JPH01195103A - Radial tire - Google Patents

Abstract

PURPOSE:To secure operation stability and wear-resistance and to improve performance on snow and ice by setting the pattern rigidity in the circumferential direction of a block and the pattern rigidity in the lateral direction of a tread pattern within a designated range. CONSTITUTION:When the pattern rigidity Ky in the circumferential direction of a pattern block 3 formed into a tread 2 and the pattern rigidity Kx (unit: kgf/mm) in the lateral direction of a tire are calculated according to the expression I, each rigidity is set in such a manner that Ky is 100-300, Kx is more than 150 and less than 350, and a difference Kx-Ky therebetween is Kx-Ky>50. The ratio SL/SS of the actual ground contact area SL of the tread 2 to the apparent ground contact area SS to which non-ground contact portion is added is set at 0.5-0.8. Further, the tensile elastic modulus E of the tread rubber is set at 120kgf/cm<2>-200kgf/cm<2> By this arrangement, performance on snow and ice can be improved without damaging operation stability and wear-resistance.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention improves steering stability by regulating the circumferential pattern stiffness Ky of blocks arranged in the tread portion and the tire lateral pattern stiffness Kx. The present invention relates to a radial tire that can improve running performance on snow and ice without reducing wear resistance and wear resistance.

[Conventional technology]

By planting a large number of studs on the tread surface, the tire can run on snowy roads and even icy roads.
Studded tires with increased friction against snowy and icy road surfaces are known. However, such studded tires have a problem in that when there is no snowfall, the studs scrape the road surface and the dust from the studs scrapes the road surface, causing great damage to the road surface.

[Problem to be solved by the invention]

In order to eliminate the above-mentioned problems, so-called studless tires that do not have stands installed have appeared, but these tires mainly have low rigidity in the circumferential direction of the block, such as improving the low-temperature characteristics of the tread rubber and changing the trend pattern. Although the coefficient of friction was increased by doing so, the blocks tend to wear unevenly and durability cannot be expected.

Furthermore, attempts were made to a)) increase the groove area relative to the land area of the red section, and b) increase the siping, but in this method, the block was multi-eared in both the lateral and circumferential directions. The stiffness decreases, and although the on-ice performance improves due to this decrease, there is a problem that the handling stability and the wear resistance of the block are inferior.

As a result of various analyzes of the shapes of conventionally used block patterns, the inventor found that: a) In conventional studless tires, the stiffness of the block pattern in the lateral direction and the stiffness in the circumferential direction of the tire are the same as the stiffness value. This block pattern is insufficient to improve performance on snow and ice.

(g) Also, when calculating the rigidity value of the block pattern, it is necessary to take into account the decrease in rigidity caused by the siping interposed on the surface of the block. (c) Also, the tread portion 2 deforms elastically when it makes contact with the ground. By this,
For example, an oval contact area S with the long axis in the circumferential direction as shown by the solid line in FIG. It was found that there was a significant influence.

Therefore, by using the basic mechanical formula regarding stiffness and adding the above conditions to the basic formula, it is possible to calculate the stiffness value using the formula even if the tread has a block pattern with a complex shape. They discovered this.

The present invention is intended to improve the performance of tires by calculating and limiting pattern stiffness. The aim is to provide radial tires that can improve performance.

[Means to solve the problem]

The present invention has a tire circumferential direction pattern stiffness Kykgf/m defined by the following formula for each block arranged in the tread part.
a+, tire lateral pattern stiffness Ky kgf/- is a radial tire in the following relationship.

Here 100<Ky<300 150≦Kx≦350 Kx-Ky>50 n: Number of blocks in the ground area.

h Niblock height E Nidred part rubber tensile modulus G: Shear modulus (=E/3) Ixy: Block cross-sectional moment of inertia with respect to the tire lateral direction Iyk: Block cross-sectional moment of inertia with respect to the circumferential direction Cross-sectional area Wll Maximum block width l in the direction perpendicular to the tangential force: Projected length 11 of the siping 6 in the direction perpendicular to the tangential force: Depth of the siping.

The tread portion 2 has a ratio SL/SS of the actual ground contact area @SL of the portion of the tread portion 3 in contact with the ground to the apparent ground contact area SS including the portion not in contact with the ground, which is greater than 0.5 and 0. .8, and the tread portion 2 has a tensile modulus E of greater than 120 kgf/cj and 200 kg
It is made of rubber smaller than f/cni.

[Effect]

The radial tire configured as described above can improve running performance on ice without deteriorating longitudinal stability and wear resistance compared to conventional tires, and it is possible to improve running performance on ice using an actual vehicle. This can be determined in advance based on the results of numerical calculations prior to testing.

〔Example〕

An embodiment of the present invention will be described below based on the drawings.

In FIG. 1, the radial tire 1 of the present invention has two main grooves 11A and II along the circumferential direction of the tire in the tread portion 2.
A plurality of blocks 3 are provided between the main grooves 11A and IIB, between the main groove 11A and one tread end B1, and between the main groove 11B and the other tread end B2.
A first block group 12A, a second block group 12B1, and a third block group 12C are formed by arranging .-- in the circumferential direction of the tire.

The first block group 12A is divided into two block rows 13A, 13B by a sub-groove 14 that passes through the middle position of the main grooves 11A, 11B and is bent in a zigzag shape, and intersects with the main grooves 11A, IIB. Each of the block rows 13A, 1
Blocks 3A, 3B, and 3B with the same shape and size as 3B.
.--. are formed respectively. In this embodiment, the blocks 3A and 3B have the same shape and are arranged with their front and back directions reversed.

In the second block group 12B, a plurality of blocks 3C-. The block group 12C is also the second block group 12B.
Similarly, blocks 3D divided by horizontal grooves 16 are formed. In this example, block 3C and block 3D are
They have the same shape with the front and back facing in opposite directions.

Further, a plurality of sipes 6- extending in the tire radial direction are formed on the surface of each block 3A, 3B, 3C, and 3D.

In this way, the tread portion 2 has a large number of independent blocks 3A..., 3B-..., 3C..., 3D...
... (generally referred to as block 3) is formed.

Next, pattern rigidity will be explained.

(A) First, check the rigidity of the single block 3.
Do 4. Assuming that the block 3 is a cantilever beam with one end fixed as shown in FIG. 2, the rigidity of the beam due to bending and shearing is expressed by the following basic equation.

At uni KP niblock rigidity F: Ground surface linear force yniblock displacement h Ni block height E Rubber tensile modulus of red part G: Shear modulus (=E/3) I Niblock second moment of area Ak Niblock cross-sectional area It is.

However, actual blocks have complex shapes, and the shape of each block is calculated using a nucleophilic bracket coordinate transformation formula, and the stiffness Kpx in the tire lateral direction and the stiffness Kp'l in the circumferential direction of a single block are calculated respectively. seek.

Here, lxk: Moment of inertia of the block section relative to the tire lateral direction Iyk: Moment of inertia of the block section relative to the circumferential direction.

For equations (2) and (3), experimental apparatus 2 shown in Fig. 3 is used.
0 was used to determine the relationship between the amount of deformation y of the test block 21 and the tangential force F required for the deformation.

In addition, during the experiment, the test block 21 was placed on a movable trolley 22, and the top surface of the block was pressed with a pressing tool 23.
The lower end of the test block 21 was moved by pressing it against the truck 22 using the hydraulic cylinder 24. Note that the tangential force F and the amount of deformation y were detected by a load cell 25 and a differential transformer 26 provided on both sides of the truck 22.

Comparing the experimental values obtained in the above experiment with the calculated values according to the formula (1), the results are as shown in FIG. 4 (the value is on the line 45@), confirming the validity of the formula (1).

(B) On the other hand, for example, block 3 as shown in FIG.
If sipes 6 are present on the surface of the block, the sipes 6 reduce the block rigidity. Therefore, the above equations (2) and (3) need to be corrected for the influence of siping 6.

In order to find this correction value, using the same experimental apparatus 20 shown in FIG.
Through similar operations, it was confirmed that the rigidity of the block decreased when the siping 29 was provided.

Figure 5 shows the ratio of the block stiffness Kp with siping to the block stiffness Kp without siping, that is, the rate of decrease in block stiffness due to siping = K' p/Kp
This shows the measurement results when the siping depth hs was changed in three stages.If this experimental result is further organized by the siping depth hs, as shown in the graph of Fig. 6, (in l-) i
It was found that 7w and h s / h change linearly.

If we derive the experimental formula for the stiffness reduction rate of the block from the above experimental results, then -1--(0,233X-A-0, (Foundation)--
・・・−・(4) K: Decrease in rigidity of block due to siping, Wh:
Maximum block width 2 in the direction perpendicular to the tangential force: Projected length of the siping in the direction perpendicular to the tangential force, : Depth of the siping is obtained.

(C) Therefore, the rigidity in the circumferential direction in the lateral direction of the tire is determined by equations (2), (3), and (4), taking into account the influence of the siping of the block.・−・−(6) becomes.

(D) Next, the pattern rigidity is obtained by calculating the sum of the rigidities of each block 3 (indicated by a solid line in FIG. 1) within the ground contact area S.

That is, in the tire lateral direction, −・−・−−−−−・・・・・(7) Also, in the circumferential direction, Ky=Σ′, 8 ・・−−−・・−・・−・- (8) In this way, the pattern rigidity of the block in the tire lateral direction and the circumferential direction can be defined by equations (7) and (8).

The rigidity of each block located at the periphery of the ground contact region S is calculated as a block having the size of the portion that truly contacts the ground, excluding the portion located in the non-ground contact portion.

In the present invention, the tread portion 2 in the radial tire
The pattern rigidity of the block meters is set within the following range.

b) Circumferential pattern stiffness K)l is 100kgf/
The tire lateral pattern stiffness Kx is 350kgf.
/Peng is smaller than C) Circumferential pattern stiffness Ky is 50 kgf/I from tire lateral pattern stiffness Kx! It is set to a range of less than the value obtained by subtracting In.

Note that the pattern rigidity in the circumferential direction K)! For reference, the range of each numerical limitation of pattern stiffness Kx in the tire lateral direction is shown in a diagram as shown in FIG.

If the pattern stiffness K)+ in the circumferential direction is less than 100 kgf/mm, the uneven wear of the blocks during road running will be large and the durability of the tire will be significantly reduced. Furthermore, if the pattern stiffness Kx in the tire lateral direction exceeds 350 kgf/peng, the coefficient of friction on snow becomes small and the performance on snow decreases.

Furthermore, if the pattern stiffness Ky in the circumferential direction becomes larger than the value obtained by subtracting 350 kgf/m from the pattern stiffness Kx in the lateral direction of the tire, the steering stability during road running is impaired.

Therefore, by regulating the pattern rigidity Ky in the circumferential direction and the pattern rigidity Kx in the tire lateral direction as described above,
It is possible to form a block pattern that can improve performance on snow and ice while maintaining steering stability and durability.

In addition, the tread portion 2 has, in the portion where the tread portion 2 contacts the ground, that is, the ground contact area S, the actual ground contact area SL of the blocks 3 . . . The ratio S L to the apparent ground contact area ss becomes
/S S is preferably set to be greater than 0.5 and less than 0°8. If the SL/SS ratio is less than 0.5, wear resistance, especially uneven wear, will be significantly reduced, and if the SL/SS ratio is more than 0.8, the space between the blocks will become narrow, leading to problems such as snow chewing on snow. occurs, and performance on snow deteriorates.

Furthermore, the tensile modulus E of the tread portion 2 is 120 kgf/c.
s! If it is less than 200kgf10, the durability will be reduced as the block 3 will be crushed. If it exceeds this, the frictional force of the rubber adhesion decreases and the performance on snow and ice deteriorates.

Therefore, it is desirable that the tensile modulus E be in the range of 120 to 200 kg/c.

The radial tire of the present invention can be formed in various patterns other than the block pattern shown in FIG. 1, as long as the pattern rigidity of the blocks is within the above range.

[Comparative test]

A tire of tire size 165R3/BP-PW794B having a block pattern shown in FIG. 1 was manufactured as a prototype, and a performance test was conducted.

Note that a test was also conducted on a conventional type with a different block pattern shape, and compared with the example.

The comparison results are shown in Table 1.

〔Effect of the invention〕

The radial tire of the present invention has numerically regulated pattern rigidity in the circumferential direction and pattern rigidity in the lateral direction of the blocks arranged in the tread, so it can be used on snow without reducing handling stability and wear resistance. It can improve running performance on ice.

Furthermore, since the pattern rigidity can be calculated in advance by waiting for the completion of the prototype, the time required for prototyping and performance confirmation can be significantly reduced, which is also useful for shortening the development period and reducing costs.

[Brief explanation of the drawing]

Fig. 1 is a developed view of a tire tread surface showing one embodiment of the present invention, Fig. 2 is a perspective view showing the action of the block, Fig. 3 is a perspective view showing an outline of a device for testing block rigidity, and Fig. 4 is a perspective view showing an outline of a device for testing block rigidity.
The figure is a graph comparing calculated values and measured values of block rigidity, Figure 5.6 is a graph showing the decrease in block rigidity due to siping, and Figure 7 is a graph illustrating the region of pattern rigidity defined by the present invention. be. 2-) red section, 3--block.

Claims (3)

[Claims] (1) Pattern rigidity Kykgf/mm of each block arranged in the tread portion in the tire circumferential direction defined by the following formula,
The tire lateral pattern stiffness Kxkgf/mm is a radial tire having the following relationship. 100<Ky<300 150≦Kx≦350 Kx-Ky>50 Here ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ n: Number of blocks in the ground area h: Block height E : Rubber tensile elastic modulus of tread portion G: Shear elastic modulus (=E/3) Ixk: Block cross-sectional moment of inertia in the tire lateral direction Ixk: Block cross-sectional moment of inertia in the circumferential direction Ak: Block cross-sectional area Wk: Tangential force Maximum plastic width l in the direction perpendicular to the tangential force: Projected length h_s of the siving in the direction perpendicular to the tangential force: Depth of the siving. (2) The tread portion has a ratio SL of the actual ground contact area SL of the portion where the tread portion contacts the ground and the apparent ground contact area SS which is the actual ground area SL plus the portion not in contact with the ground.
The radial tire according to claim 1, characterized in that /SS is larger than 0.5 and smaller than 0.8. (3) The tread portion has a rubber tensile modulus E of 120k.
Claim 1 or 2, characterized in that it is made of rubber having a gf/cm^2 greater than 200 kgf/cm^2,
Radial tires listed.