Patent Application
20210122194
The present technology relates to a pneumatic tire, more specifically relates to a pneumatic tire capable of providing good improvement of steering stability performance on dry road surfaces and improvement of steering stability performance on wet road surfaces in a compatible manner, and additionally capable of improving braking performance on dry road surfaces by devising a chamfer shape of a sipe.
In the related art, a plurality of sipes is formed on a rib defined by a plurality of main grooves in a tread pattern of a pneumatic tire. By forming these sipes, drainage properties are ensured, and the steering stability performance on wet road surfaces is delivered. However, when a lot of sipes are disposed in a tread portion for enhancing the steering stability performance on wet road surfaces, there are disadvantages in which the steering stability performance on dry road surfaces, the braking performance and uneven wear resistance performance lower due to lowering of rigidity of a rib.
Additionally, various kinds of pneumatic tires in which sipes are formed in a tread pattern, and chamfered are proposed (for example, see Japanese Unexamined Patent Publication No. 2013-537134). When sipes are formed and chamfered, an edge effect may be lost depending on a chamfer shape, and the steering stability performance on dry road surfaces or the steering stability performance on wet road surfaces may be insufficiently improved depending on a chamfer dimension.
The present technology provides a pneumatic tire capable of providing good improvement of steering stability performance on dry road surfaces and improvement of steering stability performance on wet road surfaces in a compatible manner, and additionally capable of improving braking performance on dry road surfaces by devising a chamfer shape of a sipe.
A pneumatic tire of the present technology includes a plurality of main grooves extending in a tire circumferential direction in a tread portion including sipes extending in a tire lateral direction on a rib defined by the main grooves, in which the rib includes the sipe extending from one of the main grooves and the sipe extending from another one of the main grooves, the main grooves being positioned on both sides of the rib, respectively; one end portion of both end portions of the sipe opens into the main groove and another end portion terminates within the rib; in a case that two of the sipes extending from main grooves on both sides of the rib are regarded as a pair of sipes when a distance in a tire circumferential direction between end portions of the two of the sipes that terminate within the rib is not greater than 15 mm, the pair of sipes include edges on a leading side and edges on a trailing side; chamfered portions shorter than a total sipe length of the pair of sipes are formed on respective edges on the leading side and on the trailing side; non-chamfered regions on which no other chamfered portion exists exist on portions opposing to respective chamfered portions in the pair of sipes; a maximum depth x (mm) of the sipe and a maximum depth y (mm) of the chamfered portion satisfy Relationship (1) below; and a sipe width of the sipe is constant in a range from an end portion positioned inside in a tire radial direction of the chamfered portion to a groove bottom of the sipe.
x×0.1≤y≤x×0.3+1.0 (1)
In the present technology, in a pneumatic tire including a sipe extending in a tire lateral direction on a rib defined by main grooves, by providing respective chamfered portions shorter than a total sipe length of a pair of sipes on edges on a leading side and on a trailing side of the pair of sipes, whereas providing non-chamfered regions on which no other chamfered portion exists on respective portions opposing to chamfered portions in the pair of sipes, it is possible to enhance a drainage effect based on the chamfered portion, and at the same time, to effectively remove a water film on the non-chamfered region by an edge effect. Accordingly, it is possible to improve steering stability performance on wet road surfaces significantly. Additionally, since the chamfered portion and the non-chamfered region are provided on the respective edges on the leading side and on the trailing side in a mixed manner, it is possible to maximally enjoy an effect of enhancing the above-described wet performance during braking and driving. In addition, an area to be chamfered may be minimized in comparison with a sipe chamfered as in the related art, thus it is possible to improve steering stability performance on dry road surfaces. As a result, it is possible to provide good improvement of the steering stability performance on wet road surfaces and improvement of the steering stability performance on dry road surfaces in a compatible manner. Further, by providing the pair of sipes configured with two sipes terminating within the rib and extending from the different main grooves, the rib is formed to be continuous at a portion at or near a central portion of the rib without being divided by the pair of sipes, thus it is possible to improve tread rigidity in a tire circumferential direction and improve braking performance on dry road surfaces.
In the present technology, the chamfered portion preferably projects from the other end portion of the sipe and extends in a length direction of the sipe. Disposing the chamfered portion as described above makes it possible to provide good improvement of block rigidity and enhancement of drainage properties in a compatible manner.
In the present technology, a total sipe length of the pair of sipes is preferably from 0.4 to 1.0 times a rib width of the rib. As described above, by setting the total sipe length of the pair of sipes to an appropriate length, it is possible to provide good improvement of the steering stability performance on dry road surfaces and improvement of the steering stability performance on wet road surfaces in a compatible manner, and improve the braking performance on dry road surfaces. More preferably, the length is from 0.5 to 0.7 times the width.
In the present technology, preferably, the sipe is inclined with respect to the tire circumferential direction. As described above, by making the sipe inclined, it is possible to improve rigidity of the rib and further improve the steering stability performance on dry road surfaces.
In the present technology, an inclination angle on an acute angle side with respect to the tire circumferential direction of the sipe is preferably from 40° to 80°. As described above, by setting the inclination angle on the acute angle side with respect to the tire circumferential direction of the sipe, it is possible to improve the steering stability performance on dry road surfaces more effectively. More preferably, the angle is from 50° to 70°.
In the present technology, the chamfered portion is preferably disposed on the acute angle side of the sipe. In this way, it is possible to further enhance uneven wear resistance performance. Alternatively, the chamfered portion is preferably disposed on an obtuse angle side of the sipe. Accordingly, the edge effect increases, thereby making it possible to further improve the steering stability performance on wet road surfaces.
In the present technology, at least part of the sipe preferably curves or bends in a plan view. By forming at least part of the sipe as described above, a total amount of the edge of each of the sipes increases, thereby making it possible to improve the steering stability performance on wet road surfaces. The whole sipe may be an arc.
In the present technology, the chamfered portion preferably opens into the main groove. Accordingly, it is possible to further improve the steering stability performance on wet road surfaces. Alternatively, the chamfered portion preferably terminates within the rib. Accordingly, it is possible to further improve the steering stability performance on dry road surfaces.
In the present technology, an overlap length of the chamfered portion formed on the edge on the leading side of the sipe and the chamfered portion formed on the edge on the trailing side of the sipe is preferably from −30% to 30% of the total sipe length. As described above, by appropriately setting the overlap length of the chamfered portion with respect to the total sipe length, it is possible to provide good improvement of the steering stability performance on dry road surfaces and improvement of the steering stability performance on wet road surfaces in a compatible manner. More preferably, the overlap length is from −15% to 15% of the total sipe length.
In the present technology, the chamfered portion is preferably disposed on a position of the edge on the leading side and on a position of the edge on the trailing side of the sipe. Disposing the chamfered portions as described above makes it possible to improve the uneven wear resistance performance.
In the present technology, a maximum width of the chamfered portion is preferably from 0.8 to 5.0 times a sipe width of the sipe. As described above, by appropriately setting the maximum width of the chamfered portion with respect to the sipe width, it is possible to provide good improvement of the steering stability performance on dry road surfaces and improvement of the steering stability performance on wet road surfaces in a compatible manner. More preferably, the maximum width is from 1.2 to 3.0 times the sipe width.
In the present technology, the chamfered portion preferably extends in parallel with the sipe. Accordingly, it is possible to improve the uneven wear resistance performance and provide good improvement of the steering stability performance on dry road surfaces and improvement of the steering stability performance on wet road surfaces in a compatible manner.
The configuration of the present technology is described in detail below with reference to the accompanying drawings. Note that, in
As illustrated in
A carcass layer 4 is mounted between the pair of bead portions 3, 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction and is folded back around bead cores 5 disposed in each of the bead portions 3 from a tire inner side to a tire outer side. A bead filler 6 having a triangular cross-sectional shape formed from rubber composition is disposed on a periphery of the bead core 5.
On the other hand, a plurality of belt layers 7 is embedded on an outer circumferential side of the carcass layer 4 in the tread portion 1. These belt layers 7 include a plurality of reinforcing cords that inclines with respect to the tire circumferential direction and the direction of the reinforcing cords of the different layers intersect each other. In the belt layers 7, an inclination angle of the reinforcing cords with respect to the tire circumferential direction ranges from, for example, 10° to 40°. Steel cords are preferably used as the reinforcing cords of the belt layers 7. For the purpose of improving high-speed durability, at least one layer of a belt cover layer 8 formed by arranging reinforcing cords at an angle of, for example, not greater than 5° with respect to the tire circumferential direction, is disposed on an outer circumferential side of the belt layers 7. Nylon, aramid, or similar organic fiber cords are preferably used as the reinforcing cords of the belt cover layer 8.
Also, a plurality of main grooves 9 extending in the tire circumferential direction is formed in the tread portion 1. These main grooves 9 define a plurality of ribs 10 in the tread portion 1.
Note that the tire internal structure described above is exemplary in a pneumatic tire, but is not limited thereto.
In
As illustrated in
The sipes 111 and 112 oppose with each other within the same rib 10. In these opposing sipes 111 and 112, a distance between the respective end portions 11D in the tire circumferential direction is a distance D. That is, the distance D is a distance between the same portions (bottom ends of the end portions 11D in
In the sipes 111 and 112, respective lengths, from one end portion to the other end portion, in the tire lateral direction are sipe lengths L111 and L112. In the chamfered portions 12A and 12B, respective lengths, from one end portion to the other end portion, in the tire lateral direction are chamfer lengths LA and LB. Additionally, a total of the sipe length L111 of the sipe 111 and the sipe length L112 of the sipe 112 is a total sipe length L of the pair of sipes 11. At this time, chamfer lengths LA and LB of the respective chamfered portions 12A and 12B are formed so as to be shorter than the total sipe length L.
The pair of sipes 11 include an edge 11A as the leading side with respect to a rotation direction R, and an edge 11B as the trailing side with respect to the rotation direction R. In the pair of sipes 11, respective chamfered portions 12 are formed on the edge 11A on the leading side and the edge 11B on the trailing side.
The chamfered portions 12 include a chamfered portion 12A as the leading side with respect to the rotation direction R, and a chamfered portion 12B as the trailing side with respect to the rotation direction R. Non-chamfered regions 13 on which no other chamfered portion exists exist on portions opposing to these chamfered portions 12. That is, there is a non-chamfered region 13B as the trailing side with respect to the rotation direction R on a portion opposing to the chamfered portion 12A and there is a non-chamfered region 13A as the leading side with respect to the rotation direction R on a portion opposing to the chamfered portion 12B. The chamfered portion 12 and the non-chamfered region 13 on which no other chamfered portion exists are disposed to be adjacent on the edge 11A on the leading side and the edge 11B on the trailing side of the pair of sipes 11, respectively, as described above.
x×0.1≤y≤x×0.3+1.0 (1)
In the above-described pneumatic tire, by providing the respective chamfered portions 12 shorter than the total sipe length L of the pair of sipes 11 on the edge 11A on the leading side and the edge 11B on the trailing side of the pair of sipes 11, and providing the respective non-chamfered regions 13 on which no other chamfered portion exists on the portions opposing to chamfered portions 12 in the pair of sipes 11, it is possible to enhance the drainage effect based on the chamfered portion 12, and at the same time, to effectively remove a water film on the non-chamfered region 13 on which the chamfered portion 12 is not provided by the edge effect. Accordingly, it is possible to improve steering stability performance on wet road surfaces significantly. Additionally, since the chamfered portion 12 and the non-chamfered region 13 on which no chamfered portion exists are provided on the edge 11A on the leading side and the edge 11B on the trailing side, respectively, in a mixed manner, it is possible to maximally enjoy an effect of enhancing the above-described wet performance during braking and driving. Further, by providing the pair of sipes 11 configured with the two sipes 111 and 112 terminating within the rib 10 and extending from the different main grooves 9, the rib 10 is formed to be continuous at a portion at or near the central portion of the rib 10 without being divided by the pair of sipes 11, thus it is possible to improve the tread rigidity in the tire circumferential direction and improve the braking performance on dry road surfaces.
Additionally, in the above-described pneumatic tire, the maximum depth x (mm) and the maximum depth y (mm) need to satisfy the above-described Relationship (1). By providing the sipes 111 and 112 and the chamfered portions 12 so as to satisfy the above-described Relationship (1), an area to be chamfered may be minimized in comparison with a sipe chamfered as in the related art, thus it is possible to improve the steering stability performance on dry road surfaces. As a result, it is possible to provide good improvement of the steering stability performance on wet road surfaces and improvement of the steering stability performance on dry road surfaces in a compatible manner. Here, in a case of y<x×0.1, the drainage effect based on the chamfered portion 12 becomes insufficient, and conversely in a case of y>x×0.3+1.0, the steering stability performance on dry road surfaces lowers due to decrease in rigidity of the rib 10. Especially, a relationship of y≤x×0.3+0.5 is preferably satisfied.
The rib 10 has a constant width in the tire lateral direction, and a width of the rib 10 is a rib width L0. At this time, the total sipe length L of the pair of sipes 11 is preferably from 0.4 to 1.0 times the rib width L0 of the rib 10, and more preferably from 0.5 to 0.7 times L0. As described above, by setting the total sipe length L of the pair of sipes 11 to an appropriate length, it is possible to provide good improvement of the steering stability performance on dry road surfaces and improvement of the steering stability performance on wet road surfaces in a compatible manner, and improve the braking performance on dry road surfaces. Here, when the total sipe length L of the pair of sipes 11 is smaller than 0.4 times the rib width L0 of the rib 10, a sufficient effect of enhancing the steering stability performance on wet road surfaces may not be obtained, and when the L exceeds 1.0 times L0, a sufficient effect of enhancing the braking performance on dry road surfaces may not be obtained.
The sipes 111 and 112 are formed, as illustrated in
In the present technology, a side having the inclination angles θ111 and θ112 on the acute angle side of the sipes 111 and 112 is an acute angle side, and a side having the inclination angles θ111 and θ112 on the obtuse angle side of the sipes 111 and 112 is an obtuse angle side. The chamfered portions 12A and 12B formed on the edges 11A and 11B of the sipes 111 and 112, respectively, are formed on the acute angle side of the sipes 111 and 112, respectively. In this way, since the acute angle sides of the sipes 111 and 112 are chamfered, it is possible to further enhance the uneven wear resistance performance. Alternatively, the chamfered portions 12A and 12B may be formed on the obtuse angle sides of the sipes 111 and 112, respectively. Since the chamfered portions 12A and 12B are formed on the obtuse angle sides of the sipes 111 and 112, respectively, as described above, the edge effect increases, thereby further improving the steering stability performance on wet road surfaces.
In the present technology, although the curve as the whole shape of each of the above-described sipes 111 and 112 makes it possible to improve the steering stability performance on wet road surfaces, additionally, part of each of the sipes 111 and 112 may have a curving or bending shape in a plan view. By forming the sipes 111 and 112 as described above, total amounts of the edges 11A and 11B of the respective sipes 111 and 112 increase, thereby making it possible to improve the steering stability performance on wet road surfaces.
End portions of the respective chamfered portions 12A and 12B, positioned closer to the main grooves 9, communicate with the main grooves 9 positioned on both side of the rib 10, respectively. Since the chamfered portions 12A and 12B are formed as described above, it is possible to further improve the steering stability performance on wet road surfaces. Alternatively, the end portions of the respective chamfered portions 12A and 12B, positioned closer to the main grooves 9 may terminate within the rib 10 without communicating with the main grooves 9. Since the chamfered portions 12A and 12B are formed as described above, it is possible to further improve the steering stability performance on dry road surfaces.
The chamfered portion 12 is disposed on a position of the edge 11A on the leading side of the sipe 111 and on a position of the edge 11B on the trailing side of the sipe 112. Disposing the chamfered portions 12 as described above makes it possible to improve the uneven wear resistance performance. Here, when the chamfered portion 12 is disposed on more than one positions of the edge 11A on the leading side of the sipe 111 and on more than one positions of the edge 11B on the trailing side of the sipe 112, the number of sections increases, thus the uneven wear resistance performance tends to deteriorate.
As illustrated in
An outer edge portion in a longitudinal direction of the chamfered portion 12 is formed in parallel with an extension direction of the sipes 111 and 112. Since the chamfered portion 12 extends in parallel with the sipes 111 and 112 as described above, it is possible to improve the uneven wear resistance performance and provide good improvement of the steering stability performance on dry road surfaces and improvement of the steering stability performance on wet road surfaces in a compatible manner.
As illustrated in
As the chamfered portions 12A and 12B of the pair of sipes 11, besides examples illustrated in
With reference to a pneumatic tire that has a tire size of 245/40R19, that includes a plurality of main grooves extending in a tire circumferential direction in a tread portion, and sipes extending in a tire lateral direction on a rib defined by the main grooves, tires in Conventional Examples 1 and 2, Comparative Examples 1 and 2, and Examples 1 to 12 were manufactured with the following: the disposition of chamfers (both sides or one side), structure of sipe (communicating or not communicating), comparison of total sipe length L and chamfer lengths LA and LB, presence or absence of chamfer of portion opposing to chamfered portion, maximum depth x of sipe (mm), maximum depth y of chamfered portion (mm), inclination angle on acute angle side with respect to tire circumferential direction of sipe, chamfered position of sipe (acute angle side or obtuse angle side), shape of entire sipe (straight lines or curved), presence or absence of opening into main groove of chamfered portion, percentage of overlap length L1 of chamfered portion with respect to total sipe length L, number of chamfered positions (one or two), maximum width W1 of chamfered portion with respect to sipe width W (W1/W), shape of chamfer (parallel or non-parallel), and total sipe length L with respect to rib width L0 (L/L0), set according to Table 1 and Table 2.
With reference to these test tires, sensory evaluation for the steering stability performance on dry road surfaces and the steering stability performance on wet road surfaces by a test driver, visual evaluation for the uneven wear resistance performance, and evaluation for the braking performance on dry road surfaces were performed, and results were shown altogether in Table 1 and Table 2.
In Table 1 and Table 2, “structure of sipe” is referred to as “communicating” when both of the end portions of the sipes communicate with the respective main grooves positioned on both sides of the rib, and is referred to as “not communicating” when one of the end portions does not communicate with the main groove and terminates within the rib. In the respective tires in Conventional Example 1, Comparative Examples 1 and 2, and Examples 1 to 12, in a range from an end portion positioned inside the chamfered portion in the tire radial direction to the groove bottom of the sipe, the sipe width is constant.
The sensory evaluation for the steering stability performance on dry road surfaces and the steering stability performance on wet road surfaces was performed with each of the test tires assembled on wheels having a rim size of 19×8.5 J, and mounted on a vehicle, and under an air pressure condition of 260 kPa. Evaluation results were expressed as index values, Conventional Example 1 being assigned an index value of 100. Larger index values indicate excellent steering stability performance on dry road surfaces and excellent steering stability performance on wet road surfaces.
The visual evaluation for the uneven wear resistance performance was performed by visually evaluating appearance of the test tires after driving 4000 km with each of the test tires assembled on wheels having a rim size of 19×8.5 J, and mounted on a vehicle, and under an air pressure condition of 260 kPa. Evaluation results were expressed as index values, Conventional Example 1 being assigned an index value of 100. Larger index values indicate excellent uneven wear resistance performance.
The evaluation for the braking performance on dry road surfaces was performed by measuring a braking distance on a dry road surface from an initial velocity of 100 km/h to complete stop, with each of the test tires assembled on wheels having a rim size of 19×8.5 J, and mounted on a vehicle, and under an air pressure condition of 260 kPa. The evaluation results were expressed as index values using the reciprocal of the measurement values, with the Conventional Example 1 being assigned the index value of 100. Larger index values indicate excellent braking performance on dry road surfaces.
As understood from Table 1 and Table 2, by devising the shapes of chamfered portions formed on the sipe, the uneven wear resistance performance was enhanced and the steering stability performance on dry road surfaces and the steering stability performance on wet road surfaces were enhanced at the same time for the tires in Examples 1 to 12. Additionally, the braking performance on dry road surfaces of the tires in Examples 1 to 12 was enhanced at the same time.
On the other hand, in Comparative Example 1, since the maximum depth y of the chamfered portion was set to be very shallow, the effect of enhancing the steering stability performance on wet road surfaces was not obtained. Additionally, in Comparative Example 2, since the maximum depth y of the chamfered portion was set to be very deep, an effect of enhancing the steering stability performance on dry road surfaces was not obtained.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-025845 | Feb 2016 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2017/005360 | 2/14/2017 | WO | 00 |
