JP6130899B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire that can suppress a single flow of a vehicle while suppressing a decrease in cornering power (CP).

  From the viewpoint of drainage, the traveling road surface is provided with a so-called cant slope that becomes a downward slope from the center line side toward the road shoulder side. And when driving | running | working on the road surface which has the said cant, a tire receives the force which turns to a road shoulder direction from a road surface, and produces the one flow of a vehicle.

  Therefore, a lateral flow force (PRCF) in a direction opposite to the force received from the road surface is generated in the tire, and the one-way flow is suppressed by balancing the lateral flow force (PRCF) and the force received from the road surface. ing.

  As a means for generating a lateral flow force (PRCF) in the tire, for example, as shown in FIG. 5, a point-symmetric tread pattern having a center on the tire equatorial plane Co is adopted, and the tire is applied to the shoulder land portion a. A shoulder lateral groove b that is inclined with respect to the axial line is formed. As a result, the shoulder block a1 has a parallelogram shape, and when the block is deformed, a rotational moment M in the same direction is generated in the left and right shoulder blocks a1, and a lateral flow force (PRCF) can be generated. The rotational moment M can be increased as the angle θ of the shoulder lateral groove b increases.

  However, when the rotational moment M is generated by the angle θ, there is a problem that the cornering power (CP) is greatly reduced as the block rigidity is lowered, and the steering stability is adversely affected.

  In addition, there are the following prior art documents related to this case.

Japanese Patent Laid-Open No. 7-246806

  It is an object of the present invention to provide a pneumatic tire capable of generating a lateral moment (PRCF) by generating a rotational moment in a tire while suppressing a decrease in cornering power (CP) and suppressing a single flow of a vehicle. It is said.

The present invention comprises, in the tread portion, a point-symmetric tread pattern having a center on the tire equatorial plane,
In addition, each of the tread portions includes a plurality of circumferential main grooves including a pair of shoulder main grooves arranged closest to the tread grounding end side and a center main groove arranged between the pair of shoulder main grooves. It is divided into a plurality of land portions including a shoulder land portion disposed between the shoulder main groove and the tread grounding end, and a center land portion disposed between the shoulder main groove and the center main groove,
And each said shoulder land part is a pneumatic tire provided with a shoulder transverse groove extending in a direction crossing the shoulder land part,
The shoulder lateral groove has an axial groove portion whose groove width center extends parallel to the tire axial line, and the tire axial length Ly of the axial groove portion is a land portion in the tire axial direction of the shoulder land portion. More than 10% of the width,
In addition, the shoulder lateral groove arranged in one shoulder land portion is chamfered by notching the corner portion where the groove wall surface and the tread surface intersect with only the groove wall surface on the tire rotation direction first side of the groove wall surfaces on both sides. A portion is provided in a range including the axial groove portion,
The shoulder lateral groove arranged on the other shoulder land portion is chamfered by notching the corner portion where the groove wall surface and the tread surface intersect with only the groove wall surface on the rear side in the tire rotation direction of the groove wall surfaces on both sides. The portion is provided in a range including the axial groove portion,
The center land portion is provided with a plurality of center lateral grooves extending in the tire axial direction from the shoulder main groove in the tire circumferential direction,
In addition, the center land portion is not provided with grooves or sipes communicating between the center lateral grooves.

In the pneumatic tire according to the present invention, a plurality of the shoulder lateral grooves are provided in the tire circumferential direction,
It is desirable that the shoulder land portion is not provided with a groove or sipe that communicates between the shoulder lateral grooves.

In the pneumatic tire according to the present invention, the shoulder lateral groove includes an inclined groove portion extending in an inclined direction with respect to the tire axial direction on the inner side in the tire axial direction of the axial groove portion,
The chamfered portion is preferably provided only in the axial groove portion.

  The “tread grounding end” means the position of the outermost end in the tire axial direction of the tread grounding surface that comes into contact when a normal load is applied to a tire that is assembled with a normal rim and filled with a normal internal pressure. The “regular rim” is a rim determined for each tire in a standard system including a standard on which a tire is based. For example, JAMMA is a standard rim, TRA is “Design Rim”, or ETRTO. Then means "Measuring Rim". The “regular internal pressure” is the air pressure defined by the standard for each tire. If JATMA, the maximum air pressure, if TRA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” Means "INFLATION PRESSURE", but in the case of passenger car tires, it is 180 kPa. The “regular load” is a load determined by the standard for each tire, and if it is JATMA, the maximum load capacity, and if it is TRA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” If it is ETRTO, it is "LOAD CAPACITY".

  In the pneumatic tire of the present invention, as described above, in the shoulder lateral groove disposed in one shoulder land portion, a chamfered portion is provided only on the groove wall surface on the tire rotation direction first arrival side, and is disposed on the other shoulder land portion. In the shoulder lateral groove, the chamfered portion is provided only on the groove wall surface on the rear arrival side in the tire rotation direction.

  In the pneumatic tire, the contact length is different between the contact end side and the tire equatorial plane side. Therefore, when the tire rolls, a braking force in the direction opposite to the traveling direction acts on the shoulder land portion. On the other hand, by providing the chamfered portion, the magnitude of the braking force acting on the shoulder land portion can be changed. That is, a braking force acting on one shoulder land portion having a chamfered portion formed on the first arrival side groove wall surface, and a braking force acting on the other shoulder land portion having a chamfered portion formed on the rear arrival side groove wall surface, A difference can be provided. Based on this difference, a rotational moment having a center on the tire equator plane can be generated in the ground contact surface. That is, a lateral flow force (PRCF) can be generated in the tire.

  In order to effectively generate the rotational moment, it is necessary to make the tread pattern a point-symmetric pattern. Further, it is preferable that the shoulder lateral groove extends in the tire axial direction as much as possible in order to obtain a large difference in braking force. Therefore, an axial groove is provided in the shoulder lateral groove, and the tire axial direction length Ly of the axial groove is set to 10% or more of the land width of the shoulder land.

  Also, since this mechanism is different from the conventional one in which the shoulder block is formed in a parallelogram shape and the rotation moment M is generated in the block itself, the block rigidity is not greatly changed. Therefore, it is possible to suppress a decrease in cornering power (CP) and to ensure excellent steering stability.

It is an expanded view of the tread part which shows the pneumatic tire of one Example of this invention. It is an expanded view which expands and shows a tread part. (A) is the sectional view on the aa 'line of the shoulder lateral groove in FIG. 1, (B) is the sectional view on the bb' line. It is a schematic diagram explaining the generation | occurrence | production mechanism of the rotational moment M of this application. It is an expanded view of the tread pattern explaining a prior art.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, the pneumatic tire 1 according to the present embodiment includes a tread portion 2 having a point-symmetric tread pattern having a center on the tire equatorial plane Co.

  In the tread pattern, the tread portion 2 includes a plurality of circumferential main grooves 3 including a pair of shoulder main grooves 3s arranged closest to the tread ground end Te. As a result, the tread portion 2 is divided into a plurality of land portions 4 including shoulder land portions 4s arranged between the shoulder main grooves 3s and the tread ground contact Te.

  In this example, the circumferential main groove 3 includes the pair of shoulder main grooves 3s and, for example, one center main groove 3c disposed between the pair of shoulder main grooves 3s. The land portion 4 includes the pair of shoulder land portions 4s and a pair of center land portions 4c disposed between the shoulder main groove 3s and the center main groove 3c. However, the present invention is not limited to this, and a plurality of (for example, two) center main grooves may be provided between the pair of shoulder main grooves 3s, 3s. 3 can also be configured.

  In this example, the case where the shoulder main groove 3s and the center main groove 3c are formed as linear grooves extending linearly in the tire circumferential direction is shown. Such a straight groove can be preferably used to suppress unstable behavior such as vehicle wobble. However, in addition to the linear groove, a zigzag groove (including a wave shape) may be employed.

  The widths W3s and W3c and the depths D3s and D3c (not shown) of the shoulder main groove 3s and the center main groove 3c can be variously determined according to common practice. For example, in the case of a tire for a passenger car, the groove width W3c is preferably 2.5 to 4.5% of the tread ground contact width TW, and the groove width W3s is preferably 4.0 to 7.0% of the tread ground contact width TW. . The groove depths D3s and D3c are preferably 6.0 to 9.0 mm. The groove widths W3s and W3c mean widths measured in the direction perpendicular to the longitudinal direction of the grooves on the tread surface 2S, and the same applies to other grooves.

  Various arrangement positions of the shoulder main groove 3s and the center main groove 3c can be determined according to the custom. For example, when there is one center main groove 3c, the center of the groove width passes on the tire equatorial plane Co. For the shoulder main groove 3s, the tire axial direction distance Ls from the tire equatorial plane Co at the center of the groove width is preferably 15% to 30% of the tread ground contact width TW. The rigidity balance between the shoulder land portion 4s and the center land portion 4c is improved, which is advantageous in handling stability.

  Next, a plurality of shoulder lateral grooves 5 extending in a direction crossing the shoulder land portion 4s are provided at each shoulder land portion 4s at a circumferential pitch P. Each shoulder lateral groove 5 extends from the outer side in the tire axial direction of the tread grounding end Te to the inner side in the tire axial direction, and its inner end terminates in the shoulder land portion 4s without intersecting the shoulder main groove 3s in this example. Yes. The inner end of the shoulder lateral groove 5 and the shoulder main groove 3 s are connected by a joint sipe 6 that extends at the same inclination as the shoulder lateral groove 5. As a result, the shoulder land portion 4 s of this example is divided into a plurality of shoulder blocks 7 by the shoulder lateral grooves 5 and the joint sipes 6.

  As shown in FIG. 2, in the shoulder land portion 4s, the shoulder lateral groove 5 has an axial groove portion 5A whose groove width center extends parallel to the tire axial line. The axial length Ly of the axial groove 5A is 10% or more of the land width W4s in the tire axial direction of the shoulder land 4s. The axial groove 5A is preferably disposed adjacent to the tread ground contact Te to increase the rotational moment. It also helps to reduce the cornering power (CP).

  In addition, the tire axial direction length L5 of the shoulder lateral groove 5 in the shoulder land portion 4s is preferably 75% or more of the land portion width W4s from the viewpoint of drainage and grip properties. The upper limit of the length L5 may be 100% of the land width W4s, that is, the shoulder lateral groove 5 and the shoulder main groove 3s may intersect. However, from the viewpoint of block rigidity, it is preferable that the length L5 is 90% or less of the land width W4s, and the joint sipes 6 are interposed between the shoulder lateral grooves 5 and the shoulder main grooves 3s.

  The shoulder lateral groove 5 of the present example includes an inclined groove portion 5B extending incline with respect to the tire axial direction line on the inner side in the tire axial direction of the axial groove portion 5A. This inclined groove portion 5B is useful for improving drainage. When the angle θ5 of the inclined groove portion 5B with respect to the tire axial direction is large, the block rigidity tends to be lowered, and the generation of the rotational moment M is disadvantageous. From such a point of view, the angle θ5 is preferably 25 ° or less, more preferably 20 ° or less, and particularly preferably gradually increased toward the inner side in the tire axial direction. The shoulder lateral groove 5 can be formed only by the axial groove 5A without providing the inclined groove 5B. In this case, Ly = L5. Therefore, the upper limit of the tire axial direction length Ly of the axial groove portion 5A is allowed up to 100% of the land portion width W4s.

  As shown in FIGS. 1, 3 (A), (B), the shoulder lateral groove 5 </ b> L disposed on one (left side in FIG. 1) of the shoulder land portion 4 sL has a tire rotation direction first arrival in the groove wall surface Sw on both sides. The chamfered portion 20f is formed only on the side groove wall surface Swf. On the other hand, the shoulder lateral groove 5R disposed on the other shoulder land portion 4sR (right side in FIG. 1) has a chamfered portion 20r only on the groove wall surface Swr on the rear side in the tire rotation direction of the groove wall surfaces Sw on both sides. It is formed.

  The chamfered portion 20f includes a slope S that cuts out a corner portion Qf where the groove surface Swf on the first arrival side and the tread surface 2S intersect, and is provided in a range including the axial groove portion 5A. Further, the chamfered portion 20r includes a slope S that cuts out a corner portion Qr where the groove wall surface Swr on the rear arrival side and the tread surface 2S intersect, and is provided in a range including the axial groove portion 5A.

  The chamfered portions 20f and 20r have the same dimensions as each other and are formed at symmetrical positions around the tire equatorial plane Co. In this example, a preferable case in which the chamfered portions 20f and 20r are formed over the entire length of the shoulder lateral groove 5 is shown. However, the chamfered portions 20f and 20r may be formed only in the axial groove portion 5A.

  By providing such chamfered portions 20f and 20r, a rotational moment M having a center on the tire equatorial plane Co can be generated in the ground contact surface K as shown in FIG. PRCF) can be generated. The generation mechanism of the rotational moment M is as follows.

  The pneumatic tire has a substantially elliptical contact surface shape in which the contact length KL is longer on the tire equatorial plane side than the contact end side. Therefore, due to the difference in the contact length KL, when the tire rolls, a slip with the road surface occurs on the contact end side, and a braking force F in a direction opposite to the traveling direction acts on the shoulder land portion 4s. On the other hand, by providing the chamfered portions 20f and 20r, the magnitude of the braking force F acting on the shoulder land portion 4s can be changed. That is, the braking force FL acting on one shoulder land portion 4sL having the chamfered portion 20f formed on the first arrival side, and the braking force FR acting on the other shoulder land portion 4sR having the chamfered portion 20r formed on the rear arrival side. Can make a difference. Based on this difference (FL−FR), a rotational moment M having a center on the tire equatorial plane Co can be generated in the ground contact surface K.

  If the tread pattern is not a point-symmetric pattern, the rotational moment M cannot be obtained effectively. Also, when the tire axial length Ly of the axial groove portion is less than 10% of the land width W4s, the left-right braking force difference (FL-FR) becomes small and the rotational moment M cannot be obtained effectively. .

  Here, when the chamfering width Wa and the chamfering depth Hb (shown in FIGS. 3A and 3B) in the chamfered portions 20f and 20r are each less than 0.5 mm, the rotational moment M is sufficiently generated. Can not be. Further, the effect of the chamfered portions 20f and 20r on the rotational moment M cannot be expected to rise even when the chamfering width Wa and the chamfering depth Hb exceed 1.5 mm, respectively. In addition, when the chamfering width Wa and the chamfering depth Hb are each 2.0 mm or more, the block rigidity is reduced and the cornering power (CP) is greatly reduced. From such a viewpoint, the chamfering width Wa is preferably 0.5 mm or more and less than 2.0 mm, and the chamfering depth Hb is preferably 0.5 mm or more and less than 2.0 mm. In particular, the ratio Wa / Hb between the chamfering width Wa and the chamfering depth Hb is 1.0 or more, more preferably 1.5 or more, in order to reduce cornering power (CP) while ensuring a high rotational moment M. Is preferable.

  The chamfer width Wa is preferably less than 0.1 times the circumferential pitch P between the shoulder lateral grooves 5 and 5. When the circumferential pitch P changes due to a variable pitch or the like, the smallest circumferential pitch P is adopted. The chamfering depth Hb is also preferably less than 0.5 times the groove depth D5 of the shoulder lateral groove 5. When the chamfer width Wa is 0.1 times or more of the circumferential pitch P, and when the chamfer depth Hb is 0.5 times or more of the groove depth D5, the block rigidity is reduced and the cornering power (CP) is reduced. Becomes larger.

  The groove width W5 and the groove depth D5 of the shoulder lateral groove 5 can be variously determined according to common practice. For example, in the case of a passenger car tire, the groove width W5 is preferably 2.0 to 6.0 mm, and the groove depth D5 is preferably 4.0 to 7.5 mm.

  In this example, between the shoulder lateral grooves 5 and 5 adjacent in the circumferential direction, one or two shoulder lateral sipes 8 parallel to the shoulder lateral grooves 5 are formed. The shoulder lateral sipe 8 is preferably a so-called closed sipe in which both ends are interrupted in the shoulder land portion 4s. The shoulder lateral sipe 8 makes the block rigidity uniform, and helps to prevent the shoulder land portion 4s from sliding locally with the road surface and reducing the difference in braking force (FL-FR). The shoulder sipe 8 has a width that closes the sipe when touched, specifically, a width of 1.0 mm or less, like the other sipe. The same applies to other sipes.

  Next, as shown in FIG. 2, the center land portion 4 c is formed with the center lateral groove 9 extending from the shoulder main groove 3 s to the inside in the tire axial direction. An angle θ9 of the center lateral groove 9 with respect to the tire axial direction line is larger than an angle θ5 of the inclined groove portion 5B, and is preferably set in a range of 25 to 60 °. In this example, the inner end of the center lateral groove 9 terminates in the center land portion 3s without intersecting the center main groove 3c. Further, the inner end of the center lateral groove 9 and the center main groove 3c are connected by a joint sipe 10 extending at the same inclination as the center lateral groove 9. As a result, the center land portion 4 c of this example is divided into a plurality of center blocks 11 by the center lateral groove 9 and the joint sipes 10.

  A tie bar 12 that protrudes from the groove bottom is provided at the outer end of the center lateral groove 9. In this example, the joint sipe 10 and the tie bar 12 are formed, so that the block rigidity of the center land portion 4c is kept high while sufficiently ensuring drainage. A bottom sipe 12a is provided on the bottom surface of the tie bar 12 to ensure drainability during wear.

  The center lateral groove 9 is not formed with a chamfered portion like the shoulder lateral groove 5. The reason is that the center lateral groove 9 is formed near the tire equatorial plane Co, and therefore has little influence on the rotational moment M. On the other hand, since the ground contact pressure is high on the tire equatorial plane Co side, when a chamfered portion is provided, adverse effects on uneven wear and the like increase.

  In the center land portion 4c, one or two center lateral sipes 13 parallel to the center lateral groove 9 are formed between the center lateral grooves 9 and 9 adjacent in the circumferential direction in order to make the block rigidity uniform. .

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  Pneumatic tires (215 / 60R16) having the tread pattern of FIG. 1 as a basic pattern were prototyped based on the specifications in Table 1, and their lateral flow force (PRCF) and cornering power (CP) were measured.

The common specifications are as follows.
Tread grounding width TW = 150mm
<Center main groove>
Groove width W3c / tread grounding width TW = 2.8%
Groove depth D3c = 7.4 mm
<Shoulder main groove>
Groove width W3s / tread contact width TW = 4.8%
Groove depth D3s = 7.4mm
Installation position Ls / tread grounding width TW = 23%
<Center lateral groove>
Groove width W9 = 2.0-3.0mm
Groove depth D9 = 5.2mm
Angle θ9 = 35-50 °
<Shoulder lateral groove>
Groove width W5 = 4.0mm
Groove depth D5 = 6.0mm
Axial length L5 / shoulder land width W4s = 85%

  In Comparative Example 3 and Examples 1 to 17, the chamfered portion is formed only on the groove wall surface on the first arrival side in the shoulder lateral groove disposed on one side in the axial direction, and on the shoulder lateral groove disposed on the other side in the axial direction. It is formed only on the groove wall surface on the rear arrival side. The chamfered portion is formed over the entire length of the shoulder lateral groove. The shoulder lateral grooves of Comparative Examples 2 and 3 do not have an axial groove portion, and the entire lateral groove is inclined at an angle θ5 of about 20 °.

(1) Cross flow force (PRCF) and cornering power (CP)
Using a flat belt testing machine, running on the belt at a speed of 80 km / h under the conditions of rim (16 × 7JJ), internal pressure (210 kPa), longitudinal load (4.55 kN), camber angle (0 °), The lateral flow force (PRCF) and cornering power (CP) generated at that time were measured.
-With respect to the lateral flow force, the amount of increase from Comparative Example 1 was indicated as plus (+) with Comparative Example 1 as a reference. A larger lateral flow force is preferable for suppressing a single flow of the vehicle caused by the cant.
The cornering power is indicated by minus (−) with respect to the amount of decrease from Comparative Example 1 on the basis of Comparative Example 1. Higher cornering power is preferable for steering stability.

 As shown in the table, it can be confirmed that the tires of the examples can secure a large lateral flow force while suppressing a decrease in cornering power (CP) and can suppress a single flow of the vehicle caused by the cant.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 2S Tread surface 3 Circumferential main groove 3s Shoulder main groove 4 Land part 4s Shoulder land part 5 Shoulder side groove 5A Axial direction groove part 8 Shoulder side sipe 20f, 20r Chamfer part Co Tire equatorial plane Qf, Qr Corner Part S Slope Sw Groove wall surface Swf First-arrival groove wall surface Swr Later-arrival groove wall surface Te Tread grounding end

Claims (3)

In the tread part, it has a point-symmetric tread pattern with the center on the tire equator plane,
In addition, each of the tread portions includes a plurality of circumferential main grooves including a pair of shoulder main grooves arranged closest to the tread grounding end side and a center main groove arranged between the pair of shoulder main grooves. It is divided into a plurality of land portions including a shoulder land portion disposed between the shoulder main groove and the tread grounding end, and a center land portion disposed between the shoulder main groove and the center main groove,
And each said shoulder land part is a pneumatic tire provided with a shoulder transverse groove extending in a direction crossing the shoulder land part,
The shoulder lateral groove has an axial groove portion whose groove width center extends parallel to the tire axial line, and the tire axial length Ly of the axial groove portion is a land portion in the tire axial direction of the shoulder land portion. More than 10% of the width,
In addition, the shoulder lateral groove arranged in one shoulder land portion is chamfered by notching the corner portion where the groove wall surface and the tread surface intersect with only the groove wall surface on the tire rotation direction first side of the groove wall surfaces on both sides. A portion is provided in a range including the axial groove portion,
The shoulder lateral groove arranged on the other shoulder land portion is chamfered by notching the corner portion where the groove wall surface and the tread surface intersect with only the groove wall surface on the rear side in the tire rotation direction of the groove wall surfaces on both sides. The portion is provided in a range including the axial groove portion,
Wherein the center land portion, the center lateral grooves extending obliquely from the shoulder main groove inwardly in the tire axial direction is provided a plurality in the tire circumferential direction,
In addition, the pneumatic tire is characterized in that the center land portion is not provided with grooves or sipes communicating between the center lateral grooves. A plurality of the shoulder lateral grooves are provided in the tire circumferential direction,
The pneumatic tire according to claim 1, wherein the shoulder land portion is not provided with a groove or sipe that communicates between the shoulder lateral grooves. The shoulder lateral groove includes an inclined groove portion extending in a direction inclined with respect to the tire axial direction on the inner side in the tire axial direction of the axial groove portion,
The pneumatic tire according to claim 1 or 2, wherein the chamfered portion is provided only in the axial groove portion.

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