Method of electromagnetic heating of tyres for vulcanization

Abstract

This application discloses an electromagnetic heating method for tire vulcanization, comprising the following steps: Step one, dividing the tire mold into multiple regions corresponding to the tire crown, bead, and sidewall; applying heating power to each region using an electromagnetic heating device, the heating power matching the heat required by each region during the vulcanization process; Step two, dividing the tire vulcanization process into at least two dynamic control stages, including a rapid heating stage and a constant-temperature vulcanization stage; and calling an independent, pre-set set of control parameters for each dynamic control stage to perform real-time closed-loop feedback adjustment of the heating power. This electromagnetic heating method for tire vulcanization enables efficient, energy-saving, and intelligent precise temperature control throughout the entire tire vulcanization process, thereby achieving high-quality, low-energy, and intelligent tire manufacturing.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of tire vulcanization technology. More specifically, the present invention relates to an electromagnetic heating method for tire vulcanization. Background Technology

[0002] Tire vulcanization is a key process in rubber product manufacturing. Its core lies in causing a cross-linking reaction in raw rubber through heating, forming a finished tire with excellent physical and mechanical properties. In modern tire factories, the vulcanization process is usually completed inside a vulcanizing machine, where the heating system directly acts on the tire mold to ensure that the tire tread, sidewall, belt layer, and other parts undergo a full and uniform vulcanization reaction under set temperature and pressure.

[0003] Currently, the most commonly used tire vulcanizing heating technologies in industry include two main types: steam hot plate and resistance wire hot plate. Steam hot plate technology generates high-temperature steam in a boiler, which is then piped to the hot plate of the vulcanizing machine. The latent heat released by the condensation of the steam heats the mold. Resistance wire hot plate technology converts electrical energy into heat energy by embedding resistance heating elements inside the hot plate, which are then connected to heat the mold when energized.

[0004] Despite the widespread application of these technologies, significant technical shortcomings remain, hindering further improvements in tire product quality and production energy efficiency. Firstly, steam heating results in substantial heat loss during steam generation, transportation, and condensation, leading to a tire crown energy consumption ratio as high as 38%–42%. While resistance wire heating has a shorter heat transfer path, its energy conversion efficiency and heat dissipation from the heating plate still result in a tire crown energy consumption ratio of 32%–35%, indicating low overall energy utilization efficiency, which is inconsistent with the development trend of green manufacturing. Secondly, steam heating causes a temperature difference of 5–10℃ on the mold surface due to uneven steam flow and poor condensate drainage. Although resistance wire heating improves temperature uniformity, the temperature difference in the mold still exists at 2–5℃ due to the distribution density of heating elements and thermal response lag. This uneven temperature field leads to inconsistent vulcanization rates in different parts of the tire, easily resulting in localized over-vulcanization (leading to rubber aging and embrittlement) or under-vulcanization (leading to insufficient strength and poor wear resistance), severely affecting the consistency and reliability of the overall tire performance. Summary of the Invention

[0005] To address one or more of the technical problems mentioned above, this invention provides an electromagnetic heating method for tire vulcanization, which enables precise temperature control that is efficient, energy-saving, and intelligent throughout the entire tire vulcanization process, thereby achieving high-quality, low-energy, and intelligent tire manufacturing.

[0006] The tire vulcanization electromagnetic heating method provided by the present invention includes the following steps: Step 1, dividing the tire mold into multiple regions corresponding to the tire crown, bead, and sidewall, and applying heating power to each region through an electromagnetic heating device, wherein the heating power is matched with the heat power required by each region during the vulcanization process; Step 2, dividing the tire vulcanization process into at least two dynamic control stages, including a rapid heating stage and a constant temperature vulcanization stage, and calling an independent, pre-set set of control parameters for each dynamic control stage to perform real-time closed-loop feedback adjustment of the heating power.

[0007] In some embodiments, the electromagnetic heating device includes an outer ring area, an inner ring area, and a middle ring area for heating the tire crown area, the tire bead area, and the tire sidewall area of ​​the tire mold in sequence, and the number of turns density of the electromagnetic coil of the electromagnetic heating device decreases sequentially in the outer ring area, the inner ring area, and the middle ring area.

[0008] In some embodiments, along the radial direction of the electromagnetic heating device, the turns density of the electromagnetic coil in the outer ring region, inner ring region, and middle ring region is 1.35 turns / cm-1.45 turns / cm, 1.05 turns / cm-1.15 turns / cm, and 0.85 turns / cm-0.95 turns / cm, respectively.

[0009] In some embodiments, closed-loop feedback adjustment is obtained by the following formula:

[0010] ;

[0011] ;

[0012] ;

[0013] Where P(t) is the power value of the electromagnetic coil in the current cycle, and P(t-1) is the power value of the electromagnetic coil in the previous cycle. denoted as , where is the power adjustment value of the electromagnetic coil in the current cycle, e(t) is the temperature error at the current moment, e(t-1) and e(t-2) are the temperature errors of the previous cycle and the cycle before that, respectively, Kp, Ki, and Kd are the proportional coefficient, integral coefficient, and derivative coefficient, respectively, T is the preset target temperature, and T(t) is the measurement value of the temperature sensor installed in the tire mold in the current cycle.

[0014] In some embodiments, during the rapid heating phase, the target temperature T1 is 150℃+N, 0℃<N≤10℃, wherein Kp is 5.2, Ki is 0.05, and Kd is 0.8.

[0015] In some embodiments, the constant temperature vulcanization stage includes: a temperature adjustment stage, the temperature adjustment range of which is from T1 to T2, where T2 is 150℃-N, wherein Kp is 2.5, Ki is 0.35, and Kd is 1.2 during the temperature adjustment stage; and a temperature constant stage, the temperature range of which is 150℃±2℃, wherein Kp is 2.0, Ki is 0.1, and Kd is 0.5 during the temperature constant stage.

[0016] In some embodiments, the steps further include: setting a preset time point, and when the preset time point is reached, switching from the rapid heating stage to the temperature adjustment stage; or, when the temperature of all temperature measuring points reaches 95%-99% of the set temperature, switching from the rapid heating stage to the temperature adjustment stage.

[0017] In some embodiments, the steps further include: providing a ferrite magnetic strip on the non-heating side of the electromagnetic coil within the electromagnetic heating device, the ferrite magnetic strip being parallel to the electromagnetic coil, wherein the ferrite magnetic strip is arranged radially along the radial direction of the electromagnetic coil and covers the electromagnetic coil radially.

[0018] In some embodiments, a plurality of ferrite magnetic strips are provided, and the plurality of ferrite magnetic strips are distributed at equal intervals along the circumference of the electromagnetic coil.

[0019] In some embodiments, the coverage method of the ferrite magnetic strip is matched with the turns density of the electromagnetic coil, wherein the ferrite magnetic strip is fully covered in the outer and inner ring regions; and in the middle ring region, the ferrite magnetic strip is truncated or the cross-sectional area of ​​the ferrite magnetic strip is reduced.

[0020] The tire vulcanization electromagnetic heating method described above achieves the following: 1) By providing different heating power to different areas through the electromagnetic heating device, the heating power can be precisely applied to the required parts, ensuring the uniformity of tire vulcanization and thus significantly improving the tire's dynamic balance, durability, and safety. 2) By dividing the temperature control state into different segments for segmented control, ineffective power output is avoided, resulting in significant overall energy savings. In practical applications, the heating efficiency of the electromagnetic heating device is over 95%. Combined with optimized temperature control, the mold can be heated from 30°C to 150°C in just 25 minutes during the rapid heating phase, significantly improving production efficiency. Simultaneously, the energy consumption of the tire crown area can be reduced to 30%-33%, saving more than 10% energy compared to traditional methods, further significantly reducing energy consumption. 3) Different electromagnetic heating zones and control parameter groups can be flexibly set according to the vulcanization process curves of tires of different specifications (different rubber thicknesses and formulations), making the tire vulcanization electromagnetic heating method of this invention highly versatile and adaptable to various processes. Attached Figure Description

[0021] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent upon reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of the invention are illustrated by way of example and not limitation, and like or corresponding reference numerals denote like or corresponding parts, wherein:

[0022] Figure 1 This is a schematic flowchart of the tire vulcanization electromagnetic heating method according to an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the structure of a tire vulcanizing machine according to one embodiment of the present invention, which shows a single-mold tire mold;

[0024] Figure 3 for Figure 2 The diagram shows the structure of the electromagnetic heating device in the tire vulcanizing machine.

[0025] Figure 4 This is a schematic diagram of a tire vulcanizing machine according to another embodiment of the present invention, showing a multi-mode tire mold. Detailed Implementation

[0026] The technical solutions of the embodiments of this disclosure 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 disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0027] Figure 1 A flowchart illustrating the steps of a tire vulcanization electromagnetic heating method 100 according to an embodiment of the present invention is shown. Figure 2 A schematic diagram of a tire vulcanizing machine according to one embodiment is shown, in which a single-mold tire mold is shown. Figure 3 The structure of the electromagnetic heating device 300 is shown. For example... Figure 1 As shown, and in combination Figure 2 and Figure 3 The tire vulcanization electromagnetic heating method 100 includes the following steps:

[0028] Step S1: Divide the tire mold 200 into multiple regions corresponding to the tire crown 201, tire bead 202 and tire sidewall 203. Apply heating power to each region through the electromagnetic heating device 300. The heating power is matched with the heat required by each region during the vulcanization process.

[0029] Step 2 S2: Divide the tire vulcanization process into at least two dynamic control stages, including a rapid heating stage and a constant temperature vulcanization stage. Call an independent, pre-set set of control parameters for each dynamic control stage to perform real-time closed-loop feedback adjustment of the heating power.

[0030] Knownly, a tire includes a tread (including a shoulder), a bead, and a sidewall connecting the tread and the bead. In a specific implementation of the tire vulcanization electromagnetic heating method 100 according to an embodiment of the present invention:

[0031] In step S1, as Figure 2 and Figure 3 As shown, the mold cavity of the tire mold 200 is divided into multiple regions corresponding to the tire crown 201, tire bead 202, and tire sidewall 203, i.e. Figure 3 The crown, bead, and sidewall regions shown are concentrically arranged in a ring along the mold cavity of the tire mold 200. During the tire vulcanization heating process, the required heat power (demand power) differs between the crown 201, bead 202, and sidewall 203. In this application, the electromagnetic heating device 300 provides different heating power to different regions, allowing the heating power to be precisely applied to the desired areas, avoiding ineffective power output, achieving significant energy savings, and ensuring consistency in the degree of vulcanization across all parts of the tire.

[0032] In step S2, the rapid heating stage typically refers to the mold preheating stage, which is the initial stage of vulcanization. During this stage, the mold needs to be rapidly heated from room temperature (e.g., 20–30°C). This process involves the mold undergoing an endothermic phase to allow the tire carcass to quickly reach the rubber crosslinking conditions. The isothermal vulcanization stage typically includes a temperature adjustment stage and a temperature constant-temperature stage. In the temperature adjustment stage, as the tire vulcanizes, the rubber crosslinking reaction releases a small amount of heat, causing a slight increase in the internal temperature of the tire. This requires fine-tuning through the mold cooling system to avoid localized overheating and to counteract the heat released by the rubber crosslinking reaction during the mid-stage of vulcanization. The temperature constant-temperature stage precisely maintains the mold temperature at the basic process temperature. In summary, the temperature control requirements for the rapid heating stage and the isothermal vulcanization stage differ. The rapid heating stage experiences large temperature fluctuations and requires a fast system response. The isothermal vulcanization stage, on the other hand, has lower requirements for temperature control. Therefore, according to this application, by calling an independent, pre-set set of control parameters for each dynamic control stage to perform real-time closed-loop feedback adjustment of the heating power, it is possible to implement different control logics for different temperature control requirements, thereby effectively meeting the goal of intelligent and precise temperature control throughout the tire vulcanization process.

[0033] Through the above method, the tire vulcanization electromagnetic heating method 100 of this embodiment of the invention has the following advantages:

[0034] 1) By using the electromagnetic heating device 300 to provide different heating power to different areas, the heating power can be precisely applied to the required parts, ensuring the uniformity of tire vulcanization, thereby greatly improving the dynamic balance, durability and safety of the tire.

[0035] 2) By dividing the temperature control into different states for segmented control, ineffective power output is avoided, resulting in significant overall energy savings. In practical applications, the electromagnetic heating device 300 achieves a heating efficiency of over 95%. Combined with optimized temperature control, during the rapid heating phase, the mold can be heated from 30℃ to 150℃ in just 25 minutes, significantly improving production efficiency. Simultaneously, the energy consumption of the tire crown 201 section can be reduced to 30%-33%, saving more than 10% energy compared to traditional methods, further demonstrating significant energy conservation and consumption reduction.

[0036] 3) Different electromagnetic heating zones and control parameter groups can be flexibly set according to the vulcanization process curves of tires of different specifications (different rubber thickness and formula), so that the tire vulcanization electromagnetic heating method 100 of the present invention has strong versatility and process adaptability.

[0037] Please refer to Figure 2 and Figure 3 In some embodiments, the electromagnetic heating device 300 may include an outer ring area 301, an inner ring area 302, and a middle ring area 303 for heating the tire crown area, the bead area, and the sidewall area of ​​the tire mold 200 in sequence, and the number of turns of the electromagnetic coil 2 of the electromagnetic heating device 300 decreases sequentially in the outer ring area 301, the inner ring area 302, and the middle ring area 303.

[0038] In this application, the electromagnetic heating device 300 may include a substrate 1 and an electromagnetic coil 2 encapsulated within the substrate 1. The electromagnetic coil 2 is electrically connected to a controller (not shown in the figure). The electromagnetic coil 2 is arranged concentrically in a ring within the substrate 1 (e.g., Figure 3 (As shown). The number of turns of the electromagnetic coil 2 decreases sequentially in the outer ring region 301, the inner ring region 302, and the middle ring region 303, forming a gradient configuration.

[0039] With the above settings, the number of turns of the electromagnetic coil 2 is distributed in a gradient. When the input power of the controller is consistent, the electromagnetic coil 2 with a gradient distribution can generate different degrees of heating power in different areas. This ensures that the generated heat power distribution is precisely matched with the heat dissipation and heat demand of each area of ​​the mold, so as to better form an inherent gradient magnetic field distribution on the electromagnetic coil 2 plate that matches the energy consumption requirements of the tire mold 200 (tire crown 201 > tire bead 202 > tire sidewall 203).

[0040] In this application, the electromagnetic coil 2 generates an alternating magnetic field to heat the tire mold of the tire vulcanizing machine. Simultaneously, the electromagnetic heating device 300 also includes a metal frame fixedly fitted around the base plate 1 and used to connect the base plate 1 to the tire mold. In use, the electromagnetic coil 2 generates an alternating magnetic field that directly induces eddy currents inside the tire mold, generating heat and completing the heating of the tire mold. Compared to resistance heating and indirect heating methods that require heat transfer through a medium (steam, hot oil), this electromagnetic heating device 300 has higher thermal efficiency, less energy loss, and faster heating speed. In practical applications, when preheating and heating the tire mold, the preheating time is reduced by 40-70%, improving production efficiency. The heating efficiency can reach over 95%, effectively saving approximately 10-30% or more in operating energy consumption. Furthermore, the lifespan of the heating element (in this application, the electromagnetic coil 2; in the prior art, it is an electric heating tube) can be extended from 3-5 years to 5-10 years. It also eliminates energy waste and maintenance problems caused by leaks and spills during steam or hot oil operation, essentially achieving maintenance-free operation and reducing maintenance costs.

[0041] In this application, the gradient distribution of the electromagnetic coil 2 can be customized according to the thermal field finite element analysis (FEA) results of a specific tire mold 200 to suit the needs of different tires.

[0042] In some embodiments, along the radial direction of the electromagnetic heating device 300, the turns density of the electromagnetic coil 2 in the outer ring region 301, the inner ring region 302, and the middle ring region 303 are 1.35 turns / cm-1.45 turns / cm, 1.05 turns / cm-1.15 turns / cm, and 0.85 turns / cm-0.95 turns / cm, respectively.

[0043] In this application, the electromagnetic coil 2 is sequentially formed into a high-density region, a medium-density region, and a low-density region in the outer ring region 301, the inner ring region 302, and the middle ring region 303. The high-density region corresponds to the tire crown region, the medium-density region corresponds to the tire bead region, and the low-density region corresponds to the tire sidewall region. The electromagnetic coil 2 in the high-density region has the smallest turn spacing and the largest number of turns per unit width, with a turn density of approximately 1.35 turns / cm to 1.45 turns / cm, used to generate the strongest magnetic field and achieve the highest temperature heating. The electromagnetic coil 2 in the medium-density region has a moderate turn spacing and a turn density of approximately 1.05 turns / cm to 1.15 turns / cm, used to generate a moderate magnetic field and achieve moderate temperature heating. The electromagnetic coil 2 in the low-density region has the largest turn spacing and the fewest turns per unit width, with a turn density of approximately 0.85 turns / cm to 0.95 turns / cm, generating the weakest magnetic field to prevent localized overheating.

[0044] Through the above settings, the gradient heating achieved by the gradient-set electromagnetic coil 2 allows heat energy to be precisely applied to the required parts, thereby achieving the optimal energy-saving effect.

[0045] In some embodiments, closed-loop feedback regulation can be obtained by the following formula:

[0046] ;

[0047] ;

[0048] ;

[0049] Where P(t) is the power value of electromagnetic coil 2 in the current cycle, and P(t-1) is the power value of electromagnetic coil 2 in the previous cycle. t is the power adjustment value of electromagnetic coil 2 in the current cycle, e(t) is the temperature error at the current moment, e(t-1) and e(t-2) are the temperature errors of the previous cycle and the cycle before that, respectively, Kp, Ki and Kd are the proportional coefficient, integral coefficient and derivative coefficient, respectively, T is the preset target temperature, and T(t) is the measurement value of the temperature sensor installed in the tire mold in the current cycle.

[0050] Using the above formula, this application matches a set of independent, pre-tuned optimal control parameters (Kp, Ki, Kd) for each stage to achieve intelligent temperature control throughout the entire cycle and make the intelligent temperature control more accurate.

[0051] In some embodiments, the tire vulcanization process includes a rapid heating stage and a constant-temperature vulcanization stage. Wherein:

[0052] During the rapid heating phase, the target temperature T1 is 150℃+N, where 0℃<N≤10℃. During this phase, Kp is 5.2, Ki is 0.05, and Kd is 0.8.

[0053] The rapid heating stage typically refers to the preheating stage of the mold, which is the initial stage of vulcanization. During this stage, the mold needs to be rapidly heated from room temperature (e.g., 20–30°C). This process involves the mold undergoing an endothermic phase to allow the tire carcass to quickly reach the rubber crosslinking conditions. However, due to factors such as equipment, mold, or cooled tire carcass, the mold temperature can easily fluctuate and drop during the rapid heating process. Simultaneously, overshoot must be suppressed. Therefore, during the rapid heating stage, the temperature usually needs to be rapidly increased to the initial vulcanization target temperature T1, where T1 is 150°C + N, and 0°C < N ≤ 10°C. Rapid heating of the tire carcass to quickly reach the rubber crosslinking conditions requires a fast system response. In this application, during the rapid heating stage, Kp is set to 5.2, Ki to 0.05, and Kd to 0.8. Setting a larger Kp allows the system to respond quickly and with high power to large errors. Setting a smaller Ki or using integral separation (Ki = 0 when the error exceeds a certain threshold, such as 10°C) prevents severe integral saturation due to long-term error accumulation, thus avoiding significant temperature overshoot. By setting an appropriate Kd, the derivative term can effectively "brake" when the temperature approaches the set value, smoothly approaching the target temperature.

[0054] The constant-temperature vulcanization stage can include a temperature adjustment stage and a temperature constant stage, wherein:

[0055] During the temperature adjustment phase, the temperature adjustment range is from T1 to T2, where T2 is 150℃-N. During this phase, Kp is 2.5, Ki is 0.35, and Kd is 1.2.

[0056] This stage is the mid-stage of vulcanization. The rubber crosslinking reaction is exothermic, releasing a small amount of heat (approximately 50–100 kJ / kg rubber), causing a slight increase in the internal temperature of the tire. The mold temperature needs to be readjusted, specifically through fine-tuning the mold cooling system, to prevent localized overheating. With the above settings, the control system automatically adjusts the mold temperature from T1 (150℃+N) at the initial stage of vulcanization to T2 (150℃-N). After fine-tuning and cooling, the heat released by the rubber crosslinking reaction in the mid-stage of vulcanization is effectively offset, thus maintaining the mold temperature precisely at the set value. At this point, the system is in dynamic equilibrium, with the main disturbances coming from rubber exothermics and ambient heat dissipation. In this application, by setting Kp to 2.5, Ki to 0.35, and Kd to 1.2, a smaller Kp is used to make the system response more stable and avoid frequent power fluctuations. Ki plays a crucial role; when rubber exothermics and causes a slight temperature increase, a negative error is generated. The integral term Ki continuously accumulates this negative error, thereby automatically and smoothly reducing the power output, achieving precise offsetting of the internal heat. A larger Kd can improve the system's ability to resist internal heat release and external disturbances, and maintain a flat temperature curve.

[0057] During the constant temperature phase, the temperature range is 150℃±2℃. In this phase, Kp is 2.0, Ki is 0.1, and Kd is 0.5.

[0058] This stage comprises the late vulcanization and standby phases. During this phase, the temperature of various parts of the tire gradually becomes uniform, requiring maintenance at the target vulcanization temperature of 150℃±2℃ (±2℃ being the fluctuation range) to enter a low-power heat preservation state. At this time, the system automatically restores the T2 (150℃-N) mold from the mid-vulcanization stage to the basic process temperature (e.g., 150℃). In this application, the temperature control requirements for this stage are reduced, with Kp set to 2.0, Ki to 0.1, and Kd to 0.5, prioritizing energy saving and stability.

[0059] In one embodiment, the step further includes: setting a preset time point, and when the preset time point is reached, switching from the rapid heating stage to the temperature adjustment stage. For example, the total vulcanization time is set to 40 minutes. The end point T1 of the rapid heating stage is 25 minutes. After 25 minutes, the process switches to the temperature adjustment stage, and the end point T2 of the temperature adjustment stage is 38 minutes.

[0060] In another embodiment, the steps further include: when the temperature of all temperature measuring points reaches 95%-99% (preferably 98%) of the set temperature, the system automatically switches from the rapid heating phase to the temperature adjustment phase, so as to more flexibly adapt to changes in ambient temperature. For example, the set temperature of the rapid heating phase is set to 150℃+N, and the system switches to the temperature adjustment phase when the temperature of all temperature measuring points reaches 98% of 150℃+N.

[0061] Please continue to refer to Figure 2 and Figure 3 In some embodiments, the tire vulcanization electromagnetic heating method 100 further includes: setting a ferrite magnetic strip 3 on the non-heating side of the electromagnetic coil 2 in the electromagnetic heating device 300, the ferrite magnetic strip 3 being parallel to the electromagnetic coil 2, wherein the ferrite magnetic strip 3 is arranged radially along the radial direction of the electromagnetic coil 2 and covers the electromagnetic coil 2 radially.

[0062] In this application, the ferrite magnetic strip 3 is disposed on the non-heating side of the electromagnetic coil 2, which can be used to concentrate magnetic lines of force, reduce magnetic leakage, and further strengthen the gradient magnetic field, thereby effectively ensuring the effective and precise implementation of heating power.

[0063] In some embodiments, a plurality of ferrite magnetic strips 3 are provided, and the plurality of ferrite magnetic strips 3 are distributed at equal intervals along the circumference of the electromagnetic coil 2.

[0064] With this setting, the ferrite magnetic strip 3 can be made of soft iron, A3 steel or soft magnetic alloy. The ferrite magnetic strip 3 has the characteristics of high magnetic permeability and low loss, which can be used to better concentrate magnetic lines of force, reduce magnetic leakage, and further strengthen the gradient magnetic field.

[0065] In some embodiments, the coverage method of the ferrite magnetic strip 3 is matched with the turn density of the electromagnetic coil 2. In the outer ring region 301 and the inner ring region 302, the ferrite magnetic strip 3 is covered with its full width; in the middle ring region 303, the ferrite magnetic strip 3 is covered with a stub or the cross-sectional area of ​​the ferrite magnetic strip 3 is reduced.

[0066] In this embodiment, the covering method of the ferrite magnetic strip 3 can be combined with the turns density of the electromagnetic coil 2 to collaboratively achieve zoned control of the magnetic field strength. In this application, since the spacing between the electromagnetic coils 2 in the middle ring region 303 is relatively large (low density), the ferrite magnetic strip 3 can be segmented to cover the electromagnetic coils 2, i.e., truncated coverage. Alternatively, the width of the ferrite magnetic strip 3 can be reduced, i.e., the cross-sectional area of ​​the ferrite magnetic strip 3 can be reduced, to cover the electromagnetic coils 2, so as to better adapt to the magnetic field strengthening of the low-density electromagnetic coils 2, reduce the influence of the ferrite magnetic strip 3 on the magnetic field, and ensure heating efficiency.

[0067] In some embodiments, the tire vulcanization electromagnetic heating method 100 further includes: employing a phase-shifted full-bridge resonant inverter circuit based on IGBT power modules, and controlling the output power by adjusting the phase shift angle or PWM duty cycle; setting temperature sensors in a preset area of ​​the tire mold 200, the temperature sensors collecting temperature data of each area in real time and feeding it back to the programmable logic controller (PLC). A piecewise gain scheduling control parameter group is run within the PLC. Piecewise gain scheduling is a strategy for controlling nonlinear or time-varying systems, adjusting the controller gain under different operating conditions or time periods to adapt to changes in the system's dynamic characteristics.

[0068] In conjunction with the above, a specific embodiment of a zone-controlled temperature electromagnetic heating device 300 applied to the electromagnetic heating method 100 for tire vulcanization is provided, specifically:

[0069] This embodiment provides an electromagnetic heating device 300 for vulcanizing 12R22.5 radial truck tires. The substrate 1 is made of high-temperature resistant epoxy fiberglass board with a diameter of approximately 1100 mm. Litz wire (electromagnetic coil 3) with a specification of "1000 strands x 0.1 mm" is selected and concentrically laid in CNC-machined grooves on the substrate. Based on thermal field simulation results, the radial direction is divided into three regions:

[0070] High-density area (corresponding area to the tire crown, radius 350-450mm): The turn density is designed to be 12 turns / cm.

[0071] Medium density zone (corresponding to the bead, radius 150-250mm): The turn density is designed to be 7 turns / cm.

[0072] Low-density area (corresponding area on the tire sidewall, radius 250-350mm): The turn density is designed to be 3 turns / cm.

[0073] In this embodiment, 36 PC40 manganese-zinc ferrite magnetic strips (100mm x 20mm x 5mm) are radially and closely arranged on the non-heated side of the electromagnetic coil 3, with the strips in the low-density area being shortened to 60mm. Holes are drilled at the outer edge of the tire crown, the center of the tire bead, and the thinnest part of the tire sidewall, and K-type armored thermocouples with a depth of 10mm are embedded therein.

[0074] In practical application, a Siemens S7-1200 series PLC was selected. The following settings were configured via HMI: Target vulcanization temperature: 155℃; Total vulcanization time: 40 minutes; Rapid heating phase, ending point T1: 25 minutes; Temperature adjustment phase, ending point T2: 38 minutes. After the controller starts, it executes the first stage PID parameters (rapid heating phase), with high-power IGBT output. After approximately 25 minutes, the temperature at each point reaches the range of 154-156℃. The system automatically switches to the second stage PID parameters (temperature adjustment phase), where the controller precisely adjusts the output power and actively compensates for the heat released by the rubber, ensuring that during T1 to T2, the tire crown temperature remains stable at 155℃±0.8℃, and the tire sidewall temperature remains stable at 153.5℃±0.8℃, with a temperature difference consistently less than 2℃. After T2, the system switches to the third stage PID parameters (constant temperature vulcanization phase) for low-power heat preservation until vulcanization is complete. The entire process achieves the preset precise segmented temperature control target.

[0075] In the prior art, tire vulcanizing machines are used to vulcanize tires, which can be any vehicle tire such as a bicycle, motorcycle, car, or truck tire, or an outer tire or inner tube. A tire vulcanizing machine includes a frame, a tire mold housed within the frame and having a moving mold and a stationary mold, a drive mechanism (e.g., a hydraulic device) mounted on the frame for driving the moving mold closer to or away from the stationary mold, and an electromagnetic heating device 300 for heating the tire mold.

[0076] In operation, the electromagnetic heating device 300 is first turned on to preheat and maintain the temperature of the tire mold. Once the tire mold stabilizes at the tire vulcanization temperature, the unvulcanized green tire (semi-finished tire) is placed into the stationary mold. Then, the drive mechanism is activated, driving the moving mold closer to the stationary mold to complete the mold closing action. During this process, it is ensured that all parts of the green tire are in full contact with the cavity wall of the tire mold and are heated evenly to achieve the vulcanization reaction. After vulcanization is complete, the drive mechanism reverses direction, moving the moving mold away from the stationary mold to complete the mold opening action. Finally, the vulcanized tire is removed from the tire mold, completing the entire tire vulcanization process.

[0077] Tire vulcanizing machines used for tire fluidization can be divided into single-mold tire vulcanizing machines (please refer to...). Figure 2 ) and multi-mode tire vulcanizing machine (please refer to Figure 4 When the tire vulcanizing machine is a single-mold tire vulcanizing machine, an electromagnetic heating unit 300 must be equipped on the side of both the stationary and moving molds furthest from each other. This ensures that both the stationary and moving molds receive independent and effective heating, providing suitable temperature conditions for the tire vulcanization process. When the tire vulcanizing machine is a multi-mold tire vulcanizing machine, each mold located at the edge needs to be equipped with an electromagnetic heating unit 300, positioned between it and the frame. Additionally, an electromagnetic heating unit 300 needs to be added between any two adjacent molds, ensuring that each mold has an electromagnetic heating unit 300 to heat both the moving and stationary molds, thereby ensuring that each tire mold receives uniform and sufficient heat for the tire vulcanization process.

[0078] In this invention, the electromagnetic heating device 300 in a single-mold tire vulcanizing machine provides unidirectional heating, while the electromagnetic heating device 300 in a multi-mold tire vulcanizing machine includes both unidirectional and bidirectional heating. The specific implementation parameter settings of the electromagnetic heating device 300 in this embodiment are further illustrated below, using existing single-mold and multi-mold tire vulcanizing machines as examples:

[0079] When it is a single-mold tire vulcanizing machine, the electromagnetic heating device 300 is set on both sides of the tire mold 200.

[0080] 1) The design power of electromagnetic coil 2 is 8kW, the power supply voltage of the controller is 3×380V, the voltage of electromagnetic coil 2 is 1000V, the frequency of electromagnetic coil 2 is 15-20kHz, and the inductance is 180-200uH. Electromagnetic coil 2 is made of 6²mm Litz wire, and its effective length is 38 meters. The outer diameter of electromagnetic coil 2 is 700mm, and the inner diameter is 320mm.

[0081] 2) Suitable tire mold specifications: 1 piece of 26×1.95 bicycle tire mold, the tire mold φ560-700mm is the tread, the required temperature is 170℃; the tire mold φ514-560mm is the sidewall, the required temperature is 150℃; the tire mold φ262-514mm is the bead, the required temperature is 165℃.

[0082] 3) Arrangement of turns for electromagnetic coil 2: Calculation of average circumference per turn (concentric rings, circumference ≈ π × average diameter). Specifically, tire crown 201 (radius of electromagnetic coil 2 280-350mm): average radius 315mm, circumference ≈ 1.98m / turn; tire sidewall 203 (radius of electromagnetic coil 2 257-280mm): average radius 268.5mm, circumference ≈ 1.69m / turn; tire bead 202 (radius of electromagnetic coil 2 160-257mm): average radius 208.5mm, circumference ≈ 1.31m / turn. Turns allocation scheme: total 23 turns (inductance ≈ 180-195μH). The center of electromagnetic coil 2 should deviate from the center of the mold by ≤1mm to avoid uneven temperature caused by magnetic field deviation.

[0083] 4) Turn spacing control: Crown 201: 70mm / 10 turns, turn spacing ≈7mm (wire diameter 3.5mm, gap ≈3.5mm); Bead 202: 97mm / 11-12 turns, turn spacing ≈8.1-8.8mm (gap ≈4.6-5.3mm); Sidewall 203: 23mm / 2 turns, turn spacing ≈11.5mm (gap ≈8mm).

[0084] With the above settings, the inductance of electromagnetic coil 2 is mainly determined by the number of turns (N), radial dimension, turn spacing, and permeability of the ferrite strip (at 20kHz, L≈k×N², k is a constant, and the ferrite strip can increase k by 30%-50%). Considering the dimensions of electromagnetic coil 2 (φ320-700mm) and 6²mm Litz wire, the total number of turns needs to be controlled between 23-24 turns (inductance of 23 turns ≈ 180-195μH, inductance of 24 turns ≈ 195-205μH, suitable for the 180-200μH range). Area correspondence: The radial range of electromagnetic coil 2 (inner diameter 320mm, outer diameter 700mm) is precisely aligned with the mold partition to ensure magnetic field coverage.

[0085] In this embodiment, the electromagnetic coil 2 is made of 6²mm Litz wire, which needs to be covered with a high-temperature resistant insulating layer (such as polyimide) to withstand 1000V voltage and avoid inter-turn breakdown. The ferrite magnetic strip 3 is a PC40 ferrite manganese zinc magnetic strip. The main material of the substrate 1 is FH-3. The frame of the electromagnetic heating device 300 is made of 45# steel.

[0086] It also includes the installation of ferrite magnetic strips 3, of which a total of 24 ferrite magnetic strips are evenly distributed around the circumference to prevent magnetic field fluctuations. Specifically, this includes: the mold area, the number of magnetic strips, the length of the magnetic strips, the coverage area, and their function. An example of the installation of the ferrite magnetic strips 3 is as follows:

[0087] The 201 tire crown has 24 loops, 70mm in diameter (covering a radius of 280-350mm), full-width coverage, and a reinforced magnetic field to help the 201 tire crown reach 170℃, while also increasing local inductance to compensate for insufficient number of turns. The 202 tire bead has 24 loops, 97mm in diameter (covering a radius of 257-280mm), full-width coverage, and a moderately reinforced magnetic field to stabilize the 202 tire bead at 165℃ and balance the overall inductance. The 203 tire sidewall has 24 loops, 23mm in diameter (covering only a radius of 160-257mm, truncated), truncated coverage, and a weakened magnetic field to control the 203 tire sidewall at 150℃ and avoid excessively increasing inductance.

[0088] Furthermore, the distance between the ferrite magnetic strip 3 and the electromagnetic coil 2 must be strictly controlled to 3mm (deviation ≤0.5mm), and they must be parallel and fitted together to prevent magnetic gaps from causing a decrease in inductance. The radial range of the ferrite magnetic strip 3 is completely consistent with the corresponding area of ​​the electromagnetic coil 2 (e.g., the magnetic strip of tire crown 201 does not exceed a radius of 280-350mm) to avoid magnetic field diffusion affecting temperature and inductance.

[0089] When it is a multi-mold tire vulcanizing machine, the bidirectional heating electromagnetic heating device 300 is set between adjacent tire molds 200, and the bidirectional heating electromagnetic heating device 300 does not contain ferrite magnetic strips 3. In this embodiment, the parameter design, number of turns arrangement, and turn spacing control of the electromagnetic coil 2 are the same as those of the single-mold tire vulcanizing machine described above, and will not be repeated here.

[0090] When using a multi-mold tire vulcanizing machine, the suitable tire mold specifications are: two 26×1.95mm bicycle tire molds, one on top and one on the bottom. The magnetic field of electromagnetic coil 2 is symmetrically coupled to both sides to ensure uniform heating on both sides. The center of all turns of electromagnetic coil 2 deviates from the center of the molds on both sides by ≤1mm to avoid magnetic field deviation causing a temperature difference of more than 5℃ between the two molds or different areas on the same side.

[0091] In the foregoing description of this application, unless otherwise expressly specified and limited, the terms "fixed," "installed," "connected," or "linked" should be interpreted broadly. For example, the term "linked" can refer to a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; or it can refer to the internal communication of two components or the interaction between two components. Therefore, unless otherwise expressly limited in this application, those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0092] Based on the above description of this application, those skilled in the art will also understand that the terms used, such as "upper," "lower," "front," "rear," "left," "right," "length," "width," "thickness," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," "circumferential," "center," "longitudinal," "transverse," "clockwise," or "counterclockwise," are based on the orientation or positional relationship shown in the accompanying drawings of this application. They are only for the purpose of facilitating the explanation of the present invention and simplifying the description, and do not explicitly or implicitly suggest that the device or element involved must have the specific orientation, or be constructed and operated in a specific orientation. Therefore, the above-mentioned orientation or positional relationship terms should not be understood or interpreted as a limitation on the present invention.

[0093] Furthermore, the terms "first" or "second," etc., used in this application to refer to numbers or ordinal numbers are for descriptive purposes only and should not be construed as explicitly or implicitly indicating relative importance or specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, or more, unless otherwise explicitly specified.

[0094] While numerous embodiments of the invention have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Many modifications, alterations, and alternatives will occur to those skilled in the art without departing from the spirit and essence of the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in the practice of the invention. The appended claims are intended to define the scope of protection of the invention and therefore cover equivalents or alternatives within the scope of these claims.

Claims

1. A method for electromagnetic heating in tire vulcanization, characterized in that, Includes the following steps: Step 1: Divide the tire mold into multiple regions corresponding to the tire crown, bead, and sidewall. Apply heating power to each region using an electromagnetic heating device. The heating power is matched to the heat required by each region during the vulcanization process. The electromagnetic heating device includes an outer ring region, an inner ring region, and a middle ring region for heating the tire crown region, the bead region, and the sidewall region of the tire mold in sequence. The number of turns of the electromagnetic coil in the electromagnetic heating device decreases sequentially in the outer ring region, the inner ring region, and the middle ring region. Along the radial direction of the electromagnetic heating device, the number of turns of the electromagnetic coil in the outer ring region, the inner ring region, and the middle ring region are 1.35 turns / cm-1.45 turns / cm, 1.05 turns / cm-1.15 turns / cm, and 0.85 turns / cm-0.95 turns / cm, respectively. Step two involves dividing the tire vulcanization process into at least two dynamic control stages, including a rapid heating stage and a constant-temperature vulcanization stage. For each dynamic control stage, an independent, pre-set set of control parameters is invoked to perform real-time closed-loop feedback adjustment of the heating power. This closed-loop feedback adjustment is obtained using the following formula: P(t) = P(t-1) + ΔP(t); ΔP(t)=Kp×[e(t)-e(t-1)]+Kie(t)+Kd[e(t)-2×e(t-1)+e(t-2)]; e(t) = TT(t); Wherein, P(t) is the power value of the electromagnetic coil in the current cycle, P(t-1) is the power value of the electromagnetic coil in the previous cycle, ΔP(t) is the power adjustment value of the electromagnetic coil in the current cycle, e(t) is the temperature error at the current moment, e(t-1) and e(t-2) are the temperature errors of the previous cycle and the cycle before that, respectively, Kp, Ki, and Kd are the proportional coefficient, integral coefficient, and derivative coefficient, respectively, T is the preset target temperature, and T(t) is the measurement value of the temperature sensor installed in the tire mold in the current cycle, and the rapid heating... The process involves several stages, with a target temperature T1 of 150℃ + N and 0℃ < N ≤ 10℃. During the rapid heating stage, Kp is 5.2, Ki is 0.05, and Kd is 0.

8. The constant-temperature vulcanization stage includes: a temperature adjustment stage, with a temperature range from T1 to T2, where T2 is 150℃ - N, during which Kp is 2.5, Ki is 0.35, and Kd is 1.2; and a constant-temperature stage, with a temperature range of 150℃ ± 2℃, during which Kp is 2.0, Ki is 0.1, and Kd is 0.

5.

2. The tire vulcanization electromagnetic heating method according to claim 1, characterized in that, The steps also include: A preset time point is set, and when the preset time point is reached, the rapid heating phase switches to the temperature adjustment phase; or... When the temperature at all temperature measuring points reaches 95%-99% of the set temperature, the system switches from the rapid heating stage to the temperature adjustment stage.

3. The tire vulcanization electromagnetic heating method according to claim 1, characterized in that, The step further includes: setting a ferrite magnetic strip on the non-heating side of the electromagnetic coil in the electromagnetic heating device, the ferrite magnetic strip being parallel to the electromagnetic coil, wherein the ferrite magnetic strip is arranged radially along the radial direction of the electromagnetic coil and covers the electromagnetic coil radially.

4. The tire vulcanization electromagnetic heating method according to claim 3, characterized in that, The ferrite magnetic strips are configured as a plurality of strips, which are equidistantly distributed along the circumference of the electromagnetic coil.

5. The tire vulcanization electromagnetic heating method according to claim 4, characterized in that, The coverage pattern of the ferrite magnetic strip is matched with the turn density of the electromagnetic coil. In the outer ring region and the inner ring region, the ferrite magnetic strip is fully covered; in the middle ring region, the ferrite magnetic strip is truncated or the cross-sectional area of ​​the ferrite magnetic strip is reduced.

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