Micromechanical impact detection device

Abstract

The invention relates to a micromechanical impact detection device (2) comprising: - a frame (4); - an inertial mass (5) that is movably mounted with respect to the frame (4); - an indicator (6) that is movably mounted with respect to the frame (4); - a connecting structure (7) connecting the indicator (6) to the inertial mass (5) and to the frame (4), the connecting structure (7) being configured such that a movement of the inertial mass (5) from a first initial position to a first final position brings about a correlative movement of the indicator (6) from a second initial position to a second final position; - a locking structure (8) configured such that, once it is in the locked position, the locking structure (8) prevents the inertial mass (5) from returning to the first initial position, which thereby results in the indicator (6) being kept in the second final position.

Description

[0001] DESCRIPTION

[0002] MICROMECHANICAL SHOCK DETECTION DEVICE

[0003] FIELD OF THE INVENTION

[0004] The invention relates to a micromechanical shock detection device and a shock detection assembly incorporating such a micromechanical device.

[0005] STATE OF THE ART

[0006] In some areas of activity, it is sometimes necessary to be able to monitor the health status of certain objects. In particular, it may be necessary to determine whether a piece of equipment has suffered shocks, for example due to an impact with another object or a fall of the equipment.

[0007] This may be the case, for example, for metrology instruments, transport containers, pyrotechnic materials, body protection equipment or, more generally, any sensitive material or structure.

[0008] Indeed, when these devices are subjected to shocks with an amplitude (or duration) greater than a certain value, certain essential components can be damaged, which can degrade their efficiency.

[0009] For example, body protection equipment, such as helmets or protective plates, may include sensitive components, which must be replaced or reconditioned when the equipment has suffered an impact likely to damage the component, so as not to compromise the safety of the operator whose protection is provided by the equipment.

[0010] However, it can be difficult to determine whether such equipment has suffered an impact that could damage the component. This is because component damage caused by impact is not always visually detectable.

[0011] One possible solution would be to equip certain equipment with sensors that can detect acceleration with an amplitude (or duration) greater than a certain threshold. Such sensors would be able to record a shock that could damage the equipment, which would provide information on the need to replace or recondition the equipment. However, such sensors generally require an electrical power supply to operate, to store and / or to collect the detection information generated by the sensor.

[0012] The electrical power supply for such sensors can, for example, be provided by a battery. However, adding a battery complicates the installation of these sensors, increasing their size, and requires regular monitoring of the battery's charge status.

[0013] SUMMARY OF THE INVENTION

[0014] One aim of the invention is to propose a solution to facilitate the detection of shocks suffered by components, which does not require an electrical power supply.

[0015] This aim is achieved within the framework of the present invention thanks to a micromechanical shock detection device, comprising:

[0016] - a frame,

[0017] - an inertial mass, having a first initial position, the inertial mass being mounted to move relative to the frame in a first direction of movement,

[0018] - an indicator having a second initial position, the indicator being mounted to move relative to the frame in a second direction of movement,

[0019] - a connecting structure connecting the indicator to the inertial mass and to the frame, the connecting structure being configured such that a movement of the inertial mass in the first direction of movement from the first initial position to a first final position causes a correlative movement of the indicator in the second direction of movement from the second initial position to a second final position,

[0020] - a locking structure, movable between an unlocked position and a locked position, the movement of the inertial mass in the first direction of movement from the first initial position to the first final position having the effect of moving the locking structure from the unlocked position to the locked position, the locking structure being configured so that once in the locked position, the locking structure prevents a return of the inertial mass to the first initial position, which has the effect of maintaining the indicator in the second final position. When the micromechanical shock detection device is subjected to a sudden acceleration, the inertial mass is displaced relative to the frame, causing a concomitant displacement of the indicator.

[0021] If the acceleration is below a predefined threshold, the magnitude of the inertial mass displacement is insufficient to trigger a lock of the locking structure.

[0022] On the other hand, if the acceleration is greater than or equal to the predefined threshold, the displacement of the inertial mass has sufficient amplitude to trigger a locking of the locking structure.

[0023] Once the locking structure is in the locked position, the indicator is held in the final position.

[0024] By simply observing the position of the indicator, an observer is able to determine whether or not the micromechanical shock detection device has experienced a shock with an intensity greater than a limit intensity to be detected.

[0025] The proposed micromechanical shock detection device thus makes it possible to record the occurrence of a shock which could compromise the integrity of the component.

[0026] Such a micromechanical shock detection device does not require an electrical power supply for its operation.

[0027] The micromechanical shock detection device may further have the following characteristics:

[0028] - the connecting structure comprises a first connecting beam connecting the indicator to the frame and a second connecting beam connecting the indicator to the inertial mass, such that the displacement of the inertial mass relative to the frame in the first direction of displacement causes both a bending of the first beam and a bending of the second beam, causing the displacement of the indicator in the second direction of displacement;

[0029] - the indicator comprises a screen which is adapted to mask an underlying visual cue when the indicator is in the second initial position and to reveal the visual cue when the indicator is in the second final position;

[0030] - the screen comprises a block having an external face and a series of non-opening orifices formed from the external face; - the indicator comprises a stop extending from the screen, the stop being suitable for coming into contact with the frame to limit the movement of the indicator relative to the frame in the second direction of movement;

[0031] - the locking structure comprises a first tooth fixedly mounted on the frame and a second tooth fixedly mounted on the inertial mass, and the second tooth is adapted to be engaged with the first tooth when the locking structure is in the locked position;

[0032] - the first tooth comprises a first sliding face and a first locking face, and the second tooth comprises a second sliding face and a second locking face, arranged such that during the movement of the inertial mass from the first initial position to the first final position, the second sliding face of the second tooth slides on the first sliding face of the first tooth, allowing the first tooth to cross the second tooth, after which the second locking face of the second tooth abuts against the first locking face of the first tooth, preventing the inertial mass from returning to the first initial position;

[0033] - the locking structure comprises a plurality of first teeth fixedly mounted on the frame and a plurality of second teeth fixedly mounted on the inertial mass, and each second tooth is adapted to be engaged with a respective first tooth when the locking structure is in the locked position;

[0034] - the micromechanical shock detection device comprises a suspension structure connecting the inertial mass to the frame, the suspension structure being capable of being elastically deformed when the inertial mass is displaced relative to the frame from the first initial position in the first direction, and of generating an elastic restoring force opposing the displacement of the inertial mass from the first initial position;

[0035] - the micromechanical shock sensing device comprises a first silicon layer, and the frame, the inertial mass, the indicator, the connecting structure and the locking structure are formed by etching in the first silicon layer;

[0036] - the micromechanical shock sensing device comprises a second silicon layer and the suspension structure is formed by etching in the second silicon layer; - the micromechanical shock sensing device comprises an intermediate silicon oxide layer between the first silicon layer and the second silicon layer, the intermediate silicon oxide layer connecting the suspension structure to the frame and connecting the suspension structure to the inertial mass;

[0037] - the second silicon layer and the intermediate silicon oxide layer have an opening provided opposite the indicator, in order to reveal an underlying visual marker when the indicator is in the second final position.

[0038] The invention further relates to a shock detection assembly comprising:

[0039] - a micromechanical shock detection device as defined above, and

[0040] - a support comprising a housing suitable for accommodating the micromechanical shock detection device, the housing having a bottom presenting a visual marker, the visual marker being positioned such that when the indicator is in the second initial position, the indicator covers the visual marker, the marker then not being visible to an external observer, and when the indicator is in the second final position, the indicator uncovers the visual marker, the visual marker then being visible to the external observer.

[0041] In one embodiment, the shock detection assembly further comprises a cover adapted to be assembled to the support to close the housing, the cover being visually transparent to allow an outside observer to see the visual cue through the cover.

[0042] PRESENTATION OF THE DRAWINGS

[0043] Other characteristics and advantages will emerge from the following description, which is purely illustrative and non-limiting and must be read in conjunction with the attached figures, including:

[0044] - figure 1 schematically represents, in exploded view, a shock detection assembly according to a possible embodiment of the invention,

[0045] - figure 2 schematically represents, in top view, the shock detection assembly, in an initial configuration, - figure 3 schematically represents, in top view, the shock detection assembly, in a final configuration, after detection of a shock,

[0046] - Figure 4 is a detail view showing a locking structure in the unlocked position,

[0047] - Figure 5 is a detail view showing a locking structure in the unlocked position,

[0048] - figure 6 is a top view of an indicator,

[0049] - figure 7 is a sectional view of the indicator,

[0050] - figures 8A to 8D schematically represent different possible examples of a linking structure,

[0051] - figures 9A and 9B schematically represent different possible examples of a locking structure,

[0052] - figure 10 is a photograph taken with a scanning electron microscope of a part of a micromechanical shock detection device, in accordance with a possible embodiment of the invention,

[0053] - figures 11 A and 11 B schematically represent, respectively in front view and in side view, a ballistic protection equipped with shock detection assemblies.

[0054] DETAILED DESCRIPTION OF AN EMBODIMENT

[0055] In Figure 1, the shock detection assembly 1 shown comprises a micromechanical shock detection device 2 and a housing 3 suitable for containing the micromechanical shock detection device 2.

[0056] The housing 3 comprises a support 31 and a cover 32.

[0057] The support 31 comprises a housing 33 suitable for accommodating the micromechanical shock detection device 2, so as to immobilize the micromechanical shock detection device 2 relative to the support 31.

[0058] The support 31 may for example be formed from plastic, and have a thickness of approximately 1.5 millimeters.

[0059] As illustrated in FIG. 1, the support 31 may comprise several nested housings, suitable for accommodating micromechanical shock detection devices of different sizes depending on requirements.

[0060] The cover 32 is suitable for being assembled to the support 31 to close the housing 33. In the example illustrated in FIG. 1, the cover 32 is formed from a material transparent to light radiation in a range of visible wavelengths (i.e. in a range between 380 and 780 nanometers for a wavelength in a vacuum) so as to allow an observer to observe the micromechanical shock detection device 2 through the cover 32.

[0061] The cover 32 may, for example, comprise a window having a thickness of approximately 300 micrometers.

[0062] The housing 33 has a bottom presenting a visual cue 34. The visual cue may be a raised area and / or a colored area, with a color different from that of the bottom, having dimensions sufficient to be easily visible by an observer, for example dimensions of the order of approximately 1 millimeter.

[0063] The various components of the micromechanical shock detection device 2 were formed by an etching process in a wafer comprising several layers of material. The wafer used to manufacture the micromechanical shock detection device 2 comprises a first silicon layer 21, a second silicon layer 22 and an intermediate silicon oxide layer 23 disposed between the first silicon layer 21 and the second silicon layer 22. These various layers are present in the manufactured micromechanical shock detection device 2.

[0064] The micromechanical shock detection device 2 comprises a frame 4, an inertial mass 5, an indicator 6, a connecting structure 7, one or more locking structures 8 and a suspension structure 9.

[0065] In the example illustrated in Figures 1 to 3, the frame 4 and the inertial mass 5 were formed by etching both in the first silicon layer 21 and in the second silicon layer 22. The indicator 6, the connecting structure 7 and the locking structure(s) 8 were formed by etching in the first silicon layer 21. The suspension structure 9 was formed by etching in the second silicon layer 22.

[0066] The frame 4 surrounds the inertial mass 5, the indicator 6, the connecting structure 7, the locking structure(s) 8 and the suspension structure 9.

[0067] In addition, the frame 4 delimits an opening 41 revealing the bottom of the housing 33 through the shock detection device 2. The opening 41 is provided opposite the indicator (6), through the intermediate layer of silicon oxide (23) and the second layer of silicon 22.

[0068] In the example illustrated in Figures 1 to 3, the inertial mass 5 is mounted to move relative to the frame 4 parallel to a first axis of movement X1.

[0069] In the example illustrated in Figures 1 to 3, the inertial mass 5 is capable of moving relative to the frame, parallel to the first axis of movement X1, selectively in a first direction of movement (arrow A) or in a second direction of movement (arrow B), opposite to the first direction of movement.

[0070] The inertial mass 5 is connected to the frame 4 only via the suspension structure 9, which allows the movement of the inertial mass 5 relative to the frame 4 parallel to the first axis of movement X1.

[0071] For this purpose, certain portions of the intermediate layer of silicon oxide 23 which remain after etching connect the suspension structure 9 to the frame 4 and other portions of the intermediate layer of silicon oxide 23 which remain after etching connect the suspension structure 9 to the inertial mass 5.

[0072] The suspension structure 9 is capable of being elastically deformed when the inertial mass 5 is displaced relative to the frame 4 parallel to the first displacement axis X1. When the suspension structure 9 is elastically deformed, the suspension structure 9 generates an elastic restoring force opposing the displacement of the inertial mass 9 relative to the frame 4. The value of the elastic restoring force generated by the suspension structure 9 increases with the amplitude of the displacement of the inertial mass 5 relative to the frame 4.

[0073] In the example illustrated in Figures 1 to 3, the suspension structure 9 comprises suspension beams 91 and 92 extending transversely to the first axis of movement X1. The displacement of the inertial mass 5 relative to the frame 4 parallel to the first axis of movement X1 causes a bending of the suspension beams 91 and 92.

[0074] The connecting structure 7 connects the indicator 6 to the frame 4 and to the inertial mass 5. The connecting structure 7 is configured such that a displacement of the inertial mass 5 relative to the frame 4 in the first direction X1 causes a correlative displacement of the indicator 6 relative to the frame 4 parallel to a second displacement axis X2.

[0075] In the example, illustrated in Figure 1, the second axis of movement X2 is substantially perpendicular to the first axis of movement X1. In the example, illustrated in Figures 1 to 3, the connecting structure 7 comprises a first connecting beam 71 connecting the indicator 6 to the frame 4 and a second connecting beam 72 connecting the indicator 6 to the inertial mass 5. Thus, the movement of the inertial mass 5 relative to the frame 4 parallel to the first axis of movement X1 causes both a bending of the first connecting beam 71 and a bending of the second connecting beam 72.

[0076] In the example, illustrated in Figures 1 to 3, the first connecting beam 71 and the second connecting beam 72 extend parallel to each other. In addition, when the shock detection assembly 1 is in the initial configuration (configuration illustrated in Figure 2), the first connecting beam 71 and the second connecting beam 72 extend parallel to the first axis of movement X1.

[0077] In the example illustrated in Figures 1 to 3, the connecting structure further comprises a third connecting beam 73, extending transversely to the first connecting beam 71 and to the second connecting beam 72. The third connecting beam connects the first connecting beam 71 and the second connecting beam 72 to each other.

[0078] The third connecting beam 73 connecting the first connecting beam 71 and the second connecting beam 72 together makes it possible to stiffen the connecting structure 7. The stiffness of the connecting structure 7 and the amplification capacity of the connecting structure 7 can be adjusted according to the position of the third connecting beam 73 along the first connecting beam 71 and the second connecting beam 72.

[0079] More generally, the amplification factor and the stiffness of the connecting structure 7 depend on the position of the third connecting beam 73 (which defines the bending length of the first connecting beam 71 and the second connecting beam) and the spacing between the first connecting beam 71 and the second connecting beam 72.

[0080] When the shock detection assembly 1 is in the initial configuration (configuration illustrated in FIG. 2), the third connecting beam 73 extends parallel to the second axis of movement X2.

[0081] The indicator 6 comprises a screen 61, a first stop 62 and a second stop 63. In the example illustrated in FIGS. 1 to 3, the screen 61 has a disc shape, two sides of which have been truncated. The shape of the screen 61 makes it possible to better expose the underlying visual marker 34 when the shock detection assembly 1 is in the final configuration (configuration illustrated in FIG. 3).

[0082] The first stop 62 and the second stop 63 extend projecting from the screen 61, on either side of the screen 61.

[0083] The first stop 62 is suitable for coming into contact with the frame 4 to limit the movement of the indicator 6 relative to the frame parallel to the second axis of movement X2, in a third direction of movement (arrow C). The second stop 63 is suitable for coming into contact with the frame 4 to limit the movement of the indicator 5 relative to the frame 4 parallel to the second axis of movement X2, in a fourth direction of movement (arrow D), opposite to the third direction of movement.

[0084] In the example illustrated in Figures 1 to 3, the shock detection device 1 comprises several locking structures 8.

[0085] In particular, the locking structures include a first locking structure 81 and a second locking structure 82.

[0086] The first locking structure 81 is illustrated in more detail in Figures 4 and 5.

[0087] As seen in Figures 4 and 5, the first locking structure 81 comprises a first locking beam 83 fixedly mounted on the frame 4, a plurality of first teeth 84 extending projecting from the first locking beam 83, a second locking beam 85 fixedly mounted on the inertial mass 5, and a plurality of second teeth 86 extending projecting from the second locking beam 85.

[0088] The second teeth 86 are adapted to be engaged with the first teeth 84 when the first locking structure 8 is in the locked position (position illustrated in FIG. 5).

[0089] As seen in Figures 4 and 5, the first locking beam 83 and the second locking beam 85 extend parallel to the first axis of movement X1.

[0090] The first teeth 84 and the second teeth 86 are oriented such that the tops of the first teeth 84 are directed toward the second locking beam 85 and the tops of the second teeth 86 are directed toward the first locking beam 83. In addition, as illustrated in FIG. 4, the second teeth 86 are interposed between the first teeth 84.

[0091] Each first tooth 84 comprises a first sliding face 841 and a first locking face 842. The first sliding faces 841 are oriented at an obtuse angle relative to a longitudinal direction of the first locking beam 83. The first locking faces 842 are oriented at a right angle or an acute angle relative to a longitudinal direction of the first locking beam 83.

[0092] Likewise, each second tooth 86 comprises a second sliding face 861 and a second locking face 862. The second sliding faces 861 are oriented at an obtuse angle relative to a longitudinal direction of the second locking beam 85. The second locking faces 862 are oriented at a right angle or an acute angle relative to a longitudinal direction of the second locking beam 85.

[0093] In the example illustrated in Figures 4 and 5, the angle formed by the second sliding faces 861 is equal to the angle formed by the first sliding faces 841, that is to say that the sliding faces 741 and 861 are parallel to each other.

[0094] As illustrated in Figure 4, when the micromechanical device is in the initial configuration, each second sliding face 861 of a second tooth 86 is located opposite a first sliding face 841 of a respective first tooth 84.

[0095] When the inertial mass 5 moves in the first direction of movement (arrow A), the second locking beam 85 is moved relative to the first locking beam 83 parallel to the first axis of movement X1, in the first direction. Thus, the second teeth 86 are moved relative to the first teeth 84 parallel to the first axis of movement X1, in the first direction.

[0096] Each second tooth 86 then comes into contact with a respective first tooth 84. More specifically, the second sliding face 861 comes into contact with the first sliding face 841 located opposite and slides on the first sliding face 841. During the movement of the second locking beam 85 relative to the first locking beam 83, the sliding faces 841 and 861 form guide ramps. The sliding of the second sliding face 861 on the first sliding face 841 causes elastic deformation of the locking beams 83 and 85. In other words, the locking beams 83 and 85 flex away from each other.

[0097] The second sliding face 861 slides on the first sliding face 841 until the second tooth 86 passes the first tooth 84.

[0098] Once the second tooth 86 has passed the first tooth 84, the locking beams 83 and 85 return to their initial state, moving closer to each other, due to their elasticity.

[0099] The second locking face 862 of the second tooth 86 is then located opposite the first locking face 842 of the first tooth 84.

[0100] Under the effect of the elastic restoring force exerted by the suspension structure 9 on the inertial mass 5, the second locking beam 85 is moved relative to the first locking beam 83 parallel to the first axis of movement X1, in the second direction (arrow B), opposite to the first direction.

[0101] This results in the second locking face 862 of each second tooth 86 abutting the first locking surface 842 of a respective first tooth 84, preventing a return of the inertial mass 5 to the first initial position. In this way, each second tooth 86 is engaged with a respective first tooth 84 when the first locking structure 81 is in the locked position (position illustrated in FIG. 5).

[0102] It should be noted that the second locking structure 82 operates in the same way as the first locking structure 81, except that the second locking structure is configured to move from an unlocked position to a locked position during a movement of the inertial mass 5 parallel to the first axis of movement X1, in the second direction of movement (arrow B).

[0103] Therefore, the micromechanical shock detection device 2 is called "bidirectional", in the sense that it is capable of detecting

[0104] In operation, the micromechanical shock detection device 2 is initially in the initial configuration (configuration illustrated in Figure 2).

[0105] In this initial configuration, the inertial mass 5 is in a first initial position. The indicator 6 is in a second initial position. In addition, the locking structures 8 (including the first locking structure 81 and the second locking structure 82) are in the unlocked position.

[0106] In the second initial position of the indicator 6, the indicator 6 masks the underlying visual marker 34. In other words, the underlying visual marker 34 is not visible to an observer who observes the micromechanical shock detection device 2 through the cover 32 of the housing 3.

[0107] When the micromechanical shock detection device 2 undergoes a shock, that is to say when the micromechanical shock detection device 2 undergoes a sudden acceleration, having an acceleration component parallel to the first axis of movement X1, this acceleration is transmitted by the frame 4 to the inertial mass 5 via the suspension structure 9. The suspension structure 9 then tends to deform elastically due to the inertia of the inertial mass 5.

[0108] The inertial mass 5 is then moved relative to the frame 4 parallel to the first axis of movement X1.

[0109] If the shock is directed in the first direction of movement (arrow A), then the inertial mass 5 is displaced relative to the frame 4 parallel to the first axis of movement X1, in the first direction of movement (arrow A).

[0110] Conversely, if the shock is directed in the second direction of movement (arrow B), then the inertial mass 5 is displaced relative to the frame 4 parallel to the first axis of movement X1, in the second direction of movement (arrow B).

[0111] The displacement of the inertial mass 5 relative to the frame 4 causes a bending of the connecting structure 7, and consequently a correlative displacement of the indicator 6 parallel to the second axis of displacement X2.

[0112] More precisely, the displacement of the inertial mass 5 causes a bending of the first connecting beam 71 and the second connecting beam 72. The bending of the first connecting beam 71 and the second connecting beam 72 causes the displacement of the indicator 6 parallel to the second axis of displacement X2.

[0113] If the inertial mass 5 is displaced relative to the frame 4 parallel to the first axis of displacement X1, in the first direction of displacement (arrow A), then the indicator 6 is displaced relative to the frame 4 parallel to the second axis of displacement X2, in the third direction of displacement (arrow C) (case illustrated in Figure 3). Conversely, if the inertial mass 5 is displaced relative to the frame 4 parallel to the first axis of displacement X1, in the second direction of displacement (arrow B), then the indicator 6 is displaced relative to the frame 4 parallel to the second axis of displacement X2, in the fourth direction of displacement (arrow D).

[0114] The connecting structure 7 thus makes it possible to convert a first displacement of the inertial mass 5 relative to the frame 4 having a first displacement amplitude into a second displacement of the indicator 6 relative to the frame 4 having a second displacement amplitude, greater than the first displacement amplitude.

[0115] The connecting structure 7 makes it possible, for example, to convert a first displacement of the inertial mass 5 relative to the frame 4 having a first displacement amplitude of a few tens of micrometers (less than one millimeter) into a second displacement of the indicator 6 relative to the frame 4 having a second displacement amplitude greater than or equal to one millimeter, visible to the naked eye.

[0116] For example, the amplification factor of the connecting structure may be of the order of 10: this means that a first displacement of the inertial mass relative to the frame having a first displacement amplitude (for example 80 micrometers) is converted into a second displacement of the indicator relative to the frame having a second displacement amplitude equal to 10 times the first displacement amplitude (for example 800 micrometers).

[0117] In parallel, the displacement of the inertial mass 5 parallel to the first axis of displacement X1, in the first direction of displacement (arrow A), from the first initial position (position of the inertial mass 5 illustrated in FIG. 2) also causes a correlative displacement of the second teeth 86 of the first locking device 81 relative to the first teeth 84 of the first locking device 81.

[0118] If the intensity of the shock is greater than a predefined intensity threshold, i.e. if the acceleration peak experienced by the micromechanical shock detection device 2 has a maximum value greater than a predefined threshold value, the inertial mass 5 moves from the first initial position to a first final position (position of the inertial mass 5 illustrated in FIG. 3). The movement of the inertial mass 5 parallel to the first axis of movement X1 from the first initial position to the first final position causes a correlative movement of the indicator 6 parallel to the second axis of movement X2 from the second initial position (position of the indicator 6 illustrated in FIG. 2) to a second final position (position of the indicator 6 illustrated in FIG. 3).

[0119] During the movement of the inertial mass 5 parallel to the first axis of movement X1, the suspension structure 9 exerts on the inertial mass 5 an elastic restoring force tending to oppose the movement of the inertial mass 5. Indeed, the movement of the inertial mass 5 relative to the frame 4 has the effect of elastically deforming the suspension beams 91 and 92. More precisely, the suspension beams 91 and 92 flex. By flexing, the suspension beams 91 and 92 exert on the inertial mass 5 an elastic restoring force, tending to bring the inertial mass 5 back to the first initial position.

[0120] However, the movement of the inertial mass 5 from the first initial position (position illustrated in FIG. 2) to the first final position (position illustrated in FIG. 3) has the effect of moving the first locking structure 81 from the unlocked position (position illustrated in FIG. 4) to the locked position (position illustrated in FIG. 5).

[0121] In other words, when the amplitude of the displacement of the inertial mass 6 from the first initial position exceeds a predefined displacement threshold, the first locking structure 81 moves from the unlocked position to the locked position.

[0122] Once in the locked position, the first locking structure 81 prevents a return of the inertial mass 5 to the first initial position.

[0123] Therefore, indicator 6 is held in the second final position.

[0124] In the second final position of the indicator 6, the indicator 6 no longer masks the underlying visual marker 34. In other words, the underlying visual marker 34 is visible to an observer who observes the micromechanical shock detection device 2 through the cover 32 of the housing 3.

[0125] The micromechanical shock detection device 2 is then in the final configuration, as illustrated in Figure 3.

[0126] The micromechanical shock detection device 2 operates in the same way when the inertial mass 5 is displaced relative to the frame 4 parallel to the first axis of displacement X1, in the second direction of displacement (arrow B). The indicator 6 is then displaced relative to the frame 4 parallel to the second axis of displacement X2, in the fourth direction of displacement (arrow D).

[0127] In this case, the movement of the inertial mass 5 has the effect of moving the second locking structure 82 from the unlocked position to the locked position.

[0128] By simply observing the micromechanical shock detection device 2, an observer is able to determine whether the micromechanical shock detection device 2 is in the initial configuration (in which case the visual cue is not visible) or whether the micromechanical shock detection device 2 is in the final configuration (in which case the visual cue is visible).

[0129] If the micromechanical shock detection device 2 is in the initial configuration, this means that the micromechanical shock detection device 2 has not undergone a shock whose intensity would be greater than the predefined intensity threshold.

[0130] If the micromechanical shock detection device 2 is in the final configuration, this means that the micromechanical shock detection device 2 has undergone a shock whose intensity is greater than the predefined intensity threshold.

[0131] Furthermore, in the case where the shock detection device 2 is in the final configuration, the observer is also able to determine in which direction the shock occurred, depending on the position of the indicator 6 relative to the visual marker 34.

[0132] In the example illustrated in Figures 1 to 3, if the indicator 6 is to the right of the visual marker 34, this means that the impact occurred in the first direction of movement (arrow A), while if the indicator 6 is to the left of the visual marker 34, this means that the impact occurred in the second direction of movement (arrow B).

[0133] This is why, in the embodiment illustrated in Figures 1 to 3, the micromechanical shock detection device 2 is said to be “bidirectional”, in the sense that it is capable of detecting a shock in two possible directions.

[0134] It would of course be possible to design a “monodirectional” shock detection device, which would comprise a first locking structure 81 but not a second locking structure 82. As illustrated in FIGS. 6 and 7, in one embodiment of the locking device 2, the screen 61 comprises a block 67 having an internal face 64, an external face 65, and a series of non-opening orifices 66 formed from the external face 65. The orifices 66 do not pass through the entire thickness of the block 67, and do not open onto the internal face 64.

[0135] The orifices 66 may be formed in the block 67 during the etching process of the micromechanical shock detection device 2. The orifices 66 may, for example, have a depth of 150 micrometers when the first silicon layer 21 has a thickness of 200 micrometers. Furthermore, in the example illustrated in FIGS. 6 and 7, each orifice 66 has a cross-section (section in a plane orthogonal to the axis of the orifice) of square shape having a side of 20 micrometers. The orifices 66 are positioned relative to each other with a constant pitch between two successive orifices, for example a pitch of 25 micrometers between two successive orifices. In this case, the spacing between two successive orifices is 5 micrometers.

[0136] The production of the orifices 66 in the block 67 of the movable screen 61 makes it possible to reduce the total mass of the movable screen 61. The recessing of the block 67 using the orifices 66 results in a reduction in the theoretical mass of the screen 61 which can be up to approximately 50%, and therefore leads to a reduction in the stresses generated in the connecting structure 7 which supports the cantilevered indicator 6. For example, the mass of the screen 61 without the orifices 66 may be 0.37 milligrams, while the mass of the screen 61 with the orifices 66 may be 0.17 milligrams.

[0137] Figures 8A to 8D schematically represent different possible examples of a linking structure 7.

[0138] In Figure 8A, the connecting structure 7 comprises a first connecting beam 71 connecting the indicator 6 to the frame 4, a second connecting beam 72 connecting the indicator 6 to the inertial mass 5, and a third connecting beam 73 extending transversely to the first connecting beam 71 and to the second connecting beam 72, and connecting the first connecting beam 71 to the second connecting beam 72. In other words, the connecting structure 7 has a general H shape.

[0139] With this configuration of the connecting structure 7, there may be a risk of loss of information in the event of breakage of the embedding connection between the first connecting beam 71 and the frame 4 and of the embedding connection between the second connecting beam 72 and the inertial mass 5 (the locations where the breakages occur are designated by “R”).

[0140] In Figure 8B, the connecting structure 7 comprises a first connecting beam 71, a second connecting beam 72, a third connecting beam 73 and a fourth connecting beam 74.

[0141] The first connecting beam 71 connects the frame 4 to the third connecting beam 73. The second connecting beam 72 connects the inertial mass 5 to the third connecting beam 73. The fourth connecting beam 74 connects the third connecting beam 73 to the indicator 6.

[0142] In other words, the first connecting beam 71 connects the frame 4 to the indicator 6 and the second connecting beam 72 connects the inertial mass 5 to the indicator 6 via the third connecting beam 73 and the fourth connecting beam 74.

[0143] This configuration of the connecting structure 7 makes it possible to limit the risk of loss of information. Indeed, in the event of a break, this occurs preferentially at the location of the embedded connection between the fourth connecting beam 74 and the third connecting beam 73, so that the first connecting beam 71, the second connecting beam 72 and the third connecting beam 73 remain.

[0144] In the example illustrated in Figure 8B, the fourth connecting beam 74 has a rectilinear shape.

[0145] In Figure 8C, the connecting structure 7 is identical to the connecting structure of Figure 8B, except that the fourth connecting beam 74 has a wavy shape, that is to say defining an alternation of curves in a first direction, and in a second direction, opposite to the first direction.

[0146] This configuration of the connecting structure 7 makes it possible to limit the risk of breakage of the embedded connection between the fourth connecting beam 74 and the third connecting beam 73, by increasing the flexibility of the fourth connecting beam 74.

[0147] This configuration of the connecting structure also makes it possible to limit the risk of loss of information in the event of a break in the embedded connection between the fourth connecting beam 74 and the third connecting beam 73. In FIG. 8D, the connecting structure 7 comprises a first connecting beam 71, a second connecting beam 72, a third connecting beam 73 and a fourth connecting beam 74.

[0148] The first connecting beam 71 connects the frame 4 to the third connecting beam 73. The second connecting beam 72 connects the inertial mass 5 to the third connecting beam 73.

[0149] The fourth connecting beam 74 is connected to the third connecting beam 73 via an H-shaped structure.

[0150] The fourth connecting beam 74 connects the third connecting beam 73 to the indicator 6 via the H-shaped structure.

[0151] This configuration of the connecting structure 7 makes it possible to limit the risk of breakage of the connection between the fourth connecting beam 74 and the third connecting beam 73, by increasing the elasticity of the connection thanks to the H-shaped structure.

[0152] This configuration of the connecting structure 7 also makes it possible to limit the risk of loss of information in the event of a break in the connection between the fourth connecting beam and the H-shaped structure.

[0153] Figures 9A and 9B schematically represent different possible examples of a locking structure 8.

[0154] In Figure 9A, the first locking beam 83 has a first end connected to the frame 4 by a built-in connection, and a second, free end, opposite the first end.

[0155] The locking structure 8 is configured such that when the locking structure 8 is in the locked position, the second teeth 86 exert on the first teeth 84 a compressive force, directed towards the first end of the first locking beam 83.

[0156] In other words, the second teeth 86 push the first locking beam 83 towards the embedding connection between the first locking beam 83 and the frame 4.

[0157] In Figure 9B, the first locking beam 83 has a first free end, and a second end, opposite the first end, and connected to the frame 4 by an embedding connection.

[0158] The locking structure 8 is configured such that when the locking structure 8 is in the locked position, the second teeth 86 exert a tensile force on the first teeth 84, directed towards the first free end of the first locking beam 83.

[0159] In other words, the second teeth 86 pull the first locking beam 85 away from the embedding connection between the first locking beam 85 and the frame 4.

[0160] Figure 10 is a photograph taken with a scanning electron microscope of a part of a micromechanical shock detection device 2, in accordance with a possible embodiment of the invention.

[0161] The micromechanical shock detection device 2 was produced by a photolithography and plasma etching process in a 6-inch (approximately 15 centimeters) diameter wafer, of the SOI 200 / 2 / 400 type (i.e. consisting of a first layer of silicon having a thickness of 200 micrometers, an intermediate layer of silicon oxide having a thickness of 2 micrometers, and a second layer of silicon having a thickness of 400 micrometers).

[0162] As can be seen in the photograph, the micromechanical shock detection device 2 comprises a connection structure conforming to that shown in FIG. 8B.

[0163] The detection assembly 1 has a surface footprint of the order of 1 square centimeter for a thickness of between 1 and 2 millimeters.

[0164] The detection assembly 1 can be integrated into equipment, such as ballistic protection for example.

[0165] Figures 11 A and 11 B schematically represent, respectively in front view and in side view, a ballistic protection 100 equipped with several shock detection assemblies 1a, 1b, 1c and 1c.

[0166] In Figures 11A and 11B, the ballistic protection 100 comprises a protective plate 101 having a front face 102, a rear face 103, opposite the front face, and a side face 103 (or edge) extending transversely to the front face 102 and to the rear face 103. The plate may be a plate made of ceramic material.

[0167] Plate 101 is intended to be inserted into a bulletproof vest.

[0168] In this example, the plate 101 is provided with four shock detection assemblies 1a, 1b, 1c and 1d, attached to the plate 101. The shock detection assemblies include a first shock detection assembly 1a attached to the front face 102, a second shock detection assembly 1b attached to the front face 102, a third shock detection assembly 1c attached to the side face 104 and a fourth shock detection assembly 1d attached to the side face 104 of the plate 101.

[0169] The first shock detection assembly 1 a is oriented to detect shocks suffered by the protective plate 101, in a first main detection direction X1a parallel to a first diagonal of the front face 102 of the protective plate 101.

[0170] The first shock detection assembly 1a is a bidirectional detection assembly, that is to say it is capable of detecting a shock suffered by the protective plate 101 oriented both in a first direction parallel to the first main detection direction X1a, and in a second direction, opposite to the first direction, along the first main detection direction X1a.

[0171] The second shock detection assembly 1 b is oriented to detect shocks suffered by the protective plate 101, in a second main detection direction X1 b parallel to a second diagonal of the front face 102 of the protective plate 101, different from the first diagonal.

[0172] The second shock detection assembly 1 b is also a bidirectional detection assembly, that is to say that it is capable of detecting a shock oriented both in a first direction along the second main detection direction X1 b, and in a second direction, opposite to the first direction, along the second main detection direction X1 b.

[0173] The third shock detection assembly 1c is oriented to detect shocks suffered by the protective plate 101, in a third main detection direction X1c orthogonal to the front face 102 of the protective plate 101, in a first direction.

[0174] The fourth shock detection assembly 1 d is oriented to detect shocks suffered by the protective plate 101, in the third main detection direction X1c, in a second direction, opposite to the first direction.

[0175] The third shock detection assembly 1c and the fourth shock detection assembly 1d are monodirectional detection assemblies, that is, they are each adapted to detect impacts suffered by the detection plate 101 in a single direction. The detection assemblies 1a, 1b, 1c and 1d make it possible to verify that the protective plate 101 has not suffered impacts which could damage the material of the protective plate 101 and compromise the effectiveness of the ballistic protection 100.

[0176] In the example illustrated in Figures 11 A and 11 B, the chosen installation positions of the detection assemblies 1a, 1b, 1c and 1d make it possible to detect impacts suffered by the ballistic protection 100 according to different fall configurations:

[0177] - the detection sets 1a and 1b positioned on the front face 102 of the protective plate 101 make it possible to detect falls on the 4 corners of the plate of the protective plate 101,

[0178] - the detection assemblies 1c and 1d positioned on the edge of the protective plate 101 make it possible to detect falls on the front face and on the rear face.

[0179] In the example illustrated in Figures 1 to 3, the detection assembly 1 comprises a housing 3, including a support 31. The support 31 can be fixed by gluing to the equipment to be monitored.

[0180] Alternatively, it would be possible to form the support 31 directly in a component of the equipment to be monitored, for example by providing a housing 33 directly in the component at the time of its manufacture, without it being necessary to provide a separate support 31.

Claims

CLAIMS 1. Micromechanical shock detection device (2), comprising: - a frame (4), - an inertial mass (5), having a first initial position, the inertial mass (5) being mounted to move relative to the frame (4) in a first direction of movement (X1), - an indicator (6) having a second initial position, the indicator (6) being mounted to move relative to the frame (4) in a second direction of movement (X2), - a connecting structure (7) connecting the indicator (6) to the inertial mass (5) and to the frame (4), the connecting structure (7) being configured such that a displacement of the inertial mass (5) in the first direction of displacement (X1) from the first initial position to a first final position causes a correlative displacement of the indicator (6) in the second direction of displacement (X2) from the second initial position to a second final position, - a locking structure (8), movable between an unlocked position and a locked position, the movement of the inertial mass (6) in the first direction of movement (X1) from the first initial position to the first final position having the effect of moving the locking structure (8) from the unlocked position to the locked position, the locking structure (8) being configured so that once in the locked position, the locking structure (8) prevents a return of the inertial mass (5) to the first initial position, which has the effect of maintaining the indicator (6) in the second final position.

2. Micromechanical shock detection device according to claim 1, wherein the connecting structure (7) comprises a first connecting beam (71) connecting the indicator (6) to the frame (4) and a second connecting beam (72) connecting the indicator (6) to the inertial mass (5), so that the displacement of the inertial mass (5) relative to the frame (4) in the first direction of displacement (X1) causes both a bending of the first beam (71) and a bending of the second beam (72), causing the indicator to move in the second direction of movement (X2).

3. Micromechanical shock detection device (2) according to one of claims 1 and 2, in which the indicator (6) comprises a screen (61) which is capable of masking an underlying visual marker (34) when the indicator (6) is in the second initial position and of revealing the visual marker (34) when the indicator (6) is in the second final position.

4. Micromechanical shock detection device according to claim 3, in which the screen (61) comprises a block (67) having an external face (65) and a series of non-opening orifices (66) formed from the external face (65).

5. Device according to one of claims 3 and 4, in which the indicator (6) comprises a stop (62, 63) extending from the screen (61), the stop (62, 63) being able to come into contact with the frame (4) to limit the movement of the indicator (6) relative to the frame (4) in the second direction of movement (X2).

6. Micromechanical shock detection device according to one of claims 1 to 5, in which the locking structure (8) comprises a first tooth (84) fixedly mounted on the frame (4) and a second tooth (86) fixedly mounted on the inertial mass (5), and in which the second tooth (86) is capable of being engaged with the first tooth (84) when the locking structure (8) is in the locked position.

7. Micromechanical shock detection device according to claim 6, wherein the first tooth (84) comprises a first sliding face (841) and a first locking face (842), and the second tooth (86) comprises a second sliding face (861) and a second locking face (862), arranged such that during the movement of the inertial mass (5) from the first initial position to the first final position, the second sliding face (861) of the second tooth (86) slides on the first sliding face (841) of the first tooth (84), allowing the second tooth to be crossed. (86) by the first tooth (86), after which the second locking face (862) of the second tooth (86) abuts against the first locking face (842) of the first tooth (84), preventing a return of the inertial mass (5) to the first initial position.

8. Micromechanical shock detection device according to one of claims 6 and 7, wherein the locking structure (8) comprises a plurality of first teeth (84) fixedly mounted on the frame (4) and a plurality of second teeth (86) fixedly mounted on the inertial mass (5), and wherein each second tooth (86) is adapted to be engaged with a respective first tooth (84) when the locking structure is in the locked position.

9. Micromechanical shock detection device according to one of claims 1 to 8, comprising a suspension structure (9) connecting the inertial mass (5) to the frame (4), the suspension structure (9) being capable of being elastically deformed when the inertial mass (5) is moved relative to the frame. (4) from the first initial position in the first direction, and to generate an elastic restoring force opposing the displacement of the inertial mass (5) from the first initial position.

10. Micromechanical shock detection device according to one of claims 1 to 9, comprising a first silicon layer (21) and in which the frame (4), the inertial mass (5), the indicator (6), the connecting structure (7) and the locking structure (8) are formed by etching in the first silicon layer (21).

11. A micromechanical shock detection device according to claim 10, comprising a second silicon layer (22) and wherein the suspension structure (9) is formed by etching in the second silicon layer (22).

12. Micromechanical shock detection device according to claim 11, comprising an intermediate layer of silicon oxide (23) between the first silicon layer (21) and the second silicon layer (22), the layer silicon oxide intermediate (23) connecting the suspension structure (9) to the frame (4) and connecting the suspension structure (9) to the inertial mass (5).

13. Micromechanical shock detection device according to claim 12, in which the second silicon layer (22) and the intermediate silicon oxide layer (23) have an opening (41) arranged opposite the indicator (6), in order to reveal an underlying visual marker (34) when the indicator (6) is in the second final position.

14. Shock detection assembly (1) comprising: - a micromechanical shock detection device (2) according to one of claims 1 to 13, and - a support (31) comprising a housing (33) suitable for receiving the micromechanical shock detection device (2), the housing (33) having a bottom presenting a visual marker (34), the visual marker (34) being positioned such that when the indicator (6) is in the second initial position, the indicator (6) covers the visual marker (34), the marker then not being visible to an external observer, and when the indicator (6) is in the second final position, the indicator (6) uncovers the visual marker (34), the visual marker (34) then being visible to the external observer.

15. Shock detection assembly (1) according to claim 14, comprising a cover (32) suitable for being assembled to the support (31) to close the housing (33), the cover (32) being visually transparent to allow an external observer to see the visual marker (34) through the cover (32).

Images