US 20060277900 A1
The present disclosure relates to a vehicle exhaust system component including first and second conduits having double wall constructions. The first and second conduits are connected to one another at a service joint. An aftertreatment device is mounted within the first and second conduits. The aftertreatment device has a length. The aftertreatment device is positioned within the first and second conduits such that the service joint surrounds the aftertreatment device at an intermediate location along the length of the aftertreatment device.
1. A vehicle exhaust system component comprising:
a first conduit having a double wall construction;
a second conduit having a double wall construction;
a service joint connecting the first and second conduits;
an aftertreatment device mounted within the first and second conduits, the aftertreatment device having a length, the aftertreatment device being positioned within the first and second conduits such that the service joint surrounds the aftertreatment device at an intermediate location along the length of the aftertreatment device.
2. The vehicle exhaust system component of
3. The vehicle exhaust system component of
4. The vehicle exhaust system component of
The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/662,909, filed Mar. 17, 2005, which application is hereby incorporated by reference in its entirety.
The present invention relates generally to engine exhaust treatment components housing aftertreatment devices having cores such as catalytic converters or diesel particulate filters.
To reduce air pollution, engine exhaust emissions standards have become increasingly more stringent. Aftertreatment devices have been developed to satisfy these increasingly stringent standards. For example, catalytic converters have been used to reduce the concentration of pollutant gases (e.g., hydrocarbons, carbon monoxide, nitric oxide, etc.) exhausted by engines. U.S. Pat. No. 5,355,973, which is hereby incorporated by reference, discloses an example catalytic converter. With respect to diesel engines, diesel particulate filters have been used to reduce the concentration of particulate matter (e.g., soot) in the exhaust stream. U.S. Pat. No. 4,851,015, which is hereby incorporated by reference, discloses an example diesel particulate filter. Other example types of aftertreatment devices include lean NOx catalyst devices, selective catalytic reduction (SCR) catalyst devices, lean NOx traps, or other device for removing for removing pollutants from engine exhaust streams.
At times, it is required to service aftertreatment devices. Aftertreatment devices are typically mounted in an exhaust system component such as a muffler, housing or other structure. The exhaust system components typically include service joints located adjacent the aftertreatment devices (e.g., adjacent opposite ends of the aftertreatment devices). By opening the service joint, a given aftertreatment device can be removed from its corresponding exhaust system component for servicing.
Engine exhaust can have temperatures that exceed 600 degrees Celsius. It is sometimes desirable for engine exhaust components to maintain outer skin temperatures that are substantially lower than the temperature of the exhaust passing through the components. To maintain relatively low outer skin temperatures, it is known to wrap insulation about the engine exhaust components, and to enclose the insulation within an outer protective skin/shield.
One aspect of the present disclosure relates to a service joint for engine exhaust components adapted to maintain a relatively low outer skin temperature.
A variety of other aspects of the invention are set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practicing the invention. The aspects of the invention relate to individual features as well as combinations of features. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.
While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail below. It is to be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the invention is intended to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims.
In the following detailed description, references are made to the accompanying drawings that depict various embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized, and structural and functional changes may be made without departing from the scope of the present invention.
It is preferred for the joint 20 to maintain a relatively low external skin temperature (e.g., 120 degrees Celsius or less) even though the internal substrate temperature of the aftertreatment device can be very high (e.g., above 600 degrees Celsius). This is enhanced by making use of the insulating properties of the aftertreatment device to insulate the service joint. This is also enhanced by spacing the joint from the casing of the aftertreatment device such that an intermediate layer of air or other insulating material that reduces the transfer of heat to the joint 20. One example environment where it is desirable to have aftertreatment devices with low external skin temperatures relates to configurations where the aftertreatment device is mounted near a fuel tank.
The aftertreatment device 10 is depicted including a substrate 22 (e.g., a catalytic converter or diesel particulate filter substrate) mounted within a container or can 24 (e.g., a metal canister). An insulating mounting material such as a mat 26 is positioned between the substrate 22 and the container 24. The mat 26 can also be referred to a mantle, cushioning layer, wrap, sleeve or like terms. A preferred material for the mat 26 includes a non-intumescent material. Non-intumescent materials typically do not include chemical compounds such as vermiculite that expand in reaction to elevated temperatures. Preferred mounting materials include erosion resistant fibrous mats such as ceramic fibers, aluminum fibers, silica fibers or other materials. Non-intumescent mat materials can include erosion resistant properties, and also are capable of providing compression r “spring” that provides constant holding pressure across a relatively large temperature range. Example non-intumescent materials include the CC-Max® 4 Substrate Support Mat and the CC-Max® 6 Substrate Support Mat sold by Unifrax Corporation of Niagara Falls, N.Y. Another support mat includes the Interam 1101 HT Mat sold by Minnesota Mining and Manufacturing Company of St. Paul, Minn. Intumescent mats can also be used.
The second exhaust conduit 36 also has a double wall configuration. Specifically, the second conduit 36 includes an inner wall 40 and an outer wall 42 that is concentric with the inner wall 40. Insulating material 44 is positioned between the inner and outer walls 40, 42. The inner wall 40 of the exhaust conduit 36 includes an end wall 48 (i.e., a spacer) that extends radially between the walls 40, 42 and provides a connection between the inner and outer walls 40, 42. The wall 40 includes a contact region 50 that extends radially inwardly to engage the outer surface of the container 24 of the aftertreatment device 10.
To reduce the temperature at the joint 20, the joint 20 is preferably positioned around the body of the aftertreatment device 10 to make use of the insulating properties of the mat 26. Furthermore, the joint 20 is provided with an offset 46 (i.e., a gap or spacing) between the container 24 of the aftertreatment device 10 and the outer walls 28 and 42. Preferably, the offset 46 provides an insulating effect. In certain embodiments, the insulating effect can be provided by air. In other embodiments, an insulating material other than air (e.g., fiberglass, a fibrous ceramic, ceramic paper, ceramic mat, or other materials) can be placed within the offset 46.
As described above, the aftertreatment device 10 is identified as a diesel particulate filter or a catalytic converter (i.e., a diesel oxidation catalyst). However, it will be appreciated that service joints in accordance with the principles of the present disclosure can be used in combination with a variety of aftertreatment devices. Example aftertreatment devices include catalytic converters, diesel particulate filters, lean NOx catalyst devices, selective catalytic reduction (SCR) catalyst devices, lean NOx traps, or other devices for removing for removing pollutants from the exhaust stream.
Catalytic converters are commonly used to convert carbon monoxides and hydrocarbons in the exhaust stream into carbon dioxide and water. Diesel particulate filters are used to remove particulate matter (e.g., carbon based particulate matter such as soot) from an exhaust stream. Lean NOx catalysts are catalysts capable of converting NOx to nitrogen and oxygen in an oxygen rich environment with the assistance of low levels of hydrocarbons. For diesel engines, hydrocarbon emissions are too low to provide adequate NOx conversion, thus hydrocarbons are required to be injected into the exhaust stream upstream of the lean NOx catalysts. SCR's are also capable of converting NOx to nitrogen and oxygen. However, in contrast to using HC's for conversion, SCR's use reductants such as urea or ammonia that are injected into the exhaust stream upstream of the SCR's. NOx traps use a material such as barium oxide to absorb NOx during lean burn operating conditions. During fuel rich operations, the NOx is desorbed and converted to nitrogen and oxygen by catalysts (e.g., precious metals) within the traps.
Diesel particulate filter substrates can have a variety of known configurations. An exemplary configuration includes a monolith ceramic substrate having a “honey-comb” configuration of plugged passages as described in U.S. Pat. No. 4,851,015 that is hereby incorporated by reference in its entirety. Wire mesh configurations can also be used. In certain embodiments, the substrate can include a catalyst. Exemplary catalysts include precious metals such as platinum, palladium and rhodium, and other types of components such as base metals or zeolites.
For certain embodiments, diesel particulate filters can have a particulate mass reduction efficiency greater than 75%. In other embodiments, diesel particulate filters can have a particulate mass reduction efficiency greater than 85%. In still other embodiments, diesel particulate filters can have a particulate mass reduction efficiency equal to or greater than 90%. For purposes of this specification, the particulate mass reduction efficiency is determined by subtracting the particulate mass that enters the filter from the particulate mass that exits the filter, and by dividing the difference by the particulate mass that enters the filter.
Catalytic converter substrates can also have a variety of known configurations. Exemplary configurations include substrates defining channels that extend completely therethrough. Exemplary catalytic converter configurations having both corrugated metal and porous ceramic substrates/cores are described in U.S. Pat. No. 5,355,973, that is hereby incorporated by reference in its entirety. The substrates preferably include a catalyst. For example, the substrate can be made of a catalyst, impregnated with a catalyst or coated with a catalyst. Exemplary catalysts include precious metals such as platinum, palladium and rhodium, and other types of components such as base metals or zeolites.
In one non-limiting embodiment, a catalytic converter can have a cell density of at least 200 cells per square inch, or in the range of 200-400 cells per square inch. A preferred catalyst for a catalytic converter is platinum with a loading level greater than 30 grams/cubic foot of substrate. In other embodiments the precious metal loading level is in the range of 30-100 grams/cubic foot of substrate. In certain embodiments, the catalytic converter can be sized such that in use, the catalytic converter has a space velocity (volumetric flow rate through the DOC/volume of DOC) less than 150,000/hour or in the range of 50,000-150,000/hour.
In the depicted embodiments, V-band clamps are used to hold the components together. It will be appreciated that in other embodiments, any number of different types of pipe clamps or fasteners could be used to fasten the parts together. Additionally, spacers in accordance with the present disclosure can be used on exhaust treatment devices that are not configured for ready disassembly. Moreover, while the spacers S have been shown curled/rolled back approximately 360 degrees, in other embodiments the spacers could be curled less than 360 degrees. For example,
The above specification and examples provide a complete description of the manufacture and use of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.