An embedded piezoelectric acceleration sensor structure

Abstract

This invention discloses an embedded piezoelectric accelerometer structure, belonging to the technical field of piezoelectric accelerometers. The embedded piezoelectric accelerometer structure includes a base with a groove. Two first piezoelectric elements are disposed within the groove, and an elastic mass block is positioned between the two first piezoelectric elements. The elastic mass block causes the two first piezoelectric elements to respectively adhere to two sides of the groove. The weight of the first piezoelectric elements and the elastic mass block is supported by the two sides of the groove on the base. Without the central column of the traditional shear structure, the limitation of the central column structure on miniaturization is overcome, increasing the potential for miniaturization of the sensor structure. Simultaneously, the support on both sides of the groove provides greater stiffness than the support of a single central column, allowing the sensor to achieve a wider frequency response range and smaller measurement errors.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric acceleration sensor technology, and more particularly to an embedded piezoelectric acceleration sensor structure. Background Technology

[0002] In the application of piezoelectric accelerometers, the sensor's own weight adds to the weight of the system under test, which can cause frequency response measurement errors to some extent. Therefore, many special vibration testing fields have been pursuing smaller and lighter piezoelectric accelerometers to obtain a wider frequency response range and minimize frequency response measurement errors.

[0003] Piezoelectric accelerometers typically come in two main structural forms: compression and shear. Shear-type accelerometers generally outperform compression-type accelerometers, primarily due to their wider frequency response range and smaller error. Therefore, most accelerometers used in high-frequency vibration testing are of the shear-type structure.

[0004] Currently, existing shear-type piezoelectric accelerometers can be subdivided into triangular shear, ring shear, and planar shear types according to their structural form. Although the three sub-structures differ slightly in performance, they share the following characteristics: 1. The first piezoelectric element and the mass block in the shear-type piezoelectric accelerometer are attached to a central column and are secured by a pre-tightening ring; 2. The weight of the first piezoelectric element, the mass block, and the pre-tightening ring in the shear-type piezoelectric accelerometer is entirely supported by the central column.

[0005] In order to ensure a wide frequency response range and small measurement error, existing shear-type piezoelectric accelerometers require a central column with sufficient rigidity to support the weight of the first piezoelectric element, the mass block, and the preload ring. Therefore, the cross-section of the central column cannot be reduced to a very small size. In this case, the cross-sectional dimensions of the central column, plus the dimensions of the first piezoelectric element, the mass block, and the preload ring around it, make it difficult to further miniaturize the sensor. Summary of the Invention

[0006] To address the aforementioned shortcomings of existing technologies, this invention provides an embedded piezoelectric accelerometer structure, which solves the problem that existing shear-type piezoelectric accelerometers, due to their structure of using a central column to support the first piezoelectric element, a mass block, and a pre-tightening ring, are difficult to miniaturize to a greater extent.

[0007] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0008] An embedded piezoelectric accelerometer structure is provided, which includes a base with a groove on the base. Two first piezoelectric elements are disposed in the groove, and an elastic mass block is disposed between the two first piezoelectric elements. The elastic mass block causes the two first piezoelectric elements to be respectively attached to the two sides of the groove.

[0009] The basic principle of the embedded piezoelectric accelerometer structure in this solution is as follows: The embedded piezoelectric accelerometer structure is set on the component under test. The two first piezoelectric elements and the elastic mass block form a mass spring system. Under the vibration acceleration of the component under test, the two first piezoelectric elements are subjected to alternating shear forces generated by the base and the elastic mass block, which causes the first piezoelectric elements to generate charge signals that are consistent with the vibration acceleration amplitude-frequency characteristics of the component under test, thereby realizing the measurement of the vibration acceleration of the component under test.

[0010] Furthermore, as a specific arrangement of the groove, the two sides of the groove are parallel to each other, and a gap is provided between the lower end faces of the two first piezoelectric elements and the elastic mass block and the bottom surface of the groove. This method of supporting the two first piezoelectric elements through the two sides of the groove and the elastic mass block replaces the existing technology where the shear-type piezoelectric accelerometer supports the weight of the first piezoelectric elements, the mass block, and the preload ring through a central column. This eliminates the constraint of the central column's structural size on miniaturization and increases the potential for sensor miniaturization. Simultaneously, the support form on both sides of the groove provides greater stiffness than the support of a single central column, allowing the sensor to achieve a wider frequency response range and smaller measurement errors.

[0011] Furthermore, the elastic mass block is interference-fitted between the two first piezoelectric elements, and the preload generated by the interference fit fixes the two first piezoelectric elements in the groove of the base.

[0012] Furthermore, as a specific arrangement of the elastic mass block, the elastic mass block has a hexahedral structure. The two sides of the elastic mass block are in close contact with the inner sides of the two first piezoelectric elements. The upper and lower ends of the elastic mass block are respectively provided with two centrally symmetrical contraction grooves. The length direction of the two contraction grooves is in the same direction as the width direction of the elastic mass block, the depth direction of the two contraction grooves is in the same direction as the height direction of the elastic mass block, and the width direction of the two contraction grooves is in the same direction as the length direction of the elastic mass block. The two ends of the two contraction grooves are connected to the front and back sides of the elastic mass block, respectively.

[0013] The two shrinkage grooves are parallel to each other and centrally symmetrically arranged, which can improve the elastic performance of the elastic mass block and enhance the operability of its interference fit.

[0014] Furthermore, in order to securely fix the two piezoelectric components on the side of the groove, the minimum allowable interference fit of the elastic mass block needs to be limited; that is, the interference fit of the elastic mass block needs to be greater than or equal to the minimum allowable interference fit H of the elastic mass block. min ;

[0015] The formula for calculating the minimum allowable interference of the elastic mass block is:

[0016]

[0017] Among them, H min denoted as the minimum allowable interference of the elastic mass block, m as the total mass of the elastic mass block and the two first piezoelectric elements, a as the maximum impact acceleration that the sensor can withstand, L as the depth of the contraction groove in the elastic mass block, E as the elastic modulus of the material used in the elastic mass block, T as the distance between the two contraction grooves in the elastic mass block, and W as the width of the elastic mass block.

[0018] Furthermore, as specific constraints on the parameters in the formula for calculating the minimum allowable interference of the elastic mass block, the total mass m of the elastic mass block and the two first piezoelectric elements is determined based on the sensitivity requirements of the sensor and the piezoelectric constant of the first piezoelectric elements; the depth L of the contraction groove of the elastic mass block is determined based on the depth of the base groove, and L should be greater than half of the depth of the base groove; the distance T between the two contraction grooves of the elastic mass block is determined based on the distance between the two first piezoelectric elements, and the preferred dimension of T should be greater than one-fifth of the distance between the two first piezoelectric elements; the width W of the elastic mass block is determined based on the depth L of the contraction groove of the elastic mass block, and the dimension of W should be greater than L.

[0019] Furthermore, the formula for calculating the mass of the elastic mass block is:

[0020]

[0021] Where S is the design target sensitivity of the accelerometer, and d1 and d2 are the piezoelectric coefficients of the two first piezoelectric elements, respectively.

[0022] The outer dimensions of the elastic mass block satisfy:

[0023] ρLHW≈M

[0024] H≈m+n

[0025] L≈3m

[0026]

[0027] Right now:

[0028]

[0029] Where ρ is the material density of the elastic mass block, L is the length of the elastic mass block, H is the height of the elastic mass block, and W is the width of the elastic mass block.

[0030] Furthermore, the base is the component under test. The component under test can be used as the base, and a groove can be designed on the component under test to install the first piezoelectric element and the elastic mass block. This is equivalent to embedding the sensor into the component under test, realizing the integration of the sensor and the component under test, and making the vibration acceleration measurement results more realistic and accurate.

[0031] Furthermore, a second piezoelectric element and a third piezoelectric element are provided between the two first piezoelectric elements and the two sides of the elastic mass block; there are two of each of the first, second, and third piezoelectric elements, and an insulating sheet is provided between each of the first, second, and third piezoelectric elements, with a gap between its bottom and the bottom surface of the groove.

[0032] Furthermore, the amount of charge generated by the sensor under the action of accelerations in the x, y, and z axes are respectively:

[0033]

[0034]

[0035]

[0036] Among them, Q x Let a be the amount of charge on the sensor along the x-axis. x Let d1 be the measured vibration acceleration along the x-axis, and d2 and d4 be the piezoelectric coefficients of the two first piezoelectric elements along the x-axis, respectively; Q y Let a be the amount of charge on the sensor along the y-axis. y The measured vibration acceleration is along the y-axis, and D5 and D8 are the piezoelectric coefficients of the two second piezoelectric elements along the y-axis, respectively; Q z Let a be the amount of charge on the sensor along the z-axis. z D6 and D7 represent the measured vibration acceleration along the z-axis, respectively; D6 and D7 are the piezoelectric coefficients of the two third piezoelectric elements along the z-axis; M is the mass of the elastic mass block.

[0037] The beneficial effects of this invention are as follows: Compared with the shear-type piezoelectric accelerometer in the prior art, the embedded piezoelectric accelerometer structure in this solution has the following advantages:

[0038] 1. In this design, the weight of the first piezoelectric element and the elastic mass block in the embedded piezoelectric accelerometer structure is supported by the two sides of the base groove, eliminating the central column of the traditional shear-type structure. This overcomes the limitation of the central column structure size on miniaturization and increases the potential for miniaturization of the sensor structure. At the same time, the support on both sides of the groove has greater support stiffness than that of a single central column, allowing the sensor to achieve a wider frequency response range and smaller measurement error.

[0039] 2. This solution can use the component under test as a base, design a groove on the component under test and install the first piezoelectric element and the elastic mass block. This is equivalent to embedding the sensor into the component under test, realizing the integration of the sensor and the component under test, and making the vibration acceleration measurement results more realistic and accurate.

[0040] 3. This solution innovatively proposes an elastic mass block scheme. The elastic mass block not only has the functions of a traditional mass block, but also has an elastic preload effect through interference fit, replacing the preload ring in the traditional shear-type piezoelectric accelerometer structure and reducing the complexity of the accelerometer structure. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the internal cross-sectional structure of an embedded piezoelectric accelerometer.

[0042] Figure 2 This is a three-dimensional structural diagram of an elastic mass block.

[0043] Figure 3 This is a schematic diagram of an embedded piezoelectric accelerometer structure used for measuring bolt vibration acceleration.

[0044] Figure 4 A three-dimensional structural diagram showing multiple piezoelectric elements mounted on a base.

[0045] Among them, 1. base; 2. first piezoelectric element; 3. elastic mass block; 4. bolt; 5. second piezoelectric element; 6. third piezoelectric element; 7. insulating sheet. Detailed Implementation

[0046] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0047] Example 1

[0048] like Figures 1-2As shown, this embodiment 1 provides an embedded piezoelectric accelerometer structure, which includes a base 1, a groove on the base 1, two first piezoelectric elements 2 in the groove, and an elastic mass block 3 between the two first piezoelectric elements 2. The elastic mass block 3 causes the two first piezoelectric elements 2 to be respectively attached to the two sides of the groove.

[0049] The elastic mass block 3 is interference-fitted between the two first piezoelectric elements 2, and the preload generated by the interference fit fixes the two first piezoelectric elements 2 in the groove of the base 1.

[0050] Preferably, as a specific arrangement of the elastic mass block 3, the elastic mass block 3 has a hexahedral structure. The two sides of the elastic mass block 3 are in close contact with the inner sides of the two first piezoelectric elements 2, respectively. The upper and lower ends of the elastic mass block 3 are respectively provided with two centrally symmetrical contraction grooves. The length direction of the two contraction grooves is in the same direction as the width direction of the elastic mass block 3, the depth direction of the two contraction grooves is in the same direction as the height direction of the elastic mass block 3, and the width direction of the two contraction grooves is in the same direction as the length direction of the elastic mass block 3. The two ends of the two contraction grooves are respectively connected to the front and back sides of the elastic mass block 3.

[0051] The two shrinkage grooves are parallel to each other and centrally symmetrically arranged, which can improve the elastic performance of the elastic mass block 3 and enhance the operability of its interference fit.

[0052] The base 1 is fixedly connected to the component under test and is used to support the two first piezoelectric elements 2, the elastic mass block 3, and the first piezoelectric element 2. The base 1 transmits the vibration acceleration of the component under test to the two first piezoelectric elements 2 and the elastic mass block 3.

[0053] Two first piezoelectric elements 2 are used to sense the shear force generated by the vibration acceleration of the tested component, and generate a charge signal that is consistent with the amplitude-frequency characteristics of the vibration acceleration of the tested component through the piezoelectric effect.

[0054] The elastic mass block 3 is used to generate a preload force to firmly attach the two first piezoelectric elements 2 to the two sides of the groove in the base 1. The elastic mass block 3, the two piezoelectric elements, and the base 1 form a mass spring system. Under the vibration acceleration of the component under test, the two first piezoelectric elements 2 are subjected to alternating shear forces generated by the base 1 and the elastic mass block 3, which causes the first piezoelectric elements 2 to generate charge signals that are consistent with the amplitude-frequency characteristics of the vibration acceleration of the component under test, thereby realizing the measurement of the vibration acceleration of the component under test.

[0055] Preferably, but not limited to, the two sides of the groove are parallel to each other, and a gap is provided between the lower end faces of the two first piezoelectric elements 2 and the elastic mass block 3 and the bottom surface of the groove. This method of supporting the two first piezoelectric elements 2 through the two sides of the groove and the elastic mass block 3 replaces the existing technology where the shear-type piezoelectric accelerometer supports the weight of the first piezoelectric elements 2, the mass block, and the preload ring through a central column. This eliminates the constraint of the central column's structural size on miniaturization and increases the potential for sensor miniaturization. Simultaneously, the support form on both sides of the groove provides greater stiffness than the support of a single central column, allowing the sensor to achieve a wider frequency response range and smaller measurement errors.

[0056] To ensure the two piezoelectric components are securely fixed to the side of the groove, the minimum allowable interference fit of the elastic mass block 3 needs to be limited. Specifically, the interference fit of the elastic mass block 3 must be greater than or equal to the minimum allowable interference fit H. min ;

[0057] The formula for calculating the minimum allowable interference of elastic mass block 3 is as follows:

[0058]

[0059] Among them, H min denoted as , where is the minimum allowable interference fit of the elastic mass block 3, M is the mass of the elastic mass block 3, a is the maximum impact acceleration that the sensor can withstand, n is the depth of the contraction groove of the elastic mass block 3, E is the elastic modulus of the material used in the elastic mass block 3, m is the distance between the two contraction grooves of the elastic mass block 3, and W is the width of the elastic mass block.

[0060] Specifically, the total mass m of the elastic mass block 3 and the two first piezoelectric elements 2 is determined according to the sensitivity requirements of the sensor and the piezoelectric constant of the first piezoelectric element 2; the depth L of the contraction groove of the elastic mass block 3 is determined according to the depth of the groove of the base 1, and L should be greater than half of the depth of the groove of the base 1; the distance T between the two contraction grooves of the elastic mass block 3 is determined according to the distance between the two first piezoelectric elements 2, and the preferred size of T should be greater than one-fifth of the distance between the two first piezoelectric elements 2; the width W of the elastic mass block 3 is determined according to the depth L of the contraction groove of the elastic mass block 3, and the size of W should be greater than L.

[0061] Specifically, the formula for calculating the mass of elastic mass block 3 is as follows:

[0062]

[0063] Where S is the design target sensitivity of the accelerometer, and d1 and d2 are the piezoelectric coefficients of the two first piezoelectric elements 2, respectively.

[0064] Furthermore, the outer dimensions of the elastic mass block 3 should satisfy:

[0065] ρLHW≈M (Equation 3)

[0066] Where ρ is the material density of the elastic mass block 3, L is the length of the elastic mass block 3, and H is the height of the elastic mass block 3.

[0067] Substituting equation 3 into equation 2, we get:

[0068]

[0069] Furthermore, to improve the stress distribution of the elastic mass 3 after setting two contraction grooves, and to ensure that the stress generated by the measured acceleration inside the elastic mass 3 is distributed as uniformly as possible, the following should be satisfied:

[0070] H≈m+n (Equation 5)

[0071] L≈3m (Equation 6)

[0072] Furthermore, to ensure that the elastic mass block 3, after installation and fixation, has a consistent structural stiffness coefficient in both the length L direction and the width W direction, the following should be satisfied:

[0073]

[0074] Right now:

[0075]

[0076] Furthermore, substituting equations 5, 6, and 8 into equation 4, we can obtain that the outer dimensions of the elastic mass block 3 should satisfy:

[0077]

[0078] Furthermore, to minimize the maximum external dimensions of the sensor, the preferred dimensions for the length L and height H of the elastic mass block 3 are:

[0079] L = H (Equation 10)

[0080] Furthermore, substituting Equation 10 into Equation 9, we obtain the preferred calculation formula for the length L of the elastic mass block 3:

[0081]

[0082] This solution innovatively proposes an elastic mass block 3. The elastic mass block 3 not only possesses the functions of a traditional mass block, but also provides elastic preload through an interference fit, replacing the preload ring in the traditional shear-type piezoelectric accelerometer structure and reducing the complexity of the accelerometer structure.

[0083] Example 2

[0084] like Figures 1-3 Embodiment 2 of the present invention provides an embedded piezoelectric accelerometer structure. This sensor structure is further defined based on Embodiment 1. The improvement lies in how to specifically apply the sensor structure to the component under test. For other parts not mentioned, please refer to Embodiment 1 or the prior art.

[0085] Specifically, the sensor structure is fixedly connected to the component being measured by bolt 4. In this embodiment, bolt 4 is replaced with... Figure 1 The base 1 is used in the design. During implementation, a groove is provided on the hexagonal head of the bolt 4. This groove is used to install the two first piezoelectric elements 2 and the elastic mass block 3, achieving integration of the sensor and the bolt 4. This results in a more realistic and accurate measurement of the vibration acceleration of the bolt 4. The embedded piezoelectric accelerometer structure provided by this solution supports the weight of the first piezoelectric elements 2 and the elastic mass block 3 on both sides of the groove in the base 1. The elastic mass block 3 also acts as a pre-tightening element, eliminating the central column and pre-tightening ring found in traditional shear-type piezoelectric accelerometer structures. This simplifies the structure, increases the potential for miniaturization of the sensor, and achieves a wider frequency response range and smaller measurement errors.

[0086] Example 3

[0087] like Figure 4 As shown, Embodiment 3 of the present invention provides an embedded piezoelectric accelerometer structure. This sensor structure is further defined based on Embodiment 1. The improvement lies in how to specifically set multiple piezoelectric elements on the base 1 to obtain the vibration acceleration to be measured in the x, y, and z axes. For other parts not mentioned, please refer to Embodiment 1 or the prior art.

[0088] A second piezoelectric element 5 and a third piezoelectric element 6 are provided between the two sides of the first piezoelectric element 2 and the elastic mass block 3; there are two of each of the first piezoelectric element 2, the second piezoelectric element 5 and the third piezoelectric element 6, and an insulating sheet 7 is provided between each of the first piezoelectric element 2, the second piezoelectric element 5 and the third piezoelectric element 6 and a gap is provided between them and the bottom surface of the groove.

[0089] The amount of charge generated by the sensor under the action of acceleration in the x, y, and z axes are as follows:

[0090]

[0091]

[0092]

[0093] Among them, Q x Let a be the amount of charge on the sensor along the x-axis. xLet d2 and d4 be the measured vibration acceleration along the x-axis, and d2 and d4 be the piezoelectric coefficients of the two first piezoelectric elements 2 along the x-axis, respectively; Q y Let a be the amount of charge on the sensor along the y-axis. y The measured vibration acceleration is along the y-axis, and D5 and D8 are the piezoelectric coefficients of the two second piezoelectric elements 5 along the y-axis, respectively; Q z Let a be the amount of charge on the sensor along the z-axis. z D6 and D7 represent the measured vibration acceleration along the z-axis, respectively; D6 and D7 are the piezoelectric coefficients of the two third piezoelectric elements 6 along the z-axis; M is the mass of the elastic mass block.

Claims

1. An embedded piezoelectric accelerometer structure, characterized in that, The device includes a base with a groove. Two first piezoelectric elements are disposed within the groove, and an elastic mass block is positioned between the two first piezoelectric elements. The elastic mass block causes the two first piezoelectric elements to adhere to the two sides of the groove. The two sides of the groove are parallel to each other, and a gap is provided between the lower end faces of the two first piezoelectric elements and the elastic mass block and the bottom surface of the groove. The elastic mass block is interference-fitted between the two first piezoelectric elements. The elastic mass block has a hexahedral structure, and its two sides are in close contact with the inner sides of the two first piezoelectric elements. Two centrally symmetrical contraction grooves are provided on the upper and lower end faces of the elastic mass block. The length direction of the two contraction grooves is in the same direction as the width direction of the elastic mass block, the depth direction of the two contraction grooves is in the same direction as the height direction of the elastic mass block, and the width direction of the two contraction grooves is in the same direction as the length direction of the elastic mass block. The two ends of the two contraction grooves are respectively connected to the front and back sides of the elastic mass block.

2. The embedded piezoelectric accelerometer sensor structure according to claim 1, characterized in that, The minimum allowable interference of the elastic mass block is: in, H min This is the minimum allowable interference of the elastic mass block. M The mass of the elastic mass block. a The maximum impact acceleration that the sensor can withstand. n The depth of the contraction groove of the elastic mass block. E The elastic modulus of the material used for the elastic mass block. m The distance between the two contraction grooves of the elastic mass block. W The width of the elastic mass block.

3. The embedded piezoelectric accelerometer sensor structure according to claim 2, characterized in that, The depth of the contraction groove in the elastic mass block is greater than half the depth of the groove; the distance between two contraction grooves in the elastic mass block is greater than one-fifth of the distance between the two first piezoelectric elements; the width of the elastic mass block is greater than the depth of the contraction groove in the elastic mass block.

4. The embedded piezoelectric accelerometer sensor structure according to claim 3, characterized in that, The formula for calculating the mass of the elastic mass block is: in, S To achieve the target sensitivity of the accelerometer design, d 1 and d 2 represents the piezoelectric coefficients of the two first piezoelectric elements; The outer dimensions of the elastic mass block satisfy: Right now: in, ρ The material density of the elastic mass block, L Let the length of the elastic mass block be _____. H The height of the elastic mass block. W The width of the elastic mass block.

5. The embedded piezoelectric accelerometer sensor structure according to any one of claims 1 to 4, characterized in that, The base is the component being tested.

6. The embedded piezoelectric accelerometer sensor structure according to claim 5, characterized in that, A second piezoelectric element and a third piezoelectric element are provided between the two first piezoelectric elements and the two sides of the elastic mass block; there are two of each of the first, second, and third piezoelectric elements, and an insulating sheet is provided between each of the first, second, and third piezoelectric elements, with a gap between its bottom and the bottom surface of the groove.

7. The embedded piezoelectric accelerometer sensor structure according to claim 6, characterized in that, Sensor in x, y, z The amounts of charge generated under the three axial accelerations are as follows: in, Q x For the sensor in x Axial charge quantity, a x for x Axial vibration acceleration being measured d 2 and d 4 represents the two first piezoelectric elements along... x Axial piezoelectric coefficient; Q y For the sensor in y Axial charge quantity, a y for y Axial vibration acceleration being measured D 5 and D 8 represents the two second piezoelectric elements along... y Axial piezoelectric coefficient; Q z For the sensor in z Axial charge quantity, a z for z Axial vibration acceleration being measured D 6 and D 7 represents the two third piezoelectric elements along... z Axial piezoelectric coefficient; M The mass of the elastic mass block.

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