CN112985654B - Pressure sensor and method for assembling the same - Google Patents
Pressure sensor and method for assembling the same Download PDFInfo
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- CN112985654B CN112985654B CN202110197715.0A CN202110197715A CN112985654B CN 112985654 B CN112985654 B CN 112985654B CN 202110197715 A CN202110197715 A CN 202110197715A CN 112985654 B CN112985654 B CN 112985654B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
- G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
- G01L1/2287—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges constructional details of the strain gauges
- G01L1/2293—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges constructional details of the strain gauges of the semi-conductor type
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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
- G01L19/06—Means for preventing overload or deleterious influence of the measured medium on the measuring device or vice versa
- G01L19/0618—Overload protection
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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
- G01L9/04—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 resistance-strain gauges
Abstract
The application relates to a pressure sensor and an assembling method thereof, wherein the pressure sensor comprises a pressure bearing mechanism, a pressure measuring mechanism, a pressure transmitting mechanism and an overpressure protection mechanism, a cavity is formed in the overpressure protection mechanism, a diaphragm is arranged in the cavity, the diaphragm and the cavity wall of the cavity jointly form at least one buffer space located in a pressure guide medium transmission path, and the diaphragm can shift when the pressure of the pressure guide medium in the buffer space reaches or is higher than a preset threshold value and automatically reset when the pressure of the pressure guide medium in the buffer space is lower than the preset threshold value. The pressure sensor provided by the invention can accurately measure pressure, pressure difference and flow while realizing the isolation of the external overpressure effect and the sensitive element, particularly can perform overload protection on the sensor chip when the pressure is overloaded, and can avoid secondary verification after the overload protection is completed for continuous use.
Description
Technical Field
The invention relates to the technical field of sensing devices, in particular to a pressure sensor and an assembling method thereof.
Background
A pressure sensor is a device or apparatus that senses a pressure signal and converts the pressure signal into an electrical signal. The pressure sensor is a sensor commonly used in industrial practice, is widely applied to various industrial automatic control environments, and relates to a plurality of industries such as water conservancy and hydropower, railway traffic, intelligent buildings, production automatic control, aerospace, military industry, petrochemical industry, oil wells, electric power, ships, machine tools, pipelines and the like.
Over-voltage protection capability has long been a problem for pressure sensor manufacturers. In particular, in the field of high-precision pressure sensor manufacturing, the material used as the sensing element (e.g., diffused silicon) generally has a limited pressure resistance, and when a system failure causes overpressure, the sensing element is likely to be damaged, or the zero error of the pressure sensor is too large, and even more, the pressure overload causes damage to the meter or even more loss.
Currently, such products typically employ either a flat diaphragm or a corrugated overload diaphragm as a protective element. Although the problem of damage to the sensitive element caused by pressure overload is solved to a certain extent, due to the lack of a recovery mechanism, after the product is overloaded, the pressure sensor cannot completely recover the initial state, so that the problem of zero output offset is caused, and the secondary verification of the instrument is usually required to be carried out to ensure that the instrument can be normally used again. Although the current national standard allows the secondary verification of the product after the system failure causes overvoltage, the use of the product is more complicated after all. Therefore, a better solution to the problem of insufficient overload resistance of the pressure sensor product is desired.
Therefore, in the field of manufacturing high-precision pressure sensors, particularly in terms of sensor structures, a more complete protection device needs to be developed, even if the pressure of a system to be measured is greater than the pressure which can be borne by a sensitive element, the sensitive element can be effectively protected from being damaged, other problems can not be caused, whether the device is reliable and effective or not is ensured, the original excellent performance of the sensor is ensured, and the device is the key for measuring the quality of products.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides an improved design of a pressure sensor, which realizes overload protection without secondary verification.
In one aspect, the present application provides a pressure sensor comprising:
the pressure mechanism is used for receiving external pressure to be measured;
the pressure measuring mechanism is used for sensing the pressure to be measured and converting the pressure to an electric signal; and
the pressure transmission mechanism is used for transmitting the pressure to be measured received by the pressure receiving mechanism to the pressure measuring mechanism through a pressure guide medium;
the pressure sensor further comprises an overpressure protection mechanism, a cavity is formed in the overpressure protection mechanism, a diaphragm is arranged in the cavity, the diaphragm and the cavity wall of the cavity jointly form at least one buffer space located in a pressure guide medium conduction path, and the diaphragm can shift when the pressure of the pressure guide medium in the buffer space reaches or is higher than a preset threshold value and automatically reset when the pressure of the pressure guide medium in the buffer space is lower than the preset threshold value.
The basic idea of the invention is: providing a buffer space in the pressure-transmitting medium conduction path, wherein when the pressure applied to the pressure-receiving mechanism exceeds a certain threshold value (according to a preferred and specific design scheme, the pressure can reach the maximum pressure controlled by the pressure-receiving mechanism, and for the "maximum pressure", which will be further explained below), the pressure transmitted by the pressure-transmitting medium deforms and deflects the diaphragm, so that the volume of the buffer space is increased, and the excessive pressure-transmitting medium pressed from the pressure-receiving end is absorbed, so that the sensitive element (such as a diffused silicon pressure-sensitive element and the like) of the pressure-receiving mechanism is not deformed excessively and damaged; when the pressure applied to the pressure-receiving mechanism is restored to a normal level, namely the pressure of the pressure-guiding medium in the buffer space is lower than the threshold value, the diaphragm automatically resets, so that the pressure-guiding medium can normally transmit the pressure again, and the pressure sensor is restored to an initial state, so that the original function of the pressure sensor can be realized. The function of the overpressure protection means cavity is to provide the necessary structural support for the arrangement of the damping space and its volume change (or deformation/deflection of the diaphragm).
Compared with the prior art, the invention firstly provides an automatic reset mechanism of the protection element, so that the sensor can be prevented from complicated check work of restarting after overvoltage while effectively protecting the sensitive element of the sensor. With regard to the automatic resetting of the diaphragm, appropriate structural measures may be taken, for example, in consideration of the elastic deformation characteristics of the diaphragm, to provide additional positioning support for fixedly holding the diaphragm at the critical portion(s) in a zero-offset position, so as to facilitate the diaphragm to return to the original state by itself after the offset occurs, in case of removal of excessive external force. For example, for planar membrane elements, fastening means may be provided at critical point(s), and in addition to their edge regions, one or more support points or support surfaces may be provided in the middle.
According to one embodiment of the invention, the diaphragm is a flat or corrugated diaphragm (preferably a corrugated diaphragm) which is fixed to the wall of the cavity in the edge region of its diaphragm extension and is positioned and held in a zero offset position in the central region of its diaphragm extension. This form of positional support of the diaphragm is particularly advantageous, thereby ensuring that the diaphragm automatically resets quickly and accurately after an overpressure phase.
Further, the pressure sensor may include a first base and a second base, the first base and the second base having a recess on inner sides facing each other, respectively, so that the cavity is formed in a state where the first base and the second base are assembled, peripheral surfaces of the two recesses together constitute a circumferential cavity wall of the cavity, and bottom surfaces of the two recesses constitute an end side cavity wall of the cavity, respectively.
Further, the diaphragm is clamped between the first and second bases in the edge region of its diaphragm extension face and thereby fixed to the circumferential chamber wall of the cavity, the diaphragm being positioned in the central region of its diaphragm extension face by a support table projecting from at least one of the end side chamber walls into the interior of the cavity.
The support table may be integrally configured with a bottom surface of the recess of the second base.
Here, the diaphragm divides the cavity into a first chamber on the side of the first base and a second chamber on the side of the second base.
According to a preferred and specific embodiment, the pressure-loaded mechanism includes a first pressure-loaded membrane disposed outside the first base, and a first pressure-loaded cavity is formed between the first pressure-loaded membrane and the first base; the pressure measuring mechanism comprises a pressure-sensitive element arranged in the second base; the pressure transmission mechanism is provided with a first pressure-guiding medium conduction path leading from the first pressure-receiving chamber to the first chamber and from the first chamber to the pressure-sensitive element, the first chamber constituting a first buffer space in the first pressure-guiding medium conduction path.
Further, a section of the first pressure-inducing medium conduction path leading from the first pressure-receiving chamber to the first chamber is constituted by a first pipe disposed in the first base, and a section of the first pressure-inducing medium conduction path leading from the first chamber to the pressure-sensitive element is constituted by a second pipe disposed in the second base.
Advantageously, said support table is configured as a second step boss projecting from the bottom surface of the recess of said second base, having a top projecting into said first chamber and made with an orifice communicating with said second duct, and a shoulder forming a support plane for positioning the central region of said diaphragm.
Advantageously, the diaphragm is a corrugated diaphragm having a central opening, which is fitted on top of the second step boss through the central opening and is sealingly fixed to the support plane in the edge region of the central opening.
According to an embodiment of the present invention, the pressing mechanism further includes a second pressing diaphragm disposed outside the second base, and a second pressing chamber is formed between the second pressing diaphragm and the second base; the pressure transmitting means is provided with a second pressure-guiding medium conducting path leading from the second pressure receiving chamber to the second chamber and from the second chamber to the pressure-sensitive element, the second chamber constituting a second buffer space in the second pressure-guiding medium conducting path. In this way, a suitable differential pressure type pressure sensor can be constructed.
In this case, the section of the second pressure-conducting medium conduction path leading from the second pressure chamber to the second chamber and the section of the second pressure-conducting medium conduction path leading from the second chamber to the pressure-sensitive element are each formed by a third duct and a fourth duct arranged in the second base.
In another aspect, the present application further provides a method for assembling a pressure sensor, including the following steps:
a. fixing the first pressure membrane and the first base together, and fixing the second pressure membrane and the second base together;
b. fixing the diaphragm to the second base at a corresponding position of the diaphragm at an edge region thereof and to the second base at a corresponding position of the support table at a center region thereof;
c. fixing the first base and the second base together with the diaphragm on the other side of the diaphragm;
d. securing a load cell assembly containing a pressure sensitive element to the second base;
e. and filling pressure-guiding medium.
In steps a-d, the fixation of the parts may be achieved by welding or gluing.
In step e, silicon oil may be used as the pressure guide medium, each section of the first pressure guide medium conduction path including the first pressure-receiving cavity and the first buffer space may be filled with silicon oil, and/or each section of the second pressure guide medium conduction path including the second pressure-receiving cavity and the second buffer space may be filled with silicon oil.
In summary, the pressure sensor provided by the invention can accurately measure pressure, differential pressure and flow while realizing effective isolation of external over-high pressure action and a sensitive element, especially can perform overload protection on a sensor chip when the pressure is overloaded, and can be used continuously without secondary verification after the overload protection is completed, thereby greatly improving the reliability, convenience and stability of the pressure sensor product.
Drawings
In which some exemplary embodiments of the invention are shown. The embodiments and figures disclosed herein are to be regarded as illustrative rather than restrictive. It is also noted that for purposes of clarity of illustration, certain features are not necessarily drawn to scale in the drawings.
FIG. 1 is a schematic diagram of the pressure sensor of the present invention;
FIG. 2 is a schematic representation of the operation of the pressure sensor of the present invention on side P1;
fig. 3 is a schematic diagram of the operation of the pressure sensor of the present invention on the P2 side.
Detailed Description
The following description is provided to illustrate the technical solutions of the present invention so that those skilled in the art can implement the present invention. The preferred embodiments in the following description are given by way of example only, and other obvious variations will occur to those skilled in the art. The underlying principles of the invention, as defined in the following description, may be applied to other embodiments, variations, modifications, equivalents, and other technical solutions without departing from the spirit and scope of the invention. Also, it is noted that a feature, structure, or characteristic described herein in connection with one embodiment is not necessarily limited to the particular embodiment, nor is it intended to be mutually exclusive of other embodiments, as those skilled in the art will recognize various combinations of features of different embodiments as may be contemplated within the scope of the appended claims.
The terms first, second and the like in the description and in the claims, are used for distinguishing between different objects and not necessarily for describing a particular sequential order. Furthermore, the terms "comprising"/"including" and "having," and any variant thereof, are intended to cover non-exclusive inclusions. For example, a process, method, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus. In the description of the present application, the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are merely for convenience in describing the present invention and simplifying the description, and do not mean that the corresponding device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus the above terms should not be construed as limiting the present invention. In addition, the terms "a" and "an" should be interpreted as "at least one" or "one or more," i.e., the number of an element can be one in one embodiment and the number of the element can be plural in another embodiment, i.e., the terms "a" and "an" should not be interpreted as limiting the number.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art and may be specifically interpreted based on their context within the context of the description of the relevant art.
The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
The invention aims to provide an improved design of a pressure sensor, so that the pressure sensor does not need secondary verification while realizing overload protection.
Specifically, the present application provides a pressure sensor comprising: the pressure mechanism is used for receiving external pressure to be measured; the pressure measuring mechanism 5 is used for sensing the pressure to be measured and converting the pressure to an electric signal; and at least one pressure transmission mechanism, wherein the pressure transmission mechanism is used for transmitting the pressure to be measured received by the pressure receiving mechanism to the pressure measuring mechanism 5 through the pressure guide medium 4. According to the invention, the pressure sensor further comprises an overpressure protection mechanism, which forms a cavity and in which a diaphragm (preferably a corrugated diaphragm 3) is arranged, which diaphragm together with the wall of the cavity forms at least one buffer space in the pressure-conducting path of the pressure-conducting medium, the diaphragm being capable of automatically resetting when the pressure of the pressure-conducting medium in the buffer space reaches or exceeds a predetermined threshold value and when the pressure of the pressure-conducting medium in the buffer space falls below the predetermined threshold value.
The basic idea of the invention is: a buffer space is arranged in the pressure guide medium conduction path, when the pressure applied to the pressure receiving mechanism exceeds a certain threshold value (until the maximum pressure controlled by the pressure receiving mechanism, for the maximum pressure, which will be further explained below), the pressure transmitted by the pressure guide medium deforms and deflects the diaphragm, so that the volume of the buffer space is increased, and the excessive pressure guide medium pressed from the pressure receiving end is absorbed, so that a sensitive element (such as a diffused silicon pressure sensitive element and the like) of the pressure receiving mechanism 5 is not deformed excessively and damaged; when the pressure applied to the pressure-receiving mechanism is restored to a normal level, namely the pressure of the pressure-guiding medium in the buffer space is lower than the threshold value, the diaphragm automatically resets, so that the pressure-guiding medium can normally transmit the pressure again, and the pressure sensor is restored to an initial state, so that the original function of the pressure sensor can be realized. The function of the overpressure protection means cavity is to provide the necessary structural support for the arrangement of the damping space and its volume change (or deformation/deflection of the diaphragm).
According to one embodiment of the invention, the diaphragm is a flat or corrugated diaphragm 3 (preferably a corrugated diaphragm) which is fixed to the wall of the cavity in the edge region of its diaphragm extension and is positioned and held in a zero offset position in the central region of its diaphragm extension. This form of positional support of the diaphragm is particularly advantageous, thereby ensuring that the diaphragm automatically resets quickly and accurately after an overpressure phase.
As shown in fig. 1, the pressure sensor comprises a first base 2 and a second base 6, the first base 2 and the second base 6 each have a recess on the inner side facing each other, so that the cavity is formed when the first base 2 and the second base 6 are assembled, the circumferential surfaces of the recesses together form the circumferential cavity wall of the cavity, and the bottom surfaces of the recesses each form an end-side cavity wall of the cavity.
As shown, the membrane is clamped between the first base 2 and the second base 6 in the edge region of its membrane extension face and is thereby fixed to the circumferential chamber wall of the cavity, the membrane being positioned in the central region of its membrane extension face by a support table projecting from at least one of the end side chamber walls into the interior of the cavity.
Specifically, the support table may be integrally configured on a bottom surface of a recess of the second base 6.
As shown, the diaphragm divides the cavity into a first chamber on the side of the first base 2 and a second chamber on the side of the second base 6.
As shown in the figure, the compression mechanism comprises a first compression membrane 1 arranged outside a first base 2, and a first compression cavity is formed between the first compression membrane and the first base 2; the load cell 5 comprises a pressure sensitive element mounted in a second base 6; the pressure transmission mechanism is provided with a first pressure-guiding medium conduction path leading from the first pressure-receiving chamber to the first chamber and from the first chamber to the pressure-sensitive element, the first chamber constituting a first buffer space in the first pressure-guiding medium conduction path.
The section of the first pressure-medium conducting path leading from the first pressure chamber to the first chamber is formed by a first line 14 arranged in the first base 2, and the section of the first pressure-medium conducting path leading from the first chamber to the pressure-sensitive element is formed by a second line 15 arranged in the second base 6.
It is particularly expedient that the support table is configured as a second step boss protruding from the bottom surface of the recess of the second base 6, which second step boss has a top which projects into the first chamber and is made with an aperture which communicates with the second duct 15, and a shoulder which forms a support plane 8 for positioning the central region of the diaphragm.
The diaphragm may be a corrugated diaphragm 3 having a central hole, through which the corrugated diaphragm 3 is fitted on top of the second step boss and sealingly fixed to the support plane 8 in the edge region of the central hole.
According to an embodiment of the present invention, as shown in the figure, the pressure mechanism further comprises a second pressure membrane 7 arranged outside the second base 6, and a second pressure cavity is formed between the second pressure membrane and the second base 6; the pressure transmitting means is provided with a second pressure-guiding medium conducting path leading from the second pressure receiving chamber to the second chamber and from the second chamber to the pressure-sensitive element, the second chamber constituting a second buffer space in the second pressure-guiding medium conducting path.
In this case, the section of the second pressure-conducting medium conduction path leading from the second pressure-receiving chamber to the second chamber and the section of the second pressure-conducting medium conduction path leading from the second chamber to the pressure-sensitive element are each formed by a third line 23 and a fourth line 24, which are arranged in the second base 6.
In another aspect, the present application further provides a method for assembling a pressure sensor, including the following steps:
a. fixing the first pressure membrane 1 and the first base 2 together, and fixing the second pressure membrane 7 and the second base 6 together;
b. on one side of the membrane, the membrane is fixed in its edge region to the corresponding position of the second base 6 and in its central region to the corresponding position of the support table on the second base 6;
c. on the other side of the diaphragm, the first base 2 and the second base 6 are fixed together with the diaphragm;
d. fixing a load cell assembly (e.g., corresponding electronic/electrical components, etc.) containing pressure sensitive elements with the second base 6;
e. and filling pressure-guiding medium.
Preferably, in steps a-d, the parts are secured by welding or gluing.
Preferably, in step e, silicone oil is used as the pressure guide medium, each section of the first pressure guide medium conduction path including the first pressure-receiving cavity and the first buffer space is filled with silicone oil, and/or each section of the second pressure guide medium conduction path including the second pressure-receiving cavity and the second buffer space is filled with silicone oil.
The term "maximum pressure controlled by the pressure-receiving mechanism" refers to the maximum pressure that the pressure-receiving diaphragm receives from the initial state to the state of being completely attached to the base, and at this time, even if the external pressure is further increased, higher pressure is not conducted to the inside, that is, the pressure sensor can no longer continue to perform the pressure-receiving function, and the maximum pressure depends on the elastic characteristics of the pressure-receiving diaphragm and the volume of the pressure-receiving chamber. Therefore, when designing the pressure sensor, the elastic characteristics of the pressure-sensitive diaphragm, the volume of the pressure-sensitive cavity, the elastic characteristics of the overload diaphragm (e.g., the corrugated diaphragm 3), and the volume (change) of the buffer space can be designed to match with each other according to the performance of the pressure-sensitive element (e.g., the silicon piezoresistive chip) based on the operating conditions or requirements, so that the pressure sensor can be ensured to operate normally under the set conditions, and reliable overload protection can be realized, particularly, the pressure-sensitive element cannot be damaged by excessive pressure. In this regard, it is understood that the maximum volume increase of the buffer space that can be achieved by the deformation/deflection of the diaphragm should be designed to be not less than the volume of the pressure-receiving chamber.
The working principle of the pressure sensor of the present invention is described herein below with reference to the accompanying drawings:
the pressure receiving, conducting and sensing paths (filled in black) are highlighted in fig. 2 when the manometry is performed on the P1 side: first pressurized membrane 1 tends to inwards cave to first base 2 under the pressure effect that awaits measuring for silicon oil in the first pressurized cavity 11 promotes silicon oil in the first pipeline 14 and flows to first buffer space 11, silicon oil in the first buffer space receives the extrusion, through the through-hole of second order boss top surface to flowing in the second pipeline 15, silicon oil in the second pipeline 15 finally in first pressure measuring cavity 13 direct contact to the pressure-sensitive element (silicon piezoresistive sensor chip) among the pressure-sensitive mechanism 5, thereby by pressure-sensitive element's first detection zone concrete pressure of just perception, then do further signal processing again. That is, the pressure is conducted along the first pressure-guiding medium conducting path from the first pressure-receiving chamber 11, the first duct 14, the first buffer space 12, the second duct 15 to the first pressure-measuring chamber 13, and finally to the first detection region of the pressure-sensitive element;
the pressure receiving, conducting and sensing paths (filled in black) when the manometry was performed on the P2 side are highlighted in fig. 3: the second pressed diaphragm 7 tends to be sunken into the second base 6 under the action of the pressure to be detected, so that the silicon oil in the second pressed cavity 22 pushes the silicon oil in the third pipeline 23 to flow to the second buffer space 21, the silicon oil in the second buffer space is extruded, passes through the fourth pipeline 24 and finally reaches a second detection area of a pressure-sensitive element (silicon piezoresistive sensor chip) arranged at the port of the fourth pipeline 24, and the specific pressure is sensed and then further signal processing is performed. That is, the pressure is conducted from the second pressure-receiving chamber 22, the third tube 23, the second buffer space 21, the fourth tube 24 to the second detection region of the pressure-sensitive element (silicon piezoresistive sensor chip) along the second pressure-leading medium conduction path.
In the pressure sensor, the pressure to be measured is converted into the deformation of the first pressed diaphragm 1/the second pressed diaphragm 7 and is transmitted to the pressure-sensitive element (silicon piezoresistive sensor chip) by the transmission medium, so that the function of measuring the pressure can be well completed, and the outside is isolated from the pressure-sensitive element by using the first pressed diaphragm 1/the second pressed diaphragm 7, so that the pressure-sensitive element can be prevented from being damaged and polluted by the outside; when the pressure is overloaded, the diaphragm is deformed and deflected by the pressure conducted by the pressure guide medium, so that the volume of the buffer space is increased, and the excessive pressure guide medium extruded from the pressed end is absorbed, so that the pressure-sensitive element of the pressure measuring mechanism 5 is not excessively deformed and damaged, and the pressure-sensitive element is effectively protected.
The load cell 5 of the pressure sensor comprises pressure sensitive elements which may further be arranged as silicon pressure sensitive elements, in particular silicon piezoresistive elements based on the wheatstone bridge principle, such as two silicon pressure chips of diffused silicon and monocrystalline silicon. When pressure is applied to the pressure sensing surface of the chip, the resistance formed by the PN junction arranged on the pressure sensing surface becomes large and small in pairs, and differential mode output voltage is formed, namely the output signal of the sensor, and the signal is proportional to the excitation voltage and the excitation pressure.
Based on the pressure measuring principle of the pressure sensor, the pressure sensor designed by the invention can be widely applied to the field of industrial automation control for measuring pressure, differential pressure and flow, and is an important component of a pressure transmitter, a differential pressure transmitter and a flow transmitter, wherein the flow measurement can be obtained by converting the differential pressure measurement.
The pressure sensor provided by the invention can accurately measure pressure, differential pressure and flow while realizing effective isolation of external over-high pressure action and a sensitive element, particularly can perform overload protection on the sensor chip when the pressure is overloaded, and can be used continuously without secondary verification after the overload protection is completed, so that the reliability, convenience and stability of the pressure sensor product are greatly improved.
Application example 1
The pressure sensor of the present invention can be used for measuring a differential pressure, that is, can be practically applied as a differential pressure type pressure sensor measuring a differential pressure between a side P1 (which can be set to a high pressure side) and a side P2 (which can be set to a low pressure side) as shown in fig. 1.
A first buffer space 12, a first pressure bearing cavity 11, a first pressure measuring cavity 13, a first pipeline 14 and a second pipeline 15 jointly form a closed pressure guide system, and pressure guide media 4 such as silicon oil (see fig. 2) are filled in the closed pressure guide system; the second buffer space 21, the second pressure-bearing cavity 22, the third pipeline 23 and the fourth pipeline 24 together form a closed pressure-guiding system, and a pressure-guiding medium 4 such as silicone oil is filled in the closed pressure-guiding system (see fig. 3).
Here, the main component of the load cell 5 is a sensitive element (silicon piezoresistive sensor chip); the first pressure membrane 1 and the second pressure membrane 7 can be elastic membranes so as to ensure accurate pressure collection and reduce pressure loss as much as possible.
The specific working principle is as follows:
when the pressure on the P1 side is measured, the pressure presses the first pressure chamber 11 from the outside, as shown in fig. 2, the first pressure membrane 1 tends to be recessed into the first base 2, so that the silicone oil in the first pressure chamber 11 pushes the silicone oil in the first pipe 14 to flow to the first buffer space 12, the silicone oil in the first buffer space 12 is pressed and flows to the second pipe 15 through the through hole on the top surface of the second-step boss, and the silicone oil in the second pipe 15 finally directly contacts the sensing element in the pressure measuring mechanism 5 in the first pressure chamber, so that the specific pressure is sensed by the first detection area of the sensing element, and then the signal processing is performed. Here, the pressure at P1 is conducted along the first pressure-conducting medium conduction path from the first pressure chamber 11, the first duct 14, the first buffer space 12, the second duct 15 to the first pressure-measuring chamber 13, and finally to the first detection area of the sensing element;
when the pressure on the P2 side is measured, the pressure presses the second pressure-receiving cavity 22 from the outside, as shown in fig. 3, the second pressure-receiving diaphragm 7 tends to be recessed into the second base 6, so that the silicone oil in the second pressure-receiving cavity 22 pushes the silicone oil in the third pipeline 23 to flow to the second buffer space 21, the silicone oil in the second buffer space 21 is pressed, passes through the fourth pipeline 24, and finally reaches the second detection area of the sensing element arranged at the port of the fourth pipeline 24, so that the specific pressure is sensed, and then further signal processing is performed. Here, the pressure at P2 is conducted along the second pressure-inducing medium conduction path from the second pressure-receiving chamber 22, the third conduit 23, the second buffer space 21, the fourth conduit 24 to the second detection area of the sensing element.
The sensing element converts the detected pressure difference between the P1 side and the P2 side into an electric signal, and then further performs differential mode operation to finally output an accurate differential mode electric signal.
When a large pressure difference does exist between the side P1 and the side P2, the corrugated diaphragm 3 and the supporting plane 8 of the second base 6 are welded together, so that the corrugated diaphragm 3 can be restored to the original position as soon as possible after being deformed, namely, the initial stable state of the pressure sensor is restored as soon as possible, the problem of zero output drift in the next use is solved, and the pressure sensor can be continuously used without secondary verification.
Compared with the prior art, the pressure sensor product has the advantages of high measurement precision (0.05% FS), good stability, strong overload capacity (maximum 42Mpa) and the like, and can meet the rigorous requirements that the precision of the product is not influenced after overload is born.
Application example two
The pressure sensor of the present invention can be used to measure the pressure of a medium under an atmospheric pressure environment, for example, by measuring the pressure of the medium using the P1 side.
A first buffer space 12, a first pressure cavity 11, a first pressure measuring cavity 13, a first pipeline 14 and a second pipeline 15 jointly form a closed pressure guide system, and the closed pressure guide system is filled with silicon oil (see fig. 2); the second buffer space 21, the second pressure cavity 22, the third pipeline 23 and the fourth pipeline 24 jointly form a closed pressure guide system, and the closed pressure guide system is filled with silicon oil (see fig. 3).
Here, the main component of the load cell 5 is a sensitive element (silicon piezoresistive sensor chip); the first pressure membrane 1 and the second pressure membrane 7 can be elastic membranes so as to ensure accurate pressure collection and reduce pressure loss as much as possible.
The specific working principle is as follows:
when the pressure on the P1 side is measured, the pressure presses the first pressure-receiving cavity 11 from the outside, as shown in fig. 2, the first pressure-receiving diaphragm 1 tends to be recessed into the first base 2, so that the silicone oil in the first pressure-receiving cavity 11 pushes the silicone oil in the first pipe 14 to flow to the first buffer space 12, the silicone oil in the first buffer space 12 is pressed and flows to the second pipe 15 through the through hole on the top surface of the second-step boss, and the silicone oil in the second pipe 15 finally directly contacts the sensing element (silicon piezoresistive sensor chip) in the pressure measuring mechanism 5 in the first pressure-receiving cavity, so that the specific pressure is sensed by the first sensing area of the sensing element, and then further signal processing is performed. Here, the pressure at P1 is transmitted along the pressure-conducting medium conduction path from the first pressure chamber 11, the first pipe 14, the first buffer space 12, the second pipe 15 to the first pressure-measuring chamber 13, and finally to the first detection area of the sensor;
when the pressure sensor is placed in an atmospheric environment, the P2 side is in direct contact with the atmosphere, and therefore the atmospheric pressure is used as a reference for comparison in the measurement of the P1 side. The sensor converts the detected pressure on the P1 side into an electric signal and outputs it.
Of course, when measuring the pressure of the medium in the atmospheric pressure environment, the side P1 may be placed in the atmospheric environment, and the side P2 may be used to measure the pressure of the medium.
Compared with the prior art, the pressure sensor product has the advantages of high measurement precision (0.05% FS), good stability, strong overload capacity (maximum 42Mpa) and the like, and can meet the rigorous requirements that the precision of the product is not influenced after overload is born.
The above description is only a preferred embodiment of the present application and is illustrative of the principles of the technology employed. It will be appreciated by a person skilled in the art that the scope of the invention according to the present application is not limited to the specific combination of the above-mentioned features, but also covers other embodiments where any combination of the above-mentioned features or their equivalents is made without departing from the inventive concept. For example, the above features may be replaced with (but not limited to) features having similar functions disclosed in the present application.
Claims (10)
1. A pressure sensor, comprising:
the pressure mechanism is used for receiving external pressure to be measured;
the pressure measuring mechanism is used for sensing the pressure to be measured and converting the pressure to an electric signal; and
the pressure transmission mechanism is used for transmitting the pressure to be measured received by the pressure receiving mechanism to the pressure measuring mechanism through a pressure guide medium;
the pressure sensor is characterized by further comprising an overpressure protection mechanism, wherein a cavity is formed in the overpressure protection mechanism, a diaphragm is arranged in the cavity, the diaphragm and the cavity wall of the cavity jointly form at least one buffer space located in a conducting path of a pressure guide medium, and the diaphragm can shift when the pressure of the pressure guide medium in the buffer space reaches or is higher than a preset threshold value and automatically reset when the pressure of the pressure guide medium in the buffer space is lower than the preset threshold value; the diaphragm is fixed to the cavity wall of the cavity in the edge area of the diaphragm extending surface of the diaphragm, and is positioned and kept in a zero offset position in the central area of the diaphragm extending surface of the diaphragm;
the pressure sensor comprises a first base (2) and a second base (6), wherein the first base and the second base are respectively provided with a concave part at the inner sides opposite to each other, so that the cavity is formed in the state that the first base and the second base are assembled, the peripheral surfaces of the two concave parts jointly form the circumferential cavity wall of the cavity, and the bottom surfaces of the two concave parts respectively form one end side cavity wall of the cavity; said diaphragm being positioned in its central region by a support platform projecting from at least one of said end side chamber walls into said cavity; the diaphragm divides the cavity into a first chamber at one side of the first base and a second chamber at one side of the second base (6);
the compression mechanism comprises a first compression membrane (1) arranged on the outer side of a first base (2), and a first compression cavity is formed between the first compression membrane and the first base; the load cell (5) comprises a pressure sensitive element mounted in a second base (6); the pressure transmission mechanism is provided with a first pressure-conducting medium conducting path leading from the first pressure-receiving chamber to the first chamber and from the first chamber to the pressure-sensitive element, the first chamber forming a first buffer space (11) in the first pressure-conducting medium conducting path, wherein a section of the first pressure-conducting medium conducting path leading from the first pressure-receiving chamber to the first chamber is formed by a first pipe (14) arranged in the first base (2), and a section of the first pressure-conducting medium conducting path leading from the first chamber to the pressure-sensitive element is formed by a second pipe (15) arranged in the second base (6);
the support table is configured as a second step boss protruding from the bottom surface of the recess of the second base (6), the second step boss having a top projecting into the first chamber and being made with an aperture communicating with the second duct (15), and a shoulder forming a support plane (8) for positioning the central region of the diaphragm.
2. A pressure sensor according to claim 1, characterized in that the diaphragm is a flat diaphragm or a corrugated diaphragm (3).
3. A pressure sensor according to claim 1, characterized in that the diaphragm is clamped between the first base (2) and the second base (6) in the edge area of its diaphragm extension and is thereby fixed to the circumferential chamber wall of the cavity.
4. A pressure sensor according to claim 1, wherein the support stand is integrally constructed with a recessed bottom surface of the second base (6).
5. Pressure sensor according to claim 1, characterized in that the diaphragm is a corrugated diaphragm (3) with a central hole, which is fitted on top of the second step boss through the central hole and is sealingly fixed to the support plane (8) in the edge region of the central hole.
6. A pressure sensor according to any of claims 1 to 5, wherein the pressure receiving mechanism further comprises a second pressure membrane (7) arranged outside the second base (6), a second pressure chamber being formed between the second pressure membrane and the second base; the pressure transmission means is provided with a second pressure medium conduction path leading from the second pressure receiving chamber to the second chamber and from the second chamber to the pressure-sensitive element, the second chamber constituting a second buffer space (21) in the second pressure medium conduction path.
7. A pressure sensor according to claim 6, wherein the section of the second pressure-inducing medium conducting path leading from the second pressure-receiving chamber to the second chamber and the section leading from the second chamber to the pressure-sensitive element are constituted by a third duct (23) and a fourth duct (24), respectively, arranged in the second base (6).
8. A method of assembling a pressure sensor according to claim 7, comprising the steps of:
a. fixing the first pressure membrane (1) and the first base (2) together, and fixing the second pressure membrane (7) and the second base (6) together;
b. fixing the membrane at its edge region to a corresponding position of a second base (6) and at its central region to a corresponding position of a support table on the second base, on one side of the membrane;
c. on the other side of the diaphragm, fixing the first base and the second base (6) together with the diaphragm;
d. fixing a load cell assembly containing a pressure sensitive element to a second base (6);
e. and filling pressure-guiding medium.
9. The assembly method according to claim 8, wherein in steps a-d, the fixation of the parts is achieved by welding or gluing.
10. The assembly method according to claim 8, characterized in that in step e, silicone oil is used as the pressure guide medium, and each segment of the first pressure guide medium conduction path, including the first pressure-receiving cavity, and the first buffer space, is filled with silicone oil, and/or each segment of the second pressure guide medium conduction path, including the second pressure-receiving cavity, and the second buffer space, is filled with silicone oil.
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| CN200944070Y (en) * | 2006-07-28 | 2007-09-05 | 上海威尔泰工业自动化股份有限公司 | Uniaxial pressure overload protection differential pressure sensor |
| CN203216662U (en) * | 2013-03-20 | 2013-09-25 | 福建上润精密仪器有限公司 | Novel high over load pressure-durable device for pressure/differential pressure transmitters |
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| JPS62238432A (en) * | 1986-04-10 | 1987-10-19 | Yokogawa Electric Corp | Differential pressure transmitter |
| JP2875882B2 (en) * | 1990-11-30 | 1999-03-31 | 大阪瓦斯株式会社 | Gas outflow prevention valve |
| CN1052538C (en) * | 1993-09-10 | 2000-05-17 | 横河电机株式会社 | Semiconductor type differential pressure measurement apparatus and method for manufacturing the same |
| JPH0862077A (en) * | 1994-08-23 | 1996-03-08 | Hitachi Ltd | Pressure sensor |
| JP2004028704A (en) * | 2002-06-24 | 2004-01-29 | Fuji Electric Holdings Co Ltd | Apparatus for measuring differential pressure |
| DE102014109491A1 (en) * | 2014-07-08 | 2016-02-11 | Endress + Hauser Gmbh + Co. Kg | Differential pressure measuring cell |
| CN205958170U (en) * | 2016-08-05 | 2017-02-15 | 重庆九天测控仪器制造有限公司 | Differential capsule |
| CN110006583B (en) * | 2019-04-08 | 2021-04-06 | 中电(商丘)热电有限公司 | Overload protection device for differential pressure transmitter |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN200944070Y (en) * | 2006-07-28 | 2007-09-05 | 上海威尔泰工业自动化股份有限公司 | Uniaxial pressure overload protection differential pressure sensor |
| CN203216662U (en) * | 2013-03-20 | 2013-09-25 | 福建上润精密仪器有限公司 | Novel high over load pressure-durable device for pressure/differential pressure transmitters |
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