Diesel vehicle exhaust aftertreatment apparatus and method

The aftertreatment apparatus and method of the invention concentrate diesel exhaust under low engine load conditions in a motor vehicle, such as idling, before filtering the diesel exhaust. The apparatus has a housing which is in fluid communication with a filter and other components of the diesel exhaust system. The apparatus has an exhaust concentrator to concentrate the low load diesel exhaust. The concentrated exhaust is directed a limited part of the filter and/or the catalytic device, such as the center. The exhaust concentrator is at least partially disposed within the housing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an aftertreatment apparatus and method for treating diesel exhaust in a motor vehicle.

2. Description of the Prior Art

Diesel engines are efficient, durable and economical. Diesel exhaust; however, can harm both the environment and people. To reduce this harm governments, such as the United States and the European Union, have proposed stricter diesel exhaust emission regulations. These environmental regulations require diesel engines to meet the same pollution emission standards as gasoline engines.

One part of diesel exhaust includes diesel particulate material. Diesel particulate material is mainly carbon particles or soot. One way to remove soot from diesel exhaust is with diesel traps. The most widely used diesel trap is a diesel particulate filter which nearly completely filters the soot without hindering exhaust flow. As a layer of soot collects on the surfaces of the inlet channels of the filter, the lower permeability of the soot layer causes a pressure drop in the filter and a gradual rise in the back pressure of the filter against the engine. This phenomenon causes the engine to work harder, thus decreasing engine operating efficiency. Eventually, the pressure drop in the filter and decreased engine efficiency becomes unacceptable, and the filter must either be replaced or the accumulated diesel soot must be cleaned out.

The filter is cleaned of accumulated diesel soot by burning-off or oxidation of the diesel soot to carbon dioxide which is known as regeneration. Regeneration of an existing filter is superior to filter replacement, because no interruption for service is necessary.

The regeneration process is either passive or active. Passive regeneration occurs when the filter becomes so filled with carbon particles that heat increases within the exhaust system due to excessive back pressure. The increased heat raises the temperature of the carbon to a point where the carbon ignites. This design, however, often results in thermal shock or melt down of the filter, high fuel penalty and poor filtering action.

Active regeneration uses heat generated by an outside source under controlled conditions to initiate combustion of the diesel soot. Soot slowly burns for a brief period. During this burn, the temperature in the filter rises from about 400°-600° C. to about 800°-1000° C. The highest temperatures occur near the exit end of the filter due to the cumulative effects of the wave of soot combustion from the entrance face to the exit face of the filter as the exhaust flow carries the combustion heat down the filter. Electrical power, fuel burners and microwave energy are all used as outside heat sources.

Under certain circumstances, a so-called “uncontrolled regeneration” occurs when the onset of combustion coincides with, or is immediately followed by, high oxygen content and low flow rates in the exhaust gas (such as engine idling conditions or low loads). During an uncontrolled regeneration, the combustion of the soot may produce temperature spikes within the filter which can thermally shock and crack, or even melt, the filter.

In addition to capturing carbon soot, the filter also traps ash particles, such as metal oxides, that are carried by the exhaust gas. These particles are not combustible and, therefore, are not removed during regeneration. If temperatures during uncontrolled regenerations are sufficiently high, however, the ash may eventually sinter to the filter or react with the filter, thus resulting in partial melting.

Furthermore under light loads and idling conditions, the stream of exhaust particles is too dilute to efficiently burn the soot to regenerate the filter. Under such light loads, the stream of exhaust particles is at a lower pressure and temperature than the exhaust stream at medium to full loads. This can inhibit the regeneration of the filter or lead to uncontrolled regeneration of the filter.

Therefore, it would be advantageous to increase the efficiency of the regeneration of the filter while inhibiting uncontrolled regenerations. It would be further advantageous to increase the efficiency of the diesel aftertreatment without using costly parts or requiring bulky additional equipment.

SUMMARY OF THE INVENTION

According to the invention an exhaust aftertreatment apparatus filters diesel exhaust from an engine in a motor vehicle. The apparatus has a housing in fluid communication with an entrance conduit leading from the engine and an exit conduit leading from the housing. A filter is disposed within the housing downstream from the entrance conduit.

An exhaust concentrator is at least partially disposed within the housing. The exhaust concentrator concentrates the diesel exhaust produced under low load conditions and directs the concentrated diesel exhaust to a limited area of the filter, such as the filter's center. The filter now filters the concentrated diesel exhaust. The filtered exhaust flows out of the filter and the exit conduit.

Additional effects, features and advantages will be apparent in the written description that follows.

DETAILED DESCRIPTION OF THE INVENTION

Turning to the Figures where like reference numerals refer to like structures, the present invention relates to an aftertreatment apparatus10for treating diesel exhaust gases from a diesel engine12in a motor vehicle, especially under light loads. In this disclosure, the term “light load” can refer to the diesel exhaust emissions produced by an engine under light or idling conditions.

The engine12is in fluid communication with the aftertreatment apparatus10through an entrance conduit14. Treated exhaust flows from the aftertreatment apparatus10through an exit conduit16.

The aftertreatment apparatus10includes a catalytic device18in fluid communication with a diesel particulate filter20. The catalytic device18and the filter20can both be located in one housing22(FIG. 2) or located in separate housings23,24(FIG. 3) in fluid communication with each other. When located in the same housing22, the catalytic device18and the filter20can abut one another.

The housing22is in fluid communication with the entrance conduit14, preferably with the housing end26of the entrance conduit14connecting with the housing22.

An exhaust concentrator30is at least partially disposed within a housing22(FIG. 2)24(FIG. 3) and can attach to the interior weldments of the motor vehicle. The exhaust concentrator30concentrates the diesel particulate material32under light loads and forces the diesel particulate material32to flow through a limited portion of the filter20, such as the filter center21. Under medium or heavy loads, the exhaust concentrator30allows the unconcentrated diesel particulate material32access to the entire diameter of the filter20for filtering through the entire filter.

The exhaust concentrator30can include a concentrator tube34that slidingly engages the housing end26of the entrance conduit14. The concentrator tube34can be cylindrical or flared at one end. The concentrator tube34slides from a open position during medium to heavy loads to a closed position during light loads. The concentrator tube34can slide axially or radially to abut a filter face46(FIG. 3) or a catalyst face48(FIG. 2).

As shown inFIGS. 2 and 4, the exhaust concentrator30has an actuator36with a pivot arm38pivotally attached to a base40at a pivot39and a modulator42. The pivot arm38can extend from the base40through an opening27within the housing22to the modulator42outside the housing22. The base40can attach to the housing end26of the entrance conduit14. During light loads, the modulator42pivots the pivot arm38toward the catalyst face48which slides the concentrator tube34toward the catalyst face48until abutting the catalyst face48. Under heavier loads, the modulator42pivots the pivot arm38away from the catalyst face48which slides the concentrator tube34away from the catalyst face46.

The modulator42can include anything that moves the pivot arm, such as a spring44. The spring44expands under low loads and pushes a spring arm45extending though the housing opening27and attaching to the pivot arm38. The spring arm45and the pivot arm38can be one piece or separate pieces. Under heavier loads, a turbo boost from the engine retracts the spring44, which pulls the spring arm45and pivot arm38away from the catalyst face48and moves the concentrator tube34away from the catalyst face48. The exhaust stream now freely flows across the entire catalyst face48and enters the catalytic device18.

FIG. 3shows the exhaust concentrator30at least partially disposed within a passageway28between housings23,24. The modulator43is in communication with a controller50monitoring the engine load and/or conditions within the exhaust system. Under a light load, the controller50signals the modulator43to release spring52. The concentrator tube35rotates axially and fully extends to abut the filter face46. When the controller50detects a heavier load, the controller50signals the modulator43to retract the spring52and the concentrator tube35rotates axially away from the filter face46.

Turning to the embodiment shown inFIGS. 6 and 7, the exhaust concentrator54is in fluid communication and connects with the housing end26of the entrance conduit14at the proximal end60of the housing22. The exhaust concentrator54has a concentrator tube56and an adjacent exhaust branch57with a valve58which opens and closes the exhaust branch57. Under light loads, the valve58is closed (FIG. 6) to concentrate the exhaust within the concentrator tube56and direct the flow to the center of the catalytic device20. Under heavier loads, the valve58opens to allow the exhaust to flow into the exhaust branch57which allows access to all of the catalytic device18(FIG. 7).

The concentrator tube56can have a wall64with an aperture62(FIG. 8). The aperture62can have an aperture valve59to open and close the aperture. The aperture valve59further opens the concentrator tube56during higher load conditions.

Valves can include butterfly valves, throttle valves, servo spring valves connected to a throttle plate, and the like. The valve can open and close by responding to the pressure in the exhaust branch57, such as by opening during a turbo boost. The valve can be in communication with the controller50to receive signals from the controller50to open and close.

The controller50can be in communication with sensors, the engine, the valves or the modulator. Sensors, for example, can measure temperature, pressure, and the like within the exhaust system or the engine, and send the measurement to the controller50. The controller50can be programmed to respond to set conditions to signal the exhaust concentrator to concentrate the exhaust, for example by opening and closing the valves or releasing and retracting of the springs.

A heat source, such as a fuel, electrical or microwave heating source, can be located at or near the entrance of the aftertreatment apparatus10to enhance regeneration, if desired.

The aftertreatment apparatus of the invention uses an exhaust concentrator to concentrate a dilute stream of the diesel particulate material produced by the engine under low load conditions into a concentrated stream of diesel particulate material. Instead of the dilute stream of particulate material entering the filter in a diffuse manner, the exhaust concentrator concentrates the diesel particulate material and focuses the material to a smaller location to enter the filter and/or catalytic device. This concentration increases the pressure within the exhaust conduit and the temperature to produce optimum conditions for filter regeneration under light exhaust loads while preventing uncontrolled regeneration.

The aftertreatment apparatus of the invention increases the efficiency of the regeneration of the filter while inhibiting uncontrolled regenerations, Yet, the aftertreatment apparatus neither uses costly parts nor requires bulky additional equipment.

While the Figures show the filter downstream from the catalytic device, the filter could be located upstream from the catalytic device. While the invention is shown in only one of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit and scope of the invention.