WO2019117142A1

WO2019117142A1 - Run-flat radial tire

Info

Publication number: WO2019117142A1
Application number: PCT/JP2018/045502
Authority: WO
Inventors: 知尚向山
Original assignee: 株式会社ブリヂストン
Priority date: 2017-12-12
Filing date: 2018-12-11
Publication date: 2019-06-20
Also published as: JP2019104382A

Abstract

In the present invention, a plurality of slanted grooves, which are spaced away from each other in the tire circumferential direction, are formed in regions which comprise at least 25 [%] to 75 [%] inclusive of the tread width of the tread section centered on the tire equatorial plane, and are slanted with respect to the tire equatorial plane as seen from the tire radial direction. Consequently, block sections that extend and are connected along the slanted grooves are formed between pairs of slanted grooves adjacent to each other in the tire circumferential direction.

Description

Runflat radial tire

The present disclosure relates to a run-flat radial tire that enables traveling of a certain distance even in a state where the internal pressure is lowered due to a puncture or the like.

In the inner crown area of the tread portion of the run-flat radial tire described in Patent Document 1 (Japanese Patent Laid-Open No. 2014-58317), there is one inner main crown groove continuously extending in the tire circumferential direction, and this inner crown main An inner main lug groove is provided extending continuously from the groove to the ground end on the inner side of the vehicle. A wide block is defined by the inner main lug groove inside the vehicle of the inner crown main groove.

In the case of a run flat radial tire having a relatively high section height, in order to satisfy the run flat running durability (run flat performance), it is necessary to make the side reinforcing rubber very thick to reduce the longitudinal deflection of the tire. As a result, the vertical spring constant of the tire is increased (increased), which may deteriorate the ride comfort during normal driving.

An object of the present disclosure is to reduce the amount of longitudinal deflection of a run flat radial tire during run flat running while maintaining the ride comfort during normal running.

A run flat radial tire according to a first aspect comprises a carcass straddling a pair of bead portions,
A tread portion formed on the outer side in the tire radial direction of the carcass, a main groove formed on the tire equatorial plane of the tread portion and extending in the tire circumferential direction, and at least the tread portion centered on the tire equatorial plane A plurality of inclined grooves which are formed in a region of 25% or more and 75% or less of the contact width and are inclined with respect to the tire equatorial plane and separated in the tire circumferential direction when viewed from the tire radial direction; And a block portion continuously extending along the inclined groove between the pair of inclined grooves adjacent in a direction.

According to the above configuration, the main groove extending in the tire circumferential direction is formed on the tire equatorial plane in the tread portion of the run-flat radial tire. In addition, the plurality of inclined grooves inclined with respect to the tire equatorial plane as viewed from the radial direction of the tire and separated in the circumferential direction of the tire are at least 25% to 75% of the contact width of the tread portion. It is formed. And between the pair of inclined grooves adjacent in the tire circumferential direction, a block portion continuously extending along the inclined grooves is formed.

Here, during run-flat running (when running with the internal pressure of the tire at 0 [kPa]), the tire width direction is in the range of 25% to 75% of the contact width of the tread portion. The force to compress the tread increases. However, in this region, a plurality of inclined grooves inclined with respect to the tire equatorial plane are formed, and a block portion extends continuously along the inclined grooves between the pair of inclined grooves. In other words, no groove extending in the tire circumferential direction is formed in this region.

As described above, in the region of 25% or more and 75% or less of the contact width of the tread portion, in the tire circumferential direction, which is the starting point of bending deformation of the tread portion due to the force compressing the tread portion in the tire width direction. The extending groove is not formed. For this reason, the longitudinal deflection amount of the run flat radial tire during run flat running is reduced without increasing the rigidity of the side reinforcing layer.

In other words, it is possible to reduce the amount of longitudinal deflection of the run flat radial tire during run flat running without changing the longitudinal spring constant of the run flat tire during normal running. In other words, it is possible to reduce the amount of longitudinal deflection of the runflat radial tire during runflat travel while maintaining the ride comfort during normal travel.

The run-flat radial tire according to the second aspect is the run-flat radial tire according to the first aspect, wherein the run-flat radial tire is 100% of the ground contact width outside 75% of the ground contact width of the tread centering on the tire equatorial plane. A side main groove extending in the circumferential direction of the tire is formed in the following region.

According to the above configuration, the side main groove extending in the tire circumferential direction is 100% or less of the ground contact width outside 75% of the ground contact width of the tread portion (the side far from the tire equatorial plane CL) It is formed in the area of Here, at the time of run flat running, in the region outside 75% of the contact width of the tread portion, the force for compressing the tread portion in the tire width direction is small.

For this reason, even if the side main groove extending in the tire circumferential direction is formed in the region outside 75% of the contact width of the tread portion, the amount of longitudinal deflection of the runflat radial tire during runflat running Increase is suppressed. On the other hand, by forming the side main grooves extending in the tire circumferential direction in this region, it is possible to reduce the longitudinal spring constant of the run flat tire during normal traveling.

As described above, it is possible to reduce the vertical spring constant of the run-flat tire during normal running, while suppressing an increase in the amount of longitudinal deflection of the run-flat radial tire during run-flat running. In other words, it is possible to improve the riding comfort during normal running while suppressing an increase in the amount of longitudinal deflection of the run flat radial tire during run flat running.

The run-flat radial tire according to a third aspect is the run-flat radial tire according to the second aspect, wherein the groove width of the side main groove is wider than the groove width of the main groove. I assume.

According to the above configuration, the groove width of the side main groove is wider than the groove width of the main groove. As a result, the drainage performance of the outer portion in the tire width direction in the tread portion is improved, whereby the grip performance of the run-flat radial tire can be improved in traveling when the road surface is wet.

The run-flat radial tire according to the fourth aspect is characterized in that the inclined groove extends in a curved state from the tire equatorial plane side toward the outer side in the tire width direction when viewed from the tire radial direction.

According to the above configuration, the inclined groove extends in a curved state from the tire equatorial plane side toward the outer side in the tire width direction when viewed from the tire radial direction. For this reason, as compared with the case where the inclined grooves extend linearly, it is possible to suppress the occurrence of local bending deformation in the tread portion due to the force that compresses the tread portion in the tire width direction. The amount of longitudinal deflection of the flat radial tire can be reduced.

A run flat radial tire according to a fifth aspect is the run flat radial tire according to any one of the first to fourth aspects, wherein 25% of the contact width of the tread portion when viewed from the tire radial direction. The angle between the inclined groove and the tire equatorial plane in the region of 75% or less is 60 ° to 90 °.

According to the above configuration, the angle formed between the inclined groove and the tire equatorial plane is 60 degrees or more and 90 degrees or less. Therefore, compared to the case where the angle formed by the inclined groove and the tire equatorial plane is 20 degrees or more and 30 degrees or less, bending deformation of the tread portion caused by the inclined grooves during run flat travel is suppressed The amount of longitudinal deflection of the run flat radial tire can be reduced.

A run flat radial tire according to a sixth aspect is the run flat radial tire according to any one of the first to fifth aspects, wherein the groove width of the inclined groove is an outer side in the tire width direction from the tire equatorial plane side Spread gradually towards the

According to the above configuration, the groove width of the inclined groove gradually widens from the tire equatorial plane side toward the outer side in the tire width direction. For this reason, compared with the case where the groove width of the inclined groove is constant, the drainage performance for draining the water between the run flat radial tire and the road surface to the outside of the contact surface is improved in traveling when the road surface is wet. It can be done.

A run flat radial tire according to a seventh aspect is the run flat radial tire according to any one of the first to sixth aspects, wherein the run flat radial tire is disposed outside the carcass in the tire radial direction and extends in the tire circumferential direction. The plurality of cords constituting the belt layer are disposed to be inclined with respect to the tire equatorial plane as viewed from the tire radial direction, and viewed from the tire radial direction, the tire equatorial plane is provided. The inclination direction of the inclined groove with respect to and the inclination direction of the cord with respect to the tire equatorial plane are different.

According to the above configuration, the inclination direction of the inclined groove with respect to the tire equatorial plane and the inclination direction of the cord with respect to the tire equatorial plane are different when viewed from the tire radial direction. For this reason, even when the direction of the force for compressing the tread portion generated in the tread portion during runflat running is inclined to one side with respect to the tire equatorial plane, the run during runflat running The amount of longitudinal deflection of the flat radial tire can be reduced.

According to the present disclosure, it is possible to reduce the amount of longitudinal deflection of the run flat radial tire during run flat running while maintaining the ride comfort during normal running.

It is the top view showing the slot formed in the tread part of the run flat radial tire concerning a 1st embodiment of this indication. BRIEF DESCRIPTION OF THE DRAWINGS It is the top view which showed the groove | channel and the partial cross section which were formed in the tread part of the run flat radial tire which concerns on 1st Embodiment of this indication. 1 is an enlarged plan view showing a groove formed in a tread portion of a run-flat radial tire according to a first embodiment of the present disclosure. 1 is a cross-sectional view of a run-flat radial tire according to a first embodiment of the present disclosure, cut along the tire width direction. It is the drawing which showed the evaluation result of an example of a run flat radial tire concerning a 1st embodiment of this indication, a comparative example, etc. with a table. It is drawing which showed the analysis result of the run flat radial tire concerning a 1st embodiment of this indication. It is drawing which showed the analysis result of the run flat radial tire concerning a 1st embodiment of this indication. It is drawing which showed the analysis result of the run flat radial tire concerning a 1st embodiment of this indication. It is drawing which showed the analysis result of the run flat radial tire concerning a 1st embodiment of this indication. It is drawing which showed the deformation | transformation mode of the Example of the run flat radial tire which concerns on 1st Embodiment of this indication, and a comparative example. It is drawing which showed the deformation | transformation mode of the Example of the run flat radial tire which concerns on 1st Embodiment of this indication, and a comparative example. It is the top view which showed the groove formed in the tread part concerning the comparative example of the run flat radial tire concerning a 1st embodiment of this indication. It is the top view which showed the groove formed in the tread part of the run flat radial tire concerning a 2nd embodiment of this indication.

First Embodiment
An example of a tire according to a first embodiment of the present disclosure will be described according to FIGS. 1 to 8. In addition, arrow C shown in a figure shows a tire peripheral direction, arrow R shows a tire radial direction, and arrow W shows a tire width direction. Moreover, a tire radial direction means the direction orthogonal to the rotating shaft of a tire. Furthermore, the code | symbol CL has shown the equatorial plane (tire equatorial plane) of a tire.

In the present embodiment, the side closer to the rotation axis of the tire along the tire radial direction is referred to as "the inner side in the tire radial direction", and the side farther from the rotational shaft of the tire along the tire radial direction is referred to as the "outer side in the tire radial direction". Do. Furthermore, the side closer to the tire equatorial plane CL along the tire width direction will be referred to as "the inner side in the tire width direction", and the side farther from the tire equatorial plane CL along the tire width direction will be referred to as "the outer side in the tire width direction".

(overall structure)
As shown in FIG. 4, the run-flat radial tire 10 according to the present embodiment (hereinafter referred to as "the tire 10") has the bead portion 12, the sidewall portion 14, the tread portion 16, the carcass 18, the belt layer 20, and the belt reinforcing layer. 22 and a side reinforcing layer 26.

The bead portions 12 are members each having an annular bead core 28 and are provided in a pair in the tire width direction. Further, the bead portion 12 is provided with a bead filler 29 which is formed of a rubber harder than the rubber constituting the sidewall portion 14 and extends outward from the bead core 28 in the tire radial direction.

The sidewall portion 14 is a portion respectively connected to the bead portion 12 and constitutes a pair of side surfaces of the tire 10 together with the carcass 18 and other rubber layers. The tread portion 16 is a rubber layer connected to the side wall portions 14 on both sides, is formed with a main groove 30 and the like described later, and is a portion that contacts the road surface during traveling.

The carcass 18 is disposed across the pair of bead portions 12 in a toroidal shape, and a plurality of (two in the present embodiment) carcass formed by coating a plurality of cords arranged in the radial direction with rubber. It consists of plies.

The belt layer 20 is disposed on the outer periphery of the crown portion of the carcass 18 (portion facing the tire radial direction of the carcass 18), and tightens the crown portion of the carcass 18 to increase the taga effect (tightening the tire to the rim) Effects)).

The belt reinforcing layer 22 is a member formed by winding along the outer periphery of the belt layer 20, and is, for example, a member obtained by winding a strip including a plurality of cords coated with rubber so as to cover the belt layer 20. is there. In the present embodiment, the belt reinforcing layer 22 has a two-layer structure.

The side reinforcing layer 26 is made of rubber, and is disposed on the inner side in the tire width direction with respect to the portion of the carcass 18 of the sidewall portion 14. The thickness of the side reinforcing layer 26 gradually decreases inward and outward in the tire radial direction, and the cross section of the side reinforcing layer 26 has a substantially crescent shape. Further, the hardness of the rubber forming the side reinforcing layer 26 is made higher than the hardness of the rubber forming the sidewall portion 14 so as to be able to support a load during run-flat travel.
That is, the tire 10 is a tire that enables traveling at a predetermined speed at a predetermined speed even when the air pressure becomes zero.

(Main part configuration)
Next, the groove formed in the tread portion 16 will be described.
As shown in FIG. 1, the tread portion 16 is formed with a main groove 30 and a plurality of

inclined grooves

36 and 38.

[Main groove 30]
The main groove 30 is formed on the tire equatorial plane CL of the tread portion 16 and extends in the tire circumferential direction. In the embodiment, as an example, the groove width of the main groove 30 is 8 mm, and the groove depth of the main groove 30 is 10 mm.

[Slanted groove 36]
A plurality of inclined grooves 36 are formed outside the main groove 30 in the tire width direction (left side in the drawing). The plurality of inclined grooves 36 are arranged at predetermined intervals (pitches) in the tire circumferential direction.

The inclined groove 36 is positioned such that the end on the outer side in the tire width direction is located on one side (the lower side in the figure) in the circumferential direction of the tire as compared to the end on the inner side in the tire width direction when viewed from the tire radial direction. It extends in a curved state from the tire equatorial plane CL side toward the outer side in the tire width direction. In other words, the inclined grooves 36 do not have a straight portion when viewed in the tire radial direction, and are curved in an arc.

Furthermore, the groove width of the inclined groove 36 gradually widens from the tire equatorial plane CL side toward the outer side in the tire width direction. In the present embodiment, the groove width of the end on the inner side in the tire width direction in the inclined groove 36 is, for example, 8 mm, and the groove width of the end on the outer side in the tire width direction is 20 mm. It is done. Further, the groove depth of the inclined groove 36 is, for example, 10 mm.

Furthermore, in the tread portion 16, the angle formed between the inclined groove 36 and the tire equatorial plane CL in the region of 25% to 75% of the contact width with respect to the tire equatorial plane CL is 60 [deg.]. Above, it is made 90 degrees or less.

Here, according to the 2017 JATMA YEAR BOOK, the tire 10 is mounted on a standard rim, and the “contact width” is based on the maximum load capacity in applied size and ply rating and the corresponding air pressure (maximum air pressure). The maximum width of the tire in the tire width direction at the part that contacts the road surface Where the TRA standard or ETRTO standard is applied at the place of use or production site, the respective standard is followed.

TW in the figure indicates a ground width, and T1 and T2 in the figure indicate a ground end. Also, 0.25TW in the figure indicates 25% of the ground width (area of 25% of the ground width), and 0.75TW in the figure is 75% of the ground width (ground (Area of 75% of width) is shown. In the present embodiment, the tire equatorial plane CL passes through the center of the contact width TW in the tire width direction.

The angle between the inclined groove 36 in the area H1 shown in FIG. 1 and the tire equatorial plane CL is 60 degrees or more and 90 degrees or less. Specifically, with the inclined grooves 36 and the tire equatorial plane CL projected onto the tire meridian plane in the tire radial direction, as shown in FIG. 3, the tire equatorial plane CL and the center line of the inclined grooves 36 An angle (R1 in the figure) formed with C1 is set to 60 degrees or more and 90 degrees or less. Here, in the present embodiment, the “angle” refers to the smaller angle (the inferior angle) of the angles formed by one line and another line.

And, as shown in FIG. 1, a block portion 42 (so-called land portion) continuously extending along the inclined groove 36 is formed between the pair of inclined grooves 36 adjacent in the tire circumferential direction. There is. In other words, no groove or the like extending in the tire circumferential direction is formed between the pair of inclined grooves 36 adjacent in the tire circumferential direction.

[Inclined groove 38]
As shown in FIG. 1, a plurality of inclined grooves 38 are formed outside the main groove 30 in the tire width direction (right side in the drawing). In other words, the inclined groove 38 is a kind of lateral groove, and a plurality of inclined grooves 38 are formed on the opposite side of the inclined groove 36 to the main groove 30. The plurality of inclined grooves 38 are arranged at a predetermined interval (pitch) in the tire circumferential direction. The pitch of the inclined grooves 38 and the pitch of the inclined grooves 36 have the same value, and the inclined grooves 38 are disposed at a half pitch offset from the inclined grooves 36 in the tire circumferential direction. In addition, about the inclined groove 38, the part different from the inclined groove 36 is mainly demonstrated.

The inclined groove 38 has a shape in which the inclined groove 36 is inverted in the tire width direction centering on the tire equatorial plane CL and further in the tire circumferential direction.

Specifically, when viewed from the radial direction of the tire, the inclined groove 38 is positioned on the other side (upper side in the figure) in the tire circumferential direction compared to the end in the tire width direction on the outer side in the tire width direction. Thus, it extends in a curved state from the tire equatorial plane CL side toward the outer side in the tire width direction. In other words, the inclined grooves 38 do not have a straight portion when viewed in the tire radial direction, and are curved in an arc.

Thereby, the angle formed between the inclined groove 38 in the region (H2 in the drawing) and the tire equatorial plane CL in the region (H2 in the drawing) of the tread width 16 at 25% to 75% of the tread width is at least 60 degrees. And 90 degrees or less.

Further, as shown in FIG. 1, block portions 44 extending continuously along the inclined grooves 38 are formed between the pair of inclined grooves 38 adjacent in the tire circumferential direction. In other words, no groove or the like extending in the tire circumferential direction is formed between the pair of inclined grooves 38 adjacent in the tire circumferential direction.

[Others]
In the belt layer 20, as shown in FIG. 2, a plurality of cords 20A are disposed inclined with respect to the tire equatorial plane CL. In the present embodiment, the end on the left side in the tire width direction in the cord 20A is on the other side (upper side in the figure) in the tire circumferential direction as compared to the end on the right side in the tire width direction in the cord 20A. positioned. That is, the cord 20A is inclined with respect to the tire equatorial plane CL so as to be at the upper left in the drawing. Specifically, the cord 20A is disposed to be inclined at 60 degrees or more and 70 degrees or less with respect to the tire equatorial plane CL.

Here, in the

inclined grooves

36 and 38 described above, the end on the left side in the tire width direction in the

inclined grooves

36 and 38 is compared with the end on the right side in the tire width direction in the

inclined grooves

36 and 38. It is located at one side (lower side in the figure) in the tire circumferential direction. That is, the

inclined grooves

36, 38 are inclined with respect to the tire equatorial plane CL so as to be on the upper right in the drawing.

Thus, when viewed from the tire radial direction, the inclination direction of the

inclined grooves

36 and 38 with respect to the tire equatorial plane CL is different from the inclination direction of the cord 20A with respect to the tire equatorial plane CL.

(Evaluation)
Next, since evaluation was performed using Example 255 of the first embodiment, Example 2 of the second embodiment described later, and Comparative Example using the tire of 255 / 65R18, this evaluation will be described.
[Evaluation specification]
As Example 1, as shown in FIG. 1, a tire in which a main groove 30, an inclined groove 36, and an inclined groove 38 were formed in the tread portion 16 was used.

As Example 2, as FIG. 9 shows, the tire in which the main groove 30, the inclined groove 36, the inclined groove 38, and a pair of side main groove 60 were formed in the tread part 16 was used. The pair of side main grooves 60 is outside the contact width 75 [%] of the tread portion 16 (side far from the tire equatorial plane CL) and in a region (H3 and H4 in the figure) less than the contact width 100 [%]. It is formed and extends in the tire circumferential direction (details will be described later).

As a comparative example, as shown in FIG. 8, a tire in which a main groove 30, an inclined groove 36, an inclined groove 38, and a pair of central main grooves 46 are formed in the tread portion 16 was used. The pair of central main grooves 46 are respectively formed in the region (H1 and H2 in the figure) with a contact width of 25% or more and 75% or less of the tread portion 16 and extend in the tire circumferential direction. The groove width and the groove depth of the central main groove 46 are set to the same values as the groove width and the groove depth of the main groove 30.
The specifications other than the specifications described above are the same in the first embodiment, the second embodiment, and the comparative example.

〔Evaluation item〕
-Vertical deflection of tire-
Each tire was assembled to a standard rim of JATMA standard, and a predetermined load was applied to the rim without filling air (the internal pressure was 0 [kPa]), and the tire was pressed against the road surface. Then, the amount of longitudinal deflection in the tire radial direction was measured for each tire. About the amount of longitudinal deflection, the amount of longitudinal deflection of the tire of Example 1 and Example 2 was computed by making the amount of longitudinal deflection of the tire of a comparative example into 100.

-Vertical spring constant-
Each tire was attached to a standard rim of JATMA standard, air was filled, a predetermined load was applied to the rim as a predetermined internal pressure (for example, 250 [kPa]), and the tire was pressed against the road surface. Then, the longitudinal spring constant was determined from the amount of longitudinal deflection of each tire and the generated load. About the vertical spring constant, the vertical spring constant of Example 1 and Example 2 was calculated by setting the vertical spring constant of the comparative example to 100.

〔Evaluation results〕
As shown in the table of FIG. 5, in the tires of Example 1 and Example 2, the longitudinal spring constant is maintained and the amount of longitudinal deflection of the tire is smaller than that of the tire of the comparative example.

〔analysis〕
In order to consider the evaluation described above, first, an analysis on the force for compressing the tread portion generated on the tire when the tire not filled with air (the internal pressure is 0 [kPa]) is pressed against the road will be described. Here, the force to compress the tread portion is a force that causes the tread portion to be bent and deformed so that part of the tread portion floats from the road surface (back link deformation).

The force which compresses the tread part which arose in the tread part is shown with dod in FIG. 6B and FIG. 6C. Specifically, in FIG. 6B, a force for compressing the tread portion in the tire width direction is indicated by a dod, and in FIG. 6C, a force for compressing the tread portion in the tire circumferential direction generated in the tread portion is indicated by the dod. It is shown. The portion where the dod is dense has a larger force for compressing the tread portion than the portion where the dot is coarse.

As shown in FIG. 6B, the force for compressing the tread portion in the tire width direction is large in a region of 25% or more and 75% or less of the tread width in the tread portion, and the tread width 75 [grounding width]. %] Is smaller in the region outside the tire equatorial plane CL.

Moreover, about the force which compresses a tread part to a tire peripheral direction, as FIG. 6C shows, it is small in the area | region of the whole tread part.

And from the analysis result, the direction (synthetic direction) of the synthetic force combining the force to compress the tread portion in the tire width direction and the force to compress the tread portion in the tire circumferential direction is as shown in FIG. 6D. When viewed from the radial direction of the tire, it is 60 degrees or more and 90 degrees or less (R2, R3 in the figure, for example, 78 degrees) with respect to the tire equatorial plane CL.

[Discussion]
During run flat running, the tire side portion including the sidewall portion 14 and the like, and the crown portion including the tread portion 16 and the like support the load acting on the tire because no internal pressure acts on the tire. . Here, it is known that the correlation between the longitudinal deflection ratio (longitudinal deflection amount / section height) during runflat running and the runflat durability is high, and in order to improve the runflat durability, the longitudinal dimension of the tire is increased. The amount of deflection must be reduced. And the amount of vertical deflection of a tire changes with the amount of deformation of a tire side part and a crown part. That is, by reducing the amount of deformation of the tire side portion or the crown portion, the amount of longitudinal deflection of the tire is reduced, and the run flat durability is improved.

Here, a force (compressive load) that compresses the tread portion acts on the crown portion (tread portion) during run flat traveling, and the tread portion floats from the road surface, causing buckling deformation. From the above analysis results, in the tread portion, the force for compressing the tread portion in the tire width direction is large in the region of 25% or more and 75% or less of the contact width.

In the tire of the comparative example of the evaluation described above, the central main groove 46 extending in the circumferential direction of the tire is formed in a region of 25% or more and 75% or less of the contact width in the tread portion. On the other hand, in the tires of Example 1 and Example 2, the central main groove 46 extending in the circumferential direction of the tire is formed in the tread portion at a region of 25% or more and 75% or less of the contact width. Not.

For this reason, in the tire according to the comparative example, as shown in FIG. 7B, the center main groove 46 is largely deformed during run flat traveling. That is, the central main groove 46 is a starting point of bending deformation of the tread portion. On the other hand, in the tires of Example 1 and Example 2, as shown in FIG. 7A, since there is no central main groove 46, the deformation of the crown portion is smaller than that of the tire according to the comparative example. Become.

(Summary)
As can be understood from the above evaluation results and the discussion, in the tire 10, the longitudinal spring constant can be maintained and the amount of longitudinal deflection can be reduced. In other words, it is possible to reduce the amount of longitudinal deflection of the tire 10 during run flat travel while maintaining the ride comfort during normal travel. That is, the run-flat durability can be improved while maintaining the ride comfort during normal driving.

Further, in the tire 10, a main groove 30 and

inclined grooves

36, 38 are formed. For this reason, it is possible to suppress the decrease in tire grip performance in traveling when the road surface is wet.

Further, when viewed from the radial direction of the tire, the angle (angle R1 in FIG. 3) between the

inclined grooves

36 and 38 and the tire equatorial plane CL in the region of 25% or more and 75% or less of the contact width is 60 [Degree] or more and 90 degrees or less. Here, from the analysis result described above, the direction of the synthetic strain in which the force for compressing the tread portion in the tire width direction and the force for compressing the tread portion in the tire circumferential direction is the tire equator when viewed from the tire radial direction. 60 degrees or more and 90 degrees or less with respect to the surface CL (see R2 and R3 in FIG. 6D). Therefore, compared to the case where the angle formed by the inclined groove and the tire equatorial plane CL is not less than 20 degrees and not more than 30 degrees, the deformation of the tread portion 16 caused by the inclined grooves during run flat travel is suppressed Thus, the amount of longitudinal deflection of the tire 10 can be reduced.

The

inclined grooves

36 and 38 extend in a curved state from the tire equatorial plane CL side toward the outer side in the tire width direction when viewed from the tire radial direction. Therefore, local bending deformation is suppressed in the tread portion 16 due to the force for compressing the tread portion in the tire width direction, as compared with the case where the inclined grooves extend linearly, and the longitudinal deflection of the tire 10 is obtained. The amount can be reduced.

In addition, the groove width of the

inclined grooves

36 and 38 gradually widens from the tire equatorial plane CL side toward the outer side in the tire width direction (the side farther from the tire equatorial plane CL). For this reason, compared with the case where the groove width of the

inclined grooves

36 and 38 is constant, the drainage performance for draining water between the tire 10 and the road surface to the outside of the contact surface during traveling when the road surface is wet It can be improved.

Further, as viewed from the radial direction of the tire, the inclination direction of the

inclined grooves

36 and 38 with respect to the tire equatorial plane CL is different from the inclination direction of the cord 20A with respect to the tire equatorial plane CL. For this reason, even when the direction of the force for compressing the tread portion generated in the tread portion 16 during runflat running is inclined to one side with respect to the tire equatorial plane CL, the runflat running The longitudinal deflection of the tire 10 can be reduced.

Second Embodiment
An example of a tire according to a second embodiment of the present disclosure will be described according to FIG. In addition, about the tire which concerns on 2nd Embodiment, the part different from the tire 10 of 1st Embodiment is mainly demonstrated.

In the tread portion 16 of the tire 110 according to the second embodiment, as shown in FIG. 9, a main groove 30, an inclined groove 36, an inclined groove 38, and a pair of side main grooves 60 are formed. The pair of side main grooves 60 is formed outside the contact width 75% of the tread portion 16 and in a region (H3 and H4 in the figure) smaller than the contact width 100% and in the tire circumferential direction. It extends. That is, as described in the above analysis, the pair of side main grooves 60 is formed in a region where the force for compressing the tread portion in the tire width direction during runflat travel is small.

The groove width of the side main groove 60 is, for example, 10 mm, and the groove depth of the side main groove 60 is, for example, 10 mm. The groove width of the side main groove 60 is wider than the groove width of the main groove 30. Further, the groove width of the side main groove 60 is an inclination of a portion (H3, H4 in the figure) outside the contact width 75% of the tread portion 16 and not more than the contact width 100%. It is narrowed relative to the width of the

grooves

36, 38.

As described above, by forming the side main grooves 60 extending in the tire circumferential direction in a region where the force for compressing the tread in the tire width direction during run flat running is small, the amount of longitudinal deflection during run flat running is increased. Can be reduced to lower the vertical spring constant during normal driving. That is, the ride quality during normal travel can be improved without increasing the vertical deflection amount of the tire 10 during run flat travel. In other words, compared with the tire 10, the tire 110 can reduce the amount of longitudinal deflection during run flat travel while maintaining the longitudinal spring constant (see the table shown in FIG. 5).

Further, the groove width of the side main groove 60 is wider than the groove width of the main groove 30. For this reason, the drainage performance of the portion of the tread portion 16 on the outer side in the tire width direction is improved. As a result, it is possible to improve the grip performance of the tire in traveling when the road surface is wet while suppressing the decrease in runflat durability.

Although the present disclosure has been described in detail with respect to the specific embodiments, the present disclosure is not limited to the embodiments, and various other embodiments are possible within the scope of the present disclosure. It is clear to the trader. For example, although the

inclined grooves

36 and 38 are curvilinear in the above embodiment, they may be linear. However, in this case, the effect exhibited by the curvilinear shape does not occur.

Further, although the groove width of the

inclined grooves

36 and 38 gradually changes in the above embodiment, the groove width may be constant. However, in this case, the effect exerted by the gradual change of the groove width is not exerted.

Moreover, although the direction in which the inclined groove 36 inclines with respect to the equatorial plane CL and the direction in which the inclined groove 38 inclines with respect to the equatorial plane CL are the same in the above embodiment, they may be different.

The disclosure of Japanese Patent Application 2017-238065, filed December 12, 2017, is incorporated herein by reference in its entirety.
All documents, patent applications and technical standards described herein are as specific and individually as individual documents, patent applications and technical standards are incorporated by reference. Incorporated herein by reference.
(Explanation of the code)

DESCRIPTION OF SYMBOLS 10 ... tire (run flat radial tire), 12 ... bead part, 16 ... tread part, 18 ... carcass, 20 ... belt layer, 20A ... cord,
26 ··· Side reinforcement layer, 30 · · · Main groove, 36 · · · Inclined groove,
38 · · · inclined groove, 42 · · · block portion, 44 · · · block portion,
60 ··· Side main groove, 110 ··· Tire

Claims

A carcass extending between a pair of bead portions,
A tread portion formed on the outer side in the tire radial direction of the carcass;
A main groove formed on the tire equatorial plane of the tread portion and extending in the circumferential direction of the tire;
It is formed in a region of at least 25% and at most 75% of the contact width of the tread portion with respect to the tire equatorial plane, and is inclined with respect to the tire equatorial plane when viewed from the tire radial direction. Multiple inclined grooves spaced apart,
Between the pair of inclined grooves adjacent in the tire circumferential direction, a block portion continuously extending along the inclined grooves;
Run flat radial tire with.
A side main groove extending in the tire circumferential direction is formed in a region of 100% or less of the ground contact width outside 75% of the tread width of the tread centering on the tire equatorial plane. The run flat radial tire according to claim 1.
The run flat radial tire according to claim 2, wherein the groove width of the side main groove is wider than the groove width of the main groove.
The run-flat radial tire according to any one of claims 1 to 3, wherein the inclined groove extends in a curved state from the tire equatorial plane side toward the outer side in the tire width direction when viewed from the tire radial direction.
The angle between the inclined groove and the tire equatorial plane in the region of 25% to 75% of the contact width of the tread portion, as viewed from the radial direction of the tire, is 60 ° to 90 °. The run-flat radial tire according to any one of claims 1 to 4, wherein the degree is as follows.
The run-flat radial tire according to any one of claims 1 to 5, wherein the groove width of the inclined groove gradually widens from the tire equatorial plane side toward the outer side in the tire width direction.
It has an annular belt layer disposed on the outer side in the tire radial direction of the carcass and extending in the tire circumferential direction,
The plurality of cords constituting the belt layer are disposed to be inclined with respect to the tire equatorial plane when viewed from the tire radial direction,
The run-flat radial tire according to any one of claims 1 to 6, wherein the inclination direction of the inclined groove with respect to the tire equatorial plane and the inclination direction of the cord with respect to the tire equatorial plane are different when viewed from the tire radial direction.