JP2011245938A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of surely exerting excellent steering stability by advantageously enhancing lateral force generated in the tire by effectively suppressing crushing shearing force generated just under load in a shoulder land portion, even when the shoulder land portion is formed in a region striding across an outermost side edge of a widened belt reinforcing layer.SOLUTION: This pneumatic tire includes a carcass 1, at least one belt reinforcing layer 2, one or more belt layers 3 and 4, and tread rubber 5. The shoulder land portion 10 located to stride across an outermost side edge position E of the belt reinforcing layer 2 is demarcated in the tread rubber 5 by a shoulder peripheral groove 6 continuously extending in a tread peripheral direction. A distance from a tread grounding surface 5a of the shoulder land portion 10 to the belt reinforcing layer 2 is made longer at an outside end of the belt reinforcing layer 2 of the shoulder land portion 10 as compared with a tire equator CL side.

Description

  The present invention relates to a pneumatic tire, and more particularly to a heavy duty pneumatic tire suitable for use in heavy duty vehicles such as trucks and buses. In particular, when a slip angle is given to the tire, the generated lateral force of the tire is increased. The present invention relates to a pneumatic tire that can improve steering stability.

  Conventionally, from the cord extending substantially in the tread circumferential direction, for example, by extending the cord at an angle of 5 ° or less with respect to the tread circumferential direction on the outer peripheral side of the crown region of the carcass that can have a radial structure. There is known a tire in which one or more belt reinforcing layers are provided and the diameter of the tire is suppressed by using the belt reinforcing layer. As such a tire, there exist some which were indicated by patent documents 1-3, for example.

  Here, the cord forming the belt reinforcing layer may be a linear, zigzag, or wave shape extending in the tread circumferential direction, or a small tensile force until the elongation reaches about 2%. On the other hand, if the elongation rate exceeds the elongation rate, the elongation rate decreases even with a large input, so-called one having a large initial elongation, such as a Lang twist cord, a high elongation cord, or the like can be used.

  By the way, when securing the initial elongation by making the cord of the belt reinforcing layer into a zigzag or wave-shaped extended form, to secure the initial elongation, the tires assembled with the rim are attached to a JATMA (Tha Japan Automobile Tires Associations, Inc.). .), TRA (The Tire and Rim Association, Inc.), ETRTO (The European Tire and Rim Technical Organization) and other standards filled with the highest air pressure defined by YEAR BOOK and others It is preferable that Thereby, the function which suppresses the diameter growth of a tire can fully be exhibited in a belt reinforcement layer.

  In the pneumatic tires disclosed in Patent Documents 1 to 3 described above, in order to improve the steering stability performance, the belt layers that extend so as to cross each other are widened to increase the in-plane shear rigidity, that is, the tire is generated. However, the belt reinforcing layer also has a belt for the purpose of suppressing the separation from the belt layer on the side edge of the belt reinforcing layer and improving the durability of the belt reinforcing layer itself. There is a tendency to widen the reinforcing layer.

JP 2000-62411 A JP 2009-184371 A JP 2009-126363 A

  However, when a shoulder land portion, for example, a shoulder rib is formed in a region straddling the outermost edge of the belt reinforcing layer due to the widening of the belt reinforcing layer, a lateral force SF is generated in the tire by applying a slip angle to the tire. In this case, the so-called crushing shear force CS is greatly increased at the portion immediately below the load, particularly at the side portion of the shoulder rib 100 shown in FIG. 4 on the tread center side. FIG. 4 is an explanatory cross-sectional view illustrating an enlarged portion of the shoulder rib in the tread width direction.

The crushing shear force CS is greatly increased because the portion directly under the load of the shoulder land portion is high due to the high rigidity of the tire in the circumferential direction by the belt reinforcing layer 102 (see FIG. 4). This is because the belt reinforcing layer 102 bulges and deforms to the tread center side as if it is crushed and deformed.
When the crushing shear force CS is greatly increased, the lateral force SF generated in the tire due to the application of the slip angle to the tire is offset by the crushing shear force CS. In addition, it is difficult to increase the lateral force SF as expected by increasing the width of the belt layer 104 (see FIG. 4) to increase the lateral force SF. It was difficult to improve sufficiently depending on the situation.

The crushing shear force CS is generally expressed as a product of the deformation amount of the shoulder rib 100 and the rigidity of the shoulder rib 100.
The object of the present invention is to effectively suppress the crushing shear force generated directly under the load in the shoulder land portion even when the shoulder land portion is formed in the region straddling the outermost edge of the widened belt reinforcement layer. Thus, it is an object of the present invention to provide a pneumatic tire that can advantageously improve lateral stability generated in the tire and reliably improve steering stability performance.

  The pneumatic tire according to the present invention is disposed on the outer peripheral side of the carcass crown region and the carcass ply extending in a toroidal manner between the pair of bead portions, and extends in the tread circumferential direction. At least one belt reinforcing layer made of existing cords, one or more belt layers made of cords arranged on the outer circumferential side of the belt reinforcing layer and extending obliquely with respect to the tread circumferential direction, and the outer circumferential side of the belt layer And a tread rubber that forms a tread ground surface, and is a shoulder circumferential groove extending continuously in the tread circumferential direction, straddling the tread rubber across the outermost edge position of the belt reinforcing layer. And the distance from the tread grounding surface of the shoulder land portion to the belt reinforcing layer is outside the belt reinforcing layer of the shoulder land portion. Who has been longer than the tire equator side of.

  The cord forming the belt reinforcing layer can be extended in a spiral shape in the tread width direction in the form of a straight line, a zigzag shape, a wave shape or the like in the tread circumferential direction, and the cord elongation rate is 2 %, It stretches greatly with a small tensile force, but after exceeding the elongation rate, the elongation rate decreases even with a large tensile force. be able to.

  In addition, when securing the initial elongation of the cord by extending the cord of the belt reinforcement layer in a zigzag or other detour shape, the YEAR BOOK of the standards such as JATMA, TRA, ETRTO, etc. It is preferable that the detour shape disappears in a state in which the maximum air pressure defined by others is filled, in order to sufficiently exert the diameter growth suppressing function in the use state of the pneumatic tire on the belt reinforcing layer.

The distance from the tread contact surface to the belt reinforcing layer is preferably gradually increased from the tire equator side of the shoulder land portion toward the outer side of the belt reinforcing layer.
Further, the drop height of the tire radial distance from the center in the tire width direction to the tire contact edge at the time of filling the tire internal pressure is set to 0% or more and 1.5% or less of the tire radial distance at the center in the tire width direction. It is preferable.

  By the way, the cord crossing width of the two or more belt layers formed by extending the cords so as to cross each other is preferably in the range of 65 to 90% of the tread width.

  In the pneumatic tire according to the present invention, the distance from the tread ground surface to the belt reinforcing layer of the shoulder land portion straddling the outermost edge position of the belt reinforcing layer exhibiting a high “equivalent function” is Because the outer edge of the belt reinforcement layer is longer than the tire equator side, a slip angle is given to the tire at the time of load rolling. However, as illustrated in FIG. 4, the absolute value of the deformation amount can be suppressed to be smaller than that of the conventional technique even if the bulge is deformed to the tread center side.

Therefore, in general, the crushing shear force expressed as the product of the deformation amount of the shoulder land portion and the land portion rigidity is effectively suppressed, and the offset of the lateral force generated in the tire based on the application of slip is effectively suppressed. It is possible to sufficiently prevent high steering stability.
In this tire, the distance from the tread contact surface to the belt reinforcing layer is gradually increased from the tire equator side of the shoulder land toward the outer side of the belt reinforcing layer, so that the belt moves from the shoulder center side to the shoulder outer side. Since it is pushed diagonally, the tread bulging deformation is small on the shoulder center side and large on the shoulder outer side. The crushing shearing force expressed in the product of the rigidity of the shoulder land portion and the deformation amount of the shoulder land portion and acting in the direction to cancel the generated lateral force can be reduced on the shoulder center side and increased on the shoulder outer side. Therefore, the crushing shearing force on the shoulder center side that cancels the lateral force SF can be kept small, and the lateral force SF can be improved.

  Also, when the drop in the tire radial distance from the center in the tire width direction to the tire contact edge at the time of filling the tire internal pressure is 0% or more and 1.5% or less of the tire radial distance at the center in the tire width direction The tire contact shape can be made rectangular, and the contact length outside the shoulder can be increased. Therefore, the lateral force SF of the entire tire increases as the region for generating the lateral force SF increases. In particular, as described above, the crushing shear force on the outside of the shoulder is in the direction of the lateral force SF, and thus the lateral force SF is in a further increasing direction.

  On the other hand, if it exceeds 1.5%, the tire ground contact shape becomes round due to the wide belt reinforcing layer, so that the area for generating the lateral force SF decreases and the lateral force SF decreases. Furthermore, if it is less than 0%, the contact length on the outer side of the shoulder is extended and the area for generating the lateral force SF is increased, but there is a greater concern about a decrease in wear resistance performance in the shoulder portion.

  Here, when the cord crossing width of the two or more belt layers formed by crossing the cords is in the range of 65 to 90% of the tread width, the in-plane bending rigidity of the belt composed of the belt layers is increased. Within this range, the belt width can be set so that the lateral force SF can be positively increased. That is, when the above numerical range is less than 65%, the in-plane bending rigidity of the belt is remarkably lowered, the lateral force SF is also lowered, and the width of the belt layer of two or more layers is greatly different. There is also a concern that the force (PSF) will increase. On the other hand, if the above numerical range exceeds 90%, the in-plane bending rigidity of the belt increases and the lateral force SF also increases, but there is a concern about deterioration in durability such as belt delamination.

BRIEF DESCRIPTION OF THE DRAWINGS The internal structure of the pneumatic tire which concerns on one embodiment of this invention is shown schematically, (a) is a fragmentary sectional view in alignment with a tread width direction, (b) is a partial expansion | deployment top view of a belt reinforcement layer and a belt layer. is there. It is explanatory drawing by the cross section along the tread width direction which shows the fall height of the tire grounding edge part in the pneumatic tire of FIG. The road surface contact state of the tread of a pneumatic tire is shown, (a) is a footprint diagram of the pneumatic tire according to the present invention, and (b) is a footprint diagram of a conventional pneumatic tire. It is sectional explanatory drawing which expands and illustrates the tread width direction part of a shoulder rib.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 schematically shows an internal configuration of a pneumatic tire according to an embodiment of the present invention, in which (a) is a partial cross-sectional view along the tread width direction, and (b) is a belt reinforcing layer and a belt layer portion. FIG. As shown in FIG. 1, the carcass 1 of a pneumatic tire is composed of, for example, a single carcass ply extending in a toroidal manner between a pair of bead portions (not shown), and can have a radial structure.

The belt reinforcing layer 2 disposed on the outer peripheral side in the crown region of the carcass 1 is a ribbon shape having a width of 3 to 20 mm in which a cord extending in the tread circumferential direction, for example, a plurality of cords arranged in parallel is covered with rubber. These strips can be formed by a cord wound spirally around the tire axis and extending at an angle of 5 ° or less with respect to the tread circumferential direction.
Two or more belt reinforcing layers 2 can be provided.

  Here, the cord 2a of the belt reinforcing layer 2 can be an organic fiber cord in addition to a long twisted steel cord or a high elongation steel cord having a large initial extension as described above, and in the tread circumferential direction. On the other hand, a steel cord extending in a detour shape such as a zigzag shape, a crank shape, or a wave shape may be used.

  One or more belt layers made of a cord extending at an inclination angle of 35 to 55 °, for example, with respect to the tread circumferential direction on the outer peripheral side of the belt reinforcing layer 2 (in FIG. 1, two belt layers 3 and 4 are illustrated) Here, the cords 3a and 4a forming the belt layers 3 and 4 respectively extend in opposite directions to the tread circumferential direction.

  A tread rubber 5 that forms a tread grounding surface 5a is disposed on the outer peripheral side of the belt layers 3 and 4, and, for example, two tread width outer circumferential grooves (shoulder circumferences) are provided on the tread rubber 5. (Grooves) 6 and four circumferential grooves 7a and 7b on the inner side in the tread width direction, by forming a total of six circumferential grooves, the tread ground contact surface 5a has seven land portions, for example, one at the center in the tread width direction. The rib 8 is divided by four ribs 9a and 9b on both sides of the rib 8 and two ribs (shoulder ribs) 10 at both ends in the tread width direction.

  By the way, in such a pneumatic tire, the belt reinforcing layer 2 has one or more layers, and the outermost edge in the tread width direction is attached to a product tire attached to the rim in accordance with JATMA, TRA. It is preferable that the tire diameter growth rate when filled with the highest air pressure defined by the standard YEAR BOOK, etc., such as ETRTO, is positioned on the outer side in the tread width direction than the position where A% described later. This A% here is the tire diameter corresponding to the elongation rate (%) when the cord forming the belt reinforcing layer 2 is subjected to a tensile test and the cord exhibits an elastic modulus of 10% of the breaking elastic modulus EI. It means the growth rate.

  In this pneumatic tire, the shoulder circumferential groove 6 disposed on the outermost side in the tread width direction and continuously extending in the tread circumferential direction is positioned on the tread rubber 5 across the outermost edge position E of the belt reinforcing layer 2. A shoulder rib 10 as a shoulder land portion is defined. The shoulder rib 10 is formed of an inclined surface that is gently inclined upward from the tread shoulder side toward the tread center side to allow a curved surface.

  In this pneumatic tire, in the shoulder rib 10 positioned at the outer end in the tread width direction of the tread rubber 5 when the tire internal pressure is filled, the belt reinforcing layer extends from the tread ground surface 5a at an arbitrary position of the shoulder rib 10. The portion disposed on the shoulder rib 10 of the belt reinforcing layer 2 is bent inward in the tire radial direction so that the distance up to 2 becomes longer toward the outer end (outer side in the tread width direction) of the tire ground contact surface 5a. .

  That is, as shown in FIG. 1, in the cross section along the tread width direction of the shoulder rib 10 when the tire internal pressure is filled, the belt reinforcement from the tread ground contact surface 5a at the tread width direction center side end S1 on the tire equator side of the shoulder rib 10 is performed. Compared with the distance A in the tire radial direction to the surface of the layer 2, the tread grounding surface 5a at the outer side S2 in the tread width direction outside the tread width direction central end S1 which is the outer end of the belt reinforcing layer of the shoulder rib 10 The belt reinforcing layer 2 is arranged so that the distance B in the tire radial direction from the belt to the surface of the belt reinforcing layer 2 is longer (A <B).

The distance in the tire radial direction from the tread contact surface 5a to the surface of the belt reinforcing layer 2 is gradually increased so as to gradually increase from the tire equator (tread center) CL side of the shoulder rib 10 toward the outer end of the belt reinforcing layer 2. is doing.
As a result, the rubber thickness, which is the length in the tire radial direction of the tread rubber 5, is the outer side in the tread width direction on the outer side in the tread width direction than the central side in the tread width direction compared to the center side in the tread width direction of the shoulder rib 10, that is, the tire equator side. The end, that is, the outer end of the belt reinforcing layer 2 becomes thicker.
Furthermore, in this pneumatic tire, the drop height from the tire equator CL at the tire ground contact end when the tire pressure is filled is specified.

  FIG. 2 is an explanatory view of a cross section along the tread width direction showing a drop height of a tire ground contact end portion in the pneumatic tire of FIG. 1. As shown in FIG. 2, in the cross section along the tread width direction of the tread rib 10 at the time of tire internal pressure filling, the tire radial direction distance of the tire equator CL is R, and the tire ground contact end that is the ground contact end of the tire ground contact surface 5a. The difference from the tire radial direction distance R of the tire equator CL, that is, r / R when the drop height from the tire equator CL is r, is 0 [%] or more and 1.5 [%] or less (0 A tire crown having a tire radial direction length R of the tire equator CL in the tread rib 10 is formed, which satisfies ≦ r / R ≦ 1.5).

That is, the drop in the tire radial distance from the tire equator CL to the tire ground contact edge at the center of the tire width direction when the tire internal pressure is filled is the tire radial direction of the tire equator CL with reference to the tire equator CL (100%). The distance R is 0 [%] or more and 1.5 [%] or less.
According to the pneumatic tire having such a configuration, the amount of rubber of the shoulder rib 10 of the tread rubber 5 can be increased, that is, the amount of rubber in the tread shoulder region can be increased. The crown shape has a small difference in tire diameter between the equator CL and the shoulder rib 10 and the thickness of the tread rubber 5 from the surface of the belt reinforcing layer 2 to the tire ground contact surface 5a is the belt reinforcing layer from the tire equator CL side of the shoulder rib 10. The end side of 2 is larger.

  3A and 3B show a road surface contact state of a tread of a pneumatic tire. FIG. 3A is a footprint diagram of the pneumatic tire according to the present invention, and FIG. 3B is a footprint diagram of a conventional pneumatic tire. As shown in FIG. 3, in the pneumatic tire according to the present invention, in the cross section along the tread width direction, there is little difference in tire diameter between the tire equator CL and the shoulder rib 10, and the thickness of the tread rubber 5 is Since the end portion of the belt reinforcement layer 2 is larger than the tire equator CL side of the shoulder rib 10, the tire ground contact surface 5 a is substantially grounded to the road surface from the tire equator CL side to the end portion of the belt reinforcement layer 2. (See (a)).

  That is, in the case of a conventional pneumatic tire, the tread shoulder region (the end portion side of the belt reinforcing layer 2) does not contact the road surface, and the tire contact surface has a round shape with four corners cut off (see (b)). On the other hand, in the case of the pneumatic tire according to the present invention, the tread shoulder region (the end portion side of the belt reinforcing layer 2, that is, the outer corner portion of both shoulder ribs 10) is also surely grounded to the road surface. The four corners are clearly rectangular (see (a)).

  For this reason, the rigidity with respect to the load of the shoulder rib 10 is increased, and when the tire rolls under load, the shoulder rib 10 which is crushed and deformed by the belt reinforcing layer 2 immediately under the load is bulged and deformed toward the tread center. Can be effectively suppressed as compared with the prior art. As a result, the crushing shear force in the direction to cancel the lateral force, which is expressed as the product of the shoulder rib deformation amount and the shoulder rib rigidity, is also effectively reduced, so that a slip angle is given to the tire to generate the lateral force. In this case, the offset of the lateral force due to the crushing shear force can be suppressed sufficiently small, and the steering stability can be advantageously improved.

A tire for trucks and buses with a size of 435 / 45R22.5 is assembled to a rim of 14.00 x 22.5, a drum test is performed with a filling air pressure of 900 Pa, a load load of 49 kN, and a tire of 50 km / The cornering power (CP) generated by the tire when rotating with a slip angle of 1 ° at a speed of h is measured for each of the conventional tire and example tires 1 and 2, and the conventional tire is controlled. As a result of index evaluation, the results shown in Table 1 together with the specifications were obtained.
Each tire described above has six circumferential grooves with a depth of 15 mm along the tire equator plane, and the relative ratio of the widths of the ribs defined by these circumferential grooves is determined from the tread center side. Toward the tread shoulder side, the ratio was 1: 1: 1: 1.8.

  According to the results shown in Table 1, 0% or more and 1.5 [%] with respect to the conventional tire in which the ratio (r / R) of the falling height of the tire ground contact edge portion is 1.73 [%]. Example tires 1 and 2 according to the present invention, which are the following (0 ≦ r / R ≦ 1.5), suppress the generation of a crushing shear force that cancels the lateral force SF as compared with the conventional tire, thereby reducing the lateral force. Since SF can be effectively increased, as a result, an increase in cornering power (CP) and, consequently, an improvement in steering stability can be realized.

  According to the present invention, even if the outer peripheral side portion of the belt reinforcing layer in the tire radial direction of the shoulder land portion bulges and deforms toward the tread center side by applying a slip angle to the tire during load rolling, Compared to technology, the absolute value of the deformation amount can be kept small, so when a slip angle is given to the tire, the lateral force generated by the tire can be increased and the driving stability can be improved. It is most suitable for heavy duty pneumatic tires used in heavy duty vehicles such as

DESCRIPTION OF SYMBOLS 1 Carcass 2 Belt reinforcement layer 2a Belt reinforcement layer cord 3, 4 Belt layer 3a, 4a Belt layer cord 5 Tread rubber 5a Tread ground surface 6 Shoulder circumferential groove 7a, 7b Circumferential groove 8, 9a, 9b Rib 10 Shoulder rib A, B tire Radial distance CL Tire equator E Belt reinforcement layer outermost edge position R Tire radial distance of tire equator CL r Falling height from tire equator CL S1 Tread width direction center side edge S2 Tread width direction outer position

Claims (4)

A belt reinforcing layer comprising a carcass made of one or more carcass plies extending in a toroidal shape between a pair of bead portions and a cord extending on the outer circumferential side of the crown area of the carcass and extending in the tread circumferential direction. At least one layer is disposed on the outer circumferential side of the belt reinforcing layer, and is disposed on the outer circumferential side of the belt layer by forming one or more belt layers made of cords that are inclined with respect to the circumferential direction of the tread. A pneumatic tire with tread rubber,
A shoulder circumferential groove extending continuously in the tread circumferential direction defines a shoulder land portion located across the outermost edge position of the belt reinforcing layer on the tread rubber, and from the tread ground surface of the shoulder land portion. The distance to the belt reinforcement layer is a pneumatic tire in which the outer edge of the belt reinforcement layer in the shoulder land is longer than the tire equator side.   2. The pneumatic tire according to claim 1, wherein a distance from the tread contact surface to the belt reinforcing layer is gradually increased from a tire equator side of the shoulder land portion toward an outer end of the belt reinforcing layer.   A drop height of a tire radial direction distance from a tire width direction center to a tire contact edge at the time of filling the tire internal pressure is 0% or more and 1.5% or less of a tire radial direction distance of the tire width direction center. The pneumatic tire according to 1 or 2.   The pneumatic tire according to any one of claims 1 to 3, wherein a cord crossing width of two or more belt layers formed by crossing cords is in a range of 65 to 90% of a tread width.

Images