Predictive maintenance method for a standardized signal crankshaft sensor

Abstract

Predictive maintenance method (P) for a crankshaft angular position sensor (S) (A) intended to be started by a battery-powered starter, the sensor being intended to generate a voltage signal having falling edges corresponding to the detection of rising edges of a series of teeth of a toothed wheel mounted fixed to the crankshaft rotation axis, the method being implemented by a computing unit (Uc) configured to detect a rising, or falling, edge of the voltage signal, the method comprising the following steps, implemented after detection of vehicle start-up: / a / measure (Em) a battery voltage value at crankshaft start-up, / b / acquire (Ea) a first current crankshaft rotation speed by processing the voltage signal,After detecting the vehicle starting / c / , generate (Eg) an alarm when the first determined rotation speed exceeds a predetermined threshold value for said battery voltage value. Figure of the abstract: Figure 2,

Description

Title of the invention: Predictive maintenance method for a standardized signal crankshaft sensor. Field of the invention

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

[0002] The combustion cycle of an internal engine comprises several phases whose occurrence is staggered in time for each cylinder, the synchronized control of the valves of the internal combustion engine being achieved 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 driven in rotation by the crankshaft. The crankshaft is a mechanical device which, by means of a connecting rod, transforms the rectilinear motion of a piston into a continuous rotational motion, 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 by means of a toothed wheel, also called a crankshaft target, which is fixed to the crankshaft for rotation. The wheel is associated with a dedicated sensor, called a crankshaft sensor, whose ultimate role is to determine the angular position and rotational speed of the toothed wheel. The sensor is equipped with a sensing element. For example, the wheel is metallic and the sensing element is capable of detecting metal, such as a Hall effect sensor. The wheel profile typically includes a target with markings, also called teeth, distributed around its periphery. The crankshaft sensor's function is to transform the magnetic field measured by an internal magnet into an electrical signal. According to prior art, some 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.

[0007] As illustrated by [Fig. 1], in which a normalized signal graph is shown in the lower part, the passage of a tooth of the gear associated with the crankshaft generates an electrical pulse of predetermined duration on the signal wire. More precisely, the passage of a mechanical rising edge corresponds to the generation of an electrical falling edge, while the passage of a mechanical falling edge is ignored.

[0008] The predetermined duration is representative of the direction of rotation. A forward direction of rotation is illustrated on the left side of the figure, and the predetermined duration of the pulse is then typically 45 ps for a forward direction of rotation. A reverse direction of rotation is illustrated on the right side of the figure, and the predetermined duration of the rotation is then typically 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 (otherwise regular) profile, usually corresponding to two missing reference marks, which allows a reference to be established for the crankshaft position. Such a signature generates a signal different from the other reference marks, which makes it possible to determine when the rotating target has completed a full rotation.

[0010] A commonly used rotating target comprises 60 markers distributed around the periphery of the rotating target, and two consecutive markers 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 markers plus two missing markers).

[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 that can subsequently be sent to the engine control unit. The voltage variations include rising and falling edges forming a periodic signal synchronized with the passage of the markers in front of the sensor.

[0012] From the voltage data produced by the crankshaft sensor, a person skilled in the art can calculate the rotational speed and angular position of the crankshaft to obtain the basic data necessary for determining the injection point and setting the ignition advance point.

[0013] However, the aging of the sensor leads to a decrease in its magnetic effect. Consequently, position determination using the magnet is less precise, as teeth may appear missing after processing the electrical signal, particularly through clipping.

[0014] The control unit is usually configured to detect such an alteration in the accuracy of the crankshaft's angular positioning. In such a case, the engine's angular position can be determined from the angular position of the shaft. Camshafts, however, mean that the angular position of the engine thus determined is less precise. When a fuel injection command to the engine cylinders or spark plug ignition is executed at the wrong time, it results in a loss of energy. Furthermore, instead of producing useful mechanical energy to drive the engine, the unburned or incompletely burned fuel from a misfire contributes to the emission of polluting gases into the atmosphere. The engine then operates in a degraded mode: the check engine light illuminates and the vehicle must be stopped.

[0015] One object of the invention is to propose a method for predictive maintenance of the target rotation sensor. Description of the invention

[0016] To this end, according to a first aspect of the invention, a predictive maintenance method for a crankshaft angular position sensor intended to be started by a starter powered by a battery is proposed, the sensor being intended to generate a voltage signal comprising rising and falling edges corresponding to rising and falling edge detections of a series of teeth of a toothed wheel mounted fixed to the axis of rotation of the crankshaft.

[0017] The method is implemented by a computing unit configured to detect a rising, or falling, edge of the signal, and comprises the following steps, implemented after detection of the vehicle starting: • / a / measure a battery voltage value, • / b / determine a first current crankshaft rotation speed by processing of said voltage signal, • / c / generate an alarm when the first determined rotation speed is greater than a predetermined threshold value for said measured battery voltage value.

[0018] Advantageously, the / c / alarm generation step is implemented after a post-processing step in which it is determined whether the vehicle start is carried out in a signature area of ​​the gear, the alarm generation being blocked if it is determined that the vehicle start has taken place in the signature area.

[0019] According to one possibility, prior to step / a / of acquiring a measurement (Em) of a battery voltage, the calculation unit undergoes a modeling step comprising a determination of a threshold value corresponding to a maximum crankshaft rotation speed at the moment of passage of a first tooth, for said battery voltage value.

[0020] According to a second aspect of the invention, a predictive maintenance module for a magnetic crankshaft angular position sensor is proposed, intended for The engine is started by a starter motor powered by a battery. The sensor is designed to generate a signal with falling electrical edges corresponding to the detection of rising mechanical edges of a series of teeth on a gear mounted directly to the crankshaft's rotation axis. Only one of the mechanical edges generates an electrical edge, as its signal is more precise.

[0021] The module includes a processing unit configured to detect a falling edge of the voltage signal. The processing unit is further configured to, after detecting the vehicle starting: • Measure the battery voltage value at crankshaft start-up, • Determine a first current crankshaft rotation speed by processing said signal, • generate an alarm when the first determined rotation speed is greater than a predetermined threshold value for said measured battery voltage value. Brief description of the figures

[0022] Other features and advantages of the invention will become apparent upon reading the detailed description that follows, for an understanding of which reference should be made to the accompanying drawings, in which: • [Fig. 1] illustrates in its lower part a voltage signal graph generated from the passage of teeth in front of a sensor, • [Fig. 2] illustrates an embodiment of a process according to the invention, • [Fig. 3] illustrates an embodiment of a module according to the invention and its physical environment, • [Fig. 4] includes a graph showing crankshaft rotation speeds of a first tooth depending on battery voltage value. Detailed description of the invention

[0023] The embodiments described below are not in any way limiting; variants of the invention may, in particular, be considered comprising only a selection of the features described, hereinafter isolated from the other features described, if this selection of features is sufficient to confer a technical advantage or to differentiate the invention from the prior art. This selection comprises at least one feature, preferably functional without structural details, or with only a portion of the structural details if this portion alone is sufficient to confer a technical advantage or to differentiate the invention from the prior art.

[0024] An embodiment of a predictive maintenance method P for a magnetic position sensor S is now described with reference to [Fig. 2] and [Fig. 3]. crankshaft angular A implemented by a calculation unit Uc, at the same time as a module M implementing a calculation unit Uc.

[0025] The magnetic sensor S is for example a bidirectional CPDD type sensor, for the English Crankshaft Position and Direction Determination, capable of generating pulsed voltage signals of different width depending on the direction of rotation of the crankshaft.

[0026] The magnetic sensor S is typically associated with a magnetic target C mounted fixed to the rotation of the crankshaft A.

[0027] The computing unit Uc is configured to detect a rising edge, respectively a falling edge, of the signal.

[0028] It is thus possible to determine the direction of rotation by analyzing the signal generated by the magnetic device. For example, with the sensor considered, the falling and rising electrical edges are separated by a duration of 45 ps when the toothed wheel moves in one direction of rotation, and by a duration of 90 ps when the toothed wheel moves in the other direction of rotation.

[0029] According to the invention, the method comprises the following steps, after detection of the vehicle starting: • / a / measure Em, a battery voltage value, • / b / determine Ea a first current rotational speed of the crankshaft by voltage signal processing, • Here generate Eg an alarm when the first determined rotation speed is greater than a predetermined threshold value for said measured battery voltage value.

[0030] The computing unit is configured to execute steps / a / , / b / and Here.

[0031] Steps a and b relate to the same or almost the same measurement instant.

[0032] Vehicle starting detection, i.e., crankshaft start detection, can be achieved by acquiring the vehicle battery voltage signal. Indeed, crankshaft start-up causes a significant voltage drop in the battery, indicating the moment the crankshaft starts. Typically, the battery voltage signal is acquired every millisecond.

[0033] Step / b / of acquiring the first current speed may, for example, include: • an acquisition by the sensor at a current instant, of a first rising edge, respectively falling edge, and a start of a timer, then • an acquisition by the sensor at a second current instant of a second rising edge, respectively falling edge, and a stopping of the timing.

[0034] According to one possibility, the Here step of generating an alarm is implemented after a post-processing step in which it is determined whether the vehicle start is carried out in a signature zone of the gear, the generation of an alarm being blocked if it is determined that the vehicle start was carried out in the signature zone.

[0035] The initial rotational speed can be determined from knowledge of the crankshaft target geometry and the two current times of front detection. For example, denoting t1 as the first current time and t2 as the second current time, when the target is a 60-2 target, the average speed is 6 / (t2-t1) when the start occurs outside the signature zone.

[0036] Prior to step / a / of measuring a voltage value, the calculation unit may undergo a modeling step (Ei) in which said threshold value of the first rotation speed is determined, as a function of the battery voltage value.

[0037] The / c / step of generating an alarm can be followed by a step of replacing the crankshaft sensor S performed by a human operator.

[0038] According to one embodiment, the modeling step can be carried out prior to implementing 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 another variant, the calibration step can be carried out on a vehicle whose crankshaft magnetic sensor S is new, for example after the magnetic sensor has been replaced.

[0039] Figure 4 illustrates an example of a graph where the x-axis is the battery voltage in volts and the y-axis is the crankshaft rotation speed in revolutions per minute.

[0040] Five points XI, X2, VI, V2, T are placed on the graph, whose coordinates are: • XI: 7.5 V; 71 rpm • X2: 9.6 V; 98 rpm • VI: 6.9 V; 52 rpm • V2: 9.5 V; 78 rpm • T: 8.5 V; 95 rpm.

[0041] Points VI and V2 are points for which the first tooth is not missed while points XI and X2 are points for which the tooth is missed.

[0042] Experience shows that the set of points for which the first tooth is not missed can be separated by a straight line D from the set of points for which the first tooth is missed.

[0043] Thus, given a value of battery voltage at crankshaft start, the right defines a predetermined threshold value for said value of battery voltage.

[0044] It is thus understood that point T corresponds to a first missed tooth. Indeed, the first determined rotation speed of 95 rpm is higher than the predetermined threshold value for a voltage of 8.5 which is approximately 85 rpm.

[0045] 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 computing unit UC or by the engine control unit ECU which then replaces the computing unit UC.

[0046] 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.

[0047] Of course, the invention is not limited to the examples just described, and many modifications can be made to these examples without departing from the scope of the invention. Furthermore, the various features, forms, variants, and embodiments of the invention can be combined in various ways, provided they are not incompatible or mutually exclusive.

Claims

Claims

1. Method for predictive maintenance (P) of a crankshaft angular position sensor (S) (A) intended to be started by a starter powered by a battery, the sensor being intended to generate a voltage signal comprising falling edges corresponding to detections of rising edges of a series of teeth of a toothed wheel mounted integrally with the axis of rotation of the crankshaft, the method being implemented by a calculation unit (Uc) configured to detect a falling edge of said voltage signal, the method comprising the following steps, implemented after detection of the starting of the vehicle: / a / measuring (Em) a battery voltage value, / b / determining (Ea) a first current rotation speed of the crankshaft by processing said voltage signal, / c / generating (Eg) an alarm when the first determined rotation speed is greater than a predetermined threshold value for said measured battery voltage value.

2. Method according to the preceding claim, in which step / c / of generating an alarm is implemented after a post-processing step in which it is determined whether the vehicle is started in a signature zone of the toothed wheel, the generation of an alarm being blocked if it is determined that the vehicle is started in the signature zone.

3. Method according to one of the two preceding claims, in which the calculation unit (Uc) has undergone, prior to the step / a / of measuring (Em) a battery voltage value, a modeling step (Ei) in which said threshold value of the first rotation speed is determined, as a function of the battery voltage value.

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

5. Module (M) for predictive maintenance of a magnetic sensor (S) of angular position (A) of crankshaft intended to be started by a starter powered by a battery, the sensor being designed to generate a voltage signal comprising falling edges corresponding to detections of rising edges of a series of teeth of a toothed wheel mounted integrally with the axis of rotation of the crankshaft the module comprises a calculation unit (Uc) configured to detect a falling edge of said voltage signal, and to, after detecting the vehicle starting: measure a battery voltage value when the crankshaft is started, determine a first current rotation speed of the crankshaft by processing said signal, generate an alarm when the first determined rotation speed is greater than a predetermined threshold value for said measured battery voltage value.

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