JP4583841B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire having excellent uneven wear resistance that is suitably used in a heavy-duty vehicle.

Conventionally, in heavy-duty tires, particularly tires for construction vehicles, a lag type tread pattern is often used to improve driving force and braking force and improve traction on a non-paved road. However, in such a tread pattern, the rigidity of the shoulder portion is lower than the rigidity of the central portion, so that the shoulder portion is worn earlier than the central portion due to input of lateral force or the like. Therefore, as shown in FIG. 10, the tread 51 of the pneumatic tire 50 is composed of a first block 52 arranged in the central portion 51M and a second block 53 arranged in the shoulder portion 51S, and the shoulder A technique has been proposed in which the width of the lateral groove 54 formed in the portion 51S is reduced and the block pitch P is increased, thereby increasing the rigidity of the shoulder portion 51S and suppressing the uneven wear as described above ( For example, see Patent Document 1).
JP 2001-225608 A

On the other hand, in the tire for heavy loads, the tread thickness in the tire radial direction is set larger than that of other tires in order to ensure cut resistance. However, this reduces the compression rigidity of the block, and rubber extrusion due to the incompressibility of the rubber concentrates on the part where the block first contacts the ground (stepping end). There is a tendency to become larger than. As described above, when uneven wear occurs in the tire, there is a problem that the volume of the worn rubber is increased and the wear resistance is lowered.
On the other hand, if the rubber tread thickness is reduced to increase the compression rigidity of the block, there is a concern that the cut resistance performance required for a heavy load tire is deteriorated.
In addition, when the width of the lateral groove provided in the shoulder portion is narrowed and the block pitch is increased as in the conventional example, the amount of wear of the entire block of the shoulder portion can be reduced. It was difficult to suppress uneven wear at the stepping end.

  The present invention has been made in view of the conventional problems, and by improving the tread pattern, the uneven wear of the stepped end of the block disposed on the shoulder portion is suppressed without reducing the cut-resistant performance. The purpose is to ensure the wear resistance of the tire.

As a result of intensive studies, the present inventor increases the rigidity of the stepping end of the block without reducing the block thickness by providing a shallow groove having an open end only on the circumferential groove side in the shoulder block. The present inventors have found that this can be achieved.
That is, the invention according to claim 1 of the present application is a block row comprising a plurality of blocks partitioned by a circumferential groove extending along the tire circumferential direction and a lateral groove intersecting the circumferential groove on the shoulder portion of the tread. met pneumatic tire having a circumferential length of the block is at 1/40 or more of the tire circumference to at least a portion or all of the blocks one end opening to the circumferential groove side and the other A shallow groove with a depth of 0.3 to 0.6 times the depth of the circumferential groove is provided , and the depth of the shallow groove changes in the tire axial direction. It is characterized by being .
The invention described in 請 Motomeko 2 is the pneumatic tire according to claim 1, it is obtained by reducing the depth of the shallow groove closer to both ends of the groove.

According to the present invention, in a pneumatic tire provided with a plurality of blocks in the tire tread portion, the circumferential length of the shoulder block is set to 1/40 or more of the tire outer periphery, and at least one of the shoulder block blocks . a part or the whole, one end opening to the circumferential groove side and the other end terminating inside tread edge, the Ri 0.3-0.6 Baidea the depth of the circumferential groove depth, and Since the shallow groove whose depth changes in the tire axial direction is provided to increase the rigidity of the block, the uneven wear of the shoulder block can be suppressed without deteriorating the cut resistance. it can. At this time, the shallow depth of the upper Kiasa groove closer to both ends of the groove camphor lever, it is possible to further enhance the block rigidity, it is possible to further suppress uneven wear.

Hereinafter, the best mode of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing the best mode of the present invention. FIG. 1A is a plan view showing an example of a tread pattern of a pneumatic tire 10 according to the best mode, and FIG. Sectional drawing (c) is a schematic view showing a section of a block 15 according to the present invention. On the surface of the tread 11 of the pneumatic tire 10 of this example, two circumferential grooves 12A and 12B extending along the tire circumferential direction and a plurality of lug grooves intersecting each of the circumferential grooves 12A and 12B ( And a central land portion 14 defined by the circumferential grooves 12A and 12B, and a plurality of blocks 15 defined by the circumferential grooves 12A and 12B and the lug grooves 13. The two block rows 15P and 15Q are land portions of the tread 11.
In this example, the circumferential length of the block 15 arranged in the shoulder portion 11S is set to 1/40 or more of the tire outer circumference, and one end of the block 15 is on the circumferential groove 12A side or the circumferential groove 12B side. By forming the shallow groove 16 having an opening and the other end terminating inside the tread end and having a depth d 0.3 to 0.6 times the depth D of the circumferential grooves 12A and 12B, Without deteriorating the cutting performance, uneven wear of the block 15 arranged in the shoulder portion 11S is suppressed, and the wear resistance of the tire 10 is ensured.

Next, the operation of the pneumatic tire 10 of the present invention will be described.
When the deformation state of the block at the time of kicking caused by the friction with the road surface of the tread rubber of the conventional pneumatic tire was observed in detail in the tire circumferential direction, as shown in FIG. In the vicinity of the edge, the angle α between the tread base (the part closest to the belt) and the road surface is small compared to other parts, so that the deformation of the rubber near the road surface is large and circumferential slippage occurs. Became clear. When this phenomenon is analyzed in more detail, the deformation of the rubber near the road surface is closely related to the circumferential length of the block 15Z. As shown in FIG. It has been found that the reason is that the lug groove 13 which is one factor that makes the block 15Z form an angle with respect to the road surface is not deformed. The deformation of the lug groove 13 occurs when the lug groove 13 is pushed in an oblique direction with respect to the road surface by a belt (not shown) when kicked out, so that the circumferential block of the block 15Z as shown in FIG. If the length is shortened and the lug groove 13 is accommodated in the belt lifting area A, the angle α between the surface of the tread 11 and the road surface at the stepping end can be increased, and the occurrence of the circumferential slip is suppressed. Thus, the wear resistance can be improved. However, if the block length in the circumferential direction of the block 15Z is too short, there are disadvantages such as a decrease in block rigidity.
Therefore, as shown in FIG. 4, if the shallow groove 16 as described above is formed in the block 15 and the tread surface side of the block 15 is divided as shown in FIG. However, the angle α between the surface of the tread 11 and the road surface at the stepping end can be increased. Note that the effect of the shallow groove 16 cannot be fully exhibited unless one of the shallow grooves 16 is an open end. That is, when both ends of the shallow groove 16 are open ends, the block rigidity is lowered and the deformation of the block is increased, resulting in deterioration of wear resistance and block flaking. In addition, when the open end is on the tread end side, rigidity is reduced when receiving a force from the road surface in the tire width direction from the tread end direction, and as a result, wear resistance is deteriorated. As described above, the open end is preferably on the circumferential groove 12A, 12B side.

  Thus, according to the best mode, the shoulder defined by the two circumferential grooves 12A and 12B extending along the tire circumferential direction and the lug grooves 13 intersecting the circumferential grooves 12A and 12B, respectively. One end of the block 11 of the portion 11 opens to the circumferential groove 12A, 12B side, and the other end terminates inside the tread end. The depth is 0.3 to the depth of the circumferential groove 12A, 12B. Since the shallow groove 16 that is 0.6 times is formed, the partial wear of the block 15 disposed in the shoulder portion 11S can be suppressed without deteriorating the cut resistance, and the wear resistance of the pneumatic tire 10 can be suppressed. Can be secured.

In the best mode, the depth of the shallow groove 16 is uniform. However, even if only the vicinity of the stepped end of the block 15 is divided, the uneven wear can be sufficiently suppressed. For example, the depth of the shallow groove is changed in the tire axial direction, such as the shallow groove 16V shown in FIGS. 5A and 5B is made shallower as the groove depth is closer to both ends of the groove. You may do it. Thereby, since the fall of block rigidity can be made still smaller, a deformation | transformation of a block can be suppressed and the abrasion resistance of a tire can further be improved.
In the above example, the extending direction of the shallow groove 16 is the tire equatorial plane. However, the present invention is not limited to this, and the shallow groove 16K having an angle other than a right angle with the circumferential grooves 12A and 12B as shown in FIG. May be provided.
Further, the circumferential grooves 12A and 12B may be wavy in the circumferential direction as shown in FIG. 7, and are not necessarily parallel to the tire equatorial plane.

A tire having a tread in which blocks having shallow grooves are arranged in a shoulder portion and a tire having a conventional block having no shallow grooves are manufactured and mounted on a construction dump truck. After traveling 3000 km on the road (unpaved road) at an average speed of 20 km / h, measure the difference between the amount of wear at the stepping end of the block and the amount of wear at the place with the least amount of wear in the block, and the amount of rubber wear What was converted into rubber mass was calculated and compared. The test results of the running test are shown in the table of FIG. In the tread, the depth of the circumferential grooves was 80 mm.
8, the conventional example is a tread in which a block 15Z having no shallow groove shown in FIG. 9 is arranged on the shoulder portion 11S, and Example 1 is a block in which the shallow groove according to the present invention shown in FIG. 1 is formed. In the tread, the shallow groove was a shallow groove having a uniform depth of 30 mm. Further, Example 2 is a tread having a block in which a shallow groove having a shallow groove end portion shown in FIG. 5 is formed. Here, the depth of the central portion of the groove is 30 mm, and the depth of the groove end portion is 10 mm. It was. In Example 3, the extension direction of the shallow groove shown in FIG. 6 is not 90 ° (here, 70 °) with respect to the tire equatorial plane. In Example 4, the circumferential groove shown in FIG. It is a thing.
Comparative Example 1 is an example in which the end of the shallow groove of Example 1 is expanded to the ground end, and Comparative Example 2 is an example in which the inner end of the shallow groove of Example 1 is not connected to the circumferential groove. In Example 3, the end of the shallow groove of Example 1 was expanded to the ground end, and the inner end of the shallow groove was not connected to the circumferential groove, and Comparative Example 4 was the groove depth of Example 1. In Comparative Example 5, the groove depth of Example 1 is increased (60 mm).
The test results show that the wear state is more uniform as the difference between the wear amount at the block step end and the wear amount (the wear amount difference) between the place where the wear amount is the smallest in the block is small. Moreover, it shows that it is excellent in abrasion resistance, so that the index | exponent of the wear weight when a prior art example is set to 100 is small.
As is apparent from the table, in Examples 1 to 4, the wear is more uniform and excellent in wear resistance than the conventional example, and in particular, the extension direction of the shallow groove is an angle with respect to the tire width direction. In Examples 3 and 4 having the above, the difference in wear amount is small, and the index of wear amount is small.
Moreover, the effect of the shallow groove could not be sufficiently obtained when the both ends opened at the block end as in Comparative Example 1 or when the shallow groove was in the block as in Comparative Example 2. On the other hand, even when only one end of the shallow groove was opened to the block end, when it was opened to the grounding end side as in Comparative Example 3, the uneven wear was large and the wear resistance was poor.
Further, even when the groove depth was shallow as in Comparative Example 4 or when the groove depth was large as in Comparative Example 5, the effect of the shallow groove was not obtained.
Therefore, it was confirmed that only tires having treads having blocks formed with shallow grooves according to the present invention as in Examples 1 to 4 were uniform in wear and excellent in wear resistance. It was.

  Thus, according to the present invention, the uneven wear resistance of the shoulder block can be suppressed without degrading the cut resistance, so that the excellent uneven wear resistance used suitably for heavy-duty vehicles and the like. A pneumatic tire having the following characteristics can be obtained.

It is a figure which shows the tread pattern of the pneumatic tire which concerns on the best form of this invention, and the shallow grooved block by this invention. It is a figure which shows the deformation | transformation state of the tire circumferential direction of the block at the time of kicking out. It is a figure which shows the deformation | transformation state of the block by the side of a depression end. It is a figure which shows the relationship between the deformation | transformation state of a block, and a lug groove. It is a figure which shows the deformation | transformation state of the block in the pneumatic tire of this invention. It is a figure which shows the other example of a shallow grooved block by this invention. It is a figure which shows the other example of a shallow grooved block by this invention. It is a figure which shows the specification of a block, and the result of a running test. It is a figure which shows the conventional block used for the running test. It is a figure which shows an example of the tread pattern of the conventional pneumatic tire.

Explanation of symbols

10 Pneumatic tire, 11 tread, 11S shoulder,
12A, 12B circumferential groove, 13 lug groove, 14 central land, 15 blocks,
15P, 15Q block row, 16 shallow grooves.

Claims (2)

In the pneumatic tire provided with a block row composed of a plurality of blocks partitioned by a circumferential groove extending along the tire circumferential direction and a lateral groove intersecting the circumferential groove on the shoulder portion of the tread,
The circumferential length of the block is 1/40 or more of the tire outer circumference,
At least a part or the whole of the block has one end opened to the circumferential groove side and the other end terminated inside the tread end, and the depth is 0.3 to 0.6 of the depth of the circumferential groove. is twice the shallow groove is provided,
A pneumatic tire characterized in that the depth of the shallow groove changes in the tire axial direction . The pneumatic tire according to claim 1, characterized in that the shallower the depth of the upper Kiasamizo closer to both ends of the groove.

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