Quartz vibrating beam accelerometer sensitive structure

Abstract

The application relates to the technical field of accelerometers, and provides a quartz vibrating beam accelerometer sensitive structure, which comprises a quartz flexible beam arranged at one end of a rigid beam, a quartz mass pendulum arranged at the other end of the quartz flexible beam, and a quartz tuning fork vibrating beam structure connected with the rigid beam at one end and connected with the quartz mass pendulum at the other end. The quartz vibrating beam accelerometer sensitive structure provided by the application is provided with the quartz flexible beam, the quartz mass pendulum and the quartz tuning fork vibrating beam structure, all of which are made of quartz crystal materials, so that the matching of the material thermal expansion coefficient can be improved, and the temperature drift problem caused by the mismatching of the material thermal expansion coefficient is solved.

Description

Technical Field

[0001] This invention relates to the field of accelerometer technology, and in particular to a sensitive structure for a quartz vibrating beam accelerometer. Background Technology

[0002] Quartz beam accelerometers use a mass pendulum to sense the acceleration of the measured carrier. The force-sensitive quartz beam converts the inertial force caused by acceleration into a frequency change and directly outputs a frequency proportional to the magnitude of the measured acceleration. Quartz beam accelerometers eliminate the velocity increment error caused by analog-to-digital conversion, are compatible with high-speed digital inertial navigation systems, have a low temperature drift coefficient, and offer advantages such as high accuracy, low cost, and small size. The applications of quartz beam accelerometers have expanded from low-to-medium precision fields such as navigation and flight control to high-precision fields such as gravity measurement.

[0003] A quartz beam accelerometer typically consists of a flexible beam, a sensitive mass, and a quartz resonator. The sensitive mass and the flexible beam form a pendulum assembly structure. The overall layout can utilize either a single resonator or a push-pull resonator configuration, with the resonator bonded between the sensitive mass and the base. Under the inertial force generated by the input shaft acceleration, the sensitive mass exerts axial tension, compression, or torque on the quartz beam, causing a change in the resonant beam frequency. This frequency change reflects the magnitude and direction of the input acceleration.

[0004] Quartz accelerometer sensing structures can be divided into two types: split-type and integrated-type. Honeywell, BEI, and EPSON in the United States use the split-type design, while ONERA and iXblue in France use the integrated-type design.

[0005] The existing split structure cannot solve the problem of thermal expansion coefficient matching. Due to the use of multiple materials, the thermal expansion coefficients of the materials themselves cannot be completely matched. The use of process adhesives cannot effectively guarantee the matching of thermal expansion coefficients, resulting in a large temperature drift coefficient when changing the temperature range. On the other hand, the integrated vibrating beam accelerometer uses a single vibrating beam structure. The vibrating beam has a large loss at the base. The manufacturing process of the integrated structure is difficult, and the release of the flexible beam and vibrating beam of the sensitive structure is difficult. Summary of the Invention

[0006] This invention provides a sensitive structure for a quartz vibrating beam accelerometer, which solves the defect in the prior art where multiple materials are used but their thermal expansion coefficients cannot be completely matched, thereby improving the matching of the thermal expansion coefficients of the materials.

[0007] This invention provides a sensing structure for a quartz vibrating beam accelerometer, comprising:

[0008] A quartz flexible beam, with one end mounted on a rigid beam;

[0009] A quartz mass pendulum is disposed at the other end of the quartz flexible beam;

[0010] A quartz tuning fork vibrating beam structure is located on at least one side of the quartz flexible beam, with one end of the quartz tuning fork vibrating beam structure connected to the rigid beam and the other end connected to the quartz mass pendulum.

[0011] According to the present invention, a quartz vibrating beam accelerometer sensitive structure is provided, wherein the quartz tuning fork vibrating beam structure is fixedly connected to the rigid beam and the quartz mass pendulum respectively by glass slurry.

[0012] According to the present invention, a quartz vibrating beam accelerometer sensitive structure is provided, wherein the quartz vibrating beam structure includes an upper vibrating beam structure and a lower vibrating beam structure, wherein the upper vibrating beam structure and the lower vibrating beam structure are respectively located on both sides of the quartz flexible beam.

[0013] According to the present invention, a quartz vibrating beam accelerometer sensing structure is provided, wherein both the upper and lower tuning fork vibrating beam structures comprise:

[0014] Two anchor areas, one of which is connected to the rigid beam and the other is connected to the quartz mass pendulum;

[0015] The tuning fork vibrating beam is configured as two parallel single vibrating beams located between the two anchor areas; and the two ends of the two single vibrating beams are coupled together through tuning fork nodes.

[0016] A tuning fork stress isolation beam is disposed at the end of the tuning fork node away from the tuning fork vibrating beam to achieve stress isolation effect;

[0017] Four folded beams form a rhomboid composite beam structure with the tuning fork vibrating beam. One end of the folded beam is connected to the tuning fork stress isolation beam through the folded beam joint, and the other end is connected to the corresponding anchor area.

[0018] The quartz vibrating beam accelerometer sensing structure provided by the present invention further includes:

[0019] An internal stress isolation frame is disposed on the outer periphery of the rigid beam, the quartz flexible beam and the quartz mass pendulum, and the internal stress isolation frame is connected to the rigid beam through the internal stress isolation beam;

[0020] An external stress isolation frame is disposed on the outer periphery of the internal stress isolation frame, and the external stress isolation frame is connected to the internal stress isolation frame through an external stress isolation beam.

[0021] According to the present invention, a sensitive structure for a quartz vibrating beam accelerometer further includes a temperature-sensing tuning fork, which is disposed on the external stress isolation frame.

[0022] According to the present invention, a quartz vibrating beam accelerometer sensitive structure is provided, wherein quartz mass blocks are provided at the top and bottom of the quartz mass pendulum, and the quartz mass blocks are connected to the quartz mass pendulum through a glass slurry sintering process.

[0023] According to the present invention, a sensitive structure for a quartz vibrating beam accelerometer is provided, wherein the quartz mass block is a cuboid.

[0024] According to the present invention, the bonding thickness between the quartz mass block and the quartz mass pendulum is 50μm-100μm.

[0025] According to the present invention, the sensitive structure of a quartz vibrating beam accelerometer is provided, wherein the viscosity of the glass slurry is 80-100 Pa·s, the glue removal temperature is 120°C, the pre-sintering temperature is 220-240°C, and the sintering temperature is 330-360°C.

[0026] The quartz vibrating beam accelerometer sensitive structure provided by this invention, by setting up a quartz flexible beam, a quartz mass pendulum and a quartz tuning fork vibrating beam structure, all of which are made of quartz crystal material, can improve the matching of the thermal expansion coefficients of the materials and solve the temperature drift problem caused by the mismatch of the thermal expansion coefficients of the materials. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0028] Figure 1 This is an assembly diagram of the sensitive structure of the quartz vibrating beam accelerometer provided by the present invention;

[0029] Figure 2 This is a bottom view of the sensitive structure of the quartz vibrating beam accelerometer provided by the present invention;

[0030] Figure 3 This is a schematic diagram of the quartz tuning fork vibrating beam structure provided by the present invention;

[0031] Figure 4 This is a schematic diagram of the quartz flexible beam and quartz mass pendulum with stress isolation structure provided by the present invention;

[0032] Figure 5 This is a bottom view of the quartz flexible beam with stress isolation structure and the quartz mass pendulum provided by the present invention.

[0033] Figure 6This is a front view of the quartz mass block provided by the present invention;

[0034] Figure 7 This is a side view of the quartz mass block provided by the present invention;

[0035] Figure 8 This is a front view of the temperature-measuring tuning fork provided by the present invention;

[0036] Figure 9 This is a top view of the temperature-measuring tuning fork provided by the present invention;

[0037] Figure label:

[0038] 1. Quartz flexible beam; 2. Quartz mass pendulum; 3. Quartz tuning fork vibrating beam structure; 31. Anchor zone; 32. Tuning fork vibrating beam; 33. Tuning fork stress isolation beam; 34. Folded beam; 35. Tuning fork node; 36. Folded beam node; 4. Rigid beam; 5. Internal stress isolation frame; 6. External stress isolation frame; 7. Quartz mass block; 8. Temperature-measuring tuning fork; 9. Glass slurry; 10. Internal stress isolation beam; 11. External stress isolation beam; 12. Patch area. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0040] The following is combined with Figures 1 to 9 The sensitive structure of the quartz vibrating beam accelerometer of the present invention is described. For example... Figure 1 and Figure 2 As shown, the sensitive structure of the quartz vibrating beam accelerometer of the present invention includes a quartz flexible beam 1, a quartz mass pendulum 2, and a quartz tuning fork vibrating beam structure 3. One end of the quartz flexible beam 1 is disposed on a rigid beam 4; the quartz mass pendulum 2 is disposed at the other end of the quartz flexible beam 1; the quartz tuning fork vibrating beam structure 3 is disposed on at least one side of the quartz flexible beam 1, and one end of the quartz tuning fork vibrating beam structure 3 is connected to the rigid beam 4, and the other end is connected to the quartz mass pendulum 2.

[0041] The quartz vibrating beam accelerometer sensitive structure provided by the present invention, by setting a quartz flexible beam 1, a quartz mass pendulum 2 and a quartz tuning fork vibrating beam structure 3, all of which are made of quartz crystal material, can improve the matching of the thermal expansion coefficients of the materials and solve the temperature drift problem caused by the mismatch of the thermal expansion coefficients of the materials.

[0042] Furthermore, such as Figure 1As shown, the quartz tuning fork vibrating beam structure 3 is fixedly connected to the rigid beam 4 and the quartz pendulum 2 respectively through a glass slurry sintering process, achieving a rigid connection between the structure and the rigid beam 4 and the quartz pendulum 2. The bonding gap is controlled between 50μm and 100μm. The viscosity of the glass slurry is 80-100 Pa·s, the adhesive discharge temperature is 120℃, the pre-sintering temperature is 220-240℃, the sintering temperature is 330-360℃, and the coefficient of thermal expansion is 10-13 ppm / ℃. This solves the temperature drift problem caused by the mismatch between the thermal expansion coefficients of the adhesive and the substrate, ensuring a matching seal.

[0043] like Figure 1 As shown, in an embodiment of the present invention, the quartz tuning fork resonator structure 3 includes an upper tuning fork resonator structure and a lower tuning fork resonator structure, which are located on both sides of the quartz flexible beam 1, respectively. By employing the arrangement of the upper and lower tuning fork resonator structures, the common-mode error of the tuning fork resonator is effectively suppressed.

[0044] like Figure 3 As shown, in one embodiment of the present invention, the upper tuning fork vibrating beam structure and the lower tuning fork vibrating beam structure are identical, both including two anchor areas 31, a tuning fork vibrating beam 32, a tuning fork stress isolation beam 33, and four folded beams 34. One of the two anchor areas 31 is connected to the rigid beam 4, and the other is connected to the quartz mass pendulum 2. The tuning fork vibrating beam 32 is configured as two parallel single vibrating beams located between the two anchor areas 31. The two ends of the two single vibrating beams are coupled together through tuning fork nodes 35. The tuning fork stress isolation beam 33 is located at the end of the tuning fork node 35 away from the tuning fork vibrating beam 32 to achieve stress isolation. The four folded beams 34 and the tuning fork vibrating beam 32 form a rhomboid composite beam structure. One end of the folded beam 34 is connected to the tuning fork stress isolation beam 33 through a folded beam node 36, and the other end is connected to the corresponding anchor area 31.

[0045] When the quartz pendulum 2 senses acceleration input on the sensitive axis, the relative position between the two anchor areas 31 changes, causing tensile and compressive deformation of the folded beam. When the position of the two anchor areas increases, the axial compressive force generated by the four folded beams 34 and the tuning fork vibrating beam 32 is "doubled," causing the tuning fork resonant frequency to decrease. When the position of the two anchor areas 31 decreases, the axial tensile stress generated by the four folded beams on the tuning fork vibrating beam 32 is "doubled," causing the tuning fork resonant frequency to increase. By changing the direction of the pendulum axis to the output axis direction, the influence of the tuning fork vibrating beam 32 on the stiffness of the quartz flexible beam 1 is minimized. To prevent "frequency lock-up" of the upper and lower vibrating beams, different structural parameters are required for the upper and lower vibrating beams. Both the upper and lower tuning fork vibrating beam structures are axisymmetric structures, symmetrical along both the x-axis and y-axis. The recommended structural parameter values ​​for the quartz tuning fork vibrating beam structure 3 are shown in Table 1, with a beam thickness of 60–80 μm and an angle θ = 60 degrees between the folded beam and the horizontal direction.

[0046] Table 1. Dimensional parameters of the quartz vibrating beam tuning fork structure (unit: μm)

[0047] L1 L2 L3 L4 L5 L6 W0 W1 W2 W3 W4 W5 W6 Upper vibrating beam 2000 300 350 500 35 600 50 30 500 60 800 60 500 Lower vibrating beam 2000 300 350 500 35 600 50 40 500 60 800 60 500

[0048] By adding a lever multiplier mechanism, the force-frequency coefficient of the quartz tuning fork vibrating beam structure 3 is increased, thereby improving the overall sensitivity of the sensitive structure and effectively isolating external stress, thus solving the stress isolation problem under high sensitivity conditions.

[0049] In embodiments of the present invention, such as Figure 4 and Figure 5 As shown, it also includes an internal stress isolation frame 5 and an external stress isolation frame 6. The internal stress isolation frame 5 is disposed on the outer periphery of the rigid beam 4, the quartz flexible beam 1 and the quartz mass pendulum 2, and the internal stress isolation frame 5 is connected to the rigid beam 4 through the internal stress isolation beam 10; the external stress isolation frame 6 is disposed on the outer periphery of the internal stress isolation frame 5, and is connected to the internal stress isolation frame 5 through the external stress isolation beam 11.

[0050] like Figure 2 As shown, the external stress isolation frame 6 is bonded to the substrate with silicone. The internal stress isolation frame 5 and the external stress isolation frame 6 are used to effectively isolate thermal stress. Direct bonding of the sensitive structure of the quartz vibrating beam accelerometer to the base can easily lead to thermal stress caused by the mismatch of thermal expansion coefficients, which causes changes in the zero-point output. The use of the internal stress isolation frame 5 and the external stress isolation frame 6 is actually a stress isolation method to effectively isolate the quartz flexible beam 1 and the quartz mass pendulum 2 at the bonding position, and to achieve complete isolation between the sensitive structure and the base to reduce stress.

[0051] like Figure 2 As shown, to prevent the external stress isolation frame 6 from over-positioning, a three-point bonding scheme is adopted, such as... Figure 2 As shown, it has 3 patch areas 12. The silicone viscosity is 80-120 Pa·s, the shear strength is 5.9 MPa, and it is cured at room temperature for 12 hours.

[0052] The entire sensitive structure of the quartz vibrating beam accelerometer adopts an integrated processing scheme. The quartz flexible beam 1 and the quartz mass pendulum 2 are stress-isolated by the internal stress isolation frame 5 and the external stress isolation frame 6 to prevent the influence of temperature stress and patch stress on the sensitive structure. The top view of the structure is as follows: Figure 4 As shown in Table 2, the specific structural parameters are as follows.

[0053] Table 2. Dimensional parameters of the quartz pendulum structure (unit: μm)

[0054] h1 d1 h2 d2 h3 d3 h4 d4 h5 d5 h6 600 500 400 500 600 500 600 1500 25 500 600 d6 h7 d7 L7 L8 W7 W8 W9 W10 W11 600 400 500 6600 4600 5600 3600 600 2600 600

[0055] In embodiments of the present invention, such as Figure 6 and Figure 7 As shown, quartz mass blocks 7 are provided at both the top and bottom of the quartz pendulum 2, and the quartz mass blocks 7 are connected to the quartz pendulum 2 through a glass slurry sintering process. The inclusion of quartz mass blocks 7 can improve the sensitivity of the quartz flexible beam 1 and the quartz pendulum 2 to input acceleration. The quartz mass blocks 7 adopt a cuboid structure, the bonding thickness between the quartz mass blocks 7 and the quartz pendulum 2 is 50μm-100μm, the viscosity of the glass slurry is 80-100 Pa·s, the adhesive removal temperature is 120℃, the pre-sintering temperature is 220-240℃, and the sintering temperature is 330-360℃. The use of low-temperature glass slurry to achieve a matching bond between the quartz mass blocks 7 and the quartz pendulum 2 solves the temperature drift problem caused by the mismatch of the thermal expansion coefficients of the adhesive and the substrate.

[0056] The dimensional parameters of the quartz mass block 7 are shown in Table 3.

[0057] Table 3. Dimensional parameters of quartz mass block 7 (unit: μm)

[0058] h8 d8 w12 2500 2600 2600

[0059] In an embodiment of the present invention, a temperature-sensing tuning fork 8 is also included. The temperature-sensing tuning fork 8 is disposed on the external stress isolation frame 6, and the structure of the temperature-sensing tuning fork 8 is as follows: Figure 8 and Figure 9 As shown in Table 4, the dimensional parameters are as follows. The torsional vibration mode is selected as the working mode for the fork teeth. The temperature model of the thermometric tuning fork under this torsional mode is:

[0060]

[0061] Here, Δf = f - f0; ΔT = T - T0; f and f0 are the resonant frequencies of the thermometric tuning fork 8 at temperatures T and T0 (T0 = 25℃), respectively; α0, α1, α2, and α3 are the 0th to 3rd order temperature coefficients, respectively. The thermometric tuning fork 8 adopts a double-rotation Y-cut resonator, making α2 and α3 approach zero, with a first-order temperature coefficient of 35–45 ppm / ℃, a temperature measurement range of -80℃ to 230℃, and a temperature measurement accuracy of 0.02℃.

[0062] Table 4. Dimensional parameters of the temperature-measuring tuning fork (unit: μm)

[0063] L9 L10 L11 L12 W13 W14 W15 W16 W17 h9 h10 400 400 100 200 500 60 100 50 300 80 120

[0064] The core temperature of the sensitive structure is measured using a quartz tuning fork 8. Compared with the output voltage signal of conventional temperature-sensing diodes or temperature-sensing chips, the output frequency signal of the quartz tuning fork structure has higher temperature measurement accuracy. Moreover, the quartz tuning fork is integrated with the sensitive structure, while temperature-sensing diodes or temperature-sensing chips are integrated with the PCB board. Therefore, the quartz tuning fork 8 is closer to the core temperature of the vibrating beam.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A sensing structure for a quartz vibrating beam accelerometer, characterized in that, include: A quartz flexible beam, with one end mounted on a rigid beam; A quartz mass pendulum is disposed at the other end of the quartz flexible beam; A quartz tuning fork vibrating beam structure is located on at least one side of the quartz flexible beam. One end of the quartz tuning fork vibrating beam structure is connected to the rigid beam, and the other end is connected to the quartz mass pendulum. The quartz tuning fork vibrating beam structure includes an upper tuning fork vibrating beam structure and a lower tuning fork vibrating beam structure, which are respectively located on both sides of the quartz flexible beam. The upper tuning fork vibrating beam structure and the lower tuning fork vibrating beam structure employ different structural parameters. Both the upper and lower tuning fork vibrating beam structures include: Two anchor areas, one of which is connected to the rigid beam and the other is connected to the quartz mass pendulum; The tuning fork vibrating beam is configured as two parallel single vibrating beams located between the two anchor areas; and the two ends of the two single vibrating beams are coupled together through tuning fork nodes. A tuning fork stress isolation beam is disposed at the end of the tuning fork node away from the tuning fork vibrating beam to achieve stress isolation effect; Four folded beams form a rhomboid composite beam structure with the tuning fork vibrating beam. One end of the folded beam is connected to the tuning fork stress isolation beam through the folded beam joint, and the other end is connected to the corresponding anchor area.

2. The sensitive structure of the quartz vibrating beam accelerometer according to claim 1, characterized in that, The quartz tuning fork vibrating beam structure is fixedly connected to the rigid beam and the quartz mass pendulum respectively by glass slurry.

3. The sensitive structure of the quartz vibrating beam accelerometer according to claim 1, characterized in that, Also includes: An internal stress isolation frame is disposed on the outer periphery of the rigid beam, the quartz flexible beam and the quartz mass pendulum, and the internal stress isolation frame is connected to the rigid beam through the internal stress isolation beam; An external stress isolation frame is disposed on the outer periphery of the internal stress isolation frame, and the external stress isolation frame is connected to the internal stress isolation frame through an external stress isolation beam.

4. The sensitive structure of the quartz vibrating beam accelerometer according to claim 1, characterized in that, The quartz mass pendulum is provided with quartz mass blocks at both the top and bottom, and the quartz mass blocks are connected to the quartz mass pendulum through a glass slurry sintering process.

5. The sensitive structure of the quartz vibrating beam accelerometer according to claim 4, characterized in that, The quartz mass block is a cuboid.

6. The sensitive structure of the quartz vibrating beam accelerometer according to claim 4, characterized in that, The bonding thickness between the quartz mass block and the quartz mass pendulum is 50μm-100μm.

7. The sensitive structure of the quartz vibrating beam accelerometer according to claim 4, characterized in that, The viscosity of the glass slurry is 80-100 Pa·s, the binder removal temperature is 120℃, the pre-sintering temperature is 220-240℃, and the sintering temperature is 330-360℃.

8. The sensitive structure of the quartz vibrating beam accelerometer according to claim 3, characterized in that, It also includes a temperature-sensing tuning fork, which is disposed on the external stress isolation frame.

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