JP2009255747A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure compatibility of enhancement of friction coefficient with a road surface and increase of a ground-contact area on a surface of a land part without sacrificing water discharge performance on a wet road surface, and without using a vulcanization mold of a complicated shape. <P>SOLUTION: In the pneumatic tire, the land part 11 brought into ground-contact with the road surface and a groove part 9 brought into non-ground-contact with the road surface formed lower than this, are formed on a tread part 1. The land part 11 has a low elastic layer 13 formed by a low elastic material having relatively lower modulus of elasticity, and a high elastic layer formed by a high elastic material having relatively higher modulus of elasticity than the low elastic material. The low elastic layer 13 and the high elastic layer are alternately superposed in a tire radial direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pneumatic tire in which a tread portion is formed with a land portion that is in contact with the road surface and a groove portion that is formed lower than this and is not grounded with respect to the road surface, and in particular, an improvement in a coefficient of friction with the road surface. The present invention relates to a pneumatic tire that can simultaneously suppress the deformation of the land part.

  In general, a tread portion of a pneumatic tire is formed with a groove or a sipe extending in the tire circumferential direction, the tire width direction, or a direction inclined to the tire from the viewpoint of improving braking / driving performance and steering stability. .

  As shown in FIG. 6 (a), the land portion 111 or block defined by the groove or sipe 109 applies a load perpendicular to the tread when the tire is mounted on a vehicle. In addition to receiving, shearing force is also received in a direction parallel to the road surface due to driving, braking, turning operation, and the like. At this time, the land portion 111 is deformed so as to fall obliquely as shown in FIG. Due to this deformation, a part of the surface of the land portion is lifted from the road surface, and there is a problem that the frictional force between the tire and the road surface is reduced by reducing the contact area.

  Such a decrease in the contact area when a shear force is input also occurs in summer tires, but it is more noticeable particularly in winter studless tires. This is because, in studless tires, rubber with low elastic modulus is used in the tread to increase the friction coefficient between the land surface and the road surface on snow and ice road surfaces, and the scratching effect on the road surface is enhanced and a significant friction coefficient is obtained. This is because thousands of sipes are formed per tire for the purpose of removing the water film on the ice that causes the decrease, and this reduces the rigidity of the land portion and causes the collapse and the deformation increase.

For this reason, conventionally, in order to avoid a decrease in the contact area when a shear force is input, a rubber having a high elastic modulus is used as a material of the tread portion, or grooves and sipes between land portions are partially shallowed. Also, as shown in Patent Document 1, by previously bending or bending a groove or sipe in the depth direction, the sipe wall surfaces are brought into contact with each other when the land portion comes in contact with the land portion, thereby suppressing the collapse of the land portion. The method was also adopted.
Japanese Patent Application Laid-Open No. 11-78432

  However, when rubber with a high elastic modulus is used as the material for the tread, it is difficult to ensure a high coefficient of friction between the land surface and the road surface, although it is possible to avoid a reduction in the contact area when shear force is input. It becomes. In addition, when the groove or sipe is shallow, the volume of the groove for discharging water that has entered the ground surface when traveling on a road surface covered with a water film is reduced, and drainage on wet or icy road surfaces is reduced. Performance may be reduced. Furthermore, in order to form a groove or sipe that is curved or bent in advance in the depth direction, it is necessary to use a vulcanization mold having a complicated shape, and there is a problem that the production of the vulcanization mold is complicated and expensive. .

  Therefore, the present invention aims to solve these problems, and its purpose is to sacrifice drainage performance on wet road surfaces or to use a vulcanization mold having a complicated shape. It is an object of the present invention to provide a pneumatic tire that can achieve both improvement in the coefficient of friction with the road surface and increase in the contact area on the land surface.

  The object is to provide a pneumatic tire in which a tread portion includes a land portion that is in contact with the road surface and a groove portion that is lower than the land portion and is not grounded with respect to the road surface. A low elastic layer formed of a low elastic material having a low elastic modulus, and a high elastic layer formed of a high elastic material having a relatively higher elastic modulus than the low elastic material. The highly elastic layer is achieved by a pneumatic tire characterized by being alternately laminated in the tire radial direction. Here, the “elastic modulus” means a longitudinal elastic modulus measured at room temperature. By adopting such a configuration and alternately laminating materials with different elastic moduli in the tire radial direction on the land portion, the low elastic layer having a relatively low elastic modulus is replaced by the high elastic layer having a relatively high elastic modulus. Since the deformation is suppressed, the falling deformation of the land portion when the shear force is input is reduced, and therefore the contact area of the land surface when the shear force is input is increased as compared with the conventional case. Further, since the low elastic layer having a low elastic modulus is exposed on the ground contact surface, the friction coefficient with the road surface is improved as compared with the case where the entire land portion is formed of a high elastic modulus material as shown in the prior art. Furthermore, since it is not necessary to make the grooves and sipes shallow, there is no possibility that the drainage performance on wet road surfaces or ice road surfaces will deteriorate. Moreover, it is not necessary to use a vulcanization mold having a complicated shape. In addition, the pneumatic tire which consists of the said structure can be applied suitably for various tires, such as a safety tire, a heavy load tire, and a studless tire, for example.

  The low elastic material is preferably rubber.

  The highly elastic material is preferably rubber.

  Further, the land portion includes at least two high elastic layers, and the thickness of each high elastic layer is preferably 2.5% or more and 10% or less of the height of the land portion. The “high elastic layer thickness” here refers to the distance in the tire radial direction of the high elastic layer, and the “land height” refers to the tire radial direction from the ground contact surface of the land to the groove bottom. Refer to distance.

  Furthermore, the thickness of the high elastic layer is preferably 10% or more and 50% or less of the thickness of the low elastic layer. Here, the “thickness of the low elastic layer” refers to the distance in the tire radial direction of the low elastic layer.

  Furthermore, the elastic modulus of the low elastic material is preferably in the range of 2 to 6 MPa.

  Furthermore, the elastic modulus of the highly elastic material is preferably in the range of 6 to 30 MPa.

  Further, the elastic modulus of the high elastic material is preferably 1.5 times or more and 15 times or less than the elastic modulus of the low elastic material.

  Moreover, it is preferable that at least two land portions are provided in the same ground contact region, and the stacking order of the high elastic layer and the low elastic layer in these land portions is different from each other. The term “landing area” as used herein refers to a case where the pneumatic tire contacts the road surface when the pneumatic tire is assembled on a regular rim, filled with a regular internal pressure, and loaded with a regular load. The contact surface of the tire. Here, the regular rim is “standard rim” defined by JATMA, “Design Rim” defined by TRA, or “Measuring Rim” defined by ETRTO. The normal internal pressure is “maximum air pressure” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The normal load is “maximum load capacity” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO.

  According to the present invention, both the improvement of the coefficient of friction with the road surface and the increase of the ground contact area on the land surface can be achieved without sacrificing the drainage performance on the wet road surface or using a complex-shaped vulcanization mold. Can be planned.

  An embodiment according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a plan view in which the tread pattern shape of the pneumatic tire according to the embodiment of the present invention is developed. FIG. 2 is an enlarged cross-sectional view showing a cross section taken along line XX in FIG. 1 in the pneumatic tire of the embodiment.

  The pneumatic tire of this embodiment includes a pair of bead portions, a pair of sidewall portions extending from the bead portions to the outer side in the tire radial direction, a pair of shoulder portions extending outwardly, and extending between both shoulder portions. Since the internal structure is the same as that of a general radial tire, the description thereof will be omitted.

  As shown in FIG. 1, in this embodiment, the tread portion 1 of the pneumatic tire includes a plurality of main grooves 3 extending along the tire circumferential direction and a number of lugs extending in the tire width direction and intersecting with the main grooves 3. Grooves 5 are formed, and a large number of land portions 7 having a block shape are defined by these main grooves 3 and lug grooves 5.

  In this embodiment, each land portion 7 is partitioned into four small land portions 11 by three sipes 9 extending along the tire width direction. In this embodiment, the groove depth of the sipe 9 is smaller than the groove depth of the main groove 3.

  As shown in FIG. 2, each small land portion 11 in the land portion 7 includes elastic materials having different elastic moduli, that is, a low elastic material having a relatively low elastic modulus and a high elastic material having a relatively high elastic modulus. The low elastic layer 13 and the high elastic layer 15 are formed respectively. These low elastic layers 13 and high elastic layers 15 are alternately laminated in the tire radial direction. In this embodiment, both the low-elasticity material and the high-elasticity material are rubbers, but organic fibers, metal sheets, organic material films, and the like can be appropriately selected and applied in addition to rubber.

  Next, the operation of this embodiment will be described. When the pneumatic tire of this embodiment is used while being mounted on a vehicle, the small land portion 11 receives not only a load perpendicular to the tread, but also due to driving, braking, turning operation, and the like in FIG. A shear force is also received in a direction parallel to the road surface indicated by A. That is, during driving or braking, a force in the tire circumferential direction acts on the small land portion 11 due to friction with the road surface, and when turning, in the tire width direction. Force acts. As a result, the small land portion 11 tends to fall and deform in the tire circumferential direction, the tire width direction, or the direction inclined to these. However, since the small land portion 11 is composed of elastic layers having different elastic moduli, the high elastic layer 15 having a relatively high elastic modulus acts so as to suppress the deformation of the low elastic layer 13. The fall deformation amount of the entire land portion is reduced, and the remaining ground contact area on the surface of the small land portion 11 is increased. On the other hand, since the low elastic layer 13 having a low elastic modulus can be exposed on the contact surface, the friction coefficient with the road surface is improved as compared with the case where the entire land portion is formed of a high elastic modulus material.

In FIG. 2, the small land portion 11 includes at least two high elastic layers 15, and the thickness h _H of each high elastic layer 15 is not less than 2.5% of the height _H of the small land portion 10. % Or less is preferable. This is because, when the thickness h _H of each high elastic layer 15 is less than 2.5% of the height H of the small land portion 11, the collapse of the small land portion 11 may not be sufficiently suppressed. When the thickness h _H of each high elastic layer 15 exceeds 10% of the height H of the small land portion, although the collapse deformation of the small land portion 11 can be sufficiently suppressed, the low elastic layer 13 is in contact with the high elastic layer 15. This is because, as a result of shortening the period of exposure to the ground, there is a possibility that the improvement of the friction coefficient with the road surface may not be sufficiently realized.

When the high elastic layer 15 disposed to suppress the collapse of the small land portion 11 is exposed to the ground surface, the friction coefficient may be lower than when the low elastic layer 13 is exposed to the ground surface. Therefore, the thickness h _H of the high elastic layer 15 is 10% or more of the thickness h _L of the low elastic layer 13 from the viewpoint of extending the period during which a high frictional force is exerted while sufficiently suppressing the collapse deformation. It is preferable to set it to 50% or less. Note that if the thickness h _H of the high elastic layer 15 is less than 10% of the thickness h _L of the low elastic layer 13, the collapse of the land land portion 11 cannot be sufficiently suppressed, and if it exceeds 50%, it is sufficient. May not be able to obtain a sufficient frictional force.

  The elastic modulus of the low elastic material can be preferably in the range of 2 to 6 MPa. When the elastic modulus of the low elastic material is less than 2 MPa, high adhesion to the road surface can be ensured, but it becomes excessively soft and the falling deformation of the small land portion 11 increases, and the elastic modulus of the low elastic material exceeds 6 MPa. This is because although the falling deformation of the small land portion is reduced, there is a possibility that sufficient adhesion with the road surface cannot be ensured. The elastic modulus of the highly elastic material can be preferably in the range of 6 to 30 MPa. If the elastic modulus of the highly elastic material is less than 6 MPa, the collapse deformation of the small land portion 11 may not be sufficiently suppressed. If the elastic modulus of the highly elastic material exceeds 30 MPa, the collapse deformation of the small land portion may occur. Although it can be sufficiently suppressed, when the highly elastic layer 15 is exposed to the ground contact surface, the coefficient of friction with the road surface is too small, and there is a possibility that sufficient grip performance cannot be ensured. And it is preferable that the elasticity modulus of a highly elastic material exists in 1.5 times or more and 15 times or less of the elasticity modulus of a low elastic material. The reason is that if the elastic modulus of the high elastic material is less than 1.5 times that of the low elastic material, the collapse cannot be sufficiently suppressed, and if it exceeds 15 times, the rigidity difference is too large and uneven wear. It is because it becomes the cause.

  Another embodiment according to the present invention will be described with reference to FIGS. FIG. 3A is a plan view of a developed tread pattern of a pneumatic tire according to another embodiment of the present invention, and FIG. 3B is a YY line in FIG. FIG. In addition, the same code | symbol is attached | subjected about the structure same as the said embodiment, and the description is abbreviate | omitted.

  As shown in FIG. 3A, the tread portion 1 in the pneumatic tire of this embodiment includes a plurality of main grooves 3 extending along the tire circumferential direction, and intersects the main grooves 3 in the tire width direction. A plurality of extending lug grooves 5 are formed, and a number of land portions 17 having a block shape are defined.

  As shown in FIG. 3B, each land portion 17 is made of an elastic material having a different elastic modulus, that is, a low elastic material having a relatively low elastic modulus and a high elastic material having a relatively high elastic modulus. The low elastic layer 13 and the high elastic layer 15 are formed. These low elastic layers 13 and high elastic layers 15 are alternately laminated in the tire radial direction. In this embodiment, both the low-elasticity material and the high-elasticity material are rubbers, but organic fibers, metal sheets, organic material films, and the like can be appropriately selected and applied in addition to rubber.

  Still another embodiment according to the present invention will be described with reference to FIG. FIG. 4A is a plan view in which a tread pattern shape of a pneumatic tire according to another embodiment of the present invention is developed, and FIG. 4B is a cross-sectional view taken along line B- in FIG. It is an expanded sectional view which follows a B line, and Drawing 4 (c) is an expanded sectional view which meets a CC line in Drawing 4 (a). In addition, the same code | symbol is attached | subjected about the structure same as the said embodiment, and the description is abbreviate | omitted.

  As shown in FIG. 4A, the tread portion 1 in the pneumatic tire of this embodiment includes a plurality of main grooves 3 extending along the tire circumferential direction, and intersects the main grooves 3 in the tire width direction. A plurality of extending lug grooves 5 are formed, and a large number of land portions 27 having a block shape are defined.

  As shown in FIG. 4B, each land portion 27 is made of an elastic material having a different elastic modulus, that is, a low elastic material having a relatively low elastic modulus and a high elastic material having a relatively high elastic modulus. The low elastic layer 13 and the high elastic layer 15 are formed. These low elastic layers 13 and high elastic layers 15 are alternately laminated in the tire radial direction. In this embodiment, both the low-elasticity material and the high-elasticity material are rubbers, but organic fibers, metal sheets, organic material films, and the like can be appropriately selected and applied in addition to rubber.

  In this embodiment, unlike the embodiment shown in FIG. 3, the land portions 27 b and 27 c exist in the same grounding region in which the stacking order of the high elastic layer 15 and the low elastic layer 13 is different. That is, the land portion 27b has the stacking order shown in FIG. 4B and the land portion 27c is the stacking shown in FIG. Have an order. Thereby, for example, even if the low elastic layer 13 is worn by friction with the road surface in the land portion 27b and the high elastic layer 15 is exposed, the high elastic layer 15 is in contact with the road surface in the other land portion 27c in the same ground contact area. Since the low elastic layer 13 can be exposed due to the friction of the tire, it is possible to always ensure a high coefficient of friction for the entire tire. The stacking order may be different for each adjacent land portion, or may be different for each adjacent land portion row.

  In the embodiment shown in FIGS. 1 to 4, both the main groove 3 and the lug groove 5 extend linearly, but the main groove 3 may extend in the tire circumferential direction in a zigzag shape or a wave shape. Similarly, the groove 5 may have a zigzag shape, a wave shape, or a square shape. Further, the shape of the land portions 7, 17, 27 and the shape of the small land portion 11 may be shapes other than a rectangle, for example, a circular shape, an elliptical shape, a polygonal shape, or other irregular closed shapes. good.

  The pneumatic tire according to the embodiment shown in FIGS. 1 to 3 is formed, for example, by forming a cylindrical belt or the like on a forming drum and attaching a tread rubber formed in a belt shape to the surface of the tread on the belt surface. In forming the rubber layer, a tread rubber layer having a laminated structure of a low elastic layer made of a low elastic material and a high elastic layer made of a high elastic material is formed by an extruder, and the tread rubber layer is belted on a molding drum. In addition to being able to be manufactured by sticking to a surface such as, it is possible to manufacture by sequentially laminating a low elastic material and a high elastic material on a molding drum. Further, in the embodiment shown in FIG. 4, for example, by forming a plurality of small tread rubber layers having different stacking orders from each other by an extruder and arranging them in a tire width direction on a molding drum. Can be manufactured.

  For a studless tire for a passenger car having a tire size of 195 / 65R15, a tire model of Conventional Example 1 and a tire of Examples 1 to 11 shown in Table 1 was prepared, and shear force ( The contact area of the small land portion when μ = 0.2) is calculated using the finite element method, and the result is shown in a graph in FIG. In the graph of FIG. 5, the horizontal axis shows the longitudinal elastic modulus of the high elastic layer of the land portion in the tires of Examples 1 to 11 as an index with the longitudinal elastic modulus of the small land portion of Conventional Example 1 being 1. Yes, the vertical axis shows the remaining ground contact area of the small land portions of Examples 1 to 11 as an index with the remaining ground contact area of the land portion of Conventional Example 1 being 1.

  As is apparent from the results shown in the graph of FIG. 5, by laminating the low elastic layer 13 and the high elastic layer in the tire radial direction, the remaining ground contact area of the small land portion is about 10% compared to the conventional example 1 It can be seen that it increases by 50%. It can also be seen that the larger the elastic modulus of the highly elastic material and the greater the thickness of the highly elastic layer, the greater the remaining ground contact area of the small land portion.

  By this invention, without sacrificing drainage performance on a wet road surface or using a complex-shaped vulcanization mold, the coefficient of friction with the road surface is improved and the air contact area on the land surface is increased. It has become possible to provide tires containing tires.

FIG. 1 is a developed plan view of a tread pattern shape of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view showing a cross section taken along line XX in FIG. 1 in the pneumatic tire of the embodiment. Fig.3 (a) is the top view which expand | deployed the tread pattern shape of the pneumatic tire concerning other embodiment of this invention, (b) is an expansion along the YY line in Fig.3 (a). It is sectional drawing. Fig.4 (a) is the top view which expanded the tread pattern shape of the pneumatic tire concerning other embodiment of this invention, FIG.4 (b) is BB line in Fig.4 (a). FIG. 4C is an enlarged cross-sectional view taken along line CC in FIG. 4A. It is a graph which shows the contact area remaining in the tire of a prior art example and each Example. It is an expanded sectional view in alignment with the tire peripheral direction of the land part in the pneumatic tire according to a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 3 Main groove 5 Lag groove 7, 17, 27 Land part 9 Sipe 11 Small land part 13 Low elastic layer 15 High elastic layer

Claims (9)

In a pneumatic tire in which a tread portion is formed with a land portion that is in contact with the road surface and a groove portion that is formed lower than this and is not grounded with respect to the road surface,
The land portion has a low elastic layer formed of a low elastic material having a relatively low elastic modulus and a high elastic layer formed of a high elastic material having a relatively higher elastic modulus than the low elastic material. The pneumatic tire is characterized in that the low elastic layer and the high elastic layer are alternately laminated in the tire radial direction.   The pneumatic tire according to claim 1, wherein the low elastic material is rubber.   The pneumatic tire according to claim 1, wherein the highly elastic material is rubber.   The land portion includes at least two high elastic layers, and the thickness of each high elastic layer is not less than 2.5% and not more than 10% of the height of the land portion. The pneumatic tire according to item.   The pneumatic tire according to any one of claims 1 to 4, wherein a thickness of the high elasticity layer is 10% or more and 50% or less of a thickness of the low elasticity layer.   The pneumatic tire according to any one of claims 1 to 5, wherein the low elastic material has an elastic modulus in a range of 2 to 6 MPa.   The pneumatic tire according to any one of claims 1 to 6, wherein the elastic modulus of the highly elastic material is in a range of 6 to 30 MPa.   The pneumatic tire according to any one of claims 1 to 7, wherein an elastic modulus of the high elastic material is 1.5 to 15 times an elastic modulus of the low elastic material.   The air according to any one of claims 1 to 8, wherein at least two of the land portions are provided in the same ground contact region, and a stacking order of the high elastic layer and the low elastic layer in the land portions is different from each other. Enter tire.

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