CN219265395U

CN219265395U - Small-caliber liner reflection type straight tube ultrasonic water meter

Info

Publication number: CN219265395U
Application number: CN202121902335.4U
Authority: CN
Inventors: 请求不公布姓名
Original assignee: Juelong Sensing Technology Shenzhen Co ltd
Current assignee: Juelong Sensing Technology Shenzhen Co ltd
Priority date: 2021-08-17
Filing date: 2021-08-17
Publication date: 2023-06-27
Anticipated expiration: 2031-08-17

Abstract

The utility model belongs to the technical field of flow metering equipment, in particular to a small-caliber liner reflection type straight pipe ultrasonic water meter, which aims to solve the problems of low metering range ratio, low metering precision and the gap between six principles of an optimization solution for the technical development of the ultrasonic water meter in the prior art, and is characterized in that a double-reflection type liner pipe integral structure is formed by connecting a reducing rectifying pipe between two reflection surface fixing brackets through arranging and fixing diversion and a transducer reflection surface fixing bracket at two ends of the inner side of an equal-diameter metal outer pipe by optimizing the layout of a transducer and a reflection surface in a base meter, so that a pipeline is smooth and the acoustic path between two reflection surfaces is fixed; the reflection surface materials are carefully selected, so that the performance of maximizing the metering range ratio and minimizing the starting flow is realized under the limited length of the ultrasonic water meter, the reflection surface has lossless reflection efficiency, and the ultrasonic water meter has the characteristic of no scaling after long-term use under the conditions of high temperature and harder water quality.

Description

Small-caliber liner reflection type straight tube ultrasonic water meter

Technical Field

The utility model belongs to the technical field of flow metering equipment, and particularly relates to a small-caliber liner reflection type straight tube ultrasonic water meter.

Background

In the era of big data of the internet of things, artificial intelligence and industrial automatic control, the full-electronic mode flowmeter gradually replaces a mechanical or electromechanical combined mode flowmeter for the field of raw water, heat and gas supply metering of industry and people, and the full-electronic mode flowmeter has become an irreversible big trend.

According to the requirements of practical application, the fluid metering industry or occasion expects to be compatible with standard flow metering devices with various caliber specification ranges, low pressure loss, high precision, high reliability, no abrasion devices, durability and economy. Currently, the most widely used all-electronic flow meters worldwide are electromagnetic flow meters and post-harvest ultrasonic flow meters.

The ultrasonic flowmeter is raised by technological breakthroughs of time difference timing chips (2012-2017, international companies such as AMS, D-FLOW and TI, etc.) which are advanced in sequence, and at present, the resolution of the ultrasonic flowmeter is up to 5-10 ps, so that the water metering application requirements are completely met. In contrast to electromagnetic flowmeters, ultrasonic flowmeters are sampled by time difference digital signals (electromagnetic flowmeters are sampled by analog signals). Taking a water meter as an example, the water meter has outstanding technical advantages: smaller initial flow (such as liquid with a measurable flow rate of 0.8-1 mm/s), wider measuring range ratio, conversion into fluid flow rate and temperature by using acoustic wave active measurement process time difference and synchronous compensation of the measured volume change (for which, the electromagnetic flowmeter needs to be provided with a thermometer), high precision and safety of large-caliber multichannel measurement (the electromagnetic flowmeter only has a pair of coils and corresponding electrodes, which are scrapped after faults), and various low-viscosity liquids (but the electromagnetic flowmeter cannot measure low-conductivity liquid such as purified water), and in addition, gas such as fuel gas can be measured/metered (but the electromagnetic flowmeter cannot measure gas flow).

Then, how the technological development direction and principle of upgrading and improving the ultrasonic water meter are defined, in general, the main performance indexes of the flowmeter are metering accuracy and measuring range ratio, the metering accuracy is the ratio of the flowmeter value of the flowmeter to the actual value of the flow, and improving the flow stability of the fluid and the consistency of mass production are important conditions for determining the accuracy; the range ratio is the ratio of the common flow to the minimum flow under the guarantee of the metering precision of the flowmeter, the range capable of being precisely metered is reflected, and the increase of the effective distance between the ultrasonic transducers is a necessary condition for improving the range ratio. Obviously, the higher the metering accuracy and the larger the measuring range ratio, the better the metering performance of the flowmeter.

In recent years, the metering industry has greatly improved the practical application of ultrasonic flow meters. In addition to the time difference integrating circuit, the ultrasonic flowmeter has a transducer, a transducer mounting mode, a flow channel structure and the like, wherein the performance of the transducer determines the minimum magnitude of measurable flow, and the overall architecture of the transducer determines the comprehensive performance and quality of the ultrasonic flowmeter. Taking a water meter as an example, particularly according to the constraint of a new standard of the water meter, the industry has clear the technical development direction, and the optimized solution should follow the following principle, which is summarized as follows:

(1) Sound path maximization principle: in order to make the ultrasonic water meter have a large range ratio, an acoustic path maximization mode between ultrasonic transducers should be adopted for the ultrasonic water meter, especially for the DN15 caliber which is most commonly used. Because for water meters, the wide scale ratio is an extremely important index for trade settlement, and is also the most important technical index for water meters, this is quite different from industrial flow meters. In order to make the ultrasonic water meter have a large measuring range ratio, the projection distance of the distance connecting line between two transducers of the ultrasonic water meter in the water flow direction in the main pipe should be maximized so as to obtain a larger measuring range ratio and a smaller starting flow. (for water meters, national standards raised the maximum value of the turndown ratio or flow ratio to r=1000 in 2018

In this regard, through theoretical analysis, conclusions about the quality of ultrasonic flowmeter measurements can be drawn:

in the field of water metering, the range ratio

Is defined as

Wherein, the method comprises the steps of, wherein,

the flow is a given value corresponding to the common flow under a certain pipe diameter;

to meet the minimum flow rate required by a certain metering accuracy (for example, the metering accuracy of the secondary flowmeter is +/-5%).

An important conclusion is reached by the following in-depth analysis and deduction: for fluids passing through the flow meter conduit, the measured pick-up flow (i.e., the minimum flow that the flow meter perceives to be measured)

The lower (corresponding to its flow rate)

The lower the

Related to the resolution of the time difference chip of the ultrasonic flowmeter and the pipeline structure of the flowmeter, corresponding to the resolution,

and also proportionally lower (i.e., the corresponding minimum flow rate

It becomes lower). Typically, in practice, the empirical values are

（

The total zero drift generated by the ultrasonic flowmeter circuit and the transducer and the water resistance design of the flowmeter pipeline are different). This allows the flow rate to be derived at a certain diameter (flow through the flow meter line

And (3) with

Equal time intervals) and the measuring range ratio

Spaced from two transducers

The relation between the two is:

in the above-mentioned method, the step of,

is the common flow rate of a certain caliber flowmeter,

is in combination with

The flow rate of the fluid in the corresponding flow meter line,

to meet the minimum flow rate required for a certain metering accuracy,

is in combination with

The flow rate of the fluid in the corresponding flowmeter tube, for a certain caliber flowmeter,

and

is constant (a selected value),

in order to achieve a peripheral rate of the material,

is the inner radius of the flow meter conduit,

in order to measure the weight of the liquid in the liquid container,

is the distance between the opposite surfaces of two transducers in the pipeline of the ultrasonic flowmeter,

an included angle between two transducers and connected with the water flow direction of the pipeline of the flowmeter is formed

At an acute angle when

When the water flows, the connecting line of the two transducers is consistent with the water flow direction,

,

For a known quantity related to the meter's time difference of measurement, the speed of sound,

for a known quantity related to the measurement time difference and the sound velocity of the flowmeter, let

=

Is constant and is

Time difference formula calculation through ultrasonic flowmeter

Derived, i.e

Thus, in a specific calculation,

according to

Substitution. From above

The relation of (2) can be concluded as follows:

increasing the projected distance between two transducers in the flow direction of the flowmeter pipeline

The measuring range ratio of the flowmeter can be effectively improved

。

(2) A pair of opposite-type installation principle between transducers: the opposite-type acoustic wave signals are directly transmitted and received by a pair of transducers, so that the amplitude of the effective signal is the highest. The reflection type has the advantages that the reflection type has one or a plurality of reflection surfaces, the acoustic wave energy loss (when the reflection surfaces are large enough, the acoustic energy loss is 10-20% in an ideal state, and the measurement is not affected generally), and particularly when the reflection surfaces have angle deviation or scale is formed after use, the acoustic wave energy loss can reach 40-60%, which seriously affects the normal measurement. In addition, there are reflection surfaces, and the mounting structure is complicated, and especially, improper water resistance distribution treatment of the reflection surfaces also affects the measurement accuracy.

It is important to note that the reflective ultrasonic flowmeter also has potential application advantages, and if the potential application advantages can be exerted and the existing disadvantages can be eliminated, the reflective ultrasonic flowmeter also has wide application value. In order to eliminate the disadvantages of the reflective ultrasonic flowmeter, an effective solution and a scheme should be searched for to solve the problem of acoustic energy loss of the reflective surface caused by reflected acoustic waves, to solve the problem of scaling of the reflective surface, and to solve the problem of turbulence caused by uneven resistance of the reflective surface to water flow.

(3) Consistency principles; the flow channel forming and processing technology of the ultrasonic water meter base meter has higher assembly installation precision and consistency requirements, and determines the mass production quality of the flowmeter. For reflection type, the distance between the two transducer sound waves on the two reflection surfaces is particularly ensured to be fixed, the difference caused by pipe section processing and transducer installation is avoided, the level is improved, the range of individual error compensation and precision correction of the base table can be reduced, and the complicated workload of manually correcting the individual error in the later period is reduced.

(4) Tube sealing safety principle: under the condition of the liner tube in the ultrasonic flowmeter, in order to ensure the sealing safety, a local sealing mode rather than an integral sealing mode is adopted as much as possible, so that the sealing reliability and durability of the ultrasonic flowmeter are ensured.

(5) Suitability principle: the ultrasonic water meter can be used for water metering, and is also suitable for other purposes, such as a temperature sensor convenient to install so as to meet the requirement of heat supply metering, and is used as a heat meter of heat supply metering.

(6) Simple structure, convenient assembly principle: the ultrasonic water meter has simplified structure and unique certainty in installation, so that the whole ultrasonic water meter is easy to assemble, and the flowmeter can be ensured to have higher consistency.

In contrast to the standards in accordance with the principles described above, the prior art still has drawbacks or deficiencies.

Patent application publication number CN 105890818A is a relatively typical column type small-caliber ultrasonic reflection type flowmeter applied in this mode, and the separately installed support columns cannot achieve the consistent angle of the two reflection surfaces, and the influence of the column and the reflection on the turbulence formed by the fluid is not considered, so that the small flow deviation is large, the measuring range is relatively low, and the flowmeter is mainly applied to heat supply measurement.

In view of the defects of the supporting post reflecting surface, a plug-in type reflecting surface is adopted in most cases, such as patent application publication number CN 106679749A. The reflective surface of the structure is greatly improved relative to the upright post, and the influence of the support post on the fluid is mainly removed. Experiments show that the range ratio of the plug-in type can be doubled (for DN20 caliber water meters, the column type is usually R=100, and the plug-in type is usually R=200). However, such a sloped reflective upstream surface still produces turbulence in the fluid, affecting the small flow stability, and its characteristics remain to be further improved.

Patent application publication number CN 103983316A discloses a solution for reducing water turbulence by a pod. The bullet type current stabilizer is additionally arranged at the front side of the water inlet end (water outlet end) of the reflecting surface, so that turbulence can be reduced, and the accuracy of measuring the small flow of the flowmeter can be improved. However, it can be seen from the patent drawings that no sleeve or smooth wall with gentle diameter reduction is arranged between the installation structure frame of the bullet-type current stabilizer and the middle sleeve, which inevitably blocks water flow, and particularly increases water resistance and causes turbulence to influence measurement accuracy under the condition of high flow

Patent publication CN 204373718U discloses a measuring tube section for a meter, and it can be seen that the two transducer mounting holes are relatively centered and the sound path is short, and this structure is against the principle of maximizing the sound path, so that the measuring range ratio is limited.

Through the analysis of the prior art and the six principles of the optimized solution developed according to the ultrasonic water meter technology, for the small-caliber ultrasonic water meter, the ultrasonic reflection type water meter can be effectively improved by adopting the effective technical scheme to maximize the sound path, complete the water flow channel, improve the reflection efficiency of the reflection surface, reduce the turbulence influence generated by the reflection surface, ensure that the reflection surface is used for a long time without scaling, process the whole pipe section, manufacture the base meter of the flowmeter and the like.

Disclosure of Invention

The utility model aims to solve the defects of the prior art, namely the defects of design and application of the base meter of the traditional ultrasonic reflection type flowmeter, and provides a small-caliber lining reflection type straight tube ultrasonic water meter, which comprises the following components: the ultrasonic reflection type water meter has the advantages of maximizing the sound path, improving the reflection efficiency of the reflecting surface, reducing the structural shape of the reflecting surface, which generates turbulence influence, constructing the integral structure of the water flow channel, adopting a long-term non-scaling material for the reflecting surface, processing and constructing a base meter of the flowmeter by using an integral metal outer tube, conveniently installing and fixing the meter shell, and the like, so that the integral performance of the ultrasonic reflection type water meter can be greatly improved.

The technical scheme of the utility model is as follows: the method is characterized in that the maximization of the sound path of the transducer and the reflecting surface is targeted, the layout of the transducer and the reflecting surface in a flowmeter base table is preferentially considered, and the fixed brackets of the diversion and the transducer reflecting surface are arranged and fixed at the two ends of the inner side of the equal-diameter metal outer tube of the small-diameter ultrasonic water meter, so that the maximization of the sound path of the ultrasonic transducer is realized; the two reflecting surface fixing brackets are connected by the reducing rectifying tube to form a double-reflecting type energy converter lining tube body structure, thereby realizing the completeness of a water flow passage, effectively ensuring the permanent unchanged distance between the two reflecting surfaces and enabling the flow meter processed in batches to have the flow characteristic with high consistency; the diversion and reflection surface fixing bracket is inlaid and butted into a whole by two symmetrical parts, is divided into an outer ring and a middle part, and is connected by an upper supporting rib and a lower supporting rib, so that water flow immediately and stably enters the reducing rectifying tube after passing through the supporting ribs and the reflection surface, no blocking is generated, the water flow is stable and smooth, and the structural shape generated by reducing turbulent flow of the reflection surface is formed; the reflection surface and the reflection surface material are searched through theoretical analysis, experimental analysis and experimental verification, so that the reflection surface has lossless reflection efficiency, and can be used for a long time without scaling under the conditions of high temperature and harder water quality.

The utility model relates to a small-caliber lining reflection type straight tube ultrasonic water meter, which comprises an equal-diameter metal outer tube, a diversion and reflection surface fixing bracket, a rectifying tube and a fixing seat thereof, a transducer and a transducer fixing seat thereof, a transducer and a meter bottom shell fixing nut, wherein the fixing bracket is arranged on the fixing seat of the rectifying tube; the interface and the base surface of the small-caliber lining reflection type straight pipe ultrasonic water meter and the external pipeline are equal-diameter metal outer pipes, and fixed guide and transducer reflecting surface fixing brackets are arranged and fixed at the two ends of the inner side of the equal-diameter metal outer pipes, so that the maximization of the sound path of the ultrasonic transducer is realized; the two reflecting surface fixing brackets are connected by the reducing rectifying tube to form a double-reflecting type energy converter lining tube body structure, thereby realizing the completeness of a water flow passage, effectively ensuring the permanent unchanged distance between the two reflecting surfaces and ensuring that the flow meters processed in batches have the flow characteristics with high consistency; through the optimized transducer, the reflecting surface shape and the reflecting surface material, the sound wave among the transducers is smoothly transmitted with low loss; under the cooperation of the transducer fixing seat, the instrument lower shell fixing nut and the instrument box, the small-caliber liner reflection type straight tube ultrasonic water meter is formed, and under the straight tube length limited by the small-caliber ultrasonic water meter, the sound range maximization between the ultrasonic transducers is realized, so that the ultrasonic water meter achieves the performance of maximizing the range ratio and minimizing the start flow.

The two ends of the interface between the equal-diameter metal outer tube and the outer tube are provided with tube threads, and the equal-diameter metal outer tube is provided with a transducer fixing seat, a rectifying tube fixing seat and a temperature sensor mounting seat when needed. The guide and reflecting surface fixing support is formed by embedding and butting two symmetrical parts in the middle. After butt joint, the front end is provided with a diversion cap, and the rear end is provided with a reflecting surface fixing bracket, a supporting rib and an outer tube. The rectifying tube is fixed by a rectifying tube fixing nut and is in tight fit butt joint with the diversion and reflection surface fixing support. The transducer fixing seat is internally provided with a transducer, the convex edge of the transducer is positioned by a positioning boss, and the side sealing ring and the top sealing ring are sealed; the elastic washer is positioned above the transducer and below the fixing nut; the fixing nut is positioned at the uppermost part in the transducer fixing seat and has two functions: firstly, the transducer is pressed by pressing the elastic gasket, and meanwhile, the lower end of the transducer extends into the guide and reflecting surface fixing bracket to play a role in positioning; secondly, the instrument bottom shell is fixed through a cylinder structure of the instrument bottom shell. The instrument box consists of an instrument box bottom shell and an instrument box upper shell, and a battery, a circuit board and a display screen are arranged in the instrument box. The transducer signal line is connected to the circuit board through the fixation nut central through hole.

When temperature parameters are needed or heat metering application is carried out, a temperature sensor mounting seat can be arranged at the position, close to the water outlet, of the outer end of the metal outer tube, and the temperature sensor is mounted in the temperature sensor mounting seat.

The flowmeter base outer tube is an equal-diameter metal outer tube, tube threads are arranged at two ends of the equal-diameter metal outer tube, and the outer side of the equal-diameter metal outer tube is connected with a transducer fixing seat, a rectifying tube fixing seat and a temperature sensor mounting seat when needed through laser welding.

A bullet stabilizer solution disclosed in patent application publication No. CN 103983316A has the disadvantage of affecting the flow field: after the water flow passes through CN 103983316A to disclose a bullet-shaped current stabilizer, the bullet-shaped current stabilizer is exposed to the bullet-shaped current stabilizer fixing support section, and a gentle reducing pipe body is not connected between the bullet-shaped current stabilizer fixing support section and the middle pipe, so that the water flow current stabilizer fixing support and the edge of the middle pipe orifice can be blocked, and turbulence is generated due to the increase of blocking resistance particularly under the condition of high flow, and the time difference and the flow meter precision are affected.

The guide and reflecting surface fixing support is formed by embedding and butting two symmetrical parts into a whole. After butt joint, the water-saving device is divided into an outer ring and a middle part, the two parts are connected by an upper supporting rib and a lower supporting rib instead of a plurality of supporting ribs, and the water-saving device is uniform in water diversion, is beneficial to water flow passing, and has high strength and symmetry. The water flow immediately and steadily enters the reducing rectifying tube after passing through the supporting ribs and the cylindrical side surface of the reflecting surface, no fracture exists in the process, no blocking is generated, so that the water flow is stable and smooth, the fluid characteristics are stable, and the time difference precision, namely the metering precision, is improved.

The guide and reflecting surface fixing support consists of a guide cap at the front end, a reflecting surface fixing support at the rear end, supporting ribs and an outer tube. As shown in fig. 2, the integrated deflector cap and the reflecting surface fixing bracket are formed by tightly matching and butting two parts of convex and concave structures; the sound wave elliptic reflecting surface is fixed by abutting and wrapping two parts of the guide and reflecting surface fixing support on elliptic long shafts, namely upper arc-shaped grooves and lower arc-shaped grooves, and the elliptic short shaft position is not required to be fixed, so that the enough reflecting area is ensured.

The reflecting surface is made of elliptical ZrO with thickness of 1mm, width of 9mm and length of 11mm ₂ 、Si ₃ N ₄ Or SiC material. Experiments prove that the three materials have extremely high reflection effect on ultrasonic waves, can not scale after long-term use under the conditions of high temperature and harder water quality, and can effectively ensure that the reflection intensity of the ultrasonic waves can not be attenuated for a long time.

And (3) assembling a guide and reflecting surface fixing support: the fixing rubber ring has the functions that firstly, a reflecting sheet is arranged at the reflecting surface, two parts of the diversion and reflecting surface fixing support are in butt joint and closure, and the fixing rubber ring is added for fixing; secondly, after the guide and reflecting surface fixing support is inserted into the equal-diameter metal outer tube, the rubber ring plays a role in squeezing and stabilizing, and does not play a role in sealing.

The guide cap and the rear end reflecting surface fixing support are generally round columns, and the diameters of the guide cap and the rear end reflecting surface fixing support are 9mm, so that for DN15 pipe diameter, the minimum clearance between the cylinder and the inner side is 4.42mm through calculation, and if a filter screen with meshes of 2.5-3 mm is adopted at the front end of the flowmeter, the minimum water flow clearance in the pipe can be ensured to be more than or equal to 3mm, namely the smooth passing of conventional impurities in water is ensured.

The rectifying tube is fixed in the blind hole by the rectifying tube fixing nut and the sealing ring, and is in tight fit and butt joint with the diversion and reflection surface fixing support. After butt joint, the butt joint is welded by using glue or laser, so that the two diversion and reflection surface fixing brackets and the rectifying tube are integrated. Thus, the permanent constant distance between the two reflecting surfaces and the consistency of mass production flow characteristics can be effectively ensured. The rubber ring plays a role in tightly matching the rectifying tube with the inner cavity of the metal tube and preventing water from flowing between the rectifying tube and the inner cavity of the metal tube, and does not play a role in sealing.

The transducer adopted in the utility model is a small-caliber transducer, and the structure is as follows: a front end diameter of 10mm, a rear end diameter of 14mm, a frequency of 2MHz or 4 MHz. The middle part of the transducer is provided with a groove, sealing rings can be arranged at the middle part and the upper part of the transducer, and the sealing rings are respectively side sealing and top sealing, namely two stages of sealing modes and two different sealing modes are adopted, so that the sealing safety is ensured.

The specification of the ceramic plate adopted by the transducer meets the requirement of the water meter committee of China measuring society on the frequency application standard of the ceramic vibrator of the ultrasonic transducer, namely:

the specified transducer ceramic plate vibration frequency may be: 1MHz, 2MHz, 4MHz,

the ceramic plate has the following common diameter to thickness ratio: phi 12/2mm; phi 8/1mm; phi 8/0.5mm;

the wavelength corresponding to each frequency of a certain material is as follows: 2.5mm 1.25mm 0.625mm

(assuming that the sound velocity of a sound guiding material at room temperature is 2500 m/s)

Conventionally, the larger the size of the transducer, the greater the intensity of sound waves emitted, but the larger the mounting size; the higher the frequency of the transducer, namely the shorter the wavelength, the smaller the physical diameter and the volume of the transducer, so that the transducer is convenient to install, the higher the circuit timing triggering precision is, and the more accurate the time difference calculation is. Early transducers were manufactured at a low level, i.e., low electrical/acoustic conversion efficiency, and reflective acoustic losses, so most manufacturers used larger volume 1MHz transducers (with Φ12-14 mm ceramic plates). In recent years, with the improvement of precision manufacturing level, the electric/acoustic conversion efficiency is leaved, and the electric/acoustic conversion efficiency of a transducer with small size and high frequency is greatly improved, so that the application requirements are completely met.

The commonly used DN15 inserted sheet reflective flowmeter transducer adopts a ceramic plate with the diameter of phi 12mm and the frequency of 1MHz, and the diameter of the front end of the packaged convex type transducer is phi 17mm and the diameter of the rear end thereof is phi 21mm. In view of the small dimensions in the flow channels, the interference with the fluid is minimized, and therefore the reflective surface is a stainless steel insert stamped with a width of 10 mm. The edges are arcuate due to the stamped form, and the width of the plane that can actually be used for reflection is approximately 8mm. The actual utilization of acoustic energy is about 67% (note: different widths of reflecting surfaces of different calibers, and different reflection efficiencies) at 8/12.

The utility model adopts a ceramic chip with the diameter of phi 8mm and the frequency of 2MHz or 4MHz, and the ceramic chip is packaged into a convex transducer with the diameter of phi 10mm at the front end and the diameter of phi 14mm at the rear end. Therefore, the size of the reflecting surface can be reduced, the reflecting surface is more convenient to install in a small-caliber pipeline, and the minimum gap of water flow is beneficial to the passage of impurities below 3 mm. Then, the fixed edge of the inclined reflecting surface is added, the width of the reflecting surface after installation is phi 9mm, the edge fixed part (mainly fixed by the long axis direction of the elliptical surface) is removed, the width of the effective reflecting surface is at least 8mm, and the total reflection of ultrasonic energy generated by the ceramic chip phi 8mm is completely satisfied, namely, the utilization rate of the acoustic wave energy is 100%.

The advantages of using a transducer with high frequency (2 MHz, 4 MHz) and small size (ceramic plate phi 8mm, transducer front end phi 10mm, and rear end diameter phi 14 mm) are that (taking 2MHz as an example):

(1) The overall size of the transducer is small, and the size of the transducer fixing seat is also small, so that the distance between the two transducer central lines of the 2MHz transducer and the phi 10mm transducer is increased by 7mm relative to the 1MHz transducer and the phi 17mm transducer, that is, if the transducer fixing seat is arranged close to the inner side of the outer tube thread of the metal tube, the sound path of the 2MHz transducer is 7mm longer than that of the 1MHz transducer, and the sound path increasing range ratio can be enlarged for the tube length with limited length, which is important.

(2) The wavelength of the 2MHz transducer is half of that of the 1MHz transducer, so that the triggering timing precision is higher and the time difference is more accurate for a time difference circuit triggered by the head wave.

(3) For reflective mounting, if the reflective surface is an ellipse of 8mm in width, for a 2MHz, Φ8mm ceramic wafer size, 100% of the total acoustic energy would theoretically be reflected; however, for the sizes of the ceramic plates with the dimensions of 1MHz and phi 12mm, only 67% of acoustic energy can be reflected, and the utilization rate is low.

The patent grant publication number CN 201773574U is a transducer adopted by a conventional ultrasonic reflection type flowmeter, and has the following two disadvantages: firstly, only one sealing ring can be arranged at the step of the convex transducer, so that the safety is poor; and secondly, the transducer is installed and positioned by the sealing ring, if the sealing ring is deformed (such as an organic matter is encountered), the transducer is inclined (angle change), and the emitted sound wave cannot be reflected by the reflecting surface, so that the sound energy loss is large, the time difference calculation cannot be performed, and the measurement is stopped.

The utility model provides a transducer with a 2MHz/4MHz structure and a positioning and double sealing structure, wherein the lower edge of the outer side of the transducer is a mounting positioning edge which is positioned on a positioning table at the inner side of a transducer fixing seat and is sealed by a side sealing ring and a top sealing ring. Therefore, the horizontal installation and positioning of the transducer can be ensured, the sealing safety and reliability can be ensured, and the transducer can be used for a long time.

The elastic washer is located above the transducer, and plays a role in not damaging the sealing ring and limiting the pressure applied by the fixing nut downwards when the fixing nut rotates downwards. The other function of the fixing nut is to press the instrument box base, namely, press the cylindrical shell sleeved on the transducer fixing seat, so that the function of fixing the instrument base is achieved by a simpler method. The side sealing ring is used for performing waterproof sealing between the cylindrical structure of the instrument box base and the outer side of the transducer fixing seat.

The instrument box consists of an instrument box base and an instrument box upper shell, and a battery, a circuit board and a display screen are arranged in the instrument box. The transducer signal wires are connected to the circuit board through the central hole of the fixing nut.

In the utility model, because the whole inner bushing pipe formed by the diversion and reflection surface fixing support and the rectifying pipe is not required to be sealed with the inner side of the metal outer pipe in a waterproof way, when the heat metering application is carried out, the temperature sensor mounting seat can be arranged at the position, close to the water outlet, of the outer end of the metal outer pipe, the temperature sensor can be conveniently mounted in the temperature sensor mounting seat, and the temperature measuring rod of the temperature sensor is obliquely inserted at the outer side of the diversion cover of the energy converter, so that the measurement of fluid is not influenced.

In summary, compared with the prior art, the utility model has outstanding substantial characteristics and remarkable progress, and is specifically expressed as follows:

firstly, for an ultrasonic flowmeter base table with DN15 caliber or small caliber of a given length, the utility model fully utilizes the limited length of the ultrasonic flowmeter base table, arranges and fixes the diversion and transducer reflecting surface fixing brackets at the two ends of the inner side of the equal-diameter metal outer tube, and selects transducers packaged by ceramic plates with small sizes of 2MHz/4MHz and phi 8mm for matching, thereby realizing the maximization of the sound path of the ultrasonic transducer, and further ensuring that the ultrasonic flowmeter achieves the performances of maximizing the range ratio and minimizing the starting flow.

Secondly, for DN15 caliber base meters, the technical requirements of ensuring that the water gap at the narrowest part of the flow channel is more than 3mm and that the pressure loss at the position is not increased suddenly so as not to form turbulence are needed. According to the utility model, the small-caliber transducer, the smaller phi 9mm reflecting surface width and the diameter of the reflecting surface column phi 9mm are selected, and the small-caliber transducer and the reflecting surface column phi 9mm are connected with the lining pipe by the two support columns, so that the water flow has small pressure loss, uniform flow distribution and high strength, the technical requirement that the minimum water flow gap is larger than 3mm is completely met, and conventional impurities can pass through conveniently.

Thirdly, unlike the conventional transducer which adopts a lower sealing ring for positioning, the transducer of the utility model performs high positioning through the boss in the outgoing line fixing seat, and can ensure the positioning flatness of the transducer and ensure that the ultrasonic signals can accurately reach the reflecting surface.

Fourth, the transducer adopted in the utility model is a small-caliber special-shaped transducer, the diameter of the front end of the transducer is phi 10mm, the diameter of the rear end of the transducer is phi 14mm, the frequency of the transducer is 2MHz or 4MHz, the middle part of the transducer is provided with a groove, sealing rings can be arranged at the middle part and the upper part of the transducer, and the sealing rings are respectively in side sealing and top sealing.

Fifth, the rectifying tube is tightly matched and butted with the diversion and reflection surface fixing support, and after butt joint, butt joints are formed by gluing or laser welding, so that the two diversion and reflection surface fixing supports and the rectifying tube form an integral measuring flow passage structure, the integral measuring flow passage structure is beneficial to smooth flow of water, the problem that stable flow of a flow field is influenced due to the fact that a diversion cap and a middle pipeline in the patent application publication No. CN 103983316A are disconnected is solved, and the integral measuring flow passage structure can effectively ensure that the distance between two reflection surfaces is permanently unchanged. Because the distance between the two reflecting surfaces determines the measuring range ratio of the ultrasonic flowmeter, the measuring range ratio and consistency of the flowmeter are guaranteed for mass production, and the detection and calibration of the flowmeter are greatly facilitated.

Sixth, the acoustic wave reflecting surface adopted by the utility model is made of elliptical ZrO with thickness of 1mm, width of 9mm and length of 11mm ₂ 、Si ₃ N ₄ Or SiC material. Both theory and experiment prove that the three materials have extremely high ultrasonic reflection effect, can not scale after long-term use under the conditions of high temperature and harder water quality, and can effectively ensure that the reflection intensity of ultrasonic waves can not be attenuated for a long time.

Seventh, the utility model is that the diversion and reflection surface fixing bracket, namely the diversion cap with symmetrical front end and the reflection surface fixing bracket with back end, the supporting rib and the outer tube form a stable whole, the whole outer tube and the reducing rectifying tube can be connected in a seamless way, thus ensuring the smooth flow of the fluid from the diversion cap to the reducing rectifying tube. In addition, the diversion cap and the rear end reflecting surface fixing bracket are formed by two symmetrical parts of a central surface and are formed by tightly matching and butting convex structures; the minor axis of the elliptic ceramic reflecting surface is 9mm, the major axis is 11mm, and the ceramic elliptic reflecting surface is clamped and wrapped and fixed (the minor axis is not fixed) only by the arc edges of the upper major axis and the lower major axis of the elliptic ceramic reflecting surface in a groove mode through the butted diversion and reflecting surface fixing support. Because the guide cap and the rear end reflecting surface are generally cylindrical, the diameter of the guide cap and the rear end reflecting surface is 9mm, the diameter of the reflecting surface fixing column is not increased by the structure for wrapping and fixing the elliptical ceramic reflecting surface, and for an ultrasonic water meter with DN15 caliber, the minimum gap between the guide cap and the rear end with the reflecting surface fixing column and the inner side of the outer tube is 4.42mm or more, and the smooth passing of conventional impurities in water is ensured.

Eighth, the fixing nut of the utility model realizes the function of the first generation, namely, the elastic washer is applied with force to press the transducer, and meanwhile, the lower end of the transducer extends into the guide and reflecting surface fixing bracket to play a role in positioning; secondly, it is used for compressing the fixed circuit instrument box inferior valve, has reduced the fixed device of inferior valve.

In the ninth aspect of the utility model, the two diversion and reflection surface fixing brackets and the rectifying tube form an integral measuring flow passage structure, and waterproof sealing is not needed between the integral measuring flow passage structure and the inner side of the metal outer tube, so that the temperature sensor can be conveniently installed, and the integral measuring flow passage structure is suitable for heat energy metering of heating.

Drawings

FIG. 1 is a schematic view of a small caliber liner reflective straight tube ultrasonic water meter;

FIG. 2 is a schematic view of a small-caliber inner liner reflective guide and reflective surface fixing bracket;

FIG. 3 is a schematic diagram of a small caliber liner reflective temperature sensor mounting structure;

in the figure:

11. an isodiametric metal outer tube; 111. a pipe thread; 12. a transducer mount; 121. positioning the boss; 122. a seal ring; 441. a side seal ring; 442. a top sealing ring; 44. a transducer; 443. a transducer signal line; 444. a transducer ledge; 45. spring washers; 46. a fixing nut; 13. a rectifying tube fixing seat; 33 rectifying tube; 331. blind hole 132, rectifier tube fixing nut; 131. a seal ring; 14. a temperature sensor mount; 141. a temperature sensor; 22. a guide and reflecting surface fixing bracket; 221. a deflector cap; 222. a reflecting surface fixing bracket; 2211. a concave-convex structure; fixing a rubber ring 223;23. a reflecting surface; 55. an instrument box; 55A, a bottom shell of the instrument box; 55B, an upper shell of the instrument box; 551. a battery; 552 a circuit board; 553, displaying a screen;

Detailed Description

The utility model will now be described in further detail with reference to the drawings and examples.

Examples:

as shown in fig. 3, the embodiment is a small-caliber liner reflection type straight pipe ultrasonic thermal water meter structure. The rest is shown in figure 1 except for the structure of the additional temperature sensor. The two ends of the interface between the equal-diameter metal outer tube 11 and the outer tube are provided with tube threads 111, and the equal-diameter metal outer tube 11 is provided with a transducer fixing seat 12, a rectifying tube fixing seat 13 and a temperature sensor mounting seat 14 for measuring temperature and heat energy. The guide and reflecting surface fixing support 22 is formed by embedding and butting two symmetrical parts in the middle. After the butt joint, the front end is provided with a diversion cap 221, the rear end is provided with a reflecting surface fixing bracket 222, a supporting rib and an outer tube. The rectifying tube 33 is fixed by a rectifying tube fixing nut 132 and is in tight fit and butt joint with the diversion and reflection surface fixing bracket 22. The transducer fixing seat 12 is internally provided with a transducer 44, a convex edge 444 of the transducer is positioned by a positioning boss 121, and a side sealing ring 441 and a top sealing ring 442 are sealed; the elastic washer 45 is positioned above the transducer 44 and below the fixing nut 46; the retaining nut 46 is located uppermost in the transducer mount 12 and serves two purposes: firstly, the transducer 44 is pressed by pressing the elastic gasket 45, and meanwhile, the lower end of the transducer 44 extends into the guide and reflecting surface fixing support 22 to play a role in positioning; secondly, the meter bottom case 55A is fixed by pressing the cylindrical structure of the meter bottom case 55A. The meter box 55 is composed of a meter box bottom shell 55A and a meter box upper shell 55B, and a battery 551, a circuit board 552 and a display screen 553 are arranged in the meter box 55. Transducer signal lines 443 are connected to the circuit board 552 through a central throughbore of the retaining nut 46.

In this embodiment, the hot water is measured, and the heat measurement is required by the temperature parameter, so the outer end of the metal outer tube 11 is close to the water outlet, and a temperature sensor mounting seat 14 is arranged at the position of the water outlet, and the temperature sensor 141 is mounted in the temperature sensor mounting seat 14.

The flowmeter base outer tube is an equal-diameter metal outer tube 11, and is formed by machining and laser welding of a metal tube. The two ends of the equal-diameter metal outer tube 11 are provided with tube threads 111, and the equal-diameter metal outer tube 11 is connected with a transducer fixing seat 12, a rectifying tube fixing seat 13 and a temperature sensor mounting seat 14 through laser welding.

The defects of a bullet current stabilizer scheme disclosed in the patent application publication number CN 103983316A are as follows: after the water flow passes through CN 103983316A to disclose a bullet-shaped current stabilizer, the bullet-shaped current stabilizer is exposed to the bullet-shaped current stabilizer fixing support section, and a gentle necking pipe body is not connected between the bullet-shaped current stabilizer fixing support section and the middle pipe, so that the water flow current stabilizer fixing support and the edge of the middle pipe orifice can be blocked, and turbulence is generated due to the increase of blocking resistance particularly under the condition of high flow, and the time difference and the flow meter precision are affected.

The guide and reflecting surface fixing support 22 in the embodiment is formed by embedding and butting two symmetrical parts into a whole. After butt joint, the water-saving device is divided into an outer ring and a middle part, the two parts are connected by an upper supporting rib and a lower supporting rib instead of a plurality of supporting ribs, and the water-saving device is uniform in water diversion, is beneficial to water flow passing, and has high strength and symmetry. The water flow immediately and steadily enters the necking rectifying tube after passing through the supporting ribs and the reflecting surface, no fracture exists in the process, no blocking occurs, so that the water flow is stable and smooth, the fluid characteristics are stable, and the time difference precision, namely the metering precision, is improved.

The front end of the guide and reflecting surface fixing support 22 consists of a guide cap 221, a reflecting surface fixing support 222 at the rear end, supporting ribs and an outer tube. The integrated deflector cap 221 and the reflecting surface fixing bracket 222 are formed by tightly matching and butting two parts of convex and concave structures 2211; the sound wave reflecting surface 23 is fixed by butt joint and wrapping of upper and lower arc grooves of the two parts of the guide and reflecting surface fixing support 22.

The reflecting surface 23 is made of an elliptical ZrO having a thickness of 1mm, a width of 9mm, and a length of 11mm ₂ 、Si ₃ N ₄ Or SiC material. Experiments prove that the three materials have extremely high reflection effect on ultrasonic waves, can not scale when used under the conditions of high temperature and harder water quality, and can effectively ensure that the reflection intensity of the ultrasonic waves can not be attenuated for a long time.

The guide and reflecting surface fixing support 22 is assembled: the fixed rubber ring 223 has the functions that firstly, the reflecting sheet 23 is placed at the reflecting surface 222, and two parts of the diversion and reflecting surface fixed support 22 are in butt joint and folded, and the fixed rubber ring 223 is added for fixing; secondly, after the guide and reflecting surface fixing support 22 is inserted into the equal-diameter metal outer tube 11, the effect of compaction and stability is achieved, and the rubber ring does not have a sealing effect.

The guide cap 221 and the rear end reflecting surface fixing support 222 are generally circular columns with the diameter of 9mm, so for DN15 pipe diameter, the minimum clearance between the cylinder and the inner side is 4.42mm through calculation, and if a filter screen with meshes of 2.5-3 mm is adopted at the front end of the flowmeter, the minimum water flow clearance in the pipe can be ensured to be more than or equal to 3mm, and the smooth passing of conventional impurities in water can be ensured.

The rectifying tube 33 is fixed in the blind hole 331 by the rectifying tube fixing nut 132 and the sealing ring 131, and is in tight fit and butt joint with the diversion and reflection surface fixing bracket 22. After butt joint, the butt joint is welded by gluing or laser to integrate the two guide and reflecting surface fixing brackets 22 and the rectifying tube 33. Thus, the permanent constant distance between the two reflecting surfaces and the consistency of mass production flow characteristics can be effectively ensured. The rubber ring 332 plays a role in tightly matching the rectifying tube with the inner cavity of the metal tube and preventing water from flowing between the rectifying tube and the inner cavity of the metal tube, and does not play a role in sealing.

The transducer 44 used in this embodiment is a small-caliber transducer, and its structure is: the diameter of the front end is phi 10mm,

The back end diameter Φ14mm,2MHz or 4MHz frequency. The transducer has a groove in the middle, and sealing rings in the middle and upper parts, side seal 441 and top seal 442, respectively, are used in two stages, two different sealing modes, to ensure sealing safety.

Conventionally, the larger the size of the transducer, the greater the intensity of sound waves emitted, but the larger the mounting size; the higher the frequency of the transducer, namely the shorter the wavelength, the smaller the physical diameter and the volume of the transducer, so that the transducer is convenient to install, the higher the circuit timing triggering precision is, and the more accurate the time difference calculation is. I.e. the electric/acoustic conversion efficiency is low, while the reflection type has acoustic wave loss, so most manufacturers adopt a large-volume 1MHz transducer (adopting a ceramic chip with the diameter of 12-14 mm). In recent years, with the improvement of precision manufacturing level, the electric/acoustic conversion efficiency is leaved, and the electric/acoustic conversion efficiency of a transducer with small size and high frequency is greatly improved, so that the application requirements are completely met.

Currently, a commonly used DN15 inserted sheet reflective flowmeter transducer adopts a ceramic plate with the diameter of phi 12mm and the frequency of 1MHz, and the diameter of the front end of the packaged convex transducer is phi 17mm and the diameter of the rear end thereof is phi 21mm. In view of the small size in the flow channel and the minimal interference to the fluid, a stainless steel insert with a 10mm width stamped into the DN15 caliber reflecting surface is used. The edges are arcuate due to the stamped form, and the width of the plane that can actually be used for reflection is approximately 8mm. The actual utilization of acoustic energy is about 67% (note: different widths of reflecting surfaces of different calibers, and different reflection efficiencies) at 8/12.

In the embodiment, a ceramic plate with the diameter phi 8mm and the frequency of 2MHz is adopted, and the convex transducer is packaged into a convex transducer with the front end diameter phi 10mm and the rear end diameter phi 14mm. Therefore, the size of the reflecting surface can be reduced, the reflecting surface is convenient to install in a small-caliber pipeline, and the minimum gap of water flow is beneficial to the passage of impurities below 3 mm. Then, the fixed edge of the inclined reflecting surface is added, the width of the reflecting surface after installation is phi 9mm, the edge fixed part (mainly fixed by the long axis direction of the elliptical surface) is removed, the width of the effective reflecting surface is at least 8mm, and the total reflection of ultrasonic energy generated by the ceramic chip phi 8mm is completely satisfied, namely, the utilization rate of the acoustic wave energy is 100%.

The advantages of the transducer with high frequency (2 MHz and 4 MHz) and small size (ceramic plate phi 8mm, transducer front end phi 10mm and rear end diameter phi 14 mm) are adopted:

(1) The overall size of the transducer 44 is small, and the size of the transducer holder 12 is also small, so that the distance between the two transducer center lines of the 2MHz and Φ10mm transducers is increased by 7mm relative to the 1MHz and Φ17mm transducers, that is, the sound path of the 2MHz transducer is 7mm longer than that of the 1MHz transducer assuming that the transducer holder 12 is arranged close to the inner side of the outer tube thread of the metal tube, which is important for increasing the sound path and increasing the range ratio for the limited tube length.

The patent grant publication number CN 201773574U is a transducer adopted by a conventional ultrasonic reflection type flowmeter, and has the following two disadvantages: firstly, only one sealing ring can be arranged at the step of the convex transducer, so that the safety is poor; and secondly, the transducer is installed and positioned by the sealing ring, if the sealing ring is deformed (such as an organic matter is encountered), the transducer is inclined (angle is changed), the emitted sound wave cannot be reflected by the reflecting surface, the sound wave loss is large, the time difference calculation cannot be carried out, and the measurement is terminated.

The present embodiment employs a 2MHz, dual seal structure transducer with positioning. The lower edge 444 on the outer side of the transducer 44 is an installation positioning edge and is positioned on the inner side of the transducer fixing seat 12 by a positioning boss 121, the sealing ring 441 is a side seal, and the sealing ring 442 is a top seal. Therefore, the horizontal installation and positioning of the transducer can be ensured, the sealing safety and reliability can be ensured, and the transducer can be used for a long time.

The spring washer 45 is positioned above the transducer 44 and serves to prevent damage to the seal ring 442 and to limit the pressure applied downwardly by the retaining nut 46 as the retaining nut 46 is rotated downwardly. The other function of the fixing nut 46 is to press the instrument box base 55A, i.e. to press the cylindrical housing which is fitted over the transducer holder 12, thus fixing the instrument base 55A in a relatively simple and economical way. The side seal 122 functions to waterproof seal between the cylindrical structure of the instrument case base 55A and the outside of the transducer holder 12.

The meter box 55 is composed of a meter box base 55A and a meter box upper shell 55B, and a battery 551, a circuit board 552 and a display screen 553 are arranged in the meter box. The transducer signal lines 443 are connected to the circuit board 552 through the central bore of the retaining nut 46.

In this embodiment, since the whole inner bushing tube composed of the guide and reflection surface fixing support 22 and the rectifying tube 33 is not required to be sealed with the inner side of the metal outer tube 11 in a waterproof manner, the temperature sensor mounting seat 14 can be conveniently arranged at the position of the outer end of the metal outer tube 11 close to the water outlet when the hot water metering application is performed, the temperature sensor 141 is mounted in the temperature sensor mounting seat 14, and the temperature sensor measuring rod is obliquely inserted at the outer side of the guide cover of the transducer, so that the measurement of fluid is not affected.

The application of the small-caliber liner reflective straight pipe ultrasonic water meter structure in hot water metering is described through the above embodiment, but the utility model is not limited to the above specific embodiment, and any modification or variation based on the content of the utility model is within the scope of the utility model.

Claims

1. A small-caliber lining reflection type straight tube ultrasonic water meter is characterized in that: the device comprises an equal-diameter metal outer tube (11), a diversion and reflection surface fixing bracket (22), a rectifying tube (33) and a rectifying tube fixing seat (13) thereof, a transducer (44) and a transducer fixing seat (12) thereof, a fixing nut (46) and an instrument box bottom shell (55A); the small-caliber lining reflection type straight tube ultrasonic water meter base surface is an equal-diameter metal outer tube (11), guide and reflecting surface fixing brackets (22) are fixed at two ends of the inner side of the equal-diameter metal outer tube, and a double-reflection type transducer lining tube body structure is formed by connecting the two guide and reflecting surface fixing brackets through a rectifying tube (33); under the cooperation of the transducer fixing seat (12), the meter bottom shell fixing nut (46) and the meter box (55), the small-caliber liner reflection type straight tube ultrasonic water meter is formed.

2. The small-caliber liner reflective straight tube ultrasonic water meter according to claim 1, wherein the small-caliber liner reflective straight tube ultrasonic water meter is characterized in that: the guide and reflecting surface fixing support (22) is formed by embedding and butting two parts, the whole guide and reflecting surface fixing support is divided into an outer ring and a middle part after butting, an upper supporting rib and a lower supporting rib are connected between the two parts, the front end of the guide and reflecting surface fixing support (22) is provided with a guide cap (221) and the rear end of the guide and reflecting surface fixing support is provided with a reflecting surface fixing support (222); the diversion cap (221) is formed by butt joint of two parts, and the butt joint surface is of a concave-convex structure (2211); the sound wave reflecting surface (23) is formed by butt joint and package of more than two parts of arc-shaped grooves and lower arc-shaped grooves on the guide and reflecting surface fixing support (22).

3. The small-caliber liner reflective straight tube ultrasonic water meter as claimed in claim 2, wherein: the reflecting surface (23) is made of an elliptical ZrO with a thickness of 1mm, a width of 9mm and a length of 11mm ₂ 、Si ₃ N ₄ Or SiC material.

4. The small-caliber liner reflective straight tube ultrasonic water meter according to claim 1, wherein the small-caliber liner reflective straight tube ultrasonic water meter is characterized in that: a blind hole (331) is formed in the middle of the outer side of the rectifying tube (33), and a rectifying tube fixing seat (13) is formed in the middle of the outer side of the corresponding equal-diameter metal outer tube (11); the rectifying tube fixing nut (132) and the sealing ring (131) are arranged in the rectifying tube fixing seat (13); the two ends of the rectifying tube (33) are respectively butted with the diversion and reflection surface fixing support (22), and the butted part is of a convex and concave matching structure.

5. The small-caliber liner reflective straight tube ultrasonic water meter according to claim 1, wherein the small-caliber liner reflective straight tube ultrasonic water meter is characterized in that: the transducer (44) is a transducer with a frequency of 2MHz/4MHz and a positioning and double-sealing structure, a convex edge (444) of the transducer is a positioning edge, a positioning boss (121) is arranged on the inner side of the transducer fixing seat (12), a side sealing ring (441) is arranged on the side face of the transducer, and a top sealing ring (442) is arranged on the top of the transducer.

6. The small-caliber liner reflective straight tube ultrasonic water meter according to claim 1, wherein the small-caliber liner reflective straight tube ultrasonic water meter is characterized in that: the fixed nut (46) is positioned on the transducer fixing seat (12), and the lower end of the fixed nut (46) and an elastic washer (45) below the fixed nut are positioned on the transducer (44); the upper edge of the fixing nut (46) is arranged on a cylindrical structure of the instrument box bottom shell (55A) matched with the transducer fixing seat (12).

7. The small-caliber liner reflective straight tube ultrasonic water meter according to claim 1, wherein the small-caliber liner reflective straight tube ultrasonic water meter is characterized in that: and a temperature sensor mounting seat (14) is fixed at one end, close to the water outlet, of the outer side of the equal-diameter metal outer tube (11), and a temperature sensor (141) is arranged in the temperature sensor mounting seat.