Piezoelectric high-pressure sensor

Abstract

To provide a piezoelectric high-pressure sensor that can measure pressures up to 10 kbar. [Solution] The piezoelectric high-pressure sensor of the present invention comprises a hollow cylindrical housing having a shell and a cavity, a disk-shaped diaphragm having a central region and a peripheral region, and a measuring unit having a measuring element made of piezoelectric material disposed within the cavity. The shell includes mounting means, and the piezoelectric high-pressure sensor can be mounted at the measurement location by the mounting means. The diaphragm receives the pressure to be measured by the central region, transmits this pressure along the longitudinal axis into the measuring unit, and is connected to the shell by the peripheral region through a material bond. The measuring element is rod-shaped, functions according to the piezoelectric transverse effect, and has a length along the longitudinal axis and a cross-sectional area perpendicular to the longitudinal axis, with a length-to-cross-sectional area ratio of 1.0 mm. -1 Based on the above, 1.5mm -1 The following conditions apply, and the shell diameter is 10 mm or less.

Description

[Technical Field]

[0001] The present invention relates to a piezoelectric high-pressure sensor according to the premise portion of an independent claim. [Background technology]

[0002] Piezoelectric sensors are well-known and are adapted to measure a wide variety of physical variables, such as pressure, force, strain, and acceleration. All piezoelectric sensors operate according to the same principle: a piezoelectric material generates an electric charge Q under the influence of the physical variable being measured. This charge is extracted from the surface of the piezoelectric material by electrodes. The amount of charge is proportional to the magnitude of the physical variable. This proportionality is also called linearity. The piezoelectric material and electrodes constitute the measuring unit.

[0003] Typically, a piezoelectric pressure sensor comprises a housing and a diaphragm made of a mechanically resistant material such as stainless steel. The housing is hollow cylindrical in shape and has a shell and a cavity. The diaphragm is disc-shaped with a central region and a peripheral region. The measuring unit is placed inside the cavity. The central region allows the diaphragm to absorb the pressure to be measured and transmit this pressure as an applied force to the measuring unit. The peripheral region connects the diaphragm to the shell by a bond between the materials. In this way, the cavity is airtightly sealed, and the measuring unit is protected from harmful influences from the environment. The diaphragm is configured to be flexible to transmit pressure with the smallest possible resistance. This flexibility is achieved by a small diaphragm thickness of 0.5 mm or less. In this way, the piezoelectric pressure sensor achieves high sensitivity, which is the amount of charge of the applied pressure. The piezoelectric pressure sensor can be mounted to the measuring location via the shell, for example, by a standard screw.

[0004] Special piezoelectric high-pressure sensors have been developed to measure high pressures exceeding 1 kbar (100 MPa). High pressures exceeding 1 kbar occur during extremely dynamic pressure changes, such as explosions. Accurate measurement of such extremely dynamic pressure changes requires a high measurement frequency. Furthermore, since the measurement frequency is limited by the natural frequency, piezoelectric high-pressure sensors have a high natural frequency. According to Decision XXXII-45 of the International Commission for Standardization and Testing of Small Arms and Ammunition (CIP) in October 2014, piezoelectric high-pressure sensors must have a natural frequency of 150 kHz or higher. Typically, the maximum measurement frequency is one-third of the natural frequency.

[0005] This type of piezoelectric high-pressure sensor is marketed by the applicant under the names Type 6213B and Type 6217A. Technical information relating to these sensors can be found in datasheet numbers 6217A_003-622e_02.23. Type 6217A is configured to measure pressures up to 2 kbar and has a natural frequency above 180 kHz. Type 6213B is adapted to measure pressures up to 10 kbar and has a natural frequency above 150 kHz.

[0006] For many materials, high pressures greater than 1 kbar exceed the elastic limit of the material. This must be avoided because exceeding the elastic limit leads to irreversible damage such as the collapse of the material's mechanical stability and plastic deformation or fracture. If plastic deformation or fracture occurs, linearity is no longer maintained, ultimately resulting in failure of the piezoelectric high-pressure sensor. Therefore, only a relatively small number of materials are suitable for piezoelectric high-pressure sensors. High-alloy stainless steel has proven useful for shells and diaphragms, and single crystals made from SiO2, GaPO4, etc., have proven useful as piezoelectric materials for the measuring unit. High-alloy stainless steel is ductile, and the elastic limit of the shell and diaphragm is determined in a tensile test as the 0.2% yield strength. On the other hand, single crystals of SiO2 and GaPO4 are brittle, and therefore, the elastic limit of the measuring unit is determined in a pressure test as the 0.2% compression limit.

[0007] The diaphragm transmits only a small percentage of the pressure as applied force to the measuring unit, thereby avoiding exceeding the measuring unit's 0.2% compression limit. The larger percentage of the pressure is absorbed by the shell as force. This division of pressure affects the sensitivity of the piezoelectric high-pressure sensor. The sensitivity of type 6217A, configured to measure pressures up to 2 kbar, is 13 pC / bar. In contrast, type 6213B, configured to measure pressures up to 10 kbar, i.e., five times higher, transmits a considerably smaller percentage of the pressure as applied force within the piezoelectric material, resulting in a correspondingly lower sensitivity of 1.2 pC / bar. This low sensitivity meets the minimum sensitivity criterion of 1.0 pC / bar in CIP Decision XXXII-45 from October 2014.

[0008] The shell of a piezoelectric high-pressure sensor absorbs most of the pressure as force and is therefore a solid structure. This leads to a relatively large shell diameter. Both Type 6213B and Type 6217A have an M12 male thread for mounting to the measurement location.

[0009] However, space at the measurement site is often very limited. For this reason, users of piezoelectric high-pressure sensors are very keen to reduce the shell diameter.

[0010] To achieve this, a piezoelectric high-pressure sensor named Type 6215 is commercially available under this application. In this case as well, technical information relating to Type 6215 can be found in datasheet number 6217A_003-622e_02.23. Type 6215 is equipped with an M10 male thread for mounting to the measurement location, is configured to measure pressures up to 6 kbar, has a natural frequency above 240 kHz, and a sensitivity of 1.4 pC / bar. [Prior art documents] [Non-patent literature]

[0011] [Non-Patent Document 1] North Atlantic Treaty Organization (NATO) AEP-97 (Standard Allied Engineering Publication 97) [Overview of the project] [Problems that the invention aims to solve]

[0012] The object of the present invention is to provide a piezoelectric high-pressure sensor superior to types 6213B, 6215, and 6217A. In particular, the improved piezoelectric high-pressure sensor shell has a relatively small diameter of 10 mm or less, while still being capable of measuring relatively high pressures up to 10 kbar. In addition, the improved piezoelectric high-pressure sensor shell meets the requirements of CIP Decision XXXII-45 from October 2014, namely having a natural frequency of 150 kHz or higher and a sensitivity of 1.0 pC / bar. [Means for solving the problem]

[0013] This objective is achieved by the features of the independent claim.

[0014] The present invention relates to a piezoelectric high-pressure sensor for measuring pressure up to 10 kbar, comprising a housing, a diaphragm, and a measuring unit, wherein the housing is hollow cylindrical in shape and has a shell and a cavity, the shell is designed to include at least one mounting means, the piezoelectric high-pressure sensor is mountable to the measurement location by the mounting means, the measuring unit is located in the cavity and has at least one measuring element made of piezoelectric material, the diaphragm is disc-shaped with a central region and a peripheral region, the diaphragm is configured to absorb the pressure to be measured by the central region and transmit this pressure along the longitudinal axis to the measuring unit, the diaphragm is connected to the shell by the peripheral region by a material bond, the measuring element is rod-shaped and functions according to the piezoelectric transverse effect, the measuring element has a length along the longitudinal axis and a cross-sectional area normal to (i.e., perpendicular to) the longitudinal axis, and the ratio of length to cross-sectional area is 1.0 mm -1 Based on the above, 1.5mm -1 This relates to a piezoelectric high-pressure sensor, which falls within the following range and has a shell with a diameter of 10 mm or less.

[0015] The measurement range has been increased to a maximum pressure of 10 kbar compared to Type 6215, while maintaining a shell diameter of 10 mm or less, which affects the mounting of the piezoelectric high-pressure sensor at the measurement site. This is because, according to NATO's AEP-97 (Standard Allied Engineering Publication 97) since October 2020, the M10 screw connection of the piezoelectric high-pressure sensor must have a tightening torque of no more than 20 Nm. This tightening torque corresponds to a hold-down force of 20 kN or less that holds the piezoelectric high-pressure sensor in the mounting bore. This tightening torque ensures that the combination of the hold-down force and applied force does not reach a harmful stress peak that would result in plastic deformation or breakage of the piezoelectric high-pressure sensor material.

[0016] A pressure of 10 kbar at a holding force below 20 kN results in an impact surface of 20 mm 2 or less, which is equal to 1 / 3 of the surface of the disk-shaped diaphragm. Since the impact surface is relatively small, less than 1 / 3 of the pressure is transmitted into the piezoelectric material, and thus the sensitivity of the piezoelectric high-pressure sensor is reduced. Nevertheless, in order to meet the sensitivity of 1.0 pC / bar required by the C.I.P. decision XXXII-45 since October 2014, the rod-shaped measuring unit has to be as long as possible. The reason is that the amount of charge Q generated by the measuring element, which functions according to the transverse piezoelectric effect, under the impact of the pressure on its lateral surface increases linearly along its length. The sensitivity is the ratio of the amount of charge and the applied pressure.

[0017] Furthermore, increasing the measurement range to pressures up to 10 kbar compared to type 6215 affects the diaphragm. The reason is that the piezoelectric material of the measuring unit is considerably more elastic than the material of the shell. According to Hooke's law, elasticity is the product of the modulus of elasticity and the length. The modulus of elasticity of the piezoelectric material is less than half of that of the shell material. As a result of this elasticity, while being firmly bonded to the shell by the bond between the materials via the peripheral region, further bending occurs along the longitudinal axis within the central region of the diaphragm that transmits the measured pressure into the measuring unit via the central region. This further bending manifests itself as tensile and compressive stresses in the thickness within the central region. These tensile and compressive stresses are highest within the extreme fibers of the central region. Furthermore, with a thickness of 0.5 mm or less, the thickness of the central region is small, and it is approximately one order of magnitude larger than the size of the grain boundaries of the diaphragm material, so that the tensile and compressive stresses may shift these grain boundaries within the extreme fibers and cause cracks in the diaphragm that will inevitably lead to the failure of the piezoelectric high-pressure sensor.

[0018] In order to keep the tensile and compressive stresses within the central region of the diaphragm small, the measuring element has to be as short as possible. The relationship is linear. The smaller the length of the measuring element, the smaller the tensile and compressive stresses within the central region of the diaphragm.

[0019] While the sensitivity of the piezoelectric high-pressure sensor must be high, as a solution to the dilemma that the tensile and compressive stresses within the central region of the diaphragm need to be kept small, the cross-sectional area of the measuring element is increased by the present invention such that the ratio between the length and the cross-sectional area of the measuring element is in the range from 1.0 mm -1 to 1.5 mm -1 or less.

[0020] The reason is that by increasing the cross-sectional area of the measuring element, the elasticity of the piezoelectric material is reduced quadratically, while on the other hand, the amount of charge generated under the impact of the pressure on the side surface of the measuring element is reduced linearly.

[0021] Compared to type 6215, the piezoelectric high-pressure sensor according to the present invention has the same diameter of the shell of 10 mm or less. Due to this same diameter, the type 6215 and the piezoelectric high-pressure sensor according to the present invention only have slightly different weights. Furthermore, since the natural frequency is inversely related to the weight, the natural frequency of the piezoelectric high-pressure sensor of the present invention is 150 kHz or more, that is, it is of the same size as that of type 6215.

[0022] Advantageous developments of the present invention are claimed in the dependent claims.

[0023] Hereinafter, the present invention will be described in more detail by way of exemplary embodiments with reference to the drawings.

Brief Description of the Drawings

[0024] [Figure 1] It is a longitudinal sectional view through a part of the piezoelectric high-pressure sensor 10. [Figure 2] It is a sectional view of a part of the piezoelectric high-pressure sensor 10 shown in FIG. 1 along the section line A-A.

Modes for Carrying Out the Invention

[0025] Throughout the figures, the same reference numerals denote the same objects.

[0026] Figure 1 shows a longitudinal cross-sectional view of a portion of the piezoelectric high-pressure sensor 10 along the vertical axis Z. Figure 2 shows the piezoelectric high-pressure sensor 10 in a cross-section along the cross-sectional line AA of the horizontal plane XY, which is extended by the horizontal axis X and the longitudinal 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. Hereafter, since the piezoelectric high-pressure sensor 10 is configured to be essentially rotationally symmetric with respect to the vertical axis Z, the direction along the horizontal axis X or the longitudinal axis Y will also be referred to as the "radial direction". Hereafter, an object that is far from the vertical axis Z along the horizontal axis X or the longitudinal axis Y will also be referred to as being "radially separated from the vertical axis Z". Furthermore, a first object that is surrounded by a second object along the horizontal axis X or the longitudinal axis Y will hereafter be referred to as being "radially surrounded with respect to the vertical axis Z".

[0027] The piezoelectric high-pressure sensor 10 comprises a housing 1, a diaphragm 2, and a measuring unit 3.

[0028] [Housing 1] On the one hand, housing 1 functions to protect the measuring unit 3 from harmful environmental influences such as moisture, dust, and contact. Housing 1 also functions to allow the mounting of the piezoelectric high-pressure sensor 10 at the measurement location 0.

[0029] Housing 1 is made of a mechanically resistant material. Preferably, the material of housing 1 has a resistance of 200 kN / mm². 2 This is a high-alloy stainless steel having a higher modulus of elasticity and a 0.2% yield strength of 1200 MPa or higher, preferably 1600 MPa or higher. For example, the high-alloy stainless steel is material number 1.6358 stainless steel.

[0030] Housing 1 comprises a shell 1.1 and a cavity 1.2. The shell 1.1 has a hollow cylindrical shape and extends along the longitudinal axis Z in the longitudinal cross-section shown in Figure 1. The shell 1.1 encloses the cavity 1.2, which is spaced radially away from the longitudinal axis Z. Housing 1 has an outer diameter D1 of 10 mm or less in the radial direction.

[0031] Preferably, the shell 1.1 is manufactured from multiple parts, having a first shell part 1.3 and a second shell part 1.4. The multi-part shell 1.1 functions to prevent the retaining force resulting from the mounting of the piezoelectric high-pressure sensor 10 at the measurement location 0 from entering the measurement unit 3. This retaining force distorts the measurement of pressure P, and therefore it is undesirable for it to enter the measurement unit 3.

[0032] As shown in Figure 2, along the cross-sectional line AA, the first shell portion 1.3 is radially surrounded by the second shell portion 1.4 with respect to the longitudinal axis Z. The outer diameter D1 of the housing 1 is also the outer diameter D1 of the second shell portion 1.4. The first shell portion 1.3 and the second shell portion 1.4 are only in contact with each other along the longitudinal axis Z. The first shell portion 1.3 and the second shell portion 1.4 are connected to each other by a shell connection 1.6 formed by a bond between materials. Preferably, the shell connection 1.6 formed by a bond between materials is an annular welded joint extending approximately 360° around the entire circumference of the shell 1.1. The shell connection 1.6 formed by a bond between materials forms an airtight seal.

[0033] The second shell portion 1.4 is formed to include at least one mounting means 1.5. Preferably, the mounting means 1.5 is formed as an M10 male thread. The mounting means 1.5 allows the piezoelectric high-pressure sensor 10 to be mounted in a mounting bore manufactured to match and position at the measurement location 0. The mounting bore is not shown in the figure. Preferably, the mounting bore has an M10 female thread. The M10 male and M10 female threads form an M10 threaded connection.

[0034] According to the AEP-97 standard effective October 2020, M10 screw connections must have a tightening torque of no more than 20 Nm. In the installed state, a tightening torque of 20 Nm holds the piezoelectric high-pressure sensor 10 within the mounting bore with a holding force of 20 kN or less. The force F applied by pressure P must not exceed the holding force, because otherwise the piezoelectric high-pressure sensor 1 would be ejected from the mounting bore. Therefore, the maximum possible applied force is 20 kN or less.

[0035] The shell 1.1 is oriented perpendicular to the vertical axis Z and has an end face A1 facing the diaphragm 2. The end face A1 is preferably annular in shape.

[0036] [Diaphragm 2] The diaphragm 2 functions to absorb the pressure P to be measured and transmit it as a force to the measuring unit 3. In the longitudinal cross-section shown in Figure 1, the pressure P to be measured is schematically represented by an arrow.

[0037] The diaphragm 2 is made of a mechanically resistant material. Preferably, the material of the diaphragm 2 has a resistance of 200 kN / mm 2 This is a high-alloy stainless steel having an elastic modulus exceeding [a certain value] and a 0.2% yield strength of 1200 MPa or higher, preferably 1600 MPa or higher. For example, the high-alloy stainless steel is a material named material number 1.6358 or Armox Advance.

[0038] The diaphragm 2 is disc-shaped. The diaphragm 2 has an outer diameter D2 of 8.5 mm or less in the radial direction.

[0039] The diaphragm 2 has a central region 2.1 and peripheral regions 2, 2. In the longitudinal cross-section shown in Figure 1, the central region 2.1 is located on the vertical axis Z and is radially surrounded by the peripheral regions 2.2 with respect to the vertical axis Z. The central region 2.1 and the peripheral regions 2.2 are manufactured as a single unit.

[0040] The diaphragm 2 has thicknesses T2 and T2' along the vertical axis Z. The thicknesses T2 and T2' of the diaphragm 2 are considerably smaller than the outer diameter D2. The diaphragm has a thickness T2 in the central region 2.1, and the diaphragm 2 has a thickness T2' in the peripheral region 2.2. The thickness T2 in the central region 2.1 is smaller than the thickness T2' in the peripheral region 2.2. Preferably, the thickness T2 in the central region 2.1 is 0.5 mm or less. Preferably, the thickness T2' in the peripheral region 2.2 is 3 mm or less.

[0041] The small thickness T2 of the central region 2.1 configures the diaphragm 2 to be flexible. As a result, the diaphragm 2 transmits the pressure P to be measured to the measuring unit 3 with the smallest possible resistance.

[0042] Within the central region 2.1, the diaphragm 2 has an impact surface A2. The impact surface A2 extends perpendicular to the longitudinal axis Z. The impact surface A2 is located on the surface of the diaphragm 2 facing outward from the cavity 1.2. A sealing surface 2.3 surrounds the impact surface A2 radially with respect to the longitudinal axis Z. The sealing surface 2.3 is configured to accommodate a sealant not shown in the figure. The pressure P to be measured acts directly on the impact surface A2. The size of the impact surface A2 is calculated from the ratio of the maximum possible applied force of 20 kN or less to the pressure P. For pressures P up to 10 kbar, the size of the impact surface A2 is 20 mm 2 The following applies: The impact surface A2 is preferably circular with a diameter D3 of 5.0 mm or less.

[0043] Within the central region 2.1, the diaphragm 2 has a central surface A2'. The central surface A2' extends perpendicular to the longitudinal axis Z. The central surface A2' is positioned on the surface of the diaphragm 2 facing the measuring unit 3. The central surface A2' is preferably circular in shape.

[0044] The diaphragm 2 is connected to the first shell portion 1.3 by a peripheral region 2.2. The peripheral region 2.2 has a greater thickness along the longitudinal axis Z compared to the central region 2.1. The peripheral region 2.2 has a peripheral surface A2''. The peripheral surface A2'' extends perpendicular to the longitudinal axis Z. The peripheral surface A2'' is disposed on the surface of the diaphragm 2 facing the shell 1.1. The peripheral surface A2'' preferably has an annular shape. The peripheral surface A2'' faces the end face A1 of the first shell portion 1.3. The peripheral surface A2'' is in direct planar contact with the end face A1. Preferably, the peripheral surface A2'' is configured to have the same size as the end face A1.

[0045] In the peripheral region 2.2, the diaphragm 2 is connected to the first shell portion 1.3 of the diaphragm 1.1 by a diaphragm connection 2.4 due to a bond between materials. Preferably, the diaphragm connection 2.4 due to a bond between materials is an annular weld connection extending approximately 360°. The diaphragm connection 2.4 due to a bond between materials forms an airtight seal.

[0046] [Measurement unit 3] The measurement unit 3 functions to provide a measurement signal S for the measured pressure P.

[0047] The measurement unit 3 has at least one measurement element 3.1, 3.1', 3.1''. The measurement elements 3.1, 3.1', 3.1'' function to generate an electric charge under the impact of the measured pressure P.

[0048] The measurement unit 3 is made of a piezoelectric material. Preferably, the piezoelectric material is a single crystal such as SiO2, GaPO4. Hereinafter, the present invention will be described in more detail using, as an example, a piezoelectric material of a single crystal of SiO2 or GaPO4. However, this is not intended to limit the present invention. To implement the present invention, those skilled in the art can also use calcium gallogermanate (Ca3Ga2Ge4O 14 or CGG), langasite (La3Ga5SiO 14Alternatively, other single-crystal piezoelectric materials such as LGS (light gauge steel) or tourmaline may be used.

[0049] The measuring elements 3.1, 3.1', and 3.1'' have a geometric shape that is easy to manufacture due to its large flatness. The measuring elements 3.1, 3.1', and 3.1'' are rod-shaped with two end faces and multiple side faces. The end faces are oriented perpendicular to the longitudinal axis Z. The side faces are oriented along the longitudinal axis Z. The side faces are considerably larger than the end faces. The outer end faces of the measuring elements 3.1, 3.1', and 3.1'', viewed axially, face the diaphragm 2, and the inner end faces, viewed axially, face outward from the diaphragm 2. The pressure P to be measured is transmitted to the measuring elements 3.1, 3.1', and 3.1'' by the outer end faces in the axial direction. The measuring elements 3.1, 3.1', and 3.1'' each have inner and outer side faces, viewed radially. The inner side faces in the radial direction are oriented toward the longitudinal axis Z, and the outer side faces in the radial direction face outward from the longitudinal axis Z.

[0050] The measuring elements 3.1, 3.1', and 3.1'' have a length L3 along the vertical axis Z. Preferably, the length L3 of the measuring elements 3.1, 3.1', and 3.1'' is 3.0 mm or less, and more preferably 2.4 mm or less.

[0051] The measuring elements 3.1, 3.1', and 3.1'' have a cross-sectional area A3 perpendicular to the vertical axis Z. Preferably, the cross-sectional area A3 is 1.5 mm². 2 Above, 2.5mm 2 It falls within the following range. Therefore, in the case of the three measurement elements 3.1, 3.1', and 3.1'', the total cross-sectional area A3 is 4.5 mm². 2 Above, 7.5mm 2 It is within the following range.

[0052] Therefore, the ratio of the length L3 to the cross-sectional area A3 of the measurement elements 3.1, 3.1', and 3.1'' is 1.0 mm 2 Above, 1.5mm 2 It is within the following range.

[0053] Measurement elements 3.1, 3.1', and 3.1'' are cut from a single crystal to have high sensitivity to the piezoelectric transverse effect and to generate a charge under the influence of pressure P on the side surface. SiO2 cut from the single crystal for the piezoelectric transverse effect has a piezoelectric coefficient d 12 It has a piezoelectric coefficient of d = 2.3 pC / N. GaPO4 cut from a single crystal due to the piezoelectric transverse effect has a piezoelectric coefficient of d 12 It has a piezoelectric coefficient of 4.5 pC / N. 12 Since it is not a reference symbol, it is not included in the figure.

[0054] Preferably, the measuring unit 3 has exactly three measuring elements 3.1, 3.1', and 3.1''. The three measuring elements 3.1, 3.1', and 3.1'' consist of a first measuring element 3.1, a second measuring element 3.1', and a third measuring element 3.1''. The three measuring elements 3.1, 3.1', and 3.1'' are identical. By using three quantities of measuring elements 3.1, 3.1', and 3.1'', the sensitivity of the piezoelectric high-pressure sensor 10 is increased.

[0055] The sensitivity of the piezoelectric high-pressure sensor 10 is the ratio of the amount of charge to the applied pressure P. The sensitivity is determined by the piezoelectric coefficient d of the measuring elements 3.1, 3.1', and 3.1''. 12 It is proportional to the product of the ratio of the length L3 of the measurement elements 3.1, 3.1', and 3.1'' to the cross-sectional area A3. Piezoelectric coefficient d 12 Either use SiO2 with a piezoelectric coefficient of 2.3 pC / N, or use a piezoelectric coefficient d 12 GaPO4 with a density of 4.5 pC / N is used as the piezoelectric material, and the ratio of the length L3 to the cross-sectional area A3 of the measurement elements 3.1, 3.1', and 3.1'' is 1.0 mm². -1 Above, 1.5mm -1 If the following range is used, the sensitivity will be 1.0 pC / bar or higher, and therefore the requirements of CIP Decision XXXII-45 from October 2014 will be met.

[0056] Single crystals of SiO2 and GaPO4 have elastic moduli with anisotropic elastic moduli. SiO2 cut due to the piezoelectric transverse effect exhibits an elastic modulus of 87 kN / mm² along the longitudinal axis Z. 2It has an elastic modulus of 67 kN / mm². GaPO4 cut for piezoelectric transverse effect has an elastic modulus of 67 kN / mm² along the longitudinal axis Z. 2 It has an elastic modulus of .

[0057] Compared to the elastic modulus of the material of shell 1.1, the elastic modulus of the piezoelectric material made from SiO2 is less than half, or the elastic modulus of the piezoelectric material made from GaPO4 is less than one-third. Therefore, due to these values, under the effect of pressure P, the piezoelectric material of measurement unit 3 is compressed more strongly along the longitudinal axis Z than the material of shell 1.1. Furthermore, since the diaphragm 2 is connected to shell 1.1 by material bonding within the peripheral region 2.2, while indirectly contacting the surfaces of measurement elements 3.1, 3.1', and 3.1'' via the central region 2.1, the compression of the piezoelectric material of measurement unit 3 leads to tensile and compressive stresses in the central region 2.1 of the diaphragm 2. The shorter the measurement elements 3.1, 3.1', and 3.1'' are, the smaller the tensile and compressive stresses in the central region 2.1. When the lengths L3 of the measuring elements 3.1, 3.1', and 3.1'' are 3.0 mm or less, preferably 2.4 mm or less, the tensile and compressive stresses at pressures P up to a maximum of 10 kbar are at a level that is harmless to the mechanical stability of the central region 2.1. In this context, the adjective "harmless" means that the tensile and compressive stresses within the central region 2.1 are extremely unlikely to lead to failure of the piezoelectric high-pressure sensor 10.

[0058] 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 electrodes 3.2, 3.2', 3.2'' and the ground electrodes 3.3, 3.3', 3.3'' function to extract charge from the sides of the measuring elements 3.1, 3.1', 2.1''.

[0059] 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 and silver. The signal electrodes 3.2, 3.2', 3.2'' and the ground electrodes 3.3, 3.3', 3.3'' are placed on the sides and end faces of the measuring elements 3.1, 3.1', 3.1''. The placement 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 carried out by chemical vapor deposition, physical vapor deposition, or the like. Preferably, the signal electrodes 3.2, 3.2', 3.2'' and the ground electrodes 3.3, 3.3', 3.3'' have a thickness of 200 nm or less.

[0060] Preferably, the signal electrodes 3.2, 3.2', and 3.2'' consist of a first signal electrode 3.2, a second signal electrode 3.2', and a third signal electrode 3.2''. Furthermore, the ground electrodes 3.3, 3.3', and 3.3'' preferably consist of a first ground electrode 3.3, a second ground electrode 3.3', and a third ground electrode 3.3''.

[0061] The first signal electrode 3.2 is deposited in a specific region on the radially inner side surface of the first measuring element 3.1, and extracts charge from this radially inner side surface. Furthermore, the first signal electrode 3.2 is deposited in a specific region on the axially inner end face of the first measuring element 3.1. The first ground electrode 3.3 is deposited in a specific region on the radially outer side surface of the first measuring element 3.1, and extracts charge from this radially outer side surface. Furthermore, the first ground electrode 3.3 is positioned in a specific region on the axially outer end face of the first measuring element 3.1.

[0062] The second signal electrode 3.2' is positioned within a specific region on the radially inner side surface of the second measuring element 3.1', and extracts charge from this radially inner side surface. Furthermore, the second signal electrode 3.2' is positioned within a specific region on the axially inner end face of the second measuring element 3.1'. The second ground electrode 3.3' is positioned within a specific region on the radially outer side surface of the second measuring element 3.1', and extracts charge from this radially outer side surface. Furthermore, the second ground electrode 3.3' is positioned within a specific region on the radially outer side surface of the second measuring element 3.1', and extracts charge from this radially outer side surface. Furthermore, the second ground electrode 3.3' is positioned within a specific region on the axially outer end face of the second measuring element 3.1'.

[0063] The third signal electrode 3.2'' is positioned within a specific region on the radially inner side surface of the third measuring element 3.1'', and extracts charge from this radially inner side surface. Furthermore, the third signal electrode 3.2'' is positioned within a specific region on the axially inner end face of the third measuring element 3.1''. The third ground electrode 3.3'' is positioned within a specific region on the radially outer side surface of the third measuring element 3.1'', and extracts charge from this radially outer side surface. Furthermore, the third ground electrode 3.3'' is positioned within a specific region on the axially outer end face of the third measuring element 3.1''.

[0064] The measurement signal S is provided by the charges extracted by signal electrodes 3.2, 3.2', and 3.2''. The mass signal MS is provided by the charges extracted by mass electrodes 3.3, 3.3', and 3.3''.

[0065] [Transmission Unit 4] The piezoelectric high-pressure sensor 10 has at least one transmission unit 4. The transmission unit 4 functions to transmit the charge extracted by at least one signal electrode 3.2, 3.2', 3.2'' as a measurement signal S.

[0066] The transmission unit 4 is made of a conductive material such as high-alloy stainless steel. The transmission unit 4 has a cylindrical charge collector 4.1 and a rod-shaped charge transfer device 4.2. The charge collector 4.1 and the charge transfer device 4.2 may be manufactured as a single unit or from multiple parts. If manufactured from multiple parts, they may be connected to each other electrically and mechanically by any type of mechanical connection such as material bonding, mold fitting, or force fitting.

[0067] The transmission unit 4 extends along the vertical axis Z in the longitudinal cross-section shown in Figure 1. Preferably, the transmission unit 4 extends along the vertical axis Z. The charge collector 4.1 of the transmission unit 4 is directed toward the diaphragm 2, while the charge transmission device 4.2 is directed outward from the diaphragm 2.

[0068] The charge collector 4.1 is in direct planar 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 planar contact with all three signal electrodes 3.2, 3.2', 3.2''. The direct planar contact is configured so that the charge extracted by the three signal electrodes 3.2, 3.2', 3.2'' flows to the charge collector 4.1. Thus, the charge collector 4.1 collects charge from the three signal electrodes 3.2, 3.2', 3.2'' to form a measurement signal S. The charge collector 4.2 transmits the measurement signal S.

[0069] [Preloading Unit 5] The piezoelectric high-pressure sensor 10 has at least one preloading unit 5. The preloading unit 5 functions to mechanically preload the measuring unit 3 to the transmission unit 4. Furthermore, the preloading unit 5 functions to extend the local pressure peak within the diaphragm 2 and reduce the differences in the thermal expansion coefficients of the housing 1 and the diaphragm 2 as well as the piezoelectric material of the measuring unit 3. Finally, the preloading unit 5 functions to transmit the charge extracted by at least one grounding electrode 3.3, 3.3', 3.3'' as a grounding signal MS.

[0070] The preloading unit 5 is made of a mechanically resistant material. Preferably, the material for the preloading unit 5 is high-alloy stainless steel.

[0071] In the longitudinal cross-section shown in Figure 1, the preloading unit 5 extends along the vertical axis Z. Preferably, the preloading unit 5 includes a trapezoidal compensating element 5.1, a hollow cylindrical preloading sleeve 5.2, and a hollow cylindrical preloading body 5.3.

[0072] The measured pressure P may have a local pressure peak, which is considerably higher than the pressure P and locally limited in its impact on the impact surface A2 of the diaphragm 2. Due to the small thickness of the diaphragm 2, and also in the case that the diaphragm may undesirably exceed the 0.2% compression limit of the measuring unit 3, a compensating element 5.1 is positioned between the diaphragm 2 and the measuring unit 3 along the longitudinal axis Z to prevent unhindered transmission of the pressure peak from the diaphragm 2 to the measuring unit 3. The compensating element 5.1 is in direct planar contact with the central surface A2' of the diaphragm 2 by the end facing the diaphragm 2. Thus, the pressure peak is transmitted into the compensating element 5.1 and transmitted to the measuring unit 3 over the length of the compensating element 5.1. In this way, the pressure peak is spread to a harmless size.

[0073] The piezoelectric high-pressure sensor 10 is configured for use at temperatures up to 200°C. At such high temperatures, differences in the thermal expansion coefficients of the materials of the housing 1 and diaphragm 2 and the piezoelectric material of the measuring unit 3 can lead to thermal stress, which may result in undesirable damage to the piezoelectric high-pressure sensor 10. To reduce this thermal stress, the compensation element 5.1 has a thermal expansion coefficient that is lower than that of the materials of the housing 1 and diaphragm 2 and lower than that of the piezoelectric material of the measuring unit 3.

[0074] Preferably, the compensation element 5.1 is in direct planar contact with at least one grounding electrode 3.3, 3.3', 3.3'' by an end facing the measuring unit 3. Preferably, the grounding electrodes 3.3, 3.3', 3.3'' consist of a first grounding electrode 3.3, a second grounding electrode 3.3', and a third grounding electrode 3.3'', and the compensation element 5.1 is in direct planar contact with all three grounding electrodes 3.3, 3.3', 3.3''. The direct planar contact is designed to transfer the charge extracted from the three grounding electrodes 3.3, 3.3', 3.3'' to the compensation element 5.1. Thus, the compensation element 5.1 collects the charge from the three grounding electrodes 3.3, 3.3', 3.3'' to form a grounding signal MS. Since the compensation element 5.1 is electrically connected to the diaphragm 2, and the diaphragm 2 itself is electrically connected to the shell 1.1, the grounding signal MS is transmitted accordingly.

[0075] Preferably, the compensation element 5.1 and the preloading sleeve 6.2 are manufactured as a single unit. However, they may also be manufactured from multiple parts that are mechanically connected to each other by bonding of materials.

[0076] The preloading sleeve 5.2 surrounds the measuring unit 3, spaced radially away from the vertical axis Z. The charge collectors 4.1 of the measuring unit 3 and the transmission unit 4 are positioned along the vertical axis Z between the compensation element 5.1 and the preloading body 5.3.

[0077] The end facing the preloading body 5.3 connects the preloading sleeve 5.2 to the preloading body 5.3 and the first shell portion 1.3 by a preloading sleeve connection 5.4 made of materials. Preferably, the preloading sleeve connection 5.4 made of materials is an annular welded connection that extends 360° around the entire circumference of the end of the preloading sleeve 5.2.

[0078] The preloading sleeve connection 5.4, formed by the bonding of materials, is generated under a preloading force on the charge collector 4.1 along the vertical axis Z of the measuring unit 3. The preloading force seals the micropores within the piezoelectric material of the measuring unit 3 and within the material of the charge collector 4.1 with the materials of the signal electrodes 3.2, 3.2', and 3.2''. This prevents charge from being retained within the micropores and building capacitance. Such retention of charge within the micropores leads to inaccurate measurement of pressure P, on the one hand, because not all charge is extracted and transferred during its generation time, and on the other hand, because capacitance is discharged over time, thereby causing charge to be extracted and transferred more or less over a longer period after its generation.

[0079] [Insulation element 6] The piezoelectric high-pressure sensor 10 has at least one insulating element 6. The insulating element 6 functions to electrically isolate the transmission unit 4 from the preloading unit 5.

[0080] The insulating element 6 is made of an electrically insulating and mechanically rigid material such as ceramic, Al2O3 ceramic, or sapphire.

[0081] The insulating element 6 has a hollow cylindrical shape. The insulating element 6 is positioned radially between the transmission unit 4 and the preloading unit 5.

[0082] The insulating element 6 surrounds the transmission unit 4 in the radial direction. The insulating element 6 is positioned on the side surface of the charge collector 4.1 facing outward from the measuring unit 3. The insulating element 6 is in direct planar contact with the charge collector 4.1.

[0083] The insulating element 6 is radially surrounded by the preloading unit 6. Preferably, the insulating element 6 is in direct planar contact with the preloading body 5.3 and the preloading sleeve 5.2. [Explanation of Symbols]

[0084] 0 Measurement location 1 Housing 1.1 Shell 1.2 Cavity 1.3 First shell section 1.4 Second shell section 1.5 Mounting Methods 1.6 Shell connection by bonding between materials 2 diaphragms 2.1 Central area 2.2 Peripheral Area 2.3 Sealing surface 2.4 Diaphragm connection by bonding between materials 3. Measurement Unit 3.1, 3.1', 3.1'' Measurement elements 3.2, 3.2', 3.2'' signal electrodes 3.3, 3.3', 3.3'' ground electrode 4 transmission units 4.1 Charge Collector 4.2 Charge Transfer Device 5 Preloading Units 5.1 Compensation Factors 5.2 Preloading Sleeves 5.3 Preloading Unit 5.4 Preloading sleeve connection by bonding between materials 6. Insulating elements 10. Piezoelectric high-pressure sensor AA section line A1 End face of the first shell portion A2 Impact surface of the diaphragm A2' Central surface of the diaphragm A2'' Peripheral surface of the diaphragm A3 Cross-sectional area of ​​the measurement element D1 Outer diameter of the housing D2 Diaphragm outer diameter D3 Diameter of the impact surface of the diaphragm L3 Length of the measurement element MS ground signal P pressure S measurement signal Thickness of the central region of T2 Thickness of the peripheral region T2' X horizontal axis XY horizontal plane Y-axis (longitudinal direction) Z vertical axis

Claims

1. A piezoelectric high-pressure sensor (10) for measuring pressure (P) up to 10 kbar (1000 MPa), comprising a housing (1), a diaphragm (2), and a measuring unit (3), wherein the housing (1) is hollow cylindrical in shape and has a shell (1.1) and a cavity (1.2), the shell (1.1) is formed to include at least one mounting means (1.5), the piezoelectric high-pressure sensor (10) is mountable to a measurement location (0) by the mounting means (1.5), and the measuring unit (3) is disposed within the cavity (1.2). A piezoelectric high-pressure sensor comprising at least one measuring element (3.1, 3.1', 3.1'') made of piezoelectric material, wherein the diaphragm (2) is disc-shaped and has a central region (2.1) and a peripheral region (2,2), the diaphragm (2) is configured to receive the pressure (P) to be measured by the central region (2.1) and to transmit the pressure along the vertical axis (Z) to the measuring unit (3), and the diaphragm (2) is connected to the shell (1.1) by the peripheral region (2.2) through a bonding between materials, The measuring elements (3.1, 3.1', 3.1'') are rod-shaped and function according to the piezoelectric transverse effect; the measuring elements (3.1, 3.1', 3.1'') have a length (L3) along the vertical axis (Z) and a cross-sectional area (A3) perpendicular to the vertical axis (Z); and the ratio of the length (L3) to the cross-sectional area (A3) is 1.0 mm. －１ Based on the above, 1.5 mm －１ A piezoelectric high-pressure sensor characterized by being within the following range, and the shell (1.1) having a diameter (D1) of 10 mm or less.

2. The piezoelectric high-pressure sensor (10) according to claim 1, characterized in that the measuring elements (3.1, 3.1', 3.1'') have a length (L3) of 3.0 mm or less, preferably 2.4 mm or less.

3. The measurement elements (3.1, 3.1', 3.1'') are 1.5 mm ２ Above, 2.5 mm ２ The cross-sectional area (A3) must be within the following range, and the total cross-sectional area (A3) of the three measuring elements (3.1, 3.1', 3.1'') must be 4.5 mm². ２ The above is 7.5 mm. ２ A piezoelectric high-pressure sensor (10) according to claim 1 or 2, characterized in that it is within the following range.

4. The piezoelectric high-pressure sensor (10) according to any one of claims 1 to 3, characterized in that the measurement unit (3) has exactly three measurement elements (3.1, 3.1', 3.1'').

5. The piezoelectric material of the measurement elements (3.1, 3.1', 3.1'') is SiO ２ Or GaPO ４ It is a single crystal, and SiO ２ The piezoelectric material of has an elastic coefficient of 87 kN / mm along the longitudinal axis (Z), or the piezoelectric material of GaPO ２ has an elastic coefficient of 67 kN / mm along the longitudinal axis (Z), characterized in that the piezoelectric high-pressure sensor (10) according to any one of claims 1 to 4. ４ The piezoelectric material of has an elastic coefficient of 67 kN / mm along the longitudinal axis (Z), ２ has an elastic coefficient of 67 kN / mm along the longitudinal axis (Z), characterized in that the piezoelectric high-pressure sensor (10) according to any one of claims 1 to 4.

6. The aforementioned shell (1.1) has a capacity of 200 kN / mm ２ Made from a mechanically resistant material with a higher modulus of elasticity. SiO ２ The elastic modulus of the piezoelectric material is less than half the elastic modulus of the material of the shell (1.1), or GaPO ４ The elastic modulus of the piezoelectric material manufactured is less than 1 / 3 of the elastic modulus of the material of the shell (1.1), and The piezoelectric high-pressure sensor (10) according to claim 5, characterized in that, under the influence of the pressure (P), the piezoelectric material of the measuring element (3.1, 3.1', 3.1'') is compressed more strongly along the vertical axis (Z) than the material of the shell (1.1) according to the aforementioned value.

7. The central region (2.1) causes the diaphragm to be indirectly in planar contact with the measuring elements (3.1, 3.1', 3.1''), The compression of the piezoelectric material in the measurement elements (3.1, 3.1', 3.1'') causes tensile and compressive stress within the central region (2.1). The central region (2.1) has a thickness (T2) of 0.5 mm or less, and The piezoelectric high-pressure sensor (10) according to claim 6, characterized in that, due to the length (L3) of the measuring element (3.1, 3.1', 3.1''), which is 3.0 mm or less, preferably 2.4 mm or less, the tensile and compressive stresses at pressures (P) up to 10 kbar (1000 MPa) are at a level that is harmless to the mechanical stability of the central region (2.1).

8. The piezoelectric high-pressure sensor (10) according to any one of claims 1 to 7, characterized in that the piezoelectric high-pressure sensor (10) can be mounted within the mounting means (1.5) which is manufactured to harmonize with and be positioned at the measurement location (0), the mounting means (1.5) and the mounting bore form an M10 screw connection, and the M10 screw connection has a tightening torque of 20 Nm or less in the mounted state and holds the piezoelectric high-pressure sensor (10) within the mounting bore with a holding force of 20 kN or less.

9. The diaphragm (2) has an impact surface (A2), and the impact surface (A2) extends perpendicular to the vertical axis (Z). The impact surface (A2) is positioned on the surface of the diaphragm (2) facing away from the cavity (1.2), and the pressure (P) to be measured is directly acting on the impact surface (A2) by the applied force, and The piezoelectric high-pressure sensor (10) according to claim 8, characterized in that the dimensions of the impact surface (A2) are such that the combination of the holding force and the impact force does not lead to harmful stress peaks resulting in plastic deformation or breakage within the material of the piezoelectric high-pressure sensor (10).

10. For a pressure (P) of 10 kbar (1000 MPa), the size of the impact surface (A2) is 20 mm ２ The piezoelectric high-pressure sensor (10) according to claim 9, characterized in that it is as follows.

11. The piezoelectric material of the measurement elements (3.1, 3.1', 3.1'') is a single crystal, and the piezoelectric coefficient d for the piezoelectric transverse effect is １２ The fact that the piezoelectric high-pressure sensor (10) has the piezoelectric coefficient d of the piezoelectric material of the measuring element (3.1, 3.1', 3.1'') is such that the sensitivity of the piezoelectric high-pressure sensor (10) is such that the piezoelectric coefficient d of the piezoelectric material of the measuring element (3.1, 3.1', 3.1'') is such that １２ A piezoelectric high-pressure sensor (10) according to any one of claims 1 to 10, characterized in that it is proportional to the product of the ratio of the length (L) of the measuring element (3.1, 3.1', 3.1'') to the cross-sectional area (A3).

12. The piezoelectric material of the measurement elements (3.1, 3.1', 3.1'') is SiO ２ In that case, the piezoelectric coefficient is d １２ = 2.3 pC / N, or GaPO is used as the piezoelectric material for the measurement elements (3.1, 3.1', 3.1''). ４ In that case, the piezoelectric coefficient is d １２ = 4.5 pC / N, and, The ratio of the length (L3) to the cross-sectional area (A3) of the measurement elements (3.1, 3.1', 3.1'') is 1.0 mm. －１ Above, 1.5 mm －１ The piezoelectric high-pressure sensor (10) according to claim 11, characterized in that the sensitivity of the piezoelectric high-pressure sensor (10) is 1.0 pC / bar or more when it is within the following range.

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