JP4713785B2 - Pneumatic tire - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire suitable for heavy-duty vehicles such as trucks and buses.
[0002]
[Prior art]
Various pneumatic tires having a plurality of ribs extending in the circumferential direction on a tread have been proposed as pneumatic tires used in heavy-duty vehicles such as trucks and buses.
[0003]
Pneumatic having a pattern as shown in Fig. 11 as a tire for steering under a wide range of usage conditions from medium to short distance to long distance (especially KPM 15000km or more. KPM indicates the mileage per 1mm wear) There is a tire 100.
[0004]
In the pneumatic tire (tire size: 315 / 80R22.5) 100 shown in FIG. 11, circumferential main grooves 104 are formed on both sides of the tire equatorial plane CL of the tread 102, and the circumferential main grooves 104 are formed on the outer sides in the tire axial direction. A direction main groove 106 is formed.
[0005]
The width of the tread portion of the center rib 108 is 31.4 mm, the width of the tread portion of the second rib 110 is 31.4 mm, and the width of the tread portion of the shoulder rib 112 is 50.2 mm (both are new).
[0006]
The circumferential main groove 104 has a groove width of 10.5 mm and a groove depth of 15.0 mm, and the circumferential main groove 106 has a groove width of 15.0 mm and a groove depth of 15.0 mm (both are new). Time).
[0007]
The tread width W is 246 mm (when new).
[0008]
Sipes 114 are formed in the center rib 108, the second rib 110, and the shoulder rib 112, respectively.
[0009]
The circumferential arrangement pitch of the sipes 114 is 37.6 mm for the center rib 108, 37.6 mm for the second rib 110, and 37.6 mm for the shoulder rib 112.
[0010]
The sipe 114 has a groove width of 0.5 mm and a groove depth of 12 mm (when new).
[0011]
A plurality of short sipes 116 extending linearly along the tire axial direction are formed at both ends of the center rib 108, both ends of the second rib 110, and the inner end of the shoulder rib 112.
[0012]
The short sipe 116 of the center rib 108 has a groove width of 0.7 mm, a groove depth of 12.2 mm, a tire axial length of 2.5 mm, and a circumferential arrangement pitch of 12.5 mm.
[0013]
The short sipe 116 of the second rib 110 has a groove width of 0.7 mm, a groove depth of 12.2 mm on the center rib side, 7.6 mm on the shoulder rib side, and a tire axial length of 2.2. 5 mm, provided so that the sipe is divided into three equal parts on the center rib side, and provided so that the sipe parts are divided into six equal parts on the shoulder rib side.
[0014]
The short sipe 116 of the shoulder rib 112 is provided so that the groove width is 0.7 mm, the groove depth is 12.2 mm, the tire axial length is 2.5 mm, and the sipe is divided into six equal parts. .
[0015]
The shoulder rib 112 is formed with a defense groove 118 having a groove width of 2.5 mm and a groove depth of 11.1 mm for the purpose of suppressing uneven wear near the shoulder.
[0016]
Further, a circumferential land portion 120 for suppressing uneven wear is formed at the groove bottom of the circumferential main groove 106 between the second rib 110 and the shoulder rib 112.
[0017]
[Problems to be solved by the invention]
However, the conventional pneumatic tire 100 has the following problems.
(1) Defensive groove 118 causes deterioration of shoulder edge wear due to a combination of uneven wear called shoulder edge wear (SEW) caused by dragging of the shoulder end and width direction uneven wear work in the ribs due to side forces. Although compensated, there was a problem that tears (cracks) occurred from the groove bottom of the defense groove 118.
(2) In considering shoulder edge wear, it is important to ensure the rigidity of the land portion of the shoulder portion. Therefore, conventionally, the width of the shoulder rib 112 when new is 1.30 to the width of the second rib 110. Although 1.40 has been considered good, there is a problem that shoulder edge wear deteriorates in the above range when the contribution of wear work in the width direction becomes high.
[0018]
In consideration of the above facts, the present invention is a pneumatic tire that has solved the problems of conventional pneumatic tires, that is, a vehicle for long distances that can reliably suppress shoulder edge wear and that does not deteriorate other performances. It is an object to provide a pneumatic tire suitable for the above.
[0019]
[Means for Solving the Problems]
The invention described in claim 1 is a pneumatic tire having a tread having five ribs divided by four circumferential main grooves extending along the circumferential direction, and is disposed at a central portion in the tire width direction. W1 is the width of the center rib when it is new, W2 is the width of the second rib that is placed on both sides of the center rib, and W2 is the width of the shoulder rib that is placed outside the second rib in the tire width direction. When W3, W1: W2: W3 = 1: 1 ± 0.05: 1.15 to 1.3 is satisfied, and the groove depth of the circumferential main groove is all the wear states of 2 mm or more. In the region, 1.09 × second rib width ≦ shoulder rib width ≦ 1.35 × second rib width is satisfied.
[0020]
Next, the operation of the pneumatic tire according to claim 1 will be described.
[0021]
In consideration of shoulder edge wear (uneven wear), considering that the contribution of wear work in the rib due to lateral forces such as side forces is large, the land rigidity of the rib is lower than the conventional one (ie, width) Narrower) is more effective against uneven wear.
[0022]
In the pneumatic tire according to claim 1, since the width of the shoulder rib relative to the width of the second rib at the time of a new article is narrower than that of the conventional product, shoulder edge wear can be reliably suppressed.
[0023]
In addition, in all regions in each wear state where the groove depth of the circumferential main groove is 2 mm or more, 1.09 × second rib width ≦ shoulder rib width ≦ 1.35 × second rib width is satisfied. Even after wear, shoulder edge wear can be reliably suppressed.
[0024]
Further, since the defense groove is not formed on the shoulder rib, various problems (tea from the groove bottom, chipping of the shoulder rib, etc.) due to the provision of the defense groove do not occur.
[0025]
According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the center rib, the second rib, and the shoulder rib substantially extend in the tire width direction and are more than the circumferential main groove. The groove depth is shallow, and a shallow groove having a sipe is formed at the bottom.
[0026]
Next, the operation of the pneumatic tire according to claim 2 will be described.
[0027]
The shallow groove can drain water between the road surface and the tire. For this reason, it is possible to improve the wet performance at the initial stage of wear in which the shallow groove exists.
[0028]
Further, since the sipe is formed at the bottom of the shallow groove, when the wear of the tread advances and the drainage action of the shallow groove disappears, the sipe appears and the wet performance is maintained by the edge effect of the sipe.
[0029]
The invention according to claim 3 is the pneumatic tire according to claim 2, wherein the groove depth of the sipe is 50 to 100% of the groove depth of the circumferential main groove. .
[0030]
Next, the operation of the pneumatic tire according to claim 3 will be described.
[0031]
Since the depth of the sipe is set to 50% to 100% of the groove depth of the circumferential main groove, the balance of wet performance, wear performance and uneven wear performance can be achieved.
[0032]
When the sipe depth is less than 50% of the depth of the circumferential main groove, the wet performance during wear is insufficient.
[0033]
On the other hand, when the depth of the sipe exceeds 100% of the depth of the circumferential main groove, the wear performance and the partial wear performance are degraded due to the decrease in rigidity.
[0034]
According to a fourth aspect of the present invention, in the pneumatic tire according to the second or third aspect, the sipe is arranged so as to be offset toward the tire rotation direction side of the groove bottom of the shallow groove. To do.
[0035]
Next, the operation of the pneumatic tire according to claim 4 will be described.
[0036]
By forming a shallow groove with a sipe on the rib, the rib is substantially divided into a plurality of blocks, and there is a concern that heel and toe wear may occur on the block.
[0037]
Here, by arranging the sipe in the shallow groove adjacent to the kicking end of the block, the land portion rigidity of the kicking end of the block can be reduced (compared with the stepping side).
[0038]
Lowering the land rigidity on the kicking side reduces the ground pressure at the kicking end (compared to the pressure on the stepping side at that time) in the deformation at the time of kicking (deformation caused by the brake force being applied to the block) Thus, the contact pressure distribution in the block can be made uniform.
[0039]
According to a fifth aspect of the present invention, in the pneumatic tire according to any one of the first to fourth aspects of the present invention, the second rib has the shallow groove formed with a sipe at the groove bottom. The groove depth is shallower than the circumferential main groove, and a shallow groove without a sipe is formed at the bottom.
[0040]
Next, the operation of the pneumatic tire according to claim 5 will be described.
[0041]
Since the shallow rib having a groove depth shallower than the circumferential main groove and having no sipe formed in the bottom rib is formed in the second rib, the wet performance at the initial stage of wear can be further improved.
[0042]
The invention according to claim 6 is the pneumatic tire according to any one of claims 1 to 5, wherein the shallow groove has a groove depth of 1.5 to 3 mm. Yes.
[0043]
Next, the operation of the pneumatic tire according to claim 6 will be described.
[0044]
If the groove depth of the shallow groove is less than 1.5 mm, sufficient drainage cannot be obtained, and the meaning of providing the shallow groove is lost.
[0045]
The invention according to claim 7 is the pneumatic tire according to any one of claims 2 to 6, wherein the shallow groove has a groove width of 1.5 to 3 mm. .
[0046]
Next, the operation of the pneumatic tire according to claim 7 will be described.
[0047]
If the groove width of the shallow groove is less than 1.5 mm, sufficient drainage cannot be obtained, and the meaning of providing the shallow groove is lost.
[0048]
The invention according to claim 8 is the pneumatic tire according to any one of claims 1 to 7, wherein one end of the end portion of the rib opens into the circumferential main groove, and the other end of the pneumatic tire. A plurality of short sipes terminating in the rib are formed in the circumferential direction.
[0049]
Next, the operation of the pneumatic tire according to claim 8 will be described.
[0050]
By forming a plurality of short sipes in the circumferential direction of the tire along the tire circumferential direction, one end is opened in the circumferential main groove side wall surface of the rib and the other end is terminated in the rib. The rigidity is reduced, and the occurrence of rib tears in the vicinity of the edge portion and uneven wear of the rib ends can be suppressed.
[0051]
The length of the short sipe in the tire axial direction is preferably 2 to 4 mm.
[0052]
If the length of the short sipe is less than 2 mm, the rigidity in the vicinity of the edge portion of the rib cannot be reduced, and the occurrence of rib tear cannot be suppressed.
[0053]
On the other hand, if the length of the short sipe exceeds 4 mm, the rigidity of the entire rib is lowered, which is not preferable.
[0054]
The invention according to claim 9 is the pneumatic tire according to claim 8, wherein the short sipe has a bent portion at a middle portion in a longitudinal direction, and the bent portion opens the short sipe. It is provided in parallel with the groove wall of the circumferential main groove in the groove depth direction, and the bending angle of the bent portion is in the range of 90 to 160 °.
[0055]
Next, the operation of the pneumatic tire according to claim 9 will be described.
[0056]
In deformation due to lateral force such as side force, the rib undergoes compressive deformation in the tire width direction, but it easily deforms in the width direction together with the sipe part having the bent part, so that the amount of wear work at that time can be reduced. It is possible to improve uneven wear and wear resistance.
[0057]
In addition, since the bent part is provided in parallel to the groove wall of the circumferential main groove where the short sipe opens, the sipe effect can be obtained in the same way from the new product to the end of wear. It is done.
[0058]
In addition, if the bending angle of the bent portion is less than 90 °, the rigidity of the land portion is too low, and the possibility of occurrence of sipetea increases.
[0059]
On the other hand, if the bending angle of the bent portion exceeds 160 °, the bending effect is small and the work of wear increases.
[0060]
Therefore, the bending angle of the bent portion is preferably in the range of 90 to 160 °.
[0061]
According to a tenth aspect of the present invention, in the pneumatic tire according to any one of the first to ninth aspects, a position of a top portion is set lower than a tread surface of the tread at the bottom portion of the circumferential main groove. It is characterized in that a formed stone biting prevention protrusion is formed.
[0062]
Next, the operation of the pneumatic tire according to claim 10 will be described.
[0063]
When multiple stone biting prevention protrusions are provided at the groove bottom of the circumferential main groove, when stones on the road surface try to enter the groove (when the groove attempts to bite stones), the stone biting prevention protrusions enter the stone. And stone biting resistance is improved.
[0064]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the pneumatic tire of the present invention will be described with reference to FIGS. 1 to 6.
[0065]
In FIG. 1, the arrow L direction and the arrow R direction indicate the tire axial direction, and the arrow S direction indicates the tire circumferential direction.
[0066]
As shown in FIG. 1, the tread 12 (tread width W) of the pneumatic tire 10 (tire size: 315 / 80R22.5) of the present embodiment is in the tire axial direction (arrow L direction) with the tire equatorial plane CL interposed therebetween. Further, a circumferential main groove 14 extending linearly along the tire circumferential direction (arrow S direction) is formed on both sides, and the circumferential main groove 14 extends along the tire circumferential direction on the outer side in the tire axial direction. A circumferential main groove 16 extending linearly is formed.
[0067]
Here, the tread width means a dimension from one contact end in the tire width direction to the other contact end, and the pneumatic tire is specified in JATMA YEAR BOOK (2001 edition, Japan Automobile Tire Association Standard). It is mounted on a standard rim and filled with an internal pressure that is 100% of the air pressure (maximum air pressure) corresponding to the maximum load capacity (bold load in the internal pressure-load capacity correspondence table) for the applicable size and ply rating in JATMA YEAR BOOK. (This is a load corresponding to the maximum load capacity when a single wheel in JATMA YEAR BOOK is applied.)
[0068]
When the TRA standard or ETRTO standard is applied at the place of use or manufacturing, the respective standards are followed.
[0069]
The width of the tread surface portion of the center rib 18 sandwiched between the two circumferential main grooves 14 is W1, and the width of the tread portion of the second rib 20 sandwiched between the circumferential main groove 14 and the circumferential main groove 16 is new. Is W2, and the width of the tread surface portion of the shoulder rib 22 disposed outside the circumferential main groove 16 in the tire width direction is W3 when W3 is new, W1: W2: W3 = 1: 1 ± 0.05: 1 .15 to 1.3, and in all wear regions where the groove depth of each circumferential main groove is 2 mm or more, 1.09 × width of second rib 20 ≦ width of shoulder rib 22 ≦ 1. 35 × the width of the second rib 20 is satisfied.
[0070]
In order to satisfy the following expression: 1.09 × width of second rib 20 ≦ width of shoulder rib 22 ≦ 1.35 × width of second rib 20 As shown in FIG. The angle to the normal on the tread was set optimally.
[0071]
As shown in FIGS. 1 and 2, a plurality of stone biting prevention protrusions 24 are formed along the longitudinal direction of the main groove at the bottom of the circumferential main groove 14 and the bottom of the circumferential main groove 16.
[0072]
The stone biting prevention protrusion 24 may be provided only in one of the circumferential main groove 14 and the circumferential main groove 16 or may not be provided in some cases.
[0073]
The stone biting prevention protrusion 24 is set such that the position of the top portion 24 </ b> A is lower than the tread surface 12 </ b> A of the tread 12.
[0074]
A plurality of shallow grooved sipes 26 as shown in FIG. 3 are formed in the center rib 18, the second rib 20, and the shoulder rib 22 in the tire circumferential direction.
[0075]
As shown in FIG. 1, the sipe 26 with a shallow groove formed in the center rib 18 opens to the circumferential main grooves 14 on both sides, and has a substantially V shape.
[0076]
The sipe 26 with a shallow groove formed in the second rib 20 is inclined leftwardly upward on the left side of the tire equator plane CL and upwardly upward on the right side of the tire equator plane CL. The groove 16 is open.
[0077]
The shallow grooved sipe 26 formed in the shoulder rib 22 is inclined upward to the left on the left side of the tire equatorial plane CL and upward to the right on the right side of the tire equatorial plane CL, and one end opens into the circumferential main groove 16. The other end is terminated before the grounding end 12B.
[0078]
As shown in FIG. 3, the shallow grooved sipe 26 has a shallow groove 26A that is narrower and shallower than the circumferential main groove 14 and the circumferential main groove 16, and a groove of the shallow groove 26A. It is comprised from the sipe 26B formed in the bottom.
[0079]
The groove width W4 of the shallow groove 26A is preferably in the range of 1.5 to 3.0 mm, and the groove depth D1 of the shallow groove 26A is preferably in the range of 1.5 to 3.0 mm.
[0080]
The sipe 26B is formed at the end of the shallow groove 26A on the side opposite to the tire rotation direction (arrow A direction).
[0081]
The groove depth D2 measured from the tread surface 12A of the sipe 26B is preferably in the range of 70% to 100% of the groove depth of the circumferential main groove opened by the sipe 26B.
[0082]
Further, the groove width W5 of the sipe 26B is preferably equal to or less than mm.
[0083]
As shown in FIG. 1, a shallow groove 28 is formed in the second rib 20 between the shallow grooved sipe 26 and the shallow grooved sipe 26.
[0084]
The shallow groove 28 is inclined to the left on the left side of the tire equator plane CL, and is inclined to the right side on the right side of the tire equator plane CL. One end opens in the circumferential main groove 16 and the other end terminates near the center of the rib. is doing.
[0085]
As shown in FIG. 4, the groove width W6 of the shallow groove 28 is preferably in the range of 1.5 to 3.0 mm, and the groove depth D3 of the shallow groove 28 is preferably in the range of 1.5 to 3.0 mm.
[0086]
As shown in FIG. 1, a short sipe 30 having one end opened in an adjacent circumferential main groove and the other end terminated in the rib at each end of the center rib 18, the second rib 20, and the shoulder rib 22. Are formed in the circumferential direction.
[0087]
As shown in FIG. 5 showing the vicinity of the circumferential main groove 14, the short sipe 30 has a bent portion 30A, and the bent portion 30A is formed on the groove wall 14A of the circumferential main groove 14 opened by the short sipe 30. On the other hand, it is provided in parallel in the groove depth direction.
[0088]
In the short sipe 30, it is preferable that the bending angle θ is set in a range of 90 to 160 °, and the length L1 in the tire axial direction is set in a range of 2 to 4 mm.
[0089]
Further, the groove depth D4 of the short sipe 30 is preferably set within a range of 50 to 100% of the groove depth D5 of the circumferential main groove opened by the short sipe 30, and the groove width W7 of the short sipe 30 is 1.2 mm or less is preferable.
[0090]
In the present embodiment, the width W1 of the tread portion of the center rib 18 is 35.2 mm, the width W2 of the tread portion of the second rib 20 is 35.2 mm, and the width W3 of the tread portion of the shoulder rib 22 is 42.4 mm (whichever Is also new).
[0091]
The tread width W is 242 mm (when new).
[0092]
The groove width of the circumferential main groove 14 is 12.9 mm, the groove depth of the circumferential main groove 14 is 14.6 mm, the groove width of the circumferential main groove 16 is 12.9 mm, and the groove depth of the circumferential main groove 16 is 15.0 mm (both are new).
[0093]
The stone biting prevention protrusion 24 preferably has a height of 3 to 6 mm from the groove bottom when the circumferential main groove 14 and the circumferential main groove 16 have a groove depth as described above.
[0094]
The circumferentially arranged pitch of the shallow grooved sipe 26 is 3 pitches of 34 mm, 38 mm and 41 mm for the center rib, 3 pitches of 34 mm, 38 mm and 41 mm for the second rib 20, and 34 mm, 38 mm and 41 mm for the shoulder rib 22. 3 pitches.
[0095]
In the second rib 20, the shallow groove 28 is formed at an intermediate portion between the shallow grooved sipe 26 and the shallow grooved sipe 26.
[0096]
The shallow groove 26A of the shallow grooved sipe 26 has a groove width W4 of 2 mm and a groove depth D1 of 2 mm (when new).
[0097]
The sipe 26B of the shallow grooved sipe 26 has a groove width W5 of 0.5 mm and a groove depth D2 of 12 mm (when new).
[0098]
The shallow groove 28 has a groove width W6 of 2 mm and a groove depth D3 of 2 mm (when new).
[0099]
The short sipe 30 has a groove width W7 of 0.5 mm, a groove depth D3 of 11.6 mm when the center rib 18 and the second rib 20 are on the center rib side, and the shoulder rib 22 and the second rib 20 on the shoulder rib side. In the case of the thing, the bending angle θ is 135 °, the length L1 in the tire axial direction is 3 mm, and in the center rib side of the center rib 18 and the second rib 20, the sipe with the shallow groove is divided into four equal parts. The shoulder rib 22 and the second rib 20 on the shoulder rib side are arranged so as to be divided into six equal parts.
(Function)
In the pneumatic tire 10 of this embodiment, the width W1 of the tread when the center rib 18 is new: the width W2 of the tread when the second rib 20 is new: the width W3 of the tread when the shoulder rib 22 is new = 1. Since 1 ± 0.05: 1.15 to 1.3 is satisfied, shoulder edge wear can be reliably suppressed.
[0100]
Further, in all regions in each wear state where the groove depth of each circumferential main groove is 2 mm or more, 1.09 × width of second rib 20 ≦ width of shoulder rib 22 ≦ 1.35 × width of second rib 20 Since it is satisfied, shoulder edge wear can be reliably suppressed even after wear (see FIG. 6).
[0101]
Further, since the defense groove is not formed on the shoulder rib 22, various problems (tea from the groove bottom, chipping of the shoulder rib 22, etc.) due to the provision of the defense groove do not occur.
[0102]
The shallow groove 26A and the shallow groove 28 can improve the wet performance at the initial stage of wear.
[0103]
When wear of the tread 12 progresses and the drainage action of the shallow groove 26A and the shallow groove 28 is eliminated, the sipe 26B appears and the wet performance can be maintained by the edge effect of the sipe 26B.
[0104]
When the depth of the shallow groove 26A and the shallow groove 28 is less than 1.5 mm, sufficient drainage cannot be obtained, and the meaning of providing the shallow groove 26A and the shallow groove 28 is lost.
[0105]
On the other hand, when the depth of the shallow groove 26A and the shallow groove 28 exceeds 3 mm, the rib rigidity is lowered and the heel and toe wear is deteriorated.
[0106]
If the groove width of the shallow groove 26A and the shallow groove 28 is less than 1.5 mm, sufficient drainage cannot be obtained, and the meaning of providing the shallow groove 26A and the shallow groove 28 is lost.
[0107]
On the other hand, if the groove width of the shallow groove 26A and the shallow groove 28 exceeds 3 mm, the rib rigidity is lowered and the heel-and-toe wear is deteriorated.
[0108]
Since the depth of the sipe 26B is set to 50% to 100% of the groove depth of the adjacent circumferential main groove, a balance of wet performance, wear performance and uneven wear performance can be achieved.
[0109]
Note that when the depth of the sipe 26B is less than 50% of the depth of the circumferential main groove, the wet performance during wear is insufficient. On the other hand, when the depth of the sipe 26B exceeds 100% of the depth of the circumferential main groove, the wear performance and the partial wear performance are deteriorated due to a decrease in land portion rigidity.
[0110]
Further, since the sipe 26B is formed at the end of the shallow groove 26A opposite to the tire rotation direction, the original rubber at the kicking end of the block partitioned by the sipe 26B is reduced, and the heel / Generation of AND-to-wear can be suppressed.
[0111]
Since a plurality of short sipes 30 are formed along the tire circumferential direction at the end portions in the width direction of the center rib 18, the second rib 20 and the shoulder rib 22, the rigidity near the edge portion decreases, and the occurrence of rib tears occurring near the edge portion is generated. Can be suppressed.
[0112]
If the length of the short sipe 30 is less than 2 mm, the rigidity in the vicinity of the edge portion cannot be reduced, and the occurrence of rib tears cannot be suppressed.
[0113]
On the other hand, if the length of the short sipe 30 exceeds 4 mm, the rigidity of the entire rib is lowered, which is not preferable.
[0114]
In deformation by lateral force such as side force, each rib is subjected to compression deformation in the tire width direction, but easily deforms in the width direction together with the bent portion 30A of the short sipe 30, so that the work of wear at that time is reduced. Can improve uneven wear and wear resistance.
[0115]
Further, since the bent portion 30A is provided parallel to the groove wall of the circumferential main groove where the short sipe opens, the short sipe 30 is similarly formed from the new article to the end of wear. An effect is obtained.
[0116]
Note that when the bending angle θ of the bent portion 30A is less than 90 °, the rigidity of the land portion is excessively lowered, and the possibility of occurrence of sipetea increases.
[0117]
On the other hand, when the bending angle θ of the bent portion 30A exceeds 160 °, the effect of bending is small and the work of wear increases.
[0118]
Since the stone biting prevention protrusions 24 are provided on the groove bottom of the circumferential main groove 14 and the groove bottom of the circumferential main groove 16, entry of stones on the road surface is suppressed and stone biting resistance is improved.
[0119]
In addition, the dimension of each part mentioned above is not limited to the numerical value of embodiment, It can change suitably in the range which does not deviate from the meaning of this invention.
(Test example)
In order to confirm the effect of the present invention, a tire of an example to which the present invention was applied and a conventional tire were prepared and compared.
[0120]
Example tire: The pneumatic tire 10 described in the embodiment.
[0121]
Conventional tire: The pneumatic tire 100 described in the prior art having the pattern shown in FIG.
[0122]
As shown in the graph of FIG. 7, in the conventional tire, the width of the shoulder rib 112 when new (WTD = 0. WTD = groove depth at new article−remaining groove depth at wear) is the second rib. It is 1.6 for the width of 110, and 1.87 at the end of wear.
[0123]
On the other hand, in the tire of the example, the width of the shoulder rib 22 when new is 1.20 with respect to the width of the second rib 20 and 1.32 at the end of wear.
[0124]
As a result of preparing a vehicle equipped with the tire of the conventional example and a vehicle equipped with the tire of the example, and performing a running test on a general road, the uneven wear amount of the shoulder edge wear is as shown in the graph of FIG. In the conventional tire, the amount of uneven wear was large with the progress of wear, but almost no increase was observed in the tires of the examples.
[0125]
Further, regarding the amount of heel and toe wear due to the provision of the sipe, as shown in the graph of FIG. 9, the tire of the example was less from the initial wear to the final wear compared to the conventional tire. .
[0126]
As for the edge wear of each rib, as shown in the graph of FIG. 10, in the conventional tire in which a linear short sipe is formed, the amount of uneven wear is large, but a bent short sipe is formed. Little increase was seen in the example tires.
[0127]
【The invention's effect】
As described above, since the pneumatic tire of the present invention has the above-described configuration, it has an excellent effect that shoulder edge wear can be reliably suppressed without deteriorating other performances.
[Brief description of the drawings]
FIG. 1 is a plan view of a tread of a pneumatic tire according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing an outer contour of a tread of a pneumatic tire according to an embodiment of the present invention.
FIG. 3 is a sectional view of a shallow groove with sipes.
FIG. 4 is a cross-sectional view of a shallow groove.
FIG. 5 is an enlarged perspective view of a circumferential groove.
FIG. 6 is a graph showing the relationship between the ratio of the shoulder rib width and the second rib width and the amount of wear.
FIG. 7 is a graph showing the relationship between the ratio of the shoulder rib width to the second rib width and the wear amount of the tread.
FIG. 8 is a graph showing the relationship between the amount of wear of shoulder edge wear and the amount of wear of tread.
FIG. 9 is a graph showing a relationship between a heel and toe wear amount and a tread wear amount.
FIG. 10 is a graph showing a relationship between an edge wear wear amount of ribs and a tread wear amount.
FIG. 11 is a plan view of a tread of a conventional pneumatic tire.
[Explanation of symbols]
10 Pneumatic tire
12 tread
14 Circumferential main groove
16 Circumferential main groove
18 Center rib
20 second rib
22 Shoulder rib
24 Stone chewing prevention protrusion
26 Sipe with shallow grooves
28 shallow groove
30 short sipes
30A bent part

Claims (10)

A pneumatic tire including a tread having five ribs divided by four circumferential main grooves extending along a circumferential direction,
A new width of the center rib disposed in the center portion in the tire width direction is W1, a new width of the second rib disposed on both sides of the center rib is W2, and the second rib is disposed on the outer side in the tire width direction. When the width of the new shoulder rib is W3,
W1: W2: W3 = 1: 1 ± 0.05: 1.15 to 1.3 was satisfied,
In all regions of each wear state where the groove depth of the circumferential main groove is 2 mm or more,
1. A pneumatic tire characterized by satisfying: 1.09 × second rib width ≦ shoulder rib width ≦ 1.35 × second rib width. The center rib, the second rib, and the shoulder rib are formed with a shallow groove that extends substantially in the tire width direction and is shallower than the circumferential main groove, and further has a sipe formed at the bottom. The pneumatic tire according to claim 1, wherein The pneumatic tire according to claim 2, wherein a groove depth of the sipe is 50 to 100% of a groove depth of the circumferential main groove. The pneumatic tire according to claim 2 or 3, wherein the sipes are arranged so as to be offset toward a tire rotation direction side of a groove bottom of the shallow groove. In the second rib, a shallow groove having a groove depth shallower than the circumferential main groove and having no sipe formed is formed between the shallow grooves formed with sipe at the groove bottom. The pneumatic tire according to any one of claims 1 to 4, wherein: The pneumatic tire according to any one of claims 1 to 5, wherein the shallow groove has a groove depth of 1.5 to 3 mm. The pneumatic tire according to any one of claims 2 to 6, wherein the shallow groove has a groove width of 1.5 to 3 mm. 8. A plurality of short sipes having one end opened in the circumferential main groove and the other end terminating in the rib are formed in an end portion of the rib in the circumferential direction. The pneumatic tire according to any one of the above. The short sipe has a bent portion at a middle portion in the longitudinal direction,
The bent portion is provided in parallel with the groove wall of the circumferential main groove in which the short sipe is opened in the groove depth direction,
The bending angle of the bent portion is within a range of 90 to 160 °.
The pneumatic tire according to claim 8. The stone biting prevention protrusion by which the position of the top part was set lower than the tread surface of the tread is formed in the bottom part of the circumferential main groove. The pneumatic tire described in 1.

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