LU101557B1

LU101557B1 - Exhaust gas aftertreatment system with heat shield

Info

Publication number: LU101557B1
Application number: LU101557A
Authority: LU
Inventors: Denis Laurent; Vanessa Georges; Christian G Hillard
Original assignee: Katcon Global Sa
Priority date: 2019-12-18
Filing date: 2019-12-18
Publication date: 2021-06-22

Abstract

An exhaust treatment assembly comprises a housing and a heat shield assembly being arranged around said housing, said heat shield assembly comprising at least one heat shield opening through which at least one mounting bracket and/or sensor device, which is arranged on and extending outwards from said housing, extends outward of said heat shield assembly. The heat shield opening is dimensioned so that a circumferential gap is formed between said heat shield assembly and the at least one mounting bracket and/or sensor device. A patch of a flexible heat resistant impermeable material is arranged around said at least one mounting bracket and/or sensor device and extends outwards from said at least one mounting bracket and/or sensor device so as to entirely cover the circumferential gap between said heat shield assembly and the at least one mounting bracket and/or sensor device.

Description

Exhaust gas aftertreatment system with heat shield Technical field

[0001] The present invention generally relates to an exhaust gas system for a combustion engine and more particularly to an exhaust gas aftertreatment system. Background of the Invention

[0002] Exhaust lines are used in vehicles for routing exhaust generated by a fuel- burning engine to the atmosphere surrounding the vehicle. It is required to reduce pollutant(s) in the exhaust to an environmentally-acceptable level or form before the exhaust is released to the surrounding atmosphere. Accordingly, there is a requirement to provide an exhaust line for a vehicle with an exhaust gas aftertreatment assembly that operates to reduce pollutant(s) of an exhaust to an environmentally-acceptable form.

[0003] An exhaust treatment assembly typically comprises one or more exhaust gas treatment components such as one or more catalytic converters and/or diesel particulate filters which are arranged within a common housing. Due to the high temperature of the exhaust gases, aftertreatment systems heated up to very high temperatures. As most aftertreatments are located close to the engine (to take benefit of hot gases and facilitate chemical reaction), they are also exposed to flammable liquids (like fuel, motor oil, coolant) which can ignite in contact with high temperature surfaces thereby causing a fire to start. To prevent that, it is important to make sure flammable liquids are not getting in touch with hot surfaces in case of failure. The exhaust treatment assembly therefore usually includes a heat shield assembly with an external encapsulating material arranged around the housing, the space between the housing and the encapsulating material being filled with a mat of thermally insulating material. This heat shield assembly effectively reduces the temperature at the outer surface, thereby preventing liquids to ignite and cause fire.

[0004] However it is not possible to avoid openings in the direct encapsulation of the heat shield assembly. In fact the exhaust treatment assembly comprises one or more mounting brackets which are mounted on the housing of the exhaust gas treatment component and which are used to secure the exhaust treatment assembly to the vehicle structure or the engine. Furthermore the assembly usually includes one or more sensor devices which are mounted in ports of the housing and used to monitor the catalytic reaction or the efficiency thereof. Both the mounting brackets and the sensor devices extend outwards from the housing and penetrate the heat shield assembly through openings arranged therein to protrude outside of the assembly.

[0005] In order to allow a proper installation of the encapsulation and due to process tolerances, the heat shield openings are larger than the corresponding cross section of the mounting brackets or the sensor devices, so that a circumferential gap is formed between said heat shield assembly and the mounting bracket and/or sensor device. Due to this gap, the openings let some small surfaces of the housing exposed to liquid. In most cases, this is not considered as an issue because liquid will not stay in the corresponding area and the risk the liquids to ignite is very low. In other cases however, e.g. if the opening is orientated to the top, liquid can possibly accumulate into this area and this could turn into fire. In order to alleviate this risk, manufacturers attempt to review in detail the potential path of the liquid in case of failure and to modify connections accordingly respectively provide additional covers. But these measures remain static tests and could be inefficient in a real world scenario. Furthermore these measures clearly limit packaging possibilities all the while in modern vehicies it is becoming more and more challenging to find the required mounting space for the aftertreatment components.

Object of the invention

[0006] It is therefore an object of the present invention to provide an improved exhaust treatment assembly without the above described shortcomings. This object is achieved by an exhaust treatment assembly according to claim 1.

General Description of the Invention |

[0007] In order to achieve the above mentioned object, the present invention provides an exhaust treatment assembly comprising a housing and a heat shield assembly being arranged around said housing. The heat shield assembly | comprises at least one heat shield opening through which at least one mounting bracket and/or sensor device, which is arranged on and extending outwards from | said housing, extends outward of said heat shield assembly. The heat shield opening is dimensioned so that a circumferential gap is formed between said heat shield assembly and the at least one mounting bracket and/or sensor device.

According to the present invention the exhaust treatment assembly further comprises a patch of a flexible heat resistant material, said patch of flexible heat resistant material being substantially impermeable for liquids and being arranged around said at least one mounting bracket and/or sensor device and extending outwards from said at least one mounting bracket and/or sensor device so as to entirely cover the circumferential gap between said heat shield assembly and the at least one mounting bracket and/or sensor device.

[0008] The patch of flexible heat resistant material according to the present invention is preferably arranged in contact with the mounting bracket or the sensor device and spans from the bracket or sensor device over the circumferential gap to overlap with the outer skin of the heat shield assembly. The patch thus effectively covers the opening of the heat shield assembly and prevents any liquid to come into contact with the hot surfaces of the underlying housing. Due to the fact that the material is flexible, the patch works significantly better for covering the respective opening than e.g. a thin steel sheet, i.e. the material from which the direct encapsulation is made. Any liquid falling from the engine onto the exhaust treatment assembly in the area of the mounting bracket or sensor device is received by the patch of flexible material and deflected by the flexible material towards areas with lower temperatures and thus lower risk of flaming. In this context it will be noted that the exhaust treatment assembly usually has a generally tubular form and that the patch of flexible material arranged to cover an opening on the top of the tubular form will deflect the liquid in circumferential direction towards the side of the assembly.

[0009] The patch is preferably installed on the exhaust treatment assembly by sliding the patch onto the bracket or sensor device. For this, the patch is preferably provided with a small cut, so that the patch glides along and remains in contact with the outer circumference of the bracket or sensor device. |

[0010] The patch of flexible material is preferably mounted so that the flexible material forms a slope from the bracket or sensor towards heat shield. This may | easily be achieved by the patch being positioned on the bracket or sensor device at a certain radial distance from the surrounding heat shield assembly. The flexible material will accordingly automatically take the desired sloped form which is favorable for the deflection of liquids towards areas of lower temperature. In some embodiments, a metallic guide element may be provided to be mounted or attached to the bracket or sensor below said patch of flexible heat resistant material. The metallic guide element can be shaped so as to support the flexible heat resistant material in selected areas, thereby enabling to shape the form of the patch of flexible material between the bracket or sensor device and the surrounding heat shield assembly. This allows to prevent the flexible material from sagging into the gap between shield and bracket or sensor and therefore prevents liquid from accumulating in a depression in the flexible material.

[0011] In a preferred embodiment, the patch of flexible heat resistant material comprises a densely woven textile made of heat resistant fibers. The skilled person will be well aware of suitable fibers which can resist temperatures up to 600°C. One suitable material which is preferred for its mechanical properties at high temperatures is a woven textile made of heat resistant glass fibers, e.g. e- glass fibers. The textile material made of e-glass fibers exhibits the desired flexibility to effectively cover any exposed hot temperature surfaces. At the same time a glass fiber textile, e.g. with a thickness in the range between 0.7 and

1.3 mm, has a certain stiffness even at high temperatures so as to avoid the material from sagging and forming depressions in which liquid may accumulate. Furthermore the e-glass fibers are chemically stable in contact with coolant or | motor oil so that the mechanical properties do not degenerate if the material comes into contact with these liquids.

[0012] In order to enhance the impermeability of the textile material, the textile material may be coated with a repellant suitable to repel flammable liquids such as fuel, oil or coolant. Any liquid falling on the patch of coated material will be quickly evacuated under the joint effect of the geometry and the repelling effect of the coating. In embodiments, the textile material may also be covered with a thin metallic foil, e.g. an aluminum foil having a thickness of less than 250 um and preferably less than 200 um. The thin metallic foil enhances the impermeability of the textile material without unduly reduce the flexibility of the material. At the same time the thin metallic foil acts as a heat reflector which reduces the temperature of the contact surface.

[0013] In order to effectively prevent liquids from penetrating into the gap between the bracket or the sensor device, it is preferred that the opening said patch of a flexible heat resistant material is dimensioned so as to extend beyond said circumferential gap and to cover said heat shield assembly by at least 20 mm, preferably even more. As explained above, the exhaust treatment assembly usually has a generally tubular form. In such case, it is preferred that the patch of flexible heat resistant material extends in circumferential direction from the top to at least the imaginary median plane of the tubular form, i.e. to the area of the greatest width of the tubular form. This helps to evacuate any liquids entirely away from the outer skin of the heat shield assembly. Furthermore as the outer skin of the heat shield assembly is usually formed of two half shells (a top shell and a bottom shell) which are crimped together at the area of the greatest width of the tubular form, the flexible heat resistant material may be fastened to the existing crimps of the heat shield assembly. In fact, if the patch is provided with suitable slots, the patch may be simply crimped into the existing attachments of the heat shield half shells, thereby eliminating the need to attach the patch with additional means such glue or riveting. It is however noted that other means and methods for attachment of the patch to the heat shield assembly are not excluded from the scope of the invention.

[0014] In embodiments, the patch of a flexible heat resistant material may comprise at least one beadlike structure which extends on an outer surface of said patch of a flexible heat resistant material. The beadlike structure may e.g. extend in circumferential direction of the exhaust treatment assembly. The beadlike structure is preferably configured and oriented to form a guide for liquids to guide the liquids away from high temperature surfaces towards a safe area where the temperature is cool enough to prevent any risk of fire. The beadlike structure thus effectively adds to prevent liquids to reach critical places on the exhaust treatment assembly.

[0015] The skilled person will appreciate, that the bead like structure may be formed by any suitable material integrated in or mounted on the flexible heat resistant material. In a preferred embodiment, the bead like structure is formed by a metallic cable or a strand or bundle of glass fibers integrated into the flexible heat resistant material. Brief Description of the Drawings

[0016] Further details and advantages of the present invention will be apparent from the following detailed description of not limiting embodiments with reference to the attached drawing, wherein: Fig. 1 is a cross-sectional view of a portion of an exhaust treatment assembly; Fig. 2 is a perspective view of an exhaust treatment assembly in a more compact configuration; Fig. 3 is a perspective view of the exhaust treatment assembly of Fig. 2 with installed textile patch; Fig. 4 is a perspective view from a different angle of the exhaust treatment assembly of Fig. 3. Description of Preferred Embodiments

[0017] Fig. 1 shows a cross-sectional view of a portion of an exhaust treatment assembly 10. The exhaust treatment assembly 10 typically comprises one or more exhaust gas treatment components 140 such as one or more catalytic converters and/or diesel particulate filters which are arranged within a common housing 12. A heat shield assembly 14 is arranged around the housing 12 in order to reduce the skin temperature of the exhaust treatment assembly 10. The exhaust treatment assembly 10 usually has a generally tubular form and is provided with end cones 160 having a connection port 180 for connecting the exhaust treatment assembly to exhaust gas pipes 200.

[0018] While in some configurations, the exhaust treatment assembly 10 and the respective inlet and outlet connection ports 180 with exhaust pipes 200 are arranged in a linear arrangement, the limited mounting space in modern vehicles often requires a more compact configuration with angled inlet and outiet ports 180. Figs. 2 to 4 show perspective views of such an exhaust treatment assembly in a more compact configuration.

[0019] The heat shield assembly 14 comprises at least one heat shield opening 16 through which at least one mounting bracket 18 arranged on the housing 12 extends outward of the heat shield assembly 14. In order to allow for a proper installation of the heat shield encapsulation 14 and due to process tolerances, the heat shield opening 16 is larger than the corresponding cross section of the mounting bracket 18, so that a circumferential gap 20 is formed between said heat shield assembly 14 and the mounting bracket 18. Due to this gap, the opening 16 lets some small surfaces 22 of the housing 12 exposed to liquid.

[0020] In order to shield the exposed surfaces from liquids from the ending, the exhaust treatment assembly 10 of Fig. 3 and Fig. 4 further comprises a patch 24 of a flexible heat resistant material that is arranged around the mounting bracket 18 and extends outwards from the mounting bracket so as to entirely cover the circumferential gap between said heat shield assembly and the at least one mounting bracket.

[0021] The patch 24 of a flexible heat resistant material is preferably a patch made of a densely woven textile made of heat resistant fibers, e.g. e-glass fibers. The textile material is preferably densely woven so as to be impermeable for the liquids to be faced. In order to enhance the impermeability of the textile material, the material may be coated with a repellant suitable to repel flammable liquids such as fuel, oil or coolant. Alternatively or additionally the textile material may also be covered with a thin metallic foil, e.g. an aluminum foil having a thickness of less than 250 um and preferably less than 200 um. The thin metallic foil enhances the impermeability of the textile material without unduly reduce the flexibility of the material. At the same time the thin metallic foil acts as a heat reflector which reduces the temperature of the contact surface.

[0022] The patch 24 of flexible heat resistant material is preferably arranged in contact with the mounting bracket 18 and spans from the bracket 18 over the circumferential gap to overlap with the outer skin of the heat shield assembly 14. The patch 24 may be easily installed on the exhaust treatment assembly 10 by sliding the patch 24 onto the bracket 18. For this, the patch 24 is preferably provided with a small cut 26, so that the patch 24 glides along and remains in contact with the outer circumference of the bracket 18.

[0023] The patch 14 of flexible material is preferably mounted so that the flexible 17101687 material forms a slope from the bracket 18 towards heat shield 14. This may easily be achieved by the patch 24 being positioned on the bracket 18 ata certain radial distance from the surrounding heat shield assembly. The flexible material will accordingly automatically take the desired sloped form which is favorable for the deflection of liquids towards areas of lower temperature. In some embodiments, a metallic guide element 28 (see Fig. 2) may be provided to be mounted or attached to the bracket 18 below said patch 24 of flexible heat resistant material. The metallic guide element 28 can be shaped so as to support the flexible heat resistant material in selected areas, thereby enabling to shape the form of the patch 24 of flexible material between the bracket 18 and the surrounding heat shield assembly 14.

[0024] The outer skin of the heat shield assembly 14 is usually formed of two half shells (a top shell and a bottom shell) which are crimped together in a crimping area 30 located usually at the imaginary median plane of the tubular form, i.e. to the area of the greatest width of the tubular form of the exhaust gas assembly 10. To securely attach the patch 24 of flexible heat resistant material onto the exhaust gas assembly, the patch preferably extends in circumferential direction from the bracket 18 to a crimping area 30 of the heat shield assembly 14, where it may be fastened to the existing crimps of the heat shield assembly. If the patch 24 is e.g. provided with suitable slots, the patch 24 may be simply crimped into the existing attachments of the heat shield half shells, thereby eliminating the need to attach the patch with additional means such glue or riveting.

[0025] In the embodiments shown in Fig. 2 and 3, the 24 patch of a flexible heat resistant material comprise a beadlike structure 32 which extends on an outer surface of the flexible heat resistant material. The beadlike structure 32 in the shown embodiments extends e.g. in circumferential direction of the exhaust treatment assembly 10. The beadlike structure 32 is configured and oriented to form a guide for liquids to guide the liquids away from high temperature surfaces on the port 180 or on an additional sensor port 220, on which further components like sensors of the like may be mounted, towards a safe area where the temperature is cool enough to prevent any risk of fire. The beadlike structure 32 thus effectively adds to prevent liquids to reach critical places on the exhaust treatment assembly 10. The skilled person will appreciate, that the bead like 17101687 structure may be formed by any suitable material integrated in or mounted on the flexible heat resistant material. In a preferred embodiment, the bead like structure is formed by a metallic cable or a strand or bundle of glass fibers integrated into the flexible heat resistant material.

ALL

List of Reference Symbols exhaust treatment assembly

12 housing

14 heat shield assembly

16 heat shield opening

18 mounting bracket circumferential gap

22 surfaces

24 patch of a flexible heat resistant material 26 small cut

28 metallic guide element crimping area

32 beadlike structure

140 exhaust gas treatment components

160 end cones

180 connection port

200 exhaust gas pipes

220 sensor port

Claims

1. Exhaust treatment assembly comprising a housing and a heat shield assembly being arranged around said housing, said heat shield assembly comprising at least one heat shield opening through which at least one mounting bracket and/or sensor device, which is arranged on and extending outwards from said housing, extends outward of said heat shield assembly; wherein said heat shield opening is dimensioned so that a circumferential gap is formed between said heat shield assembly and the at least one mounting bracket and/or sensor device; characterized by a patch of a flexible heat resistant material, said patch of flexible heat resistant material being substantially impermeable for liquids and being arranged around said at least one mounting bracket and/or sensor device and extending outwards from said at least one mounting bracket and/or sensor device so as to entirely cover the circumferential gap between said heat shield assembly and the at least one mounting bracket and/or sensor device.

2. Exhaust treatment assembly according to claim 1, wherein said patch of flexible heat resistant material comprises a densely woven textile made of heat resistant fibers, preferably made of heat resistant glass fibers.

3. Exhaust treatment assembly according to claim 2, wherein said textile material is coated with a repellant so as to repel flammable liquids such as fuel, oil or coolant.

4. Exhaust treatment assembly according to any one of claims 2 or 3, wherein said textile material is covered with thin metallic foil, preferably an aluminum foil having a thickness of less than 250 um, preferably less than 200 um.

5. Exhaust treatment assembly according to any one of claims 2 to 4, wherein said textile material has a thickness in the range between 0.7 and 1.3 mm.

6. Exhaust treatment assembly according to any one of claims 1 to 5, wherein said patch of a flexible heat resistant material is dimensioned so as to extend beyond said circumferential gap and to cover said heat shield assembly by at least 20 mm.

7. Exhaust treatment assembly according to any one of claims 1 to 6, wherein said at least one outer edge of said patch of a flexible heat resistant material is attached to said heat shield assembly.

8. Exhaust treatment assembly according to any one of claims 1 to 7, wherein said patch of a flexible heat resistant material comprises at least one beadlike structure, said beadlike structure extending on an outer surface of said patch of a flexible heat resistant material so as to form a guide for liquids to guide said liquids away from high temperature surfaces.

9. Exhaust treatment assembly according to claim 8, wherein said bead like structure is formed by a metallic cable or a strand of glass fibers integrated into the flexible heat resistant material.

10. Exhaust treatment assembly according to any one of claims 1 to 7, further comprising a metallic guide element, said metallic guide element mounted on below said patch of flexible heat resistant material.