Carbon fiber carbonization rate on-line detection device and method

Abstract

The present application relates to carbon fiber production manufacturing technical field, specifically disclose a kind of carbon fiber carbonization rate online detection device and method;Device includes box, guide pulley group, multichannel data collector and temperature acquisition component;Box is connected with carbonization furnace by connecting flange;Guide pulley group includes two fiber Bragg grating guide pulleys and two electrode guide pulleys, is separately arranged at the bottom between the front and rear sides of box, for measuring tension, temperature and carrying out electrical measurement;Temperature acquisition component is arranged on the fiber path between two electrode guide pulleys, measures space temperature field;Multichannel data collector collects voltage signal;Method utilizes the device, simultaneously collects the voltage, space temperature field, tension and contact point temperature signal of fiber, according to this to carry out dynamic compensation to original resistance value, and inversion output carbonization rate;The present application is through the synchronous sensing of multiple physical fields and dynamic compensation, effectively eliminates the interference of temperature and tension fluctuation in production process to measurement, realizes the online high-precision detection of carbonization rate.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber production and manufacturing technology, specifically to an online detection device and method for carbon fiber carbonization rate. Background Technology

[0002] Carbon fiber, as a high-performance material composed of carbon elements, has become an indispensable key basic material in the industrial field due to its high strength, high modulus, low density, and excellent corrosion resistance and high temperature resistance. The production process of carbon fiber is complex, among which the carbonization process is the core link to transform the precursor into carbon fiber with high carbon content and ideal microcrystalline structure, which directly determines the key indicators such as mechanical properties and electrical conductivity of the final product.

[0003] In existing technologies, the volt-ampere method based on Ohm's law is a core approach that has been widely studied and adopted. This method directly calculates the resistance value of carbon fibers by applying current to both ends and measuring the resulting voltage drop, and then obtains the resistivity by combining the fiber's geometric dimensions. Due to its direct implementation principle, relatively simple measurement system construction, and ease of achieving rapid and continuous measurement, resistance measurement based on the volt-ampere method is regarded as one of the most promising technical paths for realizing online and real-time detection of carbon fiber carbonization rate, and related research and industrial attempts are all centered around this.

[0004] However, applying the above technology to continuous, dynamic industrial production lines presents fundamental challenges. When carbon fibers move at high speeds on the production line, their resistance measurements are affected by a combination of factors, including fluctuations in the ambient temperature of the production line, the heat generated by the measuring current itself, and changes in the mechanical tension of the fibers. These interfering factors, combined with the resistance changes caused by the carbonization degree of the carbon fibers themselves, make it difficult for existing online measurement devices to accurately distinguish and isolate the interference signals, thus failing to output accurate carbonization rate data in real time. This makes it difficult to obtain stable and reliable measurement results for carbon fiber carbonization rate detection using the voltammetry method in actual production environments. Summary of the Invention

[0005] To address the technical problems in the prior art, this invention provides an online carbonization rate detection device and method for carbon fibers. The aim is to solve the problem that the existing online measurement technology based on the voltammetry method cannot effectively distinguish and eliminate the complex interferences such as temperature fluctuations, current thermal effects, and mechanical tension changes on the production line, resulting in the inability to output accurate carbonization rate data in real time.

[0006] The technical solution of the present invention is as follows:

[0007] An online carbon fiber carbonization rate detection device includes a housing, a guide wheel assembly, a multi-channel data acquisition unit, and a temperature acquisition component.

[0008] One end of the housing is provided with a connecting flange for connecting to an external carbonization furnace;

[0009] The guide wheel assembly includes a fiber grating guide wheel assembly and an electrode guide wheel assembly, used to guide and measure the running carbon fiber filaments;

[0010] The fiber grating guide wheel assembly includes two components, which are arranged on the front and rear sides of the housing along the running direction of the carbon fiber, and are used to measure the real-time tension of the carbon fiber filament.

[0011] The electrode guide wheel assembly includes two, which are disposed between the fiber grating guide wheel assembly and located at the bottom of the two fiber grating guide wheel assemblies. The two electrode guide wheel assemblies are electrically connected to an external current source for applying a constant measurement current to the carbon fiber filament.

[0012] The multi-channel data acquisition device is located outside the box, and the detection end of the multi-channel data acquisition device extends into the box and is electrically connected to two electrode guide wheel assemblies, which are used to apply current to the carbon fiber filament and extract voltage measurement signals.

[0013] The temperature acquisition component is positioned on the carbon fiber filament path between the two electrode guide wheel assemblies and is used to measure the spatial temperature field of the carbon fiber filament.

[0014] Optionally, the fiber grating guide wheel assembly includes a fixed mandrel, a rotating sleeve, a temperature-compensated grating, and a force-sensitive grating, wherein...

[0015] The two ends of the fixed mandrel are fixed to the inner wall of the box;

[0016] The rotating sleeve is rotatably connected to the fixed mandrel via symmetrically arranged bearings, and is used to contact and guide the carbon fiber filaments;

[0017] The temperature-compensated grating is fixedly mounted on a fixed spindle and connected to an external demodulator signal to provide a temperature reference signal.

[0018] The sensitive optical grating is fixed on the fixed mandrel and located between two bearings. The sensitive optical grating is connected to an external demodulator signal and is used to sense the axial strain of the fixed mandrel caused by tension.

[0019] Optionally, the electrode guide wheel assembly includes an insulated guide wheel shaft and a conductive wheel body, wherein,

[0020] The insulating guide wheel shaft is fixedly connected to the conductive wheel body to form an integral electrode guide wheel;

[0021] The conductive wheel is rotatably connected to the housing via an insulated guide wheel shaft, and is used to contact and guide the carbon fiber filaments. The outer surface of the conductive wheel is covered with a conductive coating.

[0022] The conductive wheel is electrically connected to an external current source and is used to apply a constant measuring current to the carbon fiber filament.

[0023] The detection end of the multi-channel data acquisition device is electrically connected to the conductive wheel body and is used to measure the voltage signal between the two electrode guide wheel assemblies.

[0024] Optionally, the temperature acquisition component includes a mounting bracket and a temperature acquisition device, wherein,

[0025] The mounting bracket is fixed inside the housing and spans between the conductive wheels of the two electrode guide wheel assemblies;

[0026] The temperature acquisition device includes multiple units, which are fixed on the mounting frame and arranged at intervals along the running direction of the carbon fiber filament. The temperature acquisition device is in contact with or adjacent to the surface of the carbon fiber filament and is used to simultaneously measure the temperature at different positions of the carbon fiber filament between the two electrode guide wheel assemblies.

[0027] Optionally, an online carbon fiber carbonization rate detection device may also include a drying oven;

[0028] The drying chamber is located at one end of the chamber that connects to the external carbonization furnace. The drying chamber is filled with a desiccant for drying the incoming carbon fiber filaments.

[0029] Optionally, an online carbon fiber carbonization rate detection device may also include a constant temperature blower box;

[0030] The air outlet of the constant temperature blower box is connected to the box body and is used to inject nitrogen into the box body to blow away impurities attached to the surface of the carbon fiber filaments and create a positive pressure environment. The top of the box body is provided with an exhaust outlet.

[0031] This invention also provides an online detection method for carbon fiber carbonization rate, which uses the aforementioned online carbon fiber carbonization rate detection device to perform online detection. The detection method includes:

[0032] S1: The box is sealed to the outlet of the external high-temperature carbonization furnace through the connecting flange, so that the carbon fiber produced by the high-temperature carbonization furnace is introduced into the box through the connecting flange, and then sequentially passes through the upper side of the first fiber grating guide wheel assembly, the lower side of the first electrode guide wheel assembly, the lower side of the second electrode guide wheel assembly, and the upper side of the second fiber grating guide wheel assembly before being led out.

[0033] S2: The carbon fiber filaments first enter the drying chamber, where the desiccant inside removes the surface moisture. Then, constant temperature nitrogen is continuously introduced into the chamber through a constant temperature blower to blow away impurities attached to the surface of the carbon fiber filaments, suppress pyrolysis side reactions, and form a stable constant temperature positive pressure environment inside the chamber. The exhaust port on the chamber is used to discharge reaction waste gas and excess gas.

[0034] S3: Apply a constant current of microampere or milliampere level to the conductive wheel body of the two electrode guide wheel assemblies through an external current source, so that the current flows through the carbon fiber filaments in the middle section; at the same time, the voltage signal between the two electrode guide wheel assemblies is synchronously acquired through a multi-channel data acquisition device.

[0035] S4: The temperature-compensated grating and force-sensitive grating in the fiber optic guide wheel assembly are connected to an external demodulator to collect temperature reference signals and force-temperature composite strain signals. Then, through decoupling calculation, the real-time tension of the carbon fiber filament is obtained. Multiple temperature acquisition devices in the temperature acquisition assembly are used to synchronously collect the spatial field temperature signal on the carbon fiber filament path between the two electrode guide wheel assemblies.

[0036] S5: Calculate the original resistance value based on the acquired voltage signal, and use the real-time tension of the carbon fiber filament obtained by the external demodulator and the spatial field temperature signal on the carbon fiber filament path between the two electrode guide wheel assemblies to dynamically compensate the original resistance value and obtain the compensated resistance value.

[0037] S6: Based on the known relationship between the resistivity and carbonization rate of carbon fiber, the obtained compensated resistance value is converted to obtain the carbonization rate value.

[0038] Optionally, the temperature-compensated grating and force-sensitive grating in the fiber Bragg grating guide wheel assembly are connected to an external demodulator to acquire temperature reference signals and force-temperature composite strain signals. Then, through decoupling calculations, the real-time tension of the carbon fiber filament is obtained, including:

[0039] The center wavelength shift of the temperature-compensated grating and the sensitive grating are simultaneously demodulated using an external demodulator.

[0040] Based on the center wavelength drift of the temperature-compensated grating, the first temperature value at the contact point between the fiber grating guide wheel assembly and the carbon fiber filament is calculated, and the temperature influence component of the first temperature value on the center wavelength drift of the sensitive grating is calculated.

[0041] By subtracting the temperature-affected component from the center wavelength shift of the sensitive grating, we obtain the strain wavelength shift caused solely by the tension of the carbon fiber filaments.

[0042] The real-time tension of the carbon fiber filament is calculated based on the strain wavelength drift.

[0043] Optionally, multiple temperature acquisition devices in the temperature acquisition component can be used to simultaneously acquire the spatial field temperature signal along the carbon fiber filament path between the two electrode guide wheel assemblies, including:

[0044] Along the running direction of the carbon fiber filament, the temperature at at least three different locations within the section between the two electrode guide wheel assemblies is simultaneously measured to obtain the spatial field temperature signal of the carbon fiber filament in the section between the two electrode guide wheel assemblies.

[0045] Optionally, the original resistance value is dynamically compensated to obtain a compensated resistance value, including:

[0046] Based on the real-time tension and the spatial temperature signal of the carbon fiber filament between the two electrode guide wheel assemblies, the piezoresistive effect compensation coefficient and the temperature effect compensation coefficient are determined respectively. The original resistance value is then corrected in real time based on the piezoresistive effect compensation coefficient and the temperature effect compensation coefficient to obtain the compensated resistance value.

[0047] Compared with the prior art, the online detection device and method for carbon fiber carbonization rate provided by the present invention have the following advantages:

[0048] (1) By integrating the unique device of voltammetry measurement and fiber optic multiphysics sensing, the voltage, spatial temperature field and real-time tension of carbon fiber can be collected synchronously and in situ. Based on these multidimensional data, the system uses an algorithm to dynamically decouple and compensate the measured resistance value, thereby effectively removing the coupling interference caused by temperature fluctuations and mechanical tension changes in the production environment. This allows the carbonization rate value finally output by the device to reflect the degree of evolution of the carbon fiber microstructure in a true and sensitive manner, so that the voltammetry method can obtain stable and reliable measurement results for carbon fiber carbonization rate in the actual production environment.

[0049] (2) By setting multiple temperature sensors in the electrode area, the spatial temperature distribution along the fiber is directly obtained, thereby accurately compensating for the temperature gradient effect caused by uneven airflow and Joule heating of current; at the same time, the fiber grating guide wheel assembly structure realizes synchronous in-situ decoupling of temperature and tension signals at the fiber contact point, eliminating the measurement error introduced by the piezoresistive effect. This scheme of synergistically stripping and compensating for multiple interferences from the physical source ensures the high reliability and stability of the measurement results.

[0050] (3) By integrating the sensitive grating and the temperature-compensated grating onto the fixed mandrel through the fiber grating guide wheel assembly, the radial pressure and contact temperature are directly and synchronously measured at the same physical point where the carbon fiber filament contacts the guide wheel. This allows the lattice deformation resistance change caused by production tension fluctuations to be accurately separated and subtracted from the measurement signal, thereby ensuring that the resistance value relied upon for subsequent calculations only reflects the carbonization process. This solves the core problem of tension interference not being able to be removed in traditional methods.

[0051] (4) The drying oven actively adsorbs moisture by filling it with desiccant, avoiding short circuits or errors in electrical measurements caused by surface water film; the nitrogen injected into the constant temperature blower can not only blow away surface impurities, but the positive pressure environment it creates can also effectively suppress side reactions such as pyrolysis of carbon fiber in the detection area, prevent by-products from contaminating the electrodes and fiber surfaces, and ensure that subsequent voltammetry measurements are carried out under consistent and controllable initial conditions, which greatly improves the repeatability and reliability of online detection. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the overall structure of an online carbon fiber carbonization rate detection device according to the present invention;

[0053] Figure 2 This is a schematic diagram of the fiber grating guide wheel assembly structure of an online carbon fiber carbonization rate detection device according to the present invention;

[0054] Figure 3 This is a schematic diagram of the electrode guide wheel assembly structure of an online carbon fiber carbonization rate detection device according to the present invention;

[0055] Figure 4 This is a schematic diagram of the temperature acquisition component of the growth device of the online carbonization rate detection device for carbon fibers according to the present invention.

[0056] Figure 5 This is a flowchart illustrating the steps of an online carbonization rate detection method for carbon fibers according to the present invention.

[0057] In the diagram: 1. Chamber; 2. Guide wheel assembly; 21. Fiber optic grating guide wheel assembly; 211. Fixed spindle; 212. Rotating sleeve; 213. Temperature-compensated grating; 214. Sensitive grating; 22. Electrode guide wheel assembly; 221. Insulated guide wheel shaft; 222. Conductive wheel body; 3. Multi-channel data acquisition unit; 4. Temperature acquisition component; 41. Mounting bracket; 42. Temperature acquisition unit; 5. Drying oven; 6. Constant temperature blower box. Detailed Implementation

[0058] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0059] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention based on the specific circumstances.

[0060] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention.

[0061] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0062] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0063] The following disclosure provides numerous different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples. Such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. Additionally, examples of various specific processes and materials are provided in this invention; however, those skilled in the art will recognize the applicability of other processes and / or the use of other materials.

[0064] Please see Figure 1-4 The present application proposes an online carbon fiber carbonization rate detection device, which includes a housing 1, a guide wheel assembly 2, a multi-channel data acquisition unit 3, and a temperature acquisition component 4.

[0065] like Figure 1The enclosure 1 has a connecting flange at one end for connecting to an external carbonization furnace; the guide wheel assembly 2 includes a fiber optic guide wheel assembly 21 and an electrode guide wheel assembly 22 for guiding and measuring the running carbon fiber filament; the fiber optic guide wheel assembly 21 includes two components, which are arranged on the front and rear sides of the enclosure 1 along the running direction of the carbon fiber, for measuring the real-time tension of the carbon fiber filament; the electrode guide wheel assembly 22 includes two components, which are arranged between the fiber optic guide wheel assemblies 21 and located at the bottom of the two fiber optic guide wheel assemblies 21, and the two electrode guide wheel assemblies 22 are electrically connected to an external current source for applying a constant measurement current to the carbon fiber filament; the multi-channel data acquisition unit 3 is located outside the enclosure 1, and the detection end of the multi-channel data acquisition unit (3) extends into the enclosure 1 and is electrically connected to the two electrode guide wheel assemblies 22 for applying current to the carbon fiber filament and extracting a voltage measurement signal; the temperature acquisition component 4 is arranged on the carbon fiber filament path between the two electrode guide wheel assemblies 22 for measuring the spatial temperature field of the carbon fiber filament.

[0066] Specifically, the fiber optic guide wheel assembly 21 for tension and temperature measurement, the electrode guide wheel assembly 22 for electrical measurement, and the temperature acquisition assembly 4 for spatial temperature field measurement are spatially partitioned and functionally coordinated. The carbon fiber filaments are sequentially wound around the fiber optic guide wheel assembly 21 and the electrode guide wheel assembly 22 of the guide wheel assembly 2, ensuring that the tension, spatial temperature, and voltage signals all come from the same section of the fiber being measured and are strictly synchronized in time. This provides a precise and homogeneous physical field input for subsequent data fusion and dynamic compensation, fundamentally solving the problem in traditional single voltammetry measurement where the resistance signal is coupled by multiple environmental interferences and cannot be separated. The multi-channel data acquisition unit 3 synchronously acquires all electrical signals, ensuring the temporal consistency of the data. The entire device is seamlessly integrated with the production line through the connecting flange, realizing online, continuous, and non-destructive testing of the fiber at the carbonization furnace outlet, laying a solid physical foundation for real-time inversion of the core process parameter of carbonization rate.

[0067] In some embodiments, such as Figure 2 The fiber optic grating guide wheel assembly 21 includes a fixed spindle 211, a rotating sleeve 212, a temperature-compensated grating 213, and a force-sensitive grating 214. The two ends of the fixed spindle 211 are fixed to the inner wall of the housing 1. The rotating sleeve 212 is rotatably connected to the fixed spindle 211 through symmetrically arranged bearings and is used to contact and guide the carbon fiber filaments. The temperature-compensated grating 213 is fixed to the fixed spindle 211 and is connected to an external demodulator signal to provide a temperature reference signal. The force-sensitive grating 214 is fixed to the fixed spindle 211 and is located between the two bearings. The force-sensitive grating 214 is connected to an external demodulator signal to sense the axial strain of the fixed spindle 211 caused by tension.

[0068] Specifically, the fiber grating guide wheel assembly 21 in this embodiment is a key innovative component for achieving in-situ synchronous decoupling of tension and temperature interference. Its stationary shaft and moving wheel design of the fixed mandrel 211 and rotating sleeve 212 has dual advantages: mechanically, the rotating sleeve 212 ensures the smooth passage of carbon fiber filaments and avoids friction damage; in terms of sensing, placing the precise and fragile FBG sensing system inside the stationary fixed mandrel 211 solves the problems of unreliable signal transmission and short lifespan on rotating components, ensuring the stability and high reliability of long-term measurements.

[0069] The core lies in the coordinated setup of the temperature-compensated grating 213 and the force-sensitive grating 214: the ambient temperature change sensed by the temperature-compensated grating 213 represents the thermo-optical effect and thermal expansion effect experienced by the force-sensitive grating 214; by subtracting the pure temperature influence component determined by the temperature-compensated grating 213 from the mixed wavelength drift measured by the force-sensitive grating 214, the strain caused solely by radial tension can be accurately calculated, enabling the device to directly and in real-time separate the true tension signal at the same physical contact point between the carbon fiber filament and the guide wheel, thereby providing an accurate input for subsequent compensation of resistance errors caused by the piezoresistive effect.

[0070] In some embodiments, such as Figure 3 The electrode guide wheel assembly 22 includes an insulated guide wheel shaft 221 and a conductive wheel body 222. The insulated guide wheel shaft 221 and the conductive wheel body 222 are fixedly connected to form an integral electrode guide wheel. The conductive wheel body 222 is rotatably connected to the housing 1 through the insulated guide wheel shaft 221 and is used to contact and guide the carbon fiber filament. The outer surface of the conductive wheel body 222 is covered with a conductive coating. The conductive wheel body 222 is electrically connected to an external current source and is used to apply a constant measurement current to the carbon fiber filament. The detection end of the multi-channel data acquisition unit 3 is electrically connected to the conductive wheel body 222 and is used to measure the voltage signal between the two electrode guide wheel assemblies 22.

[0071] Specifically, this embodiment ensures the accuracy and stability of the voltmeter-ammeter method measurement. The design of the insulated guide wheel shaft 221 is fundamental, ensuring complete electrical isolation between the charged conductive wheel 222 and the grounded housing 1, preventing leakage or short circuit of the measurement current, and ensuring that all injected current flows through the carbon fiber filament itself. The highly conductive coating on the surface of the conductive wheel 222 is crucial, reducing the contact resistance and contact noise between the electrode and the high-speed moving carbon fiber filament, avoiding voltage signal fluctuations caused by unstable contact points, thereby obtaining a clear and stable original electrical signal. Setting both the current injection and voltage measurement points on the conductive wheel 222 constitutes a standard four-wire measurement concept, which can effectively eliminate the influence of lead resistance. The two electrode guide wheel assemblies 22 and the carbon fiber filament located between them together form an independent measurement circuit. This circuit is physically and electrically decoupled from the fiber optic grating guide wheel assembly 21 responsible for tension and temperature measurement. This design avoids mutual interference between measurement systems and provides a guarantee for the multi-channel data acquisition unit 3 to obtain a high-fidelity original voltage signal.

[0072] In some embodiments, such as Figure 4 The temperature acquisition component 4 includes a mounting frame 41 and a temperature acquisition device 42. The mounting frame 41 is fixed inside the housing 1 and spans between the conductive wheels 222 of the two electrode guide wheel assemblies 22. Multiple temperature acquisition devices 42 are fixed on the mounting frame 41 and arranged at intervals along the running direction of the carbon fiber filament. The temperature acquisition devices 42 are in contact with or adjacent to the surface of the carbon fiber filament and are used to simultaneously measure the temperature at different locations of the carbon fiber filament.

[0073] Specifically, the core contribution of this embodiment lies in realizing direct and distributed sensing of the spatial temperature field of the measurement area. By arranging multiple temperature acquisition devices 42 between two voltage measurement points, namely between the conductive wheel 222, it is possible to synchronously acquire the continuous temperature distribution profile on this key measurement segment, namely the spatial temperature field matrix. This matrix data is crucial: First, it provides a non-uniform temperature correction reference for subsequent resistivity temperature compensation, rather than a single temperature value, thereby accurately compensating for resistance drift caused by local overheating or overcooling. This ensures that even with complex thermal disturbances, the system can obtain the true thermal state of the carbon fiber filament during energized measurement, which is one of the decisive factors in improving the accuracy and repeatability of the carbonization rate inversion model.

[0074] In some embodiments, such as Figure 1 The aforementioned online carbonization rate detection device for carbon fibers also includes a drying chamber 5; the drying chamber 5 is located at one end of the chamber 1 connected to the external carbonization furnace, and the drying chamber 5 is filled with a desiccant for drying the incoming carbon fiber filaments.

[0075] Specifically, the function of drying chamber 5 is to eliminate a key interfering factor—moisture—at the source. After the carbon fiber filaments come out of the high-temperature furnace, their surface may adsorb ambient moisture, forming a thin water film. If left untreated, this water film will cause two serious problems at the electrode contact points: first, it will cause micro-short circuits or current shunting, causing the measured resistance value to deviate significantly from the true value; second, it will accelerate electrochemical corrosion, contaminate the conductive coating of the electrode, and affect long-term contact stability. In this embodiment, by allowing the fiber to pass through a desiccant environment, CaCl2 desiccant can be used to fill drying chamber 5. Utilizing the strong physical adsorption capacity of CaCl2 desiccant, the humidity of the fiber surface and the surrounding gas is actively and efficiently reduced, thereby ensuring that the carbon fiber filaments enter the core detection area in a dry state. This creates a stable and reliable initial electrical condition for subsequent voltammetry measurements, which is an important pretreatment step to ensure measurement accuracy and long-term operational stability of the device.

[0076] In some embodiments, such as Figure 1 The aforementioned online carbonization rate detection device for carbon fibers also includes a constant temperature blower box 6; the air outlet of the constant temperature blower box 6 is connected to the box body 1 and is used to inject nitrogen into the box body 1 to blow away impurities attached to the surface of the carbon fiber filaments and create a positive pressure environment; the top of the box body 1 is provided with an exhaust outlet.

[0077] Specifically, the constant-temperature blower box 6 constructs an actively controlled macroscopic detection environment for the entire detection device; the constant-temperature nitrogen gas introduced creates a uniform and stable temperature field within the chamber 1, serving as the background for spatial temperature field measurement and reducing the direct impact of drastic fluctuations in external ambient temperature on the detection system; the continuous airflow acts as a purging and cleaning agent, effectively removing trace amounts of dust or lint from the surface of the carbon fiber filaments, preventing their accumulation on the electrodes or sensors; most importantly, the positive-pressure nitrogen environment effectively isolates external air, especially oxygen, thereby strongly suppressing possible side reactions such as oxidation and pyrolysis of the carbon fiber filaments in the detection area, avoiding unpredictable drift in resistivity caused by continuous chemical reactions on the fiber surface; the exhaust outlet ensures gas circulation and renewal, preventing the accumulation of byproduct gas and contamination of the optical window or electrode surface; these measures together ensure that the measurement process is carried out in a chemically inert, thermally stable, and physically clean environment, greatly improving the accuracy and repeatability of online detection results.

[0078] This invention also provides an online method for detecting the carbonization rate of carbon fibers, such as... Figure 5 As shown, online detection is performed using the aforementioned online carbonization rate detection device. The detection method includes:

[0079] S1: The housing is sealed to the outlet of the external high-temperature carbonization furnace through the connecting flange, so that the carbon fiber produced by the high-temperature carbonization furnace is introduced into the housing through the connecting flange, and then sequentially passes through the upper side of the first fiber grating guide wheel assembly, the lower side of the first electrode guide wheel assembly, the lower side of the second electrode guide wheel assembly, and the upper side of the second fiber grating guide wheel assembly before being led out.

[0080] Specifically, this step establishes the physical basis for the measurement; the carbon fiber filament stably passes through the detection area in a preset "high-low-high" spatial path. This path ensures that the fiber maintains stable electrical contact with the conductive wheels of the two electrode guide wheel assemblies to form a measurement circuit, while also ensuring full contact with the rotating sleeves of the two fiber grating guide wheel assemblies to transmit mechanical tension; all guide wheels work together to ensure that the fiber moves accurately and maintains stable tension during the detection process.

[0081] S2: The carbon fiber filaments first enter the drying chamber, where the desiccant inside removes the surface moisture. Then, constant-temperature nitrogen is continuously introduced into the chamber through a constant-temperature blower to blow away impurities attached to the surface of the carbon fiber filaments, suppress pyrolysis side reactions, and create a stable constant-temperature positive pressure environment inside the chamber. The exhaust port on the chamber is used to discharge reaction waste gas and excess gas.

[0082] Specifically, this step aims to eliminate environmental interference and create baseline conditions for accurate measurement. First, the desiccant in the drying chamber, such as CaCl2, deeply adsorbs moisture from the fiber surface and the air inside the chamber, preventing water molecules from conducting electricity and causing short circuits or errors in subsequent voltammetry measurements. Subsequently, the injection of constant-temperature nitrogen achieves three effects: first, it blows away dust or flocculent matter that may be attached to the fiber surface; second, the inert positive pressure environment of nitrogen can effectively suppress additional pyrolysis or condensation side reactions of high-temperature carbon fiber filaments in the detection zone, preventing byproducts from contaminating the electrode or fiber surface; and third, it maintains the overall stability of the temperature field in the detection zone, reducing temperature fluctuations caused by external airflow disturbances and reducing thermal noise at the source.

[0083] S3: Apply a constant current of microampere or milliampere level to the conductive wheel body of the two electrode guide wheel assemblies through an external current source, so that the current flows through the carbon fiber filaments in the middle section; at the same time, the voltage signal between the two electrode guide wheel assemblies is synchronously acquired through a multi-channel data acquisition device.

[0084] Specifically, this step performs a classic voltammetric method measurement; an external precision constant current source is connected to the conductive wheel of the electrode guide wheel assembly via wires, injecting a known, small, and stable DC current into the carbon fiber filament segment between the two electrode guide wheel assemblies; due to the conductive coating on the outer surface of the conductive wheel, good electrical contact with the fiber is ensured, allowing the current to flow stably; at the same time, the high-impedance voltage measurement channel of the multi-channel data acquisition unit accurately captures the voltage drop between the two electrode guide wheel assemblies; according to Ohm's law, the original resistance value of the carbon fiber filament segment can be calculated.

[0085] S4: The temperature-compensated grating and force-sensitive grating in the fiber optic guide wheel assembly are connected to an external demodulator to collect temperature reference signals and force-temperature composite strain signals. Then, through decoupling calculation, the real-time tension of the carbon fiber filament is obtained. The temperature signal of the spatial field on the path of the carbon fiber filament between the two electrode guide wheel assemblies is collected synchronously through multiple temperature acquisition devices in the temperature acquisition assembly.

[0086] Specifically, this step is the core innovation for achieving high-precision online detection. Its purpose is to synchronously and in-situ collect all the key interfering physical quantities that cause changes in resistance. These interferences are mainly divided into two categories: one is the piezoresistive effect caused by mechanical tension; the other is the complex temperature field effect caused by the environment, current thermal effect and fiber self-reaction heat. This step captures all this information completely by having two sets of sensing systems work in parallel.

[0087] In some embodiments, the center wavelength drift of the temperature-compensated grating and the force-sensitive grating are simultaneously demodulated by an external demodulator; based on the center wavelength drift of the temperature-compensated grating, the first temperature value at the contact point between the fiber optic grating guide wheel assembly and the carbon fiber filament is calculated, and the temperature influence component of the first temperature value on the center wavelength drift of the force-sensitive grating is calculated; the temperature influence component is subtracted from the center wavelength drift of the force-sensitive grating to obtain the strain wavelength drift caused only by the tension of the carbon fiber filament; based on the strain wavelength drift, the real-time tension of the carbon fiber filament is calculated.

[0088] Specifically, the system synchronously acquires the center wavelength values ​​of the temperature-compensated grating and the sensitive grating. Since the temperature-compensated grating is loosely packaged and in a mechanically free state, the change in its center wavelength is only caused by temperature changes. Therefore, by consulting the pre-calibrated "wavelength-temperature" correspondence table of the grating or by directly calculating through the calibration coefficient, the temperature value position can be obtained, that is, the real-time contact point temperature value of the contact area between the fiber optic grating guide wheel assembly and the carbon fiber filament. This process utilizes the basic principle of fiber optic grating temperature measurement, that is, its reflected wavelength will drift linearly with temperature.

[0089] After obtaining the precise contact point temperature value, the signal of the sensitive grating can be decoupled. The sensitive grating is rigidly attached to the fixed mandrel, and its center wavelength change is affected by both temperature and axial strain. The system calculates the contribution of the current temperature to the wavelength drift of the sensitive grating, i.e., the temperature influence component, based on the contact point temperature value and the temperature sensitivity coefficient calibrated by the sensitive grating itself.

[0090] Subsequently, after subtracting the temperature-affected component from the total wavelength drift measured by the sensitive grating, the remaining wavelength drift is purely caused by the axial strain of the fixed mandrel. This strain directly originates from the mechanical deformation caused by the tension of the carbon fiber filament transmitted through the guide wheel structure. Finally, based on the strain sensitivity coefficient calibrated by the sensitive grating and the mechanical transmission coefficient of the guide wheel structure, the real-time running tension of the carbon fiber filament can be calculated. .

[0091] In some embodiments, multiple temperature acquisition devices in the temperature acquisition component synchronously acquire the spatial field temperature signal on the carbon fiber filament path between the two electrode guide wheel assemblies. Specifically, along the running direction of the carbon fiber filament, the temperature at at least three different locations within the section between the two electrode guide wheel assemblies is synchronously measured to obtain the spatial field temperature signal of the carbon fiber filament in the section between the two electrode guide wheel assemblies.

[0092] These temperature acquisition devices are fiber Bragg grating-based temperature sensors, each FBG sensor based on its grating period Λ and effective refractive index. It has a specific central reflection wavelength. Satisfying the relation:

[0093] ;

[0094] When the temperature at the sensor's location changes, thermal expansion and thermo-optical effects will cause... Offset occurred This offset is related to the temperature change. The relationship between them is determined by the following formula:

[0095] ;

[0096] in, The temperature sensitivity coefficient of the FBG sensor is pre-calibrated.

[0097] During online measurement, the external fiber optic demodulator synchronously and at high speed demodulates the center wavelength of all temperature acquisition devices. , , ... The system calculates the temperature value corresponding to each measuring point in real time. , , ... The temperature data obtained at the same time and spatially distributed along the fiber constitute the spatial temperature field matrix of the measurement section.

[0098] ;

[0099] This spatial temperature field matrix The dynamics reflect the spatial temperature signal of the carbon fiber filament in the measurement section due to uneven airflow, thermal fluctuations in the constant temperature chamber, and the Joule heating effect of the current.

[0100] S5: Calculate the original resistance value based on the acquired voltage signal, and use the real-time tension of the carbon fiber filament obtained by decoupling from the external demodulator and the spatial field temperature signal on the carbon fiber filament path between the two electrode guide wheel assemblies to dynamically compensate the original resistance value and obtain the compensated resistance value.

[0101] This step is the core of data processing, aiming to remove interference components from the obtained raw resistance values; raw resistance values The original resistance value is contaminated by temperature effects, including spatial temperature gradients and piezoresistive effects caused by tension; this step utilizes the decoupled multiphysics data to analyze the original resistance value. Make real-time corrections.

[0102] In some embodiments, based on the real-time tension The spatial field temperature signal of the carbon fiber filament between the two electrode guide wheel assemblies is used to determine the piezoresistive effect compensation coefficient and the temperature effect compensation coefficient, respectively. Based on the piezoresistive effect compensation coefficient and the temperature effect compensation coefficient, the original resistance value is corrected in real time to obtain the compensated resistance value.

[0103] Specifically, based on the physical properties of carbon fiber resistivity changing with temperature, and utilizing the real-time acquired spatial temperature field matrix... The system analyzes and quantifies the comprehensive impact of the current temperature distribution on resistance measurement using the space field temperature signal. The system determines one or a set of parameters that can characterize the current degree of thermal resistance drift through the built-in algorithm, such as fitting or weighted calculation based on calibration data. These parameters constitute the temperature effect compensation coefficient at this moment. This process makes full use of the temperature gradient information contained in the space field temperature signal, so that the determined coefficients can reflect the real impact of the non-uniform temperature field.

[0104] The system uses the real-time tension of the carbon fiber filament obtained from real-time decoupling. Based on the piezoresistive effect of carbon fiber, the relationship with the current real-time tension was determined. The corresponding parameter used to quantify the resistance change caused by piezoresistive effect is the piezoresistive effect compensation coefficient.

[0105] After obtaining the aforementioned real-time compensation coefficients, the system applies a preset compensation model for final calculation. This model is described as follows:

[0106] ;

[0107] Furthermore, the calculation of tension compensation is integrated to form a complete compensation calculation formula:

[0108] ;

[0109] In this calculation: The value of the thermal effect error function term is obtained by substituting the "temperature effect compensation coefficient" determined in the first stage into the corresponding algorithm. The value of the piezoresistive effect error function term is obtained by substituting the "piezoresistive effect compensation coefficient" determined in the first stage into the corresponding algorithm.

[0110] By performing this calculation, the system achieves the desired change in the original resistance value. Real-time dynamic compensation, outputting purified resistance values. .

[0111] S6: Based on the known relationship between the resistivity and carbonization rate of carbon fiber, the obtained compensated resistance value is converted to obtain the carbonization rate value.

[0112] Specifically, the system substitutes the corrected true resistivity into the well-known "resistivity-carbonization rate" benchmark mapping model:

[0113] ;

[0114] in, The carbonization rate after compensation. To substitute the purified resistance value into the mapping function G for calculation, thereby inverting and outputting high-precision carbon fiber carbonization rate detection results in real time, and realizing accurate quantitative characterization of production process quality.

[0115] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An online carbonization rate detection device for carbon fibers, characterized in that, It includes a housing (1), a guide wheel assembly (2), a multi-channel data acquisition unit (3), and a temperature acquisition component (4), among which, One end of the housing (1) is provided with a connecting flange for connecting to an external carbonization furnace; The guide wheel assembly (2) includes a fiber grating guide wheel assembly (21) and an electrode guide wheel assembly (22) for guiding and measuring the running carbon fiber filaments; The fiber grating guide wheel assembly (21) includes two, which are arranged on the front and rear sides of the housing (1) along the running direction of the carbon fiber, and are used to measure the real-time tension of the carbon fiber filament. The electrode guide wheel assembly (22) includes two, which are disposed between the fiber grating guide wheel assembly (21) and located at the bottom of the two fiber grating guide wheel assemblies (21). The two electrode guide wheel assemblies (22) are electrically connected to an external current source for applying a constant measurement current to the carbon fiber filament. The multi-channel data acquisition device (3) is located outside the housing (1). The detection end of the multi-channel data acquisition device (3) extends into the housing (1) and is electrically connected to the two electrode guide wheel assemblies (22) for applying current to the carbon fiber filament and drawing out voltage measurement signals. The temperature acquisition component (4) is set on the carbon fiber filament path between the two electrode guide wheel assemblies (22) and is used to measure the spatial temperature field of the carbon fiber filament. The fiber grating guide wheel assembly (21) includes a fixed mandrel (211), a rotating sleeve (212), a temperature-compensated grating (213), and a force-sensitive grating (214), wherein, The two ends of the fixed mandrel (211) are fixed to the inner wall of the box (1); The rotating sleeve (212) is rotatably connected to the fixed mandrel (211) through symmetrically arranged bearings, and is used to contact and guide the carbon fiber filaments; The temperature-compensated grating (213) is fixed on the fixed spindle (211) and connected to the signal of the external demodulator to provide a temperature reference signal; The sensitive grating (214) is fixed on the fixed spindle (211) and located between two bearings. The sensitive grating (214) is connected to the signal of an external demodulator and is used to sense the axial strain of the fixed spindle (211) caused by tension. The electrode guide wheel assembly (22) includes an insulated guide wheel shaft (221) and a conductive wheel body (222), wherein, The insulating guide wheel shaft (221) is fixedly connected to the conductive wheel body (222) to form an integral electrode guide wheel; The conductive wheel (222) is rotatably connected to the housing (1) via an insulated guide wheel shaft (221) for contacting and guiding carbon fiber filaments. The outer surface of the conductive wheel (222) is covered with a conductive coating. The conductive wheel (222) is electrically connected to an external current source and is used to apply a constant measuring current to the carbon fiber filament; The detection end of the multi-channel data acquisition unit (3) is electrically connected to the conductive wheel body (222) and is used to measure the voltage signal between the two electrode guide wheel assemblies (22).

2. The online carbonization rate detection device for carbon fiber according to claim 1, characterized in that, The temperature acquisition component (4) includes a mounting bracket (41) and a temperature acquisition device (42), wherein, The mounting bracket (41) is fixed inside the housing (1) and spans between the conductive wheels (222) of the two electrode guide wheel assemblies (22); The temperature acquisition device (42) includes multiple devices, which are fixed on the mounting frame (41) and arranged at intervals along the running direction of the carbon fiber filament. The temperature acquisition device (42) is in contact with or adjacent to the surface of the carbon fiber filament and is used to simultaneously measure the temperature at different positions of the carbon fiber filament between the two electrode guide wheel assemblies (22).

3. The online carbonization rate detection device for carbon fiber according to claim 1, characterized in that, It also includes a drying oven (5); The drying chamber (5) is located at one end of the chamber (1) connected to the external carbonization furnace. The drying chamber (5) is filled with desiccant for drying the incoming carbon fiber filaments.

4. The online carbonization rate detection device for carbon fiber according to claim 3, characterized in that, It also includes a constant temperature blower box (6); The air outlet of the constant temperature blower box (6) is connected to the box body (1) and is used to inject nitrogen into the box body (1) to blow away impurities attached to the surface of the carbon fiber and create a positive pressure environment. The top of the box body (1) is provided with an exhaust outlet.

5. A method for online detection of carbon fiber carbonization rate, characterized in that, Online detection is performed using the online carbon fiber carbonization rate detection device according to any one of claims 1-4, and the detection method includes: S1: The box is sealed to the outlet of the external high-temperature carbonization furnace through the connecting flange, so that the carbon fiber produced by the high-temperature carbonization furnace is introduced into the box through the connecting flange, and then sequentially passes through the upper side of the first fiber grating guide wheel assembly, the lower side of the first electrode guide wheel assembly, the lower side of the second electrode guide wheel assembly, and the upper side of the second fiber grating guide wheel assembly before being led out. S2: The carbon fiber filaments first enter the drying chamber, where the desiccant inside removes the surface moisture. Then, constant temperature nitrogen is continuously introduced into the chamber through a constant temperature blower to blow away impurities attached to the surface of the carbon fiber filaments, suppress pyrolysis side reactions, and form a stable constant temperature positive pressure environment inside the chamber. The exhaust port on the chamber is used to discharge reaction waste gas and excess gas. S3: Apply a constant current of microampere or milliampere level to the conductive wheel body of the two electrode guide wheel assemblies through an external current source, so that the current flows through the carbon fiber filaments in the middle section; at the same time, the voltage signal between the two electrode guide wheel assemblies is synchronously acquired through a multi-channel data acquisition device. S4: The temperature-compensated grating and force-sensitive grating in the fiber optic guide wheel assembly are connected to an external demodulator to collect temperature reference signals and force-temperature composite strain signals. Then, through decoupling calculation, the real-time tension of the carbon fiber filament is obtained. Multiple temperature acquisition devices in the temperature acquisition assembly are used to synchronously collect the spatial field temperature signal on the carbon fiber filament path between the two electrode guide wheel assemblies. S5: Calculate the original resistance value based on the acquired voltage signal, and use the real-time tension of the carbon fiber filament obtained by the external demodulator and the spatial field temperature signal on the carbon fiber filament path between the two electrode guide wheel assemblies to dynamically compensate the original resistance value and obtain the compensated resistance value. S6: Based on the known relationship between the resistivity and carbonization rate of carbon fiber, the obtained compensated resistance value is converted to obtain the carbonization rate value.

6. The online detection method for carbon fiber carbonization rate according to claim 5, characterized in that, The temperature-compensated grating and force-sensitive grating in the fiber Bragg grating guide wheel assembly are connected to an external demodulator to acquire temperature reference signals and force-temperature composite strain signals. Then, through decoupling calculations, the real-time tension of the carbon fiber filament is obtained, including: The center wavelength shift of the temperature-compensated grating and the sensitive grating are simultaneously demodulated using an external demodulator. Based on the center wavelength drift of the temperature-compensated grating, the first temperature value at the contact point between the fiber grating guide wheel assembly and the carbon fiber filament is calculated, and the temperature influence component of the first temperature value on the center wavelength drift of the sensitive grating is calculated. By subtracting the temperature-affected component from the center wavelength shift of the sensitive grating, we obtain the strain wavelength shift caused solely by the tension of the carbon fiber filaments. The real-time tension of the carbon fiber filament is calculated based on the strain wavelength drift.

7. The online detection method for carbon fiber carbonization rate according to claim 5, characterized in that, Multiple temperature acquisition devices in the temperature acquisition component synchronously acquire the spatial field temperature signal along the carbon fiber filament path between the two electrode guide wheel assemblies, including: Along the running direction of the carbon fiber filament, the temperature at at least three different locations within the section between the two electrode guide wheel assemblies is simultaneously measured to obtain the spatial field temperature signal of the carbon fiber filament in the section between the two electrode guide wheel assemblies.

8. The online detection method for carbon fiber carbonization rate according to claim 5, characterized in that, Dynamically compensate for the original resistance value to obtain the compensated resistance value, including: Based on the real-time tension and the spatial temperature signal of the carbon fiber filament between the two electrode guide wheel assemblies, the piezoresistive effect compensation coefficient and the temperature effect compensation coefficient are determined respectively. The original resistance value is then corrected in real time based on the piezoresistive effect compensation coefficient and the temperature effect compensation coefficient to obtain the compensated resistance value.

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