell, An exhaust emission control device comprising a porous member having air permeability and flexibility so as to partition the inside and outside. 2. The exhaust gas purification according to claim 1, wherein the porous member has a hollow cross section, and the space layer on the inner surface side of the protective cover communicates with the outside of the protective cover so that air can flow. apparatus. The porous member is formed in a string shape extending in the circumferential direction of the frustum-shaped portion of the shell, and closes a gap between at least one end of the protective cover and the frustum-shaped portion of the shell. an exhaust emission control device as claimed in claim 1 or claim 2, characterized in that it is. The exhaust purification device according to claim 2 or 3, wherein the porous member is formed of a cylindrical metal mesh. One end portion of the protective cover is provided with a retaining portion that prevents the porous member from slipping out from the inside of the protective cover, and the porous member is located between the retaining portion and the frustum-shaped portion of the shell. The exhaust emission control device according to any one of claims 1 to 4, wherein the exhaust gas purification device is held by the exhaust gas purification device. The protective cover has a plurality of concave and convex ribs separated at least in the circumferential direction,
The exhaust purification device according to claim 5, wherein the porous member is held between the retaining portion, the plurality of ribs, and the frustum-shaped portion of the shell. The protective cover includes a pair of cover members each having a concave shape on an inner surface facing the shell, and the porous member has a portion fixed to at least one of the pair of cover members. The exhaust emission control device according to any one of claims 1 to 6.

Images