DE102010036153A1 - Exhaust diagnostic system for vehicle has test enabling module that initiates selective catalyst reduction (SCR) efficiency test after failing SCR efficiency test and while temperature of catalyst is within predetermined temperature range - Google Patents

Abstract

The exhaust diagnostic system has an SCR efficiency testing module (60), an exhaust gas temperature management module (62) and a test enabling module (74). The exhaust gas temperature management module selectively adjusts the temperature of SCR catalyst to a predetermined temperature range using intrusive exhaust gas temperature management. The test enabling module that initiates an SCR efficiency test using the SCR efficiency module after failing a prior SCR efficiency test and while the temperature of the SCR catalyst is within the predetermined temperature range. An independent claim is included for a method for resetting after operation with poor reductant quality.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61 / 242,084, filed Sep. 14, 2009. The disclosure of the above application is hereby incorporated by reference in its entirety.

This application is related to U.S. Application No. 12 / 606,512, filed October 27, 2009, which claims priority to U.S. Provisional Application No. 61 / 242,098, filed September 14, 2009. The disclosures of the above application are hereby incorporated by reference in their entirety.

TERRITORY

The present disclosure relates to vehicle exhaust systems, and more particularly to exhaust diagnostic systems and methods that test for selective catalytic reduction (SCR) efficiency.

BACKGROUND

The background description provided herein is for the purpose of generally illustrating the context of the disclosure. Work of the present inventors, to the extent that it is described in this Background section, as well as aspects of the specification that can not otherwise qualify as prior art at the time of filing, are neither express nor implied as prior art to the art This disclosure is permissible.

During combustion in a diesel engine, an air / fuel mixture is supplied to cylinders through an intake valve and compressed and burned therein. After combustion, the piston drives the exhaust gas in the cylinders into the exhaust system. The exhaust gas may contain nitrogen oxides (NO _x ) and carbon monoxide (CO).

Exhaust gas treatment systems may use selective catalytic reduction (SCR) catalysts to reduce nitrogen oxides (NOx). A catalyst converts the NOx into nitrogen N ₂ and water H ₂ O. Reductant may be added to the exhaust upstream of the SCR catalyst. For example only, the reducing agent may include anhydrous ammonia, aqueous ammonia or urea.

Exhaust gas systems with SCR catalysts are at risk from poor quality reducing agents. When a reducing agent tank has been filled with poor quality reducing agent, an exhaust gas diagnostic system detects a low SCR conversion efficiency. For some vehicles, the engine control module may limit the speed of the vehicle and / or perform other remedial actions. The poor quality reductant should be replaced with a higher quality reductant to correct the problem.

SUMMARY

An exhaust diagnostic system includes a Selective Catalytic Reduction (SCR) efficiency testing module that determines an efficiency of an SCR catalyst. An exhaust temperature management module selectively adjusts a temperature of the SCR catalyst to a predetermined temperature range using intrusive exhaust temperature management. A test activation module triggers an SCR efficiency test using the SCR efficiency module after failing a previous SCR efficiency test and while the temperature of the SCR catalyst is within the predetermined temperature range.

In other features, the SCR efficiency testing module checks the efficiency of the SCR catalyst after setting a dosage of the SCR catalyst to a predetermined level. A speed limit module limits a speed of a vehicle after the vehicle has failed the previous SCR efficiency test. A reset module resets the speed limit module when the SCR efficiency test has been passed.

In further features, the SCR catalyst has a temperature in a first temperature range after failing the previous SCR efficiency test. The first temperature range is less than and different than the predetermined temperature range.

In other features, the exhaust temperature management module increases fuel in the exhaust by adjusting fuel delivery and / or injecting HC fuel into the exhaust using a HC injector to increase the temperature of the SCR catalyst.

In further features, the SCR efficiency testing module includes a test activation module that selectively activates testing of SCR efficiency when particulate filter regeneration is not performed and / or adaptation control of the SCR catalysts is not performed.

In other features, an inlet temperature sensor detects an inlet temperature of the SCR catalyst. An outlet temperature sensor detects an outlet temperature of the SCR catalyst. The temperature of the SCR catalyst is calculated based on inlet and outlet temperatures.

In other features, the temperature calculation module calculates the temperature of the SCR catalyst based on the inlet and outlet temperatures of the SCR catalyst. A fuel adjustment module adjusts fuel delivery and / or injection of hydrocarbon (HC) fuel into the exhaust stream to increase a temperature of the SCR catalyst.

In further features, the selective catalytic reduction (SCR) efficiency module deactivates exhaust gas recirculation after the previous SCR efficiency test and before the SCR efficiency test.

Other applications will be apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will become more fully understood from the detailed description and the accompanying drawings, in which:

1 12 is a functional block diagram of an engine control system having an exhaust diagnostic system that automatically resets after poor diesel engine quality operation, in accordance with the present disclosure;

2 a functional block diagram of an exemplary implementation of a control module of the exhaust gas diagnostic system of 1 is;

3 shows a method for resetting an exhaust diagnostic system after operation with poor diesel reductant quality according to the present disclosure; and

4 a method of controlling the temperature of the SCR catalyst is illustrated.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description is merely exemplary in nature and is not intended to limit the disclosure, its application, or uses. For the sake of clarity, the same reference numbers have been used in the drawings to identify similar elements. As used herein, the phrase "at least one of A, B and C" should be understood to mean a logical (A or B or C) using a non-exclusive logical or. It should be understood that steps within a method may be performed in various order without altering the principles of the present disclosure.

The term "module" as used herein refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory executing one or more software or firmware programs, a combinatorial logic circuit, and / or other suitable components that provide the described functionality.

While the following disclosure relates to diesel engines, other types of engines, such as gasoline engines, including direct injection engines, may take advantage of the teachings herein.

After the vehicle is speed limited and / or another remedial action has been taken, it may be difficult to calculate the SCR conversion efficiency to determine when the reductant has been replaced. The lower speeds of the vehicle do not allow enough heat to build up in the SCR catalyst. Thus, the temperature of the SCR can not reach a proper temperature range for testing SCR efficiency. For example only, the temperature range during the speed limit may be <250 ° C. The testing of SCR efficiency is usually carried out at higher SCR catalyst temperatures. If the reducing agent is replaced with higher quality, there should be a way to reset the exhaust diagnostic system. At present, there is no method of resetting the exhaust diagnostic system after the speed of the vehicle is limited due to poor reducing agent quality, resulting in low SCR efficiency.

One approach to the problem involves resetting the exhaust diagnostic system using a verification tool in a service workshop. This solution is unfavorable due to the fact that review tools are readily available to the general public. Therefore, vehicle operators can reset the exhaust diagnostic system at will, which allows that non-compliant fluids, such as water, can be used instead of reducing agent. Further, customers who do not have verification tools need to visit a dealer for a reset.

The present disclosure automatically restarts a vehicle's exhaust diagnostic system (or via an intrusive maintenance test triggered by the maintenance test tool) after the SCR catalyst is operated with poor quality reductant and the vehicle speed is limited and / or another remedial action has been taken ,

The exhaust diagnostic system according to the present disclosure increases the exhaust gas temperature using an intrusive exhaust temperature management so that a temperature of the SCR catalyst is high enough to allow the efficiency of the SCR catalyst to be checked. If the SCR efficiency is above a predetermined threshold, limitations on vehicle speed and / or other remedial actions may be eliminated without the need for a scanning tool. In other words, after failing to pass the SCR efficiency test, the exhaust system diagnostic may be self-healing due to poor quality reductant (or via an intrusive maintenance test initiated by the maintenance test tool).

Now referring to 1 is a diesel engine system 10 shown schematically. The diesel engine system 10 has a diesel engine 12 and an exhaust treatment system 13 on. The exhaust treatment system 13 further includes an exhaust system 14 and a dosing system 16 , The diesel engine 12 has a cylinder 18 , an intake manifold 20 , an air mass flow (MAF) sensor 22 and an engine speed sensor 24 on. Air flows into the diesel engine 12 through the intake manifold 20 and gets through the MAF sensor 22 supervised. The air gets into the cylinder 18 guided and burned with fuel to drive pistons (not shown). Although a single cylinder 18 It should be noted that the diesel engine 12 additional cylinders 18 can have. For example, diesel engines with 2, 3, 4, 5, 6, 8, 10, 12 and 16 cylinders are conceivable.

Exhaust gas is inside the cylinder 18 generated as a result of the combustion process. The exhaust system 14 treats the exhaust gas before the exhaust gas is released to the atmosphere. The exhaust system 14 includes an exhaust manifold 26 and a diesel oxidation catalyst (DOC) 28 , The exhaust manifold 26 redirects exhaust gas leaving the cylinder through the DOC 28 , The exhaust gas is in the DOC 28 treated to reduce emissions. The exhaust system 14 further includes an SCR catalyst 30 , a temperature sensor 31 , an inlet temperature sensor 32 , an outlet temperature sensor 34 and a particle filter (PF) 36 ,

The temperature sensor 31 can be between the engine and the DOC 18 be positioned. The inlet temperature sensor 32 is upstream of the SCR catalyst 30 arranged to change the temperature at the inlet of the SCR catalyst 30 to monitor. The outlet temperature sensor 34 is downstream of the SCR catalyst 30 arranged to change the temperature at the outlet of the SCR catalyst 30 to monitor. Although the exhaust treatment system 13 is shown to be the inlet and outlet temperature sensors 32 . 34 outside the SCR catalyst 30 arranged, the inlet and outlet temperature sensors 32 . 34 within the SCR catalyst 30 be arranged to change the temperature of the exhaust gas at the inlet and outlet of the SCR catalyst 30 to monitor. The PF 36 further reduces emissions by trapping particulates (ie, soot) in the exhaust gas.

The dosing system 16 includes a metering injector 40 , the reducing agent from a reducing agent fluid supply 38 injected into the exhaust gas. The reductant mixes with the exhaust gas and further reduces emissions when the mixture with the SCR catalyst 30 comes into contact. A mixer 41 may be used to treat the reductant with the exhaust gas upstream of the SCR catalyst 30 to mix. A control module 42 regulates and controls the operation of the engine system 10 ,

An exhaust gas flow sensor 44 may generate a signal corresponding to the flow of exhaust gas in the exhaust system. Although the sensor between the SCR catalyst 30 and the PF 36 As shown, various other locations in the exhaust system may be used for measurement, including after the exhaust manifold and before the SCR catalyst 30 ,

A temperature sensor 46 creates a particulate filter temperature that corresponds to a measured particulate filter temperature. The temperature sensor 46 can be on or within the PF 36 be arranged. The temperature sensor 46 may also be upstream or downstream of the PF 36 be arranged.

Other sensors in the exhaust system may include an upstream NOx sensor 50 which generates a NOx signal based on NOx in the exhaust system. A downstream NOx sensor 52 may be downstream of the PF 36 be positioned to NOx, the PF 36 leaves, to measure. In addition, an ammonia (NH ₃ ) sensor generates 54 a signal corresponding to the amount of ammonia in the exhaust gas. The NH ₃ sensor 54 is optional, but may be used to simplify the control system due to the ability to distinguish between NOx and NH ₃ . Alternatively and / or additionally, a hydrocarbon (HC) supply may be used 56 and a KW injector 58 be provided to deliver HC into the exhaust gas that reaches the DOC catalyst.

Now referring to 2 can the control module 42 an SCR efficiency testing module 60 used to calculate the conversion efficiency of NOx on the SCR catalyst 30 to determine. The control module 42 further includes an exhaust temperature management module 62 , which is a temperature of the SCR catalyst 30 controls intrusively. The SCR efficiency testing module 60 includes a reset module 70 and a test trigger module 72 , The term "intrusive" as used herein means that the control module 42 controlling the engine out of optimal operating conditions from an emission perspective to allow the test to take place. The exam release module 72 triggers an intrusive SCR efficiency check after the SCR catalyst 30 failed a prior SCR efficiency test and a vehicle speed limit and / or other corrective action was taken.

The intrusive test trigger module 72 sends a signal to the exhaust gas temperature management module 62 to initiate an intrusive temperature control of the SCR prior to testing the SCR efficiency. The exam activation module 74 ensures that the activation conditions are fulfilled before the test.

The exhaust gas temperature management module 62 includes an SCR temperature calculation module 76 which calculates a temperature of the SCR. The temperature calculation module 76 may be the temperature of the SCR catalyst based on the inlet temperature sensor 32 , the outlet temperature sensor 34 , a model or any other suitable method. For example only, the temperature calculation module 76 the SCR temperature based on values from both the inlet and outlet temperature sensors 32 . 34 to calculate. For example only, the temperature calculation module 76 the temperature based on an average or weighted average of the inlet and outlet temperature sensors 32 . 34 to calculate.

The control module 42 , the SCR efficiency testing module 60 and / or the exhaust gas temperature management module 62 can be an operating parameter setting module 78 which sets other operating parameters before the SCR intrusive efficiency test. By way of example, other operating parameters, such as metering, NH ₃ loading, EGR and / or other conditions, may also be adjusted within respective windows prior to intrusive SCR efficiency testing.

The control module 42 includes a vehicle speed limit module 80 that limits a vehicle speed after the SCR efficiency falls below a predetermined efficiency. The control module 42 further includes a fuel delivery control module 82 which determines an amount of fuel, a fuel injection timing, a post-injection, etc. In the intrusive SCR test mode, the exhaust temperature management module provides 62 a fuel delivery. The fuel delivery setting increases a temperature of the SCR catalyst. Alternatively, inject a hydrocarbon injection module 84 Fuel in the exhaust gas upstream of the DOC catalyst 28 to generate an exotherm to raise the temperature in the SCR.

Now referring to 3 begins a control at 100 where the controller determines if an intrusive reductant quality check must be run. For example only, the intrusive reductant quality test is operated after the vehicle is placed in a speed limit mode and / or another remedial action is taken after previous SCR efficiency testing has failed.

If 100 does not apply, the control comes on 102 in a normal mode. If 100 applies, the controller goes with 104 and determines if a first set of conditions is acceptable to perform the test. For example only, the first set of conditions may include ensuring that no regeneration of the PF 36 is carried out. The PF regeneration is typically carried out when soot in the PF 36 builds. In addition, the first set of conditions may include ensuring that no adaptation is performed. An adaptation occurs when there is a problem with the SCR catalyst such that the downstream NOx sensor measurements deviate from a model by a predetermined amount. Still other conditions may be used in the first set of conditions instead of or in addition to these conditions.

If 104 not true, the controller returns 100 back. If 104 applies, the controller goes with 106 and optionally disables exhaust gas recirculation (EGR). at 108 the controller activates an intrusive SCR test to achieve a predetermined SCR temperature range. The controller switches on 108 also a dosage. at 112 determines whether sufficient NH ₃ charge on the SCR catalyst 30 is available. A time delay may be used to ensure that sufficient NH ₃ charge has been restored to provide acceptable NOx conversion.

If 112 is not true, the controller waits until a sufficient NH ₃ is present at the -load SCR. at 114 the controller determines if a second set of activation conditions has been satisfied. For example only, the second set of activation conditions may include one or more of the following conditions: exhaust flow within a predetermined range; an upstream NOx mass flow within a predetermined range; an upstream NOx concentration within a predetermined range and / or NOx sensors ready. Other conditions may be included in the second set of activation conditions.

at 118 the controller measures the SCR conversion efficiency EFF _SCR . at 120 For example, the controller generates an SCR conversion efficiency EFF _SCR as a function of upstream and downstream accumulated masses. at 124 For example, the controller generates an efficiency threshold EFF _THR as a function of upstream NOx and the SCR temperature. The threshold of the SCR conversion efficiency EFF _THR may be a percentage.

at 128 the controller determines if EFF _SCR > EFF _THR . If 128 applies, the controller explains 130 a pass status of reductant quality (and / or SCR efficiency status). If 128 does not apply, the controller explains 132 a REDUCED status of reductant quality (and / or a PASS state of SCR efficiency). The controller starts from 130 With 134 and deactivates the reductant fail mode. For example, the vehicle speed limit mode and / or other remedial actions are terminated. The controller starts from 132 and 134 With 140 where the controller terminates the intrusive exhaust temperature management and activates the EGR (if previously disabled).

Now referring to 4 a method for intrusive exhaust temperature management is shown. at 146 the controller determines if the intrusive SCR check is in progress. If 146 not true, the controller returns 146 back. If 146 applies, the controller goes with 148 where the controller determines if the SCR temperature is within a predetermined temperature range (eg, T _Lo and T _Hi ).

If 148 applies, the controller returns 146 back. If 148 does not apply, determines the controller at 152 whether the SCR temperature is greater than T _Lo . If 152 not true, the controller increases the exhaust gas temperature in any suitable manner. For example, the exhaust gas temperature by changing the fuel delivery (fuel quantity, fuel injection timing, Nachinjektion, etc.) and / or by starting or increasing the HC injection at 154 increase. The controller returns 146 back.

If 148 does not apply, determines the controller at 156 whether the SCR temperature is less than T _Hi . If 156 not true, the controller reduces the exhaust gas temperature in any suitable manner. For example, the exhaust gas temperature may be changed by changing the fuel delivery (fuel amount, fuel injection timing, post-injection, etc.) and / or stopping or reducing the HC injection 158 be reduced. The controller returns 146 back.

The broad teachings of the disclosure may be made in a variety of forms. Therefore, while this disclosure has particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification, and the following claims.

Claims (10)

Exhaust diagnostic system comprising: a Selective Catalytic Reduction (SCR) efficiency testing module that determines an efficiency of an SCR catalyst; an exhaust temperature management module that selectively adjusts a temperature of the SCR catalyst to a predetermined temperature range using intrusive exhaust temperature management; and a test activation module that triggers an SCR efficiency test using the SCR efficiency module after failing a previous SCR efficiency test and while the temperature of the SCR catalyst is within the predetermined temperature range. The exhaust diagnostic system of claim 1, wherein the SCR efficiency testing module checks the efficiency of the SCR catalyst after dosing the SCR catalyst. The exhaust diagnostic system of claim 1, further comprising a speed limit module that limits a speed of a vehicle, after the vehicle has failed the previous SCR efficiency test. The exhaust diagnostic system of claim 3, further comprising a reset module that resets the speed limit module when the SCR efficiency test has passed. Exhaust gas diagnostic system according to claim 1, wherein: the SCR catalyst has a temperature in a first temperature range after failing the previous SCR efficiency test; and the first temperature range is less than and different than the predetermined temperature range. Exhaust gas diagnostic system according to claim 1, wherein the exhaust temperature management module increases fuel in the exhaust gas by: Adjusting a fuel delivery; and or Injecting HC fuel into the exhaust using a HC injector to increase the temperature of the SCR catalyst. Exhaust gas diagnostic system according to claim 1, wherein the SCR efficiency testing module comprises a test activation module that selectively activates testing of SCR efficiency when: no particulate filter regeneration is performed; and or no adaptation control of the SCR catalyst is performed. Exhaust gas diagnostic system according to claim 1, further comprising: an intake temperature sensor that detects an intake temperature of the SCR catalyst; and an outlet temperature sensor detecting an outlet temperature of the SCR catalyst, wherein the temperature of the SCR catalysts is calculated based on the inlet and outlet temperatures. Exhaust gas diagnostic system according to claim 1, further comprising: a temperature calculation module that calculates the temperature of the SCR catalyst based on inlet and outlet temperatures of the SCR catalyst; and a fuel adjustment module that adjusts fuel delivery and / or injects hydrocarbon (HC) fuel into the exhaust stream to increase a temperature of the SCR catalyst. The exhaust diagnostic system of claim 1, wherein the selective catalytic reduction (SCR) efficiency module deactivates exhaust gas recirculation after the prior verification of SCR efficiency and prior to SCR efficiency testing.

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