Determining the direction of rotation of a crankshaft from a signal generated by a magnetic crankshaft sensor

Abstract

The method describes a technique for determining the direction of rotation of a crankshaft driving a camshaft in an internal combustion engine with at least four cylinders, using a magnetic sensor for the crankshaft and another for the camshaft. The crankshaft sensor detects the passage of teeth on a target mounted on the crankshaft, while the camshaft sensor detects the teeth on its target. The method begins with calibration to determine a reference angular deviation. Then, upon detection of a camshaft face, it is checked whether a local minimum of crankshaft speed is observed. If so, two angular distances are calculated between the camshaft faces and the minimum speed to compare with the angular deviation, thus determining the direction of crankshaft rotation. Figure for publication: Figure 1

Description

Title of the invention: Determining the direction of rotation of a crankshaft from a signal generated by a magnetic crankshaft sensor. Scope of the invention

[0001] The present invention relates to the field of sensor systems in internal combustion engines, and more particularly, to a method and device for detecting the direction of rotation of a crankshaft from a signal generated by a magnetic crankshaft sensor. The invention finds particular application in heavy vehicles and generators, where accurate detection of the direction of rotation is crucial for proper engine operation and safety. Prior art

[0002] The cycle of an internal combustion engine comprises several phases whose occurrence is staggered in time for each cylinder, the synchronized control of the valves of the heat 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 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 sensitive element. For example, the wheel is metallic and the sensitive element is capable of detecting metal, like an inductive sensor. The wheel profile typically includes a target with markings distributed around its periphery. The crankshaft sensor's function is to transform the measured magnetic field into an electrical signal and thus provide a potential signal on two wires are 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 (otherwise regular) profile, usually corresponding to two missing reference marks, which allows a reference point 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.

[0008] 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 (34 markers plus two missing markers).

[0009] Magnetic type crankshaft sensors are commonly used because of their simplicity and robustness.

[0010] 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 via electrical wires. The voltage variations include rising and falling edges forming a periodic signal synchronized with the passage of the markers in front of the sensor.

[0011] However, these sensors do not inherently offer the ability to detect the direction of rotation of the motor.

[0012] It is known to attempt to determine the direction of rotation of the crankshaft by observing a sequence comprising an acquisition of a sequence of signal fronts generated by the magnetic type crankshaft sensor and a determination of the passing of the signature.

[0013] However, it is therefore necessary to wait for a complete crankshaft rotation to ensure that the signature has passed, i.e. 360 degrees CRK.

[0014] During this 360° rotation CRK, half a turn of the camshaft was completed, and two (for a 4-cylinder engine) or three (for a 6-cylinder engine) intake / compression / combustion / exhaust phases were performed on the different cylinders. One object of the invention is to provide a method for detecting the direction of rotation of a crankshaft in an internal combustion engine by means of a magnetic sensor for the crankshaft's angular position. Description of the invention

[0015] One objective of the invention is achieved with a method for determining the direction of rotation of a crankshaft driving a camshaft of an internal combustion engine internally equipped with at least 4 cylinders by means of a magnetic crankshaft sensor and a camshaft sensor, the camshaft sensor being configured to generate a camshaft signal with edges, in response to detections of teeth crossing a camshaft target, the camshaft being mounted rotationally fixed to the camshaft, provided with a camshaft target, said target having X+1 teeth of which X are angularly equidistant, X being a multiple of the number of cylinders. The additional tooth, referred to as +1, represents the asymmetry of the camshaft.

[0016] Each tooth can be considered as an excess of material on the target or, conversely, a hollow in the material.

[0017] Advantageously, the X equally spaced teeth must not be positioned in a zone of + / - 5°CRK around top dead center (minimum speed).

[0018] Since each tooth of the camshaft target is identical, usually only one edge among the rising or falling edge is transmitted to the control unit.

[0019] According to the invention, the crankshaft sensor is configured to generate a crankshaft signal comprising edges, in response to tooth passage detections of a crankshaft target mounted to rotate with the crankshaft, the method comprising the following steps: an initial calibration step to determine a so-called decision angular deviation, then, upon receiving a current camshaft edge: determine the position of the tooth midpoint, and if so, store it (for later use), determine if a local crankshaft speed minimum has occurred between the position of the midpoint of the previous camshaft tooth and the current position of the tooth midpoint, and if so: • determine a so-called reference angular position of said crankshaft corresponding to the local minimum speed from the crankshaft signal, • determine a first angular distance (Dl) between the angular position of the middle of the previous camshaft tooth and the reference angular position, • determine a second angular distance (D2) between the reference angular position and the angular position of the midpoint of the current camshaft tooth, • determine the direction of rotation of said crankshaft by comparing the first angular distance and the second angular distance with the decision angular deviation.

[0020] A local minimum speed is located near a top dead center. The upward and downward movement of the pistons generates an acyclic motor.

[0021] Advantageously, the angular decision gap can be determined from angular positions of the teeth of the crankshaft target.

[0022] According to a second aspect of the invention, a module is proposed for determining the direction of rotation of a crankshaft driving a camshaft of an internal combustion engine of a vehicle equipped with at least 4 cylinders by means of a magnetic type crankshaft sensor and a camshaft sensor,

[0023] the camshaft sensor being configured to generate a camshaft signal comprising edges, in response to detections of tooth passage of a camshaft target of type X+l mounted rotationally fixed to the camshaft, said target having X+l teeth of which X are angularly equidistant, X being a multiple of the number of cylinders,

[0024] the crankshaft sensor being configured to generate a crankshaft signal comprising edges, in response to detections of tooth passage of a crankshaft target mounted fixed to the rotation of the crankshaft,

[0025] the vehicle comprising a computer (Cu) configured to implement the following steps:

[0026] • an initial calibration step to determine a so-called decision angular deviation, Then,

[0027] • upon receiving a current camshaft face:

[0028] to determine if a local minimum crankshaft speed has appeared between the front previous camshaft and the current front

[0029] or if so,

[0030] determine a so-called reference angular position of said crankshaft corresponding to the local minimum speed from the crankshaft signal,

[0031] determine a first angular distance (Dl) between the previous angular position of the camshaft front and the reference angular position,

[0032] determine a second angular distance (D2) between the reference angular position and the current angular position of the camshaft face,

[0033] determine the direction of rotation of said crankshaft by comparing the first angular distance and the second angular distance with the decision angular deviation. Brief description of the figures

[0034] 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:

[0035] [Fig-1] illustrates an embodiment of a module according to the invention and its physical environment,

[0036] [Fig.2] illustrates an embodiment of a process according to the invention,

[0037] [Fig.3] is a timing diagram of an example of a so-called 12+1 target for the implementation of the invention, and

[0038] [Fig.4] is a timing diagram of another example of a so-called 6+1 target for the implementation of the invention. Detailed description of the invention

[0039] 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.

[0040] An embodiment of a process P is now described with reference to [Fig. 1].

[0041] for determining the direction of rotation of a crankshaft A driving a camshaft of an internal combustion engine equipped with at least 4 cylinders by means of a magnetic type crankshaft sensor and a camshaft sensor at the same time as a module M implementing the method.

[0042] The camshaft sensor is configured to generate a camshaft signal comprising edges, in response to detections of tooth passage of a camshaft target of type X+l mounted fixed in rotation to the camshaft, said target having X+l teeth of which X are angularly equidistant, X being a multiple of the number of cylinders.

[0043] The crankshaft sensor is configured to generate a crankshaft signal with edges, in response to detections of tooth passage of a crankshaft target mounted fixed to rotate with the camshaft.

[0044] The process P according to the invention includes an initial calibration step Ec to determine a so-called decision angular deviation.

[0045] The method P further includes, upon receipt of a current camshaft front, a step Et to determine if a local minimum of crankshaft speed has appeared between the previous camshaft front and the current front.

[0046] When this is the case, the process comprises the following steps: • Determine the position of the tooth's midpoint; if so, store it. • / a / Determine a reference angular position of the crankshaft. corresponding to the local minimum speed from the crankshaft signal, • / b / determine a first angular distance (Dl) between the position angular position of the middle of the previous camshaft tooth and the reference angular position, • / c / determine a second angular distance (D2) between the position angular reference and the angular position of the center of the current camshaft tooth, • / d / determine the direction of rotation of said crankshaft by comparison with the first angular distance and second angular distance with the angular deviation of decision.

[0047] The determination of a reference angular position of the crankshaft corresponding to a local minimum speed is known to those skilled in the art and the reader may advantageously refer to publication WO2002045080.

[0048] This determination consists of generating a velocity curve in the vicinity of the top dead center of combustion of each of the cylinders and approximating this curve by a parabola obtained using the mathematical method of least squares. Knowing the minimum of the parabola corresponding to the minimum crankshaft speed, the angular position of the crankshaft corresponding to the minimum speed is then determined.

[0049] The angular decision deviation can, for example, be determined from the angular positions of the crankshaft target teeth. The angular deviations between the angular positions of the midpoints of the camshaft target teeth surrounding the minimum speed position are thus evaluated for all the minimum speeds occurring during a 720°CRK engine cycle (there will be as many as there are cylinders in the engine).

[0050] The initial calibration step may for example include a step of measuring a first angular distance between a midpoint of a tooth of the camshaft target and a minimum speed and then a second angular distance between the minimum speed and the midpoint of a tooth of the next camshaft target, in the forward direction of rotation of the engine. Target 12+1

[0051] In the context of a 12+1 target associated with 6 cylinders, one can for example measure a first angular distance equal to 23° and a second angular distance equal to 37°.

[0052] In other words, the angular distance measured between the position of the minimum speed and the position of the middle of the tooth of the previous camshaft target measures 23°, while the angular distance between the position of the minimum speed and the position of the middle of the tooth of the next camshaft target measures 37°,

[0053] Given the symmetry of the camshaft target, and the multiplicity of the number of faces relative to the number of cylinders, this profile is repeated. Taking the average of the two angular distances, a so-called decision angular deviation of 30° can be determined.

[0054] During step / d / , when the angular distance DI is less than 30°, a forward direction of rotation of the motor is inferred, while when the angular distance D2 is greater than 30°, a backward direction of rotation of the motor is deduced. Target 6+1

[0055] In the context of a 6+1 target associated with 6 cylinders, one can, for example, measure a first angular distance of 80° and a second angular distance of 40° for the tooth midlines regularly distributed on the target. For the additional front, one can, for example, measure a first angular distance of 50° and a second angular distance of 40°.

[0056] Taking the average of the two closest angular distances, we can decide on an angular difference called the decision angle equal to 45°.

[0057] During step / d / , when the angular distance DI is greater than 45°, a forward direction of rotation of the motor is inferred, while when the angular distance D2 is less than 45°, a backward direction of rotation of the motor is deduced. More generally

[0058] The determination, the so-called decision angular deviation can be determined from the engine timing diagram representing the teeth of the crankshaft and camshaft targets as a function of the absolute position of the crankshaft.

[0059] For example, [Fig.3] illustrates the theoretical timing diagram of target 12+1. A first line illustrates the angular evolution of a signal generated by the crankshaft sensor between 0 and 720°CRK, a third line illustrates the angular evolution of a signal generated by the camshaft sensor and a second line illustrates events generated by the control unit.

[0060] As can be read on [Fig.3], the angular positions of the teeth of the camshaft target are 32°, 42°, 92°, 102°, 152°, 162°, 212°, 222°, 272°, 282°, 332°, 342°, 392°, 402°, 452°, 462°, 512°, 522°, 572°, 582°, 632°, 642°, 652°, 662°, and 692°, 702°.

[0061] Each tooth thus measures 10°, and each midpoint of teeth has an angular position close to 37°, 97°, 157°, 217°, 277°, 337°, 397°, 457°, 517°, 577°, 637°, 657°, 697°

[0062] By constructing such a target, the first top dead center, that is to say the first minimum speed, is expected between the angles 97° and 157° at the 120° position, between the angles 217° and 277° at the 240° position, between the angles 337° and 397° at the 360° position, between the angles 457° and 517° at the 480° position, between the angles 577° and 637° at the 600° position, and between the angles 697° and 37° at the 0 degree position.

[0063] A theoretical deviation of 23° is therefore determined between an angular position of a camshaft target preceding a minimum speed and the minimum speed, and a theoretical angular deviation of 37° between the minimum speed and the angular position of the camshaft target following the minimum speed.

[0064] As in the previously described measurements, by averaging the two angular distances, a so-called decision angular deviation of 30° can be determined based on the theoretical knowledge of the target's timing diagram. According to another example, [Fig. 4] illustrates the theoretical timing diagram of the 6+1 target. A first line illustrates the angular evolution of a signal generated by the crankshaft sensor between 0 and 720°CRK, a third line illustrates the angular evolution of a signal generated by the camshaft sensor, and a second line illustrates events generated by the control unit.

[0065] As can be seen in [Fig. 3], the angular positions of the camshaft target teeth are 32°, 48°, 152°, 168°, 272°, 288°, 392°, 408°, 512°, 528°, 542°, 558°, 632°, 648°. The angular positions of the tooth midpoints are then 40°, 160°, 280°, 400°, 520°, 550°, 660°.

[0066] By constructing such a target, the first top dead center, that is to say the first minimum speed, is expected between the angles 40° and 160° at the 120° position, between the angles 160° and 280° at the 240° position, between the angles 280° and 400° at the 360° position, between the angles 400° and 520° at the 480° position, between the angles 550° and 660° at the 600° position and between the angles 660° and 40° at the 0 degree position.

[0067] A theoretical deviation of 50° is therefore determined between an angular position of the middle of the tooth of a camshaft target preceding a minimum speed and the minimum speed, i.e. the minimum of the possible deviations 80° and 50°, and a theoretical angular deviation of 40° between the minimum speed and the angular position of the middle of the tooth of the camshaft target following the minimum speed.

[0068] As in the previously described measurements, taking the average of the two angular distances, one can decide on an angular deviation called the decision angle equal to 45° from the theoretical knowledge of the target's chronogram.

[0069] It can be noted that a minimum speed, corresponding to top dead center number 5, occurs at the angular position 480°, between the angular position 400° and the angular position 520°. We therefore determine two theoretical deviations, respectively of 80° and 40° between the angular position of the minimum speed and the two angular positions of the targets surrounding it.

[0070] It can also be noted that a minimum speed, corresponding to top dead center number 6, occurs at angular position 600°, between angular position 550° and angular position 640°. Two theoretical deviations are therefore determined, respectively of 50° and 40° between the angular position of minimum velocity and the two angular positions of the targets surrounding it.

[0071] Also, the choice of the 50° gap as a reference is still suitable when moving a +1 tooth.

[0072] Reading the chronogram from left to right thus teaches the temporal evolution of the fronts when the engine rotates in a direction called forward direction.

[0073] Of course, when the engine rotates in a direction called reverse direction, opposite to the forward direction, the temporal evolution of the fronts is taught by reading the chronogram from right to left.

[0074] Also, for example for target 12+1, the measurement of a first angular deviation between an angular position of a camshaft target and a minimum speed of less than 30° allows us to deduce a rotation of the engine in forward motion while if the first angular deviation is greater than 30°, it is determined that the rotation of the engine is in reverse motion.

[0075] Also, for example for target 6+1, the measurement of a first angular deviation between an angular position of a camshaft target and a minimum speed greater than 45° allows us to deduce a rotation of the engine in forward motion while if the first angular deviation is greater than 45°, it is determined that the rotation of the engine is in reverse motion.

[0076] 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

Demands

1. A method for determining the direction of rotation of a crankshaft driving a camshaft of an internal combustion engine equipped with at least 4 cylinders by means of a magnetic crankshaft sensor and a camshaft sensor, the camshaft sensor being of the inductive type and configured to generate a camshaft signal comprising edges, in response to detections of tooth passage of a camshaft target of type X+l mounted to rotate with the camshaft, said target having X+l teeth of which X are angularly equidistant, X being a multiple of the number of cylinders, the crankshaft sensor being configured to generate a crankshaft signal comprising edges, in response to detections of tooth passage of a crankshaft target mounted to rotate with the crankshaft, the method comprising the following steps: an initial calibration step to determine a so-called decision angular deviation, then, upon receiving a current camshaft face: • Determine the position of the tooth's midpoint; if so, store it • determine if a local minimum crankshaft speed has occurred between the midpoint of the previous camshaft tooth and the midpoint of the current camshaft tooth, • if yes, • determine a so-called reference angular position of said crankshaft corresponding to the local minimum speed from the crankshaft signal, • determine a first angular distance (Dl) between the angular position of the middle of the previous camshaft tooth and the reference angular position, • determine a second angular distance (D2) between the angular position reference and angular position of the midpoint of the camshaft tooth current, • determine the direction of rotation of said crankshaft by comparing the first angular distance and the second angular distance with the decision angular deviation.

2. Method according to the preceding claim, wherein the decision angular deviation is determined from angular positions of the teeth of the crankshaft target.

3. Module (M) for determining the direction of rotation of a crankshaft driving a camshaft of an internal combustion engine of a vehicle equipped with at least 4 cylinders by means of a magnetic type crankshaft sensor and a camshaft sensor, the camshaft sensor being configured to generate a camshaft signal comprising edges, in response to detections of tooth passage of a camshaft target of type X+l mounted integrally in rotation with the camshaft, said target having X+l teeth of which X are angularly equidistant, X being a multiple of the number of cylinders, the crankshaft sensor being configured to generate a camshaft signal comprising edges, in response to detections of tooth passage of a crankshaft target mounted integrally in rotation with the crankshaft,The vehicle includes a control unit (CU) configured to implement the following steps: • an initial calibration step to determine a so-called decision angular deviation, then, • upon receiving a current camshaft edge: • determine if a local minimum crankshaft speed has occurred between the previous camshaft edge and the current edge • if so, • determine a so-called reference angular position of said corresponding crankshaft, at the local minimum speed from the crankshaft signal, determine a first angular distance (D1) between the previous camshaft front angular position and the reference angular position, determine a second angular distance (D2) between the reference angular position and the current camshaft front angular position, determine the direction of rotation of said crankshaft by comparing the first angular distance and the second angular distance with the decision angular deviation.

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