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 sensitive chips which are arranged in pairs in the thickness direction of the sensitive element, each sensitive chip comprises a fixing frame, a cantilever beam assembly and a mass block, the mass blocks are located in the fixing frames, the cantilever beam assemblies are connected between the fixing frames and the mass blocks, and the fixing frames are provided with opposite first sides and second sides in the thickness direction; the second sides of the fixing frames arranged in pairs face each other, and the cantilever beam assemblies are arranged close to the first sides relative to the second sides; the bonding layer is located between the sensitive chips arranged in pairs, the bonding layer covers at least part of the fixing frames and the mass blocks in the thickness direction, and the fixing frames and the mass blocks of the sensitive chips arranged in pairs are correspondingly connected through the bonding layer. The sensitive element provided by the invention can reduce the transverse sensitivity and improve the measurement accuracy.

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 based on the principle of optical interference typically consist of an optical fiber and a sensitive element, typically a movable mass. These accelerometers operate by forming an optical interference cavity between the end face of the optical fiber and the reflective surface of the mass. When the sensor is subjected to axial acceleration, the mass undergoes relative displacement due to inertia, causing the cavity length to change. Light reflects and transmits back and forth between the end face of the optical fiber and the reflective surface of the mass, forming optical interference. The light signal reflected back into the optical fiber carries information about the cavity length change, and decoding this information can restore the acceleration information corresponding to the cavity length change.

[0003] However, when the sensitive element in the related technology is subjected to lateral acceleration (i.e. parallel to the reflecting surface of the mass block), the mass block is prone to flipping and tilting, so that the cavity length change information caused by the lateral acceleration impact will be identified as axial acceleration, that is, lateral sensitivity will be generated, thereby affecting the measurement accuracy. Summary of the Invention

[0004] The present application provides a sensitive element and an acceleration sensor to solve the problem that the current sensitive element has high lateral sensitivity, which affects the measurement accuracy.

[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, the sensitive element comprising: sensitive chips, which are arranged in pairs along the thickness direction of the sensitive element itself, each sensitive chip comprising a fixed frame, a cantilever beam assembly and a mass block, the mass block being located inside the fixed frame, the cantilever beam assembly being connected between the fixed frame and the mass block, the fixed frame having a first side and a second side relative to each other along the thickness direction, the second sides of the paired fixed frames being arranged facing each other, and the cantilever beam assembly being arranged close to the first side relative to the second side; an adhesive layer being located between the paired sensitive chips, the adhesive layer covering at least part of the fixed frame and the mass block along the thickness direction, the fixed frames and the mass blocks of the paired sensitive chips being respectively connected correspondingly through the adhesive layer.

[0007] In a possible implementation, the sensitive elements provided by the present application have paired sensitive chips with the same structure, and the paired sensitive chips are mirror-imaged and arranged in opposite directions in the thickness direction.

[0008] In one possible implementation, the sensitive element provided in the present application, the adhesive layer includes a first adhesive portion and a second adhesive portion, the first adhesive portion and the second adhesive portion are spaced apart from each other, the pairs of fixed frames are bonded to each other through the first adhesive portion, and the pairs of mass blocks are bonded to each other through the second adhesive portion.

[0009] In a possible implementation, in the sensitive element provided by the present application, the orthographic projections of the cantilever beam components of the paired sensitive chips in the thickness direction at least partially overlap.

[0010] In one possible implementation, the sensitive element provided by the present application, the cantilever beam assembly includes a plurality of cantilever beam bodies, each cantilever beam body is arranged at intervals around the outer wall of the mass block, one end of the cantilever beam body is connected to the fixed frame, and the other end is connected to the mass block; wherein, in the cantilever beam assembly of the sensitive chip arranged in pairs, the orthographic projections of the corresponding cantilever beam bodies in the thickness direction at least partially overlap.

[0011] In a possible implementation, in the sensitive element provided by the present application, each cantilever beam body includes at least one of a straight beam and a curved beam.

[0012] In one possible implementation, the sensitive element provided by the present application, the cantilever beam body includes a curved beam, and the curved beam extends between the fixed frame and the mass block along at least one of a broken line trajectory and a curved trajectory; the broken line trajectory includes at least two broken line segments, and the angle between adjacent broken line segments is A, where A≥90°.

[0013] In one possible implementation, the sensitive element provided by the present application, the bending beam includes a first fold line segment and a second fold line segment, along the length direction of the first fold line segment itself, the two ends of the first fold line segment are respectively connected to the second fold line segment and are arranged at a preset angle with the second fold line segment, the two second fold line segments extend in directions away from each other, and one of the two second fold line segments is connected to the fixed frame, and the other is connected to the mass block; wherein, in the sensitive chips arranged in pairs, the corresponding first fold line segments completely overlap in the thickness direction.

[0014] In one possible implementation, the sensitive element provided by the present application, the bending beam includes an arc segment and a connecting segment, along the extension direction of the arc segment, the two ends of the arc segment are respectively connected to the connecting segment and are arranged at a preset angle with the connecting segment, the two connecting segments extend in directions away from each other, and one of the two connecting segments is connected to the fixed frame, and the other is connected to the mass block; wherein, in the sensitive chips arranged in pairs, the orthographic projection of the arc segment of one of the sensitive chips in the thickness direction forms an overlapping area with the orthographic projection of at least two arc segments of the other sensitive chip.

[0015] In one possible implementation, the sensitive element provided by the present application has the sensitive chips arranged in pairs facing away from each other in the thickness direction, and the end face of the mass block and the end face of the cantilever beam assembly are arranged coplanar with the first side of the fixed frame.

[0016] In a possible implementation, the maximum thickness of the sensitive chip of the sensitive element provided in the present application along the thickness direction is h1, where 50 μm ≤ h1 ≤ 200 μm; and the thickness of the adhesive layer along the thickness direction is h2, where 2 μm ≤ h2 ≤ 5 μm.

[0017] In a second aspect, the present application provides an acceleration sensor comprising an optical fiber and the above-mentioned sensitive element, wherein the optical fiber and the sensitive element are arranged at a predetermined distance along the thickness direction of the sensitive element, and the incident direction of the optical fiber is perpendicular to the reflective surface of the sensitive element.

[0018] The present application provides a sensitive element and an acceleration sensor, wherein the sensitive element includes a sensitive chip and an adhesive layer. The sensitive chip includes a fixed frame, a cantilever beam assembly and a mass block, wherein the mass block is located inside the fixed frame, and the cantilever beam assembly is connected between the fixed frame and the mass block. The mass block can be displaced relative to the fixed frame along the thickness direction so that the cantilever beam assembly undergoes elastic deformation. Along the thickness direction, the fixed frame has a first side and a second side relative to each other, and the cantilever beam assembly is arranged near the first side relative to the second side. The sensitive chips are arranged in pairs along the thickness direction and the paired fixed frames and mass blocks are bonded to each other through the adhesive layer, and the second sides of the paired fixed frames are arranged toward each other. Under lateral acceleration, the paired cantilever beam assemblies generate opposite inertial couples, which effectively offset the flipping torque of the bonded mass blocks through the couple balance, thereby suppressing the tilting and flipping of the bonded mass blocks, thereby reducing lateral sensitivity and improving measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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.

[0020] Figure 1 It is a structural diagram of an acceleration sensor in the prior art;

[0021] Figure 2 Schematic diagram of the structure of the sensitive element provided in the embodiment of the present application Figure 1 ;

[0022] Figure 3 for Figure 2 Schematic diagram from another perspective;

[0023] Figure 4 for Figure 3 sectional view of

[0024] Figure 5 Schematic diagram of the structure of the sensitive element provided in the embodiment of the present application Figure 2 ;

[0025] Figure 6 for Figure 5 Schematic diagram from another perspective;

[0026] Figure 7 for Figure 6 sectional view of

[0027] Figure 8 Schematic diagram of the structure of the sensitive element provided in the embodiment of the present application Figure 3 ;

[0028] Figure 9 for Figure 8 Schematic diagram from another perspective;

[0029] Figure 10 for Figure 9 sectional view of

[0030] Figure 11 A diagram illustrating a finite element simulation of lateral sensitivity provided in an embodiment of the present application;

[0031] Figure 12 A comparison diagram of the axial displacement of a single sensitive chip in the prior art and the sensitive element provided in the embodiment of the present application;

[0032] Figure 13 This is a comparison chart of the lateral sensitivity of a single sensitive chip in the prior art and the sensitive element provided in the embodiments of the present application.

[0033] Description of reference numerals:

[0034] 10-Sensitive element;

[0035] 100 - sensitive chip; 100a - upper sensitive chip; 100b - lower sensitive chip; 110 - fixing frame; 110a - first side; 110b - second side; 120 - cantilever beam assembly; 121 - cantilever beam body; 121a - straight beam; 121b - curved beam; 1211 - first fold line segment; 1212 - second fold line segment; 1213 - arc segment; 1214 - connecting segment; 130 - mass block;

[0036] 200 - adhesive layer; 210 - first adhesive portion; 220 - second adhesive portion.

[0037] 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

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] In related technologies, the sensitive element substrate usually includes a device layer, an insulating layer and a base layer stacked along the thickness direction. When etching the sensitive element substrate, the material in the non-beam area between the mass block area and the fixed frame area will be completely etched, and the material in the beam area will etch away the base layer and the insulating layer, leaving only the device layer as a connecting bridge between the fixed frame and the mass block. The cantilever beam is formed on one side of the sensitive element substrate in the thickness direction. Therefore, when the sensitive element is subjected to lateral acceleration (i.e., parallel to the reflecting surface of the mass block), the mass block is prone to flipping and tilting under the action of torque, so that the cavity length change information caused by the lateral acceleration impact will be identified as axial acceleration, that is, lateral sensitivity is generated, thereby affecting the measurement accuracy.

[0043] In view of this, the present application provides a sensitive element and an acceleration sensor, wherein the sensitive element includes a sensitive chip and an adhesive layer. The sensitive chip includes a fixed frame, a cantilever beam assembly and a mass block, the mass block is located inside the fixed frame, the cantilever beam assembly is connected between the fixed frame and the mass block, and the mass block can be displaced relative to the fixed frame along the thickness direction so that the cantilever beam assembly undergoes elastic deformation. Along the thickness direction, the fixed frame has a first side and a second side relative to each other, and the cantilever beam assembly is arranged near the first side relative to the second side. The sensitive chips are arranged in pairs along the thickness direction and the paired fixed frames and mass blocks are bonded to each other through the adhesive layer, and the second sides of the paired fixed frames are arranged toward each other. Under lateral acceleration, the paired cantilever beam assemblies generate opposite inertial couples, which effectively offset the flipping torque exerted on the bonded mass blocks through couple balance, thereby suppressing the bonded mass blocks from tilting and flipping, thereby reducing lateral sensitivity and improving measurement accuracy.

[0044] The present application will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] See also Figure 2 、 Figure 5 and Figure 8The present application provides a sensitive element 10 for an acceleration sensor. The sensitive element 10 may include a sensitive chip 100 and an adhesive layer 200. The sensitive chips 100 are arranged in pairs along the thickness direction of the sensitive element 10 itself. Each sensitive chip 100 includes a fixed frame 110, a cantilever beam assembly 120, and a mass block 130. The mass block 130 is located inside the fixed frame 110. The cantilever beam assembly 120 is connected between the fixed frame 110 and the mass block 130. Along the thickness direction, the fixed frame 110 has a first side 110a and a second side 110b opposite to each other. The second sides 110b of the paired fixed frames 110 are arranged toward each other, and the cantilever beam assembly 120 is arranged closer to the first side 110a relative to the second side 110b. The adhesive layer 200 is located between the paired sensitive chips 100 and covers at least part of the fixing frame 110 and the mass block 130 along the thickness direction. The fixing frame 110 and the mass block 130 of the paired sensitive chips 100 are respectively connected via the adhesive layer 200 .

[0046] It should be noted that the thickness direction can be understood as the sensitive direction of the sensitive element 10, that is, the target detection direction of the sensitive element 10. The transverse direction of the transverse acceleration can be understood as any direction in a plane perpendicular to the sensitive direction.

[0047] Each sensitive chip 100 may include a fixed frame 110, a cantilever beam assembly 120, and a mass block 130. The mass block 130 is located within the fixed frame 110 and is configured to respond to acceleration. When the sensitive element 10 is subjected to acceleration, the mass block 130 will displace relative to the fixed frame 110 due to inertia. The cantilever beam assembly 120, connected between the fixed frame 110 and the mass block 130, transmits the mechanical action and senses the deformation. The deformation of the cantilever beam assembly 120 and the displacement of the mass block 130 can detect the magnitude of the acceleration. For example, when the sensitive element 10 is used in an acceleration sensor based on the optical interference principle of optical fiber, the detection beam emitted by the optical fiber of the acceleration sensor will illuminate the mass block 130. When the mass block 130 is displaced in the thickness direction due to acceleration, the optical path length of the reflected light of the detection beam will change accordingly. By detecting the change in the optical path length, the magnitude of the acceleration can be calculated.

[0048] It should be noted that during the operation of the sensor element 10, lateral sensitivity refers to the degree to which the sensor element 10 responds to acceleration signals perpendicular to its sensitive direction. Excessive lateral sensitivity can reduce the accuracy of acceleration measurements. To reduce lateral sensitivity, the fixed frame 110 has a first side 110a and a second side 110b opposite each other along the thickness direction. The cantilever beam assembly 120 is positioned closer to the first side 110a relative to the second side 110b. The second sides 110b of the paired fixed frames 110 face each other. The second sides 110b of the paired fixed frames 110 are connected by an adhesive layer 200, and the paired proof masses 130 are also connected by the adhesive layer 200. In other words, the adhesive layer 200 connects the paired sensitive chips 100, enabling the paired sensitive chips 100 to respond to acceleration as a whole. The paired cantilever beam assemblies 120 are located at the same vertical distance from the adhesive layer 200 to effectively suppress the flipping of the proof masses 130 caused by lateral acceleration interference.

[0049] In specific implementations, when the sensitive element 10 is subjected to lateral acceleration, the masses 130 in the paired sensitive chips 100 will tend to move due to inertia. Because the cantilever beam assembly 120 is positioned closer to the first side 110a relative to the second side 110b of the fixed frame 110, and the second sides 110b of the paired fixed frames 110 face each other, the cantilever beam assembly 120 of each sensitive chip 100 will experience corresponding deformation and force due to the inertial force of the mass 130, and the paired cantilever beam assemblies 120 will generate opposing inertial couples.

[0050] See also Figure 2 , below, a three-dimensional coordinate system is established with the thickness direction of the sensitive element 10 as the Z axis. The paired sensitive chips 100 are an upper sensitive chip 100a and a lower sensitive chip 100b, wherein the upper sensitive chip 100a is located on the positive direction side of the Z axis, and the lower sensitive chip 100b is located on the negative direction side of the Z axis. The lateral acceleration is applied along the positive direction of the X axis as an example for explanation. When a lateral acceleration is applied along the positive direction of the X-axis, the mass block 130 of the upper sensitive chip 100a will tend to move in the negative direction of the X-axis due to inertia. Since the cantilever beam assembly 120 is connected to the fixed frame 110 at a position close to the first side 110a (the positive side of the Z-axis), the negative movement of the mass block 130 in the X-axis will drive the cantilever beam assembly 120 to generate a counterclockwise torque around the Y-axis. Meanwhile, the mass block 130 of the lower sensitive chip 100b will tend to move in the negative direction of the X-axis under the same lateral acceleration. Due to the constraint that the cantilever beam assembly 120 is close to the first side 110a (the negative side of the Z-axis) of the fixed frame 110, the negative movement of the mass block 130 in the X-axis will cause the cantilever beam assembly 120 to generate a clockwise torque around the Y-axis.

[0051] The torque generated by the cantilever beam assemblies 120 of the paired sensing chips 100 has moment vectors along the positive and negative Y-axis directions, respectively, forming inertial couples of equal magnitude and opposite directions. Consequently, the restraining action of the paired cantilever beam assemblies 120 on the upper sensing chip 100a and lower sensing chip 100b masses 130 transforms these moments into opposing moments about the Y-axis, thereby offsetting each other. Consequently, the Y-axis tilting moments experienced by the bonded masses 130 are effectively balanced, thereby suppressing any tendency for the masses 130 to tilt or flip.

[0052] Thus, the flipping torque on the bonded mass block 130 can be effectively offset by the couple balance between the paired cantilever beam assemblies 120. Under lateral acceleration, in a conventional single sensitive chip structure, the cantilever beam assembly is usually connected to the fixed frame and the mass block in a single-sided support manner. That is, the cantilever beam assembly is usually located on one side of the first side and the second side. Since the center of mass of the mass block is not located on the side, the mass block will tilt and flip due to the flipping torque, resulting in a strong response of the sensitive element to lateral acceleration, that is, a high lateral sensitivity. However, the sensitive element 10 provided in the embodiment of the present application achieves a couple balance due to the reverse inertial couple generated by the paired cantilever beam assemblies 120, which suppresses the tilting and flipping of the bonded mass block 130, reducing the response of the sensitive element 10 to lateral acceleration, thereby reducing the lateral sensitivity, thereby improving the accuracy of the acceleration measurement results.

[0053] It should also be noted that the lateral sensitivity of the sensing element 10 provided in this application can be verified by finite element simulation analysis to be lower than the lateral sensitivity of a traditional single sensing chip 100. Figure 11 The acceleration impact angle with the greatest lateral sensitivity is Figure 11 In the horizontal direction (the sensitive direction displacement is the largest when acceleration impact occurs along this direction), due to the inevitable assembly error in actual application, it is difficult for the optical fiber of the acceleration sensor to face the center position of the mass block 130. Assuming that the position where the optical fiber hits the mass block 130 is at the intersection of the circular line and the straight line of the mass block 130 shown in the figure, the diameter of the circular ring is taken from 0 to Φ3.5 (a value can be taken every 0.5). The finite element simulation analysis of the axial displacement comparison diagram of a single sensitive chip 100 and the sensitive element 10 of the present application when subjected to 1g in the axial direction (which can be understood as the thickness direction) and 1g in the lateral direction can be seen in Figure 12 , Figure 12The vertical axis represents the axial displacement value, and the horizontal axis represents the diameter of the sampling circle. It can be seen that as the diameter of the sampling circle increases, the axial displacements of the single sensitive chip 100 and the sensitive element 10 provided by this application, when subjected to an axial acceleration of 1g, are almost identical, and do not change with increasing diameter of the sampling circle. This shows that when subjected to axial acceleration, the displacement of the mass 130 is a translational movement as a whole. However, when subjected to a lateral acceleration of 1g, the axial displacements of the single sensitive chip 100 and the sensitive element 10 provided by this application differ significantly. The displacement of the single sensitive chip 100 increases with increasing diameter of the sampling circle, while the displacement of the sensitive element 10 provided by this application almost coincides with the zero line.

[0054] The comparison diagram of converting the axial displacement of a single sensitive chip 100 and the sensitive element 10 provided by the present application into lateral sensitivity after being subjected to lateral impact can be seen in Figure 13 , Figure 13 The vertical axis represents transverse sensitivity, and the horizontal axis represents the diameter of the sampling circle. As the diameter of the sampling circle increases, the transverse sensitivity of a single sensitive chip 100 increases linearly. The transverse sensitivity curve of the sensor element 10 provided herein is a straight line that nearly coincides with the zero line. These two verification methods demonstrate that the sensor element 10 provided herein can effectively reduce transverse sensitivity.

[0055] Alternatively, the adhesive forming the bonding layer 200 may include silicone-based gel, epoxy resin glue, or the like. These materials possess excellent mechanical strength and chemical stability, and are capable of withstanding complex environments such as high and low temperatures and vibration. In a specific implementation, a dispensing machine may be used to evenly apply the adhesive to at least one of the paired fixing frames 110 and at least one of the paired mass blocks 130. The paired sensitive chips 100 are then aligned and connected, and the adhesive is cured to form the bonding layer 200.

[0056] It can be understood that by setting the adhesive layer 200 to achieve the assembly of the sensitive element 10, the coating of the adhesive can be completed only through dispensing equipment. That is to say, 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.

[0057] See also Figure 2 and Figure 5 In some embodiments, the structures of the paired sensitive chips 100 are the same, and the paired sensitive chips 100 are mirror-imaged and arranged in opposite directions in the thickness direction.

[0058] That is, the upper sensor chip 100a and the lower sensor chip 100b are identical in geometry and component layout, and are connected by aligning the second side 110b of the fixing frame 110 toward each other. In a specific implementation, the upper sensor chip 100a can be configured as a forward structure, with the first side 110a of its fixing frame 110 facing upward (e.g., in the positive direction of the Z axis) and the second side 110b facing downward (e.g., in the negative direction of the Z axis). During assembly, the lower sensor chip 100b is mirrored on the XY plane, with the second side 110b of its fixing frame 110 facing upward, so that the paired second sides 110b face each other. This can be understood as flipping one of the sensor chips 100 by 180°, resulting in the components of the lower sensor chip 100b being spatially oppositely distributed relative to the upper sensor chip 100a. Therefore, the cantilever beam assembly 120 of the upper sensitive chip 100a is close to the first side 110a (the positive side of the Z axis) of the fixed frame 110, and the cantilever beam assembly 120 of the lower sensitive chip 100b is correspondingly close to the first side 110a (the negative side of the Z axis) of its fixed frame 110. When lateral acceleration is applied, the inertial force of the bonded mass blocks 130 is converted into an opposite torque around the Y axis through the constraints of the paired cantilever beam assemblies 120. The torques are equal in magnitude and opposite in direction, which can achieve couple balance and effectively offset the flipping torque exerted on the mass block 130.

[0059] See also Figure 4 、 Figure 7 and Figure 10 In some embodiments, the adhesive layer 200 includes a first adhesive portion 210 and a second adhesive portion 220 . The first adhesive portion 210 and the second adhesive portion 220 are spaced apart from each other. The paired fixing frames 110 are bonded to each other via the first adhesive portion 210 , and the paired mass blocks 130 are bonded to each other via the second adhesive portion 220 .

[0060] It is understood that the first adhesive portion 210 is correspondingly disposed between the paired fixed frames 110, covering at least a portion of the fixed frames 110 along the thickness direction, thereby firmly connecting the paired fixed frames 110 through bonding. The second adhesive portion 220 is correspondingly disposed between the paired mass blocks 130, covering at least a portion of the mass blocks 130 along the thickness direction. The partitioned bonding of the first adhesive portion 210 and the second adhesive portion 220 ensures that the fixed frames 110 provide stable support constraints, while also enabling the paired mass blocks 130 to respond as a whole to acceleration shocks in the thickness direction through the deformation of the cantilever beam assembly 120 under the action of inertial force.

[0061] See also Figure 3 、 Figure 6 and Figure 9In some embodiments, the orthographic projections of the cantilever beam components 120 of the paired sensing chips 100 in the thickness direction at least partially overlap.

[0062] This arrangement can further enhance the suppression effect of lateral sensitivity. It should be noted that when the cantilever beam assemblies 120 of the upper sensitive chip 100a and the lower sensitive chip 100b are staggered, the positional offset of the two cantilever beam assemblies 120 in the XY plane will lead to inconsistent force arm lengths, thereby causing deviations in the magnitude of the moment of the opposing inertial couple. However, the arrangement of the cantilever beam assemblies 120 of the upper sensitive chip 100a and the lower sensitive chip 100b with a projected overlapping area in the thickness direction can enhance the consistency of the force arm lengths of the two cantilever beam assemblies 120 in the XY plane, thereby generating opposing moments of similar magnitude under the action of lateral acceleration.

[0063] From the perspective of mechanical principles, when lateral acceleration is applied along the X-axis, if the orthographic projection positions of the cantilever beam assemblies 120 in the thickness direction correspond, the direction of the force arms transmitted by the inertial forces of the paired masses 130 through the cantilever beam assemblies 120 can be symmetrical in the thickness direction. For example, if the orthographic projection of the cantilever beam assembly 120 of the upper sensitive chip 100a in the XY plane overlaps with the orthographic projection of the cantilever beam assembly 120 of the lower sensitive chip 100b in the thickness direction, the force arm vectors of the two are equal in magnitude and opposite in direction, and the torque couple moment vectors generated can be opposite in direction along the Y-axis and have equal values, achieving couple balance. However, if the cantilever beam assemblies 120 are staggered, the directional deviation of the force arm vectors will cause the torque couple moment to deviate, resulting in higher lateral sensitivity than the sensitive chip 100 provided in the embodiment of the present application. Therefore, in the embodiment of the present application, the arrangement of the paired cantilever beam assemblies 120 in such a way that they at least partially overlap in the thickness direction can enhance the spatial symmetry of the cantilever beam assemblies 120 , reduce the deviation of the torque, and thus further reduce the lateral sensitivity of the sensitive element 10 .

[0064] See also Figure 3 、 Figure 6 and Figure 9 In some embodiments, the cantilever beam assembly 120 includes a plurality of cantilever beam bodies 121, each of which is spaced apart around the outer sidewall of the mass block 130. One end of the cantilever beam body 121 is connected to the fixing frame 110, and the other end is connected to the mass block 130. In the cantilever beam assemblies 120 of the paired sensor chips 100, the orthographic projections of the corresponding cantilever beam bodies 121 in the thickness direction at least partially overlap.

[0065] It should be noted that one end of each cantilever beam body 121 is fixedly connected to the inner sidewall of the fixed frame 110, and the other end extends to the outer sidewall of the mass block 130 and is fixedly connected to the mass block 130, so that the mass block 130 is suspended inside the fixed frame 110 through each cantilever beam body 121. The number of cantilever beam bodies 121 can be set to three, four, etc., wherein the cantilever beam assemblies 120 can be arranged at equal intervals around the outer sidewall of the mass block 130.

[0066] In the paired sensing chips 100, the orthographic projections of the corresponding cantilever beam bodies 121 in the cantilever beam assemblies 120 of the upper sensing chip 100a and the lower sensing chip 100b in the thickness direction at least partially overlap. That is, for a cantilever beam body 121 at a certain position on the upper sensing chip 100a, the projection in the thickness direction of the cantilever beam body 121 at the corresponding position on the lower sensing chip 100b overlaps with the former. This improves the symmetry of the cantilever beam body 121 in the thickness direction, effectively enhancing the moment balance, thereby offsetting the turning moment acting on the mass 130, reducing the response of the sensing element 10 to lateral acceleration, and improving the accuracy of acceleration measurement.

[0067] See also Figure 3 、 Figure 6 and Figure 9 In some embodiments, each cantilever beam body 121 includes at least one of a straight beam 121 a and a curved beam 121 b .

[0068] Optionally, all cantilever beam bodies 121 may be configured as straight beams 121a, or all may be configured as curved beams 121b. Alternatively, the cantilever beam body 121 may include a straight beam section 121a and a curved beam section 121b. For example, the ends of the curved beam section 121b may be connected to the straight beam section 121a, respectively. This allows the cantilever beam assembly 120 to flexibly adjust the motion characteristics and sensitivity of the mass 130 according to the requirements of different application scenarios.

[0069] When cantilever beam body 121 is a straight beam 121a, it extends in a straight line, with one end fixed to fixed frame 110 and the other end connected to mass block 130. Straight beam 121a has high rigidity and linear response characteristics, and can provide stable support and guidance for mass block 130 under acceleration, which helps improve the linearity and measurement accuracy of sensor 10.

[0070] It should also be noted that, see Figure 8 When the cantilever beam body 121 is a straight beam 121a, after the paired sensitive chips 100 are assembled, the orthographic projections of the paired cantilever beam components 120 can completely overlap in the thickness direction. This improves the moment balance of the couple, thereby offsetting the flipping moment exerted on the mass block 130, reducing the response of the sensitive element 10 to lateral acceleration, and improving the acceleration measurement accuracy.

[0071] When cantilever beam body 121 is a curved beam 121b, it may include curved shapes such as arcs or S-shapes. This increases the effective length and flexibility of cantilever beam body 121, thereby reducing the overall stiffness of cantilever beam assembly 120. Curved beam 121b has higher sensitivity and lower resonant frequency, enabling it to generate larger displacements under smaller accelerations, thereby enhancing the responsiveness of sensor 10 to weak accelerations.

[0072] Furthermore, the curved beam 121b can further optimize the mechanical properties of the cantilever beam assembly 120 by adjusting the curve shape and curvature radius. For example, the curvature radius of the curved curved beam 121b can be set based on the desired stiffness and sensitivity. A larger curvature radius can reduce stiffness and increase sensitivity, while a smaller curvature radius can enhance stiffness and linearity.

[0073] See also Figure 3 In some embodiments, the cantilever beam body 121 includes a curved beam 121b. The curved beam 121b extends along at least one of a zigzag trajectory and a curved trajectory between the fixed frame 110 and the mass block 130. The zigzag trajectory includes at least two zigzag segments, and the angle between adjacent zigzag segments is A, where A ≥ 90°.

[0074] Optionally, when the curved beam 121b extends along a zigzag trajectory, the curved beam 121b may include at least two zigzag segments, with the angle A between adjacent zigzag segments satisfying A ≥ 90°. For example, two adjacent zigzag segments may be L-shaped. By increasing the turning angle and effective length of the cantilever beam body 121, the flexibility of the cantilever beam body 121 is improved within a limited space, while reducing the overall stiffness of the cantilever beam assembly 120. For example, when the curved beam 121b extends along a Z-shaped trajectory, the two vertical segments are connected by a horizontal zigzag segment, forming a three-segment structure. Compared to the straight beam 121a structure, this structure can produce greater deformation under the same external force, thereby improving the response sensitivity of the sensor 10 to acceleration.

[0075] It is understood that setting the angle A between adjacent broken line segments in the broken line trajectory ≥ 90° can avoid stress concentration caused by sharp angles while ensuring the structural strength of the cantilever beam body 121 at the turning point. When the angle A is less than 90°, the turning point is prone to fatigue fracture due to stress concentration. However, setting the angle A ≥ 90° can evenly distribute stress across the cantilever beam body 121, extending the service life of the cantilever beam body 121.

[0076] The curved beam 121b can have a smooth, curved shape, such as an arc or S-shape, and the flexibility distribution of the cantilever beam body 121 can be adjusted by continuously varying the radius of curvature. For example, a gradually varying S-shaped curved beam 121b can achieve differential stiffness adjustment in different sections. The section near the fixed frame 110 has a larger curvature to enhance connection stability, while the section near the mass block 130 has a smaller curvature to improve deformation capability.

[0077] See also Figure 3 In some embodiments, the curved beam 121b includes a first fold line segment 1211 and a second fold line segment 1212. Along the length of the first fold line segment 1211, the first fold line segment 1211 is connected to the second fold line segment 1212 at both ends. The first fold line segment 1211 is arranged at a predetermined angle to the second fold line segment 1212. The two second fold line segments 1212 extend in directions away from each other. One of the two second fold line segments 1212 is connected to the fixed frame 110, and the other is connected to the mass block 130. In the paired sensitive chips 100, the corresponding first fold line segments 1211 completely overlap in the thickness direction.

[0078] In a specific implementation, the mass block 130 can be square in shape. Thus, four curved beams 121b can be provided, each corresponding to a side of the mass block 130, and the four curved beams 121b are equidistantly arranged around the mass block 130. The curved beam 121b can include a first folded line segment 1211 and two second folded line segments 1212. Along the length of the first folded line segment 1211, its ends are connected to the second folded line segments 1212, respectively. A predetermined angle is formed between the first folded line segment 1211 and the second folded line segment 1212. This angle is set to be greater than or equal to 90° to reduce the risk of stress concentration and accommodate the spatial layout requirements of the fixed frame 110 and the mass block 130. The two second folded line segments 1212 extend in mutually diverging directions, with one end connected to the inner wall of the fixed frame 110 and the other end connected to the outer wall of the mass block 130. When the curved beam 121b is deformed under load, the changing angles of the folded line segments disperse stress and enhance the structural fatigue resistance. Specifically, the first fold line segment 1211 may be parallel to the side of the corresponding mass block 130 , and the second fold line segment 1212 may be perpendicular to the first fold line segment 1211 .

[0079] For paired sensitive chips 100 (such as the upper sensitive chip 100a and the lower sensitive chip 100b), the corresponding first fold line segments 1211 completely overlap in the thickness direction. In other words, the orthographic projections of the first fold line segment 1211 of the upper sensitive chip 100a and the first fold line segment 1211 of the lower sensitive chip 100b on the plane perpendicular to the thickness direction (XY plane) completely overlap. When lateral acceleration acts, due to the overlapping projections of the first fold line segments 1211, the force arm vectors of the first fold line segments 1211 corresponding to the upper sensitive chip 100a and the lower sensitive chip 100b are aligned in the XY plane. In this way, the spatial symmetry of the cantilever beam assembly 120 can be enhanced, the deviation of the torque can be reduced, the flipping torque borne by the mass block 130 can be effectively offset, and the lateral sensitivity can be further suppressed.

[0080] It should also be noted that by combining the broken line segment of the curved beam 121b with the orthographic overlap design, the acceleration response capability is improved by relying on the flexibility of the broken line trajectory, and the accuracy of the torque balance is guaranteed by the orthographic overlap of the first broken line segment 1211, thereby optimizing the performance of the sensitive element 10.

[0081] See also Figure 6 In other optional embodiments, the curved beam 121b includes an arcuate segment 1213 and a connecting segment 1214. Along the extension direction of the arcuate segment 1213, the connecting segments 1214 are connected at both ends of the arcuate segment 1213 and arranged at a predetermined angle to the connecting segments 1214. The two connecting segments 1214 extend in directions away from each other, and one of the two connecting segments 1214 is connected to the fixed frame 110, while the other is connected to the mass block 130. In the paired sensitive chips 100, the orthographic projection of the arcuate segment 1213 of one sensitive chip 100 in the thickness direction overlaps with the orthographic projections of at least two arcuate segments 1213 of the other sensitive chip 100.

[0082] In a specific implementation, the mass block 130 can be circular, and the inner sidewall of the fixed frame 110 can also be circular. Three curved beams 121b can be provided, equidistantly arranged around the outer sidewall of the mass block 130. Thus, along the extension trajectory of the arc segment 1213, its two ends are connected to the connecting segments 1214, and a predetermined angle is formed between the arc segment 1213 and the connecting segment 1214. This angle is set to be greater than or equal to 90° to reduce the risk of stress concentration and adapt to the spatial arrangement requirements of the fixed frame 110 and the mass block 130. The two connecting sections 1214 extend in directions away from each other, with one end connected to the inner wall of the fixed frame 110 and the other end connected to the outer wall of the mass block 130. Thus, the arc section 1213 provides flexible deformation capability in a curved form. The setting of the connecting section 1214 facilitates the connection between the curved beam 121b and the fixed frame 110 and the mass block 130, and can ensure the structural rigidity of the curved beam 121b. Thus, when the curved beam 121b is subjected to force, it not only produces uniform deformation but also can stably transmit inertial force.

[0083] For paired sensitive chips 100 (e.g., upper sensitive chip 100a and lower sensitive chip 100b), the orthographic projection of the arc segments 1213 of one sensitive chip 100 in the thickness direction overlaps with the orthographic projections of at least two arc segments 1213 of the other sensitive chip 100. For example, the orthographic projection of a single arc segment 1213 of the upper sensitive chip 100a in the thickness direction may partially overlap with the orthographic projections of two arc segments 1213 of the lower sensitive chip 100b in the thickness direction. Thus, by increasing the number of overlapping projection dimensions, the spatial consistency of the moment arm vectors between the paired sensitive chips 100 can be improved. When lateral acceleration is applied, the single arc segment 1213 of the upper sensitive chip 100a and the multiple arc segments 1213 of the lower sensitive chip 100b at least partially overlap, making their respective moment arm vectors not only closer in length but also more symmetrical in direction due to the complementary effect of multiple overlapping segments. This effectively offsets the tipping moment of the mass 130 and further suppresses lateral sensitivity.

[0084] It should be noted that the flexibility advantage of the arc segment 1213 can improve the acceleration response sensitivity of the sensitive element 10, and the multiple sets of constraints of the overlapping positive projections of the single arc segment 1213 of the upper sensitive chip 100a and the multiple arc segments 1213 of the lower sensitive chip 100b can enhance the lateral sensitivity suppression capability of the sensitive element 10.

[0085] See also Figure 4 、 Figure 7 and Figure 10In some embodiments, on one side of the paired sensitive chips 100 facing away from each other in the thickness direction, the end surface of the mass block 130 and the end surface of the cantilever beam assembly 120 are coplanar with the first side 110 a of the fixing frame 110 .

[0086] It should be noted that a silicon wafer substrate can be used to manufacture the sensor chip 100. The silicon wafer substrate can include a device layer, an insulating layer, and a base layer stacked along the thickness direction. In specific implementation, the silicon wafer substrate can be processed using a micro-electro-mechanical systems (MEMS) process. The processing feature of the MEMS process is that the etching depth can be precisely controlled, thereby ensuring processing accuracy.

[0087] When etching the silicon wafer substrate, all material in the non-beam region between the mass block 130 and the fixed frame 110 is completely etched away. The material in the beam region etches away the base layer and the insulating layer, leaving only the device layer to form the cantilever beam body 121 between the fixed frame 110 and the mass block 130. As a result, the end faces of the mass block 130 and the cantilever beam assembly 120 are coplanar with the first side 110a of the fixed frame 110. It can also be understood that, along the thickness direction and in a direction from the first side 110a to the second side 110b, the fixed frame 110 and the mass block 130 both include a stacked device layer, an insulating layer, and a base layer, and the cantilever beam assembly 120 includes a device layer, which is coplanar with the device layers of the fixed frame 110 and the mass block 130. This arrangement synchronizes the deformation boundaries of the mass block 130 and the cantilever beam in the thickness direction. When acceleration is applied, the force starting surfaces of the mass block 130 and the cantilever beam are consistent, reducing the additional torsional moment caused by the end face height difference.

[0088] In some embodiments, along the thickness direction, the maximum thickness of the sensor chip 100 is h1, where 50 μm≤h1≤200 μm.

[0089] In other words, when selecting the substrate for fabricating the sensor chip 100, the thickness of the substrate can be any value between 50 μm and 200 μm, including the two extreme values ​​of 50 μm and 200 μm. If the substrate is too thin, it may warp during the etching process due to insufficient structural rigidity. If the substrate is too thick, the anisotropic error of the etching will be amplified, which may cause the dimensions of the cantilever beam assembly 120 to deviate from the designed value and destroy the symmetry of the force arm vector. Therefore, the maximum thickness of the sensor chip 100 is h1, which satisfies the condition of 50 μm ≤ h1 ≤ 200 μm.

[0090] In some embodiments, the thickness of the adhesive layer 200 along the thickness direction is h2, where 2 μm≤h2≤5 μm.

[0091] That is, the thickness of the adhesive layer 200 can be set to any value between 2 μm and 5 μm, such as 2 μm, 3 μm, 4 μm, 5 μm, etc.

[0092] It is understood that the adhesive layer 200 is required to stably connect the paired sensor chips 100. If the adhesive layer 200 is too thin, the effective bonding area will be insufficient, the interlayer bonding strength will weaken, and delamination will easily occur under acceleration shock. If the adhesive layer 200 is too thick, the volume shrinkage during the curing process will generate internal stress. This stress is transmitted to the sensor chip 100 along the thickness direction, interfering with the deformation synchronization of the cantilever beam assembly 120 and the mass block 130.

[0093] Based on the above embodiments, an embodiment of the present application provides an acceleration sensor, comprising an optical fiber and the sensitive element 10 provided in any of the above embodiments. Along the thickness direction of the sensitive element 10, the optical fiber and the sensitive element 10 are arranged at a predetermined distance, and the incident direction of the optical fiber is perpendicular to the reflective surface of the sensitive element 10.

[0094] See also Figure 1 The operating principle of the acceleration sensor based on the optical interference principle is to form an optical interference cavity between the end face of the optical fiber and the reflective surface of the mass block 130 of the sensitive element 10. When the sensor is subjected to axial acceleration (i.e., acceleration along the thickness direction), the mass block 130 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 130, forming optical interference. The light signal reflected back to the optical fiber carries information about the cavity length change. Decoding it can restore the acceleration information corresponding to the cavity length change.

[0095] By adopting the sensitive element 10 provided in the embodiment of the present application, the acceleration sensor can improve the accuracy of measuring acceleration of the acceleration sensor because the sensitive element 10 can reduce the lateral sensitivity.

[0096] The sensitive element 10 has been described in detail in the above embodiment and will not be described again here.

[0097] 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: The sensitive element includes: Sensitive chips are arranged in pairs along the thickness direction of the sensitive element itself, each of the sensitive chips includes a fixed frame, a cantilever beam assembly and a mass block, the mass block is located inside the fixed frame, the cantilever beam assembly is connected between the fixed frame and the mass block, along the thickness direction, the fixed frame has a first side and a second side opposite to each other, the second sides of the paired fixed frames are arranged toward each other, and the cantilever beam assembly is arranged close to the first side relative to the second side; The adhesive layer is located between the paired sensitive chips, and covers at least part of the fixing frame and the mass block along the thickness direction. The fixing frames and the mass blocks of the paired sensitive chips are respectively connected via the adhesive layer.

2. The sensitive element according to claim 1, characterized in that The sensitive chips arranged in pairs have the same structure, and the sensitive chips arranged in pairs are arranged in mirror-image orientation in the thickness direction.

3. The sensitive element according to claim 1, characterized in that The adhesive layer includes a first adhesive portion and a second adhesive portion, the first adhesive portion and the second adhesive portion are spaced apart from each other, the paired fixing frames are bonded correspondingly via the first adhesive portion, and the paired mass blocks are bonded correspondingly via the second adhesive portion.

4. The sensitive element according to claim 1, characterized in that: The orthographic projections of the cantilever beam components of the paired sensitive chips in the thickness direction at least partially overlap.

5. The sensitive element according to claim 4, characterized in that: The cantilever beam assembly includes a plurality of cantilever beam bodies, each of which is spaced apart around the outer side wall of the mass block, one end of each cantilever beam body being connected to the fixing frame, and the other end being connected to the mass block; Wherein, in the cantilever beam assemblies of the sensitive chips arranged in pairs, the orthographic projections of the corresponding cantilever beam bodies in the thickness direction at least partially overlap.

6. The sensitive element according to claim 5, characterized in that: Each of the cantilever beam bodies includes at least one of a straight beam and a curved beam.

7. The sensitive element according to claim 6, characterized in that: The cantilever beam body includes a curved beam, and the curved beam extends between the fixing frame and the mass block along at least one of a broken line trajectory and a curved trajectory; The broken line track includes at least two broken line segments, and the angle between adjacent broken line segments is A, where A≥90°.

8. The sensitive element according to claim 7, characterized in that: The curved beam includes a first fold line segment and a second fold line segment. Along the length direction of the first fold line segment, both ends of the first fold line segment are respectively connected to the second fold line segment and are arranged at a preset angle with the second fold line segment. The two second fold line segments extend in directions away from each other, and one of the two second fold line segments is connected to the fixing frame, and the other is connected to the mass block. Among the sensitive chips arranged in pairs, the corresponding first fold line segments completely overlap in the thickness direction.

9. The sensitive element according to claim 7, characterized in that: The curved beam includes an arc segment and a connecting segment. Along the extension direction of the arc segment, both ends of the arc segment are respectively connected to the connecting segment and are arranged at a preset angle with the connecting segment. The two connecting segments extend in directions away from each other, and one of the two connecting segments is connected to the fixing frame, and the other is connected to the mass block. Among the sensitive chips arranged in pairs, the orthographic projection of the arc segment of one of the sensitive chips in the thickness direction forms an overlapping area with the orthographic projections of at least two arc segments of the other sensitive chip.

10. The sensitive element according to any one of claims 1 to 9, characterized in that: The sensitive chips arranged in pairs are on one side facing away from each other in the thickness direction, and the end surface of the mass block and the end surface of the cantilever beam assembly are coplanar with the first side of the fixing frame.

11. The sensitive element according to any one of claims 1 to 9, characterized in that: Along the thickness direction, the maximum thickness of the sensitive chip is h1, wherein 50 μm ≤ h1 ≤ 200 μm; Along the thickness direction, the thickness of the adhesive layer is h2, wherein 2 μm≤h2≤5 μm.

12. An acceleration sensor, characterized in that: The invention comprises an optical fiber and the sensitive element according to any one of claims 1 to 11, wherein the optical fiber and the sensitive element are arranged at a predetermined distance along the thickness direction of the sensitive element, and the incident direction of the optical fiber is perpendicular to the reflecting surface of the sensitive element.

Images