Patent Description:
The present application relates to a heavy-duty tire, and more particularly, to a heavy-duty tire to which a technology for winding a reinforcing belt part in a circumferential direction of the tire is applied. <CIT> discloses that the pneumatic tire includes a belt layer that is formed by laminating a plurality of belt plies including the circumferential reinforcing layer. <CIT> discloses a tire comprising at least two working layers and at least one layer of circumferential reinforcing elements. The layer of circumferential reinforcing elements comprises at least a central part and two axially exterior parts, the elastic modulus of the rubber compound with which the circumferential reinforcing elements of the central part are coated being less than the modulus of the rubber compound with which the circumferential reinforcing elements of the axially exterior parts are coated. <CIT> discloses that a pneumatic tire comprises a carcass layer, a belt layer disposed on an outer side of the carcass layer in a tire radial direction, and a tread rubber disposed on the outer side of the belt layer in the tire radial direction. <CIT> discloses a method for determining stress changes in a belt layer of vehicle tyres, preferably of radial construction, having a tread, a carcass insert and a belt structure comprising at least two belt layers, wherein the belt layers have steel cords as strength members. <CIT> discloses a tire comprising an overlay ply wherein (i) the shoulder section of the overlay comprises an elastomer and short polymeric or non-polymeric reinforcing fibers present in an amount of from <NUM> to <NUM> parts fiber per hundred parts of elastomer, the short fibers having a tenacity of at least <NUM> grams per dtex, a modulus of at least <NUM> grams per dtex and a length of from <NUM> to <NUM> and wherein the fibers are aligned substantially parallel to each other in a controlled angle of orientation within the overlay wherein the orientation is selected such that it decreases tire noise, and (ii) the section of overlay in the crown of the tire comprising cords of continuous filament polymeric fibers or continuous strands of metal or combinations thereof, the cords being aligned in a circumferential direction around the tire.

In the related art, a heavy-duty tire for a truck or bus includes steel belts disposed in four layers, and a carcass disposed in a single layer. <FIG> illustrates the tire in the related art.

Recently, as a load per tire increases, a reinforcing belt is additionally applied to optimize a ground contact shape (a grounded shape of the tire when the tire is in contact with the ground surface) and enhance durability performance of the belts.

In general, in a case in which a reinforcing belt is applied between a second belt and a third belt, a single strand of steel cord is wound in a spiral coil shape at an angle of <NUM> to <NUM> degree.

Meanwhile, <NUM> to <NUM> minutes (at a working speed of <NUM> MPM (<NUM>/min)) are required for each tire to wind a single strand of steel cord spirally. To improve the working process of winding the steel cord spirally (in the form of an infinite coil) as described above, a dual-strand supply technology for supplying two strands of steel cords is also applied.

However, the technology for winding the single or two strands of steel cords has a limitation in improving the ground contact shape by inhibiting an overall growth of an outer portion of the belt.

That is, a method of winding several strands of steel cords in the form of a rolling product having a predetermined width is more effective in inhibiting an overall growth of the belt compared to the method of winding the single strand of steel cord.

Recently, as autonomous driving technologies are activated, it is preferable that tires, which are excellent in long-term durability and abraded uniformly by a ground contact shape optimized by an increase in load per tire, are applied to large-size vehicles such as trucks and buses in the future.

However, since the reinforcing belt in the related art is manufactured by winding the single or two strands of steel cords spirally, there is a problem in that the performance in manufacturing the reinforcing belt is deficient.

In addition, the dual-strand supply method also causes a spatial limitation because an additional facility needs to be manufactured. For this reason, the dual-strand supply method has a limitation in inhibiting the growth of a casing of the entire belt.

Therefore, to improve abrasion performance and durability performance of the tire to be applied to the large-size vehicle, there is a need to develop a technology for uniformizing and minimizing a ground pressure of a tread part in contact with the ground surface and minimizing the amount of growth of the tire in a circumferential direction of the tire when the vehicle travels over a long period of time.

The invention is defined by the independent claim Preferable embodiments are defined by the dependent claims. The present invention has been made in an effort to solve the above-mentioned problems, and an object of the present invention is to provide a heavy-duty tire, in which a reinforcing belt part is inserted, in a circumference direction of the tire, into at least one steel belt or between a tread part and a steel belt part, thereby improving durability, RR performance, and handling performance of the steel belt part, uniformizing a ground pressure applied to the tread part, and reducing a rate of incidence of unsuitable air pressure.

Technical problems to be solved by the present invention are not limited to the above-mentioned technical problems, and other technical problems, which are not mentioned above, may be clearly understood from the following descriptions by those skilled in the art to which the present application pertains.

To achieve the above-mentioned object, the present invention provides a heavy-duty tire as defined in claim <NUM>.

According to claim <NUM> the steel belt part comprises : a first steel belt disposed adjacent to a carcass; a second steel belt positioned above the first steel belt; a third steel belt positioned above the second steel belt; and a fourth steel belt positioned above the third steel belt. Each of a plurality of reinforcing belt parts is inserted between the second steel belt and the third steel belt and wound in the circumferential direction of the tire.

The reinforcing belt parts are respectively formed at two opposite sides and a central portion of the tread part and disposed to be spaced apart from one another.

In a preferred embodiment of the present invention, the reinforcing belt part may be manufactured by rolling the steel cord within a range of <NUM> EPI to <NUM> EPI.

In another preferred embodiment of the present invention, the reinforcing belt part may be manufactured to have a width of <NUM> to <NUM>.

The reinforcing belt parts may include rubber with which the steel cords are topped, a diameter of the steel cord may be <NUM> to <NUM>, and a thickness of the reinforcing belt part may be <NUM> to <NUM>.

In a preferred embodiment of the present invention, a tensile force of the steel cord may be <NUM>,<NUM> N, which is <NUM> kgf to <NUM>,<NUM> N, which is <NUM> kgf.

According to the present invention configured as described above, the reinforcing belt part is inserted, in the circumference direction of the tire, between two steel belts, thereby improving durability, RR performance, and handling performance of the steel belt part, uniformizing the ground pressure applied to the tread part, and reducing the rate of incidence of unsuitable air pressure.

The effects of the present invention are not limited to the above-mentioned effects, and it should be understood that the effects of the present invention include all effects that may be derived from the detailed description of the present invention or the appended claims.

Hereinafter, the present invention will be described with reference to the accompanying drawings. However, the present invention may be implemented in various different ways and is not limited to the embodiments described herein. A part irrelevant to the description will be omitted in the drawings in order to clearly describe the present invention, and similar constituent elements will be designated by similar reference numerals throughout the specification.

Throughout the present specification, when one constituent element is referred to as being "connected to (coupled to, in contact with, or linked to)" another constituent element, one constituent element can be "directly connected to" the other constituent element, and one constituent element can also be "indirectly connected to" the other element with other elements interposed therebetween. In addition, unless explicitly described to the contrary, the word "comprise/include" and variations such as "comprises/includes" or "comprising/including" will be understood to imply the inclusion of stated elements, not the exclusion of any other elements.

The terms used in the present specification are used only for the purpose of describing particular embodiments and are not intended to limit the present application. Singular expressions include plural expressions unless clearly described as different meanings in the context. In the present specification, it should be understood the terms "comprises," "comprising," "includes," "including," "containing," "has," "having" or other variations thereof are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, components, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Hereinafter, a non-claimed example to understand the present application will be described with reference to the accompanying drawings.

<FIG> is a cross-sectional side view illustrating a heavy-duty tire according to a non-claimed example to understand the present application when viewed in one direction.

Referring to <FIG>, a heavy-duty tire <NUM> according to a non-claimed example to understand the present application includes a tread part <NUM>, a steel belt part <NUM>, and a reinforcing belt part <NUM>.

When the heavy-duty tire <NUM> rotates while the vehicle travels, the tread part <NUM> comes into contact with a road surface and pushes the road surface, such that the vehicle moves. The tread part includes treads <NUM> and grooves <NUM>.

The tread <NUM> is a portion that comes into contact with the road surface. The tread <NUM> may be provided in plural, and the grooves <NUM> are formed between the plurality of treads <NUM>. Therefore, the plurality of treads <NUM> is disposed to be spaced apart from one another.

The grooves <NUM> are formed between the plurality of treads <NUM> and smoothly discharge water or foreign substances introduced while the vehicle travels in the state in which the treads <NUM> are in contact with the road surface.

The steel belt part <NUM> includes one or more steel belts <NUM>, <NUM>, <NUM>, and <NUM> disposed inside the tread part <NUM>. In this case, the one or more steel belts <NUM>, <NUM>, <NUM>, and <NUM> are a first steel belt <NUM>, a second steel belt <NUM>, a third steel belt <NUM>, and a fourth steel belt <NUM>.

The first steel belt <NUM> is disposed adjacent to a carcass.

The second steel belt <NUM> is positioned above the first steel belt <NUM>.

The third steel belt <NUM> is positioned above the second steel belt <NUM>.

The fourth steel belt <NUM> is positioned above the third steel belt <NUM>.

The reinforcing belt part <NUM> is inserted between the one or more steel belts <NUM>, <NUM>, <NUM>, and <NUM> or between the tread part <NUM> and the steel belt part <NUM>.

Specifically, the reinforcing belt part <NUM> is manufactured as a rolling product made by winding a steel cord in a circumferential direction of the tire.

In addition, the reinforcing belt part <NUM> is manufactured by rolling the steel cord within a range of <NUM> EPI to <NUM> EPI. Here, EPI represents the number of strands of steel cords per one inch.

In addition, the reinforcing belt part <NUM> is manufactured to have a width of <NUM> to <NUM>, and a thickness of the reinforcing belt part <NUM> is <NUM> to <NUM>.

The reinforcing belt part <NUM> may include a steel cord, and rubber with which the steel cord is topped.

In this case, a diameter of the steel cord is <NUM> to <NUM>, an elongation percentage of the steel cord is <NUM>% or more, and a tensile force of the steel cord is <NUM> kgf to <NUM> kgf. To this end, the reinforcing belt part <NUM> is manufactured by coating the steel cord with topping rubber by inputting the strands of steel cords, one by one, into a spinneret die through a rolling process.

The steel cord has a lower tensile force than a spiral cord in the related art but has an increased EPI, thereby obtaining an effect of inhibiting the growth of the tire and reducing a weight of the tire.

However, in the case of the spiral cord in the related art, a diameter of the steel cord may be <NUM> to <NUM>, and a tensile force of the steel cord may be <NUM> to <NUM>.

In the case of the spiral cord in the related art, a single strand of cord is directly topped with rubber or rubber is attached to and covers the entire cord after the cord is completely wound. In this case, the topping rubber on the single strand of cord is not uniform, and the adhesiveness (tack) between the spiral cord and the topping rubber is degraded, which causes an unsuitable air pressure (defect) when the tire is vulcanized.

In addition, it is difficult to reduce the weight of the spiral cord in the related art because the diameter of the cord is large and the thickness of the topping rubber (including the cord) is <NUM> or more.

In contrast, the reinforcing belt part <NUM> according to the example may be manufactured such that a thickness of the topping rubber (including the cord) is at least <NUM>. Therefore, the reinforcing belt part <NUM> may be lightweight, thereby reducing rotational resistance against the tire.

The reinforcing belt part <NUM> may be inserted at different positions according to the example.

First, the reinforcing belt part <NUM> may be wound once or twice in the circumferential direction of the tire on outermost peripheral layers of first and third steel belts <NUM> and <NUM> or outermost peripheral layers of the second and fourth steel belts <NUM> and <NUM>.

In this case, the reinforcing belt part <NUM> is spirally formed and manufactured to have a width of <NUM> to <NUM>.

Second, the reinforcing belt part <NUM> is inserted between the second steel belt <NUM> and the third steel belt <NUM> and wound in the circumferential direction of the tire.

In this case, the reinforcing belt part <NUM> has the same width as the second steel belt <NUM>.

The process of forming the reinforcing belt part <NUM> is performed for a working time of <NUM> minute or less, and the reinforcing belt part <NUM> is wound with a preset width (<NUM> to <NUM>) while receiving preset tension during the working process. Therefore, the amount of growth of the tire in the circumferential direction is reduced compared to the method in the related art (the method of winding the strands of cords one by one). For example, <NUM> to <NUM> minutes are required to wind the single strand of steel cord spirally in the related art.

Third, according to an embodiment of the present application, the reinforcing belt parts <NUM> are respectively formed at two opposite sides and a central portion of the tread part <NUM> and disposed to be spaced apart from one another.

Specifically, the reinforcing belt parts <NUM>, which are cut into predetermined widths, are formed on three portions (left, center, and right portions) with a width of <NUM> to <NUM> between the second steel belt <NUM> and the third steel belt <NUM> while receiving the preset tension in the circumferential direction.

In this case, the reinforcing belt parts <NUM> are positioned at the central portion and the two opposite sides of the tread part <NUM> when the tread part <NUM> is viewed in the normal line direction.

Because ground pressures applied to the central portion and the two opposite sides of the tread part <NUM> are typically different from one another, the reinforcing belt parts <NUM> are divided and then wound, thereby optimizing the ground contact shapes of the central portion and the two opposite sides of the tread part <NUM>.

In the case of the tire in the related art used for a truck or bus, intervals between the cords are not uniform because the strands of cords made of steel are wound one by one in the form of a spiral coil. Further, the growth of the tire in the circumferential direction of the tire cannot be uniformly inhibited because a high shearing force is generated between the second belt and the third belt.

In contrast, in the case of the reinforcing belt part <NUM> according to a non-claimed example to understand the present application, the steel cord is cut by rolling at preset intervals (EPI (number of cord strands per one inch), which makes it possible to manufacture the reinforcing belt part <NUM> in which the interval of the steel cord is <NUM> to <NUM> EPI.

However, in the case in which the strands of steel cords are wound one by one according to the forming process (SPC) in the related art, the interval between the steel cords is restricted to <NUM> to <NUM> EPI, and thus the reinforcing belt part <NUM> is cut into a width of <NUM> to <NUM>, such that a small amount of shear stress is generated between the second steel belt <NUM> and the third steel belt <NUM>.

<FIG> is a view illustrating a result of analyzing the performance of the heavy-duty tire according to a non-claimed example to understand the present application and the performance of a tire having a general structure.

In <FIG>, T1 represents a tire including four belts having a general structure, T2 represents a tire including five belts including spiral cords, T3 represents a tire (partially) including the reinforcing belt part <NUM> according to a non-claimed example to understand the present application, and T4 represents a tire (fully) including the reinforcing belt part <NUM> according to a non-claimed example to understand the present application.

Specifically, in T1, a structure of a radial tire for a truck or bus in the related art is applied to a tire having an ultra-super single (USS) size. In general, a reinforcing belt is usually applied to the USS tire (T2).

In the case in which the reinforcing belt is applied by winding the strands of cords one by one, there is a limitation in inhibiting the overall growth of the belt casing and the manufacturing time increases.

According to the analysis results illustrated in <FIG>, T1 is excellent in RR performance, but the five belts, to which the reinforcing belt is applied to optimize the belt durability and the ground contact shape, is generally applied to the USS tire. It can be seen that the RR performance in T1 results from the effect made by reducing the weight.

That is, when in T2 to T4, a weight is set to be equal to a weight in T1, the RR performance is predicted to be equal in level to the RR performance in T1.

According to a result of applying the reinforcing belt (spiral coil (SPC)) of T2, a form quotient of the periphery of the belt decreases by maximum <NUM>% compared to T3 and T4. That is, the durability performance of the reinforcing belt is best in T3 and T4 to which the reinforcing belt part <NUM> is applied.

When T4 is fully applied, the amount of overall growth of the belt is inhibited to a minimum level, the amount of shearing force between the second belt and the third belt is decreased, and the ground contact shape also becomes quadrangular, such that the ground pressure is uniformly distributed, the tire is uniformly abraded, and the belt performance is improved.

In a case in which a load index is <NUM>,<NUM>/1EA, the structure including the first to third belts and the reinforcing belt part <NUM> may be applied to improve the belt durability performance and the RR performance in comparison with the general structure in the related art.

If the load index is high (<NUM>,<NUM> or more), the reinforcing belt part <NUM> may be applied by being wound once or twice on an upper side of an outermost periphery of the fourth steel belt <NUM>, which makes it possible to inhibit the amount of growth of the belt, maintain the rigidity of the entire belt even at a high speed, and improve the handling performance.

In the case of T3, the reinforcing belt part <NUM> is partially (split) applied, which makes it possible to improve the durability of the belt and the RR performance in comparison with the general structure in the related art. However, the reinforcing belt part <NUM> is partially (split) applied between the second steel belt <NUM> and the third steel belt <NUM> (at a position at which the angle of the belt is reversed and the shearing force is maximally generated).

According to the present application described above, since the reinforcing belt part <NUM> is cut into a preset width (<NUM> to <NUM>), the adhesiveness (tack) between the reinforcing belt part and the belt part is not degraded even though the reinforcing belt part <NUM> is attached on the outermost peripheral layer of the belt or between the second steel belt <NUM> and the third steel belt <NUM>. Therefore, an incidence rate of unsuitable air pressure is low.

In addition, according to the present application, in the case in which the slitting is performed on the reinforcing belt part <NUM> with a width of <NUM> to <NUM> and the reinforcing belt part <NUM> is applied by being wound on the upper side of the outermost periphery of the belt, the reinforcing belt part <NUM> may be applied to the upper sides of the first to third steel belts, the first to fourth steel belts, the second to third steel belts, and the second to fourth steel belts.

According to a non-claimed example to understand the present invention, since the reinforcing belt part is applied to the upper side of the outermost peripheral layer of the belt, the tire may be uniformly grown under high-speed traveling and high-load conditions, the uniform ground pressure may be ensured, and the handling performance may be improved.

It will be appreciated that the above embodiments have been described above for purposes of illustration. Therefore, it should be understood that the above-described embodiments are illustrative in all aspects and do not limit the present invention.

Claim 1:
A heavy-duty tire comprising:
a tread part (<NUM>) configured to contact with a road surface;
a steel belt part (<NUM>) comprising one or more steel belts (<NUM>, <NUM>, <NUM>, <NUM>) formed inside the tread part (<NUM>); and
a plurality of reinforcing belt parts (<NUM>);
wherein the steel belt part (<NUM>) comprises:
a first steel belt (<NUM>) disposed adjacent to a carcass;
a second steel belt (<NUM>) positioned above the first steel belt (<NUM>);
a third steel belt (<NUM>) positioned above the second steel belt (<NUM>); and
a fourth steel belt (<NUM>) positioned above the third steel belt (<NUM>);
characterized in that
each of the reinforcing belt parts (<NUM>) is manufactured as a rolling product made by winding steel cords in a circumferential direction of the tire;
wherein each of the reinforcing belt parts (<NUM>) is inserted between the second steel belt (<NUM>) and the third steel belt (<NUM>) and wound in the circumferential direction of the tire; and
wherein the reinforcing belt parts (<NUM>) are respectively formed at two opposite sides and a central portion of the tread part (<NUM>) and disposed to be spaced apart from one another.