Piezoelectric high pressure sensor

Abstract

A piezoelectric high-pressure sensor for measuring pressures up to 10 kbar; having a housing, a diaphragm and a measuring cell; the housing is hollow-cylindrical and has a jacket and a cavity, in the jacket at least one mount is shaped, by means of which the piezoelectric high-pressure sensor can be mounted at a measuring point; the measuring cell is arranged in the cavity and has at least one measuring element made of piezoelectric material; the diaphragm is disc-shaped and has a central region and a peripheral region, the diaphragm is designed to receive the pressure to be measured through the central region and to transmit to the measuring cell along a vertical axis, the diaphragm is connected to the jacket material by means of the peripheral region; the measuring element is rod-shaped and works according to the piezoelectric lateral effect; the measuring element has a length along the vertical axis and a cross section perpendicular to the vertical axis; the ratio of the length to the cross section is in the range of greater than / equal to 1.0 mm ‑1 to less than / equal to 1.5 mm ‑1 ; the jacket has a diameter of less than / equal to 10 mm.

Description

Technical Field

[0001] This invention relates to a piezoelectric high voltage sensor. Background Technology

[0002] Piezoelectric sensors are widely known and suitable for measuring a wide variety of physical quantities, such as pressure, force, strain, and acceleration. All piezoelectric sensors operate on the same principle. Under the influence of the physical quantity to be measured, the piezoelectric material generates an electric charge Q. These charges are extracted from the surface of the piezoelectric material through electrodes. The amount of charge is proportional to the magnitude of the physical quantity. This proportional relationship is also known as a linear relationship. The piezoelectric material and electrodes form the measuring unit.

[0003] Piezoelectric pressure sensors typically consist of a housing and a diaphragm made of a mechanically resistant material, such as stainless steel. The housing is hollow and cylindrical, with a sheath and a cavity. The diaphragm is disc-shaped, with a central region and an edge region. The measuring element is arranged within the cavity. The diaphragm receives the pressure to be measured through the central region and transmits it as a loading force to the measuring element. The diaphragm is connected to the sheath material through the edge region. Thus, the cavity is hermetically sealed, and the measuring element is protected from harmful environments. To transmit pressure with the least possible resistance, the diaphragm is designed to be flexible. This flexibility is achieved through a very small thickness of the diaphragm, less than or equal to 0.5 mm. This gives the piezoelectric pressure sensor high sensitivity, i.e., the amount of charge generated by the applied pressure. The piezoelectric pressure sensor can be mounted at the measuring point through the sheath, for example, via a standard external thread.

[0004] Special piezoelectric high-pressure sensors have been developed to measure pressures greater than 1 kbar. These high pressures occur during highly dynamic pressure processes, such as explosions. Accurate measurement during such processes requires a high measurement frequency. Since the measurement frequency is limited by the natural frequency, piezoelectric high-pressure sensors possess a high natural frequency. According to the International Committee for Standardization and Testing of Small Arms and Ammunition (CIP) decision XXXII-45 of October 2014, the natural frequency of a piezoelectric high-pressure sensor must be greater than or equal to 150 kHz. The maximum measurement frequency is typically one-third of the natural frequency.

[0005] The applicant sells these piezoelectric high-pressure sensors under models 6213B and 6217A. Technical information about these sensors can be obtained from datasheets 6217A_003-622e_02.23. Model 6217A is designed for pressures up to 2 kbar and has a natural frequency greater than 180 kHz. Model 6213B can measure pressures up to 10 kbar and has a natural frequency greater than 150 kHz.

[0006] For many materials, high pressures above 1 kbar exceed their elastic limit. This should be avoided because beyond the elastic limit, the material's mechanical stability is no longer guaranteed, and irreversible damage, such as plastic deformation or fracture, occurs. Once plastic deformation or fracture occurs, the linear relationship cannot be maintained, ultimately leading to the failure of the piezoelectric high-pressure sensor. Therefore, only a relatively limited number of materials are suitable for piezoelectric high-pressure sensors. High-alloy stainless steel has proven suitable for sheaths and diaphragms; while single crystals made of SiO2, GaPO4, etc., are suitable as piezoelectric materials for the measuring unit. High-alloy stainless steel is ductile, and the elastic limit of the sheath and diaphragm is determined to be 0.2% yield strength (Dehngrenze) through tensile testing. Single crystals made of SiO2 and GaPO4 are brittle, therefore the elastic limit of the measuring unit is determined to be 0.2% compressive yield strength (Stauchgrenze) in pressure testing.

[0007] To avoid exceeding the 0.2% pressure yield limit of the measuring unit, the diaphragm transmits only a small portion of the pressure as a loading force to the measuring unit. The majority of the pressure is borne by the sheath. This pressure distribution affects the sensitivity of the piezoelectric high-pressure sensor. For model 6217A, designed for 2 kbar pressure, the sensitivity is 13 pC / bar. However, for model 6213B, designed for pressures up to 10 kbar (5 times higher), the loading force transmitted to the piezoelectric material is significantly smaller, resulting in a correspondingly lower sensitivity of 1.2 pC / bar. This lower sensitivity meets the minimum sensitivity requirement of 1.0 pC / bar specified in CIP Decision XXXII-45 of October 2014.

[0008] The sheath of a piezoelectric high-voltage sensor bears a large portion of the pressure as force and is therefore designed to be very robust. This results in a relatively large diameter sheath. Both Model 6213B and Model 6217A have M12 external threads for mounting at the measuring point.

[0009] However, the space at the measurement point is often very limited. Therefore, it is desirable to reduce the diameter of the sheath of the piezoelectric high-voltage sensor.

[0010] In this regard, the applicant sells a piezoelectric high-pressure sensor, model number 6215. Technical information about model 6215 can also be found in datasheets 6217A_003-622e_02.23. Model 6215 features an M10 external thread for mounting at the measuring point, is designed for pressures up to 6 kbar, has a natural frequency greater than 240 kHz, and a sensitivity of 1.4 pC / bar. Summary of the Invention

[0011] The object of this invention is to provide an improved piezoelectric high-pressure sensor compared to models 6213B, 6215, and 6217A. Specifically, this improved piezoelectric high-pressure sensor should have a relatively small diameter sheath, less than or equal to 10 mm, while still being able to measure relatively high pressures up to 10 kbar. Furthermore, this improved piezoelectric high-pressure sensor should also meet the requirements of CIP Decision XXXII-45 of October 2014 regarding the intrinsic frequency (greater than or equal to 150 kHz) and sensitivity (1.0 pC / bar).

[0012] The objective of this invention is achieved through the technical solution of this invention.

[0013] This invention relates to a piezoelectric high-pressure sensor for measuring pressures up to 10 kbar; it comprises a housing, a diaphragm, and a measuring unit. The housing is a hollow cylindrical structure with a sheath and a cavity. At least one mounting element is formed within the sheath, through which the piezoelectric high-pressure sensor can be mounted at a measurement point. The measuring unit is arranged within the cavity and has at least one measuring element made of a piezoelectric material. The diaphragm is disc-shaped, having a central region and an edge region. The diaphragm is designed to receive the pressure to be measured through the central region and transmit it to the measuring unit along a vertical axis, and the diaphragm is connected to the sheath material through the edge region. The measuring element is rod-shaped and operates according to the piezoelectric lateral effect. The measuring element has a length along the vertical axis and a cross-sectional area perpendicular to the vertical axis. The ratio of the length to the cross-sectional area is greater than or equal to 1.0 mm. -1 To less than or equal to 1.5 mm -1 Within the range; and wherein the sheath has a diameter of less than or equal to 10 mm.

[0014] Compared to model 6215, increasing the measurement range to pressures up to 10 kbar while maintaining a sheath diameter of less than or equal to 10 mm has implications for the installation of piezoelectric high-pressure sensors at the measurement point. This is because, according to Allied Engineering Standard Publication 97 (AEP-97) issued by the North Atlantic Treaty Organization (NATO) in October 2020, M10 bolt connections for piezoelectric high-pressure sensors should have a tightening torque not exceeding 20 Nm. This tightening torque corresponds to a compressive force (Niederhaltekraft) of less than or equal to 20 kN, which holds the piezoelectric high-pressure sensor in place within the mounting hole. This tightening torque ensures that the combination of compressive and loading forces does not result in harmful stress peaks in the piezoelectric high-pressure sensor material that could cause plastic deformation or fracture.

[0015] A pressure of 10 kbar and a compressive force of less than or equal to 20 kN will result in a diameter of less than or equal to 20 mm. 2 The loading surface (Beaufschlagungsfläche) is one-third the surface area of ​​the disc-shaped diaphragm. This relatively small loading surface transmits less than one-third of the pressure to the piezoelectric material, thus reducing the sensitivity of the piezoelectric high-pressure sensor. However, to meet the sensitivity requirement of 1.0 pC / bar as specified in CIP Decision XXXII-45 of October 2014, the rod-shaped measuring element must be as long as possible. This is because the amount of charge Q generated on the side of the measuring element, which operates based on the piezoelectric transverse effect, increases linearly with its length under pressure. Sensitivity is the ratio of charge to applied pressure.

[0016] However, increasing the measurement range to pressures up to 10 kbar compared to model 6215 also affects the diaphragm. This is because the piezoelectric material of the measuring unit is significantly more elastic than the sheath material. According to Hooke's Law, elasticity is the product of elastic modulus and length. The elastic modulus of the piezoelectric material is more than half that of the sheath material. This elasticity results in additional bending along the vertical axis of the diaphragm, which transmits the measured pressure through the central region to the measuring unit, and is then fixedly held in place by the sheath material through the edge regions. This additional bending manifests as tensile and compressive stresses within the thickness of the central region. These tensile and compressive stresses are highest at the edge fibers of the central region thickness. And since the thickness of the central region is less than or equal to 0.5 mm, which is approximately an order of magnitude larger than the grain boundaries of the diaphragm material, these tensile and compressive stresses may displace these grain boundaries at the edge fibers and cause the diaphragm to rupture, inevitably leading to the failure of the piezoelectric high-pressure sensor.

[0017] To minimize tensile and compressive stresses in the central region of the diaphragm, the measuring element must be as short as possible. This relationship is proportional; the shorter the measuring element, the lower the tensile and compressive stresses in the central region of the diaphragm.

[0018] To find a balance between the high sensitivity requirement of piezoelectric high-pressure sensors and maintaining low tensile and compressive stresses in the central region of the diaphragm, the present invention increases the cross-sectional area of ​​the measuring element, such that the ratio of the length to the cross-section of the measuring element is greater than or equal to 1.0 mm. -1 To less than or equal to 1.5 mm -1 Within the range.

[0019] This is because increasing the cross-sectional area of ​​the measuring element reduces the elasticity of the piezoelectric material by a square relationship, while the amount of charge generated on the side of the measuring element under pressure decreases only linearly.

[0020] Compared to model 6215, the piezoelectric high-voltage sensor of the present invention has the same sheath diameter of less than or equal to 10 mm. Due to the identical diameter, model 6215 and the piezoelectric high-voltage sensor according to the present invention differ only slightly in weight. Furthermore, since the natural frequency is inversely proportional to weight, the piezoelectric high-voltage sensor according to the present invention has a similarly high natural frequency, greater than or equal to 150 kHz, compared to model 6215.

[0021] Advantageous extensions of the invention will be described below. Attached Figure Description

[0022] The present invention will now be described in more detail with reference to the accompanying drawings and exemplary embodiments.

[0023] Figure 1 A longitudinal cross-sectional view of a portion of the piezoelectric high-voltage sensor 10 is shown.

[0024] Figure 2 It shows according to Figure 1 A portion of the piezoelectric high-voltage sensor 10 is shown along the cross-section of the cutting line AA.

[0025] The same reference numerals denote the same objects in the accompanying drawings.

[0026] List of reference numerals

[0027] 0: Measurement point

[0028] 1: Shell

[0029] 1.1: Sheath

[0030] 1.2: Cavity

[0031] 1.3: First Sheath Section

[0032] 1.4: Second Sheath Section

[0033] 1.5: Installation components

[0034] 1.6: Material-matched sheath connection

[0035] 2: Membrane

[0036] 2.1: Central Area

[0037] 2.2: Edge Region

[0038] 2.3: Sealing surface

[0039] 2.4: Membrane connection for material compatibility

[0040] 3: Measurement Unit

[0041] 3.1, 3.1', 3.1”: Measuring element

[0042] 3.2, 3.2', 3.2”: Signal electrodes

[0043] 3.3, 3.3', 3.3”: Grounding electrode

[0044] 4: Exporting Unit

[0045] 4.1: Charge Collector

[0046] 4.2: Charge Extractor

[0047] 5: Pre-tightening unit

[0048] 5.1: Compensation Components

[0049] 5.2: Pre-tightening sleeve

[0050] 5.3: Pre-tightening body

[0051] 5.4: Pre-tightening sleeve connection with material matching

[0052] 6: Insulating elements

[0053] 10: Piezoelectric high voltage sensor

[0054] A–A: Section line

[0055] A1: End face of the first sheath section

[0056] A2: Loading surface of the diaphragm

[0057] A2': Center surface of the diaphragm

[0058] A2”: Edge surface of the diaphragm

[0059] A3: Cross-section of the measuring element

[0060] D1: Outer diameter of the shell

[0061] D2: Outer diameter of the diaphragm

[0062] D3: Diameter of the loading surface of the diaphragm

[0063] L3: Length of the measuring element

[0064] MS: Grounding signal

[0065] P: Pressure

[0066] S: Measurement signal

[0067] T2: Thickness of the central region

[0068] T2': Thickness of the edge region

[0069] X: Horizontal axis

[0070] XY: Horizontal plane

[0071] Y: Vertical axis

[0072] Z: Vertical axis Detailed Implementation

[0073] Figure 1 A longitudinal section is shown along the vertical axis Z through a portion of the piezoelectric high-voltage sensor 10. Figure 2 The diagram shows a piezoelectric high-voltage sensor 10 along the section line AA in a cross-section of a horizontal plane XY formed by the horizontal axis X and the vertical axis Y. The three axes X, Y, and Z are perpendicular to each other. The horizontal plane XY is perpendicular to the vertical axis Z. Since the piezoelectric high-voltage sensor 10 is substantially rotationally symmetric with respect to the vertical axis Z, the direction along the horizontal axis X or the vertical axis Y will be referred to as the "radial direction" below. Objects spaced apart from the vertical axis Z along the horizontal axis X or the vertical axis Y will also be referred to as "radially spaced relative to the vertical axis Z" below. A first object surrounded by a second object along the horizontal axis X or the vertical axis Y will also be referred to as "radially surrounded relative to the vertical axis Z" below.

[0074] The piezoelectric high-voltage sensor 10 has a housing 1, a diaphragm 2, and a measuring unit 3.

[0075] Casing 1

[0076] On the one hand, the housing 1 protects the measuring unit 3 from harmful environmental factors such as moisture, dust, and contact. On the other hand, the housing 1 enables the piezoelectric high-voltage sensor 10 to be installed at the measuring point O.

[0077] The housing 1 is made of a mechanically resistant material. Preferably, the material of the housing 1 is high-alloy stainless steel, which has a strength greater than 200 kN / mm². 2 It has an elastic modulus of ≥1200 MPa, preferably ≥1600 MPa, and a yield strength of 0.2%. For example, the material number of high-alloy stainless steel is 1.6358.

[0078] The housing 1 has a sheath 1.1 and a cavity 1.2. According to... Figure 1 In the longitudinal section, the sheath 1.1 extends along the vertical axis Z in a hollow columnar shape. The sheath 1.1 radially surrounds the cavity 1.2 with respect to the vertical axis Z. The shell 1 has an outer diameter D1 less than or equal to 10 mm in the radial direction.

[0079] Preferably, the sheath 1.1 is manufactured in multiple parts, comprising a first sheath portion 1.3 and a second sheath portion 1.4. The multiple-part sheath 1.1 serves to prevent the compressive force generated by the installation of the piezoelectric high-pressure sensor 10 at measurement point O from being transmitted into the measuring unit 3. Such compressive force is undesirable in the measuring unit 3 because it interferes with the measurement of pressure P.

[0080] According to Figure 2 At the section line AA, the first sheath portion 1.3 is radially surrounded by the second sheath portion 1.4 relative to the vertical axis Z. The outer diameter D1 of the housing 1 is also the outer diameter D1 of the second sheath portion 1.4. The first sheath portion 1.3 and the second sheath portion 1.4 are only in contact with each other along the vertical axis Z. The first sheath portion 1.3 and the second sheath portion 1.4 are connected to each other by a material-fitting sheath connection 1.6. Preferably, the material-fitting sheath connection 1.6 is an annular welded connection that extends 360° around the entire circumference of the sheath 1.1. The material-fitting sheath connection 1.6 is hermetically sealed.

[0081] At least one mounting element 1.5 is formed on the second sheath portion 1.4. Preferably, the mounting element 1.5 has an M10 external thread. The piezoelectric high-voltage sensor 10 can be mounted via the mounting element 1.5 in a mating mounting hole disposed at the measurement point O. The mounting hole is not shown in the figure. Preferably, the mounting hole has an M10 internal thread. The M10 external thread and the M10 internal thread form an M10 bolt connection.

[0082] According to the AEP-97 standard of October 2020, M10 bolt connections should have a tightening torque not exceeding 20 Nm. In the installed state, a tightening torque of 20 Nm provides a compressive force of less than or equal to 20 kN to hold the piezoelectric high-pressure sensor 10 in the mounting hole. The applied force F of the pressure P is not allowed to exceed the compressive force, otherwise the piezoelectric high-pressure sensor 1 will be pushed out of the mounting hole. Therefore, the maximum permissible applied force is less than or equal to 20 kN.

[0083] The sheath 1.1 has an end face A1 perpendicular to the vertical axis Z and facing the diaphragm 2. Preferably, the end face A1 is annular.

[0084] Membrane 2

[0085] The diaphragm 2 has the function of receiving the pressure P to be measured and transmitting it as a force to the measuring unit 3. The pressure P to be measured is determined according to... Figure 1 The longitudinal section is schematically shown with arrows.

[0086] The diaphragm 2 is made of a mechanically resistant material. Preferably, the material of the diaphragm 2 is high-alloy stainless steel, which has a strength greater than 200 kN / mm². 2The elastic modulus and yield strength of 0.2% are greater than or equal to 1200 MPa, preferably greater than or equal to 1600 MPa. High-alloy stainless steel is, for example, a material with material number 1.6358 or named Armox Advance.

[0087] Diaphragm 2 is disc-shaped. Diaphragm 2 has an outer diameter D2 of less than or equal to 8.5 mm in the radial direction.

[0088] The membrane 2 has a central region 2.1 and an edge region 2.2. According to... Figure 1 In the longitudinal section, the central region 2.1 is arranged on the vertical axis Z and is radially surrounded by the edge region 2.2 relative to the vertical axis Z. The central region 2.1 and the edge region 2.2 are manufactured as a single piece.

[0089] Diaphragm 2 has thicknesses T2 and T2' along the vertical axis Z. The thicknesses T2 and T2' of diaphragm 2 are significantly smaller than the outer diameter D2. In the central region 2.1, the diaphragm has thickness T2; in the edge region 2.2, the diaphragm 2 has thickness T2'. The thickness T2 of the central region 2.1 is less than the thickness T2' of the edge region 2.2. Preferably, the thickness T2 of the central region 2.1 is less than or equal to 0.5 mm. Preferably, the thickness T2' of the edge region 2.2 is less than or equal to 3 mm.

[0090] Because the thickness T2 of the central region 2.1 is very small, the diaphragm 2 is designed to be flexible. Therefore, the diaphragm 2 can transmit the pressure P to be measured to the measuring unit 3 with the least possible resistance.

[0091] In the central region 2.1, diaphragm 2 has a loading surface A2. Loading surface A2 extends perpendicular to the vertical axis Z. Loading surface A2 is arranged on the side of diaphragm 2 facing away from cavity 1.2. Loading surface A2 is radially surrounded by sealing surface 2.3 relative to the vertical axis Z. Sealing surface 2.3 is designed as a seal not shown in the receiving diagram. The pressure P to be measured acts directly on loading surface A2. The size of loading surface A2 is derived from the quotient of the maximum permissible loading force less than or equal to 20 kN and the pressure P. For pressures up to 10 kbar, the size of loading surface A2 is less than or equal to 20 mm. 2 Preferably, the loading surface A2 is circular, and its diameter D3 is less than or equal to 5.0 mm.

[0092] In the central region 2.1, the diaphragm 2 has a central surface A2'. The central surface A2' extends perpendicularly to the vertical axis Z. The central surface A2' is arranged on the side of the diaphragm 2 facing the measuring unit 3. Preferably, the central surface A2' is circular.

[0093] The diaphragm 2 is connected to the first sheath portion 1.3 via an edge region 2.2. The edge region 2.2 has a greater thickness along the vertical axis Z compared to the central region 2.1. The edge region 2.2 has an edge surface A2”. The edge surface A2” extends perpendicular to the vertical axis Z. The edge surface A2” is disposed on the side of the diaphragm 2 facing the sheath 1.1. Preferably, the edge surface A2” is annular. The edge surface A2” faces the end face A1 of the first sheath portion 1.3. The edge surface A2” is in direct contact with the end face A1. Preferably, the edge surface A2” is designed to be the same size as the end face A1.

[0094] The diaphragm 2 is connected to the first sheath portion 1.3 of the diaphragm 1.1 at the edge region 2.2 via a diaphragm connection 2.4. Preferably, the diaphragm connection 2.4 is an annular welded connection that provides a 360° airtight seal.

[0095] Measurement Unit 3

[0096] The measuring unit 3 has the function of providing a measuring signal S for the pressure to be measured P.

[0097] The measuring unit 3 has at least one measuring element 3.1, 3.1', 3.1" which has the function of generating an electric charge under the action of the pressure to be measured P.

[0098] The measuring unit 3 is made of a piezoelectric material. Preferably, the piezoelectric material is a single crystal such as SiO2 or GaPO4. The invention will be described in detail below using SiO2 or GaPO4 single crystals as examples of piezoelectric materials. However, this does not constitute a limitation of the invention. Those skilled in the art can also use other single-crystal piezoelectric materials to implement the invention, such as calcium gallate (Ca3Ga2Ge4O3). 14 Or CGG), lanthanum gallium silicate (La3Ga5SiO) 14 Or LGS), tourmaline, etc.

[0099] Measuring elements 3.1, 3.1', and 3.1" have a geometry that is easy to manufacture and has high flatness. Measuring elements 3.1, 3.1', and 3.1" are rod-shaped, with two end faces and multiple side faces. The end faces are arranged perpendicular to the vertical axis Z. The side faces are arranged along the vertical axis Z. The side faces are significantly larger than the end faces. Measuring elements 3.1, 3.1', and 3.1" face the diaphragm 2 with their axial outer end faces and their axial inner end faces away from the diaphragm 2. The pressure P to be measured is transmitted to measuring elements 3.1, 3.1', and 3.1" through the axial outer end faces. Measuring elements 3.1, 3.1', and 3.1" have radially inner and radially outer side faces. The radially inner side faces the vertical axis Z, and the radially outer side faces away from the vertical axis Z.

[0100] Measuring elements 3.1, 3.1', and 3.1” have a length L3 along the vertical axis Z. Preferably, the length L3 of measuring elements 3.1, 3.1', and 3.1” is less than or equal to 3.0 mm, and more preferably less than or equal to 2.4 mm.

[0101] Measuring elements 3.1, 3.1', and 3.1" have a cross-section A3 perpendicular to the vertical axis Z. Preferably, the cross-section A3 is greater than or equal to 1.5 mm. 2 And less than or equal to 2.5 mm 2 Within the range. For the case of three measuring elements 3.1, 3.1', and 3.1", a value greater than or equal to 4.5 mm will be obtained. 2 And less than or equal to 7.5 mm 2 The total cross-section A3 within the range.

[0102] Therefore, the ratio of the length L3 of measuring elements 3.1, 3.1', and 3.1” to the cross-section A3 is greater than or equal to 1.0 mm. -1 And less than or equal to 1.5 mm -1 Within the range.

[0103] Measuring elements 3.1, 3.1', and 3.1" are cut from a single crystal, thus exhibiting high sensitivity to the piezoelectric lateral effect and generating charge on their sides under pressure P. The SiO2 cut from a single crystal specifically for the piezoelectric lateral effect possesses a piezoelectric coefficient d. 12 = 2.3 pC / N. GaPO4 cut from a single crystal to target the piezoelectric lateral effect has a piezoelectric coefficient d. 12 = 4.5 pC / N. The name of the piezoelectric coefficient d 12 This is not a reference numeral and therefore is not included in the accompanying drawings.

[0104] Preferably, the measuring unit 3 has three accurate measuring elements 3.1, 3.1', and 3.1"". These three measuring elements 3.1, 3.1', and 3.1" are composed of a first measuring element 3.1, a second measuring element 3.1', and a third measuring element 3.1"". These three measuring elements 3.1, 3.1', and 3.1" are identical. The sensitivity of the piezoelectric high-voltage sensor 10 is improved by using three measuring elements 3.1, 3.1', and 3.1"".

[0105] The sensitivity of the piezoelectric high-pressure sensor 10 is the ratio of the charge quantity to the applied pressure P. The sensitivity is related to the piezoelectric coefficient d of the measuring elements 3.1, 3.1', and 3.1" 12 The product of the length L3 of the measuring elements 3.1, 3.1', and 3.1" and the ratio of their cross-sections A3 is proportional to the piezoelectric coefficient d. 12SiO2, a piezoelectric material with a piezoelectric coefficient of 2.3 pC / N, or as a piezoelectric coefficient d 12 The piezoelectric material GaPO4 with a strength of 4.5 pC / N, and the ratio of the length L3 of the measuring elements 3.1", 3.1'", and 3.1" to the cross-section A3 is greater than or equal to 1.0 mm. -1 And less than or equal to 1.5 mm -1 Within the specified range, the sensitivity is greater than or equal to 1.0 pC / bar, which meets the requirements of CIP Decision XXXII-45 of October 2014.

[0106] Single crystals of SiO2 and GaPO4 possess elastic moduli with anisotropic elastic coefficients. SiO2 cut for piezoelectric transverse effects has an elastic modulus of 87 kN / mm² along the vertical axis Z. 2 The elastic modulus. GaPO4 cut for the piezoelectric transverse effect has a modulus of 67 kN / mm² along the vertical axis Z. 2 The elastic coefficient.

[0107] Compared to the elastic modulus of the material of the sheath 1.1, the elastic modulus of the piezoelectric material made of SiO2 is more than twice that of the material of the sheath 1.1, or the elastic modulus of the piezoelectric material made of GaPO4 is three times that of the material of the sheath 1.1. Therefore, based on these moduli, under the action of pressure P, the piezoelectric material of the measuring unit 3 is compressed more along the vertical axis Z than the material of the sheath 1.1. Furthermore, since the diaphragm 2 is indirectly in contact with the measuring elements 3.1, 3.1', 3.1” through the central region 2.1, and the diaphragm is connected to the material of the sheath 1.1 in a mating manner at the edge region 2.2, the compression of the piezoelectric material of the measuring unit 3 results in tensile and compressive stresses in the central region 2.1 of the diaphragm 2. The shorter the measuring elements 3.1, 3.1', 3.1”, the smaller the tensile and compressive stresses in the central region 2.1. When the length L3 of the measuring elements 3.1, 3.1', and 3.1" is less than or equal to 3.0 mm, preferably less than or equal to 2.4 mm, the tensile and compressive stresses are at a level that is harmless to the mechanical stability of the central region 2.1 under a pressure P up to 10 kbar. In this document, the adjective "harmless" means that the tensile and compressive stresses in the central region 2.1 are unlikely to cause the piezoelectric high-pressure sensor 10 to fail.

[0108] The measuring unit 3 has at least one signal electrode 3.2, 3.2', 3.2” and at least one ground electrode 3.3, 3.3', 3.3”. The signal electrode 3.2, 3.2', 3.2” and the ground electrode 3.3, 3.3', 3.3” have the function of intercepting charge from the side of the measuring element 3.1, 3.1', 3.1”.

[0109] The signal electrodes 3.2, 3.2', 3.2” and the ground electrodes 3.3, 3.3', 3.3” are made of conductive materials, such as aluminum or silver. The signal electrodes 3.2, 3.2', 3.2” and the ground electrodes 3.3, 3.3', 3.3” are arranged on the sides and end faces of the measuring elements 3.1, 3.1', 3.1”. The arrangement of the signal electrodes 3.2, 3.2', 3.2” and the ground electrodes 3.3, 3.3', 3.3” on the sides and end faces of the measuring elements 3.1, 3.1', 3.1” is achieved through processes such as chemical vapor deposition and physical vapor deposition. Preferably, the thickness of the signal electrodes 3.2, 3.2', 3.2” and the ground electrodes 3.3, 3.3', 3.3” is less than or equal to 200 nm.

[0110] Preferably, signal electrodes 3.2, 3.2', and 3.2" are composed of a first signal electrode 3.2, a second signal electrode 3.2', and a third signal electrode 3.2". Preferably, ground electrodes 3.3, 3.3', and 3.3" are composed of a first ground electrode 3.3, a second ground electrode 3.3', and a third ground electrode 3.3".

[0111] The first signal electrode 3.2 is partially disposed on the radially inner surface of the first measuring element 3.1, and intercepts charge from the radially inner surface. Furthermore, the first signal electrode 3.2 is also partially disposed on the axially inner end face of the first measuring element 3.1. The first ground electrode 3.3 is partially disposed on the radially outer surface of the first measuring element 3.1, and intercepts charge from the radially outer surface. Furthermore, the first ground electrode 3.3 is also partially disposed on the axially outer end face of the first measuring element 3.1.

[0112] The second signal electrode 3.2' is partially disposed on the radially inner surface of the second measuring element 3.1, and intercepts charge from this radially inner surface. Furthermore, the second signal electrode 3.2' is also partially disposed on the axially inner end face of the second measuring element 3.1'. The second ground electrode 3.3' is partially disposed on the radially outer surface of the second measuring element 3.1', and intercepts charge from this radially outer surface. Furthermore, the second ground electrode 3.3' is also partially disposed on the axially outer end face of the second measuring element 3.1'.

[0113] The third signal electrode 3.2” is partially disposed on the radially inner surface of the third measuring element 3.1”, and intercepts charge from this radially inner surface. Furthermore, the third signal electrode 3.2” is also partially disposed on the axially inner end face of the third measuring element 3.1”. The third ground electrode 3.3” is partially disposed on the radially outer surface of the third measuring element 3.1”, and intercepts charge from this radially outer surface. Furthermore, the third ground electrode 3.3” is also partially disposed on the axially outer end face of the third measuring element 3.1”.

[0114] The measurement signal S is provided using the charge extracted from the signal electrodes 3.2, 3.2', and 3.2"; the ground signal MS is provided using the charge extracted from the ground electrodes 3.3, 3.3', and 3.3".

[0115] Export Unit 4

[0116] The piezoelectric high-voltage sensor 10 has at least one output unit 4. The output unit 4 has the function of outputting the charge intercepted from at least one signal electrode 3.2, 3.2', 3.2" as a measurement signal S.

[0117] The discharge unit 4 is made of a conductive material, such as high-alloy stainless steel. The discharge unit 4 has a columnar charge collector 4.1 and a rod-shaped charge discharger 4.2. The charge collector 4.1 and the charge discharger 4.2 can be manufactured as a single piece or in multiple pieces. If they are manufactured as multiple pieces, they can be electrically and mechanically connected to each other by any mechanical connection, such as material fit connection, form fit connection, force fit connection, etc.

[0118] According to Figure 1 In the longitudinal section, the discharge unit 4 extends along the vertical axis Z. Preferably, the discharge unit 4 extends along the vertical axis Z. The discharge unit 4 faces the membrane 2 with the charge collector 4.1 facing away from the membrane 2 with the charge exporter 4.2 facing away from the membrane 2.

[0119] The charge collector 4.1 is in direct ground contact with at least one signal electrode 3.2, 3.2', 3.2" . Preferably, the signal electrodes 3.2, 3.2', 3.2" consist of a first signal electrode 3.2, a second signal electrode 3.2', and a third signal electrode 3.2" , and the charge collector 4.1 is in direct ground contact with all three signal electrodes 3.2, 3.2', 3.2" . The direct ground contact is designed such that the charge intercepted from the three signal electrodes 3.2, 3.2', 3.2" flows to the charge collector 4.1. Therefore, the charge collector 4.1 collects the charge from the three signal electrodes 3.2, 3.2', 3.2" into a measurement signal S. The charge extractor 4.2 extracts the measurement signal S.

[0120] Pre-tightening unit 5

[0121] The piezoelectric high-pressure sensor 10 has at least one pre-tightening unit 5. The pre-tightening unit 5 functions to mechanically pre-tighten the measuring unit 3 relative to the output unit 4. Furthermore, the pre-tightening unit 5 also functions to amplify local pressure peaks in the diaphragm 2 and to mitigate the difference in thermal expansion coefficients between the materials of the housing 1 and the diaphragm 2 and the piezoelectric material of the measuring unit 3. Finally, the pre-tightening unit 5 also functions to output the charge intercepted from at least one grounding electrode 3.3, 3.3', 3.3" as a grounding signal MS.

[0122] The preload unit 5 is made of a mechanically resistant material. Preferably, the material of the preload unit 5 is high-alloy stainless steel.

[0123] Pre-tightening unit 5 according to Figure 1 It extends along the vertical axis Z in the longitudinal section. Preferably, the pre-tightening unit 5 has a trapezoidal compensating element 5.1, a hollow cylindrical pre-tightening sleeve 5.2, and a hollow cylindrical pre-tightening body 5.3.

[0124] The pressure to be measured, P, may have local pressure peaks that are significantly larger than the pressure P itself, and these peaks act locally and confined to the loading surface A2 of the diaphragm 2. Because the diaphragm 2 has a very small thickness, and to prevent the pressure peaks from being transmitted unimpeded from the diaphragm 2 to the measuring unit 3, where they would undesirably cause the 0.2% pressure yield limit of the measuring unit 3 to be exceeded, a compensation element 5.1 is arranged along the vertical axis Z between the diaphragm 2 and the measuring unit 3. The compensation element 5.1 has its end facing the diaphragm 2 in direct contact with the center surface A2' of the diaphragm 2. Therefore, the pressure peaks enter the compensation element 5.1 and are transmitted to the measuring unit 3 across the length of the compensation element 5.1. In this way, the pressure peaks are broadened to a harmless level.

[0125] The piezoelectric high-voltage sensor 10 is designed for temperatures up to 200 °C. At such high temperatures, the difference in thermal expansion coefficients between the materials of the housing 1 and diaphragm 2 and the piezoelectric material of the measuring unit 3 can cause a thermal load that may result in undesirable damage to the piezoelectric high-voltage sensor 10. To mitigate this thermal load, the thermal expansion coefficient of the compensation element 5.1 is numerically smaller than that of the materials of the housing 1 and diaphragm 2, and also smaller than that of the piezoelectric material of the measuring unit 3.

[0126] Preferably, the compensation element 5.1 is in direct ground contact with at least one ground electrode 3.3, 3.3', 3.3" at its end facing the measuring unit 3. Preferably, the ground electrodes 3.3, 3.3', 3.3" consist of a first signal electrode 3.3, a second signal electrode 3.3', and a third signal electrode 3.3" and the compensation element 5.1 is in direct ground contact with all three ground electrodes 3.3, 3.3', 3.3" . The direct ground contact is designed such that the charge intercepted from the three ground electrodes 3.3, 3.3', 3.3" flows to the compensation element 5.1. Therefore, the compensation element 5.1 collects the charge from the three ground electrodes 3.3, 3.3', 3.3" into a ground signal MS. Since the compensation element 5.1 is electrically connected to the diaphragm 2, and the diaphragm 2 is electrically connected to the sheath 1.1, the ground signal MS is correspondingly derived.

[0127] Preferably, the compensating element 5.1 and the preload sleeve 6.2 are manufactured as a single piece. However, they can also be manufactured as multiple pieces and mechanically connected to each other by material matching.

[0128] The preload sleeve 5.2 surrounds the measuring unit 3 in a radially spaced manner relative to the vertical axis Z. The charge collector 4.1 of the measuring unit 3 and the output unit 4 is arranged along the vertical axis Z between the compensation element 5.1 and the preload body 5.3.

[0129] The preload sleeve 5.2 is connected to the preload body 5.3 and the first sheath portion 1.3 at one end facing the preload body 5.3 via a material-fitting preload sleeve connection 5.4. Preferably, the material-fitting preload sleeve connection 5.4 is an annular welded connection that extends 360° over the entire circumference of that end of the preload sleeve 5.2.

[0130] The pre-tightening sleeve connection 5.4 is achieved by pressing the measuring unit 3 against the charge collector 4.1 under a pre-tightening force along the vertical axis Z. This pre-tightening force closes the micropores in the piezoelectric material of the measuring unit 3 and the material of the charge collector 4.1 through the materials of the signal electrodes 3.2, 3.2', and 3.2'". This prevents charge from remaining in the micropores and forming capacitance. Such retention of charge in the micropores would interfere with the measurement of pressure P, partly because not all charge is intercepted and discharged at the moment of its generation, and partly because the capacitance discharges over time, and the charge is intercepted and discharged only after a certain period of time, either long or short, after its generation.

[0131] Insulating element 6

[0132] The piezoelectric high-voltage sensor 10 has at least one insulating element 6. The insulating element 6 has the function of electrically insulating the lead-out unit 4 relative to the pre-tightening unit 5.

[0133] The insulating element 6 is made of electrically insulating and mechanically rigid materials such as ceramics, Al2O3 ceramics, and sapphire.

[0134] The insulating element 6 is a hollow columnar shape. The insulating element 6 is arranged radially between the lead-out unit 4 and the pre-tightening unit 5.

[0135] Insulating element 6 radially surrounds the output unit 4. Insulating element 6 is arranged on the side of charge collector 4.1 facing away from measuring unit 3. Insulating element 6 is in direct ground contact with charge collector 4.1.

[0136] The insulating element 6 is radially surrounded by the preload unit 6. Preferably, the insulating element 6 is in direct contact with the preload body 5.3 and the preload sleeve 5.2.

Claims

1. A piezoelectric high voltage sensor (10) for measuring up to 10 The pressure (P) is kbar; the piezoelectric high-pressure sensor has a housing (1), a diaphragm (2), and a measuring unit (3); the housing (1) is hollow cylindrical and has a sheath (1.1) and a cavity (1.2), in which at least one mounting element (1.5) is formed, and the piezoelectric high-pressure sensor (10) can be mounted at the measuring point (0) via the mounting element (1.5); the measuring unit (3) is arranged in the cavity (1.2) and has at least one measuring element (3.1, 3.1', 3.1") made of piezoelectric material; the diaphragm (2) is disc-shaped and has a central region (2.1) and an edge region (2.2), the diaphragm (2) is designed to receive the pressure (P) to be measured through the central region (2.1) and transmit it to the measuring unit (3) along the vertical axis (Z), and the diaphragm (2) is connected to the sheath (1.1) material through the edge region (2.2); characterized in that, The measuring element (3.1, 3.1', 3.1") is rod-shaped and operates according to the piezoelectric transverse effect; the measuring element (3.1, 3.1', 3.1") has a length (L3) along the vertical axis (Z) and a cross-section (A3) perpendicular to the vertical axis (Z); the ratio of the length (L3) to the cross-section (A3) is greater than or equal to 1.0 mm. -1 To less than or equal to 1.5 mm -1 Within the range; and the sheath (1.1) has a diameter (D1) less than or equal to 10 mm.

2. The piezoelectric high-voltage sensor (10) according to claim 1, characterized in that, The length (L3) of the measuring element (3.1, 3.1', 3.1") is less than or equal to 3.0 mm, preferably less than or equal to 2.4 mm.

3. The piezoelectric high-voltage sensor (10) according to claim 1 or 2, characterized in that, The cross-section (A3) of the measuring element (3.1, 3.1', 3.1") is greater than or equal to 1.5 mm. 2 And less than or equal to 2.5 mm 2 Within the range; and the total cross-section (A3) of the three measuring elements (3.1, 3.1', 3.1") is greater than or equal to 4.5 mm. 2 And less than or equal to 7.5 mm 2 Within the range.

4. The piezoelectric high-voltage sensor (10) according to any one of claims 1 to 3, characterized in that, The measuring unit (3) has three accurate measuring elements (3.1, 3.1', 3.1").

5. The piezoelectric high-voltage sensor (10) according to any one of claims 1 to 4, characterized in that, The piezoelectric material of the measuring element (3.1, 3.1', 3.1") is a single crystal of SiO2 or GaPO4; and the piezoelectric material of SiO2 has a piezoelectricity of 87 kN / mm² along the vertical axis (Z). 2 The elastic modulus, or the piezoelectric material of GaPO4, has a modulus of 67 kN / mm² along the vertical axis (Z). 2 The elastic coefficient.

6. The piezoelectric high-voltage sensor (10) according to claim 5, characterized in that, The sheath (1.1) is made of material with an elastic modulus greater than 200 kN / mm². 2 The material is made of a mechanically resistant material; the elastic modulus of the piezoelectric material made of SiO2 is more than twice that of the material of the sheath (1.1), or the elastic modulus of the piezoelectric material made of GaPO4 is three times smaller than that of the material of the sheath (1.1); and according to these coefficients, under the action of the pressure (P), the piezoelectric material of the measuring element (3.1, 3.1', 3.1") is compressed more along the vertical axis (Z) than the material of the sheath (1.1).

7. The piezoelectric high-voltage sensor (10) according to claim 6, characterized in that, The diaphragm (2) is in indirect ground contact with the measuring element (3.1, 3.1', 3.1") through the central region (2.1); the compression of the piezoelectric material of the measuring element (3.1, 3.1', 3.1") causes tensile and compressive stresses in the central region (2.1); the central region (2.1) has a thickness (T2) of less than or equal to 0.5 mm; and for the length (L3) of the measuring element (3.1, 3.1', 3.1") being less than or equal to 3.0 mm, preferably less than or equal to 2.4 mm, the tensile and compressive stresses are at a level that is harmless to the mechanical stability of the central region (2.1) under a pressure (P) of up to 10 kbar.

8. The piezoelectric high-voltage sensor (10) according to any one of claims 1 to 7, characterized in that, The piezoelectric high-voltage sensor (10) can be installed in a mounting hole that is matched with the mounting part (1.5) arranged at the measurement point (0) via the mounting part (1.5); the mounting part (1.5) and the mounting hole form an M10 bolt connection; in the installed state, the M10 bolt connection has a tightening torque of not more than 20 Nm and holds the piezoelectric high-voltage sensor (10) in the mounting hole with a pressing force of less than or equal to 20 kN.

9. The piezoelectric high-voltage sensor (10) according to claim 8, characterized in that, The diaphragm (2) has a loading surface (A2) that extends perpendicular to the vertical axis (Z); the loading surface (A2) is arranged on the side of the diaphragm (2) opposite to the cavity (1.2), and the pressure (P) to be measured acts directly on the loading surface (A2) as a loading force; and the size of the loading surface (A2) is determined such that the combination of the pressing force and the loading force in the material of the piezoelectric high-pressure sensor (10) does not result in a harmful stress peak that would cause plastic deformation or fracture.

10. The piezoelectric high-voltage sensor (10) according to claim 9, characterized in that, For a pressure (P) of 10 kbar, the size of the loading surface (A2) is less than or equal to 20 mm. 2 .

11. The piezoelectric high-voltage sensor (10) according to any one of claims 1 to 10, characterized in that, The piezoelectric material of the measuring element (3.1, 3.1', 3.1") is a single crystal and has a piezoelectric coefficient d for the piezoelectric transverse effect. 12 Furthermore, the sensitivity of the piezoelectric high-voltage sensor (10) is related to the piezoelectric coefficient d of the piezoelectric material of the measuring element (3.1, 3.1', 3.1") 12 It is proportional to the product of the ratio of the length (L3) to the cross-section (A3) of the measuring element (3.1, 3.1', 3.1").

12. The piezoelectric high-voltage sensor (10) according to claim 11, characterized in that, For SiO2, the piezoelectric material used as the measuring element (3.1, 3.1', 3.1"), the piezoelectric coefficient d 12 = 2.3 pC / N; or for GaPO4, the piezoelectric material used as the measuring element (3.1, 3.1', 3.1"), the piezoelectric coefficient d 12 = 4.5 pC / N; and the ratio of the length (L3) to the cross-section (A3) of the measuring element (3.1, 3.1', 3.1") is greater than or equal to 1.0 mm. -1 And less than or equal to 1.5mm -1 Within the specified range, the sensitivity of the piezoelectric high-voltage sensor (10) is greater than or equal to 1.0 pC / bar.

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