Method for reasonably setting tire vulcanization safety time

Abstract

The invention discloses a method for reasonably setting tire vulcanization safety time. The method specifically comprises the following steps: S100, determining a plurality of influence factors influencing tire bubble point time; s200, determining the influence degree of each influence factor on the tire bubble point time; s300, determining a fluctuation value of each influence factor; s400, calculating a tire bubble point fluctuation value based on the influence degree of each influence factor on the tire bubble point time and self fluctuation; s500, comprehensively considering under-sulfur risk prevention and control and production efficiency, and reasonably setting vulcanization safety time; the vulcanization safety time set according to the method is the shortest time required on the premise of effectively controlling the undervulcanization risk, undervulcanization is avoided, and overvulcanization is avoided, so that the performance of a finished tire is effectively ensured; by using the vulcanizing safety time set by the method, the vulcanizing time of tire production can be effectively reduced, the vulcanizing production efficiency is improved, and meanwhile, the energy waste is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of tire vulcanization, and in particular to a method for reasonably setting a tire vulcanization safety time. Background Art

[0002] The production of rubber tires goes through four major processes: mixing, semi-finished product (including extrusion, calendering, etc.) molding, and vulcanization. The vulcanization process refers to the process of pressurizing and heating the molded tire embryo to cause the rubber molecules to cross-link from linear molecular chains to a three-dimensional network structure, thereby obtaining a finished tire with physical and mechanical properties.

[0003] To determine whether the crosslinking of rubber molecular chains is sufficient, the industry currently mainly uses the degree of vulcanization of rubber to characterize it. If the degree of vulcanization is insufficient (commonly known as "under-vulcanization"), the number of crosslinked structures formed is insufficient, resulting in low physical properties of the finished tire rubber, which in turn affects the performance of the tire; if the degree of vulcanization is too deep (commonly known as "over-vulcanization"), the crosslinked structure is destroyed, which also leads to low physical properties of the finished tire rubber, which in turn affects the performance of the tire. Therefore, in order to ensure the physical properties of the finished tire rubber, the degree of vulcanization of the rubber must be controlled in the positive vulcanization stage.

[0004] The three elements of vulcanization (temperature, time and pressure) are the main factors that constitute the vulcanization process conditions. They play a decisive role in the degree of vulcanization. Among them, the vulcanization temperature and pressure have clear process standards in tire companies. When the vulcanization temperature and pressure are determined, the degree of vulcanization is closely related to the length of the vulcanization time.

[0005] The composition of vulcanization time is shown in the following table:

[0006]

[0007] From the above table, we can see that vulcanization time = bubble point time + safety time + pressure relief time. The explanations of the terms in the calculation formula are as follows:

[0008] ①, Bubble point time: the shortest vulcanization time required for no more pores (bubbles) to appear in the tire;

[0009] ②Safety time: The safe increment of tire bubble point time under the existing vulcanization process control level, which is used to deal with the risk of insufficient sulfur caused by the fluctuation of tire bubble point time;

[0010] ③. Pressure relief time: the time required to remove the vulcanization medium inside the capsule;

[0011] ④. Non-vulcanization time: the interval between vulcanization and pot loading.

[0012] At present, there is no clear method for determining the safe time of vulcanization in the industry. Many companies blindly imitate it, which poses the following risks:

[0013] ①. The safety time setting is insufficient, and it is unable to effectively cope with the fluctuation of bubble point time. There is a greater risk of "lack of sulfur", and the performance of the finished tire cannot be guaranteed.

[0014] ② The vulcanization safety time is set too long, which makes the overall time too long. On the one hand, it causes the rubber to be vulcanized too deeply, i.e. "over-vulcanization", which deteriorates the performance of the finished tire; on the other hand, it causes low production efficiency and energy waste.

[0015] At present, many companies in the industry adhere to the principle of "better to be excessive than to be insufficient", and often set the vulcanization safety time too long, so the probability of the second risk is greater.

[0016] In summary, scientifically setting the safe time for tire vulcanization, formulating a reasonable vulcanization time, and then improving product performance are issues that need to be addressed in the field of tire vulcanization technology. Summary of the invention

[0017] The purpose of the present invention is to provide a method for reasonably setting the safe time of tire vulcanization, aiming to scientifically set the safe time of tire vulcanization, formulate a reasonable vulcanization time, and thus improve the performance of tire products.

[0018] The present invention is achieved in that:

[0019] A method for reasonably setting the tire vulcanization safety time comprises the following steps:

[0020] S100, determining factors affecting tire bubble point time;

[0021] S200, confirming the influence of each influencing factor on the tire bubble point time;

[0022] S300, confirming the fluctuation value of each influencing factor;

[0023] S400, calculating a tire bubble point fluctuation value based on the influence of each influencing factor on the tire bubble point time and its own fluctuation;

[0024] S500. Comprehensively consider the risk prevention and control of undersulfurization and production efficiency, and reasonably set the vulcanization safety time.

[0025] Furthermore, in step S100, the determined influencing factors include the rubber bubble point of the rubber itself, tire temperature, tire section thickness, rubber thermal conductivity, curing bladder thickness, bladder thermal conductivity, curing external temperature, curing internal temperature, and non-curing time.

[0026] Furthermore, the expression of heat transfer process during tire vulcanization is:

[0027]

[0028] Where u(x, t) is the temperature distribution function of the object at position x and time t, and α represents the thermal conductivity coefficient of the rubber.

[0029] Furthermore, the step S200 includes the following steps:

[0030] S210, select tire specifications, reserve the latest vulcanization point corresponding to the final rubber mixing, and measure the characteristic time at a certain temperature;

[0031] S220, reserve the corresponding rubber material and curing bladder samples on the heat transfer path, and measure the thermal conductivity of the rubber material and curing bladder and the thickness of the curing bladder;

[0032] S230, using the same batch of final rubber to produce semi-components and make tire blanks for temperature measurement, pre-burying temperature measuring wires according to the determined temperature measuring points; measuring and recording the temperature and non-vulcanization time of the tire blank before vulcanization, recording the external and internal vulcanization temperatures during vulcanization, and recording the actual vulcanization time when the equivalent vulcanization time of the rubber material at the latest vulcanization point reaches ts2, which is the tire bubble point time; after the vulcanization is completed, cutting the cross section to confirm that the latest vulcanization point position corresponds to the tire CTL thickness;

[0033] S240, adjusting one of the influencing factors, fixing the other influencing factors, repeating the buried wire temperature measurement, and confirming that the actual vulcanization time when the equivalent vulcanization time of the latest vulcanization point rubber material reaches ts2 is the tire bubble point time;

[0034] S250. Based on the above test data, calculate the influence of each influencing factor on the tire vulcanization time ω i .

[0035] Furthermore, in step S300, based on the central limit theorem, data sampling is performed on each influencing factor to obtain a normal distribution expression N(μ i , σ i 2 ).

[0036] Furthermore, when data sampling is performed, the number of samples n≥30.

[0037] Furthermore, using the formula

[0038]

[0039] Calculate the tire bubble point fluctuation value σ.

[0040] Furthermore, the vulcanization safety time is set to 4σ.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. The vulcanization safety time set according to the present invention is the shortest time required under the premise of effectively controlling the risk of under-vulcanization, that is, avoiding both under-vulcanization and over-vulcanization, thereby effectively ensuring the performance of the finished tire.

[0043] 2. The vulcanization safety time set by the present invention can effectively reduce the vulcanization time of tire production, improve vulcanization production efficiency, and reduce energy waste.

[0044] 3. Based on the fluctuation of each influencing factor and its influence on the tire bubble point time, the present invention can obtain the proportion of each influencing factor on the tire bubble point time. By continuously improving the control ability of the main influencing factors, the vulcanization safety time can be gradually shortened to achieve dynamic improvement. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is a flow chart of the method of the present invention;

[0046] Figure 2 is a method flow chart of step S200 of the present invention;

[0047] Figure 3 It is the decomposition diagram of the factors affecting the tire bubble point time;

[0048] Figure 4 It is the temperature measurement curve of the buried wire inside the tire;

[0049] Figure 5 It is a normal distribution curve graph. DETAILED DESCRIPTION

[0050] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be 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, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0051] The following is a further description with reference to the accompanying drawings and specific embodiments:

[0052] First, the underlying logic of the present invention is described:

[0053] 1. The bubble point time of tire vulcanization is determined based on the latest vulcanization point. The latest vulcanization point of the tire is generally located at the shoulder, rim or inside the rubber compound in the crown of the tire.

[0054] 2. As a thick rubber product, the bubble point time of the tire is affected by two parts: one is the bubble point of the rubber itself; the other is the internal point temperature.

[0055] 3. According to the central limit theorem, the sample mean of independent and identically distributed random variables will approach a normal distribution if the sample size is large enough (generally the sample size n≥30).

[0056] Based on the above underlying logic, the purpose of the present invention can be achieved through the following technical solutions:

[0057] A method for reasonably setting the tire vulcanization safety time, such as Figure 1 As shown, the following steps are included:

[0058] S100, determining the factors affecting the tire bubble point time. Based on the above underlying logics 1 and 2, the factors affecting the tire bubble point time are analyzed. The rubber bubble point of the rubber itself is not described here, and the focus is on analyzing the internal point temperature.

[0059] Since rubber is a poor conductor of heat, for thick rubber products such as tires, the heat history of each part during vulcanization is quite different. From the perspective of heat conduction, tire vulcanization is a non-steady-state process. In order to effectively grasp the law of temperature changes at internal points during vulcanization, it is necessary to understand the law of non-steady-state heat conduction. In the present invention, for the sake of brief description, the heat transfer process during tire vulcanization is simplified to one-dimensional heat transfer, and its expression is:

[0060]

[0061] Where u(x, t) is the temperature distribution function of the object at position x and time t, and α represents the thermal conductivity coefficient of the rubber.

[0062] From the above formula, we can see that the rate of change of temperature over time is affected by the thermal conductivity and heat transfer path of the material. By giving appropriate initial conditions and boundary conditions, the temperature distribution of an object under specific circumstances can be solved. The initial conditions describe the temperature distribution u(x, 0) of the object at the initial time t=0; the boundary conditions describe the temperature conditions on the boundary of the object, such as the temperature values ​​at x=0 and x=L.

[0063] Taking the tire surface as the boundary, the factors affecting the internal point temperature are decomposed as shown in the attached figure. Figure 3 , including tire temperature, tire section thickness, rubber thermal conductivity, vulcanization bladder thickness, bladder thermal conductivity, vulcanization external temperature, vulcanization internal temperature, and non-vulcanization time.

[0064] In summary, together with the fluctuation of the bubble point of the rubber itself, there are a total of 9 factors that affect the bubble point time of the tire. In the present invention, the bubble point of the rubber is approximately characterized by ts2.

[0065] S200: confirming the influence of each influencing factor on the tire bubble point time.

[0066] like Figure 2 As shown, the specific implementation steps are as follows:

[0067] S210. Select tire specifications, reserve the latest vulcanization point corresponding to the final rubber mixing, and measure the characteristic time (ts2, t90) at three temperatures of 140°C, 150°C, and 160°C using a vulcanometer.

[0068] S220, reserve the corresponding rubber material and vulcanization bladder samples on the heat transfer path, and measure the thermal conductivity of the rubber material and vulcanization bladder and the thickness of the vulcanization bladder.

[0069] S230, use the same batch of final rubber to produce semi-components and make tire blanks for temperature measurement, and pre-embed the temperature measurement wires according to the determined temperature measurement points. Before vulcanization, measure and record the temperature of the tire blank and the non-vulcanization time (i.e. the interval time between the mold opening of the previous batch). During the vulcanization process, record the vulcanization external temperature and internal temperature, and record the actual vulcanization time when the equivalent vulcanization time of the latest vulcanization point rubber material (with 150℃ as the standard temperature) reaches ts2, which is the tire bubble point time. See the attached for details. Figure 4 After vulcanization, cut the section to confirm that the latest vulcanization point corresponds to the tire CTL thickness.

[0070] S240, fix the other eight influencing factors, adjust one of the influencing factors, repeat the buried wire temperature measurement, and confirm that the actual vulcanization time when the equivalent vulcanization time of the latest vulcanization point rubber material (with 150°C as the standard temperature) reaches ts2 is the tire bubble point time, as follows:

[0071]

[0072]

[0073] S250. Based on the above test data, calculate the influence of each influencing factor on the tire vulcanization time ω i , as follows:

[0074]

[0075] S300: Based on the influencing factors affecting the tire bubble point time identified in step S100, it is necessary to confirm the fluctuation of each influencing factor itself, and based on the underlying logic 3, perform data sampling on each influencing factor. The specific implementation method is as follows:

[0076]

[0077] S400, based on the influence of each influencing factor on the tire bubble point time and its own fluctuation, calculate the tire bubble point fluctuation value. Specifically, under the condition of μ1 to μ9, the tire bubble point vulcanization time t determined by buried wire temperature measurement is the standard time. The tire bubble point time change value (t 实际 -t 标准 ) also presents a normal distribution, expressed as N{0, (σ1ω1) 2}~N{0,(σ9ω9) 2}.

[0078] According to the normal distribution operation rule, the total tire bubble point time change value also presents a normal distribution N(μ, σ 2 ), and N(μ,σ 2 )=N{0,(σ1ω1) 2}+...+N{0,(σ9ω9) 2}.

[0079] We can get μ=0,σ 2 ＝ (σ1ω1) 2 +...(σ9ω9) 2 .

[0080] S500. Comprehensively consider the risk prevention and control of undersulfurization and production efficiency, and reasonably set the vulcanization safety time.

[0081] like Figure 5 As shown, the area to the right of the center line represents t 实际 >t 标准 , that is, there is a risk of insufficient sulfur.

[0082] but:

[0083] 1) If the safety time is set according to 1σ, the probability of sulfur deficiency is about 158700ppm;

[0084] 2) If the safety time is set according to 2σ, the probability of sulfur deficiency is about 22700ppm;

[0085] 3) If the safety time is set according to 3σ, the probability of sulfur deficiency is about 1350ppm;

[0086] 4) If the safety time is set according to 4σ, the probability of sulfur deficiency is about 30ppm;

[0087] 5) If the safety time is set according to 5σ, the probability of sulfur deficiency is about 0.3ppm;

[0088] 6) If the safety time is set according to 6σ, the probability of sulfur deficiency is about 0.001ppm.

[0089] Based on the above probabilities, in the actual tire production process, the safety time should be set at 4σ, taking into account the risk prevention and control of undersulfurization and production efficiency.

[0090] Example

[0091] This embodiment takes a 12R22.5 all-steel radial tire product as an example for detailed description.

[0092] Reasonable steps to set the tire vulcanization safety time are:

[0093] 1. Determine the factors affecting tire bubble point:

[0094] Specifically, the latest vulcanization point of the 12R22.5 specification is located at the shoulder of the tire, and the specific latest vulcanization point corresponds to the tread base rubber. According to the factor decomposition idea that affects the internal point temperature, each influencing factor is further refined and confirmed, including tire embryo temperature, tire shoulder thickness, shoulder rubber thermal conductivity, curing bladder crown thickness, curing bladder thermal conductivity, mold sleeve steam temperature, and internal pressure steam temperature.

[0095] It should be noted that in this embodiment, each influencing factor is identified based on the actual situation of the company. In principle, the total influencing factors include but are not limited to the influencing factors that have been identified so far.

[0096] 2. Based on the factors affecting the tire bubble point time identified in step 1, it is necessary to confirm the influence of each factor on the tire bubble point time. The specific implementation steps are as follows:

[0097] 1) Based on the 12R22.5 all-steel radial tire product, the base rubber is reserved and the characteristic time (ts2, t90) at three temperatures of 140°C, 150°C and 160°C is measured by a sulfur rheometer.

[0098] 2) Reserve the normal thermal conductivity rubber and adjusted thermal conductivity rubber corresponding to the model of the 12RR.5 product tire shoulder, and measure the actual value of the thermal conductivity of the rubber. For the vulcanization bladder, prepare the ordinary thermal conductivity bladder A, ordinary thermal conductivity bladder B (same thermal conductivity as A, different thickness), and high thermal conductivity bladder C (same thickness as A, different thermal conductivity) applicable to the 12R22.5 specification of the same manufacturer, and measure the actual thickness and actual thermal conductivity of each bladder.

[0099] 3) Use the same batch of final rubber to produce semi-components and make tire blanks for temperature measurement, and pre-embed the temperature measuring wires according to the determined temperature measuring points. Measure and record the temperature of the tire blank and the non-vulcanization time (i.e. the interval time between the mold opening of the previous pot) before vulcanization. During the vulcanization process, record the external and internal vulcanization temperatures, and record the actual vulcanization time when the equivalent vulcanization time of the latest vulcanization point rubber material (with 150°C as the standard temperature) reaches ts2, which is the tire bubble point time. After the vulcanization is completed, cut the section to confirm that the latest vulcanization point position corresponds to the tire CTL thickness.

[0100] 4) Fix the other eight influencing factors, adjust one of the influencing factors, repeat the buried wire temperature measurement, and confirm that the actual vulcanization time when the equivalent vulcanization time of the latest vulcanization point rubber material (with 150°C as the standard temperature) reaches ts2 is the tire bubble point time, as follows:

[0101]

[0102] 5) Based on the above test data, calculate the influence of each influencing factor on the tire vulcanization time, as follows:

[0103]

[0104]

[0105] Supplementary explanation: ①. For the calculation of the influence degree, the focus is on the relative value of the change of each influencing factor, so there is no specific limit on the absolute value of the factor; ②. There is no specific limit on the relative value of the change of each influencing factor, so that the difference in tire bubble points can be obtained; ③. There is no limit on the number of verification experiments, so as to ensure the accuracy of the calculated values.

[0106] 3. Based on the factors affecting the tire bubble point time identified in step 1, it is necessary to confirm the fluctuation of each influencing factor and sample data for each influencing factor. The specific implementation method is as follows:

[0107]

[0108]

[0109] Based on the data obtained in step 2 and step 3, calculate the tire bubble point fluctuation value:

[0110]

[0111] 5. Set the vulcanization safety time according to 4σ.

[0112] The present invention provides a method for scientifically setting the safe time of vulcanization based on the factory process control capability, which effectively controls the risk of under-vulcanization and avoids both under-vulcanization and over-vulcanization, thereby effectively ensuring the performance of the finished tire. Under the current industry mentality of "better to over-vulcanize than under-vulcanize", the technical solution proposed by the present invention can effectively reduce the vulcanization time, improve the vulcanization production efficiency, and reduce energy waste. In addition, the method proposed by the present invention will also provide directional guidance for subsequently improving the process control capability and continuously shortening the safe time of vulcanization.

[0113] By comparison, the vulcanization safety time required for the 12R22.5 product calculated by the present invention can be shortened by 2 to 3 minutes compared with the original safety time. After the vulcanization time is shortened, the vulcanization production efficiency is increased by about 4 to 6%, and the durability of the finished product can be increased by about 2%.

[0114] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for reasonably setting the tire vulcanization safety time, characterized in that: The steps include: S100, determining factors affecting tire bubble point time; S200, confirming the influence of each influencing factor on the tire bubble point time; S300, confirming the fluctuation value of each influencing factor; S400, calculating a tire bubble point fluctuation value based on the influence of each influencing factor on the tire bubble point time and its own fluctuation; S500. Comprehensively consider the risk prevention and control of undersulfurization and production efficiency, and reasonably set the vulcanization safety time.

2. A method for reasonably setting tire vulcanization safety time according to claim 1, characterized in that: In step S100, the determined influencing factors include the rubber bubble point of the rubber itself, tire temperature, tire section thickness, rubber thermal conductivity, curing bladder thickness, bladder thermal conductivity, curing external temperature, curing internal temperature, and non-curing time.

3. A method for reasonably setting tire vulcanization safety time according to claim 1, characterized in that: The expression of heat transfer process during tire vulcanization is: Where u(x, t) is the temperature distribution function of the object at position x and time t, and α represents the thermal conductivity coefficient of the rubber.

4. A method for reasonably setting tire vulcanization safety time according to claim 1, characterized in that: The step S200 includes the following steps: S210, select tire specifications, reserve the latest vulcanization point corresponding to the final rubber mixing, and measure the characteristic time at a certain temperature; S220, reserve the corresponding rubber material and curing bladder samples on the heat transfer path, and measure the thermal conductivity of the rubber material and curing bladder and the thickness of the curing bladder; S230, using the same batch of final rubber to produce semi-components and make tire blanks for temperature measurement, pre-burying temperature measuring wires according to the determined temperature measuring points; measuring and recording the temperature and non-vulcanization time of the tire blank before vulcanization, recording the external and internal vulcanization temperatures during vulcanization, and recording the actual vulcanization time when the equivalent vulcanization time of the rubber material at the latest vulcanization point reaches ts2, which is the tire bubble point time; after the vulcanization is completed, cutting the cross section to confirm that the latest vulcanization point position corresponds to the tire CTL thickness; S240, adjusting one of the influencing factors, fixing the other influencing factors, repeating the buried wire temperature measurement, and confirming that the actual vulcanization time when the equivalent vulcanization time of the latest vulcanization point rubber material reaches ts2 is the tire bubble point time; S250. Based on the above test data, calculate the influence of each influencing factor on the tire vulcanization time ω i .

5. A method for reasonably setting tire vulcanization safety time according to claim 4, characterized in that: In step S300, based on the central limit theorem, data sampling is performed on each influencing factor to obtain the normal distribution expression N(μ i , σ i 2 ).

6. A method for reasonably setting tire vulcanization safety time according to claim 5, characterized in that: When data sampling is performed, the number of samples n≥30.

7. A method for reasonably setting tire vulcanization safety time according to claim 6, characterized in that: Using the formula Calculate the tire bubble point fluctuation value σ.

8. A method for reasonably setting tire vulcanization safety time according to claim 7, characterized in that: The set vulcanization safety time is 4σ.

Images