CN115900856A

CN115900856A - Small-caliber liner reflection type straight pipe ultrasonic water meter structure

Info

Publication number: CN115900856A
Application number: CN202110928695.XA
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: 2021-08-16
Filing date: 2021-08-16
Publication date: 2023-04-04

Abstract

The invention belongs to the technical field of flow metering equipment, in particular to a small-caliber liner reflection type straight pipe ultrasonic water meter structure, aiming at solving the problems of low metering range ratio and difference between six principles of an optimized solution scheme of the technical development of an ultrasonic water meter in the prior art, arranging and fixing diversion and transducer reflection surface fixing supports 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 flow meter base surface, and forming a double-reflection type transducer liner pipe integral structure by connecting reducing rectifying pipes between the two reflection surface fixing supports to ensure that a flow passage in the pipe is smooth and the sound path between the two reflection surfaces is fixed; the reflecting surface material is selected, so that the invention realizes the performance of maximizing the measuring range ratio and minimizing the initial flow under the limited length of the ultrasonic water meter, and the reflecting surface has lossless reflecting efficiency and has the characteristic of no scale formation after long-term use under the conditions of high temperature and hard water quality.

Description

Small-caliber liner reflection type straight pipe ultrasonic water meter structure

Technical Field

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

Background

In the era of stepping into the internet of things big data, artificial intelligence and industrial automatic control, for the fields of industrial and civil water, heat and gas supply and metering, a mechanical or electromechanical combined mode flowmeter is gradually replaced by an all-electronic mode flowmeter, and the irreversible trend is formed.

According to the actual application requirements, the fluid metering industry or occasions expect standard flow metering instruments which are compatible with various caliber specification ranges, low pressure loss, high precision, high reliability, no abrasion devices, durability and economy. At present, electromagnetic flow meters and after-market ultrasonic flow meters are the most widely used worldwide for all-electronic flow metering.

The ultrasonic flowmeter is developed along with the technical breakthrough of a time difference timing chip (in 2012-2017, advanced time difference timing chips are successively proposed by companies such as AMS, D-FLOW, TI and the like internationally, and the resolution of the ultrasonic flowmeter reaches 5-10 ps at present, so that the ultrasonic flowmeter completely meets the application requirement of water metering). Compared with an electromagnetic flowmeter, the ultrasonic flowmeter performs sampling through time difference digital signals (the electromagnetic flowmeter performs sampling through analog signals). Taking a water meter as an example, the water meter has the outstanding technical advantages that: the device has the advantages of smaller initial flow (such as liquid with flow velocity of 0.8-1 mm/s), wider range ratio, capability of actively measuring process time difference by sound waves, conversion into fluid flow velocity and temperature and synchronous compensation of measured volume change (for this reason, an electromagnetic flowmeter needs to be provided with a thermometer), higher precision and safety of large-caliber multi-channel measurement (the electromagnetic flowmeter only has one pair of coils and corresponding electrodes and is scrapped when being failed), capability of measuring various low-viscosity liquids (the electromagnetic flowmeter cannot measure low-conductivity liquids such as pure water), and capability of measuring/metering gases such as gas (the electromagnetic flowmeter cannot measure gas flow).

Generally, the main performance indexes of the flow meter are the metering precision and the range ratio, the metering precision is the ratio of the flow meter quantity value and the actual flow rate value of the flow meter, and the improvement of the flow stability and the mass production consistency of the fluid is an important condition for determining the precision; the measuring range ratio is the ratio of the common flow to the minimum flow under the guarantee of the measuring precision of the flowmeter, the range capable of accurately measuring is reflected, and the necessary condition for improving the measuring range ratio is to increase the effective distance between the ultrasonic transducers. Obviously, the higher the metering accuracy and the larger the range ratio, the better the metering performance of the flowmeter.

In recent years, the metering industry has greatly advanced the practical application of ultrasonic flow meters. The ultrasonic flowmeter is composed of a transducer, a transducer mounting mode, a flow channel structure and the like, besides a time difference integrating circuit, wherein the performance of the transducer determines the minimum value of measurable flow, and the overall structure of the ultrasonic flowmeter 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 technical development direction is clear in the industry, and the optimized solution thereof follows the following principle:

(1) The principle of sound path maximization: in order to make the ultrasonic water meter have a large range ratio, for the ultrasonic water meter, particularly the most common DN15 caliber is used, a mode of maximizing the sound path between ultrasonic transducers is adopted. The large range ratio is an extremely important index for trade settlement and is the most important technical index of the water meter, which is quite different from the industrial flow meter. In order to make the ultrasonic water meter have a large range ratio, the projection distance of the distance connecting line between the two transducers of the ultrasonic water meter in the water flow direction in the main pipe is maximized so as to obtain a large range ratio and a small starting flow. (for water meter, the national standard is that the maximum value of the range ratio or the flow ratio is increased to R =1000 in 2018)

In this regard, theoretical analysis can lead to conclusions about the measurement quality of the ultrasonic flow meter:

in the field of water metering, ratio of measuring ranges

Is defined as

Wherein, in the step (A),

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

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

The following text, by further analysis and derivation, leads to an important conclusion: the measured pick-up flow (i.e., the meter can sense the most metered flow) for a fluid passing through the meter conduitSmall flow)

The lower (corresponding to the flow rate thereof)

The lower, the

Related to the time difference chip resolution of the ultrasonic flow meter and the pipe structure of the flow meter), in response,

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

It becomes low). Generally, in practical applications, the empirical value is

（

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

And with

Equal time intervals) of the measuring range ratio

Spaced from two transducers

The relationship between them is:

in the above-mentioned formula, the compound has the following structure,

is the common flow rate of a certain caliber flow meter,

is prepared by reacting with

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

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

is prepared by reacting with

The flow velocity of the fluid in the corresponding flow meter pipeline is, for a certain caliber flow meter,

and

is a constant (selected value) and,

in the form of a circumferential ratio,

is the inner radius of the flow meter tube,

in order to be used for metering,

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

the included angle between the connecting line of the two transducers in the water flow direction of the pipeline of the flowmeter

Is acute angle when

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

,

is a known quantity related to the time difference of measurement and the speed of sound of the flowmeter,

for known quantities related to the time difference of measurement, the speed of sound of the flowmeter, let

=

Is constant, and

calculating by the equation of time difference of the ultrasonic flowmeter

To obtain, i.e.

And thus, in the specific calculation,

according to

And (6) substituting. From above

The following conclusions can be drawn from the relationship:

increase the projection distance between the two transducers in the water flow direction of the flowmeter pipeline

The range ratio of the flowmeter can be effectively improved

。

(2) The principle of the correlation type installation between a pair of transducers: the acoustic signals of the opposite type installation 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 one or more reflection surfaces, so that the sound wave energy loss is caused by sound wave reflection transmission (when the reflection surfaces are large enough, the sound energy loss in an ideal state is 10-20%, and generally cannot affect the measurement), and particularly when the reflection surfaces have angle deviation or are scaled after being used, the sound wave energy loss can reach 40-60%, so that the normal measurement is seriously affected. In addition, the existence of the reflecting surface, the installation structure thereof is complicated, and especially, the improper water resistance distribution treatment of the reflecting surface also affects the metering precision.

It is important to note that the reflection-type ultrasonic flowmeter also has potential application advantages, and if the potential application advantages can be brought into play and the existing disadvantages can be eliminated, the reflection-type ultrasonic flowmeter also has wide application value. In order to eliminate the disadvantages of the reflection type ultrasonic flowmeter, an effective solving way and a scheme are searched, the problem of sound wave energy loss caused by the reflection of sound waves on the reflecting surface is solved, the scaling problem of the reflecting surface is solved, and the problem of turbulence generated by uneven water flow resistance of the reflecting surface is solved.

(3) A consistency principle; the flow passage forming and processing technology of the ultrasonic water meter base meter has higher assembly mounting precision and consistency requirements, and determines the quality of mass production of the flow meters. For the reflection type, the distance between the two reflecting surfaces of the sound waves of the two transducers is particularly ensured to be fixed, and the difference caused by the processing of the pipe section and the installation of the transducers is avoided, so that the level is improved, the range of error compensation and precision correction of the individual base table can be reduced, and the complicated workload of manually performing error correction on the individual base table at the later stage is reduced.

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

(5) The principle of adaptability: the ultrasonic water meter can be used for water metering, and also can be used for other purposes by considering adaptation, such as convenient installation of a temperature sensor, so as to adapt to the requirement of heat supply metering and be used as a heat meter for heat supply metering.

(6) Simple structure, convenient assembly principle: the ultrasonic water meter has the advantages of simplified structure and unique certainty in installation, so that the ultrasonic water meter is easy to assemble as a whole and can ensure higher consistency of the flow meter.

In contrast to the above-described criteria, the prior art still has drawbacks or deficiencies.

Patent application publication No. CN 105890818A is a relatively typical upright post type small-bore ultrasonic reflection formula in early days, and the flowmeter who uses with this kind of mode, its support column of installing separately can't accomplish two reflection face angles unanimity, do not consider the influence that stand and reflection face formed the torrent to the fluid, so, leads to the small flow deviation great, and the range ratio is relatively low, mainly is applied to the heat supply measurement.

In view of the defects of the reflective surface of the supporting pillar, the most current uses the insert-type reflective surface, such as patent application publication No. CN 106679749A. The reflecting surface of the structure is greatly improved compared with the vertical column, and the influence of the supporting column on the fluid is mainly eliminated. Experiments show that the range ratio of the insert type water meter can be doubled (for a DN20 caliber water meter, a column type is usually R =100, and the insert type R = 200). However, the inclined reflection upstream surface still generates turbulence to the fluid, which affects the stability of small flow, and the characteristics of the reflection upstream surface still need to be further improved.

Patent application publication No. CN 103983316A discloses a solution for a dome to reduce water turbulence. The bullet-shaped current stabilizer is additionally arranged on the front side of the water inlet end (water outlet end) of the reflecting surface, so that turbulence can be reduced, and the small-flow measurement precision of the flowmeter is improved. However, it can be seen from the patent illustration that there is no sleeve or smooth pipe wall with gentle diameter reduction between the mounting structure frame and the middle sleeve of the bullet-shaped flow stabilizer, which will inevitably block the water flow, especially increase the water resistance under the condition of large flow and cause turbulence to affect the measurement accuracy

Patent publication No. CN 2043718U discloses a measuring tube section for a meter, and it can be seen that two transducer mounting holes are relatively centered and have short acoustic path, and this structure is contrary to the principle of maximizing acoustic path, so that the measuring range ratio is limited.

By analyzing the prior art and according to the six principles of the optimized solution of the technical development of the ultrasonic water meter, as for the ultrasonic water meter with small caliber, the ultrasonic reflection principle is corresponding, if an effective technical scheme is adopted, the sound path maximization, the integrity of the water flow channel, the improvement of the reflection efficiency of the reflection surface, the reduction of the turbulent flow influence generated by the reflection surface, the long-term use of the reflection surface without scaling, the processing of the integral pipe section, the manufacture of the base table of the flow meter and the like can be realized, and thus, the performance of the ultrasonic reflection water meter can be effectively improved.

Disclosure of Invention

The invention aims to solve the defects of the prior art, namely the defects of the design and the application of the base meter of the existing ultrasonic reflection-type flowmeter, and provides a small-caliber liner reflection-type straight pipe ultrasonic water meter structure, which comprises the following components: the ultrasonic reflection type water meter has the advantages that the structure maximizing the sound path and the high reflection efficiency of the reflecting surface are realized, the structural shape of the reflecting surface which generates turbulent flow influence is reduced, the whole structure of the water flowing channel is constructed, the reflecting surface is made of materials which are not scaled for a long time, the whole metal outer pipe is used for processing and constructing the base meter of the flow meter, the meter shell is convenient to install and fix, and the like, so that the overall performance of the ultrasonic reflection type water meter can be greatly improved.

The technical scheme of the invention is as follows: aiming at maximizing the sound path of the transducer and the reflecting surface, the layout of the transducer and the reflecting surface in a flowmeter base table is preferentially considered, and flow guide and transducer reflecting surface fixing supports are arranged and fixed at two ends of the inner side of an equal-diameter metal outer pipe of the small-caliber ultrasonic water meter, so that the sound path maximization of the ultrasonic transducer is realized; the two reflecting surface fixing supports are connected by the reducing rectifier tube to form a double-reflecting transducer lining tube body structure, so that the completeness of the water flow channel is realized, the permanent invariability of the distance between the two reflecting surfaces is effectively ensured, and the flow meters processed in batches have the flow characteristic with the same height; the diversion and reflection surface fixing support is integrated by two symmetrical parts which are embedded and butted, is divided into an outer ring and a middle part which are connected by an upper supporting rib and a lower supporting rib, so that water flow can stably enter a reducing rectifier tube immediately after passing through the supporting ribs and the reflection surface, no blockage can be generated, the water flow is stable and smooth, and the structural shape generated by the reduction of turbulent flow of the reflection surface is formed; through the way of theoretical analysis, experimental analysis and experimental verification, the reflecting surface and the reflecting surface material are searched, so that the reflecting surface has lossless reflection efficiency and can be used for a long time without scaling under the conditions of high temperature and hard water quality.

The invention relates to a small-caliber liner reflection type straight pipe ultrasonic water meter structure which comprises an equal-caliber metal outer pipe, a flow guide and reflection surface fixing support, a rectifying pipe and a fixing seat thereof, a transducer and a transducer fixing seat thereof, a transducer and an instrument bottom shell fixing nut; the interface between the small-caliber inner-lining reflection type straight pipe ultrasonic water meter and an external pipeline and the base meter are equal-diameter metal outer pipes, and flow guide and transducer reflecting surface fixing supports are arranged and fixed at two ends of the inner sides of the equal-diameter metal outer pipes, so that the sound path maximization of an ultrasonic transducer is realized; the two reflecting surface fixing supports are connected by a reducing rectifier tube to form a double-reflecting transducer lining tube body structure, so that the completeness of a water flow channel is realized, the permanent invariance of the distance between the two reflecting surfaces is effectively ensured, and the mass-processed flow meter has the flow characteristic with the same height; through the optimized energy converter, the shape of the reflecting surface and the material of the reflecting surface, sound waves among the energy converters are transmitted smoothly and 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 pipe ultrasonic water meter is formed, and under the straight pipe length limited by the small-caliber ultrasonic water meter, the sound path maximization among the ultrasonic transducers is realized, so that the ultrasonic water meter achieves the performance of range ratio maximization and starting flow minimization.

The equal diameter metal outer tube and the interface both ends of outer tube have the pipe thread, there are transducer fixing base, rectifier tube fixing base and install the temperature sensor mount pad additional when needing on the equal diameter metal outer tube. The guide and reflection surface fixing support is formed by inlaying and butting two symmetrical parts in the middle. After butt joint, the front end is provided with a flow guiding cap, and the rear end is provided with a reflecting surface fixing support, a supporting rib and an outer pipe. The rectifier tube is fixed by a rectifier tube fixing nut and is in close fit butt joint with the diversion and reflection surface fixing support. The transducer is arranged in the transducer fixing seat, the convex edge of the transducer is positioned by the 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; fixation nut is located the top in the transducer fixing base, and it has two effects: firstly, the energy transducer is pressed by pressing the elastic washer, and meanwhile, the lower end of the energy transducer extends into the guide and reflection surface fixing support to play a positioning role; and secondly, the bottom shell of the instrument is fixed through a cylindrical structure which compresses the bottom shell of the instrument. 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 wire is connected to the circuit board through the central through hole of the fixing nut.

When temperature parameters are needed or heat metering 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 pipe, and the temperature sensor is mounted in the temperature sensor mounting seat.

The flowmeter base table outer tube be the equal diameter metal outer tube, there is the pipe thread at its both ends, the equal diameter metal outer tube outside is connected with transducer fixing base, rectifier tube fixing base and installs the temperature sensor mount pad additional when needing through laser welding.

A bullet flow stabilizer scheme disclosed in patent application publication No. CN 103983316A has a defect that the flow field is affected: rivers have announced a bullet current regulator through CN 103983316A, expose in bullet current regulator fixed bolster section, between getting into the intermediate pipe, do not connect mild undergauge body, this will make rivers current regulator fixed bolster and interlude mouth of pipe border produce and block, especially under large-traffic circumstances, because block that the resistance increase produces the torrent, influence time difference and flowmeter precision.

The guide and reflection surface fixing bracket is integrated by inlaying and butting two symmetrical parts. After butt joint, the split type water diversion pipe 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, water is evenly shunted, water flow is facilitated to pass through, and the split type water diversion pipe has higher strength and symmetry. The water flow passes through the supporting ribs and the cylindrical side surface of the reflecting surface and then immediately and stably enters the reducing rectifier tube, no fracture exists in the process, and no blocking is generated, so that the water flow is stable and smooth, the fluid characteristic is stable, and the time difference precision is favorably improved, namely the metering precision.

The guide and reflection surface fixing bracket is composed of a guide cap at the front end, a reflection surface fixing bracket at the rear end, a supporting rib and an outer pipe. As shown in fig. 2, the integrated deflector cap and the reflecting surface fixing bracket are formed by tightly matching and butting two convex and concave structures; the sound wave elliptical reflecting surface is fixed by butting and wrapping two parts of the diversion and reflecting surface fixing support against an elliptical long shaft, namely an upper arc-shaped groove and a lower arc-shaped groove, and the position of the elliptical short shaft does not need to be fixed, so that the reflecting area is ensured to be large enough.

The reflecting surfaceFrom an oval ZrO having a thickness of 1mm, a width of 9mm and a length of 11mm ₂ 、Si ₃ N ₄ Or a SiC material. Experiments prove that the three materials not only have extremely high reflection effect on ultrasonic waves, but also can not scale after being used for a long time under the conditions of high temperature and hard water quality, and can effectively ensure that the reflection intensity of the ultrasonic waves can not be attenuated for a long time.

Assembling a guide and reflection surface fixing support: the fixed rubber ring has the effects that firstly, a reflecting sheet is placed on the reflecting surface, the guide flow and the two parts of the reflecting surface fixed support are butted and folded, and the fixed rubber ring is added for fixing; secondly, after the guide and reflection surface fixing support is inserted into the equal-diameter metal outer pipe, the effect of extruding and stabilizing is achieved, and the rubber ring does not play a sealing effect.

The guide cap and the rear-end reflecting surface fixing support are generally circular columns, the diameter of each circular column is 9mm, so that for DN15 pipe diameter, the minimum clearance between the cylindrical shape and the inner side is 4.42mm through calculation, 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 guaranteed to be more than or equal to 3mm, and conventional impurities in water can be guaranteed to pass through smoothly.

The rectifier tube is fixed in the blind hole by a rectifier tube fixing nut and a sealing ring and is in close fit butt joint with the diversion and reflection surface fixing support. After butt joint, the butt joint seam is welded by gluing or laser to integrate the two flow guide and reflection surface fixing supports and the rectifying tube. Therefore, the distance between the two reflecting surfaces can be effectively ensured to be permanently unchanged, and the consistency of the flow characteristics in batch production can be effectively ensured. The rubber ring plays the role of tightly matching the rectifying tube with the inner cavity of the metal tube and preventing water from flowing between the rectifying tube and the metal tube, and does not play a role of sealing.

The transducer adopted in the invention is a small-caliber transducer, and the structure is as follows: the front end diameter phi 10mm, the rear end diameter phi 14mm, the frequency of 2MHz or 4 MHz. The middle part of the transducer is provided with a groove, and the middle part and the upper part of the transducer can be provided with sealing rings which are respectively side sealing and top sealing, namely two-stage and two different sealing modes are adopted to ensure the sealing safety.

The specification of the ceramic chip adopted by the transducer meets the requirements of the China society for measuring Water meters committee 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 and 4MHz are selected,

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

the wavelength of a material at each frequency is: 2.5mm 1.25mm 0.625mm

(assuming sound velocity of 2500m/s at room temperature for a sound guide material)

Conventionally, the larger the size of the transducer is, the higher the intensity of the emitted sound wave is, but the installation size is large; 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 precision of circuit timing triggering is, and the more accurate the time difference calculation is. Early transducers were low in manufacturing level, i.e. low in electrical/acoustic conversion efficiency, and reflective transducers had acoustic wave loss, so most manufacturers adopted 1MHz transducers (made of phi 12-14 mm ceramic plates) with large volume. In recent years, along with the improvement of the precision manufacturing level, the electric/acoustic conversion efficiency is greatly improved, and the electric/acoustic conversion efficiency of the small-size high-frequency transducer is greatly improved, so that the application requirement is completely met.

The transducer of the common DN15 insert reflection type flowmeter adopts a phi 12mm ceramic chip, the frequency is 1MHz, the diameter phi 17mm of the front end of the packaged convex transducer is 17mm, and the diameter phi 21mm of the rear end is. The reflecting surface is a stainless steel insert stamped to have a width of 10mm, considering the small dimensions in the flow channel and minimizing the disturbance of the fluid. Due to the stamping, the edges are curved and the width of the plane that can actually be used for reflection is about 8mm. Therefore, the actual utilization rate of the sound wave energy is 8/12, which is about 67% (note that the reflection efficiency is different due to the different widths of the reflection surfaces with different apertures).

The invention adopts a phi 8mm ceramic wafer with the frequency of 2MHz or 4MHz, and the front end diameter phi 10mm and the rear end diameter phi 14mm of the convex transducer are packaged. Therefore, the size of the reflecting surface can be reduced, the reflecting surface can be conveniently installed in a small-caliber pipeline, and the minimum water flow gap is favorable for impurities below 3mm to pass through. Then, the fixed edge of the inclined reflection surface is added, the width of the installed reflection surface is phi 9mm, the fixed part of the edge is removed (mainly fixed in the long-axis direction of the oval surface), the width of the effective reflection surface is at least 8mm, and the full reflection of ultrasonic energy generated by the phi 8mm ceramic plate is completely met, namely the utilization rate of the sound wave energy is 100%.

The transducer with high frequency (2 MHz and 4 MHz) and small size (the ceramic wafer is phi 8mm, the front end of the transducer is phi 10mm, and the rear end of the transducer is phi 14 mm) has the advantages that (taking 2MHz as an example):

(1) The whole size of transducer is little, and the size of transducer fixing base is also little, and then the distance between two transducer central lines of 2MHz, phi 10mm transducer, 1MHz, phi 17 mm's transducer relatively, will increase 7mm, and that is to say, supposing that the transducer fixing base all is close to the metal pipe outside pipe thread inboard and settles, the 2MHz transducer's acoustic path is 7mm than 1MHz transducer extension, and this is for the pipe length of limited length, can enlarge the acoustic path and improve the range ratio, and is very 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 the time difference circuit triggered by the head wave.

(3) For reflective mounting, if the reflecting surface is an ellipse with a width of 8mm, for the ceramic sheet size of 2MHz and phi 8mm, 100% of all sound energy will be reflected theoretically; but for the ceramic sheet size of 1MHz and phi 12mm, only 67% of sound energy can be reflected, and the utilization rate is very low.

Patent publication No. CN 201773574U is a transducer used in a conventional ultrasonic reflection flowmeter, and has two disadvantages: firstly, a sealing ring can be only installed at the step of the convex transducer, and the safety is poor; and secondly, the mounting and positioning of the transducer are also required to be close to the sealing ring, if the sealing ring is deformed (such as touching organic matters), the transducer is inclined (the angle is changed), the emitted sound waves cannot be reflected by the reflecting surface at the moment, so that the sound energy loss is large, the time difference calculation cannot be carried out, and the metering is terminated.

The invention provides a 2MHz/4MHz transducer with a positioning and double-sealing structure, wherein the lower edge of the outer side of the transducer is an installation positioning edge, 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, and the sealing is safe and reliable and can be used for a long time.

The elastic washer is positioned above the transducer, and plays a role in preventing the sealing ring from being damaged and limiting the downward pressure applied by the fixing nut when the fixing nut rotates downwards. The fixing nut has another function of pressing the instrument box base, namely pressing 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 waterproof sealing between the cylindrical structure of the instrument box base and the outer side of the transducer fixing seat.

The instrument box is composed 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 wire is connected to the circuit board through the central hole of the fixing nut.

In the invention, because the waterproof sealing is not needed between the whole inner bushing pipe consisting of the flow guide and reflection surface fixing support and the rectifying pipe and the inner side of the metal outer pipe, when the heat metering application is carried out, the outer end of the metal outer pipe close to the water outlet can be provided with the temperature sensor mounting seat, 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 outside the flow guide cover of the transducer, thereby not influencing the measurement of fluid.

In summary, compared with the prior art, the invention has prominent substantive features and remarkable progress, which are specifically shown as follows:

firstly, for a base meter of an ultrasonic flowmeter with DN15 caliber or small caliber with given length, the invention fully utilizes the limited length of the base meter of the ultrasonic flowmeter, arranges and fixes the flow guide and the transducer reflecting surface fixing bracket at the two ends of the inner side of the equal-diameter metal outer pipe, and selects the transducer packaged by the ceramic chip with small size of 2MHz/4MHz and phi 8mm for matching, thereby realizing the maximization of the sound path of the ultrasonic transducer and further realizing the maximization of the range ratio and the minimization of the initial flow of the ultrasonic water meter.

Secondly, for the base table of DN15 caliber, the technical requirements of ensuring that the water gap at the narrowest part of the flow passage is more than 3mm and ensuring that the pressure loss at the position is not increased suddenly so as to avoid forming turbulent flow are required. The invention selects the small-caliber transducer, the smaller reflection surface width of phi 9mm and the diameter of the reflection surface column of phi 9mm, and adopts the connection with the lining pipe by two support columns, thereby obtaining the advantages of small water flow pressure loss, uniform flow distribution and high strength, completely meeting the technical requirement that the minimum water passing clearance is more than 3mm, and facilitating the passing of conventional impurities.

Thirdly, different from the conventional transducer which adopts a lower sealing ring for positioning, the transducer provided by the invention can perform height positioning through the boss in the leading-out wire fixing seat, so that the positioning smoothness of the transducer can be guaranteed, and the ultrasonic signals can accurately reach the reflecting surface.

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

Fifthly, the rectifying tube and the diversion and reflection surface fixing bracket are in close fit butt joint, and after butt joint, the butt joint seam is welded by gluing or laser, so that the two diversion and reflection surface fixing brackets and the rectifying tube form an integral measuring flow channel structure, which is favorable for smooth flow of water flow, solves the problem that the stable flow of a flow field is influenced by the disconnection between a diversion cap and a middle pipeline in the patent application publication No. CN 103983316A, and can effectively ensure that the distance between the two reflection surfaces is permanently unchanged. Because the distance between the two reflecting surfaces determines the range ratio of the ultrasonic flowmeter, the range ratio and the consistency of the flowmeter are ensured for batch production, and the detection and the calibration of the flowmeter are greatly facilitated.

Sixthly, the sound wave reflection surface adopted by the invention is formed by an oval ZrO with the thickness of 1mm, the width of 9mm and the length of 11mm ₂ 、Si ₃ N ₄ Or a SiC material. Both theory and experiment prove that the three materials not only have extremely high ultrasonic reflection effect, but also have high temperature and water qualityUnder the hard condition, the scale can not be formed after long-term use, and the reflection intensity of the ultrasonic wave can be effectively ensured not to be attenuated for a long time.

Seventh, the guide and reflection surface fixing bracket of the present invention, which is composed of a guide cap at the front end, a reflection surface fixing bracket at the rear end, a support rib and an outer tube, forms a stable whole, the outer tube of the whole can be in seamless butt joint with the reducing rectifier tube, and the smooth flow of fluid from the guide cap to the reducing rectifier tube is ensured. In addition, the flow guide cap and the rear-end reflecting surface fixing support are composed of two parts with symmetrical central surfaces and are formed by tightly matching and butting convex and concave structures; the minor axis of the elliptic ceramic reflecting surface is 9mm, the major axis is 11mm, and the ceramic elliptic reflecting surface is only clamped, wrapped and fixed in a groove mode at the arc edges of the upper major axis and the lower major axis by the butted diversion and reflecting surface fixing bracket (the minor axis is not fixed). As the whole of the diversion cap and the rear end reflecting surface is cylindrical and the diameter of the diversion 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 elliptic ceramic reflecting surface, and for the ultrasonic water meter with the DN15 caliber, the minimum gap between the diversion cap and the rear end reflecting surface fixing column and the inner side of the outer pipe is more than or equal to 3mm, so that the conventional impurities in water can pass through smoothly.

Eighth, the fixing nut of the invention realizes the function of the first generation and the second generation, wherein the first generation and the second generation are that the fixing nut compresses the transducer by applying force to the elastic washer, and meanwhile, the lower end of the transducer extends into the guide and reflection surface fixing bracket to play a role in positioning; and the second mode is that the pressing device is used for pressing and fixing the lower shell of the circuit instrument box, so that the number of fixing devices of the lower shell is reduced.

Ninth, in the invention, the two diversion and reflection surface fixing supports and the rectifying pipe 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 pipe, so that a 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 reflection type straight pipe ultrasonic water meter;

FIG. 2 is a schematic view of a small-caliber reflective-lined diversion and reflection surface fixing bracket;

FIG. 3 is a schematic view of a small bore liner reflective temperature sensor mounting configuration;

in the figure:

11. an equal-diameter metal outer pipe; 111. pipe threads; 12. a transducer fixing seat; 121. positioning the boss; 122. a seal ring; 441. a side seal ring; 442. a top seal ring; 44. a transducer; 443. a transducer signal line; 444. a transducer ledge; an elastomeric gasket; 46. fixing a nut; 13. a rectifier tube fixing seat; 33 a rectifier tube; 331. blind hole 132, rectifier tube fixing nut; 131. a seal ring; 14. a temperature sensor mounting base; 141. a temperature sensor; 22. a guide and reflection surface fixing bracket; 221. a flow guide cap; 222. a reflecting surface fixing bracket; 2211. a relief structure; a fixed rubber ring 223;23. a reflective surface; 55. an instrument case; 55A, a bottom shell of the instrument box; 55B, an upper shell of the instrument box; 551. a battery; 552 a circuit board; 553 a display screen;

Detailed Description

The invention will be further described in detail with reference to the drawings and examples.

Example (b):

as shown in fig. 3, it is a structure of a small-bore liner reflection type straight pipe ultrasonic hot water meter. Except the structure of the temperature sensor, the structure is shown in the attached figure 1. The equal diameter metal outer tube 11 and the interface both ends of outer tube have pipe thread 111, there are transducer fixing base 12, rectifier tube fixing base 13 and temperature measurement and temperature sensor mount pad 14 for the heat energy measurement on the equal diameter metal outer tube 11. The guide and reflection surface fixing bracket 22 is formed by two symmetrical parts in the middle in an embedding and butt joint mode. After 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 support rib and an outer pipe. The rectifying tube 33 is fixed by a rectifying tube fixing nut 132 and is in tight fit butt joint with the guide and reflection surface fixing bracket 22. The transducer 44 is arranged in the transducer fixing seat 12, the convex edge 444 of the transducer 44 is positioned by the positioning boss 121, and the side sealing ring 441 and the 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 holder 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 reflection surface fixing support 22 to play a positioning role; second, the meter case 55A is fixed by pressing the cylindrical structure of the meter case 55A. The meter box 55 is composed of a meter box bottom case 55A and a meter box upper case 55B, and a battery 551, a circuit board 552 and a display screen 553 are arranged in the meter box 55. The transducer signal line 443 is connected to the circuit board 552 through the center through hole of the retaining nut 46.

In the embodiment, the hot water metering is performed, and the hot water metering needs to be performed through temperature parameters, so that the temperature sensor mounting seat 14 is arranged at the outer end of the metal outer pipe 11 close to the water outlet, and the temperature sensor 141 is mounted in the temperature sensor mounting seat 14.

The outer tube of the flowmeter base meter is an equal-diameter metal outer tube 11 and is formed by machining and laser welding one metal tube. There is pipe thread 111 at 11 both ends of constant diameter metal outer tube, through laser welding on the constant diameter metal outer tube 11, be connected with transducer fixing base 12, rectifier tube fixing base 13 and temperature sensor mount pad 14.

The patent application publication No. CN 103983316A discloses a bullet current stabilizer scheme, which has the disadvantages that: rivers have announced behind the bullet current regulator through CN 103983316A, expose in bullet current regulator fixed bolster section, between getting into the middle pipeline, do not connect the gentle necking down body, this will make rivers current regulator fixed bolster and interlude mouth of pipe border produce and block, especially under the large-traffic condition, because block that the resistance increase produces the torrent, influence time difference and flowmeter precision.

The guide and reflection surface fixing bracket 22 of the present embodiment is formed by two symmetrical parts which are embedded and butted into a whole. After butt joint, the split joint 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, water is uniformly split, water flow passing is facilitated, and the split joint has higher strength and symmetry. The water flow enters the necking rectifier tube immediately and stably after passing through the supporting ribs and the reflecting surface, no fracture exists in the process, and no blocking is generated, so that the water flow is stable and smooth, the fluid characteristic is stable, and the time difference precision, namely the metering precision, is favorably improved.

The diversion and reflection surface fixing bracket 22, namely the front end, is composed of a diversion cap 221, a reflection surface fixing bracket 222, a supporting rib and an outer pipe. The integral diversion cap 221 and the reflecting surface fixing bracket 222 are formed by tightly matching and butting two convex and concave structures 2211; the sound wave reflecting surface 23 is fixed by butting and wrapping the upper and lower arc-shaped grooves of the two parts of the diversion and reflecting surface fixing bracket 22.

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

Assembling the guide and reflection surface fixing bracket 22: the fixing rubber ring 223 has the functions that firstly, the reflecting sheet 23 is placed on the reflecting surface 222, the diversion and the two parts of the reflecting surface fixing support 22 are butted and folded, and the fixing rubber ring 223 is added for fixing; secondly, after the guide and reflection surface fixing support 22 is inserted into the equal-diameter metal outer pipe 11, the effect of extruding and stabilizing is achieved, and the rubber ring does not play a sealing effect.

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

The rectifying tube 33 is fixed in the blind hole 331 by the rectifying tube fixing nut 132 and the seal ring 131, and is tightly matched and butted with the guide and reflection surface fixing support 22. After butt joint, the two diversion and reflection surface fixing brackets 22 and the rectifying tube 33 are integrated into a whole by gluing or laser welding the butt joint seam. Therefore, the distance between the two reflecting surfaces can be effectively ensured to be constant permanently, and the consistency of the flow characteristics in batch production 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 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 10mm,

The diameter phi of the rear end is 14mm, and the frequency of 2MHz or 4MHz is adopted. The middle part of the transducer is provided with a groove, and the middle part and the upper part of the transducer can be provided with sealing rings, namely a side seal 441 and a top seal 442 respectively, namely two stages and two different sealing modes are adopted to ensure the safety of sealing.

The specification of the transducer adopting the ceramic chip meets the requirements of the China Committee on Water meters of the Meter of China on the frequency application standard of the ceramic vibrator of the ultrasonic transducer, namely:

the wavelength of a material at each frequency is: 2.5mm 1.25mm 0.625mm

Conventionally, the larger the size of the transducer is, the higher the intensity of the emitted sound wave is, but the larger the installation size is; 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 precision of circuit timing triggering is, and the more accurate the time difference calculation is. That is, the electric/acoustic conversion efficiency is low, and the reflection type has acoustic wave loss, so most manufacturers adopt 1MHz transducers with larger volume (adopting phi 12-14 mm ceramic plates). In recent years, along with the improvement of the precision manufacturing level, the electric/acoustic conversion efficiency is greatly improved, and the electric/acoustic conversion efficiency of the small-size high-frequency transducer is greatly improved, so that the application requirement is completely met.

At present, a DN15 insert reflection type flowmeter transducer commonly used adopts a phi 12mm ceramic chip, the frequency is 1MHz, the front end diameter phi 17mm and the rear end diameter phi 21mm of a packaged convex transducer. Considering that the size in the flow channel is small and the interference to the fluid is reduced as much as possible, a stainless steel insert with the width of 10mm is used for the DN15 caliber reflecting surface. Due to the stamping, the edges are curved and the width of the plane that can actually be used for reflection is about 8mm. Therefore, the actual utilization rate of the sound wave energy is 8/12, which is about 67% (note that the reflection efficiency is different due to the different widths of the reflection surfaces with different apertures).

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

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

(1) The overall size of the transducer 44 is small, the size of the transducer fixing seat 12 is also small, and then the distance between the center lines of the two transducers of the 2MHz transducer and the phi 10mm transducer is 7mm larger than that of the transducers of 1MHz transducer and phi 17mm, that is, if the transducer fixing seat 12 is arranged close to the inner side of the metal pipe thread, the sound path of the 2MHz transducer is 7mm longer than that of the 1MHz transducer, which is important for enlarging the sound path and improving the range ratio for the limited pipe length.

Patent publication No. CN 201773574U is a transducer used in a conventional ultrasonic reflection flowmeter, and has two disadvantages: firstly, a sealing ring can be only installed at the step of the convex transducer, and the safety is poor; secondly, the installation and the positioning of the transducer need to be close to the sealing ring, if the sealing ring deforms (such as touching organic matters), the transducer inclines (changes in angle), the emitted sound waves cannot be reflected by the reflecting surface, the sound waves have large loss, even time difference calculation cannot be carried out, and the metering is stopped.

This embodiment employs a 2MHz, transducer with a localized, dual seal configuration. The lower edge 444 of the transducer 44 is a mounting positioning edge and is positioned on the positioning table 121 inside the transducer fixing seat 12, 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, and the sealing is safe and reliable and can be used for a long time.

The resilient washer 45 is located above the transducer 44 and serves to keep the seal 442 from being damaged and to limit the downward pressure applied by the retaining nut 46 as the retaining nut 46 is rotated downward. The fixing nut 46 is used for pressing the instrument box base 55A, namely, the cylindrical shell sleeved on the transducer fixing seat 12, so that the function of fixing the instrument box base 55A is achieved by a simple and economical method. The side packing 122 is used to seal the instrument box base 55A from the outside of the transducer holder 12.

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

In this embodiment, since there is no need for waterproof sealing between the whole inner liner composed of the diversion and reflection surface fixing support 22 and the rectifying tube 33 and the inner side of the metal outer tube 11, when hot water metering is performed, the temperature sensor mounting seat 14 can be conveniently installed at the position of the outer end of the metal outer tube 11 close to the water outlet, the temperature sensor 141 is installed in the temperature sensor mounting seat 14, and the temperature measuring rod of the temperature sensor is obliquely inserted outside the diversion cover of the transducer, so that the measurement of fluid is not affected.

The application of the reflective straight pipe ultrasonic water meter structure with a small caliber liner in hot water metering is described through the above embodiments, but the present invention is not limited to the above embodiments, and any modification or variation based on the content of the present invention falls within the scope of the present invention.

Claims

1. A small-caliber liner reflection type straight pipe ultrasonic water meter structure is characterized by comprising an equal-caliber metal outer pipe (11), a diversion and reflection surface fixing support (22), a rectifier tube (33) and a rectifier tube fixing seat (13) thereof, a transducer (44) and a transducer fixing seat (12) thereof, and a transducer and instrument bottom case fixing nut (46); the interface (111) between the small-caliber inner-lining reflection type straight pipe ultrasonic water meter and an external pipeline and the base meter are equal-diameter metal outer pipes (11), and flow guide and transducer reflecting surface fixing supports (22) are arranged and fixed at two ends of the inner sides of the equal-diameter metal outer pipes, so that the maximum sound path of an ultrasonic transducer is realized; the two reflecting surface fixing supports are connected by a reducing rectifier tube (33) to form a double-reflecting type transducer lining tube body structure, so that the completeness of a water flow channel is realized, the permanent invariance of the distance between the two reflecting surfaces is effectively ensured, and the mass-processed flow meter has the flow characteristic with the same height; through the optimized energy converter, the shape of the reflecting surface and the material of the reflecting surface, sound waves among the energy converters are transmitted smoothly without loss; under the cooperation of the transducer fixing seat (12), the lower meter shell fixing nut (46) and the meter box (55), the small-caliber liner reflection type straight pipe ultrasonic water meter is formed, under the limited length of the ultrasonic water meter, the measuring range ratio maximization and the starting flow minimization performance of measurement are realized, the reflection surface has lossless reflection efficiency, and the small-caliber liner reflection type straight pipe ultrasonic water meter can be used for a long time without scaling under the conditions of high temperature and hard water quality.

2. The small-caliber liner reflection type straight pipe ultrasonic water meter structure as claimed in claim 1, characterized in that: the diversion and reflection surface fixing support (22) is integrated by two symmetrical parts which are embedded and butted, and is divided into an outer ring and a middle part after being butted, the two parts are connected by an upper supporting rib and a lower supporting rib instead of a plurality of supporting ribs, so that the diversion of water is uniform, the water flow is facilitated to pass through, and the diversion and reflection surface fixing support has higher strength and symmetry; the front end of the diversion and reflection surface fixing support (22) is provided with a diversion cap (221), the rear end of the diversion and reflection surface fixing support is provided with a reflection surface fixing support (222), and the diversion and reflection surface fixing support consists of a support rib and an outer pipe; the flow guiding cap (221) is formed by tightly matching and butting two convex and concave structures (2211); the sound wave reflecting surface (23) is fixed by butting and wrapping the upper arc-shaped groove and the lower arc-shaped groove of the two parts of the diversion and reflecting surface fixing support (22).

3. The small-caliber liner reflection type straight pipe ultrasonic water meter structure as claimed in claim 1, characterized in that: the reflecting surface (23) is formed by an oval ZrO with the thickness of 1mm, the width of 9mm and the length of 11mm ₂ 、Si ₃ N ₄ Or a SiC material.

4. The small-caliber liner reflection type straight pipe ultrasonic water meter structure as claimed in claim 1, characterized in that: the rectifying tube (33) is fixed by a rectifying tube fixing nut (132) and a sealing ring (131), is tightly matched and butted with the guide and reflecting surface fixing support (22), and is butted and then is bonded with glue or welded with a butt joint by laser, so that the two guide and reflecting surface fixing supports (22) and the rectifying tube (33) are integrated.

5. The small-caliber liner reflection type straight pipe ultrasonic water meter structure as claimed in claim 1, characterized in that: the transducer (44) has the vibration frequency of 2MHz/4MHz and is provided with a positioning and double-sealing structure, the lower edge (444) of the outer side of the transducer is an installation positioning edge and is positioned on the positioning table (121) on the inner side of the transducer fixing seat (12), the sealing ring (441) is side-sealed, and the sealing ring (442) is top-sealed, namely two-stage and two different sealing modes are adopted to ensure the sealing safety.

6. The small-caliber liner reflection type straight pipe ultrasonic water meter structure as claimed in claim 1, characterized in that: the fixing nut (46) performs the following two-generation function: firstly, the transducer (44) is pressed by applying force to an elastic gasket (45), and meanwhile, the lower end of the transducer extends into a flow guide and reflection surface fixing support (22) to play a role in positioning; and the second one is used for pressing and fixing the lower shell (55A) of the circuit instrument box, thereby reducing the fixing devices of the lower shell.

7. The small-caliber liner reflection type straight pipe ultrasonic water meter structure as claimed in claim 1, characterized in that: the whole inner bushing consisting of the diversion and reflection surface fixing support (22) and the rectifying tube (33) and the inner side of the metal outer tube (11) do not need waterproof sealing, so that the temperature sensor (141) is convenient to install and can be used for heat energy metering.