Resistance-type air flow sensor and method of manufacturing the same

Abstract

The application discloses a resistance type airflow sensor, comprising: a front shell; a rear shell clamped at the rear end of the front shell; and a sensing element packaged between the front shell and the rear shell, wherein the sensing element comprises a hard plate base material and a sensing chip, the hard plate base material is fixedly installed with the front shell, the sensing chip is fixedly installed with the rear shell, one side of the hard plate base material is provided with a sensitive membrane, and the sensing chip is connected with the sensitive membrane through a wire harness. The protective plate is arranged on the front shell and the rear shell, the fan-shaped rubber pieces on the inner wall of the protective plate are mutually adsorbed and closed through rubber magnetic strips in the absence of airflow, a barrier is formed, and particulate matters and condensate in the airflow are effectively blocked from directly contacting the sensitive membrane; when the airflow passes, the airflow pressure pushes away the rubber pieces, allows the airflow to pass, but blocks most of the pollutants, thereby protecting the sensitive membrane from being polluted, ensuring long-term stability and accuracy of the sensor; meanwhile, the protective plate is connected with the groove through a threaded ring, is convenient to disassemble and clean, and maintenance convenience is improved.

Description

Technical Field

[0001] This invention relates to the field of airflow sensor technology, specifically to a resistive airflow sensor and its fabrication method. Background Technology

[0002] Resistive airflow sensors, due to their fast response and compact structure, are widely used in industrial ventilation, automotive exhaust monitoring, and other fields. Their performance stability and lifespan largely depend on the cleanliness of the sensitive membrane and the ease of disassembly and assembly of the housing. Existing technologies have significant defects in the sensor's inlet protective structure. Without airflow, it is difficult to form a tight barrier, allowing dust, particulate matter, and condensate to easily penetrate and adhere to the sensitive membrane, leading to abnormal deformation of the sensing element and distortion of electrical signal transmission, directly affecting detection accuracy and shortening lifespan. Furthermore, the housing often uses bolt-fastened or integrated encapsulation designs, requiring specialized tools for disassembly and assembly, making operation cumbersome and greatly inconvenient for the inspection and maintenance of the sensitive membrane. In addition, the opening pressure of the protective components cannot accurately match the detection threshold. Traditional protective plates rely on their own elastic closure; either insufficient magnetic force or elasticity leads to protection failure, or excessive opening resistance affects the sensitivity of low-pressure airflow detection, making it difficult to balance protection effectiveness and detection accuracy, thus limiting the sensor's applicability. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a resistive airflow sensor, as well as a method for manufacturing the resistive airflow sensor, so as to solve the problems mentioned in the background art.

[0004] Resistive airflow sensors include:

[0005] Front housing;

[0006] The rear housing is snapped onto the rear end of the front housing;

[0007] A sensing element is encapsulated between a front housing and a rear housing. The sensing element includes a rigid substrate and a sensing chip. The rigid substrate is fixedly installed to the front housing, and the sensing chip is fixedly installed to the rear housing. A sensitive membrane is provided on one side of the rigid substrate, and the sensing chip and the sensitive membrane are connected by a ribbon cable.

[0008] And a pair of annular protective plates, the front end of the front shell and the rear end of the rear shell are both provided with grooves, the bottom of the grooves are provided with multiple air holes, a threaded ring is fixed to the outer side of one end of the protective plate, the threaded ring is threadedly connected to the grooves one by one, and multiple fan-shaped rubber sheets are uniformly fixed to the inner wall of the protective plate in an annular shape.

[0009] Preferably, the rear housing has a docking block fixed on both the upper and lower sides of the front end, and the docking block has a limit hole at the upper end.

[0010] Preferably, the front housing has mating grooves on both the upper and lower sides of the rear end, and the mating blocks are inserted into the mating grooves one by one. The front housing has slides at both the upper and lower ends, and limit blocks are slidably connected inside the slides. The limit blocks are inserted into the limit holes.

[0011] Preferably, a side channel is provided on the outer side of the slide rail, and a slider is slidably connected inside the side channel. The slider is fixed outside the limiting block, and a return spring is connected between the lower end of the slider and the bottom end of the side channel.

[0012] Preferably, locking pins are movably inserted through the upper and lower sides of the front end of the front housing, a return spring is fixed at the rear end of the locking pin, a locking hole is opened at the lower part of the limiting block, the locking pin movably passes through the docking block and is inserted into the locking hole, and the other end of the return spring contacts the inner wall of the front housing.

[0013] Preferably, a pressure ring is sleeved on the outer side of the threaded ring, and the pressure ring contacts the front end of the locking pin.

[0014] Preferably, rubber magnetic strips are embedded and fixed on both sides of the rubber sheet, and adjacent rubber sheets are attracted to each other through the rubber magnetic strips.

[0015] The fabrication method of a resistive airflow sensor includes the following steps:

[0016] The front and rear shells are manufactured by injection molding. After demolding, they are precision-finished by CNC milling to machine the mating groove, slide, and side channel of the front shell and the mating block of the rear shell. Internal threads and air holes are machined on the grooves of the front and rear shells, and limiting holes are machined on the mating block of the rear shell.

[0017] Laser-cut rigid substrate, spin-coating a polyimide sensitive film on one side of the substrate and curing it; soldering the pins of the piezoresistive sensor chip to a ribbon cable, soldering the other end of the ribbon cable to the silver electrode of the substrate, and wrapping the solder joint with epoxy resin insulating glue; molding and vulcanizing a fan-shaped rubber sheet, embedding rubber magnetic strips on both sides of the rubber sheet and then vulcanizing it a second time; injection molding annular protective plate, ultrasonically welding a brass threaded ring on the outer side of one end of the protective plate and pre-installing a plastic pressure ring;

[0018] CNC turning and milling were used to machine the limit blocks and locking pins from brass; stainless steel cylindrical helical springs were tempered; and ABS sliders were injection molded and ultrasonically welded to the outside of the limit blocks.

[0019] Fix the sensing elements to the front and rear housings respectively; align the mating groove and insert the mating block, push the slider to insert the limit block into the limit hole, use a spring-loaded locking pin to pass through the mating block and insert into the locking hole; thread the protective plate into the housing groove.

[0020] Preferably, the parameters of the rubber sheet and rubber magnetic strip are configured according to the detection threshold of the airflow sensor during the preparation process, including:

[0021] Determine the required dynamic critical opening pressure P for the sensor. c,d A dynamic critical opening pressure balance equation is established, and then the pressure balance equation is decomposed. First, the airflow and structural fundamental parameters are determined, and then the parameters of the magnetic strip, the elasticity and viscoelasticity of the rubber sheet, and the airflow viscous force and local loss parameters are derived. Finally, the actual opening pressure is verified against the theoretically calculated P through airflow experiments. c,d If the deviation exceeds the range, the parameters are iteratively adjusted until they are consistent.

[0022] The beneficial effects of this invention are as follows: By combining the fan-shaped rubber sheet on the inner wall of the protective plate with the embedded rubber magnetic strip, the rubber sheet can be tightly closed by magnetic adsorption when there is no airflow, which can effectively block the intrusion of dust, particulate matter and condensate, avoid contamination of the sensitive membrane, ensure the normal deformation of the sensing element and the stability of electrical signal transmission, and greatly extend the service life of the sensor.

[0023] The housing adopts a precise positioning of docking blocks and docking slots, combined with a double locking structure of limit blocks and locking pillars. This not only improves the stability of the packaging and prevents the internal sensing elements from loosening, but also, through the linkage design of the protective plate pressure ring and the locking pillar, the locking pillar and limit block can be automatically unlocked by removing the protective plate without the need for special tools. This makes the disassembly and assembly of the front and rear housings convenient and reduces the difficulty of inspection and maintenance of the sensitive membrane.

[0024] By establishing a dynamic critical opening pressure balance equation, the elastic and viscoelastic parameters of the rubber sheet and key indicators such as the magnetic strength and contact area of ​​the rubber magnetic strip are derived in reverse. Combined with iterative adjustments based on airflow tests, the opening pressure of the rubber sheet is accurately matched to the detection threshold, ensuring both low-pressure airflow detection sensitivity and protective effect, thus broadening the applicable scenarios of the sensor. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall invention;

[0026] Figure 2 This is a schematic diagram showing the protective plate and the front housing of the present invention disassembled;

[0027] Figure 3 This is a schematic diagram of the rear end of the protective plate of the present invention;

[0028] Figure 4 This is a schematic diagram of the rubber sheet of the present invention;

[0029] Figure 5 This is a schematic diagram of the locking pin of the present invention;

[0030] Figure 6 This is a partial cross-sectional schematic diagram of the front housing of the present invention.

[0031] In the diagram: 1-front housing, 11-limiting block, 12-locking post, 13-reset spring one, 14-connecting groove, 15-slide rail, 16-side rail, 17-slider, 18-reset spring two, 19-locking hole, 2-rear housing, 21-connecting block, 22-limiting hole, 3-protective plate, 31-pressure ring, 32-rubber sheet, 33-threaded ring, 34-rubber magnetic strip, 4-groove, 5-air hole. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] Please see Figures 1-6 The resistive airflow sensor provided by this invention includes a front housing 1, a rear housing 2 snapped onto the rear end of the front housing 1, a sensing element encapsulated between the front housing 1 and the rear housing 2, and a pair of annular protective plates 3. The sensing element includes a rigid substrate and a sensing chip. The rigid substrate is fixedly installed to the front housing 1, and the sensing chip is fixedly installed to the rear housing 2. A sensitive membrane is provided on one side of the rigid substrate, and the sensing chip and the sensitive membrane are connected by a ribbon cable. Grooves 4 are opened at the front end of the front housing 1 and the rear end of the rear housing 2, and multiple air holes 5 are opened at the bottom of the grooves 4. A threaded ring 33 is fixed to the outer side of one end of the protective plate 3. 33 is threadedly connected to the groove 4 in a one-to-one correspondence. The inner wall of the protective plate 3 is uniformly fixed with multiple fan-shaped rubber sheets 32 in a ring shape. The sensor encapsulates the sensing element through the snap-fit ​​of the front housing 1 and the rear housing 2. The protective plate 3 is installed at both ends of the housing. Airflow enters from the direction of the protective plate 3 and flows to the sensitive membrane through the air hole 5. The rubber sheet 32 ​​is closed when there is no airflow to block external pollutants. When airflow passes through, the airflow pressure pushes the rubber sheet 32 ​​open to allow airflow to pass through. However, the rubber sheet 32 ​​can block most particles and condensate, thereby protecting the sensitive membrane from contamination and ensuring the normal deformation of the sensing element and the transmission of electrical signals.

[0034] The rear housing 2 has docking blocks 21 fixed on both the upper and lower sides of its front end. The upper end of the docking block 21 has a limit hole 22. The docking block 21 is fixed integrally with the rear housing 2. The front housing 1 has docking grooves 14 on both the upper and lower sides of its rear end. The docking blocks 21 are inserted into the docking grooves 14 one by one. The upper and lower ends of the front housing 1 have slides 15. The slides 15 are slidably connected to the limit blocks 11. The limit blocks 11 are inserted into the limit holes 22. When the rear housing 2 is connected to the front housing 1, the docking blocks 21 are inserted into the docking grooves 14 of the front housing 1. The limit holes 22 are used to cooperate with the limit blocks 11 to ensure that the rear housing 2 and the front housing 1 are accurately aligned and to limit their relative movement, thereby improving the packaging stability and preventing the sensing elements from loosening inside. After the docking blocks 21 are inserted into the docking grooves 14, the limit blocks 11 are pressed to slide in the slides 15 and insert into the limit holes 22 to form a mechanical lock and prevent the rear housing 2 from detaching.

[0035] A side channel 16 is provided on the outside of the slide 15. A slider 17 is slidably connected inside the side channel 16. The slider 17 is fixed to the outside of the limiting block 11. A return spring 18 is connected between the lower end of the slider 17 and the bottom end inside the side channel 16. The slider 17 is fixedly connected to the limiting block 11. The return spring 18 provides an upward elastic force, so that the limiting block 11 remains protruding from the outer wall of the front housing 1 when no external force is applied. When the docking block 21 is inserted into the docking groove 14, the limiting block 11 needs to be pressed to slide in the slide 15 and insert into the limiting hole 22, so that the return spring 18 is compressed.

[0036] Locking pins 12 are movably inserted through the upper and lower sides of the front end of the front housing 1. A return spring 13 is fixed at the rear end of the locking pin 12. A locking hole 19 is opened at the lower part of the limiting block 11. The locking pin 12 movably passes through the docking block 21 and is inserted into the locking hole 19. The other end of the return spring 13 contacts the inner wall of the front housing 1. When the limiting block 11 slides in the slide 15 and is inserted into the limiting hole 22, the locking pin 12 can be passed through the locking hole 19 and the other end of the return spring 13 contacts the inner wall of the front housing 1, thus locking the limiting block 11.

[0037] A pressure ring 31 is sleeved on the outside of the threaded ring 33. The pressure ring 31 contacts the front end of the locking pin 12. Before installing the protective plate 3 and the front housing 1, the pressure ring 31 is first sleeved on the outside of the threaded ring 33. After the protective plate 3 and the front housing 1 are installed, the pressure ring 31 can press the locking pin 12 tightly. In this way, the locking pin 12 can press the return spring 13 tightly. After the protective plate 3 is removed, the return spring 13 drives the locking pin 12 to move forward out of the lock hole 19 and unlock the limit block 11. At this time, the return spring 18, which is in a compressed state, drives the limit block 11 to move upward out of the limit hole 22, so that the docking block 21 is unlocked. The disassembly and assembly of the front housing 1 and the rear housing 2 are relatively convenient, which facilitates the disassembly of the front housing 1 and the rear housing 2 for maintenance of the sensitive membrane.

[0038] Rubber magnetic strips 34 are embedded and fixed on both sides of the rubber sheet 32. Adjacent rubber sheets 32 are attracted to each other through the rubber magnetic strips 34. When there is no airflow, the rubber magnetic strips 34 cause the adjacent rubber sheets 32 to attract and close each other, forming a tight protective barrier that effectively blocks dust, particles and condensate from entering. When airflow passes through, the airflow pressure overcomes the magnetic force of the rubber magnetic strips 34, pushes the rubber sheets 32 open, and allows airflow to pass through, thus extending the service life of the sensor.

[0039] This invention also provides a method for fabricating a resistive airflow sensor, comprising the following steps:

[0040] The front and rear shells are manufactured by injection molding. After demolding, they are precision-finished by CNC milling to machine the mating groove, slide, and side channel of the front shell and the mating block of the rear shell. Internal threads and air holes are machined on the grooves of the front and rear shells, and limiting holes are machined on the mating block of the rear shell.

[0041] Laser-cut rigid substrate, spin-coating a polyimide sensitive film on one side of the substrate and curing it; soldering the pins of the piezoresistive sensor chip to a ribbon cable, soldering the other end of the ribbon cable to the silver electrode of the substrate, and wrapping the solder joint with epoxy resin insulating glue; molding and vulcanizing a fan-shaped rubber sheet, embedding rubber magnetic strips on both sides of the rubber sheet and then vulcanizing it a second time; injection molding annular protective plate, ultrasonically welding a brass threaded ring on the outer side of one end of the protective plate and pre-installing a plastic pressure ring;

[0042] CNC turning and milling were used to machine the limit blocks and locking pins from brass; stainless steel cylindrical helical springs were tempered; and ABS sliders were injection molded and ultrasonically welded to the outside of the limit blocks.

[0043] Fix the sensing elements to the front and rear housings respectively; align the mating groove and insert the mating block, push the slider to insert the limit block into the limit hole, use a spring-loaded locking pin to pass through the mating block and insert into the locking hole; thread the protective plate into the housing groove.

[0044] The preparation method of the present invention will be illustrated below with reference to a specific embodiment:

[0045] A method for fabricating a resistive airflow sensor includes the following steps:

[0046] (1) Prefabrication of shell components: Select heat-resistant (-20~80℃) and impact-resistant engineering plastics (ABS resin or PC polycarbonate) to ensure long-term stability in airflow environment; use injection molding process to prepare front shell 1 and rear shell 2, and control the mold accuracy within the tolerance of ±0.05mm; after demolding, the shell is finely repaired by CNC milling to remove edge burrs, and the docking groove 14 at the rear end of the front shell, the upper and lower slides 15 and the side slides 16 are machined, and the docking block 21 at the front end of the rear shell is machined; the inner wall of the groove 4 of the front shell and the rear shell is machined with internal threads by thread turning process (to match the subsequent threaded ring), and the bottom of the groove is machined by laser drilling process. Five 1.5mm vent holes are evenly distributed in a ring, with a hole position deviation of ≤0.1mm; the upper end of the rear shell mating block 21 is machined using a CNC drilling machine. A 2mm limiting hole 22; after post-processing, wipe the surface of the housing with isopropanol solution to remove oil stains, and check the fit clearance between the mating groove 14 and the mating block 21 to ensure ≤0.1mm.

[0047] (2) Prefabrication of sensing elements: 0.8mm thick alumina ceramic substrate is selected and cut into a shape that fits the inside of the front housing by laser cutting process; 8μm thick polyimide sensitive film is coated on one side of the substrate by spin coating process, spin coating speed is 3000r / min, time is 30s, and then placed in 100℃ oven for baking and curing for 3h to ensure that the film layer is free of cracks and the flatness is ≤0.02mm; Piezoresistive sensing chip is selected and soldered on brass bracket by SMT surface mount process. The bracket size matches the mounting position of the rear housing. The soldering temperature is 240~250℃ and the holding time is 5s; The chip input / output pins are connected to the ribbon cable by soldering process. The other end of the ribbon cable is soldered to the silver electrode of the rigid board substrate. The solder joint is wrapped with epoxy resin insulating glue and cured at room temperature for 12h to avoid short circuit.

[0048] (3) Prefabrication of protective plate components: using nitrile rubber as raw material, it is pressed into a fan shape (central angle 45°, a total of 8 pieces) by molding and vulcanization process. The mold temperature is 160℃, the pressure is 10MPa, and the vulcanization time is 12min. The rubber sheet is engraved with a 1mm deep groove on both sides using a CNC engraving machine, and a 1mm thick rubber magnetic strip 34 (magnetic strength 600Gs) is embedded. It is then placed back into the mold and vulcanized at 150℃ for 8min to ensure that the bonding strength between the magnetic strip and the rubber sheet is ≥5N. The ring protective plate 3 is prepared by injection molding process, and the inner wall is reserved with a slot that matches the rubber sheet. The outer side of one end of the protective plate is fixed with a brass threaded ring 33 by ultrasonic welding process, and a plastic pressure ring 31 is pre-installed, which can slide along the threaded ring.

[0049] (4) Prefabrication of locking elements: The limit block 11 and the locking post 12 are made of H62 brass and are machined by CNC turning and milling. The limit block is machined into a T-shape with a locking hole 19 at the bottom. The locking post is machined into a cylinder with a 45° chamfer at the front end for easy insertion. The return spring is a stainless steel cylindrical helical spring. The spring constant of return spring 13 is 1.5 N / mm and the spring constant of return spring 218 is 0.8 N / mm. The spring constant is improved by tempering. The slider 17 is made of ABS plastic injection molding and is fixed to the outside of the limit block by ultrasonic welding to ensure that the sliding resistance with the side channel 16 of the front housing is ≤1N.

[0050] (5) Assembly: The pre-installed mounting position inside the front housing 1 is coated with high-temperature resistant epoxy adhesive (model E-44) with a thickness of 0.3mm. The rigid substrate with the sensitive film is attached and fixed, and cured at room temperature for 24 hours to ensure that the connection strength between the substrate and the housing is ≥10N. The mounting position inside the rear housing 2 is also coated with epoxy adhesive to fix the brass bracket of the sensor chip. After curing, the wiring is arranged and the continuity of the wiring is tested with a multimeter to ensure that there is no open circuit or short circuit. Align the mating groove 14 of the front housing 1 with the mating block 21 of the rear housing 2, and slowly insert the mating block until the edges of the two housings are completely fitted; manually push the slider 17 in the side channel 16 of the front housing, causing the limiting block 11 to slide down the slide 15, compressing the second return spring 18, until the lower end of the limiting block is fully inserted into the limiting hole 22 of the mating block, achieving initial locking of the housings; put the first return spring 13 on the rear end of the locking pin 12, and insert the locking pin through the reserved hole of the mating block 21 from the inside of the rear housing until the front end of the locking pin is inserted into the locking hole 19 of the limiting block. At this time, the first return spring is in a slightly compressed state, and the front end of the locking pin protrudes 1mm from the surface of the front housing, completing the double locking. Take the prefabricated protective plate 3, and slip the pressure ring 31 onto the free end of the threaded ring 33, so that the pressure ring is close to the body of the protective plate; align the threaded ring 33 of the protective plate with the groove 4 at the front end of the front housing 1, and rotate the protective plate clockwise with a torque wrench until the threads are fully engaged. At this time, the inner side of the pressure ring is in close contact with the front end of the locking pin 12 to prevent the locking pin from loosening; repeat the above operation to install another protective plate on the groove 4 at the rear end of the rear housing 2; visually inspect the inner wall of the protective plate. When there is no airflow, the adjacent rubber sheets 32 are attracted and closed by the rubber magnetic strip 34, with a gap ≤0.1mm, forming a complete protective barrier.

[0051] The preparation process involves configuring the parameters of the rubber sheet and rubber magnetic strip according to the detection threshold, including the following steps:

[0052] Determine the required dynamic critical opening pressure P for the sensor. c,d A dynamic critical opening pressure balance equation is established, and then the pressure balance equation is decomposed. First, the basic parameters of airflow and structure are determined, and then the parameters of magnetic strip, elasticity and viscoelasticity of rubber sheet, and viscous force and local loss of airflow are derived. Finally, the actual opening pressure and the theoretically calculated Pc,d are verified by airflow test. If the deviation exceeds the range, the parameters are iteratively adjusted until they are consistent.

[0053] Specifically, starting from the target detection threshold, the parameters of each component are quantitatively determined. First, the dynamic critical opening pressure P required by the sensor is determined. c,d P is the minimum instantaneous pressure required for the airflow to open the rubber sheet. This is determined by the requirements of the detection scenario. For example, if a scenario requires detecting an airflow pressure ≥1 Pa, then P... c,d The pressure needs to be set to 1 Pa, the pressure balance equation needs to be decomposed, and parameter correlations need to be established.

[0054] The equilibrium equation for the dynamic critical opening pressure is:

[0055] ;

[0056] in, ;

[0057] In the formula, P c,d is the dynamic critical opening pressure, and is the instantaneous pressure threshold for the rubber sheet to open; A is the effective force-bearing area of ​​the rubber sheet;

[0058] B is the magnetic flux density, describing the magnetic strength of the rubber magnetic strip; n is the number of magnetic strips; S is the contact area of ​​a single magnetic strip; α is the hysteresis coefficient, determined experimentally. denoted as δ, where μ is the instantaneous deformation rate of the rubber sheet; μ0 is the vacuum permeability, a constant; E is the elastic modulus of the rubber sheet, reflecting its elastic properties; h is the thickness of the rubber sheet; δ is the instantaneous deformation of the rubber sheet; L is the radius of the rubber sheet; ν is the Poisson's ratio of the rubber sheet; η is the viscoelastic coefficient of the rubber sheet; C D ρ is the drag coefficient; v is the airflow density; μ is the airflow velocity; ΔP is the local pressure loss of airflow through the pore; A0 is the equivalent flow area of ​​the pore; ξ is the local drag coefficient, which is related to the pore structure.

[0059] P c,d As known objectives, we solve in reverse the rubber sheet thickness h, rubber sheet radius L, rubber sheet elastic modulus E, rubber sheet viscoelastic coefficient η, rubber sheet Poisson's ratio ν, rubber magnetic flux density B, number of rubber magnetic strips n, and rubber magnetic strip contact area S.

[0060] First, determine the airflow velocity v, airflow density ρ, and airflow dynamic viscosity μ based on the detection scenario; then determine the effective force-bearing area A of the rubber sheet, the equivalent flow area of ​​the pores A0, the local resistance coefficient ξ, and the resistance coefficient C. D .

[0061] The parameters of the magnetic stripe are derived, and the total magnetic adsorption force term is: ;

[0062] The hysteresis coefficient α was calibrated experimentally based on the deformation rate of the rubber sheet. (Derived from response time requirements), reverse calculation of magnetic flux density B, single-strip contact area S, and number of magnetic strips n:

[0063] To enhance magnetic adsorption force, i.e., increase P c,d The threshold can be increased by adding B (using high-strength rubber magnetic strips), S (increasing the contact area of ​​the magnetic strips), or n (increasing the number of magnetic strips); conversely, it can be decreased.

[0064] Derivation of the elastic and viscoelastic parameters of the rubber sheet; the elastic-viscoelastic composite restoring force term is:

[0065] ;

[0066] By combining the thickness h, radius L, and Poisson's ratio ν of the rubber sheet, the elastic modulus E and viscoelastic coefficient η can be adjusted in reverse. Increasing the elastic modulus E can improve the elastic recovery force, making the rubber sheet easier to rebound and close. Increasing η can improve the viscoelastic hysteresis force. η affects the response time of the rubber sheet, and the larger η is, the slower the response. Increasing the thickness h or radius L of the rubber sheet will reduce the contribution of the elastic recovery force.

[0067] The actual opening pressure was measured through an airflow test and compared with the theoretically calculated P. c,d If the deviation exceeds the allowable range (e.g., ±5%), the parameters are iteratively adjusted until the theory matches the reality.

[0068] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for fabricating a resistive airflow sensor, characterized in that, The airflow sensor includes: Front housing (1); The rear housing (2) is snapped onto the rear end of the front housing (1); A sensing element is encapsulated between a front housing (1) and a rear housing (2). The sensing element includes a rigid substrate and a sensing chip. The rigid substrate is fixedly installed with the front housing (1), and the sensing chip is fixedly installed with the rear housing (2). A sensitive membrane is provided on one side of the rigid substrate, and the sensing chip and the sensitive membrane are connected by a ribbon cable. And a pair of annular protective plates (3), the front end of the front shell (1) and the rear end of the rear shell (2) are both provided with grooves (4), the bottom of the grooves (4) are provided with multiple air holes (5), a threaded ring (33) is fixed on the outer side of one end of the protective plate (3), the threaded ring (33) is threadedly connected to the grooves (4) one by one, and multiple fan-shaped rubber sheets (32) are uniformly fixed in annular shape on the inner wall of the protective plate (3). Rubber magnetic strips (34) are embedded and fixed on both sides of the rubber sheet (32), and adjacent rubber sheets (32) are attracted to each other through the rubber magnetic strips (34); During the fabrication of the airflow sensor, the parameters of the rubber sheet and rubber magnetic strip are configured according to the detection threshold. The configuration method is as follows: First, determine the airflow velocity v and airflow density based on the detection scenario. ρ Dynamic viscosity of airflow μ; Determine the effective force-bearing area A, the equivalent flow area of ​​the pores A0, and the local resistance coefficient of the rubber sheet. ξ Drag coefficient C D ; The parameters of the magnetic stripe are derived, and the total magnetic adsorption force term is: ; The hysteresis coefficient was calibrated through experiments. α Based on the deformation rate of the rubber sheet Calculate the magnetic flux density B, single contact area S, and number of magnetic strips n in reverse order: To enhance magnetic adsorption force, i.e., increase P c,d The threshold can be increased by B, S, or n; conversely, it can be decreased by decreasing it. Derivation of the elastic and viscoelastic parameters of the rubber sheet; the elastic-viscoelastic composite restoring force term is: ； Combining the thickness h, radius L, and Poisson's ratio of the rubber sheet ν Inversely, the elastic modulus E and viscoelastic coefficient η can be adjusted. Increasing the elastic modulus E can improve the elastic recovery force, making the rubber sheet easier to rebound and close. Increasing η can improve the viscoelastic hysteresis force. η affects the response time of the rubber sheet, and the larger η is, the slower the response. Increasing the thickness h or radius L of the rubber sheet will reduce the contribution of the elastic recovery force. The actual opening pressure was measured through an airflow test and compared with the theoretically calculated P. c,d If the deviation exceeds the allowable range, the parameters are iteratively adjusted until the theory matches the reality.

2. The method for fabricating a resistive airflow sensor according to claim 1, characterized in that: The rear housing (2) has a docking block (21) fixed on both the upper and lower sides of the front end, and the docking block (21) has a limit hole (22) at the upper end.

3. The method for preparing a resistive airflow sensor according to claim 2, characterized in that: The front housing (1) has docking grooves (14) on both the upper and lower sides of the rear end. The docking block (21) is inserted into the docking groove (14) in a one-to-one correspondence. The front housing (1) has slides (15) on both the upper and lower ends. The slides (15) are slidably connected to the limit block (11). The limit block (11) is inserted into the limit hole (22).

4. The method for preparing a resistive airflow sensor according to claim 3, characterized in that: The slide (15) has a side track (16) on the outside. A slider (17) is slidably connected inside the side track (16). The slider (17) is fixed outside the limiting block (11). A reset spring (18) is connected between the lower end of the slider (17) and the bottom end inside the side track (16).

5. The method for preparing a resistive airflow sensor according to claim 4, characterized in that: Locking pins (12) are movably inserted through the upper and lower sides of the front end of the front housing (1). A reset spring (13) is fixed at the rear end of the locking pin (12). A locking hole (19) is opened at the lower part of the limiting block (11). The locking pin (12) movably passes through the docking block (21) and is inserted into the locking hole (19). The other end of the reset spring (13) contacts the inner wall of the front housing (1).

6. The method for fabricating a resistive airflow sensor according to claim 5, characterized in that: A pressure ring (31) is sleeved on the outside of the threaded ring (33), and the pressure ring (31) contacts the front end of the locking pin (12).

7. The method for preparing a resistive airflow sensor according to any one of claims 1-6, characterized in that, Including the following steps: The front and rear shells are manufactured by injection molding. After demolding, they are precision-finished by CNC milling to machine the mating groove, slide, and side channel of the front shell and the mating block of the rear shell. Internal threads and air holes are machined on the grooves of the front and rear shells, and limiting holes are machined on the mating block of the rear shell. Laser-cut rigid substrate, spin-coating a polyimide sensitive film on one side of the substrate and curing it; soldering the pins of the piezoresistive sensor chip to a ribbon cable, soldering the other end of the ribbon cable to the silver electrode of the substrate, and wrapping the solder joint with epoxy resin insulating glue; molding and vulcanizing a fan-shaped rubber sheet, embedding rubber magnetic strips on both sides of the rubber sheet and then vulcanizing it a second time; injection molding annular protective plate, ultrasonically welding a brass threaded ring on the outer side of one end of the protective plate and pre-installing a plastic pressure ring; CNC turning and milling are used to machine brass limit blocks and locking pins; stainless steel cylindrical helical springs are tempered; ABS sliders are injection molded and ultrasonically welded to the outside of the limit blocks. Fix the sensing elements to the front and rear housings respectively; align the mating groove and insert the mating block, push the slider to insert the limit block into the limit hole, use a spring-loaded locking pin to pass through the mating block and insert into the locking hole; thread the protective plate into the housing groove.

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