Compression type piezoelectric sensor

Abstract

The invention discloses a compression type piezoelectric sensor, and belongs to the technical field of sensors. The sensor comprises a base, an elastic limiting block, a sensing stacking body, a mass block and a pre-tightening nut. The elastic limiting block is arranged at the bottom of the first mounting groove of the base and is used for buffering impact and realizing partial load protection; the mass block and the pre-tightening nut form a spherical pair through a convex spherical surface and a concave spherical surface which are matched with each other, the sphere center of the spherical pair is located in the center of the lower surface of the base, and multi-dimensional impact force can be decoupled and converted into pure compression force in the axial direction of the piezoelectric element. The impact resistance and the measuring range of the sensor are remarkably improved through the elastic limiting structure, accurate sensing and decoupling of multi-dimensional force are achieved through the spherical pair, the dynamic sensitivity is enhanced by means of the inertia effect of the mass block, and therefore stable and accurate force measurement is achieved under the large-range, high-dynamic and complex-direction impact working conditions.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and specifically to a compression piezoelectric sensor. Background Technology

[0002] Piezoelectric sensors operate based on the piezoelectric effect, converting mechanical quantities such as force, pressure, and acceleration into measurable electrical signals. With their advantages of fast dynamic response, high stiffness, and long lifespan, these sensors are widely used in industrial inspection, aerospace, intelligent robotics, and precision measurement.

[0003] In dynamic force and high-impact measurement scenarios, compression piezoelectric sensors are one of the mainstream technical solutions. Their typical structure usually employs a centralized design, where a pre-tightened nut presses the piezoelectric wafer between metal bases, causing external force to act along the wafer's thickness direction, thereby generating an electrical signal. This structure features high stiffness, good dynamic frequency response, and excellent linearity, and is widely used for high-precision dynamic force measurement such as cutting forces and impact forces.

[0004] However, traditional centralized compression structures also have significant limitations. First, pursuing high sensitivity often requires the use of thin piezoelectric wafers, but this weakens the sensor's range and rigidity, making it difficult to balance high sensitivity and high reliability under large-range impact conditions. Second, this structure is inherently sensitive to forces in only one direction. To achieve multidimensional force measurement, multiple sensors must be introduced and arranged in a complex spatial manner, which not only makes the structure bulky and difficult to assemble, but also introduces significant interdimensional coupling interference, reducing decoupling accuracy and measurement accuracy.

[0005] Therefore, in advanced applications requiring large range, high dynamic range, and multidimensional force information sensing, traditional compression piezoelectric sensors face severe challenges in structural design. The industry urgently needs a new type of piezoelectric sensor structure that can achieve breakthroughs at the mechanical principle level, simultaneously improving its range, dynamic response characteristics, and decoupled measurement capabilities for multidimensional impact forces without excessively increasing its size and complexity. Summary of the Invention

[0006] In view of the above-mentioned shortcomings of the existing technology, the purpose of this invention is to provide a compression piezoelectric sensor to solve the technical problems of traditional sensors in which it is difficult to balance sensitivity and reliability in large-range impact measurements, and difficult to use for decoupled measurement of multi-dimensional forces.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A compression piezoelectric sensor includes a base, an elastic limiting block, a sensing stack, a mass block, and a preload nut;

[0009] A first mounting groove is provided in the middle of the upper surface of the base, and an internal thread is provided at the upper end of the first mounting groove;

[0010] The elastic limiting block is adapted to be installed at the bottom of the first mounting groove, and a second mounting groove is provided in the middle of its upper surface; the sensing stack is composed of a first electrode, a piezoelectric element and a second electrode arranged in sequence, and is adapted to be installed in the second mounting groove.

[0011] The mass block is positioned above the sensor stack, and the preload nut is positioned above the mass block and is screwed into the internal thread of the base. The end face of the mass block facing the preload nut is a convex spherical surface, and the end face of the preload nut facing the mass block is a concave spherical surface. The convex spherical surface and the concave spherical surface match each other and form a spherical pair. The centers of the convex spherical surface and the concave spherical surface coincide with the center of the lower surface of the base.

[0012] Furthermore, the elastic limiting block is made of polytetrafluoroethylene.

[0013] Furthermore, the sidewall of the second mounting groove is provided with at least one axially extending limiting groove, and the first electrode and / or the second electrode are provided with limiting portions that cooperate with the limiting groove.

[0014] Furthermore, the mass block includes an upper cylindrical section and a lower cylindrical section coaxially arranged. The outer diameter of the upper cylindrical section is in clearance fit with the inner diameter of the first mounting groove, and the outer diameter of the lower cylindrical section is in clearance fit with the inner diameter of the second mounting groove.

[0015] Furthermore, there is a gap between the bottom surface of the upper cylindrical section and the upper surface of the elastic limiting block.

[0016] Furthermore, the preload nut includes an upper hexagonal nut portion and a lower threaded connection portion, the threaded connection portion being screwed into the internal thread of the base.

[0017] Furthermore, the first electrode, the piezoelectric element, the second electrode, the mass block, and the preload nut are all provided with coaxial wire-passing holes at their centers.

[0018] Furthermore, the internal thread is an ultra-fine thread.

[0019] Furthermore, the lower surface of the base extends downward to form a mounting portion, and the outer periphery of the mounting portion is provided with external threads.

[0020] Furthermore, there are two limiting grooves, which are symmetrically arranged on the side wall of the second mounting groove.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The compression piezoelectric sensor provided by this invention effectively solves the core contradictions of traditional sensors in terms of large range, high dynamic range, and multidimensional force sensing by introducing an innovative structure that combines an elastic limiting block and a spherical pair. Specifically, the elastic limiting block, made of materials such as polytetrafluoroethylene (PTFE), actively absorbs and disperses most of the impact energy through its controllable elastic deformation when subjected to high impacts, thus providing reliable "mechanical overload protection" for the core piezoelectric element. This significantly improves the sensor's tolerance limit and measurement range, while ensuring high rigidity and high frequency response characteristics of the overall structure. More importantly, the convex-concave spherical pair, precisely fitted at a specific spherical center position between the mass block and the preload nut, constitutes a decoupling core. It can automatically guide and convert complex impact forces from any direction into pure compressive forces strictly along the axis of the piezoelectric element. This design not only achieves effective sensing and decoupling of multidimensional force signals but also ensures that the sensor has both high dynamic sensitivity and excellent measurement linearity over a wide measurement range. Therefore, this structure achieves an organic unity of impact protection and force direction decoupling at the mechanical level, enabling the sensor to stably output accurate and reliable dynamic force signals under complex working conditions with large loads, high overloads, and variable directions. Attached Figure Description

[0023] To make the objectives, technical solutions, and advantages of the invention clearer, the invention will now be described in further detail with reference to the accompanying drawings, wherein:

[0024] Figure 1 This is a schematic diagram of the structure of the compression piezoelectric sensor of the present invention;

[0025] Figure 2 This is a schematic diagram of the spherical structure of the mass block and preload nut in the compression piezoelectric sensor of the present invention;

[0026] Figure 3 This is a top view of the preload nut in the compression piezoelectric sensor of the present invention.

[0027] Figure 4 This is a top view of the elastic limiting block in the compression piezoelectric sensor of the present invention.

[0028] Figure 5 This is a schematic diagram of the cross-sectional structure of the elastic limiting block in the compression piezoelectric sensor of the present invention;

[0029] In the figure, the components are: base 1, mounting part 1-1, elastic limiting block 2, sensor stack 3, first electrode 3-1, piezoelectric element 3-2, second electrode 3-3, mass block 4, upper cylinder 4-1, lower cylinder 4-2, preload nut 5, hexagonal nut part 5-1, threaded connection part 5-2, limiting groove 6, limiting part 7, wire hole 8, signal output line 9, diameter expansion part 10, base part 11, annular stepped surface 12, and accommodating cavity 13. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0032] It should be noted that similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the figures, or the orientation or positional relationship commonly used when the product is in use. They are only for the convenience of describing the 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 limitations on the invention. Furthermore, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance. In addition, the terms "horizontal," "vertical," etc., do not indicate that the component is required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted. In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0033] Example:

[0034] See Figure 1This embodiment provides a compression piezoelectric sensor, including a base 1, an elastic limiting block 2, a sensing stack 3, a mass block 4, and a preload nut 5;

[0035] A first mounting groove is provided in the middle of the upper surface of the base 1, and an internal thread is provided at the upper end of the first mounting groove;

[0036] The elastic limiting block 2 is adapted to be installed at the bottom of the first mounting groove, and a second mounting groove is opened in the middle of its upper surface; the sensing stack 3 is composed of a first electrode 3-1, a piezoelectric element 3-2 and a second electrode 3-3 arranged in sequence, and is adapted to be installed in the second mounting groove.

[0037] The mass block 4 is positioned above the sensing stack 3, and the preload nut 5 is positioned above the mass block 4 and is screwed into the internal thread of the base 1. The end face of the mass block 4 facing the preload nut 5 is a convex spherical surface; the end face of the preload nut 5 facing the mass block 4 is a concave spherical surface. The convex spherical surface and the concave spherical surface match to form a spherical pair. The centers of the convex spherical surface and the concave spherical surface coincide with the center of the lower surface of the base 1 (see...). Figure 2 (The sphere is located at point 0).

[0038] This invention effectively resolves the inherent contradiction in piezoelectric sensor design—the reliance on thin wafers for high sensitivity versus the vulnerability of thin wafers to high-range impacts—through the buffering and load-sharing design of the elastic limiting block 2. This structure preferentially absorbs energy through its own deformation when subjected to high impacts, allowing the internal thin piezoelectric wafer to maintain its high sensitivity while being protected, thus simultaneously achieving high sensitivity and a large range. Furthermore, the spherical pair between the mass block 4 and the preload nut 5 decouples multidimensional impact forces into axial loads, thereby simultaneously achieving high impact resistance and accurate multidimensional force sensing capabilities. Experimental results show that this invention can withstand a 5wg Hopkinson bar impact.

[0039] In practice, the elastic limiting block 2 is made of polytetrafluoroethylene.

[0040] In this way, it can both utilize its elasticity to buffer high-frequency impacts and protect the fragile internal piezoelectric element 3-2, and achieve reliable electrical insulation.

[0041] See Figure 4 In a specific implementation, at least one axially extending limiting groove 6 is provided on the side wall of the second mounting groove, and the first electrode 3-1 and / or the second electrode 3-3 are provided with limiting parts 7 that cooperate with the limiting groove 6.

[0042] This effectively prevents the electrodes from rotating or shifting circumferentially inside the sensor, ensuring the stability of the electrical contact and the reliability of the signal output.

[0043] In a specific implementation, the mass block 4 includes an upper cylindrical section 4-1 and a lower cylindrical section 4-2 arranged coaxially. The outer diameter of the upper cylindrical section 4-1 is in clearance fit with the inner diameter of the first mounting groove, and the outer diameter of the lower cylindrical section 4-2 is in clearance fit with the inner diameter of the second mounting groove.

[0044] This creates two radial positioning sections, ensuring the centering of the movement of mass block 4 while preventing it from getting stuck with the surrounding structure.

[0045] In practice, there is a gap between the bottom surface of the upper cylindrical section 4-1 and the upper surface of the elastic limiting block 2.

[0046] This provides space for the slight axial movement of the mass block 4 under impact and avoids rigid collisions with the elastic limiting block 2, which is beneficial for transmitting clear dynamic force signals.

[0047] join Figure 3 In specific implementation, the pre-tightening nut 5 includes an upper hexagonal nut portion 5-1 and a lower threaded connection portion 5-2, the threaded connection portion 5-2 being screwed into the internal thread of the base 1.

[0048] In this way, the hexagonal nut makes it easy to apply and precisely control the preload using standard tools, ensuring the consistency of sensor assembly.

[0049] In specific implementation, the center of the first electrode 3-1, the piezoelectric element 3-2, the second electrode 3-3, the mass block 4 and the preload nut 5 are all provided with coaxial wire holes 8 for the lead-out of the signal output line 9.

[0050] This provides a centralized and smooth routing path for signal lines, simplifies the internal wiring layout, and helps maintain the symmetry and balance of the structure.

[0051] In practice, the internal thread is an ultra-fine thread.

[0052] This allows for finer axial displacement adjustment when the preload nut 5 is engaged, thereby enabling high-precision control of the preload force.

[0053] In a specific implementation, the lower surface of the base 1 extends downward to form a mounting part 1-1, and the outer periphery of the mounting part 1-1 is provided with external threads.

[0054] This allows the sensor to be stably installed at the test position via a threaded connection, ensuring a good force transmission path.

[0055] In practice, there are two limiting grooves 6, which are symmetrically arranged on the side wall of the second mounting groove.

[0056] This provides symmetrical and balanced circumferential constraints for the electrodes, further enhancing the stability of the electrode stack.

[0057] See Figure 5 In another embodiment, the second mounting groove is a cylindrical cavity. The inner wall of the cylindrical cavity includes a coaxial upper expanded diameter section 10 and a lower base section 11. The inner diameter of the upper expanded diameter section 10 is larger than the inner diameter of the lower base section 11, thereby forming an annular stepped surface 12 at the junction of the two. The top of the sensing stack 3 is higher than the annular stepped surface 12. The base section 11 is used to limit the piezoelectric element 3-2, and the expanded diameter section 10 is used to adapt to a larger diameter mass block 4 and limit the mass block 4.

[0058] This provides a reliable radial support surface for the lower section of mass block 4, and by changing the size of the step surface, it can be adapted to mass blocks 4 of different specifications, thus enhancing the modularity and flexibility of the sensor design.

[0059] In specific implementation, a through-hole accommodating cavity 13 is provided at the bottom center of the elastic limiting block 2 for accommodating the welding position of the electrode.

[0060] This provides space for welding operations on the back of the electrode, facilitating the lead-out and connection of signal lines, without affecting the overall positioning and buffering function of the elastic limit block 2.

[0061] In specific implementation, the polarity of the first electrode 3-1 and the second electrode 3-2 can be configured according to the needs of the measurement circuit; one of them is connected to the positive input terminal of the external circuit, and the other is connected to the negative input terminal accordingly.

[0062] The working principle of the sensor described in this invention is as follows: When the sensor base 1 is subjected to external multidimensional impact, the base 1 and the preload nut 5 threadedly connected to it will generate dynamic acceleration. At this time, the mass block 4 inside the sensor, which is fixed to the spherical pair by the preload force, generates an inertial force relative to the base 1 due to its inertia. This inertial force is decoupled in direction by the spherical pair between the mass block 4 and the preload nut 5: regardless of the direction of the external impact, the geometric constraint of the spherical pair can automatically guide it and convert it into a pure dynamic compressive force strictly along the axial direction (thickness direction) of the piezoelectric element 3-2. This dynamic compressive force acts directly on the sensing stack 3 composed of the first electrode 3-1, the piezoelectric element 3-2, and the second electrode 3-3. The piezoelectric element 3-2 generates a charge signal whose magnitude is proportional to the acceleration based on the positive piezoelectric effect. Meanwhile, the elastic limiting block 2 located at the bottom of the base 1 effectively buffers and distributes the high-amplitude impact energy acting on the base 1 through its controllable elastic deformation, thereby significantly reducing the force transmitted to the piezoelectric element 3-2. This protects the brittle piezoelectric element 3-2 from damage, enables large-range measurements, and ensures that the highly sensitive thin piezoelectric wafer can operate stably in high-impact environments. Finally, the charge generated by the piezoelectric effect is collected by the two electrodes and transmitted to the subsequent circuit through the signal output line 9.

[0063] In summary, the structure of this invention achieves buffering and load distribution of high impact loads through "elastic limiting", realizes the precise conversion of multidimensional forces into a single axial force through "spherical pair decoupling", and finally completes electromechanical conversion through piezoelectric effect, thereby synergistically achieving the technical effect of large range, high dynamics and multidimensional force sensing compatibility.

[0064] 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 the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A compression piezoelectric sensor, characterized in that, Includes a base, elastic limiting block, sensor stack, mass block, and preload nut; A first mounting groove is provided in the middle of the upper surface of the base, and an internal thread is provided at the upper end of the first mounting groove; The elastic limiting block is adapted to be installed at the bottom of the first mounting groove, and a second mounting groove is provided in the middle of its upper surface; the sensing stack is composed of a first electrode, a piezoelectric element and a second electrode arranged in sequence, and is adapted to be installed in the second mounting groove. The mass block is positioned above the sensor stack, and the preload nut is positioned above the mass block and is screwed into the internal thread of the base. The end face of the mass block facing the preload nut is a convex spherical surface, and the end face of the preload nut facing the mass block is a concave spherical surface. The convex spherical surface and the concave spherical surface match each other and form a spherical pair. The centers of the convex spherical surface and the concave spherical surface coincide with the center of the lower surface of the base.

2. The compression piezoelectric sensor according to claim 1, characterized in that, The elastic limiting block is made of polytetrafluoroethylene.

3. The compression piezoelectric sensor according to claim 1, characterized in that, The sidewall of the second mounting groove is provided with at least one axially extending limiting groove, and the first electrode and / or the second electrode are provided with limiting portions that cooperate with the limiting groove.

4. The compression piezoelectric sensor according to claim 1, characterized in that, The mass block includes an upper cylindrical section and a lower cylindrical section arranged coaxially. The outer diameter of the upper cylindrical section is in clearance fit with the inner diameter of the first mounting groove, and the outer diameter of the lower cylindrical section is in clearance fit with the inner diameter of the second mounting groove.

5. The compression piezoelectric sensor according to claim 4, characterized in that, There is a gap between the bottom surface of the upper cylindrical section and the upper surface of the elastic limiting block.

6. The compression piezoelectric sensor according to claim 1, characterized in that, The preload nut includes an upper hexagonal nut portion and a lower threaded connection portion, which is screwed into the internal thread of the base.

7. The compression piezoelectric sensor according to claim 1, characterized in that, The first electrode, the piezoelectric element, the second electrode, the mass block, and the preload nut are all provided with coaxial wire holes at their centers.

8. The compression piezoelectric sensor according to claim 1, characterized in that, The internal thread is an ultra-fine thread.

9. The compression piezoelectric sensor according to claim 1, characterized in that, The lower surface of the base extends downward to form a mounting portion, and the outer periphery of the mounting portion is provided with external threads.

10. The compression piezoelectric sensor according to claim 3, characterized in that, There are two limiting grooves, which are symmetrically arranged on the side wall of the second mounting groove.

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