FR3081550A1 - METHOD FOR DIAGNOSING THE OPERATION OF A TURBOCHARGER ADAPTED TO THE GRAVITY OF THE FAILURE - Google Patents

Abstract

The invention relates mainly to a method for diagnosing the operation of a turbocharger of an internal combustion engine, characterized in that said method comprises: - a step of carrying out a first comparison between a measured position (Pos_mes) of the discharge system and an activation threshold (S_act_min, S_act_max) defined as a function of parameters related to the operation of the heat engine, - a step of determining a loop deviation (Eb) equal to the difference between a position reference of the discharge system and the measured position (Pos_mes) of the discharge system, - a step of carrying out a second comparison between the loop deviation (Eb) previously determined and a detection threshold (S_det_pos, S_det_neg), and - a step of raising faults and / or reconfiguration of the heat engine as a function of the first comparison and the second comparison previously carried out.

Description

METHOD FOR THE DIAGNOSIS OF THE OPERATION OF A TURBOCHARGER ADAPTED TO THE SEVERITY OF THE FAILURE The present invention relates to a method for diagnosing the operation of a turbocharger adapted to the severity of the failure. The invention finds a particularly advantageous application in the field of thermal engines of motor vehicles.

In a manner known per se, a turbocharger comprises a compression stage and a turbine. The compression stage compresses the intake air to optimize the filling of the combustion chambers. For this purpose, the compression stage is placed on the air intake duct, that is to say before the engine. The flow of exhaust gases rotates a wheel of the turbine which then rotates a wheel of the compression stage via a coupling shaft connecting the two wheels to each other.

Turbochargers include a discharge system associated with a discharge circuit (or by-pass in English) allowing part of the exhaust gas not to pass through the turbine wheel. The discharge system, known as variable geometry, comprises a rotor and a stator each provided with a series of orifices distributed around their circumference. The rotor can be moved angularly relative to the stator so as to align or misalign the orifices of the rotor relative to those of the stator to open or close the discharge system. It is thus possible to vary the cross section of the exhaust gases to the discharge circuit.

In order to detect a failure of the turbocharger equipped with a position feedback, the measurement of the latter is compared to its setpoint. This defines a loop difference equal to the difference between a position setpoint and the measured position of the discharge system. There is a mechanical risk in the event of a negative loop deviation (too much supercharging pressure, therefore over-speed of the turbocharger, overpressure in the air line, temperature too high, etc.) which requires, inter alia, d '' turn on a warning light on the dashboard and limit engine performance. There is also a risk of a lack of safe power in the event of a positive loop deviation (not enough boost pressure therefore lack of performance) which requires lighting an indicator on the dashboard to warn the driver.

The problem with this strategy is that there is no distinction in the blocking position. Thus, degraded modes reconfiguring the engine sometimes prove to be too severe but necessary to cover the worst case. For example, a blockage in the maximum supercharging position requires severe reconfigurations as explained above (indicator light on the dashboard, performance limitation, etc.). Since this is the same diagnosis, a blockage in the intermediate position calls for the same system reconfigurations. However, the mechanical risk is much less, even absent. This leads to unjustified after-sales service returns and over-protection of the engine. Similarly, ignition on the dashboard is necessary in the event of a blockage in minimum supercharging due to a lack of more than 50% of performance. In the intermediate position, this lack of power is no longer safe and therefore does not require a severe reconfiguration of the engine or a driver alert.

The invention aims to effectively remedy these drawbacks by proposing a method of diagnosing the operation of a combustion engine turbocharger, the turbocharger comprising a discharge system that can take different positions to vary an opening level of an exhaust gas passage section, characterized in that the method comprises:

a step of carrying out a first comparison between a measured position of the discharge system and an activation threshold defined as a function of parameters related to the operation of the heat engine,

a step of determining a loop deviation equal to the difference between a position setpoint of the discharge system and the measured position of the discharge system,

a step of carrying out a second comparison between the previously determined loop deviation and a detection threshold, and

- a step of reporting faults and / or reconfiguring the heat engine as a function of the first comparison and the second comparison previously carried out.

The invention thus allows to activate the diagnosis on critical positions for the engine or for its performance in order to apply degraded modes in line with the risk and therefore limit the return to after-sales service to the necessary extent .

According to one implementation, the operating parameters of the heat engine are as follows: engine speed, heat engine torque, intake temperature of the exhaust gases, and atmospheric pressure.

According to one implementation, if the position of the discharge system is greater than a maximum activation threshold and if the loop deviation is less than a negative detection threshold, then the method includes a step of fault escalation critical and severe reconfigurations of the heat engine.

According to one implementation, if the position of the discharge system is less than the maximum activation threshold and if the loop deviation is less than the negative detection threshold, then the method includes a step for raising a fault not critical and non-severe reconfigurations of the heat engine.

According to one implementation, if the position of the discharge system is less than a minimum activation threshold, and if the loop deviation is greater than a positive detection threshold then the method includes a step of raising critical fault and severe reconfigurations of the heat engine.

According to one implementation, if the position of the discharge system is greater than the minimum activation threshold, and if the loop deviation is greater than the positive detection threshold, then the method includes a step for raising a fault not critical and non-severe reconfigurations of the heat engine.

According to one implementation, a severe reconfiguration of the heat engine notably consists in limiting a torque of the heat engine to at least 50% of its maximum value and warning the driver by switching on the dashboard.

According to one implementation, a non-severe reconfiguration of the heat engine notably consists in limiting a torque of the heat engine at most to 50%.

The invention also relates to an engine computer comprising a memory storing software instructions for the implementation of the method of diagnosing the operation of a turbocharger as defined above.

The invention also relates to a motor vehicle comprising an engine computer as defined above.

The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These figures are given only by way of illustration but in no way limit the invention.

Figure 1 is a schematic representation of an example of thermal engine architecture implementing the method according to the invention for diagnosing the operation of the turbocharger;

Figure 2 is a schematic representation of different states of a discharge system used in the method according to the invention for diagnosing the operation of the turbocharger;

Figure 3 is a functional block diagram implementing the method according to the invention for diagnosing the operation of the turbocharger.

Figure 1 shows an example of a motor vehicle architecture 1 comprising a heat engine 5 supercharged by a turbocharger 2 comprising a compressor 3 and a turbine 4. The compressor 3 makes it possible to compress the intake air so as to optimizing the filling of the engine cylinders 5. To this end, the compressor 3 is arranged on an intake pipe 8 upstream of the engine 5. The flow of the exhaust gases rotates the turbine 4 disposed on a pipe d 'exhaust 9, which then rotates the compressor 3 via a coupling shaft. A discharge system 15 of the turbocharger 2 is arranged upstream of the turbine 4. The discharge system 15 makes it possible to manage the quantity of exhaust gas flowing through the turbine 4 and the quantity of gas passing through a discharge line 16 .

In order to maintain the density of the air acquired at the outlet of the compressor 3, use is made of a heat exchanger 10 called RAS (for charge air cooler) capable of cooling the air circulating in the pipe. intake 8. The exchanger 10 is mounted downstream of the compressor 3 and upstream of an air metering device 18.

Furthermore, a system 23 for exhaust gas recirculation (known as EGR for Exhaust Gas Recirculation in English) comprises a redirection pipe 27 for exhaust gases capable of redirecting part of the exhaust gases from an exhaust manifold 20 to the intake distributor 28 of the engine 5 after passing through an exchanger 14. Thus, part of the exhaust gases from the engine 5 is discharged towards the exterior of the motor vehicle through the line exhaust 9 and another part of the gases is recycled. The quantity of gas to be recirculated is controlled by the EGR valve 25 mounted upstream of the intake distributor 28.

An engine computer 26 is capable of driving the various components of the vehicle, in particular the injection of the heat engine 5, the discharge system 15 of the turbocharger 2, the air metering device 18, and the EGR valve 25. This computer 26 includes a memory storing software instructions for implementing the method according to the invention for diagnosing the operation of the turbocharger 2 written in more detail below.

The discharge system 15 visible in Figure 2, said to variable geometry, comprises a rotor 30 and a stator 31 each provided with a series of orifices 33 and 34 respectively distributed over their circumference. The rotor 30 can be angularly moved relative to the stator 31 so as to align or misalign the orifices of the rotor 33 relative to those 34 of the stator 31 to open or close the discharge system 15. The discharge system 15 can take different positions for varying an opening level of an exhaust gas passage section S.

Figure 2 thus shows the discharge system 15 respectively in the open position (the holes 33 and 34 are completely superposed relative to each other), in a partially open position (the holes 33 and 34 are partially superimposed relative to each other) and in a closed position (the openings 33 and 34 are completely offset from each other).

By convention, it is considered that a position of the discharge system 15 at 0% is considered to be open to obtain a minimum charge and that a position of the discharge system 15 to 100% is considered to be closed to obtain a charge Max.

Described below, with reference to FIG. 3, the method according to the invention for diagnosing the operation of the turbocharger 2.

We define an activation threshold S_act_max, S_act_min as a function of parameters related to the operation of the engine 5. The risk being a function of the Reg_mot regime, of the torque C_mot, of the intake temperature T_ad and of the atmospheric pressure P_atmo, the activation threshold S_act_min, S_act_max is defined according to these parameters.

Thus, the output of a critical maximum feedback threshold map Cart_S_rec_maxC receiving as input the engine speed Reg_mot and the engine torque C_mot as well as the output of a maximum correction mapping Cart_corr_max receiving as input an intake temperature T_ad and an atmospheric pressure P_atmo are combined with each other via the module M1 to obtain a maximum activation threshold S_act_max.

Furthermore, the output of a critical minimum feedback threshold map Cart_S_rec_minC receiving as input the engine speed Reg_mot and the engine torque C_mot as well as the output of a minimum correction mapping Cart_corr_min receiving as input a temperature of intake T_ad and an atmospheric pressure P_atmo are combined with each other via the module M2 to obtain a minimum activation threshold S_act_min.

A first comparison is made, via the modules M3-M6, between a measured position Pos_mes of the discharge system 15 and an activation threshold S_act_max, S_act_min corresponding.

Furthermore, a loop difference Eb is determined equal to the difference between a position setpoint of the discharge system 15 and the measured position Pos_mes of the discharge system 15. A negative loop loop Eb means that the turbocharger 2 is too closed and therefore generates more supercharging than expected and, conversely, a positive loop difference Eb means that the turbocharger 2 is too open and therefore generates less supercharging than expected.

A second comparison is made, via the modules M7 and M8, between the loop difference Eb previously determined and a detection threshold S_det_pos and S_det_neg corresponding. These detection thresholds S_det_pos, S_det_neg are defined as a function of the engine speed Reg_mot, of the engine torque C_mot, of the intake temperature T_ad, and of the atmospheric pressure P_atmo.

A defect escalation, for example by generation of a visual alert on the dashboard or on a control screen, and / or a reconfiguration of the heat engine 5 is performed according to the first comparison and the second previously made comparison.

More precisely, when the measured position Pos_mes of the discharge system 15 is greater than the threshold S_act_max, the critical negative loop deviation diagnosis is activated (cf. module Act_diag_neg_C). If the loop difference Eb is below the negative detection threshold S_det_neg (this corresponds to too much overfeeding) then the fault rises and generates a severe reconfiguration in line with the risk via the modules M9 and Def_bou_neg_C.

Similarly, if the loop difference Eb is detected, that is to say that the loop difference Eb is less than the negative detection threshold S_det_neg but that the position Pos_mes is less than the threshold of maximum activation S_act_max (see module Act_diag_neg_NC), a non-critical loop deviation fault rises with a non-severe reconfiguration, via the modules M10 and Def_bou_neg_NC.

The principle is similar for a positive Eb loop deviation. Thus, when the position Pos_mes of the discharge system 15 is less than the activation threshold S_act_min, the critical positive loop deviation diagnosis is activated (cf. module Act_diag_pos_C). If the loop difference Eb is greater than the positive detection threshold S_det_pos (this corresponds to a lack of supercharging), then a fault rises and generates a severe reconfiguration in line with the risk, via the modules M11 and Def_bou_pos_C.

Similarly, if the loop difference Eb is detected, that is to say that the loop difference Eb is greater than the positive detection threshold S_det_pos, but that the position Pos_mes is greater than the threshold d 'minimal activation S_act_min (cf. module Act_diag_pos_NC), a non-critical loop deviation fault rises with a non-severe reconfiguration of motor 5, via the modules M12 and Def_bou_pos_NC.

A severe reconfiguration of the heat engine 5 may consist in particular of limiting a torque C_mot of the heat engine 5 to at least 50% of its maximum value. The associated critical fault escalation may consist of a generation of a visual alert on the dashboard or a control screen.

A non-severe reconfiguration of the heat engine 5 may consist in particular in limiting a torque of the heat engine at most to 50%. It is also possible to limit the torque C_mot of the motor 5 to a lesser extent than in the case of a severe reconfiguration. Torque limitation is not always necessary, however, since the risk of damage to the motor 5 is low. It will also be possible to alert or not the driver by displaying an alert signal via the reporting of a non-critical fault, but this is not necessarily necessary, since the feeling of a non-critical malfunction of the turbocharger 2 is weak for the driver.

The activations of the diagnostics of the local loops can be carried out according to general conditions of activation of the loops for monitoring local loops 5 Cond_act, via the corresponding modules M13-M16.

Claims (10)

Claims: 1. Method for diagnosing the operation of a turbocharger (2) of a heat engine (5), said turbocharger (2) comprising a discharge system (15) which can take different positions to vary an opening level of a section exhaust gas passage (S), characterized in that said method comprises: a step of carrying out a first comparison between a measured position (Pos_mes) of the discharge system (15) and an activation threshold (S_act_min, S_act_max) defined as a function of parameters related to the operation of the heat engine (5), a step of determining a loop deviation (Eb) equal to the difference between a position reference of the discharge system (15) and the measured position (Pos_mes) of the discharge system (15), a step of carrying out a second comparison between the loop deviation (Eb) previously determined and a detection threshold (S_det_pos, S_det_neg), and - A step of reporting faults and / or reconfiguring the heat engine (5) according to the first comparison and the second comparison previously made. 2. Method according to claim 1, characterized in that the operating parameters of the heat engine (5) are as follows: engine speed (Reg_mot), torque of the heat engine (C_mot), gas intake temperature exhaust (T_ad), and atmospheric pressure (P_atmo). 3. Method according to claim 1 or 2, characterized in that if the position (Pos_mes) of the discharge system (15) is greater than a maximum activation threshold (S_act_max) and if the loop deviation (Eb) is lower than a negative detection threshold (S_det_neg) then the method includes a step of raising a critical fault (Def_bou_neg_C) and severe reconfigurations of the heat engine (5). 4. Method according to claim 3, characterized in that if the position (Pos_mes) of the discharge system (15) is less than the maximum activation threshold (S_act_max) and if the loop deviation (Eb) is less than the threshold negative detection (S_det_neg), then the method includes a step of non-critical fault escalation (Def_bou_neg_NC) and non-severe reconfigurations of the heat engine (5). 5. Method according to any one of claims 1 to 4, characterized in that if the position (Pos_mes) of the discharge system (15) is less than a minimum activation threshold (S_act_min), and if the deviation of loop (Eb) is greater than a positive detection threshold (S_det_pos) then the method comprises a step of raising a critical fault (Def_bou_pos_C) and severe reconfigurations of the heat engine (5). 6. Method according to claim 5, characterized in that if the position (Pos_mes) of the discharge system (15) is greater than the minimum activation threshold (S_act_min), and if the loop deviation (Eb) is greater than positive detection threshold (S_det_pos) then the method includes a step of raising a non-critical fault (Def_bou_pos_NC) and non-severe reconfigurations of the heat engine (5). 7. Method according to claim 3 or 5, characterized in that a severe reconfiguration of the heat engine (5) consists in particular in limiting a torque (C_mot) of the heat engine (5) to at least 50% of its maximum value. 8. Method according to claim 4 or 6, characterized in that a non-severe reconfiguration of the heat engine (5) consists in particular in limiting a torque of the heat engine at most to 50%. 9. Engine computer (26) comprising a memory storing software instructions for implementing the method for diagnosing the operation of a turbocharger (2) as defined in any one of the preceding claims. 10. Motor vehicle characterized in that it comprises an engine computer (26) as defined in claim 9.