JPH02106411A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PURPOSE:To improve wear resistance without damaging running performance on ice and snow road by specifying the relation of each inclination angle in respective groove walls of the side of lag groove firstly brought into contact with the road surface and of the side thereof secondly brought into contact therewith, as well as the negative rate of the whole tread (groove area/total area). CONSTITUTION:A tread T of tire is provided with two circumferential grooves and one central circumferential groove 1' in each of paired central sections Tc, at which a plurality of lag grooves continuous to connection grooves 2 extending to the central of the region Tc as well as crossing the respective circumferential groove 1, 1', whereby a plurality of blocks 3, 4 are partitioned. In this case, the negative ratio of the whole tread T is set to be 30 - 50%. The inclination angle (alpha) of groove wall of the side brought into contact with the road surface with respect to a normal L of lag groove 2 is set larger than the inclination angle (beta) of the groove wall 2B of the relative side secondary brought into contact therewith upon rotation of tire, and the difference of the angles is also set to be 5 - 20 degrees.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to the improvement of heavy-duty pneumatic tires, and more specifically, to improving uneven wear resistance while maintaining running performance on snow and ice. This invention relates to heavy-duty pneumatic tires.

(Prior art) In recent years, due to various problems such as spike pollution, tires for driving on snow and ice without spikes have been developed, and studless tires (also called all-weather tires) for passenger cars in particular are rapidly increasing. .

The mainstream of these studless tires is one that has improved running performance on snow and ice due to a unique block pattern formed on the tread.

In other words, the tread of conventional studless tires has
Usually, a plurality of blocks are formed in the circumferential direction of a tire, divided by a plurality of circumferential grooves and a plurality of lug grooves extending perpendicularly to the circumferential grooves from both ends of the tread,
Each block is further divided into a plurality of sub-blocks by a plurality of notches having a width such that they contact each other during load transfer.

Therefore, in conventional studless tires, when a force in the longitudinal direction consisting of driving force and braking force is applied to the tire, a large number of edges generated by the above-mentioned notches are cut on the snow due to the edge effect caused by grasping the hard road surface. Efforts have also been made to improve driving performance on ice, and their effectiveness has been recognized and they are rapidly becoming popular.

(Problem to be Solved by the Invention) As described above, development is underway to apply the effects confirmed by studless tires for passenger cars to tires for heavy loads such as small trucks and trucks/buses. The tread structure was essentially an extension of the aforementioned studless tire for passenger cars.

However, unlike passenger car tires, heavy-duty tires have large internal pressures and loads, and the external forces acting on the tread blocks are also extremely large, which causes uneven wear on the lugs formed by the lug grooves on both sides of the tread. This tends to occur, and as a result, there is a problem in that not only the driving performance on snow and ice deteriorates, but also the life of the tire is affected.

In other words, in conventional studless tires, the inclination angle of the groove wall of the lug groove in both sides of the tread is on the stepping side (the kicking side groove wall when viewed from the center of the lug groove) and the kicking side (from the center of the lug groove) of the block when the tire rotates. Because the groove walls (when viewed from the outside) were formed equally, the degree of wear on both sides would be greater on the kick-off side and smaller on the push-in side, resulting in a large difference depending on how the force was received during braking and how it deformed. This causes a tendency for the block surface to wear unevenly at an early stage, which is called heel-and-toe wear, which impedes the tire's running performance on snow and ice and the durability life of the tire.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the conventional heavy-duty pneumatic tires.

Therefore, an object of the present invention is to provide a heavy-duty pneumatic tire with improved uneven wear resistance without sacrificing performance on snow and ice.

[Structure of the Invention] (Means for Solving the Problems) That is, the heavy-duty pneumatic tire of the present invention has a pair of sidewalls and a tread extending between both sidewalls in a toroidal manner, and a tread extending over each of these parts. The tread is reinforced with an extending radial carcass and a belt layer disposed between the carcass and the tread, the tread comprising a central region and a pair of side regions, the central region having a belt layer disposed at predetermined intervals in the axial direction of the central region. at least two circumferential grooves, and a plurality of grooves extending substantially continuously from the opening positions of the pair of circumferential grooves, intersecting the circumferential grooves and connecting with the connecting grooves toward the center of the central area. lug grooves, and has a large number of blocks divided by the groove groups, the negative ratio (groove area/total area) of the entire tread is in the range of 30 to 50%, and the tire has During rotation, the stepping-in side groove wall inclination angle of the lug groove with respect to the normal line of the tire is larger than the opposing kicking-out side groove wall inclination angle, and the angle difference is 5 to 20.
It is characterized by being configured so that it has a range of degrees.

(Function) In the heavy-duty pneumatic tire of the present invention, when the tire rotates, the inclination angle of the stepping side groove wall of the lug groove with respect to the normal line of the tire is larger than the opposing kicking side groove wall inclination angle, and the angle difference is Since it is configured to be in the range of 5 to 20 degrees, the difference in the degree of wear between the stepping side groove wall and the kicking side groove wall is eliminated, and as a result, heel and toe wear is effectively improved, and unevenness on the entire block surface is reduced. occurrence can be significantly reduced.

Therefore, uneven wear, which was particularly noticeable in the lug grooves on both sides of the tread, is less likely to occur, and running performance on snow and ice can be effectively maintained.

In addition, the heavy-duty pneumatic tire of the present invention has a negative rate (groove area/total area) of the entire tread of 30 to 50%.
By regulating the speed within this range, it is possible to not only obtain ideal driving performance on snow and ice, but also to improve tire life and noise.

Therefore, the heavy-duty pneumatic tire of the present invention has significantly improved uneven wear resistance without sacrificing performance on snow and ice, and has excellent performance as an all-weather tire with a good durability life. It is particularly useful as a tire for heavy loads such as small trucks and trucks/buses.

(Example) Examples of the heavy-duty pneumatic tire of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a developed view of a tread portion showing one embodiment of a heavy-duty pneumatic tire of the present invention, and FIG. 2 is an A--A in FIG. 1.
FIG.

Although parts other than the tread are not shown in FIGS. 1 and 2, the parts other than the tread, such as the radial carcass and the belt layer, have a well-known structure.

In FIG. 1, the tread T of the pneumatic tire for heavy loads of the present invention consists of a central region Tc and a pair of both side regions Ts, and the central region Tc has at least one region disposed at a predetermined interval in the axial direction. two circumferential grooves 1.1;
By substantially dividing the axial distance between these circumferential grooves 1.1 into thirds and by arranging the central circumferential groove 1' extending parallel thereto, the tread T can be spaced approximately equally in the axial direction. 4
It is divided.

In addition, the pair of side sections Ts have a plurality of grooves extending substantially continuously from the opening position thereof, intersecting with the circumferential groove 1.1'1 and connecting with the connecting groove 2- extending toward the center of the central section Tc. By providing the lug grooves 2, the tread T is divided into a large number of blocks 3.4.

Furthermore, block 3 of the central area Tc and both side areas Ts
All of the blocks 4 are formed into a plurality of sub-blocks, for example 3A, by a plurality of cuts S extending generally parallel to the circumferential direction.
, 3B, 3C, 3D, 3E and 4A, 4B, 4C.

Here, the tread T is usually formed from relatively hard rubber, but in some cases softer rubber or foamed rubber may be used for at least a portion thereof.

The circumferential groove 1.1 and the central circumferential groove 1'' may have a linear shape parallel to the circumferential direction, but may have a broken line shape (
It is preferable that the grooves have a modified flanged shape, and the width and depth of these grooves are the widest and deepest among the grooves.

The slightly wider lug grooves 2 in the tread side areas Ts communicate with the connecting grooves 2' in the center area Tc, and are arranged so that the intervals in the circumferential direction are approximately equal.

Furthermore, it is desirable that the lug grooves 2 and the connecting grooves 2' have a bent line shape (deformed flang shape) as shown in the figure, and the fold width thereof is formed to be larger than the circumferential groove 1.1°.

The groove width of the lug groove 2 and the connecting groove 2' is the circumferential groove 1.1'
However, as shown in the figure, it is desirable that the lug grooves 2 in the tread side areas Ts are enlarged groove width portions.

The depth of the lug groove 2 and the connecting groove 2 is the circumferential groove 1.1.
Although it is the same as or slightly shallower than 1.1, there is a shallow part with a raised groove bottom in the center of the two circumferential grooves and/or the center of the circumferential groove 1.1 and the tread ends e, e-. It is also possible to provide one.

In the drawing, four cuts S are provided in a straight line in the block 3 in the central area Tc of the tread, and three cuts S are provided in a straight line in the block 4 in the both side areas Ts of the tread, parallel to the circumferential direction. The number of can be changed arbitrarily depending on the purpose.

The width of the cut S is preferably in the range of 0.5 to 1.2 mm,
As a result, the rigidity of the block as a whole is maintained at a desirable level, and at the same time, the ground contact performance is improved and a good edge effect is achieved.

Also, the depth of the cut S is 2 of the depth of the circumferential groove 1.1'1.
A range of 0 to 90%, particularly 60 to 85% is preferred.

In addition to making all the depths of the cuts S the same, the depth of cuts of the blocks 4 in the tread side regions Ts may be made larger or smaller than the depth of cuts of the blocks 3 in the central region Tc of the tread. Modifications can be made such as making the cut alternately deeper and then shallower in the axial direction within the same block, or making the depth of the cut in the longitudinal direction vary.

Furthermore, the extension of the cut S in the depth direction can be made not only in the normal direction to the block outer surface (ground plane) but also at right angles to the circumferential direction or at a slight inclination angle inward in the axial direction. .

Furthermore, the shape of the cut S may be a zigzag shape, a wave shape, a lightning bolt shape, a dogleg shape, or the like.

An important requirement for the heavy-duty pneumatic tire of the present invention having the above-mentioned configuration is the negative ratio of the entire tread T (
When the tire is rotating with the groove area/total area) in the range of 30 to 50% and the rotation direction is in the direction of arrow R as shown in Fig. 2, the depression of the lug groove 2 with respect to the normal line of the tire. The gutter wall inclination angle is larger than the opposing kick-out side gutter wall inclination angle, and the angular difference is in the range of 5 to 20 degrees.

Here, if the negative rate of the entire tread T is less than 30%, sufficient running performance on snow and ice cannot be obtained as a studless tire, and conversely, even if it exceeds 50%, running performance on snow and ice, tire life, noise, etc. This is not preferable as it causes deterioration.

Further, the inclination angle α of the stepping side groove wall 2A with respect to the tire normal line of the lug groove 2 of the tread both side areas Ts is made larger than the inclination angle β of the kicking out side groove wall 2B facing the tire when rotating, and the angle difference is By configuring it so that the angle is 5 to 20 degrees, the target tread side area T
Uneven wear at s can be effectively reduced.

Here, if the difference between the inclination angle α of the stepping-in side groove wall 2A and the inclination angle β of the opposing kick-out side groove wall 3B with respect to the normal line of the lug groove 2 to the tire is less than 5 degrees, the block will not have sufficient rigidity against input changes. As a result, the effect of improving uneven wear is small.On the other hand, when the angle exceeds 20 degrees, the capacity of the lug groove 2 itself decreases, so not only is it not possible to obtain a sufficient effect of improving driving performance on snow and ice, but the tire also deteriorates. This is undesirable because the pattern changes greatly between when it is new and when it is worn, and the deterioration in driving performance on snow and driving performance on wet roads in particular becomes remarkable.

By configuring the lug grooves 2 in the tread side regions Ts as described above, uneven wear can be effectively improved without sacrificing running performance on snow and ice.

Next, the structure and effects of the heavy-duty pneumatic tire of the present invention will be explained in more detail using test examples.

(Test example) Tire size near, 00R16, rim used: 5° 50F
, Air pressure used: 6. The block pattern shown in FIG. 1 described above was formed on the tread portion of a radial tire of Okg/c-, and this tire was evaluated.

Note that other structures such as the radial carcass and belt layer of the tire and manufacturing conditions were similar to those of conventional tires, so details will be omitted.

That is, in Fig. 1, the tread width: 140111
1% zigzag circumferential groove 1.1 groove width: 9.0 mm, depth: 15 mm, zigzag central circumferential groove 1' groove width: 5 mm
．． 5mm, depth = 15mm, groove width of lug groove 2: 8.5mm
A block pattern was formed with a depth of 15 m, a width of the connecting groove 2': 5.5 mm, and a depth of 15 mm.

Furthermore, each block 3.4 has a groove width of 0.5 mm.

Cuts S with a depth of 1011I11 were provided parallel to the circumferential direction and at intervals between caps.

Then, the tire of the present invention was manufactured by setting the inclination angle α of the stepping-in side groove wall 2A to the tire normal line of the lug groove 2 to 20 degrees, and setting the inclination angle β of the opposing kick-out side groove wall 2B to 5 degrees.

On the other hand, for comparison, the inclination angle α of the stepping-in side groove wall 2A and the inclination angle β of the opposing kick-out side groove wall 2B with respect to the normal line of the tire of the lug groove 2 are made the same as 10 degrees, so that the conventional tire was manufactured.

These two types of tires were evaluated for driving performance on snow and ice and uneven wear through a real-vehicle feeling test under the following conditions. The results are shown in the table below.

All of the following tables are shown by index evaluation when the conventional tire is set as 100, and the larger the index, the better the result.

Driving performance on snow and ice Test vehicle: Small truck, 3-ton roadway. Compacted snow and frozen road speed in winter in Hokkaido
Frequency: 20 km/h Evaluation method Nibrake performance Uneven wear Test vehicle: Small truck, 3 ton road Surface: Kanto area, DRY, WET road surface (no snow) Speed: 20 to 80 km/h (high speed driving included) Evaluation method: Comparison of wear appearance (confirmed by lugs and steps) (hereinafter in the margin of this page) From the results above, the heavy-duty pneumatic tire of the present invention:
It is clear that uneven wear resistance can be significantly improved while maintaining snow running performance and ice running performance.

[Effects of the Invention] As described in detail above, in the heavy-duty pneumatic tire of the present invention, when the tire rotates, the inclination angle of the stepping side groove wall of the lug groove with respect to the normal line of the tire is greater than that of the opposing kicking side groove wall. greater than the inclination angle, and the angle difference is 5 to 2
Since it is configured to be in the 0 degree range, the difference in the degree of wear between the stepping-in side groove wall and the kicking side groove wall is eliminated, and as a result, heel-and-toe wear is effectively improved, and unevenness on the entire block surface is prevented. can be significantly reduced.

Therefore, uneven wear, which was particularly noticeable in the lug grooves on both sides of the tread, is less likely to occur, and running performance on snow and ice can be effectively maintained.

In addition, the heavy-duty pneumatic tire of the present invention has a negative rate (groove area/total area) of the entire tread of 30 to 50%.
By regulating the speed within this range, it is possible to not only obtain ideal driving performance on snow and ice, but also to improve tire life and noise.

Therefore, the heavy-duty pneumatic tire of the present invention has significantly improved uneven wear resistance without sacrificing performance on snow and ice, and has excellent performance as an all-weather tire with a good durability life. It is particularly useful as a tire for heavy loads such as small trucks and trucks/buses.

[Brief explanation of drawings]

Fig. 1 is a developed view of a tread portion showing one embodiment of the pneumatic tire for heavy loads of the present invention, and Fig. 2- is an A in Fig. 1.
-A cross-sectional explanatory diagram. L...Tyre normal line 1.1...Circumferential groove 1'...Central circumferential groove 2...Lag groove 2''...・・・・Connection groove 2A・・・・・・Step-in side groove wall 2B・・・・・・Kick-out side groove wall 3・・・・・・Block 4・・・・・・・・・Block

Claims (1)

[Claims] A pair of sidewalls and a tread extending between both sidewalls are connected in a toroidal manner, reinforced by a radial carcass extending over each part and a belt layer disposed between the carcass and the tread, and the tread is reinforced in a central area. and at least two circumferential grooves arranged at a predetermined interval in the axial direction in the central area, and a groove in the circumferential direction from the opening position in the pair of both side areas. In the tire, the tire has a plurality of lug grooves that intersect with the groove and extend substantially continuously in connection with a connecting groove toward the center of the central region, and a plurality of blocks are formed that are divided by the groove group. The negative ratio (groove area/total area) of the entire tread is in the range of 30 to 50%, and when the tire rotates, the inclination angle of the stepping side groove wall of the lug groove with respect to the normal line of the tire is the opposite kicking side groove wall. A pneumatic tire for heavy loads, characterized in that it is constructed such that the angle is larger than the inclination angle and the angle difference is in the range of 5 to 20 degrees.