Method for automatically detecting a blockage of a sensor conduit extending between an exhaust manifold and a pressure sensor of an internal combustion engine

Abstract

The invention relates to a method for automatically detecting a blockage of a sensor duct (16) extending between an exhaust manifold (12) and a pressure sensor (14) of an internal combustion engine (10), wherein the pressure sensor is capable of recording a signal representing a relative pressure varying over time. The method comprises at least one of the following steps: a) determining an average amplitude of oscillations of the signal over a first time period while the engine is running in a steady state of operation, the sensor duct being considered blocked when the average amplitude is less than a first threshold value; b) monitoring the signal over a second time period starting from the time when the engine has been disconnected, the sensor duct being considered blocked when the integral of the signal is greater than a second threshold value.

Description

Technical Field

[0001] The invention relates to a method for automatically detecting a blockage of a sensor line extending between an exhaust manifold and a pressure sensor of an internal combustion engine.

[0002] The invention can be applied to medium and heavy vehicles, such as trucks, buses and construction equipment. Although the invention will be described with respect to trucks, the invention is not limited to this particular vehicle, but can also be used in other vehicles, such as buses, work machines and boats. Background Art

[0003] In a known manner, an internal combustion engine may include an exhaust pressure sensor for measuring the exhaust pressure (also called "back pressure") and using it as a control parameter for the engine. The exhaust pressure sensor is usually not connected directly to the exhaust manifold, but to a pipe connected to the exhaust manifold. This pipe should not be confused with the exhaust pipe that leads the exhaust gas to the atmosphere. To avoid misunderstandings, the exhaust pressure sensor pipe is named "P3 pipe" in this document.

[0004] Exhaust back pressure is the pressure measured in the exhaust manifold after the exhaust valves of the engine and before the turbine.

[0005] This pressure is controlled with the help of an EPG (exhaust pressure regulator, also called exhaust flap) for two main reasons:

[0006] The first reason is to perform exhaust braking. In fact, at increased exhaust backpressure levels, the engine must compress the exhaust gas to a higher pressure, which involves additional mechanical work and / or less energy extracted by the exhaust turbine, which may affect the intake manifold boost pressure. As a result, power will be reduced, resulting in engine braking.

[0007] The second reason is to help the engine reach the correct operating temperature faster. Over time, the exhaust gas sensor pipe (or P3 pipe) can become clogged with soot, or it can rust. All of this can reduce engine performance and reduce efficiency. For example, a partially clogged P3 pipe can make the exhaust gas sensor slow down its measurements. This will have a negative impact on the different air & gas actuators, especially on the exhaust flaps. Incorrect control of the exhaust flaps can have serious consequences for EATS (Exhaust Aftertreatment System).

[0008] JP2018048561A discloses a blockage detection system and related method for an exhaust pressure sensor tube 30a for an internal combustion engine. The disclosure explains that if the tube 30a is blocked, the pressure of the exhaust gas Ga in the exhaust passage 15 will not be fully transmitted to the exhaust pressure sensor 30, and the pressure value P sensed by the exhaust pressure sensor 30 will be significantly less than the actual pressure. The disclosure teaches monitoring the exhaust back pressure when the exhaust brake valve 22 is closed. Normally, that is, when the pressure sensor tube is unobstructed (not blocked), the exhaust back pressure should increase significantly. If the sensor does not measure this pressure increase, it means that the pressure sensor tube is at least partially blocked. In practice, D1 teaches that the pressure value P measured by the sensor after the exhaust valve brake is closed is compared with a preset value P1, and if P is lower than P1, the pressure pipeline ("P3 pipeline") is considered to be blocked. Summary of the invention

[0009] The object of the present invention is to provide a new method for detecting blockages in P3 pipes which is simple to implement (software solution) and can be used immediately (without any supplementary hardware).

[0010] The method of JP2018048561A is based on P3 sensor measurements, but the strategy is different from that of the present invention. In general, the method of the present invention is not intrusive at the engine level. On the contrary, the strategy of JP2018048561A involves obtaining control of the exhaust flap to perform the analysis, while the strategy of the present invention is completely transparent and does not require any specific control of the different actuators. Another fact is that the method of the present invention does not involve comparing the measured pressure with a predetermined value, but rather analyzing and monitoring its behavior during the driving cycle. In this example, it seems that the competitor performs the analysis based on the absolute amplitude of the P3 signal, rather than analyzing its behavior, which is what we do in our solution.

[0011] The implementation of this new approach will be able to save a lot of time and money in aftermarket operations. The solution will be able to perform predictive maintenance and notify the customer (owner) that an engine intervention is needed before a more serious problem occurs.

[0012] The object of the present invention is achieved by a method for automatically detecting a blockage of a sensor line extending between an exhaust manifold of an internal combustion engine and a pressure sensor, wherein the pressure sensor is capable of recording a signal representing a relative pressure varying over time. According to the invention, the method comprises at least one of the following steps:

[0013] a) determining an average amplitude of oscillations of the signal over a first time period when the engine is running in a steady state of operation, and when the average amplitude is less than a first threshold, the sensor conduit is considered to be blocked;

[0014] b) starting from the time when the engine has been switched off, monitoring the signal for a second time period, when the integral of the signal for said second time period is greater than a second threshold, the sensor conduit is considered to be blocked.

[0015] According to an advantageous but non-mandatory aspect of the invention, the method may include one or more of the following features considered alone or in combination:

[0016] - The first time period is comprised between 5 s and 10 s.

[0017] -The second threshold value varies depending on the exhaust pressure when the engine is shut off. For the sake of clarity, the term "is shut off" refers to the verb "shutting down" rather than the state of the engine itself. Basically, the time when the engine is shut off is the time when the driver operates the ignition key (or the like) to turn off the engine, that is, the time when the engine switches from the ON state (running) to the OFF state (not running).

[0018] - The first threshold value varies depending on the operating point of the engine.

[0019] - The first threshold is a percentage of the expected normal average amplitude that can be derived from theoretical models or experiments, typically 50%.

[0020] - The second threshold is a percentage of the expected normal pressure integral, usually 50%. The "expected normal pressure integral" is the integral value under normal circumstances (ie, when the sensor pipe is not blocked).

[0021] The second time period corresponds to the time period between the time when the engine is switched off and the time when the electronic control unit of the engine is switched off, and is comprised between 1 s and 10 s.

[0022] - When a blockage of the sensor duct is detected, a signal is sent to the driver, which signal is preferably a light displayed on the vehicle dashboard.

[0023] The steps of the method are repeatedly performed as long as the electronic control unit of the engine is switched on.

[0024] The first time period is selected to be more than at least two consecutive combustion phases, preferably three consecutive combustion phases of an ignition cycle. In a known manner, an ignition cycle comprises as many combustion phases as there are cylinders.

[0025] - The first time period is set equal to the time taken for the engine crankshaft to reach a certain number of crank angle degrees, which is intrinsic to the number of cylinders of the engine. In a known manner, in a four-stroke engine, the crankshaft rotates twice during an ignition cycle.

[0026] For 4-cylinder applications, the specific crank angle degree is equal to 22.5°, while for 6-cylinder applications, the specific crank angle degree is equal to 15°.

[0027] - The method comprises a preliminary step comprising: monitoring one or more operating parameters of the engine, such as i) engine speed and torque or ii) fuel consumption; and checking whether said operating parameters are stable, ie whether a steady state of operation has been reached, before carrying out step a).

[0028] The invention also relates to an internal combustion engine (ICE) assembly comprising an exhaust manifold, a pressure sensor and a sensor duct extending between the exhaust manifold and the pressure sensor. According to the invention, the engine assembly further comprises an electronic control unit (ECU) for detecting a blockage of the sensor duct using the method as defined above. Typically, the ECU referred to is preferably the control unit of the engine, which means that there is the same ECU for controlling the engine and for implementing the diagnostic method of the invention.

[0029] Preferably, the engine is a four-stroke engine. It can be a CI (compression ignition) engine or a SI (spark ignition) engine.

[0030] Preferably, wired or wireless means connect an electronic control unit (ECU) to the pressure sensor.

[0031] Advantageously, the electronic control unit is configured to: receive one or more operating parameters of the engine, such as i) engine speed and torque or ii) fuel consumption; and process the received information to check whether the operating parameters are stable over time, i.e. whether a stable operating state has been reached, before implementing step a) of the method.

[0032] Finally, the invention relates to a vehicle comprising an internal combustion engine assembly as defined above.

[0033] Typically, the vehicle is a medium or heavy duty vehicle, such as a truck.

[0034] Further advantages and advantageous features of the invention are disclosed in the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] With reference to the drawings, two embodiments of the invention cited as examples are described in more detail below.

[0036] In the attached picture:

[0037] - Figure 1 is a schematic diagram of a heavy vehicle (typically a truck) including an internal combustion engine having an inlet manifold and an outlet manifold;

[0038] - Figure 2yes Figure 1 A detailed view of an outlet manifold of an internal combustion engine showing an exhaust pressure sensor connected to the exhaust manifold via a sensor conduit;

[0039] - Figure 3 Included are two graphs showing the amplitude of exhaust manifold pressure oscillations versus engine operating point (torque, speed) for an unblocked P3 conduit and a blocked P3 conduit;

[0040] - Figure 4 is a graph showing the evolution of the pressure sensor measurement values ​​over time when the sensor pipe is normal (not blocked) and when the sensor pipe (P3 pipe) is blocked;

[0041] - Figure 5 is a flow chart showing the steps of the method of the present invention, i.e., a method for detecting blockage of the P3 pipe by monitoring back pressure oscillations;

[0042] - Figure 6 is a graph showing the evolution of the pressure sensor measurement values ​​over time after the internal combustion engine (ICE) is shut down, when the sensor duct is normal (not blocked) and when the sensor duct (P3 duct) is blocked;

[0043] - Figure 7 is a flow chart representing the steps of the method of the invention, namely a method for detecting a blockage in the P3 pipe by monitoring the evolution of the back pressure before it drops to zero bar (relative pressure); and - Figure 8 and Fig. 9 are two flow charts roughly representing the steps of two alternative methods of the present invention. DETAILED DESCRIPTION

[0044] Figure 1 1 shows a heavy vehicle, typically a truck 1. The truck 1 comprises an internal combustion engine (ICE) assembly 10, which comprises an inlet manifold (or intake manifold) not shown in detail and a Figure 2 The outlet manifold (or exhaust manifold) 12 is shown in detail.

[0045] In variants, the invention can obviously be applied to other types of vehicles, in general to any vehicle comprising an internal combustion engine: it may be a bus, a coach, a boat or a work machine.

[0046] The ICE assembly 10 also includes a pressure sensor 14 and a sensor conduit 16 extending between the exhaust manifold 12 and the pressure sensor 14. Hereinafter, the sensor conduit 16 may be referred to as a "P3 conduit."

[0047] The pressure sensor 14 makes it possible to record a signal representative of the relative pressure in the exhaust manifold 12 as a function of time.

[0048] The ICE assembly 10 also includes an electronic control unit (ECU), such as Figure 2 1 , for use in detecting a blockage of the sensor conduit 16 using a specific method described in detail below.

[0049] Typically, the ECU is connected to the pressure sensor 14 by wire or wirelessly, so that data measured by the pressure sensor 14 is sent to the ECU as an input parameter.

[0050] Advantageously, the above-mentioned ECU is an ECU controlling the operation of the engine. Typically, in particular, this ECU controls the strategy of fuel injection into the cylinders of the engine depending on the acceleration (throttle input) requested by the driver. In a variant, the ECU used to implement the method of the invention may be different from the ECU controlling the operation of the engine, which means that it may be a different (additional) ECU.

[0051] Typically, the exhaust pressure (or "back pressure") has at least two spikes.

[0052] The first spike is caused by the spontaneous discharge of the cylinder due to the opening of the exhaust valve. Before the end of each working stroke of the engine, the exhaust valve opens and the high-pressure combustion exhaust gas is released into the exhaust manifold. Due to the intermittent opening and closing of the engine exhaust valve, the high-pressure exhaust gas discharged from the cylinder is transmitted along the exhaust manifold in the form of compression wave pulses.

[0053] The second peak is due to the rising motion of the piston. This phase ends when the piston reaches the upper dead center (or top dead center), that is, at the end of the exhaust stroke and the beginning of the intake stroke, respectively.

[0054] Even in idle conditions and with a fully functional P3 duct 16, those wave pulses reach very significant values. When the duct 16 is partially blocked, this value decreases (approximately 5 to 6 times its normal value). When the P3 duct 16 is completely blocked, the pressure value measured by the sensor 14 becomes stable, which means that oscillations are no longer detected.

[0055] This is due to the configuration of a plug (not shown) naturally formed inside the P3 pipe 16. Precisely, this plug (or obstruction) has a porous configuration so that the actual amplitude of the pressure wave entering the P3 pipe 16 is filtered once it passes through the plug.

[0056] Figure 3 This reflects the different behavior between the pressure values ​​measured by the P3 sensor 14 in the case of a "normal" P3 pipe 16 (ie an unblocked pipe) and a blocked P3 pipe.

[0057] In general, the amplitude of the P3 oscillations is larger at high engine loads (engine torque) and high engine speeds (red areas in the engine maps). It can be noted that in the case of a blocked P3 duct (right graph), the amplitude of the P3 oscillations remains constant in all engine maps.

[0058] Even in idle conditions (engine on, vehicle stopped), the difference between the two situations is noticeable. The biggest differences, though, can be found at high engine loads and speeds.

[0059] exist Figure 4 and Figure 5 In the embodiment (embodiment a), the method for detecting a blockage in the P3 pipe comprises, when the engine 10 is running in a steady state of operation, determining an average amplitude A1 of the oscillations of the signal within a first time period T1 (recorded by the sensor 16).

[0060] For the record, an engine is considered to be in a "steady state of operation" when the amount of fuel injected in the engine cylinders is approximately stable over time. This is in contrast to a "transient state" where the amount of fuel is not truly stable. A "steady state of operation" may also be referred to as a state in which the speed and torque of the engine remain constant.

[0061] Therefore, and in order to determine whether the engine is in a stable operating state, the ECU can monitor the evolution of the amount of fuel injected into the engine cylinders. Since such control is known per se, it will not be described in further detail herein.

[0062] Typically, an example of a stable operating state is an "idling state" in which the vehicle is stopped, the engine is on and disengaged from the wheels. Another example of a stable operating state is a "coasting state" in which the vehicle is moving, the engine is on and disengaged from the wheels. Another example of a stable operating state is a "cruising state" in which the vehicle moves at a constant speed on a flat road.

[0063] Typically, the first time period T1 is comprised between 5 s and 10 s.

[0064] In detail, and as Figure 4 As shown, the ECU monitors the (electrical) signal registered by the pressure sensor 14. This signal is generally known to represent the "back pressure", ie the pressure within the exhaust manifold.

[0065] In this embodiment, if Figure 8 and Fig. 9 As shown, the method comprises the following steps:

[0066] Exhaust back pressure quick acquisition (1):

[0067] In this example, the exhaust back pressure ("raw" pressure) is obtained at each specific CAD slot (crank angle degrees) that is inherent to the number of cylinders in the engine. Typically, for a 4-cylinder application, the exhaust back pressure is obtained every 22.5° CAD (crank angle degrees), while for a 6-cylinder application, the exhaust back pressure is obtained every 15° CAD.

[0068] Crankshaft degrees are units (equal to one "normal" degree) used to measure piston travel (position), for example to adjust ignition. A four-stroke cycle engine is an internal combustion engine that uses four different piston strokes (intake, compression, power and exhaust) to complete one operating cycle. The piston makes two complete strokes in the cylinder to complete one operating cycle. The operating cycle involves two rotations of the crankshaft (720°). In other words, in a four-stroke engine, the crankshaft rotates twice for an ignition cycle. When the piston is at its highest point (i.e., top dead center (TDC)), the crankshaft angle (crank angle) is at 0° crank angle degrees.

[0069] like Figure 5 As shown, the “raw” pressure is stored in a buffer to make it available for the next step.

[0070] This step corresponds to the exhaust back pressure rapid acquisition ( Fig. 9 Steps on ).

[0071] Exhaust back pressure oscillation(3):

[0072] like Figure 5 As shown, the next step is to build a backpressure cache, ie, a data cache. This data cache stores all exhaust backpressure data measured by the sensor 14 at each crank angle event (which is inherent to the number of cylinders of the engine) so that the software solution can monitor the exhaust backpressure wave.

[0073] Then, the amplitude of the exhaust pressure wave is obtained from the difference between the maximum value and the minimum value stored in the data buffer.

[0074] To improve the robustness of the solution and to avoid skewing the diagnosis due to misfire phenomena (when one or more cylinders in the engine fail to fire properly), the buffer length can be modified (i.e. Figure 4 In order to take into account not only the exhaust pressure waves of one cylinder but also the exhaust pressure waves of multiple cylinders.

[0075] In fact, when a misfire occurs in one cylinder, the amplitude of the pressure wave drops sharply and this can be mistaken for a blockage in the P3 duct.

[0076] In other words, it is known that the cylinders of an internal combustion engine are ignited after a specific cycle called an ignition cycle. This means that the combustion phases in the cylinder are carried out in chronological order. An ignition cycle therefore comprises a number of consecutive combustion phases, the number of which obviously depends on the number of cylinders of the engine. Usually, the number of combustion phases during an ignition cycle is equal to the number of cylinders of the engine.

[0077] If the time period T1 is chosen to be less than or equal to the combustion phase of one cylinder and a misfire occurs in this particular cylinder, the amplitude of the measured wave will be very low and this can be interpreted as being caused by a blocked duct. In order to avoid this misinterpretation, the time period T1 is chosen to contain at least two, preferably three consecutive combustion phases (in three different cylinders), i.e. to last enough time to record data during at least two, preferably three consecutive combustion phases. More precisely, the time period T1 can be chosen so that the entire ignition sequence can be recorded. In this way, the wave pulses can be detected even if combustion in one or more engine cylinders has failed.

[0078] exist Figure 4 In the example of , the time period T1 has been selected to contain two combustion phases (because it contains two peaks).

[0079] Exhaust back pressure oscillation diagnosis(5):

[0080] To start the evaluation, the air & gas actuators of the engine (including the Intake Throttle Valve (ITV), Exhaust Pressure Regulator (EPG), EGR (Exhaust Gas Recirculation) Valve and Variable Geometry Turbine (VGT)) should reach the target position. In addition, the engine speed and torque should also reach the target position and maintain a stable state.

[0081] By calibration, it is possible to reach any point in the engine map. Points near idle speed can benefit from a high level of chance of performing a successful assessment during the driving cycle. However, even though the difference in the amplitude of the back pressure oscillations between a blocked and unblocked P3 duct is quite significant, it is preferred to run the diagnostics when the engine is in an idle operating state.

[0082] Once the conditions are met, the software (ie, ECU) will begin evaluating the amplitude of the exhaust backpressure oscillations.

[0083] Specifically, the ECU calculates the average amplitude of the backpressure wave during the time period T1. Figure 5 As shown, the ECU determines the maximum and minimum values ​​of the signal and calculates the amplitude of each pulse using the difference between the maximum and minimum values ​​of the pulse. The ECU then calculates the average amplitude by dividing the sum of all amplitudes by the number of pulse events (or spikes) in the signal recorded during time period T1.

[0084] When the average amplitude is less than the first threshold value, the sensor conduit 16 is considered to be blocked. In this case, a signal is sent to the driver. Preferably, this signal is a light displayed on the vehicle dashboard.

[0085] In the example, the first threshold is variable depending on the operating point of the engine, which is given by the engine torque and speed.In practice, and as mentioned above, the higher the engine load (torque) and speed, the higher the oscillation amplitude.

[0086] Engine torque and speed are parameters that are known at all times. In other words, these are input parameters provided to the ECU for controlling the operation of the engine.

[0087] Basically, the first threshold value can be derived from a pre-established 3D map, wherein a first threshold value (1D) is determined for each engine speed (2D) and torque (3D). Such a 3D map can be based on experiments and / or theoretical models.

[0088] Typically, the first threshold is a percentage of the expected normal average amplitude, such as 50%.

[0089] Another abnormal behavior that can be detected by this method is the slow "response" of the P3 sensor 14 during specific events in which the exhaust pressure is expected to change. For example, it is known that when the engine is shut down, the pressure in the exhaust manifold (or exhaust back pressure) is expected to drop to atmospheric pressure. However, when a plug (or obstruction) is formed in the P3 duct 16, that is, when the P3 duct is blocked, the plug acts as a filter, which means that the signal measured by the P3 sensor 14 does not change as quickly as the actual pressure in the exhaust manifold. Typically, when the P3 duct is blocked, the pressure sensor 16 may measure a pressure drop of 10kPa during 1ms (for example), while the actual pressure in the exhaust manifold has dropped by 50kPa in the same time period. The evolution of the signal recorded by the pressure sensor 14 after a specific event (when the pressure is expected to change) is called the "response" of the signal.

[0090] exist Figure 6 and Figure 7 In an embodiment (embodiment b), the method includes monitoring the signal during a second time period T2 starting from the time when the engine 10 has been shut down (or cut off).

[0091] In this example, the second time period corresponds to a time period between the time when the engine 10 is turned off and the time when the electronic control unit (ECU) of the engine 10 is turned off. This time period is included between 1 s and 10 s.

[0092] In this embodiment, and as Figure 8 and Fig. 9 As shown, the method comprises the following steps:

[0093] Exhaust back pressure filtering (2):

[0094] In this method, the "raw" exhaust back pressure measured by the sensor 14 is filtered by means of a finite impulse response (FIR) filter in order to prepare the signal for the next step. This step corresponds to exhaust back pressure filtering ( Fig. 9 Steps in ).

[0095] Exhaust back pressure response (4):

[0096] The target exhaust back pressure can be set by the ICE's ECU according to the engine's operating point (speed, torque). In this regard, the exhaust back pressure can be controlled by different actuators, such as EPG, VGT, ITV or WG (exhaust valve) in order to reach the target exhaust back pressure. Typically, when engine braking is to be achieved, the back pressure must be increased to a high target in order to enhance the braking effect. Another example of the need to increase back pressure is to help the engine reach the appropriate operating temperature faster, for example to enable one or more components of EATS (such as DPF) to regenerate.

[0097] Typically, when a new target exhaust back pressure is set, the pressure value measured by the pressure sensor 14 should generally change to meet the new target (with a maximum time response of 500ms). However, if the P3 pipe 16 connected to the sensor 14 is blocked, the time response may be longer, for example 900ms.

[0098] The purpose of this diagnostic is to detect when the "response" of the pressure sensor 14 becomes slow, so as to detect that the P3 out line 16 is becoming plugged.

[0099] For this purpose, an evaluation is performed every time the engine is stopped.

[0100] When the engine is switched off (ie when the ignition key is turned off), the back pressure (herein considered as a relative pressure) typically drops to 0 kPa. Therefore, an assessment may be performed at least once in each driving cycle.

[0101] When a potential diagnosis area is detected, the integral of the filtered backpressure signal [obtained in step (2)] is calculated. In fact, the integral value is an indicator of how fast the backpressure is decreasing. Therefore, the higher the integral, the slower the signal decreases (or the signal falls).

[0102] exist Figure 6In FIG. 1 , the integral of the first signal (partially blocked pipe) is represented by the shaded area. For the sake of clarity of the drawing, we have not represented the integrals of the other two curves in the same time period T2. However, we can easily see that the integral of the curve corresponding to the signal measured in the case of blocked pipe is higher than the integral of the curve in the partially blocked configuration, which itself is higher than the integral of the curve in the normal configuration.

[0103] To discretize this, the integral is considered to be a back pressure "accumulator" during the second time period T2.

[0104] Figure 6 It is possible to compare the responses for three different situations: the P3 duct is unblocked or normal (thickest / darkest line), partially blocked (thin line), and completely blocked (dashed line).

[0105] Exhaust back pressure slow response diagnosis (6):

[0106] To determine whether the integrated value of the exhaust back pressure can be used to perform a diagnosis when the engine is shut down (i.e., switched from the “ON” state to the “OFF” state), two additional complementary conditions may be considered:

[0107] (1) Engine speed condition: When the engine is shut down, the engine speed value should be within a predetermined range. This is to avoid engine speed acceleration before the engine stops, which may interfere with the back pressure behavior.

[0108] (2) Exhaust back pressure condition: When the engine is shut down, the back pressure value should be within a predetermined range. This is to avoid the back pressure level being too low or too high during the engine stop phase (which may affect the back pressure integral calculation) to improve the robustness of the diagnosis.

[0109] If all conditions are met, the integrated value calculated in step (4) is compared with a second threshold value (or fault limit).

[0110] Typically, the second threshold value varies depending on the exhaust pressure when the engine has been shut down.

[0111] In fact, the higher the exhaust back pressure when the engine is shut off, the longer it takes to reach atmospheric pressure.

[0112] Basically, the second threshold value can be derived from a pre-established 1D map, wherein a second threshold value (1D) is determined for each exhaust back pressure. Such a 1D map can be established using experimental data and / or a theoretical model.

[0113] For example, the second threshold is a percentage of the expected normal pressure integral, typically 50%.

[0114] If the integrated value of the exhaust back pressure is greater than the fault limit, a fault will be detected. This means that when the integral of the signal is greater than the second threshold value, the sensor duct 16 is considered to be blocked.

[0115] Final Decision (7):

[0116] Once an assessment is completed, the results are processed to assess the final status of the diagnosis.

[0117] Through calibration it is possible to set the alarm in two different ways:

[0118] (1) As long as one of the sub-diagnostics (backpressure oscillation or backpressure response) concludes that the P3 pipe is blocked, an alarm is triggered;

[0119] or

[0120] (2) The alarm is triggered only when both sub-diagnostics (back pressure oscillation and back pressure response) conclude that the P3 pipe is blocked. This means that if one of the sub-diagnostics concludes that the P3 pipe is not blocked, the alarm is not triggered.

[0121] Normally, when the driver receives the warning signal, he has to go to a workshop and the P3 pipe should be replaced.

[0122] Last but not least, the steps of the method are repeatedly implemented as long as the electronic control unit of the engine is turned on. Basically, as long as the driver turns the ignition key in the key lock to wake up the system, the ECU is turned on.

[0123] It should be understood that the present invention is not limited to the embodiments described above and shown in the drawings; on the contrary, those skilled in the art will recognize that many changes and modifications are possible within the scope of the appended claims.

Claims

1. A method for automatically detecting a blockage of a sensor conduit (16) extending between an exhaust manifold (12) and a pressure sensor (14) of an internal combustion engine, wherein: The pressure sensor is capable of recording a signal representing a relative pressure varying over time, wherein the method comprises at least one of the following steps: a) determining an average amplitude of the oscillations of the signal within a first time period (T1) while the internal combustion engine is running in a steady state of operation, the sensor conduit (16) being considered blocked when the average amplitude is less than a first threshold value; b) monitoring the signal during a second time period (T2) starting from the time when the internal combustion engine has been shut down, and when the integral of the signal during the second time period (T2) is greater than a second threshold value, the sensor conduit (16) is considered to be blocked.

2. The method according to claim 1, wherein: Said first time period (T1) is comprised between 5s and 10s.

3. The method according to claim 1 or 2, wherein: The second threshold value varies depending on the pressure of the exhaust gas when the internal combustion engine is shut off.

4. The method according to claim 1 or 2, wherein: The first threshold value varies depending on an operating point of the internal combustion engine.

5. The method according to claim 1 or 2, wherein: The first threshold is a percentage of the expected normal average amplitude that can be derived from theoretical models or experiments, which is 50%.

6. The method according to claim 1 or 2, wherein: The second threshold is a percentage of the expected normal pressure integral, which is 50%.

7. The method according to claim 1 or 2, wherein: The second time period corresponds to a time period between a time when the internal combustion engine is turned off and a time when an electronic control unit (ECU) of the internal combustion engine is turned off, and the second time period is included between 1 s and 10 s.

8. The method according to claim 1 or 2, wherein: When the sensor conduit (16) is detected to be blocked, a signal is sent to the driver.

9. The method according to claim 7, wherein: The steps of the method are repeatedly performed as long as the electronic control unit (ECU) of the internal combustion engine is switched on.

10. The method according to claim 1 or 2, wherein: The first time period (T1) is selected to be greater than at least two consecutive combustion phases of a firing cycle of the internal combustion engine.

11. The method according to claim 1 or 2, wherein: The first time period (T1) is set equal to the time taken for the crankshaft of the internal combustion engine to reach a specific crank angle degree, which is inherent to the number of cylinders of the internal combustion engine.

12. The method according to claim 11, wherein: For 4-cylinder applications, the specific crank angle degree is equal to 22.5°, while for 6-cylinder applications, the specific crank angle degree is equal to 15°.

13. The method according to claim 1 or 2, comprising a preliminary step, the preliminary step comprising: monitoring one or more operating parameters of the internal combustion engine; And before carrying out step a), checking whether the one or more operating parameters are stable, ie whether a stable operating state has been reached.

14. The method according to claim 13, wherein: The one or more operating parameters are i) engine speed and torque or ii) fuel consumption.

15. The method according to claim 8, wherein: The signal is a light displayed on the vehicle dashboard.

16. An internal combustion engine assembly comprising an exhaust manifold (12), a pressure sensor (14) and a sensor conduit (16) extending between the exhaust manifold and the pressure sensor, characterized in that The internal combustion engine assembly further comprises an electronic control unit (ECU) for detecting a blockage of the sensor duct (16) using the method according to claim 1 or 2.

17. The internal combustion engine assembly according to claim 16, characterized in that The internal combustion engine assembly is a four-stroke engine.

18. The internal combustion engine assembly of claim 16, wherein: Wired or wireless means connect the electronic control unit (ECU) to the pressure sensor (14).

19. The internal combustion engine assembly of claim 16, wherein: The electronic control unit is configured to receive one or more operating parameters of the internal combustion engine and to process the received information to check whether the operating parameters are stable over time, ie whether a steady state of operation has been reached, before carrying out step a) of the method.

20. The internal combustion engine assembly of claim 19, wherein: The one or more operating parameters are i) engine speed and torque or ii) fuel consumption.

21. A vehicle comprising an internal combustion engine assembly according to claim 16.

22. The vehicle according to claim 21, characterized in that The vehicle is a medium or heavy vehicle.

23. The vehicle according to claim 22, characterized in that The medium or heavy vehicle is a truck.

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