Tire

Abstract

The present invention provides a tire that can maintain wet performance and handling stability even if wear progresses in a tread portion. The tire has a tread portion (2). The tread portion (2) includes a first crown portion rubber layer (11) and a second crown portion rubber layer (12). The tangent of loss angle tan δ2 of the second crown portion rubber layer (12) is greater than the tangent of loss angle tan δ1 of the first crown portion rubber layer (11). A plurality of sipes (15) that open at a ground surface (2s) are provided in the tread portion (2). The plurality of sipes (15) extend from the ground surface (2s) at least to a position beyond the boundary between the first crown portion rubber layer (11) and the second crown portion rubber layer (12). In the plurality of sipes (15), the maximum length L2 of the sipes (15) at the second crown portion rubber layer (12) is smaller than the length L1 of the sipes (15) at the ground surface (2s).

Description

Technical Field

[0001] This invention relates to tires. Background Technology

[0002] Patent Document 1 discloses a pneumatic tire with a specified loss tangent in the base rubber layer of the tread. This pneumatic tire, by including low-heat-generating rubber in the base rubber layer with a loss tangent smaller than that of the crown rubber layer forming the outer surface of the tread, can be expected to improve wear resistance and fuel efficiency.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2017-013539

[0004] In recent years, with environmental considerations and the practical application of autonomous driving technology in vehicles, there is a need for tires that require no maintenance for a long time, especially tires that can maintain sufficient wet performance and handling stability until the end of the tread wear. Summary of the Invention

[0005] The present invention was made in view of the above-mentioned actual situation, and the main objective is to provide a tire that can maintain wet performance and handling stability even as the tread wears down.

[0006] The present invention relates to a tire having a tread portion, wherein the tread portion includes a first crown rubber layer constituting a contact patch and a second crown rubber layer disposed radially inside the first crown rubber layer. The loss tangent tanδ2 of the second crown rubber layer is larger than the loss tangent tanδ1 of the first crown rubber layer. The tread portion is provided with a plurality of sipes opening at the contact patch. The plurality of sipes extend from the contact patch at least beyond the boundary between the first crown rubber layer and the second crown rubber layer. For the plurality of sipes, the maximum length L2 of the sipe at the second crown rubber layer is smaller than the length L1 of the sipe at the contact patch.

[0007] In the tire of the present invention, the loss angle tangent tanδ1 is preferably 0.13 to 0.29.

[0008] In the tire of the present invention, the loss angle tangent tanδ2 is preferably 0.30 to 0.40.

[0009] In the tire of the present invention, it is preferable that the tread portion includes a base rubber layer disposed radially inside the second crown rubber layer, wherein the loss tangent tanδb of the base rubber layer is smaller than the loss tangent tanδ1.

[0010] In the tire of the present invention, it is preferable that the loss tangent tanδb is 0.12 or less.

[0011] In the tire of the present invention, it is preferable that a plurality of circumferential grooves extending continuously along the tire circumference are provided on the tread surface, and the maximum depth of the grooves is 75% to 100% of the maximum depth of the circumferential grooves.

[0012] In the tire of the present invention, it is preferable that the maximum length L2 of the sipe in the second crown rubber layer is 60% to 80% of the length L1 of the sipe in the contact surface.

[0013] In the tire of the present invention, it is preferable that the sipes extend in a wavy manner along the radial direction of the tire in the cross section of the sipes.

[0014] In the tire of the present invention, it is preferable that the radial wavelength of the sipes is 20% to 60% of the radial thickness of the second crown rubber layer.

[0015] In the tire of the present invention, the aforementioned sipes preferably include transverse sipes extending along the tire axial direction.

[0016] In the tire of the present invention, the aforementioned sipes preferably include longitudinal sipes extending along the tire circumference.

[0017] [The effects of the invention]

[0018] By employing the above-described structure, the pneumatic tire of the present invention can maintain wet performance and handling stability even as the tread wears down. Attached Figure Description

[0019] Figure 1 This is a radial cross-sectional view of a tire according to one embodiment of the tire of the present invention.

[0020] Figure 2 yes Figure 1 An enlarged sectional view of the land portion.

[0021] Figure 3 This is an enlarged sectional view of the land section and the cutting groove.

[0022] Figure 4 This is an enlarged cross-sectional view of the land portion when the second crown rubber layer is exposed.

[0023] Figure 5 This is an enlarged cross-sectional view of the land section and the cutter groove in other embodiments.

[0024] Figure 6 This is a cross-sectional view of the tool groove in other embodiments.

[0025] Figure 7 This is an enlarged sectional view of the longitudinal groove.

[0026] Figure 8 This is an enlarged cross-sectional view of the land section and sipes of a comparative example tire.

[0027] Explanation of reference numerals in the attached figures:

[0028] 2…tread area; 2s…ground contact area; 11…first crown rubber layer; 12…second crown rubber layer; 15…sipe; L1…length of sipe at ground contact area; L2…maximum length of sipe at second crown rubber layer. Detailed Implementation

[0029] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Figure 1 This is a radial cross-sectional view of a tire 1 in its normal configuration, representing an embodiment of the present invention. Figure 1 As shown, the present invention is preferably applied, for example, to pneumatic tires for passenger cars. However, it is not limited to this approach; the present invention can also be applied, for example, to tires for motorcycles or heavy-duty vehicles.

[0030] The term "standard condition" refers to the unloaded state where, with various sizes of pneumatic tires specified, the tire is assembled onto a standard rim and inflated to the standard internal pressure. Where tire sizes are not specified, the term "standard condition" refers to the unloaded state under standard operating conditions corresponding to the tire's intended use, without being mounted on the vehicle. In this manual, unless otherwise specified, the dimensions of all parts of the tire are values ​​measured under the aforementioned standard condition.

[0031] "Standard rim" refers to a rim that is specified for each tire within a specification system that includes the specifications the tire is based on. For example, JATMA is "standard rim", TRA is "Design Rim", and ETRTO is "Measuring Rim".

[0032] "Standard tire pressure" is the air pressure specified for each tire in the specification system, including the specifications on which the tire is based. If it is JATMA, it is the "maximum air pressure". If it is TRA, it is the maximum value recorded in the table "TIRE LOAD LIMITS ATVARIOUS COLD INFLATION PRESSURES". If it is ETRTO, it is "INFLATION PRESSURE".

[0033] In this embodiment, the tire 1 has tire components such as a carcass 6 and a belt layer 7 disposed inside. These tire components are appropriately arranged in known forms.

[0034] The tire carcass 6 extends from the bead portion 4 on one side, through the sidewall portion 3 on one side, the tread portion 2, and the sidewall portion 3 on the other side, to the bead portion 4 on the other side. In this embodiment, the tire carcass 6 is, for example, composed of two carcass ply layers 6A and 6B. These two ply layers 6A and 6B are, for example, composed of carcass cords, which are organic fibers arranged at an angle of 75 to 90 degrees relative to the tire circumference.

[0035] The belt layer 7 is composed, for example, of two belt ply layers 7A and 7B. The belt ply layers 7A and 7B are composed, for example, of belt cords arranged at an angle of 10 to 45 degrees relative to the tire circumference. For the belt cords, organic fiber cords or steel cords can be appropriately used, for example. In other embodiments, a tread reinforcement layer such as a belt layer may also be disposed on the outside of the belt layer 7.

[0036] In this embodiment, the tread portion 2 is provided with a plurality of circumferential grooves 8 extending continuously along the tire circumference. Thus, the tread portion 2 includes a plurality of land portions 9 divided by the plurality of circumferential grooves 8. However, the present invention is not limited to this method.

[0037] As a diagram used to illustrate the structure of the tread area 2, in Figure 2 An enlarged cross-sectional view of the land section 9 is shown. (See image below.) Figure 2 As shown, the tread portion 2 includes a first crown rubber layer 11 constituting the contact surface 2s and a second crown rubber layer 12 disposed radially inside the tire on the first crown rubber layer 11. In this embodiment, the tread portion 2 further includes a base rubber layer 10 disposed radially inside the tire on the second crown rubber layer 12. Thus, the tread portion 2 of this embodiment is composed of three rubber layers: the first crown rubber layer 11, the second crown rubber layer 12, and the base rubber layer 10. However, the present invention is not limited to this method. Furthermore, in Figure 2 And in the subsequent figures, different cross-sectional lines are applied to each rubber layer, but... Figure 1 In order to avoid complicating the diagram, the above cross-sectional lines have been omitted.

[0038] In this invention, the loss tangent tanδ2 of the second crown rubber layer 12 is larger than the loss tangent tanδ1 of the first crown rubber layer 11. Furthermore, in this specification, the loss tangent tanδ is a value measured using a dynamic viscoelasticity measuring device (EPLEXOR Series) manufactured by GABO Corporation under the conditions specified in JIS-K6394.

[0039] Initial strain: 5%

[0040] Amplitude of dynamic strain: ±1%

[0041] Frequency: 10Hz

[0042] Deformation mode: Elongation

[0043] Temperature measured: 30℃

[0044] Multiple sipes 15 opening at the contact patch are provided on the tread portion 2. In this embodiment, the sipes 15 are configured as transverse sipes extending along the tire axial direction. However, in this invention, the length direction of the sipes 15 is not particularly limited. Therefore, the sipes 15 can also be longitudinal sipes extending along the tire circumference. Alternatively, both transverse and longitudinal sipes can be provided on a single tread portion 2. Furthermore, since... Figure 2 This is a cross-section of land section 9 excluding the cutter groove, therefore... Figure 2 In the diagram, the bottom 15d of the tool groove 15 is represented by a dashed line.

[0045] In this specification, "groove" refers to a cutting element with a relatively small width, that is, a cutting element with a width of 1.5 mm or less between two inner walls that extend substantially parallel to each other. Furthermore, "substantially parallel" means that the angle between the two inner walls is 10° or less. Preferably, the width of the groove is 0.5 to 1.5 mm, more preferably 0.4 to 1.0 mm. The structure of the groove is not particularly limited; in other embodiments, at least one of the two groove edges may be formed by a chamfer. Additionally, a flask-shaped bottom with a width exceeding 1.5 mm may be attached to the bottom of the groove.

[0046] exist Figure 3 An enlarged cross-sectional view of the land section 9 and the cutter groove 15 is shown. Furthermore, in... Figure 3 The cross-section of the cutter groove 15 shown corresponds to a cross-section of the cutter groove 15 along its length. For example... Figure 3 As shown, the multiple sipes 15 extend from the contact surface 2s to a position at least beyond the junction 16 between the first crown rubber layer 11 and the second crown rubber layer 12. Furthermore, for the multiple sipes 15, the maximum length L2 of the sipe 15 at the second crown rubber layer 12 is smaller than the length L1 of the sipe 15 at the contact surface 2s. Moreover, the aforementioned lengths L1 and L2 refer to the so-called circumferential lengths measured parallel to the contact surface 2s of the tread portion 2 and along the length direction of the sipe 15.

[0047] By employing the above-described structure, this invention maintains wet performance and handling stability even as wear progresses on the tread 2. The reason for this is presumably due to the following mechanism.

[0048] exist Figure 4 The image shows an enlarged cross-sectional view of the land portion 9 when the tread 2 is worn down, exposing the second crown rubber layer 12 as the contact surface 2s. Figure 4As shown, in this invention, since the loss tangent tanδ2 of the second crown rubber layer 12 is larger than the loss tangent tanδ1 of the first crown rubber layer 11, the second crown rubber layer 12 can exert greater grip on wet surfaces when the wear of the tread 2 progresses and the second crown rubber layer 12 is exposed. Therefore, wet performance can be maintained.

[0049] On the other hand, in this invention, such as Figure 3 As shown, since the maximum length L2 of the groove 15 at the second crown rubber layer 12 is smaller than the length L1 of the groove 15 at the contact surface, therefore... Figure 4 As shown, the length of the sipe 15 becomes relatively smaller when the second crown rubber layer 12 is exposed. Therefore, even in the wear state where the second crown rubber layer 12 is exposed, the rigidity of the tread portion 2 can be maintained, thereby maintaining handling stability. Furthermore, in this invention, by maintaining the rigidity of the tread portion 2, it is expected that the progression of wear starting from the state where the second crown rubber layer 12 is exposed can be delayed.

[0050] In this invention, based on the above reasons, it is believed that even if the wear of the tread 2 progresses, wet performance and handling stability can be maintained.

[0051] The following describes a more detailed structure of this embodiment. Furthermore, each structure described below represents a specific embodiment. Therefore, even if the present invention does not possess the structures described below, the aforementioned effects can still be achieved. Additionally, in the tire of the present invention possessing the above features, any one of the structures described below can be applied individually, and an improvement in the performance corresponding to each structure can be expected. Furthermore, when several structures described below are applied in combination, an improvement in the combined performance corresponding to each structure can be expected.

[0052] like Figure 2 As shown, the thickness t1 of the first crown rubber layer 11 is, for example, the total thickness Ta of the tread rubber from the contact surface of the tread 2 to the outer surface of the belt layer 7 (e.g., Figure 1 As shown below (and so on), the thickness of the second crown rubber layer 12 is 25% to 35%. Additionally, the thickness t2 of the second crown rubber layer 12 is, for example, 15% to 25% of the total tread rubber thickness Ta.

[0053] Therefore, the radial distance L3 of the tire from the contact surface of the tread 2 to the junction 17 of the second crown rubber layer 12 and the base rubber layer 10 is 60% to 80% of the depth d1 of the circumferential groove 8. With this arrangement of the rubber layers, the second crown rubber layer 12, which provides greater grip, can be expected to be exposed from the latter half to the end of the wear period of the tread 2. Therefore, wet performance can be reliably maintained. Furthermore, in this embodiment, the junction 16 of the first crown rubber layer 11 and the second crown rubber layer 12, and the junction 17 of the second crown rubber layer 12 and the base rubber layer 10, extend parallel to the contact surface 2s of the tread 2.

[0054] Preferably, the loss tangent tanδ1 of the first crown rubber layer 11 is 0.13 or more, more preferably 0.15 or more, and more preferably 0.29 or less, and more preferably 0.25 or less. Preferably, the loss tangent tanδ2 of the second crown rubber layer 12 is 0.30 or more, more preferably 0.33 or more, and more preferably 0.40 or less, and more preferably 0.37 or less. Furthermore, the loss tangent tanδ1 is 50% to 65% of the loss tangent tanδ2. Such a first crown rubber layer 11 and second crown rubber layer 12 can effectively balance and perform the overall performance of the tire, and can suppress rubber peeling at the interface 16 between the first crown rubber layer 11 and the second crown rubber layer 12.

[0055] Preferably, the loss tangent tanδb of the base rubber layer 10 is smaller than the loss tangent tanδ1 of the first crown rubber layer 11. Specifically, the loss tangent tanδb is, for example, 0.12 or less, preferably 0.07 to 0.12. This suppresses excessive heating of the tread portion 2 and improves tire durability. However, the loss tangent tanδb of the base rubber layer 10 is not limited to such a range.

[0056] Furthermore, the loss tangent tanδ of each of the aforementioned rubber layers can be obtained by appropriately combining known materials, which will not be explained here.

[0057] like Figure 3 As shown, the sipe 15 in this embodiment is configured as a transverse sipe extending along the tire axial direction. In a preferred embodiment, the sipe 15 extends parallel to the tire axial direction (not shown). Furthermore, the sipe 15 completely traverses the tire tread 2 axially in the contact patch surface of the tread portion 2. On the other hand, as... Figure 4 As shown, in this embodiment, the sipe 15 is interrupted at both ends within the land portion 9 when the second crown rubber layer 12 is exposed. Therefore, the rigidity of the tread portion 2 is reliably maintained when the second crown rubber layer 12 is exposed.

[0058] like Figure 3As shown, preferably, the maximum length L2 of the sipe 15 at the second crown rubber layer 12 is 60% or more of the length L1 of the sipe 15 at the contact surface 2s, more preferably 65% ​​or more, more preferably 80% or less, and more preferably 75% or less. Such a sipe 15 helps to improve the wet performance and handling stability of the tread 2 after wear in a balanced way.

[0059] The bottom 15d of the groove 15 is disposed, for example, within the base rubber layer 10. However, the bottom 15d of the groove 15 can also be disposed within the second crown rubber layer 12. The maximum depth d2 of the groove 15 is preferably, for example, 75% to 100% of the maximum depth d1 of the circumferential groove 8. Such a groove 15 helps to improve wetland performance.

[0060] The cross-sectional structure of the cutter groove 15 along its length is not limited to the manner described above. Figure 5 Other embodiments of the blade groove 15 are shown. For example... Figure 5 As shown, in this embodiment, at the contact surface 2s of the tread 2, one end of the sipe 15 communicates with the circumferential groove 8, and the other end is interrupted within the land portion 9. Furthermore, in this embodiment, with the second crown rubber layer 12 exposed, both ends of the sipe 15 are interrupted within the land portion. Such a sipe 15 contributes to excellent handling stability.

[0061] exist Figure 6 A cross-sectional view of the cutter groove 15 according to another embodiment is shown. Furthermore, Figure 6 This represents a cross-section orthogonal to the length direction of the cutter groove 15. For example... Figure 6 As shown, in the transverse cross-section of the sipe 15, the sipe 15 can also extend in a wavy shape along the radial direction of the tire. Such a sipe 15 can improve the rigidity of the land section 9 when the opposing sipe wall surfaces contact each other, thus providing excellent handling stability. Furthermore, as in... Figure 6 The cross-sectional structure of the tool groove 15 along its length shown in the figure can also be applied to... Figure 3 The above structure is shown in the figure.

[0062] exist Figure 6 In the illustrated embodiment, the radial wavelength A1 of the sipe 15 is preferably 20% to 60% of the radial thickness t2 of the second crown rubber layer 12. This reliably improves the aforementioned effects.

[0063] exist Figure 7 An enlarged cross-sectional view of the longitudinal groove 20 extending along the tire circumference is shown. Figure 7 In the diagram, arrow A corresponds to the circumferential direction of the tire. For example... Figure 7 As shown, the groove 15 of the present invention can also be a longitudinal groove 20 extending along the tire circumference. In this case, the longitudinal groove 20 can provide axial friction for the tire, improving cornering performance on wet roads.

[0064] The tire of one embodiment of the present invention has been described in detail above, but the present invention is not limited to the specific embodiment described above and can be implemented in various ways.

[0065]

Example

[0066] As an example, a pneumatic tire with a size of 235 / 65R16C was manufactured. The tire of this example has... Figure 1 The basic structure, and the tread area is equipped with... Figure 2 The rubber layers shown in the figure have multiple stripes. Figure 3 The tool groove is shown in the image. Additionally, as a comparative example, a tool groove with... Figure 8 The tire shown here has a land portion a and a sipe b. In the comparative example tire, the loss tangent tanδ1 of the first crown rubber layer is larger than the loss tangent tanδ2 of the second crown rubber layer, and the sipe b completely traverses the land portion a in the tire axial direction. Apart from the above, the comparative example tire is essentially the same as the tire of the embodiment. For these test tires, the wet performance and handling stability of the new tires, as well as the wet performance and handling stability at 50% tire wear, were tested. Furthermore, 50% tire wear refers to the tire worn until the remaining depth of the circumferential grooves is 50% of that of a new tire. The common specifications and test methods for each test tire are described below.

[0067] Wheel rim: 16×7.0J

[0068] Tire internal pressure: 475 kPa

[0069] Test vehicle: 3000cc engine, rear-wheel drive

[0070] Test tire mounting position: all wheels

[0071] <Wet performance (new product and at 50% wear)>

[0072] The wet performance of test vehicles on wet roads was evaluated by drivers using sensory feedback, with test tires fitted with new tires or with 50% wear. The results were scored out of 100 for the wet performance of the comparative example with new tires; a higher score indicates better wet performance.

[0073] <Handling stability (new product and 50% wear)>

[0074] The handling stability of the test vehicle was evaluated by the driver's senses when driving on a dry road surface with test tires fitted with new tires or with 50% wear. The results were scored out of 100 for the handling stability of the comparative example with new tires; the higher the score, the better the handling stability.

[0075] The test results are shown in Tables 1 and 2.

[0076] Table 1

[0077]

[0078] Table 2

[0079]

[0080] As shown in Tables 1 and 2, the comparative example tire scored 60 points for wet performance and 80 points for handling stability at 50% wear. In contrast, the tire of the embodiment maintained a higher wet performance score of 77-85 points at 50% wear. Furthermore, the tire of the embodiment maintained a higher handling stability score of 87-92 points at 50% wear. As described above, it can be confirmed that the tire of the embodiment can maintain wet performance and handling stability even as the tread wear progresses.

Claims

1. A tire having a tread pattern, characterized in that, The tread portion includes a first crown rubber layer forming the contact surface, a second crown rubber layer disposed radially inside the first crown rubber layer, and a base rubber layer disposed radially inside the second crown rubber layer. The loss tangent tanδ2 of the second crown rubber layer, measured according to JIS-K6394 under the following conditions—initial strain of 5%, dynamic strain amplitude of ±1%, frequency of 10Hz, deformation mode of elongation, and measurement temperature of 30℃—is larger than the loss tangent tanδ1 of the first crown rubber layer measured under the same conditions. The loss tangent tanδb of the base rubber layer, measured under the aforementioned conditions, is smaller than the loss tangent tanδ1. The tread surface is provided with multiple sipes that open at the contact patch and multiple circumferential grooves that extend continuously along the tire circumference. The base rubber layer has a portion that extends axially along the tire at a position radially outward from the bottom of the circumferential groove. The plurality of said grooves extend from the contact surface at least beyond the junction of the first crown rubber layer and the second crown rubber layer, and toward the base rubber layer. In the plurality of said grooves, the maximum length L2 of the groove at the second crown rubber layer is smaller than the length L1 of the groove at the contact surface. A portion of the bottom of the blade groove is located within the portion of the base rubber layer.

2. The tire according to claim 1, characterized in that, The loss angle tangent tanδ1 is 0.13~0.

29.

3. The tire according to claim 1 or 2, characterized in that, The loss angle tangent tanδ2 is 0.30~0.

40.

4. The tire according to claim 1, characterized in that, The loss tangent tanδb is below 0.

12.

5. The tire according to claim 1 or 2, characterized in that, The maximum depth of the cutting groove is 75% to 100% of the maximum depth of the circumferential groove.

6. The tire according to claim 1 or 2, characterized in that, The maximum length L2 of the groove at the second crown rubber layer is 60% to 80% of the length L1 of the groove at the ground surface.

7. The tire according to claim 1 or 2, characterized in that, In the cross-section of the cutter groove, the cutter groove extends in a wavy shape along the radial direction of the tire.

8. The tire according to claim 7, characterized in that, The radial wavelength of the sipe is 20% to 60% of the radial thickness of the second crown rubber layer.

9. The tire according to claim 1 or 2, characterized in that, The cutting groove includes a transverse cutting groove extending along the tire axial direction.

10. The tire according to claim 1 or 2, characterized in that, The cutting groove includes a longitudinal cutting groove extending along the circumference of the tire.

Images