CN115680637A - Electromagnetic low-frequency bent monopole acoustic logging transmitting transducer - Google Patents

Abstract

The application discloses bent monopole sound logging emission transducer that opens of electromagnetic type low frequency includes: a central shaft tube; the soft iron cover is fixedly sleeved on the periphery of the central shaft tube and is provided with a cylindrical groove; the permanent magnet is fixedly sleeved on the periphery of the central shaft tube, is positioned in the cylindrical groove and is abutted against the bottom surface of the cylindrical groove; the soft iron bottom is fixedly sleeved on the periphery of the central shaft tube and abuts against the end face of the permanent magnet; the driving cover is fixedly sleeved on the periphery of the central shaft tube, the end part of the driving cover, facing the soft iron cover, extends into the magnetic gap, and a coil is wound on the outer wall of the end part of the driving cover, extending into the magnetic gap; the vibrating body is fixedly sleeved on the periphery of the central shaft tube and fixedly connected with the driving cover and comprises an upper connecting ring and a lower connecting ring, and a plurality of circular arc vibrating pieces are arranged between the upper connecting ring and the lower connecting ring; the electromagnetic low-frequency flextensional monopole acoustic logging transmitting transducer arranged in the mode can meet the excitation of a low-frequency sound source in a small-size environment and the aim of remote detection of acoustic waves.

Description

An electromagnetic low-frequency flexural monopole acoustic logging transmitting transducer

technical field

The present application relates to the technical field of acoustic logging, in particular to an electromagnetic low-frequency flexural monopole acoustic logging transmitting transducer.

Background technique

The attenuation of sound waves in the formation is related to frequency, the lower the frequency, the slower the attenuation and the farther the detection distance is. The frequency of the high-frequency piezoelectric monopole sound source commonly used in traditional acoustic logging is around 15kHz. To reduce the transmission frequency of the transducer, the volume of the transducer has to be increased. However, the logging instrument needs to work in a small-scale environment downhole. , so the piezoelectric monopole sound source is not conducive to long-distance detection. Commonly used flexural transducers driven by magnetostrictive materials can generate low-frequency sound sources, and have the characteristics of large strain displacement and high energy density, but magnetostrictive materials are sensitive to temperature changes. Efficiency will be greatly reduced.

Therefore, how to design an electromagnetic low-frequency bending-tensional monopole acoustic logging transmitting transducer that can satisfy the excitation of low-frequency sound sources in a small-sized environment and meet the needs of long-distance sound wave detection is a technical problem to be solved by those skilled in the art. .

Contents of the invention

The purpose of this application is to provide an electromagnetic low-frequency bending-tensional monopole acoustic logging transmitting transducer, which overcomes the problem in the prior art that low-frequency sound sources cannot be generated in downhole high-temperature, high-pressure and small-size environments. The flextensional monopole acoustic logging transmitting transducer can not only meet the requirement of small size downhole, but also can generate low-frequency sound source to meet the requirement of long-distance detection around the borehole.

In order to achieve the above purpose, the present application provides an electromagnetic low-frequency flexural monopole acoustic logging transmitting transducer, including:

Axial tube;

A soft iron cover is fixedly sleeved on the outer periphery of the central axis tube, and the soft iron cover is provided with a cylindrical groove coaxial with the central axis tube;

The permanent magnet is fixedly sleeved on the outer periphery of the central axis tube, is located in the cylindrical groove, and resists the bottom surface of the cylindrical groove;

The soft iron bottom is fixedly sleeved on the outer periphery of the central axis tube, and is opposed to the end surface of the permanent magnet away from the bottom surface of the cylindrical groove. The permanent magnet and the soft iron bottom are all connected to the cylindrical groove The inner wall is arranged at intervals to form a ring-shaped magnetic gap;

The drive cover is fixedly sleeved on the outer circumference of the central axis tube and is spaced apart from the outer wall of the central axis tube. The end of the drive cover facing the soft iron cover extends into the magnetic gap and is in contact with the outer wall of the central axis tube. The permanent magnet, the soft iron bottom, and the soft iron cover are arranged at intervals, and a coil is wound on the outer wall of the end of the drive cover extending into the magnetic gap, and the coil is located at the position generated by the permanent magnet. in a constant magnetic field;

The vibrating body is fixedly sleeved on the outer circumference of the central axis tube and is fixedly connected to the end of the driving cover away from the coil, including an upper connecting ring connected to the driving cover and fixedly connected to the central axis tube A lower connecting ring, a plurality of circular-arc vibrating pieces are arranged between the upper connecting ring and the lower connecting ring, and the circular-arc vibrating pieces are spaced apart from the outer wall of the central axis tube.

Preferably, the permanent magnet and the soft iron bottom are annular, and the inner and outer diameters of the permanent magnet and the soft iron bottom are the same, and the end surface of the soft iron cover exceeds the end surface of the soft iron bottom, that is, the Both the permanent magnet and the soft iron bottom are inside the cylindrical groove.

Preferably, the section of the circular-arc vibrating piece is an arc with a specific curvature, and the arc is rotated along the axis of the central axis tube to form the circular-arc vibrating piece, and the number of the circular-arc vibrating pieces is 8- There are 16 circular-arc vibrating pieces, and a plurality of circular-arc vibrating pieces are distributed along the circumferential direction of the central axis tube to form a concave-waisted cylinder, and vibrating piece slots are arranged between adjacent circular-arc vibrating pieces.

Preferably, the end of the drive cover protruding into the magnetic gap is provided with a groove on its outer wall, the groove is engraved with a helical pattern, and the coil is wound in the groove according to the helical pattern , and the midpoint of the coil in its height direction is on the same level as the midpoint of the soft iron bottom in its thickness direction.

Preferably, the outer wall of the central axis tube is provided with two wiring holes passing through itself, and the wires of the coil enter the central axis tube through the two wiring holes and are connected to an external circuit.

Preferably, the central axis tube is a hollow tubular structure, and a protruding platform is provided on its outer wall, a gasket is clamped between the protruding platform and the soft iron bottom, and the gasket and the The inner and outer diameters of the permanent magnet and the soft iron bottom are the same.

Preferably, the end surface of the soft iron cover facing away from the cylindrical groove bears against a gland, and the gland includes:

The lower gland is ring-shaped, sleeved on the outer periphery of the central axis tube, and used to resist the soft iron cover, and the outer diameter of the lower gland is smaller than the outer diameter of the soft iron cover;

The upper gland is cylindrical, sleeved on the outer circumference of the central axis tube, and fixedly connected with the lower gland, the lower gland is fixedly arranged on the central axis tube, and the inner wall of the upper gland A limiting groove is arranged on the top, and the limiting groove surrounds a circle along the inner wall of the gland for positioning the position of the gland on the central axis tube;

The pressing cover cooperates with the protruding platform to fix and press the soft iron cover, the permanent magnet, the soft iron bottom and the gasket on the central axis tube.

Preferably, the lower connecting ring is fixedly connected to the central axis tube through a base, and the base includes:

The upper base is ring-shaped, sleeved on the outer circumference of the central axis tube, and its end surface is provided with a fan-shaped through groove penetrating itself, the outer wall of the upper base is opposed to the inner wall of the lower connecting ring, and fixed connect;

The lower base is cylindrical, fixedly connected with the upper base, sleeved on the outer periphery of the central axis tube, and fixedly arranged on the central axis tube.

Preferably, the outer wall of the central axis tube is provided with a plurality of rounded rectangular grooves along its circumference, and the rounded rectangular grooves at the same axial position form a group of rounded rectangular grooves. On the side wall of the central axis tube Three sets of the rounded rectangular slots are arranged at intervals along the axial direction, and the plurality of rounded rectangular slots are axially staggered, and the opening positions of the rounded rectangular slots correspond to the arc vibrating plates, and the The rounded rectangular groove is used in conjunction with the fan-shaped through groove to guide the fluid inside the circular-arc vibrating plate and release internal energy.

Preferably, the driving cover material is a non-conductive high temperature resistant material.

With respect to the above-mentioned background technology, in the electromagnetic low-frequency flexural monopole acoustic logging transmitting transducer of the present application, the soft iron cover, the permanent magnet and the soft iron bottom form a magnetic circuit structure, and the magnetic circuit structure is fixedly arranged on the central shaft tube The two ends of the permanent magnet are against the soft iron cover and the soft iron bottom respectively. The soft iron bottom is covered with gaskets to prevent the permanent magnet and the soft iron bottom from breaking during the vibration process. The constant magnetic field generated by the permanent magnet passes through the soft iron cover and the soft iron bottom. The conduction of the soft iron bottom converges in the magnetic gap, which ensures the utilization of the magnetic field.

In addition, in the electromagnetic low-frequency flexural monopole acoustic logging transmitting transducer of the present invention, the vibrating body includes an upper connecting ring, a lower connecting ring and an arc vibrating plate, the driving cover is fixed to the vibrating body, and the vibrating body is connected to the central shaft. The tube is fixedly connected, and the coil on the driving cover is in the magnetic gap magnetic field. When the coil is fed with alternating current, the driving cover generates alternating force to drive the vibrating body to vibrate up and down, so that the arc vibrating plate vibrates and radiates low frequency to the surrounding Sound waves can meet the excitation of low-frequency sound sources in small-sized environments and meet the needs of long-distance detection of sound waves.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only It is an embodiment of the present application, and those skilled in the art can also obtain other drawings according to the provided drawings without creative work.

FIG. 1 is a schematic diagram of the external structure of the electromagnetic low-frequency flexural monopole acoustic logging transmitting transducer provided by the embodiment of the present application;

Fig. 2 is A-A sectional view among Fig. 1;

Fig. 3 is a schematic diagram of the central axis tube structure of the electromagnetic low-frequency flexural monopole acoustic logging transmitting transducer provided by the embodiment of the present application;

Fig. 4 is a schematic diagram of the three-dimensional structure of the gland of the electromagnetic low-frequency flexural monopole acoustic logging transmitting transducer provided by the embodiment of the present application;

Fig. 5 is a schematic diagram of the gland section structure of the electromagnetic low-frequency flexural monopole acoustic logging transmitting transducer provided by the embodiment of the present application;

Fig. 6 is a schematic cross-sectional structure diagram of the soft iron cover of the electromagnetic low-frequency flexural monopole acoustic logging transmitting transducer provided by the embodiment of the present application;

7 is a schematic diagram of the three-dimensional structure of the permanent magnet of the electromagnetic low-frequency flexural monopole acoustic logging transmitting transducer provided by the embodiment of the present application;

Fig. 8 is a schematic diagram of the three-dimensional structure of the soft iron bottom of the electromagnetic low-frequency flexural monopole acoustic logging transmitting transducer provided by the embodiment of the present application;

Fig. 9 is a schematic diagram of the three-dimensional structure of the storefront of the electromagnetic low-frequency flexural monopole acoustic logging transmitting transducer provided by the embodiment of the present application;

10 is a schematic diagram of the three-dimensional structure of the driving cover of the electromagnetic low-frequency flexural monopole acoustic logging transmitting transducer provided by the embodiment of the present application;

Fig. 11 is a schematic diagram of the cross-sectional structure of the driving cover of the electromagnetic low-frequency flexural monopole acoustic logging transmitting transducer provided by the embodiment of the present application;

12 is a schematic diagram of the three-dimensional structure of the vibrating body of the electromagnetic low-frequency flexural monopole acoustic logging transmitting transducer provided by the embodiment of the present application;

Fig. 13 is a schematic diagram of the three-dimensional structure of the base of the electromagnetic low-frequency flexural monopole acoustic logging transmitting transducer provided by the embodiment of the present application.

In the figure: 1. Central axis tube 11, protruding platform 12, wiring hole 13, rounded rectangular slot;

2. Gland 21, upper gland 22, lower gland 23, limit slot;

3. Soft iron cover 31. Cylindrical groove;

4. Permanent magnet;

5. Soft iron bottom;

6. Gasket;

7. Drive cover 71. Coil;

8. Vibration body 81, upper connecting ring 82, arc vibrating piece 83, lower connecting ring 84, vibrating piece slit;

9. Base 91, upper base 92, lower base 93, fan-shaped through groove.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the application with reference to the drawings in the embodiments of the application. Apparently, the described embodiments are only some of the embodiments of the application, not all of them. Based on the embodiments in this application, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of this application.

In order to enable those skilled in the art to better understand the solution of the present application, the present application will be further described in detail below in conjunction with the drawings and specific embodiments.

As shown in Figures 1 to 13, in this embodiment, an electromagnetic low-frequency flexural monopole acoustic logging transmitting transducer is provided, which includes a central axis tube 1, a soft iron cover 3, a permanent magnet 4, a soft The iron bottom 5, the driving cover 7 and the vibrating body 8, the soft iron cover 3, the permanent magnet 4 and the soft iron bottom 5 form a magnetic circuit structure, the magnetic circuit structure is fixedly arranged on the central axis tube 1, and the two ends of the permanent magnet 4 respectively touch the Holding the soft iron cover 3 and the soft iron bottom 5, specifically, the soft iron cover 3 is fixedly sleeved on the outer periphery of the central axis tube 1, and the soft iron cover 3 is provided with a cylindrical groove 31 coaxial with the central axis tube 1; The permanent magnet 4 is fixedly sleeved on the outer circumference of the central axis tube 1, and is located in the cylindrical groove 31, and resists the bottom surface of the cylindrical groove 31; the soft iron bottom 5 is fixedly sleeved on the outer circumference of the central axis tube 1, and is in contact with the permanent magnet 4 The end face away from the bottom surface of the cylindrical groove 31 resists, and the permanent magnet 4 and the soft iron bottom 5 are spaced apart from the inner wall of the cylindrical groove 31 to form a ring-shaped magnetic gap. The constant magnetic field generated by the permanent magnet 4 passes through the soft iron cover 3 and the soft iron cover 3 The conduction of the iron base 5 converges in the magnetic gap, which ensures the utilization of the magnetic field.

In addition, the vibrating body 8 includes an upper connecting ring 81, a lower connecting ring 83 and an arc vibrating plate 82, the driving cover 7 is fixed to the vibrating body 8, the vibrating body 8 is fixedly connected to the central axis tube 1, and the coil 71 on the driving cover 7 In the magnetic gap magnetic field, when the coil 71 is fed with an alternating current, the driving cover 7 generates an alternating force to drive the vibrating body 8 to vibrate up and down, so that the arc vibrating piece 82 vibrates and radiates low-frequency sound waves to the surroundings, which can meet the small The excitation of low-frequency sound sources in large-scale environments meets the needs of long-distance sound wave detection.

It should be noted that the driving cover 7 is fixedly sleeved on the outer circumference of the central axis tube 1, and is spaced from the outer wall of the central axis tube 1. The end of the driving cover 7 facing the soft iron cover 3 extends into the magnetic gap, and is connected to the permanent The magnet 4, the soft iron bottom 5, and the soft iron cover 3 are arranged at intervals, and the outer wall of the drive cover 7 extending into the magnetic gap is wound with a coil 71, and the coil 71 is located in the constant magnetic field generated by the permanent magnet 4.

Specifically, the above-mentioned vibrating body 8 is fixedly sleeved on the outer circumference of the central axis tube 1, and is fixedly connected to the end of the drive cover 7 away from the coil 71, including an upper connecting ring 81 connected to the drive cover 7 and fixed to the central axis tube 1. The connected lower connecting ring 83 , a plurality of circular-arc vibrating pieces 82 are arranged between the upper connecting ring 81 and the lower connecting ring 83 , and the circular-arc vibrating pieces 82 are spaced apart from the outer wall of the central axis tube 1 .

In this embodiment, the central axis tube 1, the magnetic circuit structure, the driving cover 7, and the vibrating body 8 made of metal materials together constitute an electromagnetic low-frequency bending-tensional monopole acoustic logging transmitting transducer, and the magnetic circuit structure passes through The soft iron cover 3 and the soft iron bottom 5 converge the magnetic field generated by the permanent magnet 4 in the annular magnetic gap, the coil 71 on the driving cover 7 is in the magnetic field, the driving cover 7 is fixed to the vibrating body 8, and the bottom of the vibrating body 8 is fixed On the base 9, the position of the drive cover 7 in the air gap is changed by adjusting the height of the base 9.

The electromagnetic low-frequency bending-tensional monopole acoustic logging transmitting transducer set in the above-mentioned manner has a small volume and a high emission sound pressure level, which can meet the needs of acoustic logging for low-frequency sound sources, and is conducive to popularization and use.

As shown in Fig. 6, Fig. 7, Fig. 8, in this embodiment, the permanent magnet and the soft iron bottom 5 are annular, and the inner and outer diameters of the permanent magnet 4 and the soft iron bottom 5 are the same, and the end surface of the soft iron cover 3 exceeds the soft iron bottom. The end face of the iron bottom 5, that is, the permanent magnet 4 and the soft iron bottom 5 are all inside the cylindrical groove 31.

It should be noted that, as shown in Figure 2, the soft iron cover 3, the permanent magnet 4 and the soft iron bottom 5 form a magnetic circuit structure, forming a ring-shaped magnetic gap, and the soft iron cover 3 and the soft iron bottom 5 generate the permanent magnet 4. The magnetic field lines converge into the magnetic gap, so that there is a strong magnetic flux density in the magnetic gap, which provides sufficient driving force for the vibration of the vibrating body 8 .

In this embodiment, the soft iron cover 3 has a cover-like structure, which can cover the permanent magnet 4 and the soft iron bottom 5, and the distance from the upper end of the vibrating body 8 is not less than 2.5 mm, and the outer diameter of the soft iron cover 3 is not greater than 72 mm. .

In addition, as shown in Fig. 4 and Fig. 5, the end surface of the soft iron cover 3 away from the cylindrical groove 31 bears against the gland 2, and the gland 2 includes: the lower gland 22 is ring-shaped and sleeved on the central axis tube 1 The outer circumference is used to resist the soft iron cover 3, and the outer diameter of the lower gland 22 is smaller than the outer diameter of the soft iron cover 3; the upper gland 21 is cylindrical, sleeved on the outer periphery of the central axis tube 1, and connected The cover 22 is fixedly connected, and the lower gland 22 is fixedly arranged on the central axis tube 1. Of course, the specific fixing method can be fixed by bolts or other fixing methods, which will not be described in detail here; the inner wall of the upper gland 21 is provided with a limit Groove 23 , and the limiting groove 23 circles around the inner wall of the upper gland 21 for positioning the position of the gland 2 on the central axis tube 1 .

As shown in Figures 2 and 3, the central axis tube 1 is a hollow tubular structure, and a protruding platform 11 is provided on its outer wall, and a gasket 6 is clamped between the protruding platform 11 and the soft iron bottom 5, and the gasket 6 is all identical with the inner and outer diameters of the permanent magnet 4 and the soft iron bottom 5.

In this embodiment, as shown in Fig. 7, Fig. 8 and Fig. 9, the permanent magnet 4, the soft iron bottom 5, and the spacer 6 have the same structure, and are all ring-shaped, and the permanent magnet 4, the soft iron bottom 5 and the pad The inner and outer diameters of the sheet 6 are consistent, the height of the permanent magnet 4 is 10 mm, the height of the soft iron bottom 5 is 8 mm, and the height of the spacer 6 is 3 mm.

As shown in FIG. 2 , it should be noted that the gland 2 cooperates with the protruding platform 11 to fix and compress the soft iron cover 3 , the permanent magnet 4 , the soft iron bottom 5 and the spacer 6 on the central axis tube 1 .

As shown in Figure 10 and Figure 11, in this embodiment, the driving cover 7 is divided into upper and lower parts, and the upper and lower parts are connected smoothly. 10mm groove, engraved with helical pattern in the groove, the coil 71 is wound in the groove according to the helical pattern, in this embodiment, the thickness of the upper part of the driving cover 7 is not more than 1.5mm; in addition, as shown in Figure 2, the coil 71 is in the The midpoint of its height direction is on the same horizontal plane as the midpoint of the soft iron bottom 5 in its thickness direction.

In this embodiment, as shown in Figure 12, the section of the circular arc vibrating plate 82 is an arc with a specific curvature, the resonance frequency can be adjusted by changing the curvature, and the arc rotates along the axis of the central axis tube 1 to form an arc vibrating plate 82. The number of arc vibrating pieces 82 is 8-16, and a plurality of arc vibrating pieces 82 are distributed along the circumferential direction of the central axis tube 1 to form a concave waist-shaped cylinder, and between adjacent arc vibrating pieces 82 The vibrating plate slit 84 is provided.

Specifically, the arc-shaped vibrating piece is cut into 8 equal-sized pieces through wire cutting, and each of the upper connecting ring 81 and the lower connecting ring 83 has 8 bolt holes, which are evenly distributed on the circumference, and Corresponding to the bolt holes on the driving cover 7 and the base 9 respectively; of course, other fixing methods can also be used to ensure the stable connection between the vibrating body 8 and the base 9, and the stable connection between the vibrating body 8 and the driving cover 7. In the above embodiment Among them, the slits 84 of the vibrating plate are 1.5 mm wide, and the angle between adjacent slits is 45°.

In addition, when the driving cover 7 and the vibrating body 8 are fixed, the upper surface of the upper connecting ring 81 can be in the same plane as the upper surface of the lower part of the driving cover 7, and the height of the upper connecting ring 81 is slightly greater than the height of the lower part of the driving cover 7; When fixing with the base 9, the lower connecting ring 83 is fixed with the upper base 91, and the lower surface of the lower connecting ring 83 is on the same plane as the lower surface of the upper base 91, and the height of the lower connecting ring 83 is slightly greater than the height of the upper base 91.

As shown in FIG. 3 , the outer wall of the central axis tube 1 is provided with two wiring holes 12 passing through itself. The wires of the coil 71 enter the central axis tube 1 through the two wiring holes 12 and are connected to external circuits.

As shown in Fig. 12 and Fig. 13, the lower connecting ring 83 is fixedly connected with the central axis pipe 1 through the base 9, and the base 9 includes: an upper base 91, which is ring-shaped, sleeved on the outer circumference of the central axis pipe 1, and its end surface There is a fan-shaped through groove 93 that runs through itself. The outer wall of the upper base 91 is held against the inner wall of the lower connecting ring 83 and is fixedly connected; the lower base 92 is cylindrical, fixedly connected with the upper base 91, and is sleeved in the middle. The outer periphery of the shaft tube 1 is fixedly arranged on the central shaft tube 1. The specific fixing method can be provided with threaded holes on the lower base 92, and is fixedly connected with the central shaft tube 1 by bolts. Of course, other methods can also be used for fixing, which will not be detailed here. stated.

It should be noted that, as shown in Figure 3, the outer wall of the central axis tube 1 is provided with a plurality of rounded rectangular grooves 13 along its circumference, and the rounded rectangular grooves 13 at the same axial position form a group of rounded rectangular grooves. On the side wall of the tube 1, three sets of rounded rectangular grooves are set at intervals in the axial direction, and a plurality of rounded rectangular grooves 13 are axially staggered. The angular rectangular groove 13 is used in conjunction with the fan-shaped through groove 93 to guide the fluid inside the arc vibrating plate 82 and release internal energy.

In the above embodiments, the material of the driving cover 7 is a non-conductive high temperature resistant material, such as polyether ether ketone and the like.

It should be noted that in this specification, relational terms such as first and second are only used to distinguish one entity from several other entities, and do not necessarily require or imply any such relationship between these entities. Actual relationship or sequence.

In this paper, specific examples are used to illustrate the principles and implementation methods of the present application, and the descriptions of the above embodiments are only used to help understand the methods and core ideas of the present application. It should be pointed out that those skilled in the art can make some improvements and modifications to the application without departing from the principles of the application, and these improvements and modifications also fall within the protection scope of the claims of the application.

Claims (10)

1. An electromagnetic low-frequency flextensional monopole acoustic logging launch transducer, characterized in that it comprises: Axial tube; A soft iron cover is fixedly sleeved on the outer periphery of the central axis tube, and the soft iron cover is provided with a cylindrical groove coaxial with the central axis tube; The permanent magnet is fixedly sleeved on the outer periphery of the central axis tube, is located in the cylindrical groove, and resists the bottom surface of the cylindrical groove; The soft iron bottom is fixedly sleeved on the outer periphery of the central axis tube, and is opposed to the end surface of the permanent magnet away from the bottom surface of the cylindrical groove. The permanent magnet and the soft iron bottom are all connected to the cylindrical groove The inner wall is arranged at intervals to form a ring-shaped magnetic gap; The drive cover is fixedly sleeved on the outer circumference of the central axis tube and is spaced apart from the outer wall of the central axis tube. The end of the drive cover facing the soft iron cover extends into the magnetic gap and is in contact with the outer wall of the central axis tube. The permanent magnet, the soft iron bottom, and the soft iron cover are arranged at intervals, and a coil is wound on the outer wall of the end of the drive cover extending into the magnetic gap, and the coil is located at the position generated by the permanent magnet. in a constant magnetic field; The vibrating body is fixedly sleeved on the outer circumference of the central axis tube and is fixedly connected to the end of the driving cover away from the coil, including an upper connecting ring connected to the driving cover and fixedly connected to the central axis tube A lower connecting ring, a plurality of circular-arc vibrating pieces are arranged between the upper connecting ring and the lower connecting ring, and the circular-arc vibrating pieces are spaced apart from the outer wall of the central axis tube. 2. The electromagnetic low-frequency flexural monopole acoustic logging transmitting transducer according to claim 1, wherein the permanent magnet and the soft iron bottom are ring-shaped, and the permanent magnet and the The inner and outer diameters of the soft iron bottom are the same, and the end surface of the soft iron cover exceeds the end surface of the soft iron bottom, that is, both the permanent magnet and the soft iron bottom are inside the cylindrical groove. 3. The electromagnetic low-frequency flexural monopole acoustic logging transmitting transducer according to claim 1, wherein the section of the circular-arc vibrating plate is an arc with a fixed curvature, and the arc is along the The axis of the central axis tube rotates to form the circular arc vibrating pieces, the number of the circular arc vibrating pieces is 8-16, and a plurality of the circular arc vibrating pieces are distributed along the circumferential direction of the central axis tube, forming a concave Waist-shaped cylinder, and vibrating plate slots are arranged between adjacent arc vibrating plates. 4. The electromagnetic low-frequency bending-tensional monopole acoustic logging transmitting transducer according to claim 1, characterized in that, the end of the drive cover extending into the magnetic gap is provided with a A groove, the groove is engraved with a helical pattern, the coil is wound in the groove according to the helical pattern, and the midpoint of the coil in the height direction is the same as that of the soft iron bottom in the thickness direction The midpoint is on the same horizontal plane. 5. The electromagnetic low-frequency bending-tensional monopole acoustic logging transmitting transducer according to claim 1, characterized in that, the outer wall of the central axis tube is provided with two wiring holes through itself, and the The wires of the coil enter the central axis tube through the two wiring holes, and are connected with the external circuit. 6. The electromagnetic low-frequency flexural monopole acoustic logging launch transducer according to claim 2, wherein the central axis tube is a hollow tubular structure, and a protruding platform is provided on its outer wall, so that A gasket is clamped between the protruding platform and the soft iron bottom, and the inner and outer diameters of the gasket, the permanent magnet and the soft iron bottom are the same. 7. The electromagnetic low-frequency flexural monopole acoustic logging transmitting transducer according to claim 6, characterized in that, the end face of the soft iron cover away from the cylindrical groove bears against a gland, and the Gland includes: The lower gland is ring-shaped, sleeved on the outer periphery of the central axis tube, and used to resist the soft iron cover, and the outer diameter of the lower gland is smaller than the outer diameter of the soft iron cover; The upper gland is cylindrical, sleeved on the outer circumference of the central axis tube, and fixedly connected with the lower gland, the lower gland is fixedly arranged on the central axis tube, and the inner wall of the upper gland A limiting groove is arranged on the top, and the limiting groove surrounds the inner wall of the upper gland for a circle, and is used to locate the position of the gland on the central axis tube; The pressing cover cooperates with the protruding platform to fix and press the soft iron cover, the permanent magnet, the soft iron bottom and the gasket on the central axis tube. 8. The electromagnetic low-frequency flexural monopole acoustic logging transmitting transducer according to claim 1, wherein the lower connecting ring is fixedly connected to the central shaft tube through a base, and the base includes: The upper base is ring-shaped, sleeved on the outer circumference of the central axis tube, and its end surface is provided with a fan-shaped through groove penetrating itself, the outer wall of the upper base is opposed to the inner wall of the lower connecting ring, and fixed connect; The lower base is cylindrical, fixedly connected with the upper base, sleeved on the outer periphery of the central axis tube, and fixedly arranged on the central axis tube. 9. The electromagnetic low-frequency flextensional monopole acoustic logging transmitting transducer according to claim 8, wherein the outer wall of the central axis tube is provided with a plurality of rounded rectangular grooves along its circumference, and the same axis The rounded rectangular grooves at the position form a rounded rectangular groove group, and three rounded rectangular groove groups are arranged at intervals along the axial direction on the side wall of the central axis tube, and a plurality of the rounded rectangular grooves are in the form of Axially staggered, the opening position of the rounded rectangular groove corresponds to the circular arc vibrating piece, and the rounded rectangular groove is used in conjunction with the fan-shaped through groove to provide the inner side of the circular arc vibrating piece. The fluid guides the flow and discharges the internal energy. 10 . The electromagnetic low-frequency bending-tensional monopole acoustic logging transmitting transducer according to any one of claims 1-9, characterized in that the driving cover material is a non-conductive high-temperature-resistant material. 11 .

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