JP7077556B2 - Pneumatic tires for passenger cars - Google Patents

Description

The present invention relates to pneumatic tires for passenger cars.

Conventionally, for example, a run-flat tire described in Patent Document 1 has an involute curve in which the contour shape of the tire surface from the equatorial plane of the tire to the maximum width position of the tire is gradually reduced toward the outside in the tire axial direction. The CTT structure to be formed is intended to improve steering stability and wear resistance, and to be applicable to a high flatness size with a tire flatness ratio of up to 65%. This run-flat tire is made from a carcass carcass that extends from the tread portion through the sidewall portion to the bead core of the bead portion, and from the inner and outer belt plies that are placed inside and outside the tread portion in the radial direction. A run flat having a tread reinforcing cord layer including at least a belt layer and a sidewall reinforcing rubber layer located on the tire cavity surface side and arranged on the sidewall portion, and having a tire flatness ratio of 30% to 65%. For tires, the width DW of the tread contact surface where the tread surface touches the ground when the rim is assembled to the regular rim and the regular internal pressure is applied and the regular load is applied is 0.9 times or less of the ply width BW of the outer belt ply. The rubber thickness T from the radial outer surface to the tread surface of the tread reinforcing cord layer is Ta for the rubber thickness on the tire equatorial surface and the rubber thickness at the outer end of the ply of the outer belt ply. Tc, where the rubber thickness between the outer end of the ply and the equatorial surface of the tire is Tb, the relationship of Ta> Tb> Tc, 0.6 × Ta ≧ Tc ≧ 0.1 × Ta, 6 mm> Tc. Fulfill.

Further, for example, the pneumatic tire described in Patent Document 2 is intended to improve the wear resistance of the center region while maintaining the wear resistance of the shoulder region under high internal pressure conditions. In this pneumatic tire, the tread surface of the tread portion has a plurality of different radius of curvature including at least a central arc located in the center in the tire width direction and a shoulder side arc in which the central arc is continuous outward in the tire width direction. Formed by an arc, built into a regular rim and filled with 5% of the regular internal pressure, in a cross-sectional view in the tire meridional direction, the virtual extension of the shoulder arc and the outermost part of the tread in the tire width direction. The intersection of the side arc with the virtual extension line is used as the reference point, the intersection of the tire equatorial plane and the profile of the tread plane is used as the center crown, and the straight line connecting the reference point and the center crown and the center crown are passed through. The angle formed by the straight line parallel to the tire width direction is θ, the radius of curvature of the central arc is Rc, the radius of curvature of the shoulder arc is Rs, and the inner end of the shoulder arc from the tire equatorial plane in the tire width direction. Let L be the reference expansion width that is the arc length to the position, and let the tread expansion width that is the arc length in the tire width direction between the points that pass through the reference point and the reference line parallel to the tire equatorial plane intersects the tread plane. When TDW is used and the flatness is β, the tread surface is 0.025 × β + 1.0 ≦ θ ≦ 0.045 × β + 2.5, 10 ≦ Rc / Rs ≦ 50, 0.2 ≦ L / (TDW). / 2) Formed by satisfying ≤0.7, and further provided with a belt reinforcing layer arranged outside the tire radial direction of the belt layer, on the shoulder side arc and from the tire equatorial plane to the tread unfolding half width TDW / 2. When the position of 85% is the point Q and the intersection of the vertical line drawn from the point Q to the arc on the shoulder side and the outer surface in the tire radial direction of the cord constituting the belt reinforcing layer is the point R, the points Q and R are The distance ts of is within the range of 4.0 mm ≦ ts ≦ 8.0 mm.

Further, for example, the pneumatic tire described in Patent Document 3 is intended to improve the riding comfort while suppressing the wear of the tread surface. In this pneumatic tire, the belt layer is arranged on the outer side of the carcass layer in the tread portion in the tire radial direction, and the tread surface of the tread portion is a central arc located in the center in the tire width direction and a tire having a central arc. It is formed by a plurality of arcs with different radius of curvature including at least a continuous shoulder arc on the outside in the width direction, and is incorporated into a regular rim and filled with 5% of the regular internal pressure. , The intersection of the virtual extension of the shoulder arc and the virtual extension of the outermost side arc in the tire width direction at the tread is the reference point, and the intersection of the profile of the tire equatorial plane and the tread plane is the center crown. The angle formed by the straight line connecting the reference point and the center crown and the straight line passing through the center crown and parallel to the tire width direction is θ, the radius of curvature of the central arc is Rc, and the radius of curvature of the shoulder arc. Is Rs, the reference expansion width which is the arc length from the equatorial plane of the tire to the inner end position of the arc on the shoulder side in the tire width direction is L, and the reference line passing through the reference point and parallel to the equatorial plane of the tire becomes the tread surface. The tread development width, which is the arc length in the tire width direction between the intersecting points, is TDW, the flatness is β, the tire cross-sectional width is SW, the tire cross-sectional height is SH, and the pattern is from the outermost position in the tire radial direction. When the radial dimension of the tire to the end is a and the effective belt width in the belt layer is BW, the tread surface is 0.04 × β + 2.0 ≦ θ ≦ 0.06 × β + 3.5, 12 ≦ Rc / Rs ≦ 30, 0.2 ≦ L / (TDW / 2) ≦ 0.7, 0.55 ≦ TDW / SW ≦ 0.65, 0.21 ≦ a / SH ≦ 0.32, 1.00 ≦ BW / Satisfy TDW ≦ 1.10.

Further, for example, the pneumatic tire described in Patent Document 4 aims to improve steering stability performance while reducing rolling resistance. This pneumatic tire includes a pair of bead portions, a sidewall portion connected to the bead portion, and a tread portion connecting the sidewall portions, and the ratio of the total width SW to the outer diameter OD is SW / OD ≦ 0. The tread profile, which satisfies the relationship of 3 and is the contour line of the surface of the tread portion in the cross-sectional view in the tire meridional direction, is located at the center arc located in the center of the tire width direction and the outermost part of the tread portion in the tire width direction. Formed by connecting multiple arcs with different radius of curvature, including at least a side arc that is located and a shoulder arc that is continuous with the side arc and then located on the outside in the tire width direction. In the cross-sectional view in the tire meridional direction, the intersection of the extension line of one shoulder side arc and the extension line of the side arc is set as one first reference point and passes through one first reference point. The intersection of the straight line perpendicular to the tread profile and the tread profile is set as the second reference point on one side, and the intersection of the extension line of the other shoulder arc and the extension line of the side arc is the first reference point on the other side. , The intersection of the straight line perpendicular to the tread profile passing through the other first reference point and the tread profile is the other second reference point, and from one second reference point to the other second reference point. The length along the tread profile is the tread expansion width TDW, the intersection of the tire equatorial plane and the tread profile is the profile center, and the straight line connecting the second reference point and the profile center and the straight line parallel to the tire width direction. When the angle between the lines is the dip amount θ, 0.85 ≤ TDW / SW ≤ 0.95 (excluding TDW / SW = 0.85), 1.5 ° ≤ θ ≤ 4.5 ° Satisfy the relationship.

Japanese Unexamined Patent Publication No. 2002-301914 Japanese Unexamined Patent Publication No. 2012-09173 Japanese Unexamined Patent Publication No. 2013-166416 Japanese Patent No. 5541416

By the way, in recent years, it has been required to maintain excellent rolling resistance and wear resistance while ensuring excellent quietness.

Therefore, the present invention has been made in view of the above, and an object thereof is to provide a pneumatic tire for a passenger car capable of improving quietness performance while suppressing deterioration of rolling resistance and low wear performance. do.

In order to solve the above-mentioned problems and achieve the object, the pneumatic tire for a passenger vehicle according to one aspect of the present invention has a ground contact width from the equatorial plane of the tire to the ground contact end as TW in a cross-sectional view in the tire meridional direction. With no load installed in the regular rim and filled with the regular internal pressure, the total thickness of the tread portion on the equatorial plane of the tire is Gc, and the normal line to the tread profile of the surface of the tread portion on the ground contact end. The total thickness of the tread portion in the direction is Gs, and the angle formed by the straight line connecting the center point on the equatorial plane of the tire and the ground contact end and the straight line passing through the center point and parallel to the tire width direction is formed. When the drop amount θ and the flatness ratio are β, 0.02 × β + 1.6 ≦ θ ≦ 0.05 × β + 2.35, −0.053 × β + 7.2 ≦ TW / [(Gc + Gs) / 2] The relationship of ≦ −0.053 × β + 8.2 is satisfied.

Further, in the pneumatic tire for a passenger car according to one aspect of the present invention, it is preferable to satisfy the relationship of 15.8 ≦ (Gc + Gs) / 2 ≦ 18.0.

Further, in the pneumatic tire for a passenger car according to one aspect of the present invention, when the tire cross-sectional width in the tire width direction from the equatorial plane of the tire to the maximum width position of the tire is set to SW in the cross-sectional view in the tire meridional direction, 0. It is preferable to satisfy the relationship of 60 ≦ TW / SW ≦ 0.75.

According to the present invention, the angle θ, which is the amount of dip with respect to the flatness β, is optimized, and TW / [(Gc + Gs) / 2, which is the relationship between the contact width TW and the total thickness Gc, Gs with respect to the flatness β. ] Is optimized. Specifically, by specifying the total thickness Gc of the tread portion on the equatorial plane of the tire and the total thickness Gs of the tread portion at the ground contact end to be relatively large, the volume of the tread portion is increased and the tread portion is quiet. It becomes possible to improve the sex. However, if the volume of the tread portion is increased, the rolling resistance increases, which affects the improvement of fuel efficiency. Therefore, by specifying the contact width TW to be small, it is possible to suppress the deterioration of the rolling resistance. Further, if the ground contact width TW is specified to be small, the ground contact area tends to be small and the wear resistance performance tends to be deteriorated. By reducing θ), it is possible to secure the ground contact area and suppress the deterioration of wear resistance performance. As a result, the quietness performance can be improved while suppressing the deterioration of rolling resistance and low wear performance.

FIG. 1 is a cross-sectional view of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged view of a part of the meridian cross section of the tread portion of the pneumatic tire according to the embodiment of the present invention. FIG. 3 is a chart showing the results of a performance test of a pneumatic tire according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment. In addition, the components of this embodiment include those that can be easily replaced by those skilled in the art, or those that are substantially the same. Further, the plurality of modifications described in this embodiment can be arbitrarily combined within a range self-evident by those skilled in the art.

FIG. 1 is a cross-sectional view of the meridian of the pneumatic tire according to the present embodiment. FIG. 2 is an enlarged view of a part of the meridian cross section of the tread portion of the pneumatic tire according to the present embodiment.

In the following description, the tire radial direction refers to the direction orthogonal to the rotation axis (not shown) of the pneumatic tire, and the tire radial inner side is the side toward the rotation axis in the tire radial direction and the tire radial outer side. Refers to the side away from the axis of rotation in the tire radial direction. Further, the tire circumferential direction means a circumferential direction with the rotation axis as a central axis. The tire width direction means a direction parallel to the rotation axis, the inside in the tire width direction is the side toward the tire equatorial plane (tire equatorial line) CL in the tire width direction, and the outside in the tire width direction is the tire width direction. Refers to the side away from the tire equatorial plane CL. The tire equatorial plane CL is a plane orthogonal to the rotation axis of the pneumatic tire and passing through the center of the tire width of the pneumatic tire. The tire equatorial line is a line on the tire equatorial plane CL and along the tire circumferential direction of the pneumatic tire. In the present embodiment, the tire equatorial line is designated by the same reference numeral “CL” as the tire equatorial plane.

Further, the pneumatic tire of the present embodiment is a pneumatic tire for a passenger car.

As shown in FIG. 1, the pneumatic tire of the present embodiment has a tread portion 2, shoulder portions 3 on both sides thereof, and sidewall portions 4 and bead portions 5 sequentially continuous from each shoulder portion 3. .. Further, the pneumatic tire includes a carcass layer 6, a belt layer 7, a belt reinforcing layer 8, and an inner liner layer 9.

The tread portion 2 is exposed at the outermost side in the tire radial direction of the pneumatic tire, and the surface thereof becomes the contour of the pneumatic tire. A tread surface 21 is formed on the outer peripheral surface of the tread portion 2, that is, on the tread surface that comes into contact with the road surface during traveling. Although not specified in the drawing, the tread surface 21 is provided with a main groove extending along the tire circumferential direction and a groove such as a lug groove intersecting the tire circumferential direction. In the tread portion 2, the portion that is arranged outside the carcass layer 6, the belt layer 7, the belt reinforcing layer 8, and the inner liner layer 9 in the tire radial direction to form the tread surface 21 that is the outer peripheral surface of the tread portion 2 is It consists of a rubber material (tread rubber).

The shoulder portion 3 is a portion on both outer sides of the tread portion 2 in the tire width direction. The sidewall portion 4 is exposed to the outermost side in the tire width direction in the pneumatic tire. The bead portion 5 has a bead core 51 and a bead filler 52. The bead core 51 is formed by winding a bead wire, which is a steel wire, in a ring shape. The bead filler 52 is a rubber material arranged in a space formed by folding the end portion of the carcass layer 6 in the tire width direction at the position of the bead core 51.

In the carcass layer 6, each end portion in the tire width direction is folded back from the inside in the tire width direction to the outside in the tire width direction by a pair of bead cores 51, and is hung in a toroid shape in the tire circumferential direction to form a tire skeleton. Is. The carcass layer 6 has a plurality of carcass cords (not shown) arranged side by side in the tire circumferential direction while having an angle of 90 degrees (± 5 degrees) with respect to the tire circumferential direction and being covered with coated rubber. Is. The carcass cord is made of organic fibers (polyester, rayon, nylon, etc.). As shown in FIG. 1, the carcass layer 6 is provided with at least one layer. In FIG. 2, the carcass layer 6 shows the form of two layers.

The belt layer 7 has a multi-layer structure in which at least two belts 71 and 72 are laminated, is arranged on the outer periphery of the carcass layer 6 in the tire radial direction in the tread portion 2, and covers the carcass layer 6 in the tire circumferential direction. Is. The belts 71 and 72 are formed by coating a plurality of cords (not shown) arranged side by side at a predetermined angle (for example, 20 degrees to 30 degrees) with respect to the tire circumferential direction with a coated rubber. The cord is made of steel or organic fiber (such as polyester, rayon or nylon). Further, the overlapping belts 71 and 72 are arranged so that their cords intersect each other.

The belt reinforcing layer 8 is arranged outside the outer circumference of the belt layer 7 in the tire radial direction and covers the belt layer 7 in the tire circumferential direction. In the present embodiment, the belt reinforcing layer 8 has reinforcement layers 81, 82, and 83 arranged in three layers so as to cover the outer periphery of the belt layer 7. The reinforcing layers 81, 82, and 83 have a plurality of cords arranged side by side in the tire width direction parallel to the tire circumferential direction (including an error of 0 degrees: ± 5 degrees) so as to be along the tire circumferential direction. It is covered with. The cord is made of steel or organic fiber (such as polyester, rayon or nylon). The reinforcing layers 81, 82, and 83 are provided by winding a strip-shaped (for example, width 10 [mm]) strip material in the tire circumferential direction. In the belt reinforcing layer 8 shown in FIGS. 1 and 2, the reinforcing layer 81 on the belt layer 7 side is formed larger in the tire width direction than the belt layer 7 and is arranged so as to cover the entire belt layer 7. The reinforcing layer 82 on the outer side in the tire radial direction is arranged only at the end portion in the tire width direction of the reinforcing layer 81 so as to cover the end portion in the tire width direction of the belt layer 7, and the reinforcing layer 83 on the outer side in the tire radial direction of the reinforcing layer 82 is a belt. It is arranged so as to cover the end portion of the layer 7 in the tire width direction. The configuration of the belt reinforcing layer 8 is not limited to the above.

The inner liner layer 9 is the inner surface of the tire, that is, the inner peripheral surface of the carcass layer 6, and both ends in the width direction of each tire reach the positions of the bead cores 51 of the pair of bead portions 5, and are in a toroid shape in the tire peripheral direction. It is hung and pasted. The inner liner layer 9 is for suppressing the permeation of air molecules to the outside of the tire. The inner liner layer 9 may extend to the inside of the tire of the bead portion 5.

In the pneumatic tire of the present embodiment, the ground contact width from the tire equatorial plane CL to the ground contact end T is TW in the cross-sectional view in the tire meridian direction shown in FIGS. 1 and 2. The ground contact end T is a tire circumference in which the tread surface 21 touches the road surface when a pneumatic tire is rim-assembled on a regular rim, a regular internal pressure (230 kPa in this embodiment) is applied, and 70% of the regular load is applied. Both outermost ends in the tire width direction of the ground contact area in the direction. The ground contact width TW is a dimension in the tire width direction from the tire equatorial plane CL to the ground contact end T in the ground contact region.

Here, the regular rim is a "standard rim" specified by JATMA, a "Design Rim" specified by TRA, or a "Measuring Rim" specified by ETRTO. The normal internal pressure is the "maximum air pressure" specified by JATTA, the maximum value described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or "INFLATION PRESSURES" specified by ETRTO. The normal load is the "maximum load capacity" specified by JATTA, the maximum value described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "LOAD CAPACITY" specified by ETRTO.

Further, in the pneumatic tire of the present embodiment, in the cross-sectional view in the tire meridional direction shown in FIG. 2, the tire equator is in a state of no load incorporated in a normal rim and filled with a normal internal pressure (230 kPa in the present embodiment). The total thickness of the tread portion 2 on the surface CL is Gc, and the total thickness of the tread portion 2 in the normal direction with respect to the tread profile of the surface (tread surface 21) of the tread portion 2 on the ground contact end T is Gs. The angle formed by the straight line L1 connecting the center point O on the tire equatorial plane CL and the ground contact end T and the straight line L2 passing through the center point O and parallel to the tire width direction is defined as the drop amount θ, and the flatness ratio is β. And.

The total thickness Gc and the total thickness Gs of the tread portion 2 are the thickness including the tread rubber, the carcass layer 6, the belt layer 7, the belt reinforcing layer 8, and the inner liner layer 9 of the tread portion 2. The tread profile is a contour line forming the tread surface 21 which is the surface of the tread portion 2 excluding grooves such as a main groove and a lug groove in a cross-sectional view in the meridian direction, and is formed by a combination of a plurality of arcs. The center point O on the tire equatorial plane CL is the intersection of the tire equatorial plane CL and the tread profile. The flatness β is the ratio of the tire cross-sectional height SH to the tire cross-sectional width SW + SW. The tire cross-sectional width SW + SW is the width in the tire width direction between the portions located outside in the tire width direction in a no-load state in which the tire is rim-assembled on the regular rim and filled with the regular internal pressure (230 kPa in this embodiment). That is, it is the distance between the portions farthest from the tire equatorial surface CL in the tire width direction, and is the width excluding the pattern and characters on the side surface of the tire. In FIG. 1, the area from the tire equatorial surface CL to one outside in the tire width direction is represented as SW, and the tire cross-sectional width including the tire equatorial surface CL to the outside on both sides in the tire width direction is SW + SW. The tire cross-sectional height SH is ½ of the difference between the outer diameter and the rim diameter of a tire in a no-load state in which the tire is rim-assembled on a regular rim and filled with a regular internal pressure (230 kPa in this embodiment).

The pneumatic tire of the present embodiment satisfies the relationship of the following equations (1) and (2).
0.02 × β + 1.6 ≦ θ ≦ 0.05 × β + 2.35 ... (1)
-0.053 x β + 7.2 ≤ TW / [(Gc + Gs) / 2] ≤ -0.053 x β + 8.2 ... (2)

According to such a pneumatic tire, the angle θ, which is the amount of depression with respect to the flatness β, is optimized, and the contact width TW and the total thickness Gc, Gs with respect to the flatness β are TW / [. (Gc + Gs) / 2] is optimized. Specifically, the total thickness Gc of the tread portion 2 at the tire equatorial plane CL and the total thickness Gs of the tread portion 2 at the ground contact end T are specified so as to be relatively large, so that the total thickness Gs of the tread portion 2 can be relatively large. It is possible to improve quietness by increasing the volume. However, if the volume of the tread portion 2 is increased, the rolling resistance increases, which affects the improvement of fuel efficiency. Therefore, by specifying the contact width TW to be small, it is possible to suppress the deterioration of the rolling resistance. .. Further, if the ground contact width TW is specified to be small, the ground contact area tends to be small and the wear resistance performance tends to be deteriorated. By reducing θ), it is possible to secure the ground contact area and suppress the deterioration of wear resistance performance. As a result, the quietness performance can be improved while suppressing the deterioration of rolling resistance and low wear performance.

Further, it is preferable that the pneumatic tire of the present embodiment satisfies the relationship of the following formula (3).
15.8 ≦ (Gc + Gs) / 2 ≦ 18.0 ... (3)

According to this pneumatic tire, the tire equatorial surface CL is defined by defining the relationship between the total thickness Gc of the tread portion 2 at the tire equatorial surface CL and the total thickness Gs of the tread portion 2 at the ground contact end T. Since the volume in the vicinity is not too large, the deterioration of rolling resistance can be further suppressed, and the influence on the wear resistance performance can be further suppressed accordingly, so that the quiet performance is improved while suppressing the deterioration of rolling resistance and low wear performance. The effect of tire tread can be remarkably obtained.

Further, it is preferable that the pneumatic tire of the present embodiment satisfies the relationship of the following formula (4).
0.60 ≤ TW / SW ≤ 0.75 ... (4)

According to this pneumatic tire, the vertical spring is made smaller by defining the relationship between the ground contact width TW and the cross-sectional width SW so that the cross-sectional width SW (SW + SW) is wider than the ground contact width TW. It can be easily bent and the quietness performance can be further improved.

In this embodiment, performance tests on tire performance (quiet performance, wear resistance, rolling resistance) were performed on a plurality of types of pneumatic tires under different conditions (see FIG. 3).

In this performance test, a pneumatic tire with a tire size of 215 / 55R17 was assembled to the rim of a 17 × 7JJ aluminum wheel and filled with air pressure (230 kPa).

In the quiet performance evaluation method, the sound pressure level (dB) in the vehicle when the test vehicle (passenger car with a displacement of 1.6 L, front engine and front drive) travels on the dry test road at a speed of 60 km / h is measured. .. Then, based on this measurement result, the sound pressure level is evaluated using the conventional example as a reference (0). This evaluation shows that the lower the value of the sound pressure level is, the better the quietness performance.

In the evaluation method of wear resistance performance, the maximum groove depth in the ground contact area (within the ground contact width) when traveling 10,000 km on the dry test road in a test vehicle (passenger car with a displacement of 1.6 L and front engine front drive). The amount of remaining groove (groove depth) at the position is measured. Then, based on this measurement result, an index evaluation is performed using the conventional example as a reference (100). This index evaluation indicates that the larger the value, the better the wear resistance performance.

In the method for evaluating rolling resistance, the rolling resistance of the test tire to which a load (4.2 kN) is applied is measured by a steel drum type rolling resistance tester at a speed of 80 km / h after 20 minutes of preliminary running. Then, based on this measurement result, an index evaluation is performed using the conventional example as a reference (100). This index evaluation shows that the larger the value, the lower the rolling resistance and the better.

In the conventional pneumatic tire shown in FIG. 3, θ and TW / [(Gc + Gs) / 2] are out of the specified range. In the pneumatic tires of Comparative Examples 1 and 2, θ is out of the specified range, and in the pneumatic tires of Comparative Examples 3 and 4, TW / [(Gc + Gs) / 2] is out of the specified range. In the pneumatic tire of the embodiment, θ and TW / [(Gc + Gs) / 2] are within the specified range.

As shown in the test results of FIG. 3, it can be seen that the pneumatic tire of the embodiment has improved quietness while suppressing deterioration of rolling resistance and low wear performance.

2 Tread part 21 Tread surface 3 Shoulder part 4 Side wall part 5 Bead part 51 Bead core 52 Bead filler 6 Carcus layer 7 Belt layer 71,72 Belt 8 Belt reinforcement layer 81,82,83 Reinforcement layer 9 Inner liner layer CL Tire equatorial surface L1 straight line L2 straight line O center point SW tire cross-sectional width T ground contact end TW ground contact width β flatness rate θ angle (drop amount)

Claims (3)

An inner liner layer, a carcass layer, a belt layer, a belt reinforcing layer, and a tread rubber are provided from the inside to the outside of the tread portion in the tire radial direction, and the belt reinforcing layer is formed larger in the tire width direction than the belt layer. The first reinforcing layer that covers the entire belt layer and the first reinforcing layer are arranged only at the tire width direction end portion of the first reinforcing layer so as to cover the tire width direction end portion of the belt layer on the tire radial outer side. It has a second reinforcing layer and a third reinforcing layer arranged so as to cover the end portion of the belt layer in the tire width direction on the outer side in the tire radial direction of the second reinforcing layer.
In a cross-sectional view in the tire meridional direction, the inner liner layer is formed on the tire equatorial surface in a no-load state in which the contact width from the tire equatorial plane to the ground end is set as TW and is incorporated into a regular rim to fill the regular internal pressure. The total thickness of the tread portion including the carcass layer, the belt layer, the first reinforcing layer, and the tread rubber is Gc, and the inner on the ground contact end in the normal direction with respect to the tread profile of the surface of the tread portion. The total thickness of the tread portion including the liner layer, the carcass layer, the belt layer, the first reinforcing layer, the second reinforcing layer, the third reinforcing layer, and the tread rubber is Gs, and is on the tire equatorial plane. When the angle formed by the straight line connecting the center point of the tire and the ground contact end and the straight line passing through the center point and parallel to the tire width direction is the dip amount θ, and the flatness ratio is β, 0.02 × β + 1 Pneumatic tires for passenger cars that satisfy the relationship of .6 ≤ θ ≤ 0.05 x β + 2.35, -0.053 x β + 7.2 ≤ TW / [(Gc + Gs) / 2] ≤ -0.053 x β + 8.2. The pneumatic tire for a passenger car according to claim 1, which satisfies the relationship of 15.8 ≦ (Gc + Gs) / 2 ≦ 18.0. Claim 1 that satisfies the relationship of 0.60 ≤ TW / SW ≤ 0.75 when the tire cross-sectional width in the tire width direction from the equator surface of the tire to the maximum width position of the tire is SW in the cross-sectional view in the tire meridional direction. Or the pneumatic tire for a passenger car according to 2.

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