Particulate filter device monitoring system for an internal combustion engine

A particulate filter device monitoring system for an internal combustion engine includes a particulate accumulation register configured to store an amount of particulate in a particulate filter. The particulate accumulation register includes a particulate accumulation trigger zone having a power limiting mode trigger. A power limiting mode trigger module is configured to limit output power of the internal combustion engine when the amount of particulate accumulation reaches the power limiting mode trigger. A particulate accumulation model module includes a particulate accumulation model configured to calculate changes in particulate accumulation in the particulate accumulation register at a first sampling rate when particulate accumulation is outside the particulate accumulation trigger zone, and at a second sampling rate when particulate accumulation is within the particulate accumulation trigger zone.

FIELD OF THE INVENTION

The subject invention relates to engine emission monitoring systems and, more particularly, to a particulate filter device monitoring system for an internal combustion engine.

BACKGROUND

Exhaust gas emitted from an internal combustion engine, particularly a diesel engine, is a heterogeneous mixture that contains gaseous emissions such as, but not limited to, carbon monoxide (“CO”), unburned hydrocarbons (“HC”) and oxides of nitrogen (“NOx”), as well as condensed phase materials (liquids and solids) that constitute particulate matter (“PM”). Catalyst compositions, typically disposed on catalyst supports or substrates, are provided in an engine exhaust system as part of an aftertreatment system to convert certain, or all of these exhaust constituents into non-regulated exhaust gas components.

One type of exhaust treatment technology for reducing emissions is a particulate filter (“PF”). The PF is designed to remove diesel particulate matter, or soot, from exhaust gas of an engine. The particulate matter removed from the exhaust is entrapped by, and entrained in, the PF. When accumulated soot reaches a predetermined level the PF is either replaced or regenerated. Replacement or regeneration facilitates that soot removal continues at desired parameters.

Many engines include a controller having a soot out model that predicts soot accumulation in the PF. The soot out monitor employs various engine operating parameters to predict soot accumulation levels in the PF. The operating parameters include duration and number of accelerations, duration of operation at constant RPM above idle, and idle time. Inaccurate soot accumulation predictions could lead to premature replacement or cleaning of a PF, or operating conditions in which soot is not removed at desired levels. Prediction inaccuracies tend to occur after prolonged periods of low speed operation. During lower speeds, accurate pressure change readings are difficult to obtain. Once normal highway speed is resumed, the controller may sense a sudden increase in a rate of soot accumulation. The sudden change in soot accumulation could cause the controller to force the engine into a reduced power mode which necessitates maintenance. Accordingly, it is desirable to provide a soot out model with the flexibility to adjust soot accumulation rates following low speed and idle operations.

SUMMARY OF THE INVENTION

In accordance with an exemplary embodiment, a particulate filter device monitoring system for an internal combustion engine includes a particulate accumulation register configured to store an amount of particulate in a particulate filter. The particulate accumulation register includes a particulate accumulation trigger zone having a power limiting mode trigger. A power limiting mode trigger module is configured to limit output power of the internal combustion engine when the amount of particulate accumulation reaches the power limiting mode trigger. A particulate accumulation model module includes a particulate accumulation model configured to calculate changes in particulate accumulation in the particulate accumulation register at a first sampling rate when particulate accumulation is outside the particulate accumulation trigger zone, and at a second sampling rate when particulate accumulation is within the particulate accumulation trigger zone.

In accordance with another exemplary embodiment, an internal combustion engine includes an internal combustion engine including an exhaust gas conduit, a particulate filter device fluidically connected to the exhaust gas conduit, and a particulate filter device monitoring system having a control module configured to monitor particulate accumulation in the particulate filter device. The control module includes a particulate accumulation register configured to store an amount of particulate in a particulate filter. The particulate accumulation register includes a particulate accumulation trigger zone having a power limiting mode trigger. A power limiting mode trigger module is configured to limit output power of the internal combustion engine when the amount of particulate accumulation reaches the power limiting mode trigger. A particulate accumulation model module includes a particulate accumulation model configured to calculate changes in particulate accumulation in the particulate accumulation register at a first sampling rate when particulate accumulation is outside the particulate accumulation trigger zone and at a second sampling rate when particulate accumulation is within the particulate accumulation trigger zone.

In accordance with yet another exemplary embodiment, a method of monitoring a particulate filter of an internal combustion engine includes calculating an amount of particulate in a particulate filter device, determining whether the amount of particulate is within a particulate trigger zone, calculating a rate of increase of the particulate in the particulate filter device at a first sampling rate if the amount of particulate is outside the particulate accumulation trigger zone, and calculating the rate of increase of particulate at a second sampling rate, that is lower than the first sampling rate, if the amount of particulate is within the particulate accumulation trigger zone.

DESCRIPTION OF THE EMBODIMENTS

The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. As used herein, the term “module” refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, and/or a combinational logic circuit, When implemented in software, a module can be embodied in memory as a non-transitory machine-readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method.

Referring now toFIG. 1, an exemplary embodiment is directed to a particulate filter device monitoring system10for an internal combustion (“IC”) engine12. IC engine12may be a diesel engine or a gas engine. An exhaust gas conduit14, which may comprise several segments, transports exhaust gas15from the engine12to various aftertreatment devices. More specifically, engine12is configured to receive an intake air20through an air intake passage22. Intake air passage22includes an intake mass airflow sensor24for determining the intake air mass of the engine12. In accordance with an aspect of an exemplary embodiment, intake mass airflow sensor24may take the form of a vane meter. In accordance with another aspect of the exemplary embodiment, intake mass airflow sensor24may take the form of a hot wire type intake mass airflow sensor. It should be understood that other types of sensors may also be used. Intake air20mixes with fuel (not shown) to form a combustible mixture. The combustible mixture is compressed to combustion pressure in a combustion chamber of engine12producing work, (i.e., engine output and exhaust gases15). Exhaust gases15pass from the engine12to various aftertreatment devices of the particulate filter device monitoring system10as will be detailed more fully below.

In the exemplary embodiment as illustrated, aftertreatment devices of particulate filter device monitoring system10include a first oxidation catalyst (“OC”) device30, a selective catalytic reduction (“SCR”) device32, a second OC device34, and a particulate filter (“PF”) device36. As can be appreciated, particulate filter device monitoring system10, of the present disclosure, may include various combinations of one or more of the aftertreatment devices shown inFIG. 1, and/or other aftertreatment devices (e.g., lean NOxtraps), and is not limited to the present example.

First OC device30includes a casing40having an inlet41in fluid communication with exhaust gas conduit14and an outlet42. Casing40may surround a flow-through metal or ceramic monolith substrate43. Similarly, second OC device34includes a casing45having an inlet46and an outlet47. Casing45may surround a flow-through metal or ceramic monolith substrate48. Flow-through metal or ceramic monolith substrate43, and/or48may include an oxidation catalyst compound disposed thereon. The oxidation catalyst compound may be applied as a wash coat and may contain platinum group metals such as platinum (“Pt”), palladium (“Pd”), rhodium (“Rh”) or other suitable oxidizing catalysts, or combinations thereof. The OC devices30and34are useful in treating unburned gaseous HC and CO, which are oxidized to form carbon dioxide and water.

SCR device32may be disposed downstream of first OC device30and upstream of second OC device34. In a manner similar to first and second OC devices30and34, SCR device32includes a casing50that houses a flow-through ceramic or metal monolith substrate51. Casing50includes an inlet52in fluid communication with outlet42of first OC device30, and an outlet53in fluid communication with inlet46of second OC device34. Substrate51may include a SCR catalyst composition applied thereto. The SCR catalyst composition may contain a zeolite and one or more base metal components such as iron (“Fe”), cobalt (“Co”), copper (“Cu”) or vanadium (“V”) which can operate efficiently to convert NOx constituents in the exhaust gas15in the presence of a reductant such as ammonia.

PF device36may be disposed downstream of SCR device32and the second OC device34. PF device36operates to filter exhaust gas15of carbon and other particulates (soot). PF device36includes a casing56having an inlet57fluidically coupled to outlet47of second OC device34, and an outlet58that may discharge to ambient. Casing56may surround a ceramic wall flow monolith particulate filter59. Ceramic wall flow monolith particulate filter59may have a plurality of longitudinally extending passages (not separately labeled) that are defined by longitudinally extending walls (also not separately labeled). The passages include a subset of inlet passages that have an open inlet end and a closed outlet end, and a subset of outlet passages that have a closed inlet end and an open outlet end. Exhaust gas15entering ceramic wall flow monolith particulate filter59through the inlet ends of the inlet passages is forced to migrate through adjacent longitudinally extending walls to the outlet passages. It is through this wall flow mechanism exhaust gas15is filtered of carbon and other particulates. The filtered particulates are deposited on the longitudinally extending walls of the inlet passages and, over time, will have the effect of increasing exhaust gas15backpressure experienced by the engine12. It is appreciated, that ceramic wall flow monolith particulate filter59is merely exemplary in nature and that the PF device36may include other particulate filter devices such as, wound or packed fiber filters, open cell foams, sintered metal fibers, etc. The increase in exhaust gas15backpressure caused by the accumulation of particulate matter in ceramic wall flow monolith particulate filter59typically requires that the PF device36is periodically replaced, cleaned, or regenerated. Regeneration involves the oxidation or burning of the accumulated carbon and other particulates in what is typically a high temperature environment (>600° C.).

A control module60is operably connected to, and monitors, engine12and the particulate filter device monitoring system10through a number of sensors.FIG. 1illustrates control module60in communication with the engine12, intake mass airflow sensor24, first and second temperature sensors62and64for determining the temperature profile of the first OC device30, third and fourth temperature sensors66and68for determining the temperature profile of the SCR device32, fifth and sixth temperature sensors69and70for determining the temperature profile of the second OC device34, and seventh and eighth temperature sensors72and74for determining the temperature profile of the PF device36, and a tachometer75for determining engine speed and engine accelerations.

The control module60determines, in part, an amount of particulate matter, or soot accumulation, in PF device36. Soot accumulation in PF device36leads to an increase in exhaust gas backpressure on engine12. The increase in exhaust gas backpressure caused by the accumulation of soot in ceramic wall flow monolith particulate filter59typically requires that the PF device36is periodically replaced, cleaned, or regenerated. Regeneration involves the oxidation or burning of the accumulated carbon and other particulates in what is typically a high temperature environment (>600° C.).

In accordance with one exemplary aspect of the invention, control module60includes logic that monitors operating parameters of engine12including temperatures, accelerations, and exhaust mass flow. Exhaust mass flow is based on the intake air mass of the engine12, which is measured by the intake air mass airflow sensor24, as well as a fuel mass flow of the engine12. Specifically, the exhaust mass flow is calculated by adding the intake air mass of the engine12and the fuel mass flow of the engine12. Based on the monitored parameters, control module60calculates an amount of particulate accumulation and a rate of change of particulate accumulation in PF device36.

FIG. 2is an illustration of a dataflow diagram that illustrates various elements that may be embedded within the control module60. Various embodiments of the particulate filter device monitoring system10ofFIG. 1, according to the present disclosure, may include any number of sub-modules embedded within the control module60. As can be appreciated, the sub-modules, shown inFIG. 2, may be combined or further partitioned as well. Inputs to control module60may be sensed from the particulate filter device monitoring system10, received from other control modules (not shown), or determined by other sub-modules or modules. In the embodiment, as shown inFIG. 2, control module60includes a memory102, a regeneration control module104, a regeneration mode trigger module106, a soot accumulation counter module108, an idle time counter module110, an interrupt module112, and a fuel injection control module114. Control module60also includes a regeneration mode switch116and a particulate or soot accumulation register118.

In one embodiment, the memory102of the control module60stores a number of configurable limits, maps, and variables that are used to calculate soot accumulation and control regeneration of PF device36ofFIG. 1. Each of the modules104-114interfaces with the memory102to retrieve and update stored values as needed. For example, the memory102can provide values to the regeneration control module104for supporting determination of a soot load in soot accumulation register118, and thresholds for activating regeneration mode trigger106based on vehicle operating conditions120and exhaust conditions122.

The regeneration control module104may apply algorithms known in the art to determine when to set a regeneration mode switch116to activate regeneration mode trigger module106when an amount of particulate in PF device36ofFIG. 1reaches a particular threshold value. For example, the regeneration mode switch116may be set when the soot load in soot accumulation register118exceeds a threshold defined in the memory102. Regeneration of the PF device36ofFIG. 1can be based on, or limited, according to a particulate accumulation model module130connected to regeneration control module104. Regeneration control module104compares vehicle operating conditions120and exhaust conditions122with a particulate accumulation model132provided in particulate accumulation model module130to calculate soot accumulation and a rate of change of soot accumulation in PF device36, and determine when a regeneration cycle is indicated. The vehicle operating conditions120and the exhaust conditions122can be provided by sensors or other modules. For example, the seventh and eighth temperature sensors72,74(shown inFIG. 1) send electrical signals to the control module60, ofFIG. 1, to indicate a temperature profile of the PF device36ofFIG. 1. Factors such as engine speed, exhaust temperature, time elapsed since a last regeneration, distance traveled since a last regeneration, fuel consumed since a last regeneration, and a modeled soot level can also be used to determine when the regeneration mode switch116should be set. In addition, particulate accumulation model module130can set a reduced power mode when accumulated particulate reaches or exceeds a predetermined value.

In accordance with an exemplary embodiment, control module60includes a power limiting mode trigger module140operatively connected to particulate accumulation model module130. Power limiting control module140includes a power limiting mode trigger142that signals an engine controller (not shown) to reduce power output of engine12until a maintenance action is taken to reduce the amount of particulate in ceramic wall flow monolith particulate filter59. Power limiting mode trigger142represents a particular amount of particulate stored in soot accumulation register118. When operating at low speeds, such as idle, for a prolonged period, particulate accumulation model132does not calculate particulate accumulation. Thus, when transitioning from low speed operation to highway speed operation, particulate accumulation model module130may detect a sudden change in particulate accumulation and prematurely signal power limiting mode trigger module140to initiate power limiting mode trigger142before regeneration is enabled. In order to reduce the need for premature maintenance cycles, particulate accumulation model module130includes a sampling rate limiting model148that changes a sampling rate of particulate accumulation during select periods.

Sampling rate model148includes a particulate accumulation trigger zone that defines a set of particulate accumulation values and power limiting mode trigger142as shown inFIG. 3. InFIG. 3, the particulate accumulation trigger zone spans values D, E, F and G with value G representing the power limiting mode trigger142. When particulate accumulation, in soot accumulation register118, is outside (above or below) the particulate accumulation trigger zone, particulate accumulation model module130signals sampling rate model148to sample particulate accumulation at a first sampling rate (SR1). However, when particulate accumulation is within the particulate accumulation trigger zone, particulate accumulation model module130triggers sampling rate model to sample particulate accumulation at a second, reduced rate (SR2). In accordance with one aspect of the exemplary embodiment, SR1may be 1000 g/sec and SR2is less than SR1. SR1may be an order of magnitude greater than SR2. For example, SR2could be 10 g/sec. The change, e.g., reduction in sampling rate, provides time for corrective action. For example, when the amount of particulate in particulate accumulation register118enters the particulate accumulation trigger zone, particulate accumulation model module130signals regeneration control module104to begin a regeneration cycle of ceramic wall flow monolith particulate filter59. The reduction in sampling rate provides time for regeneration to lower the amount of particulate in ceramic wall flow monolith particulate filter59and reduce instances of premature power limiting.

Turning toFIG. 4, and with continued reference toFIGS. 1, 2 and 3, a flowchart illustrates a method for monitoring particulate or soot accumulation in PF device36, ofFIG. 1, that can be performed by the control module60ofFIG. 1in accordance with the present disclosure. As can be appreciated in light of the disclosure, the order of operation within the method is not limited to the sequential execution as illustrated inFIG. 4, but may be performed in one or more varying orders as applicable and in accordance with the present disclosure. It should also be appreciated that in various embodiments, the method can be scheduled to run based on predetermined events, and/or run continually during operation of the engine12ofFIG. 1.

In one example, the method may begin at block200. At block204, control module60ofFIG. 1determines whether engine12ofFIG. 1is operating. If engine12is operating, at block206control module60determines an amount of particulate within PF device36ofFIG. 1. In block208, the amount of particulate within PF device36is stored in particulate accumulation register118ofFIG. 2. In block210, control module60determines whether the amount of particulate in particulate accumulation register118is within a particulate trigger zone ofFIG. 3. If the amount of particulate in particulate accumulation register118is not within the particulate accumulation trigger zone, particulate accumulation model module130samples particulate accumulation at SR1ofFIG. 3in block212.

If the amount of particulate is within the particulate accumulation trigger zone ofFIG. 3, particulate accumulation model module130samples particulate accumulation at SR2ofFIG. 3in block230. In block232, control module60activates regeneration control module104to begin regeneration of PF device36. After starting regeneration, particulate accumulation model module130determines if the amount of particulate in particulate accumulation register118remains, or has reached, the low power trigger in block233. If the low power trigger has been reached, control module60activates power limiting module140to reduce power output of engine12, in block250. If the power limiting mode trigger142has not been reached, particulate accumulation module determines, in block234, whether the particulate within particulate accumulation register118remains in the particulate accumulation trigger zone. If the amount of particulate within particulate accumulation register118remains in the particulate accumulation trigger zone, particulate accumulation model module130continues to sample at SR2, in block230. If the amount of particulate within particulate accumulation register118is no longer in the particulate accumulation trigger zone, control module60returns to block206.