JPH10138709A - Pneumatic tire for heavy load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve deflected abrasion resistance by specifying proportion of a cross-section secondary moment and an area of a block tread and a storage elastic modulus. SOLUTION: A plural number of main grooves extending linearly along a tire peripheral direction T are provided on a tread part 1, and grooves 3 extending linearly between the main grooves along a tire cross direction are arranged with specified pitches along the tire peripheral direction T. A large number of blocks 4 partitioned by these main grooves 2 and the cross grooves 3 are formed on the tread part 1. Proportion I/S of a cross-section secondary moment I against the tire peripheral direction T of each of the blocks 4 and an area S of its block tread 4a is made 50mm<2> <=I/S<=105mm<2> . In the meantime, a storage elastic modulus E', which is one of rubber materials constituting the tread part on which the blocks 4 are provided is made 6MPa<=E'<=12MPa. Consequently, it is possible to secure a favourable edge effect and a favourable adhesive effect of the blocks and to doubly secure ice performance and deflected abrasion resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy-duty pneumatic tire used as a studless tire for buses, trucks and the like, and more specifically, to achieve both opposing performances on ice and uneven wear resistance. And a pneumatic tire for heavy loads.

[0002]

2. Description of the Related Art In general, a studless tire has a large number of blocks formed on a tread portion of a tread portion, and a sipe extending in the width direction of the tire and having openings on both sides is provided on the tread portion of each block. It increases the sticking effect and exerts high performance on ice.

By the way, a heavy load pneumatic tire used for a bus, a truck or the like is subjected to much higher load and shear stress than a pneumatic tire used for a passenger car or the like. Therefore, if the studless tire used for the heavy-duty pneumatic tire is simply configured as described above, uneven wear (heel and toe wear) occurs in the block, and both on-ice performance and uneven wear resistance are achieved. It is difficult.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heavy-duty pneumatic tire used as a studless tire, which is capable of achieving both on-ice performance and uneven wear resistance. Is to do.

[0005]

[MEANS FOR SOLVING THE PROBLEMS]
Akira has set a main groove extending in the tire circumferential direction on the tread of the tread.
As well as the lateral groove extending in the tire width direction
At a predetermined pitch, and divided by the main groove and the lateral groove
A large number of blocks are formed, and the tire width is
Sipe extending in the direction of at least one side opening into the main groove
The heavy duty pneumatic tire provided with
Moment of inertia with respect to the tire circumferential direction
The ratio I / S to the area S of the lock tread is 50 mm^Two≤I / S≤
105mm ^TwoWhile the rubber that composes the tread
Storage modulus E 'set to 6MPa ≤ E' ≤ 12MPa
It is characterized by.

[0006] As described above, the cross section of the block in the tire circumferential direction 2
The value expressed by the ratio of the next moment to the area of the tread surface of the block, that is, the equivalent second moment of area of the block is set to 50 mm ² or more, while the storage elastic modulus is set to 6 MPa or more, so that a high load can be obtained. As a pneumatic tire for heavy loads on which high shear stress acts, sufficient block rigidity can be ensured, so that high uneven wear resistance can be exhibited.

On the other hand, by setting the upper limit of the second moment of area equivalent to 105 mm ² and the upper limit of the storage elastic modulus to 12 MPa, both the edge effect and the sticking effect in the block are ensured. High performance on ice can be obtained. Therefore, both on-ice performance and uneven wear resistance can be achieved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 shows an example of a heavy-duty pneumatic tire of the present invention used as a studless tire. Tread surface (tread surface)
1, a plurality of main grooves 2 extending linearly along the tire circumferential direction T are provided, and lateral grooves 3 linearly extending between the main grooves along the tire width direction are defined along the tire circumferential direction T. Are arranged at the same pitch.

A large number of blocks 4 defined by the main grooves 2 and the lateral grooves 3 are formed on the tread surface 1. Each block 4 is provided with one sipe 5 extending linearly along the tire width direction and having both sides open to the main groove 2. CL is the tire equator line. In the present invention, in the heavy duty pneumatic tire provided with the block pattern as described above, the tire circumferential direction T
The ratio I / S of the second moment of area (the second moment of area in the circumferential direction) I to the (tire rotation direction) and the area S of the block tread surface 4a is in the range of 50 mm ² ≦ I / S ≦ 105 mm ² .

According to the present inventors, as a result of earnestly studying the relationship between block rigidity and uneven wear, the relationship between block rigidity and performance on ice, and the relationship between block height and uneven wear, the graphs shown in FIGS. . In FIG. 2, the horizontal axis represents I / S and the vertical axis represents uneven wear (m
The relationship between block rigidity and uneven wear when m) is shown.
The contact pressure is 7 kg / cm ² . From the figure, although the uneven wear amount increases with an increase in the shearing force, a so-called I / S,
When the equivalent second moment of area becomes smaller at around 50 mm ² for any shearing force, the uneven wear amount sharply increases.

On the other hand, FIG. 3 shows the relationship between block rigidity and performance on ice when I / S is on the horizontal axis and friction coefficient is on the vertical axis. Note that HS in the drawing indicates JISA hardness. As shown in the figure, the lower the rubber hardness, the higher the friction coefficient on ice, but the equivalent second moment of area decreases with increasing rubber hardness for all rubber hardnesses. Thereby, the upper limit of the equivalent second moment of area can be determined.

FIG. 4 shows the relationship between block height and uneven wear with the horizontal axis representing the block height [mm] and the vertical axis representing the uneven wear amount [mm]. From the figure, in the practical range (12 to 16 mm) as a heavy-duty pneumatic tire used on icy and snowy roads, the change in block height has little effect on uneven wear. As shown, the equivalent second moment of area is the dominant factor. Therefore, in the present invention, the ratio I / S of the circumferential moment of inertia I to the area S of the block tread is defined as described above.

In the present invention, the storage elastic modulus E ', which is one of the physical properties of the rubber constituting the tread portion provided with the block 4, is set in the range of 6 MPa≤E'≤12 MPa.
Thus, the value I / I obtained by dividing the second moment of inertia I in the tire circumferential direction of the block 4 by the area S of the tread surface 4a of the block 4 is obtained.
S, that is, the equivalently calculated ^second moment of area is 50 mm ²
As described above, by keeping the storage elastic modulus E ′ of the rubber forming the block at 6 MPa or more, the rigidity of the block as a heavy-duty pneumatic tire on which high load and high shear stress are exerted is ensured, and high uneven wear resistance is obtained. On the other hand, by setting the upper limit of the second moment of area and the upper limit of the storage elastic modulus E 'to be equivalently, 105 mm ² and 12 MPa, respectively, a good edge effect and a sticking effect of the block are ensured, and a high ice Since the performance can be exhibited, it is possible to achieve both the performance on ice and the resistance to uneven wear.

If the equivalent second moment of area I / S is less than 50 mm ² , the block 4 becomes too small, and the uneven wear resistance of the block 4 deteriorates. Conversely, I / S
Exceeds 105 mm ² , the blocks become too large, and the edge effect decreases due to the decrease in the number of blocks.
When the storage elastic modulus E 'is less than 6 MPa, the uneven wear resistance of the block is reduced. On the other hand, when the storage elastic modulus E' is more than 12 MPa, the performance on ice is deteriorated due to the reduced adhesive effect of the block.

In the present invention, the groove depth D of the lateral groove 3 can be set to 55 to 70% of the groove depth of the main groove 2. If the groove depth D is less than 55%, the performance on snow cannot be secured, and the tire cannot be used as an original winter tire. Conversely 7
If it is larger than 0%, there is a problem that the life after the middle stage of wear is reduced. The area ratio of all block treads to the tread surface 1 (all treads) can be 60 to 75%. If the area ratio is less than 60%, the number of grooves increases, resulting in a shortage of the ground contact area, and the performance on ice cannot be sufficiently ensured. On the other hand, if it exceeds 75%, the performance on snow cannot be sufficiently ensured because the number of grooves is reduced.

In the above embodiment, the sipe 5 is formed as a sipe having both sides opened in the main groove.
A sipe in which only one side communicates with the main groove may be used. In the present invention, each block may be provided with one sipe having at least one side open to the main groove. The storage elastic modulus E ′ is a value at 0 ° C. The measuring method is as follows: using a viscoelastic spectrometer (manufactured by Iwamoto Seisakusho), elongation deformation, strain rate 10 ± 2%, frequency 20H
It was measured at 0 ° C. under the conditions of z.

[0017]

【Example】

Example A The tire size was made common to 11R22.5 14PR,
In the tire provided with the block pattern shown in FIG.
Tires 1 to 3 of the present invention, comparative tires 1 and 2, and a conventional tire having I / S as shown in Table 1 were produced.

In each of the test tires, the storage elastic modulus E 'of the tread rubber is 9.0 MPa. The groove depth of the lateral groove is 6 times the groove depth of the main groove.
5% and the area ratio of the block tread is 65%. Each of these test tires was mounted on a standard rim and the air pressure was 725 kPa
Then, it was mounted on a truck (2-D), a load of 2000 kgf was applied per tire, and an evaluation test on performance on ice and uneven wear resistance was performed under the following measurement conditions.
The results shown in Table 1 were obtained. On-ice performance On the icy road test course, the on-ice performance was evaluated by a feeling test by a test driver, and the result was shown as an index value with the conventional tire being 100. The larger the value, the better the performance on ice. If the value is 95 or more, it can be said that the performance on ice is practically high. Uneven wear resistance The amount of step wear (heel and toe wear) of the block at about 20,000 km traveling on a general road was measured, and the result was shown as an index value with the conventional tire being 100. The larger the value, the better the uneven wear resistance.

[0019]

[Table 1]

As is apparent from Table 1, the I / S is 50 mm
^It is understood that the tire of the present invention having a size of ² to 105 mm ² can achieve both on-ice performance and uneven wear resistance. Example B The tires of the present invention 4 to 6 and the comparative tires 3 were prepared by changing the storage elastic modulus E ′ of the tread rubber as shown in Table 2 in the tire having the same tire size as the above and having the block pattern shown in FIG. And No. 4 were produced respectively.

In each of the test tires, the I / S is 80 mm ² , the lateral groove depth is 65% of the main groove depth, and the area ratio of the block tread surface is 65%. Each of the test tires was subjected to an on-ice performance and an uneven wear resistance evaluation test under the same conditions as above, and the results shown in Table 2 were obtained.

[0022]

[Table 2] As is evident from Table 2, the tire of the present invention in which the storage elastic modulus E 'of the tread rubber is 6 to 12 MPa can achieve both on-ice performance and uneven wear resistance.

[0023]

As described above, the present invention relates to a heavy duty pneumatic tire for studless use in which a block is provided with a sipe, and is equivalent to the ratio of the second moment of inertia of the block in the tire circumferential direction to the area of the block tread surface. By setting the typical second moment of area and the storage elastic modulus of the tread rubber in the specific ranges described above, it is possible to achieve both on-ice performance and uneven wear resistance.

[Brief description of the drawings]

FIG. 1 is a development view of a main portion of a tread surface showing an example of a heavy-duty pneumatic tire of the present invention.

FIG. 2 is a graph showing a relationship between block rigidity and uneven wear.

FIG. 3 is a graph showing a relationship between block rigidity and performance on ice.

FIG. 4 is a graph showing the relationship between block height and uneven wear.

[Explanation of symbols]

 Reference Signs List 1 tread surface (tread portion tread surface) 2 main groove 3 lateral groove 4 block 4a block tread surface 5 sipe CL tire equator line T tire circumferential direction

Claims (3)

[Claims] 1. A main groove extending in a tire circumferential direction is provided on a tread surface of a tread portion, and lateral grooves extending in a tire width direction are arranged at a predetermined pitch in a tire peripheral direction, and a large number of blocks defined by the main grooves and the lateral grooves are provided. In a heavy-duty pneumatic tire provided with a sipe extending in the tire width direction in the block and having at least one side open to the main groove, a second moment of area I of the block with respect to a tire circumferential direction and an area of the block tread surface The ratio I / S to S is 50mm ²
A heavy-duty pneumatic tire in which the storage elastic modulus E ′ of the rubber constituting the tread portion is set to 6 MPa ≦ E ′ ≦ 12 MPa while ≦ I / S ≦ 105 mm ² . 2. The heavy duty pneumatic tire according to claim 1, wherein the groove depth of the lateral groove is set to 55 to 70% of the groove depth of the main groove. 3. The area ratio of the entire block tread to the tread tread is 60 to 75%.
The pneumatic tire for heavy loads according to the description.