Preparation method of bending-resistant sensor cable for high-speed motor train unit

Abstract

The invention relates to the technical field of rail transit cables, in particular to a preparation method of a bending-resistant sensor cable for a high-speed motor train unit. The preparation method comprises the steps of conductor three-layer twisting and annealing, insulating layer gradient extrusion and plasma treatment, filling, twice wrapping, double-layer shielding, double-layer sheath co-extrusion and irradiation crosslinking post-treatment. The structure of the bending-resistant sensor cable sequentially comprises a high-elasticity fiber rope filler, a copper alloy conductor with a TPEE insulating layer, a thin flame-retardant cloth wrapping layer, an elastic silica gel inner shielding layer, a tinned copper wire and fiber filament outer shielding layer, a thin non-woven fabric wrapping layer and a cross-linked polyurethane double-layer sheath from inside to outside. The bending resistance of the cable exceeds 500,000 times, the cable works stably at the temperature of-50 DEG C to 125 DEG C, the service life is prolonged by 2-3 times, and the cable is suitable for the harsh environment of the high-speed motor train unit.

Description

Technical Field

[0001] This invention relates to the field of rail transit cable technology, and in particular to a method for preparing a bend-resistant sensor cable for high-speed trains. Background Technology

[0002] High-speed trains operate in complex environments, and sensor cables must withstand frequent bending, vibration, high and low temperature cycles, and electromagnetic interference. In existing technologies, sensor cables often suffer from conductor breakage or insulation cracking due to insufficient bending resistance, affecting train operation safety. Therefore, developing a method for manufacturing sensor cables with ultra-high bending resistance, interference resistance, and environmental adaptability is of great significance. Summary of the Invention

[0003] To address the shortcomings of existing high-speed train sensor cables, which are prone to conductor breakage, insulation cracking, shielding performance degradation, and sheath wear under frequent bending, complex electromagnetic environments, and high and low temperature cycling conditions, resulting in short service life and insufficient safety and reliability, this invention aims to provide a method for manufacturing a bend-resistant sensor cable for high-speed trains. This method significantly improves the cable's bend resistance, anti-interference ability, environmental adaptability, and structural stability, meeting the stringent requirements of high-speed trains for sensor cables, ensuring train operation safety, and extending maintenance cycles.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A method for manufacturing a bend-resistant sensor cable for high-speed trains includes the following steps:

[0006] (1) Preparation of conductor layer: 90 to 110 tin-plated copper alloy monofilaments with a diameter d = 0.06-0.08 mm are concentrically stranded in three layers. The tin-plated copper alloy monofilaments are selected to combine the excellent conductivity of copper with the high mechanical strength of the alloy. The tin plating layer can effectively isolate air and moisture and avoid oxidation and corrosion of copper wire. The inner layer monofilaments are stranded in the forward direction with an inclination angle of α1 = 20°-25°, the middle layer monofilaments are stranded in the forward direction with an inclination angle of α2 = 25°-30°, and the outer layer monofilaments are stranded in the reverse direction with an inclination angle of α3 = 35°-45°. The forward stranding of the inner and middle layers can improve the structural compactness of the conductor layer and reduce the gaps between monofilaments. The reverse stranding of the outer layer can offset the torque stress generated by the stranding of the inner and middle layers and prevent the conductor from deforming or breaking due to torque concentration when the cable is bent. After annealing, a conductor layer with an elongation at break δ ≥ 25% is obtained; copper alloy monofilaments undergo lattice distortion due to mechanical extrusion during stranding, leading to increased material brittleness. Annealing can restore the ordered arrangement of the lattice, improving the material's plasticity.

[0007] (2) Insulation treatment: A modified heat-resistant elastomer is extruded over the conductor layer obtained in step (1) to form an insulation layer with a thickness of t = 0.35-0.55 mm;

[0008] (3) Filling: The conductors with insulation are arranged in a ring and filled with high-elasticity fiber rope in the middle; the high elasticity of the fiber rope can absorb the impact energy when the cable is bent or vibrated, buffer the compressive stress on the conductor and insulation, and prevent the insulation from being damaged by hard collision.

[0009] (4) First wrapping treatment: Wrap a thin flame-retardant cloth around the surface of the filled cable semi-finished product; improve the overall flame retardant level of the cable to meet the fire safety requirements of the EMU; isolate impurities and moisture and protect the internal structure;

[0010] (5) Shielding treatment: An inner shield and an outer shield are sequentially installed on the outside of the thin flame-retardant cloth wrapping.

[0011] (6) Second wrapping treatment: Use thin non-woven fabric to wrap the cable again; solve the problem of isolation protection and adhesion between the shielding layer and the sheath layer, which is different from the flame retardant function of the first wrapping.

[0012] (7) Preparation of reinforced sheath layer: A double sheath layer is formed on the surface of the cable after the second wrapping using a double-layer co-extrusion process;

[0013] (8) Post-processing: The cable is subjected to irradiation cross-linking treatment and then naturally cooled to obtain the finished cable.

[0014] Further: In step (1), the stranding pitch P satisfies P=K×D, where K is the pitch multiple coefficient, with a value of 10-12; and D is the outer diameter of the conductor layer.

[0015] Further: The modified heat-resistant elastomer mentioned in step (2) is a blend of TPEE and ω1 = 1-3wt% nano boron nitride, where ω1 is the amount of nano boron nitride added. TPEE itself has excellent heat resistance, elasticity, and wear resistance, while the addition of nano boron nitride can further improve the thermal conductivity and breakdown strength of the insulation layer; a gradient extrusion process is adopted, and the extrusion temperature from the feed section to the die head section meets the following requirements: T e (x) = 180 + 50 × (x / L), where T e (x) represents the extrusion temperature at this location, x is the distance from the starting point of the feed section, and L is the total screw length. The design logic of the gradient extrusion process is as follows: the temperature of 180℃ in the feed section (x=0) can prevent TPEE particles from melting and agglomerating too early, ensuring smooth feeding; from the feed section to the die head section (x=L), the temperature gradually increases to 230℃ (180+50×1), which allows the blend of TPEE and nano boron nitride to gradually and fully melt and mix evenly, avoiding material degradation or uneven mixing due to sudden temperature rise, and ultimately ensuring uniform insulation layer thickness and no air bubbles or impurities.

[0016] Furthermore: In step (2), the outer surface of the insulating layer is plasma treated to form an interface layer with a roughness Ra = 0.8-1.2 μm, which improves the interlayer bonding force and adapts to the structural stability under high-frequency bending scenarios.

[0017] Furthermore, the inner shielding layer mentioned in step (5) is a vinyltriethoxysilane-modified elastic silicone layer with a thickness s1 = 0.15-0.25 mm. Elastic silicone itself possesses excellent elasticity, temperature resistance, and insulation. After modification with vinyltriethoxysilane, the silane groups can form a cross-linked structure with the silicone molecular chain, improving the mechanical strength and aging resistance of the silicone, while also enhancing its adhesion to the outer shielding layer. It effectively absorbs low-frequency electromagnetic interference, improving signal transmission accuracy; adapts to cable bending requirements, preventing shielding layer cracking; and withstands high and low temperatures to cope with the extreme working environment of high-speed trains.

[0018] Further: The outer shielding layer mentioned in step (5) is a mixed woven mesh of tin-plated copper alloy wire with a diameter d = 0.15-0.20 mm and 1600 Dtex para-aramid fiber. The mixed woven structure has both high shielding effectiveness and high flexibility. After flattening a single tin-plated copper alloy wire, multiple flattened tin-plated copper alloy wires are spirally wound around a para-aramid fiber filament, with a weaving coverage C. v ≥90%, shielding high-frequency interference to avoid braking and traction control errors caused by interference.

[0019] Further: The inner sheath described in step (7) is a cross-linked polyurethane doped with ω3 = 3-5wt% multi-walled carbon nanotubes. The cross-linked polyurethane itself has high elasticity, wear resistance and oil resistance. The conductivity of carbon nanotubes can reduce the surface resistance of the sheath and avoid static electricity caused by friction. ω3 is the amount of carbon nanotubes added.

[0020] Furthermore: the outer sheath described in step (7) is a cross-linked polyurethane with ω4 = 30-40wt% nano aluminum hydroxide and ω5 = 4-6wt% amino silicone oil modifier added; nano aluminum hydroxide is the core flame retardant, which decomposes and absorbs heat and releases water vapor at high temperature, while forming an Al2O3 ceramic protective layer to block oxygen from contacting combustibles, achieving a dual flame retardant effect of "heat absorption and cooling + physical barrier"; the amino silicone oil modifier can improve the weather resistance and lubricity of the sheath.

[0021] Furthermore: In step (7), the surface of the outer sheath is formed with a diameter of [missing information] through a micro-injection molding process. A hemispherical micro-protrusion array with a micro-protrusion density ρ = 50-80 pieces / mm 2This ensures that the surface friction coefficient μ ≤ 0.3. The principle is to reduce the actual contact area: when the cable contacts the external support or pipeline, only the tip of the micro-protrusion is subjected to force, and the actual contact area is only 10-20% of that of the smooth surface. Reducing the contact area can significantly reduce sliding friction.

[0022] Further: In step (8), the irradiation crosslinking treatment involves placing the cable in a traction beam-down device with an electron energy of 2.4 to 2.6 MeV and performing γ-electron beam irradiation crosslinking with a beam current / line speed of 10 / 12. After crosslinking, the cable is left to stand for 16 hours and its thermal elongation is tested, and the elongation is controlled within the range of 30-50%.

[0023] Furthermore, the structure of the bending-resistant sensor cable, from the inside out, consists of: high-elasticity fiber rope filling, copper alloy conductor with TPEE insulation layer, thin flame-retardant cloth wrapping, elastic silicone inner shielding layer, tinned copper wire + fiber outer shielding layer, thin non-woven cloth wrapping, and cross-linked polyurethane double sheath.

[0024] The present invention has the following beneficial effects:

[0025] This invention significantly improves the conductor's flexibility and elongation at break through a three-layer gradient stranded tin-plated copper alloy conductor design combined with annealing treatment. The use of nano-boron nitride modified insulation and plasma surface treatment enhances the insulation's heat resistance and interfacial bonding. The double-layer structure of the composite shielding layer (modified silicone + hybrid braided mesh) achieves dual reinforcement of electromagnetic shielding and mechanical protection, increasing the braided coverage to over 90%. The reinforced sheath layer, through a carbon nanotube-reinforced inner layer, a composite flame-retardant outer layer, and surface micro-protrusions, simultaneously optimizes mechanical properties, flame retardancy, and wear resistance, reducing the coefficient of friction to below 0.3. Irradiation cross-linking treatment further enhances the stability of the material's molecular structure, ultimately enabling the cable to withstand over 500,000 bends and maintain stable performance in environments ranging from -50℃ to 125℃. Its service life is 2-3 times longer than existing technologies, significantly reducing maintenance costs and improving the safety redundancy of train operation. Attached Figure Description

[0026] Figure 1 This is a cable structure diagram of a method for preparing a bend-resistant sensor cable for high-speed trains proposed in this invention. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] A method for manufacturing a bend-resistant sensor cable for high-speed trains includes the following steps:

[0029] 1. Preparation of conductor layer

[0030] Material selection: 100 tin-plated copper alloy monofilaments with a diameter d = 0.07 mm (containing 99.5% copper, 0.3% tin and 0.2% silver) were selected. The tin plating layer thickness was 5 μm, which has both conductivity and corrosion resistance.

[0031] Stranding process: A three-layer concentric stranding machine is used. The inner layer of 50 monofilaments is stranded in the forward direction at an angle of α1 = 22°, the middle layer of 30 monofilaments is stranded in the forward direction at an angle of α2 = 28°, and the outer layer of 20 monofilaments is stranded in the reverse direction at an angle of α3 = 40°. Based on the outer diameter D of the conductor layer (calculated as D = 0.8 mm), the stranding pitch is set to 8.8 mm according to the pitch formula P = K × D (K = 11) to ensure a tight structure and to counteract torque.

[0032] Annealing treatment: The stranded conductor was placed in a continuous annealing furnace and held at 380℃ for 1.5h. After cooling to room temperature in the furnace, the elongation at break was measured to be δ=28%, the lattice distortion was completely restored, and the plasticity met the bending requirements.

[0033] 2. Insulation treatment

[0034] Material preparation: TPEE was mixed with 2wt% nano boron nitride (particle size 50nm) and granulated by twin-screw extruder to obtain modified heat-resistant elastomer particles.

[0035] Gradient extrusion: A Φ65mm single-screw extruder (total screw length L=2000mm) is used, according to the gradient temperature formula T. e (x) = 180 + 50 × (x / L) Set temperature: Feed section (x = 0) 180℃, Compression section (x = 800mm) 200℃, Homogenization section (x = 1500mm) 220℃, Die head section (x = 2000mm) 230℃; The conductor layer is pulled through the extruder and extruded to form an insulation layer with a thickness of t = 0.45mm. The extrusion speed is 2m / min, ensuring that the insulation layer is free of bubbles and the thickness deviation is ≤ ±0.02mm.

[0036] Plasma treatment: Atmospheric pressure plasma treatment machine (power 500W, argon flow rate 15L / min) is used to treat the outer surface of the insulating layer for 30s to form an interface layer with roughness Ra=1.0μm, which improves the adhesion of subsequent interlayers.

[0037] 3. Fill

[0038] Six insulated conductors are arranged in a regular hexagonal ring (center spacing 1.2mm). A high-elastic polyester fiber rope (diameter 1.0mm) is used to fill the center gaps using a wire feeding machine. The filling tension is controlled at 5N to ensure tight filling without compressing the conductors.

[0039] 4. First wrapping process

[0040] A dual-station wrapping machine is used to wrap a thin flame-retardant cloth (made of glass fiber coated with flame-retardant silicone, 0.1mm thick) with an overlap of 50% onto the surface of the filled semi-finished product. The wrapping tension is 8N and the rotation speed is 300r / min to form a flame-retardant isolation layer.

[0041] 5. Shielding treatment

[0042] Inner shield preparation: Vinyltriethoxysilane modified elastic silicone (modifier addition amount 5wt%) is extruded onto the surface of flame retardant cloth through an extruder to form an inner shield layer with a thickness of s1 = 0.2 mm. The extrusion temperature is 160℃. After cooling, the silicone hardness is Shore A50, which has high elasticity and temperature resistance.

[0043] Outer layer shielding preparation: (1) Flatten tin-plated copper alloy wire with a diameter d = 0.18 mm through a rolling mill (thickness 0.08 mm); (2) Using 1600 Dtex para-aramid fiber as the core, spirally wind 3 flat copper wires (pitch 5 mm); (3) Use a braiding machine to braid the above composite wire onto the inner layer shielding surface, with a braiding angle of 30° and a coverage rate of C. v =92%, forming an outer shield that balances shielding and flexibility.

[0044] 6. Second wrapping treatment

[0045] A single-station wrapping machine is used to wrap a thin non-woven fabric (polypropylene, 0.05mm thick) with an overlap of 40% onto the outer shielding surface with a wrapping tension of 3N. This is used to isolate the shielding layer from the sheath layer and improve adhesion.

[0046] 7. Preparation of reinforced sheath layer

[0047] A double-layer co-extrusion machine (inner layer Φ45mm, outer layer Φ65mm) is used to achieve simultaneous forming of the inner and outer sheaths:

[0048] Inner sheath: Cross-linked polyurethane (model TPU345X) is mixed with 4wt% multi-walled carbon nanotubes (diameter 20nm) and granulated, extruded at 190℃, with an extrusion thickness of 1.8mm.

[0049] Outer sheath: Cross-linked polyurethane is mixed with 35wt% nano-aluminum hydroxide (particle size 100nm) and 6wt% amino silicone oil and granulated. The extrusion temperature is 200℃, and the extrusion thickness is 2.2mm. The outer sheath is formed on the outer surface of the sheath through a micro-injection mold at the die head. A hemispherical micro-protrusion array with a micro-protrusion density ρ = 65 pieces / mm 2 After cooling, the surface friction coefficient μ was measured to be 0.28.

[0050] 8. Post-processing

[0051] The cable is placed in a traction-type beam-down device with an electron energy of 2.4–2.6 MeV and subjected to γ-electron beam irradiation crosslinking at a beam current / line velocity of 10 / 12 to achieve deep crosslinking of each layer of material; then it is naturally cooled to room temperature to obtain the finished cable.

[0052] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for manufacturing a bend-resistant sensor cable for high-speed trains, characterized in that, Includes the following steps: (1) Preparation of conductor layer: 90 to 110 tin-plated copper alloy monofilaments with a diameter d = 0.06-0.08 mm are concentrically stranded in three layers. The inner layer monofilaments are stranded in the forward direction with an inclination angle of α1 = 20°-25°, the middle layer monofilaments are stranded in the forward direction with an inclination angle of α2 = 25°-30°, and the outer layer monofilaments are stranded in the reverse direction with an inclination angle of α3 = 35°-45°. After annealing, a conductor layer with an elongation at break δ ≥ 25% is obtained. (2) Insulation treatment: A modified heat-resistant elastomer is extruded over the conductor layer obtained in step (1) to form an insulation layer with a thickness of t = 0.35-0.55 mm; (3) Filling: Arrange the conductors with insulation layer in a ring and fill the middle with high elastic fiber rope; (4) First wrapping treatment: Wrap a thin flame-retardant cloth around the surface of the filled cable semi-finished product; (5) Shielding treatment: An inner shield and an outer shield are sequentially installed on the outside of the thin flame-retardant cloth wrapping. (6) Second wrapping treatment: Use thin non-woven fabric to wrap the cable again; (7) Preparation of reinforced sheath layer: A double sheath layer is formed on the surface of the cable after the second wrapping using a double-layer co-extrusion process; (8) Post-processing: The cable is subjected to irradiation cross-linking treatment and then naturally cooled to obtain the finished cable.

2. The method for preparing a bend-resistant sensor cable for high-speed trains according to claim 1, characterized in that: In step (1), the stranding pitch P satisfies P=K×D, where K is the pitch multiple coefficient, with a value of 10-12; and D is the outer diameter of the conductor layer.

3. The method for preparing a bend-resistant sensor cable for high-speed trains according to claim 1, characterized in that: The modified heat-resistant elastomer mentioned in step (2) is a blend of TPEE and ω1 = 1-3 wt% nano boron nitride, where ω1 is the amount of nano boron nitride added. A gradient extrusion process is adopted, and the extrusion temperature from the feed section to the die head section meets the following condition: T e (x) = 180 + 50 × (x / L), where T e (x) represents the extrusion temperature at that location, x represents the distance from the starting point of the feed section, and L represents the total length of the screw.

4. The method for preparing a bend-resistant sensor cable for high-speed trains according to claim 1, characterized in that: In step (2), the outer surface of the insulating layer is plasma treated to form an interface layer with a roughness Ra = 0.8-1.2 μm.

5. The method for preparing a bend-resistant sensor cable for high-speed trains according to claim 1, characterized in that: The inner shielding layer mentioned in step (5) is a vinyltriethoxysilane modified elastic silicone layer with a thickness of s1 = 0.15-0.25 mm.

6. The method for preparing a bend-resistant sensor cable for high-speed trains according to claim 1, characterized in that: The outer shielding layer mentioned in step (5) is a mixed woven mesh of tin-plated copper alloy wire with a diameter d = 0.15-0.20 mm and para-aramid fiber with a diameter of 1500-1700 Dtex. After flattening a single tin-plated copper alloy wire, multiple flattened tin-plated copper alloy wires are spirally wound around a para-aramid fiber filament, with a weaving coverage C. v ≥90%.

7. The method for preparing a bend-resistant sensor cable for high-speed trains according to claim 1, characterized in that: The inner sheath mentioned in step (7) is a cross-linked polyurethane doped with ω3 = 3-5 wt% multi-walled carbon nanotubes, where ω3 is the amount of carbon nanotubes added.

8. The method for preparing a bend-resistant sensor cable for high-speed trains according to claim 1, characterized in that: The outer sheath mentioned in step (7) is a cross-linked polyurethane with added ω4 = 30-40 wt% nano aluminum hydroxide and ω5 = 4-6 wt% amino silicone oil modifier; In step (7), the outer sheath surface is formed with a diameter of [missing information] through a micro-injection molding process. A hemispherical micro-protrusion array with a micro-protrusion density ρ = 50-80 pieces / mm 2 This ensures that the surface friction coefficient μ ≤ 0.

3.

9. The method for preparing a bend-resistant sensor cable for high-speed trains according to claim 1, characterized in that: In step (8), the irradiation crosslinking treatment involves placing the cable in a traction beam-down device with an electron energy of 2.4 to 2.6 MeV and performing γ-electron beam irradiation crosslinking with a beam current / line speed of 10 / 12. After crosslinking, the cable is left to stand for 16 hours and its thermal elongation is tested, and the elongation is controlled within the range of 30-50%.

10. A method for preparing a bend-resistant sensor cable for high-speed trains according to claim 1, characterized in that: The structure of the bending-resistant sensor cable, from the inside out, consists of: high-elasticity fiber rope filling, copper alloy conductor with TPEE insulation layer, thin flame-retardant cloth wrapping, elastic silicone inner shielding layer, tinned copper wire + fiber outer shielding layer, thin non-woven cloth wrapping, and cross-linked polyurethane double sheath.

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