MX2009001667A

MX2009001667A - Strategy for using exhaust stroke post-injection to elevate exhaust temperature for diesel particulate filter regeneration.

Info

Publication number: MX2009001667A
Application number: MX2009001667A
Authority: MX
Inventors: Russell P Zukouski; Paul L Berke
Original assignee: Int Engine Intellectual Prop
Priority date: 2006-08-16
Filing date: 2007-08-07
Publication date: 2009-03-26
Also published as: WO2008021816A2; JP2010501052A; CA2660478A1; KR20090052362A; BRPI0716415A2; EP2054590A4; CN101529059A; US20080028750A1; EP2054590A2; WO2008021816A3

Abstract

An engine control system (28) causes combustion chambers (20) to be fueled during an engine cycle by a main injection (38) ending no later than substantially at the TDC between compression and expansion strokes of the cycle without any further injection of fuel during the expansion stroke, and then during the exhaust stroke of the cycle, by a post-injection (40) for elevating the temperature of the gases into a regeneration temperature range for regenerating a diesel particulate filter (36).

Description

STRATEGY FOR USING POSTER SHOCK INJECTION TO RAISE THE EXHAUST TEMPERATURE FOR FILTER REGENERATION IN DIESEL PARTICLES FIELD OF THE INVENTION This invention relates generally to internal combustion engines for propelling motor vehicles, particularly to diesel engines having diesel particulate filters (DPFs) as after-treatment devices in their fuel systems. escape .

BACKGROUND OF THE INVENTION A known system for treating exhaust gases passing through an exhaust system of a diesel engine comprises a diesel oxidation catalyst (DOC) associated with a diesel particulate filter. (DPF). The combination of these two treatment devices promotes chemical reactions in the exhaust gases and traps the matter in diesel particulates (DPM) as the gases flow through the exhaust system of the engine, thus avoiding significant quantities of engine pollutants. in the atmosphere. A DPF requires regeneration from time to time in order to maintain efficiency to trap particles. The regeneration involves creating conditions that will burn trapped particles whose unrevised accumulation could in some way alter the effectiveness of DPF. The creation of conditions to initiate and continue regeneration generally involves raising the temperature of exhaust gas entering DPF to a suitably high temperature. Because a diesel engine normally operates relatively cold and pure, post-injection diesel fuel has been used as part of a DPF regeneration strategy to raise exhaust gas temperatures that enter DPF while still having oxygen in excess to burn the trapped particulate matter. When a vehicle is being operated in a conductive manner for the regeneration of the DPF, such as cruising on a highway, the regeneration process can be carried out with little or no significant effect on the quality of vehicle handling and can be initiated either by the driver or automatically by a regeneration start strategy even before the DPF is loaded with DPM to a degree where forced regeneration could be sent by the engine control system. The inventors have discovered that a "short" post-injection of fuel, which means that an injection is carried out during the expansion, or power, collides within a range of about 60 ° after the The upper dead center (ATDC) makes a contribution to the torque of the arrow that has a sufficiently noticeable effect on the quality of handling of the vehicle that some drivers may consider objectionable. The compensation for this "short" post-injection effect in order to reduce its influence on the quality of vehicle handling requires an extensive development effort in order to achieve the best possible calibration. One consideration that must be taken into account is the ability of the fuel injectors to supply "short" post-ejections that is needed very soon after the main injection. Certain fuel injectors that have convenient attributes may have difficulty, however, in providing a "short" post-injection that is required very soon after a main injection. The difficulty is pronounced more as the engine speed increases in a high speed range. While a "far" post-injection is used during the expansion shock, which means an injection that occurs during the end of a "close" post-injection, it can direct any aspect of the fuel injector's ability to supply a post. -injection at a desired time during the expansion shock, a post-injection that is very "far" in the expansion shock It can cause significant washing of the cylinder walls which can lead to the dilution of engine oil. These discoveries and recognitions have led the inventors to look for an alternative and better solution for using the post-injection to raise the temperature of the exhaust to levels to initiate and maintain the regeneration of DPF.

SUMMARY OF THE INVENTION The present invention refers to a novel strategy that provides said solution. In contrast to the search for an optimal calibration for post-injection by repeated start regeneration using different amounts of post-injection and times within a time range immediately after TDC in the expansion shock and then evaluating the results for To ensure an optimum, the inventors have discovered that a final post-injection in the exhaust stroke can be as effective to initiate and maintain the regeneration of DPF, with less impact on the quality of vehicle handling and without requiring an extensive development effort. , such as when "close" post-injection is used during the expansion stroke. In addition, the invention avoids aspects that refer to the capacity of an injector of fuel to supply a post-injection in the close proximity to a main injection (thus avoiding modifications to the injector and / or control injector driver) and aspects that relate to excessive cylinder wall washing which contributes to the dilution of engine oil. The delay of the post-injection to a time within a range that expands a last portion of the gas stroke has been found not to form the potentially objectionable torque lift mentioned above nor the washing of the objectionable cylinder wall while the , giving the fuel injectors, particularly the hydraulically driven ones, the "recharging" time between the main injection and providing the same effect as "near" post-injection (expansion stroke) to initiate and maintain the DPF regeneration. The invention can be implemented in existing systems through appropriate modifications of algorithms that control the time of fuel injections. Therefore, no additional hardware is needed. The optimum time during the exhaust stroke can be developed by calibration adjustment during the driving test with less effort than required when using "close" post-injection (expansion stroke).

Accordingly, a generic aspect of the present invention relates to a diesel engine comprising a fuel system for injecting diesel fuel into combustion chambers when the fuel is burned to drive the engine, an exhaust system through which the gases created by combustion passes into the atmosphere and comprises a device after the treatment that treats the gases before leaving the exhaust system but sometimes requires regeneration by raising the temperature of the gases to a regeneration temperature range and a system of motor control to process various data in order to control various aspects of the motor operation including the proportion of fuel carried out by the fuel ratio system and regeneration of the device after treatment. In consequence of a request for regeneration, the control system causes the system to provide fuel to fuel the combustion chambers during a motor cycle for a combustion chamber in a main injection that terminates substantially before the TDC between the compression and expansion shocks to the cycle without any additional fuel injection during the expansion shock, and then during the cycle exhaust shock, by a post-injection to raise the temperature of the gases in the regeneration temperature range.

Another generic aspect relates to a motor vehicle driven by a motor as just described. Yet another generic aspect relates to a method for initiating the regeneration of an after-treatment device for exhaust gases in an exhaust system of a diesel engine having a fuel ratio system for injecting diesel fuel into the exhaust chambers of the engine. combustion in where the fuel is burned to drive the engine and a motor control system to process various data in order to control various aspects of operation of another including the proportion of fuel carried out by the fuel ratio system and the regeneration of the device after treatment. The method comprises influencing the regeneration causing the fuel system to provide fuel to the combustion chambers during a motor cycle for a combustion chamber by a main injection which does not end after substantially the TDC between the compression and expansion shocks of the cycle without any additional fuel injection during the expansion shock and then during the exhaust shock of the cycle, by a subsequent injection. The foregoing, together with the additional aspects and advantages of the invention, will be observed in the following description of a currently preferred embodiment of the invention. invention that describes the best mode contemplated at this time to carry out the invention. This specification includes drawings, now briefly described in summary as follows.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a general schematic diagram of an internal combustion engine that forms a strategy for initiating and maintaining the regeneration of DPF in accordance with the principles of the present invention. Figure 2 is a fuel injection time diagram illustrating the strategy.

DESCRIPTION OF THE PREFERRED MODALITY Figure 1 shows an example of a turbocharger diesel engine 10 having an absorption system 12 through which the charging air enters and an exhaust system 14 through which the exhaust gas escapes. It results from combustion, not being included all the details of the two systems that are normally present. When used in a motor vehicle, such as a truck, the engine 10 is coupled through a drive train 16 to drive the wheels 18 that propel the vehicle. The engine 10 comprises cylinders 20 forming combustion chambers in which fuel is injected through fuel injectors 22 for burning with the air of the charge that has entered through the absorption system 12. The energy released by combustion drives the engine via the pistons 24 connected to an arrow 26 which leads to a drive train 16 to propel the vehicle. Fuel injectors 22 are under the control of an engine control system 28 comprising one or more processors, which process various data to develop data to control various aspects of engine operation including controlling the hydraulic fluid pressure supplied to fuel injectors. Fuel 22 (reference number 30) and time control of the operation of valve mechanisms in the fuel injectors that use the hydraulic fluid to force the fuel out of the injectors enters the combustion chambers. The absorption valves 32 control the intake of charge air in the cylinders 20, and the exhaust valves 34 control the flow of combustion gases through the exhaust system 14 and finally to the atmosphere. However, before entering the atmosphere, the combustion gases are treated by one or more devices after treatment. The device shown herein to which the present invention relates is a diesel particulate filter, or DPF, 36.

Several sensors are associated with the devices after processing to give information to the control system 28. One piece of information is the degree to which DPF 36 is loaded with particles. The control system 28 contains algorithms that execute repeatedly to process certain data for various control purposes An algorithm uses information about the DPF particles that are loaded to initiate regeneration when conditions are adequate even if DPF is loaded below of a level that requires forced regeneration and forces regeneration when DPF is loaded to the level that is required for forced regeneration. With the engine 10 in operation, a main fuel injection is substantially at TDC between the compression shock C and the expansion, or power, shock P, as represented by the injection 38 in Figure 2 illustrating conventional diesen combustion. (C) When the control system 28 requests the regeneration of DPF 36, the main injections such as 38 continue, but now a new specific post-injection strategy is employed. The strategy does not employ post-injection during the expansion shock, but rather a post-injection during the exhaust shock E, preferably for a time at the end of the exhaust shock but ahead of the TDC which occurs between the end of the exhaust shock and the start of the next consumption shock I, as represented by the post-injection 40 in figure 2. The strategy continues until regeneration starts and also with the purpose of maintaining the regeneration When the regeneration strategy ends, the post-injection during the exhaust shock concludes. Certain diesel engines can sometimes operate by alternative diesel combustion, as distinguished from CD combustion and while the engine has been described in the present operation by CD combustion, it is thought that the principles of the invention can be applied to a engine that operates by alternative diesel combustion as long as the control system allows the regeneration of DPF while the engine is in operation. Alternative diesel combustion is a generic term for certain processes and systems such as Homogeneous Load Compression Ignition (HCCI), Controlled Self-ignition (CAI), Dilution Controlled Combustion Systems (CDS), and highly pre-blended Combustion Systems (HPCS). When an engine is operated by an alternative diesel combustion process, the effect of injections occurs until the main combustion occurs that can be considered equivalent to a main DC combustion injection.

It should also be understood that the use of post-injection during the exhaust shock rather than during the expansion shock may be only one element of a more compressed regeneration strategy that uses injection other than fuel only to initiate and maintain regeneration of DPF. While a currently preferred embodiment of the invention has been illustrated and described, it should be appreciated that the principles of the invention apply to all embodiments within the scope of the following claims.

Claims

CLAIMS 1. - A diesel engine comprising: a fuel ratio system for injecting diesel fuel into combustion chambers where the fuel is burned to drive the engine; an exhaust system through which the gases created by combustion pass into the atmosphere and which comprise a device after the treatment that treats the gases before leaving the exhaust system but which sometimes requires regeneration due to the temperature rise of the gases a range of regeneration temperature; an engine control system for processing various data to control various aspects of engine operation including the proportion of fuel carried out by the fuel ratio system and regeneration of the device after treatment; wherein as a result of a request for regeneration, the control system causes the fuel ratio system to provide fuel to the combustion chambers, punctures an engine cycle for a combustion chamber by a main injection which does not end after substantially the TDC between the compression and expansion cycle crashes without any additional fuel injection during the expansion shock and then during the exhaust shock of the cycle, by a post-injection to raise the temperature of the gases in the regeneration temperature range. 2. - A diesel engine according to claim 1, wherein the post-injection is caused closer to TDC than to BDC. 3. - A diesel engine according to claim 1, wherein the main injection causes the engine to operate by conventional diesel combustion. . - A diesel engine according to claim 1, wherein the device after the treatment comprises a diesel particulate filter. 5. A diesel engine according to claim 4, wherein the post-injection is caused closer to TDC than to BDC. 6. - A motor vehicle comprising: a diesel engine to turn the drive wheels through a drive train to propel the vehicle: a fuel ratio system for injecting diesel fuel into the combustion chambers of the engine in which the fuel is fitted to propel the vehicle; an exhaust system through which the gases created by combustion pass into the atmosphere and which comprises a device after the treatment that treats the gases before leaving the exhaust system but sometimes requires regeneration by raising the temperature of the gases to a regeneration temperature range, a control system to process various data to contour various aspects of engine operation including the proportion of fuel carried out by the fuel ratio system and regeneration of the device after treatment; wherein in consequence of a request for regeneration, the control system causes the fuel fuel proportion system to the combustion chambers during a motor cycle for a combustion chamber by a main injection that does not end after substantially the TDC between the compression shock and cycle expansion without additional fuel injection during the expansion shock, and then during the exhaust shock of the cycle by a post-injection to raise the temperature of the gases in the regeneration temperature range. 7. - A motor vehicle according to claim 6, wherein the post-injection occurs closer to TDC than BDC. 8. - A motor vehicle according to claim 6, wherein the main injection causes the engine to operate by conventional diesel combustion. 9. A motor vehicle according to claim 6, wherein the device after treatment comprises a diesel particulate filter. 10. A motor vehicle according to claim 9, where post-injection occurs closer to TDC than to BDC. 11. A method for initiating the regeneration of a device after exhaust gas treatment in an exhaust system of a diesel engine that has a combustion system for injecting diesel fuel into the combustion chambers where the fuel is burn to drive the motor and a motor control system to process various data to control various aspects of the motor operation including the proportion of fuel carried out by the fuel ratio system and the regeneration of the device after treatment, the method comprising: initiating regeneration causing the fuel proportioning system to provide fuel to the combustion chambers during a motor cycle for a combustion chamber by a main injection that does not end after substantially the TOC between the collisions of compression and expansion of the cycle without any additional fuel injection during the expansion shock, and then during the exhaust shock of the cycle, by a post-injection. 12. A method according to claim 11, comprising causing the post-injection to occur closer to TDC than to BDC. 13. A method according to claim 11, comprising injecting the main injection in a manner that causes the engine to operate by conventional diesel combustion.