High-precision quartz crystal vibrating beam accelerometer

Abstract

A high-precision quartz crystal vibrating beam accelerometer comprises a base, a meter core and a shell, a circuit board is packaged in the base, and the meter core is packaged on the base through the shell; the meter core comprises a mass pendulum, two resonant beams and two circular damping plates which are all made of quartz crystal materials; the mass pendulum comprises two semicircular bases, two semicircular pendulum tongues and a circular flexible layer, the two semicircular bases and the two semicircular pendulum tongues are symmetrically bonded to the two sides of the circular flexible layer respectively, and receding gaps are formed between the semicircular bases and the semicircular pendulum tongues; the resonant beam is radially arranged above a strip-shaped groove in the center of the outer end surface of the semicircular base, one end of the resonant beam is bonded with the semicircular base, and the other end of the resonant beam is bonded with the semicircular swing tongue and electrically connected with the circuit board; the two circular damping plates are connected to the two sides of the two semicircular bases in a semi-symmetrical bonding mode through the inner end faces, the resonance beams are located in strip-shaped holes of the circular damping plates, and the semicircular concave tables and the semicircular swing tongues are opposite to form vibration gaps.

Description

Technical Field

[0001] The invention belongs to the technical field of accelerometers, and in particular relates to a high-precision quartz crystal vibration beam accelerometer. Background Art

[0002] The accelerometer is the basic measurement unit of the inertial navigation and inertial guidance system. It is installed inside the missile (arrow) to measure the acceleration of the missile (arrow) and obtain its velocity and position by integrating the acceleration. The quartz vibrating beam accelerometer is a new type of high-precision solid-state sensor based on the force-frequency characteristics of the quartz vibrating beam. Compared with the traditional vibrating string and pendulum integrating gyro accelerometers, it has the advantages of high accuracy, small size, and digital output.

[0003] The quartz vibration beam accelerometer is generally composed of a resonant beam, a mass pendulum, a damping plate, a housing, and an excitation oscillation circuit. When the acceleration of the external carrier is sensed, the mass pendulum swings along the input axis of the accelerometer due to the inertial force. The mechanical frequency of one quartz vibration beam increases due to the tension, and the mechanical frequency of the other quartz vibration beam decreases due to the pressure. The carrier acceleration can be obtained by solving the frequency difference of the double vibration beams through the excitation circuit.

[0004] At present, the more mature split-type quartz vibrating beam accelerometers on the market all adopt a composite design of a metal mass pendulum and a quartz resonant beam, which has the following engineering and technical problems: 1) The processing technology of the flexible beam of the high-elastic alloy metal mass pendulum is complex and the cost is relatively high; 2) The mass pendulum and the resonant beam are connected by gluing, and the mismatch in thermal expansion coefficients between the materials and the creep of the adhesive make it difficult to improve the accuracy of the accelerometer. The current highest accuracy is no higher than 100μg. Summary of the invention

[0005] The present invention provides a high-precision quartz crystal vibration beam accelerometer to overcome the deficiencies of the prior art.

[0006] The technical solution adopted by the present invention is: a high-precision quartz crystal vibration beam accelerometer, comprising a base, a watch core and a shell, wherein a circuit board is encapsulated in the base, the watch core is arranged on the base, and the shell is sleeved on the base to seal the watch core in the shell; the watch core comprises a mass pendulum, two resonance beams, and two circular damping plates, all of which are made of quartz crystal materials;

[0007] The mass pendulum comprises two semicircular bases, two semicircular swing tongues, and a circular flexible layer, wherein the two semicircular bases and the two semicircular swing tongues are symmetrically bonded to two sides of the circular flexible layer, and a clearance gap is provided between the semicircular bases and the straight edges of the semicircular swing tongues;

[0008] The outer end face of the semicircular base is radially provided with a strip groove penetrating the straight edge thereof in the center, the resonance beam is radially arranged above the strip groove, one end of the resonance beam is bonded to the semicircular base, and the other end is bonded to the semicircular swing tongue, and the circuit board is electrically connected to the resonance beam;

[0009] The circular damping plate has a strip hole in the center radially and a semicircular concave platform on half of the inner end surface, and the two circular damping plates are symmetrically bonded to the two sides of the two semicircular bases through the other half of the inner end surface, and the resonant beam is located in the strip hole, and the semicircular concave platform and the semicircular swing tongue are opposite to form a vibration gap.

[0010] The thickness of the semicircular base and the semicircular swing tongue is 1.2mm-4.2mm, and the thickness of the circular flexible layer is 0.02mm-0.2mm; the diameters of the semicircular base, the semicircular swing tongue and the circular flexible layer are all 22mm, and the area of ​​the semicircular swing tongue is 70mm 2 ~250mm 2 .

[0011] The depth of the semicircular concave platform is 30-60 μm.

[0012] The inner end of the base is provided with a circular boss, the watch movement is coaxially fixed to the end of the circular boss, and the opening end of the shell is sleeved on the periphery of the circular boss and sealed by laser welding.

[0013] The shell is filled with nitrogen.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. The mass pendulum of the present invention is a three-layer composite structure, and a flexible layer is used to replace the high-elastic alloy metal flexible beam of the traditional solution, which can effectively reduce the processing difficulty and cost of the flexible beam. The material of the flexible layer is the same as the material of the resonant beam, and has the advantages of small specific stiffness, small thermal expansion coefficient, high chemical stability, good elastic stability, and low elastic modulus.

[0016] 2. The present invention utilizes the strong processability and mature processing technology of the current quartz crystal material. The pendulum tongue, base, and flexible layer are connected to form a mass pendulum by bonding, and the mass pendulum is also connected to the upper and lower resonant beams by bonding. Compared with the traditional gluing method, the bonding connection is more firm and reliable. In particular, the connection of homogeneous materials can avoid the problems of adhesive creep, poor stability caused by mismatch of thermal expansion coefficients, and large changes in zero bias with ambient temperature during long-term use of the existing technology, thereby improving the adaptability to work in harsh environments.

[0017] 3. According to theoretical calculations, the embodiments of the present invention can achieve indicators such as accelerometer accuracy not higher than 50 μg, scale factor greater than or equal to 80 Hz / g, and strong environmental adaptability (resistance to vibration, impact, etc.). BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is an exploded schematic diagram of the structure of the present invention;

[0019] Figure 2 Schematic diagram of the mass pendulum structure of the present invention;

[0020] Figure 3 It is a schematic diagram of the structure of the circular damping plate of the present invention;

[0021] Figure 4 It is a schematic diagram of the appearance structure of the present invention. DETAILED DESCRIPTION

[0022] The following is combined with Figure 1-4 The present invention is described in detail with specific embodiments.

[0023] Reference Figure 1 A high-precision quartz crystal vibration beam accelerometer, comprising a base 1, a watch core 2 and a shell 3, wherein the base 1 is encapsulated with a circuit board 1-1, the watch core 2 is arranged on the base 1, and the shell 3 is mounted on the base 1 to enclose the watch core 2 in the shell 3; the watch core 2 comprises a mass pendulum 21, two resonant beams 22, and two circular damping plates 23, all of which are made of quartz crystal material;

[0024] Reference Figure 2 The mass pendulum 21 includes two semicircular bases 211, two semicircular swing tongues 212, and a circular flexible layer 213. The two semicircular bases 211 and the two semicircular swing tongues 212 are symmetrically bonded to the two sides of the circular flexible layer 213, and there is a clearance gap between the semicircular base 211 and the straight edges of the semicircular swing tongues 212; the outer end surface of the semicircular base 211 has a strip groove 214 radially penetrating the straight edge thereof in the center thereof, the resonant beam 22 is radially arranged above the strip groove 214, and one end of the resonant beam 22 is bonded to the semicircular base 211, and the other end is bonded to the semicircular swing tongue 212, and the circuit board 1-1 is electrically connected to the resonant beam 22;

[0025] Reference Figure 3 The circular damping plate 23 has a strip hole 231 in the center radial direction, and a semicircular recess 232 in half of the inner end surface, and the two circular damping plates 23 are symmetrically bonded to the two sides of the two semicircular bases 211 through the other half of the inner end surface, and the resonant beam 22 is located in the strip hole 231, and the semicircular recess 232 and the semicircular swing tongue 212 form a vibration gap relative to each other.

[0026] In one embodiment, the thickness of the semicircular base 211 and the semicircular swing tongue 212 are both 1.2 mm to 4.2 mm, and the thickness of the circular flexible layer 213 is 0.02 mm to 0.2 mm; the diameters of the semicircular base 211, the semicircular swing tongue 212, and the circular flexible layer 213 are all 22 mm, and the area of ​​the semicircular swing tongue 212 is 70 mm2 to 250 mm2. By increasing the area of ​​the semicircular swing tongue 212, the scale factor of the vibration beam accelerometer can be effectively improved.

[0027] In one embodiment, the depth of the semicircular concave platform 232 is 30-60 μm. By adjusting the depth of the semicircular concave platform 232, suitable squeeze film damping is provided for the swing tongue.

[0028] In one embodiment, the inner end of the base 1 has an annular boss 1-2, the movement 2 is coaxially bonded and fixed to the end of the annular boss 1-2, and the opening end of the shell 3 is sleeved on the outer periphery of the annular boss 1-2 and sealed by laser welding.

[0029] In one embodiment, the housing 3 is filled with dry nitrogen to keep the air pressure of the watch movement stable.

[0030] In one embodiment, the circular damping plate 23 and the semicircular base 211 are provided with through holes 4, and the external lead of the resonant beam 22 is connected to the circuit board 1-1 through the through hole 4. The base 1 is provided with lead holes 1-3, and the leads of the circuit board 1-1 are led out from the lead holes 1-3.

[0031] The present invention senses the input of external environmental acceleration through the mass pendulum 21, excites the two quartz resonant beams 22 to vibrate based on the principle of piezoelectric effect, and collects the mechanical frequency characteristics of the vibration; the circular damping plate 23 of the present invention has a concave platform on the inner side, which has a limiting effect on the semicircular swing tongue, while improving the impact and vibration resistance of the accelerometer, providing compression film damping for the swing tongue, and improving the dynamic response characteristics of the accelerometer; the circuit board 1-1 is provided with an excitation oscillation circuit for realizing the transmission and collection of the input and output signals of the accelerometer; the shell 3 can maintain the internal air pressure environment of the accelerometer and protect the watch movement 2.

[0032] The present invention can effectively improve the scale factor K of the vibration beam accelerometer by increasing the area S of the semicircular swing tongue 212, increasing the inertial force arm L, reducing the resonance beam reaction force arm I, reducing the resonance beam thickness t and the single tuning fork beam width ω.

[0033] The base 1, the mass pendulum 21, the two resonant beams 22, and the two circular damping plates 23 of the present invention are all made of the same crystal material, which creates conditions for bonding. The bonding connection between the parts can adopt optical adhesive bonding or low-temperature bonding technology, and the bonding temperature should not be higher than 500°C. In order to ensure that the bonding strength is not less than 10MPa, the roughness of the bonding surface of the parts should not be greater than 5nm, and the flatness should not be greater than 3μm.

[0034] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention. Therefore, all equivalent changes made to the contents described in the claims of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A high-precision quartz crystal beam accelerometer, characterized in that: The invention comprises a base (1), a watch movement (2) and a housing (3); the base (1) encapsulates a circuit board (1-1); the watch movement (2) is arranged on the base (1); the housing (3) is mounted on the base (1) to enclose the watch movement (2) in the housing (3); the watch movement (2) comprises a mass pendulum (21), two resonant beams (22), and two circular damping plates (23), all of which are made of quartz crystal material; The mass pendulum (21) comprises two semicircular bases (211), two semicircular swing tongues (212), and a circular flexible layer (213); the two semicircular bases (211) and the two semicircular swing tongues (212) are symmetrically bonded to two sides of the circular flexible layer (213), and a clearance gap is provided between the straight edges of the semicircular bases (211) and the semicircular swing tongues (212); The center of the outer end surface of the semicircular base (211) is radially provided with a strip groove (214) penetrating the straight edge thereof, the resonant beam (22) is radially arranged above the strip groove (214), one end of the resonant beam (22) is bonded to the semicircular base (211), and the other end is bonded to the semicircular swing tongue (212), and the circuit board (1-1) is electrically connected to the resonant beam (22); The circular damping plate (23) has a strip hole (231) in the central radial direction, and a semicircular concave platform (232) in half of the inner end surface, and the two circular damping plates (23) are symmetrically bonded to the two sides of the two semicircular bases (211) through the other half of the inner end surface, and the resonant beam (22) is located in the strip hole (231), and the semicircular concave platform (232) and the semicircular swing tongue (212) are relatively formed to form a vibration gap.

2. The high-precision quartz crystal beam accelerometer according to claim 1, characterized in that: The thickness of the semicircular base (211) and the semicircular swing tongue (212) are both 1.2 mm to 4.2 mm, and the thickness of the circular flexible layer (213) is 0.02 mm to 0.2 mm; the diameters of the semicircular base (211), the semicircular swing tongue (212), and the circular flexible layer (213) are all 22 mm, and the area of ​​the semicircular swing tongue (212) is 70 mm 2 ~250mm 2 .

3. The high-precision quartz crystal beam accelerometer according to claim 1, characterized in that: The depth of the semicircular concave platform (232) is 30 to 60 μm.

4. The high-precision quartz crystal beam accelerometer according to claim 1, characterized in that: The inner end of the base (1) is provided with a circular boss (1-2), the watch movement (2) is coaxially fixed to the end of the circular boss (1-2), and the opening end of the housing (3) is sleeved on the periphery of the circular boss (1-2) and sealed by laser welding.

5. The high-precision quartz crystal beam accelerometer according to claim 1, 2, 3 or 4, characterized in that: The shell (3) is filled with nitrogen.

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