pneumatic tires

Abstract

Pneumatic tire (1) having grooves in a tread section (10), wherein the ratio of a total width SW and an outer diameter OD of the pneumatic tire SW / OD SW / OD ≤ 0.3 fulfilled and in a ground contact area of ​​the tread section (10), if - a groove area ratio in a soil contact area GR is, - a ground contact width W is, - an area with a width of 50% of the ground contact width W and an equatorial plane CL of the tire as its center is a central area AC, - a groove area ratio in the central area AC GCR is, - a ground contact area in the tire width direction on an outside of the center area AC is a shoulder area AS and - a groove area ratio in the shoulder area AS GSR is such that the ground contact area of ​​the tread section (10) is formed in such a way that 10% ≤ GR ≤ 25% 0.1 < GSR / GCR ≤ 0.4 is fulfilled.

Description

Technical field

[0001] The present invention relates to a passenger car pneumatic tire with lower fuel consumption. State of the art

[0002] Prior art has proposed pneumatic tires that reduce rolling resistance to contribute to lower fuel consumption in vehicles, particularly hybrid (HV) and electric (EV) vehicles. In recent years, due to increasing environmental awareness, there has been even greater demand for pneumatic tires that contribute more significantly to lower fuel consumption.

[0003] Reducing the overall width (SW) of a pneumatic tire so that the front projection area is lowered in order to reduce air resistance around the tire is known as a method for reducing the rolling resistance of pneumatic tires (see for example WO 2011 / 135774 A1).

[0004] The state of the art also includes the publications JP 2012- 91 736 A, EP 2 554 402 A1, WO 2012 / 066 725 A1, DE 690 01 738 T2 and EP 2 223 812 B1. Summary of the invention Problems to be solved by the invention

[0005] However, the method described above reduces the ground contact width because the overall width of the pneumatic tire is reduced, making it necessary to increase the outer diameter (OD) to maintain a constant load capacity. Therefore, the ground contact length of the pneumatic tire becomes comparatively longer.

[0006] Increasing the ground contact length of the pneumatic tire significantly improves water drainage (wet performance). Conversely, reducing the ground contact width decreases lateral force (CF), which can reduce steering stability.

[0007] Accordingly, one object of the present invention is to provide a pneumatic tire that is able to reduce rolling resistance and improve the associated deterioration in steering stability performance. Means to solve the problem

[0008] To solve the problem described above, the present invention is a pneumatic tire having grooves in a tread section, wherein the ratio of a total width SW and an outer diameter OD of the pneumatic tire is SW / OD. SW / OD≤0.3 is met and in a ground contact area of ​​the tread section, if a groove area ratio with respect to a ground contact area is GR, a ground contact width is W, an area with a width of 50% of the ground contact width W and an equatorial plane of the tire as its center is a center area AC, a groove area ratio in the center area AC is GCR, a ground contact area in the tire width direction on an outside of the center area AC is a shoulder area AS, and a groove area ratio in the shoulder area AS is GSR, the ground contact area of ​​the tread section is formed in such a way that: 10%≤GR≤25%0.1 < GSR / GCR ≤ 0.4 is fulfilled. Effect of the invention

[0009] According to the pneumatic tire of the present invention, rolling resistance can be reduced while improving the associated deterioration in steering stability performance.

[0010] The present invention can also be sufficiently understood from the following description of preferred embodiments of the present invention together with the accompanying drawings. Brief description of the drawings Fig. Figure 1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment of the present invention. Fig. Figure 2 is a development view illustrating a section of the tread section of the pneumatic tire according to an embodiment of the present invention. Fig. Figure 3 is a development view illustrating a section of the tread section of the pneumatic tire according to a modified example of the embodiment of the present invention. Fig. Figure 4 is a unfolded view illustrating a section of the tread section of the pneumatic tire according to a prior art example. Best method for implementing the invention. Implementation forms.

[0011] The following is a description of a pneumatic tire 1 according to an embodiment of the present invention with reference to the drawings. Fig. Figure 1 is a meridian cross-sectional view of the pneumatic tire 1 according to the embodiment of the present invention. It should be noted that the pneumatic tire 1 according to the present embodiment has a meridian cross-sectional shape similar to that of a prior art pneumatic tire. Here, the meridian cross-sectional shape of the pneumatic tire refers to the cross-sectional shape of the pneumatic tire as it appears on a plane perpendicular to the equatorial plane of the tire CL.

[0012] In the following description, "tire radial direction" refers to a direction perpendicular to the rotation axis AX of the pneumatic tire 1. Furthermore, "tire circumferential direction" refers to the direction of rotation around the rotation axis AX as the center (see Fig.2) Furthermore, “tire width direction” refers to the direction parallel to the axis of rotation AX; “inside in tire width direction” refers to the side facing the equatorial plane of the tire (tire equator line) CL in the tire width direction; and “outside in tire width direction” refers to the side that is opposite the equatorial plane of the tire CL in the tire width direction. “Equatorial plane of the tire CL” refers to a plane that is perpendicular to the axis of rotation AX of the pneumatic tire 1 and that passes through the center of the tire width of the pneumatic tire 1. “Tire equator line” refers to a line along the circumferential direction of the pneumatic tire 1 that lies on the equatorial plane of the tire CL. In this description and the drawings, the “tire equator line” is given the same reference symbol “CL” as the equatorial plane of the tire.

[0013] In the tire meridian cross-sectional view, the pneumatic tire 1 according to the present embodiment has a pair of tire bead sections 2, sidewall sections 3 which are connected to the tire bead sections, and a tread section 10 which is connected to the sidewall sections.

[0014] It should be noted that there is no specific limitation regarding the internal structure of the pneumatic tire in the present invention. The internal structure of the pneumatic tire varies depending on the performance or design required for the pneumatic tire and is preferably determined, for example, by tests or simulation to meet various requirements.

[0015] The pneumatic tire 1 according to the present embodiment is designed such that the ratio of the total width SW and the outer diameter OD is given by the relationship SW / OD≤0.3 fulfilled.

[0016] It should be noted that in the present invention, the overall width SW is the distance between the two sidewalls, including any features on the sidewalls, when the pneumatic tire 1 is mounted on a rim and inflated to an internal pressure of 230 kPa (or a specified internal pressure) to indicate the dimensions of the pneumatic tire 1 in its unloaded state. Furthermore, the outer diameter OD is the outer diameter of the tire at that time. It should be noted that the internal pressure of 230 kPa is selected to specify the dimensions of the pneumatic tire as stated above. Therefore, it should be noted that, provided the pneumatic tire 1 according to the present invention is inflated to an internal pressure within the normally used range, the effect of the present invention will be evident, and inflating to an internal pressure of 230 kPa is not essential for the implementation of the present invention.

[0017] Here, the rim used in the present invention has a diameter compatible with the inner diameter of the pneumatic tire 1 and has a nominal rim width corresponding to the specified rim width Rm (mm) given in Table 2, which is closest to the value (Rm = K1 × Sn) obtained from the product of the nominal tire cross-sectional width Sn and the coefficient K1 from Table 1 according to the aspect ratio of the tire mounted on the rim, as specified in ISO 4000-1:2001. [Table 1] aspect ratio K1 20-25 0,92 30-40 0,90 45 0,85 50-55 0,80 60-70 0,75 75-95 0,70 [Table 2] Nominal rim width Rm (mm) 3 76,2 3,5 88,9 4 101,6 4,5 114,3 5 127 5,5 139,7 6 152,4 6,5 165,1 Nominal rim width Rm (mm) 7 177,8 7,5 190,5 8 203,2 8,5 215,9 9 228,6 9,5 241,3 10 254

[0018] Fig.Figure 2 is a developed view illustrating a section of the tread section 10 of the pneumatic tire 1 according to an embodiment of the present invention. Four longitudinal grooves 12A, 12B extending in the circumferential direction of the tire and rib sections 14A, 14B, 14C, separated by the longitudinal grooves 12A, 12B, are formed on the tread section 10 of the pneumatic tire 1 according to the present embodiment. A plurality of transverse grooves 16A, 16B, 16C, extending in a direction that intersects the circumferential direction of the tire, and grooves arranged on the tread section 10 that differ from the longitudinal grooves 12A, 12B, are formed in the rib sections 14A, 14B, and 14C, respectively. It should be noted that in this patent specification grooves 12, 16 refer to the longitudinal grooves 12 and the transverse grooves 16 and in the present invention transverse grooves 16 have a groove width of not less than 1.5 mm.

[0019] In the pneumatic tire 1 according to the present embodiment, when the flat ground surface is brought into contact with a load corresponding to 80% of the load capacity, the groove area ratio GR in the ground contact area, the groove area ratio GCR in the middle area AC and the groove area ratio GSR in the shoulder area AS are designed such that they satisfy the following relationships: 10%≤GR≤25% 0.1 <GSR / GCR≤0,4

[0020] In the present invention, the ground contact area G is the area of ​​the ground contact patch when the pneumatic tire 1 is mounted on the rim as described above, inflated to an internal pressure of 230 kPa, and in contact with a flat ground surface with an applied load corresponding to 80% of the load capacity. The ground contact width W is the maximum width in the tire width direction within the ground contact area. The ground contact length L is the maximum length in the tire circumference direction within the ground contact area. Furthermore, in the present invention, the load capacity is defined based on ISO 4000-1: 1994. For a size for which the load capacity index is not specified in the ISO standard, the load capacity can be determined by a separate calculation, taking into account compliance with the standards of the respective country, and in this case, the load capacity is calculated based on the standards of the respective country.Therefore, in the present invention, the load capacity for each tire size is calculated from the following calculation equation (c), which is published in "Calculation of Load Capacity" in the notes to JIS D 4202-1994, which is the calculation equation for the actual load capacity that is in the. JIS patent specification is used. X=K×2.735×10−5×p0.585×Sd1.39×(DR−12.7+Sd) where X = load capacity (kg) K = 1.36 P = 230 (= air pressure (kPa)) Sd=0.93×S0.75−0.637 d S0.75=S×((180°−Sin−1(Rm / S)) / 131.4°) S = designed cross-sectional width (mm) R m = Rim width corresponding to the designed cross-sectional width (mm) d=(0.9−aspect ratio(−))×S0.75−6.35 D R = Reference value for the rim diameter (mm)

[0021] Furthermore, the groove area ratio GR is the ratio of the groove area to the sum of the web section area and the groove area within the ground contact area G (= ground contact area).

[0022] Furthermore, as in Fig. Figure 2 illustrates that the center area AC is an area within the ground contact area G with a width of 50% of the ground contact width W, with the equatorial plane of the tire CL as its center, and the shoulder area AS is an area within the ground contact area G that is subordinated to the outside of the center area AC in the tire width direction. Furthermore, the groove area ratio GCR in the center area AC is the ratio of the groove area to the sum of the rib section area and the groove area in the center area AC, and the groove area ratio GSR in the shoulder area AS is the ratio of the groove area to the sum of the rib section area and the groove area in the shoulder area AS.

[0023] According to the pneumatic tire 1 of the present embodiment, the following actions and effects can be achieved.

[0024] (1) The pneumatic tire 1 according to the present embodiment is designed such that the ratio of the total width SW and the outer diameter OD corresponds to the relationship in the preceding equation <1> This is fulfilled. Accordingly, the overall width SW relative to the outer diameter OD is smaller than that of a standard-sized pneumatic tire (for example, 205 / 55R16 (SW / OD = 0.32)). As a result, the frontal projection area of ​​the pneumatic tire 1 is smaller, thus reducing the air resistance around the tire, and therefore the rolling resistance of the pneumatic tire 1 can be reduced. On the other hand, if the overall width SW is simply reduced, the load capacity of the pneumatic tire 1 is reduced. However, by fulfilling the equation <1> The outer diameter OD is increased in relation to the total width SW, so that the reduction in load capacity can be suppressed.

[0025] (2) The pneumatic tire 1 according to the present embodiment is designed such that the groove area ratio GR, with respect to the ground contact area, has a value in the range given by the preceding equation <2> The specified area is defined. This area of ​​the groove area ratio GR is set lower than in a normal pneumatic tire. Accordingly, steering stability can be increased by increasing the stiffness of the tread section 10 by increasing the ground contact area of ​​the rib sections 14. If the groove area ratio GR is above 25%, the stiffness of the tread section 10 is reduced, making it impossible to achieve sufficient lateral grip, and steering stability cannot be increased.Furthermore, if the overall width SW is narrow, the water drainage properties are improved as mentioned above, but if the groove area ratio GR is reduced to less than 10%, the grooves 12, 14 provided on the tread section 10 are reduced, so that not enough water drainage can be achieved in the ground contact area G, making it difficult to maintain the overall water drainage properties.

[0026] (3) The pneumatic tire 1 according to the present embodiment is designed such that the groove area ratio GCR in the central region AC and the groove area ratio GSR in the shoulder region AS satisfy the relationship of the above equation <3> This fulfills the requirements. Accordingly, fewer grooves are provided in the shoulder area AS than in the middle area AC. As a result, the reduction in water drainage properties due to the comparatively low groove area ratio GR can be suppressed by applying the above equation. <2> This requirement is met. Furthermore, the stiffness of the tread section 10 in the shoulder area AS is increased by increasing the area of ​​the rib sections 14 located in the shoulder area AS and in contact with the ground compared to that in the central area AC. As a result, sufficient lateral grip can be achieved, and therefore steering stability can be improved.

[0027] (4) As described in (1), the pneumatic tire 1 according to the present embodiment has an outer diameter OD that is comparatively larger and an overall width SW that is comparatively narrower than that of a pneumatic tire of normal size. Therefore, it is assumed that reduced space requirements on the vehicle, improvements in design, and also improved wet performance due to the longer ground contact length, in particular resistance to aquaplaning, can be achieved.

[0028] It should be noted that the groove area ratio GR is more preferentially satisfied by the relationship: 10%≤GR≤20% This is because steering stability can be further improved by increasing the stiffness of the tread section 10 by increasing the area of ​​the web sections 14 that are in contact with the ground in the ground contact area G.

[0029] Furthermore, preferably at least one longitudinal groove 12, extending in the tire's circumferential direction, is provided in the central area AC. This is because the deterioration in water drainage properties can be suppressed by reducing the groove area ratio GR while maintaining a sufficient groove area in the central area AC. For a similar reason, the groove width of the longitudinal groove 12 provided in the central area AC is more preferably wide, in particular not less than 7 mm, and more preferably not fewer than two longitudinal grooves 12 are provided in the central area AC.

[0030] Furthermore, preferably at least two transverse grooves 16C, extending from the ground contact width edge WE, which is the edge in the tire width direction of the ground contact area G, which is arranged in the shoulder area AS, to the equatorial line of the tire CL, are provided within the ground contact area G of the tread section 10, and the ratio of the pitch distance A between adjacent transverse grooves 16C and the ground contact length L is satisfied: 0.2 By providing the transverse grooves 16C in this way, the reduction in water drainage properties in the shoulder area AS can be suppressed. Here, the pitch spacing A refers to the dimension at the point where the pitch distance between the transverse grooves 16C, which are arranged adjacent to each other in the tire's circumferential direction, is greatest (see Fig. 2).

[0031] ​If the ratio "A / L" is equal to or less than 0.2, the circumferential length of the rib sections 14C between the lateral grooves 16C in the shoulder area AS is shortened. As a result, the tread stiffness in the shoulder area AS is reduced, and it is difficult to improve steering stability. If the ratio "A / L" is greater than 0.5, the number of lateral grooves arranged in the shoulder area AS is reduced, and it is difficult to counteract the reduction in water drainage properties.

[0032] Furthermore, for a similar reason to equation <5> Preferably, 28 to 72 transverse grooves 16C are provided around the circumference of the pneumatic tire 1 in the shoulder areas AS, located on both sides of the equatorial line of the tire CL. Providing the transverse grooves 16C in this way can suppress the reduction in water drainage properties in the shoulder areas AS. (Modified example)

[0033] Fig.Figure 3 is a flattened view illustrating a section of the tread of the pneumatic tire according to a modified example of the embodiment of the present invention. This modified example differs from the present embodiment in that the transverse grooves 16C are not connected to the longitudinal grooves 12.

[0034] The longitudinal grooves 12 running in the tire's circumferential direction and the transverse grooves 16C extending from the ground contact edge WE, located in the shoulder region AS, to the equatorial line of the tire CL, are provided in the tread section 10 of the pneumatic tire 1 according to this modified example; however, the transverse grooves 16C are not connected to the longitudinal grooves 12. In other words, in this modified example, the inner edge 16Ci of the transverse groove 16C, located in the tire's width direction, is not connected to the longitudinal groove 12C, which is located on the outermost side in the tire's width direction.

[0035] First, the reduction in water drainage properties can be suppressed by providing the transverse grooves 16C in the shoulder area AS. If the transverse groove 16C is not connected to the longitudinal groove 12C, as in the present modified example, the rib section 14C is not divided by the transverse groove 16C, but is integral to it. In this way, the stiffness of the tread section 10 is increased, particularly in the shoulder area AS, so that sufficient lateral force can be achieved, which is desirable with regard to improving steering stability.

[0036] It should be noted that, as in Fig.Figure 3 illustrates that, more preferably, the inner edge 16Ci is positioned in the tire width direction of the transverse groove 16C within a region ASC that is 30% to 80% of the width of the shoulder region AS, in other words, 1 / 4 of the ground contact width W from the ground contact width edge WE. This is because, as mentioned above, both the reduction in water drainage properties can be suppressed by providing the transverse grooves 16C and the stiffness of the shoulder region AS can be increased. However, the inner edge 16Ci can also be positioned outwards from the region ASC.

[0037] Furthermore, the depth of the transverse groove 16C, which extends from the ground contact width edge WE (the edge in the tire width direction of the ground contact area G located in the shoulder region AS) to the equatorial line of the tire CL, is preferably less than the depth of the longitudinal groove 12. This is because a shallower depth of the transverse groove 16C increases the stiffness of the tread section 10, particularly in the shoulder region AS, thus ensuring sufficient lateral grip and improving steering stability. Examples

[0038] Various tire performance tests, such as RRC index, fuel efficiency index, steering stability, and resistance to aquaplaning (water drainage properties), were carried out under different conditions on pneumatic tires according to exemplary designs.

[0039] In these performance tests, each test tire was mounted on a rim of a compatible size, as described above, and was inflated to an internal pressure of 230 kPa for the respective vehicle tests.

[0040] The following is a description of the test procedures for the performance tests that were carried out on the test tires. (RRC index)

[0041] Using a drum tester with a drum diameter of 1707.6 mm, the rolling resistance was measured according to ISO 28580 under conditions of an air pressure of 210 kPa and a speed of 80 km / h. The evaluation results were expressed using the reciprocal as the measured value, indexed to 100, representing the state of the art. Lower index values ​​indicate lower rolling resistance. (Fuel efficiency performance)

[0042] The test tires were mounted on a front-wheel-drive vehicle with an 1800 cc engine and driven for 50 laps at a speed of 100 km / h on a 2 km test track. The fuel consumption improvement rate was measured relative to the fuel consumption of a state-of-the-art example, with a value of 100. Higher index values ​​indicate better fuel consumption. (Steering stability)

[0043] The test tires were mounted on a standard rim and fitted to a passenger car (1800 cc engine). The feel when changing lanes during three laps of a 2 km test track was evaluated by three experienced drivers. The evaluation results for the average score for each test tire were expressed as an index, with the average of the feel score from comparison example 1 serving as 100. Higher index values ​​indicate superior steering stability. (Aquaplaning resistance)

[0044] Aquaplaning resistance was assessed by conducting a straight-line aquaplaning test and measuring the speed at which aquaplaning occurred. In this straight-line aquaplaning test, the test vehicle was driven into a water basin with a water depth of 10 mm while the speed was increased, and the tire slip ratio was measured. The speed at which the slip ratio reached 10% was taken as the speed at which aquaplaning occurred. In this test, the measurement results for tests other than the prior art example were expressed as an index, with the measurement results of the prior art example serving as 100. In this embodiment, higher index values ​​indicate better aquaplaning resistance.

[0045] The following is a description of each of the test tires and the performance test results. (Example of the state of the art)

[0046] The pneumatic tire according to the prior art example was a tire of size 205 / 55R16, the value of “SW / OD” was 0.32, in other words, the equation <1> not fulfilled. The tread section of the pneumatic tire, according to the prior art example, exhibited the in Fig. 4 illustrated tread pattern patterns. (Examples 1 to 14)

[0047] The pneumatic tires according to embodiments 1 to 14 had tire sizes that differed from one another, and “SW / OD” had values ​​within the range of 0.3 to 0.21; in other words, equation <1> fulfilled. On the tread section 10 of the pneumatic tires according to embodiments 1 to 14, tread profile patterns were created based on the one described in Fig. Four illustrated tread pattern patterns, adapted to the respective tire size, are provided.

[0048] Performance tests for the RRC index and the fuel efficiency index were carried out for the state-of-the-art example and embodiments 1 to 14. Table 3 shows the dimensions for each test tire and the performance test results. [Table 3-I] State of the art example Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Nominal width 205 185 195 175 185 155 165 175 aspect ratio 55 55 50 60 50 60 55 50 Inner diameter (inches) 16 17 18 17 19 17 18 20 OD (mm) 632 640,8 657,2 647,8 672,6 623,8 644,2 688 SW / OD 0,32 0,30 0,30 0,28 0,28 0,26 0,26 0,26 RRC Index 100 99 99 98 98 98 96 96 Fuel efficiency index 100,0 100,1 100,1 100,1 100,1 100,1 100,2 100,1 [Table 3-II] Example 8 Example 9 Example 10 Example 11 Example 12 Example 13 Example 14 Nominal width 145 155 165 145 155 145 145 aspect ratio 65 60 55 70 60 65 55 Inner diameter (inches) 17 19 20 17 20 19 21 OD (mm) 626,8 674,6 695 641,8 700 677,6 698,4 SW / OD 0,24 0,24 0,24 0,23 0,23 0,22 0,21 RRC Index 97 95 96 95 93 94 93 Fuel efficiency index 100,2 100,3 100,2 100,3 100,3 100,2 100,2

[0049] According to the performance test results in Table 3, the test tires according to embodiments 1 to 14, which the equation <1> They met a better RRC index and fuel efficiency index than the state-of-the-art example, and therefore the rolling resistance was reduced.

[0050] (Embodiments 15 to 17 and Comparative Examples 1 to 3) The pneumatic tires according to embodiments 15 to 17 and comparative examples 1 to 3 had a tire size of 165 / 55R20. The pneumatic tire according to comparative example 1 was a test tire in which only the tire size was changed from the prior art example. Furthermore, the pneumatic tires according to embodiments 15 to 17 and comparative examples 2 to 3 were test tires in which the GSR / GCR ratio was 0.4 and the groove area ratio GR varied within the range of 6 to 30%. In these cases, embodiments 15 to 17 satisfied the relationships of all equations. <1> until <3> However, comparison examples 1 to 3 did not satisfy the relationship of equation <2> .

[0051] Comparative Example 1 was a reference tire for steering stability, as explained above. In other words, in the present invention, the tire size for steering stability was changed to a tire size with a narrow width and large diameter for reduced rolling resistance, so that a tire with reduced steering stability was used as a reference. Furthermore, the extent to which the steering stability of the pneumatic tires was improved according to the exemplary embodiments with respect to Comparative Example 1 was evaluated.

[0052] In this process, the tread section of the pneumatic tires was provided according to the embodiments and comparative examples with the tread profile pattern of the prior art example; in other words, the tread profile pattern of Fig.4. The tread pattern was modified as a basis to adapt it to the groove area ratio (GR) and other dimensional parameters for the respective test tire. For example, the tread section of the pneumatic tire according to embodiment 15 exhibited the pattern shown in Fig. 2 illustrated tread pattern patterns. Similarly, the pneumatic tires according to the exemplary embodiments and comparative examples were tested using the tread pattern of Fig. 4 as a basis and by varying the groove area of ​​the longitudinal grooves 12 and the transverse grooves 16 and the number of longitudinal grooves 12 and their positions in the tire width direction, different patterns were produced which were adapted to the dimensional parameters of the respective test tire, as in the case of the one in Fig. 2 illustrated tread pattern patterns.

[0053] For the pneumatic tires according to the prior art example, embodiments 15 to 17 and comparative examples 1 to 3, performance tests were carried out for the fuel efficiency index, steering stability and resistance to aquaplaning (referred to as "aquaplaning performance" in Table 4 and also in Tables 5 to 7). Table 4 shows numerical values ​​of the dimensions for each test tire and the performance test results. [Table 4] State of the art example Comparative example 1 Comparative example 2 Example 15 Example 16 Example 17 Comparative example 3 Nominal width 205 165 165 165 165 165 165 aspect ratio 55 55 55 55 55 55 55 Inner diameter (inches) 16 20 20 20 20 20 20 OD (mm) 632 695 695 695 695 695 695 SW / OD 0,32 0,24 0,24 0,24 0,24 0,24 0,24 GR (%) 30 30 8 15 20 25 30 GSR / GCR 1,0 1,0 0,4 0,4 0,4 0,4 0,4 Fuel efficiency index 100 100,3 100,3 100,3 100,3 100,3 100,3 Steering stability 106 100 105 104 103 102 98 Aquaplaning performance 100 108 92 101 105 106 107

[0054] According to the performance test results in Table 4, the test tires according to embodiments 15 to 17, which describe the relationships of the equations, had <1> until <3> They met the requirements, achieving a higher fuel efficiency index than the state-of-the-art example and higher steering stability than comparison example 1. In other words, these test tires had reduced rolling resistance, and the associated deterioration in steering stability performance was improved.

[0055] The pneumatic tires according to embodiments 20 to 22, non-inventive examples 18 and 19, and comparative example 4 were test tires with a tire size of 165 / 55R20, the groove area ratio GR was 20%, and the CSR / GCR varied within the range of 0.0 to 1.2. As mentioned above, the tread sections of the pneumatic tires according to these examples had a tread pattern that was determined using the one described in Fig.4 was modified as a basis. In this case, embodiments 20 to 22 satisfied the relationships of the equations. <1> until <3> Furthermore, embodiments 20 to 22 satisfied the relationship of equation <4> .

[0056] Performance tests for fuel efficiency index, steering stability, and aquaplaning resistance were carried out on the pneumatic tires according to the prior art example, embodiments 20 to 22, the non-inventive examples 18 and 19, and comparative examples 1 and 4. Table 5 shows the numerical values ​​of the dimensions of each test tire, the test conditions, and the performance test results. [Table 5] State of the art example Comparative example 1 Comparative example 4 Example 18 Example 19 Example 20 Example 21 Example 22 Nominal width 205 165 165 165 165 165 165 165 aspect ratio 55 55 55 55 55 55 55 55 Inner diameter (inches) 16 20 20 20 20 20 20 20 OD (mm) 632 695 695 695 695 695 695 695 SW / OD 0,32 0,24 0,24 0,24 0,24 0,24 0,24 0,24 GR (%) 30 30 20 20 20 20 20 20 GSR / GCR 1,0 1,0 1,2 0,8 0,6 0,4 0,2 0,0 Fuel efficiency index 100 100,3 100,3 100,3 100,3 100,3 100,3 100,3 Steering stability 106 100 95 101 102 103 102 102 Aquaplaning performance 100 108 97 101 104 105 103 99

[0057] According to the performance test results in Table 5, the pneumatic tires according to embodiments 20 to 21, which additionally describe the relationship of equation <4> fulfilled the requirements for superior steering stability and resistance to aquaplaning compared to the tires of Example 18 and Comparison Example 4. (Examples 23 to 28)

[0058] The pneumatic tires according to embodiments 23 to 28 had a tire size of 165 / 55R20, and as mentioned above, the tread sections of the pneumatic tires according to embodiments 23 to 28 had tread profile patterns that were created using those in Fig. 4 as a basis were varied. Here, embodiments 25 to 27 additionally satisfied the relationship of equation <5> , however, embodiments 23, 24 and 28 did not satisfy the relationship of equation <5> .

[0059] Performance tests for fuel efficiency index, steering stability, and aquaplaning resistance were carried out on the pneumatic tires according to the prior art example, comparative example 1, and embodiments 23 to 28. Table 6 shows the numerical values ​​of the dimensions of each test tire, the test conditions, and the performance test results. [Table 6] State of the art example Comparative example 1 Example 23 Example 24 Example 25 Example 26 Example 27 Example 28 Nominal width 205 165 165 165 165 165 165 165 aspect ratio 55 55 55 55 55 55 55 55 Inner diameter (inches) 16 20 20 20 20 20 20 20 OD (mm) 632 695 695 695 695 695 695 695 SW / OD 0,32 0,24 0,24 0,24 0,24 0,24 0,24 0,24 GR (%) 30 30 20 20 20 20 20 20 GSR / GCR 1,0 1,0 0,4 0,4 0,4 0,4 0,4 0,4 A / L 0,2 0,2 0,1 0,2 0,3 0,4 0,5 0,6 Fuel efficiency index 100 100,3 100,3 100,3 100,3 100,3 100,3 100,3 Steering stability 106 100 101 103 104 104 105 106 Aquaplaning performance 100 108 102 104 106 105 104 101

[0060] According to the performance test results in Table 6, the pneumatic tires according to embodiments 25 to 27, which correspond to the equation <5> They achieved superior resistance to aquaplaning compared to the other embodiments. In other words, the water drainage properties were improved.

[0061] (Embodiments 29 to 30, Comparative Example 5) The pneumatic tires according to embodiments 29 to 30 and Comparative Example 5 had a tire size of 165 / 55R20. The tread section of the pneumatic tire according to Comparative Example 5 had a tread pattern that was developed using the one in Fig. 4 as a basis was modified as described above. On the other hand, the tread sections of the pneumatic tires according to embodiments 29 and 30 had tread profile patterns in which the transverse grooves running from the ground contact width edge to the equatorial line of the tire were not connected to the longitudinal grooves, as in Fig.Figure 3 illustrates a modified example of the foregoing embodiment. Furthermore, the depth of the transverse grooves provided in the tread section of the pneumatic tire according to embodiment 30 was 5 mm, which is less than the 8 mm depth of the longitudinal grooves. It should be noted that the tread sections of the pneumatic tires according to embodiments 29 and 30 are illustrated in Fig. Three illustrated tread pattern patterns were shown.

[0062] Performance tests for fuel efficiency index, steering stability, and aquaplaning resistance were carried out on the pneumatic tires according to the prior art example, embodiments 29 and 30, and comparative examples 1 and 5. Table 7 shows the numerical values ​​of the dimensions of each test tire, the test conditions, and the performance test results. It should be noted that under the entry "Transverse groove connection" in Table 7, "Connection" indicates that the transverse grooves, which extend from the edge of the road contact width to the equatorial line of the tire, are connected to the longitudinal grooves, and "No connection" indicates that the transverse grooves are not connected to the longitudinal grooves. Furthermore, under the entry "Groove depth (longitudinal / transverse)" in Table 7, for example, "8 / 5" indicates that the depth of the longitudinal grooves was 8 mm and the depth of the transverse grooves, which extend from the edge of the road contact width to the equatorial line of the tire, was 5 mm. [Table 7] State of the art example Comparison example 1 Comparative example 5 Example 29 Example 30 Nominal width 205 165 165 165 165 aspect ratio 55 55 55 55 55 Inner diameter (inches) 16 20 20 20 20 OD (mm) 632 695 695 695 695 SW / OD 0,32 0,24 0,24 0,24 0,24 GR (%) 30 30 30 18 18 GSR / GCR 1,0 1,0 1,0 0,4 0,4 A / L 0,2 0,2 0,2 0,3 0,3 transverse groove connection Connection Connection Connection No connection No connection Groove depth (circumference / transverse) 8 / 8 8 / 8 8 / 8 8 / 8 8 / 5 Fuel efficiency index 100 100,3 100,3 100,3 100,3 Steering stability 106 100 102 105 106 Aquaplaning performance 100 108 103 104 104

[0063] According to the performance test results in Table 7, the pneumatic tires according to embodiments 29 and 30, in which the transverse grooves extending from the ground contact edge to the equatorial line of the tire were not connected to the longitudinal grooves, had a better fuel efficiency index than the prior art example and exhibited superior steering stability compared to Comparative Example 1 and Comparative Example 5, and furthermore, the steering stability was equal to that of the prior art example. In other words, these test tires had the advantages of reduced rolling resistance and simultaneously improved steering stability.

[0064] Furthermore, the steering stability index of the pneumatic tire according to embodiment 30, in which the depth of the transverse grooves provided on the tread section and extending from the ground contact width edge to the equatorial line of the tire was less than that of the longitudinal grooves, was higher than that of embodiment 29, in which the groove depth was the same depth of 8 mm for both the longitudinal and transverse grooves.

[0065] It should be noted that the present invention has been described in detail on the basis of specific embodiments, but a person skilled in the art may make various changes and modifications without deviating from the scope of the claims and the concepts of the present invention.

[0066] The present invention is defined as follows.

[0067] (1) Pneumatic tire having grooves on a tread section wherein the ratio of the total width SW to the outer diameter OD of the pneumatic tire SW / OD SW / OD≤0.3 fulfilled and in the ground contact area of ​​the tread section, if the groove area ratio with respect to the ground contact area is GR, the ground contact width is W, the area with a width of 50% of the ground contact width W and the equatorial plane of the tire as its center is the center area AC, the groove area ratio in the center area AC is GCR, the ground contact area on the outside in the tire width direction from the center area AC is the shoulder area AS, and the groove area ratio in the shoulder area AS is GSR, the ground contact area of ​​the tread section is formed in such a way that 10%≤GR≤25%0.1 < GSR / GCR ≤ 0.4 is fulfilled.

[0068] (2) Pneumatic tires according to (1) or (2), wherein at least two transverse grooves extending from the ground contact width edge in the shoulder area to the equatorial line of the tire are provided in the ground contact area of ​​the tread section and the ratio of the pitch spacing A of the transverse grooves to the ground contact length L 0.2 fulfilled.

[0069] (3) Pneumatic tires according to (2) wherein the longitudinal groove extending in the direction of the tire circumference is provided in the tread section and the transverse grooves are not connected to the longitudinal groove.

[0070] (4) Pneumatic tires according to (3) wherein the depth of the transverse grooves is less than the depth of the longitudinal groove.

[0071] ​(5) Pneumatic tires according to (1) wherein in the tread section the longitudinal groove which extends in the circumferential direction of the tire and the transverse groove which extends from the ground contact width edge in the shoulder area to the equatorial line of the tire are provided and the transverse groove is not connected to the longitudinal groove.

[0072] (6) Pneumatic tires according to (5) wherein the depth of the transverse groove is less than the depth of the longitudinal groove. Industrial applicability

[0073] The pneumatic tire according to the present invention can advantageously be used as a pneumatic tire for lower fuel consumption in passenger cars. REFERENCE MARK: 1 pneumatic tire 10 tread section 12, 12A, 12B, 12C Longitudinal groove 14, 14A, 14B, 14C Bridge section 16, 16A, 16B, 16C Transverse groove SW Total width OD outer diameter W ground contact width AC Midrange AS shoulder area GR groove area ratio GCR groove area ratio in the middle area GSR groove surface ratio in the shoulder area

Claims

[1] Pneumatic tire (1) having grooves in a tread section (10) wherein the ratio of a total width SW and an outer diameter OD of the pneumatic tire SW / OD SW / OD≤0.3 fulfilled and in a ground contact area of ​​the tread section (10), if - a groove area ratio in a soil contact area GR is, - a ground contact width W is, - an area with a width of 50% of the ground contact width W and an equatorial plane CL of the tire as its center is a central area AC, - a groove area ratio in the central area AC GCR is, - a ground contact area in the tire width direction on an outside of the center area AC is a shoulder area AS and - a groove area ratio in the shoulder area AS GSR is such that the ground contact area of ​​the tread section (10) is formed in such a way that 10%≤GR≤25% 0.1 <GSR / GCR≤0,4 is fulfilled. [2] Pneumatic tires (1) according to claim 1, wherein at least two transverse grooves (16, 16A, 16B, 16C) extending from the ground contact width edge in the shoulder area to an equatorial line of the tire are provided in the ground contact area of ​​the tread section (10) and the ratio of a pitch A of the transverse grooves (16, 16A, 16B, 16C) and a ground contact length L 0.2 fulfill. [3] Pneumatic tire (1) according to claim 2, wherein a longitudinal groove (12, 12A, 12B, 12C) extending in the circumferential direction of the tire is provided in the tread section (10) and the transverse grooves (16, 16A, 16B, 16C) are not connected to the longitudinal groove (12, 12A, 12B, 12C). [4] Pneumatic tire (1) according to claim 3, wherein the depth of the transverse grooves (16, 16A, 16B, 16C) is less than the depth of the longitudinal groove (12, 12A, 12B, 12C). [5] Pneumatic tires (1) according to claim 1, ​wherein in the tread section (10) a longitudinal groove (12, 12A, 12B, 12C) extending in the direction of the tire circumference and a transverse groove (16, 16A, 16B, 16C) which runs from a ground contact width edge in the shoulder area to an equatorial line of the tire are provided and the transverse groove (16, 16A, 16B, 16C) is not connected to the longitudinal groove (12, 12A, 12B, 12C). [6] Pneumatic tire (1) according to claim 5, wherein the depth of the transverse groove (16, 16A, 16B, 16C) is less than the depth of the longitudinal groove (12, 12A, 12B, 12C).

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