A single crystal silicon flexible accelerometer

Abstract

The present application provides a single crystal silicon flexible accelerometer, comprising a meter head 1 and a servo circuit module 2, wherein: the servo circuit module 2 is arranged on the meter head 1; the meter head 1 comprises: a magnetic steel 3, a lower capacitor plate 4, a detection mass component 5, an upper adapter plate 11, and a shell 12; the detection mass component 5 comprises a torquer coil 6, a first pad 7, a single crystal silicon pendulum 8, and a second pad 10; the magnetic steel 3, the lower capacitor plate 4, the detection mass component 5, and the upper adapter plate 11 are placed in the shell 12 from bottom to top. The magnetic steel 3 is used to stably provide a uniform magnetic field; the lower capacitor plate 4 constitutes the fixed area of ​​the differential capacitor; the torquer coil 6 and the magnetic steel constitute a permanent magnet torquer; the single crystal silicon pendulum 8 includes a fixed plate, a movable plate and a flexible beam 9, the movable plate constitutes the moving area of ​​the differential capacitor, and together with the lower capacitor plate 4 forms a differential capacitor meter; the fixed plate is fixedly connected between the lower capacitor plate and the upper transfer plate through upper and lower bosses; the upper transfer plate 11 is used to transfer electrical signals.

Description

Technical Field

[0001] The invention relates to the technical field of inertial instruments and meters, and in particular to a single crystal silicon flexible accelerometer. Background Art

[0002] Accelerometer is an inertial instrument that measures the linear acceleration of a moving carrier and is one of the core components of an inertial navigation system. There are many types of accelerometers on the market, including liquid-floating pendulum accelerometers, optical accelerometers, silicon microaccelerometers, flexible accelerometers, integrating gyro accelerometers, etc. However, in the field of high-precision inertial navigation, the most widely used accelerometer products are still mainly flexible accelerometers. Flexible accelerometers have the advantages of simple structure, small size, long life, high accuracy and sensitivity, small temperature coefficient, and stable performance. They are widely used in inertial navigation systems of aircraft, missiles, rockets, ships, and vehicles, as well as in oil drilling, construction, dam inclination measurement, and earthquake monitoring.

[0003] The most common flexible accelerometer is the quartz flexible accelerometer, which consists of a meter head and a servo circuit module. The quartz pendulum is the most critical component of the accelerometer and the most direct sensitive component of the acceleration signal. The flatness of the quartz pendulum and the parallelism of its interface with the torquer directly affect the performance of the sensor. At present, due to the limitations of process conditions, it is difficult to ensure the flatness of the etched quartz pendulum and the parallelism of its interface with the torquer. The qualified rate of high-precision pendulums is very low, which restricts the improvement of the comprehensive performance of this type of accelerometer. Summary of the invention

[0004] The purpose of the present invention is to provide a flexible accelerometer based on single crystal silicon material with high precision, good consistency, small size and high stability.

[0005] In order to solve the above technical problems, the present application provides a single crystal silicon flexible accelerometer, the single crystal silicon flexible accelerometer comprising a meter head (1) and a servo circuit module (2), wherein:

[0006] The servo circuit module (2) is arranged on the meter head (1);

[0007] The meter head 1 includes: a magnetic steel 3, a lower capacitor plate 4, a detection mass component 5, an upper transfer plate 11, and a housing 12; the detection mass component 5 includes a torquer coil 6, a first pad 7, a single crystal silicon pendulum 8, and a second pad 10, and is used to sense the linear acceleration vector of the carrier;

[0008] The shell 12 is a cavity structure with magnetic conductivity; the shell 12 is sequentially placed with a magnetic steel 3, a lower capacitor plate 4, a detection mass component 5, and an upper transfer plate 11 from bottom to top; a through hole is provided in the middle of the magnetic steel 3, and the magnetic steel 3 is fixed to the inner bottom surface of the shell 12 to stably provide a uniform magnetic field; the upper surface of the lower capacitor plate 4 is provided with two centrally symmetrical gold-plated areas, and the two gold-plated areas constitute the fixed area of ​​the differential capacitor; the torquer coil 6 is a circular coil, and the torquer coil 6 is arranged under the single crystal silicon pendulum 8 through a first pad 7; the torquer coil 6 and the magnetic steel 3 constitute a permanent magnet torquer; the single The crystalline silicon pendulum piece 8 includes a stator, a movable piece and two flexible beams 9. The stator is a special-shaped plate structure with a through hole in the middle, and the movable piece is a special-shaped plate structure arranged on the periphery of the stator. The movable piece is fixedly connected to the stator through the flexible beams 9. The movable piece can rotate and swing around the flexible beams 9 under the action of inertia force. The movable piece constitutes the dynamic area of ​​the differential capacitor. The movable piece and the lower capacitor plate 4 together constitute a differential capacitor meter; an upper boss and a lower boss are provided on the stator, the upper boss is used for crimping with the upper transfer plate 11, and the lower boss is used for crimping with the lower capacitor plate 4; the upper transfer plate 11 has a conductive strip plated with a gold film, which is used to transfer the electrical signals of the differential capacitor meter and the permanent magnet torquer.

[0009] Preferably, the single crystal silicon pendulum piece 8 is a pendulum piece made of single crystal silicon material and is manufactured by MEMS silicon micromachining technology.

[0010] Preferably, the thickness of the flexible beam 9 is 8 to 10 micrometers. When an acceleration signal is input, the detection mass assembly 5 will rotate and swing around the flexible beam 9.

[0011] Preferably, the magnetic steel 3 is made of permanent magnetic material.

[0012] Preferably, the torquer coil 6 is wound with copper wire, the number of coil turns is 200, and the diameter of the copper wire is 0.04 mm.

[0013] Preferably, the housing 12 is made of a soft magnetic alloy material.

[0014] Preferably, the chassis of the lower capacitor plate 4 and the chassis of the upper transfer plate 11 are both made of ceramic materials and have insulation and heat conduction functions.

[0015] Preferably, the first cushion block 7 and the second cushion block 10 are cushion blocks made of high specific gravity alloy material.

[0016] The present invention has the following characteristics:

[0017] 1. The core component of quality inspection, the pendulum, is a monocrystalline silicon integral pendulum made using MEMS silicon micromachining technology. The pendulum has good processing flatness and high precision in detail processing. At the same time, the monocrystalline silicon material has small elastic hysteresis, small thermal expansion coefficient, good thermal conductivity, and large elastic modulus, which is conducive to achieving low temperature coefficient, good temperature uniformity and high structural stability. At the same time, due to the semiconductor properties of silicon material, it can form one pole of the capacitor without the process of gold plating, thereby reducing the introduction of additional stress;

[0018] 2. The detection mass component supports the detection mass through a micron-level (8-10 micron) flexible beam with high sensitivity;

[0019] 3. The capacitance differential measurement method has high displacement detection resolution. The differential capacitance detector is formed by integrating the lower capacitor plate with the single crystal silicon pendulum. It has a simple structure, small size, easy to implement in terms of process, and can be sensitive to small acceleration changes.

[0020] 4. The permanent magnetic force feedback method has a simple structure, can realize closed-loop control, has few factors affecting stability, and can easily achieve high stability of the scale factor.

[0021] Beneficial effects of the invention: The invention proposes a single-crystal silicon flexible accelerometer, which has the characteristics of high precision, good consistency, small size and high stability. Single-crystal silicon material has advantages over quartz material, can adopt MEMS silicon micromachining technology to achieve ultra-high precision processing, and has semiconductor properties itself. The invention has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic diagram of the structure of a single crystal silicon flexible accelerometer provided by the present invention;

[0023] Figure 2 A schematic diagram of the structure of a meter header provided by the present invention;

[0024] Figure 3 The figure is a working principle diagram of the single crystal silicon flexible accelerometer provided by the present invention.

[0025] Among them, 1-header, 2-servo circuit module, 3-magnetic steel, 4-lower capacitor plate, 5-detection mass component, 6-torquer coil, 7-first pad, 8-single crystal silicon pendulum, 9-flexible beam, 10-second pad, 11-upper adapter plate, 12-shell. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings and specific implementations. Those skilled in the art should understand that the description is exemplary, and the present invention is not limited to the specific implementation mode. Those skilled in the art may make various combinations, modifications and changes to the present invention. Those skilled in the art should understand that as long as they do not depart from the purpose and spirit of the present invention, various combinations, modifications and changes made to the present invention should all fall within the scope of the present invention, and the scope of protection of the present invention is given by the attached claims.

[0027] With the rapid development of the semiconductor industry, domestic MEMS process technology has also achieved great progress. The use of MEMS silicon micromachining technology can achieve ultra-precision processing of silicon structures at the micron or even nanometer level. At the same time, it is easy to achieve arrayed, low-cost and high-efficiency production, which significantly improves the consistency and pass rate of the produced silicon structure, thus triggering a revolution in the field of high-precision sensors. It also enables us to change the manufacturing material of the pendulum, the core component of the flexible accelerometer, from quartz to single crystal silicon.

[0028] The technical solution of the present invention is as follows: the accelerometer utilizes the detection mass of the precision elastic element to sense the acceleration signal and convert it into angular displacement, and then detects the angular displacement through the capacitance differential measurement method, thereby outputting an electrical signal proportional to the acceleration signal. The accelerometer is composed of a servo circuit and a meter head, wherein the meter head includes a detection mass component, a magnetic steel made of a permanent magnetic material, a lower capacitor plate with a gold-plated film, an upper adapter plate and a shell, the detection mass component includes a single crystal silicon pendulum piece and a mass block and a torquer coil bonded to the pendulum piece, the torquer coil, the mass block and the outer part of the pendulum piece constitute a pendulum mass, which is fixedly connected between the lower capacitor plate and the upper adapter plate through two flexible beams arranged on the pendulum mass and the upper and lower bosses arranged in the middle part of the pendulum piece.

[0029] The working principle of the accelerometer proposed by the present invention is as follows: when an acceleration signal is input, the detection mass component is sensitive to acceleration and rotates and swings around the flexible beam to generate angular displacement; a capacitance detector is formed between the coating area on the lower capacitor plate and the single crystal silicon swing piece; when no acceleration signal is input, the detection mass component is in a balanced position, the capacitance formed between the coating area on both sides of the fixed plate and the single crystal silicon swing piece is equal, and no differential current is generated; when the detection mass component is sensitive to the acceleration signal and rotates and swings, the capacitance formed between the coating area on both sides of the lower capacitor plate and the swing piece becomes larger on one side and smaller on the other side, and the difference generates an induced current; a permanent magnetic force feedback torquer component is formed between the coil of the detection mass component and the magnetic steel made of permanent magnetic material; when the detection mass component is deflected, an induced current is generated, and the current is affected by the magnetic field after passing through the coil to generate feedback force, so as to pull the detection mass component back to the balanced position; the servo circuit module converts and amplifies the current signal to output a voltage signal, and after the voltage signal is obtained, the acceleration signal can be obtained through a certain algorithm; the full sealing of the accelerometer is achieved by laser welding between the shell and the servo circuit module.

[0030] like Figure 1 As shown, the accelerometer of the present invention is composed of a meter head 1 and a servo circuit module 2, which form a complete closed-loop feedback system, work according to Newton's law of mechanics, and indirectly measure the acceleration signal of the carrier by measuring the inertial force exerted on the carrier. They are sealed by laser welding to ensure the stability of the internal structure of the meter head.

[0031] The meter head is the main working part of the accelerometer. Its structural diagram is as follows: Figure 2As shown, it includes a magnetic steel 3, a lower capacitor plate 4, a detection mass component 5, an upper transfer plate 11, and a shell 12. The magnetic steel 3 is made of permanent magnetic material and can stably provide a uniform magnetic field. The shell 12 is made of soft magnetic alloy material and has good magnetic permeability. The magnetic steel 3 and the shell 12 are bonded together by glue. The lower capacitor plate 4 is a disc made of ceramic material. The ceramic material has good thermal conductivity to facilitate the timely heat dissipation of the accelerometer during operation. There are two gold-plated areas on the ceramic disc, and these two areas constitute the fixed area of ​​the differential capacitor. The detection mass component 5 is the core component of the single crystal silicon flexible accelerometer involved in the present invention, which can directly sense the acceleration signal. It is composed of a torquer coil 6, a first pad 7, a single crystal silicon pendulum 8, and a second pad 10. The single crystal silicon pendulum piece 8, due to the semiconductor properties of its material, constitutes the dynamic area of ​​the differential capacitor, and it and the above-mentioned lower capacitor plate 4 together form a differential capacitor meter; the torquer coil 6, the first pad 7 and the second pad 10 and the dynamic plate on the periphery of the single crystal silicon pendulum piece together constitute the pendulum mass, and they are bonded together with glue, wherein the first pad 7 and the second pad 10 are made of a high specific gravity alloy material, which has a high density and can provide sufficient weight in a small volume, and the pendulum mass is connected to the fixed plate in the middle of the single crystal silicon pendulum piece 8 through a flexible beam 9, and the thickness of the flexible beam 9 is in the micron range. When an acceleration signal is input, the pendulum mass will rotate and swing around the flexible beam 9; the torquer coil 6 is wound with copper wire, and it and the magnetic steel 3 form a permanent magnet torquer; the upper transfer plate 11 is also made of a disc made of ceramic material, and there is a conductive band plated with a gold film on the disc for transferring signals. The fixed plate is provided with two upper and lower bosses for fixing the detection mass assembly 5 between the lower capacitor plate 4 and the upper transfer plate 11. There is a gap between the upper transfer plate 11 and the second pad 10. In the structure of the present invention, some parts need to be hollowed out to facilitate wiring, such as Figure 2 The holes on the middle and lower capacitor plates 4 and the notches on the circumference of the moving plate are used for wiring.

[0032] Combination Figure 3The working principle of the single crystal silicon flexible accelerometer involved in the present invention is that when the accelerometer is in a static state, the distance between the moving plate of the single crystal silicon swing piece 8 and the two gold-plated areas of the lower capacitor plate 4 is equal, and the differential capacitance is zero. When an acceleration signal is input, the detection mass component 5 is sensitive to the acceleration and swings around the flexible beam 9. At this time, the distance between the two ends of the single crystal silicon swing piece 8 and the two gold-plated areas of the lower capacitor plate 4 is no longer equal, resulting in a capacitance difference. The differential capacitor is sensitive to the capacitance difference and generates a current proportional to the capacitance difference. The current is filtered, integrated, amplified, and processed by the servo circuit module 2 and then loaded on the torquer coil 6. The current-carrying torquer coil generates an electromagnetic torque in the opposite direction to the torque brought by the acceleration under the action of the magnetic field generated by the magnetic steel 3, so that the detection mass component 5 generates an acceleration with the same direction and equal magnitude as the input acceleration, so that the detection mass component 5 returns to the equilibrium position (the differential capacitance is 0). At this time, by using the force feedback principle, a current proportional to the input acceleration is obtained on the torquer coil 6. The current can be analyzed and calculated by the servo circuit module 2 to obtain the input acceleration signal, thereby realizing the measurement of acceleration.

Claims

1. A single crystal silicon flexible accelerometer, characterized in that: The single crystal silicon flexible accelerometer comprises a meter head (1) and a servo circuit module (2), wherein: The servo circuit module (2) is arranged on the meter head (1); The meter head (1) comprises: a magnetic steel (3), a lower capacitor plate (4), a detection mass component (5), an upper transfer plate (11), and a housing (12); the detection mass component (5) comprises a torquer coil (6), a first pad (7), a single crystal silicon pendulum (8), a flexible beam (9), and a second pad (10), and is used to sense the linear acceleration vector of the carrier; The shell (12) is a cavity structure with magnetic conductivity; a magnetic steel (3), a lower capacitor plate (4), a detection mass component (5), and an upper transfer plate (11) are placed in the shell (12) from bottom to top; a through hole is arranged in the middle of the magnetic steel (3), and the magnetic steel (3) is fixed to the inner bottom surface of the shell (12) for stably providing a uniform magnetic field; the lower capacitor plate (4) is a chassis with insulating and heat-conducting functions, and the upper surface of the lower capacitor plate (4) is provided with two centrally symmetrical gold-plated areas, and the two gold-plated areas constitute a fixed area of ​​differential capacitance; the torquer coil (6) is a circular coil, and the torquer coil (6) is arranged under the single crystal silicon pendulum (8) through a first pad (7); the torquer coil (6) and the magnetic steel (3) constitute a permanent magnet The invention relates to a torque device; the monocrystalline silicon swing plate (8) comprises a fixed plate, a movable plate and two flexible beams (9); the fixed plate is a special-shaped plate-like structure with a through hole in the middle; the movable plate is a special-shaped plate-like structure arranged on the periphery of the fixed plate; the movable plate is fixedly connected to the fixed plate through the flexible beams (9); the movable plate can rotate and swing around the flexible beams (9) under the action of inertial force; the movable plate constitutes a moving area of ​​the differential capacitor; the movable plate and the lower capacitor plate (4) together constitute a differential capacitor; the fixed plate is provided with an upper boss and a lower boss; the upper boss is used for pressing with the upper transfer plate (11); the lower boss is used for pressing with the lower capacitor plate (4); the upper transfer plate (11) is a chassis with insulating and heat-conducting functions; the upper transfer plate (11) has a conductive strip plated with a gold film, which is used for transferring electrical signals between the differential capacitor and the permanent magnet torque device; The working principle of the single crystal silicon flexible accelerometer is that when the accelerometer is in a stationary state, the distance between the moving plate of the single crystal silicon swing plate (8) and the two gold-plated areas of the lower capacitor plate (4) is equal, and the differential capacitance is zero. When an acceleration signal is input, the detection mass component (5) is sensitive to the acceleration and swings around the flexible beam (9). At this time, the distance between the two ends of the single crystal silicon swing plate (8) and the two gold-plated areas of the lower capacitor plate (4) is no longer equal, resulting in a capacitance difference. The differential capacitance meter is sensitive to the capacitance difference and generates a current proportional to the capacitance difference. The current is filtered by the servo circuit module (2). After integration and amplification, the current is loaded on the torque device coil (6). Under the action of the magnetic field generated by the magnetic steel (3), the current-carrying torque coil generates an electromagnetic torque in the opposite direction to the torque caused by the acceleration, so that the detection mass component (5) generates an acceleration with the same direction and magnitude as the input acceleration, so that the detection mass component (5) returns to the equilibrium position; at this time, using the force feedback principle, a current proportional to the input acceleration is obtained on the torque device coil (6), and the current can be obtained through analytical calculation of the servo circuit module (2) to obtain the input acceleration signal, thereby realizing the measurement of acceleration.

2. The single crystal silicon flexible accelerometer according to claim 1, characterized in that: The single crystal silicon pendulum piece (8) is a pendulum piece made of single crystal silicon material and is manufactured by using MEMS silicon micromachining technology.

3. The single crystal silicon flexible accelerometer according to claim 1, characterized in that: The thickness of the flexible beam (9) is 8 to 10 micrometers. When an acceleration signal is input, the detection mass component (5) will rotate and swing around the flexible beam (9).

4. The single crystal silicon flexible accelerometer according to claim 1, characterized in that: The magnetic steel (3) is made of permanent magnetic material.

5. The single crystal silicon flexible accelerometer according to claim 1, characterized in that: The torquer coil (6) is wound from copper wire, the number of coil turns is 200, and the copper wire diameter is 0.04 mm.

6. The single crystal silicon flexible accelerometer according to claim 1, characterized in that: The shell (12) is made of soft magnetic alloy material.

7. The single crystal silicon flexible accelerometer according to claim 1, characterized in that: The bottom plate of the lower capacitor plate (4) and the bottom plate of the upper transfer plate (11) are both made of ceramic material.

8. The single crystal silicon flexible accelerometer according to claim 1, characterized in that: The first cushion block (7) and the second cushion block (10) are cushion blocks made of high specific gravity alloy material.

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