JP2003063212A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of surely suppressing shoulder edge wear and suitable for a long-distance vehicle for without deterioration of other performances. SOLUTION: Shoulder edge wear can be surely suppressed by satisfying a width W1 of a tread part when a center rib 18 is new: a width W2 of the tread part when a second rib 20 is new: a width W3 of the tread part when a shoulder rib 22 is new=1:1±0.05:1.15 to 1.3. In all regions of each wear state having a groove depth >=2 mm in each peripheral direction main groove, shoulder edge wear can be surely suppressed also after wear by satisfying 1.09×a width of the second rib 20<=a width of the shoulder rib 22<=1.35×the width of the second rib 20. Since a defense group is not formed in the shoulder rib 22, tear and chipping of the shoulder rib 22 are not generated.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD 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]

2. Description of the Related Art As pneumatic tires used in heavy-duty vehicles such as trucks and buses, various pneumatic tires having a plurality of circumferentially extending ribs on a tread have been proposed.

For medium to short distance to long distance (especially KPM1
5000 km or more. KPM indicates a traveling distance per 1 mm wear. 11) is a pneumatic tire 100 having a pattern as shown in FIG.

In the pneumatic tire 100 (tire size: 315 / 80R22.5) 100 shown in FIG.
No. 02 tire equatorial plane CL is sandwiched between the circumferential main grooves 10 on both sides.
4 are formed, and the circumferential main groove 106 is formed on the outer side in the tire axial direction.

The width of the tread surface of the center rib 108 is 31.
4mm, the width of the tread of the second rib 110 is 31.4mm,
The width of the tread portion of the shoulder rib 112 is 50.2 mm (all are new).

The circumferential main groove 104 has a groove width of 10.5 m.
m, the groove depth is 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 (all of which are new).

The tread width W is 246 mm (when new).

Center rib 108, second rib 11
0 and shoulder rib 112 have sipe 114
Are formed.

The sipe 114 has a circumferential pitch of 37.6 mm for the center rib 108 and a second rib 110.
Is 37.6 mm, and the shoulder rib 112 is 37.6 mm.
mm.

The sipe 114 has a groove width of 0.5 mm and a groove depth of 12 mm (when new).

At both ends of the center rib 108, both ends of the second rib 110, and the inner end of the shoulder rib 112,
A plurality of short sipes 116 linearly extending along the tire axial direction are formed.

The short sipe 116 of the center rib 108 is
The groove width is 0.7 mm, the groove depth is 12.2 mm, the tire axial length is 2.5 mm, and the circumferential pitch is 12.5 mm.
Is.

The short sipe 116 of the second rib 110 is
The groove width is 0.7 mm, and the groove depth is 12.2 mm on the center rib side and 7.6 m on the shoulder rib side.
m, the length in the tire axial direction is 2.5 mm, the center rib side is provided so as to divide the sipes into three equal parts, and the shoulder rib side is provided so as to be equally divided into six parts.

The short sipe 1 of the shoulder rib 112
The groove 16 has a groove width of 0.7 mm, a groove depth of 12.2 mm, a tire axial length of 2.5 mm, and is provided so as to divide the sipes into six equal parts.

A defense groove 118 having a groove width of 2.5 mm and a groove depth of 11.1 mm is formed on the shoulder rib 112 for the purpose of suppressing uneven wear near the shoulder.

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]

However, the above conventional pneumatic tire 100 has the following problems. (1) The uneven wear called shoulder edge wear (SEW) caused by the dragging of the shoulder end and the deterioration of the shoulder edge wear due to the combination of the uneven wear work in the width direction in the rib due to the side force are prevented by the defense groove 118. I was compensated,
There is a problem that a tear (crack) is generated from the groove bottom of the defense groove 118. (2) When considering shoulder edge wear,
Since it is important to secure the rigidity of the land part of the shoulder part,
Conventionally, it has been said that the width of the shoulder rib 112 when new is 1.30 to 1.40 with respect to the width of the second rib 110, but when the contribution of the wear work in the width direction becomes high, In the range, there was a problem that the shoulder edge wear deteriorates.

In consideration of the above facts, the present invention is a pneumatic tire which solves the problems of the conventional pneumatic tire, that is, a shoulder edge wear can be surely suppressed and other performance is not deteriorated. An object of the present invention is to provide a pneumatic tire suitable for an automobile.

[0019]

The invention according to claim 1 is a pneumatic tire having a tread with five ribs sectioned by four circumferential main grooves extending in the circumferential direction. , A new width of the center rib arranged in the central portion in the tire width direction is W1, a new width of the second ribs arranged on both sides of the center rib is W2, and the second rib is arranged outside of the second rib in the tire width direction. If the width of the new shoulder rib is W3, W1: W2: W3 =
1: 1 ± 0.05: 1.15 to 1.3, and 1.09 × second rib width ≦ in all regions in each wear state where the groove depth of the circumferential main groove is 2 mm or more. It is characterized in that the width of the shoulder rib ≦ 1.35 × the width of the second rib is satisfied.

Next, the operation of the pneumatic tire according to claim 1 will be described.

In consideration of shoulder edge wear (uneven wear), considering that the contribution of the wear work in the rib due to the lateral force such as side force is large, the rigidity of the land portion of the rib is lower than that of the conventional one ( That is, the narrower the width), the higher the effect against uneven wear resistance.

In the pneumatic tire according to the first aspect, the width of the shoulder rib with respect to the width of the second rib when it is new is narrower than that of the conventional product, so that the shoulder edge wear can be surely suppressed.

Further, in all areas 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 Since it is satisfied, the shoulder edge wear can be surely suppressed even after abrasion.

Further, since the defense groove is not formed in 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.

The invention according to claim 2 is the pneumatic tire according to claim 1, wherein the center rib, the second rib and the shoulder rib extend substantially in the tire width direction, and The groove depth is shallower than the groove,
Furthermore, it is characterized in that a shallow groove having sipes is formed at the bottom.

Next, the operation of the pneumatic tire according to claim 2 will be described.

The shallow groove can drain water between the road surface and the tire. Therefore, it is possible to improve the wet performance in the initial stage of wear when the shallow groove exists.

Further, since the sipe is formed at the bottom of the shallow groove, when the wear of the tread progresses 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.

According to a third aspect of the present invention, in the pneumatic tire according to the second aspect, the groove depth of the sipe is 50 to 100% of the groove depth of the circumferential main groove. It has a feature.

Next, the operation of the pneumatic tire according to claim 3 will be described.

The sipe depth is set to 50 of the groove depth of the circumferential main groove.
Since it is set to 100% to 100%, it is possible to balance the wet performance, the wear performance and the uneven wear performance.

The sipe depth is 50% of the depth of the circumferential main groove.
If it is less than this, the wet performance at the time of abrasion becomes insufficient.

On the other hand, when the depth of the sipes exceeds 100% of the depth of the circumferential main groove, the rigidity is lowered and the wear performance and the uneven wear performance are deteriorated.

According to a fourth aspect of the present invention, in the pneumatic tire according to the second or third aspect, the sipe is arranged on the side of the groove bottom of the shallow groove on the tire rotation direction side. Is characterized by.

Next, the operation of the pneumatic tire according to claim 4 will be described.

By forming a shallow groove with a sipe in the rib, the rib is substantially divided into a plurality of blocks, which may cause heel-and-toe wear in the blocks.

By disposing the sipe in the shallow groove adjacent to the kick-out end of the block, the rigidity of the land portion at the kick-out end of the block (compared to the stepping side) can be lowered.

By lowering the rigidity of the land portion on the kick-out side, the ground contact pressure at the kick-out end is large at the time of deformation (deformation caused by the brake force being applied to the block) at the time of kicking out (compared to the ground pressure at the stepping side at that time). ) Can be lowered to make the contact pressure distribution in the block uniform.

The invention according to claim 5 provides the pneumatic tire according to any one of claims 1 to 4, wherein:
In the second rib, between the shallow grooves having sipes formed at the groove bottom, shallow grooves having a groove depth smaller than that of the circumferential main groove and having no sipes formed at the bottom are formed. Is characterized by.

Next, the operation of the pneumatic tire according to claim 5 will be described.

Since the shallow groove having a groove depth smaller than that of the main groove in the circumferential direction and no sipes formed at the bottom is formed in the second rib, the wet performance in the initial stage of wear can be further improved.

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.

Next, the operation of the pneumatic tire according to claim 6 will be described.

If the 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.

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.

Next, the operation of the pneumatic tire according to claim 7 will be described.

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 becomes meaningless.

The invention according to claim 8 is the pneumatic tire according to any one of claims 1 to 7, wherein:
At the end of the rib, a plurality of short sipes are formed in the circumferential direction, one end of which is open to the circumferential main groove and the other end of which ends in the rib.

Next, the operation of the pneumatic tire according to claim 8 will be described.

By forming a plurality of short sipes along the tire circumferential direction, one end of which is open to the circumferential main groove and the other end of which is terminated in the circumferential main groove side wall surface of the rib. It is possible to suppress the rigidity near the edge portion, reduce the occurrence of rib tear occurring near the edge portion, and suppress uneven wear of the rib end.

The length of the short sipes in the tire axial direction is 2
-4 mm is preferred.

If the length of the short sipe is less than 2 mm, the rigidity near the edge portion of the rib cannot be reduced, and the occurrence of rib tear cannot be suppressed.

On the other hand, if the length of the short sipe exceeds 4 mm,
It is not preferable because the rigidity of the entire rib is lowered.

According to a ninth aspect of the invention, in the pneumatic tire according to the eighth aspect, the short sipe has a bent portion at an intermediate portion in the longitudinal direction, and the bent portion has a bent portion of the short sipe. It is provided so as to be parallel to the groove wall of the circumferential main groove that opens, in the groove depth direction, and the bending angle of the bent portion is in the range of 90 to 160 °. .

Next, the operation of the pneumatic tire according to claim 9 will be described.

When deformed by a lateral force such as side force, the ribs are compressed and deformed in the tire width direction, but the ribs are easily deformed in the width direction together with the sipe portion having the bent portion, so the amount of wear work at that time is reduced. Is possible, uneven wear,
The wear resistance performance can be improved.

Further, since the bent portion is provided in parallel with the groove wall of the circumferential main groove in which the short sipes are opened in the groove depth direction, the sipes are similarly provided from the time of new to the end of wear. You can get the effect.

The bending angle of the bent portion is 90.
If it is less than °, the rigidity of the land part will be lowered too much, and the possibility of sipetea occurring will increase.

On the other hand, the bending angle of the bent portion is 16
If it exceeds 0 °, the effect of bending is small and the work of wear increases.

Therefore, the bending angle of the bent portion is preferably within the range of 90 to 160 °.

According to a tenth aspect of the present invention, in the pneumatic tire according to any one of the first to ninth aspects, at the bottom of the circumferential main groove, the position of the apex is from the tread surface of the tread. It is characterized in that a stone trapping prevention protrusion set to be low is formed.

Next, the operation of the pneumatic tire according to claim 10 will be described.

If a plurality of stone trapping protrusions are provided on the groove bottom of the circumferential main groove, the stone trapping protrusions are provided when a stone on the road surface tries to enter the groove (when the groove tries to trap stones). Prevents stones from entering and improves resistance to stones.

[0064]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the pneumatic tire of the present invention will be described with reference to FIGS.

In FIG. 1, arrow L direction and arrow R
The direction indicates the tire axial direction, and the arrow S direction indicates the tire circumferential direction.

As shown in FIG. 1, the pneumatic tire 10 of the present embodiment (tire size: 315 / 80R22.5)
Tread 12 (tread width W) has tire equatorial plane C
Tire axial direction across L (arrow L direction and arrow R direction)
Circumferential main grooves 14 extending linearly along the tire circumferential direction (arrow S direction) are formed on both sides.
A circumferential main groove 16 linearly extending along the tire circumferential direction is formed on the outer side in the tire axial direction.

Here, the tread width means a dimension from one ground contact end in the tire width direction to the other ground contact end, and a pneumatic tire is referred to as JATMA YEAR BOOK (2001).
It is attached to the standard rim specified in the fiscal year edition, Japan Automobile Tire Manufacturer's Association), and the air pressure corresponding to the maximum load capacity (bold load in the internal pressure-load capacity correspondence table) in the applicable size and ply rating in JATMA YEAR BOOK This is the case where 100% of the internal pressure of the maximum air pressure) is filled and a normal load (a load corresponding to the maximum load capacity when a single wheel in JATMA YEAR BOOK is applied) is applied.

At the place of use or the place of manufacture, TRA
When the standards and ETRTO standards are applied, follow each standard.

The width of the tread portion of the new center rib 18 sandwiched between the two circumferential main grooves 14 is W1, the circumferential main groove 14 is
The width of the new tread portion of the second rib 20 sandwiched between the main rib 16 and the circumferential main groove 16 is W2, and the width of the new tread portion of the shoulder rib 22 arranged outside the circumferential main groove 16 in the tire width direction is the new width. If W3, W1: W2: W3 = 1: 1 ±
0.05: 1.15 to 1.3, 1.09 × width of the second rib 20 ≦ shoulder rib 22 in all regions in which each circumferential main groove has a groove depth of 2 mm or more in each wear state Width ≦ 1.35 × width of the second rib 20 is satisfied.

1.09 × width of second rib 20 ≦
Width of shoulder rib 22 ≦ 1.35 × second rib 20
2 is satisfied, the angles θ1 to θ5 of the rib side wall (the angle with respect to the normal line standing on the tread) are optimally set as shown in FIG.

As shown in FIGS. 1 and 2, the circumferential main groove 1
A plurality of stone trapping preventing projections 24 are formed along the main groove longitudinal direction on the bottom of the No. 4 and the bottom of the circumferential main groove 16.

It should be noted that the stone trapping prevention protrusion 24 is formed in the circumferential main groove 1.
4 and the circumferential main groove 16 may be provided in only one of them, and may not be provided in some cases.

The stone trapping prevention projection 24 is set such that the position of the top portion 24A is lower than that of the tread surface 12A of the tread 12.

On the center rib 18, the second rib 20, and the shoulder rib 22, a plurality of shallow grooved sipes 26 as shown in FIG. 3 are formed in the tire circumferential direction.

As shown in FIG. 1, the sipe 26 with a shallow groove formed on the center rib 18 has a circumferential main groove 14 on both sides.
It has a substantially V shape.

The sipe 26 with a shallow groove formed on the second rib 20 goes up to the left on the left side of the tire equatorial plane CL,
On the right side of the tire equatorial plane CL, it is inclined to the right,
The openings are formed in the circumferential main groove 14 and the circumferential main groove 16, respectively.

The sipe 26 with a shallow groove formed on 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 the other end terminates before the ground end 12B.

As shown in FIG. 3, the sipe 26 with a shallow groove is provided.
Is composed of a shallow groove 26A having a groove width narrower and a shallower depth than the circumferential main groove 14 and the circumferential main groove 16, and a sipe 26B formed at the groove bottom of the shallow groove 26A. There is.

The groove width W4 of the shallow groove 26A is 1.5 to 3.0 mm.
Is preferable, and the groove depth D1 of the shallow groove 26A is 1.5.
It is preferably within the range of to 3.0 mm.

The sipe 26B is formed at the end of the groove bottom of the shallow groove 26A on the side opposite to the tire rotation direction (arrow A direction).

The groove depth D2 measured from the tread surface 12A of the sipe 26B is preferably within the range of 70% to 100% of the groove depth of the circumferential main groove of the sipe 26B.

The groove width W5 of the sipe 26B is preferably mm or less.

As shown in FIG. 1, in the second rib 20, a shallow groove 28 is formed between the sipe 26 with a shallow groove and the sipe 26 with a shallow groove.

The shallow groove 28 is inclined to the left on the left side of the tire equatorial plane CL and is inclined to the right on the right side of the tire equatorial surface CL. One end of the shallow groove 28 is open to the circumferential main groove 16 and the other end is in the center of the rib. It ends in the vicinity.

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 in the range of 1.5 to 3.0 mm. Is preferred.

As shown in FIG. 1, one end of each of the center rib 18, the second rib 20, and the shoulder rib 22 is opened to the adjacent circumferential main groove, and the other end is terminated in the rib. A plurality of short sipes 30 are formed in the circumferential direction.

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 the circumferential main groove 14 in which the short sipe 30 opens.
Is provided in parallel with the groove wall 14A in the groove depth direction.

The short sipe 30 has a bending angle θ of 90.
Set within the range of up to 160 °, the length L1 in the tire axial direction
Is preferably set within the range of 2 to 4 mm.

The groove depth D4 of the short sipe 30 is 50 to 1 which is the groove depth D5 of the circumferential main groove of the short sipe 30 which opens.
It is preferable to set it within the range of 00%, and short sipes 3
The groove width W7 of 0 is preferably 1.2 mm or less.

In this embodiment, the tread width W1 of the center rib 18 is 35.2 mm, the tread width W2 of the second rib 20 is 35.2 mm, and the tread width W3 of the shoulder rib 22 is 42.4 mm. Yes (all are new).

The tread width W is 242 mm (when new).

The circumferential main groove 14 has a groove width of 12.9 mm, the circumferential main groove 14 has a groove depth of 14.6 mm, the circumferential main groove 16 has a groove width of 12.9 mm, and the circumferential main groove 16 has a groove width. The depth is 15.
It is 0 mm (all are new).

When the circumferential main groove 14 and the circumferential main groove 16 have the groove depths as described above, the stone trapping preventing projection 24 preferably has a height of 3 to 6 mm from the groove bottom.

The circumferential pitch of the sipe 26 with shallow grooves is 34 mm, 38 mm, and 41 m for the center rib.
m 3 pitch, second rib 20 34mm, 38m
m and 41 mm, and the shoulder rib 22 has 34 mm, 38 mm, and 41 mm pitches.

In the second rib 20, the shallow groove 28 is formed in the intermediate portion between the sipe 26 with the shallow groove and the sipe 26 with the shallow groove.

The shallow groove 26A of the sipe 26 with shallow groove has a groove width W4 of 2 mm and a groove depth D1 of 2 mm (when new).

The sipe 26B of the sipe 26 with a shallow groove has a groove width W5 of 0.5 mm and a groove depth D2 of 12 mm (when new).

The shallow groove 28 has a groove width W6 of 2 mm and a groove depth D3.
Is 2 mm (when new).

The short sipe 30 has a groove width W7 of 0.5 mm,
The groove depth D3 is the center rib 18 and the second rib 20.
11.6 mm on the center rib side, 12.1 mm on the shoulder rib 22 and the second rib 20 on the shoulder rib side, the bending angle θ is 135 °, the length L1 in the tire axial direction is 3 mm, and the center rib is 18 and the second rib 20 on the center rib side are arranged so as to divide the space between the sipe with the shallow groove into four equal parts, and on the shoulder rib 22 and the second rib 20 on the shoulder rib side are arranged so as to be equally divided into six parts. There is. (Operation) In the pneumatic tire 10 according to the present embodiment, the width W1: the second rib 2 of the tread portion of the center rib 18 when new.
0 width of the tread portion at the time of new article W2: width of the tread portion of the shoulder rib 22 at the time of new article W3 = 1: 1 ± 0.05: 1.15
Since 1.3 is satisfied, shoulder edge wear can be reliably suppressed.

Further, 1.09 × width of second rib 20 ≦ width of shoulder rib 22 ≦ 1.35 × in all regions in which each circumferential main groove has a groove depth of 2 mm or more in each worn state.
Since the width of the second rib 20 is satisfied, the shoulder edge wear can be reliably suppressed even after abrasion (see FIG. 6).

Further, since the defense groove is not formed in 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.

The shallow groove 26A and the shallow groove 28 can improve the wet performance in the initial stage of wear.

The wear of the tread 12 progresses and the shallow groove 26A
When the drainage action of the shallow groove 28 disappears, the sipe 26B appears on the tread surface 12A, and the wet performance can be maintained by the edge effect of the sipe 26B.

The depth of the shallow groove 26A and the shallow groove 28 is 1.5 mm.
If it is less than this, sufficient drainage cannot be obtained, and there is no point in providing the shallow groove 26A and the shallow groove 28.

On the other hand, the depth of the shallow groove 26A and the shallow groove 28 is 3
If it exceeds mm, the rib rigidity will decrease and the heel and
Toe wear deteriorates.

The groove width of the shallow groove 26A and the shallow groove 28 is 1.5 mm.
If it is less than this, sufficient drainage cannot be obtained, and there is no point in providing the shallow groove 26A and the shallow groove 28.

On the other hand, the groove width of the shallow groove 26A and the shallow groove 28 is 3
When it exceeds mm, the rib rigidity is lowered and the heel and toe wear is deteriorated.

Since the depth of the sipe 26B is set to 50% to 100% of the groove depth of the adjacent circumferential main groove, the wet performance, the wear performance and the uneven wear performance can be balanced.

If the depth of the sipe 26B is less than 50% of the depth of the circumferential main groove, the wet performance at the time of abrasion becomes insufficient. On the other hand, if the depth of the sipe 26B exceeds 100% of the depth of the circumferential main groove, the rigidity of the land portion is decreased, and the wear performance and the uneven wear performance are deteriorated.

Further, since the sipe 26B is formed at the end of the shallow groove 26A on the side opposite to the tire rotation direction, the original rubber at the kicking end of the block delimited by the sipe 26B is reduced. It is possible to suppress the occurrence of heel and toe wear.

Since a plurality of short sipes 30 are formed in the widthwise ends of the center rib 18, the second rib 20, and the shoulder rib 22 along the tire circumferential direction, the rigidity near the edge portion is lowered and the rib tear generated near the edge portion is reduced. Can be suppressed.

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 rib tear cannot be suppressed.

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.

When deformed by a lateral force such as side force, each rib undergoes compressive deformation in the tire width direction, but since it is easily deformed in the width direction together with the bent portion 30A of the short sipe 30, the amount of wear work at that time is increased. Can be reduced, and uneven wear and wear resistance can be improved.

Further, since the bent portion 30A is provided parallel to the groove wall of the circumferential main groove in which the short sipe is opened in the groove depth direction, it is similarly short from the time of new product to the end of wear. The effect of sipe 30 is obtained.

If the bending angle θ of the bending portion 30A is less than 90 °, the rigidity of the land portion is lowered too much, and the possibility of sipetea occurring increases.

On the other hand, when the bending angle θ of the bending portion 30A exceeds 160 °, the bending effect is small and the wear work amount increases.

The bottom of the circumferential main groove 14 and the circumferential main groove 16
Since the stone trapping preventing projection 24 is provided on the groove bottom, the stones are prevented from entering the road surface and the stone trapping resistance is improved.

Note that the dimensions and the like of the above-mentioned parts are not limited to the numerical values of the embodiment, and can be changed as appropriate without departing from the spirit of the present invention. (Test Example) In order to confirm the effect of the present invention, the tire of the example to which the present invention was applied and the tire of the conventional example were prepared and compared.

Tire of Example: The pneumatic tire 10 described in the embodiment.

Conventional tire: The pneumatic tire 100 described in the prior art having the pattern shown in FIG.

As shown in the graph of FIG. 7, in the tire of the conventional example, the shoulder rib 112 at the time of new product (WTD = 0. Note that WTD = groove depth when new product−remaining groove depth when worn).
Is 1.6 with respect to the width of the second rib 110,
It is 1.87 at the end of wear.

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 it is 1.32 at the end of wear.

A vehicle equipped with the tire of the conventional example and a vehicle equipped with the tire of the example were prepared, and a running test was conducted on an ordinary road. As a result, the uneven wear amount of the shoulder edge wear is shown in the graph of FIG. As shown, the tire of the conventional example has a large increase in the uneven wear amount with the progress of wear, but the tires of the examples hardly show the increase.

In addition, since the sipe is provided, the heel
As for the amount of wear to and toe, as shown in the graph of FIG. 9, the tire of the example was smaller than the tire of the conventional example from the initial wear to the final wear.

Regarding the edge wear of each rib,
As shown in the graph of FIG. 10, the uneven wear amount is large in the conventional tire having the linear short sipe, but hardly increased in the tire having the bent short sipe. It was

[0127]

As described above, since the pneumatic tire of the present invention has the above-mentioned constitution, it has an excellent effect that the shoulder edge wear can be surely suppressed without deteriorating other performances. .

[Brief description of 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 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 amount of wear and the ratio between the width of the shoulder rib and the width of the second rib.

FIG. 7 is a graph showing the relationship between the ratio of the shoulder rib width to the second rib width and the tread wear amount.

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 heel and toe wear amount and tread wear amount.

FIG. 10 is a graph showing the relationship between the amount of edge wear of ribs and the amount of wear of treads.

FIG. 11 is a plan view of a tread of a conventional pneumatic tire.

[Explanation of symbols]

10 pneumatic tires 12 treads 14 circumferential main groove 16 circumferential main groove 18 Center rib 20 second rib 22 Shoulder rib 24 Stone trap prevention protrusion 26 Sipe with shallow groove 28 shallow groove 30 short sipes 30A bent part

Claims (10)

[Claims] 1. A pneumatic tire having a tread with five ribs sectioned by four circumferential main grooves extending along the circumferential direction, the center rib being disposed at a central portion in the tire width direction. When the width when new is W1, the width when new of the second ribs arranged on both sides of the center rib is W2, and the width when new of the shoulder ribs arranged outside the second rib in the tire width direction is W3 , W1: W2: W3 = 1: 1 ± 0.05: 1.15-1.
3 is satisfied and 1.09 × second rib width ≦ shoulder rib width ≦ 1.35 × second rib width in all the worn states in which the groove depth of the circumferential main groove is 2 mm or more, A pneumatic tire characterized by satisfying. 2. The center rib, the second rib,
And the shoulder ribs, which extend substantially in the tire width direction, have a shallower groove depth than the circumferential main groove, and further have a shallow groove with a sipe formed at the bottom. Item 1. The pneumatic tire according to Item 1. 3. 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. 4. The pneumatic tire according to claim 2, wherein the sipe is arranged on one side of the groove bottom of the shallow groove on the tire rotation direction side. 5. The second rib includes a shallow groove having a depth smaller than that of the circumferential main groove and having no sipe formed at the bottom, between the shallow grooves having sipe formed at the groove bottom. It is formed, The pneumatic tire of any one of Claim 1 thru | or 4 characterized by the above-mentioned. 6. The pneumatic tire according to claim 1, wherein the shallow groove has a groove depth of 1.5 to 3 mm. 7. The shallow groove has a groove width of 1.5 to 3 mm, according to any one of claims 2 to 6.
The pneumatic tire according to item. 8. A plurality of short sipes are formed in the circumferential direction at one end of the rib, one end of the rib opening to the circumferential main groove and the other end terminating inside the rib. The pneumatic tire according to any one of claims 1 to 7. 9. The short sipe has a bent portion at an intermediate portion in the longitudinal direction, and the bent portion extends in a groove depth direction with respect to a groove wall of the circumferential main groove in which the short sipe opens. The pneumatic tire according to claim 8, wherein the pneumatic tires are provided in parallel and the bending angle of the bending portion is within a range of 90 to 160 °. 10. A stone trapping prevention protrusion having a top position set lower than a tread surface of the tread is formed at a bottom portion of the circumferential main groove. The pneumatic tire according to any one of 1.