Pendulous reed processing method for reducing electrostatic interference torque of quartz flexible accelerometer

Abstract

The invention relates to a pendulous reed processing method of a quartz flexible accelerometer for reducing electrostatic interference torque, which comprises the following steps of: 1, in a pendulous reed design stage, designing that the area of a C-shaped coating area on a pendulous reed pendulous tongue is larger than the areas of C-shaped areas of an upper magnetic conductive ring and a lower magnetic conductive ring, namely R1 is smaller than (R3-0.15 mm) and R2 is larger than (R4 + 0.15 mm), R1 and R2 are respectively the inner diameter and the outer diameter of the C-shaped coating area of the pendulous reed pendulous tongue, and R2 is larger than (R4 + 0.15 mm); r3 and R4 are the inner diameter and the outer diameter of the C-shaped area of the magnetic conductive ring respectively; 2, in the pendulous reed processing stage, micron / nano-scale periodic structures or random pit textures are processed on the surface of the pendulous reed through a plasma etching method or a femtosecond laser etching method, and the roughness of an electrostatic charge accumulation area on the pendulous reed is increased; and 3, before general assembly of the accelerometer core, electrostatic charges on the pendulous reed are eliminated by a plasma cleaning method or a method of blowing ionic wind by an electrostatic ion removal fan. According to the method, the electrostatic interference torque between the pendulous reed and the upper and lower magnetic conductive rings in the accelerometer can be effectively reduced, and the stability precision of the accelerometer is improved.

Description

Technical Field

[0001] The present invention belongs to the field of sensor technology, and in particular relates to a pendulum processing method for a quartz flexible accelerometer for reducing electrostatic interference torque, which effectively reduces the electrostatic interference torque exerted on the detection mass of the sensitive acceleration in the accelerometer, thereby improving the stability and accuracy of the accelerometer. Background Art

[0002] Quartz flexible accelerometer is the most widely used accelerometer currently, used in various types of navigation and guidance systems such as aerospace, aviation, navigation, and land use. Quartz flexible accelerometer consists of upper magnetic ring component 1, pendulum component 2, lower magnetic ring component 3, connecting ring 5, isolation ring 6, shell 4, etc. Figure 1 As shown in the figure, the upper and lower magnetic ring components and the pendulum component are connected by a connecting ring. The upper and lower magnetic rings and the connecting ring are laser welded to form the meter core. The meter core is adhesively bonded to the housing via an isolation ring to form the accelerometer. In the accelerometer, the pendulum component consists of a pendulum and a torquer coil. The pendulum tongue and torquer coil form the acceleration-sensitive detection mass. The upper (lower) magnetic ring components include the upper (lower) magnetic ring, magnet, pole piece, and thermomagnetic compensation ring, forming the magnetic circuit. The torquer coil is located in the working air gap of the magnetic circuit, forming a permanent magnet torquer. Furthermore, the gold film on the pendulum tongue and the end faces of the upper and lower magnetic rings form a differential capacitance sensor.

[0003] The principle block diagram of the quartz flexible accelerometer is as follows: Figure 2 As shown. Under the action of the force, the pendulum tongue deflects relative to its "mechanical zero position" (the position of the pendulum when there is no force) by an angle , the dynamic equation of the detection mass around the output axis is:

[0004] ……………… Where: ——Detection mass moment of inertia, ; ——test mass damping coefficient, ; ——The stiffness of the pendulum flexible beam along the input axis direction, ; - the angle of deflection of the test mass relative to its "mechanical zero position", ; - The torquer applies torque, ; ——Test quality, ; - the distance from the center of mass of the test mass to the pivot axis, ; - Input acceleration, ; - disturbance torque, .

[0005] Depend on Figure 2 As can be seen, the quartz flexure accelerometer is a differential closed-loop accelerometer. When there is no acceleration input, the proof mass, consisting of the pendulum, tongue, and torquer coil, is at the "electrical zero position" of the differential capacitance sensor. When there is acceleration input, the proof mass deflects in accordance with the inertial force, moving away from the "electrical zero position," causing the differential capacitance sensor to generate an output. This output is converted into a torque feedback current by the servo circuit and input into the torquer coil, generating an electromagnetic feedback torque that returns the proof mass to the "electrical zero position." After reaching steady state, there is an angle of deviation between the proof mass position and the "electrical zero position." The electromagnetic feedback torque generated by this angle of deviation balances the inertial torque. Therefore, the feedback current in the torquer coil corresponds to the input acceleration. By detecting the magnitude and direction of the torque feedback current, the magnitude and direction of the input acceleration can be determined.

[0006] It is particularly important to explain that when there is no acceleration input, the detection mass is at the "electrical zero position". Since the "electrical zero position" and the "mechanical zero position" of the detection mass (referring to its position when not subject to external force) usually do not coincide, an elastic restoring torque is generated in the flexible beam of the pendulum at this time, and the detection mass is also affected by various interference torques. Therefore, a torque feedback current is required to generate feedback torque for balance. The acceleration corresponding to the torque feedback current is the accelerometer bias.

[0007] In quartz flexure accelerometers, the test mass is subject to various interference torques, including torque generated by the torsional deformation of the pendulum flexure beam, zero-position torque of the permanent magnetic torquer (the output torque of the torquer when there is no input current), and electrostatic interference torque. Electrostatic interference torque, generated by the electrostatic force between the pendulum tongue and the end face of the magnetic ring, is a key factor affecting the stability and accuracy of the accelerometer.

[0008] The structure of the quartz flexible accelerometer's pendulum is shown in Figure 3. Its tongue has both coated and uncoated areas. The coated area serves as the moving electrode of the capacitive sensor, connecting to the external circuit and preventing static charge accumulation. However, the uncoated area, made of quartz glass and non-conductive, accumulates static charge during storage, assembly, and use, forming a static charge accumulation zone. The structure of the upper and lower magnetic rings is shown in Figure 4. The inner C-shaped area serves as the fixed electrode of the capacitor, also connecting to the external circuit and preventing static charge accumulation. However, the C-shaped areas of the upper and lower magnetic rings face the pendulum's tongue. Static charge in the static charge accumulation zone of the pendulum induces charge in the C-shaped area of ​​the magnetic rings, generating an electrostatic force and, in turn, an electrostatic interference torque. Because the static charge in the static charge accumulation zone of the pendulum changes dynamically with the use of the accelerometer, it generates an unstable interference torque, which affects the stability and accuracy of the accelerometer.

[0009] Therefore, further measures should be taken to reduce the electrostatic interference torque in the quartz flexible accelerometer and further improve the stability and accuracy of the accelerometer. Summary of the Invention

[0010] In view of the deficiencies of the prior art, the present invention proposes a method for processing a pendulum of a quartz flexible accelerometer for reducing electrostatic interference torque.

[0011] The above-mentioned purpose of the present invention is achieved through the following technical solutions: A method for processing a quartz flexible accelerometer pendulum to reduce electrostatic interference torque comprises the following steps: Step 1. During the design phase of the pendulum, the C-shaped coating area on the pendulum tongue is designed to be larger than the C-shaped areas of the upper and lower magnetic conductive rings, that is, R1 < (R3-0.15mm), R2 > (R4+0.15mm), where R1 is the inner diameter of the C-shaped coating area on the pendulum tongue, R2 is the outer diameter of the C-shaped coating area on the pendulum tongue, R3 is the inner diameter of the C-shaped area of ​​the magnetic conductive ring, and R4 is the outer diameter of the C-shaped area of ​​the magnetic conductive ring; Step 2: During the swing plate processing stage, the roughness of the static charge accumulation area on the swing plate is increased; Step 3: Before assembling the accelerometer core, eliminate the static charge on the pendulum.

[0012] Moreover, in step 2, a plasma etching method is used to process a micron / nanoscale periodic structure or a random pit texture on the surface of the pendulum piece, so that the surface roughness of the pendulum piece reaches Ra 0.1μm to 0.5μm.

[0013] Moreover, in step 2, a femtosecond laser etching method is used to process a micron / nanoscale periodic structure or a random pit texture on the surface of the pendulum piece, so that the surface roughness of the pendulum piece reaches Ra 0.1μm to 0.5μm.

[0014] Furthermore, in step 3, a plasma cleaning method is used to eliminate the static charge on the rotor before the final assembly of the movement.

[0015] Furthermore, in step 3, the static charge on the pendulum is eliminated before the movement is assembled by using a de-staticizing ionizing blower to blow ionized air.

[0016] The advantages and positive effects of the present invention are: The present invention adopts corresponding measures to reduce the generated static charge in the design stage, the pendulum piece processing stage and the first assembly stage after the pendulum piece processing, thereby effectively reducing the electrostatic interference torque between the pendulum piece and the upper and lower magnetic rings in the accelerometer, thereby improving the stability and accuracy of the accelerometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a diagram of the structure of a quartz flexible accelerometer; Figure 2 This is a block diagram of the working principle of the quartz flexible accelerometer; Figure 3a This is the front structure diagram of the pendulum; Figure 3b This is the reverse side structure diagram of the pendulum; Figure 4a This is the structural diagram of the upper magnetic ring; Figure 4b This is the structure diagram of the lower magnetic ring; In the figure: 1-upper magnetic conductive ring component; 2-pendulum component; 3-lower magnetic conductive ring component; 4-housing; 5-connecting ring; 6-isolating ring. DETAILED DESCRIPTION

[0018] The structure of the present invention will be further described below with reference to the accompanying drawings and through examples. It should be noted that the present examples are descriptive rather than restrictive.

[0019] The present invention proposes a method for processing the pendulum of a quartz flexible accelerometer to reduce electrostatic interference torque, based on the following principles: In a quartz flexure accelerometer, electrostatic force is generated between the static charge accumulation area of ​​the pendulum (see Figure 3) and the C-shaped areas of the upper and lower magnetic rings (see Figure 4). The Coulomb law for calculating the electrostatic force is as follows: ………………………… Where: ——electrostatic force, N; ——the electric charge of two point charges, C; ——distance between charges, m; — electrostatic force constant, .

[0020] Therefore, the method to reduce the electrostatic interference torque is as follows: 1) Increase the distance between the static charge accumulation area of ​​the pendulum and the C-shaped area of ​​the upper and lower magnetic rings The axial distance (perpendicular to the pendulum) between the pendulum tongue and the upper and lower magnetic rings is determined by the design of the differential capacitance sensor and is difficult to change. However, the radial distance can be modified. By making the coating area on the pendulum tongue larger than the C-shaped area of ​​the upper and lower magnetic rings, the static charge accumulation area of ​​the pendulum is further away from the C-shaped area of ​​the upper and lower magnetic rings. This increases the radial distance, reduces the electrostatic force, and thus reduces the electrostatic interference torque.

[0021] 2) Reduce the total amount of static charge generated in the static charge accumulation area of ​​the pendulum Static charge is generated and accumulated when the pendulum contacts and rubs against other objects. Reducing the effective area of ​​contact and friction with the pendulum can reduce the total amount of static charge. As shown in Figure 3, the size of the static charge accumulation area on the pendulum is determined by the pendulum structure. However, increasing its roughness can reduce the effective area of ​​contact and friction with other objects, thereby reducing the total amount of static charge, thereby reducing the electrostatic force and, in turn, the electrostatic interference torque.

[0022] In the present invention, the contact area of ​​the pendulum is reduced by increasing the roughness of the pendulum. There are two specific implementation methods: One is to process micron / nanoscale periodic structures or random pit textures on the surface of the pendulum through plasma etching method; the other is to process micron / nanoscale periodic structures or random pit textures on the surface of the pendulum through ultrafast laser induced etching method.

[0023] 3) Eliminate static charge accumulated on the pendulum before final assembly During the final assembly of the accelerometer movement, static charge has accumulated on the pendulum due to the previous steps. Taking measures to eliminate the static charge at this time can effectively reduce the electrostatic interference torque in the accelerometer after assembly.

[0024] In the present invention, there are two methods to eliminate the static charge on the pendulum: one is to perform ion cleaning on the pendulum, usually using a glow discharge cleaning method; the other is to blow ion wind to the pendulum through an ion blower.

[0025] In summary, by adopting the above corresponding measures in the three stages of the design stage of the pendulum, the processing stage of the pendulum and the first assembly stage of the quartz flexible accelerometer, the electrostatic interference torque in the quartz flexible accelerometer can be effectively reduced.

[0026] The present invention provides a method for processing a pendulum of a quartz flexible accelerometer for reducing electrostatic interference torque, comprising the following steps: Step 1. During the design phase of the pendulum, the C-shaped coating area on the pendulum tongue is designed to be larger than the C-shaped areas of the upper and lower magnetic rings. Specifically, R1 < (R3 - 0.15mm) and R2 > (R4 + 0.15mm) (as shown in Figures 3 and 4). R1 ​​is the inner diameter of the C-shaped coating area on the pendulum tongue, R2 is the outer diameter of the C-shaped coating area on the pendulum tongue, R3 is the inner diameter of the C-shaped area of ​​the magnetic ring, and R4 is the outer diameter of the C-shaped area of ​​the magnetic ring. This increases the distance between the pendulum and the C-shaped areas, reduces the electrostatic force, and thus the electrostatic interference torque. However, while satisfying the requirements of R1 < (R3 - 0.15mm) and R2 > (R4 + 0.15mm), the design of R1, R2, R3, and R4 must meet the detection resolution requirements of the accelerometer's differential capacitance sensor.

[0027] Step 2: During the swing plate processing stage, plasma etching or femtosecond laser etching is used to increase the roughness of the static charge accumulation area on the swing plate surface to Ra 0.1μm~0.5μm, thereby reducing its effective area of ​​contact and friction with other objects, thereby reducing the total amount of static charge generated, achieving the purpose of reducing electrostatic force, and further reducing the electrostatic interference torque.

[0028] 1. Method of increasing the surface roughness of the pendulum using plasma etching a) Process equipment: LSK-8B ion beam etcher b) Process parameters: Etching ion source settings: Cathode current: 7.13A Arc voltage: 50V Screen grid voltage: 750V Acceleration voltage: 200V Neutralization current: 4.25A Coupling coefficient: 1.25 Process gas: Argon Flow setting: 45sccm c) Process: 1) Place the pendulum in the working chamber of the ion beam etcher, with one side of the pendulum facing the direction of ion beam bombardment; 2) Evacuate the working chamber of the ion beam etcher to 3×10-3Pa; 3) Argon gas is introduced with a flow rate of 45 sccm. The vacuum degree in the working chamber is about 2×10-2 Pa. 4) Turn on the etching ion source and perform ion beam etching on the surface of the pendulum for 10 minutes; 5) Operate the workbench so that the other side of the pendulum is aligned with the direction of ion beam bombardment; 6) Turn on the etching ion source and perform ion beam etching on the other side of the swing plate for 10 minutes; 7) Stop the argon flow, restore the working chamber pressure to normal, and remove the pendulum.

[0029] 2. Method of increasing the surface roughness of the rotor using femtosecond laser etching a) Process equipment: Femtosecond laser system with a wavelength of 1030nm, a repetition rate of 20kHz, and a pulse width of 290fs b) Process parameters: laser single pulse energy 50μJ, scanning speed 40mm / s, scanning number 1 c) Process: 1) Place the pendulum on the workbench and adjust the position so that the laser focus is located on the upper surface of the pendulum; 2) Turn on the femtosecond laser system and scan the upper surface of the pendulum in a line scanning manner (line spacing 10μm); 3) Adjust the position of the pendulum so that the laser focus is located on the lower surface of the pendulum; 4) Turn on the femtosecond laser system and scan the lower surface of the pendulum piece in a line scanning manner (line spacing 10μm); 5) Remove the pendulum and turn off the device.

[0030] Step 3: Before assembling the accelerometer core, use a plasma cleaning method or a de-ionizing blower to blow ionized air to eliminate the static charge on the pendulum before assembling the core, thereby reducing the electrostatic interference torque in the accelerometer after assembly.

[0031] 1. Use plasma cleaning to remove static charge on the rotor a) Process equipment: OPS SY-DT07 plasma cleaning machine b) Process parameters: Back vacuum: 30 Pa Stabilization time: 10 s Power supply: 300 W Discharge time: 120 s Process gas: Air (filter-dried) c) Process: 1) Place the pendulum component in the working chamber of the plasma cleaning machine through the tooling; 2) Turn on the plasma cleaning machine and clean the pendulum parts according to the set parameters; 3) Remove the pendulum component and turn off the device.

[0032] 2. Use the anti-static ion blower to blow ion air to remove the static charge on the pendulum a) Process equipment: Tronovo MODEL TR7045 anti-static ion blower b) Process parameters: FAN SPEED is level II c) Process: 1) Turn on the POWER and WARM AIR switches of the de-ionizing blower; 2) Use plastic tweezers to hold the pendulum component and place it at the outlet of the de-ionizing blower, and blow ion air for 30 seconds; 3) Remove the pendulum component and turn off the device.

[0033] After processing the pendulum of a certain type of high-precision quartz flexible accelerometer through the above three steps, the six-month stability of the accelerometer's bias value was significantly improved compared with the product with unprocessed pendulum.

[0034] Although the embodiments and drawings of the present invention are disclosed for illustrative purposes, those skilled in the art will understand that various replacements, changes and modifications are possible without departing from the spirit of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A method for processing a quartz flexible accelerometer pendulum to reduce electrostatic interference torque, characterized in that: The steps include: Step 1. During the design phase of the pendulum, the C-shaped coating area on the pendulum tongue is designed to be larger than the C-shaped areas of the upper and lower magnetic conductive rings, that is, R1 < (R3-0.15mm), R2 > (R4+0.15mm), where R1 is the inner diameter of the C-shaped coating area on the pendulum tongue, R2 is the outer diameter of the C-shaped coating area on the pendulum tongue, R3 is the inner diameter of the C-shaped area of ​​the magnetic conductive ring, and R4 is the outer diameter of the C-shaped area of ​​the magnetic conductive ring; Step 2: During the swing plate processing stage, the roughness of the static charge accumulation area on the swing plate is increased; Step 3: Before assembling the accelerometer core, eliminate the static charge on the pendulum.

2. The method for processing a quartz flexible accelerometer pendulum to reduce electrostatic interference torque according to claim 1, characterized in that: In step 2, a plasma etching method is used to process a micron / nanoscale periodic structure or a random pit texture on the surface of the pendulum piece, so that the surface roughness of the pendulum piece reaches Ra 0.1μm to 0.5μm.

3. The method for processing a quartz flexible accelerometer pendulum piece to reduce electrostatic interference torque according to claim 1, characterized in that: In step 2, a femtosecond laser etching method is used to process a micron / nanoscale periodic structure or a random pit texture on the surface of the pendulum piece, so that the surface roughness of the pendulum piece reaches Ra 0.1μm to 0.5μm.

4. The method for processing a pendulum of a quartz flexible accelerometer for reducing electrostatic interference torque according to claim 1, characterized in that: In step 3, plasma cleaning is used to eliminate static charges on the rotor before final assembly of the watch movement.

5. The method for processing a pendulum piece of a quartz flexible accelerometer for reducing electrostatic interference torque according to claim 1, characterized in that: In step 3, the static charge on the pendulum is eliminated before the movement is assembled by using a de-ionizing blower to blow ionized air.

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