Method of determining the amount of particulate accumulated in a particulate filter

• US 6,941,750 B2
• Filed: 01/24/2003
• Issued: 09/13/2005
• Est. Priority Date: 01/25/2002
• Status: Expired due to Term

• Current Assignee: C.R.F. Societa Consortile Per Azioni
• Original Assignee: Cefla Societa' Cooperativa
• Inventors: Boretto, Gianmarco, Corrias, Silvio
• Primary Examiner(s): NGUYEN, TU MINH
• Application Number:
  US10/350,365
• Publication Number:
  US 20030167757A1
• Time in Patent Office: 963 Days
• Field of Search: 602/74, 602/95, 602/97, 603/11, 602/76, 602/77, 55D/IG.30, 555/23, 731/181, 73/233.1, 73/233.2
• US Class Current: 60/297
• CPC Class Codes: F01N 11/002 the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus
• CPC Class Codes: F01N 13/009 having two or more separate purifying devices arranged in series
• CPC Class Codes: F01N 13/0093 the purifying devices are of the same type
• CPC Class Codes: F01N 13/0097 the purifying devices are arranged in a single housing
• CPC Class Codes: F01N 3/035 with catalytic reactors , e.g. catalysed diesel particulate filters
• CPC Class Codes: F01N 9/002 of filter regeneration, e.g. detection of clogging
• CPC Class Codes: F02B 37/00 Engines characterised by provision of pumps driven at least for part of the time by exhaust
• CPC Class Codes: F02D 2041/1411 using a finite or infinite state machine, automaton or state graph for controlling or modelling
• CPC Class Codes: F02D 2200/0812 Particle filter loading
• CPC Class Codes: G01N 2015/084 Testing filters
• CPC Class Codes: Y02T 10/40 Engine management systems
• CPC Class Codes: Y10S 55/30 Exhaust treatment

Abstract

A method of determining the amount of particulate accumulated in a particulate filter, is based on determining possible variations in the spatial distribution and/or physical-chemical properties of the particulate as a function of engine operating conditions and past particulate accumulation in the particulate filter. A number of reference values defining a relationship between the amount of particulate accumulated in the particulate filter and the pressure drop across the particulate filter are mapped, each of the reference values relating to a respective steady engine operating condition in which particulate is accumulated in the particulate filter. In a given engine operating condition, an operating value of the parameter is then determined as a function of the reference value of the parameter relative to the same steady engine operating condition, and of past particulate accumulation in the particulate filter.

Claims

1. A method of determining the amount of particulate (m_S) accumulated in a particulate filter (9), comprising the step of determining the variation in spatial distribution and accumulation patterns of the particulate along channels in said particulate filter (9) as a function of engine operating conditions and past particulate accumulation in said particulate filter (9), whereby different categories of said accumulation patterns are associated with different engine operating conditions.

2. A method as claimed in claim 1, characterized by comprising the step of determining at least one of the variation in spatial distribution of the particulate in said particulate filter (9) and the variation in the physical-chemical properties of the particulate due to partial regenerations (e.g. NOx-based spontaneous regeneration) and prolonged vehicle disuse (“

parking”

effect).

3. A method as claimed in claim 1, characterized by also comprising the steps of:

determining a state index (I_PART) of the particulate in said particulate filter (9); and

activating regeneration of said particulate filter (9) on the basis of said state index (I_PART) of the particulate in said particulate filter (9).

4. A method as claimed in claim 3, characterized in that said state index (I_PART) of the particulate in said particulate filter (9) is determined according to the following equation:

$I_{\mathrm{PART}}=\frac{{\mathrm{\beta <br><br>}}_{\mathrm{MAX}}-{\mathrm{\beta <br><br>}}_{\mathrm{MOD}}}{{\mathrm{\beta <br><br>}}_{\mathrm{MAX}}-{\mathrm{\beta <br><br>}}_{\mathrm{MIN}}}<br><br>\text{\hspace{1em}<br><br>}<br><br>0<<br><br>I_{\mathrm{PART}}<<br><br>1$

where;

I_PART is said state index of the particulate;

β

_MOD is said operating value of parameter β

; and

β

_MAX and β

_MIN are memorized maximum and minimum values of parameter β

.

5. A method of determining the amount of particulate (m_S) accumulated in a particulate filter (9), comprising the steps of:

determining at least one of the variation in spatial distribution of the particulate in said particulate filter (9) and the variation in the physical-chemical properties of the particulate as a function of engine operating conditions and past particulate accumulation in said partical filter (9);

determining at least one of the variation in spatial distribution of the particulate in said particulate filter (9) and the variation in the physical-chemical properties of the particulate as a function of exhaust gas temperature and flow and past particulate accumulation in said partical filter (9).

6. A method of determining the amount of particulate (m_S) accumulated in a particulate filter (9), comprising the steps of:

determining at least one of the variation in spatial distribution of the particulate in said particulate filter (9) and the variation in the physical-chemical properties of the particulate as a function of engine operating conditions and past particulate accumulation in said partical filter (9);

determining a number of reference values (β

_MAP) of a parameter (β

) defining a relationship between the amount of particulate (m_S) accumulated in said particulate filter (9) and the pressure drop (Δ

P_DPF) across the particulate filter (9), each of said reference values (β

_MAP) relating to a respective steady engine operating condition corresponding to a particular steady particulate accumulation condition in the particulate filter (9);

determining an operating value (β

_MOD) of said parameter (β

) relative to the current engine operating condition as a function of the reference value (β

_MAP) of said parameter (β

) relative to the same engine operating condition, and of past particulate accumulation in said particulate filter (9); and

determining the amount of particulate (m_S) accumulated in said particulate filter (9) in the current engine operating condition as a function of the operating value (β

_MOD) of said parameter (β

) calculated for said current engine operating condition.

7. A method as claimed in claim 6 characterized in that each of said reference values (β

_MAP) of said parameter (β

) is determined at an initial calibration step by accumulating particulate in the particulate filter (9) for a given length of time in the steady engine operating condition associated with said reference value (β

_MAP).

8. A method as claimed in claim 6, characterized in that said step of determining an operating value (β

_MOD) of said parameter (β

) relating to the current engine operating condition comprises the steps of;

comparing the reference value (β

_MAP) of said parameter (β

) relating to the current engine operating condition with a previous operating value (β

<sub>MOD—

OLD</sub>) of the parameter (β

);

if the reference value (β

_MAP) is less than or equal to said previous operating value (β

<sub>MOD—

OLD</sub>) making said operating value (β

_MOD) equal to said reference value (β

_MAP) in a time depending on engine operating conditions;

if said reference value (β

_MAP) is greater than said previous operating value (β

<sub>MOD—

OLD</sub>), waiting until an amount of particulate greater than a predetermined amount (threshold) accumulates in said particulate filter (9), and calculating said operating value (β

_MOD) as a function of said reference value (β

_MAP) and said previous operating value (β

<sub>MOD—

OLD</sub>).

9. A method as claimed in claim 8, characterized in that said operating value (β

_MOD) is calculated according to the following equation;

${\mathrm{\beta <br><br>}}_{\mathrm{MOD}}={\mathrm{\beta <br><br>}}_{\mathrm{MAP}}-\frac{m_{\mathrm{S\_OLD}}}{m_S}·<br><br>\left({\mathrm{\beta <br><br>}}_{\mathrm{MAP}}-{\mathrm{\beta <br><br>}}_{\mathrm{MOD\_OLD}}\right)$

where;

β

_MOD is said operating value of parameter β

;

β

_MAP is said reference value of parameter β

;

β

MOD<sub>—

OLD</sub> is said previous operating value of parameter β

;

m_S is the new amount of particulate accumulated; and

m<sub>S—

OLD</sub> is the previously determined amount of particulate accumulated.

10. A method of determining the amount of partical (m_S) accumulated in a particulate filter (9), comprising the step of:

determining the at least one of the variation in spatial distribution of the particulate in said particulate filter (9) and the variation in the physical-chemical properties of the particulate as a function of the engine operating conditions and past particulate accumulation in said particulate filter (9);

evaluating the final corrected value m<sub>S—

CORR</sub> of particulate accumulated in a particulate filter (9), through the calculation of an offset Δ

m, to be added to the value of particulate accumulated in a particulate filter (m_S) estimated without considering at least one of the variation in spatial distribution of the particulate in said particulate filter (9) and the variation in the physical-chemical properties of the particulate due to partial regenerations (e.g. NOx-based spontaneous regeneration) and prolonged vehicle disuse (“

parking”

effect).

11. A method of determining the amount of particulate (m_S) accumulated in a particulate filter (9), comprising the steps of:

determining the at least one of the variation in spatial distribution of the particulate in said particulate filter (9) and the variation in the phyaical-chemical properties of the particulate as a function of the engine operating conditions and past particulate accumulation in said particulate filter (9);

determining an offset Δ

m after a certain amount of time after key-on, according to the following equation;

Δ

m=m<sub>S—

CORR—

ECU</sub>−

m_S

where;

m<sub>S—

CORR—

ECU</sub> is the value of m<sub>S—

CORR</sub> stored in the electronic control unit at the previous key-off;

m_S is the value of particulate accumulated in a particulate filter estimated without considering at least one of the variation in spatial distribution of the particulate in said particulate filter (9) and the variation in the physical-chemical properties of the particulate due to prolonged vehicle disuse (“

parking”

effect).

12. A method of determining the amount of particulate (m_S) accumulated in a particulate filter (9), comprising the step of:

determining the at least one of the variation in spatial distribution of the particulate in said particulate filter (9) and the variation in the phyaical-chemical properties of the particulate as a function of the engine operating conditions and past particulate accumulation in said particulate filter (9);

determining an offset Δ

m after a partial regeneration (e.g. NOx-based spontaneous regeneration), according to the following equation;

Δ

m=m<sub>S—

CORR</sub>−

m_S

where;

m<sub>S—

CORR</sub> is the value of particulate accumulated in a particulate filter before a partial regeneration (e.g. NOx-based spontaneous regeneration), decremented at every time step, during said partial regeneration state, with an experimentally estimated instantaneous value of particulate regenerated m_NOx (a function of the engine operating conditions).

m_S is the value of particulate accumulated in a particulate filter estimated without considering at least one of the variation in spatial distribution of the particulate in said particulate filter (9) and the variation in the physical-chemical properties of the particulate due to partial regeneration (e.g. NOx-based spontaneous regeneration).