Cable for a power-assisted bicycle

Abstract

The application discloses a kind of electric cables for power-assisted bicycles, belongs to cable technical field, and its technical scheme main points are a kind of electric cables for power-assisted bicycles, the cable includes conductor structure layer, insulating layer, self-repairing layer and shielding layer from inside to outside in sequence, the conductor structure layer includes by silver-plated copper wire helical stranding into inner layer and outer layer that is reversely wound on inner layer at 45 ° angle composition, the helical pitch of silver-plated copper wire is 6-10mm, the outer layer of the conductor structure layer adopts the shape memory alloy wire with diameter of 0.1mm;The insulating layer material is composed of polyurethane and silicone rubber, and the two ends of the conductor structure in the length direction are covered with silicone rubber, and the middle section of the conductor structure is covered with polyurethane.By winding shape memory alloy outside silver-plated copper wire and using different materials as insulating layer, the bending stress of the conductor structure can be effectively dispersed, and the fatigue life of the cable is improved.

Description

Technical Field

[0001] This invention relates to the field of cable technology, and in particular to a cable for power-assisted bicycles. Background Technology

[0002] Electric bicycles, a type of two-wheeled transportation powered by batteries and equipped with motors and torque sensors, have experienced rapid development in recent years. They automatically adjust motor assistance by triggering sensor signals through human pedaling, achieving collaborative work between human and motor power. This has greatly facilitated people's travel and has been widely used in urban commuting and leisure activities, promoting the further popularization of green travel concepts. It has also spurred the development of related industries, such as battery technology and motor manufacturing, which have seen continuous innovation and progress due to the development of electric bicycles.

[0003] Cable routing is a crucial aspect of the design and manufacturing process of electric bicycles. Currently, the conventional solutions for routing bicycle cables in confined spaces include using a single-layer stranded conductor, a uniformly thick insulation layer, and a general shielding layer. The single-layer stranded conductor, due to its structural characteristics, possesses a degree of flexibility, allowing it to adapt to cable bending to some extent; the uniformly thick insulation layer provides basic insulation protection for the conductor; and the general shielding layer provides some shielding for internal signals within the cable, preventing external interference.

[0004] However, these existing technologies have significant drawbacks. Single-layer stranded conductors are prone to breakage under frequent bending, which greatly reduces the cable's lifespan; the uniform thickness of the insulation layer cannot effectively distribute bending stress, resulting in uneven stress on the conductor and making it susceptible to localized damage; ordinary shielding layers are prone to cracking during bending, leading to a decrease in shielding effectiveness and consequently affecting the stability of signal transmission. These problems result in insufficient flexibility and poor fatigue resistance in existing cables, making it difficult to meet the performance requirements of high-end bicycles. Summary of the Invention

[0005] To address the problems in the prior art, this invention provides a power-assisted bicycle cable that effectively disperses the bending stress of the conductor structure and improves the cable's fatigue life by winding a shape memory alloy around silver-plated copper wire and using different materials as the insulation layer.

[0006] The present invention provides a power-assist bicycle cable, which adopts the following technical solution:

[0007] A power-assist bicycle cable, comprising, from the inside out, a conductor structure layer, an insulation layer, a self-healing layer, and a shielding layer. The conductor structure layer consists of an inner layer of silver-plated copper wire spirally twisted together and an outer layer wound in opposite directions at a 45° angle onto the inner layer. The spiral pitch of the silver-plated copper wire is 6-10 mm. The outer layer of the conductor structure layer uses shape memory alloy wire with a diameter of 0.1 mm. The insulation layer material is composed of polyurethane and silicone rubber, with silicone rubber covering both ends of the conductor structure along its length and polyurethane covering the middle section of the conductor structure.

[0008] By adopting the above technical solution, the conductor structure layer consists of an inner layer of silver-plated copper wire spirally twisted together and an outer layer wound in the opposite direction at a 45° angle on the inner layer. The specific spiral pitch of the silver-plated copper wire can enhance the flexibility and fatigue resistance of the conductor structure, reducing the risk of breakage during frequent bending. The outer layer of the conductor structure layer uses shape memory alloy wire with a diameter of 0.1mm. Shape memory alloy wire has shape memory characteristics, which can restore the initial shape during frequent bending of the power bicycle cable, effectively avoiding the breakage problem caused by frequent bending and improving the fatigue resistance of the cable. At the same time, the superelasticity of the shape memory alloy wire can maintain elastic recovery ability under large strain, making the cable easier to install when wiring in a confined space, and reducing mechanical fatigue and signal attenuation during bending, ensuring the stability of signal transmission. The insulation layer uses segmented coatings of polyurethane and silicone rubber. Silicone rubber covers both ends of the conductor structure along its length, while polyurethane covers the middle section. Because the ends have a greater bending curvature and require greater deformation, the highly elastic silicone rubber effectively buffers the bending stress at the ends. The middle section has a relatively smaller bending curvature but requires wear resistance; therefore, polyurethane, with its certain rigidity and toughness, is used to disperse the bending stress in the middle section. The combination of these two materials effectively disperses the bending stress throughout the entire conductor structure, preventing uneven stress on the conductor and improving the cable's fatigue resistance and signal transmission stability. The self-healing layer can repair damaged areas of the cable, further improving its service life and stability.

[0009] Preferably, in the insulating layer, the thickness of the silicone rubber segment is 30-35 μm, and the thickness of the polyurethane segment is 45-55 μm.

[0010] Preferably, the slurry used in the self-healing layer comprises the following raw materials in parts by weight: 100 parts of polyurethane-polysiloxane copolymer, 5-15 parts of chain extender containing dynamic disulfide bonds, 3-10 parts of dimer containing quadruple hydrogen bonds, 2-5 parts of nano-silica, 0.15-0.25 parts of silane coupling agent, 0.3-0.5 parts of catalyst, and 230-250 parts of organic solvent.

[0011] Preferably, the chain extender containing dynamic disulfide bonds is one of 4,4′-diaminodiphenyl disulfide and 4,4′-dihydroxydiphenyl disulfide.

[0012] Preferably, the catalyst is tributylphosphine.

[0013] By employing the above technical solution, polyurethane-polysiloxane copolymer, as the matrix, can simultaneously generate good interfacial affinity and repair effects on both silicone rubber and polyurethane segments. By introducing dynamic disulfide bonds and quadruple hydrogen bonds into the copolymer network, under the stimulation of bending friction heat and the action of a catalyst, the dynamic disulfide bonds can undergo exchange reactions. This exchange reaction allows the molecular chains to recombine, thus providing molecular-level driving force for self-repair. At around 35℃, the dimer containing quadruple hydrogen bonds further promotes molecular chain movement and recombination through the breaking and recombination of hydrogen bonds, repairing more than 80% of microcracks within 24 hours, enhancing self-repair capability, and extending cable life. Nano-silica, modified with a silane coupling agent, is uniformly dispersed in the system, acting as a reinforcement and providing an obstacle to crack propagation paths. It can also form an interaction network with other components, contributing to improved cable fatigue resistance.

[0014] Preferably, the slurry used in the self-healing layer is obtained by the following preparation method:

[0015] S1. Disperse nano-silica in a mixed solution of ethanol and water, add silane coupling agent, stir and react at 60-70℃ for 2-3 hours, then centrifuge and dry to obtain modified nano-silica.

[0016] S2. Add the polyurethane-polysiloxane copolymer, the chain extender containing dynamic disulfide bonds, and the dimer containing four hydrogen bonds to an organic solvent, and stir at 60-80℃ for 2-3 hours under nitrogen protection to obtain a copolymer solution.

[0017] S3. Add modified nano-silica and catalyst to the copolymer solution, and stir at high speed to disperse evenly to obtain the repair layer slurry.

[0018] Preferably, the shielding layer is woven from aluminum foil and polyester fibers using a twill weave method, with the polyester fiber weave tension being 15-20 cN and the aluminum foil weave tension being 8-12 cN, and the weave angle being 30-45° radial to cable axis; the polyester fiber spacing is 0.5 mm, and the aluminum foil thickness is 0.02 mm.

[0019] Preferably, the aluminum foil is obtained by the following pretreatment method before weaving: the aluminum foil is subjected to plasma treatment for 3-5 minutes, then immersed in a silane coupling agent solution, reacted at 60-65°C for 30 minutes, and then taken out and dried.

[0020] Preferably, the shielding layer is obtained using the following preparation method:

[0021] (1) Coat the aluminum foil surface with adhesive evenly, with a wet coating thickness of 10-15 μm, and then dry it with hot air at 80-100℃ for 2-3 min;

[0022] (2) Cut the coated aluminum foil into aluminum foil strips and weave them with the coated side facing the polyester fiber side;

[0023] (3) After weaving, cure at 110-120℃ and 0.3-0.5MPa for 5-10 minutes.

[0024] More preferably, the adhesive is a conductive polyurethane adhesive.

[0025] By adopting the above technical solution, plasma surface treatment of aluminum foil can enhance the surface roughness and activity of aluminum foil. Treatment with silane coupling agent can enhance the bonding strength between aluminum foil and adhesive. Weaving aluminum foil and polyester fiber with a twill weave structure makes the shielding layer more flexible and less prone to breakage when repeatedly bent. At the same time, the adhesive can firmly bond the fiber and aluminum foil, preventing cracking.

[0026] In summary, the present invention has the following beneficial effects:

[0027] 1. The conductor structure layer adopts an inner layer of silver-plated copper wire spirally twisted and an outer layer of reverse winding at a 45° angle. The pitch of the silver-plated copper wire spiral is 6-10mm, which improves the flexibility of the cable and reduces the bending resistance by 40% compared with existing cables, making installation more convenient. At the same time, it achieves a bending life of more than 7,000 bends at a bending radius of 3 times the diameter, which significantly improves the fatigue resistance and avoids breakage under frequent bending.

[0028] 2. The insulation layer is composed of polyurethane and silicone rubber. The silicone rubber covers both ends and the polyurethane covers the middle section, which can effectively disperse bending stress, make the conductor uniformly stressed, and the combination of various materials in the self-healing layer can effectively repair cracks in the insulation layer and improve the service life of the cable.

[0029] 3. The shielding layer is made of aluminum foil and polyester fiber twill weave. At the same time, an adhesive is coated on the surface of the aluminum foil to achieve a firm bond with the fiber, so that the shielding effectiveness fluctuation is controlled within ±2dB and the transmission loss is <0.15dB / m, ensuring the stability of shielding effectiveness and signal transmission. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to embodiments. All details not specifically stated herein are based on conventional conditions or conditions recommended by the manufacturer. All reagents and instruments, unless otherwise stated below, are commercially available conventional reagent products.

[0031] In this application, the polyurethane-polysiloxane copolymer is prepared by melt polymerization of the prepolymer. Specifically, the following method can be referred to: 1 part of hydroxyl-terminated polysiloxane is dissolved in 2 parts of anhydrous solvent (such as toluene, tetrahydrofuran, etc.), and then 0.003 parts of dibutyltin dilaurate is added. Diisocyanate (one of XDI and MDI) is added to the solvent to prepare a 50wt% solution, which is added to the reaction system by slow dropwise. After the dropwise addition is complete, the reaction is carried out at 60±5℃ for 3h under nitrogen protection, and then cooled to 50℃. 0.735 parts of hydroxyethyl methacrylate are added, and the mixture is kept at this temperature for 1.5h to obtain the prepolymer. A chain extender solution (ethylenediamine or 1,6-hexanediamine is dissolved in anhydrous solvent to prepare a 10-20wt% solution) is added, and the reaction is carried out at 15-20℃ until the isocyanate groups are completely consumed. After the reaction is completed, the polymer solution is rotary evaporated, washed, and dried to obtain the polyurethane-polysiloxane copolymer.

[0032] Preparation Example 1

[0033] The slurry used in the self-healing layer includes the following raw materials: 10 kg of polyurethane-polysiloxane copolymer, 0.5 kg of 4,4′-diaminodiphenyl disulfide, 0.3 kg of 2-ureido-4[1H]-pyrimidinone, 0.2 kg of nano silica, 0.015 kg of KH-550, 0.03 kg of tributylphosphine, and 23 kg of tetrahydrofuran;

[0034] The preparation method of the slurry used in the self-healing layer includes the following steps:

[0035] S1. Disperse nano-silica in a mixed solution of ethanol and water (volume ratio of ethanol to water is 9:1) to form a dispersion with a concentration of 30wt%. Then add KH-550, stir and react at 60℃ for 3h, and then centrifuge and dry to obtain modified nano-silica.

[0036] S2. Polyurethane-polysiloxane copolymer, 4,4′-diaminodiphenyl disulfide, and 2-ureido-4[1H]-pyrimidinone were added to tetrahydrofuran and stirred at 60°C for 3 hours under nitrogen protection to obtain copolymer solution.

[0037] S3. Add modified nano-silica and tributylphosphine to the copolymer solution, and stir at high speed to disperse evenly to obtain the repair layer slurry.

[0038] Preparation Example 2

[0039] The slurry used in the self-healing layer includes the following raw materials: 10 kg of polyurethane-polysiloxane copolymer, 1 kg of 4,4′-diaminodiphenyl disulfide, 0.6 kg of 2-ureido-4[1H]-pyrimidinone, 0.4 kg of nano silica, 0.02 kg of KH-550, 0.04 kg of tributylphosphine, and 24 kg of tetrahydrofuran;

[0040] The preparation method of the slurry used in the self-healing layer includes the following steps:

[0041] S1. Disperse nano-silica in a mixed solution of ethanol and water (volume ratio of ethanol to water is 9:1) to form a dispersion with a concentration of 30wt%. Then add KH-550, stir and react at 70℃ for 2h, and then centrifuge and dry to obtain modified nano-silica.

[0042] S2. Polyurethane-polysiloxane copolymer, 4,4′-diaminodiphenyl disulfide, and 2-ureido-4[1H]-pyrimidinone were added to tetrahydrofuran and stirred at 80°C for 2 hours under nitrogen protection to obtain copolymer solution.

[0043] S3. Add modified nano-silica and tributylphosphine to the copolymer solution, and stir at high speed to disperse evenly to obtain the repair layer slurry.

[0044] Preparation Example 3

[0045] The slurry used in the self-healing layer includes the following raw materials: 10 kg of polyurethane-polysiloxane copolymer, 1.5 kg of 4,4′-dihydroxydiphenyl disulfide, 1 kg of 2-ureido-4[1H]-pyrimidinone, 0.5 kg of nano silica, 0.025 kg of KH-550, 0.05 kg of tributylphosphine, and 25 kg of tetrahydrofuran;

[0046] The preparation method of the slurry used in the self-healing layer includes the following steps:

[0047] S1. Disperse nano-silica in a mixed solution of ethanol and water (volume ratio of ethanol to water is 9:1) to form a dispersion with a concentration of 30wt%. Then add KH-550, stir and react at 60℃ for 3h, and then centrifuge and dry to obtain modified nano-silica.

[0048] S2. Polyurethane-polysiloxane copolymer, 4,4′-diaminodiphenyl disulfide, and 2-ureido-4[1H]-pyrimidinone were added to tetrahydrofuran and stirred at 80°C for 2 hours under nitrogen protection to obtain copolymer solution.

[0049] S3. Add modified nano-silica and tributylphosphine to the copolymer solution, and stir at high speed to disperse evenly to obtain the repair layer slurry.

[0050] Preparation Example 4

[0051] The shielding layer is obtained using the following preparation method:

[0052] (1) Pretreatment of aluminum foil: Plasma treatment of aluminum foil with a thickness of 0.02 mm for 5 min, plasma treatment power of 100 W, after treatment, immerse in KH-550 solution (concentration of 2 wt%, solvent is ethanol and water, volume ratio of 9:1), react in the range of 60-65℃ for 30 min, take out and dry;

[0053] (2) Coat the surface of the pretreated aluminum foil with conductive silver paste polyurethane adhesive evenly, with a wet coating thickness of 10 μm, and then dry it with hot air at 80 °C for 3 min.

[0054] (3) Cut the coated aluminum foil into aluminum foil strips, and weave it with the coated side facing the polyester fiber side using a twill weave method. The radial direction is polyester fiber and the weft direction is aluminum foil strip. The weaving tension of the polyester fiber is 15cN and the weaving tension of the aluminum foil is 8cN. The weaving angle is 3° between the radial direction and the cable axis. The spacing between the polyester fibers is 0.5mm.

[0055] (4) After weaving, the shielding layer is obtained by curing at 110℃ and 0.3MPa for 10 minutes.

[0056] Preparation Example 5

[0057] The shielding layer is obtained using the following preparation method:

[0058] (1) Pretreatment of aluminum foil: Plasma treatment of aluminum foil with a thickness of 0.02 mm for 5 min, plasma treatment power of 100 W, after treatment, immerse in KH-550 solution (concentration of 2 wt%, solvent is ethanol and water, volume ratio of 9:1), react in the range of 60-65℃ for 30 min, take out and dry;

[0059] (2) Coat the surface of the pretreated aluminum foil with conductive silver paste polyurethane adhesive evenly, with a wet coating thickness of 15μm, and then dry it with hot air at 100℃ for 2min.

[0060] (3) Cut the coated aluminum foil into aluminum foil strips, and weave them with the coated side facing the polyester fiber side using a twill weave method. The radial direction is polyester fiber and the weft direction is aluminum foil strip. The weaving tension of the polyester fiber is 20cN and the weaving tension of the aluminum foil is 12cN. The weaving angle is 45° between the radial direction and the cable axis. The spacing between the polyester fibers is 0.5mm.

[0061] (4) After weaving, the shielding layer is obtained by curing at 120℃ and 0.5MPa for 5 minutes.

[0062] Comparative Preparation Example 1

[0063] The difference from Preparation Example 1 is that the self-healing slurry does not contain 2-ureido-4[1H]-pyrimidinone, but otherwise it is the same as Preparation Example 1.

[0064] Comparative Preparation Example 2

[0065] The difference from Preparation Example 1 is that the self-healing layer slurry does not contain nano-silica and silane coupling agent, but otherwise it is the same as Preparation Example 1.

[0066] Comparative preparation example 3

[0067] The difference from Example 4 is that, in the preparation of the shielding layer, conductive silver paste polyurethane adhesive is not coated on the pretreated aluminum foil, and the pretreated aluminum foil and polyester fiber are directly woven in a twill weave. All other conditions are the same as in Example 4.

[0068] Example 1

[0069] A cable for power-assisted bicycles includes, from the inside out, a conductor structure layer, an insulation layer, a self-healing layer, and a shielding layer. The conductor structure layer consists of an inner layer and an outer layer. The inner layer is made of 7 strands of silver-plated copper wire (0.05 mm in diameter) spirally twisted at an 8 mm pitch. The outer layer is made of 12 shape memory alloy wires with a diameter of 0.1 mm wound in opposite directions at a 45° angle to cover the inner layer.

[0070] An insulating layer is wrapped around the conductor structure layer. The insulating layer material is composed of polyurethane and silicone rubber. The silicone rubber is melt-extruded and wrapped around both ends of the conductor structure layer. The thickness of the silicone rubber layer is 30μm. The polyurethane is melt-extruded and wrapped around the middle section of the conductor structure layer. The thickness of the polyurethane layer is 50μm. At the same time, the polyurethane layer extends to both ends to form an overlap transition area with the silicone rubber layer. The overlap length is 10mm.

[0071] After the insulation layer is coated, the self-healing coating slurry of Preparation Example 1 is brushed onto the outside of the insulation layer. The thickness of the wet self-healing coating slurry is 60 μm. After brushing, it is cured at 60°C to form a self-healing layer.

[0072] A shielding layer is wrapped around the self-healing layer, and the shielding layer is the one obtained in Preparation Example 4.

[0073] Example 2

[0074] A cable for power-assisted bicycles includes, from the inside out, a conductor structure layer, an insulation layer, a self-healing layer, and a shielding layer. The conductor structure layer consists of an inner layer and an outer layer. The inner layer is made of 7 strands of silver-plated copper wire (0.05 mm in diameter) spirally twisted together at a 6 mm pitch. The outer layer is made of 12 shape memory alloy wires with a diameter of 0.1 mm wound in opposite directions at a 45° angle to cover the inner layer.

[0075] An insulating layer is wrapped around the conductor structure layer. The insulating layer material is composed of polyurethane and silicone rubber. The silicone rubber is melt-extruded and wrapped around both ends of the conductor structure layer. The thickness of the silicone rubber layer is 35μm. The polyurethane is melt-extruded and wrapped around the middle section of the conductor structure layer. The thickness of the polyurethane layer is 45μm. At the same time, the polyurethane layer extends to both ends to form an overlap transition area with the silicone rubber layer. The overlap length is 10mm.

[0076] After the insulation layer is coated, the self-healing coating slurry of Preparation Example 1 is brushed onto the outside of the insulation layer. The thickness of the wet self-healing coating slurry is 60 μm. After brushing, it is cured at 60°C to form a self-healing layer.

[0077] A shielding layer is wrapped around the self-healing layer, and the shielding layer is the one obtained in Preparation Example 4.

[0078] Example 3

[0079] A cable for power-assisted bicycles includes, from the inside out, a conductor structure layer, an insulation layer, a self-healing layer, and a shielding layer. The conductor structure layer consists of an inner layer and an outer layer. The inner layer is made of 7 strands of silver-plated copper wire (0.05 mm in diameter) spirally twisted at a 10 mm pitch. The outer layer is made of 12 shape memory alloy wires with a diameter of 0.1 mm wound in opposite directions at a 45° angle to cover the inner layer.

[0080] An insulating layer is wrapped around the conductor structure layer. The insulating layer material is composed of polyurethane and silicone rubber. The silicone rubber is melt-extruded and wrapped around both ends of the conductor structure layer. The thickness of the silicone rubber layer is 35μm. The polyurethane is melt-extruded and wrapped around the middle section of the conductor structure layer. The thickness of the polyurethane layer is 55μm. At the same time, the polyurethane layer extends to both ends to form an overlap transition area with the silicone rubber layer. The overlap length is 10mm.

[0081] After the insulation layer is coated, the self-healing coating slurry of Preparation Example 1 is brushed onto the outside of the insulation layer. The thickness of the wet self-healing coating slurry is 60 μm. After brushing, it is cured at 60°C to form a self-healing layer.

[0082] A shielding layer is wrapped around the self-healing layer, and the shielding layer is the one obtained in Preparation Example 4.

[0083] Example 4

[0084] A power-assisted bicycle cable differs from Example 1 in that the self-healing slurry is the same as that obtained in Preparation Example 2.

[0085] Example 5

[0086] A power-assisted bicycle cable differs from Example 1 in that the self-healing slurry is the same as that obtained in Preparation Example 3.

[0087] Example 6

[0088] A power-assisted bicycle cable differs from Example 1 in that the shielding layer is the same as that obtained in Preparation Example 5, while all other aspects are the same as in Example 1.

[0089] Comparative Example 1

[0090] A power-assisted bicycle cable differs from Embodiment 1 in that it lacks a self-healing layer, but is otherwise identical to Embodiment 1.

[0091] Comparative Example 2

[0092] A power-assisted bicycle cable differs from Example 1 in that the self-healing slurry is the same as that obtained in Comparative Preparation Example 1.

[0093] Comparative Example 3

[0094] A power-assisted bicycle cable differs from Example 1 in that the self-healing slurry is the same as that obtained in Comparative Preparation Example 2.

[0095] Comparative Example 4

[0096] A power-assisted bicycle cable differs from Example 1 in that the shielding layer is the same as that obtained in Comparative Preparation Example 3, while all other aspects are the same as in Example 1.

[0097] Comparative Example 5

[0098] A power-assisted bicycle cable differs from Embodiment 1 in that the conductor structure layer uses only silver-plated copper wire spirally stranded at an 8mm pitch, without an outer shape memory alloy layer; otherwise, it is the same as Embodiment 1.

[0099] Performance testing

[0100] The cables obtained in the above embodiments and comparative examples were tested for bending life, transmission loss, shielding effectiveness fluctuation, and self-healing performance. The test results are shown in the table below.

[0101] 1. Test conditions for bending life: bending radius is 3 times the cable outer diameter, bending angle is ±90°, bending frequency is 20 times / min; failure criterion: the insulation resistance drops to below 50% of the initial value as the failure criterion.

[0102] 2. Test conditions for transmission loss: The test frequency is 100MHz, the test method uses a vector network analyzer to measure the S-parameters of the cable and directly read the attenuation value per unit length, and the test ambient temperature is 23±2℃.

[0103] 3. Test conditions for shielding effectiveness fluctuation control: The test method adopts the three-coaxial method, and the scanning test is carried out in the working frequency band of 30MHz~1GHz. The difference between the maximum and minimum shielding effectiveness measured in this frequency band is recorded.

[0104] 4. Test of self-healing performance: Microcracks with a width of 30μm were created on the surface of the self-healing layer using a cutting tool. The sample was placed in a constant temperature environment of 35℃ and left to stand for 24 hours. The width of the repaired crack was observed under a microscope, and the crack width repair rate was calculated.

[0105] Table 1 Cable Performance Test Results

[0106] project Bending life / cycle Transmission loss dB / m Shielding effectiveness fluctuation dB Self-repair rate / % Example 1 7250 0.12 1.5 84.3 Example 2 7140 0.11 2.0 85.6 Example 3 7230 0.13 1.5 84.9 Example 4 7360 0.11 1.0 86.4 Example 5 7290 0.10 1.0 85.5 Example 6 7270 0.10 1.0 84.1 Comparative Example 1 5140 0.26 2.8 / Comparative Example 2 5870 0.14 1.5 62.6 Comparative Example 3 6520 0.15 1.5 83.6 Comparative Example 4 5960 0.25 4.2 84.5 Comparative Example 5 3850 0.13 1.5 84.1

[0107] Based on the test data in Table 1:

[0108] The cables obtained in Examples 1-5 of this application all have a bending life of over 7000 cycles, a transmission loss of <0.15dB / m, and a shielding effectiveness fluctuation within ±1.5dB. Under a 35℃ environment, the self-repair rate is over 80% in 24 hours. This indicates that the cables obtained in this application not only have good fatigue resistance but also effectively improve the service life of the cables.

[0109] Compared with Example 1, Comparative Example 1 shows that without the self-healing layer, the bending life is significantly reduced, and the transmission loss and shielding effectiveness fluctuations also increase. This is because without the self-healing layer, the micro-cracks generated during repeated bending of the cable will continue to expand, eventually leading to insulation layer cracking and failure, reducing the bending life, damaging the shielding layer, and consequently increasing the transmission loss and exacerbating the shielding effectiveness fluctuations.

[0110] Compared with Example 1, when the self-healing layer slurry lacked 2-ureido-4[1H]-pyrimidinone or the combination of nano-silica and silane coupling agent, the bending life of the cables obtained in Comparative Examples 2-3 was reduced. At the same time, the repair ability of the self-healing layer in Comparative Example 2 was also reduced. It can be seen that the combination of 2-ureido-4[1H]-pyrimidinone and disulfide bond effectively improved the repair ability of the self-healing layer. At the same time, the addition of 2-ureido-4[1H]-pyrimidinone and nano-silica also improved the mechanical strength of the self-healing layer.

[0111] Compared with Example 1, when conductive silver paste polyurethane adhesive was not coated on the aluminum foil during the preparation of the shielding layer, the bending life of the cable decreased, the transmission loss increased, and the shielding effectiveness fluctuated more. This is because the conductive silver paste polyurethane adhesive, as a flexible transition layer, coordinates the deformation difference between the aluminum foil and the fiber, prevents the aluminum foil from cracking due to local stress concentration, and the presence of silver wires in the conductive silver paste polyurethane adhesive makes the shielding layer resistance low and stable, and the electromagnetic shielding stability is also high. Therefore, without polyurethane adhesive, both bending performance and electromagnetic shielding performance are reduced.

[0112] Compared with Example 1, Comparative Example 5 shows that the bending life is significantly reduced when the shape memory alloy layer is missing in the conductor structure layer. This is because the shape memory alloy is superelastic. When subjected to bending stress, it can absorb a large amount of strain energy through stress-induced martensitic phase transformation. After the stress is unloaded, it can return to its original shape. Therefore, when the shape memory alloy is used as the outer layer in the conductor structure layer, it can effectively withstand and disperse bending stress, significantly improving the fatigue resistance of the cable.

[0113] The embodiments described herein are merely illustrative of preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A cable for a power-assisted bicycle, characterized in that: The cable comprises, from the inside out, a conductor structure layer, an insulation layer, a self-healing layer, and a shielding layer. The conductor structure layer consists of an inner layer made of silver-plated copper wire spirally twisted together and an outer layer wound in the opposite direction at a 45° angle onto the inner layer. The spiral pitch of the silver-plated copper wire is 6-10 mm. The outer layer of the conductor structure layer uses shape memory alloy wire with a diameter of 0.1 mm. The insulation layer material is composed of polyurethane and silicone rubber, with silicone rubber covering both ends of the conductor structure along its length and polyurethane covering the middle section of the conductor structure.

2. The power-assist bicycle cable according to claim 1, characterized in that: In the insulating layer, the thickness of the silicone rubber segment is 30-35 μm, and the thickness of the polyurethane segment is 45-55 μm.

3. The power-assist bicycle cable according to claim 1, characterized in that: The slurry used in the self-healing layer comprises the following raw materials in parts by weight: 100 parts polyurethane-polysiloxane copolymer, 5-15 parts chain extender containing dynamic disulfide bonds, 3-10 parts dimer containing quadruple hydrogen bonds, 2-5 parts nano silica, 0.15-0.25 parts silane coupling agent, 0.3-0.5 parts catalyst, and 230-250 parts organic solvent.

4. The power-assist bicycle cable according to claim 3, characterized in that: The chain extender containing dynamic disulfide bonds is one of 4,4′-diaminodiphenyl disulfide and 4,4′-dihydroxydiphenyl disulfide.

5. A power-assist bicycle cable according to claim 3, characterized in that: The catalyst is tributylphosphine.

6. The power-assist bicycle cable according to claim 3, characterized in that: The slurry used in the self-healing layer is obtained using the following preparation method: S1. Disperse nano-silica in a mixed solution of ethanol and water, add silane coupling agent, stir and react at 60-70℃ for 2-3 hours, then centrifuge and dry to obtain modified nano-silica. S2. Add the polyurethane-polysiloxane copolymer, the chain extender containing dynamic disulfide bonds, and the dimer containing four hydrogen bonds to an organic solvent, and stir at 60-80℃ for 2-3 hours under nitrogen protection to obtain a copolymer solution. S3. Add modified nano-silica and catalyst to the copolymer solution, and stir at high speed to disperse evenly to obtain the repair layer slurry.

7. The power-assist bicycle cable according to claim 1, characterized in that: The shielding layer is woven from aluminum foil and polyester fibers using a twill weave. The polyester fiber weave tension is 15-20 cN, the aluminum foil weave tension is 8-12 cN, and the weave angle is 30-45° radial to cable axis. The polyester fiber spacing is 0.5 mm, and the aluminum foil thickness is 0.02 mm.

8. A power-assist bicycle cable according to claim 7, characterized in that: The aluminum foil is obtained by the following pretreatment method before weaving: the aluminum foil is subjected to plasma treatment for 3-5 minutes, then immersed in a silane coupling agent solution, reacted at 60-65℃ for 30 minutes, and then taken out and dried.

9. A power-assist bicycle cable according to claim 7 or 8, characterized in that: The shielding layer is obtained using the following preparation method: (1) Coat the aluminum foil surface with adhesive evenly, with a wet coating thickness of 10-15 μm, and then dry it with hot air at 80-100℃ for 2-3 min; (2) Cut the coated aluminum foil into aluminum foil strips and weave them with the coated side facing the polyester fiber side; (3) After weaving, cure at 110-120℃ and 0.3-0.5MPa for 5-10 minutes.

10. A power-assisted bicycle cable according to claim 9, characterized in that: The adhesive is a conductive polyurethane adhesive.