JPS59109406A - Pneumatic radial tyre for heavy load - Google Patents

Abstract

PURPOSE:To make the thickness of a rubber stock thin and improve durability, steering property, and stability by setting the upper end height of a metal cord reinforcement layer arranged at the outside of a bead section, core arrangement angle, and the thickness of the rubber stock to specified values respectively. CONSTITUTION:The height Hs of the upper end 2-a of a metal cord reinforcement layer 2 arranged at the outside of a carcass ply that is wound around a bead bundle 3 is made higher than Hc of the upper end 1-a of the carcass ply 1. In addition, the angle of the metal cord arrangement is below 20 deg. near the upper end 2-a with respect to the circumferential direction of a tyre and is made larger by 10 deg. than the angle of the upper end 2-a arrangement a little closer to a bead base section 6 from the contact starting point Pf between a rim flange B and a rim cushion section 5. Furthermore, the relationship between the thickness d of a rubber stock and the thickness D from a carcass 4 before it is folded to the external surface of the bead section is set to satisfy d/D<=0.4. As a result, even if the rubber stock is made thin and light, durability, steering, property and stability can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the bead area of a pneumatic radial tire for trucks, buses, and other heavy transport vehicles, which is made of a single carcass ply. A heavy-load pneumatic radial with a bead reinforced structure that maintains and improves durability, maneuverability, stability, etc. even when the rubber stock that is inserted between the inside and outside is made thinner and lighter. Regarding tires.

Conventionally, this type of radial tire has a metal cord carcass ply terminated at a position where it is rolled up along the inner periphery of a bead bundle, and at least one metal cord reinforcing layer is disposed outside the carcass ply. This reinforcing layer is placed at the bead end to prevent separation failure between the cord and cord covering rubber, which tends to occur near the end of metal coated carcass plies, and to protect against the reaction force of air pressure received from the rim. , the arrangement height is shown in the case where the upper terminal of the reinforcing layer is higher than the carcass ply terminal as shown in Fig. 1-a, and vice versa as shown in Fig. 1-b! It is either low or low. In Figures 1-a and 1-b, 1 indicates the carcass ply, 1-a indicates the upper end of the carcass ply, 2 indicates the metal cord reinforcing layer, and 2-a indicates the upper end of the metal cord reinforcing layer. , 2-b is the lower end of the metal cord reinforcing layer, 3 is the bead bundle, 4 is the inner liner layer, 5 is the rim cushion part, A is the rim sear 1 part,
6 represents a bead base portion, and B represents a rim flange ring portion. Furthermore, in addition to the arrangement of metal cord reinforcement layers, various combinations of fiber cord reinforcement layers are used to prevent sudden changes in rigidity between the metal cords of the carcass ply and the surrounding rubber, further improving durability and improving maneuverability. Techniques for ensuring stability and stability have been proposed so far.

However, such a structure in which several metal cord reinforcing layers and fiber cord reinforcing layers are arranged near the ends of the metal cord carcass ply complicates the tire manufacturing process and is disadvantageous in terms of work efficiency and manufacturing cost. Furthermore, in response to recent social demands for resource and energy conservation, these have become new obstacles in achieving tire weight reduction. Furthermore, in the case of such a structure, the thickness of the rubber stock interposed between the winding side and the winding side of the carcass ply, which is wound from the inside to the outside around the annular bead bundle, is thinned, reducing the tire weight. If an attempt is made to achieve this, the strain-relieving effect at the carcass ply terminals, which is a function of the rubber stock, will be reduced, and the rigidity of the bead portion will be reduced, making the above-mentioned separation more likely to occur.

Further, in some cases, a problem may arise in which the cornering characteristics are deteriorated, resulting in insufficient maneuverability and stability.

For this reason, in addition to the arrangement of the metal cord reinforcement layer, the need to combine the fiber cord reinforcement layer is greater in the case of thin bead portions of the rubber stock, and therefore, even if the rubber stock is made thinner, the tire weight In some cases, the result is no change, but the manufacturing cost increases and the tire manufacturing process becomes more complicated.

By the way, to explain the basic structure of the bead reinforcement structure in a radial tire, which consists of a carcass ply excluding the fiber reinforcement layer and one layer of metal cord reinforcement layer, as described above, as shown in Figure 1-a, the rim seat part The arrangement height of the metal cord reinforcing layer upper terminals 2-a is higher than the arrangement height of the carcass ply winding terminal 1-a of the carcass ply A, and the carcass ply winding terminal from the rim sheet part A as shown in Fig. 1-b. There is a configuration in which the arrangement height of the metal cord reinforcing layer upper terminal 2-a is lower than the arrangement height of the metal cord reinforcement layer 1-a. In this case, the lower end 2-b of the metal cord reinforcing layer is arranged so that it is wrapped around the inner circumference of the bead bundle 6 and stopped at the side, as shown in Figures 1-a and 1-1. In addition, there are cases in which the bead bundle is wound above the bead bundle and extended at a point near the position corresponding to the end of the carcass ply winding on the inner surface of the tire.

By the way, when the arrangement height of the upper terminal of the metal cord reinforcement layer is higher than the arrangement height of the carcass ply winding terminal, most of the failures that occur at the bead part are due to separation from the upper terminal of the metal cord reinforcement layer, and the carcass ply Separation from the carcass winding end, which is observed when the height of the upper end of the metal cord reinforcing layer is lower than the winding end, is not observed. In the former case, as shown by the arrow in Figure 1-b, the carcass ply is caused by the force exerted on the inner surface of the tire due to air pressure and the reaction force from the rim 7 lunge. This is because the shearing force directed toward the winding end is blocked by the metal cord reinforcing layer disposed outside the carcass ply winding portion. On the other hand, in the former configuration, separation is inevitably likely to occur at the upper end of the metal cord reinforcing layer. This separation is caused by the fact that when the air pressure and the tire are under load, a tensile force acts in the tire radial direction near this terminal as shown by the arrow in Figure 1-a, resulting in a highly rigid terminal. This is because strain tends to concentrate on the rubber around the part. In conventional technology, there is an example of a tire that uses a high elongation wire with a large elongation as a metal cord reinforcing layer in order to alleviate the concentration of strain, but in this tire, high strength and high modulus cannot be achieved throughout the cord. Also, high elongation wire was expensive and not an appropriate method.

In particular, as shown in Fig. 1-c, the arrangement height of the metal cord reinforcing layer terminal 2-b' on the first layer of the inner liner is higher than that of the metal cord reinforcing layer terminal 2-a' on the carcass ply winding side. It has excellent durability, and it is possible to reduce the thickness of the rubber stock interposed between the winding side and winding side of the carcass ply, but the first problem is the amount of metal cord reinforcing layer used. - 1-a, which requires about twice as much as the tire with the configuration shown in Figures a and b, and has a rubber stock thickness sufficient to meet the practical level of quality in terms of weight.

The result is the same as the tire with the configuration shown in Figure b, but the cost is increased. Furthermore, when the rubber stock thickness is reduced in tires with these basic configurations, the function g(α) representing the effect of load transfer on cornering power characteristics is:
Load transfer efficient
The value of increases. In addition, it has been confirmed that cornering characteristics tend to decrease, with changes in slip angle becoming larger.

Next, we will explain this function g(α): Among the mechanical characteristics of tires, cornering force and self-lining torque are two of the mechanical characteristics that have a large influence on the steering stability of a car. Varies depending on air pressure and slip angle. When sudden steering is not involved, cornering force is approximately proportional to the slip angle (α), and its proportionality constant is expressed as cornering power. Since the value of cornering power varies greatly depending on the tire load, changes in the cornering power value due to changes in tire load during cornering of the vehicle affect the behavior of the vehicle. Taking these things into consideration, g(α) is one of the functions for expressing the cornering power characteristics of a tire as a parameter of the load dependence of cornering force.

This g(α) represents the effect of load movement, and I, oad
It is called a transfer coefficient.
Since it represents the influence of load movement, the smaller the value, the more linear the steering characteristic will be with respect to the lateral acceleration7, and the larger the value, the more the automatic steering tendency will appear at high lateral accelerations. Therefore, it can be said that g(α) is clever with a small Ql. Also, g(α) is, as shown in Figure 2,
Cornering/(In terms of war characteristics, cornering curve represents the degree of curvature of the war curve, and can be determined from the following formula.

In this formula, t represents the tire average load, and is a value of the 80th factor of the JIS thickest load, which is considered to be a regular load. △
Fy is the cornering force (FyO, 4b and FYl) at a certain slip angle when the tire average load is applied (W), the corner 1 non-long force (Fyp) and when the tire average load is ±60 load ((l-VO2)b) , 6)
difference from the average, △FYI = Fyp(Fyo4p'+
Fy+6i)/2.

The present invention has been made in view of the above-mentioned circumstances, and is lightweight by reducing the thickness of the rubber stock that is interposed between the carcass ply wound from the inside to the outside around the annular bead bundle. To provide a heavy-load pneumatic radial tire having a bead reinforced structure which can prevent separation failure between a cord and cord covering rubber in a carcass ply even when the carcass ply is damaged, and is excellent in durability, maneuverability, stability, etc.

For this reason, the present invention provides a pneumatic tire with a radial structure having a bead portion in which one layer of carcass ply is rolled up from the inside to the outside around an annular bead bundle, in which the bead portion is disposed outside the carcass ply winding portion. The upper end of the metal cord reinforcing layer is located higher than the carcass ply winding end. It is 20 degrees or less relative to the position where the rim flange and the tire rim cushion start contact and closer to the bead base, it is more than 10 degrees larger than the arrangement angle near the upper end. The rubber stock thickness d at the position is 1/D≦0.4 with respect to the thickness D from the carcass ply to the outer surface of the beet portion before folding at the position.

Embodiments of the present invention will be described below with reference to the drawings. Note that in Figures 3-a and 3-b, 1-
The same parts as in Fig. a, Fig. 1-b, and Fig. 1-c are indicated by the same numbers and symbols.

Figures 3-a and 3-b show an embodiment of the present invention. In these figures, a single-layer carcass ply 1 made of metal cords arranged approximately 90'' with respect to the tire circumferential direction is wound around an annular bead bundle 6 from the inside of the tire to the outside.
The bead portion has a shape that conforms to the shallow bottom rim and wide flat bottom rim shown in JISD421-13. One metal cord reinforcing layer 2 is arranged outside the carcass ply winding portion, and the upper end 2-a of the metal cord reinforcing layer 2 is arranged at a higher position than the carcass ply winding end 1-a. The cord arrangement angle of the metal coat reinforcing layer 2 with respect to the tire circumferential direction is 20° or less with respect to the tire circumferential direction near the upper end 2-a, and the rim flange B
The arrangement angle closer to the repeat base portion 6 than the contact start point Pf between the tire rim and the tire rim mount portion 5 is 10° or more larger than the arrangement angle near the upper terminal 2-a.

The thickness d of the rubber stock at the position of the winding end 1-a of the twisted carcass ply 1 is d/D≦ with respect to the thickness D from the carcass ply to the outer surface of the bead portion before folding at that position. It is 0.4. (d=4mm).

The metal cord reinforcing layer 2 preferably has a cord direction elastic modulus (E+, ) of 3000 K977 or more.

Note that this chord direction elastic modulus (Er, ) is a value determined by the following equation.

E+, once (AE).

Here, n is the width 1. The number of cords inserted per mm, P is the cord diameter, and (AE)C is the cord direction spring constant of the cord. In addition, in this case, - cuff X3 consisting of a twisted metal cord.
(0,175) IW or I X 27' (0,175
) For cords such as IW that have a wrapping wire each month, this is the cord diameter excluding the wrapping wire.

The upper terminal 2-a of the metal cord reinforcing layer 2 is located higher than the carcass ply winding terminal 1-a, and the height Hs is 1.5 inc or more i of the height Hf. It is preferable.

Further, the cord arrangement angle of the metal cord reinforcing layer 2 is 20° or less with respect to the tire circumferential direction near the upper end, and the contact start point Pf between the rim flange B and the tire rim cushion portion 5
The arrangement angle near the bead base portion 6 is 10° or more greater than the arrangement angle near the upper end. In order to create a difference in the arrangement angle in this way, it is possible to create a difference in angle by shaping the plastic deformation area with rolls in advance, or, for example, cut a metal cord calender sheet to a specified width at 30 degrees, and then cut the upper end The width 1107n located at 1107n is passed between rolls with a high rotation speed, and the remaining width is passed between rolls with a slow rotation speed, thereby changing the angle of the former side to 17 degrees. Alternatively, after bonding the metal cord reinforcing layer to the molding drum during the green tire molding process, the reinforcing cord layer portion located at the upper end may be cut at a smaller angle than the cutting angle using a rotating roll.

For reference, with conventional tires, the angle change due to lift during the vulcanization process from green tires is a maximum of 7 to 8
If a metal cord reinforcing layer cut at 30" is used, θ at the upper end 2-a is 28°, and the lift rate is approximately O at the carcass winding end position. 30°, the contact start point. The angle θ2 at the same height as Pf is 32° and 35' at the east side of the bead.

According to the present invention, the lower the arrangement angle at the folded portion of the upper end, the longer the actual length of the cord becomes, resulting in the use of extra material. Therefore, considering the balance between the reduction in interest rate and weight due to the thinning of the rubber stock and the increase in material cost and weight due to the substantial increase in the thickness of the metal cord layer, the arrangement of the upper terminal of the metal cord layer The angle is 1
It is preferable that the angle is 0° or more. By setting the arrangement angle with respect to the tire circumferential direction at the upper end of the metal cord reinforcing layer to 20 degrees or less, the end of the metal cord reinforcing layer can be easily deformed in the tire radial direction, and the actual modulus of the cord layer is equal to that of rubber. As the modulus approaches, the difference in relative strain between the terminal and surrounding rubber decreases, improving durability without reducing maneuverability or stability.

However, in the prior art, in order to set the arrangement angle of the upper end of the metal cord reinforcing layer to 20 degrees or less, the cutting angle of the metal cord reinforcing layer must be 20 degrees or less during the green tire molding process. In this case, the metal cord reinforcing layer is bonded to the carcass ply as part of the forming procedure, and in the process of winding the carcass ply around the bead bundle, wrinkles tend to occur in the metal cord reinforcing layer at the lower part of the bead bundle, resulting in a wavy shape. It is easy to cause an uneven shape on the lower side of the bead bundle. This causes vehicle body vibration due to poor fitting with the rim, and separation of the rim knot rubber metal cord reinforcing layer at the rim seat. In contrast, in the method according to the present invention,
The above-mentioned upper end 'l-
By making the arrangement angle 10" or more larger than the arrangement angle near a, wrinkles do not occur and it becomes possible to easily wind it around the bead bundle.

EXAMPLES The effects of the present invention will be specifically explained below with reference to Examples.

The tire evaluated in the example was tire size 825 R2014P.
It is a rib tire mainly used for highways of R, and the rim used is 6.
50 T x 20, the shape of the tire rim cushion part is designed to correspond to the T rim flange shape. Also, the height of the T rim flange is 38 mm''C from the rim seat part.

The carcass ply consists of one cord layer made of 3 +9 (0,22) IW metal cord, and the metal coat reinforcement layer is made of 7 x 3 (0,15) cord with a cord diameter of 1.19 mm, and the number of cords is 26. ENt150 ynm was used.

Furthermore, in order to explain the effects of the conventional tire and the tire according to the present invention, tires with the following six specifications were manufactured and evaluated.

The height Hs (-61 inches) of the upper end of the metal cord reinforcing layer is higher than the undisposed height Hc (=51 inches) of the carcass ply rolled-up end shown in Figure 1-a without being separated. The thickness d of the rubber stock that constitutes the carcass ply winding side and the winding end is 9 mm.
, the thickness D including the rim cushion part 1 is 20 +
nm (d/D =, 0.45), the cutting angle of the metal cord reinforcing layer is 25°, the arrangement angle after vulcanization is 01-22° at the two end parts, the rim flange, tire lino, and gusson yong part. Arrangement angle θ at the same height as the contact starting point Pf
2: The thickness d of the rubber stock of the conventional tire frame of 27° and the same tire frame was reduced to 4 myn (('/D =,
0.25) Tire (B) had the same specifications as tire (4) except for the above, and the thickness d of the rubber stock shown in Figures 3-a and b was 4 mm, the same as tire (B), and metal cord reinforcement was used. Tire C) according to the invention with a layer arrangement angle of d/1)20.25 arranged at 15° to θ and 32° to θ2.

Furthermore, the arrangement height shown in FIG. 1-b is such that the height Hs (=43 mm) of the upper end of the metal cord reinforcing layer is lower than the height Hc (=51 mm) of the unarranged end of the carcass, The rubber stock thickness d is 9 mrn (
d/D=0.50), the cutting angle of the metal cord reinforcing layer is 25°, the placement angle after vulcanization is θ′24°, θ2=2
7° tire 0 and rubber stock thickness d 4 m + π
(d/D = 0.27) This tire [F] has the same specifications as Tire 0 except for the fact that it is thinner. Above, the lower terminal of the metal cord reinforcement layer is stopped on the east side of the bead 5
In addition to the specified tire, the tire shown in Figure 1-c has the same specifications as the tire (G), except that one end of the metal cord reinforcing layer is extended by a single layer of inner liner, and its arrangement height is 60 mm. Yes (d/D2 0.27).

These tires (4) to (g) were selected and shown in the table below.

(1) Figure 4 shows the results of an indoor durability test using an indoor rotating drum tester. The drum durability test conditions are load 3.
050Kg, air pressure 7.2K9/d, speed 45/h
It is r. According to the test conditions, past data has shown that if a tire of 8.25R20 can be driven over approximately 16,000km, it is at a level that does not pose a problem in terms of practical durability.

Here, the tires that are at a level that poses no problem in terms of practical durability are Tires, (C), ■, and In.

However, a tire with a thinner rubber stock is out of the practical performance range, and in order to increase the durability to a practical level, it is necessary to add a fiber cord reinforcement layer in addition to the metal cord reinforcement layer as described above. I have no choice but to find a way to increase it. However, this method is not a good idea considering that the structure of the bead portion becomes complicated and the productivity also deteriorates.

Similarly, in tires (T), despite the thin comstock thickness, the durability level 7 is actually the highest level/L among the 6 specifications, but the material cost is high and the heavy metal cord reinforcement layer is used. This results in an increase in cost and weight that exceeds the weight reduction achieved by the rubber stock, making it unpractical except for special usage conditions where durability is required. It's not a good idea.

The tire C) according to the present invention is within a practical durability range, and when the tire C) is placed at the same height as the tire (4), the angle changes at the upper end if the same metal cord calender material is used. The extra cutting width required increases the amount of metal coat reinforcing layer used compared to the tire cover, but the amount increases by 7 to 10% and is a large width compared to the weight reduction of the rubber stock. 12 in 7 in total tires.
It becomes lighter.

(2) Figure 5 shows the function g(α) representing the influence of load movement on cornering power characteristics: Load tran
The relationship between sfercoefficient and slip angle is shown.

The tires used are tire size 825 R201.
4PR1 air pressure 7.25Kf°f, rim 6.50T
X 20, average load 2 1620 kg.

As you can see from this, from the carcass ply winding-beard end unplaced height Hc, the metal cord reinforcement layer upper end unplaced height H5
The tire prisoner has a high configuration (B).

(C) is less affected by the thickness of the rubber stock;
The value of g(α) is small and still shows a linear change with respect to the slip angle.

On the other hand, tires [F], (G), and (G) with configurations in which the carcass ply rolled-up end height H8 is lower than the metal cord reinforcing layer upper end height H8 are lower than the tires with the former configuration. The value of α) is large, and the change is still not linear with respect to the slip angle. %, the tire (G) with the thinner stock rubber has a large change in slip angle,
This is at a level that poses a practical problem. Furthermore, tire (2) is judged to be at the minimum level without any practical problems, based on past data.

As described above, the tire according to the present invention having a configuration in which the height of the metal cord reinforcing layer where the two side ends are not placed is higher than the height of the carcass winding first and second ends has excellent cornering power characteristics, and the above-mentioned The disadvantage of durability, which drops significantly when the thickness of the rubber stock is made thinner, is improved, and weight reduction becomes possible.

Furthermore, in order to reduce weight without changing the carcass line, which has a pre-designed equilibrium shape, it is necessary to reduce the weight of the inner liner and bead parts of the tire, which do not affect or have little effect on the carcass line. It is necessary to Therefore, in the present invention, the problem of deterioration in tire performance due to changing the carcass line is less likely to occur.

Therefore, according to the present invention, even when the carcass ply is wound around the annular bead bundle from the inner part j to the outside and the thickness of the rubber stock interposed between the two is made thinner and lighter, the carcass ply does not have a kel cord. It is possible to provide a heavy-load pneumatic radial tire with a bead reinforced structure that can prevent separation failure with the cord covering rubber and has excellent durability, maneuverability, stability, etc.

[Brief explanation of drawings]

Figure 1-a, 1st. Figure 1-B and Figure 1-C are explanatory cross-sectional views of the bead portion of an example of a conventional tire, respectively, and Figure 2 shows the load (Kri) and cornering force (
Figures 3-a and 3-b are cross-sectional diagrams of the bead portion of an example of the tire of the present invention, respectively, and Figure 4 is a graph showing the relationship between the tire weight and weight (Kg). Figure 5 is an explanatory diagram showing the results in a graph. Figure 5 is an explanatory diagram showing the relationship between the function g (α) representing the influence of load transfer on cornering power characteristics and the slip angle (degrees) for various tires. . 1... Carcass ply, 2... Metal cord reinforcement layer,
1-a... Carcass ply upper end, 2-a... Metal cord reinforcing layer upper end, 2-b... Metal cord reinforcing layer lower end, 3... Bead bundle, 4... Inner liner single layer , 5... Rim cushion portion, 6... Bead base portion, A... Rim seat portion, B... Rim flange ring portion. Figure 2 Figure 3-b Figure 4

Claims (1)

[Claims] In a pneumatic tire with a radial structure having a bead portion in which a single layer of carcass ply is wound from the inside to the outside around an annular bead bundle, the bead portion is formed of a single layer of metal cord reinforcing layer disposed outside the rolled-up portion of the carcass ply. The upper terminal of the metal cord reinforcing layer is located higher than the carcass ply winding terminal, and the cord arrangement angle of the metal cord reinforcing layer is 20" or less with respect to the tire circumferential direction near the upper terminal, From the contact start point between the rim flange and the tire rim cushion part to the bead base part, the angle is more than 10° larger than the arrangement angle near the upper end, and furthermore, the rubber stock thickness d at the carcass ply winding end position is at that position. d for the thickness D from the carcass ply to the outer surface of the bead before folding at
A pneumatic radial tire for heavy loads, characterized in that /D≦0.4.