JPS6012243B2 - Fuel saving pneumatic tires - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to fuel-efficient pneumatic tires and proposes improvements in fuel consumption, especially in tires of the type with a bias structure carcass, mainly for large, medium and small trucks and buses. It is something.

Regarding fuel consumption, the typical characteristic of tires is rolling resistance, which is caused by internal energy loss (hysteresis loss) due to repeated deformation during tire rolling, friction loss occurring between the tread surface in the contact patch and the road surface, and aerodynamic loss. Become.

The proportion of these losses in rolling resistance is generally said to be as follows.

A Internal energy loss due to deformation 90-95%
Friction loss in the ground plane 5-10% Aerodynamic loss 1
．． 5 to 3% The internal energy loss that has the greatest effect on rolling resistance is generally expressed by the following formula.

202Sm6・V of internal energy loss here.

...stress amplitude, ...0 strain amplitude, V...volume, where E2 represents the loss modulus and E* represents the elemental elastic modulus, s
There is a relationship of in6=E2/E*. In order to reduce rolling resistance, materials should be shaped and used with little internal energy loss. It can be said that the structure can be effective by reducing deformation and reducing the volume of the material in areas where the deformation is large. By the way, from the above point of view, the tread rubber of the bias carcaster has a larger movement within the ground contact surface than the radial carcaster, and the tread rubber in the shoulder area in particular is subject to compression deformation as well as bending deformation, and the volume of the shoulder area itself is quite large. Since the rolling resistance is large, there remains a big disadvantage in terms of rolling resistance.

Therefore, an effective way to reduce the rolling resistance of a bias carcaster is to reduce the wall thickness of the shoulder area, and reducing the volume of the tread rubber in the shoulder area reduces the movement of the tread in the shoulder area. A considerable effect can be expected by reducing the amount.

However, in general bias carcass tires, if the shoulder wall thickness is made thinner, the crown radius of the tread becomes smaller during internal pressure filling, and the tread wears out faster in the center, resulting in a marked drop in wear resistance. Next, as a method to reduce the tread thickness at the shoulder part while maintaining a large crown radius, as shown in Figs. It is conceivable to position it further outward.

In this way, when the carcass shape of the tread portion is kept close to flat and the crown radius of the tread is kept large, the shape of the crown portion under no load approaches the shape under load, which reduces bending deformation of the tread of the crown portion and the carcass. can be made smaller.

The following two carcass shapes are considered necessary here.

One method is to bring the cord angle of the entire bias carcass closer to the circumferential line of the tire, thereby flattening the entire carcass shape.

The carcass shape at this time is as shown by the broken line in FIG. However, in the case of this method, the tire width becomes significantly larger as shown in Figure 1, and it becomes necessary to secure a large tire storage space in the car cocoon. This method is therefore practically unsuitable.Another method is to arrange the high modulus cord in the breaker, especially at an angle closer to the circumference of the tire. This is done by applying a ``hoop effect'' using the breaker, and ``The shape of the carcass at this time is as shown by the broken line in Figure 2.''

However, with this method, there is a large difference in rigidity due to the difference in material between the carcass and the breaker, and a large difference in angle between the cords of the carcass and the breaker. do not have. A. In manufacturing, the carcass and breaker are formed on the same drum after the green case is formed, and then molded by toroidal deformation in the vulcanizer. ,
The diameter of these carcass and breaker is 1.4 in the vulcanizer.
Since a toroidal deformation that expands by ~1.7 times is forced, the carcass cord and breaker cord undergo large angular changes separately.

At this time, there is a large angle difference between the carcass cord and the breaker cord, so they are affected by the angle change,
In particular, it is difficult to obtain an angle close to the target circumferential direction for the breaker cord.At the same time, the outermost layer of the carcass cord and the innermost layer of the cord under playing force are not stretched and have a wavy shape, making it difficult to obtain the correct angle. Cord tension cannot be obtained. Furthermore, in terms of performance, due to the large difference in rigidity between the carcass and the breaker, separation occurs early between the carcass and the breaker, which is a fatal flaw.

However, if this method were to be realized by overcoming these difficulties, the movement of the tread could be suppressed by effectively increasing the stiffness of the tread by the breaker.
The energy loss due to tread deformation is reduced, and the friction between the tread surface and the road surface is also reduced, so this method has the advantage of reducing rolling resistance and significantly improving wear resistance.

In order to realize such an effective structure, the inventor conducted extensive experiments to clarify the breaker structure and tire cross-sectional structure that are sufficiently effective in reducing rolling resistance, and further investigated the relationship between the carcass and breaker. Recognizing the usefulness of providing a buffer layer between organic fiber cords with specific physical properties,
I put it out.

In other words, in a pneumatic tire that has a bias structure carcass using organic fiber cords and has a breaker placed around the carcass at the crown, the value of the characteristic value K expressed by the following formula for the breaker is 300.
100% modulus is 30k9/
The breaker and the carcass are made of at least two layers of rubberized cord cloth coated with a rubber of at least 100% rubber and laminated crosswise with each other in an inclined arrangement such that the average cord angle with respect to the equator of the totya is 20 to 350. In between, a buffer layer made of organic fiber cord whose characteristic value K is much smaller than that of the breaker is interposed, and this buffer layer is wider than the breaker and faces the buttress part, A fuel-saving pneumatic tire characterized by having a cross-sectional width that does not reach the peak part.

K=E・S=T/Here, K is the tensile strength of one cord, E is Young's modulus, S is the cross-sectional area of the cord, T is the tension applied to the cord, and is the cord when tension T is applied. Indicates the distortion that occurs in

(Category 1 above) In a pneumatic tire having a bias structure carcass using organic fiber cords and having a breaker arranged around the carcass in the crown part, the characteristic value K expressed by the following formula as the breaker is Codes with a value of 300k9 or higher, 100% modulus of 3
The rubberized cord cloth is coated with rubber of 0k9/m or more and is made of at least two layers of rubberized cord cloth laminated crosswise with each other in a diagonal arrangement such that the average cord angle with respect to the equator of the tire is 20 to 350. A buffer layer made of organic fiber cords whose characteristic value K is much smaller than that of the breaker is interposed between the breaker and the carcass, and this buffer layer is wider than the breaker and faces the buttress part. However, it has a cross-sectional width that does not reach the bead part, and the crown part in which these breakers and buffer layers are embedded has a ratio of the total thickness in the shoulder area to the total thickness in the center area of 1.0 to 1. 1.4, and the crown radius is 1.1 to 1.1 of the tire maximum width. A fuel-saving pneumatic tire characterized by a needle sound.

K=E・S=T/Where, K is the tensile strength of one cord, E is Young's modulus, S is the cross-sectional area of the cord, T is the tension applied to the cord, and ' is the cord strength when tension T is applied. This shows the distortion that occurs.

(Second invention) Hereinafter, it will be explained with reference to the drawings. In FIG. 3, 1 is a crown portion, 2 is a bias carcass, and 3 is a breaker.

The breaker 3 is made of rubber having a 100% modulus of 30 kg or more, and a cord having the above-mentioned characteristic value K of at least 300 k9 or more, preferably 500 kg or more, is embedded at an average angle of 20 to 35 degrees with respect to the tire circumferential direction, and the cords intersect with each other. It consists of at least two layers. The buffer layer 4 is located between the bias carcass 2 and the breaker 3 and consists of at least one rubberized cord layer made of an organic fiber cord having a much lower K value than the breaker cord.

Its width is wider than the breaker 3 and faces the buttress part, but both ends do not reach the bead. In addition to the basic structure having the breaker 3 and the buffer layer 4 as described above, the ratio of the total thickness B in the shoulder region to the total thickness A in the center region of the crown portion is preferably 1.0 to 1.4 times. is 1.0 to 1.2 times, and 1.1 to 1.9 times the tire width SW, preferably 1.2 to 1.3 times. can be further reduced.

The following table shows the effects of the present invention in comparison with conventional tires for the embodiments of the present invention.

Here, the conventional tire had almost the same structure as the tire of the present invention, except that the characteristic value K of the breaker cord was low and the tire did not have a buffer layer.

Example test results In addition, in the indoor drum test, in Examples A, B, and C, due to the presence of the buffer layer, the failure location shifted between the playing force layers or between the breaker and the tread, similar to the failure in the radial structure. Intermittent breakdowns have been eliminated, and durability has been significantly improved.

By eliminating this problem in terms of durability, the present invention can significantly reduce rolling resistance and further improve wear resistance.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a tire that compares the general shape NI of a conventional tire with a shape P that provides low rolling resistance by changing the carcass cord angle, and Figure 2 is a cross-sectional view of a tire that similarly uses a high modulus breaker cord. FIG. 3 is a cross-sectional view of a tire showing a comparative example of the low rolling resistance shape Q. FIG. 3 is a cross-sectional view of a tire showing an embodiment of the present invention. 1... Crown part, 2... Bias structure carcass, 3... Breaker, 4...
・Buffer layer, 5... Buttress part, A...
・Crown center total thickness, B... Crown shoulder total thickness, CR... Crown radius,
SW... Tire width. Figure 1 Figure 2 Figure 3

Claims (1)

[Scope of Claims] 1. A pneumatic tire having a bias structure carcass using organic fiber cords and having a breaker arranged around the carcass at the crown, where the breaker has a characteristic value K expressed by the following formula. Value is 300k
100% modulus is 30kg/c
using at least two layers of rubberized cord cloth coated with rubber of m^2 or more and laminated crosswise to each other in an inclined arrangement such that the average cord angle with respect to the equator of the tire is 20 to 35 degrees; A buffer layer made of organic fiber cords whose characteristic value K is much smaller than that of the breaker is interposed between the breaker and the carcass, and this buffer layer is wider than the breaker and faces the buttress part. A fuel-efficient pneumatic tire characterized by having a cross-sectional width that does not reach the bead portion. Note K=E・S=T/_6 Here, K is the elongation resistance of one cord, E is Young's modulus, S is the cross-sectional area of the cord, T is the tension applied to the cord, and ε is the cord when tension T is applied. Indicates the distortion that occurs in 2 In a pneumatic tire that has a bias structure carcass using organic fiber cords and has a breaker arranged around the carcass in the crown part, the value of the characteristic value K expressed by the following formula as the breaker is 300k.
100% modulus is 30kg/c
using at least two layers of rubberized cord cloth coated with rubber of m^2 or more and laminated crosswise to each other in an inclined arrangement such that the average cord angle with respect to the equator of the tire is 20 to 35 degrees; A buffer layer made of organic fiber cords whose characteristic value K is much smaller than that of the breaker is interposed between the breaker and the carcass, and this buffer layer is wider than the breaker and faces the buttress part. However, the cross-sectional width does not reach the bead portion, and the crown portion in which the breakers and the buffer layer are buried has a ratio of the total thickness in the shoulder region to the total thickness in the center region of 1.0 to 1. 4, and the crown radius is 1.1 to 1.9 times the maximum width of the tire. K=E・S=T/εHere, K is the elongation resistance of one cord, E is Young's modulus, S is the cross-sectional area of the cord, T is the tension applied to the cord, and ε is the tension applied to the cord when tension T is applied. Indicates the resulting distortion.