Predictive maintenance method for the crankshaft sensor of a piston engine and associated module

Abstract

A method for predictive maintenance (P) of a magnetic crankshaft angular position sensor, the magnetic sensor being designed to generate a voltage signal whose envelope (E) has an amplitude that varies with the rotational speed of the crankshaft associated with the sensor in an internal combustion engine. The method comprises a step (Ed) for detecting wear of the magnetic sensor from a set of current parameters, the set of current parameters comprising at least one current engine rotational speed. The detection step comprises acquiring (a1) a current engine rotational speed, acquiring (a2) a current amplitude value, determining (Ec) the deviation between the current amplitude value of the voltage signal and a nominal operating range at the current rotational speed, and generating (Et) an alarm when the deviation exceeds a predetermined threshold. Abstract figure: Figure 2

Description

Title of the invention: Method for predictive maintenance of the crankshaft sensor of a piston engine and associated module Field of the invention

[0001] The present invention relates to the field of predictive maintenance of parts associated with a piston thermal engine. It relates in particular to the predictive maintenance of the rotation sensor of a crankshaft of such an engine. Prior art

[0002] The combustion 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.

[0003] 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.

[0004] 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.

[0005] 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.

[0006] 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 rotational 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 distributed around its periphery. The function of the crankshaft sensor is to transform the measured magnetic field into an electrical signal and thus to provide a potential signal on two wires connected to it. The crankshaft sensor is typically mounted near the flywheel which serves as a rotating target or supports such a target.

[0007] 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 markers, and which makes it possible to fix a reference for the crankshaft position. Such a signature generates a signal different from other references, which makes it possible to determine when the rotating target has completed a complete rotation.

[0008] 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 (36 marks plus two missing marks).

[0009] 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.

[0010] From the voltage data produced by the crankshaft sensor, the person skilled in the art knows how to calculate the rotational speed and the angular position of the crankshaft to obtain the basic data necessary for determining the injection point and adjusting the ignition advance point.

[0011] However, aging of the sensor leads to a reduction in its magnetic effect. As a result, the determination of the position by means of the magnet is less precise, teeth may appear missing after processing of the electrical signal, in particular by clipping.

[0012] The control unit is usually configured to detect such an alteration in the precision of the angular positioning of the crankshaft. In such a case, the angular position of the engine can be determined from the angular position of the camshaft, but the angular position of the engine thus determined is then less precise. When a command to inject fuel into the engine cylinders or to fire the spark plugs is carried out at the wrong time, this results in a loss of energy. In addition, instead of producing mechanical energy useful for driving the engine, the unburned fuel during a misfire, or poorly burned, contributes to an emission into the atmosphere of polluting gases. The engine thus operates in a degraded mode: the engine warning light comes on and the vehicle must be immobilized.

[0013] An aim of the invention is to propose a method for predictive maintenance of the target rotation sensor. Statement of the invention

[0014] To this end, there is proposed, according to a first aspect of the invention, a method for predictive maintenance of a magnetic crankshaft angular position sensor, the magnetic sensor being provided to generate a voltage signal whose envelope has an amplitude which varies with the rotation speed of said crankshaft associated with the sensor within a thermal engine.

[0015] The method is implemented by a calculation unit having undergone a modeling step comprising a determination of a nominal voltage operating range of the crankshaft sensor as a function of a set of parameters, the set of parameters comprising at least one rotation speed of the heat engine.

[0016] The method comprises a step of detecting the wear of the magnetic sensor from a set of current parameters, the set of current parameters comprising at least one current rotation speed of the heat engine, the detection step comprising: • an acquisition of a current rotation speed of the thermal engine, linked to a current rotation speed of the crankshaft, • an acquisition of a current value of the amplitude of the envelope of the voltage signal generated by the magnetic sensor, • a determination of a difference between said current amplitude value of the voltage signal and the nominal operating range, at said current rotation speed of the heat engine, and • generation of an alarm when the deviation is greater than a predetermined threshold.

[0017] According to one possibility, the current amplitude value of the voltage signal can be determined from an acquisition of the voltage generated by the crankshaft sensor over a predetermined time window.

[0018] In one embodiment, the current rotational speed of the heat engine can be determined from an acquisition of the voltage generated by the crankshaft sensor over a predetermined time window.

[0019] Preferably, the step of generating an alarm is followed by a step of replacing, or repairing, the crankshaft sensor carried out by a human operator.

[0020] Advantageously, the set of current parameters may further comprise a current temperature, the difference then being further determined from the current temperature. The set of calibration parameters may then further comprise calibration temperatures.

[0021] According to a second aspect of the invention, a predictive maintenance module is proposed for a magnetic crankshaft angular position sensor, the magnetic sensor being designed to generate a voltage signal whose envelope has an amplitude which varies with the rotation speed of the crankshaft associated with the sensor within a heat engine.

[0022] The module implements a calculation unit having undergone a modeling step comprising a determination of a nominal operating range in voltage of the crankshaft sensor as a function of a set of parameters, the set of parameters comprising at least one rotation speed of the thermal engine.

[0023] The module is further configured to detect wear of the magnetic sensor from a set of current parameters, the set of current parameters comprising at least one current rotation speed of the heat engine, the detection comprising: • an acquisition of a current rotation speed of the thermal engine, linked to a current rotation speed of the crankshaft, • an acquisition of a current value of the amplitude of the envelope of the voltage signal generated by the magnetic sensor, • a determination of a difference between the current amplitude value of the voltage signal and the nominal operating range at said current rotation speed of the heat engine, and • generation of an alarm when the deviation is greater than a predetermined threshold. Brief description of the figures

[0024] 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 method according to the invention, • [Fig.2] illustrates an embodiment of a module according to the invention and its physical environment, and • [Fig.3] includes a graph of the evolution of the rotation speed of a thermal engine and a graph of a voltage signal generated by a magnetic sensor. • [Fig.4] illustrates a nominal operating domain obtained by the process of [Fig.l]. Detailed description of the invention

[0025] 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 by compared to the state of the prior art.

[0026] There is now described, with reference to [Fig.l] and [Fig.2], an embodiment of a method P for predictive maintenance of a magnetic sensor S of crankshaft angular position A implemented by a calculation unit Uc, at the same time as a module M implementing a calculation unit Uc.

[0027] The magnetic sensor S is designed to generate a voltage signal whose envelope E has an amplitude which varies with the rotation speed of the crankshaft A associated with the sensor within a heat engine (see [Fig.3] below). The magnetic sensor S is typically associated with a magnetic target C mounted integral with the rotation of the crankshaft A.

[0028] The calculation unit undergoes a calibration step Em, the calibration step Em comprising a determination of a nominal voltage operating range of the crankshaft sensor as a function of a set of parameters. The calibration step may also be called a “modeling step”.

[0029] According to one embodiment, the calibration step Em is carried out prior to the implementation of the method according to the invention, for example on a test vehicle representative of another vehicle equipped with the module M according to the invention. According to a variant, the calibration step Em can be implemented on a vehicle whose crankshaft magnetic sensor S is new, for example after the replacement of the magnetic sensor.

[0030] The set of parameters comprising at least one rotation speed of the thermal engine.

[0031] The nominal operating range is for example determined by a curve expressing the maximum voltage delivered by the magnetic sensor S as a function of the set of parameters.

[0032] [Fig. 3] illustrates an example of a graph G1 of the evolution of the rotation speed of a heat engine as a function of time and a graph G2 of a voltage signal generated at the same times by a magnetic sensor, said voltage signal being an alternating signal whose amplitude is delimited by an envelope E.

[0033] [Fig.4] illustrates an example of a nominal operating range obtained during the calibration step. The maximum voltage is plotted on the abscissa axis while the rotational speed of the engine is plotted on the ordinate axis. The curve results from segments that connect a set of calibration points. It is observed that the maximum voltage delivered by the magnetic sensor S increases with the increase in the rotational speed of the thermal engine.

[0034] The module M is configured to implement a step Ed of detecting the wear of the magnetic sensor S from a set of current parameters, the set of current parameters comprising at least one current speed of rotation of the heat engine.

[0035] The detection step comprises an acquisition al of a current rotation speed of the thermal engine, linked to a current rotation speed of the crankshaft (A).

[0036] The current rotational speed of the engine can be determined from the voltage generated by the crankshaft sensor S over a predetermined time window. This method is also known to those skilled in the art.

[0037] According to one variant, the current rotational speed of the engine may be received from the engine control unit ECU configured to determine the current rotational speed of the engine.

[0038] The detection step further comprises a step a2 of acquiring a current amplitude value of the voltage signal generated by the magnetic sensor.

[0039] It is for example possible to carry out a measurement of the voltage on a wire over a period of a predetermined tooth of the target C. The period can be identified by analysis of the succession of rising and falling edges, according to procedures known to those skilled in the art.

[0040] According to a variant, the current amplitude value of the voltage signal can be received from an engine control unit (ECU), configured to determine the current voltage.

[0041] The detection step further comprises a determination Ec of a difference between the current voltage value and the nominal operating range, at the current rotation speed of the heat engine.

[0042] The difference between the current voltage value and the nominal operating range is for example the Euclidean distance, that is to say the length separating the current amplitude value of the voltage signal and the nominal operating range.

[0043] The current parameter set may include a current temperature. The current temperature may be measured, for example, by means of temperature sensors. The module may alternatively receive the current temperature information from the engine control unit ECU. This is usually the oil or cooling water temperature, which are closest to the sensor value and the crankshaft target.

[0044] When the set of calibration parameters does not include calibration temperatures and the set of current parameters includes a current temperature, the deviation is further determined from the current temperature.

[0045] When the set of calibration parameters includes calibration temperatures and the set of current parameters includes a current temperature, the deviation can be directly determined.

[0046] The method P further comprises a step of generating Et an alarm when the deviation is greater than a predetermined threshold.

[0047] The step of generating Et an alarm can be followed by a step of repairing or replacing Er the crankshaft sensor S carried out by a human operator.

[0048] 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.

[0049] Finally, the method according to the invention and the corresponding module can be implemented with sensors other than magnetic, provided that the sensor is sensitive to the passage of reference elements of the target.

[0050] 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. In addition, the various characteristics, forms, variants and embodiments of the invention can be associated with each other in various combinations to the extent that they are not incompatible or exclusive of each other.

Claims

Claims

1. Method for predictive maintenance (P) of a magnetic sensor (S) of angular position of crankshaft (A), the magnetic sensor being provided to generate a voltage signal whose envelope (E) has an amplitude which varies with the rotation speed of said crankshaft (A) associated with said sensor within a heat engine, the method being implemented by a calculation unit (Uc) having undergone a modeling step (Em) comprising a determination of a nominal voltage operating range of the crankshaft sensor as a function of a set of parameters, said set of parameters comprising at least one rotation speed of the heat engine, the method comprising a step of detecting (Ed) the wear of said magnetic sensor from a set of current parameters, said set of current parameters comprising at least one current rotation speed of the heat engine,said detection step comprising: an acquisition (al) of a current rotation speed of the heat engine, linked to a current rotation speed of the crankshaft (A), an acquisition (a2) of a current amplitude value of the envelope (E) of the voltage signal generated by the magnetic sensor, a determination (Ec) of a difference between said current amplitude value of the voltage signal and said nominal operating range at said current rotation speed of the heat engine, and a generation (Et) of an alarm when the difference is greater than a predetermined threshold.,

2. Method according to the preceding claim, in which the current amplitude value of the voltage signal is determined from an acquisition of the voltage generated by the crankshaft sensor (S) over a predetermined time window.

3. Method according to one of the two preceding claims, in which the current rotation speed of the heat engine is determined from an acquisition of the voltage generated by the crankshaft sensor (S) over a predetermined time window.

4. Method according to any one of the preceding claims, in which the step of generating an alarm is followed by a step of replacing (Er) the crankshaft sensor (S) carried out by an operator human.

5. A method according to any preceding claim, wherein said set of current parameters further comprises a current temperature, the deviation being further determined from said current temperature.

6. Method according to the preceding claim, in which the set of calibration parameters further comprises calibration temperatures.

7. Module (M) for predictive maintenance of a magnetic sensor (S) of angular position (A) of a crankshaft, the magnetic sensor being provided to generate a voltage signal whose envelope (E) has an amplitude which varies with the rotation speed of said crankshaft (A) associated with said sensor within a heat engine, the module implementing a calculation unit (Uc) having undergone a modeling step (Em) comprising a determination of a nominal voltage operating range of the crankshaft sensor as a function of a set of parameters, said set of parameters comprising at least one rotation speed of the heat engine, the module being configured to detect wear of said magnetic sensor from a set of current parameters, said set of current parameters comprising at least one current rotation speed of the heat engine,said detection comprising: an acquisition (al) of a current rotation speed of the thermal engine, linked to a current rotation speed of the crankshaft (A), an acquisition (a2) of a current amplitude value of the envelope (E) of the voltage signal generated by the magnetic sensor, a determination (Ec) of a difference between said current amplitude value of the voltage signal and said nominal operating range at said current rotation speed of the thermal engine, and a generation (Et) of an alarm when the difference is greater than a predetermined threshold.,

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