Vibration sensor

Abstract

The invention relates to a vibration sensor comprising a housing (1) having a central axis (Z) in which a PCB circuit (2) is arranged. The PCB circuit (2) has a central portion (20) centred on the central axis (Z) from which distinct lateral portions (21a-21d) extend, wherein flexible zones (22a-22d) connect the central portion (20) to the lateral portions (21a-21d), and wherein each lateral portion (21a-21d) forms an angle of 90° or more with respect to the central portion (20). At least two MEMS sensitive elements (3a-3c) for detecting vibration are mounted on the inner faces (210a-210c) of the lateral portions (21a-21c) of the circuit (2), wherein the sensitive axes (30a-30c) of the MEMS sensitive elements (3a-3c) are parallel to the inner face (210a-210d) of the corresponding lateral portion (21a-21d) and form a three-dimensional reference frame.

Description

[0001] TITLE: Vibration Sensor

[0002] Technical field

[0003] The invention relates to the field of MEMS-based vibration sensors (micro-electro-mechanical systems in English, or micro-electro-mechanical system in French), intended to be installed on or coupled to a test structure subjected to vibrations.

[0004] Prior art

[0005] A vibration sensor can be used to monitor the vibration state of a structure, such as industrial equipment such as a machine tool, a pump, a motor, etc. Vibration detection can be achieved by means of accelerometer-type sensors based on a piezoelectric sensitive element or a MEMS sensitive element.

[0006] Furthermore, vibration sensors intended to be installed in or on industrial equipment must generally meet industrial standards imposing, for example, their dimensions, their compactness being generally sought.

[0007] For the vibration measurement of industrial equipment exhibiting high-frequency vibrations, the use of sensors based on a piezoelectric sensitive element is preferred. Indeed, this type of piezoelectric sensor has the overall advantage of being usable over a very wide frequency range with a large dynamic range, and is well suited for the detection of high-frequency vibrations, particularly for frequencies greater than or equal to 10 kHz. This type of sensor generally comes in the form of a cylindrical housing composed of a base provided with means for mounting the housing on the industrial equipment, as well as a cylindrical casing provided with a through hole suitable for signal output.The base and the cylindrical casing delimit a volume in which the piezoelectric sensitive element is arranged as well as the electronic card integrating electronic components, the electronic card being further coupled to a signal output connector. Due to the dimensions imposed by industrial standards, the piezoelectric sensitive element and the electronic card are generally arranged in stages in the direction of the height of the cylinder so as to limit the size. In addition, the small surface area available on the electronic card generally does not allow the integration of components converting the analog signal into a digital signal. The integration of an analog-digital converter in the housing would require increasing the size of the housing, which would degrade the sensor measurements in the high frequencies.Furthermore, attachment to a bearing surface of industrial equipment is usually achieved through stud mounting (screw coupling and non-through central tapped hole in the base), so that the attachment axis coincides with the central axis of the cylinder and is perpendicular to the bearing plane. This type of attachment is preferred to ensure adequate transmission of high-frequency vibrations and to reduce the contribution of parasitic vibrations.

[0008] Silicon MEMS sensing elements, also known as MEMS chips, can also be used instead of piezoelectric sensing elements. Compared to piezoelectric elements, MEMS elements can be manufactured collectively on a silicon wafer and have a smaller footprint compared to piezoelectric devices. The integration of MEMS chips in modules intended for measuring the vibrations of industrial equipment therefore has a definite advantage. In particular, it is possible to produce 3-axis vibration sensors with a smaller footprint and a digital signal output.

[0009] Some manufacturers of 3-axis MEMS vibration sensors propose to maintain the cylindrical shape of the housing by positioning the MEMS sensitive elements on a printed circuit board whose surface carrying the MEMS sensitive elements contains the central axis of the cylinder and is oriented perpendicular to the transfer plane of the equipment. To enable measurement along 3 axes, certain sensitive axes of these MEMS sensitive elements are thus oriented out of plane (i.e. perpendicular to the surface of the printed circuit). Due to the constraints linked to the manufacture of the MEMS sensitive element from silicon wafer, this out of plane orientation of the sensitive axes reduces the bandwidth of the sensor and therefore restricts the use of the 3-axis MEMS vibration sensor to low frequencies. Generally, the bandwidth of this type of sensor in 3-axis mode is less than 10 kHz.To meet the needs of high-frequency vibration measurement along the 3 measurement axes, for example for measuring vibrations on a machine tool, some manufacturers propose positioning on the industrial equipment a module integrating several single-axis MEMS vibration sensors, each adapted to high frequencies. To optimize the size and use at high frequencies, this type of module is generally parallelepiped and must be fixed to the industrial equipment by means of four screws. However, this type of fixing is not easily adjustable on all industrial equipment. In addition, the volume occupied by the sensors for measurement along the 3 measurement axes remains significant.

[0010] Statement of the invention

[0011] In this context, the present invention thus aims to propose an alternative vibration sensor solution based on MEMS sensitive elements adapted to high frequency measurements, in particular greater than or equal to 10kHz.

[0012] The invention also aims to propose a 3-axis vibration sensor suitable for high-frequency measurements on the 3 measurement axes.

[0013] The vibration sensor advantageously has suitable dimensions that meet the various industrial standards for integration into industrial equipment.

[0014] The invention thus relates to a vibration sensor comprising:

[0015] - a housing with a central axis comprising a base coupled to a cover defining an internal volume in which a PCB (Printed Circuit Board) circuit support is arranged, the base comprising a central protrusion projecting into the internal volume and being configured to ensure the fixing of the housing to a vibrating structure;

[0016] - the PCB circuit support has at least flexible zones, and is formed of at least one central portion centered on the central axis and from which at least two distinct lateral portions extend, said flexible zones electrically connecting the central portion to the lateral portions, each lateral portion forming an angle greater than or equal to 90° relative to the central portion;

[0017] - at least two MEMS vibration detection sensitive elements mounted on the internal faces of the lateral portions of the circuit support, and positioned so that the sensitive axes of the MEMS sensitive elements are parallel to the internal face of the corresponding lateral portion and form a three-dimensional reference frame; and

[0018] - signal output means.

[0019] For example, the signal output means may comprise a signal output connector centered on the central axis, attached to the central portion and opening outside the housing through a through hole in the cover.

[0020] Thus, unlike the vibration sensors of the prior art in which at least one sensitive detection axis coincides with the central axis of the housing, all of the sensitive axes of the invention are offset relative to the central axis of the housing. The MEMS sensitive elements are thus transferred not to a plane including the central axis of the housing, but to one or more surfaces substantially parallel to a plane including the central axis of the housing. In other words, the sensitive axes are distant from the central axis Z of the housing. The PCB circuit support may for example have four lateral portions, substantially forming with the central portion a cube or a parallelepiped open on one of its sides. The lateral and central portions are thus preferably quadrangular.

[0021] Each central and lateral portion has an internal face and an opposite external face. The internal face of the central portion is the one facing the central protrusion and the internal faces of the lateral portions are those facing the central axis.

[0022] The PCB circuit support is preferably in the form of a flex-rigid type printed circuit (or PCB), that is to say that it is made in a single piece of material and certain areas are thinned allowing the PCB to be folded at these thinned areas. Thus, these thinned areas form the flexible areas connecting the lateral portions to the central portion. The thickness of each flexible area is thus less than that of the lateral and central portions. In practice, the formation of the angle between a lateral wall and the central portion is achieved by folding at these thinned areas. Due to the elastic properties of these thinned areas, the thinned areas will more or less return to their initial shape after deformation, so that the lateral portions can be slightly inclined relative to the central axis of the package.

[0023] Thus, the angle formed between a lateral portion and the central portion can be between 90° and 95°.

[0024] Furthermore, due to this elastic return of the flexible zones, certain parts of the lateral portions may come into abutment on the internal wall of the housing, and in particular on the internal wall of the cover. Indeed, when inserting the folded PCB circuit support into the cover, the lateral portions tend to move away from the central axis due to this elastic return. By dimensioning the internal volume of the cover, and therefore of the housing, relative to the surface area of ​​the PCB circuit necessary to accommodate all the MEMS sensitive elements and electronic components, the verticality or near-verticality of these lateral portions is ensured, and therefore the orthogonality of the sensitive axes.In other words, unlike existing solutions in which the PCB circuit is held on a specific support inside the housing by gluing or screwing, the PCB circuit can be held in place in the housing by taking advantage of the restoring force effect of the flexible zones ensuring the immobilization in abutment of the vertical edges on the internal wall.

[0025] Thus, a portion of the outer face of each side portion may be in contact with (or abut on) an area of ​​the inner wall of the lid. For example, the vertical edges of the side walls may abut on the inner surface of the lid. It is also possible to provide protruding protrusions on the inner wall of the lid and / or the base, for example in the form of wedges or ribs, acting as stops for the outer faces of the side portions.

[0026] In practice, to finally immobilize the circuit support in the housing, the internal volume can be filled with a resin. Encapsulation with the resin also protects the PCB support, as well as the elements attached to this support, from possible corrosion or condensation.

[0027] In practice, the resin can be injected into the internal volume of the case via through holes provided for this purpose and made in the base.

[0028] During manufacture, the closure of the case by assembling the base to the lid, combined with the injection of the resin, can induce stresses on the side portions so that the angle formed between a side portion and the central portion can be between 85° and 90°. To remedy this defect, and to allow the side portions to return to a position in which the angle formed with the central portion is between 90° and 95°, it is possible to provide a spacing between the low edges (i.e. those opposite the flexible zones in the direction of the central axis) of the side walls and the bottom of the base. The distance (in the direction of the central axis) between a low edge and the bottom of the base can be between 0.2mm and 1mm, for example 0.5mm, in order to allow the elastic return of the flexible zones.

[0029] Alternatively, it is also possible to partially pre-fill the internal volume of the enclosure after positioning the PCB circuit support in the lid and before closing the enclosure by assembling the lid to the base, so that the enclosure can be free of through holes dedicated to resin injection.

[0030] Advantageously, all or part of the electronic components associated with these MEMS sensitive elements are transferred to the internal face of the central portion.

[0031] For example, these electronic components may include a controller and an analog-to-digital converter for generating digital signals at the output of the sensor. The signal output connector may be attached to the outer surface of the central portion to open at the output of the sensor through the through-hole of the cover, and electrical connections such as vias may be provided to electrically connect the connector to the electronic components arranged on the inner face of the central portion. Alternatively, depending on the available surfaces, it is also possible to mount electronic components on all or part of the side walls.

[0032] Preferably, the MEMS sensitive elements are of the micro-electromechanical device type with interdigitated capacitive combs produced in a substrate with sensitive axis(es) in the plane, i.e. parallel to the plane of the substrate. Each MEMS sensitive element can thus comprise one sensitive axis or two sensitive axes.

[0033] Advantageously, the outer profile of the housing is hexagonal in shape. This profile is particularly favored to facilitate the fixing of the sensor on industrial equipment with existing tools.

[0034] The vibration sensor may further have one or more of the following characteristics:

[0035] - the vibration sensor is a 3-axis sensor suitable for high-frequency measurements (greater than or equal to 10kHz), according to the 3 measurement axes;

[0036] - the vibration sensor comprises three single-axis MEMS sensitive elements, each distributed over a lateral portion, the sensitive axes being oriented so as to form a three-dimensional, preferably orthonormal, reference frame;

[0037] - the vibration sensor comprises a single-axis MEMS sensitive element mounted on one of the lateral portions, and a 2-axis MEMS sensitive element mounted on another of the lateral portions, and the sensitive axes being oriented so as to form a three-dimensional, preferably orthonormal, reference frame;

[0038] - the vibration sensor comprises two 2-axis MEMS sensitive elements each distributed over a lateral portion, the sensitive axes being oriented so as to form a three-dimensional, preferably orthonormal, reference frame;

[0039] - the central protrusion is configured to ensure stud mounting;

[0040] - the central protrusion is a blind hole tapped and open to the outside of the housing;

[0041] - the central protrusion defines a fixing axis which coincides with the central axis, and the distance of the internal faces of the lateral portions relative to this fixing axis can be between 5mm and 10mm, for example of the order of 8mm;

[0042] - the signal output connector can be replaced by an electrical cable directly to the central portion and exiting the housing through the through hole in the cover. This type of connection without a physical connector is little used in the industrial world of vibration metrology, but allows to obtain a sensor with good high frequency behavior while reducing the size of the sensor;

[0043] - the sensor can integrate electronic components necessary for signal transfers according to the communication protocol used;

[0044] - the housing may be made of a metallic material suitable for the intended application, for example steel, aluminum or titanium;

[0045] - the base can be metallic and the cover can be made of thermoplastic material to allow radio waves to pass through, a radio antenna can thus be integrated into the housing. This configuration makes it possible to do without the output connector or the electrical cable;

[0046] - the external diameter of the case can be between 20mm and 30mm, for example around 25mm or 26.5mm;

[0047] - the height of the housing is preferably less than or equal to 20mm, for example around 18mm (without the connector), which allows the first resonance mode to be greater than 20kHz;

[0048] - the assembly of the cover to the base can be carried out by any means, for example by screwing, welding, gluing or even stamping, in order to seal the housing and protect the electronic components from electromagnetic disturbances which are very present on industrial equipment.

[0049] The invention thus takes advantage of the use of MEMS sensitive elements perfectly suited for high-frequency vibration measurements and whose dimensions are much smaller than those of a piezoelectric sensitive element. Due to their reduced dimensions, it is thus possible to decenter or offset the sensitive axes from the fixing axis or the central axis without impacting the performance of these sensitive elements, nor on the transmission of vibrations, nor on the overall size.

[0050] The invention thus makes it possible to produce a 3-axis vibration sensor suitable for high-frequency measurements on the 3 measurement axes, and meeting the dimensional constraints dictated by the various industrial standards. Brief description of the drawings

[0051] Other characteristics and advantages of the invention will emerge clearly from the description given below, for information purposes only and in no way limiting, with reference to the appended figures, in which:

[0052] - figure 1 is a schematic representation of the sensor according to one embodiment of the invention;

[0053] - Figure 2 is an exploded view of the sensor of Figure 1;

[0054] - figure 3 is a sectional view of the sensor of figure 1 along the section plane AA;

[0055] - Figure 4 is a schematic representation of an unfolded PCB circuit support, according to one embodiment of the invention;

[0056] - figure 5 is a sectional view of the sensor of figure 1 along the section plane BB;

[0057] - figure 6 is a sectional view of the sensor of figure 1 along the section plane AA, in which the lateral portions abut on the internal surface of the housing;

[0058] - figure 7 is a schematic representation of an angle according to a variant;

[0059] - figure 8 is a schematic representation of an angle according to another variant;

[0060] - figure 9 is a sectional view of the sensor of figure 1 along the section plane CC;

[0061] - figure 10 is a sectional view of the sensor of figure 1 along the section plane CC, according to another embodiment;

[0062] - Figure 11 is a perspective view of the sensor of Figure 10;

[0063] - figure 12 is a sectional view of the sensor of figure 1 along the section plane AA according to an embodiment in which a spacing is provided between the lower edges and the bottom of the base.

[0064] Description of an embodiment

[0065] A 3-axis vibration sensor suitable for high-frequency measurements on the 3 measurement axes, according to embodiments illustrated in Figures 1 to 11, is described below.

[0066] The vibration sensor thus comprises a housing 1 formed by the assembly of two parts, a first part forming the cover 11 or hood and a second part forming the base 10. The housing 1 has a central axis Z as well as an internal volume 12. The sensor further comprises a PCB circuit support 2 arranged in the internal volume 12 of the housing 1. The PCB circuit support 2 is formed of at least one central portion 20 centered on the central axis Z and from which at least two lateral portions 21a-21d extend. For example, the PCB support circuit 2 illustrated in FIG. 4 comprises four lateral portions 21a-21d. In particular, flexible zones 22a-22d are located between the central portion 20 and the lateral portions 21a-21d, and in particular make it possible to electrically connect the central portion 20 to the lateral portions 21a-21d.These flexible zones 22a-22d connecting the lateral portions 21a-21d to the central portion 20 are configured to be folded or curved so that each lateral portion 21a-21d forms with the central portion 20 an angle α less than 180° and greater than or equal to 90°. Each central portion 20 and lateral portion 21a-21d thus has an internal face 200, 210a-210d and an opposite external face, the external faces being those facing the internal wall of the housing 1.

[0067] In practice, the PCB circuit support 2 is in the form of a printed circuit (or PCB) of the flex-rigid type, that is to say that it is made in a single piece in a material and certain zones are thinned to allow folding. Thus, these thinned zones form the flexible zones 22a-22d connecting the lateral portions 21a-21d to the central portion 20. The thickness of each flexible zone 22a-22d is thus less than that of the lateral portions 21a-21d and central 20. The central 20 and lateral 21a-21d portions may have different shapes, for example quadrangular. As illustrated in FIG. 4, the PCB circuit support 2 may have four lateral portions 21a-21d, and once folded, forms a cube or a parallelepiped open on one of its sides.Thus, when the folded PCB circuit support 2 is positioned in the internal volume 12, the central portion 20 is centered on the central axis Z and perpendicular to this central axis Z, and the faces of the lateral portions 21a-21d each form an angle α of between 90° and 95° with the central portion 20.

[0068] To enable vibration detection, at least two MEMS sensitive elements 3a-3c for vibration detection suitable for high-frequency measurements are mounted on the internal faces 210a-210c of the lateral portions 21a-21c of the PCB circuit support 2. The MEMS sensitive elements 3a-3c are advantageously of the microelectromechanical device type with interdigitated capacitive combs produced in a substrate with sensitive axis(es) in the plane, i.e. parallel to the plane of the substrate. Each MEMS sensitive element 3a-3c can thus comprise a single sensitive axis or two sensitive axes. The sensitive axes 30a-30c of the MEMS sensitive elements 3a-3c are parallel to the internal face 210a-210d of the lateral portion 21a-21d on which the sensitive element is mounted and form a three-dimensional reference frame. The set of sensitive axes 30a-30c is therefore distant from the central Z axis of the housing.For example, as illustrated in Figure 4, three single-axis MEMS sensitive elements 3a-3c are each mounted on the inner face of a lateral portion 21a-21c. Thus, when the angle α formed between each lateral portion 21a-21d and the central portion 20 is equal to 90° (Figure 7), the sensitive axes 30a-30c form an orthonormal three-dimensional reference frame. In practice, due to the elastic properties of the thinned zones 22a-22d, these thinned zones will more or less return to their initial shape after deformation, so that the lateral portions 21a-21d can be slightly inclined (Figure 8) relative to the central axis Z of the package. Due to this elastic return of these flexible zones 22a-22d, certain parts of the lateral portions 21a-21d can come into abutment (Figures 6 and 9) on the internal wall of the housing 1, for example on the internal wall 111 of the cover 11.Indeed, when inserting the folded PCB circuit support 2 into the cover 11, the lateral portions 21a-21d tend to move away from the central axis Z due to this elastic return. By dimensioning the internal volume of the cover 11, and therefore of the housing 1, relative to the surface area of ​​the PCB circuit 2 necessary to accommodate all of the MEMS sensitive elements 3a-3c and the electronic components, the verticality or quasi-verticality of these lateral portions 21a-21d is ensured, and therefore the orthogonality of the sensitive axes 30a-30c. Thus, the PCB circuit 2 is not held by gluing or screwing onto a specific support of the housing, but is advantageously held in place in the housing by the effect of the restoring force of the flexible zones 22a-22d which ensures the immobilization in abutment of the vertical edges 211 of the lateral portions 21a-21d on the internal wall (Figure 5, Figure 6 and Figure 9).In addition, all sensitive axes 30a-30c are distant from the central Z axis of the housing.

[0069] In a variant illustrated in Figures 10 and 11, the inner wall of the housing 1 may be provided with projecting protrusions in the form of ribs 5, so that the outer faces of the lateral portions 21a-21d abut on these ribs 5. In other words, the elastic return is limited not by the vertical edges 211 abutting on the inner wall of the cover 11, but by the outer faces abutting on the shims or ribs 5. In Figure 11, the lateral portion 21a is not shown to allow a better visualization of the ribs 5. In practice, these protrusions 5 may have different profiles insofar as they are configured to perform the function of a stop and thus limit the opening angle of the lateral portions 21a-21d. In this variant, the inner cavity of the housing may be octagonal in shape.

[0070] Electronic components associated with the MEMS sensitive elements 3a-3c may be provided on the inner face 200 of the central portion 20, and / or on free areas of the lateral portions 21a-21d. For example, these electronic components may include a controller and an analog-to-digital converter for generating digital signals at the output of the sensor.

[0071] To ensure the output of the signals, a signal output connector 4 can be fixed to the external surface of the central portion 20 to open at the output of the sensor through a through hole 110 of the cover 11, and electrical connections of the via type can be provided to electrically connect the connector to the electronic components arranged on the internal face 200 of the central portion 20.

[0072] According to another variant, the output of the signals can be provided by an electrical cable adapted to signal transfers according to an industrial communication protocol. This cable is connected directly to the central portion 20 and exits the housing 1 through the through hole 110 of the cover 11. According to another variant, the sensor can integrate wireless communication means.

[0073] In practice, to finish immobilizing the PCB circuit support 2 in the housing, the internal volume 12 can be filled with a resin. In practice, the resin can be injected into the internal volume 12 of the housing via through holes provided for this purpose and made in the base 10, after assembling the cover 11 with the base 10. In another implementation, to avoid making through holes for injecting the resin, the resin can be poured into the internal volume of the cover 11 after positioning the PCB circuit support 2 in the cover 11 and before closing the housing by assembling the cover 11 to the base 10.

[0074] The assembly of the cover 11 to the base 10 can be carried out by any means, for example by screwing, welding, gluing or even stamping, in order to seal the housing and protect the electronic components from electromagnetic disturbances very present on industrial equipment. Thus, the base 10 and the cover 11 can have thicker zones to allow assembly by screwing. For example, the base can include in its thick zones through holes intended for the passage of screws, and the cover 11 can also include in its thick zones tapped holes configured to cooperate with screws. In practice, the external profile of the housing is hexagonal in shape, this profile facilitating the fixing of the sensor on industrial equipment with existing tools.

[0075] To fix the sensor on a vibrating structure, a central protrusion 100 is provided at the base 10. This central protrusion 100 projects into the internal volume 12 of the housing and is for example in the form of a tapped blind hole open to the outside of the housing 1. In practice, the central protrusion 100 defines a fixing axis which coincides with the central axis Z.

[0076] The sensor mounting can be done as follows:

[0077] - production of the PCB 2 circuit support integrating the various electronic components as well as the sensitive modules 3a-3c;

[0078] - bending of the PCB support 2 at the flexible zones 22a-22d;

[0079] - insertion of the PCB support 2 thus folded into the cover 11 with fixing to the connector when the connector is provided;

[0080] - depending on the dimensions of the cover, and due to the elastic return of the flexible zones 22a-22d, the lateral portions 21a-21d move apart slightly to come into abutment on the internal wall of the cover 11;

[0081] - assembly of the cover 11 with the base 10, for example by screwing; and

[0082] - pouring the resin into the internal volume of the housing 1 to fix and protect the assembly. The assembly of the base to the cover and the injection of the resin can induce stresses on the lateral portions which can prevent the free elastic return of the lateral portions. It is thus possible to dimension the housing so as to maintain a spacing E, as illustrated in Figure 12, between the lower edges 212 of the side walls 21a-21d and the bottom of the base 101, after assembly of the cover 11 with the base 10 in order to allow this free elastic return.

[0083] In another variant, the last two steps above, namely assembly and resin casting, can be reversed as mentioned above. In other words, after insertion of the PCB support 2 into the cover 11, the resin is cast into the volume of the cover, before assembly of the cover 11 with the base 10. This variant avoids the use of through holes for resin injection.

[0084] The invention thus makes it possible to produce a 3-axis vibration sensor integrating MEMS sensitive elements whose sensitive axes are offset from the central axis of the sensor, and adapted to industrial equipment.

Claims

CLAIMS 1. Vibration sensor characterized in that it comprises: - a housing (1) with a central axis (Z) comprising a base (10) coupled to a cover (11) defining an internal volume (12) in which a PCB circuit support (2) is arranged, the base (10) comprising a central protrusion (100) projecting into the internal volume (12) and being configured to ensure the fixing of the housing (10) to a vibrating structure; - the PCB circuit support (2) has at least flexible zones (22a-22d), and is formed of at least one central portion (20) centered on the central axis (Z) and from which extend at least two distinct lateral portions (21a-21d), said flexible zones (22a-22d) electrically connecting the central portion (20) to the lateral portions (21a-21d), each lateral portion (21a-21d) forms an angle (a) greater than or equal to 90° with respect to the central portion (20); - at least two MEMS sensitive elements (3a-3c) for vibration detection mounted on the internal faces (210a-210c) of the lateral portions (21a-21c) of the circuit support (2), and positioned so that the sensitive axes (30a-30c) of the MEMS sensitive elements (3a-3c) are parallel to the internal face (210a-210d) of the corresponding lateral portion (21a-21d) and form a three-dimensional reference frame; and - signal output means.

2. Vibration sensor according to claim 1, wherein the signal output means comprise a signal output connector (4) centered on the central axis (Z), fixed to the central portion (20) and opening outside the housing (1) through a through hole (110) of the cover (11).

3. Vibration sensor according to claim 1 or 2, wherein the angle (a) formed between a lateral portion (21a-21d) and the central portion (20) is between 90° and 95°.

4. Vibration sensor according to one of claims 1 to 3, in which a part of the outer face of each lateral portion (21a-21d) is in contact with an area of ​​the inner wall (111) of the cover (11).

5. Vibration sensor according to one of claims 1 to 4, in which the internal volume (12) is filled with a resin.

6. Vibration sensor according to one of claims 1 to 5, in which all or part of the electronic components associated with these MEMS sensitive elements (3a-3c) are transferred to the internal face (200) of the central portion (20).

7. Vibration sensor according to one of claims 1 to 6, in which the MEMS sensitive elements (3a-3c) are of the micro-electromechanical device type with interdigitated capacitive combs produced in a substrate with sensitive axis(es) in the plane.

8. Vibration sensor according to one of claims 1 to 7, wherein the outer profile of the housing (1) is hexagonal in shape.

9. Vibration sensor according to one of claims 1 to 8, wherein the sensor is configured for vibration measurements at frequencies greater than 10kHz.

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