JP3373900B2 - Pneumatic tire - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire which, while traveling on ice and snowy roads, retains its adhesive force and maintains its running performance on snow, and at the same time has improved braking performance on ice.

[0002]

2. Description of the Related Art Spike tires are known as tires that can effectively run on ice. However, this product causes road surface damage such as scraping off the road surface with spikes when traveling on general roads, and therefore, in recent years, the emergence of products that replace spiked tires is desired.

In response to the above demand, so-called studless tires without spikes have also appeared, but these tires are assumed to be used under low internal pressure and low load for passenger cars, for example. , The total length of the siping s is large, and the tread portion is formed of a soft rubber material, and the adhesive friction force F between the ice surface i and the tread upper surface 2A (see FIG. 5).
(Shown in FIG. 6) and the road surface digging frictional force K (shown in FIG. 6) to maintain the running performance on ice.

[0004]

However, when such a tire is used for a bus, a truck, a light truck, etc., it is usually used under a higher internal pressure and a higher load than those of passenger cars. Moreover, since the weight of the vehicle is large and the inertial force is large, the coefficient of sliding friction on the ice surface is reduced, and braking on the ice is significantly insufficient.

In order to improve the braking performance on ice, low-hardness rubber is used as the tread rubber to enhance the adhesive force and improve the lateral edge component of siping, thereby improving the drainage property and the road surface frictional force. Is known to be effective.

However, the above-mentioned measures that exceed the limit result in a lack of pattern rigidity, which naturally has a limit. Furthermore, the braking performance on ice and the running performance on snow cannot be achieved at the same time, and a tire that emphasizes braking performance on ice has a problem that the pattern rigidity is insufficient on snow and the snow running function cannot be obtained.

In the block provided in the tread portion, the inventor covers the wall surface facing forward and backward in the rotation direction with a reinforcing layer made of hard rubber, while increasing the edge component of siping provided on the upper surface of the block to a high value. It has been found that the regulation can enhance braking on ice while maintaining snow running performance.

An object of the present invention is to provide a pneumatic tire capable of satisfying both snow running performance and ice dynamic braking performance.

[0009]

The present invention provides a tread portion.
A pneumatic tire having a block pattern in which blocks rising from the bottom surface of the groove are arranged by providing a circumferential groove and a lateral groove , wherein the block is a tire rotation method.
A small width that extends close to the front wall and extends substantially parallel to the lateral groove.
The horizontal sub-grooves of the
It is divided into a lock piece and a later block piece ,
The block has a JIS A hardness of 40 to 6 at 0 ° C.
A base made of rubber of 5 degrees and standing up from the bottom of the groove, a front wall surface (7A) facing the front and rear of the tire rotation direction of this base ,
Before facing the wall surface (7B) and the rotation direction of the lateral sub-groove
The rubber thickness for covering the sub-wall surface (7a) and the sub-wall surface (7b) facing backward is 0.5 to 3.0 mm and the JIS A hardness is 80 to 9.
It is composed of a reinforcing layer made of rubber of 5 degrees, is provided with siping on the upper surface of the tread of the base, and is a length (mm) projected on the meridian plane of the tire per unit area (mm ² ) of the upper surface of the tread. and sipes and 0.05 to 0.20 mm / mm ² to the length ratio is, moreover fitted with a tire in a normal rim and suddenly from a speed of 60 km / H on ice road surface in a normal state obtained by adding a normal internal pressure and normal load in braking the braking state, the lateral sub-groove, the block after the
Set the groove width WG1 where one piece is held by the previous block piece,
The front wall of the block piece after the normal state and the braking state
The pneumatic tire is characterized in that the angle difference between the surface (7A) and the front sub wall surface (7a) with respect to the radial line is 2 to 3 degrees.

[0010]

The front and rear wall surfaces of the base of the block are provided with reinforcing layers made of rubber having a rubber thickness of 0.5 to 3.0 mm and a JISA hardness of 80 to 95 degrees. By providing such a reinforcing layer, the block has increased pattern rigidity in the tire rotation direction, and the braking performance on ice is increased. Moreover, the base of the block is formed of rubber having a low hardness and retains its adhesiveness, so that the grip performance is maintained during traveling on snow and on ice.

Further, the siping length ratio, which is the length (mm) of the siping per unit area (mm2) projected on the tire ^meridian on the upper surface of the tread, is increased to 0.05 to 0.20 mm / cm2 to increase the siping density. There is. This improves drainage and enhances the effect of moat digging. As a result, the drainage performance is improved and the digging effect is enhanced to enhance the braking performance on ice.

Moreover, the angle difference between the normal state of the tire and the sudden braking state in which the vehicle is suddenly braked at a speed of 60 km / H on the icy road surface in this regular state with respect to the tire radius line on the rear wall surface of the block is 2 to 3 degrees. Therefore, the tilt of the block during braking can be maintained in an optimum state, and the above-described braking performance on ice can be further improved and stabilized.

As described above, according to the present invention, by organically combining and integrating the above-mentioned components, it is possible to improve the braking performance on ice while maintaining various traveling performances on ice and snow.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 to 4, the pneumatic tire 1 has a tread portion 2 in a block pattern in which a plurality of blocks 4 that stand up from the groove bottom surface 3 are arranged.

The pneumatic tire 1 has the tread portion 2
A pair of sidewall portions 13 and 13 extending inward from the both ends of the tire in the radial direction of the tire and a bead portion 14 to which the rim R is fitted are provided inward of the sidewall portions 13 in the radial direction.

Further, a carcass 16 which folds around the bead core 15 of the bead portion 14 from the tread portion 2 through the sidewall portion 13 and a belt which is arranged inside the tread portion 2 and outside the carcass 16 in the tire radial direction. And layer 17.

The carcass 16 is a so-called radial or semi-radial directional array in which the carcass cords are arranged at an angle of 60 to 90 degrees with respect to the equator C of the tire in the present embodiment, and a steel cord as the carcass cord. In addition, nylon, polyester, rayon and other fiber cords are used.

The belt layer 17 is composed of two belt plies 17A, 17A in which the belt cords are arranged at an angle of 0 to 30 degrees with respect to the tire equator. In this embodiment, each belt ply 17A is a belt cord. Are stacked in different directions so that the plies cross each other. As the belt cord, an organic fiber cord such as nylon, polyester, rayon or a metal cord such as steel is used as in the carcass 16.

In this embodiment, the block 4 connects a pair of circumferential grooves 9 and 9 extending in the circumferential direction on both sides of the tire equator C and the circumferential grooves 9 and 9 as shown in FIG. Surrounded by a plurality of central lateral grooves 10 and surrounded by a plurality of central blocks 4A arranged in the circumferential direction, and surrounded by a plurality of lateral grooves 11 connecting the circumferential groove 9 and the tread edge E. The blocks 4B on the plurality of sides arranged in the circumferential direction are included.

In this example, the circumferential groove 9 is linearly wound, and both the central and side lateral grooves 10 and 11 extend in a direction substantially parallel to the tire axis. The circumferential groove 9 and the lateral grooves 10 and 11 have a groove depth HG of 0.07 to 0.09 times the tread width WT, and a groove width WG of 0.02 to 0.02 times the tread width WT. It is preferably 0.05 times. In this embodiment, a small vertical groove 20 extending in the circumferential direction near the tread edge E is provided on the side block 4B.
The vertical small grooves 20 prevent lateral slippage of the tire.

The central block 4A is close to the wall surface 7A of the tire rotation direction front, lateral minor groove 12 of small width traverses extending substantially parallel to the central lateral grooves 10, the center of this horizontal auxiliary groove 12 The block 4A is divided into a front block piece 21 and a rear block piece 22. Note that in this embodiment,
As shown in Fig. 2, the side block 4B also has the same shape.
Is made.

In this example, in the block 4A, the inclination .theta.1 of the front wall surface 7A with respect to the tire radius line is 20 to 45.
The inclination θ2 of the rear wall surface 7B with respect to the tire radius line is set in the range of −10 to 10 degrees. Further, the groove width WG1 of the lateral sub-groove 12 can be appropriately selected within the range of 1.0 to 3.0 mm, and the groove depth thereof is substantially equal to the groove depth HG of the circumferential groove 9. It is preferable.

The central block 4A is formed by a base portion 5 standing upright from the groove bottom surface 3 and a reinforcing layer 6 which covers the front wall surface 7A and the rear wall surface 7B of the base portion 5, respectively.

The base 5 is made of a relatively soft rubber having a JISA hardness of 40 to 65 degrees at a temperature of 0 ° C., while the reinforcing layer 6 has a rubber thickness T of 0.5 to 0.3.
It is formed by using a rubber having a mm and a JIS A hardness of 80 to 95 degrees. Also, it faces forward in the direction of rotation of the lateral sub-groove 12.
The sub-wall surface 7a and the sub-wall surface 7b, which faces rearward, are also covered with the reinforcing layer 6 having the above-described configuration.

If the hardness of the base portion 5 is less than 40 degrees, the block rigidity becomes low and the snow running performance deteriorates. If the hardness exceeds 65 degrees, the reinforcing layers 6 and 6 are provided, so that the block rigidity of the entire block 4A is reduced. As a result, the adhesion effect on the ice surface I becomes small and the braking performance on ice is poor.

Further, the rubber thickness T of the reinforcing layer 6 is 0.5 mm.
When the rubber hardness is less than 80 degrees or the rubber hardness is less than 80 degrees, the reinforcing effect of the block 7B is small and the snow running performance is deteriorated. Conversely, the rubber thickness T exceeds 3 mm or the rubber hardness is 95
Beyond that, the overall rigidity of the block 4A increases,
The tackiness on the ice surface I is poor, and the braking performance on ice is reduced.

A plurality of sipes 8 are provided on the tread upper surface 2A of the base 5 in the central block 4A.

In the present embodiment, the siping 8 is arranged on the rear block piece 22, connecting the circumferential grooves 9 on both sides, and arranged substantially parallel to the tire axis, and has a siping width of 0.
2 to 2.0 mm, the siping depth of the circumferential groove 9 is 0.3 to
It is 0.7 times.

Further, the distribution density of these sipes 8 is regulated as follows. It is arranged on the tread upper surface 2A of the central block 4A. The lengths of the sipings 8 projected onto the tire meridian planes are calculated one by one, and ^the sum of these lengths is divided by the tread upper surface 2A, in other words, the siping per unit area (mm2) of the tread upper surface 2A. length projected in the tire meridian plane of the 8 (mm), and the defines this value as Saipi ⁱⁿ g length ratio. This siping length ratio is regulated within the range of 0.05 to 0.20 mm / mm 2.

The siping length ratio is 0.05 mm / mm2
The road surface digging ^contact stiffness frictional force is poor 6 below,
0.20mm / mm while braking ability on ice road is insufficient
If it exceeds 2, the block rigidity will be low and the snowability will be poor.

Further, the block 4A also regulates the fall of the block during braking.

The pneumatic tire 1 is mounted on the regular rim R, and the regular state (state of FIG. 3) in which the regular internal pressure and the regular load determined for the tire are applied, and the ice-state road surface in this regular state, that is, In the braking state where the vehicle is suddenly braked from the speed of 60 km / H on the ice surface I (state of FIG. 4), the inclination angle of the rear block piece 22 with respect to the circumferential direction, that is, the radial line of the front wall surface 7 and the rear wall surface 7B is measured. The angle difference α is in the range of 2 to 3 degrees.

In order to comply with such regulation of the angle difference α,
Since the block 4A is provided with the lateral sub-groove 12 extending in the tire axial direction and having a small width, the rear block piece 22 is held by the front block piece 21 at the time of sudden braking, so that The inclination angle of the block piece 22 can be adjusted by the dimension of the groove width WG1 of the lateral sub-groove 12, as shown in FIG. By thus restricting the groove width WG1 size for each type of tire, it is possible to adjust the angle difference α to the radial line of the rear wall surface 7B to the most preferable value of 2 to 3 degrees. Moreover, the lateral sub-groove 12
By providing the above, the angle difference α can be made constant during braking on the ice I and during braking on snow, and the braking characteristic value can be stabilized, so that the steering stability can be further enhanced. .

In the pneumatic tire 1 of the present embodiment, the rear block piece 22 is located on the front side in the tire rotation direction, as shown by the dashed line arrow in FIG. By installing,
It is also possible to use the method in which the driving force, that is, the stabilization of the tire grip force is more important than the braking ability.

The side of the block 4B, the center is the block 4A substantially similarly formed, ^have a horizontal block pieces 21 before being divided by the sub grooves 12, after the block piece 22, and after the block piece 22 Has a siping length ratio of 0.05
A plurality of sipes 8 ... 0.20 mm / mm2 are provided.

The block may be formed in a trapezoidal shape or another polygonal shape other than a square shape, and the siping direction may be inclined with respect to the tire axial direction. Furthermore, in the tread portion, at a position other than the ground plane that grounds in the normal state,
It is also possible to form ribs in which ribs are arranged in place of blocks or block patterns, and the present invention can be modified into various aspects.

[0037]

SPECIFIC EXAMPLES Tires (Examples 1 to 3) having a tire size of 215SR15, having the configuration shown in FIGS. 1 and 2 and having the specifications shown in Table 1 were prototyped and their performances were tested. The conventional tires (Conventional Examples 1 to 7) having no reinforcing layer were also tested and their performances were compared.

The test conditions are as follows. a) Braking performance test on ice Attach a speedometer, braking distance measuring device and test tire to the test vehicle, run on the test road surface formed by the ice disk at a constant speed of 60 km / H , and brake suddenly with a four-wheel lock The braking distance until the vehicle stopped was measured, and the friction coefficient was calculated from each value of the total weight, speed and braking distance of the test vehicle, and displayed as an index with Conventional Example 1 as 100. The larger the value, the higher the friction coefficient and the better.

B) On-snow braking performance test A snowy road surface was run at a constant speed of 60 km / H, and braking and evaluation were carried out in accordance with the above-mentioned on-ice braking performance test. The test results are shown in Table 1.

[0040]

[Table 1]

As a result of the test, it was confirmed that the performance of the example was compatible with the snow running performance and the ice braking performance.

[0042]

As described above, the pneumatic tire of the present invention is provided with the above-mentioned constitution, and can improve the braking performance on ice while maintaining various traveling performance on ice and snow. In addition, it can be suitably used as a tire for ice and snow roads used in heavy-duty vehicles such as small trucks, buses, and trucks.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a developed plan view showing the tread pattern.

FIG. 3 is a sectional view taken along line XX.

FIG. 4 is a sectional view showing the operation.

FIG. 5 is a diagram showing grounding when the block is running.

FIG. 6 is a diagram showing grounding when the block is running.

[Explanation of symbols]

2 tread section 2A tread top 3 groove bottom 4A, 4B block 5 base 6 Reinforcement layer Wall in front of 7A Wall after 7B 8 siping R rim Rubber thickness of T reinforcement layer

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B60C 1/00 B60C 11/00-11/24

Claims (2)

(57) [Claims] 1. A tread portion is provided with a circumferential groove and a lateral groove.
According to the pneumatic tire having a block pattern in which blocks rising from the groove bottom surface are arranged, the blocks are close to the front wall surface in the tire rotation direction.
Crossing a small lateral sub-groove extending substantially parallel to the lateral groove.
Allows the front block piece in front of the rotation direction and the
The block has a JISA hardness of 40 to 6 at 0 ° C.
A base made of rubber of 5 degrees and standing up from the bottom of the groove, a front wall surface (7A) facing the front and rear of the tire rotation direction of this base ,
Before facing the wall surface (7B) and the rotation direction of the lateral sub-groove
The rubber thickness for covering the sub-wall surface (7a) and the sub-wall surface (7b) facing backward is 0.5 to 3.0 mm and the JIS A hardness is 80 to 9.
It is composed of a reinforcing layer made of rubber of 5 degrees, is provided with siping on the upper surface of the tread of the base, and the length (mm) of the siping per unit area (mm ² ) of the upper surface of the tread projected on the meridian surface of the tire. in a siping the length ratio is 0.05 to 0.20 mm / mm ^2, yet fitted with tires in a normal rim and 60 km / H on ice road surface in a normal state obtained by adding a normal internal pressure and normal load
In the braking state where the vehicle is suddenly braked from the speed of
, The latter block piece is held by the front block piece.
After setting the groove width WG1 to the normal state and the braking state,
The wall surface (7A) in front of the block piece and the sub-wall surface (7A) in front of
A pneumatic tire characterized by having an angle difference of 2 to 3 degrees with respect to a radial line with respect to a) . 2. The block is of the front wall (7A)
The inclination θ1 with respect to the tire radius line is 20 to 45 degrees, and the rear wall
The inclination θ2 of the surface (7B) with respect to the tire radius line is −10.
The range of 10 degrees is set, and the range of 1 is set.
Pneumatic tire.