Method for determining catalyst cool down temperature

• US 6,742,330 B2
• Filed: 04/26/2002
• Issued: 06/01/2004
• Est. Priority Date: 10/16/2000
• Status: Expired due to Fees

• Current Assignee: Engelhard Corporation (BASF SE), TNO Automotive
• Original Assignee: Engelhard Corporation (BASF SE), TNO Automotive
• Inventors: Genderen, Mathijs Van
• Primary Examiner(s): TRAN, BINH Q
• Application Number:
  US10/134,063
• Publication Number:
  US 20020194841A1
• Time in Patent Office: 767 Days
• Field of Search: 602/74, 602/76, 602/77, 602/85, 602/86, 602/95, 602/97, 603/03, 701/102, 701/112, 701/113, 731/181
• US Class Current: 60/286
• CPC Class Codes: B01D 53/90 Injecting reactants
• CPC Class Codes: B01D 53/9431 Processes characterised by a specific device
• CPC Class Codes: B01D 53/9495 Controlling the catalytic process
• CPC Class Codes: F01N 13/009 having two or more separate purifying devices arranged in series
• CPC Class Codes: F01N 2570/18 Ammonia
• CPC Class Codes: F01N 2610/02 the substance being ammonia or urea
• CPC Class Codes: F01N 2610/08 with prior mixing of the substances with a gas, e.g. air
• CPC Class Codes: F01N 2610/12 the substance being in solid form, e.g. pellets or powder
• CPC Class Codes: F01N 2900/0404 using a data filter
• CPC Class Codes: F01N 2900/14 said parameters being related to the exhaust gas
• CPC Class Codes: F01N 2900/1402 Exhaust gas composition
• CPC Class Codes: F01N 2900/1622 Catalyst reducing agent absorption capacity or consumption amount
• CPC Class Codes: F01N 2900/1808 Pressure
• CPC Class Codes: F01N 3/103 Oxidation catalysts for HC and CO only
• CPC Class Codes: F01N 3/208 Control of selective catalytic reduction [SCR], e.g. dosing of reducing agent
• CPC Class Codes: F01N 5/02 the devices using heat
• CPC Class Codes: F01N 9/005 using models instead of sensors to determine operating characteristics of exhaust systems, e.g. calculating catalyst temperature instead of measuring it directly
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A diesel powered vehicle is provided with an SCR system which uses an external reducing reagent to convert NOx emissions in a manner which accounts for the effects of NOx transient emissions on the reducing catalyst. Actual NOx emissions produced by the engine are filtered using a variable NOx time constant in turn correlated to the reductant/NOx storage capacity of the reducing catalyst at its current temperature to account for changes in the SCR system attributed to NOx transient emissions. Catalyst temperature is filtered using a variable catalyst time constant corresponding to current space velocity of the exhaust gas to account for changes in the catalyst temperature attributed to NOx transient emissions. The reductant is metered on the basis of the filtered, corrected NOx concentration applied at a NSR ratio based, in turn, on the filtered, corrected reducing catalyst temperature.

Claims

1. In a method for controlling emissions in the exhaust gases of a vehicular internal combustion engine passing through a catalyst by regulating the engine and/or an external reactant metered to the exhaust gases in response to a number of sensed and/or calculated variables, including the functional temperature of the catalyst, the improvement comprising the steps of:

a) sensing the ambient temperature

b) filtering the functional catalyst temperature determined by the emission control method at the time the engine is shut off by a first order filter using a cool down time constant established as a function of time elapsed from engine shut down at any given catalyst temperature at shut down or as a function of the difference in temperature between ambient temperature and catalyst shut down temperature to establish a functional cool down temperature of the catalyst and

c) using the functional cool down temperature as the functional catalyst temperature in the emission control method upon restart of the engine.

2. The method of claim 1 wherein said step of filtering said functional catalyst temperature to produce said cool down catalyst temperature is represented by a first order cool down filter, said cool down filter implemented in the continuous time domain by the transfer function $H$

(s)=1τ

·

s+1

where τ

is a function of time such as implemented by a timer or the difference between ambient and catalyst temperature at shut down.

3. The method of claim 2 wherein said first order filter in discrete form is represented by the following equation which is processed by a microprocessor:

${\mathrm{TCool}}_{\mathrm{Filt}}=\frac{\mathrm{TAmb}<br><br>\left(n\right)-{\mathrm{TCool}}_{\mathrm{Filt}}<br><br>\left(n-1\right)}{{\mathrm{\tau <br><br>}}_{\mathrm{Cool}}}+{\mathrm{TCool}}_{\mathrm{Filt}}<br><br>\left(n-1\right)$

where;

4. The method of claim 2 wherein said filtering step is implemented by two first order filters in parallel, with each filter having ambient temperature as input and predicting said functional cool down catalyst temperature as output, whereby freezing or drifting to faulty values when the engine is restarted after a short stop is minimized.

5. The method claim 3 wherein said filtering step when implemented by two filters in parallel in discrete form is represented by the following equation which is processed by a microprocessor:

${\mathrm{TCool}}_{\mathrm{Filt1},2}=\frac{\mathrm{TAmb}<br><br>\left(n\right)-{\mathrm{TCool}}_{\mathrm{Filt1},2}<br><br>\left(n-1\right)}{{\mathrm{\tau <br><br>}}_{\mathrm{Cool1},2}}+{\mathrm{TCool}}_{\mathrm{Filt1},2}<br><br>\left(n-1\right)$

and