JPH0579521B2 - - Google Patents

Description

[Detailed description of the invention]

The invention comprises a radial carcass, two beads, a tread, and a band-shaped tread reinforcement, the carcass consisting of two cord fabric plies, the radially inner ply of which carries a core member. The radially outer ply of the cord fabric ply terminates outside the carcass fold with respect to the axis of the bead ring at the bead portion, and the carcass The present invention relates to a pneumatic vehicle tire which is coated on the inside with a rubber protective layer and on the outside with a sidewall strip. This type of strip-shaped radial tire is standard for both passenger cars and light trucks. The carcass is then made of two identical cord fabric plies, the direction of extension of which cord threads is substantially within a tolerance of 90°, measured with respect to the center plane of the width in the circumferential direction of the tire. There is. Such cord woven plies are made of well-established cord materials such as rayon, nylon or polyester and, depending on the material, the cord strand structure and the packing density of the cord strands, the carcass cord strands are exposed to air pressure and loads. It has the strength to ensure that the carcass absorbs the alternating stresses that occur. Such a carcass also has a strength reserve of several times the puncture pressure required for safety against puncture pressures. As is well known, carcass ply is made of one filament (also called a single yarn) made of extremely fine fibers twisted into several hundred bundles, or two filaments made of two.
A cord or cords made by applying a covering to a book or three cords are arranged appropriately to make a blind weave, and then coated with rubber or the like to form a rubberized fabric layer. This is referred to as a cord fabric ply, but in the following specification, the term "cord filament" will be used to leave room for choice since the carcass ply may be either a cord or a filament. For example, rayon 1220/2 means a cord made of 1220 dtex rayon and is made by combining two strands and applying a coating, while nylon 1400/1 is a cord made of 1220 dtex rayon.
This means making a single fiber from 1400 dtex nylon and using it as the ply material. The term "packing density" also refers to the elements in a cord structure that consist of filaments or cords.
It is expressed as a percentage of the ratio of the actual number to the number that can be lined up tightly and seamlessly every 1 dm. In other words, it is the actual percentage of cord fibers when the maximum number of cord fibers arranged flat in 1 dm is taken as 100%. Therefore, since 1 dm is 100 mm, this packing density numerically matches the value obtained by multiplying the diameter of the cord filaments in mm by the actual number of cord filaments. Adding a percentage to that number is also the packing density. The known carcass, which is formed from two identical plies of cord fabric with equal and sufficient packing density (usually around 75%) and a rubberized layer, accounts for a significant proportion of the tire weight. This carcass weight has not changed at all until now. Although there are various requirements placed on tires today in terms of safety, driving position, economy and comfort, the principle of always making them as light as possible but not at the expense of safety is important. Light weight tires significantly reduce rolling resistance, and low rolling resistance means energy savings. This is especially important when raw materials are in short supply. A single layer carcass would likely result in higher weight loss. A band-shaped radial tire equipped with such a single carcass would, however, have the significant disadvantage of an unfavorable running position. The flex area of the tire, i.e. the portion of the tire between the tread shoulder and the tire bead, may be undesirably large, and the flex area provides lateral stability, stability through changes in direction of travel, and zonation. This has a negative effect on the curve driving posture of radial tires. The invention therefore consists in making a pneumatic tire for a vehicle as defined in the preamble of claim 1 in such a way that the weight of the carcass is considerably reduced and that the carcass meets the requirements with respect to strength. The object of the present invention is to create a tire in such a way that it has characteristics comparable to standard tires having an ordinary two-layer carcass in accordance with the driving conditions and driving position. This object is achieved according to the invention in a pneumatic vehicle tire of the type mentioned at the outset by the measures defined in claim 1. Due to the shape according to the present invention, the inner carcass ply essentially takes charge of the strength of the carcass, and even if there are bumps on the road, the tires can cope with it, so the car's posture This satisfies the function of stabilizing the vehicle, that is, ensuring a good running posture, and also guarantees a reduction in weight. The bending area of the tire is more favorable than that of the standard tire described above. Preferably, the central axis of the side wall for bending stress is located in a region close to the inner carcass ply. This can be achieved with an auxiliary layer having a low packing density of the cord and/or a low cord thread count of the cord. According to a further feature, the cord-less auxiliary layer as the radially outer carcass ply can be different from the inner carcass ply, which is responsible for the strength, with regard to the cord filament structure and the cord fabric material. The support can also be made from threads (single threads) instead of cords. A large number of industrial threads are used for this purpose. For example, a single thread of polyamide or aromatic polyamide can be provided because of its preferred specific gravity and, in the case of alumamide, its tensile strength, which can be compared to a metal web, and especially because of its physical properties in the auxiliary layer. In all application situations, including mixed structures in the carcass, there is a more or less considerable weight loss in the carcass and thus also in the tire;
The tire thereby has a low rolling resistance. Additionally, it would also be possible to construct the rubberized layer of the auxiliary layer with a reduced thickness. Particularly advantageously, this thickness can be reduced by up to 50% over the cord diameter or thread diameter compared to conventional rubberized layers. For example, the total thickness D is d (cord diameter)
It can be made equal to +2×0.05mm. The auxiliary layer may also have a higher modulus of elasticity than the radially inner carcass with respect to the rubberized layer. The elastic modulus of the auxiliary layer may significantly exceed the normal value which is in the range of 102 Kg/cm ² for a 300% module, ie from 153 to 204 Kg/cm ² . In this way it is possible to maintain a relatively light carcass ply, but the overlying and substantially parallel cord strands of those layers are placed next to each other in the auxiliary layer at a relatively wide lateral distance. To position. These carcass plies are rubberized due to the few weft fibers present and are equivalent to a large mesh net whose strength is provided on the inner layer. A particularly advantageous embodiment of the invention will now be described with reference to the drawings. FIG. 1 shows a cross section of a pneumatic vehicle tire, and FIG. 2 shows a detail of the carcass in a spatial partial view. FIG. 1: A pneumatic vehicle tire 1 comprises a radial carcass 2 comprising two cord woven plies 12,
14 and two beads 3. The tread is shown at 6 and the tread reinforcement is shown at 7. This reinforcing section 7 is made up of two or three cord layers 8, 9 arranged in the form of a band between the carcass 2 and the tread. On the inside, the carcass 2 is covered with a rubber protective layer 10, which consists of a rubber mixture which in tubeless tires has only a low air permeability. For example, halobutyl rubber can be considered as the material. On the outside the carcass 2 is covered by a rubber strip 11;
This essentially forms the tire sidewall. The radially inner carcass ply 12 surrounds a bead ring 4 made of steel wire and a core member (filler) 5 made of a rubber mixture from the inside in the axial direction to the outside. The ends of the plies form carcass folds 13 within the core element 5. The radially inner carcass ply 12 consists of rubberized cord threads, which consist of a conventional number of cord threads. That is, they are relatively closely spaced. The number of cord threads per decimeter measured within the upper area of the bead ring is, for example, for a rayon cord of cord type 1840/2:
Approximately 100 to 130 cord filaments (epdm=ends pro
decimeter). Instead of rayon, nylon strands and polyester strands are also carcass cord materials of choice. Furthermore, aromatic polyamide cords or flexible thin metal cords are also possible as carcass green material. The relatively high packing density of the carcass plies 12 provides the necessary strength for a radial tire to take on the alternating stresses caused by air pressure and loads, and also the desired flexibility for good riding posture and comfort. It is to ensure the sex. This simultaneously prevents the butyl rubber layer 10 from penetrating into the carcass. The packing density of the inner carcass ply 12 according to the present invention is 55% to 95%. The radially outer carcass ply 14 surrounds the inner ply 12 over its entire arcuate circumference in cross-section of the tire and is located outside the core element 5 and the carcass flap 13 in the bead area. This carcass ply 14 is formed with fewer cord filaments. This ply can in this respect have a low packing density and/or a small number of threads for each cord thread. It is particularly advantageous for the packing density to be 20 to 70% lower than the packing density in the inner ply, although packing densities of a minimum of 20% are permissible. Rayon, nylon, polyester and aromatic polyamide can also be selected as cord materials. A radially outer carcass ply 14 containing only 25 to 60 cord strands per decimeter, depending on the twist (single yarn) material and cord type, significantly reduces the weight of the carcass. The small auxiliary layer of filaments plays an important role in ensuring a good running posture. As shown in FIG. 2, this auxiliary layer is placed on the carcass ply 12 like a net with a wide mesh width due to the weft fibers in the auxiliary layer. The carcass ply 14 forms a well-defined bending region 15 in this regard. This area is narrow compared to a single ply carcass, but wider compared to a two ply carcass consisting of two identical, tightly packed plies of cord fabric. Furthermore, since the carcass ply 14 formed as an auxiliary layer is provided, the center line 16 of the bending stress of the side wall is aligned with the carcass ply 1 on the inside in the radial direction.
Preferably, it is located in an area near 2. By both measures the general running position of the strip tire is improved. Due to the weight saved in the carcass, the tire gains favorable rolling resistance. Next, the weight of the ply according to the prior art and the weight of the ply according to the present invention will be compared using FIGS. 3 and 4. In FIG. 3, which shows a prior art carcass, the inner ply and the outer ply are of the same construction, and if both plies are the same, the weight of the cord will increase accordingly if the packing density is high. On the other hand, if the packing density increases, the proportion of rubber that fills the remainder of the ply volume and thus the remainder of the weight of the ply decreases. The rubber weight and cord weight of the inner and outer plies are the same. These add up to the total weight of the ply, and likewise for the inner and outer plies. Adding the total weight of both plies gives the total weight of the inner and outer plies and thus the total weight of the ply structure. In contrast, FIG. 4 illustrates the weight distribution of the carcass according to the invention. Section C, hatched from top left to bottom right in this figure, represents the total weight bandwidth of the cord in the outer ply. The value of this interval is between 80 and 30% of the weight of the cord of FIG. Therefore, this section shows values reduced by 20 to 70% compared to those in Figure 3. The vertically hatched section G indicates the weight bandwidth of the rubber of the outer ply. This interval is the value of Figure 3.
Between 100 and 50%. The sum of both sections yields the total weight bandwidth of the outer ply. Adding to this the weight of the inner ply corresponding to the total weight of the inner ply results in a section having a weight bandwidth value that is the inner ply and the outer ply as a whole. All values in this section are less than or equal to the total weight values of the inner and outer plies in FIG. 3 representing the prior art. Comparing these graphs, the reduction in carcass weight according to the invention compared to prior art carcass can therefore be clearly discerned. It is technically undesirable for the cord fiber packing density of the inner carcass ply 12 to be greater than 95%. This is because otherwise there would be too little rubberized layer between the filaments, and there would be no strong bond between the top and bottom halves of the ply, and both rubberized layers of the filament ply would be too thin. This is because the adhesion is not sufficient. Additionally, the inner and outer carcass plies are exposed to different amounts of stress. Therefore, the inner carcass ply needs to withstand the internal pressure of the tire. In the case of inner carcass plies, if the cord fiber packing density is lower than 55%, the rubberized layer between the cord fibers will not collapse uniformly, which will lead to an uneven carcass layer. Therefore, the rubberized layer between the cord strands is completely crushed by the tire internal pressure in areas where the packing density is low. In the case of the outer carcass ply, this load due to internal tire pressure no longer exists. There is therefore no risk here of non-uniform conditions in the carcass layer;
Lower cord fiber packing densities can be used. Due to the lower stress, the thickness of the rubberized layer of the outer carcass plies can also be reduced. But compared to the thickness of ordinary rubberized layer 50
It should not be reduced by more than %, because otherwise it would approach the diameter of the cord filament. Furthermore, the packing density of the outer carcass ply is 20 to 70% higher than that of the inner carcass ply.
Low value (i.e. 30% to 80% of inner carcass ply)
However, the minimum packing density is 20% in order to reduce the total weight of the tire. The selection of this packing density primarily results from the different dimensions of the tire. For example, for a size 135-13 tire, the inner carcass ply has a cord fiber packing density of 55%;
The outer carcass plies should have a cord fiber packing density of 20%, for which size 19
For a 5/70-15 tire, the inner carcass ply should have a packing density of 95% and the outer carcass ply should have a packing density of 60%. When the packing density of the outer carcass ply becomes lower than the packing density of the inner carcass ply to more than 70% of the above critical value, the ply will become unstable in order to ensure tire strength, and reduced to less than 20%. In some cases, the economical advantages that can be obtained over the inner carcass ply by purposely making the outer carcass ply different from each other may become meaningless. In order to maintain its function as a carcass ply, the packing density of the outer carcass ply should be at least 20%. Pneumatic tires have various requirements regarding safety, running posture, economy, and ride comfort. Generally speaking, there are two types of running postures: a guiding posture and a deflection posture. This driving attitude includes driving direction stability, deflection accuracy, stability with changes in driving direction, control of the vehicle in limit conditions, and reverse torque attitude. This running attitude is favorable based on the shape and arrangement of the auxiliary layer. For safety, the ability to maintain air pressure against puncture pressure can be cited. For economic reasons, in addition to the typical costs, the rolling resistance is also calculated, which results in a negligible energy cost. Resilience, tire uniformity, and quiet running are important factors for good ride comfort. Good values in elastic performance are obtained with the auxiliary layer. The following table is an example of an inner carcass ply and an outer carcass ply, showing the attributes of each material that result in the lowest packing density. Materials each having desired properties can be selected and combined to create a carcass compatible with the present invention consisting of inner and outer carcass plies.

【table】

[Table] Example for a carcass where the radially outer ply is an auxiliary layer 1 The radially inner ply 12 is cord type 18
Made of 40/2 rayon. Number of cords present per denmeter: 130 This corresponds to a packing density of 93.6%. The cord diameter is 0.72mm. The layer thickness is 1.38mm. The thickness of the rubberized layer is therefore 0.33 mm above and below the cord diameter. Tension is 18.5Kg. The fabric strength is 2405Kg/dm. Rubberized layer mixture
The 300% module is 92.8Kg/ ^cm2 . The weight of the fabric is
It was found to be 1503g/ ^m2 . The outer ply 14 as an auxiliary layer is cord type 14.
Made from 00/1 nylon. Number of fibers present per decimate: 110 This is a fiber diameter of 0.43 mm, which corresponds to a packing density of 47.3%. The thickness of the rubberized layer is 0.11 mm. The tension is 11.4Kg. Fabric strength is 1254Kg/dm
It is. 300% module of rubberized layer mixture
It is 193.7Kg/ ^cm2 . The fabric weight was found to be 750g/ ^m2 . The fabric strength of the auxiliary layer is 48% lower compared to the radially inner ply. The weight loss in the auxiliary layer is measured to be 50% compared to the inner ply. The reduction in thickness of the rubberized layer over the cord filament diameter in the auxiliary layer is 67%. The 300% modulus of the rubberized layer of the auxiliary ply is 109% higher compared to the rubberized layer of the inner ply. By using the above-mentioned auxiliary layer, the weight of the tire is significantly reduced. The auxiliary layer improves the stability within the driving position, which remains safe. The auxiliary layer further improves the elastic carcass profile. The resulting favorable flex area again results in improved continuous toughness, high speed characteristics and rolling resistance.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a pneumatic vehicle tire, Fig. 2 shows the details of the carcass in a spatial partial view, and Fig. 3 shows the weight versus packing density in a carcass belonging to the prior art. FIG. 4 is a graph showing the relationship between weight and packing density of a carcass according to the present invention. Reference number in the diagram 1...Pneumatic tire for vehicle,
2...Radial carcass, 3...Bead part, 4
... Bead ring, 5 ... Core member, 6 ... Tread, 7 ... Tread reinforcement part, 8, 9 ... Cord layer, 10 ... Rubber protective layer, 11 ... Rubber strip, 12 ... Inner carcass ply , 13...Carcass folding, 14...Outer carcass ply, 15...Bending area.

Claims (1)

[Claims] 1. A pneumatic tire 1 for a vehicle having a tire tread 6 reinforced by a band-shaped tread reinforcing portion 7 and a radial carcass 2, wherein the radial carcass is composed of two cord fabric plies. , whose radially inner carcass ply 12 wraps around the bead ring 4 with the core member 5 from its inside to the outside to form a carcass fold 13, and whose radially outer carcass ply 14 of the cord fabric ply wraps around the bead ring 4 with the core member 5 from its inside to outside to form a carcass fold 13. In a pneumatic vehicle tire, the inner carcass ply 12 surrounds the inner carcass ply 12 with its entire arcuate periphery in cross-section and ends outside the carcass flap 13 in the area of the bead ring 4. The fabric has a cord fiber packing density between 55 and 95%, and the outer carcass ply 14 has a packing density that is 20 to 70% lower than that of the inner carcass ply, but has the lowest cord fiber packing density. Filament packing density is 20
%, characterized in that the radially outer carcass ply 14 has a rubberized layer that is reduced by up to 50% compared to a normal rubberized layer. Included tires. 2. The pneumatic tire for a vehicle according to claim 1, wherein the radially outer carcass ply 14 has fewer fibers per cord than the radially inner carcass ply 12. 3. Vehicle air according to claim 1 or 2, characterized in that cord fabrics having different materials and fiber structures are used for the radially inner and outer carcass plies 12, 14. Included tires. 4. The carcass ply 14 on the outside in the radial direction is made of a woven fabric made of a single thread (fiber) instead of a cord. Pneumatic tires for vehicles. 5. The radially inner and outer carcass plies are provided with rubberized layers having different elastic moduli, the outer ply 14 having a rubberized layer with a higher elastic modulus. A pneumatic tire for a vehicle according to one of claims 1 to 4.