Variable-stiffness anti-fatigue flexible cable

Abstract

The invention provides a variable-stiffness anti-fatigue flexible cable, and relates to the technical field of cables, and the flexible cable comprises a heat conduction channel which is arranged along the axial direction of the cable in a penetrating manner, a conductor which is spirally arranged around the heat conduction channel, a filling layer which wraps the heat conduction channel and the conductor, a shielding layer of which the inner side is provided with a storage cavity, and an adjusting layer which comprises a plurality of rigid adjusting units. Wherein heat conduction liquid is arranged in the heat conduction channel, a heat conduction pipe is embedded in the filling layer, the heat conduction pipe is provided with a valve port, the heat conduction pipe is communicated with the storage cavity, and each rigid adjusting unit is a flexible bag filled with a phase change material. Liquid heat triggers the phase-change material to expand through the shielding layer, so that the rigidity adjusting unit extends to enhance local rigidity, the effect of inhibiting excessive bending is achieved, the short-time hardness of a bending part is higher than that of a peripheral area due to expansion retention of the phase-change material, and the purpose of dynamically transferring a bending stress point is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of cables, in particular to a flexible cable with variable stiffness and fatigue resistance. Background Art

[0002] Flexible cable is an electrical conductor component with high flexibility and bending properties. It is a power and signal transmission cable used in dynamic environments. It is an indispensable flexible link in modern industry and technology. It is widely used in equipment that needs to move frequently or be used in complex environments. Whether it is an industrial robot, servo motor, or automation equipment, flexible cable can provide reliable power and signal transmission solutions.

[0003] However, flexible cables can still be overbent during use. When the bend radius falls below a safe threshold (e.g., ≥6 times the cable diameter for low-voltage cables), fatigue cracks can form in the conductor and insulation due to tensile / compressive stress. Actual cases show that insulation rupture (accounting for 37%) and conductor breakage (accounting for 28%) are the primary failure modes. This is particularly true at the outlet of J-tubes in offshore wind turbines, where a single overbend can cause sheath tears and short-circuit the core wires.

[0004] In addition, when a flexible cable is bent, repeated bending at the same position may cause fatigue failure. This is because during the first bending, the outer conductor of the cable undergoes plastic deformation due to tensile stress (such as lattice slip of the copper conductor), and the inner conductor undergoes micro-bending due to compressive stress. As a result, the yield strength of the material in this area decreases after the cable is straightened, forming a mechanically weak area. As a result, subsequent stress continues to concentrate in this area, making it easier to bend again, ultimately leading to local permanent deformation, increased resistance or short circuit.

[0005] In the existing technology, the volume of the phase change material can be changed according to the working state of the cable by utilizing the temperature of the conductor itself in the cable, thereby changing the rigidity of the cable; however, the existing technology can only change the overall rigidity of the cable, but cannot change the local rigidity of the cable, and cannot solve the problems of excessive bending of the cable and repeated bending in the same position.

[0006] Therefore, in order to solve the above problems, the present invention proposes a flexible cable with variable stiffness and fatigue resistance, which aims to improve the ability to prevent the flexible cable from excessive bending and dynamically transfer bending stress points. Summary of the Invention

[0007] The object of the present invention is to provide a flexible cable with variable stiffness and fatigue resistance, aiming to solve the problems of excessive bending and repeated bending of the flexible cable at the same position.

[0008] To achieve the above object, the present invention adopts the following technical solution: a flexible cable with variable stiffness and fatigue resistance, comprising: A heat conduction channel is provided along the axial direction of the cable, and a heat conduction liquid is provided in the heat conduction channel; Conductors, multiple groups of which are spirally arranged around the heat-conducting channel; A filling layer covers the heat conduction channel and the conductor, wherein a heat conduction pipe is embedded in the filling layer and the heat conduction pipe is provided with a valve port; The shielding layer has a storage cavity inside, and the heat pipe is connected to the storage cavity; The adjustment layer comprises a plurality of rigidity adjustment units spirally arranged along the axial direction of the cable, each rigidity adjustment unit being a flexible capsule filled with phase change material; Among them, when the cable bends, the displacement of the conductor squeezes the heat conduction channel, driving the high-temperature liquid into the storage cavity through the heat conduction pipe. The heat of the liquid triggers the expansion of the phase change material through the shielding layer, causing the rigidity adjustment unit to stretch to enhance local rigidity.

[0009] Preferably, a plurality of the rigidity adjustment units are evenly arranged along the circumference of the cable, and the adjustment layer is the only rigidity adjustment structure of the cable, without the need for an external bend limiter or power supply device.

[0010] Preferably, the spiral direction of the rigidity adjustment unit is opposite to the spiral direction of the conductor.

[0011] Preferably, the adjustment layer is divided into multiple sections along the axial direction of the cable, each section of the adjustment layer comprises multiple rigid adjustment units along the axial direction of the cable, and every two sections of the adjustment layer are separated by a partition.

[0012] Preferably, a temperature memory alloy wire is embedded in the flexible bag of the rigidity adjustment unit, and its phase change temperature is higher than the phase change material in the rigidity adjustment unit, which can limit the excessive expansion of the flexible bag.

[0013] Preferably, the valve port can conduct in both directions according to the pressure difference, so that the heat conduction channel and the liquid in the storage cavity pass through the valve port when the pressure changes.

[0014] Preferably, the valve port is a tapered microporous structure, and each valve port includes two tapered microporous structures in opposite directions.

[0015] Preferably, a plurality of heat-conducting pipes in the filling layer are provided along the circumferential direction of the heat-conducting channel, and a plurality of heat-conducting pipes are provided along the axial direction of the cable.

[0016] Preferably, an insulating layer is provided between the conductor and the filling layer, and the outer side of the adjustment layer is covered with a protective layer.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention arranges a heat conduction channel and a rigidity adjustment unit. When the cable is bent, the conductor squeezes the heat conduction channel, driving the high-temperature liquid to flow into the storage cavity. The phase change material in the rigidity adjustment unit expands, thereby improving the rigidity of the bent portion, achieving the purpose of self-reinforcement of the bent portion and realizing the effect of suppressing excessive bending. In addition, after the phase change material absorbs heat, the temperature is retained, so that the hardness of the bent portion is temporarily higher than that of the surrounding area. When the cable is bent for the second time, the stress is automatically transferred to the adjacent flexible section, thereby achieving the purpose of dynamically transferring the bending stress point, avoiding fatigue caused by repeated bending at the same position, and solving the problem of cable damage caused by bending at the same position. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the cross section of the flexible cable of the present invention.

[0019] Figure 2 It is a structural schematic diagram of the adjustment layer in the present invention.

[0020] Figure 3 It is a schematic structural diagram of the conductor in the present invention.

[0021] Reference numerals: 1. Conductor; 2. Insulation layer; 3. Filling layer; 31. Heat pipe; 32. Valve port; 4. Heat conduction channel; 5. Shielding layer; 51. Storage cavity; 6. Adjustment layer; 61. Rigidity adjustment unit; 7. Protective layer. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] In order to improve the ability of flexible cables to resist excessive bending and fatigue, Figures 1 to 3 As shown, the present invention proposes a variable stiffness and fatigue-resistant flexible cable, which adds a "mechanical trigger + thermal response" synergistic mechanism to achieve bending self-adjusting stiffness. The flexible cable includes: a heat conduction channel 4, a conductor 1, a filling layer 3, a shielding layer 5, an adjustment layer 6 and a protective layer 7 arranged from the inside to the outside.

[0024] The heat-conducting channel 4 is arranged to pass through the cable axially, and a heat-conducting liquid is provided in the heat-conducting channel 4; the heat-conducting channel 4 is located in the center of the cable, and the heat-conducting liquid can be a silicone oil-based liquid for heat conduction. The thermal conductivity of the silicone oil-based liquid is stable in the range of 70°C to 120°C (0.54 to 0.56 W / m·K), and it can efficiently transfer heat to the phase change material, shortening the response time of the rigidity adjustment unit 61; the silicone oil-based liquid has a low viscosity of about 5 mPa·s at 25°C, which can better match the tapered microporous structure of the valve port 32; the silicone oil-based liquid has high oxidation resistance and does not need to be replaced.

[0025] Conductor 1 is spirally arranged in multiple groups around heat conduction channel 4, and is covered with insulation layer 2. When the cable bends, the outer strands of conductor 1 are stretched and the inner strands are compressed. The spiral structure causes the outer conductor 1 to move inward during bending, while the inner conductor 1 moves outward, creating a dynamic balance.

[0026] The filling layer 3 covers the heat conduction channel 4 and the conductor 1. A heat conduction pipe 31 is embedded in the filling layer 3. The heat conduction pipe 31 is provided with a valve port 32. One end of the heat conduction pipe 31 is connected to the heat conduction channel 4, and the other end extends to the outside of the filling layer 3. The valve port 32 is located near one end of the filling layer 3.

[0027] There are multiple heat pipes 31 in the filling layer 3 along the circumference of the heat conduction channel 4 and along the axial direction of the cable, so that the rigidity adjustment unit 61 can respond promptly every time the cable bends; the heat pipes 31 can be corrugated copper tubes.

[0028] Filling layer 3 is made of silicone rubber composited with nitrile rubber to ensure that filling layer 3 meets the requirements of elastic support, thermal conductivity, and fatigue resistance. The Shore hardness of the silicone rubber composited with nitrile rubber is 60A to 70A, which is moderately hard and soft and meets the buffering requirements when the cable is bent. The thermal conductivity coefficient is 0.25 to 0.35 W / (m·K), which is higher than that of ordinary rubber and facilitates heat transfer from the heat pipe 31 to the phase change material. It is resistant to high and low temperatures of -50°C to 180°C and can adapt to various extreme working conditions.

[0029] The shielding layer 5 is provided with a storage cavity 51 on the inner side. The storage cavity 51 is annular and is provided in plurality along the axial direction of the cable. The storage cavity 51 corresponds to the heat pipe 31 along the axial direction of the cable, and the heat pipe 31 is connected to the storage cavity 51. The shielding layer 5 adopts a multi-layer structure and can use a structure in which aluminum foil and tinned copper wire woven mesh are bonded by conductive adhesive to meet the thermal conductivity, flexibility and electromagnetic shielding functions.

[0030] The inner layer of the shielding layer 5 is made of ultra-thin aluminum foil, which is designed to fit the storage cavity 51 and has a thermal conductivity of ≥200W / (m·K), achieving efficient heat conduction to the phase change material. The outer layer is made of tinned copper wire braided mesh to maintain the dynamic flexibility of the cable; hot-melt conductive adhesive is used in the middle to ensure that there is no peeling between the aluminum foil and the copper mesh while maintaining axial elasticity. The hot-melt conductive adhesive can be silicone-based.

[0031] The adjustment layer 6 includes a plurality of rigidity adjustment units 61 arranged spirally along the axial direction of the cable. Each rigidity adjustment unit 61 is a flexible capsule filled with phase change material. A temperature memory alloy wire is embedded in the flexible capsule of the rigidity adjustment unit 61. The phase change temperature of the temperature memory alloy wire is 10-15°C higher than that of the phase change material in the rigidity adjustment unit 61, which can limit the excessive expansion of the flexible capsule. The spiral arrangement of the rigidity adjustment unit 61 enables the phase change material to expand and extend along the length direction of the rigidity adjustment unit 61, thereby causing the cable to tend to extend axially and enhance local rigidity.

[0032] The flexible sac is made of fluororubber with a wall thickness of 0.5 to 1 mm. Fluororubber is oil-resistant and has high-temperature stability. The phase change material is a paraffin-based composite material with a phase change temperature of 50°C ± 5°C and a volume expansion rate of ≥ 25%. It has low cost and high latent heat. The paraffin-based composite material can also add 1% to 3% nano-alumina to improve thermal conductivity, and octadecyl alcohol can be added to inhibit supercooling.

[0033] The temperature memory alloy wire is made of Nitinol material, and its phase change temperature is 60-65°C. When the phase change material is abnormally overheated, the alloy wire contracts and tightens the flexible capsule wall to limit excessive expansion, thereby completing the protection of the cable when the phase change material fails.

[0034] Multiple rigidity adjustment units 61 are evenly arranged along the circumference of the cable. The adjustment layer 6 is the only rigidity adjustment structure of the cable. It does not require an external bending restriction device or an additional power supply device. Adaptive rigidity adjustment is achieved through the conversion of thermal energy and mechanical energy. Moreover, after the volume of the phase change material increases, the rigidity adjustment unit 61 forms a local high-rigidity area, dynamically controlling the bending radius within a safe threshold.

[0035] The adjustment layer 6 is divided into multiple sections along the cable axis. Each section of the adjustment layer 6 includes multiple rigid adjustment units 61 along the cable axis. Each two sections of the adjustment layer 6 are separated by a partition. The segmented partition can be made of glass fiber reinforced polypropylene to avoid thermal deformation affecting the sealing.

[0036] The spiral direction of the rigidity adjustment unit 61 is opposite to that of the conductor 1. Figure 2 and Figure 3 It can be seen that the spiral direction of the adjustment unit 61 is opposite to that of the conductor 1; the spiral direction of the conductor 1 is opposite to that of the rigidity adjustment unit 61, which can make the temperature distribution more uniform and ensure that the rigidity of the corresponding area is improved when the cable is bent. At the same time, the opposite spiral direction can disperse the stress of the cable.

[0037] The heat pipe 31 is close to the conductor 1 , and the liquid in the heat pipe 31 is also at a relatively high temperature. After the liquid enters the storage cavity 51 , the phase change material in the rigidity adjustment unit 61 can respond in time.

[0038] The valve port 32 is bidirectional and allows for bidirectional flow based on pressure differentials, allowing the liquid in the heat conduction channel 4 and the storage chamber 51 to pass through the valve port 32 when pressure changes. The valve port 32 has a tapered microporous structure with a pore size range of 0.2–0.5 mm. It opens when the pressure differential between the two ends exceeds 0.1 MPa. The valve port 32 allows for communication based on the pressure differential between the two sides. When the pressure on one side is greater than the other, the liquid on the high-pressure side flows to the low-pressure side. When there is no pressure differential between the two sides, the liquid is blocked to prevent backflow.

[0039] The valve port 32 is a conical channel as a whole, and the aperture gradually shrinks from the inlet to the outlet. Two conical channels in opposite directions are provided at one valve port 32, which can respond to different pressure differences and realize two-way passage of the heat-conducting liquid; when the cable is bent, the heat-conducting liquid enters the storage cavity 51 from the heat-conducting channel 4 through one of the conical channels of the valve port 32; when the cable returns to the straight state, the heat-conducting liquid enters the heat-conducting channel 4 from the storage cavity 51 through the other conical channel of the valve port 32, thereby realizing the heating of the phase change material and completing the circulation of the heat-conducting liquid.

[0040] The tapered microporous structure of the valve port 32 can be completed simultaneously when the filling layer 3 is manufactured. The tapered microporous structure of the valve port 32 can also be processed by laser drilling technology. A KrF excimer laser can be used in conjunction with a double mask exchange table to complete the processing of the tapered microporous structure.

[0041] The protective layer 7 covers the outside of the adjustment layer 6 and can apply a certain pressure to the rigidity adjustment unit 61 after the phase change material expands, so that the rigidity adjustment unit 61 can stably stretch along the axial direction, thereby improving the local rigidity of the cable.

[0042] When the cable bends, conductor 1 displaces and squeezes heat-conducting channel 4, driving high-temperature liquid through heat pipe 31 and into storage chamber 51. The heat from the liquid, flowing through shielding layer 5, triggers the expansion of the phase-change material, causing the stiffness-adjusting unit 61 to stretch, thereby increasing local stiffness. The heat generated by the initial bend is transferred through the liquid to the phase-change material, triggering a localized stiffness increase. The stiffness-enhanced area forms a bending stress barrier, forcing the secondary bend to shift position.

[0043] The phase change material in the rigidity adjustment unit 61 can increase in volume when the temperature rises. The rigidity adjustment unit 61 stretches in the spiral direction when it increases, so that the cable tends to stretch, thereby increasing the rigidity of this part of the cable.

[0044] When the cable bends, the conductor 1 squeezes the heat conduction channel 4, transferring the heat of the high-temperature liquid to the phase change material of the rigidity adjustment unit 61, increasing its volume and thus improving local rigidity; when the cable changes from a bent state to a straight state, the high-temperature liquid returns to the heat conduction channel 4, and the phase change material will no longer be affected by the high-temperature liquid. However, due to temperature retention, the phase change material needs time to recover its volume. This process can be controlled within 5 minutes. When the phase change material is still expanding, the rigidity of the original bending position of the cable is higher than that of the nearby area. During this time, when the cable bends again, it will automatically avoid the original bending position with high rigidity; after a period of time, the phase change material at the original bending position recovers its original volume, and the cable in this area also recovers its original flexibility, giving full play to the role of the flexible cable.

[0045] In this embodiment, the thermal channel 4 and the rigidity adjustment unit 61 ensure that when the cable bends, the conductor 1 squeezes the thermal channel 4, driving the high-temperature liquid into the storage chamber 51. This triggers the expansion of the phase-change material, instantly increasing the rigidity of the bend, and dynamically controlling the bend radius within a safe threshold. Simultaneously, the phase-change material retains its temperature after absorbing heat, temporarily increasing the rigidity of the bend area above that of the surrounding area. During a second bend, stress is automatically transferred to the adjacent flexible section, reducing local stress concentration, preventing repeated fatigue at the same location, and extending the cable's service life.

[0046] When the cable is bent, it includes a bending triggering stage, a thermal response stage and a rigidity maintenance stage.

[0047] Bending triggering stage: when the cable bends, the spiral conductor 1 moves centripetally to squeeze the heat conduction channel 4 , driving the high-temperature liquid in the heat conduction channel 4 to flow into the storage chamber 51 through the valve port 32 .

[0048] When the flexible cable is bent, the conductor 1 at the bent position, due to its spiral structure, causes the outer conductor at the bent position to move toward the inside of the bend, and the inner conductor compensates for the displacement outward, squeezing the central heat conduction channel 4, so that the liquid in the heat conduction channel 4 enters the storage cavity 51 along the heat conduction pipe 31. The liquid in the heat conduction channel 4 is close to the conductor 1, so that the temperature of the liquid is higher than that of the outside.

[0049] Thermal response stage: The heat of the high-temperature liquid is transferred to the phase change material through the shielding layer 5, triggering volume expansion, causing the rigidity adjustment unit 61 to stretch axially, and the adjustment layer 6 to form a local rigid area.

[0050] When these high-temperature liquids enter the storage cavity 51, the shielding layer 5 transfers the heat to the rigidity adjustment unit 61 of the adjustment layer 6. The phase change material in the flexible capsule of the rigidity adjustment unit 61 heats up and increases in volume, thereby enhancing the rigidity of this part and preventing the cable from excessively bending at the bending part.

[0051] Rigidity maintenance stage: The phase change material absorbs heat and remains at a constant temperature, and the bending stress is transferred to the adjacent area, which inhibits the cable from bending twice at the same position.

[0052] When the flexible cable is withdrawn from the bent state, the temperature of the phase change material remains stagnant after absorbing heat, and the phase change material is still in an expanded state. The conductor 1 and the heat conduction channel 4 have returned to their original state. At this time, the pressure in the storage cavity 51 is greater than the heat conduction channel 4, causing the heat conduction liquid in the storage cavity 51 to return to the heat conduction channel 4. However, the hardness of this area is temporarily higher than that of the surrounding area. During the second bending, the stress is automatically transferred to the adjacent flexible segment, avoiding repeated fatigue at the same position, and the cable will not bend repeatedly at the same position.

[0053] When the original bending position of the flexible cable does not continue to bend, the phase change material at that position will gradually restore its original volume after a period of time, thereby gradually reducing the rigidity of the cable in that area until the flexibility of this part of the cable is fully restored.

[0054] It should be noted that the process of suppressing excessive bending damage in this embodiment is: When the cable bends, conductor 1 squeezes heat-conducting channel 4, driving high-temperature liquid into storage chamber 51. This triggers the expansion of the phase-change material, instantly increasing the rigidity of the bend. Compared to traditional flexible cables that rely solely on the material's tensile strength, such as tensile-cord structures, which only delay damage by 5% to 15%, this solution leverages the expansion of the phase-change material within the rigidity adjustment unit 61 to create a localized high-rigidity region. This dynamically controls the bend radius within a safe threshold, preventing cracking of the insulation layer 2 or breakage of the conductor 1.

[0055] The process of eliminating the "weak zone effect" in this implementation is: When the cable returns from a bent state to a straightened state, the phase change material absorbs heat and retains its temperature, temporarily increasing the hardness of the original bent area compared to the surrounding area. During a second bend, stress is automatically transferred to the adjacent flexible section, preventing repeated fatigue at the same location and reducing local stress concentration. When the cable is no longer bent at the original bent location, the phase change material gradually shrinks and returns to its original size, gradually reducing the local rigidity until the cable's original performance is restored, ensuring the cable's flexibility during use.

[0056] The present invention utilizes the bending action that is originally required of the cable and the temperature of the conductor 1 inside the cable, so that when the cable is bent, the temperature near the conductor 1 is transferred to the phase change material of the adjustment layer 6, and the rigidity of the local conductor 1 is increased by the volume change of the phase change material, thereby completing the self-regulation of the cable stiffness. At the same time, the stiffness increase in this area will be retained for a period of time, thereby changing the bending position of the cable afterwards, solving the problem of cable damage caused by bending at the same position.

[0057] The above are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A flexible cable with variable stiffness and fatigue resistance, characterized in that: Including settings from inside to outside: A heat conduction channel is provided along the axial direction of the cable, and a heat conduction liquid is provided in the heat conduction channel; Conductors, multiple groups of which are spirally arranged around the heat-conducting channel; A filling layer covers the heat conduction channel and the conductor, wherein a heat conduction pipe with a valve port is embedded in the filling layer; The shielding layer has a storage cavity inside, and the heat pipe is connected to the storage cavity; The adjustment layer comprises a plurality of rigidity adjustment units spirally arranged along the axial direction of the cable, each rigidity adjustment unit being a flexible capsule filled with phase change material; Among them, when the cable bends, the conductor's centripetal displacement squeezes the heat conduction channel, driving the high-temperature liquid into the storage cavity through the valve mouth. The heat of the liquid triggers the expansion of the phase change material, causing the rigidity adjustment unit to stretch axially to form a local rigid area, inhibiting excessive bending and transferring stress points.

2. The flexible cable according to claim 1, wherein The rigidity adjustment units are arranged in multiple numbers evenly along the circumference of the cable, and the adjustment layer is the only rigidity adjustment structure of the cable.

3. The flexible cable according to claim 2, wherein: The spiral direction of the rigidity adjustment unit is opposite to the spiral direction of the conductor.

4. The flexible cable according to claim 3, wherein: The adjustment layer is divided into multiple sections along the axial direction of the cable. Each section of the adjustment layer includes multiple rigid adjustment units along the axial direction of the cable. Every two sections of the adjustment layer are separated by a partition.

5. The flexible cable according to claim 1, wherein A temperature memory alloy wire is embedded in the flexible bag of the rigidity adjustment unit to limit excessive expansion of the flexible bag.

6. The flexible cable according to claim 1, wherein The valve port can conduct in both directions according to the pressure difference, so that the heat conduction channel and the liquid in the storage cavity pass through the valve port when the pressure changes.

7. The flexible cable according to claim 6, characterized in that The valve port is a tapered microporous structure, and each valve port includes two tapered microporous structures in opposite directions.

8. The flexible cable according to claim 1, wherein A plurality of heat-conducting pipes are provided in the filling layer along the circumferential direction of the heat-conducting channel, and a plurality of heat-conducting pipes are provided along the axial direction of the cable.

9. The flexible cable according to claim 1, wherein: An insulating layer is provided between the conductor and the filling layer, and a protective layer is covered on the outer side of the regulating layer.

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