Method for determining the temperature of an internal combustion engine

Abstract

Method for determining the operating temperature of an engine with the following steps: - engine calibration by determining an initial angular correction value (VAC) to know the actual position of a camshaft, - recording the initial VAC, a calibration temperature, and a calibration speed, - determination of an operating VAC, - determination of a speed NRef and calculation of an equivalent calibration VAC for a speed NRef and an equivalent operating VAC for NRef, - calculation of an angular difference DA between the equivalent calibration VAC and the equivalent operating VAC, - determination of the operating temperature from the difference DA, with the VAC varying linearly with the temperature at constant speed according to a slope PTEMP, the temperature corresponding to the calibration temperature plus the difference DA divided by the slope PTEMP. Figure 3A.

Description

Title of the invention: Method for determining the temperature of an internal combustion engine

[0001] The present disclosure relates to a method for determining the temperature of an internal combustion engine. It relates more particularly to four-stroke engines, that is to say, engines comprising, on the one hand, a crankshaft and, on the other hand, at least one camshaft. Technical field

[0002] The technical field of the present invention is thus the field of engine control of internal combustion engines. To ensure proper operation of the engine and in particular to comply with pollutant emission standards, it is necessary to control various operating parameters of the engine, such as for example the temperature of the fluids ensuring proper operation of the engine.

[0003] In an internal combustion engine, one or more cylinders are made in an engine block and delimit with a cylinder head and pistons (one piston for each cylinder) each time a combustion chamber. For each combustion carried out in the engine, the corresponding piston is moved and rotates a crankshaft. To control the gas flows entering and leaving each combustion chamber, valves are provided each time and the opening and closing of these valves are controlled by at least one camshaft.

[0004] To know the position of the pistons in the engine, it is usual to use, on the one hand, a sensor associated with a target linked to the crankshaft, and, on the other hand, a sensor associated with a target linked to a camshaft. Knowledge of this position is essential for proper operation of the engine, as are other parameters including the temperature of the engine coolant. This liquid, or more generally coolant, is most often water (with additive(s)) or oil. The temperature of this fluid is a parameter monitored more particularly in an engine, in particular by an on-board diagnostic system also known by the acronym "OBD system" (from the English On Board Diagnostic). Prior art

[0005] In an internal combustion engine, the temperature of the coolant is conventionally given by a temperature sensor which is connected to a control and management system of said engine. The temperature of the coolant (water or oil) which circulates in the engine and substantially standardizes the temperature in the engine will hereinafter be referred to more generally as "engine temperature". Whether it is the temperature of the water or the oil (or possibly the temperature given by a specific sensor placed in a location whose temperature is significant), we consider as a shortcut that this quantity corresponds to a characteristic quantity of the engine.

[0006] When the temperature sensor fails (it no longer provides the engine temperature or provides an incorrect temperature), engine management must then be carried out in a degraded mode.

[0007] The present disclosure aims to provide means for overcoming the failure of an engine temperature sensor in an internal combustion engine, that is to say to make it possible to know the temperature of the engine even in the event of failure, or absence, of a temperature sensor. Summary

[0008] According to the present disclosure, there is provided a method for determining an operating temperature of an internal combustion engine comprising, on the one hand, a crankshaft, a first target associated with this crankshaft and a crankshaft position sensor cooperating with said first target, and, on the other hand, a camshaft, a second target associated with said camshaft and a camshaft position sensor cooperating with said second target, said method comprising a preliminary calibration phase with the following steps: - calibration of the engine by determining an initial corrective angular value corresponding to the difference between an actual position of a relief front of the second target and a theoretical position of said relief front under known or estimated conditions of temperature and engine speed, - storage of the initial corrective angular value, of a calibration temperature corresponding to the engine temperature during calibration and of a calibration engine speed corresponding to the engine speed during calibration, said method then comprising phases of measuring the engine temperature implementing the following steps: - determination of a corrective operating angular value corresponding to the difference between an actual position of a relief front of the second target and a theoretical position of said relief front under known engine speed conditions corresponding to an operating engine speed, - considering that at constant temperature a corrective angular value varies linearly with the engine speed according to a first known slope depending on the type of engine, determination of an engine speed NRef and calculation, on the one hand, of a corrective angular calibration value equivalent to the angular calibration value for the engine speed NRef and, on the other hand, of a corrective angular operating value equivalent to the angular operating value for the engine speed NRef - calculation of an angular difference DA between the equivalent calibration corrective angular value and the equivalent operating corrective angular value, - determination of the operating temperature of the engine from the angular difference DA considering that at constant speed a corrective angular value varies linearly with the temperature of the engine according to a second known slope depending on the type of engine, the operating temperature of the engine corresponding to the calibration temperature increased by the angular difference DA divided by the second slope.

[0009] Such a method therefore makes it possible to know the engine temperature solely from the signals supplied by the crankshaft position sensor and by the camshaft position sensor (and the associated electronics).

[0010] The reference engine speed may be, for example but not limited to, the operating engine speed or the engine speed during calibration.

[0011] In a method as presented above, the characteristics set out in the following paragraphs may, optionally, be implemented, independently of one another or in combination with one another:

[0012] - the calibration temperature is a measured temperature;

[0013] - the preliminary calibration phase is carried out when the engine ;

[0014] - the first slope of the linear function of the corrective angular value in function of the engine speed at constant engine temperature, on the one hand, and the second slope of the linear function of the corrective angular value as a function of the engine temperature at constant engine speed, on the other hand, are determined on a standard vehicle, and the value of the first slope and the value of the second slope are stored;

[0015] - the internal combustion engine is equipped with a programmed distribution system variable acting on the angular position of a camshaft, and in that the corrective operating angular value is determined when the angular position of said camshaft is known; in this case, the corrective operating angular value is preferably determined when the engine speed corresponds to an idle speed and / or when the engine is in foot lift conditions.

[0016] According to another aspect, a computer program is provided comprising instructions for implementing a method presented above when this program is executed by a processor, in particular an electronic control unit of an internal combustion engine.

[0017] According to another aspect, there is provided a non-transitory, computer-readable recording medium on which such a program is recorded.

[0018] According to another aspect, there is provided an electronic system for managing an internal combustion engine, configured to implement all the steps of a method above, and comprising: - a crankshaft sensor, configured to detect the passages of the relief fronts of a crankshaft target; - a camshaft sensor, configured to detect the passages of the relief fronts of a camshaft target; - a computer equipped with an electronic memory, configured to: - receive as input data provided by the crankshaft sensor and data provided by the camshaft sensor, - provide instructions for implementing the steps of a method above, and - determine engine temperature.

[0019] According to another aspect, there is provided a motor vehicle with: - a crankshaft equipped with a target and associated with a crankshaft sensor, - a camshaft equipped with a target and associated with a camshaft sensor, characterized in that it comprises an electronic system according to the preceding paragraph. In such a vehicle, the internal combustion engine may be equipped with a variable valve timing system. Brief description of the drawing

[0020] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawing, in which:

[0021] [Fig. 1] is a graphical representation illustrating a correlation to engine speed constant between, on the one hand, a corrective value of angular position of a camshaft and, on the other hand, an engine temperature.

[0022] [Fig.2] is a graphical representation illustrating a temperature correlation constant engine (for three distinct temperatures) between, on the one hand, a corrective value of angular position of a camshaft and, on the other hand, an engine speed.

[0023] [Fig.3A] is a graphical representation explaining how to obtain an engine temperature from a measurement point according to a first method in accordance with the present disclosure.

[0024] [Fig.3B] is a graphical representation explaining how to obtain an engine temperature from a measurement point according to a second method in accordance with the present disclosure.

[0025] [Fig.4] is a flowchart for implementing a method according to the present di popularization.

[0026] [Fig.5] is a schematic view of a vehicle for implementing the present disclosure. Description of the embodiments

[0027] The present description is made in relation to an internal combustion engine, of the four-stroke type. In a manner known to those skilled in the art, an internal combustion engine comprises one or more cylinders, inside each of which there is a combustion chamber and in each of which slides a piston connected by a connecting rod to a crankshaft. Each combustion chamber is associated with at least one intake valve for managing gas flows entering the combustion chamber and at least one exhaust valve for managing gas flows leaving the combustion chamber. The opening and closing of the valves are controlled by at least one camshaft. A single camshaft can control all the valves or at least one separate camshaft can be provided for the intake valves and at least one other shaft is then provided for the exhaust valves.Furthermore, preferably a variable valve timing system (known by the English acronym VVT for Variable Valve Timing) is provided. Such a system known to those skilled in the art comprises a motor, for example an electric motor, which makes it possible to introduce an angular offset for a camshaft in a predetermined angular range relative to a reference position while the camshaft is rotated by the crankshaft.

[0028] To determine the angular position of a camshaft (as a function of its rotational drive by the crankshaft and, where appropriate, as a function of the offset introduced by the variable timing system), it is known to secure a camshaft target to the camshaft in question and to associate with it a camshaft sensor making it possible to determine the angular position of the camshaft target. The target has reliefs at its periphery which are most often in the form of teeth. For a camshaft target, the teeth (or more generally reliefs) are of variable angular length and their distribution at the periphery of the target is not necessarily regular.

[0029] Similarly, to know the angular position of a crankshaft, it is known to secure a crankshaft target to the crankshaft and to associate with it a crankshaft sensor making it possible to determine the angular position of the crankshaft target. The target has reliefs on its periphery which are most often in the form of teeth. For a crankshaft target, the teeth (or more generally reliefs) are most often similar and their distribution on the periphery of the target is generally regular, apart from the absence of one or two consecutive teeth.

[0030] Most often, a camshaft sensor is distinct from a crankshaft sensor. It is then necessary to carry out, in a manner known to those skilled in the art, a calibration to compensate for the effects linked to speed during a learning phase of the camshaft position. Indeed, the sensors (camshaft and crankshaft) have different response times and the rotation speed of a camshaft is half that of the crankshaft. Thus, during engine operation, it is known to determine a corrective angular value to correct the angular value of the camshaft from the signal given by the camshaft sensor.

[0031] It is proposed by the present disclosure, in a completely original manner, to use this corrective angular value, with other data / measurements, to determine the engine temperature. This temperature is given by a temperature sensor. Most often, the temperature of the coolant is taken into account but another temperature measurement can be carried out (oil temperature or specific sensor). The engine temperature is a data item chosen during the design of the engine and which makes it possible to check the good health of the engine. It is used to optimize the thermal efficiency of the engine and limit pollutant emissions. It is also used to optimize comfort inside the vehicle.

[0032] Due to its importance, the engine temperature is one of the parameters that are monitored in the engine and are used to establish a diagnosis related to an anomaly. On-board diagnostic systems also known by the acronym "OBD system" (from the English On Board Diagnostic) monitor this parameter in particular.

[0033] In the event of a failure of an engine temperature sensor (no data supply or obviously erroneous data), the engine must operate in a degraded mode.

[0034] The present disclosure, however, makes it possible to determine the engine temperature in a completely original manner from only the signals provided by the crankshaft sensor and the camshaft sensor as explained below.

[0035] Learning of the position of the fronts of the teeth of the target camshaft is carried out so as to determine the actual position of these fronts relative to the position given directly by the camshaft sensor. This learning, in the case of an engine equipped with a variable timing system acting on the angular position of a camshaft (known by the acronym VVT), is carried out when said variable timing system is in a reference position. This position is a constant mechanical value. However, at the origin of the present disclosure, it was found in an original manner that the calculated position (from the signal from the camshaft sensor) varied with the engine temperature.

[0036] [Fig. 1] represents measurement points which were carried out at a constant regime, that is, the rotation speed of the crankshaft was constant. In the example illustrated, the rotation speed was approximately 800 revolutions per minute (or rpm), and more precisely, this speed was between 790 and 810 rpm.

[0037] In this [Fig.l], the horizontal axis (abscissa) indicates the value of the correction to apply to the value of the angular position of the camshaft to obtain the actual position of said camshaft. The vertical axis (ordinate) corresponds to the engine temperature (e.g. the engine coolant temperature).

[0038] We note in [Fig.l] that all the measurement points are grouped around a straight line. By making a linear interpolation, we determine that when the engine temperature goes from 10 to 100°C, the corrective angular value (to determine the exact position of the camshaft) varies linearly from 6.8°CRK (i.e. 6.8° of crankshaft rotation) to 5.2°CRK. We thus determine a first slope PTEMP (in °CRK / °C) by the formula:

[0039] PTEMP=(5.2-6.8) / (100-10)=-1.6 / 90=-0.017°CRK / °C.

[0040] Of course, all the values ​​given in this description are purely illustrative and non-limiting values.

[0041] Similarly, when the engine temperature is constant, the corrective angular value varies linearly with the engine speed. This is illustrated by [Fig.2] on which three sets of measurement points are grouped, a first set of measurement points made at a temperature of 99°C, a second at 75°C and a third at 50°C (temperatures given for purely illustrative and non-limiting purposes like the other numerical values, even if no particular mention is made).

[0042] In this [Fig.2], we again have the corrective angular values ​​on the abscissa but here, on the ordinate, we have the rotation speed of the motor.

[0043] As illustrated in [Fig.2], three parallel lines emerge by interpolation, which therefore have the same slope PRPM. In this example of realization, we have, as indicated in [Fig.2]:

[0044] PRPM=0.4°CRK / 1000 rpm

[0045] that is to say that if the corrective angular value determined at a rotation speed of 2000 rpm is 5°CRK, then at the same engine temperature, the determination of the corrective angular value will give a value of 5.4°CRK at 3000 rpm.

[0046] The PTEMP and PRPM values, i.e. the variations of the corrective angular values ​​respectively as a function of the engine temperature and the engine rotation speed, are linked to the engine type and do not vary from one engine to another (when these two engines are similar). These values ​​are then determined once and for all on a standard vehicle and are then stored in similar vehicles manufactured subsequently.

[0047] To then determine the engine temperature on a particular engine, it is necessary to create a reference which takes into account the assembly tolerances. It is therefore necessary to determine, as early as possible, a measurement point for the corrective angular value by knowing the engine speed and the engine temperature.

[0048] It is thus proposed to measure the corrective angular value to create said reference when the engine is first started. It is planned to make several adjustments during this first start-up. This is therefore an approach that does not disrupt the manufacture of a vehicle. This first start-up is carried out just after leaving the factory and the engine temperature is then uniform. It can be assumed here that the engine temperature sensor, which is brand new, gives a reliable temperature. In the absence of a temperature sensor, this temperature can be estimated. In the illustrative figures, the engine temperature during this first measurement is 25°C.

[0049] This first measurement is thus carried out during a calibration phase. In general, when first started, the engine is left to run at idle. If the engine is equipped with a variable valve timing system acting on the angular position of a camshaft, this system is not active and the camshaft is in its reference position.

[0050] Under these conditions, as illustrated in Figures 2 and 3 (3A and B), a reference point Vini is obtained with the following characteristics (purely for illustrative purposes): corrective angular calibration value of 5.75°CRK at a calibration temperature of 25°C measured at a calibration engine speed of 800 rpm (or tr / min).

[0051] These values ​​are then stored in a memory of an electronic unit used for engine management and also known by the English acronym CPU.

[0052] A determination of the engine temperature is now described with reference to [Fig.3A],

[0053] In [Fig.3A], the point Vini is represented.

[0054] Preferably as soon as possible, the actual position of the camshaft is learned. This requires the camshaft to be in a stable and known position, for example its reference position. Learning is also preferably done at a substantially constant speed. These conditions are, for example, met when the engine is idling or when lifting the foot, i.e. when the driver removes his foot from the accelerator. Learning is then carried out. As with the first calibration when the engine is first started, generally about ten rotations of the engine are sufficient to obtain the corrective angular value.

[0055] In the example illustrated, learning is carried out at an operating speed of 1810 rpm and provides the measuring point VI with an operating corrective angular value of 5.15°CRK.

[0056] To find the engine temperature when determining the measuring point VI, it is proposed to “slide” the point V1 on the isothermal straight line of slope PTEMP in the graph (Corrective angular value / engine speed) of [Fig.3A] until reaching a straight line DI of equation

[0057] Engine speed = NRef

[0058] In [Fig.3A], the value chosen for NRef is the value of 800 rpm corresponding to the calibration engine speed.

[0059] The point at the intersection of the isotherm and the straight line DI is named V2 in [Fig.3A]. The difference in engine speed between the operating engine speed for determining point VI and the calibration engine speed is 1010 rpm. Point V2 is therefore located at the abscissa (5.15 - PRPM*1.01) or 4.75°CRK.

[0060] Since V2 and Vini are on the same line Dl, which is an iso-regime line, the difference between the abscissas of V2 and Vini gives here the difference between the corresponding temperatures of the isotherms passing through V2 and Vini using the slope PTEMP defined on the standard car.

[0061] In the present numerical example, the difference in abscissa between V2 and Vini is 1°CRK. The temperature difference delta_T between the two isothermal lines passing through these points is given by

[0062] Delta_T = (4.75-5.75) / PTEMP

[0063] Let

[0064] Delta_T = 1 / 0.017 = 59°C

[0065] The calibration temperature being 25°C, the engine temperature when determining the measuring point V1 was:

[0066] T = 25 + 59 = 84°C.

[0067] [Fig.3B] illustrates a variant making it possible to also determine the engine temperature when learning the actual position of the camshaft from the corrective angular value determined during this learning.

[0068] It is assumed here that the learning provides the same measurement point V1 as for [Fig.3A], i.e. that the learning is done at a speed of 1810 rpm and gives a corrective angular value of 5.15°CRK.

[0069] The idea in the present disclosure is to move point V1 and / or point Vini on their respective isotherms to bring them onto the same iso-regime line (line parallel to the abscissa axis in Figures 3). Once on this iso-regime line, as indicated above, the difference in abscissa between the two moved points makes it possible to know the temperature difference of the corresponding isotherms. The two points VI and Vini can be moved. However, to simplify the calculations, it is preferable to move only one. In the example of [Fig.3A], point VI has been moved to bring it onto the same iso-regime as point Vini. In [Fig.3B], point Vini is brought onto the iso-regime line of VL. Point Vini is then moved along the isothermal line T=25°C to arrive on the iso-regime line cor- corresponding to the calibration engine speed, i.e. 1810 rpm.

[0070] Taking into account the PRPM slope of the isothermal lines on the diagram of [Fig.3B], the point Vini is moved to the position V3 corresponding to the intersection of the isotherm @ 25°C and the iso-regime @ 1810 rpm. The abscissa of the point V3 is then given by:

[0071] 5.75°CRK + PRPM*l.010 = 6.15°CRK

[0072] Here we find an abscissa difference of 1°CRK which corresponds, as seen above, to a temperature difference Delta_P of 59°C. The engine temperature is thus also 84°C.

[0073] [Fig.4] summarizes the different steps for obtaining the temperature of an internal combustion engine from the signals provided, on the one hand, by a crankshaft sensor and, on the other hand, by a camshaft sensor.

[0074] Here we consider an internal combustion engine comprising, on the one hand, a crankshaft, a first target associated with this crankshaft and a crankshaft position sensor cooperating with said first target, and, on the other hand, a camshaft, a second target associated with said camshaft and a camshaft position sensor cooperating with said second target.

[0075] In a known manner, due, on the one hand, to the nature (which may be) different of the sensors used in cooperation with the crankshaft target and the camshaft target, and, on the other hand, to the distinct rotation speeds of the crankshaft and the camshaft, it is known to determine a corrective angular value to know the exact position of the camshaft relative to the crankshaft from the signal provided by the camshaft sensor.

[0076] A first step 100 corresponds to the determination of the law which exists, on the one hand, between the corrective angular values ​​and the engine speed and, on the other hand, between the corrective angular values ​​and the engine temperature. This law is substantially linear and it is this hypothesis which is made subsequently. It is therefore appropriate to determine the slopes of the lines representing the variation of the corrective angular value as a function of the engine speed (PRPM slope) and as a function of the engine temperature (PTEMP slope). Preferably, these values ​​are determined by tests on a standard car. However, other methods can be envisaged, for example by simulation. It is also possible to envisage the creation of a table grouping the slope values ​​as a function of the sensors used. It is then sufficient for this first step 100 to read the values ​​in said table.The PRPM and PTEMP values ​​will then be stored in a memory of a management unit of the engine in question.

[0077] A second step 200 is a calibration step. This involves, preferably as early as possible, determining a triplet (corrective calibration angular value; calibration engine speed; calibration engine temperature) for the engine in question. This second step also provides for the storage of this triplet in a memory of the aforementioned engine management unit.

[0078] This second step 200 is carried out once and for all, preferably at the first start-up of the engine. In general, other calibrations are carried out during this start-up.

[0079] A third step is carried out repeatedly, preferably as soon as the conditions are met to make a determination of a corrective angular value. This third step is subdivided into sub-steps to provide at the end the operating temperature of the engine.

[0080] A first sub-step 310 provides for a determination of a corrective operating angular value corresponding to the difference between an actual position of a tooth front of the second target and a theoretical position of said tooth front under known engine speed conditions. During this first learning sub-step 310, the engine speed preferably varies little (for example + / - 1% or + / - 2%) and the average speed (or average speed) during said sub-step is stored.

[0081] A second sub-step 320 provides for a determination of a reference engine speed NRef and the calculation, on the one hand, of a corrective angular calibration value equivalent to the angular calibration value for the engine speed NRef and, on the other hand, of a corrective angular operating value equivalent to the angular operating value for the engine speed NRef. It is therefore provided here on a graph representing the corrective angular values ​​and the engine speeds, to move on its isotherm the point (corrective angular calibration value; calibration engine speed) corresponding to the measurement made in the second step 200 and / or to move on its isotherm the point (corrective angular operating value; operating engine speed) to bring them onto the same straight line for which the engine speed is NRef.Preferably, the reference engine speed NRef will be chosen from one of the following two values: calibration engine speed or operating engine speed. In this case, only one point on the graph is moved.

[0082] A third sub-step 330 then corresponds to the calculation of an angular difference DA between the equivalent corrective calibration angular value and the equivalent corrective operating angular value. This difference DA corresponds to an angular value in °CRK, that is to say an angular difference measured at the crankshaft.

[0083] The fourth and final step 340 is then a step of determining the operating temperature of the engine from the angular difference DA by considering that at constant speed a corrective angular value varies linearly with the temperature of the engine according to the slope PTEMP, the operating temperature engine operation corresponding to the calibration temperature increased by the angular difference DA divided by the slope PTEMP.

[0084] The method described above is preferably implemented by an electronic unit on board a vehicle, for example a motor vehicle. This electronic unit can be called a management unit and is also known by the English acronym CPU. As illustrated schematically in [Fig.5], there is a vehicle V powered by an engine M, said engine being electronically managed by at least one electronic unit CPU. The engine M is an internal combustion engine comprising at least one camshaft which can be associated with a variable valve timing system, for example a variable valve timing system using an electric motor to vary the valve timing program. Industrial application

[0085] The present technical solution can be applied in particular in engine control.

[0086] In a completely original manner, it is proposed here to determine an engine temperature using only the sensors (and the associated electronics) associated with a crankshaft target and a camshaft target.

[0087] It is thus possible to allow normal management of the engine even in the event of failure of a temperature sensor intended to provide the temperature of the engine in question.

[0088] It is also possible here in the design of an engine to save a temperature sensor and to determine the engine temperature only as explained in the present disclosure.

[0089] The present disclosure is not limited to the proposed embodiments and the variants mentioned described above, only as examples, but it encompasses all the variants that a person skilled in the art may envisage within the framework of the protection sought.

Claims

1. Claims Method for determining an operating temperature of an internal combustion engine comprising, on the one hand, a crankshaft, a first target associated with this crankshaft and a crankshaft position sensor cooperating with said first target, and, on the other hand, a camshaft, a second target associated with said camshaft and a camshaft position sensor cooperating with said second target, said method comprising a preliminary calibration phase (200) with the following steps: - calibration of the engine by determining an initial corrective angular value corresponding to the difference between an actual position of a tooth front of the second target and a theoretical position of said tooth front under known or estimated conditions of temperature and engine speed, - storage of the initial corrective angular value, of a calibration temperature corresponding to the engine temperature during calibration, and of a calibration engine speed corresponding to a value representative of the engine speed during calibration, said method then comprising engine temperature measurement phases implementing the following steps: - determination of a corrective operating angular value corresponding to the difference between an actual position of a tooth front of the second target and a theoretical position of said tooth front, under known engine speed conditions corresponding to an operating engine speed, - considering that at constant temperature a corrective angular value varies linearly with the engine speed according to a first known slope (PRPM) depending on the type of engine, determination of a reference engine speed NRef and calculation, on the one hand, of a corrective angular calibration value equivalent to the angular calibration value for the reference engine speed NRef and, on the other hand, of a corrective angular operating value equivalent to the angular operating value for the reference engine speed NRef - calculation of an angular difference DA between the equivalent calibration corrective angular value and the equivalent operating corrective angular value, - determination of the engine operating temperature from the angular difference DA, considering that at constant speed a corrective angular value varies linearly with the engine temperature according to a second known slope (PTEMP) depending on the type of engine, the engine operating temperature corresponding to the calibration temperature increased by the angular difference DA divided by the second slope.

2. Method according to claim 1, characterized in that the calibration temperature is a measured temperature.

3. Method according to claim 1 or 2, characterized in that the preliminary calibration phase is carried out when the engine is first started.

4. Method according to one of claims 1 to 3, characterized in that the first slope (PRPM) of the linear function of the corrective angular value as a function of the engine speed at constant engine temperature, on the one hand, and the second slope (PTEMP) of the linear function of the corrective angular value as a function of the engine temperature at constant engine speed, on the other hand, are determined on a standard vehicle, and in that the value of the first slope (PRPM) and the value of the second slope (PTEMP) are stored.

5. Method according to one of claims 1 to 4, characterized in that the internal combustion engine is provided with a variable program distribution system acting on the angular position of a camshaft, and in that the corrective operating angular value is determined when the angular position of said camshaft is known.

6. Method according to claim 5, characterized in that the corrective operating angular value is determined when the engine speed corresponds to an idle speed and / or when the engine is in foot lift conditions.

7. Electronic system for managing an internal combustion engine, configured to implement all the steps of a method according to one of claims 1 to 6, and comprising: - a crankshaft sensor, configured to detect the passages of the relief fronts of a crankshaft target; - a camshaft sensor, configured to detect the passages of the relief fronts of a camshaft target; - a computer provided with an electronic memory, configured to: - receive as input data supplied by the crankshaft sensor and data provided by the camshaft sensor, - providing instructions for implementing the steps of a method according to one of claims 1 to 6, and - determining an engine temperature.

8. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to implement all the steps of a method according to one of claims 1

9. a o. Motor vehicle comprising an internal combustion engine with: - a crankshaft equipped with a target and associated with a crankshaft sensor, - a camshaft equipped with a target and associated with a camshaft sensor, characterized in that it comprises an electronic system according to claim 7.

10. Motor vehicle according to claim 9, characterized in that the internal combustion engine is equipped with a variable valve timing system.

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