A piezoelectric element high-temperature relaxation pre-tightening structure and a pre-tightening method thereof

Abstract

The application discloses a kind of inhibiting piezoelectric element high-temperature relaxation pre-tightening structure and its pre-tightening method, it includes fixed platform, fixed platform is provided with stud, stud is sequentially set with first insulator, piezoelectric element, second insulator, outer cone compensation body and inner cone compensation body from below to top, the upper end of stud is matched with the pre-tightening nut for compressing inner cone compensation body, the upper end of outer cone compensation body is provided with first annular taper face, the lower end of inner cone compensation body is provided with the second annular taper face matched with first annular taper face;First annular taper face and second annular taper face of the scheme occur relative sliding due to the difference of radial expansion, and drive inner cone compensation body to move upwards, to generate the amount of size increase in height direction, and the amount of size increase can be used as the pre-tightening compensation amount that piezoelectric element and stud in height direction due to the difference of thermal expansion amount at working temperature, to further inhibit the relaxation phenomenon of piezoelectric element at high temperature on pre-tightening structure.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of piezoelectric element fixing device, and particularly relates to a piezoelectric element high-temperature relaxation pre-tightening structure and a pre-tightening method thereof. BACKGROUND

[0002] Piezoelectric elements are widely used to make various piezoelectric mechanical sensors, such as acceleration sensors and pulse pressure sensors, due to their good dynamic response characteristics. With the continuous breakthroughs in the high-temperature resistance of piezoelectric elements, piezoelectric mechanical sensors are increasingly used in high-temperature environments. Currently, the working temperature of some piezoelectric acceleration sensors has reached more than 700 DEG C, and the working temperature of some piezoelectric pulse pressure sensors has reached more than 500 DEG C.

[0003] In the structure of high-temperature-resistant piezoelectric mechanical sensors, piezoelectric elements are usually stacked with other structural parts and fastened by a metal pre-tightening structure. However, piezoelectric elements usually have a relatively small coefficient of thermal expansion, while metals usually have a relatively large coefficient of thermal expansion, which leads to the risk of relaxation of the pre-tightening structure of the piezoelectric element in a high-temperature environment. Once the pre-tightening structure of the piezoelectric element relaxes in a high-temperature environment, it may cause the piezoelectric mechanical sensor to degrade or even fail in high-temperature working conditions.

[0004] In theory, a material with a relatively large coefficient of thermal expansion can be used to make structural parts stacked with piezoelectric elements to compensate for the small coefficient of thermal expansion of piezoelectric elements. However, it is difficult to select an engineering material that has both a large coefficient of thermal expansion and excellent high-temperature resistance, so it is difficult to effectively solve the problem of relaxation of the pre-tightening structure of the piezoelectric element in a high-temperature environment. As the application of high-temperature-resistant piezoelectric mechanical sensors increases and the use temperature increases, it becomes increasingly urgent to solve the problem of relaxation of the pre-tightening structure of the piezoelectric element in a high-temperature environment. SUMMARY

[0005] In view of the above problems of the prior art, the present application provides a piezoelectric element high-temperature relaxation pre-tightening structure and a pre-tightening method thereof, which solves the problem of relaxation of piezoelectric elements in a high-temperature environment.

[0006] To achieve the above object, the technical scheme adopted by the present application is as follows:

[0007] In a first aspect, a piezoelectric element high-temperature relaxation pre-tightening structure is provided, which comprises a fixing platform, a threaded stud is arranged on the fixing platform, the threaded stud is sequentially sleeved with a first insulator, a piezoelectric element, a second insulator, an outer conical compensation body and an inner conical compensation body from bottom to top, a pre-tightening nut for compressing the inner conical compensation body is matched with the upper end of the threaded stud, the upper end of the outer conical compensation body is provided with a first annular conical surface, and the lower end of the inner conical compensation body is provided with a second annular conical surface matched with the first annular conical surface.

[0008] Further, the first insulator, the piezoelectric element, the second insulator, the outer cone compensator and the inner cone compensator are all circular rings, the first annular taper is arranged at the upper end of the outer ring surface of the outer cone compensator, and the second annular taper is arranged at the lower end of the inner ring surface of the inner cone compensator.

[0009] Further, the taper of the first annular taper is the same as the taper of the second annular taper, and the first annular taper is attached to the second annular taper.

[0010] Further, the maximum radial dimension of the first annular taper is smaller than the maximum radial dimension of the second annular taper.

[0011] Further, the thermal expansion coefficient of the outer cone compensator is greater than the thermal expansion coefficient of the inner cone compensator.

[0012] Further, the radial dimension of the stud is smaller than the inner circle dimension of the piezoelectric element, the outer cone compensator and the inner cone compensator.

[0013] In a second aspect, a pre-tightening method for a piezoelectric element high-temperature relaxation pre-tightening structure is provided, which comprises the following steps:

[0014] S1: According to the difference in the thermal expansion amount of the piezoelectric element and the stud in the height direction at the working temperature, calculate the pre-tightening compensation amount required by the piezoelectric element in the height direction;

[0015] S2: Calculate the axial dimension increase amount of the inner cone compensator and the outer cone compensator at the working temperature in combination with the structural parameters of the inner cone compensator and the outer cone compensator;

[0016] S3: Let the pre-tightening compensation amount equal to the axial dimension increase amount, calculate the taper angle of the first annular taper or the second annular taper, and obtain the corresponding inner cone compensator and outer cone compensator;

[0017] S4: The first insulator, the piezoelectric element, the second insulator, the outer cone compensator and the inner cone compensator are coaxially sleeved on the stud from bottom to top, and then the pre-tightening nut is screwed onto the stud until the pre-tightening nut presses the inner cone compensator.

[0018] Further, the calculation formula of the pre-tightening compensation amount in step S1 is:

[0019]

[0020] wherein, is the pre-tightening compensation amount, λ L and λ Y are the thermal expansion coefficients of the stud and the piezoelectric element, respectively, H L and H Y are the height between the fixed platform and the pre-tightening nut and the height of the piezoelectric element, respectively, is the difference between the working temperature and the normal temperature;

[0021] The calculation formula of the axial dimension increase amount in step S2 is:

[0022]

[0023] The calculation formula of the taper angle in step S3 is:

[0024]

[0025] wherein, is the axial dimension increase amount, λ1 and λ2 are the thermal expansion coefficients of the outer taper compensator and the inner taper compensator respectively, R A is the maximum radial radius of the outer taper compensator, θ is the taper angle of the first annular taper surface or the second annular taper surface.

[0026] The beneficial effects of the present application are:

[0027] 1. The present scheme cooperates the first annular taper surface on the outer taper compensator with the second annular taper surface on the inner taper compensator, and utilizes the difference between the thermal expansion coefficients of the outer taper compensator and the inner taper compensator. When heated to the working temperature, the first annular taper surface and the second annular taper surface slide relative to each other due to the difference in radial expansion, and drive the inner taper compensator to move upward, thereby generating an amount of size increase in the height direction. The amount of size increase can serve as the pre-tightening compensation amount of the piezoelectric element and the stud in the height direction due to the difference in thermal expansion amount at the working temperature, and further suppresses the relaxation of the piezoelectric element on the pre-tightening structure at high temperature.

[0028] 2. The present scheme adjusts and designs the taper angle θ , so that the axial dimension increase amount ΔH2 of the inner taper compensator and the outer taper compensator at the working temperature meets the pre-tightening compensation amount ΔH1 required by the piezoelectric element. In addition, the difference adjustment between the thermal expansion coefficient λ1 of the outer taper compensator and the thermal expansion coefficient λ2 of the inner taper compensator, as well as the adjustment of the maximum radial radius R A of the outer taper compensator, can also adjust the axial dimension increase amount, and further adjust the degree of suppression of the relaxation of the piezoelectric element on the pre-tightening structure at high temperature, so as to be flexibly applied to different engineering application scenarios. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a schematic diagram of a piezoelectric element high-temperature relaxation pre-tightening structure.

[0030] Figure 2 is a schematic diagram of the sliding cooperation of the outer taper compensator and the inner taper compensator.

[0031] Wherein, 1, fixed platform, 2, the first insulator, 3, piezoelectric element, 4, the second insulator, 5, outer cone compensator, 6, inner cone compensator, 7, stud, 8, pre-tightening nut. DETAILED DESCRIPTION

[0032] The specific embodiments of the present application are described below to facilitate the understanding of the present application for those skilled in the art, but it should be clear that the present application is not limited to the scope of the specific embodiments, and for those skilled in the art, it is obvious that various changes are within the spirit and scope of the present application defined and determined by the appended claims, and all the inventions utilizing the concept of the present application are within the scope of protection.

[0033] As shown in Figure 1 The high-temperature relaxation pre-tightening structure for suppressing piezoelectric elements of the present scheme includes a fixed platform 1, a vertical stud 7 is arranged on the fixed platform 1, the stud 7 is sequentially sleeved from bottom to top with a first insulator 2, a piezoelectric element 3, a second insulator 4, an outer cone compensator 5 and an inner cone compensator 6, the piezoelectric element 3 is used to sense the acting force generated by the measured mechanical physical quantity and output a measurement electrical signal through piezoelectric effect; the upper end of the stud 7 is fitted with a pre-tightening nut 8 for compressing the inner cone compensator 6, the upper end of the outer cone compensator 5 is provided with a first annular taper, and the lower end of the inner cone compensator 6 is provided with a second annular taper matched with the first annular taper.

[0034] The first insulator 2, the piezoelectric element 3, the second insulator 4, the outer cone compensator 5 and the inner cone compensator 6 are all in the shape of a circular ring, and the radial dimension of the stud 7 is smaller than the inner circular dimension of the first insulator 2, the piezoelectric element 3, the second insulator 4, the outer cone compensator 5 and the inner cone compensator 6, so as to avoid assembly interference.

[0035] The thermal expansion coefficient of the outer cone compensator 5 is greater than that of the inner cone compensator 6, the first annular taper is arranged at the upper end of the outer ring surface of the outer cone compensator 5, the second annular taper is arranged at the lower end of the inner ring surface of the inner cone compensator 6, the taper of the first annular taper is the same as that of the second annular taper, and the first annular taper is in close contact with the second annular taper, and the maximum radial dimension of the first annular taper is smaller than that of the second annular taper.

[0036] When the temperature of this solution is increased from room temperature to operating temperature, since the coefficient of thermal expansion of the piezoelectric element 3 is usually smaller than that of the stud 7, the thermal expansion of the piezoelectric element 3 in the height direction is less than that of the stud 7, resulting in the loosening of the piezoelectric element 3. However, due to the difference in the coefficients of thermal expansion of the outer cone compensator 5 and the inner cone compensator 6, the expansion of the first annular cone surface is greater than that of the second annular cone surface. The first annular cone surface exerts a thrust on the second annular cone surface, driving the inner cone compensator 6 to move upwards. Therefore, the first insulator 2 and the piezoelectric element 3... In addition to the increase in height caused by the thermal expansion of the parts themselves in the height direction, the stack formed by the second insulator 4, the outer cone compensator 5 and the inner cone compensator 6 can also generate an additional increase in axial size in the height direction through the cooperation of the first annular cone surface on the outer cone compensator 5 and the second annular cone surface on the inner cone compensator 6. The increase in axial size can be used as a pre-tightening compensation amount generated by the difference in thermal expansion between the piezoelectric element 3 and the stud 7 in the height direction at the operating temperature, thereby suppressing the phenomenon of loosening of the pre-tightening structure of the piezoelectric element 3 at high temperature.

[0037] This solution also provides a pre-tightening method for suppressing high-temperature relaxation of the pre-tightening structure of a piezoelectric element, which includes the following steps:

[0038] S1: Based on the difference in thermal expansion between the piezoelectric element 3 and the stud 7 in the height direction at the operating temperature, calculate the required preload compensation for the piezoelectric element 3 in the height direction. The formula for calculating the preload compensation is as follows:

[0039]

[0040] in, For the preload compensation amount, λ L and λ Y The coefficients of thermal expansion, H, are the stud 7 and the piezoelectric element 3, respectively. L and H Y These represent the height between the fixed platform 1 and the preload nut 8, and the height of the piezoelectric element 3, respectively. This is the difference between the operating temperature and the normal operating temperature.

[0041] S2: Based on the structural parameters of the inner conical compensator 6 and the outer conical compensator 5, calculate the increase in axial dimensions of the inner conical compensator 6 and the outer conical compensator 5 at the operating temperature;

[0042] like Figure 2 As shown, at room temperature, point A on the first annular cone surface with the maximum radial radius coincides with point B on the second annular cone surface. The maximum radial radius of point A is R. A The radius of the loop where point B is located is R. B Then R A = R B .

[0043] When the ambient temperature rises , the maximum radial radius R A of the point A on the outer cone compensation body 5 increases due to the increased amount of thermal expansion :

[0044]

[0045] wherein λ1 is the thermal expansion coefficient of the outer cone compensation body 5.

[0046] And the ring radius R B of the point B on the inner cone compensation body 6 increases due to the increased amount of thermal expansion :

[0047]

[0048] wherein λ2 is the thermal expansion coefficient of the inner cone compensation body 6.

[0049] Since λ1 > λ2, we have > Therefore, the ring where the point A on the outer cone compensation body 5 is located will no longer fit the ring where the point B on the inner cone compensation body 6 is located, but needs to fit to a position lower than the ring where the point B on the inner cone compensation body 6 is located, i.e. a position larger than the ring radius R B of the point B. In this process, the inner cone compensation body 6 will move upward due to the pushing force of the outer cone compensation body 5, and the cone angle of the first ring-shaped cone surface and the second ring-shaped cone surface is assumed to be θ at normal temperature. Since R A is much larger than , R B is much larger than , the cone angle of the outer cone compensation body 5 and the inner cone compensation body 6 at high temperature can also be considered as θ , and then the ring radius R A of the point A on the outer cone compensation body 5 can be obtained.

[0050]

[0051] The calculation formula of the increased amount of axial dimension is:

[0052]

[0053] S3: Let the pre-tightening compensation amount equal to the increased amount of axial dimension, calculate the cone angle of the first ring-shaped cone surface or the second ring-shaped cone surface, and obtain the corresponding inner cone compensation body 6 and outer cone compensation body 5. The calculation formula of the cone angle is:

[0054]

[0055] S4: The first insulator 2, the piezoelectric element 3, the second insulator 4, the outer cone compensator 5 and the inner cone compensator 6 are coaxially sleeved on the stud 7 from bottom to top in sequence, and then the pre-tightening nut 8 is screwed onto the stud 7 until the pre-tightening nut 8 is pressed against the inner cone compensator 6.

[0056] In particular, in the specific implementation of the present scheme, the taper angle θ According to the actual situation, a certain degree can be appropriately increased, so that the increase of the axial dimension is slightly greater than the pre-tightening compensation amount; by adjusting the design of the taper angle θ , the increase of the axial dimension of the inner cone compensator 6 and the outer cone compensator 5 at the working temperature satisfies the pre-tightening compensation amount required by the piezoelectric element 3 ; in addition, the difference adjustment between the thermal expansion coefficient λ1 of the outer cone compensator 5 and the thermal expansion coefficient λ2 of the inner cone compensator 6 and the adjustment of the maximum radial radius R A of the outer cone compensator 5 can also adjust the increase of the axial dimension, and further adjust the degree of inhibition of the relaxation of the piezoelectric element 3 under the pre-tightening structure at high temperature, so as to be flexibly applied to different demand engineering application scenarios.

Claims

1. A pre-tightening method for suppressing high-temperature relaxation of a piezoelectric element's pre-tightening structure, characterized in that, The pre-tightening structure includes a fixed platform, on which a stud is provided. From bottom to top, the stud is fitted with a first insulator, a piezoelectric element, a second insulator, an outer conical compensator, and an inner conical compensator. The upper end of the stud is fitted with a pre-tightening nut for pressing the inner conical compensator. The upper end of the outer conical compensator is provided with a first annular conical surface, and the lower end of the inner conical compensator is provided with a second annular conical surface that mates with the first annular conical surface. The first insulator, the piezoelectric element, the second insulator, the outer cone compensator, and the inner cone compensator are all annular in shape. The first annular cone surface is opened at the upper end of the outer annular surface of the outer cone compensator, and the second annular cone surface is opened at the lower end of the inner annular surface of the inner cone compensator. The maximum radial dimension of the first annular conical surface is smaller than the maximum radial dimension of the second annular conical surface, and the coefficient of thermal expansion of the outer conical compensator is greater than the coefficient of thermal expansion of the inner conical compensator. The pre-tightening method includes the following steps: S1: Calculate the required preload compensation for the piezoelectric element in the height direction based on the difference in thermal expansion between the piezoelectric element and the stud in the height direction at the operating temperature; S2: Based on the structural parameters of the inner and outer conical compensators, calculate the increase in axial dimensions of the inner and outer conical compensators at the operating temperature; S3: Let the preload compensation amount equal to the increase in axial dimension, calculate the cone angle of the first or second annular cone surface, and obtain the corresponding inner cone compensator and outer cone compensator. S4: The first insulator, piezoelectric element, second insulator, outer cone compensator and inner cone compensator are coaxially mounted on the stud from bottom to top, and then the preload nut is screwed onto the stud until the preload nut presses the inner cone compensator. The formula for calculating the preload compensation amount in step S1 is: in, For the preload compensation amount, λ L and λ Y The coefficients of thermal expansion, H, are the stud and the piezoelectric element, respectively. L and H Y These represent the height between the fixed platform and the preload nut, and the height of the piezoelectric element, respectively. This is the difference between the operating temperature and the normal operating temperature. The formula for calculating the increase in axial dimension in step S2 is: The formula for calculating the cone angle in step S3 is: in, R represents the increase in axial dimension, where λ1 and λ2 are the coefficients of thermal expansion of the outer and inner conical compensators, respectively. A The maximum radial radius of the outer cone compensator. θ The cone angle is the angle of the first or second annular cone.

2. The pre-tightening method for suppressing high-temperature relaxation of the piezoelectric element pre-tightening structure according to claim 1, characterized in that, The taper of the first annular conical surface is the same as that of the second annular conical surface, and the first annular conical surface and the second annular conical surface are in contact.

3. The pre-tightening method for suppressing high-temperature relaxation pre-tightening structure of piezoelectric element according to claim 1, characterized in that, The radial dimension of the stud is smaller than the inner circle dimensions of the piezoelectric element, the outer conical compensator, and the inner conical compensator.

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