Method for estimating pressure in an intake manifold

Abstract

The present invention relates to a method for estimating the pressure in an intake manifold of an indirect injection combustion engine, comprising: a pressure sensor measuring the pressure in the intake manifold, the intake manifold being in fluid communication with a combustion cylinder in which a piston is guided in translation and connected to a rotating crankshaft. The method comprises the following steps: measuring, by the pressure sensor, a maximum pressure value substantially corresponding to the maximum pressure in the intake manifold during a previous engine cycle; measuring, by the pressure sensor, a minimum pressure value substantially corresponding to the minimum pressure in the intake manifold during a previous engine cycle; determining, based on the crankshaft angular position and the engine speed, a precalculated average correction factor for the pressure; and estimating, based on the average correction factor and the minimum and maximum pressure values, the pressure in the intake manifold for the crankshaft angular position of the current engine cycle.

Description

Technical Field

[0001] The present invention relates to a method for estimating the pressure in the intake manifold. In internal combustion engines, knowledge of this pressure can in particular allow compensation for variations thereof, in order to better control the amount of fuel injected into the manifold. The invention is more particularly applicable to indirect injection engines with a small intake manifold volume. Background Art

[0002] Traditionally, the intake system of a combustion engine comprises a throttle body which allows regulating the flow of gas for supplying an intake manifold in fluid communication with one or more combustion cylinders.In each combustion cylinder a piston is guided in translation.

[0003] Particularly, in the case of a combustion engine called an indirect injection combustion engine, air-fuel mixing for combustion is performed at the intake manifold.

[0004] In this regard, a preparatory fuel injector, the injection tip of which is deployed in the intake manifold, injects fuel directly therein as explained above, the mixture then being drawn into the combustion chamber via the opening of one or more intake valves and via the downward movement of the piston in its cylinder.

[0005] The ratio of the air-fuel mixture is crucial for optimal combustion in the combustion cylinder. In particular, to deliver a given amount of fuel via an injector, it is necessary to know the instantaneous flow rate of said injector in order to be able to adapt its injection time (corresponding to the time separating the opening and closing of the injector). The instantaneous flow rate depends, among other factors, on the pressure difference between the pressure of the fuel in the injector and the pressure downstream of the injector. The latter corresponds to the pressure at the end of the injector and, therefore, to the pressure at the intake manifold. This pressure varies more or less significantly during the engine cycle, particularly when the intake manifold is small in volume.

[0006] Indeed, it is understood that the larger the volume of the intake manifold, the smaller the negative pressure resulting from the opening of one or more intake valves associated with the combustion cylinders in fluid communication with the intake manifold.

[0007] Combustion engines with a small intake manifold volume are equipped in, for example, lawn mowers, scooters, and motorcycles.

[0008] In this case, the pressure in the intake manifold depends on atmospheric pressure, crankshaft angular position, engine speed and engine load.

[0009] Advantageously, the pressure in the intake manifold can be estimated based on very few pressure acquisitions in the manifold. This allows for addressing the real-time requirements of the system, that is, the limited time required to acquire and process pressure data during an engine cycle. This also allows for extending the life of the sensor and reducing the memory required to store the measurements from the sensor, which in turn reduces material costs and, in particular, the cost of the sensing electronics.

[0010] Furthermore, it is advantageous to be able to estimate this pressure at each injection moment in the engine cycle, thereby determining the instantaneous flow rate of the injector at the moment when it is supposed to inject, and thus deriving the injection time for that injector. This allows, in particular, for good combustion in the cylinder and reduced pollutant emissions. In the case of engines not installed in motor vehicles, the injection time of the injectors is generally corrected using one of the following two methods.

[0011] The first method involves estimating the intake manifold pressure for the current engine operating point based on a table of intake manifold pressure values associated with reference engine operating points. However, this table of manifold pressure values only includes a few reference engine operating points, and therefore, the estimated pressure corresponding to the pressure at the reference operating point closest to the current engine operating point is inaccurate. In this regard, this method proposes artificially modifying the gas flow rate calculated at the intake manifold inlet to inject more or less fuel based on this gas flow rate in order to reduce the difference between the actual intake manifold pressure and the pressure estimated based on the closest operating point. This method is unsatisfactory because the use of values for a small number of engine operating points and the inaccurate modification of the calculated gas flow rate as a compensation tool often result in an underestimation of the intake manifold pressure.

[0012] The second method involves correcting the intake manifold pressure based on calculating its average value. The former is obtained from multiple acquisitions of the intake manifold pressure during an engine cycle. However, this method is only relevant when the manifold pressure fluctuations during the same engine cycle are small. It is therefore irrelevant for engines with small intake manifold volumes.

[0013] In particular, the use of the first method in a 90° V-twin lawn mower engine resulted in an underestimation of the pressure in the intake manifold from 0 to 340 mbar, while the use of the second method resulted in an overestimation of the pressure in the intake manifold from 0 to 330 mbar. Therefore, neither of these two methods is satisfactory for allowing a correct estimation of the pressure in the intake manifold.

[0014] Furthermore, neither of these two methods is suitable for taking into account different pressure variations from one cylinder to another during the same cycle, which is for example the case for a V-cylinder engine, especially a 90° (or another angle different from 180°) V-twin engine. Summary of the Invention

[0015] A first object of the present disclosure is therefore to propose a method for estimating the pressure in the intake manifold of a combustion engine.

[0016] A second object of the present disclosure is to obtain an accurate estimate of the pressure in the intake manifold independent of engine load, and even if the pressure varies significantly in the manifold during the engine cycle.

[0017] A third object of the present disclosure is to obtain this estimate based on a small number of acquisitions made by sensors during an engine cycle.

[0018] A fourth object of the present disclosure is to provide a method of accounting for differences in pressure variations from one cylinder to another in an engine, such as a 90° V-twin engine.

[0019] A fifth object of the present disclosure is to propose a method for correcting the quantity of fuel injected into the intake manifold according to an estimate of the pressure in the intake manifold obtained by implementing a method for estimating the pressure in the intake manifold.

[0020] The present disclosure proposes a method for estimating the pressure in the intake manifold of an indirect injection combustion engine, comprising: a pressure sensor measuring the pressure in the intake manifold, the intake manifold being in fluid communication with a combustion cylinder in which a piston is guided in translation and is connected to a rotating crankshaft;

[0021] The method is characterized in that it comprises the following steps:

[0022] - a maximum pressure value measured by the pressure sensor that substantially corresponds to the maximum pressure in the intake manifold during a previous cycle of the engine,

[0023] - measuring by the pressure sensor a minimum pressure value which substantially corresponds to the minimum pressure in the intake manifold during a previous cycle of the engine,

[0024] - determining a precalculated mean pressure correction factor as a function of the crankshaft angular position and as a function of the engine speed, and

[0025] - estimating the pressure in the intake manifold for the crankshaft angle position of the current engine cycle from the average correction factor and from the minimum and maximum pressure values.

[0026] According to an embodiment, the measurement of the maximum pressure value is performed at an instant directly before the intake phase of the combustion cylinder, and the measurement of the minimum pressure value is performed at an instant directly before the compression phase of the combustion cylinder.

[0027] According to an embodiment, the average correction factor is determined from a table of correction factors comprising a plurality of average correction factors each associated with the engine speed and the determined angular position,

[0028] And the determination of the average correction factor comprises: selecting in the table an average correction factor associated with the engine speed and associated with the corresponding angular position or closest to the current speed of the engine and the determined crankshaft angular position.

[0029] According to an embodiment, the average correction factor for the determined engine speed and for the determined angular position is equal to the average of the correction factors with the same determined engine speed and the same determined angular position,

[0030] And the correction factor is obtained from the following formula:

[0031] [Mathematical formula 1]

[0032]

[0033] Among them F c corresponds to the correction factor,

[0034] P r the actual pressure value measured on the test bench in the intake manifold corresponding to the angular position determined for the current engine cycle,

[0035] P maxt The maximum intake manifold pressure value on the test bench corresponding to the previous engine cycle, and

[0036] P mint Minimum intake manifold pressure value on the test bench corresponding to the previous engine cycle.

[0037] According to an embodiment, the estimation of the pressure in the intake manifold comprises using the following formula:

[0038] [Mathematical formula 2]

[0039] P col =P max +(P min -P max )×F ac

[0040] Among them, P col the pressure in the intake manifold corresponding to the current cycle of the engine for the crankshaft angular position,

[0041] P maxcorresponds to the maximum pressure value of the engine cycle measured during the measuring step and preceding the current cycle,

[0042] P min corresponds to a minimum pressure value in the intake manifold of an engine cycle preceding the current cycle and measured during the measuring step, and

[0043] F ac corresponds to an average correction factor for the crankshaft angular position determined during the determining step.

[0044] According to an embodiment, an intake manifold is in fluid communication with a plurality of combustion cylinders,

[0045] The steps for measuring the pressure value for each combustion cylinder are:

[0046] The method comprises the additional step of calculating the average minimum pressure value, and

[0047] The average minimum pressure value is used instead of the minimum pressure in estimating the pressure in the intake manifold.

[0048] The present disclosure provides a method for correcting the amount of fuel injected in an indirect injection engine, comprising: a pressure sensor measuring pressure in an intake manifold, the intake manifold being in fluid communication with a combustion cylinder, a piston being guided in translation in the combustion cylinder and connected to a rotating crankshaft, the engine further comprising an injector, an end of which is disposed in the intake manifold, the method comprising the following steps:

[0049] - estimating the pressure in the middle of the injection in the intake manifold by implementing the method for estimating the pressure as proposed above for a crankshaft angle position in the middle of the injection of the injector,

[0050] - determining the instantaneous flow rate of the injector at the middle moment of injection based on the pressure in the intake manifold and the pressure of the fuel in the injector,

[0051] - Modify the injection time of the injector according to the instantaneous flow rate of the injector at the intermediate moment of injection.

[0052] The present disclosure proposes a computer program product comprising code instructions for implementing the steps of the method as described in detail above.

[0053] The present disclosure proposes a computer adapted to control an indirect injection engine, the indirect injection engine comprising a pressure sensor measuring the pressure in an intake manifold, the intake manifold being in fluid communication with a combustion cylinder, a piston guided in translation in the combustion cylinder and connected to a rotating crankshaft, the engine also comprising an injector, the end of which is disposed in the intake manifold, the computer further being adapted to control the steps of implementing the method as described above.

[0054] Finally, the present disclosure proposes an indirect injection engine comprising: a pressure sensor that measures the pressure in an intake manifold, the intake manifold being in fluid communication with a combustion cylinder, a piston being guided in a translational manner in the combustion cylinder and being connected to a rotating crankshaft, the engine also comprising an injector, the end of which is disposed in the intake manifold; and a computer adapted to control the steps of implementing the method as described above.

[0055] The method proposed according to the present invention thus allows the pressure in the intake manifold to be estimated with very few acquisitions per engine cycle. In this case, only one acquisition of the minimum pressure value and another acquisition of the maximum pressure value (generally corresponding to the ambient pressure) are required per engine cycle. This allows, in particular, adaptation to the real-time constraints of the system and, in particular, to the time required to acquire and process pressure measurements during an engine cycle. This also allows the lifetime of the sensor to be increased.

[0056] Furthermore, due to the use of a table of average correction factors that are associated only with engine speed and crankshaft angular position, an estimate of the pressure in the intake manifold is rendered independent of engine load.

[0057] Unlike known methods based on average values, the method is also robust to large variations in the intake manifold pressure, since it allows the intake manifold pressure to be estimated over the entire engine cycle and, in particular, over the entire angular range of the crankshaft. In this configuration, the method allows the intake manifold pressure to be estimated for different engine geometries, and in particular for V-cylinder engines in which there is a specific phase shift between the cylinders, which results in different pressure variations in the intake manifold.

[0058] This estimation of the pressure in the intake manifold can be used, in particular, to determine the injection timing in order to calculate the instantaneous flow rate of the injector delivering the injection. This ultimately allows the amount of fuel injected to be calculated by estimating the injection time, and thus optimizes the efficiency of the engine while limiting pollutant emissions. This is the purpose of the method for estimating the correction to the amount of injected fuel. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Other features, details, and advantages will become apparent upon reading the following detailed description and analyzing the accompanying drawings, in which:

[0060] Figure 1

[0061] [ Figure 1 ] represents an embodiment of a method for estimating the pressure in the intake manifold.

[0062] Figure 2

[0063] [ Figure 2 ] represents an embodiment of a combustion engine in which the estimation method can be implemented.

[0064] Figure 3

[0065] [ Figure 3 ] represents the change in pressure in the intake manifold of a 90° V-twin engine.

[0066] Figure 4

[0067] [ Figure 4 ] represents two diagrams, each showing the crankshaft angular position during an engine cycle on the abscissa axis and the correction factor value on the ordinate axis.

[0068] More precisely, the left-hand graph shows a plurality of correction factor curves for a given engine speed, each curve representing a different engine load. As for the right-hand graph, it shows an average correction factor curve for a given engine speed in the left-hand graph and corresponds to the average of the correction factor curves of the left-hand graph.

[0069] Figure 5

[0070] [ Figure 5 ] represents a method for estimating a correction of the amount of fuel injected by the injector into the intake manifold. DETAILED DESCRIPTION

[0071] Now refer to [ Figure 2 ], Figure 2 In a non-exhaustive manner, an indirect injection combustion engine 1 (hereinafter indicated by the term engine 1) is shown for implementing the reference [ Figure 1 ] describes a method for estimating the pressure in the intake manifold.

[0072] The engine 1 thus comprises an intake manifold 2 which is in fluid communication with one or more combustion cylinders 3 via one or more intake valves 7 associated with each combustion cylinder 3. In this case, when the one or more intake valves 7 associated with a combustion cylinder 3 are open, effective fluid communication exists between the intake manifold 2 and the combustion cylinder 3. A throttle body 9 is also shown and is used to regulate the flow of gas supplied to the intake manifold 2 and, by extension, the flow of gas injected into the one or more combustion cylinders 3, in accordance with the position of the corresponding one or more valves 7.

[0073] In the remainder of the application, in a non-limiting manner and for ease of reading, it will be considered that each combustion cylinder 3 is associated with a single intake valve 7 , although it may comprise a plurality of intake valves.

[0074] In the embodiment shown, the intake manifold 2 is in communication with two combustion cylinders 3. The method for estimating the pressure in the intake manifold is particularly adapted to be implemented in a V-twin engine, for example a 90° V-twin engine.

[0075] In each combustion cylinder 3 , a piston 5 is guided in a translational manner and is connected to a crankshaft 8 via a connecting rod 6 .

[0076] The engine 1 comprises an injector 10 having an injector tip allowing it to inject fuel at the intake manifold 2. It also comprises a pressure sensor 4 adapted to measure the pressure in the intake manifold 2. Furthermore, it may comprise a control for achieving [ Figure 1 ] for estimating the pressure in the intake collector 2. The computer thus includes a memory storing code instructions for implementing the method. Advantageously, the computer controlling the implementation of the method is an engine control unit. Of course, any other computer suitable for controlling the implementation is conceivable.

[0077] In this case, the pressure in the intake manifold 2 depends on the amount of air it contains. For example, during the intake phase A1 in the combustion cylinder 3, the transfer of air from the intake manifold 2 towards the combustion cylinder 3 creates a negative pressure in the intake manifold 2. This negative pressure is represented by [ Figure 3 ], where the curve represents the actual pressure P in the intake manifold as a function of time over a number of engine cycles r This relates to the change in pressure in a 90° V-twin engine measured on a test bench. n Corresponding to different intake stages.

[0078] It is understood that the larger the volume of the intake manifold 2, the greater the n The smaller the negative pressure observed during the intake phase A, the smaller the volume passing through the intake manifold 2 towards the combustion cylinder 3 will be compared to the total volume of the manifold. In contrast, for an engine having an intake manifold 2 with a small volume (typically a V-twin engine, and in particular a 90° V-twin engine), during the intake phase A n The negative pressure observed in the intake manifold 2 during this time will be large.

[0079] In addition, when none of the cylinders of the engine 1 is in the intake phase, that is, when the engine 1 is in the two intake phases A n -A n+1 If the two intake A n -A n+1If the time intervals are sufficient, the pressure in the intake manifold 2 gradually rises to reach a maximum value that is substantially equal to atmospheric pressure. In fact, since the negative pressure in the intake manifold 2 is caused by the passage of air from the intake manifold 2 toward the combustion cylinders 3 and, therefore, by the decrease in the amount of air in the intake manifold 2, it is understood that when air no longer passes from the intake manifold 2 toward the combustion cylinders 3 and enters the intake manifold 2 via the intake gas flow regulated by the throttle 9, the amount of air in the intake manifold gradually increases again. Thus, the pressure in the intake manifold 2 gradually rises until it reaches a maximum pressure value corresponding to the pressure of the intake gas flow. In other words, if two consecutive intake manifolds A n -A n+1 The time gap between the two successive intakes A is sufficient to reach atmospheric pressure. n -A n+1 When the time between the intake and the n+1 Before the pressure rises to the position located by the intake A n The induced negative pressure then has a value intermediate between that which corresponds to the atmospheric pressure and a maximum value.

[0080] Now refer to [ Figure 1 ] An embodiment of a method for estimating the pressure in the intake manifold 2 is described.

[0081] The method for estimating the pressure in the intake manifold 2 thus comprises a first step 110 of measuring, by the pressure sensor 4 , a maximum pressure value P corresponding substantially to the maximum pressure in the intake manifold 2 during a cycle of the combustion engine. max .

[0082] Those skilled in the art are familiar with pressure sensors that allow the detection of relative pressure minima and maxima. In this case, the pressure sensor 4 is advantageously a pressure sensor of this type, and the pressure measurement is performed for a pressure maximum over the engine cycle that corresponds to an absolute pressure maximum over the engine cycle.

[0083] In the case of a pressure sensor 4 which is not capable of detecting relative pressure extremes, it is advantageous to directly measure the pressure during the intake phase A of the combustion cylinder 3. n The pressure value P before the moment max measurement.

[0084] In fact, as explained above, during the intake phase of the combustion cylinder 3, that is, when the intake valve 7 of the combustion cylinder 3 is open and the piston 5 descends in the combustion cylinder 3, air from the intake manifold 2 is introduced into the combustion cylinder 3, and therefore, a negative pressure is observed in the intake manifold 2. In other words, the transfer of air from the intake manifold 2 toward the combustion cylinder 3 brings about a negative pressure in the intake manifold 2. Here, directly during the intake phase A of the combustion cylinder 3n The previous instant corresponds to a pressure maximum in the intake manifold 2 .

[0085] Depending on the engine model, this will involve an absolute or relative pressure maximum. In practice, when the engine 1 comprises an intake manifold 2 in fluid communication with only one combustion cylinder 3, it will involve an absolute pressure maximum, since a negative pressure in the intake manifold 2 will only occur once per engine cycle.

[0086] On the other hand, when the engine 1 includes an intake manifold 2 in fluid communication with a plurality of combustion cylinders 3, there are as many intake phases A as there are combustion cylinders 3 during the engine cycle. n In this sense, as much negative pressure is observed in the intake manifold 2 as in the combustion cylinder 3. In an engine having a configuration known as "inline" or "flat", this can be achieved during the intake phase A of each combustion cylinder 3 of the engine cycle. n The maximum pressure value P previously measured max The measurement of has only a minor effect, since each of these measurements will give essentially the same result. In contrast, in other engine configurations, referred to in the remainder of this document as "phase-shifted" engines, the intake phase A of a given combustion cylinder 3 is n The value of the previous pressure measurement P max will be compared with another intake phase A of another combustion cylinder 3 during the same engine cycle. n+k The value of the previous pressure measurement P max Significantly different. Figure 3 This phenomenon is well illustrated in ], where Figure 3 It is clearly shown that at different intake stages A n Before, the actual pressure P in the intake manifold 2 r The values at the maximum value of are not the same. Therefore, in [ Figure 3 ] shows the intake phase A corresponding to the intake manifold 2 in the first combustion cylinder 3 over a plurality of successive engine cycles. n The maximum pressure value P of the previous maximum pressure maxC1 and corresponds to the intake phase A in the manifold in the second combustion cylinder 3 n+1 Another maximum pressure value P of the previous maximum pressure maxC2 .

[0087] In particular, during the intake phase A in the first cylinder n The previous maximum pressure value P maxC1 Greater than the intake phase A in the second cylinder n+1 The previous maximum pressure value P maxC2In practice, in a 90° V-twin engine, the engine geometry is such that the duration t between two consecutive intake phases A1 (intake into the first combustion cylinder) and A2 (intake into the second combustion cylinder) is 12 The duration t between the subsequent consecutive intake phases A2 (intake into the second combustion cylinder) and A3 (intake into the first combustion cylinder of the subsequent engine cycle) is 23 There is a difference between the two phases of the engine cycle. This difference is due to the different angular displacements of the crankshaft 8 between phases A1-A2 and A2-A3. A "phase-shifted" engine is defined as an engine for which the intake manifold 2 is in fluid communication with the plurality of combustion cylinders 3 and for which the angular displacement of the crankshaft 8 is different between two identical phases of the engine cycle executed in two successive different combustion cylinders. In other words, once the angular displacement of the crankshaft is A1-A2, the angular displacement of the crankshaft 8 is A2-A3. n-1 and A n Between and in A n and A n+1 If they are not the same, it involves an engine called "phase shifting".

[0088] For example, in a 90° V-twin engine, the actual pressure P in the intake manifold is r The curve is shown in [ Figure 3 ], if we consider that the intake phase A1 is performed in the first cylinder 3 when the crankshaft 8 is at 0° CRK, the intake phase A2 in the second cylinder 3 will be performed when the crankshaft 8 is at 270° CRK (360-90° due to the engine geometry). The unit ° CRK represents the angular position of the crankshaft 8, which for a 4-stroke engine varies between 0 and 720° CRK in each engine cycle. The crankshaft 8 thus travels 270° CRK between the intake phase A1 in the first combustion cylinder 3 and the intake phase A2 in the second combustion cylinder 3 of the engine.

[0089] If we now focus on the displacement of the crankshaft 8 at 270° CRK between the intake A2 in the second cylinder 3 of the current engine cycle and the intake A3 in the first cylinder 3 of the subsequent engine cycle, we know that this intake A3 is performed at 720° CRK in the current cycle (equivalent to 0° CRK in the subsequent engine cycle) because this is the beginning of a new engine cycle. The crankshaft 8 has therefore already experienced 450° CRK (720-270°) between the intake A2 in the second cylinder 3 and the intake A3 in the first cylinder 3. The angular displacement of the crankshaft 8 is therefore not equal between the two intakes A1 and A2 (270° CRK) of the 90° V-twin engine and the two intakes A2 and A3 (450° CRK). Therefore, there is an "angular offset" of the crankshaft 8 between two identical engine phases in different combustion cylinders 3. This angular offset reflects the fact that the crankshaft 8 does not perform the same angular displacement between two identical engine phases in different combustion cylinders 3. The phenomenon of angular deviation is observed for all engines whose combustion cylinders 3 are not arranged in a configuration known as “in-line” or “flat” (that is to say for the “phase-shifted” engines already described above).

[0090] To this extent, it is understood that the time interval t12 between the intake air A1 and the intake air A2 is spaced apart from the time interval t2 between the intake air A2 and the intake air A3. 23 do not correspond to the same value, since the angular displacement of the crankshaft 8 is not the same. 12 Therefore, the time interval t 23 Short, as in [ Figure 3 However, as explained above, the pressure in the intake manifold 2 rises between two consecutive intake phases and therefore it rises during the duration t 12 and t 23 During the rise. Figure 3 In the example, the duration t 23 Ratio duration t 12 The pressure in the intake manifold 2 is therefore 23 rises in a more pronounced manner during the period and it is for this reason that the pressure value P maxC1 Specific pressure value P maxC2 big.

[0091] It is therefore understood that the use of the mean value as the value for estimating the pressure in the intake manifold is completely irrelevant for correcting the injection time of the injector 10 when a “phase-shifted” engine is involved. Figure 3] shows very well that the pressure value in the intake manifold 2 at the time of injection in the first combustion cylinder 3 is completely different from the pressure value in the manifold at the time of injection in the second combustion cylinder 3. The selection of the average pressure value in the intake manifold of the engine cycle for correcting the injection timing of the injector 10 in the combustion cylinder 3 therefore does not allow adaptation to the situation described above for a 90° V-twin engine and more generally for all "phase-shifted" engines.

[0092] While the case of a 90° V-twin engine has been discussed above, it is also understood that the average value in a single- or two-cylinder engine, excluding "angular offset," is also inaccurate if the pressure in the intake manifold 2 fluctuates significantly relative to its small volume. In particular, for a given injection moment, it is possible that the average pressure in the intake manifold 2 does not correspond at all to the actual pressure at that moment. In this case, an error in the estimated pressure in the intake manifold 2 affects the estimated instantaneous flow rate of the injector 10, thus affecting the injector's injection timing and ultimately the amount of fuel injected into the intake manifold 2. Inaccurate amounts of injected fuel can, among other things, lead to increased pollutant emissions and poor combustion in the cylinders.

[0093] Return to value P max The measurement, in the embodiment in which the engine 1 is a "phase-shifted" engine, is advantageously carried out directly in two successive intake phases A corresponding directly in the engine cycle. n -A n+1 Between the maximum displacement of the crankshaft after the intake A n Intake phase A of combustion cylinder 3 n The pressure value P at the previous moment max This allows to obtain the absolute maximum pressure value in the engine cycle. Figure 3 ] in the example, the pressure value P max Therefore, it is equal to the pressure value P in each engine cycle maxC1 .

[0094] This first step thus allows obtaining the maximum pressure value P in the current engine cycle. max , which value will then be used to estimate the pressure in the intake manifold 2 for the following engine cycle.

[0095] The method then comprises a second step 120 of measuring, by the pressure sensor 4, a minimum pressure value P corresponding substantially to the minimum pressure in the intake manifold 2 during a cycle of the engine. min .

[0096] In the case of a pressure sensor 4 which is not capable of detecting relative pressure extremes, the minimum pressure value P is advantageously implemented at a point in time directly before the compression phase of the combustion cylinder 3 . minThe compression phase is the phase after the intake phase, and the minimum pressure value P in the intake manifold 2 is min It is therefore measured at the end of the intake phase of combustion cylinder 3. In fact, throughout the intake phase, air passes from intake manifold 2 towards combustion cylinder 3, and since then, the negative pressure observed in intake manifold 2 is at its maximum at the end of the intake phase, since the maximum amount of air has passed through intake manifold 2 towards combustion cylinder 3.

[0097] In the case where the intake manifold 2 is in fluid communication with a plurality of combustion cylinders 3, this step may be performed as many times as there are combustion cylinders 3, so as to have a plurality of pressure values P during an engine cycle. min In practice, just as for the pressure maximum in the intake manifold 2 during the engine cycle, the pressure minimum for a "phase-shifted" engine may vary significantly during the engine cycle. For example, in [ Figure 3 ], the diagram shows a first minimum pressure value P corresponding to the pressure minimum of the engine cycle after the air intake phase A1 in the first combustion cylinder 3 of the engine. minC1 Also shown is a second minimum pressure value P corresponding to another pressure minimum after the air intake phase A2 in the second combustion cylinder 3 of the engine. minC2 . Pressure value P minC2 Significantly smaller than the pressure value P minC1 , because due to the geometry of the 90° V-twin engine, the pressure in the intake manifold 2 has not yet risen after intake A1 to the value it had before said intake A1. Therefore, during intake A2, the pressure drops again to below the minimum pressure value P minC1 level.

[0098] In an embodiment comprising a plurality of combustion cylinders 3, the average minimum pressure value P is calculated (125). amin An optional additional step may be to calculate the pressure value P measured by the pressure sensor 4 during the cycle of the engine by a computer, for example by calculating min Therefore, in the case of a 90° V-twin engine, the average minimum pressure value P amin Can be equal to the minimum pressure P minC1 and P minC2 The sum is divided by 2. This is only possible if the correction factor F, which we will return to later, has already been c This calculation step 125 is implemented when similar steps are implemented during the calculation of .

[0099] As already explained in the introduction, the pressure in the intake manifold 2 depends on the angular position of the crankshaft 8, the engine speed N of the engine 1 and the engine load. In this case, the value P of the engine cycle min (or P amin) and P max The remainder of the method is used to determine the pressure in the intake manifold 2 of the subsequent engine cycle. In practice, these are relevant values, since the engine speed N and the engine load are substantially the same between two consecutive engine cycles. In this way, the method allows the determination of the minimum pressure value P of the preceding engine cycle by simply acquiring one or more minimum pressure values P of the preceding engine cycle. min and the maximum pressure value P max The pressure in the intake manifold 2 is estimated for the current engine cycle without requiring further acquisition.

[0100] In particular, the method for estimating the pressure in the intake manifold allows to estimate the pressure in the intake manifold according to the pressure values P measured during the execution of the method. min (or P amin , if necessary) and P max Get the actual pressure P of the intake manifold 2 obtained on the test bench r (For 90° V-twin engines, as in [ Figure 3 ]). The actual pressure P of the manifold measured on the test bench r will be considered to be the current pressure in the intake manifold 2 during the execution of the method. In the subsequent steps it is therefore a matter of taking the value P acquired during the execution of the method (and therefore during the current operation of the engine) min (or P amin ) and P max The actual pressure P measured on the test bench r Curve association.

[0101] Here, the method includes a third step 130 of determining a mean pressure correction factor F based on the determined crankshaft angle position V°CRK and the engine speed N. ac The crankshaft angular position V°CRK varies between 0 and 720°CRK in each cycle of the engine (a four-stroke engine). The engine speed N is the number of revolutions made by the engine in a specific time, which is generally expressed in revolutions per minute (rpm), and it is this unit that will be used in the equations that will be described in detail later.

[0102] Average correction factor F ac Allows for the calculation to be based on one or more minimum pressures P collected during a previous engine cycle. min and maximum pressure P max Estimate the pressure P in the intake manifold 2 during the current engine cycle col Pressure P col indicates the estimated pressure in the intake manifold 2 when the method is implemented, and the pressure P r Indicates the pressure observed in intake manifold 2 on the test bench.

[0103] Average correction factor F acis calculated on a test bench before implementing the method and depends on both the engine speed N and the crankshaft angle V°CRK. It is therefore associated with the determined engine speed N and the determined crankshaft angle position V°CRK. It can be stored in a memory of a computer adapted for implementing the control method or in any other memory accessible by this computer. In fact, the memory includes a table T which can, for example, include the average correction factor Fac A set of average correction factors F in ac , where each average correction factor F ac is associated with the crankshaft angle position V°CRK and with the engine speed N in order to have an average correction factor F corresponding to the current operation of the engine (and in particular to the current engine speed N) during the execution of the method. ac Table T of average correction factors Fac It is preferably stored directly in the memory of a computer controlling the implementation of the method.

[0104] Advantageously, the average correction factor F is determined (130) ac Corresponds to: Table T of the average correction factor Fac The average correction factor F is selected which is associated with the engine speed N which is closest to the current engine speed N during use of the method and which is associated with the crankshaft angle position V°CRK which is closest to the determined crankshaft angle position V°CRK ac .

[0105] Before developing the rest of the method for estimating the pressure in the intake manifold, it is proposed below that the average correction factor F associated with the crankshaft angular position V° CRK is calculated for a determined engine speed N. ac For constructing a table of average correction factors T Fac For the present invention, it will only involve changing the crankshaft angle position V°CRK and / or the determined engine speed N.

[0106] Therefore, for a determined engine speed N and for a determined crankshaft angle position V°CRK, the average correction factor F can be obtained. ac The correction factor F was previously calculated in an intermediate manner c The correction factor F c It also depends on the engine load parameter, which means that for a determined crankshaft angle position V°CRK and for a determined engine speed N, there are a number of correction factors F c , each correction factor F c Also correlated with the engine load value.

[0107] Therefore, the correction factor F is calculated based on the following formula c :

[0108] [Mathematical formula 3]

[0109]

[0110] Among them F c corresponds to the correction factor,

[0111] P r the actual pressure value measured on the test bench in the intake manifold corresponding to the crankshaft angle position V°CRK determined for the current engine cycle,

[0112] P maxt The maximum intake manifold pressure value on the test bench corresponding to the previous engine cycle, and

[0113] P mint The minimum intake manifold pressure value on the test bench corresponding to the previous engine cycle.

[0114] The pressure value (P) is measured for a combustion engine of the same type (same nature) as the combustion engine on which the method will be implemented later - that is, a combustion engine whose intake manifold 2 has substantially the same volume, is in fluid communication with the same number (number) of combustion cylinders 3 and, if necessary, has the same crankshaft "angular offset" r 、P maxt 、P mint ).

[0115] Advantageously, the pressure value P maxt and one or more pressure values P mint They are measured at essentially the same crankshaft angle position V°CRK as the crankshaft angle position V°CRK for which they are to be measured during implementation of the method.

[0116] Furthermore, if an additional calculation step 125 is carried out during the method, that is, if a plurality of pressure values P measured during the preceding engine cycle are present, min In the case of c The value of P mint is determined by the value P corresponding to the previous cycle on the test bench mint The minimum average value P of all or part of the average value amint Of course, the minimum mean value P determined during the execution of the method is calculated in the same way amin and the minimum mean value P determined on the test bench amint That is, if the minimum value P based on a group of combustion cylinders mint The calculation allows calculation of the correction factor F c The minimum mean value P amint , then step 125 of the method would correspond to the minimum value P measured for a group of combustion cylinders 3 minThe same calculation.

[0117] In this case, the correction factor F is therefore calculated based on the following formula c :

[0118] [Formula 4]

[0119]

[0120] Among them F c corresponds to the correction factor,

[0121] P r the actual pressure value measured on the test bench in the intake manifold corresponding to the crankshaft angle position V°CRK determined for the current engine cycle,

[0122] P maxt The maximum intake manifold pressure value on the test bench corresponding to the previous engine cycle, and

[0123] P amint corresponds to the minimum pressure value P measured on the test bench from the previous engine cycle mint The average minimum pressure value obtained for all or part of the

[0124] Correction factor F c This corresponds to the actual pressure P that would be observed in the intake manifold on the test bench for a determined engine speed N and for a determined engine load. r and the minimum pressure value P measured in the intake manifold 2 on the test bench mint (or P amint , if necessary) and the maximum pressure value P maxt Associated factors.

[0125] To obtain the average correction factor F ac This involves the correction factor F associated with the crankshaft angle position V°CRK determined for the engine speed N (determined for different load values of the engine). c The average correction factor F associated with the crankshaft angle position V°CRK determined for the determined engine speed N is taken as the average correction factor F. ac Therefore, relative to the correction factor F c Got rid of the engine load parameter.

[0126] exist[ Figure 4 The left line diagram of FIG. 1 shows a plurality of correction factors F for the determined engine speed N. c The horizontal axis of the line graph corresponds to different crankshaft angle positions V°CRK during the engine cycle, while the vertical axis corresponds to the correction factor F cEach curve in the left-hand line graph therefore includes a number of correction factors F c , which represents the correction factor F calculated for the engine load value determined at each crankshaft angle position V°CRK in the engine cycle c value.

[0127] Based on these correction factors F c The value of CRK can therefore be used to determine the average correction factor F for the determined engine speed N according to the crankshaft angle position V°CRK by using the average value. ac This is the curve of Figure 4 The object of the right line graph in ]. The average correction factor F is obtained on the vertical axis ac The value of and different crankshaft angle positions V°CRK are obtained on the horizontal axis. The average correction factor F ac The curve of thus corresponds to the correction factor F calculated for the engine speed N determined over the entire crankshaft angle range V°CRK c In other words, the curve in the right-hand diagram corresponds to the correction factor F associated with the corresponding engine load and represented in the left-hand diagram. c In other words, for a given angular position V°CRK, the average correction factor F ac = equal to the correction factor F associated with this angular position V°CRK for different values of engine load c average.

[0128] Average correction factor F ac This corresponds to the actual pressure P observed in the intake manifold during the current engine cycle. r and one or more minimum pressure values P measured in the intake manifold 2 on the test bench in the preceding engine cycle for the determined engine speed N. mint (or P amint ) and the maximum pressure value P maxt The associated factor. It is relative to the correction factor F c Got rid of the engine load parameter.

[0129] In addition, in addition to the average correction factor F ac It is possible to get rid of the fact that the engine load parameter is not included, and it is understood that the table T of the average correction factor Fac Need to be much smaller than including all correction factors F c The size of the table corresponds to the memory size. In particular, the factor between the two memory sizes corresponds to the factor in the calculation of the correction factor F c The number of engine load values to consider when

[0130] Return to reference [ Figure 1] The execution of the proposed method thus already determines the average correction factor F for the determined engine speed N and for the determined crankshaft angle position V°CRK ac .

[0131] The method thus comprises a fourth step 140 of: for the determined crankshaft angular position V°CRK (corresponding to the average correction factor F ac The crankshaft angle position V°CRK) estimates the pressure P in the intake manifold 2 col .

[0132] Based on one or more minimum pressure values P measured during the previous engine cycle during measuring steps 110 and 120 min (P amin , if necessary) and the maximum pressure value P max and the average correction factor F ac To estimate the pressure P of the current engine cycle col .

[0133] In practice, once the average correction factor F has been determined ac ——It makes the pressure value P measured on the test bench mint (or P amint ) and P maxt The actual pressure value P in the intake manifold 2 measured on the test bench r By correlating the two, it is possible to estimate the angular position V°CRK for the current engine cycle, which corresponds to the average correction factor F determined at the end of step 130. ac Angular position V°CRK——pressure P in intake manifold 2 col This involves making the value P based on the measurement on the test bench mint and P maxt and is based on the actual pressure P measured on the test bench r Pre-calculated average correction factor F ac and the pressure value P measured during the execution of the method min and P max In order to obtain the pressure P of the intake manifold 2 col .

[0134] In particular, the pressure P in the intake manifold can be estimated based on the following equation col :

[0135] [Formula 5]

[0136] P col =P max +(P min -P max )×F ac

[0137] Among them, P col the pressure in the intake manifold corresponding to the determined crankshaft angle position V°CRK for the current engine cycle,

[0138] P max corresponds to the maximum pressure value of the previous engine cycle measured during step 110 of the method,

[0139] P min corresponds to the minimum pressure value in the intake manifold of the previous engine cycle measured during step 120 of the method, and

[0140] F ac corresponds to the average correction factor precalculated on the test bench for the determined crankshaft angle position V°CRK.

[0141] In which the calculation of the average minimum pressure value P is realized amin In an embodiment of step 125, the pressure P is estimated based on the following formula col :

[0142] [Formula 6]

[0143] P col =P max +(P amin -P max )×F ac

[0144] Among them, P col the pressure in the intake manifold corresponding to the determined crankshaft angle position V°CRK for the current engine cycle,

[0145] P max corresponds to the maximum pressure value of the previous engine cycle measured during step 110 of the method,

[0146] P amin corresponds to the average minimum pressure value calculated during step 125 of the method, and

[0147] F ac corresponds to the average correction factor precalculated on the test bench for the determined crankshaft angle position V°CRK.

[0148] By implementing this method, it is possible to determine the pressure P in the intake manifold 2 of the engine for each angular position of the crankshaft 8 col In other words, it is thus possible to determine the pressure downstream of the end of the injector 10 for each angular position of the crankshaft 8. Therefore, as long as the angular position of the crankshaft 8 at a given moment is known, the instantaneous flow rate of the injector 10 at that moment can be obtained. In particular, the intermediate moment t of the injection of the crankshaft 8 at the injector 10 can be determined by using the following formula:mi Angular position of:

[0149] [Formula 7]

[0150]

[0151] Where V mi corresponds to the crankshaft angle position in °CRK at the center of the injection of the injector 10,

[0152] V ei corresponds to the crankshaft angle position in °CRK at the end of injection of the injector 10,

[0153] T i corresponds to the injection time of the injector 10 in ms, and

[0154] N corresponds to the engine's revolutions per minute.

[0155] This equation is of course modulo 720° CRK, since the crankshaft 8 performs two revolutions during the engine cycle (four-stroke engine).

[0156] The crankshaft angle position in the combustion cylinder at the end of injection is a known value. In the same way, the injection time Ti is known, and the term allows to convert it to correspond to the injection time T i Therefore, from the crankshaft angle position V at the end of injection of the injector 10, ei °CRK minus the angle corresponding to half the displacement of the crankshaft 8 during the injection, in order to find the angle at the time t mi Angular position V of the crankshaft 8 in the middle of the injection of the injector 10 mi °CRK.

[0157] Thus, by using methods known to those skilled in the art, it is possible to calculate the injection time t of the injection in the previous engine cycle by using the intermediate time t of the injection in the previous engine cycle. mi Estimated pressure P col To determine the instantaneous flow rate of the injector 10 in the current engine cycle.

[0158] Now refer to [ Figure 5 ] A method for correcting the amount of fuel injected by the injector 10 into the intake manifold 2 is described.

[0159] The method comprises a first step 210 of determining the crankshaft angle position V in the middle of the injection of the injector 10 by mi The method for estimating the pressure in the intake manifold as described above is implemented to estimate the pressure P in the middle of the injection in the intake manifold 2. col .

[0160] The method comprises a second step 220 of: based on the pressure P in the intake manifold 2 col and the pressure of the fuel in the injector 10 to determine the injection intermediate time t mi The instantaneous flow rate of the injector 10.

[0161] Since the instantaneous flow rate is calculated based on the pressure value in the intake manifold 2, the pressure P obtained by this method is col The value of is more accurate than the pressure value obtained by the methods proposed in the prior art (especially those based on average values), the instantaneous flow obtained at the end of this step is therefore itself more accurate.

[0162] Finally, the method comprises a final step 230 of: according to the intermediate moment t of injection mi The injection time of the injector 10 is modified according to the instantaneous flow rate of the injector 10 so as to correct the amount of fuel injected by the injector 10 .

[0163] The method for estimating the pressure in the intake manifold according to the present invention thus allows accurate estimation of the pressure in the intake manifold for each crankshaft position at a determined engine speed, with very few pressure measurements in the manifold. In particular, a minimum pressure measurement and a maximum pressure measurement are sufficient for this estimation, which, among other things, allows responding to the real-time demands of the system, extending the life of the pressure sensor, and reducing the storage memory associated with the sensor.

[0164] In this case, the fact that the method according to the invention allows estimating the pressure in the intake manifold for each crankshaft angular position allows obtaining a precise pressure estimate even when the pressure variations in the engine are large during the same engine cycle.

[0165] In the same way, being able to estimate the pressure in the intake manifold for each crankshaft angular position allows the method to be used for different engine geometries and in particular for “phase-shifted” engines such as 90° V-twin engines without loss of estimation accuracy.

[0166] This ultimately allows estimating the pressure in the intake manifold at the moment of fuel injection, rather than basing it on an average pressure value that is necessarily quite different from the actual pressure in the intake manifold at that exact moment. In this way, the method for estimating the pressure in the manifold can also be used to correct the amount of fuel injected. Indeed, as explained above, obtaining an accurate estimate of the pressure in the intake manifold at the moment of injection allows obtaining the exact instantaneous flow rate of the injector at that moment, and therefore allows the fuel quantity to be corrected by modifying the injection time of the injector according to its instantaneous flow rate.

Claims

1. A method for estimating the pressure (P) in the intake manifold (2) of an indirect injection combustion engine (1) col ) method, including: a pressure sensor (4) measuring the pressure in an intake manifold (2) in fluid communication with a combustion cylinder (3) in which a piston (5) is guided in translation and is connected to a rotating crankshaft (8), The method is characterized in that It includes the following steps: a maximum pressure value (P) measured (110) by the pressure sensor (4) corresponding substantially to the maximum pressure in the intake manifold (2) during a previous cycle of the engine max ), - a minimum pressure value (P) measured (120) by the pressure sensor (4) that substantially corresponds to the minimum pressure in the intake manifold (2) during a previous cycle of the engine min ), - Determine (130) a pre-calculated average correction factor (F) for the pressure based on the crankshaft angular position (V°RK) and the engine speed (N) ac ),as well as -Based on the average correction factor (F ac ) and the minimum pressure value (P min ) and the maximum pressure value (P max ) estimates (140) the pressure (P) in the intake manifold (2) for the crankshaft angle position (V°C RK) of the current engine cycle col ).

2. The method according to claim 1, wherein The maximum pressure value (P max ) of the measurement (110), and performing a minimum pressure value (P min ) measurement (120).

3. The method according to any one of claims 1 and 2, characterized in that Based on a plurality of average correction factors (F) each associated with the engine speed (N) and the determined angular position (V°RK) ac ) correction factor table (T Fac ) to determine the average correction factor (F ac ), and the average correction factor (F ac ) determination (130) includes: in the table (T Fac ) is selected from the average correction factor (F) associated with the engine speed (N) and the corresponding angular position (V°C RK) or the one closest to the current engine speed (N) and the determined crankshaft angular position (V°C RK) ac ).

4. The method according to any one of claims 1 and 2, wherein: The average correction factor (F) for the determined engine speed (N) and for the determined angular position (V°RK) ac ) is equal to the correction factor (F) with the same determined engine speed (N) and the same determined angular position (V°RK) c ), And the correction factor (F c ): Among them F c corresponds to the correction factor, P r the actual pressure value measured on the test bench in the intake manifold corresponding to the angular position (V°RK) determined for the current engine cycle, P maxt The maximum intake manifold pressure value on the test bench corresponding to the previous engine cycle, and P mint Minimum intake manifold pressure value on the test bench corresponding to the previous engine cycle.

5. The method according to any one of claims 1 and 2, characterized in that Estimate (140) the pressure P in the intake manifold (2) col This includes using the following formula: P col =P max +(P min -P max )×F ac Among them, P col The pressure in the intake manifold corresponding to the current cycle of the engine for the crankshaft angular position (V°RK), P max corresponds to the maximum pressure value of the engine cycle measured during the measuring step (110) and preceding the current cycle, P min corresponds to the minimum pressure value in the intake manifold of the engine cycle preceding the current cycle and measured during the measuring step (120), and F ac corresponds to an average correction factor for the crankshaft angular position (V°C RK) determined during the determination step (130).

6. The method according to any one of claims 1 and 2, wherein: An intake manifold (2) is in fluid communication with a plurality of combustion cylinders (3), and measuring (120) the pressure value (P) for each combustion cylinder (3) min ), And the method includes calculating (125) an average minimum pressure value (P amin ), and using the average minimum pressure value (P amin ) instead of the minimum pressure (P min ).

7. A method for correcting the amount of injected fuel of an indirect injection engine (1), comprising: A pressure sensor (4) measures the pressure in an intake manifold (2) in fluid communication with a combustion cylinder (3), in which a piston (5) is guided in translation and is connected to a rotating crankshaft (8), the engine (1) also comprising an injector (10) whose end is arranged in the intake manifold (2), the method being characterized in that it comprises the following steps: - by the crankshaft angle position (V mi ) implements a method for estimating pressure according to any one of the preceding claims to estimate (210) the pressure (P) in the middle of the injection in the intake manifold (2) col ), - Based on the pressure (P col ) and the pressure of the fuel in the injector (10) to determine (220) the intermediate time of injection (t mi ) the instantaneous flow rate of the ejector (10), - According to the middle moment of injection (t mi ) The instantaneous flow rate of the injector (10) modifies (230) the injection time of the injector (10).

8. A computer program product comprising code instructions recorded on a computer-readable medium for implementing the steps of the method according to any one of the preceding claims when the code instructions are run on a computer.

9. A computer adapted to control an indirect injection engine (1), the indirect injection engine (1) comprising a pressure sensor (4) measuring the pressure in an intake manifold (2), the intake manifold (2) being in fluid communication with a combustion cylinder (3), a piston (5) being guided in translation in the combustion cylinder (3) and being connected to a rotating crankshaft (8), the engine (1) also comprising an injector (10), the end of which is arranged in the intake manifold (2), It is characterized by: The computer is further adapted to control the steps of carrying out the method according to any one of claims 1 to 7.

10. An indirect injection engine (1) comprising a pressure sensor (4) measuring the pressure in an intake manifold (2), the intake manifold (2) being in fluid communication with a combustion cylinder (3) via one or more intake valves (7), a piston (5) being guided in translation in the combustion cylinder (3) and being connected to a rotating crankshaft (8), the engine (1) also comprising an injector (10), the end of which is arranged in the intake manifold (2), It is characterized by The engine further comprises a computer as claimed in claim 9.

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