Large-size inlaid radial magnetic circuit and manufacturing method thereof

Abstract

The application discloses a large-size inlaid radial magnetic circuit and a manufacturing method thereof, wherein the magnetic circuit comprises a magnetic conducting bowl, a permanent magnet, a magnetic conducting column and a protection ring; the permanent magnet is oriented along a radial direction; after magnetic lines of force pass through a magnetic gap along the permanent magnet in the radial direction, the magnetic lines of force return to the permanent magnet through the magnetic conducting column and the magnetic conducting bowl; the manufacturing method solves the technical problem that a large-size permanent magnet ring element cannot be prepared and oriented in the radial direction by using a current process; the large-size inlaid radial magnetic circuit manufactured by the method has the advantages of good magnetic line of force distribution uniformity, large magnetic gap size, high magnetic flux density, good process performance, low cost and the like, and can meet the application requirement of a moving coil type underwater acoustic transducer.

Description

Technical Field

[0001] This invention relates to the field of radial magnetic circuit technology, specifically to a large-size interlocking radial magnetic circuit and its manufacturing method. Background Technology

[0002] Sound waves are considered the only form of information carrier and energy capable of long-distance propagation in seawater. Low-frequency sound waves experience minimal propagation loss in water, making them suitable for long-distance transmission. Active acoustic emission technology, particularly operating in the tens to hundreds of hertz frequency range, has significant applications in national economy and defense technology. Dynamic transducers, due to their non-contact acoustic radiation system and magnetic circuit, can achieve ultra-low frequency acoustic emission within limited size and weight, making them ideal for use as ultra-low frequency underwater acoustic transducers.

[0003] According to the magnetic effect of electric current, the driving force for the reciprocating vibration of a moving-coil transducer is provided by the Ampere force F, where F = BLi, B represents the magnetic flux density passing through the coil's magnetic field, L represents the coil length, and i represents the driving current. To increase the radiating sound source level of the moving-coil transducer, the Ampere force must be as large as possible. However, the upper limit of the driving current i is almost determined by the current-carrying capacity of the coil. Excessive driving current will cause the coil to generate excessive Joule heat, causing the transducer to malfunction. Usually, the current-carrying capacity of the coil can be increased by thickening the wire diameter. However, given a fixed magnetic gap size, thickening the wire diameter will reduce the number of coil turns, i.e., reduce the total length of the coil. Therefore, increasing the driving Ampere force to improve the electroacoustic energy conversion efficiency of the transducer, increasing BL is the most direct and effective way.

[0004] The most typical application of moving-coil transducers is in various loudspeakers, where the magnetic circuit size is relatively small and manufacturing is relatively easy. However, moving-coil transducers operating underwater face significant resistance due to the much higher characteristic impedance of water compared to air. To achieve high-power acoustic emission, greater resistance must be overcome, thus requiring a larger magnetic circuit to provide a static magnetic field. Magnetic circuit types used in moving-coil transducers mainly include axial and radial magnetic circuits. Axial magnetic circuits offer advantages such as high magnetic flux density, simple structure, and low cost, but suffer from poor uniformity of magnetic field lines and a smaller gap size. Radial magnetic circuits, on the other hand, offer advantages such as uniform magnetic field lines and a larger gap size. Figure 1 As shown, since the polarity of the entire outer diameter surface of the radially oriented magnetic circuit is the same, while that of the entire inner diameter surface is opposite, the radial orientation of the permanent magnet is very difficult due to the repulsive force during the manufacturing process, and the manufacturing cost is high, especially for large-sized radial magnetic circuits.

[0005] Therefore, how to fabricate a large-size radial magnetic circuit with a large magnetic gap size and good uniformity of magnetic field lines to meet the application requirements of ultra-low frequency acoustic emission of high-power moving-coil underwater acoustic transducers has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0006] To address the shortcomings of existing technologies, such as poor uniformity of magnetic field line distribution and small magnetic gap size in traditional axial magnetic circuits, and high cost and difficult manufacturing of large-size radial magnetic circuits, this invention provides a large-size interlocking radial magnetic circuit and its manufacturing method for underwater acoustic transducers. The magnetic circuit has advantages such as large magnetic gap size, high magnetic flux density, good uniformity of magnetic field line distribution, good manufacturability, and low cost, which can meet the application requirements of moving-coil underwater acoustic transducers.

[0007] According to a first aspect, the present invention provides a large-size inlaid radial magnetic circuit, the radial magnetic circuit comprising: a protective ring and magnetically conductive pillars, permanent magnets and magnetically conductive bowls nested from the inside out, wherein there is a magnetic gap between the magnetically conductive pillars and the permanent magnets, and the permanent magnets are composed of several permanent magnet tiles inlaid together, which are radially oriented, and the inner radial outer diameter orientation direction can be either "N pole → S pole" or "S pole → N pole".

[0008] After passing through the magnetic gap along the radial direction of the permanent magnet, the magnetic lines of force return to the permanent magnet via the magnetic guide post and the magnetic guide cup.

[0009] The protective ring covers the permanent magnet and is fixedly connected to the magnetic cup by the protective ring mounting bolts.

[0010] The permanent magnet materials include, but are not limited to, various neodymium iron boron, ferrite, samarium cobalt and other permanent magnet materials; the magnetic cup and magnetic post materials include, but are not limited to, soft magnetic alloy, permalloy, electrical pure iron, low carbon steel and other magnetic materials; and the protective ring materials include, but are not limited to, various non-metallic materials and lightweight metal materials.

[0011] According to a second aspect, the present invention also provides a method for fabricating a large-size interlocking radial magnetic circuit, comprising:

[0012] Step 1: Clean the surfaces of the magnetic post, permanent magnet, and magnetic bowl;

[0013] Step 2: Apply adhesive to the mating surfaces of the permanent magnet tile and the magnetic cup;

[0014] Step 3: Place the permanent magnet tiles one by one along the surface of the magnetic cup that mates with the permanent magnet tile towards the bottom. After each permanent magnet tile is in place, use a torque wrench to fix the permanent magnet tile to the magnetic cup with permanent magnet mounting bolts according to the designed torque value.

[0015] Step 4: Repeat step 3 until all permanent magnet tiles are installed; after the adhesive has cured, use a non-magnetic mold to fill the gaps in the permanent magnet mounting bolt heads with potting compound.

[0016] Step 5: After the potting compound has cured, apply adhesive to the mating surfaces of the protective ring, permanent magnet, and magnetic cup. Place the protective ring along the inner wall of the permanent magnet towards the bottom. After the protective ring is in place, fix the protective ring to the magnetic cup using the protective ring mounting bolts.

[0017] Step 6: After the adhesive has cured, apply adhesive to the mating surfaces of the magnetic post and the magnetic cup. Then, hoist the magnetic post and slowly place it into the designated position along the magnetic circuit axis. Subsequently, fix the magnetic post to the magnetic cup using the magnetic post mounting bolts. After the adhesive has cured, the overall assembly of the magnetic circuit is completed.

[0018] Further, step 1 includes:

[0019] Wipe the magnetic posts, permanent magnets, and magnetic cups with anhydrous ethanol to remove surface dust and stains; and / or...

[0020] The surfaces of the magnetic bowl, permanent magnet, and magnetic column are cleaned using plasma surface cleaning equipment.

[0021] Furthermore, in step 5, when installing the protective ring, it is necessary to ensure that the protective ring and the permanent magnet are coaxially aligned.

[0022] Furthermore, the top of the magnetic post is provided with a threaded hole;

[0023] In step 6, when hoisting the magnetic column, it is necessary to ensure that the magnetic column and the magnetic bowl are coaxial.

[0024] Furthermore, in step 5, before installing the protective ring mounting bolt, thread-locking adhesive is applied to the threads of the protective ring mounting bolt.

[0025] In step 6, before installing the magnetic post mounting bolt, thread-locking adhesive is applied to the threads of the magnetic post mounting bolt.

[0026] Furthermore, the adhesive is a room-temperature curing epoxy resin adhesive.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) It solves the process problem of fabricating and radially oriented large-size permanent magnet rings that cannot be achieved by current technology, and can effectively reduce the eddy current loss of integrally formed permanent magnet rings, and can suppress the temperature rise problem of transducer operation to a certain extent.

[0029] (2) The large-size inlaid radial magnetic circuit produced has the advantages of large magnetic gap size, high magnetic flux density, good processability and low cost, which can improve the electroacoustic conversion efficiency of the moving coil transducer.

[0030] (3) The magnetic gap magnetic field lines of the radial magnetic circuit have good uniformity, which is beneficial to improving the linearity of the transducer radiated sound waves.

[0031] (4) The use of a protective ring design can improve the shock and vibration resistance of the magnetic circuit, and enhance the reliability and environmental adaptability of the underwater acoustic transducer. Attached Figure Description

[0032] Figure 1 Schematic diagram of a radially oriented ring magnet;

[0033] Figure 2 This is a cross-sectional view of the large-size interlocking radial magnetic circuit in Example 1;

[0034] Figure 3 This is a schematic diagram of the permanent magnet structure in Example 1;

[0035] Figure 4 This is a schematic diagram of the magnetic field lines distribution in the large-size interlocking radial magnetic circuit of Example 1;

[0036] Figure 5 The magnetic flux density distribution curve along the axial direction of the magnetic gap in the large-size interlocking radial magnetic circuit in Example 1 is shown.

[0037] Figure label:

[0038] 1-Magnetic guide bowl, 2-Permanent magnet mounting bolt, 3-Permanent magnet, 4-Potting glue, 5-Threaded hole, 6-Magnetic guide post, 7-Magnetic guide post mounting bolt, 8-Protective ring, 9-Protective ring mounting bolt. Detailed Implementation

[0039] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0040] Example 1

[0041] like Figure 2 As shown, this invention provides a large-size interlocking radial magnetic circuit, comprising: a protective ring 8 and, from the inside out, nested magnetic guide pillars 6, permanent magnets 3, and magnetic cups 1. The magnetic guide pillars 6 are fixed inside the magnetic cups 1 by magnetic guide pillar mounting bolts 7. The permanent magnets 3 are fixed to the magnetic cups 1 by permanent magnet mounting bolts 2. The bolt head gaps of the permanent magnet mounting bolts 2 are filled with potting compound 4. The protective ring 8 covers the magnetic cups 1 and the permanent magnets 3 and is fixed by protective ring mounting bolts 9. The permanent magnets 3 are radially oriented, with magnetic lines of force almost perpendicular to the magnetic circuit axis. After passing through the magnetic gap radially along the permanent magnets 3, they return to the permanent magnets 3 via the magnetic guide pillars 6 and the magnetic cups 1. A current flowing through the coil in the direction cutting the magnetic lines of force is subjected to an axial Ampere force. When the magnitude and direction of the current change, the coil drives the acoustic emission system of the transducer to vibrate and radiate sound waves into the medium.

[0042] Furthermore, such as Figure 3As shown, the permanent magnet 3 is radially oriented, and the orientation direction of the inner radial and outer diameter can be either "N pole → S pole" or "S pole → N pole". The permanent magnet 3 is realized by inlaying permanent magnet tiles into a ring. The number of tiles can be designed according to requirements. In this embodiment, it is made of 8 permanent magnet tiles. The materials can be selected from various permanent magnet materials including but not limited to neodymium iron boron, ferrite, samarium cobalt, etc. In this embodiment, neodymium iron boron with high magnetic energy product and high coercivity is selected.

[0043] The permanent magnet 3 and the magnetic cup 1 are coaxially fitted and fastened together by the permanent magnet mounting bolt 2 to the designed torque value. The potting compound filling the gaps in the bolt heads of the permanent magnet mounting bolt 2, after curing, conforms to the inner surface of the permanent magnet 3. Here, the machining of the circular hole on the permanent magnet 3 is limited by current technology and is often achieved by drilling. However, drilling can easily cause cracks in the permanent magnet 3 along the tangent direction of the circular hole. The potting compound reduces the possibility of localized material detachment near the circular hole.

[0044] Furthermore, the magnetic guide post 6 and the magnetic guide bowl 1 are coaxially fitted and fastened together by the magnetic guide post mounting bolts 7. A threaded hole 5 is pre-drilled on the upper end face of the magnetic guide post 6 to facilitate installation and hoisting of the entire magnetic circuit. The materials of the magnetic guide bowl 1 and the magnetic guide post 6 include, but are not limited to, soft magnetic alloys, permalloy, electrical pure iron, and low-carbon steel. In this embodiment, to maximize the magnetic flux density B of the magnetic gap, the materials for the magnetic guide bowl 1 and the magnetic guide post 6 are selected as 1J22 high-saturation soft magnetic alloys, which are machined and then subjected to vacuum hydrogen annealing.

[0045] Furthermore, the protective ring 8 is a thin-walled, folded-edge circular ring structure, coaxially fitted with the permanent magnet 3. The end face of the protective ring 8 mates with the end face of the magnetic cup 1, and is fastened by the protective ring mounting bolt 9. The magnetic cup 1 is designed with a circular groove structure, with the protective ring 8 coaxially fitted. Because the permanent magnet 3 is a brittle material, it is prone to internal or surface cracks, or even local material detachment, when subjected to cutting forces, impact forces, and vibrations during material machining, screw fastening, transportation, and use. The main function of the protective ring 8 is to improve the integrity and reliability of the magnetic circuit, and to prevent foreign matter from rubbing against the transducer coil in the magnetic gap annular cavity when local material detachment occurs in the permanent magnet 3. The material of the protective ring 8 includes, but is not limited to, various non-metallic materials or lightweight metallic materials. In this embodiment, the protective ring 8 is made of magnesium alloy or aluminum alloy with anodized surface treatment to ensure the insulation of the protective ring surface.

[0046] The specific preparation method is as follows:

[0047] Step 1: Before starting the assembly process, all components must be cleaned, especially the mating surfaces of the magnetic cup 1, permanent magnet 3, and magnetic post 6. Wipe with anhydrous ethanol to remove surface dust and stains. Alternatively, use plasma cleaning equipment to clean the surfaces of the magnetic cup 1 and magnetic post 6 to improve the adhesion of the structural components.

[0048] Step 2: Apply adhesive to the mating surfaces of the permanent magnet tile and the magnetic cup 1. The adhesive may include, but is not limited to, various room temperature curing epoxy resin adhesives.

[0049] Step 3: Place the permanent magnet 3 tiles one by one along the mating surface of the magnetic guide bowl 1 towards the bottom using a special tool. After each tile is in place, use a torque wrench to tighten the permanent magnet mounting bolt 2 into the corresponding threaded hole of the magnetic guide bowl 1 to the designed torque value. The special tool has a guiding structure for the permanent magnet 3 tiles and uses a lead screw or gear-rack mechanism with reduction to slowly place the permanent magnet 3 tiles into the designated position along the mating surface of the magnetic guide bowl 1, avoiding collisions between the permanent magnet 3 and any hard structures during the installation process.

[0050] Step 4: Repeat Step 3 until all tiles are installed and the adhesive has cured. Fill the gap between the bolt heads of permanent magnet mounting bolts 2 and 3 using a non-magnetic mold with room-temperature curing potting compound 4 and wait for it to cure.

[0051] Step 5: Apply adhesive to the mating surfaces of the protective ring 8, the magnetic cup 1, and the permanent magnet 3. Place the protective ring 8 along the inner surface of the permanent magnet 3 towards the bottom, ensuring that the protective ring 8 and the permanent magnet 3 are coaxially mated. The end face of the protective ring 8 mates with the end face of the magnetic cup 1. Before installing the protective ring mounting bolt 9, apply an appropriate amount of threadlocker to the threads, then tighten the protective ring mounting bolt 9 and wait for the adhesive to cure.

[0052] Step 6: Apply adhesive to the mating surfaces of the magnetic guide post 6 and the magnetic guide bowl 1. Use a high-tensile strength tooling to hoist the magnetic guide post 6, ensuring it is coaxial with the magnetic guide bowl 1 and positioned above it. The threaded hole 5 is used for fixing the magnetic guide post to the tooling. The high-tensile strength tooling, using a lead screw or a gear-rack mechanism with reduction gears, is slowly placed into the designated position along the magnetic circuit axis via a central or circumferential positioning guide device. Before installing the magnetic guide post mounting bolt 7, apply a suitable amount of threadlocker to the threads for protection and to prevent loosening. Then tighten the bolt 7 and allow the adhesive to cure, completing the overall assembly of the magnetic circuit. (The last sentence is a repetition of the previous one and can be omitted.)

[0053] like Figure 4-5As shown, the large-size interlocking radial magnetic circuit manufactured by the above method exhibits good uniformity in the distribution of magnetic field lines along the magnetic path and a large magnetic gap size. The magnetic gap width is as long as 5 mm, the height reaches 70 mm, and the average magnetic flux density along the center line of the magnetic gap reaches 0.86 T.

[0054] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. A method for fabricating a large-size interlocking radial magnetic circuit, characterized in that, The radial magnetic circuit includes: a protective ring and a magnetic guide column, a permanent magnet and a magnetic guide bowl nested from the inside out. There is a magnetic gap between the magnetic guide column and the permanent magnet. The permanent magnet is composed of several permanent magnet tiles. After the magnetic lines of force pass through the magnetic gap along the radial direction of the permanent magnet, they return to the permanent magnet via the magnetic guide column and the magnetic guide bowl. The permanent magnet and the magnetic cup are installed coaxially and fastened by the permanent magnet mounting bolts. The potting compound filling the gap of the permanent magnet mounting bolt head is conformal to the inner surface of the permanent magnet after curing. The protective ring covers the permanent magnet and is fixedly connected to the magnetic cup by protective ring mounting bolts. The protective ring is a thin-walled, folded-edge circular ring structure, and the material of the protective ring includes non-metallic materials or lightweight metallic materials; the method includes: Step 1: Clean the surfaces of the magnetic post, permanent magnet, and magnetic bowl; Step 2: Apply adhesive to the mating surfaces of the permanent magnet tile and the magnetic cup; Step 3: Place the permanent magnet tiles one by one along the surface of the magnetic cup that mates with the permanent magnet tile towards the bottom. After each permanent magnet tile is in place, use a torque wrench to fix the permanent magnet tile to the magnetic cup with permanent magnet mounting bolts according to the designed torque value. Step 4: Repeat step 3 until all permanent magnet tiles are installed; after the adhesive has cured, use a non-magnetic mold to fill the gaps in the permanent magnet mounting bolt heads with potting compound. Step 5: After the potting compound has cured, apply adhesive to the mating surfaces of the protective ring, permanent magnet, and magnetic cup. Place the protective ring along the inner wall of the permanent magnet towards the bottom. After the protective ring is in place, fix the protective ring to the magnetic cup using the protective ring mounting bolts. Step 6: After the adhesive has cured, apply adhesive to the mating surfaces of the magnetic post and the magnetic cup. Then, hoist the magnetic post and slowly place it into the designated position along the magnetic circuit axis. Subsequently, fix the magnetic post to the magnetic cup using the magnetic post mounting bolts. After the adhesive has cured, the overall assembly of the magnetic circuit is completed.

2. The method as described in claim 1, characterized in that, Step 1 includes: Wipe the magnetic posts, permanent magnets, and magnetic cups with anhydrous ethanol to remove surface dust and stains; and / or... The surfaces of the magnetic bowl, permanent magnet, and magnetic column are cleaned using plasma surface cleaning equipment.

3. The method as described in claim 1, characterized in that, In step 5, when installing the protective ring, it is necessary to ensure that the protective ring and the permanent magnet are coaxially aligned.

4. The method as described in claim 1, characterized in that, The top of the magnetic column is provided with a threaded hole; In step 6, when hoisting the magnetic column, it is necessary to ensure that the magnetic column and the magnetic bowl are coaxial.

5. The method as described in claim 1, characterized in that, In step 5, before installing the protective ring mounting bolt, thread-locking adhesive is applied to the threads of the protective ring mounting bolt. In step 6, before installing the magnetic post mounting bolt, thread-locking adhesive is applied to the threads of the magnetic post mounting bolt.

6. The method according to any one of claims 1-5, characterized in that, The adhesive is a room-temperature curing epoxy resin adhesive.

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