JPH11348510A - Heavy load studless tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase traction on an ice surface while enhancing riding comfort simultaneously. SOLUTION: A heavy load studless tire with a block pattern maintains K to be 50 mm<2> or more, where K is a ratio of the cross-section secondary moment in a rotation direction R of the tire to a ground contact area of the tire of each main block 4' whose contact are 4x exceeds 1% of the total area of a tread face 1. The studless tire also maintains a ratio KA/KB in a range of 2.0-4.0, where KA is ratio of each main block 4'A allocated at a center area A comprising left and right areas between a center line CL and each of tire contact area edges E and extending as wide as not less than 0.3 times of a tread expanded width W, and KB is a ratio of each main block 4'B allocated at shoulder areas B on the both sides.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy duty studless tire used for a bus or a truck, and more particularly to a heavy duty studless tire having improved traction on ice and ride comfort.

[0002]

2. Description of the Related Art In general, a heavy load studless tire used for a bus or a truck has a main groove 12 extending in a tire circumferential direction T and a lateral groove 13 extending in a tire width direction on a tread surface 11, as shown in FIG. The main grooves 1
A large number of blocks 14 having the same shape are formed by 2 and the lateral groove 13. A sipe 15 extending in the tire width direction is provided on the ground contact surface 14a of each block 14. The main groove and the lateral groove secure the groove area to exhibit high on-snow performance, while ensuring the on-ice performance by the edge effect of blocks and sipes.

[0003] In recent years, with the increase in engine output of large vehicles, traction (starting and braking performance) particularly on icy roads has become important.
The improvement was strongly demanded. In addition, the studless tire having the above-described block pattern tends to be inferior in ride comfort to general tires (summer tires and all-season tires).

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heavy load studless tire capable of improving traction on ice and improving ride comfort.

[0005]

In order to achieve the above object, the present invention provides a plurality of main grooves extending in a tire circumferential direction on a tread surface, and lateral grooves extending in a tire width direction are arranged at a predetermined pitch in a tire circumferential direction. In the heavy load studless tire having a large number of blocks defined by the main grooves and the lateral grooves and provided with sipes on the ground surfaces of the plurality of blocks, the total area of the tread surface located between the tire ground ends is determined. The ratio K of the ^second moment of area to the tire rotation direction and the contact area of each main block having an area exceeding 1% on the contact surface with respect to the tire rotation direction is set to 50 mm ² or more, and the tread between the tire contact points from the tire center line to the left and right. the ratio K _a of each major block disposed in the center region a which is a range of up to 0.3 times the width W, the center region a on both sides of the shoulder region B The ratio K _B of each main block arranged
And the ratio K _A / K _{B is set} to 2.0 ≦ K _A / K _B ≦ 4.0.

As described above, in the main block disposed in the center region of the tread surface and the main block disposed in the shoulder region, the ratio K of the second moment of area to the ground contact area is obtained.
_A, since the ratio K _A / K _B of K _B is specified above, a high applied load acts, moreover the heavy duty studless tire load greatly varies, the tire center region significantly affects the starting and braking The block rigidity in the rotation direction can be effectively increased, whereby traction on an icy road surface can be improved, and riding comfort can be improved.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be specifically described below with reference to the embodiment shown in the drawings. FIG. 1 shows an example of a main portion of a tread surface of a heavy load studless tire according to the present invention. A plurality of main grooves 2 extending straight in a tire circumferential direction T are provided on a tread surface 1. Between the main grooves 2, lateral grooves 3 extending in the tire width direction are arranged at a predetermined pitch in the tire circumferential direction, and the main grooves 2 and the lateral grooves 3 define a large number of blocks 4.
A plurality of sipes 5 extending in the tire width direction are provided on the ground contact surface 4x of each block 4.

Each block 4 has an area exceeding 1% of the total area of the tread surface 1 located between the tire grounding ends E (the total area without the main groove 2 and the lateral groove 3). 4x, and has a ratio K of 50 mm ² or more between the second moment of area in the tire rotation direction R and the contact area of the contact surface 4x when mounted on a vehicle. In addition, in the block pattern of FIG.
Since there is no directionality, both directions are the tire rotation directions R.

The tread surface 1 is located in the center area A.
With respect to the tire rotation direction R of each main block 4'A placed
Ratio of the second moment of area to the contact area of the contact surface 4x
K_AAnd shoulder regions B on both sides of the center region A.
Of each placed block 4'B in the tire rotation direction R
Ratio K between the surface second moment and the contact area of the contact surface 4x _B
And the ratio K_A/ K_BIs 2.0 ≦ K_A/ K_B≦ 4.0
At the center area A of the tread surface 1.
The block rigidity in the ear rotation direction R is lower than that of the shoulder region B.
Higher than that.

However, the center area A referred to here is an area extending from the tire center line CL to the right and left up to 0.3 times the tread development width W between the tire grounding ends E, and each 0% on both sides thereof. The area having a width of .2 W is the shoulder area B.

Thus, the center area A of the tread surface 1
In the main blocks 4'A and 4'B of the shoulder region B and the ratio of the ratio of the moment of inertia to the ground contact area K _A and K _B as specified above, a high load is applied and In heavy load studless tires having large fluctuations, the block rigidity in the tire rotation direction R in the center region A, which greatly affects starting and braking, can be effectively increased, so that traction on icy roads such as frozen roads is improved. And the ride comfort can be improved.

When the ratio K is less than 50 mm ² , the rigidity of the block becomes insufficient, and the tire is not suitable for a heavy duty tire.
The upper limit is preferably about 300 mm ² from the viewpoint of exhibiting the function as a studless tire. Ratio K _A
/ When K _B is less than 2.0, it is not possible to increase the block rigidity of the center region A sufficiently, it is difficult to effectively improve the on-ice traction. vice versa,
Even if the value exceeds 4.0, the length of the blocks in the tire circumferential direction becomes long, and the traction on ice cannot be effectively improved due to a decrease in the edge effect due to a decrease in the number of blocks.

FIG. 2 shows another example of a heavy load studless tire according to the present invention. In the above embodiment, each block 4
Has a contact area exceeding 1% with respect to the total area of the tread surface 1, but in this embodiment, the block 4
With a main block 4 'having a ground contact area exceeding 1%,
And a sub-block 4 '' having a ground contact area of 1% or less. The sub-block 4 ″ is formed to be elongated in the tire circumferential direction so as to suppress skidding on ice.

The main block 4 'is arranged so that the total contact area of the center area A and the shoulder areas B is 60% or more of the total contact area of the blocks of the respective areas A and B. A plurality of sipes 5 extending in the tire width direction are formed on the ground contact surface 4x of the main block 4 '. Thus, the main block 4 'and the sub block 4''
Also in a tire in which are mixed, the same effect as described above can be obtained by increasing the block rigidity of the main block 4'A in the center region A as described above.

In the present invention, in the embodiment described above,
Although an example in which a plurality of sipes 5 are provided in each main block 4 'is shown, it is sufficient that each main block 4' is provided with at least one sipe extending in the tire width direction. Further, the sipe may be one in which both ends communicate with the main groove, one in which only one side communicates with the main groove, and one in which both ends are located in the block and do not communicate with the main groove.

The present invention is applied to a heavy-duty studless tire used for heavy-duty vehicles such as trucks and buses. A heavy-duty tire referred to herein is a JATMA Y.
It refers to truck and bus tires specified in EAR BOOK (1998).

The above-mentioned tire contacting end E is a JAT
The air pressure (maximum air pressure) corresponding to the maximum load capacity in single wheel use described in the air pressure-load capacity correspondence table of MA YEAR BOOK (1998), and the grounding end measured by adding the maximum load. However, when a plurality of maximum load capacities according to the number of plies (ratings) are described in the same column, the maximum load capacities at the designated number of plies are used.

[0018]

[Example] The tire size is made common to 11R22.5,
In the tread pattern of FIG. 1, the ratio K _A / K _B is shown in Table 1.
Tires 1 to 3 of the present invention and comparative tires 1 to 1
3 and the conventional tire shown in FIG.
For each test tire, the tire rotation direction R of each block
The ratio K of the second moment of area to the contact area with respect to
mm ² or more.

Each of these test tires was rim size 22.5
A rim of × 7.50 was mounted on a truck with an air pressure of 800 kPa and a load of 3,000 kgf per tire. An evaluation test was conducted on traction on ice and riding comfort under the following measurement conditions. The results shown in Table 1 were obtained.

On-ice traction property On an ice track test course at an ice temperature of −2 ° C. to −8 ° C. and an air temperature of −3 ° C. to −5 ° C., the time required from the start until reaching a speed of 20 km / h was measured. The evaluation was made using an index value with the conventional tire being 100. The larger the value, the better the traction on ice.

Ride Comfort On the test course, a feeling test was conducted by panelists, and the result was evaluated by an index value with the conventional tire being 100. The larger the value, the better the ride comfort.

[0022]

[Table 1]

From Table 1, it can be seen that the tire of the present invention has traction on ice and ride comfort of 105 or more, and both performances can be effectively improved.

[0024]

As described above, the studless tire for heavy load according to the present invention has a ratio K between the second moment of area and the contact area of each main block in the tire rotation direction of 50 mm ^2.
As described above, the ratio K _A / K _B of the ratio K _A of each main block arranged in the center area to the ratio K _B of each main block arranged in the shoulder area is 2.0 ≦ K _A / K _B ≦ 4. 0
Accordingly, the block rigidity in the tire rotation direction in the center region can be effectively increased, and traction on ice and riding comfort can be improved.

[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 load studless tire of the present invention.

FIG. 2 is a development view of a main portion of a tread surface showing another example of the heavy load studless tire of the present invention.

FIG. 3 is a development view of a main portion of a tread surface showing a conventional heavy load studless tire.

[Explanation of symbols]

1 tread surface 2 main groove 3 lateral groove 4, 4A, 4B
Block 4x Ground surface 4 ', 4'A, 4'B
Main block 4 '' Secondary block 5 Sipe A Center area B Shoulder area CL Tire center line E Tire contact edge R Tire rotation direction T Tire circumferential direction W Tread development width

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B60C 11/11 B60C 11/12 C 11/12 11/04 A

Claims (3)

[Claims] 1. A plurality of main grooves extending in a tire circumferential direction are provided on a tread surface, 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 divided by the main grooves and the lateral grooves. In a heavy duty studless tire in which blocks are formed and a sipe is provided on a ground surface of a plurality of blocks, each main surface having an area exceeding 1% of the total area of the tread surface located between the tire grounding ends on the ground surface. A center having a ratio K of the second moment of area to the contact area of the block with respect to the tire rotation direction of not less than 50 mm ² and a range from the tire center line to the right and left up to 0.3 times the tread development width W between the tire contact points. the ratio K _a of each major block arranged in the area a, the ratio of the ratio K _B of each main block disposed in the center region a on both sides of the shoulder region B K _a / Heavy duty studless tire in which the K _B to _{2.0 ≦ K A / K B ≦} 4.0. 2. The heavy load studless tire according to claim 1, wherein the total contact area of the main blocks in the center region A and the shoulder regions B occupies 60% or more of the total contact area of the blocks in each of the regions A and B. . 3. The heavy load studless tire according to claim 1, wherein at least one sipe is provided on a ground contact surface of each main block in a tire width direction.