Low rolling resistance cap ply and tire

Abstract

The present application relates to low rolling resistance crown belt and tire, wherein the low rolling resistance tire comprises, from outside to inside, a tread rubber layer, a crown belt layer, a belt layer and a cord layer, the crown belt layer is continuously spirally wound along the tire circumferential direction, and the load force difference of the crown belt cord at 0.5% deformation and 3% deformation under normal driving temperature of the tire is between 0.6-1.3 cN / D. The present application realizes the effect of reducing the rolling resistance of the tire by optimizing the performance of the crown belt cord, specifically, by limiting the load force difference of the crown belt cord within the change range under normal driving temperature to reduce the energy consumed by the crown belt at the tire ground contact surface, thereby achieving the technical effect of reducing resistance to a certain extent.

Description

Technical Field

[0001] This invention relates to the field of tire manufacturing technology, and more specifically to a low rolling resistance tire. Background Technology

[0002] As is well known, nearly one-third of a vehicle's fuel consumption during driving is due to overcoming tire rolling resistance. Therefore, choosing low rolling resistance tires can effectively reduce fuel consumption and is also more environmentally friendly. With the implementation of labeling regulations and the rapid development of electric vehicles, tire manufacturers are actively developing tires with even lower rolling resistance.

[0003] Existing methods for reducing rolling resistance primarily focus on lowering the weight of tire compounds and components. This mainly involves adjusting the compound of the tread and sidewall, which account for a significant portion of the tire's weight. However, low-rolling-resistance compounds often result in poor wear resistance or reduced handling performance. Alternatively, weight reduction can be achieved by lowering the weight of components with a large weight percentage, such as the carcass, inner liner, RC / triangle rubber, and reinforcing layers. However, reducing weight often leads to a decrease in safety performance or other characteristic losses. Since the crown layer has a small weight percentage, finite element analysis shows that when a tire is traveling on a hard road surface, the majority of its rolling resistance loss is due to energy consumption: approximately 50% in the tread, 20% in the base (including the crown layer), 10% in the belt layer, and 10% in the sidewall (including the carcass). Therefore, research on reducing rolling resistance from the crown layer perspective is relatively limited.

[0004] In the existing technology, there is very little research on reducing rolling resistance from the crown layer. Research on the influence of the crown layer on tire rolling resistance has only made progress since 2015.

[0005] Utility model patent CN207496401U uses aramid / nylon 66 composite impregnated cord fabric to replace ordinary steel wires and crown belts. Compared with ordinary radial passenger car tires of the same specifications, the weight is reduced by about 8%, and the rolling resistance is reduced by about 18%. However, using blended fiber cords instead of steel wires reduces the strength of the cord layer, poses a risk to tire puncture performance, and makes it difficult to guarantee tire safety.

[0006] The invention patent CN111086358A uses a crown strip to wrap around the tire circumferentially to form a crown layer, which binds the belt layer, improves high-speed performance, reduces the weight of the crown layer material, and thus reduces the rolling resistance of the tire. However, the reduction is limited, with a maximum reduction of 3%.

[0007] Invention patent CN109835118B forms a thin strip of cord textile layer by weaving and placing multiple cord strands, rather than twisting multiple cord strands to form a crown layer cord. This reduces tire rolling resistance by reducing weight, but the process is complex and increases manufacturing costs.

[0008] Invention patent CN108944272B improves durability and tire rolling resistance by adjusting the design of the belt layer and simultaneously applying a tensile load of 660N to the crown belt cords per unit number of crown belt cords with an elongation of less than 0.06, thereby reducing the rolling resistance value by up to 4%.

[0009] Invention patent CN114761253B defines the tangential modulus of the crown belt layer at 1.3% elongation as ranging from 200 daN / mm to 650 daN / mm by using three polyester multifilament strands or two aramid or aramid copolyamide multifilament strands and one aliphatic polyamide or polyester multifilament strand. This, combined with a single-layer belt layer, improves tire rolling resistance, reducing it by up to 4%. However, the use of a single-layer belt layer reduces the strength of the belt layer, potentially jeopardizing tire puncture resistance and compromising tire safety. Summary of the Invention

[0010] The present invention aims to provide a technical solution to improve tire rolling resistance based on the improved performance of the crown layer fiber, and thus provide a tire with low rolling resistance.

[0011] The technical solution of the present invention provides a crown layer with low rolling resistance.

[0012] The crown layer comprises crown layer cords formed by continuous spiral winding in the circumferential direction of the tire, and the difference in load force between the crown layer cords at 0.5% deformation and 3% deformation at normal tire operating temperature is between 0.6 and 1.3 cN / D.

[0013] Preferably, the difference in load force between the crown layer cord at 0.5% deformation and 3% deformation at normal tire operating temperature is between 0.7 and 1.0 cN / D.

[0014] Preferably, the normal operating temperature of the tire is 90-125℃.

[0015] Preferably, the M100 of the crown layer adhesive is between 2.0 and 3.0 MPa, and the M300 is between 10.0 and 14.0 MPa.

[0016] Preferably, the M100 of the crown band layer rubber compound is 2.5 MPa, the M300 is 12 MPa, and the calendering thickness of the crown band layer is 1.1 mm.

[0017] The present invention also provides a low rolling resistance tire, comprising a tread rubber layer, a crown layer, a belt layer and a ply layer arranged sequentially from the outside to the inside, characterized in that the crown layer is disposed between the belt layer and the tread rubber layer, the crown layer covers the belt layer, and the crown layer is any of the low rolling resistance crown layer described above.

[0018] This invention achieves the effect of reducing tire rolling resistance by optimizing the performance of the crown layer cords. Specifically, it reduces the energy consumed by the crown layer at the tire contact surface by limiting the load force difference of the crown layer cords within the range of normal driving temperature, thereby achieving the technical effect of drag reduction to a certain extent. Attached Figure Description

[0019] Figure 1 This is the stress curve of the coronal layer obtained from finite element analysis. Detailed Implementation

[0020] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. In this specification, the dimensions of the drawings do not represent the actual dimensions. They are only used to illustrate the relative positional and connection relationships between the components. Components with the same name or the same reference numeral represent similar or identical structures and are limited to illustrative purposes.

[0021] The present invention aims to provide a pneumatic radial tire with low rolling resistance. By controlling the load force difference of the crown belt cord under different deformation, the deformation of the crown belt layer during tire operation can be controlled. Combined with a low-modulus crown belt layer rubber compound formulation, the rolling resistance can be significantly optimized.

[0022] Generally, during normal driving (speed not exceeding 120 km / h), the temperature of the crown layer of a semi-steel tire is around 120°C, and this temperature range may fluctuate between 90-125°C depending on the situation. The properties of material fibers are generally significantly affected by temperature; therefore, the changes in the mechanical properties of the crown layer fibers, such as the material modulus, between room temperature and when the tire is in motion are often significant. To study and optimize the rolling resistance of the tire during driving, the mechanical properties of the fibers under driving conditions should be considered. This application uses crown layer performance optimization at 120°C as an example; however, it should be understood that specific improvements are not limited to around 120°C, but rather have a certain feasible range. This range may be the aforementioned 90-125°C, or it may be other temperatures determined based on the temperature rise value under the tire's target driving conditions.

[0023] For the commonly used 205 / 55R16 semi-steel radial tire, to study the influence of the crown belt ply performance on tire rolling resistance, we first analyzed the tire's driving conditions. We selected four groups of different types of crown belt ply cords for preliminary testing and finite element analysis. Table 1 shows the relevant data. Figure 1 This is the stress curve of the coronal layer.

[0024]

[0025] Note: Inflation status refers to 100% inflation, and load status refers to 100% inflation and 100% load.

[0026] Table 1: Stress and Strain of Cords in the Crown Layer

[0027] Table 1 shows that the load value of the crown belt ply cord at 0.5% elongation at 120℃ is basically consistent with the deformation and stress of the crown belt ply under tire inflation. Under load, the maximum deformation of the crown belt ply cord is between 3% and 4%. The higher the modulus of the crown belt ply cord, the smaller its cord deformation, with a minimum of 3%. If the cord deformation under load is 3%, then obviously, its stress value should be almost identical to the load value of the cord at 3% elongation at 120℃.

[0028] In reality, during tire operation, the load state represents the force situation at the tire's contact patch, while the charging state can be broadly considered as the force situation at the circumferential non-contact points. The tire's operation can be simplified as a cyclical loading and unloading of loads along its circumference, resulting in periodic changes in the force situation at various points along the tire's circumference. The table also shows that under load and inflation conditions, the crown belt layer and cords deform synchronously, with energy dissipated by the material deformation, leading to increased rolling resistance. Therefore, a well-designed crown belt layer that reduces its performance under inflation and load conditions can reduce power loss in the crown belt layer, resulting in reduced rolling resistance.

[0029] The maximum deformation range of the crown belt ply cords under normal tire use is expected to be between 3-4%. Within this range, reasonable and targeted improvements can be made to the crown belt ply to optimize the tire's rolling resistance. The main idea is to reduce energy loss caused by changes in force on the crown belt ply during normal driving. Following this approach, we take the maximum deformation under inflation as 3% and the maximum deformation under load as 0.5%, considering the impact of the difference in load force between the two states on the final rolling resistance.

[0030] The prototype tires were made in the following sizes: 205 / 55R16, 245 / 45R18, and 255 / 45R20. The crown belt layer had a calendered thickness of 1.1 mm, and the cords in the crown belt layer were continuously spirally wound along the tire's periphery.

[0031] Comparative Example 1 uses Nylon 66, a conventional crown layer material, and the difference in load force at 120°C with 3% and 0.5% deformation is 0.4 cN / D (cN / D, centineut / denier).

[0032] Comparative Example 2 uses polyester material, and the difference in load force at 120°C under 3% and 0.5% deformation is 0.5 cN / D.

[0033] Comparative Example 3 is a conventional aramid and nylon 66 blended material (one aramid fiber and one nylon 66 fiber). The difference in load force at 120°C under 3% and 0.5% deformation is 1.7 cN / D.

[0034] Examples 1, 2, 3, 4, and 5 all use polyester materials. At 120°C, the load force difference at 3% and 0.5% deformation is 0.8 cN / D, 1.0 cN / D, 1.3 cN / D, 0.6 cN / D, and 0.7 cN / D, respectively. In practice, fiber cords with a controllable load force difference of 0.6–1.3 cN / D at 120°C with 3% and 0.5% deformation include rayon cords and polyester cords (including but not limited to polyethylene terephthalate and polyethylene naphthalate). However, due to the high cost of rayon cords, polyester cords are preferred.

[0035] The mechanical properties of fiber materials are affected by the raw yarn, twisting, and impregnation processes. The properties of the raw yarn are influenced by the intrinsic viscosity of the chips, spinning speed, cooling equipment, and drawing process. Simultaneously, the twist degree and twisting method, as well as the impregnation temperature, affect the strength and modulus of the cord. In general, the tensile profile of polyester materials can be adjusted by modifying the molecular weight of the crystalline region and the orientation degree of the amorphous region. Extensive research has been conducted in the industry on methods for adjusting the tensile properties of polyester cords, which will not be described in detail here.

[0036] Meanwhile, conventionally, polyester materials have low polarity and lack hydrogen-bonding groups, making it difficult for the impregnation solution to penetrate the interior of the cord. Standard RFL impregnation solutions cannot achieve good adhesion between polyester cords and rubber. Currently, there is extensive research in the industry on improving the impregnation of polyester cords, including the use of two-stage or multi-stage impregnation processes, modification of single-stage impregnation processes, and surface modification of polyester materials. The polyester cord used in this invention, after two-stage impregnation and impregnation optimization, exhibits resistance to 100°C steam aging comparable to conventional nylon materials, and utilizes a mature impregnation formulation from the supplier.

[0037] The results shown in the table below are obtained from testing the tires on a tire testing machine according to national standards:

[0038]

[0039] Note: 1. Rolling resistance is the test value of each scheme / the test value of Comparative Example 1, and the average of 3 specifications is shown;

[0040] 2. The load force difference is the load force difference under 3% and 0.5% deformation at 120℃.

[0041] Table 2: Rolling resistance test data for different schemes

[0042] Based on experimental results, it can be basically determined that controlling the load force difference between 3% and 0.5% deformation of the crown belt ply cord at 120°C to be between 0.6 and 1.3 cN / D can reduce rolling resistance by 3% to 5%. More preferably, controlling the load force difference between 3% and 0.5% deformation of the crown belt ply cord at 120°C to be between 0.7 and 1.0 cN / D can reduce rolling resistance by 4% to 5%. For example, in Example 1, controlling the load force difference between 3% and 0.5% deformation of the crown belt ply cord at 120°C to be between 0.8 cN / D can reduce rolling resistance by approximately 5%. Referring to existing technologies, achieving a 3-5% reduction in tire rolling resistance has reached and partially exceeded the average level of existing technologies. This improvement is significant. Existing methods for reducing rolling resistance by adjusting the crown layer or the crown layer and belt layer often result in reduced safety performance, increased complexity, or limited reduction in rolling resistance. This invention significantly reduces rolling resistance without compromising safety performance. Furthermore, it adds another means to improve rolling resistance performance. When used in conjunction with other methods, it can achieve an even lower level of tire rolling resistance.

[0043] Qualitatively, when the load force difference between the crown layer cords at 120℃ with 3% and 0.5% deformation is less than 0.6 cN / D, their binding force on the belt layer is limited, resulting in large deformation of the crown layer components and thus significant heat generation, which may be a potential cause of increased energy consumption. When the load force difference between the crown layer cords at 120℃ with 3% and 0.5% deformation is greater than 1.3 cN / D, the adjacent belt layer components and tread components have significant differences in modulus and stiffness, lacking a suitable and effective transition between the crown layer and the tread. This leads to greater energy consumption due to the interaction between different material layers of the tire, which may also be one of the reasons for increased energy consumption.

[0044] To confirm the practicality of the scheme for adjusting the load force difference of the crown belt ply cords, we also tested other performance characteristics of the experimental tires. Taking Example 1 and Comparative Example 1 as examples, their detailed tire performance is shown in the table below:

[0045]

[0046] Table 3: Comparison of other performance characteristics between Example 1 and Comparative Example 1

[0047] The experiment continued. At 120℃, the difference in load force between 3% and 0.5% deformation of the crown belt cord, within the range of 0.6–1.3 cN / D, resulted in a maximum reduction in rolling resistance of 5%. To further reduce rolling resistance, the crown belt compound formulation was studied. Extensive testing showed that by changing the type and proportion of carbon black, and thus altering the crown belt compound modulus, the corresponding tire performance could be optimized. The test results are shown in Table 4.

[0048]

[0049] Table 4: Effects of different coronal band layer formulations on test results

[0050]

[0051] Note: 1. The prototype tires are 205 / 55R16, 245 / 45R18, and 255 / 45R20, with a crown belt layer calendering thickness of 1.1mm;

[0052] 2. The basic performance of the formulation is the test result at 160℃ for 15 minutes;

[0053] 3. Rolling resistance is the test value of each scheme / the test value of Comparative Example 1, and the average of 3 specifications is shown.

[0054] 4. M100 is the tire's 100% constant tensile stress;

[0055] 5. M300 represents the tire's 300% constant tensile stress;

[0056] 6. TS is the tensile strength of the tire.

[0057] Continued from Table 4: The Influence of Different Coronary Band Formulations on Test Results

[0058] According to the test results in Table 4, by adjusting the type and amount of carbon black and the modulus of the formulation, to achieve a crown belt layer formulation with M100 at 2.0–3.0 MPa and M300 at 10.0–14.0 MPa, and with a load force difference of 0.6–1.3 cN / D between 3% and 0.5% deformation at 120°C, the rolling resistance of the tire can be reduced by 7%–10%. Conversely, with a crown belt layer formulation of M100 at 2.5 MPa and M300 at 12 MPa, and a load force difference of 0.8 cN / D between 3% and 0.5% deformation at 120°C, the rolling resistance of the tire can be reduced by 10%. Examples g and h demonstrate that simply changing the amount of carbon black used is insufficient to achieve the desired rolling resistance (M100 at 2.0–3.0 MPa and M300 at 10.0–14.0 MPa). A preferred approach is to replace the commonly used small-particle carbon black (N3XX series) for the crown layer with larger particle size carbon black or silica (traditional formulations typically use N3XX series small-particle carbon black). Examples a, b, c, and d, and comparative examples c, d, e, and f demonstrate that using N5XX and N6XX series carbon black, while reducing their usage by 5–10 parts, results in a more suitable modulus for the rubber compound. More preferably, using N6XX series carbon black provides an even better reduction in rolling resistance. Examples e and f, and comparative example f, demonstrate that using functional silica, while reducing its usage by 0–20 parts, results in a more suitable modulus for the rubber compound.

[0059] To confirm the impact of changing the composition of the crown belt compound on other tire effects, this application also tested other data of tires made from combinations of Comparative Example 1 and Example 1, and Comparative Example a and Example b in the table above. The test results are shown in Table 5. The data in the table show that controlling the load force difference between the crown belt cord at 3% and 0.5% deformation at 120°C in the range of 0.6 to 1.30 cN / D, combined with low-modulus crown belt compounds of M100 at 2.0 to 3.0 MPa and M300 at 10 to 14 MPa, can reduce tire rolling resistance by approximately 7% to 10%, while maintaining tire safety performance.

[0060]

[0061] Table 5: Test data of prototype tires with different combination schemes

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A low rolling resistance crown layer, characterized in that, The crown layer comprises crown layer cords formed by continuous spiral winding in the circumferential direction of the tire, and the difference in load force between the crown layer cords at 0.5% deformation and 3% deformation at normal tire operating temperature is between 0.6 and 1.3 cN / D. The normal operating temperature of the tires is 90-125℃.

2. The low rolling resistance crown layer as described in claim 1, characterized in that, The difference in load force between the crown layer cord and the 0.5% and 3% deformation at normal tire operating temperature is between 0.7 and 1.0 cN / D.

3. The low rolling resistance crown layer as described in claim 1, characterized in that, The M100 of the crown layer rubber compound is between 2.0 and 3.0 MPa, and the M300 is between 10.0 and 14.0 MPa.

4. The low rolling resistance crown layer as described in claim 3, characterized in that, The M100 of the crown band layer rubber compound is 2.5 MPa, the M300 is 12 MPa, and the calendering thickness of the crown band layer is 1.1 mm.

5. A low rolling resistance tire, comprising, from the outside to the inside, a tread rubber layer, a crown belt layer, a belt layer, and a ply layer, characterized in that, The crown layer is disposed between the belt layer and the tread rubber layer, the crown layer covers the belt layer, and the crown layer is the low rolling resistance crown layer as described in any one of claims 1-4.

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