GB2478541A

GB2478541A - Method for the management of an after treatment device in a multi-cylinder internal combustion engine

Info

Publication number: GB2478541A
Application number: GB1003838A
Authority: GB
Inventors: Fiorello Losano
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2010-03-09
Filing date: 2010-03-09
Publication date: 2011-09-14
Anticipated expiration: 2030-03-09
Also published as: GB2478541B; GB201003838D0

Abstract

A method for the management of an aftertreatment device in a multicylinder internal combustion engine, the method comprising a phase of measuring a parameter representative of the temperature of the exhaust gases and, in case said temperature is below a predetennined threshold, at least a phase of temporary de-activation of at least one cylinder of said engine is performed, until an increase of temperature of the exhaust gases entering said aftertreatment device is obtained. The method may be used to provide a high exhaust gas temperature to burn off soot from a diesel particulate filter (DPF) as part of the DPF regeneration process. An associated computer program for control of an electronic control unit (ECU) is also disclosed.

Description

METHOD FOR MANAGING ThE AFTERTREATMENT SYSTEM OF AN INTERNAL

CCLUSTION ENGINE

TEcHNICPIL FIElD

The present disclosure relates to a method for managing the aftertreatment system of an internal caitustion engine.

BAcKOUND The Diesel Particulate Filter (also referred as DPF in the present description) is a device located in the exhaust line of diesel engines; such device is designed to trap the soot to clean the exhaust gas, in order to comply to specific regulation emission limits.

Electronics systems managing the engine are capable to recognize when the filter is full; at this time they command a so called DPF regeneration process: this is, in principle, a process to empty out the filter based on soot auto combustion inside the trap itself. DPF regeneration is achieved by exhaust gas temperature increase (up to 600 °C) for short time (around 10 minutes). The regeneration process frequency is generally linked to DPF loading time or mileage and can vary depending on several factors, especially the driving style, and typically occurs in a range of one event every 200/1000 km.

The main means to achieve the needed temperature for regenerating the DPF are the so-called late fuel injections that are activated during the regeneration process.

While being generally used in the field, this regeneration method has the disadvantage of requiring further fuel injections in addition to a main torque-providing injection, leading to an increase of fuel consumption.

A further thsadvantage of the above solution is that, during time, it leads to undesirable accumulation of fuel in the oil sump.

According to another solution, a fuel injection system is provided downstream of the motor in the exhaust manifold to inject fuel therein for the same objective.

This system also has the drawback of fuel consumption and, moreover, it requires a certain number of additional components to be installed in the vehicle.

In general it must also be considered that reaching the exhaust gases temperatures needed for the DPF regeneration process to work properly is not easy, especially during city driving modes.

In addition, aftertreatment systems used to contain emissions of NOR, as Selective Catalytic Reduction systems (SCR), require an adequate exhaust gases temperature as well, for example around 200°C to allow periodic injections of urea in order to avoid NH3 slip and deposits.

An object of an embodirrent of the method disclosed is to provide an increase of the temperature of the exhaust gases that reach the aftertreatment system of an Internal Combustion Engine in a fuel-economic way.

A further object of an ernbodirrent of the method disclosed is to provide an increase of the temperature of the exhaust gases that allows performing a DPF regeneration process.

Still another object of the method is to provide an increase of the temperature of the exhaust gases that is useful for correct urea injection in a SCR system.

Another object is to provide an increase of the temperature of the exhaust gases that reach the aftertreatment system, using the engine itself and by taking advantage from the computational capabilities of the Electronic Control Unit (ECU) of the vehicle.

Another object of the present disclosure is to meet these goals by means of a simple, rational and inexpensive solution.

These objects are achieved by a method, by an engine, by a computer program and computer program product, and by an electromagnetic signal having the features recited in the independent claims.

The dependent claims delineate preferred and/or especially advantageous aspects of the method.

SUbtRY An embodiment of the disclosure provides for a method for the management of an aftertreatment device in a multicylinder Internal Combustion Engine engine, the method comprising a phase of measuring a parameter representative of the temperature of the exhaust gases and, in case the temperature is below a predetermined threshold, at least a phase of temporary de-activation of at least one cylinder of said engine is performed until an increase of temperature of the exhaust gases entering said aftertreatnnt device is obtained.

This embodiment has the advantage of providing an increase of temperature in the exhaust gases that reach the aftertreatrnent device when driving conditions or other factors would render difficult to reach the working temperature for the aftertreatinent device.

Another embodiment of the method provides for the fact that the deactivation phase of one or more cylinders is performed through corrrnon rail management by avoiding to inject fuel in said cylinders.

This embodiment has the advantage of providing the increase of teniperature in a simple and effective way, using devices already present in a Diesel engine.

Another embodiment of the method provides for the fact that the deactivation phase of one or more cylinders is performed using a Variable Valve Actuation system.

This embodiment has the advantage of allowing proper air amount to go only to active cylinders, since inactive cylinders will run with closed valves.

A further embodiment of the method provides for the fact that said parameter representative of the exhaust gas temperature is measured by a temperature sensor at the turbine outlet.

This embodiment has the advantage of providing a temperature signal useful for the actuation of the method using a device that is normally already present in a Diesel engine.

In still another embodiment of the method a the deactivation phase of the cylinders is performed until the temperature necessary for the activation of a DPF regeneration is reached.

This embodiment has the advantage of allowing the performance of DPF regeneration process without using late injections or any other form of fuel injection in the exhaust manifold of the engine.

In a further embodiment of the method a the deactivation phase of the cylinders is performed until the temperature necessary for the injection of urea into the SCR system is reached.

This embodiment has the advantage of allowing the performance of urea injection a SCR system without using late injections or any other form of fuel injection in the exhaust manifold of the engine.

The method according to one of its aspects can be realized in the form of a computer program comprising a program-code to carry out all the steps of the method and in the form of a computer program product comprising means for executing the computer program.

The computer program product comprises, according to a preferred embodiment, a control apparatus for a Diesel engine, for example the ECU of the engine, in which the program is stored so that the control apparatus defines such embodiment or embodiments in the same way as the method. In this case, when the control apparatus executes the computer program all the steps of the method according to the embodiments described are carried out.

The method according to a further aspect can be also realized in the form of an electromagnetic signal, said signal being modulated to carry a sequence of data bits which represent a computer program to carry out all steps of the method.

A still further aspect of the disclosure provides an internal combustion engine specially arranged for carrying out the method claimed.

BRIEF DESCRIPTION OF THE DRWINGS

The various embodiments will now be described, by way of example, with reference to the accompanying drawing, in which: Figure 1 is a flowchart of an embodiment of the method.

DETAILED DESCRIPTION OF THE DRAWINGS

A preferred embodiment is now described with reference to the enclosed drawing.

The method is applicable to any Internal Combustion Engine (ICE).

In Diesel engines, Corn-non Rail technology allows to deactivate any number of cylinders, by simply avoiding to inject fuel in these cylinders at a certain time. The comnon rail management allows such operation easily via Engine Control Unit (ECU).

Also, in an internal combustion engine, the exhaust gas temperature is basically depending on the load.

Therefore in an embodiment of the method herein described it is provided for deactivate temporarily one or more cylinders in an Internal Combustion Engine (ICE) for obtaining higher exhaust gas temperatures, when driving conditions or other external factors render difficult to reach the working temperature for the correct working of aftertreatment devices, such as the DPF or the SCR.

As a consequence of such cylinder deactivation, cylinders in firing mode have higher Brake Mean Effective Pressure (BMEP), maintaining same total output Torque of the ICE and so have higher temperatures.

In fact it must be considered that the temperature at the end of corrustion is basically proportional to: Hi / (1 + A) where A is the ratio Air/Fuel, and Hi is the specific Heat of Fuel.

Parameter A is decreasing increasing the Torque, therefore gas temperature is increasing.

For example a temperature increase of around 170 °K at 2.000 RPM and of 2 bar BMEP can be obtained by a 2-cylinder deactivation in a 4-cylinder Diesel engine using a Variable Valve Actuation System to deactivate valves in appropriate cylinders At low speed low torque demand, a certain nurriber of cylinders can be de-activated using an appropriate Variable Valve Actuation system.

In this case proper air amount goes only to active cylinders, since inactive cylinders run with closed valves.

The higher temperature obtained by one or more cylinder deactivation can therefore be used to better manage a DPF system, or in general any aftertreatment system that needs an adequate working temperature, for examples systems such as the SCR for the reduction of NO of emissions.

Specifically, with reference to fig. 1 the temperature of exhaust gases directed to the aftertreatment system can be monitored by one or more sensors already generally present in modern vehicles.

For example, the exhaust gas temperature can be measured by a temperature sensor at the turbine outlet.

Other methods for measuring the temperature or a parameter representative thereof can be used, depending on the engine.

According to an embodiment of the method, after having measured the temperature, a check is performed to determine if this temperature is below a predetermined threshold and, in the affirmative, one or more cylinders are deactivated so as to obtain an increase of temperature to reach the temperature needed by the aftertreatment system.

The increase of temperature can be made steeper increasing the number of cylinders that are simultaneously deactivated.

For example the deactivation phase of the cylinders is performed until a temperature increase at turbine outlet of at least 170 °K is reached.

The method above can be repeated at predetermined or random intervals during the use of the vehicle.

In particular, the method may be performed in conjunction with a DPF regeneration procedure; in this case, the cylinders may be deactivated until the temperature necessary for the activation of a DPF regeneration is reached.

The method may be also performed when it is necessary to reach the temperatures needed for the activation of the SCR; in this case, for example, the cylinders may be deactivated until the temperature necessary for the injection of urea into the SCR system is reached.

The method described is especially interesting for Diesel Connon Rail having an architecture V6 or V8, where impact on Noise, Vibration, and Harshness (NVH) of the deactivation phase is reduced.

In particular, deactivating for example two cylinders in a 6-cylinder or in a 8-cylinder engine allow for better thermodynamic conditions of operation for the cylinder that are firing, better Brake Specific Fuel Consumption (BSFC) and a better fuel economy.

While at least one exemplary embodirrnt has been presented in the foregoing surrmary and detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing surtmary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents.

Claims

1. Method for the management of an aftertreatment device in a multicylinder Internal Combustion Engine, the method comprising a phase of measuring a parameter representative of the temperature of the exhaust gases and, in case said temperature is below a predetermined threshold, at least a phase of temporary de-activation of at least one cylinder of said engine is performed, until an increase of temperature of the exhaust gases entering said aftertreatment device is obtained.

2. Method according to claim 1, in which the deactivation phase of one or more cylinders is performed through common rail management by avoiding to inject fuel in said cylinders.

3. Method according to claim 1, in which the deactivation phase of one or more cylinders is performed using a Variable Valve Actuation system.

4. Method according to claim 1, in which said parameter representative of the exhaust gas temperature is measured by a temperature sensor at the turbine outlet.

5. Method according to claim 1, in which the deactivation phase of the cylinders is performed until the temperature necessary for the activation of a DFF regeneration is reached.

6. Method according to claim 1, in which the deactivation phase of the cylinders is performed until the temperature necessary for the injection of urea into the SCR system is reached.

7. Internal combustion engine, the combustion engine having associated sensors for the measurement of parameters representative of the temperature of exhaust gas, characterized in that the internal combustion engine comprises an ECU configured for carrying out the method according to any of the preceding claims.

8. A computer program comprising a computer-code suitable for perfonning the method according to any of the claims 1-6.

9. Computer program product comprising a computer program according to claim 8.

10. Pn electromagnetic signal modulated as a carrier for a sequence of data bits representing the computer program according to claim 8.