GB2479196A

GB2479196A - Method for regenerating a particulate filter using a navigation system

Info

Publication number: GB2479196A
Application number: GB1005562A
Authority: GB
Inventors: Javier Castellano
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2010-04-01
Filing date: 2010-04-01
Publication date: 2011-10-05
Anticipated expiration: 2030-04-01
Also published as: GB2479196B; CN102213130A; CN102213130B; GB201005562D0

Abstract

A method for regenerating a diesel particulate filter 6 of a motor vehicle 1 having a navigation system 4, where the method comprises determining if the filter requires regeneration, if so determining if a the future route is known, if known determining if optimum regeneration is possible and if it is possible determining a desired start point and end point of the regeneration based on the planned route, using a navigation system, and initiating and ending the regeneration at the determined points. The start point conditions may include reaching a geographic location and the end point conditions may include reaching a geographic location and reaching an elapsed time after regeneration starts. Preferably the start point is determined by determining at least one of the type of road, expected speed, expected terrain and expected traffic conditions. If the optimal conditions for regeneration are not met it may be determined if the particulate filter is overloaded and if so the best start and stop points are determined for carrying out a forced regeneration.

Description

A Method for Regenerating a Particulate Filter This invention relates to automotive vehicles and in particular to a method for regenerating a diesel particulate filter fitted to a motor vehicle.

Particulate filters are used in the exhaust systems of internal combustion engines, especially diesel engines, (diesel particulate filters or DPF) to trap and remove particulate matter which is primarily formed of carbon based material. As the engine exhaust passes through the DPF, the particulates are trapped in the filter and accumulate over time. This accumulation leads to an increase in the resistance of the exhaust gas flow through the DPF, and therefore, to an increase in the backpressure on the engine.

This increase in backpressure has an adverse effect on engine operation, and especially on fuel consumption. In order to reduce backpressure to acceptable levels, the DPF is periodically regenerated by burning off the accumulated particulates, most of which are combustible.

A DPF should only be regenerated when it is necessary to do so for a number of reasons.

Firstly, the filtering efficiency of the DPF increases with increased particulate loading.

Secondly, in order to achieve regeneration, the exhaust gas temperature must be elevated to a temperature above that achieved during normal engine operation, consequently regeneration results in higher fuel consumption and potential dilution of the engine oil.

Thirdly, regeneration is most effective when the particulate loading is sufficiently high and homogenous throughout the filter.

There are a number of conventional methods that may be used to increase the exhaust gas temperature to the requisite level (e.g. above 450[deg.] C.) in order to initiate a regeneration event. Regardless of the method used to increase exhaust gas temperature, it is necessary to estimate the load on the DPF so that regeneration events are initiated at optimal intervals.

The DPF load may be inferred from reference values that depend on engine operating conditions, or it can be measured more directly by sensing the exhaust pressure upstream and downstream of the DPF and solving an equation describing the relationship between the mass flow through the DPF and the sensed pressures. The effective restriction used in this equation establishes the dependence on the load accumulated in the DPF. By first solving the equation for the effective restriction and then solving the equation describing the effective restriction for the load, the load of the DPF can be estimated.

The creation of conditions for initiating and continuing regeneration will generally involve elevating the temperature of exhaust gas entering the DPF to a suitably high temperature and, because a diesel engine typically runs relatively cool and lean, the post-injection of diesel fuel is normally used to elevate exhaust gas temperatures entering the DPF while still leaving excess oxygen for burning the trapped particulate matter.

Although regeneration can be carried out in many circumstances, the ideal conditions are when the engine is operating at a relatively high load in a relatively steady state condition. Such conditions exist when a vehicle is cruising on a motorway/ freeway at a relatively high speed.

In these circumstances the regeneration process may be conducted with little or no significant effect on vehicle driveability and the required elevated exhaust gas temperature is readily achieved. As a contrast to this optimum case, driving in a stop/start manner in a city is not a desirable condition for regeneration as it is difficult to produce the high temperatures required and the loss of driveability is in some cases unacceptable.

Furthermore in some cases, because such city journeys are often short in duration, regeneration will not be completed due to the fact that the operator of the motor vehicle will have terminated the journey before regeneration has completed.

It is a problem with many prior art methods for

regenerating a DPF that regeneration will commence as soon as a predetermined soot loading is estimated to exist in the DPF and this may result in a relatively high incidence of incomplete or ineffective regeneration as the operating conditions of the motor vehicle are not taken into account.

It is an object of this invention to provide a method for regenerating a diesel particulate filter that is adaptive to the operating conditions of the motor vehicle and the condition of the diesel particulate filter so as to minimize the risk of incomplete or ineffective regeneration.

According to a first aspect of the invention there is provided a method for regenerating a diesel particulate filter of a motor vehicle having a navigation system, wherein the method comprises determining whether the diesel particulate filter requires regenerating and, if the diesel particulate filter requires regenerating, determining whether the future route is known and, if the future route is known, determining whether optimum regeneration is possible for the known route and, if optimum regeneration is possible for the known route, determining a desired start point for the regeneration and a desired end point for the regeneration, initiating regeneration when the start point conditions are met and ending the regeneration when the end point conditions are met.

The start point conditions may include reaching a specific geographic location on the known route.

Alternatively, the start point conditions may include reaching a predetermined elapsed time after the route has started.

The start point conditions may further include at least one of confirming that the motor vehicle is travelling above a predetermined minimum speed, confirming that the engine is running above a predetermined speed and confirming that the engine is operating above a predetermined load.

The end point conditions may include at least one of reaching a specific location on the known route and reaching a predetermined elapsed time after regeneration has started.

Determining a desired start point for the regeneration may include at least one of determining the type of road to be travelled along on the route, determining the expected speed of the vehicle at various locations along the route, determining the expected terrain of the route and determining the expected traffic conditions for various locations along the route.

Determining a desired start point for the regeneration may include at least one of determining from the navigation system the type of road to be travelled along, the expected speed of the vehicle at various locations along the route, the expected terrain for the route and the expected traffic conditions for various locations along the route and, based upon the gathered information information, calculating a optimum regeneration window time so as to minimize the penalty on at least one of fuel economy, engine oil contamination and/or one or more other factors that affect regeneration quality.

If the optimum conditions for regeneration are not met, the method may further comprise determining whether the diesel particulate filter is overloaded and, if the diesel particulate filter is overloaded, carrying out a forced regeneration of the diesel particulate filter.

The method may further comprise determining the best possible start and stop points for the forced regeneration.

If a future route is not known the method may further comprise carrying out a regeneration of the diesel particulate filter based upon historical data.

According to a second aspect of the invention there is provided a motor vehicle having a diesel engine supplying exhaust gases to a diesel particulate filter, an electronic controller to control the timing and volume of fuel injected into each cylinder of the engine and a navigation system operatively connected to the electronic controller wherein the electronic controller is operable to determine whether the diesel particulate filter requires regenerating and, if the diesel particulate filter requires regenerating, determine from the navigation system whether the future route is known and, if the future route is known, determine whether optimum regeneration is possible for the known route and, if optimum regeneration is possible for the known route, determine a desired start point for the regeneration and a desired end point for the regeneration and initiate the regeneration of the diesel particulate filter when the start point conditions are met and end the regeneration of the diesel particulate filter when the end point conditions are met.

Determining a desired start point for the regeneration may include at least one of determining from the navigation system the type of road to be travelled along, the expected speed of the vehicle at various locations along the route, the expected terrain for the route and the expected traffic conditions for various locations along the route.

If the optimum conditions for regeneration are not met for the known route, the electronic controller may be further operable to determine whether the diesel particulate filter is overloaded and, if the diesel particulate filter is overloaded, may be further operable to carry out a forced regeneration of the diesel particulate filter.

The electronic controller may be further operable to determine the best possible start and stop points for the forced regeneration.

If a future route is not known the electronic controller may be further operable to carry out a regeneration of the diesel particulate filter based upon historical data.

The invention will now he described by way of example with reference to the accompanying drawing of which:-Fig.l is a schematic representation of a motor vehicle constructed in accordance with one aspect of the invention; Fig.2 is a high level flow chart showing a method for regenerating a diesel particulate filter according to a further aspect of the invention; Fig.3 is a diagram showing how an algorithm to provide the optimum time for regeneration can be represented as a Matlab/Simulink process; Fig.4 is a graph showing a relationship between a fuel economy factor and time; Fig.5 is a graphical representation of vehicle speed versus time for a real driving cycle; and Fig.6 is a graph showing a relationship between penalty function 13(t) and time for the driving cycle shown in Fig.5.

Referring now to Figs. 1 and 2 there is shown a motor vehicle 1 having a diesel engine 2 the exhaust gasses from which flow via an exhaust pipe 5 to a diesel particulate filter DPF 6 and from the DPF 6 out to atmosphere via a tail pipe 7.

Although the vehicle 1 is shown with only a single primary mover in the form of the diesel engine 2 it will be appreciated that other forms of motive power such as one or more electric motors could be provided in what is commonly referred to as a hybrid configuration.

The diesel engine 2 is operatively connected to an electronic controller 3 which controls the timing and volume of fuel injected into the various cylinders of the engine 2. The electronic controller 3 also controls in this case the regeneration of the DPF 6 as will be described in more detail hereinafter.

The electronic controller 3 receives inputs from a number of sources including in this case one or more vehicle sensors 8, one or more engine sensors 9 and a navigation system 4.

The vehicle sensors 8 may include for example one or more sensors providing information regarding the speed of the vehicle.

The engine sensors 9 may include for example information regarding the rotational speed of the engine 2, operator power demand, operating temperature of the engine, the pressure of the exhaust gases upstream from the DPF 6, the pressure of the exhaust gases downstream from the DPF 6 and the temperatures of the exhaust gases at one or more selected positions.

The navigation system 4 uses GPS technology to determine the current position of the motor vehicle 1 and includes means (not shown) to input a desired destination. The means used to input such a destination may include a keypad, rotary input device or pressure sensitive screen for direct input of a destination by an operator of the motor vehicle 1 or means to permit a destination to be uploaded from another device or source such as a mobile phone address book or contacts list, a computer address book or contacts list or be uploaded from the internet. That is to say, the invention is not limited to any specific means of inputting a desired destination into the navigation system 4.

The navigation system 4 is operable to determine for any chosen route the type of roads to be travelled along. That is to say, whether the road is in a city environment, is a minor road, is in a residential area, is a main road or is a fast road such as a motorway or freeway.

In some embodiments of the invention the navigation system 4 is also provided with terrain information so that for any known route it is able to determine which parts of the route are uphill, which parts are downhill and for which parts the terrain is generally flat.

In some other embodiments the navigation system 4 is provided with real time traffic information and so is able to predict traffic delays due to, for example, accidents, roads works or congestion.

In use, the electronic controller 3 is operable to determine whether the DPF 6 requires regenerating. This may be done either by modelling techniques based upon historical data of engine operation or by the use of pressure sensors located upstream and downstream from the DPF 6. US Patent 6,405,528 for example discloses one method for determining the loading of a diesel particulate filter.

If the DPF 6 requires regenerating, the electronic controller 3 determines from the navigation system 4 whether the future route is known, that is to say, whether a destination has been set and a route calculated to take the motor vehicle 1 to the desired destination. If the future route is known, then the electronic controller 3 is operable to determine whether optimum regeneration is possible for the known route. This determination will include evaluatinq the types of roads to be travelled, the predicted time that the vehicle will be travelling on a particular section of the route and whether a particular section of the route is likely to allow the motor vehicle 1 to be operated in a relatively steady state high load condition such as is required for optimum regeneration. If there are several sections of the route where an optimum regeneration could occur then the electronic controller 3 will compare the various options to determine which is preferred. This may comprise simply choosing the one that will occur soonest or may comprise choosing a section where the probability of an uninterrupted regeneration is most likely or one where the conditions are superior to other possibilities.

The electronic controller 3 is then operable to determine a desired start point for the regeneration and a desired end point for the regeneration. This comprises for the selected section of the route determining a geographic -10 -location at the start of the section where regeneration is to commence and either determining a geographic location where regeneration is to end or determining a predicted time for regeneration and then setting a timer duration corresponding to the required regeneration time. The timer is started when the start geographical location is reached and when it runs out regeneration is halted.

In some embodiments the selection of the start point may also include determining the type of terrain for various sections of the route and choosing if possible a section of route that provides a predominantly uphill road section.

That is to say, the terrain can be used to distinguish between various sections of the route that may all be potentially suitable for optimum regeneration.

In some other embodiments the selection of the start point may also include determining the traffic conditions for various sections of the route and choosing if possible a section of route that provides no traffic delays. That is to say, the traffic conditions can be used to distinguish between various sections of the route that may all be potentially suitable for optimum regeneration.

It will be appreciated that in some embodiments both terrain and traffic conditions can be used together to determine the optimum section of road where regeneration should take place and as a consequence the desired start point for the regeneration.

In one embodiment determining a desired start point for the regeneration includes determining from the navigation system the type of road to be travelled along, the expected speed of the vehicle at various locations along the route, the expected terrain for the route and the expected traffic conditions for various locations along the route and, based upon the gathered information, calculating a optimum -11 -regeneration window time so as to minimize the penalty on at least one of fuel economy, engine oil contamination and/or one or more other factors that affect regeneration quality.

In some embodiments the electronic controller 3 may be further arranged to check from the vehicle sensors 8 whether the motor vehicle 1 is in fact travelling at the expected speed and/or from the engine sensors 9 whether the engine is rotating at the expected speed or the engine is operating at the expected load before carrying out the regeneration.

That is to say, although all of the information from the navigation system may indicate that the motor vehicle 1 should be travelling at a relatively high speed/load this may not be the case due to unforeseeable conditions such as bad weather or an accident.

Once everything is in place for regeneration the electronic controller 3 initiates the regeneration of the DPF 6 when the start point conditions are met by increasinq the volume of fuel injected into the engine 2 and retardinq the timing of the injection of fuel into the engine 2 by the use of one or more late or post injections of fuel. The effect of this is to increase the temperature of the exhaust gasses entering the DPF 6 to a level where the accumulated soot can be burnt off. The controller 3 is then operable to end the regeneration of the DPF 6 when the end point conditions have been met and to restore the timing and volume of fuel supplied to the engine 2 to a normal runninq state.

If the optimum conditions for regeneration are not met for the known route, the electronic controller 3 is further operable to determine whether the DPF 6 is overloaded, that is to say, the accumulation of particulates (soot) is so great as to be affecting the economical running of the engine 2 or the emission performance of the motor vehicle 1.

-12 -If the DPF 6 is overloaded, the electronic controller 3 is then operable to carry out a forced regeneration of the DPF 6. A forced regeneration is one where although the conditions for regeneration are not ideal, regeneration takes place in order to remove at least some of the particulate build up in the DPF 6.

In some embodiments the electronic controller 3 is further operable to determine the best possible start and stop points for the forced regeneration. That is to say, select start and stop points that will result in the minimum oil dilution, fuel usage and loss of driveability.

If a future route is not known the electronic controller 3 may be further operable to carry out a regeneration of the diesel particulate filter based upon historical data. That is to say, even if a route has not been set, regeneration of the DPF 6 is still possible. In this case historical data is used to determine when to start the regeneration. That is to say, data about previous journeys is used to estimate what the type of journey is likely to be today. Even though a destination has not been set the navigation system 4 is still able to provide details of the current geographical position and from this in combination with the historical data a prediction of when it is best to regenerate can be deduced. For example, if the historical data indicates that at weekends the motor vehicle 1 often travels along a motorway for several miles and today is a weekend day and the current geographical location coincides with a motorway, then this is a good indication that now would be a good time to carry out the regeneration.

Whereas, if the historical data indicates that from Monday through Friday the motor vehicle 1 is often travelling in a stop/ start manner along a particular city road and the navigation system indicates that the motor vehicle 1 is currently on that road and it is a Tuesday, then the -13 -indication is that now would be a bad time to start regeneration.

Although the invention has been described above with respect to an embodiment in which the logical operations required to determine the start and stop points are all carried out in the electronic controller 3 it will be appreciated that this need not be the case and these operations could be carried out in the navigation system 4 and merely a control signal sent to the electronic controller 3. Furthermore it will be appreciated that the electronic controller 3 could comprise of several interconnected controllers or the electronic controller 3 and the navigation system 4 could be formed as a single unit.

Referring now to Fig.2 there is shown a method for regenerating a diesel particulate filter in accordance with one embodiment of the invention.

The method starts at block 100 which may correspond to a key-on event. Then in block 110 it is determined whether the DPF 6 needs to be regenerated. This determination can be in any convenient manner such as for example modelling of the usage of the DPF 6 since the last regeneration or by measuring the pressure drop produced by the current particulate loading and comparing the current pressure drop with a predetermined value. For Euro V emission regulations there are primarily two ways of estimating soot load. The first one (!vClosed Loop!!) estimates soot based on the measured pressure difference across the DPF. For a given exhaust gas flow, the higher the pressure the higher the soot stored. The second method (!vOpen Loop!!) is a calculation based on the engine smoke generation as measured on a dynamometer. A second-by-second integration is performed with the smoke from the engine being monitored and used to produce a soot figure for a range of operating -14 -conditions. This accumulated data can then be used to estimate the accumulated particulates in the DPF 6 over time based upon usage of the motor vehicle 1.

If the DPF 6 does not require regeneration the method loops back to block 100. In this case the method may continue immediately back to block 110 or it may start again when the next key-on event occurs.

If in block 110 it is determined that regeneration of the DPF 6 would be beneficial then in block 120 it is determined whether the future route is known. This is simply a case of determining whether a destination for the current trip has been set. If the answer is NO' then the method branches to block 170 where in the example being described it is determined whether the DPF 6 is so full that immediate regeneration is advised. If the DPF 6 is not overloaded then the method loops back to block 100. As before, the method may then continue immediately back to block 110 or it may restart again when the next key-on event occurs. In other embodiments the block 170 may be omitted and the method advances directly to block 175.

If at block 170 it is determined that regeneration is required because the DPF 6 is overloaded then this regeneration is conducted in block 175 based upon historical data stored in the electronic controller 3. That is to say, even if the destination is not known, pattern of the driving behaviour could be extracted by analyzing the data of the past cycles from the navigation system. For example, the engine could schedule the regenerations on favourable!vlonq weekend journeys!! and avoid!vshort weekdays commuting!!.

Another example would be to avoid rush hour traffic jams in favour of off-peak journeys. The method then advances to block 180 described below.

-15 -Returning to block 120, if the route is known, then the method advances to block 130 where the optimum conditions for regeneration to start and stop are determined. In block the optimum engine loads and optimum periods of time required for regeneration are established. For example, it may be determined that to achieve complete regeneration based upon the current particulate loading, the engine 2 must be operating a 40% load for 6 minutes or that the vehicle must be travelling at more than lOOkph for 8 minutes or that the exhaust gas flow must be greater than 150 kg/h for 7 minutes to achieve optimum regeneration with minimum loss of fuel economy and minimal oil dilution.

Then in block 140 the parameters set in block 130 are compared to information about the known route to determine whether any sections of the route match the required parameters. It is possible for a long route that several sections will match these parameters and then block 140 will also determine which of the selected sections best matches the optimum conditions for regeneration. It will be appreciated that the various sections may overlap one another and that the sections need not be sequential portions of the route. If are of the suitable sections are equally matched then generally the first opportunity to regenerate the DPF 6 is chosen. But if there are minor differences then the best possible section of the route is selected. In some embodiments this selection may include the use of information regarding the terrain for the various sections or real life traffic conditions. For example a section that is predominantly uphill would be preferable to a level section and a level section would be preferable to a predominantly downhill section. Similarly a section with no known delays would be preferable to a section with known delays.

From block 140 a predetermined starting point and a predetermined stop point for the regeneration are produced.

-16 -The start point normally comprises a geographical reference that when reached causes the regeneration to start. But it could also include a further test for vehicle speed or some other parameter. For example and without limitation, the start point condition could be configured as "if the current location is 51 degrees 10 minutes 28.5 seconds North; 0 degrees 7 minutes, 40.67 seconds West and the current vehicle speed is above lOOkph then start regeneration else seek next opportunity to regenerate at optimum conditions".

It will be appreciated that other combinations of geographical location and instantaneous operating condition of the motor vehicle 1 or the engine 2 such as engine speed, engine load and exhaust gas flow could be used.

The stop point can simply be a further geographical point or could be an amount of time that has to elapse after regeneration has started.

Then in block 150 the regeneration of the DPF 6 takes place in accordance with the start and stop points set in block 140 by the electronic controller 3 adjusting the volume and timing of the fuel injected to the engine 2 in order to increase the exhaust gas temperature to a temperature suitable for DPF regeneration such as for example 470 to 500°C.

The method then advances to block 180 where it is determined whether the regeneration was successful. This can be either an estimate based upon whether the desired conditions have subsisted for the required period of time or may be by direct measurement of the pressure drop across the DPF 6.

If it is confirmed in block 180 that the regeneration was successful the method ends at block 190 otherwise the method reverts to block 100 where in this case step 110 is immediately performed and the method is re-run.

-17 -If in block 140 it is determined that the conditions for optimum regeneration do not occur for the known route then the method branches to block 145 where it is determined whether the DPF 6 is so full that immediate regeneration is advised. If the DPF 6 is not overloaded then the method loops back to block 100. As before, the method may then continue immediately back to block 110 or it may restart again when the next key-on event occurs.

If at block 145 it is determined that regeneration is required because the DPF 6 is overloaded then this regeneration is conducted based upon standard conditions.

That is to say, the regeneration takes place using standard or predetermined fuel supply volume and timing values. The method then advances to block 180 described above.

Although not shown on Fig.2, in some embodiments even though the test at block 140 has been failed indicating that the current route is not suitable for optimum regeneration if at block 145 it is determined that regeneration must be carried out because the DPF loading is so high as to be compromising engine performance and emission performance then the method can include the step of determining the best start and stop points for the known route that ensure that the regeneration will take place as soon as possible but in the best possible conditions. That is to say, rather than regeneration of the DPF 6 starting immediately regeneration may be delayed until a section of the route is reached where the best conditions for regeneration in the known route are present.

Referring now to Figs.3 to 6 based on the navigation system and using inputs such as expected destination, traffic conditions, gradients...etc, the future vehicle speed profile can be estimated and represented by: -18 -v(t) or v(s) (1) Depending whether the speed profile is represented as a function of journey time or as vehicle geographical location.

The following description of the system is time based but a spatial based formulation would be equivalent.

If we define the penalty function as: = ...+(t) (2) and ct)+c22(t)+...+c(t)=1 (3) Where: -j1(t),ijí2(t)...iji(t) represent each of the factors that describe the quality of a regeneration (fuel economy, oil contamination, engine emissions, regeneration ability...) and that can be related to vehicle speed and thus, journey time.

The penalty function is constrained to (t)E(O,1) if each of the penalty factors is also defined in the same interval kjJ(t)E (o,i) For example, the fuel economy factor could be defined by a curve like that shown in Fig.4 where 0 means that the regeneration fuel penalty is very high, whereas 1 means that the regeneration penalty is low.

If we define t),c(t)...c(t) as weight functions to assign different contributions to the penalty factors depending on their importance. For example, if there is more interest in optimizing the fuel economy than the oil contamination, one would assign a bigger (t) to one factor than the other.

-19 -The objective then, is to find the maximum of the penalty function over the course of the next known or estimated journey.

If the expected time in regeneration is defined as treg (for example 600 seconds), we can then define a favourability or penalty function S(t) as to how favourable it is to do a regeneration that's lasts treg where the maximum value of t+treg (t)= J(t)dt t defines the optimum regeneration window across the expected journey. However, it is not the magnitude of the maximum value of (t) that is of interest but the moment or location in the journey when it happens. That is to say, in this case the moment when a regeneration started treg seconds before would be completed with the optimum conditions as defined in the penalty function. The above algorithm can be implemented as a block diagram in Simulink® as shown in Fig.3.

In one non-limiting example a real driving cycle is fed into the system as v(t) as shown in Fig.5 and a penalty function is defined, based on two penalty factors with equal weight, !vOil Dilution!! and Fuel Economy!!.

Based on this, the integration is performed and the result of 1(t) is shown in Fig.6.

From this function, the maximum value and the moment this occurs can be extracted. In the case shown in Fig.6, the maximum of 1(t) happens at 1258 seconds. That means that an optimum regeneration lasting 600 seconds should finish -20 -after 1258 seconds after the cycle started indicated by the point P' on the chart.

Therefore the optimum regeneration should start 658 seconds after the cycle started or an equivalent geographical location for a space based system, where the final outcome would be a geographical starting point.

Therefore, in summary, whenever possible regeneration of the DPF 6 occurs only when the optimum conditions for regeneration are present thereby reducing the risk of incomplete regeneration, excessive fuel usage, excessive oil dilution and poor driveability from occurring.

It will be appreciated that the fact that a vehicle is currently travelling at speed on a fast road does not necessarily mean that a successful regeneration will occur.

The motor vehicle may, for example, be near to the end of that section of fast road or the motor vehicle may be close to its final destination. However, in the case of a method in accordance with this invention, by surveying the known route and selecting a section where the optimum conditions occur both in terms of suitable vehicle operating conditions and expected duration, the highest possible probability of a successful and complete regeneration is obtained.

It will be appreciated by those skilled in the art that although the invention has been described by way of example with reference to one or more embodiments it is not limited to the disclosed embodiments and that one or more modifications to the disclosed embodiments or alternative embodiments could be constructed without departing from the scope of the invention as set out in the appended claims.

Claims

-21 -Claims 1. A method for regenerating a diesel particulate filter of a motor vehicle having a navigation system, wherein the method comprises determining whether the diesel particulate filter requires regenerating, and, if the diesel particulate filter requires regenerating, determining whether the future route is known, and, if the future route is known, determining whether optimum regeneration is possible for the known route, and, if optimum regeneration is possible for the known route, determining a desired start point for the regeneration and a desired end point for the regeneration, initiating regeneration when the start point conditions are met and ending the regeneration when the end point conditions are met.
2. A method as claimed in claim 1, wherein the start point conditions include reaching a specific geographic location on the known route.
3. A method as claimed in claim 1 or 2, wherein the end point conditions include at least one of reaching a specific location on the known route and reaching a predetermined elapsed time after regeneration has started.
4. A method as claimed in any of claims 1 to 3, wherein determining a desired start point for the regeneration includes at least one of determining the type of road to be travelled along on the route, determining the expected speed of the vehicle at various locations along the route, determining the expected terrain of the route and determining the expected traffic conditions for various locations along the route.
5. A method as claimed in any of claims 1 to 4, wherein, if the optimum conditions for regeneration are not -22 -met, the method further comprises determining whether the diesel particulate filter is overloaded, and, if the diesel particulate filter is overloaded, carrying out a forced regeneration of the diesel particulate filter.
6. A method as claimed in claim 5, wherein the method further comprises determining the best possible start and stop points for the forced regeneration.
7. A motor vehicle having a diesel engine supplying exhaust gases to a diesel particulate filter, an electronic controller to control the timing and volume of fuel injected into each cylinder of the engine, and a navigation system operatively connected to the electronic controller, wherein the electronic controller is operable to determine whether the diesel particulate filter requires regenerating, and, if the diesel particulate filter requires regenerating, to determine from the navigation system whether the future route is known, and, if the future route is known, to determine whether optimum regeneration is possible for the known route, and, if optimum regeneration is possible for the known route, to determine a desired start point for the regeneration and a desired end point for the regeneration and initiate the regeneration of the diesel particulate filter when the start point conditions are met and end the regeneration of the diesel particulate filter when the end point conditions are met.
8. A motor vehicle as claimed in claim 7, wherein the start point conditions include reaching a specific geographic location on the known route.
9. A motor vehicle as claimed in claim 7 or 8, wherein the end point conditions include at least one of reaching a specific location on the known route and reaching a predetermined elapsed time after regeneration has started.

-23 -
10. A motor vehicle as claimed in any of claims 7 to 9, wherein determining a desired start point for the regeneration includes at least one of determining from the navigation system the type of road to be travelled along, the expected speed of the vehicle at various locations along the route, the expected terrain for the route, and the expected traffic conditions for various locations along the route.
11. A motor vehicle as claimed in any of claims 7 to 10, wherein, if the optimum conditions for regeneration are not met for the known route, the electronic controller is further operable to determine whether the diesel particulate filter is overloaded, and, if the diesel particulate filter is overloaded, to carry out a forced regeneration of the diesel particulate filter.
12. A motor vehicle as claimed in claim 11, wherein the electronic controller is further operable to determine the best possible start and stop points for the forced regeneration.
13. A method for regenerating a diesel particulate filter of a motor vehicle substantially as described herein with reference to the accompanying drawing.
14. A motor vehicle substantially as described herein with reference to the accompanying drawing.