Downhole butt-welded radio energy coupling mechanism

Abstract

This invention discloses a downhole docking wireless power coupling mechanism, comprising a magnetic coupling coil assembly, coaxially nested inner and outer cylinders. A magnetic coupling coil assembly is fixed to the inner wall of both the outer and inner cylinders. The magnetic coupling coil assembly includes a coil, radial magnetic cores, and axial magnetic cores. Multiple axial magnetic cores, equally spaced along the circumference, are fixed to the inner and outer cylinders respectively. A coil is fixed to the inner side of each inner and outer cylinder, surrounded by corresponding axial magnetic cores. Multiple radial magnetic cores, arranged radially along the coil's direction, are arranged on the opposite end faces of the coils in the inner and outer cylinders. This invention alters the magnetic circuit topology of the coupling mechanism, reducing radial space occupation and weight, and decreasing the sensitivity of coupling performance to strict coaxial alignment of the transmitting and receiving ends. It also changes the distribution of the alternating magnetic field in the vicinity of the cylinder, suppressing eddy current losses.

Description

Technical Field

[0001] This invention relates to the field of downhole power transmission technology in oil drilling, and in particular to a downhole docking wireless power coupling mechanism. Background Technology

[0002] Wireless power transfer technology offers an effective solution to the problems associated with contact-based power transfer. This technology utilizes high-frequency electromagnetic fields to transfer electrical energy, allowing for electrical isolation and sealing between the energy transmitter and receiver. The entire energy transfer process is highly adaptable to environmental factors such as humidity, dust, and vibration, offering high safety and reliability. It also provides electrical equipment with greater flexibility, ease of use, and lower maintenance requirements, avoiding direct mechanical wear at the contact interface and thus extending equipment lifespan. In oil wells, wireless power transfer technology can simplify downhole operations, improve oilfield extraction efficiency, and reduce extraction costs.

[0003] Currently, downhole wireless power transmission commonly employs cylindrical (coaxial) coupling mechanisms. However, this structure reveals the following three prominent problems under the complex operating conditions of actual oil wells:

[0004] First, the large radial space occupies a significant portion, obstructing downhole flow: In typical applications such as measurement while drilling (MWD / LWD) and rotary steerable systems, the annular space clearance of downhole tools is typically only a few millimeters to a dozen millimeters. Traditional fully enclosed cylindrical coupling mechanisms require the construction of a complete cylindrical magnetic circuit between the inner and outer sleeves, occupying a large amount of radial space, severely compressing the mud flow channels, and affecting drilling fluid circulation and bottom hole cooling. Furthermore, their integral structure requires high machining precision, has high manufacturing costs, and is both large in size and weight, resulting in insufficient flexibility in the integrated assembly of downhole tools and difficulty in adapting to different well diameters and tool specifications. Secondly, high coaxiality is required, making mechanical alignment difficult: The outer cylinder of the transmitter and the inner cylinder of the receiver in a cylindrical structure typically need to maintain high coaxiality and keep radial deviation within a small range to ensure uniform air gap and stable coupling efficiency. However, at depths of several thousand meters in wells, ambient temperatures can reach over 150°C and pressures exceed 100 MPa. Combined with uneven formation compression and drill string torsional vibration, the drill string is prone to millimeter-level radial offset and angular deviation. At this point, the cylindrical mechanism struggles to maintain precise alignment, leading to either a significant decrease in coupling efficiency or, in severe cases, mechanical interference or even stuck drill accidents due to excessively small local air gaps. Furthermore, blind installation operations downhole cannot be manually calibrated, resulting in high maintenance costs. Third, severe eddy current losses and poor heat dissipation conditions: In traditional cylindrical coupling mechanisms, the continuous metal cylinder is adjacent to a high-frequency alternating magnetic field, which easily generates strong induced currents in the shell and leads to significant eddy current losses. These losses are further converted into heat, causing local temperature rise in the mechanism. However, the downhole heat dissipation conditions are extremely poor—surrounded by high-temperature formations, with limited mud convection and narrow annular gaps—making it difficult for heat to be effectively dissipated. This can easily lead to a chain of failures such as core demagnetization, insulation aging, and even coil overheating and burnout, seriously threatening the long-term reliability of the system.

[0005] Therefore, there is an urgent need for a new downhole docking wireless power coupling mechanism to solve the above-mentioned technical problems. Summary of the Invention

[0006] The present invention aims to solve the above-mentioned technical problems, namely, to solve the problems of large radial space occupation, obstruction of downhole flow channels, stringent coaxiality requirements, difficult mechanical matching, serious eddy current loss, and poor heat dissipation conditions in the existing downhole wireless power transmission commonly adopts cylindrical (coaxial) coupling mechanism.

[0007] To this end, the present invention provides a downhole docking wireless power coupling mechanism, comprising a magnetic coupling coil assembly, a coaxially nested inner cylinder and an outer cylinder. A magnetic coupling coil assembly is fixed to the inner wall of the outer cylinder near the bottom of the inner cylinder and to the bottom of the inner cylinder. The magnetic coupling coil assemblies in the inner and outer cylinders are symmetrically distributed along their axial directions. Each magnetic coupling coil assembly includes a coil, a radial magnetic core, and an axial magnetic core. Multiple axial magnetic cores are fixed to the inner wall of the inner cylinder and the inner wall of the outer cylinder at equal intervals along the circumferential direction. A coil is fixed to the inner side of each of the corresponding multiple axial magnetic cores in the inner and outer cylinders. Multiple radial magnetic cores are arranged radially along the coil's radial direction on the opposite end faces of the coil in the inner and outer cylinders. The radial magnetic cores are fixedly connected to the axial magnetic cores. The magnetic coupling coil assembly in the inner cylinder and the magnetic coupling coil assembly in the outer cylinder together form a low magnetic reluctance circuit for magnetic flux closure.

[0008] In a specific embodiment of the above-mentioned downhole docking wireless power coupling mechanism, an annular protrusion is provided at a local position on the inner wall of the outer cylinder. The annular protrusion is coaxially arranged with the outer cylinder to form two through holes with different inner diameters inside the outer cylinder. The inner diameter of the through hole used to accommodate the inner cylinder is adapted to the outer diameter of the inner cylinder. When the inner cylinder is sleeved inside the outer cylinder, its bottom end abuts against the annular protrusion. The magnetic coupling coil assembly inside the outer cylinder is installed on the inner wall of the through hole adapted to the outer diameter of the inner cylinder.

[0009] In the specific implementation of the above-mentioned downhole docking wireless power coupling mechanism, both the axial magnetic core and the radial magnetic core are strip-shaped.

[0010] In a specific embodiment of the above-mentioned downhole docking wireless power coupling mechanism, the length of the axial magnetic core is greater than the sum of the thicknesses of the coil and the radial magnetic core.

[0011] In a specific embodiment of the above-mentioned downhole docking wireless power coupling mechanism, the absolute value of the difference between the diameter of the working circle formed by the plurality of radial magnetic cores and the average diameter of the coil is 0~5mm.

[0012] In a specific embodiment of the above-mentioned downhole docking wireless power coupling mechanism, the axial distance between the end faces of the inner cylinder coil and the outer cylinder coil is 8 to 20 mm to form a coupling air gap.

[0013] In the specific implementation of the above-mentioned downhole docking wireless power coupling mechanism, the spacing between adjacent radial magnetic cores is matched with the length of the radial magnetic core, so that the magnetic flux can cover the outer area of ​​the coil and form a continuous magnetic conduction path with the axial magnetic core.

[0014] In the specific implementation of the above-mentioned downhole docking wireless power coupling mechanism, the spacing between two adjacent axial magnetic cores is 0.5 to 1.0 times the width of the axial magnetic core.

[0015] The spacing between two adjacent axial magnetic cores is 3–15 mm. Compared with the prior art, the beneficial effects of the present invention are: The coupling mechanism designed in this invention replaces the traditional fully enclosed continuous cylindrical magnetic core with a circumferentially discrete array of strip-shaped magnetic cores, fundamentally changing the magnetic circuit topology of the coupling mechanism. By reconstructing the integral annular magnetic circuit into multiple discrete magnetic circuit channels, not only is the radial space occupation and mechanism weight reduced, but the discretely distributed axial magnetic core array also decomposes the continuous circumferential magnetic circuit into multiple locally closed magnetic flux channels. When there is a certain radial offset or angular deviation, each channel mainly exhibits local changes in magnetic reluctance and magnetic flux distribution, which can mitigate the decrease in coupling performance caused by the overall air gap imbalance of the traditional continuous cylindrical magnetic circuit, thus relaxing the requirement for strict coaxial alignment. At the same time, this structure changes the distribution of the alternating magnetic field in the vicinity of the cylinder, reducing the intensity of the induced current in the conductive cylinder, which helps to reduce eddy current losses and additional heat generation. The coupling mechanism proposed in this invention, while taking into account power transmission capability, has the characteristics of low eddy current loss, low cost, small size, and suitability for downhole blind installation operations. Attached Figure Description

[0016] The embodiments of this application will now be described with reference to the accompanying drawings, in which: Figure 1 This is a schematic diagram of the external structure of the downhole docking wireless power coupling mechanism provided by the present invention; Figure 2 yes Figure 1Top view; Figure 3 yes Figure 2 A partial sectional view along the AA direction; Figure 4 This is a schematic diagram of a traditional coupling mechanism; Figure 5a It is the cross-sectional magnetic flux density mode of a traditional docking coupling mechanism; Figure 5b It is the cross-sectional magnetic flux density mode of the docking wireless power coupling mechanism designed in this application; Figure 6a It is the magnetic flux density along the axis of a traditional docking coupling mechanism; Figure 6b It is the magnetic flux density along the axis of the docking wireless power coupling mechanism designed in this application.

[0017] List of reference numerals in the attached diagram: 1. Inner cylinder; 2. Outer cylinder; 3. Axial magnetic core; 4. Radial magnetic core; 5. Coil. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0019] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the system or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the use of terms such as "first" and "second" to define components is merely for the convenience of distinguishing the aforementioned components. Unless otherwise stated, these terms have no special meaning and should not be construed as indicating or implying relative importance.

[0020] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "setting," and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0021] This invention relates to a downhole docking wireless power coupling mechanism, comprising a magnetic coupling coil assembly, a coaxially nested inner cylinder and an outer cylinder. A magnetic coupling coil assembly is fixed to the inner wall of the outer cylinder near the bottom of the inner cylinder and to the bottom of the inner cylinder. The magnetic coupling coil assemblies in the inner and outer cylinders are symmetrically distributed along their axial directions. Each magnetic coupling coil assembly includes a coil, a radial magnetic core, and an axial magnetic core. Multiple axial magnetic cores, equally spaced along the circumference, are fixed to the inner and outer cylinders respectively. A coil is fixed to the inner side of each of the corresponding multiple axial magnetic cores in the inner and outer cylinders. Multiple radial magnetic cores, arranged radially along the coil, are provided on the opposite end faces of the coil in the inner and outer cylinders. The radial magnetic cores are fixedly connected to the axial magnetic cores. The magnetic coupling coil assemblies in the inner and outer cylinders together form a low magnetic reluctance circuit for magnetic flux closure. This invention solves the problems of large radial space occupation, obstruction of downhole flow channels, stringent coaxiality requirements, difficult mechanical coordination, severe eddy current loss, and poor heat dissipation conditions that are commonly used in existing downhole wireless power transmission systems that employ cylindrical (coaxial) coupling mechanisms.

[0022] The following is a detailed description of the downhole docking wireless power coupling mechanism provided in the embodiments of the present invention, with reference to the accompanying drawings.

[0023] This invention provides a downhole docking wireless power coupling mechanism, including a magnetic coupling coil assembly, a coaxially nested inner cylinder and an outer cylinder. A magnetic coupling coil assembly is fixed on the inner wall of the outer cylinder near the bottom of the inner cylinder and at the bottom of the inner wall of the inner cylinder. The magnetic coupling coil assemblies in the inner and outer cylinders are symmetrically distributed along their axial directions. The magnetic coupling coil assembly includes a coil, a radial magnetic core, and an axial magnetic core. Multiple axial magnetic cores are fixed on the inner wall of the inner cylinder and the inner wall of the outer cylinder, respectively, and are arranged at equal intervals along the circumferential direction. A coil is fixed on the inner side of the corresponding multiple axial magnetic cores in the inner and outer cylinders. Multiple radial magnetic cores are arranged radially along the coil on the opposite end faces of the coil in the inner cylinder and the coil in the outer cylinder. The radial magnetic cores are fixedly connected to the axial magnetic cores. The magnetic coupling coil assembly in the inner cylinder and the magnetic coupling coil assembly in the outer cylinder together form a low magnetic reluctance circuit for magnetic flux closure.

[0024] Specifically, the outer and inner cylinders can be made of metal materials that meet the mechanical strength requirements of downhole drilling. Both the axial and radial magnetic cores are strip-shaped.

[0025] In this application, the outer cylinder and its internal magnetic coupling coil assembly can be used as the transmitting end, and the inner cylinder and its internal magnetic coupling coil assembly can be used as the receiving end. When an alternating current is applied to the transmitting coil, an alternating magnetic flux is formed in the low-resistivity path formed by the radial and axial magnetic cores of the transmitting end. This alternating magnetic flux is coupled to the receiving end through the coupling air gap between the opposite end faces of the inner and outer cylinder coils, and together with the receiving end magnetic core assembly, forms a closed magnetic circuit. Since the magnetic flux passing through the receiving end coil alternates periodically with time, an alternating electromotive force is induced in the receiving coil according to the law of electromagnetic induction, thereby realizing the coupled transmission of wireless power.

[0026] In this application, a ring-shaped protrusion is provided at a local location on the inner wall of the outer cylinder. The ring-shaped protrusion is coaxially arranged with the outer cylinder to form two through holes with different inner diameters inside the outer cylinder. The inner diameter of the through hole used to accommodate the inner cylinder is adapted to the outer diameter of the inner cylinder. When the inner cylinder is fitted inside the outer cylinder, its bottom end rests against the ring-shaped protrusion. The magnetic coupling coil assembly inside the outer cylinder is installed on the inner wall of the through hole adapted to the outer diameter of the inner cylinder. This structural design of the inner and outer cylinders helps to maintain a good alignment between the magnetic coupling coil assembly inside the inner cylinder and the magnetic coupling coil assembly inside the outer cylinder in the axial position.

[0027] In the above embodiment, the strip-shaped axial magnetic cores are arranged at equal intervals along the inner walls of the inner and outer cylinders in a circumferential direction, providing a low magnetic resistance path for magnetic flux passing through the air gap. This coupling mechanism can be applied to downhole measurement while drilling (MWD / LWD) systems or rotary steering systems.

[0028] In this application, the length of the axial magnetic core is greater than the sum of the thicknesses of the coil and the radial magnetic core.

[0029] In this application, the axial distance between the end faces of the inner cylinder coil and the outer cylinder coil is 8 to 20 mm, thereby forming a coupling air gap between the magnetic coupling coil assembly in the inner cylinder and the magnetic coupling coil assembly in the outer cylinder for magnetic flux to cross.

[0030] In this application, the absolute value of the difference between the diameter of the working circle formed by multiple radial magnetic cores and the average diameter of the coil is 0~5mm. The spacing between adjacent radial magnetic cores is matched with the length of the radial magnetic cores so that the magnetic flux can cover the outer area of ​​the coil and form a continuous magnetic conduction path with the axial magnetic core.

[0031] In one embodiment of this application, the average diameter of the coil is 97.45 mm, the included angle between the centers of two adjacent radial magnetic cores is 15° to 30°, which can be 15° or 20°; the length of the radial magnetic core is greater than or equal to 50 mm, which can be 50 mm; the length of the axial magnetic core is 20 mm to 30 mm, which can be 20 mm. The ratio of the spacing between two adjacent axial magnetic cores to the width of the axial magnetic core can be 0.5 to 1.0; the corresponding spacing is 3 to 15 mm, which can be 5 mm or 10 mm.

[0032] The following simulation analysis compares the traditional docking coupling mechanism with the docking wireless power coupling mechanism designed in this application. For ease of comparison, the two structures use the same number of coil turns and main dimensional boundary conditions in the simulation: both inner and outer cylinders are made of Steel AISI 4340 material, and the magnetic cores are made of ferrite material with a relative permeability of 2400; the outer cylinder has an outer diameter of 171.45 mm, an upper wall thickness of 5 mm, and a lower wall thickness of 10 mm; the inner cylinder has an outer diameter of 161.45 mm and a wall thickness of 5 mm; the coil is made of tightly wound Litz wire with a diameter of 2 mm, with 20 turns on both the primary and secondary sides.

[0033] Traditional docking coupling mechanisms employ a fully enclosed continuous cylindrical magnetic core. For example... Figure 5a and Figure 5b As shown, Figure 5a For the cross-sectional magnetic flux density mode of a traditional docking coupling mechanism, Figure 5b The cross-sectional magnetic flux density mode of the docking wireless power coupling mechanism designed for this application is shown in the figure. As can be seen from the figure, the magnetic field distribution trends of the two structures are generally similar, and there is a certain amount of magnetic leakage around the coupling air gap in both. Figure 6a This refers to the magnetic flux density along the axial direction of a traditional docking coupling mechanism. Figure 6b The magnetic flux density along the axial direction of the docking wireless power coupling mechanism designed for this application is shown. Both coupling mechanisms exhibit four peaks in magnetic flux density near the end of the magnetic core, with the flux density in the central region of the coil being approximately one-quarter of the peak value, and lower near the cylinder. This indicates that under current simulation conditions, this application can still achieve magnetic field distribution characteristics close to those of conventional structures while reducing the amount of magnetic core used.

[0034] Table 1 below presents the simulation results for the conventional docking coupling mechanism and the improved coupling mechanism of this application. As can be seen from Table 1, the mutual inductance and self-inductance of the conventional docking coupling mechanism are slightly higher than those of the docking wireless power coupling mechanism designed in this application, but the coupling coefficients of the two are the same. This result shows that, under current simulation conditions, the coupling mechanism designed in this application can maintain a magnetic coupling level close to that of the conventional structure while reducing the amount of magnetic core used.

[0035] Table 1 shows the simulation results of the traditional docking coupling mechanism and the improved coupling mechanism proposed in this application.

[0036] In traditional coupling mechanisms, the receiving end uses a continuous cylindrical metal shell to surround the magnetic circuit. Under high-frequency alternating magnetic field excitation of tens to hundreds of kHz, a complete induced eddy current loop is formed on the surface of the shell along the circumferential direction. According to Faraday's law of electromagnetic induction, the larger the area surrounded by this eddy current loop and the more continuous the path, the higher the induced electromotive force and eddy current intensity, resulting in greater eddy current losses. Eddy current losses not only directly consume transmission power but also convert into heat, causing the mechanism's temperature to rise, which is particularly serious in the high-temperature, heat-limited environment of downhole drilling. This application replaces the continuous magnetic core on the inner wall of the receiving end's inner cylinder with a discrete axial magnetic core array spaced along the circumferential direction, causing the main magnetic flux to close more along the low magnetic reluctance path formed by the magnetic cores and changing the distribution of the alternating magnetic field in the vicinity of the conductive cylinder. The spatial distribution of the induced current in the conductive cylinder becomes more localized, and the large-scale circumferential induced current is weakened, thus reducing the overall eddy current loss. Combining the simulation results and Table 2, it can be seen that the eddy current loss of the coupling mechanism designed in this application is significantly reduced.

[0037] Table 2 shows the eddy current loss results for the traditional docking coupling mechanism and the improved coupling mechanism of this application.

[0038] In the above embodiments, the improved docking coupling mechanism maintains good coupling performance while reducing the amount of magnetic cores used. Its magnetic circuit equivalent mechanism can be analyzed from the following aspects: Magnetic flux guiding efficiency: Although the discrete axial magnetic cores in the improved structure only cover a portion of the inner wall of the cylinder, the magnetic flux tends to concentrate along low magnetic reluctance paths. The main magnetic flux crossing the air gap will still converge at the location of the axial magnetic cores and complete the magnetic circuit closure through the discrete axial magnetic cores. Although there is a small amount of leakage flux in the gap region between the axial magnetic cores, its impact on the total coupled magnetic flux is relatively limited. Self-inductance and mutual inductance: such as... Figure 5a , 5b and Figure 6a , 6b As shown, the magnetic flux density distribution trends of the two coupling mechanisms are generally similar, and both exhibit four peaks near the end of the magnetic core. Due to the larger amount of magnetic core used, the traditional structure has slightly higher absolute values ​​of self-inductance and mutual inductance than the improved structure, but the coupling coefficients are the same for both. This indicates that the improved structure can still maintain an effective magnetic flux coupling level close to that of the traditional structure under the current simulation conditions. A comprehensive comparison of the three indicators—magnetic core usage, coupling coefficient, and eddy current loss—shows that the improved docking coupling mechanism maintains a similar coupling level while reducing the amount of magnetic core used, and exhibits lower eddy current loss.

[0039] Suppressing eddy current losses: The discrete magnetic core array changes the magnetic field distribution around the cylinder, reduces the alternating magnetic flux linked by the conductive cylinder, and makes the induced current more localized, thereby reducing additional eddy current losses and helping to improve energy transmission efficiency.

[0040] Good equivalent performance of magnetic circuit: Discrete axial magnetic cores utilize the characteristic of concentrated magnetic flux conduction along a low magnetic resistance path. Under the condition of reducing the amount of magnetic core, the coupling coefficient can still be maintained close to that of traditional structures under current simulation conditions, thus balancing material cost and transmission performance.

[0041] Reduced space occupation: Replacing the fully enclosed cylindrical core with a discrete strip core can reduce the amount of core used and radial space occupation, reduce manufacturing costs and mechanism weight, and reduce the sensitivity of coupling performance to strict coaxial alignment.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the embodiments of the present invention.

Claims

1. A downhole docking wireless power coupling mechanism, characterized in that, The system includes a magnetic coupling coil assembly, a coaxially nested inner cylinder and an outer cylinder. A magnetic coupling coil assembly is fixed to the inner wall of the outer cylinder near the bottom of the inner cylinder, and to the bottom of the inner wall of the inner cylinder. The magnetic coupling coil assemblies in the inner and outer cylinders are symmetrically distributed along their axial directions. Each magnetic coupling coil assembly includes a coil, a radial magnetic core, and an axial magnetic core. Multiple axial magnetic cores, equally spaced along the circumference, are fixed to the inner wall of the inner cylinder and the inner wall of the outer cylinder, respectively. A coil is fixed to the inner side of each of the corresponding multiple axial magnetic cores in the inner and outer cylinders. Multiple radial magnetic cores, arranged radially along the coil, are provided on the opposite end faces of the coil in the inner and outer cylinders. The radial magnetic cores are fixedly connected to the axial magnetic cores. The magnetic coupling coil assemblies in the inner and outer cylinders together form a low magnetic reluctance circuit for magnetic flux closure.

2. The downhole docking wireless power coupling mechanism according to claim 1, characterized in that, The inner wall of the outer cylinder is provided with an annular protrusion at a local position. The annular protrusion is coaxially arranged with the outer cylinder to form two through holes with different inner diameters inside the outer cylinder. The inner diameter of the through hole used to accommodate the inner cylinder is adapted to the outer diameter of the inner cylinder. When the inner cylinder is sleeved inside the outer cylinder, its bottom end rests on the annular protrusion. The magnetic coupling coil assembly inside the outer cylinder is installed on the inner wall of the through hole adapted to the outer diameter of the inner cylinder.

3. The downhole docking wireless power coupling mechanism according to claim 1, characterized in that, Both the axial magnetic core and the radial magnetic core are strip-shaped.

4. The downhole docking wireless power coupling mechanism according to claim 3, characterized in that, The length of the axial magnetic core is greater than the sum of the thicknesses of the coil and the radial magnetic core.

5. The downhole docking wireless power coupling mechanism according to claim 3, characterized in that, The absolute value of the difference between the diameter of the working circle formed by the plurality of radial magnetic cores and the average diameter of the coil is 0~5mm.

6. The downhole docking wireless power coupling mechanism according to claim 1, characterized in that, The axial distance between the end faces of the inner cylinder coil and the outer cylinder coil is 8 to 20 mm to form a coupling air gap.

7. The downhole docking wireless power coupling mechanism according to claim 3, characterized in that, The spacing between adjacent radial magnetic cores is matched with the length of the radial magnetic cores so that the magnetic flux can cover the outer region of the coil and form a continuous magnetic conduction path with the axial magnetic core.

8. The downhole docking wireless power coupling mechanism according to claim 3, characterized in that, The spacing between two adjacent axial magnetic cores is 0.5 to 1.0 times the width of the axial magnetic core.

9. The downhole docking wireless power coupling mechanism according to claim 8, characterized in that, The spacing between two adjacent axial magnetic cores is 3 to 15 mm.

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