A high-resistivity conductor wire for nuclear magnetic resonance and its manufacturing method

Abstract

This invention discloses a high-resistivity conductor wire for nuclear magnetic resonance imaging (NMR) and its manufacturing method, relating to the technical field of conductor wires for NMR imaging equipment. The conductor wire includes a central skeleton fiber core and conductor filaments spirally wound around the core. It also includes at least one insulating spacer spirally wound parallel to the conductor filaments, located between adjacent turns of conductor filaments to maintain electrical isolation. A PET film layer is disposed on the surface of the core wire to suppress axial movement of the conductor filaments. The manufacturing method includes core wire preparation and parallel winding of the conductor filaments and spacer. This invention effectively avoids short circuits between adjacent turns of conductor filaments, improves resistance consistency and winding structure stability, reduces the dependence of production on equipment precision, and can stably output high resistance values ​​in the range of 10000Ω / m to 100000Ω / m, making it suitable for conductor wires used in NMR imaging.

Description

Technical Field

[0001] This invention relates to the field of conductor wires for magnetic resonance imaging (MRI) equipment, and specifically to a high-resistivity conductor wire for MRI and its manufacturing method. Background Technology

[0002] The conductor wires used in magnetic resonance imaging (MRI) equipment must have specific resistance values ​​to meet core requirements such as coil impedance matching, heat control, and imaging quality. In existing technologies, high-resistivity conductor wires typically use high-resistivity metal wires such as nickel-chromium alloys or copper-nickel alloys as the conductive body. These metal wires are wound around the surface of a fiber core using a spiral wrapping process to form a wrapped wire. Since the fiber core itself is an insulating material, the DC resistance of the wrapped wire is primarily determined by the unfolded length of the metal wire.

[0003] Currently, typical product solutions in the industry include: using 0.040mm diameter nickel-chromium alloy bare wire wrapped around 2250D polyester fiber core wire, and controlling the wrapping pitch at around 0.055mm to obtain a resistance of about 32800Ω / m; using 0.02mm diameter nickel-chromium alloy wire wrapped around fiber core wire to obtain a higher resistance value of about 99000Ω / m.

[0004] The aforementioned existing technologies have the following insurmountable technical defects in actual production and use: First, fluctuations in the winding pitch can easily lead to short circuit risks. Due to limitations in the mechanical precision of the winding equipment and the stability of tension control, it is difficult to maintain an absolutely constant winding pitch. When the pitch fluctuates and shrinks, the conductor wires of adjacent turns are prone to direct contact, causing local short circuits. This results in a significant decrease in the effective resistance of that section of conductor wire, which cannot meet the stringent resistance precision requirements of nuclear magnetic resonance coils.

[0005] Secondly, pitch fluctuations directly lead to poor resistance consistency. The resistance per meter of the wrapped wire is directly related to the wrapping pitch: the smaller the pitch, the more wrapping turns per unit length, the longer the conductor wire unfolds, and the higher the resistance per meter; conversely, an increased pitch results in a decreased resistance per meter. Random fluctuations in pitch will cause large dispersion in the resistance per meter of the finished product, leading to insufficient batch consistency.

[0006] Third, product quality is highly dependent on the precision of the wrapping equipment. When the equipment is in good condition, the risks of short circuits and resistance fluctuations can be controlled within an acceptable range; however, when the equipment experiences mechanical wear, aging of the control system, or other performance degradation, the pitch control precision decreases significantly, the product defect rate increases sharply, the process stability is insufficient, and the equipment maintenance cost is high.

[0007] Fourth, the conductor wire is prone to shifting and displacement after wrapping. During the wrapping process, subsequent coating with an outer insulation layer, and use, the conductor wire is prone to axial movement on the surface of the fiber core, which further aggravates pitch fluctuations and short-circuit risks, resulting in insufficient long-term stability of the wrapping structure.

[0008] Furthermore, if the surface of the wrapped wire is smooth and regular, the adhesion will be insufficient when extruding polytetrafluoroethylene (commonly known as Teflon), TPU, PP, TPEE, or nylon insulation layers. Long-term use will easily cause the insulation layer to fall off, affecting the reliability of the product. Summary of the Invention

[0009] To address the aforementioned shortcomings of existing technologies, the present invention aims to provide a high-resistivity nuclear magnetic resonance conductor wire and its manufacturing method, thereby solving the technical problems of existing wrapped conductor wires, such as easy short circuits between adjacent turns due to pitch fluctuations, poor resistance consistency, unstable wrapping structure, excessive dependence on equipment accuracy, and insufficient adhesion of the outer insulation layer, and achieving stable output of high resistance values ​​over a wide range of 10000Ω / m to 100000Ω / m.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: A high-resistivity nuclear magnetic resonance (NMR) conductor wire includes a central skeleton fiber core and conductor filaments spirally wound around the outer periphery of the core. It also includes at least one linear insulating spacer. The insulating spacer is spirally wound parallel to the conductor filaments with the same direction of rotation and pitch around the outer periphery of the core, and is located between adjacent turns of the conductor filaments to maintain electrical isolation between them. After winding, the insulating spacer is held in the lateral gap between adjacent turns of the conductor filaments, forming a physical barrier.

[0011] The core wire surface is provided with a PET film layer that can suppress the axial movement of the conductor wire. If the PET film layer is wrapped, the preferred method is to wrap the PET film around the outer surface of the core wire with a threaded wrapping method and control the overlap rate of adjacent PET film wrapping (or use thermal bonding to fix adjacent PET films). This can ensure that the core wire surface is flat and smooth and the friction is uniform.

[0012] Furthermore, the fineness of the central skeleton fiber core is 1000D to 10000D, and the core is selected from aramid fiber or polyaramid fiber. This fineness range provides sufficient structural support strength and wrapping stability, while controlling the finished wire diameter within a reasonable range.

[0013] Furthermore, when the insulating spacer is an insulating fiber, the fineness of the insulating fiber is 7D to 100D, and the insulating fiber is selected from at least one of aramid fiber, polyaramid fiber, nylon fiber, or polyester fiber. This fineness range can ensure the insulation effect while avoiding excessive increase in the finished wire diameter.

[0014] Furthermore, the insulating spacer is an enameled wire, and the insulating varnish layer on the surface of the enameled wire has stable and reliable insulating properties.

[0015] Furthermore, the diameter of the enameled wire is larger than that of the conductor wire, and a micro-uneven structure is formed on the outer surface of the conductor wire after wrapping, which can improve the adhesion of the subsequent outer insulation layer. Moreover, although the diameter of the conductor wire is larger than that of the enameled wire, a micro-uneven structure can also be formed on the outer surface of the conductor wire after wrapping, the enameled wire is in a concave position at this time. This structure may cause short circuits due to contact between the protruding conductor wires after wrapping, especially when an outer insulation layer is extruded after wrapping.

[0016] Furthermore, the outer surface of the central skeleton fiber core is covered with a PET film layer, and the conductor filament and the insulating spacer are wrapped around the outside of the PET film layer. The PET film layer can increase the friction between the conductor filament and the core surface, and suppress the axial movement of the conductor filament.

[0017] Furthermore, the conductor wire is a nickel-chromium alloy wire with a diameter of 0.015mm to 0.050mm. The basic resistance value can be flexibly adjusted by adjusting the diameter of the conductor wire.

[0018] Furthermore, the winding pitch of the conductor wire is 0.04mm to 0.20mm, and the meter resistance of the conductor wire is 10000Ω / m to 100000Ω / m, covering the mainstream resistance specifications required for nuclear magnetic resonance coils.

[0019] Furthermore, the outermost side of the conductor wire is extruded with a polytetrafluoroethylene (PTFE) or TPU, PP, TPEE, or nylon insulation layer. The PTFE insulation layer is made of one of FEP, PFA, or ETFE, providing outer insulation protection for the conductor wire.

[0020] This invention provides a method for manufacturing the above-mentioned high-resistivity nuclear magnetic resonance conductor wire, comprising the following steps: S1: Prepare the central skeleton fiber core wire. According to the target resistance and finished wire diameter requirements, select fibers with a fineness in the range of 1000D to 10000D. Single fibers or multiple fibers can be used. S2: Align the conductor wire with at least one insulating spacer in parallel and place them side by side. Wrap them around the outside of the core wire with the same common spiral using a wrapping device. Control the wrapping pitch to be 0.04mm to 0.20mm so that the insulating spacer is located exactly between two adjacent turns of the conductor wire, thereby achieving electrical isolation between adjacent turns of the conductor wire.

[0021] Furthermore, after step S2, step S3 is also included: forming a polytetrafluoroethylene, TPU, PP, TPEE, or nylon insulation layer on the outside of the wrapped wire through an extrusion process to meet the outer insulation requirements of the product.

[0022] Compared with the prior art, the present invention has the following significant advantages: For the wrapping of micro-conductor wires (0.015~0.05mm in diameter), conventional filler sizes are too large (much larger than the conductor wire diameter), making it impossible to accurately embed and synchronously wrap within tiny pitches (0.04mm level). It is generally believed in the industry that achieving physical isolation at this scale would significantly increase the finished wire diameter or lead to wrapping disorder. This invention, by selecting linear spacers with specific fineness (7D~100D), precisely solves the micro-embedding problem at this scale.

[0023] By placing parallel wrapped insulating spacers between adjacent conductor wires, the adjacent conductor wires are always physically and electrically isolated. Even if the wrapping pitch changes within a certain range due to equipment fluctuations, there will be no problem of direct contact and short circuit of the conductor wires, which greatly improves the electrical reliability of the product. The insulating spacers can mechanically limit the wrapping position of the conductor wires, making the distribution of conductor wires on the core wire more uniform and orderly, and significantly improving the consistency of the wrapping pitch. This effectively reduces the fluctuation range of the resistance per meter and improves the product resistance accuracy and batch consistency. The PET film layer on the core wire surface can increase the friction between the conductor wire and the core wire surface, effectively suppressing the axial movement of the conductor wire after wrapping, further ensuring the long-term reliability of pitch stability and electrical performance. Furthermore, because the insulating spacer provides active short-circuit protection and the PET film suppresses conductor wire movement, even if the winding equipment experiences a decrease in precision due to wear and aging, the product can still maintain qualified electrical performance, improving process stability and product yield, and reducing the maintenance costs and precision requirements of production equipment. When using enameled wire with a diameter different from that of the conductor wire as the insulating spacer, a micro-uneven structure will form on the surface of the wire after winding, which can significantly improve the bonding force between the extruded insulation layer and the wire, preventing the outer insulation layer from falling off. By combining conductor wires of different diameters, different types of insulating spacers, and adjusting the winding pitch, the resistance per meter can be flexibly adjusted within the range of 10,000 Ω / m to 100,000 Ω / m, covering various resistance specifications required by nuclear magnetic resonance coils. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the conductor wire cross-sectional structure of Embodiment 1 of the present invention; Figure 2 This is a partially enlarged schematic diagram of the conductor wire wrapping structure in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the conductor wire cross-sectional structure of Embodiment 3 of the present invention; Figure 4 This is a schematic diagram of the conductor wire cross-sectional structure of Embodiment 5 of the present invention; Figure 5 This is a schematic diagram of the manufacturing process of the present invention.

[0025] In the diagram: 1 is the central skeleton fiber core wire, 2 is the conductor wire, 3 is the insulating spacer, 4 is the PET film layer, and 5 is the insulating layer. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0027] The aramid fiber (K-type fiber) described in this application is a high-strength, high-modulus synthetic fiber suitable for winding around a cored wire skeleton; K1000D and K3000D are fineness specifications, with the numbers representing denier (D) values, i.e., the weight in grams of 9000 meters of fiber. The polytetrafluoroethylene (PTFE), commonly known as Teflon, includes commonly used extrusion grades such as FEP, PFA, and ETFE.

[0028] The core concept of this invention is to introduce parallel-wound insulating spacers into the structure of traditional wound conductor wires. These spacers separate adjacent turns of conductor wire, structurally solving the problems of short circuits and resistance fluctuations caused by pitch variations. Simultaneously, the PET film layer can suppress conductor wire movement, further improving structural stability. The technical solution is described in detail below through several embodiments.

[0029] Example 1 like Figure 1 , Figure 2 As shown, the high-resistivity nuclear magnetic resonance conductor wire of this embodiment includes a central skeleton fiber core wire 1, a conductor wire 2, and an insulating spacer 3.

[0030] In this embodiment, the central skeleton fiber core 1 is composed of three K1000D aramid fibers joined together, with a total fineness of 3000D, falling within the range of 1000D to 10000D. The conductor wire 2 is a nickel-chromium alloy wire with a diameter of 0.02mm. The insulating spacer 3 is polyaramid fiber with a fineness of 15D.

[0031] After the conductor wire 2 and the insulating spacer 3 are aligned parallel to each other, they are wrapped together in a spiral manner around the outside of the central skeleton fiber core wire 1, with the wrapping pitch controlled at 0.075mm. After the wrapping is completed, the insulating spacer 3 is located exactly between two adjacent turns of conductor wire 2, completely separating the adjacent turns of conductor wire 2 and maintaining reliable electrical isolation between them.

[0032] Tests showed that the resistance per meter of the conductor wire in this embodiment was 99206Ω / m, and the finished wire diameter was 0.70mm.

[0033] In this embodiment, polyarylate fiber, as an insulating spacer, can effectively separate adjacent turns of nickel-chromium conductor wire. Even if there are slight fluctuations in the wrapping pitch, the conductor wire will not experience contact short circuit. At the same time, the insulating fiber can limit the wrapping position of the conductor wire, making the wrapping pitch more uniform and significantly improving the stability of the resistance value.

[0034] Example 2 The high-resistivity nuclear magnetic resonance conductor wire in this embodiment has a basically the same overall structure as that in Embodiment 1, except that: The central skeleton fiber core wire 1 is made of a single K3000D aramid fiber with a fineness of 3000D; the insulating spacer 3 is made of two polyaramid fibers with a fineness of 15D. The wrapping pitch is controlled at 0.09mm.

[0035] The resistance per meter of the conductor wire in this embodiment was tested to be 79360Ω / m, and the finished wire diameter was 0.65mm.

[0036] This embodiment uses two polyaramid fibers as spacers, which further increases the insulation distance and separation strength between adjacent conductor wires. Even if the wrapping pitch fluctuates significantly, the electrical isolation between adjacent conductor wires can still be reliably guaranteed, and the short-circuit protection capability is stronger. It is suitable for production scenarios where the equipment precision is generally low.

[0037] Example 3 like Figure 3 As shown, the high-resistivity nuclear magnetic resonance conductor wire in this embodiment has a basically the same overall structure as that in Embodiment 1, except that: The central skeleton fiber core wire 1 is made of a single K3000D aramid fiber; the insulating spacer 3 is enameled copper wire with a diameter of 0.026mm and a cured insulating varnish layer on its surface. The wrapping pitch is controlled at 0.072mm.

[0038] Tests showed that the resistance per meter of the conductor wire in this embodiment was 99882Ω / m, and the finished wire diameter was 0.68mm.

[0039] In this embodiment, the insulating varnish layer on the surface of the enameled copper wire has excellent and stable insulation performance, which can reliably separate adjacent turns of conductor wire; at the same time, the diameter of the enameled copper wire is different from that of the conductor wire, and a micro-uneven structure will be formed on the outer surface of the wire after wrapping. When the insulation layer is extruded in the future, the contact area and mechanical interlocking force between the insulation layer and the wire can be increased, which significantly improves the adhesion reliability of the outer insulation layer.

[0040] Example 4 The high-resistivity nuclear magnetic resonance conductor wire in this embodiment has a basically the same overall structure as that in embodiment 3, except that: The central skeleton fiber core 1 is made of nylon N2250D fiber with a fineness of 2250D; the conductor wire 2 is a nickel-chromium alloy wire with a diameter of 0.04mm; and the insulating spacer 3 is an enameled copper wire with a diameter of 0.048mm. The wrapping pitch is controlled at 0.065mm.

[0041] Tests showed that the resistance per meter of the conductor wire in this embodiment was 26892 Ω / m, and the finished wire diameter was 0.65 mm.

[0042] This embodiment achieves a lower resistance value of approximately 27,000 Ω / m by using a conductor wire with a larger diameter and adjusting the wrapping pitch, meeting the application requirements for low resistance specifications; at the same time, the difference in wire diameter between the enameled wire and the conductor wire can also improve the adhesion of the subsequent insulation layer.

[0043] Example 5 like Figure 4 As shown, the high-resistivity nuclear magnetic resonance conductor wire in this embodiment has a basically the same overall structure as that in Embodiment 3, except that: The central skeleton fiber core 1 is made of nylon N2250D fiber, and the outer surface of the core is pre-wrapped with a PET film layer 4. The conductor wire 2 and the insulating spacer 3 are wrapped around the outside of the PET film layer 4. The conductor wire 2 is a copper-nickel alloy wire with a diameter of 0.02mm, and the insulating spacer 3 is an enameled copper wire with a diameter of 0.026mm. The wrapping pitch is controlled at 0.07mm.

[0044] Tests showed that the resistance per meter of the conductor wire in this embodiment was 98690Ω / m, and the finished wire diameter was 0.66mm.

[0045] In this embodiment, the PET film layer 4 can further improve the insulation performance of the core wire surface on the one hand, and increase the friction between the conductor wire and the core wire surface on the other hand, effectively suppressing the axial movement of the conductor wire during the wrapping process and subsequent use, making the wrapping structure more stable, and further ensuring the long-term stability of the resistance value.

[0046] Example 6 The high-resistivity nuclear magnetic resonance conductor wire in this embodiment has a basically the same overall structure as that in Embodiment 1, except that: The central skeleton fiber core wire 1 is made of a single K1500D polyarylate fiber with a fineness of 1500D; the conductor wire 2 is a nickel-chromium alloy wire with a diameter of 0.015mm; and the insulating spacer 3 is a polyarylate fiber with a fineness of 7D. The wrapping pitch is controlled at 0.04mm.

[0047] Tests showed that the resistance per meter of the conductor wire in this embodiment was 99850Ω / m, and the finished wire diameter was 0.58mm.

[0048] This embodiment covers the lower limits of core wire fineness, conductor wire diameter, and wrapping pitch, verifying the feasibility and structural reliability of the high resistance range endpoints.

[0049] Example 7 The high-resistivity nuclear magnetic resonance conductor wire in this embodiment has a basically the same overall structure as that in Embodiment 1, except that: The central skeleton fiber core wire 1 is made of a single K10000D aramid fiber with a fineness of 10000D; the conductor wire 2 is a nickel-chromium alloy wire with a diameter of 0.050mm; and the insulating spacer 3 is an aramid fiber with a fineness of 100D. The wrapping pitch is controlled at 0.20mm.

[0050] Tests showed that the resistance per meter of the conductor wire in this embodiment was 25180Ω / m, and the finished wire diameter was 0.75mm.

[0051] This embodiment covers the upper limits of core wire fineness, conductor wire diameter, insulation fiber fineness, and wrapping pitch, verifying the feasibility and structural reliability of the low resistance range endpoints.

[0052] Manufacturing method examples like Figure 5 As shown, the method for manufacturing high-resistivity nuclear magnetic resonance conductor wires according to the present invention specifically includes the following steps: S1: Prepare the central skeleton fiber core wire. According to the target resistance and finished wire diameter requirements, select fibers with a fineness in the range of 1000D to 10000D. Aramid fibers or polyarylate fibers can be used. Single fibers or multiple fibers can be selected as needed. A layer of PET film is uniformly wrapped around the surface of the core wire to form a PET film layer. During the wrapping process, the tension of the film is controlled to be uniform to avoid wrinkling. The PET film is wrapped around the outer surface of the core wire using a threaded wrapping method, and adjacent wrapped PET films are fixed by thermal bonding to control the overlap rate of the wrapping.

[0053] S2: Align the conductor wire with at least one insulating spacer in parallel, and spirally wrap them together around the outer periphery of the core wire (PET film layer) using a wrapping device (the spiral direction of the conductor wire is the same as that of the PET film layer when wrapping). Control the wrapping pitch within the range of 0.04mm to 0.20mm to ensure that the insulating spacer is located exactly between two adjacent turns of conductor wire, so as to achieve reliable electrical isolation between adjacent turns of conductor wire. In practice, the conductor wire and the insulating spacer can be aligned parallel to each other and fed into the same guide hole of the winding machine with their respective appropriate wrapping tension. By controlling the wire feeding angle, the two are spirally wrapped side by side on the surface of the core wire. During the wrapping process, the insulating spacer is naturally embedded between the two adjacent turns of conductor wire.

[0054] S3: According to the outer insulation requirements of the product, polytetrafluoroethylene, TPU, PP, TPEE, or nylon insulation layer is formed on the outside of the wrapped wire through extrusion process. The material can be selected from FEP, PFA or ETFE according to the usage requirements.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-resistance nuclear magnetic resonance conductor wire comprising a central skeleton fiber core wire and a conductor wire spirally wrapped around the outer periphery of the core wire, characterized by: It also includes at least one linear insulating spacer, which is arranged side by side with the conductor wire and synchronously spirally wound around the outer periphery of the core wire with the same direction of rotation and the same pitch, and the insulating spacer is located between two adjacent turns of the conductor wire so that the conductor wires of adjacent turns are electrically isolated; The surface of the core wire is provided with a PET film layer that can suppress the axial movement of the conductor wire.

2. The high-resistivity nuclear magnetic resonance conductor wire according to claim 1, characterized in that: The fineness of the central skeleton fiber core is 1000D to 10000D, and the core is selected from aramid fiber or polyaramid fiber.

3. The high-resistivity nuclear magnetic resonance conductor wire according to claim 1, characterized in that: The insulating spacer is an insulating fiber with a fineness of 7D to 100D, and the insulating fiber is selected from at least one of aramid fiber, polyaramid fiber, nylon fiber or polyester fiber.

4. The high-resistivity nuclear magnetic resonance conductor wire according to claim 1, characterized in that: The insulating spacer is enameled wire.

5. The high-resistivity nuclear magnetic resonance conductor wire according to claim 4, characterized in that: The diameter of the enameled wire is larger than the diameter of the conductor wire.

6. The high-resistivity nuclear magnetic resonance conductor wire according to claim 1, characterized in that: The conductor wire is a nickel-chromium alloy wire or a copper-nickel alloy wire, and the diameter of the conductor wire is 0.015 mm to 0.050 mm.

7. The high-resistivity nuclear magnetic resonance conductor wire according to claim 1, characterized in that: The winding pitch of the conductor wire is 0.04mm to 0.20mm, and the meter resistance of the conductor wire is 10000Ω / m to 100000Ω / m.

8. The high-resistivity nuclear magnetic resonance conductor wire according to claim 1, characterized in that: The outermost layer of the conductor wire is extruded with a polytetrafluoroethylene (PTFE), TPU, PP, TPEE, or nylon insulation layer, wherein the PTFE insulation layer is made of one of FEP, PFA, or ETFE.

9. A method for manufacturing a high-resistivity nuclear magnetic resonance conductor wire as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1: Prepare a central skeleton fiber core, wherein the fineness of the core is 1000D to 10000D; S2: Wrap a PET film around the outer surface of the core wire; then, align the conductor wire and at least one insulating spacer in parallel, and spirally wrap them together side by side with the same direction of rotation and the same pitch around the outer circumference of the core wire, controlling the wrapping pitch to be 0.04mm to 0.20mm, so that the insulating spacer is located between two adjacent turns of the conductor wire; wherein, the conductor wire and the insulating spacer are fed into the same wrapping guide hole with their respective appropriate tensions; S3: A polytetrafluoroethylene, TPU, PP, TPEE, or nylon insulation layer is extruded onto the outside of the wrapped wire.

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