JP5847404B2 - tire - Google Patents

Description

  The present invention relates to a tire in which a sipe is formed in a tread portion and spike pins are arranged.

  2. Description of the Related Art Conventionally, a pneumatic tire (hereinafter referred to as a tire) for running on an icy and snowy road called a spike tire has a plurality of grooves formed in a tread portion and a land portion defined by the plurality of grooves. In addition, a sipe is formed in the land portion, and a spike pin is disposed.

  Further, in the tire according to the related art, the tread portion is configured by two layers of a surface layer (cap layer) disposed on the surface and an inner layer (base layer) disposed on the inner side in the tire radial direction. The thing is also proposed (for example, refer patent document 1).

  In such a tire, the tip end portion of the spike pin protrudes from the surface of the surface layer, and the base end portion of the spike pin is embedded in the inner layer. The tire having such a configuration can ensure the retention of the spike pin by using rubber having a high rubber hardness (for example, Shore A hardness) for the inner layer.

JP 2009-23602 A

  However, the tire according to the prior art has the following problems.

  First, in the tire according to the related art, when rubber having high rubber hardness is used for the inner layer, the rigidity of the entire tread portion is increased, and the sipe may not be easily opened. In such a case, there is a problem that the effect of scratching corners formed on land by sipe cannot be sufficiently obtained, and the performance on ice and snow is difficult to improve.

  In addition, as a method for making the sipe easy to open, a method of using a rubber having a low rubber hardness for the surface layer is also conceivable. However, in such a method, the rigidity of the corner portion formed in the land portion by sipe is lowered, and as a result, the scratching effect of the corner portion is lowered. Therefore, such a method is not preferable. Therefore, in the tire according to the prior art, another method for suppressing the rigidity of the entire tread portion without reducing the rubber hardness of the surface layer has been demanded.

  Secondly, in the tire according to the prior art, when the wear of the tread portion progresses to such an extent that the surface layer disappears, a considerable number of spike pins fall off and the inner layer is exposed next to the surface layer. In such a case, since the inner layer having high rubber hardness and inferior on ice / snow performance than the surface layer comes into contact with the road surface, there is a problem that the on-ice / snow performance is drastically lowered.

  Therefore, the present invention has been made in view of the above points, and is a case where the tread portion is worn while the sipe is easily opened to improve the performance on ice and snow while securing the spike pin. However, an object of the present invention is to provide a tire that can suppress a sudden drop in performance on ice and snow.

  First, a first feature of the present invention is that a tread portion (tread) including a surface layer (surface layer 100) that contacts the road surface and an inner layer (inner layer 200) disposed on the inner side in the tire radial direction of the surface layer. Part 1), the surface layer is formed with a plurality of grooves (vertical grooves 10 and lateral grooves 20) and a land part (land part 40) partitioned by the plurality of grooves, In the land portion, a sipe (sipe 50) is formed and a spike pin (spike pin 60) is disposed, and the tread portion is disposed between the surface layer and the inner layer. An intermediate layer (intermediate layer 300) is provided, and the rubber hardness of the intermediate layer is lower than the rubber hardness of the surface layer, and the intermediate layer is made of foamed rubber in which a void is provided inside the member. Is the gist.

  According to such a tire, the tread portion includes the surface layer, the intermediate layer, and the inner layer, and the rubber hardness of the intermediate layer is formed lower than the rubber hardness of the surface layer. In such a tire, not only the surface layer but also the surface layer and the intermediate layer are arranged on the outer side in the tire radial direction of the inner layer. That is, according to such a tire, when a rubber having a high rubber hardness is used for the inner layer in order to hold the spike pin, the rubber hardness of the intermediate layer is reduced without reducing the rubber hardness of the surface layer. Therefore, the rigidity as the whole tread part can be suppressed. In this way, it becomes possible to easily open the sipe formed in the land part while suppressing the rigidity of the entire tread part, so the performance on ice and snow due to the scratching effect of the corner part formed in the land part by the sipe Can be improved.

  According to such a tire, the tread portion is constituted by three layers of a surface layer, an intermediate layer, and an inner layer. In other words, as the surface layer is worn, the intermediate layer made of foamed rubber with excellent performance on ice and snow is exposed, so the performance on ice and snow does not decrease rapidly but gradually decreases. become. In this way, even if the tread portion is worn, it is possible to suppress a sudden decrease in performance on ice and snow.

  A second feature of the present invention relates to the first feature, and in the tread width direction cross section of the tread portion, the inner layer is recessed inward in the tire radial direction in a central region (central region A1) in the tread width direction. It has a recess (recess 210), and the gist is that the thickness (T31) of the intermediate layer in the central region in the tread width direction is formed so as to increase in accordance with the recess of the recess.

  According to such a tire, the inner layer has a recess in the center region in the tread width direction, and the thickness of the intermediate layer is formed to increase according to the recess of the recess. In other words, even when rubber with high rubber hardness is used for the inner layer, a concave portion with a thin inner layer is formed in the central region in the tread width direction, and a middle portion with a low rubber hardness is formed by the amount of the concave portion of the inner layer. The layer is formed to have a large thickness. Therefore, since the tire can suppress the rigidity in the central region, the sipe can be easily opened and the performance on ice and snow can be improved.

  A third feature of the present invention relates to the first feature, wherein, in the tread width direction cross-section of the tread portion, the inner layer has a recess recessed inward in the tire radial direction in a central region in the tread width direction. The spike pin is disposed in an outer region that is an outer region in the tread width direction than a central region in the tread width direction, and the thickness of the surface layer is increased according to the recess of the recess. The gist is that the intermediate layer is formed only in the outer region.

  A fourth feature of the present invention relates to the first to third features, wherein the spike pin includes a proximal end portion embedded in the tread portion, a distal end portion protruding from the surface layer, and the proximal end portion. A gist is provided with a shaft part connecting with the tip part, and the base end part is arranged so as to be in contact with the inner layer or embedded in the inner layer.

  According to the features of the present invention, while securing the spike pin, the sipe can be easily opened to improve the performance on ice and snow, and the performance on ice and snow is drastically reduced even when the tread portion is worn. It is possible to provide a tire that can suppress this.

FIG. 1 is a partial development view of a tread surface of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an AA cross-sectional view of the tread portion of the pneumatic tire according to the embodiment of the present invention. FIG. 3 is a tread sectional view showing another example of the pneumatic tire according to the embodiment of the present invention. FIG. 4 is an enlarged tread sectional view showing another example of the pneumatic tire according to the embodiment of the present invention. FIG. 5 is a view showing a pneumatic tire according to a comparative example.

  Next, an embodiment of a pneumatic tire according to the present invention will be described with reference to the drawings. Specifically, (1) Configuration of pneumatic tire, (2) Configuration of tread part, (3) Action / effect, (4) Modification example, (5) Comparative evaluation, (6) Other embodiments will be described. .

  In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, the part from which the relationship and ratio of a mutual dimension differ also in between drawings may be contained.

(1) Configuration of Tire FIG. 1 is a partial development view of the tread portion 1 of the pneumatic tire according to the present embodiment. The pneumatic tire according to the present embodiment is an icy and snowy road running tire called a spike tire. The pneumatic tire assembled to the rim wheel (not shown) may be filled with an inert gas such as nitrogen gas instead of air.

  Further, in the pneumatic tire according to the present embodiment, in the tread portion 1, the longitudinal groove 10 formed along the tire circumferential direction Tc, the lateral groove 20 formed in a direction intersecting the longitudinal groove 10, and the longitudinal groove 10. And a land portion 40 formed by being partitioned by the lateral groove 20.

  Here, in the pneumatic tire according to the present embodiment, the range in the tread width direction Tw of the tread portion 1 is a range in which a normal load is applied to the pneumatic tire having a normal internal pressure, and is in contact with the road surface. The normal internal pressure is an air pressure defined by the tire measuring method of the Year Book 2008 version of JATMA (Japan Automobile Tire Association). The regular load is a load corresponding to the maximum load capacity when a single wheel of Year Book 2008 version of JATMA (Japan Automobile Tire Association) is applied.

  Further, a sipe 50 is formed on the land portion 40 of the tread portion 1 and a spike pin 60 (also referred to as a stud pin) is disposed.

(2) Configuration of Tread Portion Next, the configuration of the tread portion 1 of the pneumatic tire according to the present embodiment will be described with reference to FIG. FIG. 2 shows a cross-sectional view of the tread portion 1 shown in FIG.

  The tread portion 1 according to the present embodiment is disposed between the surface layer 100 that contacts the road surface, the inner layer 200 disposed inside the tire radial direction Td of the surface layer 100, and the surface layer 100 and the inner layer 200. The intermediate layer 300 is provided. That is, the tread portion 1 is configured by three layers of the inner layer 200, the surface layer 100, and the intermediate layer 300 on the outer side in the tire radial direction Td from the belt layer 80.

  The surface layer 100 is disposed on the outermost surface among the three layers constituting the tread portion 1 and is grounded to the road surface. In the surface layer 100, a plurality of grooves such as the vertical grooves 10 and the horizontal grooves 20 and land portions 40 defined by the plurality of grooves are formed. In the land portion 40, a sipe 50 is formed and a spike pin 60 is arranged.

  The spike pin 60 includes a proximal end portion 61 embedded in the tread portion 1, a distal end portion 62 protruding from the surface layer 100, and a shaft portion 63 that connects the proximal end portion 61 and the distal end portion 62. The base end portion 61 of the spike pin 60 is disposed so as to be in contact with the inner layer 200 or embedded in the inner layer 200. The spike pin 60 is preferably embedded in the inner layer 200 with a length of about one third of the total length.

  In the present embodiment, the spike pin 60 is not disposed in the central region A1 in the tread width direction Tw of the tread portion 1 but is disposed in the outer region A2. Here, the central region A1 is a central region when the tread portion 1 is divided into a plurality of portions in the tread width direction Tw. Specifically, as shown in FIG. 2, the central region A1 is a central region when the tread portion 1 is equally divided into three in the tread width direction Tw. Further, the outer area A2 is an area other than the central area A1 in the tread width direction Tw, that is, an area outside the central area A1 in the tread width direction Tw. The reason why the spike pins 60 are not arranged in the central region A1 is that the number of spike pins 60 is reduced in order to prevent the spike pins 60 from scraping the road surface.

  The inner layer 200 is disposed on the innermost side in the tire radial direction Td among the three layers constituting the tread portion 1. The inner layer 200 has a recess 210 that is recessed in the tire radial direction Td in the central region A1 in the tread width direction Tw cross section. The recess 210 is formed in the inner layer 200 so as to extend in the tire circumferential direction Tc.

  The inner layer 200 is formed so that the thickness T21 in the central region A1 is reduced and the thickness T22 in the outer region A2 is increased by having the recess 210 in the central region A1 described above. In other words, in the cross section in the tread width direction Tw, the area of the central region A1 of the inner layer 200 is formed to be smaller than the respective areas of the outer region A2.

  The intermediate layer 300 is disposed between the surface layer 100 and the inner layer 200. The thickness of the intermediate layer 300 is formed so as to increase according to the recess of the recess 210 in the central region A1. Specifically, as shown in FIG. 2, the intermediate layer 300 is formed such that its thickness T31 is increased so as to compensate for the thickness T22 of the inner layer 200 that decreases in the central region A1. In other words, in the tread width direction Tw cross section, the area of the central region A1 of the intermediate layer 300 is formed so as to be larger than the respective areas of the outer region A2. In the present embodiment, the intermediate layer 300 is not provided in the outer region A2.

  Further, the intermediate layer 300 according to the present embodiment is made of foamed rubber in which voids are provided by foaming inside the member. It is preferable to apply a foaming rate of the foamed rubber constituting the intermediate layer 300 within a range of 12 to 26%. The foaming ratio is a volume ratio between the volume of the foam rubber intermediate layer 300 and the voids. The intermediate layer 300 composed of such foamed rubber can ensure low rubber hardness and performance on ice and snow. Moreover, the space | gap in foamed rubber may be formed by the open cell, and may be formed by the closed cell.

  Next, the rubber hardness of each of the surface layer 100, the inner layer 200, and the intermediate layer 300 will be described. Here, in the present embodiment, the rubber hardness is indicated by a Shore A hardness that conforms to the provisions of JIS K 6253. The Shore A hardness is a value representing the rubber hardness measured by the durometer type A, and the larger the value, the higher the rubber hardness.

  In the present embodiment, the rubber hardness of the surface layer 100 is lower than the rubber hardness of the inner layer 200. Further, the rubber hardness of the intermediate layer 300 is lower than the rubber hardness of the surface layer 100. That is, the rubber hardness of the intermediate layer 300 is the lowest among the three layers constituting the tread portion 1, and the rubber hardness of the inner layer 200 is the highest among the three layers. This is due to the following reason. That is, the inner layer 200 has a high rubber hardness in order to hold the spike pin 60. Further, the intermediate layer 300 has a low rubber hardness in order to suppress the rigidity of the entire tread portion 1.

  Specifically, the rubber hardness constituting the surface layer 100 is preferably in the range of Shore A “50 to 56”. On the other hand, the rubber hardness constituting the inner layer 200 is preferably 2 points or more higher than the Shore A hardness of the rubber constituting the surface layer 100. That is, the rubber hardness is preferably in the range of Shore A “52 to 58”. In addition, it is preferable to apply a rubber hardness constituting the intermediate layer 300 that is 4 to 6 points lower than the Shore A hardness of the rubber constituting the surface layer 100. That is, the rubber hardness is preferably in the range of Shore A “44 to 52”.

  In the pneumatic tire having such a configuration, for example, when the thickness T0 in the tire radial direction Td of the tread portion 1 is 12.5 mm, the thickness of the inner layer 200 is 2.0 mm in the central region A1, and the surface layer The thickness of 100 is preferably 6.2 mm, and the thickness of the intermediate layer 300 is preferably 4.3 mm. On the other hand, in the outer region A2, it is preferable that the inner layer 200 has a thickness of 6.3 mm, the surface layer 100 has a thickness of 6.2 mm, and the intermediate layer has a thickness of 0 mm, that is, the intermediate layer 300 is not provided.

(3) Action / Effect Next, the action and effect of the pneumatic tire according to the present embodiment will be described.

  In the pneumatic tire according to the present embodiment, the tread portion 1 includes a surface layer 100, an inner layer 200, and an intermediate layer 300. The rubber hardness of the surface layer 100 is lower than the rubber hardness of the inner layer 200, and the rubber hardness of the intermediate layer 300 is lower than the rubber hardness of the surface layer 100.

  Thus, in such a pneumatic tire, not only the surface layer 100 but also the surface layer and the intermediate layer 300 are disposed outside the inner layer 200 in the tire radial direction Td. That is, according to such a pneumatic tire, when rubber having a high rubber hardness is used for the inner layer 200 in order to hold the spike pin 60, the rubber of the intermediate layer 300 can be obtained without reducing the rubber hardness of the surface layer 100. By reducing the hardness, the rigidity of the tread portion 1 as a whole can be suppressed.

  Moreover, according to the pneumatic tire which concerns on this embodiment, the inner layer 200 has the recessed part 210 in center area | region A1 of the tread width direction Tw. Further, the thickness of the intermediate layer 300 in the central region A1 is formed so as to increase in accordance with the recess of the recess 210 of the inner layer 200.

  That is, even when rubber having a high rubber hardness is used for the inner layer 200, a concave portion 210 in which the thickness of the inner layer 200 is reduced is formed in the central region A1 in the tread width direction Tw. A low intermediate layer 300 is formed. Therefore, the pneumatic tire according to the present embodiment can suppress the rigidity in the central region A1 in the tread width direction Tw.

  Thus, according to the pneumatic tire according to the present embodiment, the rigidity of the tread portion 1 as a whole can be suppressed and the sipe 50 formed in the land portion 40 can be easily opened in the central region A1. The performance on ice and snow due to the scratching effect of the corner formed in the land portion 40 by the sipe 50 can be improved. Note that the pneumatic tire according to the present embodiment is particularly effective in improving the performance on snow such as braking performance and acceleration performance on the road surface on snow.

  Moreover, according to such a pneumatic tire, the tread portion 1 is configured by three layers of the surface layer 100, the inner layer 200, and the intermediate layer 300. That is, when the surface layer 100 is worn, the intermediate layer 300 made of foamed rubber having excellent performance on ice and snow is exposed before the inner layer 200 is exposed. It will gradually decrease without decreasing. In this way, even if the tread portion 1 is worn, it is possible to suppress a sudden drop in performance on ice and snow. In addition, the pneumatic tire according to the present embodiment is particularly effective for suppressing a decrease in performance on ice such as braking performance and acceleration performance on an ice surface.

(4) Modification example (4.1) Modification example 1
Modification 1 of the pneumatic tire according to this embodiment will be described. In the pneumatic tire according to this modified example, as shown in FIG. 3, the intermediate layer 300 is arranged not only in the central region A1 but also in the outer region A2. Specifically, in the central region A1, the inner layer 200 has a recess 210, and the intermediate layer 300 is formed so that the thickness T31 increases according to the recess of the recess 210 of the inner layer 200. On the other hand, in the outer region A2, the inner layer 200 is formed to have a thickness T22 larger than that of the central region A1 in order to hold the spike pin 60, and the intermediate layer 300 has a smaller thickness T32. Is formed.

  In the pneumatic tire having such a configuration, for example, when the thickness T0 in the tire radial direction Td of the tread portion 1 is 12.5 mm, the thickness T11 of the surface layer 100 is set to 4.2 mm in the central region A1, It is preferable that the thickness T21 of the layer 200 is 2.0 mm and the thickness T31 of the intermediate layer 300 is 6.3 mm. On the other hand, in the outer region A2, it is preferable that the thickness T12 of the surface layer 100 is 4.2 mm, the thickness T22 of the inner layer 200 is 6.3 mm, and the thickness T33 of the intermediate layer 300 is 2.0 mm.

  According to such a pneumatic tire, since the rigidity of the tread portion 1 can be suppressed not only in the central region A1 but also in the outer region A2, the sipe 50 not only in the central region A1 but also in the outer region A2 can be easily opened. It becomes possible. Therefore, the performance on ice and snow due to the scratching effect of the corner formed in the land portion 40 by the sipe 50 can be improved.

(4.2) Modification 2
Modification 2 of the pneumatic tire according to this embodiment will be described. In the pneumatic tire according to this modified example, as shown in FIG. 4, the inner layer 200 has a recess 210 that is recessed in the tire radial direction Td in the central region A1. In the central region A1, the thickness T11 of the surface layer 100 is formed so as to increase according to the recess of the recess 210. The intermediate layer 300 is disposed only in the outer region A2. The spike pin 60 is disposed in the outer region A2 that is an outer region of the tread width direction Tw than the central region A1 in the tread width direction Tw.

  Specifically, in such a pneumatic tire, in the central region A1, the inner layer 200 is formed such that the thickness T21 of the inner layer 200 is reduced by having the recess 210. Further, in the central region A1, the surface layer 100 is formed so that the thickness T11 is increased by the amount that the thickness T21 of the inner layer 200 is decreased.

  On the other hand, in the outer region A2, the inner layer 200 is formed so that the thickness T22 of the inner layer 200 is increased to hold the spike pin 60, and the surface layer 100 is formed so that the thickness T11 is decreased. . Further, the intermediate layer 300 is disposed only in the outer region A2. That is, the central region A1 is composed of two layers of the surface layer 100 and the inner layer 200, and the outer region A2 is composed of three layers of the surface layer 100, the inner layer 200, and the intermediate layer 300. ing.

  According to such a pneumatic tire, in the central region A1, the rigidity of the tread portion 1 as a whole can be suppressed by reducing the thickness T21 of the inner layer 200. Further, in the outer region A2, the inner layer 200 having a large thickness T22 is disposed to hold the spike pin 60, but the intermediate layer 300 having a low rubber hardness is disposed, so that the rigidity of the tread portion 1 can be suppressed. it can.

  Further, the tread portion 1 is constituted by three layers of the surface layer 100, the inner layer 200, and the intermediate layer 300 in the outer region A2. That is, as the surface layer 100 is worn, the intermediate layer 300 made of foamed rubber having excellent performance on ice and snow is exposed, so the performance on ice and snow is reduced stepwise without abruptly decreasing. can do.

(5) Comparative Evaluation Next, in order to further clarify the effects of the present invention, comparative evaluation performed using pneumatic tires according to the following examples will be described. Specifically, (5.1) Comparative evaluation related to performance on snow and (5.2) Comparative evaluation related to performance on ice will be described. In addition, this invention is not limited at all by these examples. For example, in the following comparative evaluation, evaluation was made on pneumatic tires for passenger cars, but it should be noted that the present invention is also effective for pneumatic tires for light trucks and the like.

(5.1) Comparative Evaluation Regarding Performance on Snow First, comparative evaluation regarding performance on snow will be described.

(5.1.1) Description of comparative examples and examples (performance on snow)
The following Comparative Example 1 and Example 1 were prepared for performance on snow. In addition, as for the pneumatic tires of Comparative Example 1 and Example 1, those equivalent to new ones were prepared.

  As shown in FIG. 5, a conventionally known pneumatic tire according to Comparative Example 1 in which the tread portion 1 is constituted by two layers of a surface layer and an inner layer.

  Specifically, as the pneumatic tire according to Comparative Example 1, a tire whose thickness T0 in the tire radial direction Td of the tread portion 1 is “12.5 mm” was used. In the pneumatic tire according to Comparative Example 1, the thickness T1 of the surface layer 100 is “6.2 mm” and the thickness T2 of the inner layer 200 is “6.3 mm” in both the central region A1 and the outer region A2. The thing which is is used.

  Next, Example 1 will be described. As shown in FIG. 3, in the pneumatic tire according to the first embodiment, the inner layer 200 is provided with a recess 210 in the central region A1, and the thickness of the intermediate layer 300 increases according to the recess of the recess 210. We used what is. In addition, the pneumatic tire according to Example 1 used the one in which the intermediate layer 300 is disposed not only in the central region A1 but also in the outer region A2.

  Specifically, in the central region A1, the inner layer 200 has a recess 210, and the intermediate layer 300 is formed so that the thickness T31 increases according to the recess of the recess 210 of the inner layer 200. On the other hand, in the outer region A2, the inner layer 200 is formed to have a thickness T22 larger than that of the central region A1 in order to hold the spike pin 60, and the intermediate layer 300 has a smaller thickness T32. Is formed.

  In the pneumatic tire according to Example 1, a tire whose thickness T0 in the tire radial direction Td of the tread portion 1 is “12.5 mm” was used. In the pneumatic tire according to Example 1, in the central region A1, the thickness T11 of the surface layer 100 is “4.2 mm”, the thickness T21 of the inner layer 200 is “2.0 mm”, and the thickness T31 of the intermediate layer 300 is What was "6.3 mm" was used. On the other hand, in the outer region A2, the surface layer 100 has a thickness T12 of “4.2 mm”, the inner layer 200 has a thickness T22 of “6.3 mm”, and the intermediate layer 300 has a thickness T33 of “2.0 mm”. It was. Further, as shown in the above-described embodiment, the intermediate layer 300 is formed of foamed rubber having a rubber hardness lower than that of the surface layer 100 and the inner layer 200.

(5.1.2) Evaluation method (performance on snow)
The pneumatic tires of Comparative Example 1 and Example 1 were evaluated under the following conditions.

・ Tire size: 195 / 65R15
・ Rim size: 6.5J
・ Internal pressure condition: 240 kPa
・ Brake performance evaluation method: After driving on a snowy road surface at a vehicle speed of 30 km / h, braking was applied to decelerate and the time required for the vehicle speed to reach 5 km / h (deceleration time) was measured. ・ Acceleration performance evaluation method: vehicle speed of 10 km After driving on the road surface on snow at / h, acceleration was performed by stepping on the accelerator and the time required for the vehicle speed to reach 35 km / h (acceleration time) was measured (5.1.3) Evaluation results (snow performance)
The evaluation results of each pneumatic tire will be described with reference to Table 1. Table 1 shows a comparative evaluation result regarding performance on snow.

Here, in Table 1, “Snow braking performance” represents an index when the deceleration time of the comparative example is used as a reference (100). The larger the index, the shorter the deceleration time and the better the braking performance. Indicates that “Snow acceleration performance” represents an index when the acceleration time of the comparative example is used as a reference (100). The larger the index, the shorter the acceleration time and the better the acceleration performance.

  As shown in Table 1, it was proved that the pneumatic tire according to Example 1 has an effect of improving both the acceleration performance on snow and the braking performance on snow when compared with the pneumatic tire according to Comparative Example 1. Therefore, it was found that the performance on ice and snow was improved in the pneumatic tire according to Example 1.

(5.2) Comparative evaluation on performance on ice Next, comparative evaluation on performance on ice will be described.

(5.2.1) Description of comparative examples and examples (performance on ice)
The following Comparative Examples 1 and 2 and Examples 1 to 4 were prepared for performance on ice. The pneumatic tires of Comparative Example 2, Example 2, and Example 4 were prepared as worn as a result of running on the snowy and snowy road surface for a predetermined period. Also, the pneumatic tires of any of Comparative Example 2, Example 2, and Example 4 were used in which the groove depth was reduced to about 4 mm and the remaining number of spike pins 60 was reduced to about 20. Below, each pneumatic tire is demonstrated concretely.

  As the pneumatic tire according to the comparative example 1, as shown in FIG. 5, a conventionally known tire in which the tread portion 1 is constituted by two layers of a surface layer 100 and an inner layer 200 is used.

  In the pneumatic tire according to Comparative Example 2, as a result of wear of the tread portion 1 of the pneumatic tire shown in FIG. 5, the surface layer 100 is eliminated and the inner layer 200 is exposed in both the central region A1 and the outer region A2. I used what is.

  As shown in FIG. 3, in the pneumatic tire according to the first embodiment, the inner layer 200 is provided with a recess 210 in the central region A1, and the thickness of the intermediate layer 300 increases according to the recess of the recess 210. We used what is.

  In the pneumatic tire according to Example 2, as shown in FIG. 3, as a result of the tread portion 1 of the pneumatic tire according to Example 1 being worn, the surface layer 100 is eliminated in the central region A1 and the outer region A2, and the intermediate tire What exposed the layer 300 was used. The intermediate layer 300 is formed of foamed rubber having a lower rubber hardness than the surface layer 100 and the inner layer 200 as shown in the above-described embodiment.

  As the pneumatic tire (not shown) according to Example 3, a tire in which the intermediate layer 300 is disposed over the central region A1 and the outer region A2 was used. In addition, as compared with the pneumatic tire according to the example 1, the pneumatic tire according to the example 3 used the inner layer 200 in which the concave portion 210 was not provided.

  Specifically, in the pneumatic tire according to Example 3, a tire whose thickness T0 in the tire radial direction Td of the tread portion 1 is “12.5 mm” was used. In the pneumatic tire according to the third embodiment, the thickness T12 of the surface layer 100 is “4.2 mm”, the thickness T22 of the inner layer 200 is “6.3 mm”, and the intermediate layer 300 in the central region A1 and the outer region A2. The one having a thickness T33 of “2.0 mm” was used.

  In the pneumatic tire according to Example 4, as a result of wear of the tread portion of the pneumatic tire according to Example 3, the surface layer 100 is eliminated and the intermediate layer 300 is exposed in the central region A1 and the outer region A2. Was used.

(5.2.2) Evaluation method (performance on ice)
Evaluation was performed using the pneumatic tires of the comparative example and the example under the following conditions. Since the tire size, rim size, and internal pressure conditions are the same as those described in the above section 4.1.2, the braking performance evaluation method and the acceleration performance evaluation method will be described.

・ Brake performance evaluation method: After running on an icy road surface at a vehicle speed of 30 km / h, the brake was applied to decelerate and the time required for the vehicle speed to reach 5 km / h (deceleration time) was measured. ・ Acceleration performance evaluation method: vehicle speed of 10 km After driving on the ice surface at / h, step on the accelerator to accelerate and measure the time (acceleration time) required for the vehicle speed to reach 35 km / h (5.2.3) Evaluation results (on-ice performance)
The evaluation results of each pneumatic tire will be described with reference to Table 2. Table 2 shows the comparative evaluation results regarding the performance on ice.

Here, in Table 2, “on-ice braking performance” represents an index when the deceleration time of the pneumatic tire according to Comparative Example 1 equivalent to that of a new product is set as a reference (100), and the larger this index is, It shows that the deceleration time is short and the braking performance is excellent. “Acceleration performance on ice” represents an index when the acceleration time of the pneumatic tire according to Comparative Example 1 equivalent to that of a new article is set as a reference (100). The larger the index, the shorter the acceleration time, and the acceleration performance. Indicates that it is excellent.

  As shown in Table 2, when compared with the pneumatic tire according to Comparative Example 1, the pneumatic tires according to Example 1 and Example 3 have substantially the same effects on both ice acceleration performance and ice braking performance. It was proved. In addition, the pneumatic tires according to Example 2 and Example 4 after wear may have an effect of improving both the acceleration performance on ice and the braking performance on ice when compared with the pneumatic tire according to Comparative Example 2 after wear. Proven. Therefore, it turned out that the pneumatic tire which concerns on Example 2 and Example 4 can suppress that a performance on ice falls rapidly, even if it is a case where a tread part is worn out.

  When Example 2 and Example 4 are compared, in terms of acceleration performance on ice, the pneumatic tire according to Example 2 having the recess 210 has a slight grip force because it has a higher grip force with respect to the contact surface. Excellent acceleration performance on ice. In terms of braking performance on ice, the pneumatic tire according to Example 4 having no recess 210 has a slight but excellent braking performance on ice because the rigidity of the tread portion is higher.

  Thus, in the pneumatic tire according to the present invention, it is found that, compared with the comparative example, the performance on snow can be improved, and even when the tread portion 1 is worn, a rapid decrease in performance on ice can be suppressed. It was.

(6) Other Embodiments As described above, the contents of the present invention have been disclosed through the embodiments of the present invention. However, it is understood that the description and drawings constituting a part of this disclosure limit the present invention. Should not. From this disclosure, various alternative embodiments, examples, and operational techniques will be apparent to those skilled in the art.

  For example, in the above-described embodiment, the case where the intermediate layer 300 is formed of foamed rubber has been described as an example. However, the present invention is not limited to this. For example, rubber including walnuts or egg shells is used. Also good. That is, the intermediate layer 300 may be any material as long as it has higher performance on ice and snow than the inner layer 200 and has lower rubber hardness than the surface layer 100.

  In the above-described embodiment, as an example, the thicknesses of the surface layer 100, the inner layer 200, and the intermediate layer 300 are indicated by numerical values. However, based on the ratios corresponding to the numerical values, pneumatic tires having various thicknesses are used. Applicable.

  Moreover, the present invention may be a pneumatic tire filled with air, nitrogen gas, or the like as a tire, or may be applied to a solid tire that is not filled with air, nitrogen gas, or the like.

  As described above, the present invention naturally includes various embodiments that are not described herein. Therefore, the technical scope of the present invention is determined only by the invention specifying matters according to the scope of claims reasonable from the above description.

A1 ... Center region, A2 ... Outer region, Tc ... Tire circumferential direction, Td ... Tire radial direction, Tw ... Tread width direction, 1 ... Tread portion, 10 ... Vertical groove, 20 ... Horizontal groove, 40 ... Land portion, 50 ... Sipe , 60 ... spike pin, 61 ... proximal end portion, 62 ... tip portion, 63 ... shaft portion, 80 ... belt layer, 100 ... surface layer, 200 ... inner layer, 300 ... intermediate layer, 210 ... concave portion

Claims (3)

A tread portion having a surface layer that contacts the road surface and an inner layer disposed on the inner side in the tire radial direction of the surface layer, the surface layer being partitioned by a plurality of grooves and the plurality of grooves; A land portion to be formed, a sipe is formed in the land portion, and a spike pin is disposed,
The tread portion includes an intermediate layer disposed between the surface layer and the inner layer,
The rubber hardness of the intermediate layer is lower than the rubber hardness of the surface layer,
The intermediate layer is made of foamed rubber with voids provided inside the member,
The rubber hardness of the surface layer is lower than the rubber hardness of the inner layer,
In the cross section in the tread width direction,
The inner layer has a recess recessed in the tire radial direction inside in a central region in the tread width direction, and is formed so that the thickness decreases according to the recess of the recess,
The spike pin is disposed only in an outer region that is an outer region in the tread width direction than a central region in the tread width direction,
The thickness of the surface layer is formed to increase according to the recess of the recess,
The intermediate layer is disposed only in the outer region where the thickness of the surface layer is smaller than the thickness of the surface layer in the central region and the thickness of the inner layer is larger than the thickness of the inner layer in the central region. A tire characterized by being. The tread portion has a two-layer structure of the surface layer and the inner layer in the central region, and has a three-layer structure of the surface layer, the intermediate layer, and the inner layer in the outer region. The tire according to claim 1. The spike pin includes a base end portion embedded in the tread portion, a tip portion protruding from the surface layer, and a shaft portion connecting the base end portion and the tip portion.
3. The tire according to claim 1, wherein the base end portion is disposed so as to be in contact with the inner layer or embedded in the inner layer.

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