Micromechanical impact counter device
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- SILMACH
- Filing Date
- 2024-08-23
- Publication Date
- 2026-07-01
Smart Images
Figure EP2024073673_27022025_PF_FP_ABST
Abstract
Description
[0001] DESCRIPTION
[0002] TITLE: MICROMECHANICAL SHOCK COUNTING DEVICE
[0003] FIELD OF THE INVENTION
[0004] The invention relates to a micromechanical shock counting device, and a shock counting assembly incorporating such a device.
[0005] STATE OF THE ART
[0006] In some areas of activity, it is sometimes necessary to be able to monitor the health of certain objects. In particular, it may be necessary to quantify the number of shocks suffered by a piece of equipment, as this number of shocks is likely to influence the equipment's lifespan.
[0007] For example, the lifespan of a firearm depends on the number of shots fired by the firearm, or unwanted events (drops, accidental shock, vibrations, etc.) suffered by the firearm.
[0008] However, in a firearms fleet consisting of a large number of firearms, it is generally not possible to know precisely the history of these events for each firearm in the firearms fleet.
[0009] In the absence of knowledge of this history, each firearm is generally revised at the end of a period of use of a predefined duration, for example every year. This can generate unnecessary revision costs when the firearm has undergone few events during the period of use. On the contrary, a revision could prove necessary, while the period of use is not yet over, because the firearm has undergone a large number of events in a very short time.
[0010] SUMMARY OF THE INVENTION
[0011] One aim of the invention is to propose a solution for reliably determining the number of shocks suffered by a piece of equipment.
[0012] This aim is achieved within the framework of the present invention thanks to a micromechanical shock counting device, comprising:
[0013] - a frame, - an inertial mass having a predefined neutral position and capable of being moved relative to the frame from the neutral position to a first operating position and from the first operating position to a second operating position under the effect of an acceleration undergone by the micromechanical device,
[0014] - a suspension structure connecting the inertial mass to the frame, the suspension structure being capable of generating an elastic restoring force tending to oppose the movement of the inertial mass from the neutral position to the first operating position and from the first operating position to the second operating position,
[0015] - a drive tooth connected to the inertial mass, and capable of meshing with a counting wheel to drive the counting wheel in rotation by an angular step when the inertial mass is moved from the first operating position to the second operating position,
[0016] - a locking structure capable of adopting a locked configuration when the inertial mass is initially moved from the neutral position to the first operating position, such that once the inertial mass is in the first operating position, the locking structure prevents a return of the inertial mass to the neutral position while allowing a movement of the inertial mass from the first operating position to the second operating position and from the second operating position to the first operating position, and that once the inertial mass is in the first operating position, the suspension structure is in a first state of elastic deformation in which the elastic restoring force has a first non-zero minimum value,and the inertial mass is moved relative to the frame from the first operating position to the second operating position only if a value of the acceleration experienced by the micromechanical device exceeds a predefined trigger threshold value, after which the inertial mass is moved from the second operating position to the first operating position under the effect of the elastic restoring force exerted by the suspension structure.,
[0017] Thanks to the suspension structure and the locking structure, the drive tooth only rotates the counting wheel by one step when the acceleration experienced by the micromechanical shock counting device exceeds the predefined trigger threshold value. Thus, only shocks or events producing an acceleration greater than the trigger threshold value are counted by the device.
[0018] By simply observing the position of the counting wheel (possibly using an optical instrument), it is possible to determine at any time the number of shocks or events that the micromechanical shock counting device has undergone.
[0019] Such a micromechanical shock counting device does not require an electrical power supply for its operation.
[0020] Furthermore, it is possible to equip the same equipment with several micromechanical shock counting devices, each micromechanical shock counting device having its own trigger threshold value, different from the trigger threshold values of the other micromechanical shock counting devices, in order to count different types of events experienced by the equipment.
[0021] It is also possible to equip each piece of equipment in a fleet of equipment with one or more shock counting devices, in order to be able to monitor the wear status of each piece of equipment at any time, and depending on this wear status, send the equipment for maintenance or overhaul.
[0022] The micromechanical shock counting device may further have the following characteristics:
[0023] - the suspension structure comprises a first flexible beam extending along a first axis and connecting the inertial mass to the frame, and a second flexible beam extending along a second axis and connecting the inertial mass to the frame, the second axis forming a non-zero angle with the first axis;
[0024] - the locking structure comprises a first locking tooth attached to the frame and a second locking tooth attached to the inertial mass, the second locking tooth being adapted to be engaged with the first locking tooth when the inertial mass is moved from the neutral position to the first operating position, preventing a return of the inertial mass to the neutral position;
[0025] - the first locking tooth comprises a first sliding face and a first locking face, and the second locking tooth comprises a second sliding face and a second locking face, arranged such that during the movement of the inertial mass from the neutral position to the first operating position, the second sliding face of the second locking tooth slides on the first sliding face of the first locking tooth, allowing the first tooth to cross the second tooth, after which the second locking face of the second locking tooth abuts against the first locking face of the first locking tooth, preventing the inertial mass from returning to the neutral position;
[0026] - the frame has a notch allowing the insertion of a tool to exert a thrust on the inertial mass to move the inertial mass from the neutral position to the first position;
[0027] - when the inertial mass is in the neutral position, the suspension structure is in an undeformed state in which the elastic restoring force is zero;
[0028] - when the inertial mass is in the second operating position, the suspension structure is in a second state of elastic deformation in which the elastic restoring force has a second non-zero value greater than the first non-zero value;
[0029] - the suspension structure comprises a braking structure capable of immobilizing the counting wheel when the inertial mass is moved from the second operating position to the first operating position under the effect of the elastic restoring force exerted by the suspension structure;
[0030] - one of the inertial mass and the frame has a stop suitable for coming into contact with the other of the inertial pass and the frame so as to limit a movement of the inertial mass beyond the second operating position;
[0031] - the frame, the inertial mass, the suspension structure, the drive tooth and the locking structure are formed by etching in the same layer of semiconductor material.
[0032] The invention further relates to a shock counting assembly, comprising a micromechanical shock counting device as defined previously, and a counting wheel capable of being driven in rotation by the drive tooth by an angular pitch each time the inertial mass is moved from the first operating position to the second operating position or from the second operating position to the first operating position.
[0033] The shock counting assembly may further have the following features:
[0034] - the counting wheel has graduations making it possible to identify the position of the drive tooth relative to the counting wheel and to deduce from this a number of shocks which have been experienced by the shock counting device;
[0035] - the shock counting assembly comprises a support on which the micromechanical shock counting device and the counting wheel are mounted, and a protective cover suitable for being assembled on the support, the protective cover having a visually transparent window to allow an external observer to view the position of the drive tooth relative to the counting wheel through the protective cover or to allow the position of the drive tooth relative to the counting wheel to be read by means of an optical detector.
[0036] PRESENTATION OF THE DRAWINGS
[0037] 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:
[0038] - figure 1 represents, schematically, in perspective, a shock counting assembly, in accordance with a possible embodiment of the invention,
[0039] - figure 2 shows, schematically, in exploded view, the shock counting assembly of figure 1,
[0040] - figure 3 shows, schematically, in top view, the shock counting assembly of figures 1 and 2,
[0041] - figure 4 shows, schematically, in partial view, a micromechanical shock counting device forming part of the shock counting assembly, when the inertial mass is in the neutral position,
[0042] - figure 5 represents, schematically, in partial view, a micromechanical shock counting device, when the inertial mass is in a first operating position, - figure 6 represents, schematically, in partial view, a micromechanical shock counting device, when the inertial mass is in a second operating position,
[0043] - Figure 7 schematically represents equipment in which shock counting units are integrated.
[0044] DETAILED DESCRIPTION OF AN EMBODIMENT
[0045] In Figures 1 to 3, the shock counting assembly 1 comprises a support 2, a counting wheel 3, a micromechanical shock counting device 4 and a protective cover 5.
[0046] The support 2 has a support surface 21 having a flat part 22 and a depression part 23.
[0047] The counting wheel 3 and the micromechanical shock counting device 4 are mounted side by side on the support 2. The counting wheel 3 and the micromechanical shock counting device 4 extend in the same plane.
[0048] The counting wheel 3 is rotatably mounted relative to the support 2 around an axis of rotation, by means of a shaft 31. The micromechanical shock counting device 4 is fixedly mounted relative to the support 2.
[0049] The counting wheel 3 is mounted on the support 2, opposite the depression portion 23, so that the counting wheel 3 is not in contact with the support surface 21, but is kept at a distance from the support surface 21. This allows the counting wheel 3 to rotate relative to the support 2, around the axis of rotation 31, without rubbing on the support surface 21.
[0050] The counting wheel 3 is a toothed wheel. More specifically, the counting wheel 3 comprises counting teeth 32 arranged along the periphery of the counting wheel 3. The counting teeth 32 are spaced apart from each other with a predefined constant angular pitch between two successive counting teeth. The counting wheel 3 may comprise between 180 and 1000 teeth, for example comprise 250 teeth.
[0051] The counting wheel 3 may have a pitch between 25 and 137 micrometers (pm), for example equal to 103 pm.
[0052] The counting wheel 3 may have a diameter between 7 and 9 millimeters (mm), for example equal to 8 mm. The angular pitch may be between 0.36 and 2 degrees, for example equal to 1.44 degrees.
[0053] The counting wheel 3 may be formed by a molding process or by an etching process in a material wafer, for example by an etching process in a silicon wafer. The counting wheel 3 may have a thickness of 200 micrometers.
[0054] The counting wheel 3 further has markings or graduations 33. The graduations 33 may include numbers which make it possible to locate the counting teeth 32 for counting the events.
[0055] The protective cover 5 is suitable for being assembled on the support 3. Once the protective cover 5 is assembled on the support 3, the counting wheel 3 and the micromechanical shock counting device 4 are located between the support 3 and the protective cover 5. The protective cover 5 thus protects the counting wheel 3 and the micromechanical shock counting device 4. The protective cover 5 can be fixed on the support 3, for example by means of fixing screws 51.
[0056] In the example illustrated in Figures 1 to 3, the protective cover 5 has a visually transparent window 52 to allow an external observer to at least partially view the counting wheel 3 through the protective cover 5, without it being necessary to remove the protective cover 5.
[0057] As illustrated more precisely in Figures 3 and 4, the micromechanical shock counting device 4 comprises a frame 41, an inertial mass 42, a suspension structure 43, a braking structure 44, a drive structure 45 and a locking structure 46.
[0058] The various components of the micromechanical shock counting device 4 were all formed simultaneously, by an etching process in a single wafer comprising one or more layers of material. The wafer used to manufacture the micromechanical shock counting device 4 may comprise a single layer of material. The layer of material has, for example, a thickness of approximately 200 micrometers. The material of the layer is, for example, silicon. Thus, the frame 41, the inertial mass 42, the suspension structure 43, the braking structure 44, the drive structure 45 and the locking structure were all obtained by an etching process in the same wafer.
[0059] The shock counting assembly 1 further comprises a first positioning pin 11 and a second positioning pin 12, fixedly mounted on the support 2, and extending projecting from the support surface 22. The first positioning pin 11 may have a cylindrical shape of revolution. Similarly, the second positioning pin 12 may have a cylindrical shape of revolution. The frame 41 has a rectangular opening 411 and a notch 412. The micromechanical shock counting device 4 is positioned in contact with the flat portion 22 of the support surface 21. The micromechanical shock counting device 4 is positioned so that the first positioning pin 11 is in contact with two edges of the rectangular opening 411 and the second positioning pin 12 is received in the notch 412.Thus, the first positioning pin 11, the rectangular opening 411, the second positioning pin 12 and the notch 412 make it possible to position the micromechanical shock counting device 4 in a predefined position relative to the support 2 (and therefore relative to the counting wheel 3) with great precision.
[0060] Once the micromechanical shock counting device 4 is positioned relative to the support 2, the frame 41 can be fixed to the support 2, for example by gluing to the flat part 22 of the support surface 21.
[0061] The inertial mass 42 is connected to the frame 41 only by the suspension structure 43. The suspension structure 43 holds the inertial mass 42 above the depression 23 formed in the support surface 21. Thus, the inertial mass 42 is not in contact with the support surface 21, but is kept at a distance from the support surface 21. This allows the inertial mass 42 to be moved relative to the support 2 without generating friction.
[0062] In the example illustrated in Figures 3 and 4, the inertial mass 42 has the shape of an annular sector, that is to say a portion of a ring delimited by two radial planes, namely a first radial plane and a second radial plane, each passing through the axis of the ring, and forming between them a non-zero angle. In the example illustrated in Figures 3 and 4, the angle between the first radial plane and the second radial plane is an acute angle.
[0063] In the example illustrated in Figures 3 and 4, the suspension structure 43 comprises a first suspension beam 431 and a second suspension beam 432. The first suspension beam 431 connects the inertial mass 42 to the frame 41. More specifically, the first suspension beam 431 has a first end connected to the frame 41 and a second end, opposite the first end, connected to the inertial mass 42. Similarly, the second suspension beam 432 connects the inertial mass 42 to the frame 41. More specifically, the second suspension beam 432 has a first end connected to the frame 41 and a second end, opposite the first end, connected to the inertial mass 42.
[0064] The first suspension beam 431 and the second suspension beam 432 are positioned relative to each other so that they diverge from each other towards their second end, so as to form a suspension structure 43 of generally triangular shape.
[0065] The first suspension beam 431 extends along a first radial axis. The first radial axis may be included in the first radial plane. The second suspension beam 432 extends along a second radial axis. The second radial axis may be included in the second radial plane. The second radial axis forms a non-zero angle with the first radial axis. The angle between the first radial axis and the second radial axis may be between 10 and 45 degrees, for example equal to 30 degrees.
[0066] The inertial mass 42 is capable of being moved relative to the frame 41. The movement of the inertial mass 42 is guided by the suspension structure 43, which undergoes elastic deformation during the movement of the inertial mass 42 relative to the frame 41. More precisely, the movement of the inertial mass 42 is enabled by simultaneous bending of the first suspension beam 431 and the second suspension beam 432. The movement of the inertial mass 42 can be likened to a rotation of the inertial mass 42 relative to the frame 41, in a plane parallel to the flat portion 22 of the support surface 21.
[0067] When deformed, the suspension structure 43 is capable of generating an elastic restoring force tending to oppose the displacement of the inertial mass 43.
[0068] The inertial mass 43 has stops 431 suitable for coming into contact with the frame 41 so as to limit the amplitude of the displacement of the inertial mass 43 relative to the frame 41.
[0069] The frame 41 has a notch 413 allowing the insertion of a tool between the frame 41 and the inertial mass 42, in order to exert a thrust on the inertial mass 42 to move the inertial mass 42 relative to the frame 41 during the initialization of the shock detection device 4. Alternatively, the notch could be formed in the inertial mass 42.
[0070] In the example illustrated in Figures 3 and 4, the drive structure 45 comprises a drive beam 451 and one or more drive teeth 452.
[0071] The drive beam 451 has a first end connected to the inertial mass 42 and a second free end, opposite the first end. The second end carries the drive teeth 452. The drive beam 451 extends along a third axis. The third axis may be substantially perpendicular to the second radial axis.
[0072] The drive teeth 452 extend projecting towards the counting wheel 3.
[0073] More specifically, when the counting wheel 3 and the micromechanical shock counting device 4 are mounted side by side on the support 2, the drive teeth 452 of the drive structure 45 are engaged with the teeth of the counting wheel 3. In addition, due to the relative positioning between the counting wheel 3 and the shock counting device 4 (positioning predefined by the positioning pins 11 and 12), the drive beam 451 is slightly bent, so that the drive beam exerts on the drive teeth 452 an elastic restoring force tending to permanently keep the drive teeth 452 engaged between the teeth of the counting wheel 3.
[0074] Each drive tooth 452 comprises a drive face 453 and a sliding face 454. Similarly, each tooth 32 of the counting wheel 3 comprises a drive face 323 and a sliding face 324.
[0075] When the drive teeth 452 of the drive structure 45 are engaged with the teeth of the counting wheel 3, the drive face 453 of each drive tooth 452 is located opposite a drive face 323 of a tooth 32 of the counting wheel 3. The sliding face 454 of each drive tooth 452 is located opposite a sliding face 324 of a tooth 32 of the counting wheel 3.
[0076] The braking structure 44 comprises a braking beam 441 and a braking shoe 442. The braking beam 441 has a first end connected to the frame 41 and a second free end, opposite the first end. The second end carries the braking shoe 442.
[0077] When the counting wheel 3 and the micromechanical shock counting device 4 are mounted side by side on the support 2, the braking pad 442 is in contact with the counting wheel 3. In addition, due to the relative positioning between the counting wheel 3 and the shock counting device 4 (positioning predefined by the positioning pins 11 and 12), the braking beam 441 is slightly bent, so that the braking beam 441 exerts on the braking pad 442 an elastic restoring force tending to keep the braking pad 442 pressed against the teeth 32 of the counting wheel 3. Thus, the braking pad 441 prevents free rotation of the counting wheel 3 relative to the support 2.
[0078] As illustrated in Figures 3 and 4, the locking structure 46 includes a first locking tooth 461 mounted on the frame 41 and a second locking tooth 462 mounted on the inertial mass 42.
[0079] The first tooth 461 comprises a first sliding face 463 and a first locking face 464, and the second tooth 462 comprises a second sliding face 465 and a second locking face 466.
[0080] The locking structure 46 may further comprise a locking beam 467. In the example illustrated in FIGS. 3 and 4, the locking beam 467 connects the first locking tooth 461 to the frame 41. The locking beam 467 has a first end connected to the frame 41 and a second free end, carrying the first locking tooth 461. Alternatively, the locking structure 46 could comprise a locking beam connecting the second tooth 462 to the inertial mass 42.
[0081] During the manufacture of the micromechanical shock counting device 4, immediately after the step of etching the material layer, the inertial mass 43 is initially in a neutral position (position illustrated in FIG. 4). In addition, the locking structure 46 is initially in an unlocked configuration (configuration illustrated in FIG. 4). In this configuration, the second locking tooth 462 is not engaged with the first locking tooth 461, and the suspension structure 43 is not deformed, so that the suspension structure 43 does not exert an elastic restoring force on the inertial mass 42. Before putting the shock counting assembly 1 into operation, the micromechanical shock counting device 4 must be initialized.For this purpose, the inertial mass 43 is moved relative to the frame 41 from the neutral position (position illustrated in FIG. 4) to a first operating position (position illustrated in FIG. 5).
[0082] For this purpose, the inertial mass 43 is pushed in a first direction of movement (arrow A), for example using a tool. The tool can be inserted into the notch 413 of the frame 41 to exert a thrust on the inertial mass 43, in order to bring the inertial mass 43 from the neutral position (Figure 4) to the first operating position (Figure 5).
[0083] The movement of the inertial mass 43 from the neutral position (Figure 4) to the first operating position (Figure 5) has the effect of generating an elastic deformation of the suspension structure 43. The first suspension beam 431 and the second suspension beam 432 are elastically deformed. More precisely, the first suspension beam 431 and the second suspension beam 432 are bent. The suspension structure 43 exerts on the inertial pass 42 an elastic restoring force F, tending to oppose the movement of the inertial mass in the first direction, and to bring the inertial mass 42 back to the neutral position.
[0084] During movement of the inertial mass 43 from the neutral position to the first operating position, the locking structure transitions from the unlocked configuration (Figure 4) to a locked configuration in which the second locking tooth 462 is engaged with the first locking tooth 461.
[0085] More specifically, during the movement of the inertial mass 42 from the neutral position to the first operating position, the second sliding face 465 of the second tooth 462 comes into contact with the first sliding face 463 of the first tooth and slides on the first sliding face 463 of the first tooth 461, allowing the second tooth 462 to cross over the first tooth 461, after which the second locking face 466 of the second tooth 462 abuts against the first locking face 464 of the first tooth 461, preventing the inertial mass 42 from returning to the neutral position. Once the second locking tooth 462 is engaged with the first locking tooth 461, the locking structure 46 is in the locked configuration (configuration illustrated in FIG. 5).
[0086] In this configuration, the locking structure prevents a return of the inertial mass from the first operating position to the neutral position.
[0087] In addition, the suspension structure 43 is in a first state of elastic deformation in which the elastic restoring force F has a first predefined non-zero minimum value F1.
[0088] The shock counting assembly 1 is then ready for operation.
[0089] In use, the shock counting assembly 1 may be subjected to a sudden acceleration (shock) which is transmitted to the inertial mass 42.
[0090] If the acceleration transmitted to the inertial mass 42 is insufficient to overcome the elastic restoring force F1 exerted by the suspension structure 43 on the inertial mass 42, then this acceleration is insufficient to cause a displacement of the inertial mass 42 relative to the frame 41 in the first direction. Indeed, the restoring force F1 exerted by the suspension structure opposes a displacement of the inertial mass 43 relative to the frame 41 in the first direction.
[0091] On the other hand, if the acceleration transmitted to the inertial mass 42 is sufficient to overcome the elastic restoring force F1, then this acceleration tends to cause a displacement of the inertial mass 43 relative to the frame 41 in the first direction of displacement (arrow A).
[0092] However, the counting wheel 3 is held stationary by the braking structure 44.
[0093] If the value of the acceleration experienced by the shock counting assembly 1 exceeds a predefined trigger threshold value, then this acceleration is sufficient to cause a displacement of the inertial mass 42 relative to the frame 41 in the first direction (arrow A) and a crossing of the teeth 32 of the counting wheel 3 by the drive teeth 452.
[0094] In other words, the acceleration of the inertial mass 42 is sufficient for the drive teeth 452, which mesh with the teeth 32 of the counting wheel 3, to pass over the teeth 32 of the counting wheel 3. The sliding face 424 of each drive tooth 452 slides against a sliding face 324 of a tooth 32 of the counting wheel 3 located opposite, allowing each drive tooth 452 to pass over a tooth 32 of the counting wheel 3.
[0095] This crossing is enabled by a bending of the drive beam 451 of the drive structure 45.
[0096] The inertial mass 43 is moved from the first operating position (illustrated in Figure 5) to a second operating position (illustrated in Figure 6).
[0097] When the inertial mass 42 is in the second operating position, the suspension structure 42 is in a second state of elastic deformation in which the elastic restoring force F has a second non-zero value F2, greater than the first non-zero value F1.
[0098] Once the shock has passed, the inertial mass 42 is returned to the first operating position by the elastic return force F exerted by the suspension structure 43 on the inertial mass 42. Under the effect of the elastic return force F, the inertial mass 42 is moved relative to the frame 41 from the second operating position (position illustrated in FIG. 6) to the first operating position (position illustrated in FIG. 5).
[0099] The movement of the inertial mass 42 from the second operating position to the first operating position simultaneously causes a movement of the drive teeth 452 in a second direction of movement (arrow B).
[0100] More precisely, during the movement of the inertial mass 42 from the second operating position to the first operating position, the drive face 453 of each drive tooth 452 comes to bear against a drive face 323 of a tooth 32 of the counting wheel 3 located opposite, and exerts on the drive face 323 of the tooth 32 of the counting wheel 3 a thrust force, which has the effect of rotating the counting wheel 3 by one step.
[0101] Once the inertial mass 42 has returned to the first operating position, the previous steps can be repeated when a new shock occurs.
[0102] Each time the shock counting assembly 1 experiences a new shock whose intensity is sufficient to move the inertial mass 42 from the first operating position to the second operating position, the counting wheel 3 rotates one step.
[0103] More precisely, the inertial mass 42 is moved from the first operating position to the second operating position and then from the second operating position to the first operating position, causing, by means of the drive tooth 452, a rotation of the counting wheel 3 by one step.
[0104] Thus, by a simple observation of the angular position of the counting wheel 3, an observer is able to determine a number of shocks experienced by the shock counting assembly 1 during the elapsed period.
[0105] More precisely, the observer can determine a position of the drive tooth(s) 452 relative to the counting wheel 3 by means of the graduations 33.
[0106] The graduations 33 make it possible to read the number of teeth 32 which have been crossed by the drive tooth(s) 32, and consequently the number of events which have triggered the shock counting assembly 1 during the elapsed period.
[0107] The shock counting assembly 1 may be integrated into equipment to be monitored, such as equipment likely to be subjected to repeated shocks, for example a firearm, a shell launcher, or any other projectile launcher, to count the number of shots fired by the firearm, the shell launcher, or the projectile launcher.
[0108] Figure 7 schematically represents a core 6 suitable for insertion into a stock of a firearm.
[0109] The core 6 has a plurality of housings 61, each housing 61A being suitable for receiving a respective shock counting assembly 1A, 1B, 1C.
[0110] Each shock counting set 1A, 1B, 1C may have a trigger threshold different from the trigger thresholds of the other shock counting sets, so as to be able to count shocks having different intensities.
[0111] Acceleration trigger thresholds can be between 100 and 2500 G.
[0112] Different trigger thresholds can be achieved by adjusting the dimensions of the suspension structures of the counting devices of the different shock counting sets 1A, 1B and 1C. For example, a trigger threshold can be adjusted by changing the width of the suspension beams.
Claims
CLAIMS 1. Micromechanical shock counting device (4), comprising: - a frame (41), - an inertial mass (42) having a predefined neutral position, and capable of being moved relative to the frame (41) from the neutral position to a first operating position and from the first operating position to a second operating position under the effect of an acceleration undergone by the micromechanical device (4), - a suspension structure (43) connecting the inertial mass (42) to the frame (41), the suspension structure (43) being capable of generating an elastic return force (F) tending to oppose the movement of the inertial mass from the neutral position to the first operating position and from the first operating position to the second operating position, - a drive tooth (452) connected to the inertial mass (43), and capable of meshing with a counting wheel (3) to drive the counting wheel (3) in rotation by an angular step when the inertial mass is moved from the first operating position to the second operating position, - a locking structure (46) capable of adopting a locked configuration when the inertial mass (43) is initially moved from the neutral position to the first position, such that once the inertial mass (42) is in the first operating position, the locking structure (43) prevents a return of the inertial mass (42) to the neutral position while allowing a movement of the inertial mass (42) from the first operating position to the second operating position and from the second operating position to the first operating position, and that once the inertial mass (42) is in the first operating position, the suspension structure (43) is in a first state of elastic deformation in which the elastic restoring force (F) has a first non-zero minimum value (F1),and the inertial mass (42) is moved relative to the frame (41) from the first operating position to the second operating position only if a value of the acceleration experienced by the micromechanical device (4) exceeds a predefined trigger threshold value, after which the inertial mass (42) is, moved from the second operating position to the first operating position under the effect of the elastic restoring force (F) exerted by the suspension structure (43).
2. Micromechanical shock counting device (4) according to claim 1, wherein the suspension structure (43) comprises a first flexible beam (431) extending along a first axis and connecting the inertial mass (42) to the frame (41), and a second flexible beam (432) extending along a second axis and connecting the inertial mass (42) to the frame (41), the second axis forming a non-zero angle with the first axis.
3. Micromechanical shock counting device (4) according to one of claims 1 and 2, wherein the locking structure (46) comprises a first locking tooth (461) attached to the frame (41) and a second locking tooth (462) attached to the inertial mass (42), the second locking tooth (462) being adapted to be engaged with the first locking tooth (461) when the inertial mass (42) is moved from the neutral position to the first operating position, preventing a return of the inertial mass (42) to the neutral position. 4.Micromechanical shock counting device (4) according to claim 3, wherein the first locking tooth (461) comprises a first sliding face (463) and a first blocking face (464), and the second locking tooth (462) comprises a second sliding face (465) and a second blocking face (466), arranged such that during the movement of the inertial mass (42) from the neutral position to the first operating position, the second sliding face (465) of the second locking tooth (462) slides on the first sliding face (463) of the first locking tooth (461), allowing the first tooth (461) to cross the second tooth (462), after which the second blocking face (466) of the second locking tooth (462) abuts against the first blocking face (464) of the first locking tooth (462), preventing a return of the inertial mass (42) to the neutral position.
5. Micromechanical shock counting device (4) according to one of claims 1 to 4, in which the frame (41) has a notch (413) allowing insertion of a tool to exert a thrust on the inertial mass. (42) to move the inertial mass (42) from the neutral position to the first position.
6. Micromechanical shock counting device (4) according to one of claims 1 to 5, wherein when the inertial mass (42) is in the neutral position, the suspension structure (43) is in a non-deformed state in which the elastic restoring force (F) is zero.
7. Micromechanical shock counting device according to one of claims 1 to 6, wherein when the inertial mass (42) is in the second operating position, the suspension structure (43) is in a second state of elastic deformation in which the elastic restoring force (F) has a second non-zero value (F2) greater than the first non-zero value (F1).
8. Micromechanical shock counting device (4) according to one of claims 1 to 7, wherein the suspension structure (43) comprises a braking structure (44) capable of immobilizing the counting wheel (3) when the inertial mass (43) is moved from the second operating position to the first operating position under the effect of the elastic return force (F) exerted by the suspension structure (43).
9. Micromechanical shock counting device (4) according to one of claims 1 to 8, in which one of the inertial mass (43) and the frame (41) has a stop (421) capable of coming into contact with the other of the inertial pass (43) and the frame (41) so as to limit a displacement of the inertial mass (42) beyond the second operating position.
10. Micromechanical shock counting device (4) according to one of claims 1 to 9, in which the frame (41), the inertial mass (42), the suspension structure (43), the drive tooth (452) and the locking structure (46) are formed by etching in the same layer of semiconductor material.
11. Shock counting assembly (1), comprising a micromechanical shock counting device (4) according to one of claims 1 to 10, and a counting wheel (3) capable of being driven in rotation by the drive tooth (452) by an angular step each time the inertial mass (42) is moved from the first operating position to the second operating position or from the second operating position to the first operating position.
12. Shock counting assembly (1) according to claim 11, in which the counting wheel (3) has graduations (33) making it possible to identify the position of the drive tooth (452) relative to the counting wheel (3) and to deduce therefrom a number of shocks which have been experienced by the shock counting device (4).
13. Shock counting assembly (1) according to one of claims 11 and 12, comprising a support (2) on which the micromechanical shock counting device (4) and the counting wheel (3) are mounted, and a protective cover (5) suitable for being assembled on the support (2), the protective cover (5) having a visually transparent window (52) to allow an external observer to view the position of the drive tooth (452) relative to the counting wheel (3) through the protective cover (5) or to allow the position of the drive tooth (452) relative to the counting wheel (3) to be read by means of an optical detector.