Sensitive element and acceleration sensor

Abstract

The invention relates to the technical field of sensors, in particular to a sensitive element and an acceleration sensor. The sensitive element comprises a limiting body which is provided with an installation cavity and limiting grooves arranged in pairs, and the limiting grooves arranged in pairs are located on the two sides of the installation cavity respectively in the thickness direction and communicate with the installation cavity; the sensitive element body comprises a fixed frame, a cantilever beam assembly and a mass block, the mass block is located in the fixed frame, and the cantilever beam assembly is connected between the mass block and the fixed frame; wherein the fixing frame is connected with the limiting body, the cantilever beam assembly can elastically deform, the wall face forming the limiting groove in an enclosing mode comprises stop faces arranged towards the mass block in the thickness direction, the mass block has the moving freedom degree relative to the fixing frame between the paired stop faces, and the stop faces are used for limiting the maximum displacement amount of the mass block in the thickness direction. Therefore, the probability of plastic deformation and even fracture of the cantilever beam assembly is effectively reduced, and the reliability and the service life of the sensitive element are improved.

Description

Technical Field

[0001] The present application relates to the field of sensor technology, and in particular to a sensitive element and an acceleration sensor. Background Art

[0002] Accelerometers typically contain a sensitive element fabricated using a micro-electro-mechanical systems (MEMS) process. This element typically consists of a movable mass and an elastic beam connected to it. In actual use, when the accelerometer is subjected to external acceleration, the mass inertia causes relative displacement, and the elastic beam subsequently deforms. By detecting the deformation of the elastic beam, the magnitude of the acceleration can be sensed and measured.

[0003] However, due to the tiny size of the sensitive element, the allowable displacement of its mass block is usually only on the order of microns to tens of microns. Under impacts exceeding the rated range, the excessive displacement of the mass block can easily cause plastic deformation or even fracture of the elastic beam. Summary of the Invention

[0004] The present application provides a sensitive element and an acceleration sensor, which can reduce the probability of plastic deformation or even fracture of a cantilever beam assembly.

[0005] In order to achieve the above objectives, the technical solutions of this application are as follows:

[0006] In the first aspect, the present application provides a sensitive element for an acceleration sensor, comprising: a limiting body, the limiting body having an installation cavity and a pair of limiting grooves, along the thickness direction of the sensitive element itself, the paired limiting grooves are respectively located on both sides of the installation cavity and are connected to the installation cavity, along the thickness direction, the limiting groove is formed by the side surface of the limiting body facing the installation cavity and is recessed in the direction away from the installation cavity; a sensitive element body is arranged in the installation cavity, the sensitive element body comprises a fixed frame, a cantilever beam assembly and a mass block, the mass block is located inside the fixed frame, and the cantilever beam assembly is connected between the mass block and the fixed frame; wherein the fixed frame is connected to the limiting body, the cantilever beam assembly can be elastically deformed, and the wall surface enclosing the limiting groove includes a stop surface arranged toward the mass block along the thickness direction, the mass block has freedom of movement relative to the fixed frame between the pair of stop surfaces, and the stop surface is used to limit the maximum displacement of the mass block in the thickness direction.

[0007] In one possible implementation, the sensitive element provided in the present application has a limiting groove with a depth of h along the thickness direction, a rated displacement of the mass block of x, and a maximum displacement of the mass block of y, and the depth, rated displacement, and maximum displacement satisfy: x≤h<y.

[0008] In one possible implementation, the sensitive element provided in the present application, the limiting body includes limiting plates arranged in pairs, the limiting plates of the pair are provided with limiting grooves on one side facing each other in the thickness direction, and the limiting plates of the pair are spaced apart in the thickness direction to form an installation cavity.

[0009] In one possible implementation, the sensitive element provided by the present application, the cantilever beam assembly includes a plurality of cantilever beam bodies, and the plurality of cantilever beam bodies are arranged at intervals along the outer wall of the mass block; the limiting plate is provided with a first hollow portion connected to the limiting groove, and the orthographic projections of the plurality of cantilever beam bodies in the thickness direction are at least partially located within the first hollow portion, so that at least part of the cantilever beam body is exposed to the first hollow portion.

[0010] In one possible implementation, the sensitive element provided by the present application is further provided with a second hollow portion connected to the limiting groove, and the second hollow portion is spaced apart from the first hollow portion to form a stop surface at the interval between the second hollow portion and the first hollow portion; the mass block has a reflective area, and the orthographic projection of the second hollow portion in the thickness direction is located within the mass block, and the orthographic projection of the reflective area in the thickness direction is located within the second hollow portion, so that the reflective area is exposed to the second hollow portion.

[0011] In one possible implementation, in the sensitive element provided in the present application, along the thickness direction, the orthographic projection area of ​​the mass block is a1, the orthographic projection area of ​​the second hollow portion is a2, and the orthographic projection area of ​​the reflective area is a3, wherein a3<a2<a1.

[0012] In one possible implementation, the sensitive element, the limiting plate and the sensitive element body provided in the present application all include a semiconductor substrate. Along the thickness direction, the maximum thickness of the limiting plate is d1, and the maximum thickness of the sensitive element body is d2, where d1=d2.

[0013] In one possible implementation, the sensitive element provided in the present application, the limiting body also includes a blocking piece, and along the thickness direction, the height dimension of the blocking piece matches the thickness dimension of the fixed frame; the blocking piece is connected between the outer edges of the pair of limiting pieces and is enclosed with the limiting pieces to form an installation cavity with an installation opening, so that the sensitive element body is embedded in the installation cavity through the installation opening to be fixedly connected to the pair of limiting pieces.

[0014] In one possible implementation, the sensitive element provided in the present application further includes an adhesive layer. Along the thickness direction, the fixed frame has a first side and a second side relative to each other, and the pair of limiting plates are respectively located on the first side and the second side and are bonded to the fixed frame through the adhesive layer.

[0015] In a second aspect, the present application provides an acceleration sensor comprising the above-mentioned sensitive element.

[0016] The present application provides a sensitive element and an acceleration sensor, wherein the sensitive element includes a limiting body and a sensitive element body. The limiting body has a mounting cavity and a pair of limiting grooves. The pair of limiting grooves are located on both sides of the mounting cavity along the thickness direction and are connected to the mounting cavity to provide mounting space and displacement space for the sensitive element body. In the thickness direction, the limiting groove is formed by a surface of the limiting body facing the mounting cavity, which is recessed away from the mounting cavity. The sensitive element body includes a fixed frame, a cantilever beam assembly, and a mass block. The mass block is located inside the fixed frame, and the cantilever beam assembly is connected between the mass block and the fixed frame. The mass block can be displaced relative to the fixed frame along the thickness direction to cause the cantilever beam assembly to undergo elastic deformation. The avoidance of enclosing the limiting groove includes a stop surface arranged toward the mass block along the thickness direction. The mass block has freedom of movement relative to the fixed frame between the pair of stop surfaces. Under the action of acceleration, the mass block moves between the pair of stop surfaces along the thickness direction. When the acceleration exceeds the rated range of the sensor, the mass will strike the stop surface, limiting its maximum displacement in the thickness direction. This stop surface effectively reduces the probability of plastic deformation or even fracture of the cantilever beam assembly, thereby improving the reliability and service life of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0018] Figure 1 A schematic diagram of the structure of a sensitive element provided in an embodiment of the present application;

[0019] Figure 2 for Figure 1 Exploded diagram;

[0020] Figure 3 for Figure 2 Schematic diagram of the structure of the middle limit piece;

[0021] Figure 4 A schematic diagram of the structure of the sensor body provided in an embodiment of the present application;

[0022] Figure 5 A schematic diagram of a sensing element provided in an embodiment of the present application from another angle;

[0023] Figure 6 Another structural schematic diagram of the limiting body provided in an embodiment of the present application.

[0024] Description of reference numerals:

[0025] 10-Sensitive element;

[0026] 100 - limiting body; 110 - mounting cavity; 120 - limiting groove; 121 - stop surface; 130 - limiting piece; 131 - first hollow portion; 132 - second hollow portion; 133 - connecting surface; 140 - enclosure piece; 150 - adhesive layer;

[0027] 200 - Sensitive element body; 210 - Fixing frame; 210a - First side; 210b - Second side; 220 - Cantilever beam assembly; 220a - Cantilever beam body; 230 - Mass block; 231 - Reflection area;

[0028] X-thickness direction.

[0029] The above drawings illustrate specific embodiments of the present application, which will be described in more detail below. These drawings and the textual description are not intended to limit the scope of the present application in any way, but rather to illustrate the concepts of the present application to those skilled in the art by reference to specific embodiments. DETAILED DESCRIPTION

[0030] To make the purpose, technical solutions, and advantages of this application more clear, the technical solutions in the embodiments of this application will be described in more detail below in conjunction with the drawings in the preferred embodiments of this application. Obviously, the described embodiments are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0031] It should be noted that in the description of the embodiments of the present application, terms such as "upper", "lower", "inside", and "outside" indicating orientation or positional relationships are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of description. They do not indicate or imply that the device or component must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the embodiments of the present application.

[0032] In addition, it should be noted that the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or suggesting relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0033] In this application, unless otherwise expressly specified or limited, terms such as "installed," "connected," and "fixed" should be interpreted broadly. For example, they may refer to fixed connections, detachable connections, or integration; mechanical connections, electrical connections, or communication; direct connections or indirect connections through an intermediate medium; and internal connections between two components or interactions between two components. Those skilled in the art will understand the specific meanings of these terms in this application based on specific circumstances.

[0034] Due to the tiny size of the sensitive element, the allowable displacement of its mass block is usually only on the order of microns to tens of microns. Under impacts exceeding the rated range, excessive displacement of the mass block can easily cause plastic deformation or even fracture of the elastic beam.

[0035] In view of this, the present application provides a sensitive element and an acceleration sensor, wherein the sensitive element includes a limiting body and a sensitive element body. The limiting body has a mounting cavity and a pair of limiting grooves. Along the thickness direction, the pair of limiting grooves are respectively located on both sides of the mounting cavity and are connected to the mounting cavity to provide mounting space and displacement space for the sensitive element body. Along the thickness direction, the limiting groove is formed by a surface of the limiting body facing the mounting cavity that is recessed away from the mounting cavity. The sensitive element body includes a fixed frame, a cantilever beam assembly, and a mass block. The mass block is located inside the fixed frame, and the cantilever beam assembly is connected between the mass block and the fixed frame. The mass block can be displaced relative to the fixed frame along the thickness direction to cause the cantilever beam assembly to undergo elastic deformation. The avoidance of enclosing the limiting groove includes a stop surface arranged toward the mass block along the thickness direction. The mass block has freedom of movement relative to the fixed frame between the pair of stop surfaces. Under the action of acceleration, the mass block moves between the pair of stop surfaces along the thickness direction. When the acceleration exceeds the rated range of the sensor, the mass will strike the stop surface, limiting its maximum displacement in the thickness direction. This stop surface effectively reduces the probability of plastic deformation or even fracture of the cantilever beam assembly, thereby improving the reliability and service life of the sensor.

[0036] The present application will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] See also Figure 1 、 Figure 2 and Figure 5The present application provides a sensitive element 10 for an acceleration sensor. The sensitive element 10 may include a limiting body 100 and a sensitive element body 200. The limiting body 100 has an installation cavity 110 and a pair of limiting grooves 120. Along the thickness direction X of the sensitive element 10 itself, the pair of limiting grooves 120 are respectively located on both sides of the installation cavity 110 and are connected to the installation cavity 110. Along the thickness direction X, the limiting grooves 120 are formed by a side surface of the limiting body 100 facing the installation cavity 110, which is recessed in a direction away from the installation cavity 110. The sensitive element body 200 is arranged in the installation cavity 110. The sensitive element body 200 includes a fixed frame 210, a cantilever beam assembly 220 and a mass block 230. The mass block 230 is located inside the fixed frame 210, and the cantilever beam assembly 220 is connected between the mass block 230 and the fixed frame 210. In which, the fixed frame 210 is connected to the limiting body 100, the cantilever beam assembly 220 can be elastically deformed, and the wall surface enclosing the limiting groove 120 includes a stop surface 121 arranged toward the mass block 230 along the thickness direction X. The mass block 230 has freedom of movement relative to the fixed frame 210 between the paired stop surfaces 121, and the stop surface 121 is used to limit the maximum displacement of the mass block 230 in the thickness direction X.

[0038] It should be noted that the limit body 100 serves as a support structure for the sensor body 200. The limit body 100 may be made of a silicon-based material, a ceramic material, or the like to stably support the sensor body 200. The mounting cavity 110 may be located in the middle region of the limit body 100 in the thickness direction X. The shape and size of the mounting cavity 110 may be configured to match the fixing frame 210 to facilitate embedding the fixing frame 210 within the limit body 100.

[0039] Optionally, the outer contour of the fixing frame 210 may include a circle, a square, etc., and thus, the outer contour of the limiting body 100 may also include a circle, a square, etc.

[0040] The limiting grooves 120 arranged in pairs are respectively located on both sides of the installation cavity 110 in the thickness direction X, and are connected to the installation cavity 110. In this way, the mass block 230 can generate displacement in response to the impact of acceleration in the connected space formed by the installation cavity 110 and the limiting grooves 120. Among them, the groove width size of the limiting groove 120 can be set according to the frame width size of the fixed frame 210. For example, the maximum groove width of the limiting groove 120 is r1, and the maximum frame width of the fixed frame 210 is r2, r2≤r1≤1.2×r2. As a result, the limiting groove 120 can provide lateral redundancy, which can reduce the risk of the mass block 230 and the cantilever beam assembly 220 colliding with the side wall of the limiting groove 120 within the rated displacement range of the mass block 230 and the rated deformation range of the cantilever beam assembly 220.

[0041] The rated displacement range of the mass block 230 can be understood as the maximum displacement of the mass block 230 along the thickness direction X within the rated range of the sensor body 200. The rated deformation range of the cantilever beam assembly 220 can be understood as the maximum deformation of the cantilever beam within the rated displacement range of the mass block 230.

[0042] It should be noted that the fixing frame 210 can be made of a material compatible with the limiting body 100 to ensure the stability of the connection between the fixing frame 210 and the limiting body 100. The fixing frame 210 can include a circular ring, a square frame, etc., to surround the outside of the mass block 230. The two sides of the fixing frame 210 in the thickness direction X are in contact with the inner wall of the installation cavity 110, and can be fixedly connected to the limiting body 100 by bonding, gluing, etc. The mass block 230 is located at the inner center of the fixing frame 210. The mass of the mass block 230 affects the response sensitivity of the sensor body 200 to acceleration. Therefore, the mass of the mass block 230 can be set according to the required sensitivity of the sensor body 200. Optionally, the shape of the mass block 230 can include a circle, a square, etc., and a predetermined gap is provided between the outer periphery of the mass block 230 and the inner frame of the fixing frame 210 to ensure that the mass block 230 can move freely relative to the fixing frame 210 under the action of acceleration.

[0043] It should also be noted that the wall surfaces enclosing the limiting groove 120 include stop surfaces 121 disposed along the thickness direction X, facing the mass block 230. The paired stop surfaces 121 correspond to the two sides of the mass block 230 along the thickness direction X, and a predetermined gap is provided between the stop surfaces 121 and the surface of the mass block 230. When the accelerometer is subjected to external acceleration, the mass block 230 will displace relative to the fixed frame 210 due to inertia. According to Newton's second law, the displacement of the mass block 230 is proportional to the magnitude of the acceleration. Under the influence of acceleration, the mass block 230 moves along the thickness direction X between the paired stop surfaces 121, and the cantilever beam assembly 220 undergoes elastic deformation. When the acceleration exceeds the rated measurement range of the sensor body 200, the mass block 230 will collide with the stop surfaces 121 due to the excessive displacement. The provision of the stop surface 121 effectively limits the displacement of the mass 230 in the thickness direction X, thereby reducing the probability of excessive deformation and plastic deformation or even fracture of the cantilever beam assembly 220. This arrangement can improve the overload resistance and reliability of the sensor 10 and extend the service life of the sensor 10.

[0044] During the manufacturing process of the sensor 10, the limiting body 100 and the sensor body 200 can be manufactured using a micro-electromechanical system (MEMS) process. Through processes such as photolithography, etching, and bonding, the size and shape of the limiting groove 120 and the thickness and length of the cantilever beam assembly 220 can be precisely controlled to ensure the performance consistency and reliability of the sensor 10.

[0045] In some optional embodiments, the stop surface 121 may be provided with raised portions distributed in an array. Thus, when the mass block 230 strikes the stop surface 121, the raised portions can disperse the impact force toward the periphery through discrete contact points, reducing the probability of stress concentration on the stop surface 121 and thereby reducing the probability of damage to the stop surface 121 caused by the instantaneous impact force of the mass block 230. In a specific implementation, the raised portions can be formed on the stop body 100 through an etching process.

[0046] See also Figure 5 In some embodiments, along the thickness direction X, the depth of the limiting groove 120 is h, the rated displacement of the mass block 230 is x, the maximum displacement of the mass block 230 is y, and the depth, rated displacement and maximum displacement satisfy: x≤h<y.

[0047] When acceleration acts on the sensitive element 10, the mass block 230 generates displacement under the action of the inertial force, and the displacement is proportional to the magnitude of the acceleration. The rated displacement x corresponds to the rated measurement range of the sensitive element body 200. Setting the depth h of the limiting groove 120 to be no less than the rated displacement x can ensure that the mass block 230 has enough space to move freely under the rated range to cover the measurement range of the rated range of the sensitive element body 200. If the depth h of the limiting groove 120 is set to be less than the rated displacement x, the mass block 230 will come into contact with the stop surface 121 of the limiting plate 130 before reaching the rated displacement, resulting in the deformation of the cantilever beam assembly 220 being obstructed, resulting in the inability to cover the measurement range of the rated range.

[0048] The maximum displacement y can be understood as the displacement of mass block 230 corresponding to the ultimate acceleration that sensor body 200 can withstand. At this point, the displacement of mass block 230 exceeds the measurement range, potentially causing plastic deformation or even fracture of cantilever beam assembly 220. Therefore, by setting h to be less than y, when the acceleration exceeds the rated range, mass block 230 will contact stop surface 121 of limiting groove 120 before reaching the maximum displacement, reducing the probability of damage to cantilever beam assembly 220.

[0049] By satisfying the dimensional relationship of x≤h<y, the sensitive element 10 can not only realize acceleration measurement under the rated range, but also protect the sensitive element body 200 through the limit body 100 when the acceleration is overloaded, thereby improving the reliability and service life of the sensitive element 10.

[0050] In specific implementations, the rated displacement x and maximum displacement y can be set based on the rated range, the material used for the sensor body 200, the structure of the cantilever beam assembly 220, and the like. For example, the rated measurement range of the sensor body 200 is ±50g. Finite element simulation calculations show that the maximum displacement x of the mass block 230 under 50g acceleration is 10μm. At this time, the cantilever beam assembly 220 is in the linear range of elastic deformation. When the displacement of the mass block 230 reaches 15μm, the cantilever beam assembly 220 will exceed the elastic limit and begin to plastically deform. The critical value of the plastic deformation of the cantilever beam assembly 220 can be set to the maximum displacement y. At this time, the depth h of the limiting groove 120 can be set to 10μm≤h<15μm. Optionally, the depth h of the limiting groove 120 can be set to 10μm, 11μm, 12μm, etc.

[0051] See also Figure 2 and Figure 3 In some embodiments, the limiting body 100 includes a pair of limiting plates 130, and the pair of limiting plates 130 are provided with limiting grooves 120 on the side facing each other in the thickness direction X, and the pair of limiting plates 130 are spaced apart in the thickness direction X to form an installation cavity 110.

[0052] In a specific implementation, the limiting body 100 may include a pair of limiting plates 130. The limiting plates 130 may be manufactured using a MEMS process using a silicon wafer. A sunken limiting groove 120 is formed on one side of the limiting plate 130 facing the other in the thickness direction X. Optionally, the limiting groove 120 may be formed on the limiting plate 130 using an etching process. The depth of the limiting groove 120 may be set according to the rated measurement range of the sensor body 200 to ensure the displacement space of the mass block 230 under the rated acceleration.

[0053] It should be noted that the pairs of limiting plates 130 are arranged at intervals along the thickness direction X to form an installation cavity 110 between the pairs of limiting plates 130. The pairs of limiting plates 130 face one side of each other and have a connecting surface 133 outside the limiting groove 120. The positive projection of the connecting surface 133 in the thickness direction X can be a circular ring, a square frame, etc. to match the shape of the fixed frame 210.

[0054] The spacing between the paired connecting surfaces 133, i.e., the height of the mounting cavity 110 in the thickness direction X, can be set based on the thickness of the fixing frame 210 to ensure that, after the sensor body 200 is installed in the mounting cavity 110, the mass block 230 can move within the connecting space formed by the limiting groove 120 and the mounting cavity 110. When the acceleration exceeds the rated range, the mass block 230 strikes the stop surface 121. The rigid structure of the limiting plate 130 limits the displacement of the mass block 230, thus preventing the cantilever beam from failing due to excessive deformation.

[0055] See also Figure 2 and Figure 4 In some embodiments, the cantilever beam assembly 220 includes a plurality of cantilever beam bodies 220 a, which are spaced apart and arranged along the outer wall of the mass block 230. The limiting plate 130 is provided with a first hollow portion 131 that communicates with the limiting groove 120. The orthographic projections of the plurality of cantilever beam bodies 220 a in the thickness direction X are at least partially located within the first hollow portion 131, so that at least a portion of the cantilever beam bodies 220 a are exposed to the first hollow portion 131.

[0056] The cantilever beam bodies 220a can be provided in three, four, or more configurations. For example, three cantilever beam bodies 220a can be provided, and the three cantilever beam bodies 220a can be evenly spaced on the outer wall of the mass block 230, with one end of the cantilever beam body 220a connected to the mass block 230 and the other end connected to the fixed frame 210. Four cantilever beam bodies 220a can also be provided, and the four cantilever beam bodies 220a can be symmetrically distributed. For example, when the mass block 230 is square, the four cantilever beam bodies 220a are respectively connected to the four sides of the mass block 230 and to the corresponding positions of the fixed frame 210, so that the inertial force of the mass block 230 in the thickness direction X can be evenly transmitted to each cantilever beam body 220a, reducing the risk of stress concentration or deformation deviation caused by single-point support.

[0057] Optionally, the shape of the cantilever beam body 220 a may include a straight bar shape, a broken line shape, an S shape, etc. The specific shape of the cantilever beam body 220 a may be set according to the sensitivity and range requirements of the sensor body 200 .

[0058] It should be noted that the limiting plate 130 defines a first hollow portion 131. The shape and number of the first hollow portions 131 can be configured based on the arrangement and number of the cantilever beam bodies 220a. For example, when there are four cantilever beam bodies 220a arranged in a cross shape, four first hollow portions 131 can be provided, with the four first hollow portions 131 spaced apart around the mass 230 so that each first hollow portion 131 corresponds to a cantilever beam body 220a. Alternatively, two second hollow portions 132 can be provided, etc., to expose the cantilever beam bodies 220a to the first hollow portions 131.

[0059] Optionally, the first hollow portion 131 may include a fan-shaped hollow portion, a strip-shaped hollow portion, etc.

[0060] This arrangement makes it easier for operators to observe the state of the cantilever beam body 220a through the first hollow portion 131, so as to monitor whether the cantilever beam body 220a has problems such as cracks, deformation or failure during production debugging or subsequent maintenance. For example, during the production stage, operators can observe the deformation state of the cantilever beam when subjected to force through the first hollow portion 131, and monitor in real time whether it has process defects, thereby improving the manufacturing accuracy and yield rate of the sensitive element 10. During maintenance, the cantilever beam body 220a can be subjected to a micro-tensile test through the first hollow portion 131 to obtain parameters such as the real-time hardness and elastic modulus of the cantilever beam body 220a material, and compare them with the design values ​​to assess the degree of aging, thereby avoiding acceleration measurement distortion caused by failure of the cantilever beam body 220a. Therefore, by providing the first hollow portion 131, the maintenance cost of the sensitive element 10 over its entire life cycle can be effectively reduced, and the long-term reliability of the sensitive element 10 under complex working conditions can be improved.

[0061] See also Figure 2 and Figure 3 In some embodiments, the limiting plate 130 is further provided with a second hollow portion 132 that communicates with the limiting groove 120. The second hollow portion 132 is spaced apart from the first hollow portion 131, so that a stop surface 121 is formed at the gap between the second hollow portion 132 and the first hollow portion 131. The mass block 230 has a reflective region 231. The orthographic projection of the second hollow portion 132 in the thickness direction X is located within the mass block 230, and the orthographic projection of the reflective region 231 in the thickness direction X is located within the second hollow portion 132, so that the reflective region 231 is exposed to the second hollow portion 132.

[0062] It should be noted that when the sensitive element 10 is used in an acceleration sensor based on the optical interference principle of optical fibers, the detection beam emitted by the acceleration sensor's optical fiber will illuminate the mass block 230. When the mass block 230 is displaced in the thickness direction X due to acceleration, the optical path of the reflected light of the detection beam will change accordingly. By detecting the change in the optical path, the magnitude of the acceleration can be calculated. Therefore, in order to ensure that the detection beam is illuminated on the mass block 230, the limiting plate 130 is provided with a second hollow portion 132. The second hollow portion 132 is arranged away from the fixed frame 210 relative to the first hollow portion 131, and the first hollow portion 131 and the second hollow portion 132 are spaced apart on the limiting plate 130. The stop surface 121 is formed in the solid portion between the first hollow portion 131 and the second hollow portion 132.

[0063] In a specific implementation, the size and shape of the second hollow portion 132 can be configured based on the reflective region 231 of the mass block 230 to ensure that the reflective region 231 is exposed to the second hollow portion 132 in the thickness direction X, thereby allowing the probe beam to be irradiated into the reflective region 231 of the mass block 230. The orthographic projection area of ​​the reflective region 231 in the thickness direction X can be understood as the orthographic projection area of ​​the probe beam. In other words, the orthographic projection area of ​​the second hollow portion 132 in the thickness direction X must be greater than or equal to the orthographic projection area of ​​the probe beam to ensure effective incidence of the probe beam.

[0064] In the manufacturing process, the second hollow portion 132 and the first hollow portion 131 can be etched through the same mask and formed on the limiting piece 130 at one time to ensure the position accuracy and structural symmetry of the second hollow portion 132 and the first hollow portion 131.

[0065] In some embodiments, along the thickness direction X, the orthographic projection area of ​​the mass block 230 is a1, the orthographic projection area of ​​the second hollow portion 132 is a2, and the orthographic projection area of ​​the reflective region 231 is a3, wherein a3<a2<a1.

[0066] The orthographic projection area a1 of the mass block 230 defines the overall contour of the mass block 230. To ensure the mass block 230's freedom of movement within the retaining groove 120 and effective contact with the stop surface 121, the orthographic projection area a1 of the mass block 230 is set to be larger than the orthographic projection area a2 of the second hollow portion 132. Specifically, the portion of the edge of the mass block 230 that extends beyond the second hollow portion 132 forms the impact area that contacts the stop surface 121.

[0067] The orthographic projection area a3 of the reflective region 231 is set to be smaller than the area a2 of the second hollow portion 132 to ensure that the reflective region 231 is completely within the orthographic projection of the second hollow portion 132, thereby reducing the risk of the limiting plate 130 blocking the probe beam. In other words, the second hollow portion 132 is provided with a predetermined amount of redundancy compared to the reflective region 231 of the mass block 230. This arrangement ensures that the reflective region 231 remains within the second hollow portion 132, reducing the probability that the probe beam's spot on the mass block 230 will shift to the limiting plate 130 due to assembly errors between the optical fiber and the mass block 230.

[0068] See also Figure 5 In some embodiments, the limiting piece 130 and the sensor body 200 both include semiconductor substrates. Along the thickness direction X, the maximum thickness of the limiting piece 130 is d1, and the maximum thickness of the sensor body 200 is d2, where d1=d2.

[0069] It should be noted that both the limiting plate 130 and the sensor body 200 may include a semiconductor substrate, which may be a silicon wafer. Along the thickness direction X, the maximum thickness d1 of the limiting plate 130 is designed to be equal to the maximum thickness d2 of the sensor body 200, i.e., d1 = d2. In other words, the limiting plate 130 and the sensor body 200 may be manufactured using semiconductor substrates of the same specifications. This improves processing consistency and facilitates assembly of the limiting plate 130 and the sensor body 200. During the manufacturing process, multiple semiconductor substrates of the same specifications may be processed separately to obtain the limiting plate 130 and the sensor body 200, respectively. In a specific implementation, at least a portion of the semiconductor substrates are processed using the same mask plate to form the limiting plate 130 having the limiting groove 120, the first hollow portion 131, and the second hollow portion 132. At least a portion of the semiconductor substrates are etched away with a portion of material through an etching process to form the cantilever beam body 220a, thereby obtaining the sensor body 200.

[0070] It is understood that when the sensor body 200 and the stopper 130 are bonded together using a bonding process, the use of semiconductor substrates of uniform thickness allows for standardized bonding pressure and temperature parameters, eliminating the need for process calibration for different thicknesses, thereby improving automated production efficiency. Furthermore, using semiconductor substrates of the same specifications can simplify supply chain management and reduce raw material inventory costs in practical applications.

[0071] See also Figure 6In some embodiments, the limiting body 100 further includes a retaining piece 140. Along the thickness direction X, the height of the retaining piece 140 matches the thickness of the fixing frame 210. The retaining piece 140 is connected between the outer edges of the pair of limiting pieces 130 and encloses the limiting pieces 130 to form a mounting cavity 110 having a mounting opening. The sensor body 200 is embedded in the mounting cavity 110 through the mounting opening to be fixedly connected to the pair of limiting pieces 130.

[0072] To facilitate assembly between the sensor body 200 and the pair of limiting pieces 130, the limiting body 100 may further include a retaining piece 140. Along the thickness direction X, the height of the retaining piece 140 may match the thickness of the fixing frame 210 of the sensor body 200, thereby ensuring a secure connection between the sensor body 200 and the pair of limiting pieces 130 after assembly.

[0073] Optionally, the enclosure piece 140 may include an annular frame with an elastic snap-fit ​​structure. For example, when the limiting piece 130 and the sensor body 200 are both circular, the enclosure piece 140 extends around the circumference of the installation cavity 110 and is connected to the limiting piece 130. The extension path of the enclosure piece 140 may be half the circumference of the limiting piece 130. At least one of the two free ends of the enclosure piece 140 is provided with an elastic claw, which may include a barbed protrusion extending toward the center of the installation cavity 110. When the sensor body 200 is inserted into the installation cavity 110, the elastic claw is elastically deformed due to radial pressure. The barb passes the outside of the fixing frame 210 and then returns to its original position, forming a mechanical lock, so that the sensor body 200 is clamped into the installation cavity 110.

[0074] It is understood that the retaining plate 140 can be made of a semiconductor substrate or high-strength polymer material of the same material as the limiting plate 130, and can be manufactured through micro-nano processing (such as photolithography, etching) or injection molding. During the assembly process, the retaining plate 140 is connected to the outer edges of the paired limiting plates 130 to jointly enclose a mounting cavity 110 with a mounting opening. The size of the mounting opening can be set to be equal to or slightly smaller than the outer contour of the sensor body 200 to ensure the embedding stability of the sensor body 200.

[0075] Optionally, the enclosure sheet 140 and the fixed frame 210 are tightly fitted in the thickness direction X. A bonding process can be used to allow atoms on the surfaces of the enclosure sheet 140 and the fixed frame 210 to diffuse into each other under high temperature and high pressure, forming a high-strength covalent bond. Alternatively, a curing adhesive can be used to fill the gap between the two through coating and dispensing, and a secure bond is achieved after curing. This ensures the precise positioning of the sensor body 200 within the mounting cavity 110 and effectively prevents the fixed frame 210 from shifting or shaking under acceleration.

[0076] See also Figure 5 In other optional embodiments, the sensitive element 10 further includes an adhesive layer 150 . Along the thickness direction X, the fixed frame 210 has a first side 210 a and a second side 210 b opposite to each other. The pair of limiting pieces 130 are respectively located on the first side 210 a and the second side 210 b and are bonded to the fixed frame 210 through the adhesive layer 150 .

[0077] That is to say, in order to achieve a reliable connection between the sensitive element body 200 and the paired limiting plates 130, the sensitive element body 200 and the limiting plates 130 can also be firmly connected by setting an adhesive layer 150 between the limiting plates 130 and the fixing frame 210 of the sensitive element body 200.

[0078] Optionally, the adhesive forming the bonding layer 150 may include silicone-based gel, epoxy resin glue, etc. These materials have excellent mechanical strength and chemical stability, and can withstand complex environments such as high and low temperatures, vibration, etc. In a specific implementation, a dispensing machine can be used to evenly apply the adhesive to the first side 210a and the second side 210b of the fixed frame 210, or the adhesive can be applied to the corresponding position of the limiting piece 130. After the fixed frame 210 and the limiting piece 130 are aligned and connected, the adhesive is cured to form the bonding layer 150.

[0079] It is understandable that by setting the adhesive layer 150 to achieve the assembly of the limiting piece 130 and the sensitive element body 200, the coating of the adhesive can be completed only by dispensing equipment, that is, the assembly of the sensitive element 10 can be achieved through the operations of gluing, laminating and curing on the production line, thereby simplifying the assembly process and shortening the production cycle. In addition, the bonding process has relatively low requirements for the processing accuracy of parts, and the dimensional tolerance between the limiting piece 130 and the fixing frame 210 can be moderately compensated by the adhesive layer 150, thereby reducing the scrap rate and further improving production efficiency. In addition, the rapid curing characteristics of the adhesive can further increase the circulation speed of the sensitive element 10 production line, which can meet the needs of large-scale mass production, and achieve cost reduction and efficiency improvement while ensuring product quality.

[0080] On the basis of the above embodiments, an embodiment of the present application provides an acceleration sensor, comprising the sensitive element 10 provided by any of the above embodiments.

[0081] It is understood that the acceleration sensor may include a capacitive acceleration sensor, a piezoresistive acceleration sensor, an optical acceleration sensor, etc. By adopting the sensitive element 10 provided in the embodiment of the present application, the acceleration sensor can reduce the failure risk of the acceleration sensor in an impact environment, thereby extending its service life, because the limiting piece 130 of the sensitive element 10 can limit the displacement of the mass 230 of the sensitive element body 200.

[0082] When the acceleration sensor includes an optical acceleration sensor, the optical acceleration sensor may include an optical fiber and a sensitive element 10. The operating principle of the optical acceleration sensor is to form an optical interference cavity between the end face of the optical fiber and the reflective region 231 of the mass block 230. When the acceleration sensor is subjected to axial acceleration, the mass block 230 produces relative displacement due to inertia, causing the cavity length of the interference cavity to change. Light is reflected and transmitted back and forth between the end face of the optical fiber and the reflective surface of the mass block, forming optical interference. The light signal reflected back to the optical fiber carries information about the cavity length change. Decoding this information can restore the acceleration information corresponding to the cavity length change.

[0083] The sensitive element 10 has been described in detail in the above embodiment and will not be described again here.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A sensitive element for an acceleration sensor, characterized in that: include: A limiting body, the limiting body having a mounting cavity and a pair of limiting grooves, wherein along the thickness direction of the sensitive element itself, the pair of limiting grooves are respectively located on both sides of the mounting cavity and are arranged in communication with the mounting cavity, and along the thickness direction, the limiting grooves are formed by a surface of the limiting body facing the mounting cavity and concave in a direction away from the mounting cavity; A sensitive element body is disposed in the mounting cavity, the sensitive element body comprising a fixing frame, a cantilever beam assembly and a mass block, the mass block being located inside the fixing frame, and the cantilever beam assembly being connected between the mass block and the fixing frame; In which, the fixed frame is connected to the limiting body, the cantilever beam assembly is capable of elastic deformation, and the wall surface enclosing the limiting groove includes a stop surface arranged toward the mass block along the thickness direction, and the mass block has freedom of movement relative to the fixed frame between the paired stop surfaces, and the stop surface is used to limit the maximum displacement of the mass block in the thickness direction.

2. The sensitive element according to claim 1, characterized in that Along the thickness direction, the depth of the limiting groove is h, the rated displacement of the mass block is x, the maximum displacement of the mass block is y, and the depth, the rated displacement and the maximum displacement satisfy: x≤h<y.

3. The sensitive element according to claim 1, characterized in that The limiting body includes limiting pieces arranged in pairs, the limiting pieces in the pair are provided with the limiting grooves on one side facing each other in the thickness direction, and the limiting pieces in the pair are spaced apart in the thickness direction to form the installation cavity.

4. The sensitive element according to claim 3, characterized in that: The cantilever beam assembly includes a plurality of cantilever beam bodies, and the plurality of cantilever beam bodies are arranged at intervals along the outer side wall of the mass block; The limiting plate is provided with a first hollow portion connected to the limiting groove, and the orthographic projections of the plurality of cantilever beam bodies in the thickness direction are at least partially located within the first hollow portion, so that at least part of the cantilever beam bodies are exposed to the first hollow portion.

5. The sensitive element according to claim 4, characterized in that: The limiting piece is further provided with a second hollow portion communicating with the limiting groove, and the second hollow portion is spaced apart from the first hollow portion to form the stop surface at the space between the second hollow portion and the first hollow portion; The mass block has a reflective area, the orthographic projection of the second hollow portion in the thickness direction is located within the mass block, and the orthographic projection of the reflective area in the thickness direction is located within the second hollow portion, so that the reflective area is exposed to the second hollow portion.

6. The sensitive element according to claim 5, characterized in that: Along the thickness direction, the orthographic projection area of ​​the mass block is a1, the orthographic projection area of ​​the second hollow portion is a2, and the orthographic projection area of ​​the reflection area is a3, wherein a3<a2<a1.

7. The sensitive element according to any one of claims 3 to 6, characterized in that: The limiting piece and the sensitive element body both include a semiconductor substrate. Along the thickness direction, the maximum thickness of the limiting piece is d1, and the maximum thickness of the sensitive element body is d2, wherein d1=d2.

8. The sensitive element according to claim 3, characterized in that: The limiting body further comprises a blocking piece, and along the thickness direction, the height dimension of the blocking piece matches the thickness dimension of the fixing frame; The enclosure piece is connected between the outer edges of the pair of limiting pieces and encloses the limiting pieces to form the installation cavity with an installation opening, so that the sensitive element body is embedded in the installation cavity through the installation opening to be fixedly connected to the pair of limiting pieces.

9. The sensitive element according to claim 3, characterized in that: It also includes an adhesive layer. Along the thickness direction, the fixing frame has a first side and a second side opposite to each other. The paired limiting pieces are respectively located on the first side and the second side and are bonded to the fixing frame through the adhesive layer.

10. An acceleration sensor, characterized in that: The method comprises the sensitive element according to any one of claims 1 to 9.

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