FR2808559A1 - Diesel engine, fitted with exhaust particle filter, has engine operational control system in which pressure differential unit evaluates pressure difference between points in front of and behind particle filter - Google Patents

Abstract

Pressure differential unit has first absolute pressure sensor (10) fitted in the exhaust line (2) up stream of the particle filter (4) and second pressure sensor (6) fitted outside the exhaust line, in the engines air admission system. Second sensor is designed to measure the atmospheric pressure and the pressure differential unit includes a computer (9) which estimates the pressure differential from the measurements made by the two sensors. The computer includes a comparator for the pressures measured by the sensors and a corrector for the pressure differential estimate calculated during engine operation as a function of the initial comparison results provided by the sensors.

Description

The present invention relates to a system for controlling the operation of an exhaust line of a diesel engine, in particular of a motor vehicle equipped with a particle filter and comprising means for evaluating the differential pressure between a point located upstream of the particulate filter and a point downstream of the particulate filter.

Such a control system is described for example in patent application FR-A-2,774,424.

In the device described in this document, the control system includes means for controlling the flow rate of the exhaust gases flowing in the particulate filter. The operation of the control means is controlled by control means receiving, at the input, information relating to the operating conditions of the filter delivered by sensors located in the line, one of the sensors being constituted by a pressure sensor. differential across the particle filter.

The differential pressure sensor has two pressure taps, one provided upstream of the particulate filter, and the other provided downstream of the particulate filter.

Thus, to use such a sensor, it is necessary to provide two tappings on the exhaust line. Each of these tappings is extended by a tube extending to the actual measuring member of the differential pressure sensor.

Consequently, for the implementation of a differential pressure sensor, it is necessary to make two holes in the exhaust line as well as to use tubes of great length. Such a structure, for measuring the differential pressure, is expensive and harms the reliability of the exhaust line.

The object of the invention is to propose a system for controlling the operation of an exhaust line which does not have the drawback mentioned above.

To this end, the subject of the invention is a system for controlling the operation of an exhaust line of the aforementioned type, characterized in that the said differential pressure evaluation means comprise a first pressure sensor installed on the exhaust line upstream of the particulate filter and a second pressure sensor located outside the exhaust line, which second sensor is adapted to measure atmospheric pressure, and in that said evaluation means also include means for calculating an estimate of the differential pressure from the measurements collected by the first and second sensors.

According to particular embodiments, the control system includes one or more of the following characteristics - said differential pressure evaluation means comprise a single pressure sensor installed on the exhaust line; - The first pressure sensor installed on the exhaust line is an absolute pressure sensor; the first pressure sensor is installed on the exhaust line immediately upstream of the particulate filter; - The second pressure sensor is installed in the air intake means of the engine; and said calculation means comprise means for comparing initial measurements collected by the first and second sensors before starting the engine and means for correcting the estimate of the differential pressure calculated during engine operation, depending on the result of the comparison of the initial measurements collected by the first and second sensors.

The invention will be better understood on reading the description which follows, given solely by way of example, and done with reference to the single figure which is a schematic view of an exhaust line associated with a Diesel engine and incorporating a control system according to the invention.

In this figure is shown a diesel engine of an auto bile vehicle designated by the reference 1. At the output of this engine is connected an exhaust line 2 incorporating a system for controlling its operation according to the invention.

Immediately downstream of the engine 1, the exhaust line 2 com carries a turbocharger 3 where the exhaust gases are caused to circulate in the turbine portion of this turbocharger. Downstream of the turbocharger is installed a particulate filter 4.

The vehicle engine is also associated with means for supplying it with fuel.

These means comprise for example a common supply system for all the injectors of the engine designated by the reference 5 in this figure and known, in the state of the art, under the name of "common rail". This supply system includes means for admitting atmospheric air. The latter, as known per se, are equipped with a pressure sensor 6 intended to collect a value representative of atmospheric pressure.

This engine supply system is also provided with command injectors, for example electric, one of which is designated by the reference 7. The system for controlling the operation of the exhaust line comprises, arranged downstream of the particle filter, a pilot-operated valve 8 allowing selective closure of the exhaust line.

For controlling the pilot-operated valve 8 and the injectors 7, the control system includes a central information processing unit 9. This is connected to the valve 8 and to each of the injectors 7.

The central information processing unit 9 is adapted to control the degree of opening of the valve 8, as well as of the injectors 7, as a function of an estimate of the differential pressure prevailing between a point disposed upstream of the filter. and a point located downstream of the particulate filter.

Although, in the description given here, the control of the operation of the exhaust line is ensured by the adjustment of the valve 8 and of the injectors 7, any other operating parameter of the exhaust line can be modified to ensure his control.

To determine an evaluation of the differential pressure, the control system comprises a first absolute pressure sensor 10 im planted on the exhaust line upstream of the particulate filter 4 and a pressure sensor located outside the line exhaust, this second sensor being adapted to measure atmospheric pressure. In the embodiment envisaged, the second sensor is formed by the sensor 6 installed at the air intake inlet of the engine. The sensors 6 and 10 are connected to the central information processing unit 9.

In the embodiment illustrated in the figure, the first sensor 10 is disposed between the turbocharger 3 and the particle filter 4. However, the sensor 10 can be placed at any point of the exhaust line located between the engine 10 and the particle filter 4. Advantageously, the absolute pressure sensor 10 is arranged immediately upstream of the particle filter, in the immediate vicinity of its inlet.

The sensor 10 is adapted to determine the pressure inside the exhaust line, this pressure being evaluated relative to the vacuum. The central information processing unit 9 comprises means for calculating an estimate of the differential pressure between a point of the exhaust line disposed upstream of the particulate filter and a point of the exhaust line arranged in downstream of the particulate filter from the measurements collected by the first and second sensors 6 and 10. 'The estimate rests on the assumption that the pressure downstream of the particulate filter is substantially identical or little different from the pressure atmospheric measured by the sensor 6.

The estimate of the differential pressure is obtained by difference between the values measured by the first sensor 10 and the second sensor 6. From the differential pressure thus evaluated, the central information processing unit 9 controls the valve 8 and the injectors 7, in order to avoid deterioration of the particle filter during the exotherm observed during the regeneration phases thereof.

In addition, the central information processing unit 9 comprises means making it possible, before starting the engine, to carry out a pressure measurement from the first and second sensors. It includes means making it possible to compare the measured values and means making it possible to correct the estimate of the differential pressure subsequently calculated as a function of the difference observed between the values of pressure measured before starting the engine. These means make it possible to compensate for any measurement and calibration errors of the pressure sensors. Indeed, before starting the engine, the first and second sensors are both subjected to atmospheric pressure and should therefore collect identical measurement values.

Thus, the central information processing unit 9 makes it possible, by taking into account, in the evaluation of the differential pressure, of the possible offset in the pressures initially measured by the sensors, to compensate for the calibration errors of these sensors .

It is understood that with a control system as described here, only a tap is required on the exhaust line for the installation of the absolute pressure sensor 10. Thus, the cost of the exhaust line is reduced.

Claims (1)

<U> CLAIMS </U> 1.- System for controlling the operation of an exhaust line (2) of a diesel engine (1), in particular of a motor vehicle, equipped with a particle filter (4) and comprising means for evaluating the differential pressure between a point situated upstream of the particulate filter (4) and a point situated downstream of the particulate filter (4), characterized in that said means for evaluating the differential pressure comprise a first pressure sensor (10) located on the exhaust line (2) upstream of the particulate filter and a second pressure sensor (6) located outside the exhaust line (2), which second sensor (6) is suitable for measuring atmospheric pressure, and in that said evaluation means further comprise means (9) for calculating an estimate of the differential pressure from the measurements collected by the first and cond sensors (6, 10). 2. A control system according to claim 1, characterized in that said means for evaluating the differential pressure comprises a single pressure sensor (10) located on the exhaust line (2). 3. Control system according to claim 1 or 2, characterized in that the first pressure sensor (10) located on the exhaust line is an absolute pressure sensor. 4. Control system according to any one of the preceding claims, characterized in that the first pressure sensor (10) is located on the exhaust line (2) immediately upstream of the particle filter (4). 5. Control system according to any one of the preceding claims, characterized in that the second pressure sensor (6) is installed in the air intake means of the engine (1). 6. Control system according to any one of the preceding claims, characterized in that said calculation means (9) comprise means for comparing initial measurements collected by the first and second sensors before starting the engine and the means for correcting the estimate of the differential pressure calculated during engine operation, based on the result of the comparison of the initial measurements collected by the first and second sensors.