JPS5816906A - High-pressure pneumatic radial tire for passenger car - Google Patents

Abstract

PURPOSE:To reduce the resistance to the rolling of a tire without deteriorating the feeling of ride, by making a lower tread layer of rubber of prescribed properties and placing the layer outside a belt layer surrounding a carcass. CONSTITUTION:At least one layer of carcass 4, in which a ply is curved back around a bead core 6 outwards in the radial direction of a tire, and at least two layers of belts 3, in which high-elasticity-modulus cords crossed with each other at a relatively small angle to the circumferential center line of the tire around the carcass 4 are coated with rubber, are provided to reinforce the body of the tire. A lower tread layer 2 covering the belts 3 and an upper tread layer 1 located on the lower tread layer are provided outside the belts. The lower tread layer 2 is made of rubber, the elasticity modulus of which at 25% elongation is 2.0- 8.0kg/cm<2> and the dynamic elasticity modulus of which is 8.2-33.0kg/cm<2>.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high internal force pneumatic tire for passenger cars, particularly 26.2 to 3.0 ky/cr! An attempt was made to realize an advantageous improvement in rolling resistance by using an inflated vehicle with a relatively high internal pressure, without the drawbacks such as deterioration of shooting and riding comfort, and reduction of restoring torque during cornering. It is something to do.

At a time when energy conservation is being called for, research into reducing the rolling resistance of tires has been strongly promoted in order to reduce the fuel consumption of automobiles. It is effective to reduce the internal friction loss caused by the deformation of the inner tire.For example, in order to reduce the internal friction loss of the tread rubber and reduce the rolling resistance, the loss tangent ( ta
It is common to deal with this by using a rubber compound that lowers the loss modulus (()) while increasing the rebound modulus (Res l I 1ence 1).However, in this case, the rolling resistance is improved. Undesirably, depending on the degree of
This type of tire has the drawback of deteriorating its wet performance, which is one of the important characteristics, and this relationship is as shown in Figure 7 using the tread rubber's impact elasticity as an index. Therefore, the above measures are Unless other measures are taken to prevent the deterioration of wet performance, a dramatic improvement in rolling resistance can be expected, and there is no particularly effective means for maintaining wet performance. It is not possible.

As a second-best measure, attempts have been made to apply a rubber compound that reduces internal friction, especially to the sidewalls, in the same way as described above regarding the characteristics of tread rubber, but in reality, the rolling resistance is around the 3rd factor. Not only is it useful for improving only , or less than that, but it also has the disadvantage that the damping characteristics of the tire for imaging deteriorate, which is accompanied by disadvantages affecting the important ride comfort performance of the tire.

In addition, reducing the weight of the tire by changing the carcass from a two-layer structure to a seven-layer structure, or narrowing the belt width in particular reduces rolling resistance, so it is unavoidable that there is a limit to its effectiveness.

By the way, in addition to the above-mentioned rubber compounding that reduces internal friction and weight reduction of tires, we are also considering a method to improve rolling resistance by increasing the internal pressure of the tire and reducing the amount of deformation when a certain load is applied. It is being However, in this case, as the amount of deformation decreases, the contact area of the tire also decreases, resulting in a decrease in frictional resistance on dry and wet road surfaces, making it difficult to use a tread rubber compound with low internal friction. It becomes. In addition, the reduction in deformation due to high internal pressure does not fully demonstrate the effect of the rubber compounding that lowers the internal friction of the sidewall rubber.In particular, it is especially important to combine the above-mentioned eaves lighting method to increase the safety factor. It is clear that it is difficult to implement it because it reduces the
Not only is it not possible to improve the rolling resistance of tires, but in addition, high internal pressure increases the impact force when the tire hits a protrusion on the approximate surface, worsening the vibration comfort Tfl'. Moreover, a slip angle is added to the tire'j1. This also causes a reduction in the restoring torque required when turning a corner, resulting in a deterioration of steering stability, etc., making it difficult to put it into practical use.

The present inventors have fundamentally investigated the deformation state of tires with high internal pressure, and have improved the rolling resistance suitable for such tires without actually deteriorating the vibration comfort performance or reducing the restoring torque. In other words, this invention has found that e++ J of each constituent part of a tire with high internal pressure
+rq= This is derived from original research and development that clarified how the ratio contributing to loss changes compared to tires with normal internal pressure.

Now, the deformation of a tire while driving occurs concentratedly in the contact area of the tire and its vicinity, but there is also deformation directly below the rotation axis of the tire, and deformation in the vicinity where the tire enters and leaves the contact area. The aspect is different, and it is especially important to understand these individually in order to reduce rolling resistance derived from resistance to these deformations. As shown in Table 1 below, the contribution rate to the internal friction loss of each part of the tire is / , 7 kg/c-
Compared to the case of
~! , 2. selected as a representative example of Okg/crl. ! ;kg/
When it comes to enemies, you'll find things that are vastly different. The tread part C, the part extending between the tread ends or shoulders, the bead part which is restrained and fixed to the flange of the wheel rim, and the sidewall part are:
Refers to the remaining portion between the tread portion and the beat portion.

According to Table 1, in the case of high internal pressure tires, the tread portion VC is lower near the tire axis directly below compared to normal internal pressure tires.
On the other hand, the above contribution rate increases and the contribution rate from the sidewall part to the bead part decreases, but on the other hand, the approach rate at the sidewall part is large in the vicinity of entering and leaving the contact area. known. Therefore, it can be said that reducing the internal friction loss in areas where this contribution is large is the most suitable method for improving the rolling resistance of tires with high internal pressure.

First of all, the inventors further investigated the internal friction loss of the tread near the rotation axis of the tire, and found that the deformation pattern is different in the part near the tread surface and in the part adjacent to the belt layer. I found something different 0
In other words, in the former, deformation is determined by the force transmitted between the tire and the road surface, whereas in the latter, deformation is controlled by the deformation received by the belt layer being transmitted as shear strain. 0 Focusing on the latter deformation and considering that the deformation that the belt layer undergoes is largely determined by the tension or rigidity of the belt layer, the shear strain that the tread rubber adjacent to the belt layer undergoes is It is understood that it is almost constant regardless of physical properties. Based on this new knowledge of constant distortion,
Originally, the internal friction loss EL due to shear strain of the tread rubber adjacent to the belt layer is expressed as the following equation (1), so the loss tangent and loss modulus represented by tan δ in equation (1) , or rather, rather than changing the rebound modulus, as a new perspective on the physical properties of tread rubber, by changing the modulus G in the static case and the dynamic modulus (ν in the dynamic case) Knowledge 75 has been obtained that rolling resistance can be improved by reducing internal friction loss.

This finding shows that in a tire that has a tread rubber f, 21-12, arranged so as to completely cover the belt layer, and an undertread layer on the sidebar, the rubber of the undertread layer has a modulus and a dynamic elastic modulus. By selecting from a low physical property range: l:I7. 〇Actually, the physical properties of the rubber of the undertread layer can be changed to 2! Modulus at extension (
2 below! % Mod) and under conditions of high internal pressure by changing the dynamic modulus (tire internal pressure = , 2,
Figures 2a, 2b show the results of measuring the rolling resistance (j kg/crd). From this, the 2% Mod of the undertread layer is 2.0 +cy/crl ~r
, Okg/cr! l and the dynamic elastic modulus is ♂, 2
kg/c〃t~33. In the case of okq/enemy, it is possible to advantageously reduce the rolling resistance to an index of 23 to zk! It has come.

Note that the dynamic elastic modulus is a value measured using a mechanical spectrometer (manufactured by Rheometrics) under the conditions of z, dynamic shear strain amplitude/%.

By the way, as mentioned earlier, when the internal pressure of a tire is increased, the amount of deformation of the tire when a certain load is applied decreases, and the contact area of the tire also decreases at the same time. It is also clear that the ground pressure of the tire increases accordingly. As a result, a larger compressive strain acts on the tread rubber than under normal internal pressure, and this also acts on the undertread layer as if superimposed on the shear strain to which the deformation of the belt layer is transmitted.

Therefore, as mentioned above, the undertread layer, 2J
od and dynamic elastic modulus from low physical properties increases the amount of compressive deformation of the tread, which in turn weakens the impact force when the tire hits a protrusion on the road surface, improving vibration riding comfort due to high internal pressure. 4. It also means that it can be used as a side dish.

What is more convenient is the λ layer structure f7? t, 2196 Mod of the tread rubber, and the difference in dynamic elastic modulus, the uneven deformation during ground contact applied to the radially outer tread rubber is dispersed in the undertread layer, resulting in uniform contact between the tire and the road surface. is obtained. This is especially effective when a slip angle is added to the tire and when turning around a corner, and even if the tire has a high internal pressure, the restoring torque does not actually decrease. Focusing on the state of deformation of the sidewall portion, which makes a large contribution to internal friction loss in the vicinity of entering and exiting the ground contact surface, there are two types of deformation: bending deformation that occurs out of the plane and shear deformation that occurs in the plane. Although shear deformation is small directly below the tire axis, it is particularly important near the area where the tire enters and leaves the contact patch, accounting for 71% of the total deformation of the sidewall. Therefore, as a result of focusing on the strain caused by this shear deformation, that is, the shear strain, the inventors obtained the following important knowledge. .

In other words, the distribution of shear strain in the thickness direction of the sidewall is maximum near the carcass ply cord, and the shear deformation of the sidewall is almost determined by the tension of the carcass ply. The shear strain of rubber depends on its physical properties, and it is said that it undergoes approximately constant strain.

Based on this knowledge of constant strain, we can use equation (1), which shows the internal friction loss due to shear strain as shown above, to calculate the internal friction loss due to shear strain. They came to the knowledge that the rolling resistance can be improved by lowering the mother modulus G in the static case and the dynamic elastic modulus G' in the dynamic case.

This finding is based on the above-mentioned characteristic that the shear strain is greatest around the carcass ply+:AY1. By applying it to the covering rubber of the carcass cord, that is, the carcass coating rubber, the effectiveness of i. can be demonstrated. Actually, the carcass coating rubber is small
By changing od, under Takayama-cho conditions (internal pressure = ko, jkf/
Figures 3a and 3 show the results of measuring all changes in rolling resistance with
Shown in Figure b. According to this figure, what is the carcass coating rubber? t qA Mod is approximately according to the prior art,
J 'Icy/eta, the rolling resistance is ioo
When 23% Mod is especially A, OIc
y/cd~, z, o kg/cl, and the dynamic elastic modulus is J', 2~. By setting the range of 2θ, IA kg/ra, the rolling resistance of tires with high internal pressure can be reduced to 3~r.
It was confirmed that it could be improved to reach 3.

The dynamic elastic modulus is the result of measurement using a mechanical spectrometer (Rheometrics M) under the conditions of J'θ°C, /jHz, dynamic shear strain vibration 1] / 4.

In this way, B% Mod of carcass coating rubber.

When the dynamic elastic modulus and dynamic elastic modulus are selected from low physical property values, the vibration riding comfort and steering stability of the tire with high internal pressure are further improved.

This invention aims to advantageously improve the rolling resistance of tires subjected to high internal pressure as described above. The main idea is to select from a particularly low range of physical properties, and it is assumed that the tire will be used at a higher internal pressure than normal.

By the way, what is the internal pressure of the tires? , jkg/cl, but if the internal pressure is slightly higher than this, or if -214Mod of the top tread layer is 27%M of the undertread rubber. If compressive strain is too concentrated in the undertread rubber due to the disparity in physical properties between the chiander tread rubber and the top tread rubber, which is more than Jj times higher than d, reduce the rolling resistance improvement type. However, in such a case, consideration can be given to making the loss modulus and loss tangent of the undertread rubber lower than those of the top tread rubber to meet the purpose.

In addition to these, the present invention uses a sieve modulus cord belt to reduce the 2t % Mod and dynamic modulus of undertread rubber and carcass coating rubber, particularly under severe conditions. Although there is a concern that separation may occur due to discontinuity in rigidity, this is especially true for belt cord covering rubber, that is, 2j% Mod of belt coating rubber.
This problem can be easily solved by selecting the dynamic elastic modulus from a low range of physical properties to reduce the difference in stiffness.

Actually, the undertread rubber's 14 Mod and dynamic elastic modulus are 11 f'L6. jkri Z・i and mu,
Okg/crl, carcass coating rubber, 2
J'% MO(+) and dynamic elastic modulus of 6.
01 (y/cnl) and 20.01 (y/cnl) and 2t of belt coating rubber according to conventional practice.
% Mod and dynamic elastic modulus are each 1 skp/c
J and 19 Ly/cJ for tire A, respectively t, o yang ~ and φ〃 to 32.9! Tire B lowered to
Table 2 shows the results of a comparative study of durability against separation. Here, the case where the Jj%Mod and dynamic elastic modulus of the undertread rubber, carcass coating rubber, and belt coating rubber are equivalent to those of a conventional tire is set as 100, and the larger the index, the better.

According to this example, if the 2j % Mod and dynamic modulus of the undertread rubber and carcass coating rubber are low (-), the durability will deteriorate to an index of rO under severe conditions. , it is clear that by lowering the −j % Mo, 1 and dynamic modulus of the belt coating rubber, the drawbacks can be fully compensated for.

The fact that the reduction in rolling resistance that this invention aims at as described above is further promoted by lowering the total 2t % Mod and dynamic elastic modulus of the belt coating rubber is that the belt layer is lowered when the tire is rolling. This is knowledge derived from analysis of the deformation state, and here, deformation of the belt layer means shear deformation (interlayer shear deformation) that occurs between the belt layers of the It is particularly important that the internal friction loss is concentrated near the ends of the belt layer and increases the internal friction loss.

In other words, the strain caused by the glabellar shear deformation of the belt layer is almost uniquely determined by various quantities such as the curvature of the tire tread, the curvature of the belt layer, the angle at which the heald cord is arranged, and the width of the belt layer. Therefore, even if the physical properties of the coating rubber covering the belt cord are changed,
It is subjected to approximately constant strain, and based on the knowledge of this constant strain, it shows an internal energy loss EL. Formula (1) above is correct,
Unlike the conventional technology, there is no need to change the loss tangent, loss modulus, or rebound modulus, but rather when it is static, Mod
In the dynamic case of G1, internal friction loss can be reduced and rolling resistance can be improved by lowering G', which is the dynamic modulus of elasticity.

This improvement in rolling resistance is achieved by placing it in the tread section, which has a particularly large effect on the internal friction loss of a tire with high internal pressure, and by reducing the rolling resistance of the tire as it relates to other components. - Advantageous. Actually, the 2j modulus and dynamic elastic modulus of the coating rubber of the belt cord were changed, and the results were calculated under high internal pressure (internal pressure -λ, s kp/
The results of measuring the change in rolling resistance at c+4) are shown in Figures Hiroa and 4Lb. According to this figure, the coating rubber of the belt cord has a! The Mod in charge is/! , Ok
When the rolling resistance at g/c1zf is expressed as 100 in index display, 1.2j%Moat is "9/r11.1. d
- above, /θ, Oconnection /- or less, and the dynamic elastic modulus is 16.
It is clear that by setting the range of uO, j to IcpAvl or more, it is possible to achieve a remarkable improvement in the rolling resistance of the tire to an index of 9.2 to rt.

This dynamic elastic modulus was measured using a mechanical spectrometer (manufactured by Rheometrics) under the same conditions as described above. In addition, 5.1% Mod, is 44, Oky/c
d, dynamic elastic modulus is / l, , , 2 kg/crI
If it is less than , the belt cord layer to be arranged between / will be too soft, making it difficult to mold the tire and making it difficult to put it to practical use.

In order to confirm the specific effects of this invention, 1It77
The results of testing on tires of 2008 size are described below.

First, regarding the physical properties of the undertread layer rubber, the 2j coefficient Ma
d and dynamic modulus of elasticity are respectively li/- and 37. ≠lCv/
Reed in m and carcass coating rubber, 2j%M
od and dynamic elastic modulus are 3 yang 4 and 3 ♂ 0.2, respectively.
The internal pressure of the control tire is l(V/(i)/
, 7 kr/i and koj kg/ctd The 0 index shown in Table 3 is the result of measuring the rolling resistance under the conditions of 7 kr/i and 7 ky/cJ, and 100 indicates high internal pressure. What are the benefits of tires? :/! It can be seen that it reaches %.

Table 5. Rolling resistance measurement results (index rate → good) Next, for the rubber material t1 of the undertread layer, 2j[M
od and dynamic elastic modulus of 6. Yo Ic7/nl and
26. θgin/-, and the carcass coating rubber's modulus of J' and dynamic elasticity are A and 01cy, respectively.
/- and co0. Regarding Example 1 of the present invention, which was lowered to ≠kg/c-, the internal pressure was /, 71y/cJ and 2,
Table 4 shows the results of measuring the rolling resistance under the condition of J kg/d.
Shown below. According to this, when the internal pressure is /,7ky/-, the rolling resistance has already been improved to jJ by an index, but the addition of λ-1
The benefits of high internal pressure are further increased by 2/4, resulting in improved rolling resistance that is advantageous for tires with high internal pressure1
~ It is clear to get. The physical properties and dimensions of the tire components other than the undertread layer and carcass coating rubber were all set to the same conditions as the control tire.

Table 4. Rolling resistance measurement results (index rate → good) Furthermore, Coj%Mo of the belt coating rubber of Example 1
d and dynamic elastic modulus/j, Okg/lri and t
! 7.0 k4/l:d, while z and o respectively
Turning to Example 2 of this invention in which kf/al was lowered to 32.9' kg/-! The results of measuring the resistance are shown in Table 5. In this case, the advantage of high internal pressure is
It is clear that there is an increase in r4.

Table 5. Rolling resistance measurement results (index rate → good) Next, the Ni-control tires were mounted on a drum with protrusions along with each tire of Example 1.2! Id + rotation, and the magnitude of the force generated on the rotation axis of the tire during that time was compared to conduct a vibration riding comfort test, and the results shown in Table 6 were obtained.◎Table 6. Vibration ride comfort test results (large index → good) In other words, it is clear that the tire according to the present invention is not actually accompanied by deterioration in vibration ride comfort performance due to high internal pressure.

Table 7 also shows the results of comparing the restoring torques during cornering for similar tires.

Table 7. Restoration torque measurement results (index dog → good) In other words, it is clear that the tire according to the present invention is accompanied by a decrease in restoring torque due to high internal pressure.Finally, the high internal pressure (J, Okg /l:
+ Wow, when we compared the results of running on a drum under severe conditions of high load (JI8 load, 2oo (1) load), there was no particular difference between the tires and the control tires.

As mentioned above, according to this invention, the internal pressure is 21.2 kf.
The rolling resistance of pneumatic radial tires for passenger cars used at high internal pressures up to /crIf3, OIcy/c1ft has been improved by reducing the rolling resistance of pneumatic radial tires for passenger cars used at high internal pressures up to OIcy/c1ft, which are accompanied by deterioration of vibration riding comfort and a decrease in restoring torque during cornering, which are disadvantages of high internal pressure tires. without any
This can be advantageously reduced.

[Brief explanation of the drawing]

Figure 1 is a graph showing the contradictory tendency between the rolling resistance index and the wet performance index corresponding to the impact elasticity modulus of the tread rubber, and Figures 2a, 21) are graphs showing the contradictory tendency between the rolling resistance index and the wet performance index, which correspond to the impact elasticity modulus of the tread rubber. Graph showing the effect on rolling resistance, Part 3a
Fig. 3b, carcass coating rubber and Fig. ≠a,
Figure ≠b is a graph showing similar effects on belt coating rubber, and Figure 5 is a sectional view of a pneumatic radial tire suitable for carrying out the present invention. /...Top tread layer, Co...Undertread layer, 3...Belt, μ...Carcass layer, j...Side wall rubber, 6...Bead core. Fig.1 Fig.2a

Claims (1)

[Scope of Claims] 1. At least / in which a ply serving as a rubber coating of organic fiber cords arranged substantially within the radial plane of the tire is wound around a bead core and turned outward in the radial direction of the tire.
J layer carcass and at least two layers of belts encircling the carcass and forming a rubber coating of high modulus cords arranged crosswise to each other at a relatively small angle to the center circumference of the tire. Cooperatively operates, ko, 2~J, 0$/r
It is equipped with sidewall rubber on both sides of the carcass as a body reinforcement that can withstand the high internal pressure of TI, and the belt has a two-layer tread rubber structure consisting of an undertread layer that completely covers this and a top tread layer that overlaps this. Each pneumatic radial tire is arranged f, and the undertread layer is 2! The modulus when stretched is 2
A high internal pressure pneumatic radial tire for passenger cars characterized by having rubber physical properties of , 0-f, O1cylct&, a dynamic modulus of elasticity of 1.2 to 33, and OkLj/ct& The cord covering rubber of the belt is 1 The tire according to claim 1, having the following rubber physical properties: .2j4 elongated modulus≠, θ~/0, Okg/cri, dynamic elastic modulus 16.2~pO, t'ktllo&. 3. The tire according to claim 1 or 2, wherein the undertread layer is made of rubber having a lower loss modulus and a loss of 1 and a tangent than the top tread layer. 4. At least one layer of carcass, which is made by wrapping a braai, which is a rubber coating of organic fiber cords arranged in the substantial radial plane of the tire, in place of the bead core and folding it outward in the radial direction of the tire, and this carcass. At least two layers of belts enclosing the circumference and forming a rubber coating of high modulus cords arranged crosswise to each other at a relatively small angle with respect to the center circumference of the tire, cooperating with each other, 3.01o7/c
The carcass is equipped with sidewall rubber on both sides of the carcass to strengthen the body to withstand high internal pressure, and the outer circumference of the belt has a two-layer structure: an undertread layer that completely covers the undertread layer, and a top tread layer that overlaps this. A pneumatic radial tire in which tread rubber is arranged respectively, the cord-coated rubber of the sword-cass: , zt 4 has a tensile R modulus of j , 0- A , Okg/ad, and
Dynamic elastic modulus is 1.2-20. ≠ky/crI, the undertread layer has a modulus at %-zr% elongation of 2,0-,,I,Oky/ctA, and!
A high internal pressure pneumatic radial tire for a passenger car, characterized by having rubber physical properties with a 1flt elastic modulus of 1.2 to 3.0 kg/ca. 5. The belt cord "4I covered rubber has rubber physical properties of 2!T elongated modulus 1.θ~/0, Okg/crl, dynamic elastic modulus 16.ko~ao, 5ky7- In the tire 06 described above, the under tread layer is compared to the top tread layer,
6. The tire according to claim 4, which is a rubber having a very low loss modulus and loss tangent.