Pneumatic radial tires for passenger cars

Abstract

To provide a pneumatic radial tire for a passenger vehicle that can improve a ground-contact shape of the tire to suppress motion performance from deteriorating.SOLUTION: A pneumatic radial tire for a passenger vehicle, in which a cross-section width SW of the tire and an outer diameter OD of the tire satisfy a predetermined relation, is provided with a layer arranged, outside in a tire radial direction of a belt, only at a half part on one side in a tire width direction, to cover at least an end of the belt.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This invention relates to a pneumatic radial tire for passenger cars. [Background technology]

[0002] As a pneumatic radial tire for passenger cars that improves fuel efficiency, the applicant has proposed a narrow-width, large-diameter pneumatic radial tire for passenger cars in which the relationship between the tire's cross-sectional width SW and the tire's outer diameter OD is set to a predetermined relationship (for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2011 / 135774 brochure [Overview of the project] [Problems that the invention aims to solve]

[0004] In recent years, the development of vehicles for personal mobility has progressed, and it is conceivable to use narrow-width, large-diameter pneumatic radial tires for passenger cars, particularly those with a small tire cross-sectional width SW.

[0005] However, when the tire's cross-sectional width SW is small, there is a risk that the contact patch shape will deteriorate and handling performance will decrease, especially when a large camber angle is applied or when the camber angle increases due to a change in the camber angle. Furthermore, such narrow, large-diameter pneumatic radial tires for passenger cars are often used at high internal pressures, and in such cases, the problem of deteriorated contact patch shape becomes particularly pronounced.

[0006] Therefore, the present invention aims to provide a pneumatic radial tire for passenger cars that can improve the contact patch shape and suppress the deterioration of driving performance. [Means for solving the problem]

[0007] The gist of the present invention is as follows: (1) A pair of bead sections, A carcass consisting of one or more carcass plies that toroidally span between a pair of bead sections, The carcass comprises a belt consisting of one or more belt layers, which is positioned on the radially outer side of the crown portion of the tire. The cross-sectional width SW of the aforementioned tire is less than 165 (mm), The ratio SW / OD of the tire's cross-sectional width SW to its outer diameter OD is 0.26 or less, or the tire's cross-sectional width SW (mm) and outer diameter OD (mm) are given by the following relational expression: OD(mm)≧-0.0187×SW(mm) 2 Satisfying +9.15 × SW(mm) - 380(mm), A pneumatic radial tire for passenger cars, characterized by having a layered layer positioned on the radial side of the belt and covering at least the end of the belt, on only one half in the width direction of the tire. Furthermore, "covering the ends of the belt" means covering the ends of each layer if the belt has two or more layers.

[0008] In this specification, "rim" refers to the standard rim for the applicable size (Measuring Rim in the ETRTO STANDARDS MANUAL, Design Rim in the TRA YEAR BOOK) which is an industrial standard valid in the region where the tire is produced and used, and which is listed or will be listed in the future in the STANDARDS MANUAL of the ETRTO (The European Tyre and Rim Technical Organisation) in Japan, the STANDARDS MANUAL of the ETRTO (The European Tyre and Rim Technical Organisation) in Europe, and the YEAR BOOK of the TRA (The Tire and Rim Association, Inc.) in the United States. (That is, the "rim" in "wheel" above includes not only current sizes but also sizes that may be included in the above industrial standards in the future. An example of "sizes that will be listed in the future" is the size listed as "FUTURE DEVELOPMENTS" in the ETRTO 2013 edition.) However, in the case of a size not listed in the above industrial standards, it refers to a rim with a width corresponding to the width of the tire bead. Furthermore, "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity of a single wheel in the applicable size and ply rating as described in JATMA, etc., and in the case of sizes not listed in the above industrial standards, "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity specified for each vehicle on which the tire is mounted. Furthermore, "maximum load capacity" refers to the load corresponding to the maximum load capacity mentioned above.

[0009] (2) The belt is further provided with one or more cap layers on the outer side in the tire radial direction and on the inner side in the tire radial direction of the layer layer, The pneumatic radial tire for passenger cars according to (1) above, wherein the number of cords etched into the cap layer is greater in one half in the tire width direction than in the other half in the tire width direction. If the number of nails driven in is not constant, the number of nails driven in refers to the average number of nails driven in one half or the other half in the tire width direction. In addition, when the tire has two or more cap plies, the "number of cords implanted in the cap ply" shall be obtained by dividing the total number of strands of all plies in the cross-section in the tire width direction by the total width of all plies in the tire width direction of the cap ply, and converting it to the unit (number / 50 mm).

[0010] (3) The carcass comprises a carcass body portion extending toroidally between a pair of bead portions, and a carcass folded-back portion formed by folding back around a bead core embedded in the bead portion from the carcass body portion. The end of the carcass folded-back portion on one half in the tire width direction is located closer to the inner side in the tire radial direction than the end of the carcass folded-back portion on the other half in the tire width direction, for the pneumatic radial tire for passenger cars described in the above (1) or (2). [Advantages of the Invention]

[0011] According to the present invention, it is possible to provide a pneumatic radial tire for passenger cars that can improve the grounding shape and suppress a decrease in motion performance. [Brief Description of the Drawings]

[0012] [Figure 1] It is a schematic view showing the cross-sectional width SW and outer diameter OD of the tire. [Figure 2] It is a cross-sectional view in the tire width direction of the pneumatic radial tire for passenger cars according to an embodiment of the present invention. [Figure 3] It is a schematic diagram for explaining changes in the grounding shape. [Figure 4] It is a diagram for explaining the arrangement of RFID. [Figure 5] It is a cross-sectional view in the tire width direction of the pneumatic radial tire for passenger cars of a modified example. [Embodiments for Carrying Out the Invention]

[0013] Hereinafter, embodiments of the present invention will be exemplified and described in detail with reference to the drawings.

[0014] FIG. 1 is a schematic view showing the cross-sectional width SW and the outer diameter OD of a tire. A pneumatic radial tire for a passenger car according to an embodiment of the present invention (hereinafter also simply referred to as a tire) has a cross-sectional width SW of the tire of less than 165 (mm), and the ratio SW / OD of the cross-sectional width SW to the outer diameter OD of the tire is 0.26 or less, and has a narrow-width and large-diameter shape. By making the cross-sectional width SW of the tire narrower than the outer diameter OD of the tire, air resistance can be reduced, and by making the outer diameter OD of the tire larger than the cross-sectional width SW of the tire, deformation of the tread rubber near the ground contact surface of the tire can be suppressed, and rolling resistance can be reduced. As a result, the fuel efficiency of the tire can be improved. The SW / OD is preferably 0.25 or less, and more preferably 0.24 or less. It is preferable that the above ratio is satisfied when the internal pressure of the tire is 200 kPa or more, more preferably satisfied when the internal pressure is 220 kPa or more, and even more preferably satisfied when the internal pressure is 280 kPa or more. This is because the rolling resistance can be reduced. On the other hand, it is preferable that the above ratio is satisfied when the internal pressure of the tire is 350 kPa or less. This is because the riding comfort can be improved. Here, the cross-sectional width SW of the tire is preferably 105 to 145 mm, and more preferably 115 to 135 mm. Also, when the cross-sectional width SW and the outer diameter OD of the tire satisfy the above ratio, the aspect ratio of the tire is more preferably 45 to 70, and even more preferably 45 to 65. While there are no specific limitations on tire sizes, some examples include 105 / 50R16, 115 / 50R17, 125 / 55R20, 125 / 60R18, 125 / 65R19, 135 / 45R21, 135 / 55R20, 135 / 60R17, 135 / 60R18, 135 / 60R19, 135 / 65R19, 145 / 45R21, and 145 / 5 The tire size can be any of the following: 5R20, 145 / 60R16, 145 / 60R17, 145 / 60R18, 145 / 60R19, 145 / 65R19, 155 / 45R18, 155 / 45R21, 155 / 55R18, 155 / 55R19, 155 / 55R21, 155 / 60R17, 155 / 65R18, 155 / 70R17, or 155 / 70R19.

[0015] Alternatively, the tire's section width SW is less than 165 mm, and the tire's section width SW (mm) and outer diameter OD (mm) are related by the following formula: OD(mm)≧-0.0187×SW(mm) 2 +9.15 × SW (mm) - 380 It satisfies the requirements and has a narrow width and large diameter shape. By satisfying the above relationship, air resistance and rolling resistance can be reduced, thereby improving the fuel efficiency of the tire. In the third embodiment, the tire's cross-sectional width SW and outer diameter OD are preferably such that the ratio SW / OD satisfies the above relationship, is 0.26 or less, more preferably 0.25 or less, and even more preferably 0.24 or less. This is because it can further improve the tire's fuel efficiency. The above relationship and / or ratio is preferably satisfied when the tire internal pressure is 200 kPa or higher, more preferably 220 kPa or higher, and even more preferably 280 kPa or higher, because it can reduce rolling resistance. On the other hand, the above relationship and / or ratio is preferably satisfied when the tire internal pressure is 350 kPa or lower, because it can improve ride comfort. Here, the tire section width SW is preferably 105 to 145 mm, and more preferably 115 to 135 mm. Furthermore, when the tire's cross-sectional width SW and outer diameter OD satisfy the above relationship, the aspect ratio of the tire is more preferably 45 to 70, and more preferably 45 to 65. While there are no specific limitations on tire sizes, some examples include 105 / 50R16, 115 / 50R17, 125 / 55R20, 125 / 60R18, 125 / 65R19, 135 / 45R21, 135 / 55R20, 135 / 60R17, 135 / 60R18, 135 / 60R19, 135 / 65R19, 145 / 45R21, and 145 / 5 The tire size can be any of the following: 5R20, 145 / 60R16, 145 / 60R17, 145 / 60R18, 145 / 60R19, 145 / 65R19, 155 / 45R18, 155 / 45R21, 155 / 55R18, 155 / 55R19, 155 / 55R21, 155 / 60R17, 155 / 65R18, 155 / 70R17, or 155 / 70R19.

[0016] The tire of this embodiment is a pneumatic radial tire for passenger cars. This tire is particularly suitable for use on personal mobility vehicles. This tire can be mounted on vehicles with a relatively large camber angle (e.g., 10° or more).

[0017] Figure 2 is a cross-sectional view in the width direction of a pneumatic radial tire for a passenger car according to one embodiment of the present invention. Figure 2 shows a cross-sectional view in the width direction of the tire in a standard state, with the tire mounted on a rim, filled to a specified internal pressure, and unloaded. As shown in Figure 2, this tire 1 has a carcass 3 made of radially arranged cord plies that spans toroidally between a pair of bead portions 2. In addition, this tire 1 has a belt 4 consisting of two belt layers 4a and 4b in the illustrated example and a tread 5 in order on the radially outer side of the carcass 3.

[0018] In this example, a bead core 2a is embedded in each of the pair of bead portions 2. In this invention, the cross-sectional shape and material of the bead core 2a are not particularly limited and can be a configuration commonly used in pneumatic radial tires for passenger cars. In this invention, the bead core 2a can also be divided into a plurality of small bead cores. Alternatively, in this invention, a configuration without a bead core 2a is also possible.

[0019] The illustrated example tire 1 has a bead filler 2b with a substantially triangular cross-section on the radially outer side of the bead core 2a. The cross-sectional shape of the bead filler 2b is not limited to this example, nor is the material particularly limited. Alternatively, the tire can be made lighter by omitting the bead filler 2b.

[0020] In this embodiment, the tire 1 may have a rim guard. Furthermore, in this embodiment, additional members such as rubber layers or cord layers may be provided in the bead portion 2 for reinforcement or other purposes. Such additional members can be provided at various positions relative to the carcass 3 and bead filler 2b.

[0021] In the example shown in Figure 2, the carcass 3 consists of one carcass ply. However, in the present invention, the number of carcass plies is not particularly limited and can be two or more. Also, in the example shown in Figure 2, the carcass 3 has a carcass body portion 3a that straddles a pair of bead portions 2 in a toroidal manner, and a folded portion 3b that is folded back from the carcass body portion 3a around the bead core 2a. On the other hand, in the present invention, the carcass folded portion 3b can be wrapped around the bead core 2a, or it can be a structure in which it is sandwiched between a plurality of divided small bead cores. As shown in the illustrated example, it is preferable that the end 3c of the carcass folded portion of one half in the tire width direction (right side in the illustration) is located radially inward of the end 3c of the carcass folded portion 3b of the other half in the tire width direction (left side in the illustration). On the other hand, the end 3c of the folded portion of the carcass in one half (right side in the illustration) in the tire width direction may be located radially outward from the end 3c of the folded portion of the carcass in the other half (left side in the illustration) in the tire width direction, or they may be at the same height. In this example, the end 3c of the folded portion of the carcass 3b is located radially outward from the radially outer end of the bead filler 2b and radially inward from the tire's maximum width position, both in one half and the other half in the tire width direction. This makes it possible to lighten the tire while ensuring the rigidity of the sidewall. On the other hand, in the present invention, the end 3c of the folded portion of the carcass 3b may be located radially inward from the radially outer end of the bead filler 2b, or it may be located radially outward from the tire's maximum width position. Alternatively, the end 3c of the folded portion 3b of the carcass can be an envelope structure, positioned between the carcass body 2a and the belt 4 in the tire radial direction, and located inward in the tire width direction from the end of the belt 4 (for example, the end of the belt layer 4b). For example, in one half of the tire width direction, the end 3c of the folded portion 3b of the carcass can be positioned radially outward from the radially outer end of the bead filler 2b and radially inward from the tire's maximum width position, while in the other half of the tire width direction, it can be positioned radially outward from the tire's maximum width position.Furthermore, if the carcass 3 is composed of multiple carcass plies, the positions of the ends 3c of the carcass folded portion 3b (e.g., positions in the tire radial direction) can be the same or different between the carcass plies. The number of cords woven into the carcass 3 is not particularly limited, but can be in the range of 20 to 60 cords / 50 mm, for example. Also, various structures can be adopted for the carcass lines. For example, in the tire radial direction, the position of the maximum width of the carcass can be brought closer to the bead portion 2 side or closer to the tread 5 side. For example, the position of the maximum width of the carcass can be set in the range of 50% to 90% relative to the tire cross-sectional height, radially outward from the bead baseline. The above "radial arrangement" is 85° or more with respect to the tire circumferential direction, preferably 90° with respect to the tire circumferential direction.

[0022] The tire of this embodiment preferably has one or more inclined belt layers made of rubberized cords that extend inclined with respect to the circumferential direction of the tire, and it is most preferable to have two layers in order to balance weight reduction and suppression of distortion of the contact surface shape. However, from the viewpoint of weight reduction, the belt layer can be one layer, and from the viewpoint of suppressing distortion of the contact surface shape, it is also possible to have three or more layers. In the example shown in Figure 2, of the two belt layers 4a and 4b, the width in the tire width direction of the outer belt layer 4b in the tire radial direction is smaller than the width in the tire width direction of the inner belt layer 4a in the tire radial direction. On the other hand, the width in the tire width direction of the outer belt layer 4b in the tire radial direction can be larger than the width in the tire width direction of the inner belt layer 4a in the tire radial direction, or they can be the same. The width in the tire width direction of the belt layer with the largest width in the tire width direction (belt layer 4a in the illustrated example) is preferably 90 to 115% of the contact width, and particularly preferably 100 to 105% of the contact width. Note that "contact width" refers to the distance in the tire width direction between the contact ends E. "Contact point" refers to both ends of the tire's contact surface in the tire's width direction when the tire is mounted on the rim, filled to the specified internal pressure, and subjected to the maximum load. In this embodiment, metal cords, particularly steel cords, are most preferably used as the belt cords for belt layers 4a and 4b, but non-metallic materials, such as organic fiber cords (e.g., Kevlar®), can also be used. Steel cords mainly consist of steel and may contain various trace elements such as carbon, manganese, silicon, phosphorus, sulfur, copper, and chromium. In this embodiment, monofilament cords, cords made of multiple filaments, and cords made of multiple filaments twisted together can be used for belt layers 4a and 4b. Various twisting structures can be adopted, and the cross-sectional structure, twist pitch, twisting direction, and distance between adjacent filaments can also vary. Furthermore, cords made of filaments of different materials twisted together can be used, and the cross-sectional structure is not particularly limited, with various twisting structures such as single twist, layer twist, and multi-twist being possible. In this embodiment, it is preferable that the inclination angle of the belt cords of belt layers 4a and 4b be 10° or more with respect to the tire circumferential direction. In this embodiment, it is preferable that the inclination angle of the belt cords of belt layers 4a and 4b be a high angle, specifically 20° or more with respect to the tire circumferential direction, preferably 35° or more, and particularly in the range of 55° to 85° with respect to the tire circumferential direction. This is because setting the inclination angle to 20° or more (preferably 35° or more) increases the rigidity in the tire width direction, which can improve handling stability performance, especially during cornering. It is also because it can reduce shear deformation of the interlayer rubber and reduce rolling resistance.

[0023] In the illustrated example, the tread rubber constituting the tread 5 consists of one layer. However, in this embodiment, the tread rubber constituting the tread 5 may be formed by laminating multiple different rubber layers in the tire radial direction. The multiple rubber layers can have different tangent loss, modulus, hardness, glass transition temperature, material, etc. Furthermore, the ratio of the thicknesses of the multiple rubber layers in the tire radial direction may change in the tire width direction, and the bottom of the circumferential main groove, for example, may be made of a different rubber layer from the surrounding area. The tread rubber constituting the tread 5 may also be formed of multiple different rubber layers in the tire width direction. The multiple rubber layers can have different tangent loss, modulus, hardness, glass transition temperature, material, etc. Furthermore, the ratio of the widths of the multiple rubber layers in the tire width direction may change in the tire radial direction, and only a limited part of the area, such as only near the circumferential main groove, only near the contact edge, only the shoulder land area, or only the center land area, may be made of a different rubber layer from the surrounding area.

[0024] The tire 1 of this embodiment has an inner liner 8 on the inner surface 7 of the tire (also simply referred to as the inner surface 7 of the tire). The thickness of the inner liner 8 is preferably about 1.5 mm to 2.8 mm, because it can effectively reduce in-vehicle noise in the 80 to 100 Hz range. The air permeability coefficient of the rubber composition constituting the inner liner 8 is 1.0 × 10⁻⁶. -14 cc·cm / (cm 2 ·s·cmHg) or more, 6.5×10 -10 cc·cm / (cm 2 It is preferable that the value be less than or equal to (s·cmHg).

[0025] Here, it is preferable that the negative ratio of the tread surface is greater in one half in the tire width direction than in the other half in the tire width direction. The "tread surface" refers to the surface that comes into contact with the road surface when the tire is mounted on the rim, filled to the specified internal pressure, and subjected to the maximum load. The "negative ratio" refers to the ratio of the total groove area of ​​grooves with a groove width (opening width) of 2 mm or more to the total area of ​​the tread surface. This is because relatively reducing the rigidity of the tread in one half in the tire width direction enhances the effect of improving the contact shape described later, thereby further improving the tire's performance. In the case of narrow-width, large-diameter tires as described above, high drainage can be ensured due to the narrow width, so a single circumferential main groove extending in the tire width direction can be provided in one half in the tire width direction, making the negative ratio of one half in the tire width direction greater than the negative ratio of the other half in the tire width direction.

[0026] As shown in Figure 2, this tire has a layer layer 9 positioned on the radially outer side of the belt 4 on only one half in the tire width direction, and covering at least the end of the belt 4. In addition, this tire has one or more cap layers 8 (one layer in the illustrated example) on the radially outer side of the belt 4 and radially inner side of the layer layer 9.

[0027] The cap layer 8 is formed by a ribbon-shaped member consisting of a rubberized layer of cords arranged substantially parallel to each other, which is wound spirally in the circumferential direction of the tire. In the illustrated example, the width of the cap layer 8 in the tire width direction is greater than the width of the belt 4 in the tire width direction. For example, organic fiber cords can be used for the cords of the cap layer 8. As shown in the illustration, it is preferable that the number of cords woven into the cap layer 8 is greater in one half of the tire width direction than in the other half. In this example, the number of cords woven into the cap layer 8 is constant in one half of the tire width direction, and the number of cords woven into the cap layer 8 is also constant in the other half of the tire width direction. On the other hand, for example, the number of cords woven into the cap layer 8 may be configured to gradually decrease from the outer end in the tire width direction of the cap layer 8 in one half of the tire width direction to the outer end in the tire width direction of the cap layer 8 in the other half of the tire width direction. Furthermore, it is preferable that the width of the cap layer 9 in the tire width direction is greater in one half of the tire width direction than in the other half. In this case, the number of cords inserted into the cap layer 8 in one half of the tire width direction can be the same as the number of cords inserted into the cap layer 8 in the other half of the tire width direction.

[0028] The layer 9 consists of a ribbon-shaped member made of rubberized layers of cords arranged substantially parallel to each other, wound spirally in the circumferential direction of the tire. In the illustrated example, the layer 9 covers one half of the belt 4 in the tire width direction. More specifically, the outer end of the layer 9 in the tire width direction is located further outward in the tire width direction than the outer end of the belt layer 4a in the tire width direction, and the inner end of the layer 9 in the tire width direction is located further inward in the tire width direction than the inner end of the belt layer 4b in the tire width direction. For example, organic fiber cords can be used for the cords of the layer 9.

[0029] The following describes the effects and advantages of the passenger car pneumatic radial tire of this embodiment. In the following, the effects and advantages are described when "one half in the tire width direction" is positioned on the inside when mounted on the vehicle (and when "the other half in the tire width direction" is positioned on the outside when mounted on the vehicle).

[0030] The pneumatic radial tire for passenger cars in this embodiment is a narrow-width, large-diameter tire in which the tire's cross-sectional width SW and the tire's outer diameter satisfy the above-mentioned relationship, and in particular, the cross-sectional width SW is less than 165 mm. With such a tire, air resistance can be reduced, and rolling resistance can also be reduced, thereby improving the tire's fuel efficiency. On the other hand, as schematically shown to the left of the arrow in Figure 3, with such tires, when a large camber angle is applied, or when a large camber angle is achieved during cornering, the contact patch shape becomes excessively elongated, degrading the contact patch shape and potentially reducing handling stability and other dynamic performance. While not particularly limited, this problem becomes especially pronounced when used at high internal pressures. In contrast, the tire of this embodiment is equipped with a layer layer 9 located on the radial side of the belt 4, but only on one half in the tire width direction (the inner half when mounted on the vehicle). This makes the rigidity of the outer tread portion when mounted on the vehicle relatively smaller than that of the inner tread portion when mounted on the vehicle, allowing the contact length to extend more easily. As schematically shown to the right of the arrow in Figure 3, this prevents the contact shape from becoming too elongated when a large camber angle is applied, thereby suppressing deterioration of the contact shape. Therefore, according to the pneumatic radial tire for passenger cars of this embodiment, the contact patch shape can be improved and the deterioration of handling performance can be suppressed. Furthermore, compared to the case where layer 9 is provided on half of both sides in the tire width direction, the tire can be made lighter and rolling resistance can be further reduced.

[0031] Here, one or more cap layers 8 are further provided on the outer side of the belt 4 in the tire radial direction and on the inner side of the layer layer 9 in the tire radial direction, and it is preferable that the number of cords inserted into the cap layer 8 is greater in one half in the tire width direction than in the other half in the tire width direction. When the "one half in the tire width direction" is the inner side when mounted on the vehicle, this configuration makes the rigidity of the outer tread portion when mounted on the vehicle even more relatively smaller than the rigidity of the inner tread portion when mounted on the vehicle, making it easier for the contact length to extend and further suppressing deterioration of the contact shape. For similar reasons, it is also preferable that the width of the cap layer 8 in the tire width direction is greater in one half of the tire width direction than in the other half.

[0032] Furthermore, the carcass 3 consists of a carcass body portion 3a that toroidally straddles the pair of bead portions 2, and a carcass folded portion 3b that is folded back from the carcass body portion 3a around the bead core 2a embedded in the bead portion 2. Preferably, the end of the carcass folded portion 3b of one half in the tire width direction is located inward in the tire radial direction than the end of the carcass folded portion 3b of the other half in the tire width direction. When one half in the tire width direction is positioned on the inside when mounted on the vehicle, this configuration allows for a relative increase in the rigidity of the outer part of the tire when mounted on the vehicle, which contributes greatly to the handling performance, thereby effectively improving handling performance. Note that the position of the end of the carcass folded portion 3b does not significantly contribute to the contact shape described above, and therefore does not hinder the improvement effect of the contact shape described above. Furthermore, as shown in Figure 5, let m1 be a straight line passing through a point on the tread surface at the tire's equatorial plane and parallel to the tire's width direction, and let m2 be a straight line passing through the contact end E and parallel to the tire's width direction. The distance between lines m1 and m2 in the tire's radial direction is the drop height L. CR Let TW be the tread width of the tire, and the ratio L CR It is preferable that / TW is greater than 0.045. This results in a relatively rounded crown shape, which allows the contact patch to be rounded, with the contact length of the shoulder portion being shorter than that of the center portion. This prevents the contact patch from becoming too elongated when the camber angle changes, further suppressing deterioration of the contact patch. "Contact edge" refers to both ends of the contact surface (the surface that contacts the road surface) in the tire width direction when the tire is mounted on the rim, filled to the specified internal pressure, and subjected to the maximum load. "Tread width" refers to the distance in the tire width direction between the contact edges when the tire is mounted on the rim, filled to the specified internal pressure, and unloaded.

[0033] <Tire and rim assembly> The tire-rim assembly described here is formed by incorporating the above-mentioned pneumatic radial tire for passenger cars into a rim. With this tire-rim assembly, the same effects and advantages as those described for the above-mentioned pneumatic radial tire for passenger cars can be obtained. In this case, the internal pressure of the tire-rim assembly is preferably 200 kPa or more, more preferably 220 kPa or more, and even more preferably 280 kPa or more. This is because a higher internal pressure can further reduce rolling resistance. On the other hand, the internal pressure of the tire-rim assembly is preferably 350 kPa or less. This is because it can improve ride comfort.

[0034] <How to use pneumatic radial tires for passenger cars> The method of using the passenger car pneumatic radial tire described here involves using the passenger car pneumatic radial tire described above. By using the passenger car pneumatic radial tire in this manner, the same effects and advantages as those described above can be obtained. In this case, it is preferable to use an internal pressure of 200 kPa or higher, more preferably 220 kPa or higher, and even more preferably 280 kPa or higher. This is because a higher internal pressure can further reduce rolling resistance. On the other hand, it is preferable to use an internal pressure of 350 kPa or lower. This is because it can improve ride comfort.

[0035] <Examples with communication devices> Figure 4 shows the widthwise half of the tire, which has a layered structure. As shown in Figure 4, the tire may be equipped with an RF tag as a communication device 50. The RF tag comprises an IC chip and an antenna. The RF tag may be positioned, for example, sandwiched between multiple identical or different components that make up the tire. This makes it easier to attach the RF tag during tire production and improves the productivity of tires equipped with RF tags. In this example, the RF tag may be positioned, for example, sandwiched between the bead filler and other components adjacent to the bead filler. The RF tag may also be embedded within any of the components that make up the tire. This reduces the load on the RF tag compared to when it is sandwiched between multiple components that make up the tire. This improves the durability of the RF tag. In this example, the RF tag may be embedded within a rubber component such as tread rubber or side rubber. It is preferable that the RF tag is not positioned at a boundary between components with different rigidity in the peripheral length direction, which is the direction along the outer surface of the tire in a cross-sectional view in the tire width direction. This prevents the RF tag from being positioned in a location where strain is likely to concentrate due to rigidity differences. Therefore, the load on the RF tag can be reduced. This improves the durability of the RF tag. In this example, it is preferable that the RF tag is not placed at a boundary between the end of the carcass and a member adjacent to the end of the carcass (e.g., side rubber) in a cross-sectional view in the tire width direction. The number of RF tags is not particularly limited. A tire may have only one RF tag or two or more RF tags. Here, an RF tag is used as an example of a communication device, but a different communication device may be used.

[0036] The RF tag may be placed, for example, on the tire tread. In this way, the RF tag will not be damaged by side cuts of the tire. The RF tag may be placed, for example, in the center of the tread in the tire width direction. The center of the tread is a position where flexing is less likely to concentrate in the tread. In this way, the load on the RF tag can be reduced. This can improve the durability of the RF tag. In addition, differences in communication with the RF tag from both outer sides of the tire in the tire width direction can be suppressed. In this example, the RF tag may be placed, for example, within a range of 1 / 2 of the tread width centered on the tire equator in the tire width direction. The RF tag may be placed, for example, at the tread edge in the tire width direction. If the position of the reader that communicates with the RF tag is predetermined, the RF tag may be placed, for example, at one tread edge close to this reader. In this example, the RF tag may be placed, for example, within a range of 1 / 4 of the tread width in the tire width direction, with the tread edge as the outer edge.

[0037] The RF tag may be positioned on the inner side of the tire cavity, for example, beyond the carcass, which includes one or more carcass plies spanning between the bead portions. This makes the RF tag less susceptible to damage from impacts applied from outside the tire, such as side cuts or nail punctures. As an example, the RF tag may be positioned in close contact with the inner surface of the carcass facing the inner cavity. As another example, if there is another component on the inner side of the tire cavity beyond the carcass, the RF tag may be positioned, for example, between the carcass and the other component located on the inner side of the carcass facing the inner cavity. An example of another component located on the inner side of the tire cavity beyond the carcass is the inner liner that forms the inner surface of the tire. As yet another example, the RF tag may be attached to the inner surface of the tire facing the inner cavity. By configuring the RF tag to be attached to the inner surface of the tire, it becomes easier to attach the RF tag to the tire and to inspect and replace the RF tag. In other words, the ease of attachment and maintenance of the RF tag can be improved. Furthermore, by attaching the RF tag to the inner surface of the tire, it is possible to prevent the RF tag from becoming the core of a tire failure compared to a configuration in which the RF tag is embedded inside the tire. Also, if the carcass has multiple carcass plies and there are positions where multiple carcass plies overlap, the RF tag may be placed between the overlapping carcass plies.

[0038] The RF tag may be positioned, for example, on the tire tread, outside the belt, which includes one or more belt plies, in the radial direction of the tire. For example, the RF tag may be positioned outside the belt in the radial direction of the tire, in close contact with the belt. Another example is when a reinforcing belt layer is provided, the RF tag may be positioned outside the reinforcing belt layer in the radial direction of the tire, in close contact with the reinforcing belt layer. Yet another example is when the RF tag is embedded in the tread rubber, outside the belt in the radial direction of the tire. By positioning the RF tag outside the belt in the tire tread, communication with the RF tag from the outside of the tire in the radial direction is less likely to be hindered by the belt. Therefore, communication with the RF tag from the outside of the tire in the radial direction of the tire can be improved. Alternatively, the RF tag may be positioned inside the belt in the tire tread, for example. In this way, the outside of the RF tag in the radial direction of the tire is covered by the belt, making the RF tag less susceptible to damage from impacts from the tread surface or nail punctures. As an example, the RF tag may be positioned in the tire tread between the belt and the carcass located radially inward from the belt. Furthermore, if the belt comprises multiple belt plies, the RF tag may be positioned between any two belt plies in the tire tread. In this manner, the outer radial side of the RF tag is covered by one or more belt plies, making the RF tag less susceptible to damage from impacts from the tread surface or nail punctures.

[0039] The RF tag may be placed, for example, in the sidewall or bead portion of the tire. The RF tag may be placed, for example, in the sidewall or bead portion on one side that is close to the reader that can communicate with the RF tag. This improves the communication between the RF tag and the reader. As an example, the RF tag may be placed between the carcass and the side rubber, or between the tread rubber and the side rubber. The RF tag may be placed, for example, between the position of the tire's maximum width and the position of the tread surface in the tire's radial direction. This improves the communication between the RF tag and the outside of the tire in the tire's radial direction compared to a configuration where the RF tag is placed inside the tire's maximum width position in the tire's radial direction. The RF tag may be placed, for example, inside the tire's maximum width position in the tire's radial direction. This places the RF tag near the highly rigid bead portion. Therefore, the load on the RF tag can be reduced. This improves the durability of the RF tag. As an example, the RF tag may be placed adjacent to the bead core in the tire's radial or tire width direction. Strain is less likely to concentrate near the bead core. Therefore, the load on the RF tag can be reduced. This improves the durability of the RF tag. In particular, it is preferable to position the RF tag radially inward from the position of the tire's maximum width, and radially outward from the bead core of the bead portion. By doing so, the durability of the RF tag can be improved, and communication between the RF tag and the reader is less likely to be hindered by the bead core, thereby improving the communication performance of the RF tag. Furthermore, if the side rubber is composed of multiple identical or different rubber members adjacent in the radial direction of the tire, the RF tag may be positioned sandwiched between the multiple rubber members that make up the side rubber.

[0040] The RF tag may be positioned sandwiched between the bead filler and a member adjacent to the bead filler. In this way, the RF tag can be positioned in a location where strain is less likely to concentrate due to the placement of the bead filler. Therefore, the load on the RF tag can be reduced. This improves the durability of the RF tag. The RF tag may also be positioned sandwiched between, for example, the bead filler and the carcass. The part of the carcass that sandwiches the RF tag together with the bead filler may be located on the outside in the tire width direction relative to the bead filler, or on the inside in the tire width direction. If the part of the carcass that sandwiches the RF tag together with the bead filler is located on the outside in the tire width direction relative to the bead filler, the load on the RF tag due to impacts and damage from the outside of the tire in the tire width direction can be further reduced. This improves the durability of the RF tag. The bead filler may also have a portion that is positioned adjacent to the side rubber. In such cases, the RF tag may be positioned sandwiched between the bead filler and the side rubber. Furthermore, the bead filler may have a portion positioned adjacent to the rubber chafer. In such cases, the RF tag may be positioned sandwiched between the bead filler and the rubber chafer.

[0041] The RF tag may be positioned, for example, sandwiched between a rubber chafer and a side rubber. In this way, the RF tag can be positioned in a location where strain is less likely to concentrate due to the placement of the rubber chafer. Therefore, the load on the RF tag can be reduced. This improves the durability of the RF tag. The RF tag may also be positioned, for example, sandwiched between a rubber chafer and a carcass. In this way, the load on the RF tag due to impacts and damage from the rim can be reduced. Therefore, the durability of the RF tag can be improved.

[0042] The RF tag may be disposed sandwiched between a wire chafer and another member adjacent to the inside or outside in the tire width direction of this wire chafer. By doing so, when the tire is deformed, the position of the RF tag becomes difficult to fluctuate. Therefore, the load applied to the RF tag when the tire is deformed can be reduced. Thereby, the durability of the RF tag can be improved. Another member adjacent to the wire chafer on the inside or outside in the tire width direction may be, for example, a rubber member such as a rubber chafer. Also, another member adjacent to the wire chafer on the inside or outside in the tire width direction may be, for example, a carcass.

[0043] A belt reinforcing layer may be further provided on the radially outer side of the belt. For example, the belt reinforcing layer may be formed by continuously winding a cord made of polyethylene terephthalate in a spiral shape in the tire circumferential direction. Here, the cord is subjected to an adhesive treatment by applying a tension of 6.9×10 -2 N / tex or more, and the elastic modulus at a load of 29.4 N measured at 160°C may be 2.5 mN / dtex·% or more. Further, the belt reinforcing layer may be arranged so as to cover the entire belt or may be arranged so as to cover only both ends of the belt. Further, the winding density per unit width of the belt reinforcing layer may vary at the width direction positions. By doing so, load noise and flat spots can be reduced without degrading high-speed durability.

[0044] As described above, embodiments of the present invention have been described, but the present invention is not limited to the above embodiments at all. For example, in the above example, an example having a single cap layer was shown, but for weight reduction of the tire, a configuration without a cap layer can also be adopted.

Description of Reference Numerals

[0045] 1: Pneumatic radial tire for passenger car (tire), 2: Bead part, 2a: Bead core, 2b: Bead filler, 3: Carcass, 4: Belt, 4a, 4b: Belt layer, 5: Tread, 6: Inner surface of tire, 7: Inner liner, 8: Cap layer, 9: Layer layer, 50: Communication device, CL: Tire equatorial plane

Claims

1. A pair of bead sections, A carcass consisting of one or more carcass plies that toroidally span between a pair of bead sections, The carcass comprises a belt consisting of one or more belt layers, which is positioned on the outer side in the radial direction of the crown portion of the tire. The cross-sectional width SW of the aforementioned tire is less than 165 (mm), The ratio SW / OD of the tire's cross-sectional width SW to its outer diameter OD is 0.26 or less, or the tire's cross-sectional width SW (mm) and outer diameter OD (mm) are given by the following relational expression: OD (mm)≧-0.0187×SW (mm) ２ Satisfying +9.15 × SW (mm) - 380 (mm), A layer is provided on only one half in the tire width direction, positioned on the radial side of the belt and covering at least the end of the belt. The belt is further provided with one or more cap layers on the outer side in the tire radial direction and on the inner side in the tire radial direction of the layer layer, The number of code insertions in the cap layer is greater in one half of the tire width direction than in the other half of the tire width direction. A pneumatic radial tire for passenger cars, characterized in that the number of cords embedded in the cap layer gradually decreases from the outer edge in the tire width direction of the cap layer in one half of the tire width direction to the outer edge in the tire width direction of the cap layer in the other half of the tire width direction.

2. The carcass consists of a carcass body portion that spans a pair of bead portions in a toroidal manner, and a carcass folded portion that is folded back from the carcass body portion around the bead core embedded in the bead portion. The pneumatic radial tire for passenger cars according to claim 1, wherein the end of the folded portion of the carcass in one half in the tire width direction is located radially inward of the end of the folded portion of the carcass in the other half in the tire width direction.

3. The pneumatic radial tire for passenger cars according to claim 1 or 2, wherein the tread surface of the tread portion has only one circumferential main groove, and the circumferential main groove is located in one half in the tire width direction.

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