Position sensor

Abstract

Examples are shown using a position sensor to determine the angular position of an electric motor rotor and a vehicle equipped with such a sensor. Figure from the abstract: [Fig. 3a]

Description

Title of the invention: Position sensor technical field

[0001] This disclosure relates to the field of position sensors. Previous technique

[0002] The control of an electric motor takes into account numerous parameters. The angular position of the electric motor's rotor is one of these parameters.

[0003] The angular position of the electric motor rotor can be determined by several means, including by means of an inductive position sensor. The angular position of the rotor estimated by inductive position sensors may contain an error.

[0004] The present disclosure improves this situation. Summary

[0005] In this regard, a position sensor is proposed for determining an angular position of an electric motor rotor comprising N pairs of poles, with N corresponding to an integer greater than or equal to 2, the sensor comprising: a target adapted to be fixed on the rotor so that it is driven in rotation with the rotor during the operation of the electric motor; a printed circuit board comprising a primary winding, two secondary windings, an electrical generator, and a signal processing unit; the primary winding surrounding the secondary windings; the secondary windings having a shape adapted to each generate a sinusoidal electrical signal, the generated electrical signals having a predetermined phase shift between them; the electric generator being adapted to deliver a current in such a way as to create an inductive coupling between the primary winding and the secondary windings, the inductive coupling being modulated by the position of the target; the signal processing unit being adapted to obtain a cosine electrical signal and a sine electrical signal from sinusoidal electrical signals, these signals allowing to determine an angular position of the rotor of the electric motor; in which a circular surface of the target, intended to be positioned opposite the secondary windings, is provided with N substantially identical openings, arranged periodically around an axis perpendicularly passing through the center of the circular surface, the openings having a substantially isosceles trapezoidal shape; and in which a ratio between the area of ​​an opening of the circular surface and a solid area of ​​the circular surface extending between two consecutive openings is different from 50%.

[0006] Optionally, a solid surface between two openings corresponds to a fin and has substantially an isosceles trapezoidal shape, and in which the base of the trapezoid forming the fin with the greatest length constitutes a portion of the perimeter of the circular surface.

[0007] Optionally, the circular surface includes a hub and the fins extend periodically from this hub.

[0008] Optionally, the base of the trapezoid of an opening with the smallest length is arc-shaped and is formed by a portion of the perimeter of the hub.

[0009] Optionally, the ratio between the surface area of ​​an opening and a solid surface of the circular surface extending between two consecutive openings is greater than 50%.

[0010] Optionally, the ratio between the surface of an opening and a solid surface of the circular surface extending between two consecutive openings is between 55% and 85% not inclusive.

[0011] Optionally, the ratio between the surface of an opening and a solid surface of the circular surface extending between two consecutive openings is between 70% and 80% not inclusive.

[0012] Optionally, the ratio between the surface area of ​​an opening and a solid surface of the circular surface extending between two consecutive openings is less than 50%.

[0013] Optionally, the ratio between the surface of an opening and a solid surface of the circular surface extending between two consecutive openings is between 15% and 45% not inclusive.

[0014] The application also relates to a vehicle comprising such a sensor. Brief description of the drawings

[0015] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analysis of the accompanying drawings, on which:

[0016] [Fig. 1] schematically represents an example of a position sensor according to the present disclosure.

[0017] [Fig.2] schematically represents an example of a vehicle carrying a sensor of position according to this disclosure.

[0018] [Fig.3a] schematically represents a first example of a sensor target of position according to this disclosure identifying certain elements of the target in dotted lines.

[0019] [Fig.3b] schematically represents the first example of the sensor target position according to this disclosure without the identification of certain elements of the target in dotted lines.

[0020] [Fig.4a] schematically represents a second example of a sensor target of position according to this disclosure identifying certain elements of the target in dotted lines.

[0021] [Fig.4b] schematically represents the second example of the sensor target position according to this disclosure without the identification of certain elements of the target in dotted lines.

[0022] [Fig. 5a] schematically represents a third example of a sensor target of position according to this disclosure identifying certain elements of the target in dotted lines.

[0023] [Fig.5b] schematically represents the third example of the sensor target position according to this disclosure without the identification of certain elements of the target in dotted lines.

[0024] [Fig.6a] schematically represents a fourth example of a sensor target of position according to this disclosure identifying certain elements of the target in dotted lines.

[0025] [Fig.6b] schematically represents the fourth example of the sensor target position according to this disclosure without the identification of certain elements of the target in dotted lines.

[0026] [Fig.7a] schematically represents a fifth example of a sensor target of position according to this disclosure identifying certain elements of the target in dotted lines.

[0027] [Fig.7b] schematically represents the fifth example of the sensor target position according to this disclosure without the identification of certain elements of the target in dotted lines.

[0028] [Fig.8a] schematically represents a sixth example of a sensor target of position according to this disclosure identifying certain elements of the target in dotted lines.

[0029] [Fig.8b] schematically represents the sixth example of the sensor target position according to this disclosure without the identification of certain elements of the target in dotted lines.

[0030] [Fig.9a] schematically represents a seventh example of a sensor target of position according to this disclosure identifying certain elements of the target in dotted lines.

[0031] [Fig.9b] schematically represents the seventh example of the position sensor target according to the present disclosure without the identification of certain target elements in dotted lines.

[0032] [Fig. 10] schematically represents two graphs for three different target examples of a position sensor according to this disclosure. The upper graph illustrates the signal levels received by secondary windings of a position sensor according to this disclosure. The lower graph illustrates the error levels in the angular position of a position sensor according to this disclosure. Description of the implementation methods

[0033] The inventors propose to estimate the angular position of an electric motor rotor by using an inductive position sensor. This sensor uses the principle of induction to determine the position of a chosen element, in particular the angular position of an electric motor rotor.

[0034] It should be noted that the terminologies used associated with sensors such as "position sensor", "angular position sensor", "inductive sensor", and "inductive position sensor" will be used interchangeably in this disclosure to refer to a sensor enabling the determination of an angular position of a rotating element using the principle of induction.

[0035] In this case, the inductive sensor creates an inductive coupling between two windings: a primary winding, also called the transmitter winding, and a secondary winding, also called the receiver winding. A magnetic target, positioned on the element whose position is to be determined, modulates, according to its position, a magnetic field created by the primary winding. In this way, the currents induced by the magnetic field in the secondary winding are representative of the target's position and, therefore, by extension, representative of the position of the selected element, which can thus be determined by signal processing. More precisely, the magnetic field created by the primary winding causes the generation of eddy currents on the surface of the magnetic target, which themselves generate a magnetic field in the opposite direction to that generated by the primary winding.It is this opposing magnetic field that enables the generation of induced currents in the secondary winding; the target's position is determined from these induced currents by signal processing. The inductive position sensor thus comprises a printed circuit board with the windings and control electronics that generate the electrical signals in the primary winding and process the induced signals in the secondary windings, and a magnetic target positioned on the element whose position is to be determined.

[0036] The inventors have particularly noted that when the inductive sensor comprises a primary winding surrounding at least two secondary windings with cosine and sine function shapes, the intrinsic characteristics of the sensor lead to the formation of current harmonics that introduce an error in the position determined by the sensor. They have also noted that the order of the harmonics that significantly impact the error in the position determined by the sensor depends on the number and arrangement of the sensor's secondary windings.

[0037] The inventors have observed, for example, that a first inductive sensor topology comprising a primary winding surrounding only two secondary windings whose shape corresponds to a projection in polar coordinates into a space delimited by the primary winding of a sinusoidal shape in a Cartesian plane, results in the formation of even harmonics of rank equal to or greater than 4 in the electrical signal used to determine the target's position. Furthermore, since the amplitude of the harmonics decreases with their rank, the inventors have noted that the 4th harmonic introduces the largest proportion of the error in the target's position determined by this first sensor topology.

[0038] The inventors also noted that a second inductive sensor topology, comprising a primary winding surrounding only three secondary windings whose shape corresponds to a projection in polar coordinates into a space bounded by the primary winding of a sinusoidal shape in a Cartesian plane, results in the formation of even harmonics of rank equal to or greater than 6 on the signals used to determine the target's position. Furthermore, for this second sensor topology, the inventors identified that the 6th harmonic introduced the largest proportion of the error in the determined target position.The error generated by the second sensor topology on the angular position of the target, carried mainly by the 6th harmonic, is thus less than the error generated by the first sensor topology since its error is, for its part, mainly carried by the 4th harmonic.

[0039] In this application, the term "inductive sensor topology" refers to the shape and arrangement of the primary and secondary windings. In particular, a given sensor topology comprises the same number of secondary windings with the same predetermined phase shift between them, as well as a primary winding that surrounds the secondary windings in the same way (for example, by encircling them).

[0040] The inventors have thus identified solutions that make it possible to reduce the error of the inductive position sensor by modifying the arrangement and number of primary coils. However, these solutions, although making it possible to reduce the error on the Target positioning solutions are complex to implement because they require defining and manufacturing suitable secondary windings and processing the signals appropriately based on these defined secondary windings. These solutions are therefore costly in terms of research and development and focus primarily on the electronic part (the printed circuit board) of the inductive position sensor.

[0041] In this disclosure, the inventors propose an ingenious solution that consists of modifying the geometry of the target modulating the electromagnetic field to reduce the error in the position determined by the sensor. Thus, unlike the solutions identified so far by the inventors, the solution presented in this disclosure involves a modification of the magnetic target and is therefore not related to the electronic part of the position sensor. It does not involve modifying the number, shape, or arrangement of the coils, nor the processing of the induced signals, but rather modifying the geometry of the target on which the eddy currents are generated.The solution proposed in this disclosure thus makes it possible to reduce the error in the position determined by the sensor in a simple way, since modifying the geometry of the target only requires modifying the machining of that part, and does not require modifying the design or configuration of the sensor's printed circuit board. The proposed solution therefore contradicts a common technical misconception among the solutions identified by the inventors, which held that reducing the error generated by an inductive position sensor required only modifying the sensor's printed circuit board and not the target itself.

[0042] Furthermore, since only the geometry of the target is modified to reduce the error in the solution proposed by this disclosure, this solution can be easily implemented on existing position sensors to improve their operation by simply replacing the target they use with a new target according to this disclosure.

[0043] With reference to [Fig. 1], an example of a position sensor 1 for determining the angular position of an electric motor rotor (not shown) is now presented. The position sensor 1 can, in particular, be mounted in a vehicle 10 comprising an electric motor (not shown), as schematically illustrated in [Fig. 2].

[0044] Angular position can be defined as a measure of the rotational position of an element with respect to a reference axis. The reference axis can, for example, correspond to the axis around which the rotor is driven in rotation.

[0045] The electric motor comprises N pairs of poles. N denotes an integer greater than or equal to 2. A pair of poles N of an electric motor consists of two opposite magnetic poles which generate a magnetic field.

[0046] The position sensor 1 includes a target 11 adapted to be fixed to the rotor of the electric motor so that it rotates with the rotor during its rotational movement. The target is an inductive target, that is, a target that allows the conduction of an electric current (in particular the conduction of eddy currents), and therefore the generation of a magnetic field. The target 11 is consequently made of a conductive material, for example a metal, in particular iron, copper, aluminum, or a specific metal alloy.

[0047] The position sensor 1 also includes a printed circuit board 12. The printed circuit board 12 may consist of a plate or substrate, generally made of insulating material, on which conductive tracks are arranged. These tracks connect different electronic components to each other to form a functional electrical circuit.

[0048] The printed circuit board 12 includes a primary winding 121p, K secondary windings 121s and an electrical generator 122. K is a natural number greater than or equal to 2. The primary winding surrounds the secondary windings 121s.

[0049] In a known manner, when setting up the sensor, the printed circuit board 12 must be fixedly positioned opposite the target 11. More specifically, the secondary windings 121 of the printed circuit board 12 must be positioned opposite the target to receive the magnetic field generated by the target and thus generate electrical signals.

[0050] The electric generator 122 is adapted to deliver a current in such a way as to create an inductive coupling between the primary winding 121p and the secondary windings 121s.

[0051] The inductive coupling between the windings 121 is modulated by the angular position of the target 11. In particular, the electrical generator 121 can be an alternating current generator connected to the primary winding 121p, such that the current generated in the primary winding 121p produces a magnetic field that generates eddy currents in the target. The eddy currents flowing in the target also produce a magnetic field, which generates an induced current in the secondary windings 121s. The phase shift between the currents generated in the secondary windings 121s allows the angular position of the target 11 to be determined.

[0052] The secondary windings 121s have a shape adapted to each generate a sinusoidal electrical signal as a function of the angular position of the target 11. The secondary windings 121s are arranged, in particular, to exhibit a predetermined phase shift between them. This predetermined phase shift is a function of the number K of secondary windings 121s. This is a known arrangement of windings in an angular position sensor. Thus, the electrical signals generated by the windings secondary 121s, due to the geometric phase shift between these windings, exhibit a phase shift which allows the angular position of the target to be determined.

[0053] The secondary windings 121s may, for example, have a known shape corresponding to a projection in polar coordinates, within a space delimited by the primary winding, of a sinusoidal shape in a Cartesian plane. In particular, the primary winding 121p may be circular and encircle the secondary windings 121s. In these known examples, the secondary windings 121s lie in a plane radial to the circle formed by the surrounding primary winding 121p.

[0054] In early examples, there are two secondary windings 121s (K=2), and the phase shift between them corresponds to 180° or ir / 2 radians.

[0055] In second examples, there are three secondary windings 121s (K=3), and the phase shift between them corresponds to 120° or ir / 3 radians.

[0056] The position sensor 1 may also include a signal processing unit 13. The signal processing unit 13 may be configured to obtain a cosine electrical signal and a sine electrical signal from the sinusoidal electrical signals of the position sensor 1.

[0057] Various known techniques allow the cosine and sine signals to be obtained for this type of angular position sensor.

[0058] In particular, in examples in which the position sensor comprises only two secondary windings 121s, the cosine and sine signals can directly correspond to the two electrical signals generated by the two secondary windings.

[0059] In other examples where the position sensor also comprises only two secondary windings 121s, one of the two secondary windings can provide a so-called cosine+ signal and a so-called cosine- signal, while the other secondary winding can provide a so-called sine+ signal and a so-called sine- signal. In these other examples, the cosine electrical signal is obtained by subtracting the cosine+ and cosine- signals, while the sine electrical signal is obtained by subtracting the sine+ and sine- signals. This differentiation of signals (cosine+ / cosine- and sine+ / sine-) reduces the intrinsic noise of the cosine and sine signals compared to cosine and sine signals obtained directly from the electrical signals generated by the secondary windings.

[0060] In examples where the position sensor comprises only three secondary windings 121s, the cosine and sine electrical signals can be obtained by a complex calculation step (via a Park Transform, for example) to project the three signals generated by the secondary windings 121s (system three-phase) in a coordinate space comprising only two signals (two-phase system).

[0061] In examples, the signal processing unit 13 can also be configured to estimate the angular position of the target (and therefore of the electric motor rotor) from the determined cosine and sine electrical signals. Obtaining the angular position of the target from the cosine and sine signals is also a process known to those skilled in the art.

[0062] Returning to target 11, as explained previously, it is the clever modification of the target determined by the inventors that makes it possible to reduce the angle error in the angular position of the target position determined using the sensor.

[0063] With reference to Figures 3 to 9, several examples of target 11 according to this disclosure are shown below. The features represented by dashed lines in these figures are illustrated for the purpose of delimiting certain areas used to describe the target. These dashed features do not necessarily correspond to physical boundaries of the target, which are represented by solid lines. Furthermore, when a dashed area overlaps a solid line, the solid line does represent a physical boundary of the target. Each figure has been shown twice to clearly visualize the physical boundaries of target 11, and the boundaries of certain areas of target 11, which do not necessarily have a physical reality, represented by dashed lines.Thus, figures 3a, 4a, 5a, 6a, 7a, 8a and 9a include the dotted outlines of target 11, while figures 3b, 4b, 5b, 6b, 7b, 8b to 9b do not.

[0064] The target 11 comprises a circular surface 110. This circular surface 110 is shown as a dashed line in the figures. The circular surface 110 comprises N openings. N corresponds to the number of pole pairs of the electric motor. In the examples in Figures 3 to 9, it is understood that this is a target associated with a motor having 5 pole pairs. The solution presented in this disclosure can, however, be adapted for motors having a different number N of pole pairs.

[0065] Furthermore, in the examples shown in Figures 3 to 6 and in the example shown in Figures 8, the openings 111 correspond to recesses made in the circular surface 110 of the target, for which the circular surface 110 delimits a physical surface of the target. In other examples, they are simply openings made in a surface 110a, which may be larger than the circular surface 110 and which delimits the physical surface of the target. In other words, the circular surface 110 may correspond to a virtual surface in the sense that it does not necessarily delimit a physical surface of the target. The surface The physical area of ​​the target may, for example, be delimited by a surface larger than the circular surface 110, such as the surface 110a. Such examples are shown in particular in Figures 7 and 9.

[0066] The circular surface 110 is intended to be positioned opposite the secondary windings 121s of the printed circuit board 12 of the inductive position sensor 1. This is a known arrangement for this type of inductive sensor. In this case, it is this positioning that will allow the inductive coupling required by the sensor.

[0067] In examples where the primary winding 121p surrounds the secondary windings 121s, the circular surface 110 of the target 11 may have an area equal to the area delimited by the circle forming the primary winding 121p. More precisely, it is these two surfaces (circular surface 110 and area delimited by the circle forming the primary winding 121s) that are positioned opposite each other during the operation of the sensor.

[0068] As shown in the figures, the openings 111 are arranged periodically around a central axis of the circular surface 110. The central axis corresponds to the axis passing perpendicularly through the center of the circular surface 110. In particular, in examples where the primary winding 121p encircles the secondary windings 121s, during sensor operation, the central axis of the circular surface 110 of the target 11 should ideally pass through the center of the surface delimited by the primary winding 121p. In which case, the printed circuit board 12 and the target 11 would be perfectly positioned relative to each other.

[0069] The fact that the openings 111 are arranged periodically around a central axis of the circular surface 110 should be understood as the fact that each opening 111 is substantially separated from the next one on the circular surface 110 by the same angular distance.

[0070] The openings 111 have a substantially isosceles trapezoidal shape. This shape corresponds to the known shape of the openings 111 of the inductive sensor target 11. In particular, the bases of the isosceles trapezoid forming the openings 111 of the inductive sensor target may have an arcuate shape, as shown in the figures.

[0071] In this disclosure, a ratio between the area of ​​an opening 111 of the circular surface 110 and a solid area 112 of the circular surface extending between two consecutive openings is different from 50%. When considering the ratio between the area of ​​an opening 111 of the circular surface 110 and a solid area 112 of the circular surface extending between two consecutive openings, the surfaces 111 and 112 to be considered are surfaces extending between two of the same radii of the circular surface 110. In other words, if the calculation of the area of ​​an opening 111 of the circular surface 110 is determined between a first radius and a second ray, the calculation of the full surface 112 between two consecutive openings of the circular surface 110 to be considered to determine the ratio will also be between the first ray and the second ray.

[0072] In the prior art, the ratio between the surface area of ​​an aperture 111 and a solid surface 112 between two consecutive apertures is always chosen to be equal to 50%. The topology of the inductive sensors has been designed in this way.

[0073] The inventors observed that by introducing an asymmetry in the proportions of these surfaces (surfaces 111 and 112) on the target 11, the angular error of the target 111's intrinsic position, inherent in the topology of the inductive sensor, was reduced. Consequently, the inventors overcame a technical misconception that assumed the target should have a solid / hollow surface ratio of the circular surface 110 equal to 50%. In particular, the inventors observed that, up to a certain limit, the further the ratio deviated from 50%, the lower the error. This limit can be determined experimentally.

[0074] In examples, particularly those shown in Figures 3 to 9, the solid surface 112 between two openings 111 of the circular surface 110 can correspond to a fin and can have a substantially isosceles trapezoidal shape. In particular, at least one of the bases (bl, b2) of the trapezoid of the solid surface 112 can have an arched shape. In these examples, the base bl of the trapezoid forming a fin with the greatest length (the larger base bl of the trapezoid) can constitute a portion of the perimeter of the circular surface 110, as shown in the various figures.

[0075] In initial examples, the circular surface 110 may include a hub M, and the fins may extend periodically from this hub M. In particular, the fins may extend periodically over the radial surface of the hub. In these initial examples, the base b2 of the trapezoid forming a fin with the shortest length (the small base b2 of the trapezoid) may be arc-shaped and may be formed by a portion of the perimeter of the hub M. It is understood that, similarly, the small base of the trapezoid of an opening 111 with the shortest length is arc-shaped and is formed by a portion of the perimeter of the hub M. These initial examples are shown in particular in Figures 3 to 6 and in Figure 9.

[0076] The fact that the fins extend periodically around the hub M of the circular surface 110 should be understood as the fact that each fin is separated from the next one, on the radial surface of the hub, by the same angular gap.

[0077] In second examples, the circular surface 110 may include a ring A whose center corresponds to the axis passing perpendicularly through the center of the circular surface 110. In these second examples, the fins extend periodically from this ring A. In particular, the fins may extend periodically (i.e., be separated consecutively by the same angular distance) from a radial surface of ring A. In these second examples, the small base b2 of the trapezoid forming a fin can have an arc shape and can be constituted by a portion of the perimeter of ring A. These second examples are notably represented in Figures 7.

[0078] In third examples, the fins can extend from the perimeter of the circular surface 110 towards the center of this circular surface 110, and the small base b2 of the trapezoid forming a fin extends freely. These third examples differ from the examples shown in Figures 9 in that the small base b2 of the trapezoid forming a fin extends freely and is therefore not formed by a portion of the perimeter of a hub M. In these third examples, there is therefore neither a hub M nor a ring A. These third examples are notably shown in Figures 8.

[0079] In some examples, the ratio between the area of ​​an opening 111 and a solid area 112 of the circular surface 110 extending between two consecutive openings 111 is greater than 50%. In other words, this means that there is a greater proportion of open areas (corresponding to the openings 111) than of solid areas 112 in the circular surface 110 (between two identical radii of this surface). These examples are particularly advantageous since the material used to manufacture the target 111 is reduced, so that the manufacturing cost of such a target 11 is reduced. These second examples are notably represented in Figures 3, 4, 8 and 9. The inventors noted, however, that the higher the ratio of the area of ​​an opening 111 to a solid area 112 of the circular surface 110, the lower the signal level received by the secondary windings 121s due to inductive coupling.

[0080] Advantageously, the ratio between the area of ​​an aperture 111 and a solid area 112 of the circular surface 110 extending between two consecutive apertures 111 is between 55% and 85% inclusive, or between 60% and 85% inclusive, or preferably between 70% and 80% inclusive. Indeed, the inventors observed that a ratio between the area of ​​an aperture 111 and a solid area 112 of the circular surface 110 extending between two consecutive apertures 111 of between 70% and 80% inclusive represented a favorable compromise between signal level and error level in the angular position of the target.

[0081] In some examples, the ratio between the area of ​​an opening 111 and a solid area 112 of the circular surface 110 extending between two consecutive openings 111 is less than 50%. In other words, this means that there is a greater proportion of solid areas 112 than of open areas (corresponding to the openings 111) in the circular surface 110 (between two identical radii of this surface). These second examples are shown in particular in Figures 5 to 7. In these examples, and within certain limits, the higher the ratio of solid to hollow surface area, the stronger the signal level, and the lower the level of angular error in the target's angular position, up to a certain limit beyond which the angular error begins to increase again. This limit can be determined experimentally.

[0082] Advantageously, the ratio between the area of ​​an aperture 111 and a solid area 112 of the circular surface 110 extending between two consecutive apertures 111 is between 15% and 45% inclusive, or between 20% and 45% inclusive, or preferably between 20% and 30% inclusive. Indeed, the inventors observed that a ratio between the area of ​​an aperture 111 and a solid area 112 of the circular surface 110 extending between two consecutive apertures 111 of between 20% and 30% inclusive represented an attractive compromise with a high signal level and a low level of error in the angular position of the target.

[0083] Fig. 10 represents two graphs illustrating, for the top graph, the levels of the signal received by the secondary windings 121s, and for the bottom graph, the error levels in the angular position of the target 111, for three different ratios.

[0084] More specifically, on the top graph, the x-axis represents the angular position of the target in degrees (ranging between 0 and 360°), while the y-axis represents a level of the signal received by the secondary windings 121s in mV (millivolt).

[0085] In the lower graph, the x-axis represents the angular position of the target in degrees (it is the same x-axis as the upper figure), while the y-axis represents an electrical angle error, in the angular position of the target 111, in degrees.

[0086] The curves L1 correspond to a ratio between the surface of an opening 111 and a solid surface 112 of the circular surface 110 extending between two consecutive openings 111 equal to 50% (between two same radii of this surface).

[0087] The L2 curves correspond to a ratio between the surface area of ​​an opening 111 and a solid surface 112 of the circular surface 110 extending between two consecutive openings 111 equal to 40%. Thus, the empty surfaces occupy 40% of the space of the circular surface 110 while the solid surfaces occupy the remaining 60% of the space (between two identical radii of this surface).

[0088] The L3 curves correspond to a ratio between the surface area of ​​an opening 111 and a solid surface 112 of the circular surface 110 extending between two consecutive openings 111 equal to 25%. Thus, the empty surfaces occupy 25% of the space of the circular surface 110 while the solid surfaces occupy the remaining 75% of the space (between two identical radii of this surface).

[0089] As can be seen in this figure, the L1 curves (50% ratio) are the least interesting in terms of angle error level and signal level. The L3 curves (25% ratio) exhibit both the best signal level received by the 121s secondary windings and the lowest angle error level.

[0090] Thus, the solution proposed in this disclosure makes it possible to reduce the angular error in the position determined from the inductive sensor by modifying the geometry of the target. This solution therefore does not consist of modifying a design or configuration of the sensor's printed circuit board, and thus goes against a technical bias of the solutions identified by inventors to date, which were all focused on some modification of the printed circuit board (configuration, design, shape and arrangement of coils, signal processing, etc.).

Claims

Demands

1. Position sensor (1) for determining an angular position of an electric motor rotor comprising N pole pairs, with N corresponding to an integer greater than or equal to 2, the sensor comprising: a target (11) adapted to be fixed on the rotor so that it is driven in rotation with the rotor during the operation of the electric motor; a printed circuit board (12) comprising a primary winding (121p), two secondary windings (121s), an electrical generator (122), and a signal processing unit (13); the primary winding (121p) surrounding the secondary windings (121s); the secondary windings (121s) having a shape adapted to each generate a sinusoidal electrical signal, the generated electrical signals having a predetermined phase shift between them;the electric generator (122) being adapted to deliver a current so as to create an inductive coupling between the primary winding (121p) and the secondary windings (121s), the inductive coupling being modulated by the position of the target (11); the signal processing unit (13) being adapted to obtain a cosine electrical signal and a sine electrical signal from the sinusoidal electrical signals, these signals allowing to determine an angular position of the rotor of the electric motor; in which a circular surface (110) of the target (11) intended to be positioned opposite the secondary windings (121s) is provided with N substantially identical openings (111), arranged periodically around an axis passing perpendicularly through the center of the circular surface (110), the openings (111) having substantially an isosceles trapezoidal shape;and in which a ratio between the area of ​​an opening (111) of the circular surface (110) and a solid area (112) of the circular surface (110) extending between two consecutive openings (111) is different from 50%.;

2. A sensor according to claim 1, wherein a solid surface (112) between two openings (111) corresponds to a fin and substantially has an isosceles trapezoidal shape, and wherein a base (bl) of the trapezoid forming the fin with the greatest length constitutes a portion of the perimeter of the circular surface (110).

3. Sensor according to the preceding claim, wherein the circular surface (110) comprises a hub (M) and the fins extend periodically from this hub (M).

4. Sensor according to the preceding claim, wherein the base of the trapezoid of an opening (111) having the smallest length is arc-shaped and is constituted by a portion of the perimeter of the hub (M).

5. Sensor according to any one of the preceding claims, wherein the ratio between the area of ​​an opening (111) and a solid area (112) of the circular surface (110) extending between two consecutive openings (111) is greater than 50%.

6. Sensor according to any one of the preceding claims, wherein the ratio between the area of ​​an aperture (111) and a solid area (112) of the circular surface (110) extending between two consecutive apertures (111) is between 55% and 85% not inclusive.

7. Sensor according to any one of claims 1 to 6, wherein the ratio between the area of ​​an opening (111) and a solid area (112) of the circular surface (110) extending between two consecutive openings (111) is between 70% and 80% not inclusive.

8. Sensor according to any one of claims 1 to 4, wherein the ratio between the area of ​​an opening (111) and a solid area (112) of the circular surface (110) extending between two consecutive openings (111) is less than 50%.

9. Sensor according to any one of claims 1 to 4 or 8, the ratio between the area of ​​an opening (111) and a solid area (112) of the circular surface (110) extending between two consecutive openings (111) is between 15% and 45% not inclusive.

10. Vehicle (10) comprising a sensor according to any one of the preceding claims.