4a, 4b may be monofilament cords, cords made of a plurality of filaments aligned in parallel, or cords made of a plurality of filaments twisted together. Various twist structures can be used, and the cross-sectional structure, twist pitch, twist direction, and distance between adjacent filaments can also be varied. Furthermore, cords made of twisted filaments of different materials can also be used, and there are no particular restrictions on the cross-sectional structure, and various twist structures such as single twist, layer twist, and multiple twist can be used.

In this embodiment, the inclination angle of the belt cords in the belt layer 4a, 4b is preferably 10° or more with respect to the tire circumferential direction. In this embodiment, the inclination angle of the belt cords in the belt layer 4a, 4b is preferably in a high angle, specifically 20° or more and preferably 35° or more with respect to the tire circumferential direction, and particularly in the range of 55° to 85° with respect to the tire circumferential direction. This is because by making the inclination angle 20° or more (preferably 35° or more), the rigidity in the tire width direction can be increased, and the steering stability performance, particularly during cornering, can be improved. In addition, this is because it reduces the rolling resistance by reducing the shear deformation of the interlayer rubber.

In the illustrated example, the tread rubber that makes up the tread 5 is composed of a single layer. On the other hand, in this embodiment, the tread rubber that makes up the tread 5 may be formed by laminating a plurality of rubber layers in the tire radial direction. The plurality of rubber layers may have different loss tangents, modulus, hardness, glass transition temperatures, materials, and the like. In addition, the ratio of the thickness of the plurality of rubber layers in the tire radial direction may vary in the tire width direction, and also, the bottom of the circumferential main groove, etc., may be made of a rubber layer that differs from the surrounding area. In addition, the tread rubber that makes up the tread 5 may be formed with a plurality of rubber layers that differ in the tire width direction. The plurality of rubber layers may have different loss tangents, modulus, hardness, glass transition temperatures, materials, and the like. In addition, the ratio of the tire widthwise width of the plurality of rubber layers may vary in the tire radial direction, and also, only a limited area, such as only the area near the circumferential main groove, only the area near the ground contact edge, only the shoulder land portion, or only the center land portion, may have a rubber layer that differs from the surrounding area.

The tire 1 of this embodiment has an inner liner 8 on the inner surface 7 of the tire (simply referred to as the tire inner surface 7). The thickness of the inner liner 8 is preferably about 1.5 mm to 2.8 mm. This is because it can effectively reduce the noise inside the car, which is between 80 and 100 Hz. The air permeability coefficient of the rubber composition that makes up the inner liner 8 is preferably 1.0×10⁻¹⁴cc·cm/(cm²·s·cmHg) or more, and 6.5×10⁻¹⁰cc·cm/(cm²·s·cmHg) or less.

Here, it is preferable that the negative ratio of the tread surface is greater in one tire width-direction half than in the other tire width-direction half. The “tread surface” refers to the outer surface around the entire circumference of the tire that is in contact with the road surface when the tire is mounted on the rim, filled with the prescribed internal pressure, and rolled under a maximum load. In addition, the “negative ratio” refers to the ratio of the total area of grooves with a width (opening width) of 2 mm or more to the total area of the tread surface. This is because it is possible to further improve the driving performance of the tire by relatively reducing the rigidity of the tread portion on the one tire width-direction half, thereby further improving the shape of the ground contact patch described below. It will be noted that in the case of the tire sizes with narrow width and large diameter as described above, since the narrow width ensures high drainage performance, only one circumferential main groove extending in the tire circumferential direction is provided in the one tire width-direction half, so that the negative ratio in the one tire width-direction half can be larger than the negative ratio in the other tire width-direction half.

As illustrated in FIG. 2, this tire comprises a layer 9 only in one tire width-direction half, that is arranged on the outer side in the tire radial direction of the belt 4 and covers at least the end of the belt 4. In addition, this tire comprises one or more (in the illustrated example, one) cap layers 8 on the outer side in the tire radial direction of the belt 4 and on the inner side in the tire radial direction of the layer 9.

The cap layer 8 is made up of ribbon-shaped members consisting of rubber-coated cords arranged in approximately parallel and wound spirally in the tire circumferential direction. In the illustrated example, the tire widthwise width of the cap layer 8 is larger than the tire widthwise width of the belt 4. For the cords of the cap layer 8, for example, organic fiber cords can be used. As illustrated, it is preferable that the number of cords per unit width in the cap layer 8 is greater in one tire width-direction half than in the other tire width-direction half. In this example, the number of cords per unit width in the cap layer 8 in one tire width-direction half is constant, and the number of cords per unit width in the cap layer 8 in the other tire width-direction half is also constant. On the other hand, for example, it is also possible to configure the number of cords per unit width to gradually decrease from the tire widthwise outer end of the cap layer 8 in one tire width-direction half to the tire widthwise outer end of the cap layer 8 in the other tire width-direction half.

In addition, it is also preferable that the tire widthwise width of the cap layer 9 is greater in one tire width-direction half than in the other tire width-direction half. In this case, the number of cords per unit width in the cap layer 8 in one tire width-direction half can be the same as the number of cords per unit width in the cap layer 8 in the other tire width-direction half.

The layer 9 is made up of ribbon-shaped members consisting of rubber-coated cords arranged in approximately parallel and wound spirally in the tire circumferential direction. In the illustrated example, the layer 9 covers the end of the belt 4 in one tire width-direction half. More specifically, the tire widthwise outer end of the layer 9 is located on the outer side in the tire width direction than the tire widthwise outer end of the belt layer 4a, and the tire widthwise inner end of the layer 9 is located on the inner side in the tire width direction than the tire widthwise inner end of the belt layer 4b. For the cords of the layer 9, for example, organic fiber cords can be used.

The effects of the pneumatic radial tire for passenger vehicles according to this embodiment will be described below. The following explains the effects when the “one tire width-direction half” is on the inner side when the tire is mounted on a vehicle (when the “other tire width-direction half” is on the outer side when the tire is mounted on a vehicle).

The pneumatic radial tire for passenger vehicles in this embodiment is a tire with narrow-width and large-diameter having a cross-sectional width SW of less than 165 mm, among the tires with narrow-width and large-diameter that satisfies the above relational expression between the cross-sectional width SW and the outer diameter of the tire. According to this tire, air resistance can be reduced in particular, and rolling resistance can also be reduced, so the fuel efficiency of the tire can be improved.

On the other hand, as schematically illustrated on the left side of the arrow in FIG. 3, in such tires, when a large camber angle is applied or when the camber angle becomes large during cornering, the shape of the ground contact patch becomes too narrow, the shape of the ground contact patch deteriorates, and there is a risk that the driving performance, such as steering stability, will deteriorate. Although not limited to any particular case, this problem becomes particularly noticeable when used at high internal pressure.

In response to this, the tire in this embodiment has the layer 9 arranged on the outer side in the tire radial direction of the belt 4 only in one tire width-direction half (the inner side when the tire is mounted on a vehicle). This makes the rigidity of the tread portion on the outer side when the tire is mounted on the vehicle relatively less than that on the inner side when the tire is mounted on the vehicle, so that to make it easier to extend the ground contact length. As schematically illustrated on the right side of the arrow in FIG. 3, this prevents the shape of the ground contact patch from becoming too elongated when a large camber angle is applied, and it is possible to control the deterioration of the shape of the ground contact patch.

Therefore, according to the pneumatic radial tire for passenger vehicles in this embodiment, it is possible to improve the shape of the ground contact patch and control a decline in driving performance.

In addition, compared to the case where the layer 9 is provided in the tire width-direction halves on both sides, the tire can be made lighter and rolling resistance can be further reduced.

Here, it is preferable that one or more cap layers 8 are further provided on the outer side in the tire radial direction of the belt 4 and on the inner side in the tire radial direction of the layer 9, and the number of cords per unit width in the cap layer 8 is greater in one tire width-direction half than in the other tire width-direction half. When the “one tire width-direction half” is set to the inner side when the tire is mounted on the vehicle, this configuration makes the rigidity of the tread portion on the outer side when the tire is mounted on the vehicle even more relatively smaller than the rigidity of the tread portion on the inner side when the tire is mounted on the vehicle, making it easier to extend the ground contact length, and further suppressing the deterioration of the shape of the ground contact patch.

For the same reason, it is also preferable that the tire widthwise width of the cap layer 8 is greater in one tire width-direction half than in the other tire width-direction half.

In addition, it is preferable that the carcass 3 consists of a carcass body portion 3a that straddles in a toroidal shape between the pair of bead portions 2, and carcass turn-up portions 3b that are folded back from the carcass body portion 3a around bead cores 2a embedded in the bead portions 2, and an end of the carcass turn-up portion 3b in one tire width-direction half is located on the inner side in the tire radial direction than an end of the carcass turn-up portion 3b in the other tire width-direction half. When the “one tire width-direction half” is set to the inner side when the tire is mounted on the vehicle, this configuration can effectively improve the driving performance by increasing the rigidity of the tire on the outer side when the tire is mounted on the vehicle, which contributes greatly to the driving performance. It will be noted that the position of the end of the carcass turn-up portion 3b does not significantly contribute to the shape of the ground contact patch described above, so it does not interfere with the improvement effect on the shape of the ground contact patch described above.

In addition, as illustrated in FIG. 5, when the distance in the tire radial direction between a straight line m1, which passes through a point on the tread surface at the tire equatorial plane and is parallel to the tire width direction, and a straight line m2, which passes through the ground contact edge E and is parallel to the tire width direction, is defined as drop height L_CR, and the tread width of the tire is defined as TW, it is preferable that the ratio L_CR/TW is greater than 0.045. This allows the crown shape to be relatively round, and thus the shape of the ground contact patch can be made round, with the ground contact length in the shoulder portion shorter than that of the center portion. This prevents the shape of the ground contact patch from becoming too narrow when the angle of the camber changes, and further controls the deterioration of the shape of the ground contact patch. The “ground contact edge” refers to the two edges of the ground contact patch (the part that makes contact with the road surface) of the tire when the tire is mounted on the rim, filled with the prescribed internal pressure, and loaded with the maximum load. The “tread width” refers to the distance between the ground contact edges of the tire when the tire is mounted on the rim, filled with the prescribed internal pressure, and unloaded.

A tire and rim assembly here is formed by mounting the above-mentioned pneumatic radial tire for passenger vehicles on the rim. According to this tire and rim assembly, it is possible to obtain the same effects as those described for the above-mentioned pneumatic radial tire for passenger vehicles. At this time, the internal pressure of the tire and rim assembly is preferably 200 kPa or more, it is more preferable to be 220 kPa or more, and it is even more preferable to be 280 kPa or more. This is because the rolling resistance can be further reduced by increasing the internal pressure. On the other hand, the internal pressure of the tire and rim assembly is preferably 350 kPa or less, as this improves ride comfort.

The method for using the pneumatic radial tire for passenger vehicles uses the above-mentioned pneumatic radial tire for passenger vehicles. According to the method for using the pneumatic radial tire for passenger vehicles, it is possible to obtain the same effects as those described above for the pneumatic radial tire for passenger vehicles. At this time, it is preferable to use it with an internal pressure of 200 kPa or more, and it is even more preferable to use it with an internal pressure of 220 kPa or more, and it is even more preferable to use it with an internal pressure of 280 kPa or more. This is because the rolling resistance can be further reduced by increasing the internal pressure. On the other hand, it is preferable to use it with an internal pressure of 350 kPa or less, as this improves ride comfort.