CN111928991B - Integrated micro pore pressure sensor - Google Patents
Integrated micro pore pressure sensor Download PDFInfo
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- CN111928991B CN111928991B CN202010946348.5A CN202010946348A CN111928991B CN 111928991 B CN111928991 B CN 111928991B CN 202010946348 A CN202010946348 A CN 202010946348A CN 111928991 B CN111928991 B CN 111928991B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
- G01L9/02—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning
- G01L9/06—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning of piezo-resistive devices
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L19/00—Details of, or accessories for, apparatus for measuring steady or quasi-steady pressure of a fluent medium insofar as such details or accessories are not special to particular types of pressure gauges
- G01L19/14—Housings
- G01L19/148—Details about the circuit board integration, e.g. integrated with the diaphragm surface or encapsulation
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Abstract
本发明公开了一体式微型孔压传感器。该传感器中：主壳体内沿轴线方向依次设置有过滤器安装槽口、感应元件安装槽、通气管道，多孔过滤器安装在过滤器安装槽内，感应元件安装在感应元件安装槽内，感应元件尾端的传感器线缆通过通气管道伸出主壳体外与通气线缆连接；感应元件包括环形封装壳体、压阻式芯体、定位板、传感器线缆，定位板和环形封装壳体构成凹型芯体安装槽，压阻式芯体设置在定位板上；凹型芯体安装槽内填充和涂抹设置有无应力胶；感应元件安装槽和通气管道相接的地方构成用于对感应元件进行轴向定位的台阶面；感应元件通过粘结剂与感应元件安装槽固连。该微型孔压传感器可适用于土工离心试验，且故障率低、稳定性高、抗干扰性能强。
The present invention discloses an integrated micro-pore pressure sensor. In the sensor: a filter installation slot, a sensing element installation slot, and a ventilation duct are sequentially arranged in the main shell along the axial direction, a porous filter is installed in the filter installation slot, a sensing element is installed in the sensing element installation slot, and a sensor cable at the tail end of the sensing element extends out of the main shell through the ventilation duct to connect with the ventilation cable; the sensing element includes an annular packaging shell, a piezoresistive core, a positioning plate, and a sensor cable, the positioning plate and the annular packaging shell constitute a concave core installation slot, and the piezoresistive core is arranged on the positioning plate; the concave core installation slot is filled and smeared with stress-free glue; the place where the sensing element installation slot and the ventilation duct meet constitutes a step surface for axial positioning of the sensing element; the sensing element is fixedly connected to the sensing element installation slot by an adhesive. The micro-pore pressure sensor can be applied to geotechnical centrifuge tests, and has a low failure rate, high stability, and strong anti-interference performance.
Description
Technical Field
The invention relates to the technical field of geotechnical test sensors, in particular to an integrated micro pore pressure sensor.
Background
And (3) the geotechnical centrifugal test is to compensate the stress loss of soil or rock structures at each position of the centrifugal model by means of a geotechnical centrifugal machine, so that the stress level is similar to or equal to that of the prototype. When an over-compression dynamic load is applied, the actual prototype dynamic characteristics and failure mechanism can be presented more accurately.
Pore water pressure is generally the water pressure of saturated soil when the pore medium is filled with water, and is a positive pressure above atmospheric pressure. The pore water pressure is divided into hydrostatic pore water pressure and hyperstatic pore water pressure.
The static pore water pressure is caused by the dead weight of the groundwater in the foundation soil, namely, the pore water pressure below the static groundwater is the static pore water pressure.
Hyperstatic pore water pressure-under the action of dynamic loads such as earthquake waves, blasting, traffic loads and the like, the part of pore water pressure exceeding the hydrostatic pore water pressure is called hyperstatic pore water pressure.
The pore pressure sensor is a key measuring sensor for monitoring the increase and dissipation of hyperstatic pore water pressure in saturated/unsaturated soil, and can directly reflect the soil stress state and stability of geotechnical engineering physical models, geotechnical structures, construction site foundations and the like.
The integrated pore pressure sensor has one main casing, and the porous filter in the front end of the casing is not detachable.
The porous filter is used for separating soil particles from pore fluid, so that the pore fluid can freely enter and exit the sensor to act on the sensor sensing element, and further the pressure of the pore fluid is changed.
In the field of geotechnical earthquake engineering, accurate measurement of pore water pressure is an important research direction of engineering experiments, and can directly reflect soil softening and liquefying catastrophe processes in site foundations, geotechnical structures and geotechnical model experiments. Because special structures such as a porous filter and a ventilation cable of the integrated miniature pore pressure sensor have great differences with the conventional pressure sensor, the test accuracy of the integrated miniature pore pressure sensor is commonly influenced by a plurality of factors. More critical is, different from the conventional vibration table and the on-site in-situ test, the geotechnical centrifugal test is to compensate the stress loss of the soil body under the environment of N times of high centrifugal acceleration, and when the super-compression dynamic load (the frequency is tens to hundreds of Hz and the load duration is less than 1 s) is applied, the super-static pore water pressure in the soil body completes the rapid growth process along with the vibration acceleration in the moment, and the geotechnical centrifugal test usually requires the integral micro pore pressure sensor to have the characteristics of high frequency response, good stability, low failure rate, strong anti-interference capability and the like so as to ensure the accuracy and reliability of the test result of the geotechnical centrifugal test, and further illustrates the importance of the integral micro pore pressure sensor with excellent performance on the geotechnical test.
Before 2010, an international standard pore water pressure sensor PDCR-81 is a high-precision, high-frequency response and high-stability integrated miniature pore pressure sensor widely used in domestic and foreign geotechnical centrifugal tests, and is considered as a standard pore water pressure sensor in the geotechnical centrifugal test. However, because the sales amount of the PDCR-81 is smaller than that of other types of sensors of the Druck company, the global geotechnical test unit loses the main source of the high-precision and high-frequency response integrated pore pressure sensor since the Drauck company announces that the PDCR-81 integrated micro pore pressure sensor is out of production in 2010. As the inventory of PDCR-81 integrated pore pressure sensors of each geotechnical engineering research unit has been depleted, the need for developing alternative PDCR-81 integrated pore pressure sensors has increased over the past 10 years.
In recent years, the integrated pore pressure sensor developed by various domestic manufacturers has the problems of low frequency response performance, low measurement precision, high fault rate, poor stability, poor anti-interference performance and the like due to the defects of self structural design, packaging, waterproof structure and the like, and is not suitable for the pore water pressure measurement requirement of the high-frequency response and high-precision geotechnical centrifugation test, while the integrated sensor newly developed by foreign manufacturers has higher frequency response performance and measurement precision, but has more problems in the aspects of fault rate, anti-interference performance and waterproof performance.
Specifically, the integrated micro air pressure sensor in the prior art has the following disadvantages:
(1) In the sense element packaging mode
In the prior art, the internal sensing elements of the HC-25 integrated pore pressure sensor are all arranged on the circular glass ring in the shell, so that the stress effect on two sides of the sensor can be effectively reduced, but materials such as fine soil particles are doped in pore fluid, the sensing elements of the sensor are directly contacted with the measured pore fluid, irreversible damage and destruction of the sensing elements are easily caused, and the sensor is one of the main factors of high failure rate of the sensor in the prior art. The KYB integrated pore pressure sensor is formed by reforming a soil pressure sensor, a strain sensing film is packaged on the inner side of a pressure sensing surface of a shell by using an adhesive, and the pore fluid pressure is measured by deformation and deflection of the strain sensing film, but the response speed of the strain sensing film is smaller than that of an HC-25 type sensor, and the strain sensing film cannot adapt to and meet the measurement requirement of a geotechnical centrifugal test.
(2) In terms of porous filter mounting means
In the prior art, HC-25, KYB type and other integrated micro pore pressure sensors, the porous filters at the front ends of the sensors are directly fixed through adhesives, and when the integrated micro pore pressure sensors in the prior art are in saturated fluid monitoring environments such as geotechnical centrifugal tests, geotechnical structures, site foundations and the like for a long time, the porous filters of the sensors are easy to fall off, so that the sensors are caused to break down.
(3) In the aspect of waterproof sealing mode of the sensor
The waterproof structure at the tail of the HC-25 and KYB integrated miniature pore pressure sensor in the prior art is mainly used for being connected with a ventilation cable and playing a role in waterproof sealing of the cable. However, according to a large number of experimental results, although the waterproof structure can play a certain sealing effect, the waterproof structure is found in saturated fluid under a high centrifugal acceleration environment for a long time, a large amount of water vapor is easy to accumulate in the ventilation cable of the sensor, so that the accuracy and reliability of the measurement pore pressure data result of the integrated miniature pore pressure sensor are affected, and the ventilation cable is blocked directly by the water vapor more seriously, so that the integrated pore pressure sensor cannot work normally.
(4) Sensor cavity-free structural design
In the prior art, the traditional domestic sensors such as HC-25 and KYB integrated micro pore pressure sensors and the like do not consider the structural design of a sensor cavity (the cavity refers to a cavity gap between a porous filter and a sensing element), so that impurities such as tiny soil particles of pore fluid in a soil body enter the sensor from the porous filter, the bridge between the porous filter and the sensing element can be directly caused, stress concentration of the sensing element is further caused, sensor test data are larger, and irreversible damage to the sensing element is more serious.
Therefore, the novel structure integrated miniature pore pressure sensor is urgently required to be developed, can be suitable for high-frequency response and high-precision geotechnical centrifugation tests, has low failure rate, high stability and strong anti-interference performance, and has important practical significance for solving the related technical problem of neck clamping.
Disclosure of Invention
In view of the above, the present invention aims to provide an integrated micro pore pressure sensor with a novel structure and excellent performance, which is applicable to high-frequency response and high-precision geotechnical centrifugation tests, and has the advantages of low failure rate, high stability and strong anti-interference performance.
In order to achieve the above purpose, the present invention provides the following technical solutions:
An integrated micro bore pressure sensor comprising a porous filter, a sensing element, a main housing and a venting cable, wherein:
The main shell is internally provided with a filter mounting notch, an induction element mounting groove and an air duct in sequence along the axis direction, the porous filter is mounted in the filter mounting groove, the induction element is mounted in the induction element mounting groove, and a sensor cable at the tail end of the induction element extends out of the main shell through the air duct so as to be connected with the air duct;
The sensor comprises an annular packaging shell, a piezoresistive core body, a positioning plate and a sensor cable, wherein the positioning plate is fixedly arranged at one end of the annular packaging shell so as to form a concave core body mounting groove in the annular packaging shell, the piezoresistive core body is positioned in the concave core body mounting groove and arranged on the side surface of the positioning plate, the sensor cable is connected with the piezoresistive core body and penetrates through the positioning plate to extend into the ventilation pipeline, and the positioning plate is provided with a communication hole;
The concave core body mounting groove is filled and smeared with stress-free glue;
the joint of the induction element mounting groove and the ventilation pipeline forms a step surface for axially positioning the induction element;
The side surface of the positioning plate, which is far away from the annular packaging shell, is fixedly connected with the step surface through an adhesive, and/or the outer wall of the annular packaging shell is fixedly connected with the induction element mounting groove through an adhesive.
Optionally, in the integrated micro pore pressure sensor, the through hole in the sensing element mounting groove is a first step hole, and in the first step hole:
the hole section close to the multi-cavity filter is a first hole section matched with the annular packaging shell;
The hole section close to the ventilation pipeline is a second hole section matched with the positioning plate;
the aperture of the first hole section is smaller than the aperture of the second hole section.
Optionally, in the integrated micro pore pressure sensor, a spacer groove is provided between the filter mounting notch and the sensing element mounting groove, wherein:
The aperture of the spacing groove is smaller than the diameter of the end part of the porous filter so as to axially limit the porous filter;
the annular inner wall surface of the spacing groove, the porous filter positioned on two sides of the spacing groove and the induction element form a cavity structure with the thickness of 0.1mm to 0.5 mm.
Optionally, in the integrated micro pore pressure sensor, the aperture of the spacing groove is smaller than the aperture of the first pore section.
Optionally, in the integrated micro pore pressure sensor, an end opening (040) matched with the shape of the porous filter, a sealing ring positioning groove matched with a positioning sealing ring and a filter glue sealing groove for filling sealing grease are sequentially arranged in the filter mounting notch along the axis direction.
Optionally, in the integrated micro pore pressure sensor, the aperture of the end opening (040) is D1, the aperture of the seal ring positioning groove is D2, and the aperture of the filter seal groove is D3, and D2> D3> D1.
Optionally, in the integrated micro pore pressure sensor, one end of the porous filter is a cylindrical side wall structure, the other end of the porous filter is a conical side wall structure, the positioning sealing ring is adapted to the cylindrical side wall structure, and the conical side wall structure is located in the filter sealing groove.
Optionally, in the integrated micro pore pressure sensor, a barb tower head structure for connecting the ventilation cable is arranged on the main casing, a through hole communicated with the ventilation pipeline is arranged in the barb tower head structure, and barb steps are arranged on the outer side of the barb tower head structure.
Optionally, in the integrated micro pore pressure sensor, a sealing groove for filling sealing grease is formed in an end portion of the main casing, which is used for connecting the ventilation cable, and the barb pagoda head structure connecting end is located at the bottom of the sealing groove.
Optionally, in the integrated micro pore pressure sensor, the through hole in the ventilation pipeline is a second stepped hole, in the second stepped hole, a hole section adjacent to the sensing element mounting groove is a third hole section, a hole section connected with the barb pagoda head structure is a fourth hole section, and the aperture of the third hole section is larger than that of the fourth hole section.
According to the technical scheme, in the integrated micro pore pressure sensor provided by the invention, the sensor chip level packaging is realized through the stress-free glue and the adhesive, the device level packaging is realized through the main shell, and the electromagnetic shielding, the electric insulation, the side stress isolation, the thermal isolation and the like of the induction element in the sensor are realized through the whole sensor. The annular packaging shell can protect the piezoresistive core body from the stress on two sides of the sensor to the greatest extent, ensure the piezoresistive core body to work normally, and the stress-free adhesive can directly avoid the direct contact between the sensing element and the pore fluid, thereby effectively preventing impurities such as fine particles in the saturated fluid from damaging the sensing element and greatly reducing the failure rate of the sensor. Therefore, the integrated micro pore pressure sensor provided by the invention has higher long-term stability and anti-interference performance, and can be suitable for high-frequency response and high-precision geotechnical centrifugation tests.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is an isometric view of a first exploded construction of an integrated micro-scale pore pressure sensor according to an embodiment of the present invention;
FIG. 2 is an isometric view of a second split structure of an integrated micro-pore pressure sensor according to an embodiment of the present invention;
FIG. 3 is an isometric view of a first integral structure of an integrated micro-pore pressure sensor according to an embodiment of the present invention;
FIG. 4 is an isometric view of a second integral structure of an integrated micro-pore pressure sensor according to an embodiment of the present invention;
FIG. 5 is a front view of an integrated micro-pore pressure sensor according to an embodiment of the present invention;
FIG. 6 is a cross-sectional view of an integrated micro-pore pressure sensor provided by an embodiment of the present invention;
FIG. 7 is an isometric view of a porous filter provided in an embodiment of the present invention;
FIG. 8 is a side view of a porous filter provided in an embodiment of the present invention;
FIG. 9 is a schematic structural diagram of a seal ring according to an embodiment of the present invention;
FIG. 10 is a first isometric view of an inductive element according to an embodiment of the present invention;
FIG. 11 is a second isometric view of an inductive element according to an embodiment of the present invention;
FIG. 12 is a first perspective isometric view of a main housing provided with a barbed pagoda head structure provided in an embodiment of the present invention;
FIG. 13 is a second perspective isometric view of a main housing provided with a barbed pagoda head structure provided in an embodiment of the present invention;
FIG. 14 is a cross-sectional view of a main housing provided with a barbed pagoda head structure provided in an embodiment of the present invention;
Fig. 15 is a schematic structural diagram of a ventilation cable according to an embodiment of the present invention.
Wherein:
01-porous filter, 02-positioning sealing ring, 03-sensing element, 04-stainless steel main shell,
05-Barb pagoda head structure, 06-ventilation cable;
011-side face of the porous filter, 012-trapezoidal end face of the porous filter;
031-annular package housing, 032-piezoresistive core, 033-concave core mounting groove,
034-Positioning plate, 035-sensor cable, 036-vent;
040-end opening, 041-sealing ring positioning groove, 042-filter sealing groove,
043-Sensor cavity structures, 044-sensing element mounting slots, 045-vent tubing,
046-Sealing grooves;
051-barb steps.
Detailed Description
The invention discloses an integrated micro-pore pressure sensor with a novel structure and excellent performance, which is applicable to high-frequency response and high-precision geotechnical centrifugal tests, and has the advantages of low failure rate, high stability and strong anti-interference performance.
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1 to 15, fig. 1 is an isometric view of a first exploded structure of an integrated micro-pore pressure sensor according to an embodiment of the present invention; fig. 2 is an isometric view of a second exploded structure of an integrated micro-pore pressure sensor provided by an embodiment of the present invention, fig. 3 is an isometric view of a first integrated structure of an integrated micro-pore pressure sensor provided by an embodiment of the present invention, fig. 4 is an isometric view of a second integrated structure of an integrated micro-pore pressure sensor provided by an embodiment of the present invention, fig. 5 is a front view of an integrated micro-pore pressure sensor provided by an embodiment of the present invention, fig. 6 is a cross-sectional view of an integrated micro-pore pressure sensor provided by an embodiment of the present invention, fig. 7 is an isometric view of a porous filter provided by an embodiment of the present invention, fig. 8 is a side view of a porous filter provided by an embodiment of the present invention, fig. 9 is a schematic view of a structure of a seal ring provided by an embodiment of the present invention, fig. 10 is a first isometric view of an inductive element provided by an embodiment of the present invention, fig. 11 is a second isometric view of an inductive element provided by an embodiment of the present invention, fig. 12 is a first isometric view of a main housing provided with a barb structure of a main head provided by an embodiment of the present invention, fig. 6 is a cross-sectional view of a main housing provided by a barb of the present invention, fig. 13 is a perspective view of a main housing provided by a barb of the present invention, fig. 14 is provided by a main cable is provided by a perspective view of a main housing provided by a barb of the present invention provided by a main embodiment of the present invention.
The embodiment of the invention provides an integrated micro pore pressure sensor (also called an integrated micro pore pressure sensor or simply called a sensor) with a novel structure and excellent performance. The integrated micro pore pressure sensor comprises a porous filter 01, a sensing element 03, a main shell 04 and a ventilation cable 06, and further comprises a positioning sealing ring 02 and a barb pagoda head structure 05.
Specifically, in the integrated micro pore pressure sensor, a filter mounting notch, a sensing element mounting groove 044 and an air duct 045 are sequentially provided in the main housing 04 along the axial direction, the porous filter 01 is mounted in the filter mounting groove, the sensing element 03 is mounted in the sensing element mounting groove 044, and a sensor cable 035 at the tail end of the sensing element 03 extends out of the main housing 04 through the air duct 045 to be connected with the air cable 06.
Specifically, in the integrated micro pore pressure sensor, the sensing element 03 includes an annular packaging housing 031, a piezoresistive core 032, a positioning plate 034 and a sensor cable 035, wherein the positioning plate 034 is fixedly arranged at one end of the annular packaging housing 031 so as to form a concave core mounting groove 033 in the annular packaging housing 031, the piezoresistive core 032 is positioned in the concave core mounting groove 033 and is arranged on the side surface of the positioning plate 034, the sensor cable 035 is connected with the piezoresistive core 032 and extends into the ventilation pipe 045 through the positioning plate 034, and the positioning plate 034 is provided with a communication hole 036.
Wherein:
the annular packaging shell 031 is used for protecting the piezoresistive core 032 from the stress on two sides of the sensor, so as to ensure that the piezoresistive core 032 can work normally;
The piezoresistive core 032 is mainly used for sensing the pressure value of pore fluid in the saturated/unsaturated soil body to be measured, and forming a Wheatstone bridge circuit by arranging four equivalent diffused silicon resistors, so that the pressure value of the pore fluid is converted into a voltage variation and output;
The front surface of the concave core body mounting groove 033 is windowed, and the inside is filled and smeared with non-stress glue which is used as an edge isolation protection layer of the piezoresistive core body 032 so as to prevent impurities such as tiny soil particles in pore fluid in the soil body from directly acting on the piezoresistive core body 032 to cause irreversible damage to the piezoresistive core body 032;
the sensing element mounting groove 044 is used for mounting and positioning the sensing element 03 to prevent the sensing element 03 from changing in position, wherein a step surface 0441 for axially positioning the sensing element 03 is formed at the joint of the sensing element mounting groove 044 and the ventilation pipeline 045;
The side surface of the positioning plate 034 far away from the annular packaging shell 031 is fixedly connected with the step surface 0441 through an adhesive to fix the sensing element 03, and/or the outer wall of the annular packaging shell 031 is fixedly connected with the sensing element mounting groove 044 through an adhesive to fix the sensing element 03;
The communicating hole 036 and the ventilation pipeline 045 mainly have the function of enabling the piezoresistive core 032 to communicate with the external atmospheric pressure, so that the sensor measures the external pressure variation by taking the atmospheric pressure as a reference, and the normal operation of the sensor is that the communicating hole 036 and the ventilation pipeline 045 cannot be blocked.
According to the technical scheme, in the integrated micro pore pressure sensor provided by the embodiment of the invention, the sensor chip level packaging is realized through the stress-free glue and the adhesive, the device level packaging is realized through the main shell 04, and the electromagnetic shielding, the electric insulation, the side stress isolation, the thermal isolation and other treatments are performed on the induction element 03 in the sensor. Moreover, the annular packaging shell 031 can protect the piezoresistive core 032 to the greatest extent from the stress on two sides of the sensor, ensure the piezoresistive core 032 to work normally, and the stress-free adhesive can directly avoid the direct contact between the sensing element 03 and the pore fluid, thereby effectively preventing the sensing element 03 from being damaged by impurities such as fine particles in the saturated fluid, and greatly reducing the failure rate of the sensor. Therefore, the integrated micro pore pressure sensor provided by the embodiment of the invention has higher long-term stability and anti-interference performance, and can be suitable for high-frequency response and high-precision geotechnical centrifugation tests.
Specifically, the main housing 04 is a stainless steel housing. The ventilation cable 06 is made of silica gel wires, has the characteristics of good pressure resistance, wear resistance, corrosion resistance and the like, is used for protecting the sensor cable 035, and can not be blocked in the sensor during operation. See in particular fig. 11 to 14.
Preferably, in the inductive element 03, the diameter of the annular enclosure 031 is smaller than the diameter of the positioning plate 034. Correspondingly, the through hole in the sensing element mounting groove 044 is a first stepped hole, wherein a hole section close to the multi-cavity filter 01 is a first hole section matched with the annular packaging shell 031, a hole section close to the ventilation pipeline 045 is a second hole section matched with the positioning plate 034, and the aperture of the first hole section is smaller than that of the second hole section.
Specifically, during production, the sensing element 03 is mounted in the sensing element mounting groove 044 by means of electron beam welding.
In order to further optimize the technical solution, in the integrated micro-pore pressure sensor, a spacing groove 043 is provided between the filter mounting notch and the sensing element mounting groove 044 in an inward protruding manner, and in particular, see fig. 6 and 14. Wherein:
the aperture of the spacing groove 043 is smaller than the diameter of the end part of the porous filter 01 so as to axially limit the porous filter 01;
The annular inner wall surface of the spacer 043 and the porous filter 01 and the sensing element 03 located at both sides of the spacer 043 constitute a cavity structure a having a thickness of 0.1mm to 0.5mm. Typically, the recess core mounting groove 033 is filled with an unstressed glue, that is, a cavity structure a of 0.1mm to 0.5mm thickness is maintained between the unstressed glue and the porous filter 01. That is, the gap distance between the porous filter and the sensing element is controlled to be within 0.5mm, preferably 0.1mm to 0.5mm.
In the use process, the porous filter 01 separates soil particles from pore fluid, so that the pore fluid in the soil body can freely enter and exit the cavity structure a, and then acts on the sensing element 03.
Through the structural design of the cavity, the sensing element 03 can be prevented from being affected by stress on two sides of the sensor to the greatest extent, and the sensing element 03 is directly prevented from being contacted with pore fluid, so that impurities such as fine particles in saturated fluid are effectively prevented from damaging the sensing element 03. That is, the cavity structure design can effectively prevent the bridging between the porous filter 01 and the sensing element 03 caused by impurities such as tiny soil particles of pore fluid in the soil body, and effectively protect the sensing element 03 of the sensor. (in the prior art, the integrated micro pore pressure sensor is often not provided with the cavity structure, so that impurities such as tiny soil particles of pore fluid in soil body easily cause bridging of a porous filter and an induction element, and further cause stress concentration phenomenon, and the measured data of the sensor have larger deviation from the actual situation.)
Specifically, the aperture of the spacing groove 043 is smaller than the aperture of the first hole section of the sensing element mounting groove 044, thereby being capable of performing an axial limiting function on the sensing element 03.
In a specific embodiment, an end opening 040 matched with the shape of the porous filter 01, a sealing ring positioning groove 041 matched with a positioning sealing ring 02 (such as an O-shaped sealing ring) and a filter sealing groove 042 for filling sealing grease are sequentially arranged in the filter mounting notch of the integrated miniature pore pressure sensor along the axial direction. Wherein the aperture of the end opening 040 is D1, the aperture of the sealing ring positioning groove 041 is D2, and the aperture of the filter sealing groove 042 is D3, and D2 is more than D3 and more than D1.
Thus, when the porous filter 01 is mounted in the filter mounting notch, the end opening 040 can circumferentially position the porous filter 01 to prevent the porous filter 01 from shaking, the positioning sealing ring 02 is mounted in the sealing ring positioning groove 041 to position and seal the porous filter 01, and the filter sealing groove 042 is filled with sealing grease (also called sealing glue) which is fully contacted with the end part (specifically a conical side wall structure 012) of the porous filter 01, so that the sealing between the main casing 04 and the porous filter 01 is further realized, and the fixing effect on the porous filter 01 is realized.
Therefore, in the integrated micro pore pressure sensor, the sealing ring positioning groove 041 and the positioning sealing ring 02 are arranged, and the phenomenon that the porous filter falls off due to the fact that the sensor is in saturated fluid for a long time can be effectively prevented through the matching of the filter sealing groove 042 and sealing glue.
Specifically, the positioning sealing ring 02 is made of fluorine rubber, has the characteristics of good high temperature resistance, high pressure resistance, water resistance, oil resistance, strong corrosion resistance and the like, and has the main functions of being matched with the side face 011 of the porous filter to position and fix the porous filter 01, as shown in fig. 9.
Specifically, before a geotechnical test is performed, the integrated micro pore pressure sensor can select a proper porous filter 01 according to the permeability of different soil types in a field test or a geotechnical physical model test, and the configurable porous filter 01 of the integrated micro pore pressure sensor mainly comprises a stainless steel sintered filter, a fine sintered bronze filter and a porous ceramic filter, and can select a filtering particle size range of 20 um-0.2 mm.
Preferably, as shown in fig. 7 and 8, one end of the porous filter 01 is provided with a cylindrical side wall structure 011, the other end is provided with a conical side wall structure 012, the positioning sealing ring 02 is matched with the cylindrical side wall structure 011, and the conical side wall structure 012 is positioned in the filter sealing groove 042. The filter glue seal groove is filled with sealing grease and is fixedly bonded with the conical side wall structure 012, so that the contact glue seal area is enlarged, the function of fixing the porous filter is further played, and the porous filter is not easy to loosen and fall off when the integrated micro pore pressure sensor is in a saturated fluid long-term monitoring environment such as a geotechnical centrifugal test, a geotechnical structure, a site foundation and the like, and the failure rate of the integrated micro pore pressure sensor is reduced.
Referring to fig. 6 and fig. 12 to 14, in order to further optimize the above technical solution, in the above integrated micro-hole pressure sensor, a barb tower head structure 05 for connecting the ventilation cable 06 is provided on the main housing 04, a through hole communicating with the ventilation pipe 045 is provided in the barb tower head structure 05, and a barb step 051 is provided on the outer side of the barb tower head structure 05. The outer diameter of the end part of the ventilation cable 06 connected with the barb pagoda head structure 05 is larger, and the inner through hole of the ventilation cable is matched with the barb pagoda head structure 05 and is tightly connected.
Referring to fig. 2,6 and 12 to 14, in the embodiment, a sealing groove 046 is provided on an end portion of the main housing 04 for connecting the ventilation cable 06, and a connection end of the barb tower head structure 05 is located at a bottom of the sealing groove 046. The sealing groove 046 is used for filling sealing grease, so that the connection between the main housing 04 and the ventilation cable 06 is sealed. The waterproof structure composed of the sealing groove 046, the barb pagoda head structure 05 and the sealing grease has the main functions of connecting the sensor main shell with the ventilation cable and playing the roles of waterproof and sealing the cable. Wherein, barb pagoda head structure 05 is used for further closely cooperating with ventilation cable 06, ensures that the inside sensor can not intaking, and ensures that ventilation tube 045 is linked together with the atmospheric pressure.
Therefore, in the integrated miniature pore pressure sensor, a novel waterproof sealing structure with a barb pagoda head structure and sealing grease matched is adopted, so that the sealing performance of a sensor cable can be effectively improved, and the integrated miniature pore pressure sensor is better suitable for the long-term monitoring requirement of saturated fluid in a geotechnical centrifugation test.
Specifically, in the integrated micro pore pressure sensor, the through hole in the ventilation pipe 045 is a second stepped hole. In the second stepped hole, a hole section adjacent to the sensing element mounting groove 044 is a third hole section, a hole section connected with the barb tower head structure 05 is a fourth hole section, and the aperture of the third hole section is larger than that of the fourth hole section.
In addition, the integrated micro pore pressure sensor provided by the embodiment of the invention comprises the following specific using steps:
(1) The integrated miniature pore pressure sensor is placed in 95% alcohol for soaking for 2h. And then, taking out the integrated micro pore pressure sensor, placing the integrated micro pore pressure sensor in heated 100 ℃ airless water, boiling and cleaning for 5min until no bubbles emerge on the surface of a porous filter of the integrated micro pore pressure sensor, and repeating the steps for 3-5 times to finish the cleaning work of the integrated micro pore pressure sensor.
(2) And placing the cleaned integrated micro pore pressure sensor in a vacuum saturation tank, slowly injecting saturated fluid airless water, vacuumizing for 1.0h, opening the saturation tank, properly stirring, facilitating the discharge of bubbles in water, vacuumizing again for 0.5h, and repeating the steps for 8-10 times to complete the saturation process of the porous filter in the integrated micro pore pressure sensor.
(3) The integrated miniature pore pressure sensor is placed in a calibration device, a sensor ventilation cable is connected with a data acquisition instrument, and various performance indexes (static performance: parameters such as sensitivity, static correlation coefficient, linearity and the like, dynamic performance: parameters such as response time, frequency response rate and dynamic correlation coefficient) of the sensor are calibrated according to relevant national standards and industry specifications of pressure sensor performance test methods (GB/T15478-2015) and geotechnical centrifugal model test technical specifications (DL/T5102-2013).
(4) And taking out the integrated micro pore pressure sensor after calibration from the calibration device, placing the integrated micro pore pressure sensor in saturated fluid for soaking until a porous filter of the integrated micro pore pressure sensor is coated with a layer of vaseline when the sensor is required to be laid in a geotechnical test, so as to prevent the porous filter from being contacted with air.
In summary, the integrated micro pore pressure sensor provided by the embodiment of the invention has the following advantages:
(1) The induction element packaging mode comprises the following steps:
The integrated micro pore pressure sensor provided by the embodiment of the invention is an integrated geotechnical test integrated micro pore pressure sensor, and the internal sensing element is arranged in the annular packaging shell, so that the stress effect on two sides of the sensor can be effectively reduced;
The concave core mounting groove of the sensing element is filled and coated with non-stress glue to serve as an insulating isolation protection layer, so that irreversible damage to the piezoresistive core caused by direct action of impurities such as tiny soil particles in pore fluid in a soil body on the piezoresistive core can be effectively avoided.
Furthermore, through annular encapsulation casing to and the packing and the coating of unstressed glue, form dual protection to sensor sensing element for piezoresistive core body is compared with the encapsulation mode of traditional sensor in the past, can furthest reduce strong and weak electromagnetic interference, both sides stress effect, improves thermal isolation and electric insulation intensity, in order to adapt to various abominable operational environment such as geotechnique centrifugation test, in order to reduce the fault rate and the damage of integral type miniature hole pressure sensor.
(2) The porous filter mounting mode is as follows:
In the integrated miniature pore pressure sensor provided by the embodiment of the invention, the O-shaped sealing ring is arranged on the porous filter through the sealing ring positioning groove, so that the position of the porous filter is positioned through the O-shaped sealing ring, and the porous filter is fully bonded with the conical side wall structure at the end part of the porous filter in a manner of sealing the groove and filling sealing grease, so that the contact sealing area is enlarged, the function of fixing the porous filter is further realized, and the porous filter is not easy to loosen and fall off when the integrated miniature pore pressure sensor is in a saturated fluid long-term monitoring environment such as a geotechnical centrifugal test, a rock-soil structure, a site foundation and the like, and the fault rate of the integrated miniature pore pressure sensor is reduced.
(3) Waterproof sealing mode of sensor:
In the integrated miniature pore pressure sensor provided by the embodiment of the invention, one end of the main shell is provided with the sealing groove for filling sealing grease so as to seal the ventilation cable, and furthermore, the barb pagoda head structure is tightly matched with the ventilation cable, so that water vapor and accumulated water drops are prevented from entering the sensor, and the ventilation pipeline is communicated with atmospheric pressure, so that the sensor can work normally. The sealing groove, the sealing grease and the barb pagoda head structure are combined, so that good waterproof sealing and bearing functions can be achieved on the ventilation cable. And a large number of experimental results prove that the waterproof structure provided by the invention has better waterproof sealing effect compared with the waterproof structure of the traditional sensor, and when the waterproof structure is in a saturated soil body in a high-centrifugal acceleration environment of a geotechnical centrifugal test for a long time, no water vapor accumulation is found in the ventilation cable of the sensor, so that the accuracy and reliability of the pore water pressure measurement value of the integrated micro pore pressure sensor are ensured.
(4) Sensor cavity structural design:
In the integrated micro pore pressure sensor provided by the embodiment of the present invention, a cavity structure (i.e., a cavity structure a between the porous filter 01 and the sensing element 03 shown in fig. 6) is designed. When impurities such as tiny soil particles of pore fluid in the soil body enter the sensor through the porous filter, the phenomenon of stress concentration caused by bridging between the porous filter and the sensing element due to the existence of the cavity structure can be avoided, so that the sensor is prevented from being damaged. However, considering that the frequency response rate of the sensor is proportional to the size of the cavity structure, the cavity structure is not too large, and a large number of bubbles are easily accumulated due to the too large cavity, so that the frequency response lag and the amplitude attenuation of the sensor are caused, and therefore, the thickness of the cavity structure (namely, the gap distance between the porous filter and the sensing element) in the integrated micro pore pressure sensor provided by the embodiment of the invention is controlled within 0.5 mm.
Finally, it is further noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises an element.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (5)
1. An integrated micro pore pressure sensor, characterized in that it comprises a porous filter (01), an inductive element (03), a main housing (04) and a ventilation cable (06), wherein:
A filter mounting notch, a sensing element mounting groove (044) and a ventilation pipeline (045) are sequentially arranged in the main shell (04) along the axial direction, the porous filter (01) is mounted in the filter mounting groove, the sensing element (03) is mounted in the sensing element mounting groove (044), and a sensor cable (035) at the tail end of the sensing element (03) extends out of the main shell (04) through the ventilation pipeline (045) so as to be connected with the ventilation cable (06);
The induction element (03) comprises an annular packaging shell (031), a piezoresistive core (032), a positioning plate (034) and a sensor cable (035), wherein the positioning plate (034) is fixedly arranged at one end of the annular packaging shell (031) so as to enable the annular packaging shell (031) to internally form a concave core mounting groove (033), the piezoresistive core (032) is positioned in the concave core mounting groove (033) and is arranged on the side surface of the positioning plate (034), and the sensor cable (035) is connected with the piezoresistive core (032) and penetrates through the positioning plate (034) to extend into the ventilation pipeline (045), and a communication hole (036) is formed in the positioning plate (034);
the concave core body mounting groove (033) is filled and smeared with stress-free glue;
a step surface (0441) for axially positioning the induction element (03) is formed at the joint of the induction element mounting groove (044) and the ventilation pipeline (045);
The side surface of the positioning plate (034) far away from the annular packaging shell (031) is fixedly connected with the step surface (0441) through an adhesive, and/or the outer wall of the annular packaging shell (031) is fixedly connected with the sensing element mounting groove (044) through an adhesive;
the through hole in the sensing element mounting groove (044) is a first stepped hole, and the through hole is formed in the first stepped hole:
the hole section close to the porous filter (01) is a first hole section matched with the annular packaging shell (031);
the hole section close to the ventilation pipeline (045) is a second hole section matched with the positioning plate (034);
the aperture of the first hole section is smaller than the aperture of the second hole section;
A spacer groove (043) is arranged between the filter mounting notch and the sensing element mounting groove (044) in an inward protruding manner, wherein:
The aperture of the spacing groove (043) is smaller than the diameter of the end part of the porous filter (01) so as to axially limit the porous filter (01), and the aperture of the spacing groove (043) is smaller than the aperture of the first hole section of the sensing element mounting groove (044) so as to axially limit the sensing element (03);
a cavity structure with the thickness of 0.1mm to 0.5mm is formed between the annular inner wall surface of the spacing groove (043) and the porous filter (01) and the sensing element (03) which are positioned at the two sides of the spacing groove (043);
An end opening (040) matched with the shape of the porous filter (01), a sealing ring positioning groove (041) matched with the positioning sealing ring (02) and a filter sealing groove (042) for filling sealing grease are sequentially arranged in the filter mounting notch along the axial direction;
The aperture of the end opening (040) is D1, the aperture of the sealing ring positioning groove (041) is D2, and the aperture of the filter sealing groove (042) is D3, and D2 is more than D3 and more than D1;
One end of the porous filter (01) is a cylindrical side wall structure (011), the other end of the porous filter is a conical side wall structure (012), the positioning sealing ring (02) is matched with the cylindrical side wall structure (011), and the conical side wall structure (012) is positioned in the filter sealing groove (042).
2. The integrated micro-pore pressure sensor of claim 1, wherein the spacer grooves (043) have a smaller pore size than the first pore section.
3. The integrated micro-pore pressure sensor according to claim 1, wherein a barb tower head structure (05) for connecting the ventilation cable (06) is arranged on the main shell (04), a through hole communicated with the ventilation pipeline (045) is arranged in the barb tower head structure (05), and barb steps (051) are arranged on the outer side of the barb tower head structure (05).
4. A micro-pore pressure sensor as claimed in claim 3, wherein a sealing groove (046) for filling sealing grease is arranged on the end part of the main shell (04) for connecting the ventilation cable (06), and the connecting end of the barb pagoda head structure (05) is positioned at the bottom of the sealing groove (046).
5. The integrated micro-pore pressure sensor according to claim 3, wherein the through hole in the ventilation pipe (045) is a second stepped hole, in the second stepped hole, a hole section adjacent to the sensing element mounting groove (044) is a third hole section, a hole section connected with the barb tower head structure (05) is a fourth hole section, and the aperture of the third hole section is larger than that of the fourth hole section.
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| JP6969832B1 (en) * | 2021-06-01 | 2021-11-24 | 和之 横田 | Strain gauge transducer |
| CN114329726B (en) * | 2021-12-31 | 2022-08-12 | 西南交通大学 | A method for evaluating the alignment of railway bridges based on train running performance |
| CN118583345B (en) * | 2024-06-25 | 2025-01-24 | 天津大学 | Device and method for quickly measuring pore pressure in barrel foundation soil during sinking |
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| CN205981540U (en) * | 2016-08-15 | 2017-02-22 | 西安森瑟斯传感器有限责任公司 | Stifled pressure transmitter of ice that shocks resistance |
| CN110057492A (en) * | 2019-05-23 | 2019-07-26 | 王永志 | A kind of miniature ventage piezometer and its application method |
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