An impact acceleration sensor

Abstract

This invention discloses an impact acceleration sensor, comprising: a ceramic substrate; a thick-film strain gauge resistor disposed on the upper surface of the ceramic substrate; a thick-film bridge resistor disposed on the upper surface of the ceramic substrate, the thickness of the thick-film bridge resistor being less than the thickness of the thick-film strain gauge resistor; a conductive layer formed on the upper surface of the ceramic substrate, connecting the thick-film strain gauge resistor and the thick-film bridge resistor to form a Wheatstone bridge; a ceramic cover plate disposed above the thick-film strain gauge resistor, the lower surface of the ceramic cover plate being connected to the upper surface of the thick-film strain gauge resistor and maintaining a gap between it and the upper surface of the thick-film bridge resistor; a conductor electrically connected to the conductive layer for guiding electrical signals to the back side of the ceramic substrate; and a mass block disposed on the upper surface of the ceramic cover plate. Beneficial effects: It is not easily damaged under the action of solid shock waves generated by instantaneous impact, and the structure is stable. Compared with existing silicon piezoresistive cantilever beam products, the cost is reduced by approximately two orders of magnitude, which can meet the needs of large-volume, low-cost applications.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and in particular to an impact acceleration sensor. Background Technology

[0002] There are currently two main types of impact acceleration sensors used to measure large impact acceleration (approximately 50,000 to 300,000 g): one is the piezoelectric impact acceleration sensor, and the other is the silicon piezoresistive cantilever beam impact acceleration sensor.

[0003] Piezoelectric impact accelerometers convert acceleration signals into charge signals using the piezoelectric effect of piezoelectric materials. They require a charge amplifier, are bulky and expensive, and are not suitable for low-cost, high-volume applications.

[0004] Silicon piezoresistive cantilever beam impact accelerometers are manufactured using MEMS technology. They utilize the piezoresistive effect of single-crystal silicon, with a piezoresistive resistor diffused at the root of the cantilever beam. When the mass is subjected to acceleration, stress is generated in the cantilever beam, causing a change in resistance. This type of sensor adopts the mass-plus-cantilever beam structure of low-frequency vibration accelerometers, but stress concentration occurs at the root of the cantilever beam. Under the action of solid shock waves generated during instantaneous impact, the root of the cantilever beam is prone to fracture, resulting in low reliability and requiring screening. Furthermore, due to the complexity of MEMS manufacturing processes, the cost of this type of sensor is difficult to reduce.

[0005] In addition, existing technologies also disclose a ceramic thick-film accelerometer (such as CN2427809Y), which uses thick-film resistors printed on a strip-shaped Al2O3 ceramic cantilever beam to form a Wheatstone bridge. Although this type of sensor is partially compatible with thick-film manufacturing processes, it still uses a cantilever beam structure and suffers from stress concentration and reliability issues under impact acceleration conditions.

[0006] Therefore, designing an impact acceleration sensor that is simple in structure, low in cost, highly reliable, and suitable for measuring large impact acceleration has become an urgent technical problem to be solved. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, the present invention provides an impact acceleration sensor to solve the above-mentioned technical problems.

[0008] The technical solution adopted by this invention to solve the technical problem is as follows: An impact acceleration sensor was designed, comprising: Ceramic substrate; A thick-film strain gauge is disposed on the upper surface of the ceramic substrate; A thick-film bridge circuit fixed resistor is disposed on the upper surface of the ceramic substrate, and the thickness of the thick-film bridge circuit fixed resistor is smaller than the thickness of the thick-film strain resistor. A conductive layer is formed on the upper surface of the ceramic substrate, connecting the thick film strain resistor and the thick film bridge fixed resistor to form a Wheatstone bridge. A ceramic cover plate is disposed above the thick film strain resistor. The lower surface of the ceramic cover plate is fixedly connected to the upper surface of the thick film strain resistor and maintains a gap with the upper surface of the thick film bridge fixed resistor. A conductor, electrically connected to the conductive layer, is used to lead electrical signals to the back side of the ceramic substrate; A mass block is fixedly mounted on the upper surface of the ceramic cover plate.

[0009] To better address the aforementioned technical deficiencies, the present invention also provides a more advanced technical solution: In some embodiments, the ceramic substrate is provided with conductive vias, and the conductor is placed in the conductive vias and electrically connected to the conductive layer.

[0010] In some embodiments, the thick-film strain resistor and the thick-film bridge fixed resistor are both formed by sintering thick-film resistor paste screen-printed on the ceramic substrate. The ceramic substrate, the thick-film strain resistor, and the ceramic cover plate are bonded together into a rigid whole by sintering the thick-film resistor paste.

[0011] In some embodiments, two thick-film strain gauges and two thick-film bridge fixed resistors are provided and disposed on both sides of the two thick-film strain gauges. The two thick-film strain gauges and the two thick-film bridge fixed resistors are connected to form a Wheatstone bridge through the four conductive layers.

[0012] In some embodiments, both thick-film strain resistors are equilateral right-angled structures and are centrally symmetrically arranged, together forming a U-shaped structure.

[0013] In some embodiments, both thick-film strain resistors are in the form of a semi-circular arc, a U-shaped structure, or a chamfered structure, and are arranged symmetrically.

[0014] In some embodiments, multiple conductors are provided, each corresponding to one end of a bridge arm of the Wheatstone bridge.

[0015] In some embodiments, the mass block is made of metal and is bonded to the upper surface of the ceramic cover plate with structural adhesive.

[0016] In some embodiments, the thickness of the thick-film strain resistor is 16-18 micrometers, and the thickness of the thick-film bridge fixed resistor is 10-12 micrometers.

[0017] In some embodiments, when the impact acceleration acts on the mass block and is converted into inertial force, the inertial force is transmitted through the ceramic cover plate and applied to the upper surface of the thick-film strain gauge, causing a change in resistance due to the piezoresistive effect, thereby detecting the impact acceleration. The thick-film bridge circuit fixed resistor maintains the gap with the ceramic cover plate, thus not bearing the pressure generated by the impact acceleration, and is only used for bridge circuit balancing, improving measurement accuracy and long-term sensor stability. The resistance change of the thick-film strain gauge is converted into a voltage signal output through a Wheatstone bridge.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This solution abandons the traditional cantilever beam structure, adopting a stacked structure of ceramic substrate-thick-film strain gauge-ceramic cover plate-mass block. This eliminates the stress concentration problem at the root of the cantilever beam. The ceramic substrate, thick-film strain gauge, and ceramic cover plate are bonded together into a rigid whole through high-temperature sintering, resulting in a robust structure that is not easily damaged by solid shock waves generated by instantaneous impacts, ensuring structural stability and reliability. Furthermore, this solution uses standard materials and processes for manufacturing thick-film resistors (screen printing, sintering, etc.), eliminating the need for complex MEMS processing steps. Compared to existing silicon piezoresistive cantilever beam products, this significantly reduces costs, meeting the needs of high-volume, low-cost applications. In addition, the overall structure is compact, eliminating the need for external charge amplifiers and other supporting equipment, which is beneficial for sensor miniaturization. A Wheatstone bridge is used to directly convert resistance changes into voltage signal output, simplifying the signal processing circuit and eliminating the need for complex charge amplification circuits. Attached Figure Description

[0019] Figure 1 A schematic diagram of the structure of an impact acceleration sensor according to one embodiment of the present invention; Figure 2 A schematic diagram of the impact acceleration sensor from another perspective; Figure 3 This is a top view of the impact acceleration sensor. Figure 4 for Figure 3 Cross-sectional view of position AA in the middle; Figure 5 for Figure 3 Cross-sectional view of the BB position in the middle; Figure 6 A diagram illustrating the hidden ceramic cover and mass block on the impact acceleration sensor. Figure 1 ; Figure 7 A diagram illustrating the hidden ceramic cover and mass block on the impact acceleration sensor. Figure 2 ; Figure 8 A diagram illustrating the hidden ceramic cover and mass block on the impact acceleration sensor. Figure 3 ; Figure label: 1. Ceramic substrate; 2. Thick film strain gauge; 3. Thick film bridge fixed resistor; 4. Conductive layer; 5. Ceramic cover plate; 6. Conductor; 7. Mass block. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0021] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0022] In the description of this invention, unless otherwise explicitly defined, terms such as setting, installing, connecting, and fixing should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0023] Example 1

[0024] refer to Figures 1 to 6 As shown, the impact acceleration sensor provided by the present invention includes: a ceramic substrate 1, a thick film strain resistor 2, a thick film bridge fixed resistor 3, a conductive layer 4, a ceramic cover plate 5, a conductor 6, and a mass block 7.

[0025] A thick-film resistor paste is printed on the upper surface of the ceramic substrate 1 using a screen printing process, and then sintered at high temperature to form the thick-film strain resistor 2 and the thick-film bridge fixed resistor 3. The thick-film resistor paste is preferably a ruthenium-based thick-film resistor paste. The ceramic substrate 1 is preferably a 96% Al2O3 ceramic substrate.

[0026] Two thick-film strain gauges 2 are provided, each with an equilateral right-angle structure and positioned opposite each other, forming a U-shaped structure. The width of one longitudinal end of each thick-film strain gauge 2 is the same as the width of its transverse end. The thickness of each thick-film strain gauge 2 is 16-18 micrometers, specifically 16, 17, or 18 micrometers, preferably 18 micrometers. Two thick-film bridge circuit fixing resistors 3 are provided and positioned outside the two thick-film strain gauges 2. Both thick-film bridge circuit fixing resistors 3 have an I-shaped, Z-shaped, or U-shaped structure, etc., and have the same resistance value as the thick-film strain gauges 2.

[0027] The thickness of the thick-film bridge circuit fixed resistor 3 is less than the thickness of the thick-film strain gauge 2, that is, the top surface height of the thick-film bridge circuit fixed resistor 3 is lower than the top surface height of the thick-film strain gauge 2. The thickness of the thick-film bridge circuit fixed resistor 3 is 10-12 micrometers, specifically 10 micrometers, 11 micrometers, or 12 micrometers, preferably 12 micrometers.

[0028] The conductive layer 4 is also formed on the upper surface of the ceramic substrate 1 by screen printing and sintering. The four conductive layers 4 connect the ends of the two thick-film strain resistors 2 and the ends of the two thick-film bridge fixed resistors 3 to form a Wheatstone bridge. The material of the conductive layer 4 is preferably a palladium-silver conductor or a gold conductor.

[0029] A ceramic cover plate 5 is positioned above the thick-film strain gauge 2. The ceramic substrate 1, the thick-film strain gauge 2, and the ceramic cover plate 5 are bonded together into a rigid whole by high-temperature sintering at 850℃. Since the thickness of the thick-film bridge circuit fixed resistor 3 is less than the thickness of the thick-film strain gauge 2, a vertical gap is maintained between the lower surface of the ceramic cover plate 5 and the upper surface of the thick-film bridge circuit fixed resistor 3, and the thick-film bridge circuit fixed resistor 3 does not bear pressure from the ceramic cover plate 5.

[0030] Conductors 6 are placed within conductive vias on the ceramic substrate 1 and electrically connected to the conductive layer 4, used to guide electrical signals to the back side of the ceramic substrate 1. Four conductors 6 are provided, and four conductive vias are provided on the ceramic substrate 1. The four conductors 6 are placed within the four conductive vias, corresponding to the four bridge arm endpoints (positive power supply, negative power supply, positive signal, and negative signal) of the Wheatstone bridge. The conductors 6 are made of copper, silver, gold, palladium-silver alloy, etc.

[0031] The mass block 7 is bonded to the upper surface of the ceramic cover plate 5 with epoxy resin structural adhesive, or the lower part of the mass block 7 is embedded in the groove at the top of the ceramic cover plate 5. The mass block 7 is made of metal or ceramic, specifically tungsten alloy, copper alloy, or stainless steel, etc., and has a high density to obtain sufficient inertial force in a small volume.

[0032] The working process of the impact acceleration sensor in this embodiment is as follows: When the sensor is subjected to an impact acceleration along the normal direction (vertical direction) of the ceramic substrate 1, the mass block 7 generates an inertial force. This inertial force is transmitted through the ceramic cover plate 5 and applied to the upper surface of the thick-film strain gauge 2. Under pressure, the cross-sectional area of ​​the thick-film strain gauge 2 changes due to the piezoresistive effect, thus changing its resistance. The two thick-film strain gauges 2, together with the two fixed thick-film bridge resistors 3 with constant resistance, constitute a Wheatstone bridge, directly converting the resistance change into a voltage signal output.

[0033] When the sensor is subjected to lateral impact acceleration, the mass block 7 generates a lateral inertial force. This force is transmitted to the thick film strain resistor 2 through the ceramic cover plate 5. Since the two thick film strain resistors 2 are opposite equilateral right angles, the lateral force causes part of the width of each resistor to increase (resistance decreases) and another part to increase (resistance increases). The total resistance remains unchanged, so the bridge output is basically unaffected by the lateral acceleration.

[0034] Example 2

[0035] refer to Figure 7 As shown, another impact acceleration sensor provided by the present invention differs from Embodiment 1 in that: the two thick film strain resistors 2 are shaped as two opposing semicircles and are arranged in a centrally symmetrical or axially symmetrical manner; the shape of the thick film bridge fixed resistor 3 is slightly adjusted; and the rest of the structure is the same as that of Embodiment 1.

[0036] Example 3

[0037] refer to Figure 8 As shown, another impact acceleration sensor provided by the present invention differs from Embodiment 1 in that the two thick-film strain resistors 2 are shaped as two opposing U-shaped structures and are arranged in a centrally symmetrical or axisymmetric manner. The shape of the thick-film bridge circuit fixed resistor 3 is slightly adjusted, and the rest of the structure is the same as that in Embodiment 1.

[0038] The above descriptions are merely some embodiments of the present invention. For those skilled in the art, various modifications and improvements can be made without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. An impact acceleration sensor, characterized in that, include: Ceramic substrate; A thick-film strain gauge is disposed on the upper surface of the ceramic substrate; A thick-film bridge circuit fixed resistor is disposed on the upper surface of the ceramic substrate, and the thickness of the thick-film bridge circuit fixed resistor is smaller than the thickness of the thick-film strain resistor. A conductive layer is formed on the upper surface of the ceramic substrate, connecting the thick film strain resistor and the thick film bridge fixed resistor to form a Wheatstone bridge. A ceramic cover plate is disposed above the thick film strain resistor. The lower surface of the ceramic cover plate is fixedly connected to the upper surface of the thick film strain resistor and maintains a gap with the upper surface of the thick film bridge fixed resistor. A conductor, electrically connected to the conductive layer, is used to lead electrical signals to the back side of the ceramic substrate; A mass block is fixedly mounted on the upper surface of the ceramic cover plate.

2. The impact acceleration sensor according to claim 1, characterized in that, The ceramic substrate has conductive vias, and the conductor is placed in the conductive vias and electrically connected to the conductive layer.

3. An impact acceleration sensor according to claim 1 or 2, characterized in that, Both the thick-film strain gauge and the thick-film bridge fixed resistor are formed by sintering thick-film resistor paste screen-printed on the ceramic substrate. The ceramic substrate, the thick-film strain gauge, and the ceramic cover plate are bonded together into a rigid whole by sintering the thick-film resistor paste.

4. An impact acceleration sensor according to claim 1, characterized in that, Two thick-film strain gauges and two thick-film bridge fixed resistors are provided and disposed on both sides of the two thick-film strain gauges. The two thick-film strain gauges and the two thick-film bridge fixed resistors are connected to form a Wheatstone bridge through the four conductive layers.

5. An impact acceleration sensor according to claim 1, characterized in that, Both thick-film strain resistors are equilateral right-angled structures and are centrally symmetrically arranged, forming a square-shaped structure together.

6. An impact acceleration sensor according to claim 1, characterized in that, Both of the thick-film strain resistors are in the form of a semi-circular arc, a U-shaped structure, or a c-shaped structure, and are arranged symmetrically.

7. An impact acceleration sensor according to claim 1, characterized in that, Multiple conductors are provided, each corresponding to one of the bridge arm endpoints of the Wheatstone bridge.

8. An impact acceleration sensor according to claim 1, characterized in that, The mass block is made of metal and is bonded to the upper surface of the ceramic cover plate with structural adhesive.

9. An impact acceleration sensor according to claim 1, characterized in that, The thickness of the thick film strain gauge is 16-18 micrometers, and the thickness of the thick film bridge fixed resistor is 10-12 micrometers.

10. An impact acceleration sensor according to claim 1, characterized in that, When the impact acceleration acts on the mass block and is converted into inertial force, the inertial force is transmitted through the ceramic cover plate and applied to the upper surface of the thick film strain resistor, causing the resistance of the thick film strain resistor to change due to the piezoresistive effect, so as to detect the impact acceleration; the thick film bridge fixed resistor maintains the gap with the ceramic cover plate, so as not to bear the pressure generated by the impact acceleration, and is only used for bridge balance.

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