FR2774421A1 - Operational control of diesel engine exhaust particle filter - Google Patents

Abstract

The management unit (15), controlling e.g. air intake (1) and admission (3,5), exhaust gas recirculation (EGR) (6,4), and fuel injection (7,8), also operates the regenerative unit (13) for the particle filter (14), assisted by signals received from pressure (11) and temperature (12) sensors inserted on either side of the filter. The filter pressure drop, under given engine operating conditions, indicates to the management unit the degree of fouling, and the unit determines when regeneration is required by reference to previously recorded levels. Regeneration, achievable by e.g. burning off, supplementary fuel burn, EGR variation, etc., may be intermittent, the frequency dependent on the various parameters, or continue till the monitored pressure and temperature are satisfactory. The general condition of the filter can be assessed by checking recorded variations in relevant parameters over an arbitrary distance (km run).

Description

 The present invention relates to a system for managing the operation of a particle filter associated with a diesel engine, in particular of a motor vehicle, and placed in the exhaust line thereof.

 We know that one of the most important concerns of equipment manufacturers and motor vehicle manufacturers is the reduction of the pollution generated by their operation.

 This is particularly the case for diesel engines.

 Different solutions have therefore been envisaged in an attempt to reduce the pollution levels of these engines.

 Thus, for example, it has already been proposed in the prior art, to integrate particulate filters into the exhaust lines of these diesel engines.

 These are then adapted to trap particles or soot contained in the exhaust gases of these engines and burn them during a regeneration phase of the filter.

 Various means of assisting in the regeneration of these filters have already been developed in the state of the art.

 However, the functioning of these filters and / or of the means for assisting the regeneration of these is still poorly understood.

 The object of the invention is therefore to solve these problems.

 To this end, the subject of the invention is a system for managing the operation of a particle filter associated with a diesel engine, in particular of a motor vehicle, and placed in the exhaust line thereof, characterized in that it includes means for controlling the level of fouling of the particulate filter, means for comparing this level of fouling of the filter with a predetermined fouling threshold to trigger the operation of means for assisting the regeneration of the filter, means for controlling the triggering and progress of the regeneration of the filter and means for controlling the operation and integrity of the filter.

The invention will be better understood with the aid of the description which follows, given solely by way of example and made with reference to the appended drawings, in which
- Fig.l shows a block diagram illustrating the general structure of a system for managing the operation of a particle filter associated with a diesel engine of a motor vehicle; and
- Fig.2 shows a flowchart illustrating the operation of such a system.

 In fact, in FIG. 1, the general structure of a system for managing the operation of a particle filter associated with a diesel engine of a motor vehicle and placed in the exhaust line thereof is recognized.

 Conventionally, the engine M is supplied with air through an air inlet pipe provided with a flow meter and an intake air temperature sensor, designated by the general reference 1 in this figure.

Then, this air passes through the portion of compressor designated by the general reference 2a of a turbocharger
T if the engine is fitted with such a turbocharger.

 The air then passes through a charge air exchanger designated by the general reference 3 if this is equipped with it.

 The engine M can also be equipped with an EGR type exchanger designated by the general reference 4, associated with an inlet throttle designated by the general reference 5 in this figure and with an EGR valve designated by the general reference 6.

 The engine M can also be equipped with a fuel supply system of the COMMON RAIL type, for example designated by the general reference 7, equipped with electromagnetic control injectors, one of which is designated by the general reference 8 in this figure. .

 The engine is also equipped with a speed sensor 9 and an intake air pressure sensor 10.

 At the outlet of this engine, the exhaust gases optionally pass through the turbine portion 2b of the turbocharger T before engaging in the rest of the exhaust line E of the vehicle.

 As indicated above, this exhaust line can be equipped with a particle filter F and in this case, it can be equipped with a differential pressure sensor designated by the general reference 11 for determining the pressure difference between the inlet and the outlet of this filter.

 Temperature sensors designated by the general reference 12 in this figure, can also be arranged upstream and / or downstream of this particulate filter F and this can also be equipped with a system for supplying energy to the exhaust gas, for the regeneration of the filter, designated by the general reference 13 and which will be described in more detail below.

 The particulate filter itself is designated by the general reference 14 in this figure.

 The various sensors fitted to the engine M, the air inlet pipe therein and the gas exhaust line from it, are connected to a central information processing unit 15 making it possible to manage the operation of this filter and of the means for assisting in the regeneration thereof, this central unit also being able to receive information from a vehicle accelerator pedal position sensor, designated by the general reference 16 in this figure and a vehicle speed sensor designated by the general reference 17.

 According to the invention, the particulate filter management system comprises means for controlling the level of fouling of this filter, means for comparing this level of fouling of the filter with a fouling threshold determined to trigger the operation of the means for assisting the regeneration of the filter, means for controlling the triggering and progress of the regeneration of the filter and means for controlling the operation and integrity of the filter.

 These various means can for example be integrated into the central information processing unit 15 which is then appropriately programmed to implement a first step of controlling the fouling level of the particle filter, designated by the reference general 18 in figure 2.

 It is indeed known that the pressure drop generated by the particle filter and measured for example by a sensor such as the differential pressure sensor 11 described with reference to FIG. 1, at the terminals of this filter, is representative of the amount of particles or soot trapped in the filter.

 For a given amount of soot, the pressure drop depends on the flow rate and the temperature of the exhaust gases passing through this filter.

 We also know that for each couple, gas flow rate and gas temperature, there is a pressure drop in the exhaust line, which results in the fact that it is possible to measure only the absolute pressure in upstream of the particulate filter to find out the amount of soot in this filter.

 The exhaust gas flow and temperature depend on the torque and the engine operating speed.

 This means that it is possible to know the amount of soot in the particulate filter thanks, for example, to the differential pressure measured for each torque, speed and operating torque of the engine.

 It can therefore be seen that the amount of soot in the filter can thus be determined by measuring the differential pressure tP at the terminals of the particle filter, associated with knowledge of the flow rate and temperature of the exhaust gases or any other parameter. of engine operation, i.e. for example further engine speed and torque, boost pressure, fuel flow, etc.

 Once this level of fouling has been determined, the central information processing unit 15 is adapted to compare this level of fouling with a determined fouling threshold S1, during a step designated by the general reference 19 on the Figure 2, in order to trigger or not the operation of the means for assisting the regeneration of this filter.

 It will in fact be understood that the determined fouling threshold being able to be programmable and stored in storage means of this central information processing unit 15, it is possible to establish a level from which it is considered necessary to become to trigger the regeneration of the filter.

 It will then be understood that the triggering of the means for assisting the regeneration of the filter is determined for any point of engine operation, when the pressure drop across the particulate filter, as measured or calculated from the pressure absolute upstream of this filter, exceeds a threshold which, as indicated above, can be programmable.

 This then allows the central information processing unit 15 to trigger at 20 the operation of the means for assisting the regeneration of this filter.

 A number of means can be used to aid the regeneration of this type of filter.

 These means may for example include a burner, a throttle control system at the intake, an EGR valve control system, a turbocharger control system, a fuel injection system, in particular by reversing the advance. main fuel injection, etc.

 These means for assisting the regeneration of the particle filter can then be triggered by the central unit 15 for a predetermined period of time which can, for example, be programmable, with an adjustable frequency or continuously.

 The regeneration of the particle filter, that is to say its triggering and its unfolding, is controlled by the central information processing unit 15 during a step designated by the general reference 21 in FIG. 2.

 Thus, for example, the operation of the regeneration assistance means can be regulated for example in intensity and in frequency by the unit 15 on the basis of the analysis of the parameters described above and in particular of the gas temperature. exhaust.

 The detection of the regeneration of the particulate filter is based for example on the estimation of the fact that the latter is regenerated when, for any point of engine operation, the pressure drop across the terminals of this particulate filter is located in below a predetermined threshold value, which can also be programmable and stored in storage means of the central information processing unit.

 It is then understood that in this case also, the differential pressure tP across the particle filter for the determined operating point of the engine, is compared with a corresponding threshold value S2 to determine, when the differential pressure is less than the predetermined value , that the filter is sufficiently regenerated in order to cut off the operation of the means for assisting the regeneration of this filter, as illustrated by the steps designated by the general references 22 and 23 respectively in FIG. 2.

 A measurement of the temperature of the gases downstream of the particulate filter can also be carried out in order to complete the detection of the regeneration of this filter and possibly to limit this temperature during this regeneration by controlling the operation of the means for assisting the regeneration, by example by limiting or cutting the operation of these.

 Thus, for example, regeneration can be detected if the temperature of the exhaust gases is higher than a maximum possible temperature for the given operating point of the engine, that is to say for example as a function of the engine speed. , of the torque thereof, of the air flow and of the assistance means engaged or by a measurement of variation of this temperature of the gases over a determined period of time, which is also compared with a corresponding value.

 It goes without saying of course that to reduce or avoid regeneration detection errors, both for triggering the operation of the regeneration aid means and for detecting the end of this regeneration, the parameters can also be analyzed. indicated above over a predetermined period of time.

 Once each regeneration is detected, it can also be provided that the engine operation control computer records the mileage carried out since the previous regeneration to allow a diagnosis of the proper functioning of the particle filter.

 This then makes it possible, for example, for the central information processing unit 15 to check the integrity and the proper functioning of the particle filter during a step designated by the general reference 24 in FIG. 2.

 This check is based on the estimation of the fact that the particle filter can be damaged, when after a predetermined taxiing, that is to say for example a programmable distance traveled by the vehicle, the loss load across the particulate filter remains less than the pressure drop of a new or lightly loaded particulate filter.

 This then makes it possible, for example, to initiate a backup strategy which can go as far as a request for maintenance intervention or repair of this filter.

 It is then possible to establish a relationship between the mileage traveled by the vehicle and the time necessary to travel this mileage in order to control the filter.

 Furthermore, during this step 24, the central information processing unit can also be adapted to detect a clogging of this filter.

In fact, the clogging of the filter can be detected when the pressure drop across the filter exceeds a predetermined pressure drop, which can for example be programmable and stored in the storage means of the central unit 15,
This detection of clogging of the filter can also lead to the implementation of a strategy for protecting this particulate filter to avoid its destruction during too brutal regeneration due to the excessive amount of soot in the filter and / or a backup strategy which may lead to a request for intervention for maintenance or repair.

 Of course, other methods of detecting this clogging can be envisaged, such as for example by analyzing the evolution over the life of the vehicle, of the minimum differential pressure on one, several or all of the operating points. of the motor.

 It goes without saying of course that the various programmable parameters described above can be corrected for example to take into account the change in the behavior of the particulate filter at the engine control level in order to change the level of assistance required during regeneration. and to change the parameters making it possible to determine the state of the particle filter, that is to say the fact that it is dirty, regenerated, clogged or damaged.

 It goes without saying of course that other embodiments of such a system can be envisaged.

Claims (5)

 1. Management system for the operation of a particle filter (F) associated with a diesel engine (M), in particular of a motor vehicle, and placed in the exhaust line (E) thereof, characterized in that it comprises means (15) for controlling the level of fouling of the particulate filter (F), means (15) for comparing this level of fouling of the filter with a predetermined fouling threshold to trigger the operation of means aid for regenerating the filter, means (15) for controlling the triggering and progress of the regeneration of the filter and means (15) for controlling the operation and integrity of the filter.  2. System according to claim 1, characterized in that the control means (15) are adapted to analyze the pressure drop across the particle filter (F) for at least one engine operating point.  3. System according to claim 2, characterized in that the pressure drop across the particle filter (F) is determined by a differential pressure sensor (11) across the particle filter (F).  4. System according to any one of the preceding claims, characterized in that the control and comparison means comprise a central information processing unit (15) connected to different sensors for reading different operating parameters thereof. .  5. System according to claim 4, characterized in that the central information processing unit (15) is connected to means (12) for measuring the temperature of the exhaust gases to regulate the operation of the means of helps regeneration of the particulate filter.