Improved method for synchronizing a heat engine using a camshaft target.

Abstract

Method (P) for determining the angular position of a camshaft target (C) equipped with a plurality of teeth, the method comprising the following steps: - acquiring a signal consisting of rising and falling edges representing the passage of the teeth of the target (C), - calculating, for each of M significant edges associated with the teeth of the target (C), a theoretical ratio CP(j) as a function of known angular deviations P(j) between the edges, then - upon each reception of a new significant edge, starting the execution of an independent sub-method (SP1) for determining an index of the edge located at the camshaft sensor, each sub-method being based on a comparison between actual ratios CT(k) as a function of time intervals Tk and the theoretical ratios CP(j), synchronization being achieved when one of said sub-methods has a success state Ps,The angular position of the camshaft target is then determined from the angular position of the significant index front associated with said sub-process. Figure for the abbreviation: Figure 2,

Description

Title of the invention: Improved method for synchronizing a thermal engine using a camshaft target. Field of invention

[0001] The present invention relates to an improved method for synchronizing a heat engine by means of a camshaft target. Prior art

[0002] An internal combustion engine must be phased, or synchronized, in order to determine and optimize the best time to burn the fuel in the cylinder, i.e. to optimize fuel consumption in particular.

[0003] Throughout the text, synchronization refers to the determination of the angular position of the internal combustion engine during the combustion cycle.

[0004] The cycle of an internal combustion engine comprises several phases whose occurrence is offset in time for each cylinder, the synchronized control of the valves of the thermal engine being carried out by the camshaft.

[0005] In order for the combustion cycle to proceed normally, it is necessary to have a reliable angular reference on the basis of which each phase of each cylinder is determined.

[0006] The camshaft is rotated by the crankshaft. The crankshaft is a mechanical device which, by means of a connecting rod, allows the transformation of the rectilinear movement of a piston into a continuous rotational movement, and vice versa, thus ensuring the transmission of the combustion energy of the fuel in the cylinders into mechanical energy.

[0007] Thus, knowledge of the angular position of the crankshaft makes it possible to know a reliable angular reference on the basis of which each phase of each cylinder is determined.

[0008] Such a reference is available via a toothed wheel, also called a target, integral in rotation with the crankshaft. The wheel is associated with a dedicated sensor, called a crankshaft sensor, whose role ultimately is to allow the determination of the angular position and the rotation speed of the toothed wheel. The sensor is equipped with a sensitive element. According to one example, the wheel is metallic and the sensitive element is capable of detecting metal, such as a Hall effect sensor. The profile of the wheel typically includes a target which is provided with markers, also called teeth, distributed around its periphery. The function of the crankshaft sensor is to transform the measured magnetic field into an electrical signal. According to the state of the art, certain sensors are connected to the control unit by three wires (ground, power supply and signal) and have the ability to determine the direction of rotation of a crankshaft target. The passage of a tooth of the gear associated with the crankshaft generates an electrical pulse on the signal wire. The predetermined duration is representative of the direction of rotation (typically 45 ps for a forward direction of rotation, and 90 ps for a reverse direction of rotation). The crankshaft sensor is typically mounted near the flywheel which serves as a rotating target or supports such a target.

[0009] The rotating target has a signature, also called a long tooth or gap, formed by a singularity in the profile (otherwise regular) usually corresponding to two missing marks, and which makes it possible to fix a reference for the position of the crankshaft. Such a signature generates a signal different from the other marks, which makes it possible to determine when the rotating target has completed a complete rotation.

[0010] A commonly used rotating target includes 60 marks distributed around the periphery of the rotating target, and two consecutive marks removed to create the signature. Such a target is called a 60-2 rotating target. Another known rotating target is the 36-2 rotating target (34 marks plus two missing marks).

[0011] The rotation of the rotating target causes periodic changes in the magnetic flux due to the passage of the markers, which are transformed by the sensor into voltage variations which can subsequently be sent to the engine management computer. The voltage variations comprise rising edges and falling edges forming a periodic signal synchronized with the passage of the markers in front of the sensor.

[0012] During the rotation of the engine, the crankshaft axis makes two rotations while the camshafts only make one.

[0013] Additional information is therefore obtained using the camshaft sensor. The camshaft sensor cooperates, in a manner known per se, with a disc-shaped camshaft target, which is mounted integrally with the camshaft. The camshaft target is toothed on its periphery, possibly with an irregular distribution of the teeth. In particular, the teeth may be irregularly spaced and / or of different lengths (the length of a tooth corresponding to its angular extent, along the periphery of the camshaft target). The camshaft target thus has an asymmetry, making it possible to achieve correct phasing, that is to say, to determine with certainty where each cylinder is positioned in the combustion cycle. The position of the camshaft target is read by the camshaft sensor, which detects times of passage of the teeth in line with said camshaft sensor.

[0014] In practice, the camshaft sensor generates a signal taking a low value in the absence of a tooth in line with said sensor, and a high value in the presence of a tooth in line with said sensor. right of said sensor.

[0015] The transition between the low value and the high value of the signal forms a rising edge of the signal, associated with the detection of a rising edge of a tooth of the camshaft target. The transition between the high value and the low value of the signal forms a falling edge of the signal, associated with the detection of a falling edge of a tooth of the camshaft target.

[0016] The synchronization methods according to the prior art compare information obtained using the camshaft sensor with information obtained using the crankshaft sensor, so as to determine the position of the engine.

[0017] However, the methods are based on recognition of the signature of the crankshaft target, so they are ineffective in case of crankshaft sensor failure or possibly in case of strong acceleration.

[0018] Another synchronization method is known which overcomes the failure of the crankshaft sensor, based on an identification of the tooth of the camshaft target which is located to the right of the camshaft sensor, described in document FR1255482, the main steps of which are described below.

[0019] This other synchronization method is based on a measurement of time intervals separating significant edges of the signal generated by the camshaft sensor, and on the use of ratios between several of these measured time intervals.

[0020] Each tooth of the camshaft target is designated by its index i, where i is an integer ranging from 1 to M the number of teeth on the camshaft target.

[0021] A theoretical ratio CP(j), j ranging from 1 to M, is calculated from known angular deviations P(j), between tooth fronts of the camshaft target, from the formula below: 1^

[0022] where P(j) denotes the angular distance between the significant front j and the previous front,

[0023] where N is called the order of index calculation. It is an integer greater than or equal to 1. In the simplest case, we will take N = 1. In special cases, we can take N = 2 or even N = 3.

[0024] For N = 1, the expression of CP(j) simplifies to: PQ') + PÜ-3) P(j - 2) + P(j - 1)]^

[0025] The calculation unit is configured to calculate time intervals Tk separating CP(j) CP(j) = CT(k) = CT(k) = two significant fronts immediately following each other on said signal;

[0026] As soon as possible, the following index is calculated: - i) where T(k) is the duration of the time interval between the significant edge k and the previous significant edge.

[0027] It is necessary to wait for 4N + 1 edges to be able to calculate the above index. It is therefore relevant to choose the order N = 1 to be able to calculate such an index after 4N intervals between edges, i.e. at the fifth edge when N = 1. The index is therefore a ratio of time intervals.

[0028] When N is chosen to have the value N = 1, the expression of CT(k) simplifies to: T(k) + T(k - 3) T(k — 2) + T(k - l)] Kal

[0029] CT(k) is thus a real ratio equivalent to the theoretical ratio CP(j), but based on measurements of time intervals on the signal generated by the camshaft sensor.

[0030] In other words, the definition of CT(k) is similar to the definition of the real ratio CP(j) except that the known angular deviations between the significant fronts of the teeth of the camshaft target are replaced by time intervals Tk. It is therefore necessary to tolerate an uncertainty, represented by an uncertainty margin coefficient, also called tolerance coefficient Ck.

[0031] If the rotation speed of the engine is uniform, then we have CT(j)=CP(j) for j from 1 to M. In reality, when the engine is rotating, and in particular during the first few revolutions, the rotation speed is not uniform at all.

[0032] In order to take into account the acyclisms of the engine, and / or the variations in acceleration at start-up, it is usual to compare the index CT(k) calculated with each of the characteristics CP(j), and in particular with intervals INT(j) framing each CP(j) respectively.

[0033] INT(j) is defined by L Ck .

[0034] Following these comparisons, we eliminate from the sublist the edges j for which the index CT(k) is outside the interval INT(j).

[0035] By iterating the process, it is thus possible to gradually eliminate the hypotheses deemed unrealistic, until there remains only one plausible value for the index of the tooth of the camshaft target currently located opposite the sensor.

[0036] A disadvantage of this method is the duration of the synchronization of the internal combustion engine, since the camshaft sensor must detect at least 5 to 6 rising and falling tooth fronts in order to carry out the synchronization.

[0037] Indeed, the definition of the theoretical ratio Rth requires having the measurement of 4 time intervals between two rising and falling tooth edges, respectively, in order to be able to calculate this ratio. It is therefore necessary to detect 5 rising and falling tooth edges, respectively, in order to be able to begin the analysis of the ratios. In addition, there often remain, after the fifth tooth edge, several plausible hypotheses for the index of the tooth currently located in relation to the sensor, which implies waiting for a sixth rising and falling edge, respectively. In the event of electromagnetic disturbance, and / or unusual variation in rotation of the motor, the algorithm described above is faulty. No more plausible edges are then determined, or a bad plausible edge is judged.

[0038] The algorithm must then start again and detect 5 or 6 new rising, respectively falling, tooth fronts in order to be able to synchronize the camshaft target.

[0039] As an example, for a three-cylinder engine, the internal combustion engine takes about 460° CRK (crankshaft rotation angle, in °) to synchronize when the crankshaft sensor and the camshaft sensor are operational, whereas if the crankshaft sensor is defective, synchronization based on the method described above will take more than 1000° CRK. On this engine, considering a starter speed of 200 rpm, this is a 450 ms delay on start-up. This additional time is largely felt by the driver.

[0040] The invention aims to overcome the drawbacks of the prior art and in particular to reduce the synchronization time in the event of a problem occurring in the synchronization. Statement of the invention

[0041] To this end, according to a first aspect of the invention, there is proposed a method for determining the angular position of a camshaft target mounted integral with a camshaft and having a plurality of teeth distributed angularly in an irregular manner around the periphery of the target, the method being implemented by a calculation unit configured to:

[0042] acquiring a signal generated by a sensor associated with the camshaft target, said sensor being configured to detect the passage of the teeth of the camshaft target and to generate in response a signal comprising rising edges and falling edges associated respectively with rising edges or falling edges of said teeth, the plurality of teeth forming, for the sensor, a series of M significant edges when the camshaft rotates one revolution, each significant edge being associated with a predetermined index allowing it to be identified; and

[0043] storing time intervals separating two significant edges immediately following one another on said signal;

[0044] store, for each of the M significant edges, a theoretical ratio CP(j), j ranging from 1 to M, determined from known angular deviations P(j), between known significant edges of the camshaft target.

[0045] The calculation unit is further configured to, upon each reception of a new significant front, start the execution of a new independent sub-process for determining an index of the significant front of the camshaft target located at the right of the camshaft sensor, said sub-process comprising:

[0046] / a / a definition of a sublist of significant fronts consisting of all of the significant fronts,

[0047] / b / a determination of a current value taken by a real ratio CT(k) function of a first set of time intervals Tk, where the definition of the real ratio CT(k) is similar to the definition of the theoretical ratio CP(j) except that the known angular deviations are replaced by the corresponding time intervals Tk between the significant fronts,

[0048] / c / a comparison of said current value of said real ratio CT(k) with each among several predetermined reference intervals INT(j), each reference interval INT(j) being defined as a function of the respective value taken by a theoretical ratio CP(j) and a tolerance factor Ck, and where each value considered of the theoretical ratio CP(j) is associated with one among several predetermined hypotheses relating to the index of the significant front located at the right of the camshaft sensor,

[0049] / d / depending on the result of each comparison, a discrimination of the indices of edge that can correspond to the index of the significant edge located at the right of the camshaft sensor, and edge indices that cannot correspond to the index of the significant edge located at the right of the camshaft sensor, by deleting the edge indices from the list that cannot correspond to the index of the significant edge located at the right of the camshaft sensor,

[0050] ld wait for the reception of a new significant edge, replace each edge j of the list by its immediate successor j+1 modulo M, then repeat steps / c / to / d / until obtaining a single significant edge of index ii in the list at step / d / ,

[0051] / f / if the current value taken by the real ratio CT(k) belongs to an interval of confidence determined by a predetermined confidence factor, the predetermined confidence factor being less than the tolerance factor Ck, said sub-process enters a successful state

[0052] The synchronization being carried out when one of said sub-processes has a success state Ps, the angular position of the camshaft target then being determined from the angular position of the significant front of index ii associated with said sub-process.

[0053] Advantageously, during step / f / , if the current value taken by the real ratio CT(k) does not belong to said predetermined confidence interval and the current value taken by the real ratio CT(k) belongs to a reference interval determined by the tolerance factor Ck, said sub-process goes into a waiting state.

[0054] Preferably, for each of the M significant fronts, the theoretical ratios CP(j), j ranging from 1 to M, are defined by: rpr . _ [sfLpq - i + i)-z^ pq-o'i L SV

[0055] where P(j) denotes the angular distance between the significant front j and the previous front,

[0056] where N is an integer greater than or equal to 1 called the order of the index calculation,

[0057] and the real ratio CT(k), k ranging from 1 to M, is defined by: rT( ,. _ [g=x T(k - i + 1) - Ï^T(k - i)' ■ u [ ] Nil

[0058] where T(k) is the duration of the time interval between the significant front k and the previous significant front.

[0059] Advantageously, N=1, the expressions of CP(j) and CT(k) becoming: ' 0) [?( / - 2) + PU - 1)]^

[0060] And

[0061] The tolerance factor can be chosen to be greater than or equal to 2.3.

[0062] The confidence factor is preferably less than or equal to 1.8.

[0063] Advantageously, the significant fonts immediately following one another are rising or falling edges.

[0064] According to one aspect of the invention, there is provided a computer program comprising program code instructions for executing the steps of the synchronization method according to the first aspect of the invention, when said program runs on a computer.

[0065] According to a second aspect of the invention, there is proposed a module for determining the angular position of a camshaft target mounted integrally with a camshaft and having a plurality of teeth distributed angularly in an irregular manner around the periphery of the target, comprising a calculation unit configured to:

[0066] acquiring a signal generated by a sensor associated with the camshaft target, said sensor being configured to detect the passage of the teeth of the camshaft target and to generate in response a signal comprising rising edges and falling edges associated respectively with rising edges and falling edges of said teeth,

[0067] the plurality of teeth forming, for the sensor, a series of M significant edges when the camshaft rotates one revolution, each significant edge being associated with a predetermined index allowing it to be identified; and

[0068] calculating time intervals separating two significant edges from a series of M significant edges immediately following one another on said signal;

[0069] calculate, for each of the M significant edges, a theoretical ratio CP(j), j ranging from 1 to M, from known angular deviations P(j), between tooth edges of the camshaft target,

[0070] characterized in that the calculation unit is further configured to:

[0071] upon each reception of a new significant front, start the execution of a new independent sub-process (SP1) for determining an index of the front located at the right of the camshaft sensor.

[0072] Said sub-process comprises:

[0073] / a / a definition of a list of significant fronts consisting of all of the significant fronts,

[0074] / b / a determination of a current value taken by a real ratio CT(k) function of a first set of time intervals Tk, where the definition of the actual ratio CT(k) is similar to the definition of the theoretical ratio CP(j) except that the known angular deviations are replaced by the corresponding time intervals Tk between the significant fronts of the teeth of the camshaft target,

[0075] / c / a comparison of said current value of said real ratio CT(k) with each among several predetermined reference intervals INT(j), each reference interval INT(j) being defined as a function of the respective value taken by a theoretical ratio CP(j) and a tolerance factor Ck, and where each considered value of the theoretical ratio CP(j) is associated with one among several predetermined hypotheses relating to the index of the front located at the right of the camshaft sensor,

[0076] / d / depending on the result of the comparison, a discrimination of the front indices which can correspond to the index of the front located to the right of the camshaft sensor, and front indices which cannot correspond to the index of the front located to the right of the camshaft sensor,

[0077] ld wait for the reception of a new significant edge, replace each edge j of the list by its immediate successor j+1, then repeat steps / c / to / d / until obtaining a single significant edge of index ii in the list at step / d / ,

[0078] / f / if the current value taken by the real ratio CT(k) belongs to an interval of confidence determined by a predetermined confidence factor (es), the predetermined confidence factor being less than the tolerance factor Ck, said sub-process (SP1) passes into a success state (Ps).

[0079] Synchronization is carried out when one of said sub-processes has a success state Ps, the angular position of the camshaft target then being determined from the angular position of the significant front of index f associated with said sub-process.

[0080] According to another aspect of the invention, there is provided a motor vehicle comprising a module according to the invention. Brief description of the figures

[0081] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which one will refer to the appended drawings in which: • [Fig.l] illustrates an embodiment of a module according to the invention and its physical environment, • [Fig.2] illustrates the states of a sub-process according to the invention, • [Fig.3] illustrates a first example of implementation of the invention, • [Fig.4] illustrates a second example of implementation of the invention, Detailed description of the invention

[0082] The embodiments described below being in no way limiting, it will be possible in particular to consider variants of the invention comprising only a selection of characteristics described, subsequently isolated from the other characteristics described, if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art. This selection comprises at least one characteristic, preferably functional without structural details, or with only a part of the structural details if this part alone is sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art.

[0083] An embodiment of a method P for determining the angular position of a camshaft target C of a vehicle engine, together with an angular position determination module and a vehicle equipped with said module.

[0084] The camshaft target C is mounted integrally with a camshaft A and has a plurality of teeth distributed irregularly around the periphery of the camshaft. A target having a plurality of teeth distributed angularly regularly with the exception of a particular zone, or several, is a target whose teeth are distributed irregularly. This is for example the case of a target having 60 teeth distributed regularly with the exception of a zone in which one or two teeth are missing. In other words, a target having a regular distribution and one or more irregularities is a target having a plurality of teeth distributed irregularly.

[0085] The sensor S is typically associated with the target C mounted integrally in rotation with the camshaft A.

[0086] The camshaft target C has a plurality of teeth distributed irregularly around the periphery of the camshaft A, each tooth being associated with a predetermined index allowing it to be identified.

[0087] The sensor S is configured to detect the passage of the teeth of the camshaft target C and to generate in response a signal comprising rising edges and falling edges associated respectively with rising edges and falling edges of said teeth. Such a signal is represented in the following figures.

[0088] The calculation unit Uc is configured to acquire a signal generated by the camshaft sensor S.

[0089] For the remainder of the description, the notion of significant edge is introduced; a significant edge is a type of edge that is processed by the identification logic implemented in the calculation unit Uc. For certain types of camshaft target, the significant edges are the rising and falling edges, whereas for other types of camshaft targets, only the rising or falling edges are significant edges. For certain targets, the immediately succeeding significant edges are falling edges.

[0090] The number of significant edges on a camshaft target revolution is denoted M in the following.

[0091] The calculation unit Uc is also configured to calculate time intervals Tk separating two significant fronts immediately following one another on the signal.

[0092] Theoretical ratios

[0093] The calculation unit is further configured to store, for each of the M significant edges, a theoretical ratio CP(j), j ranging from 1 to M, determined from known angular deviations P(j), between known significant tooth edges of the shaft target. CP(j) = cams.

[0094] As in the prior art, the theoretical ratios CP(j), j ranging from 1 to M, can be defined by: g =1 pu - j+1) - i^pu - iy

[0095] where P(j) denotes the angular distance between the significant edge j and the previous edge,

[0096] where N is an integer greater than or equal to 1 called the order of the index calculation.

[0097] Preferably, N=1, and the expression CP(j) becomes:

[0098] Still other theoretical ratios can be used.

[0099] Independent sub-process SP1

[0100] With reference to [Fig.2], the calculation unit is further configured to execute an independent sub-process SP1 for determining an index of the front located at the right of the camshaft sensor.

[0101] [Fig.2] schematically represents a sub-process SP1. The sub-process SP1 comprises an initial step Pi, which is followed by a state Ps or a state Pf.

[0102] The initial phase Pi includes:

[0103] / a / a definition of a sublist of significant fronts consisting of all of the significant fronts,

[0104] / b / a determination of a current value taken by a real ratio CT(k) function of a first set of time intervals Tk, where the definition of the real ratio CT(k) is similar to the definition of the theoretical ratio CP(j) except that the known angular deviations are replaced by the corresponding time intervals Tk between the significant fronts,

[0105] / c / a comparison of said current value of said real ratio CT(k) with each among several predetermined reference intervals INT(j), each reference interval INT(j) being defined as a function of the respective value taken by a theoretical ratio CP(j) and a tolerance factor Ck, and where each value considered of the theoretical ratio CP(j) is associated with one among several predetermined hypotheses relating to the index of the significant front located at the right of the camshaft sensor,

[0106] / d / depending on the result of each comparison, a discrimination of the indices of front which can correspond to the index of the significant front located to the right of the sensor camshaft, and front indices that cannot correspond to the index of the front located to the right of the camshaft sensor, by deleting the front indices from the list that cannot correspond to the index of the significant front located to the right of the camshaft sensor,

[0107] ld wait for the reception of a new significant edge, replace each edge j in the list by its immediate successor j+1 modulo M, then repeat steps / c / to / d / until obtaining a single edge in the list at step / d / ,

[0108] / f / if the current value taken by the real ratio CT(k) belongs to an interval of confidence determined by a predetermined confidence factor (es), the predetermined confidence factor being lower than the tolerance factor, said sub-process SP1 passes into a success state Ps.

[0109] The comparison between a current value of real ratio CT(k) and a predetermined interval INT(j) consists of determining whether said value is inside or outside said interval. When said value is inside the interval INT(j), then the corresponding hypothesis relating to the index of the edge located at the right of the sensor is a hypothesis considered to be plausible. In other words, said tooth index is considered to be able to correspond to the index of the edge located at the right of the camshaft sensor. Conversely, when said value is outside the interval INT(j), then the corresponding hypothesis relating to the index of the edge located at the right of the sensor is a hypothesis considered to be implausible. In other words, said edge index is considered to be unable to correspond to the index of the edge located at the right of the camshaft sensor.

[0110] It is thus possible to gradually eliminate the least realistic hypotheses, until only one plausible value remains, for the index of the front of the camshaft target currently located opposite the sensor.

[0111] Preferably, each interval INT(j) is delimited by a lower bound and an upper bound, with:

[0112] the lower bound equal to the quotient of the value taken by the theoretical ratio CP(j) divided by the tolerance factor, and

[0113] the upper limit equal to the product of the value taken by the theoretical ratio CP(j) multiplied by the tolerance factor.

[0114] The tolerance interval is defined by a lower bound Vinf and an upper bound Vsup, with Vinf=CP(j) / Ck and Vsup=CP(j)*Ck.

[0115] Preferably, the confidence interval is delimited by a lower bound and an upper bound, with:

[0116] the lower bound equal to the quotient of the value taken by the theoretical ratio CP(j) divided by the confidence factor Ce, and

[0117] the upper limit equal to the product of the value taken by the theoretical ratio CP(j) multiplied by the confidence factor Ce.

[0118] The confidence interval is defined by a lower bound Vinf and an upper bound Vsup, with Vinf= CP(k) / Cc and Vsup= CP(k)*Cc.

[0119] Optionally, if a success state Ps is reached, i.e. if the condition es is verified, the sub-process SP1 can continue with a new step / c / .

[0120] Furthermore, when the condition of step / f / is not verified, said sub-process SP1 goes into a failure state (Pf) if (cf) the current value taken by the real ratio CT(k) does not belong to a confidence interval determined by the tolerance factor Ck.

[0121] Optionally, the sub-process SP1 can go into a waiting state Ph if the current value taken by the real ratio CT(k) does not belong to said predetermined confidence interval and the current value taken by the real ratio CT(k) belongs to a reference interval determined by the tolerance factor Ck (ch).

[0122] As in the prior art, the real ratios CT(k), k ranging from 1 to M, can be defined by: SU T(k - i + 1) - SS T(k - i) ^T(ki)

[0123] where T(k) is the duration of the time interval between the significant front k and the previous significant front.

[0124] Preferably, N=1, and the expression CP(j) becomes: CT(k) T(k) + T(k — 3) T(k — 2) + T(k - 1)

[0125] Preferably, the tolerance factor is greater than or equal to 2.3, or even greater than or equal to 2.5 or even greater than or equal to 2.8.

[0126] Preferably, the confidence factor is less than or equal to 1.8.

[0127] Upon receipt of each significant edge, the method P starts the execution of an independent sub-method SP1 for determining an index of the significant edge of the camshaft target located at the right of the camshaft sensor. Example 1

[0128] [Fig. 3] includes a graph of the signal generated by the camshaft sensor in the upper part as a function of time, illustrates in the middle part the execution of the different sub-processes also as a function of time, as well as the synchronization state in the lower part also as a function of time. The synchronization state Sw corresponds to a non-synchronized state, the synchronization state Ss corresponding to a synchronized state.

[0129] The signal graph comprises rising edges and falling edges. The angular positions corresponding to the rising or falling edges are specified on a line arranged above the graph. On a line arranged below the graph are indicated the indices of the edges associated with the rising or falling edges.

[0130] By convention, the number j preceded by the hash symbol, i.e. by the symbols #j with j varying from 1 to n, denotes the real edge of rank j in the series of n real edges of the toothed wheel. The value j=1 is assigned to the first edge located just after the reference zone in the forward direction of rotation of the toothed wheel. Each time a new edge is detected, the value j is incremented and the angular position of the toothed wheel is thus known.

[0131] We thus observe that the signal represented presents: • a rising edge associated with angular position 12 and edge #6, then • a falling edge associated with angular position 74 and edge #1, then • a rising edge associated with angular position 132 and edge #2, then • a falling edge associated with angular position 314 and edge #3, then • a rising edge associated with angular position 492 and edge #4, then • a falling edge associated with angular position 554 and edge #5, then • a rising edge associated with angular position 12 and edge 6, then • a falling edge associated with angular position 74 and edge #1, then • a rising edge associated with angular position 132 and edge #2, then • a falling edge associated with angular position 314 and edge #3, then • a rising edge associated with angular position 492 and edge #4, then • a falling edge associated with angular position 554 and edge #5, then • a rising edge associated with angular position 12 and edge #6.

[0132] In the example shown, the method according to the invention is initialized after the reception of front #1. The method according to the invention then has a state Sw.

[0133] Upon receipt of each significant edge, the method P starts the execution of an independent sub-method SP1 for determining an index of the edge located at the right of the camshaft sensor.

[0134] As illustrated: • the execution of process SP1 is started upon receipt of the new rising edge corresponding to edge #2, process SP1 presenting state Ps from edge #6; • the execution of the SP2 process is started upon receipt of the new rising edge corresponding to edge #3, the SP2 process presenting the Ps state from edge #1; • the execution of the SP3 process is started upon receipt of the new rising edge corresponding to edge #4, the SP3 process having the Ps state from edge #2; • the execution of the SP4 process is started upon receipt of the new rising edge corresponding to edge #5, the SP4 process presenting the Ps state from edge #3; • the execution of process SP5 is started upon receipt of the new rising edge corresponding to edge #6, process SP5 presenting state Ps from edge #4.

[0135] Synchronization is performed when one of said sub-processes, here the process SP1, has a success state Ps, the angular position of the camshaft target then being determined by the index of the front associated with said confidence ratio of said sub-process.

[0136] In the example illustrated, synchronization is achieved around the angular position 632° at 200 revolutions per minute, i.e. after 526 ms. Example 2

[0137] As previously, [Fig.4] includes a graph of the signal generated by the camshaft sensor in the upper part as a function of time, illustrates in the middle part the execution of the different sub-processes also as a function of time, as well as the synchronization state in the lower part also as a function of time. The synchronization state Sw corresponds to a non-synchronized state, the synchronization state Ss corresponding to a synchronized state.

[0138] [Fig.4] further includes a diagram arranged between the signal graph and the various sub-processes illustrating the synchronization state according to the prior art.

[0139] The signal shown is identical to that of [Fig.3]. However, the rising edge corresponding to edge #4 is not generated by the sensor, and is therefore not processed by the method according to the invention.

[0140] As in the invention, the method according to the prior art is initialized after the reception of edge #1 and then has a step Cw of waiting for the passage of 5 consecutive rising edges to determine the index of the edge at the sensor. Since the rising edge of edge #4 is not generated by the sensor, the method according to the prior art does not succeed. A new method according to the prior art is restarted upon reception of the following rising edge, i.e. the rising edge corresponding to edge #3. A method was also launched after the reception of edge #2 but also did not succeed.

[0141] In the example illustrated, the synchronization according to the prior art is carried out around edge #1 in an angular position 1414° at 200 revolutions per minute, i.e. after 1175 ms, the method according to the prior art passing to state Cs.

[0142] In the example shown, the method according to the invention is always initialized after the reception of front #1. The method according to the invention then has a state Sw.

[0143] Upon receipt of each significant edge, the method P starts the execution of an independent sub-method SP1 for determining an index of the edge located at the right of the camshaft sensor.

[0144] As illustrated: • the execution of process SP1 is started upon receipt of the new rising edge corresponding to edge #2, process SP1 presenting state Ph from edge #2 (one revolution later), then state Pf from the following edge #3; • the execution of process SP2 is started upon receipt of the new rising edge corresponding to edge #3 (one revolution later), process SP2 having state Pf from edge #3; • the execution of the SP3 process is started upon receipt of the new rising edge corresponding to edge #6 (one revolution later), because the rising edges corresponding to edges #4 and #5 are not seen), the SP3 process having the Ps state from edge #6; • the execution of the SP4 process is started upon receipt of the new rising edge corresponding to edge #1 (one revolution later), the SP4 process presenting the Ps state from edge #1; • the execution of the SP5 process is started upon receipt of the new rising edge corresponding to edge #2 (one revolution later), the SP5 process presenting the Ps state from edge #2.

[0145] The synchronization being carried out when one of said sub-processes has a success state Ps, here the sub-process SP3, the angular position of the camshaft target then being determined by the index of the front associated with said confidence ratio of said sub-process.

[0146] In the example illustrated, synchronization is carried out at the passage of front #4, around the angular position of 1080° at 200 revolutions per minute, i.e. after 900 ms. The synchronization duration of the method according to the invention is thus shorter than that according to the prior art.

[0147] The module M according to the invention can be implemented in the form of an electronic module comprising a memory in which is stored a computer program product comprising instructions intended to be executed by the calculation unit UC or by the engine control unit ECU which then replaces the calculation unit UC.

[0148] Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention. Furthermore, the various features, forms, variations and embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive.

Claims

Claims

1. Method (P) for determining the angular position of a camshaft target (C) mounted integrally with a camshaft (A) and having a plurality of teeth distributed angularly in an irregular manner around the periphery of the target, the method being implemented by a calculation unit (Uc) configured to: acquiring a signal generated by a sensor (S) associated with the camshaft target, said sensor being configured to detect the passage of the teeth of the camshaft target and to generate in response a signal comprising rising edges and falling edges associated respectively with rising edges or falling edges of said teeth, the plurality of teeth forming, for the sensor, a series of M significant edges when the camshaft rotates one revolution, each significant edge being associated with a predetermined index (#1, #2, #3, #4, #5, #6) allowing it to be identified; and calculate time intervals separating two significant fronts immediately following one another on said signal; storing, for each of the M significant fronts, a theoretical ratio CP(j), j ranging from 1 to M, determined from known angular deviations P(j) between known significant fronts of the camshaft target, characterized in that the calculation unit is further configured to: upon each reception of a new significant front start the execution of a new independent sub-process (SP1) for determining an index of the significant front of the camshaft target located at the right of the camshaft sensor, said sub-process comprising: / a / a definition of a list of significant edges consisting of all significant edges, / b / a determination of a current value taken by a real ratio CT(k) function of a first set of time intervals Tk, where the definition of the real ratio CT(k) is similar to the definition of the theoretical ratio CP(j) except that the known angular deviations are replaced by the corresponding time intervals Tk between the significant fronts, / c / a comparison of said current value of said actual ratio CT(k) with each of several predetermined reference intervals INT(j), each reference interval INT(j) being defined as a function of the respective value taken by a theoretical ratio CP(j) and a tolerance factor Ck, and where each considered value of the theoretical ratio CP(j) is associated with one of several predetermined hypotheses relating to the index of the significant front located at the right of the camshaft sensor, / d / depending on the result of each comparison, a discrimination of the front indices which can correspond to the index of the significant front located at the right of the camshaft sensor, and of the front indices which cannot correspond to the index of the significant front located at the right of the camshaft sensor, by deleting from the list the front indices which cannot correspond to the index of the significant front located at the right of the camshaft sensor, ld waiting for the reception of a new significant front, replacing each front j of the list by its immediate successor j+1 modulo M,then repeat steps / c / to / d / until you obtain a single significant edge of index h in the list from step / d / , / f / if the current value taken by the real ratio CT(k) belongs to a confidence interval determined by a predetermined confidence factor (es), the predetermined confidence factor being less than the tolerance factor Ck, said sub-process (SP1) passes into a success state (Ps), the synchronization being carried out when one of said sub-processes has a success state Ps, the angular position of the camshaft target then being determined from the angular position of the significant index front associated with said sub-process.

2. Method according to claim 1, in which during step / f / , if the current value taken by the real ratio CT(k) does not belong to said predetermined confidence interval and the current value taken by the real ratio CT(k) belongs to a reference interval determined by the tolerance factor Ck (ch), said sub-method (SP1) goes into a waiting state (Ph).

3. Method according to claim 1, in which for each of the M significant fronts, the theoretical ratios CP(j), j ranging from 1 to M, are defined by: ï™dP(j~i} U where P(j ) denotes the angular distance between the significant front j and the CPQ) = previous edge, where N is an integer greater than or equal to 1 called the order of the index calculation, and the real ratio CT(k), k ranging from 1 to M, is defined by: T(k - i + 1) - X^T(k - 01 where T(k) is the duration of the time interval between the significant edge k and the previous significant edge.

4. Method according to the preceding claim, in which N=1, the expressions of CP(j) and CT(k) becoming: CPÜ> . [ 1 P(j — 2) + P(j - 1) N>1 and Hk) + T(k-3) ' ( ) [T(k - 2) + T(k - 1)]^

5. Method according to the preceding claim, in which the tolerance factor is greater than or equal to 2.

3.

6. Method according to the preceding claim, in which the confidence factor is less than or equal to 1.

8.

7. A method according to any preceding claim, wherein the immediately succeeding significant edges are falling edges or rising edges.

8. A computer program comprising program code instructions for performing the steps of the synchronization method according to any one of the preceding claims, when said program is running on a computer.

9. Module (M) for determining the angular position of a camshaft target (C) mounted integrally with a camshaft (A) and having a plurality of teeth distributed angularly in an irregular manner around the periphery of the target, comprising a calculation unit (Uc) configured to: acquire a signal generated by a sensor (S) associated with the camshaft target cams, said sensor being configured to detect the passage of the teeth of the camshaft target and to generate in response a signal comprising rising edges and falling edges associated respectively with rising edges or falling edges of said teeth, the plurality of teeth forming, for the sensor, a series of M significant edges when the camshaft rotates one revolution, each significant edge being associated with a predetermined index (#1, #2, #3, #4, #5, #6) allowing it to be identified; and calculate time intervals separating two significant edges of a series of M significant edges immediately following one another on said signal; storing, for each of the M significant fronts, a theoretical ratio CP(j), j ranging from 1 to M, determined from known angular deviations P(j), between known significant fronts of the tooth of the camshaft target, characterized in that the calculation unit is further configured to: upon each reception of a new significant front start the execution of a new independent sub-process (SP1) for determining an index of the front located at the right of the camshaft sensor, said sub-process comprising: / a / a definition of a sublist of significant edges consisting of all significant edges, / b / a determination of a current value taken by an actual ratio CT(k) as a function of a first set of time intervals Tk, where the definition of the actual ratio CT(k) is similar to the definition of the theoretical ratio CP(j) except that the known angular deviations are replaced by the corresponding time intervals Tk between the significant fronts of the teeth of the camshaft target, / c / a comparison of said current value of said actual ratio CT(k) with each of several predetermined reference intervals INT(j), each reference interval INT(j) being defined as a function of the respective value taken by a theoretical ratio CP(j) and a tolerance factor Ck, and where each considered value of the theoretical ratio CP(j) is associated with one of several predetermined hypotheses relating to the index of the significant front located at the right of the camshaft sensor, / d / as a function of each result of the comparison, a discrimination of the front indices which can correspond to the index of the significant front located at the right of the camshaft sensor, and of the front indices which cannot cannot correspond to the index of the significant front located to the right of the camshaft sensor, by removing from the list the front indices which cannot correspond to the index of the significant front located to the right of the camshaft sensor, ld wait for the reception of a new significant edge, replace each edge j in the list by its immediate successor j+1 modulo M, then repeat steps / c / to / d / until obtaining a single significant edge of index ii in the list of step / d / , / f / if the current value taken by the real ratio CT(k) belongs to a confidence interval determined by a predetermined confidence factor (es), the predetermined confidence factor being lower than the tolerance factor Ck, said sub-process (SP1) passes into a success state (Ps), the synchronization being carried out when one of said sub-processes has a success state Ps, the angular position of the camshaft target then being determined from the angular position of the significant index front associated with said sub-process.

10. Motor vehicle comprising a module according to the preceding claim.

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