Patent Application
20070289288
As those of ordinary skill in the art will understand, various features of the embodiments illustrated and described with reference to the Figure may be combined with other features to produce embodiments that are not explicitly illustrated or described. The combination of features illustrated provides a representative embodiment for typical applications. However, various combinations and modifications of the features consistent with the teachings of this disclosure may be desired for particular applications or implementations.
Referring now to
Pump 20 is fluidly coupled to storage tank 12 and in communication with controller 50, which controls operation of pump 20. During operation, pump 20 pumps emissions treatment substance 14 from tank 12 to pressurize a supply line 22. A dosing or metering valve 24 is selectively controlled by controller 50 in response to current operating conditions or parameters of exhaust system 30 and/or engine 80 to deliver emissions treatment substance 14 via a corresponding nozzle or injector 26 to exhaust system 30 upstream of a mixing element or mixer 34, which mixes the exhaust stream from engine 80 with injected emissions treatment substance 14. Exhaust system 30 includes various emissions control/treatment devices that may include a pre-oxidation catalyst 40, a selective catalytic reduction (SCR) catalyst 42, and a diesel particulate filter (DPF) 44, for example. Of course, the presence and/or sequence of particular emissions treatment/control devices may vary depending upon the particular type of fuel, engine control strategy, and other factors affecting a particular application or implementation.
As also illustrated in
In the representative embodiment illustrated, space 16 of storage tank 12 is continuously coupled or vented to exhaust system 30 via fluid coupling 60. A coupling with bidirectional flow between space 16 and exhaust system 30 directs any vapors from storage tank 12 generally away from the vehicle and occupants, particularly during filling of emissions treatment substance storage tank 12 or refueling of the vehicle. While venting of tank 12 away from an associated filling tube (not shown) reduces or eliminates detection of odor during filling of tank 12 and during vehicle refueling by vehicle operators/occupants, additional benefits of judicious routing of fluid coupling 60 may be provided by coupling tank 12 to a device (or upstream of a device) that can decompose or store the vapor for future treatment to reduce or eliminate vapor escape from system 10. In the representative embodiment illustrated in
As those of ordinary skill in the art will appreciate, system 10 may include an emissions treatment system temperature sensor 62 and/or pressure senor 64 in addition to one or more conventional sensors 66 and actuators 68 to control system 10. Various sensors and actuators may communicate with at least one dedicated or general-purpose controller 50 that includes a microprocessor 92, also called a central processing unit (CPU), in communication with a memory management unit (MMU) 94 to control engine 80, exhaust system 30, and the emissions treatment system. MMU 94 controls movement of data and/or instructions among various computer readable storage media 96 and communicates data to and from CPU 92. The computer readable storage media preferably include volatile and nonvolatile or persistent storage in read-only memory (ROM) 98, keep-alive memory (KAM) 100, and random-access memory 102, for example. KAM 100 may be used to store various engine and/or ambient operating variables while CPU 92 is powered down. Computer-readable storage media 96 may be implemented using any of a number of known memory devices such as PROMs (programmable read-only memory), EPROMs (electrically PROM), EEPROMs (electrically erasable PROM), flash memory, or any other electric, magnetic, optical, or combination memory devices capable of storing data, some of which represent executable instructions, used by CPU 92 in controlling system 10. Computer-readable storage media 96 may also include floppy disks, CD-ROMs, hard disks, and the like depending upon the particular application. CPU 92 communicates with the sensors and actuators via an input/output (I/O) interface 104. Interface 104 may be implemented as a single integrated interface that provides various raw data or signal conditioning, processing, and/or conversion, short-circuit protection, and the like. Alternatively, one or more dedicated hardware or firmware chips may be used to condition and process particular signals before being supplied to CPU 92. Some controller architectures do not contain an MMU 94. If no MMU 94 is employed, CPU 92 manages data and connects directly to ROM 98, KAM 100, and RAM 102. Of course, more than one controller 90 or more than one CPU 92 may be used to provide system control and each controller 90 may contain multiple ROM 98, KAM 100, and RAM 102 coupled to MMU 94 or CPU 92 depending upon the particular application.
As previously described, controller 50 may control engine 80 in addition to various components of the emissions treatment system, such as pump 20 and injector 26. Controller 50 controls operation of pump 20 to pressurize supply line 22 with emissions treatment substance 14. Various components in exhaust system 30, such as catalysts 40, 42 and DPF 44 obstruct exhaust flow and create exhaust pressure or back pressure during operation of engine 80. The exhaust pressure pressurizes coupling 60 and emissions storage tank 12 to reduce vapor formation within tank 12 and impede vapor transmission or escape from tank 12. When pressure within tank 12 exceeds the pressure in exhaust system 30, vapors may enter exhaust system 30 from tank 12 where they are stored or reacted by SCR catalyst 42.
As such, passive venting of the emissions substance treatment system using urea through the exhaust system upstream of an ammonia storage device according to the present disclosure reduces or eliminates escaping ammonia. Any ammonia that escapes is redirected through the exhaust system, which is generally away from the refueling area and less likely to be objectionable to the operator or passengers. Passive venting does not require modifications to the vehicle control system and adds minimal cost/complexity to the vehicle. Continuous coupling of the emissions treatment substance storage tank to the exhaust passively pressurizes the storage tank during operation of the engine to reduce vaporization in the storage tank and to reduce or delay vapor migration from the storage tank and/or any subsequent escape of vapors while not using additional energy/power to operate a fan or other device to control venting. As such, the embodiments reduce or eliminate detectable odor associated with the release of untreated vapors from a vehicle emissions treatment system
While the best mode has been described in detail, those familiar with the related art will recognize various alternative designs and embodiments within the scope of the following claims.
