FR2877431A1 - NON-CONTACT POSITION SENSOR - Google Patents

Abstract

The present invention relates to a contactless position sensor, consisting of a first magnetic structure comprising at least one permanent magnet (1) moving in a main air gap (4) and a second magnetic structure comprising at least two ferromagnetic elements (3, 8 ) defining at least one secondary measurement air gap (5) in which is placed at least one magnetosensitive element (6), characterized in that said secondary air gap (5) has a median plane parallel to the plane containing the longitudinal line of the magnet permanent (1), said median plane of the secondary air gap (5) being perpendicular to the transverse axis of said permanent magnet (1).

Description

NON-CONTACT POSITION SENSOR

  The present invention relates to the field of rotary or linear position sensors, and more particularly the position sensors intended for measuring the position of the air intake valve for combustion engines, without this application being exclusive.

  The prior art is known from the French patents FR2670286, FR2715726 and FR2790549 describing sensors of the state of the art, having a stator part consisting of at least one ferromagnetic part defining at least one measurement gap of which the plane is substantially parallel to the axis of rotation of the movable part.

  For an application such as the air intake valve position measurement for internal combustion engines, the level of reliability is such that it is necessary to integrate two independent detection means to ensure complete redundancy that allows that even in case of failure of one of the magneto-sensitive elements the sensor continues to operate.

  It is therefore necessary to have two measurement gaps in the magnetic circuit in order to accommodate two magneto-sensitive elements or to place the two magneto-sensitive elements in the same measurement gap.

  This redundancy inevitably leads to an increase in the final price of the sensor. In the case where the two magneto-sensitive elements are housed in the same measuring gap this results in an increase: E is the thickness of the gap (probes stacked one behind the other), E is the surface of the measuring gap (probes placed side by side).

  In both cases, this inevitably leads to a decrease in the variation of the signal, which is undesirable for the purpose of optimizing the signal-to-noise ratio of the sensor as well as its resolution.

  Moreover, from the point of view of the industrial process, the magnetosensitive elements that can be integrated in this type of sensor do not lend themselves easily to mounting on a printed circuit. Indeed, these components have connections in the form of son that it is necessary to pass through the holes of a printed circuit, it is this operation which from the industrial point of view presents difficulties and therefore an additional cost.

  The sensor described here is not limited to the use of magnetosensitive element having redundancy.

  Also known in the state of the art a sensor described in US Patent US5861745 describing another position sensor, consisting of at least one stator part defining a measurement gap whose plane is parallel to the axis of rotation of the rotor part itself constituted by at least one permanent magnet, cooperating with the stator parts to produce a flow variation in the measurement gap proportional to the angular position of the rotor part.

  The structure described in the above patent also leads to the use of the same magneto-sensitive elements as those already described above and therefore leads to the same difficulties from the point of view of industrialization.

  Recent developments in the field of magneto-sensitive sensors incorporating Hall effect probes, have allowed the appearance of new components such as MLX 90277 from Melexis available as a component that can be integrated flat directly on a printed circuit (see Figure 26 SMD component - Surface Mount Device). This component also incorporates two Hall effect probes in the same housing which allows for complete redundancy, essential feature in most automotive applications (throttle position sensor, valve ...). It is important to note that conventional magneto-sensitive elements can also be mounted flat on a PCB (see Figure 17).

  The object of the present invention is therefore to overcome the drawbacks mentioned above by proposing an improved position sensor, the magnetic circuit of which makes it possible to use magneto-sensitive elements that can be mounted directly flat on a printed circuit board (integrating a redundancy or not) which facilitates the industrial process inducing a lower manufacturing cost.

  For this purpose, the invention relates in its most general sense to a position sensor (rotary or linear), in particular for detecting the position of the air intake valve, constituted by a first magnetic structure comprising at least a permanent magnet 1 and a second magnetic structure comprising at least two ferromagnetic parts 3, 8 defining a measuring gap 5, oriented parallel to the axis of rotation of the movable part, in which at least one magneto-sensitive element is placed. The orientation of the air gap being defined by the orientation of the field lines which borrows the same gap (see Figure 1).

  The invention generally relates to a non-contact position sensor constituted by a first magnetic structure comprising at least one permanent magnet 1 moving in a main air gap 4 and a second magnetic structure comprising at least two ferromagnetic elements 3, 8 defining the minus a secondary measurement gap in which is placed at least one magnetosensitive element 6, characterized in that said secondary gap 5 has a median plane parallel to the plane containing the longitudinal line of the permanent magnet 1, said median plane of the secondary air gap 5 being perpendicular to the transverse axis of said permanent magnet 1. We show in Figure 2 the definition of the center line in the case of a tile magnet and for a parallelepiped magnet.

  According to a first embodiment, the permanent magnet 1 moves linearly in the main gap 4 having a planar geometry.

  According to a second embodiment, the permanent magnet 1 rotates in the main gap 4 having a semicylindrical geometry.

  According to a particular variant of this second embodiment, the non-contact rotary position sensor is constituted by a first magnetic structure comprising at least one permanent magnet 1 moving in a main air gap 4 and a second magnetic structure comprising at least two elements. ferromagnetic devices 3, 8 defining at least one secondary measurement gap in which at least one magnetosensitive element 6 is placed, characterized in that the axis of rotation of the first magnetic structure passes perpendicularly through the plane defined as said secondary air gap 5 of measurement .

  According to a preferred embodiment, the magnet magnet substantially perpendicular to the direction of displacement moves alone in the gap created between the fixed stator parts and a fixed yoke 2.

  According to one variant, the magnet is integral with a yoke 2 and this assembly moves relative to the stator parts.

  According to a first embodiment, the magnet is of parallelepipedal shape and moves linearly in the main air gap 4 formed by the stator part and the cylinder head 2. The magnetosensitive element is placed in the secondary gap oriented in a direction perpendicular to the direction of movement of the moving part.

  According to a second embodiment, the parallelepiped-shaped magnet is integral with a ferromagnetic yoke 2, this rotor assembly moves linearly in front of the stator parts which define the measuring gap.

  According to a third embodiment, the parallelepipedic magnet is secured to a ferromagnetic yoke 2 having a tangential notch in which is housed this thin magnetic magnet substantially perpendicular to the direction of travel.

  According to another embodiment, the magnet is of cylindrical shape magnetized substantially in the direction of the thickness. This integral magnet, recessed or not on a ferromagnetic yoke rotates in front of the stator portion for collecting the flow.

  The present invention will be better understood on reading the description which follows, with reference to the appended drawings relating to nonlimiting embodiments, in which: FIGS. 1, 2 and 3 represent a view of a linear sensor incorporating a probe having the features described above; Figures 4, 5, 6 and 7 show a view of a single magnet rotary sensor; - Figure 8 shows a view of a symmetrical rotary sensor with two magnets; - Figures 9, 10, 11 and 12 show a view of a ring magnet sensor and external stator; Figures 13 and 14 show views of a rotary ring magnet and inner stator sensor; Fig. 15 shows a view of a sensor using a disk magnet; FIGS. 16, 17 and 18 show an alternative with one or two magnets of angular width close to 120; FIG. 19 is a view of a sensor with four measurement gaps using a bipolar ring magnet; Figures 21 and 22 show a linear sensor with 2 and four magnets; Figures 23 and 24 show various embodiments of a linear sensor with a bolt; FIG. 25 represents a rotary sensor with its integration in its housing as well as the printed circuit on which the probe rests directly; Figures 26 and 27 show particular embodiments of the computer circuit.

  The object of the invention is to propose a simple and reliable solution to the integration of magneto-sensitive elements in the form of SMD component and relates to non-contact position sensors intended for linear or angular position measurement. in applications such as air intake valve position sensors.

  The position sensor described in the following is intended for linear or angular position measurement.

  Such a linear position measuring sensor application is described in FIGS. 3, 4 and 5. This sensor uses a magnetized parallelepiped magnet substantially perpendicular to the direction of displacement. This magnet moves either alone between a fixed yoke and two fixed stators. These two stators define the measuring gap such that the plane of said gap is substantially parallel to the direction of movement of the magnet. In this gap can be placed a Surface Mount Device probe type MLX 90277. A sensor of the same type can be made: E with a magnet secured to a ferromagnetic yoke, this assembly constitutes the rotor and moves in front of the stator part ; With an integral magnet and recessed on a ferromagnetic yoke, this assembly constitutes the rotor and moves in front of the stator portion.

  Figures 6, 7, 8, 9 and 10 show a view of a rotary sensor using a single pole magnet. This cylindrical magnet, magnetized substantially radially, is either glued directly to a cylindrical yoke, or embedded in a ferromagnetic yoke having a notch substantially perpendicular to the direction of travel. The magnet can also be mobile alone in the air gap defined by the stators and the fixed yoke. In another variant more particularly adapted to the measurement of small angular displacement, the magnet can be advantageously of parallelepipedal shape magnetized substantially according to its thickness. This magnet can be as in the case of a magnet of cylindrical recessed form, glued or not on a ferromagnetic cylinder head. The use of a parallelepiped magnet makes it possible to use a material with high remanence and thus to optimize the sensitivity of the sensor. The two stators define a measuring gap whose plane is traversed by the axis of rotation of the rotor part.

  In other variants described in FIGS. 11, 12, 13 and 14, the use of a substantially radially magnetized two-pole ring magnet is shown. In the various structures proposed, the magnet may be bonded to a ferromagnetic yoke, or may move alone in rotation in the gap defined by the stators and the yoke. By their shape, the stators define an axial air gap (in reference to the field lines that run through it) allowing the integration of a flat probe. In these structures, the magnet is inside the stators.

  The use of a ring magnet is not limited to the configurations described above: in FIGS. 15 and 16, variants of ring magnet sensors with the stator parts placed inside the magnet are proposed. The stators define a measuring gap whose plane is perpendicular to the axis of rotation of the moving part. These configurations have the advantage of having a natural shielding of the magneto-sensitive element of the external parasitic fields.

  In Figure 17, a disk magnet variant is shown. The bipolar magnet is substantially axially magnetized and may either be movable alone or bonded to a ferromagnetic yoke.

  For applications requiring detection of angular travel substantially greater than 180 or unipolar strokes greater than 90, variants with bipolar magnet tiles are shown in FIGS. 18 and 19. The angular width of the magnet is substantially equal to 240, this magnet either moves alone in the air gap defined between the cylinder head and the stator parts, or is stuck on the cylinder head. The stator parts defined by two ferromagnetic elements of angular width substantially equal to 120 and 240 define two axial measurement gaps placed substantially at 120 from one another at the periphery of the sensor. Such a sensor may also use a single magnet magnet substantially radially bonded or recessed on a ferromagnetic yoke, this sensor is shown in FIG.

  For applications requiring the detection of the position on a complete revolution, the structure of FIG. 21 makes it possible to obtain two phase-shifted signals of 90 such as those represented in FIG. 22. The stator is composed of four identical ferromagnetic elements of angular width substantially. equal to 90. These four stators define four measuring gaps whose planes are substantially perpendicular to the axis of rotation of the rotor part. The rotor consists of a substantially radially magnetized tubular magnet. This magnet moves either alone in the air gap created between a ferromagnetic yoke and the stators or with a ferromagnetic cylinder head on which it is glued. By using the linear part of each of the signals it is then possible to reconstruct a linear signal on 360.

  FIGS. 23 and 24 show an exemplary embodiment of a U-shaped linear bolt-type sensor on which two magnets magnetized substantially according to the thickness are glued. These magnets can be either unipolar or bipolar type. Inside the rotor structure are two ferromagnetic parts defining a measuring gap whose plane is parallel to the moving direction of the moving part.

  Figure 25 shows an angular position sensor with its integration in a housing. In these two figures, we see the simplicity provided by this structure for fixing the magneto-sensitive element which is directly soldered flat on a printed circuit. Such an assembly has a very high resistance to shock and vibration. The printed circuit and the magneto-sensitive element thus integrates very easily into the measuring gap of the sensor. The flat integration of the magneto-sensitive element also makes it possible to obtain a sensor whose height is reduced, which can be an advantage for certain applications. In addition, the stator parts used in this sensor are identical, which allows optimization of the final cost of the sensor.

Claims (13)

  1. Non-contact position sensor, constituted by a first magnetic structure comprising at least one permanent magnet (1) moving in a main air gap (4) and a second magnetic structure comprising at least two ferromagnetic elements (3, 8) defining the minus a secondary measurement gap (5) in which at least one magnetosensitive element (6) is placed, characterized in that said secondary air gap (5) has a median plane parallel to the plane containing the longitudinal line of the permanent magnet (1 ), said median plane of the secondary air gap (5) being perpendicular to the transverse axis of said permanent magnet (1).   Position sensor according to claim 1, characterized in that the permanent magnet (1) moves linearly in the main gap (4) having a planar geometry.   3. Position sensor according to claim 1, characterized in that the permanent magnet (1) rotates in the main air gap (4) having a semi-cylindrical geometry.   4. A non-contact rotary position sensor according to claim 3, constituted by a first magnetic structure comprising at least one permanent magnet (1) moving in a main gap (4) and a second magnetic structure comprising at least two ferromagnetic elements ( 3, 8) defining at least one measuring secondary air gap (5) in which at least one magnetosensitive element (6) is placed, characterized in that the axis of rotation of the first magnetic structure crosses perpendicularly the defined plane said air gap secondary (5) measurement.   5. Non-contact linear position sensor according to claim 1, consisting of a first magnetic structure comprising at least one permanent magnet (1) moving in a main gap (4) and a second magnetic structure comprising at least two ferromagnetic elements (3). , 8) defining at least one measurement gap (5) in which at least one magnetosensitive element (6) is located, characterized in that the axis of translation of the first magnetic structure is parallel to the plane defined as said secondary air gap ( 5) measurement.   6. Position sensor according to claim 1, characterized in that the measuring gap defined by the stator parts can integrate a magneto-sensitive element in the form of a SMD component that can be directly mounted on a printed circuit.   Position sensor according to claim 1, characterized in that the first magnetic structure is constituted by a ferromagnetic yoke (2) on which at least one magnet is bonded (either in the form of magnets in the form of magnetic tiles substantially radially, either in the form of parallelepiped magnets, magnetized in a direction perpendicular to the plane of the main face, and therefore parallel to a radial direction passing through the center of the magnet considered].   8. Position sensor according to claim 1, characterized in that the first magnetic structure is constituted by a ferromagnetic parallelepipedic cylinder head, on which is bonded at least one parallelepiped magnet, magnetized in a direction substantially perpendicular to the plane of the main face.   9. Position sensor according to claim 1 or 2, characterized in that the magnet is of parallelepiped shape magnetized substantially along its thickness.   10. Position sensor according to claim 3, characterized in that the magnet is substantially magnet axially disc shaped.   11. Position sensor according to claim 1, characterized in that the magnet is a magnet two poles magnetized substantially radially.   Angle position sensor according to Claim 1, characterized in that the stator part consists of four identical stators defining at least two measurement gaps and that the rotor part is a two pole ring magnet of angular width substantially equal to 180. .   13. linear position sensor according to claim 2, characterized in that the stator part consists of two ferromagnetic plates and the movable part is composed of a U-shaped piece on which is bonded at least two magnet magnets substantially following thickness.