FOR THE EMISSION SYSTEM OF A VEHICLE

TECHNICAL FIELD

[0001] The present system and method relate to reductant dosing used in vehicle emission systems. Particularly, the present system and method relate to controls for reductant dosing to coincide with depletion of reductant with scheduled service periods.

BACKGROUND

[0002] Emerging technologies for control of emissions, particularly NO _x control in diesel engine exhaust, rely on delivery of ammonia gas~a reductant in NO _x emission control- generated from solid materials stored in tanks or other types of containers carried onboard vehicles. The solid ammonia carrier material, which is heated on the vehicle to produce the needed ammonia gas, may be provided in a variety of forms, including two currently being proposed as ammine complexes and ammonium carbonate. The tanks are intended to serve during fixed intervals, such as the time or travel distance between consecutive oil changes or the like, and should be replaced at service stations by trained technicians. Ideally, the quantity of ammonia carried on a vehicle would be completely used up by the scheduled service time. However, in reality, due to variability in vehicle configurations and driving conditions, the ammonia consumption rate is highly variable, and two scenarios are likely.

[0003] The first scenario is when there remains an unused amount of ammonia and replacement of a tank (or other storage media) may result in waste of ammonia-containing material, thus increasing the cost of operating the vehicle. The second scenario is the complete opposite and occurs when the ammonia is used up before a scheduled service interval. This is an unsatisfactory condition as well, as it may lead to the vehicle being non-compliant with emission regulations.

[0004] The present invention addresses and solves each of these potential problems and provides improvements in the area of reductant dosing control which has environmental and cost benefits. Solutions to other problems associated with the handling and disposal of ammonia- containing tanks and vehicle fuel economy, may also be achieved by the present system and method.

SUMMARY

[0005] There is disclosed herein an improved system and method for reductant dosing control in a vehicle emission system which avoids the disadvantages of prior systems while affording additional structural and operating advantages.

[0006] Generally speaking, the method of the present application is directed to reductant dosing control for an emissions system on a motorized vehicle, and comprises the steps of storing reductant on the vehicle, recording data about the vehicle and the reductant storage, recording a vehicle service point, determining a consumption rate of the reductant during vehicle operation, estimating a point for total consumption of the reductant, comparing the estimated point of total consumption to the recorded vehicle service point, and adjusting the consumption rate of the stored reductant until the estimated point of total consumption and the recorded vehicle service point approximately coincide. The critical points for service and consumption can be recorded as a function of vehicle operation time or a function of driving distance (e.g., vehicle mileage).

[0007] In another embodiment, the method of the present application is directed to reductant dosing control for reducing NO _x emission in an emissions system on a motorized vehicle, and comprises the steps of storing reductant on the vehicle, recording data about the vehicle and the reductant storage, recording a vehicle service point, determining a consumption rate of the reductant during vehicle operation, estimating a point for total consumption of the reductant, comparing the estimated point of total consumption to the recorded vehicle service point, and adjusting engine operating parameters and NOx emission thereby adjusting the consumption rate of the stored reductant until the estimated point of total consumption and the recorded vehicle service point approximately coincide. The critical points for service and consumption can be recorded as a function of vehicle operation time or a function of driving distance (e.g., vehicle mileage).

[0008] In an embodiment of a reductant dosing control system, a known amount of reductant (e.g., ammonia in a solid carrier material) for a vehicle emissions system is stored on a vehicle. System memory records data from the vehicle relevant to use of the reductant, including recording at least one vehicle service point to occur after a determined period of vehicle operation. The system includes computing software or hardware which operates as a means for determining a consumption rate of the stored reductant, means for estimating a point for total consumption of the reductant, means for comparing the estimated point of total consumption to the recorded vehicle service point, and as a means for adjusting the consumption rate of the stored reductant until the estimated point of total consumption and the recorded vehicle service point approximately coincide.

[0009] These and other aspects of the invention may be understood more readily from the following description and the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] For the purpose of facilitating an understanding of the subject matter sought to be protected, there are illustrated in the accompanying drawings embodiments thereof, from an inspection of which, when considered in connection with the following description, the subject matter sought to be protected, its construction and operation, and many of its advantages should be readily understood and appreciated. The components in the drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the following description and throughout the numerous drawings, like reference numbers are used to designate corresponding parts.

[0011] FIGURE 1 is a flow chart illustrating an embodiment of the present reductant dosing control method; and

[0012] FIGURE 2 is a schematic of an embodiment of the present reductant dosing control system.

DETAILED DESCRIPTION

[0013] While this invention is susceptible of embodiment in many different forms, there is shown in the drawings, and will herein be described in detail, preferred embodiments of the invention, including embodiments of the various components of the invention, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to embodiments illustrated.

[0014] Referring to FIGURES 1 and 2, there are illustrated embodiments of both a reductant dosing control method and dosing control system, generally designated by the numeral 10, as well as the various steps or components thereof. The method and system 10 are designed for use in combination with an emission system for a vehicle, particularly an after-treatment system, such as SCR, which utilize ammonia gas for reducing NO _x in a vehicle exhaust stream.

[0015] FIGURE 1 is a flow chart illustrating an embodiment of the method for controlling the reductant dosing in a vehicle. The method begins with installation of original solid ammonia carrier tanks (or other container forms) to a new vehicle. The ammonia carrier may be in any of the various chemical forms, such ammine complexes or ammonium nitrate (for additional examples see SAE 2009-01-0907), and is typically held in at least one tank (though several may be used) secured to the vehicle frame. Heating elements are used to cause ammonia gas release into an engine exhaust stream as a NO _x reductant. The total amount of ammonia being secured to the vehicle is recorded at 12.

[0016] At the same time, relevant information about the vehicle is also recorded at 14. The information should include the next service interval (box 16), in time (e.g., days or hours of operation) or mileage, and may also include the vehicle's current mileage, mileage (or time) since the last service, date and time of the current tank addition, current ammonia storage level in a tank, and any other information about the vehicle which may help in the dosing control. The initial consumption rate of the ammonia reductant may be set according to those currently known and used, including a stoichiometric injection strategy, a storage-based strategy, or some combination of such consumption strategies.

[0017] During operation of the vehicle, the actual consumption of ammonia may be calculated at 18, as a function of time of operation or as a function of mileage. The most accurate calculation of the ammonia consumption rate should be favored.

[0018] From the consumption rate, an estimated point of exhaustion of the on-board ammonia can be readily determined, knowing the initial amount of on-board ammonia (previously recorded). This calculation should be performed periodically within the time interval before the next scheduled service of the vehicle. Preferably, the period before calculation should be in the range of from about 1% to about 50% of the remaining interval (time or distance) before service. For example, if the next scheduled service is in 5,000 miles (or 100 driving hours), then the period for calculation of an estimated exhaustion point could be between 50 miles (or 1 hour) and 2,500 miles (or 50 hours)— i.e., between the preferred 1% and 50% endpoints. As the point for service gets closer, which it does for subsequent calculations, the interval for calculation of the exhaustion point can be reduced, if desired. For example, the next calculation of the estimated exhaustion point might be between 1% and 50% of the remaining interval of 2,500 miles (or 50 hours). The calculation, and recalculation, of the estimated exhaustion point is performed at 20 on the flow chart.

[0019] Next, at 22, the estimated exhaustion point (from box 20) is compared to the recorded service point (from box 16) to determine if the two coincide. If they do not, a calculation is made to determine the engine NO _x emission level which will result in complete consumption of the remaining ammonia at the service point. At 24 on the flow chart, the engine operation parameters of the engine and/or vehicle are then automatically adjusted to achieve the determined NO _x emission level necessary. Effectively, the adjustment of the engine out NO _x emissions results in a new ammonia consumption rate. However, merely adjusting the consumption rate could lead to non-compliance with environmental emission regulations.

[0020] Finally, to maintain accuracy for changing vehicle operation conditions, the recalculation of the estimated exhaustion point and the readjustment of the engine operation parameters to coincide the exhaustion point and the actual service point, may be required. This occurs at boxes 18-24, as it is merely a repeating of the corresponding steps at desired intervals.

[0021] Referring now to the schematic illustrated in FIGURE 2, the general components of the dosing control system 10 can be more readily understood.

[0022] As described above in the details of the method, the system also begins with the on- loading of a known amount of reductant (NH ₃ as part of a solid carrier) for the vehicle emissions system. The solid ammonia carrier material is packed into suitable storage tanks 30 which are secured to the vehicle frame (not shown). Relevant data of the reductant, such as the total amount added, the vehicle, such as the current mileage and the last and next service points, and other general information, such as the date and time of addition of the current ammonia tanks, can be input to a system memory 32 by any suitable data entry means (not shown). The system memory 32 may be already on the vehicle from another system used for other purposes, or it may be newly added system memory. The system memory is used to store data from the vehicle relevant to use of the reductant, as detailed previously.

[0023] The system 10 also requires a computer 34 which serves as the means for determining a consumption rate of the stored reductant by the emissions system during vehicle operation. The system computer 34 can also provide the means for estimating a point for total consumption of the reductant based on the consumption rate, as well as the means for comparing the estimated point of total consumption to the recorded vehicle service point. These calculations and comparisons are simple and would be suitable for any on-board vehicle computer. Likewise, the system computer 34 can also be used for providing the means for adjusting the consumption rate of the stored reductant until the estimated point of total consumption and the recorded vehicle service point approximately coincide. The vehicle on-board computer (not shown) is probably already charged with optimizing engine operation parameters and could readily make the necessary adjustments to achieve the desire engine out NO _x for the current dosing control system 10.

[0024] It should be emphasized that the above-described embodiments of the present invention, particularly, any "preferred" embodiments, are possible examples of implementations merely set forth for a clear understanding of the principles for the invention. Many variations and modifications may be made to the above-described embodiment(s) of the invention without substantially departing from the spirit and principles of the invention. All such modifications are intended to be included herein within the scope of this disclosure and the present invention, and protected by the following claims.

[0025] The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. While particular embodiments have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made without departing from the broader aspects of applicants'

contribution. The actual scope of the protection sought is intended to be defined in the following claims when viewed in their proper perspective based on the prior art.