Patent Application
20250001806
The present disclosure relates to a tire.
Patent Document 1 listed below discloses a tire in which a plurality of lateral grooves are provided in a land portion.
The lateral groove comprises a first portion extending from a first longitudinal edge of the land portion, a second portion extending from a second longitudinal edge of the land portion, and a connecting portion connecting between the first portion and the second portion. The connecting portion comprises a raised bottom portion.
In the tire of Patent Document 1, the lateral grooves comprising the above-mentioned connecting portions are provided in order to improve the steering stability on dry road surfaces and on-snow performance.
In recent years, there has been an increasing demand for all-season tires which can be used regardless of the season. This type of tire is required to have good wet performance and on-snow performance as well as steering stability on dry road surfaces.
The present disclosure was made in view of this situation, and a primary objective of the present disclosure is to provide a tire improved in wet performance and on-snow performance while maintaining steering stability on dry road surfaces.
According to the present disclosure, a tire comprises:
Therefore, in the tire according to the present disclosure, as the above-described configuration is employed, wet performance and on-snow performance can be improved while maintaining steering stability on dry road surfaces.
An embodiment of the present disclosure will now be described in detail in conjunction with accompanying drawings. Incidentally, the drawings may include exaggerated depictions different from actual dimensional relationships in order to facilitate understanding of the present disclosure.
The tire 1 in this embodiment is a pneumatic tire for a passenger car, and is designed as so-called all-season tire (also called all-weather tire) which can be suitably used to drive on snowy roads in addition to wet roads and dry roads. However, the present disclosure may be applied to pneumatic tires for heavy duty vehicles such as trucks and buses as well as non-pneumatic tires so-called airless tires in which pressurized air is not used or filled to support the tire load.
As shown in
More specifically, in the tire 1 in this embodiment, the tread portion 2 is composed of five land portions 4 divided by four circumferential grooves 3.
In
In this application, the term “sipe” refers to a fine groove or cut of which main portion has a small width of not more than 1.5 mm or has no substantial width when measured between the two opposite walls (hereinafter referred to as “sipe walls”). Here, the main portion refers to a portion where the opposite two sipe walls extend in the tire radial direction in substantially parallel to each other.
The expression “substantially parallel” means that the angle formed between the two sipe walls is at most 10 degrees. Such sipe may be provided with a chamfer as described later. Further, such sipe may be provided with a so-called flask bottom, namely, the width of the sipe can be increased more than 1.5 mm in a portion near the sipe bottom.
Contrary to such a sipe, what is referred to as a groove in this application, has two opposite groove walls which do not come into contact with each other even when ground pressure is applied and maintains a substantial drainage path. Thus, the groove width of each groove is, for example, 2.0 mm or more.
In the tire 1 in this embodiment, the orientation of the tread portion 2 (tread pattern) when the tire is mounted on a vehicle is specified such that the first tread edge T1 is to be outboard of the vehicle, and the second tread edge T2 is to be inboard of the vehicle.
Such tire mounting direction is indicated, for example, on the tire sidewall portions (not shown) with letters, symbols or the like.
The present disclosure is, however, not limited to such embodiment, and may be embodied as a tire of which mounting direction on a vehicle is not specified.
The first tread edge T1 and the second tread edge T2 correspond to the axially outermost edges of the ground contacting surface of the tread portion 2 when the tire under a standard state is placed on a flat surface at a camber angle of 0 degrees by applying 70% of a standard tire load.
In the case that the tire 1 is a type of pneumatic tire for which various standards have been established, the standard state is a state of the tire which is mounted on a standard wheel rim and inflated to a standard tire pressure but loaded with no tire load.
In the case that the tire 1 is a tire for which various standards are not yet established or a non-pneumatic tire, the standard state means a standard usage state according to the purpose of use of the tire and in a condition in which the tire is not installed on a vehicle and no tire load is applied.
In this application including specification and claims, dimensions and positions of each part or portion of the tire refer to those under the standard state unless otherwise noted.
The standard wheel rim is a wheel rim specified for the tire 1 in a standard system including standards on which the tire 1 is based, for example, the “Standard rim” in JATMA, “Design Rim” in TRA, “Measuring Rim” in ETRTO.
The standard tire pressure is air pressure specified for the tire 1 in a standard system including standards on which the tire 1 is based, for example, the “maximum air pressure” in JATMA, “INFLATION PRESSURE” in ETRTO, and the maximum air pressure listed in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in TRA.
The standard tire load is a load specified for the tire 1 in a standard system including standards on which the tire 1 is based, for example, the “maximum load capacity” in JATMA, “LOAD CAPACITY” in ETRTO, and the maximum tire load listed in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in TRA.
In the case that various standards have not been established for the tire 1, the standard tire load refers to the maximum load that can be applied when using the tire 1 according to the above-mentioned standards.
In this embodiment, the circumferential grooves 3 include a first shoulder circumferential groove 5, a second shoulder circumferential groove 6, a first crown circumferential groove 7, and a second crown circumferential groove 8.
The first shoulder circumferential groove 5 is disposed closest to the first tread edge T1 among the circumferential grooves 3.
The second shoulder circumferential groove 6 is disposed closest to the second tread edge T2 among the circumferential grooves 3.
The first crown circumferential groove 7 is disposed between the first shoulder circumferential groove 5 and the tire equator C.
The second crown circumferential groove 8 is disposed between the second shoulder circumferential groove 6 and the tire equator C.
The distance L1 in the tire axial direction from the tire equator C to the groove center line of the first shoulder circumferential groove 5 is preferably not less than 20%, but not more than 35% of a tread width TW.
The distance L1 in the tire axial direction from the tire equator C to the groove center line of the second shoulder circumferential groove 6 is preferably not less than 20%, but not more than 35% of the tread width TW.
The distance L2 in the tire axial direction from the tire equator C to the groove center line of the first crown circumferential groove 7 is preferably not less than 5%, but not more than 15% of the tread width TW.
The distance L2 in the tire axial direction from the tire equator C to the groove center line of the second crown circumferential groove 8 is preferably not less than 5%, but not more than 15% of the tread width TW.
Here, the tread width TW is the distance in the tire axial direction from the first tread edge T1 to the second tread edge T2 measured under the standard state of the tire.
In this application, when a numerical range of a parameter is described, it means a numerical range of the average value of the parameter unless otherwise noted. The “average value” can be obtained for example by dividing a measurement target for the parameter into multiple micro-regions of appropriate size, measuring the parameter of each micro-region, summing up the measured values of parameter of the micro-regions. and dividing the sum total by the number of the micro-regions.
It is preferable that the groove width W1 of each of the circumferential grooves 3 is at least 3 mm.
It is preferable that the groove width W1 of each of the circumferential grooves 3 is not less than 3.0%, but not more than 7.0% of the tread width TW.
The depth of each of the circumferential grooves 3 is preferably not less than 5 mm, but not more than 10 mm in the case that the tire 1 is a pneumatic tire for passenger cars.
In each of the first crown circumferential groove 7, the second crown circumferential groove 8 and the second shoulder circumferential groove 6 in this embodiment, each of the groove edges on both sides extends linearly on a straight line which is parallel to the tire circumferential direction.
However, in the first shoulder circumferential groove 5, the groove edge on the first tread edge T1 side extends linearly on a straight line in parallel to the tire circumferential direction, whereas the groove edge on the second tread edge T2 side extends in a zigzag shape. Such zigzag groove edge helps to improve on-snow traction performance.
The land portions 4 in this embodiment include a crown land portion 10, a first middle land portion 11, a second middle land portion 12, a first shoulder land portion 13 and a second shoulder land portion 14.
The crown land portion 10 in this embodiment is defined between the first crown circumferential groove 7 and the second crown circumferential groove 8. Thereby, the crown land portion 10 is positioned on the tire equator C.
The first middle land portion 11 is defined between the first shoulder circumferential groove 5 and the first crown circumferential groove 7.
The second middle land portion 12 is defined between the second shoulder circumferential groove 6 and the second crown circumferential groove 8.
The first shoulder land portion 13 is defined axially outside the first shoulder circumferential groove 5 and includes the first tread edge T1.
The second shoulder land portion 14 is defined axially outside the second shoulder circumferential groove 6 and includes the second tread edge T2.
As shown in
The second middle land portion 12 has a first longitudinal edge 12a on the first tread edge T1 side, a second longitudinal edge 12b on the second tread edge T2 side, and a ground contacting top surface 12s between the first longitudinal edge 12a and the second longitudinal edge 12b.
The first middle land portion 11 is provided with a plurality of first middle lateral grooves 21 extending from the first longitudinal edge 11a to the second longitudinal edge 11b.
The first middle lateral grooves 21 are inclined with respect to the tire axial direction to a first direction (in the drawins, the inclination is upward to the right) while extending from the first longitudinal edge 11a to the second longitudinal edge 11b of the first middle land portion 11.
Here, the first direction means a direction toward one side in the tire circumferential direction, and the under-mentioned second direction means a direction toward the other side in the tire circumferential direction.
The second middle land portion 12 is provided with a plurality of second middle lateral grooves 22 extending from the first longitudinal edge 12a to the second longitudinal edge 12b.
Each of the second middle lateral grooves 22 comprises a first oblique portion 22A and a second oblique portion 22B.
The first oblique portion 22A extends from the first longitudinal edge 12a toward the second longitudinal edge 12b of the second middle land portion 12, while inclining with respect to the tire axial direction to a second direction opposite to the first direction (in the drawing, the inclination is downward to the right).
The second oblique portion 22B extends from the second longitudinal edge 12b toward the first longitudinal edge 12a of the second middle land portion 12, while inclining with respect to the tire axial direction to the second direction (in the drawing, the inclination is upward to the right, namely, opposite to the first oblique portion 22A).
According to the present disclosure, in the plan view of the tread portion 2, when virtual extension zones 23 are respectively defined by extending circumferential extents of the respective second middle lateral grooves 22 toward the first tread edge T1 in parallel to the tire axial direction (in
Thus, according to the present disclosure, the first middle lateral grooves 21 and the second middle lateral grooves 22 are arranged in the tire circumferential direction so that the overlapping area satisfies the above limitation. By employing such groove arrangement, the tire 1 can be improved in wet performance and on-snow performance while maintaining steering stability on dry road surfaces (hereinafter simply referred to as the steering stability). The reason is as follows.
In the present disclosure, since the first middle lateral grooves 21 and the second middle lateral grooves 22 are provided with the above-described inclining directions, they can exhibit high drainage performance on wet road surfaces and can generate shear forces in multiple directions by snow columns, namely, compacted snow blocks when running on snow. Thus, it is possible to improve the wet performance and on-snow performance.
If the positions in the tire circumferential direction of the first middle lateral grooves 21 are the same as the positions in the tire circumferential direction of the second middle lateral grooves 22, the rigidity of the tread portion 2 in the tire circumferential direction is locally reduced due to these coincident lateral grooves 21 and 22, and the steering stability on dry road surfaces is liable to be deteriorated.
However, in the present disclosure, since the overlapping area between the virtual extension zone 23 of the second middle lateral groove 22 and the opening of the first middle lateral groove 21 is limited as described above, the occurrence of the above-mentioned problems is suppressed, and thereby, it becomes possible to maintain the steering stability on dry road surfaces.
According to the present disclosure, in order to surely improve the wet performance and on-snow performance, the second middle lateral grooves 22 are arranged in relation to the first middle lateral grooves 21 such that circumferential extents of the second middle lateral grooves 22 respectively overlap with circumferential extents of the respective first middle lateral grooves 21 in the tire circumferential direction.
From the viewpoint of improving the wet performance, on-snow performance, and steering stability on dry road surfaces in a well-balanced manner, the above-mentioned overlapping area is preferably set to be not less than 10%, but not more than 30% of the area of the opening.
More detailed configurations in the present embodiment will be described below.
Each of the first middle lateral grooves 21 extends with a constant groove width.
The angle θ6 of each of the first middle lateral grooves 21 with respect to the tire axial direction is preferably not less than 15 degrees, more preferably not less than 20 degrees, but preferably not more than 50 degrees, more preferably not more than 40 degrees.
Further, the angle θ6 increases toward the second longitudinal edge 11b, therefore, the first middle lateral groove 21 is curved. Such first middle lateral groove 21 can improve on-snow traction performance and on-snow cornering performance in a well-balanced manner.
When the first middle lateral groove 21 is curved, the angle θ6 means the average angle of the first middle lateral groove 21 with respect to the tire axial direction.
Here, an average angle of a curved or nonlinear groove can be obtained by dividing the groove into a number of small groove segments, summing up the angles of the small groove segments, and dividing the sum total of the angles by the number of the small groove segments.
As shown in
As shown in
The lateral groove with the chamfer 21c can prevent a portion around the groove opening, of the ground contacting top surface 11s from lifting off the road surface. This helps to uniform the ground pressure and prevent uneven wear.
From the viewpoint of ensuring such effects, the width W5 of the chamfer 21c or sloped surface 24 as shown in
In this embodiment, it is preferable that the chamfer 21c is provided on each side of the first middle lateral groove 21.
Further, it is preferable that the chamfers 21c are provided over the entire length of the first middle lateral groove 21 as shown in
The width of each of the chamfers 21c is constant over 80% or more of the first middle lateral groove 21 in the length direction thereof.
In this embodiment, as shown in
As shown in
As shown in
When the outer surface 28s of the groove bottom 28 is divided into three equal parts in the groove width direction, the sipe 29 is disposed in the central part.
The depth d3 from the ground contacting top surface 11s to the bottom of the sipe 29 is set in a range from 130% to 170% of the above-mentioned depth d2.
Such first portion 26 helps to improve the steering stability, on-snow performance and wet performance in a well-balanced manner.
As shown in
The depth d4 of the second portion 27 is preferably set to be not less than 80%, but not more than 120% of the depth d3 of the first portion 26.
Such second portion 27 helps to improve the steering stability and wet performance in a well-balanced manner.
It is preferable that, as shown in
Such first middle lateral groove 21 can surely exhibit the above-described effects.
In the present embodiment, the first middle lateral grooves 21 provided on the first middle land portion 11 include two types: one is such that the first portion 26 is located closer to the first tread edge T1 than the second portion 27, and the other is such that the second portion 27 is located closer to the first tread edge T1 than the first portion 26.
These two types of first middle lateral grooves 21 in which the first portions 26 are located at different positions are preferably arranged alternately in the tire circumferential direction. Thereby, wear resistance of the first middle land portion 11 can be improved.
In this embodiment, the first middle land portion 11 is provided with a plurality of terminating middle sipes 30.
When the ground pressure is applied to the portion around the sipe, the two sipe walls in the main portion come into contact with each other owing to the above-described configuration of the sipe, and the apparent rigidity of the portion around the sipe can be maintained.
Each of the terminating middle sipes 30 extends from the first longitudinal edge 11a or the second longitudinal edge 11b, and has a closed end within the ground contacting top surface 11s.
In this embodiment, the terminating middle sipes 30 include first terminating middle sipes 31 extending from the first longitudinal edge 11a, and second terminating middle sipes 32 extending from the second longitudinal edge 11b.
The first terminating middle sipes 31 and the second terminating middle sipes 32 help to improve the wet performance and on-snow performance as well as the wear resistance performance.
In this embodiment, between every two of the circumferentially adjacent first middle lateral grooves 21, there is disposed only one terminating middle sipe 30. And preferably, the first terminating middle sipes 31 and the second terminating middle sipes 32 are alternately arranged in the tire circumferential direction. Thereby, wear resistance is further improved.
In this example, the terminating middle sipes 30 each extend linearly, and are inclined with respect to the tire axial direction to the above-mentioned first direction toward the second longitudinal edge 11b from the first longitudinal edge 11a.
The angle θ7 of the first terminating middle sipe 31 with respect to the tire axial direction is, for example, not less than 15 degrees, but not more than 50 degrees, preferably not more than 25 degrees.
The angle θ8 of the second terminating middle sipe 32 with respect to the tire axial direction is larger than the angle θ7 of the first terminating middle sipe 31. Specifically, the angle θ8 is, for example, not less than 15 degrees, preferably not less than 30 degrees, but not more than 50 degrees, preferably not more than 40 degrees. Such terminating middle sipe 30 improves traction performance and cornering performance on wet roads and snowy roads in a well-balanced manner.
The length L6 in the tire axial direction of each of the terminating middle sipes 30 is, for example, not less than 35%, preferably not less than 40%, but not more than 65%, preferably not more than 60% of the maximum width W6 of the ground contacting top surface 11s of the first middle land portion 11.
Thereby, while maintaining the wear resistance performance of the first middle land portion 11, the above-mentioned effects can be exhibited.
Here, the length L6 corresponds to the length in the tire axial direction of a center line which divides the width of the sipe into two equal parts. The same applies to the description of the length of the sipe descrived below.
As shown in
From the viewpoint of exhibiting this effect, the maximum width W4 of the chamfer 30c, namely, the sloped surface 19 is at least 50% of the sipe width W3 at the main portion of the sipe.
The maximum width W4 of the sloped surface 19 is preferably not less than 0.5 mm, more preferably not less than 1.0 mm, but preferably not more than 2.0 mm, more preferably not more than 1.5 mm.
The depth d1 of the chamfer 16c is, for example, not less than 0.5 mm, but not more than 2.0 mm.
In this embodiment, as shown in
The second middle lateral groove 22 is composed of only the first oblique portion 22A and the second oblique portion 22B.
The first oblique portion 22A and the second oblique portion 22B are connected with each other in the central part when the ground contacting top surface 12s of the second middle land portion 12 is divided into three equal parts in the tire axial direction. Thus, the length L7 in the tire axial direction of the first oblique portion 22A and the length L8 in the tire axial direction of the second oblique portion 22B are between 40% and 60% of the maximum width W7 of the ground contacting top surface 12s of the second middle land portion 12.
Thereby, on-snow performance is improved while suppressing uneven wear of the second middle land portion 12.
The angle θ9 of the first oblique portion 22A with respect to the tire axial direction is, for example, not less than 5 degrees, but not more than 25 degrees.
The first oblique portion 22A may be curved so that the angle θ9 gradually increases toward the second tread edge T2 side.
The angle θ10 of the second oblique portion 22B with respect to the tire axial direction is, for example, not less than 5 degrees, but not more than 25 degrees.
The second oblique portion 22B may be curved so that the angle θ10 gradually increases toward the first tread edge T1 side.
Thereby, the drainage performance of the second middle lateral groove 22 is improved.
The angle θ11 between the first oblique portion 22A and the second oblique portion 22B is an obtuse angle, for example, and preferably in a range from 105 degrees to 135 degrees. Thereby, while suppressing uneven wear of the second middle land portion 12, the above-mentioned effects can be obtained.
When at least one of the first oblique portion 22A and the second oblique portion 22B is not straight, the angle θ11 is defined as an angle between a straight line drawn between both ends of the groove center line of the first oblique portion 22A and a straight line drawn between both ends of the groove center line of the second oblique portion 22B.
In each of the second middle lateral grooves 22, one of the first oblique portion 22A and the second oblique portion 22B is provided with a sipe in the groove bottom portion, but the other of the first oblique portion 22A and the second oblique portion 22B is provided with no sipe in the groove bottom portion.
In each of the second middle lateral grooves 22, for the region where the sipe is provided in the groove bottom portion, the above described structure of the first portion 26 (shown in
On the other hand, for the region where no sipe is provided in the groove bottom portion, the structure of the second portion 27 (shown in
Such second middle lateral grooves 22 can surely improve the wet performance and on-snow performance while maintaining the steering stability.
The second middle land portion 12 is provided with
It is preferable that these two types of second middle lateral grooves 22 with different sipe arrangements are alternately arranged in the tire circumferential direction.
This improves the wear resistance of the second middle land portion 12.
The second middle land portion 12 is provided with a plurality of transverse middle sipes 35.
The transverse middle sipes 35 each extend from the first longitudinal edge 12a to the second longitudinal edge 12b of the second middle land portion 12.
In this embodiment, one or two transverse middle sipes 35 are provided between every two of the circumferentially adjacent second middle lateral grooves 22.
The transverse middle sipe 35 comprises a first sipe segment 36 and a second sipe segment 37 which has different inclining directions with respect to the tire axial direction.
The first sipe segment 36 is inclined with respect to the tire axial direction to the second direction while extending from the first longitudinal edge 12a.
As a result, the first sipe segment 36 extends along the first oblique portion 22A of the second middle lateral groove 22, and the angular difference therebetween is 5 degrees or less.
The angle θ12 of the first sipe segment 36 with respect to the tire axial direction is not less than 5 degrees, but not more than 25 degrees.
The second sipe segment 37 is inclined with respect to the tire axial direction to the first direction toward the second longitudinal edge 12b.
As a result, the second sipe segment 37 extends along the second oblique portion 22B of the second middle lateral groove 22, and the angular difference therebetween is 5 degrees or less.
The angle θ13 of the second sipe segment 37 with respect to the tire axial direction is not less than 5 degrees, but not more than 25 degrees.
By providing the first sipe segment 36 and second sipe segment 37 as described above, the transverse middle sipe 35 can provide frictional force in multiple directions on wet road surfaces.
The length L9 in the tire axial direction of the first sipe segment 36 is, for example, not less than 40%, but not more than 60% of the maximum width W7 in the tire axial direction, of the ground contacting top surface 12s of the second middle land portion 12.
Preferably, the length L9 of the first sipe segment 36 is substantially the same as the length L7 in the tire axial direction of the first oblique portion 22A of the second middle lateral groove 22.
The length L10 in the tire axial direction of the second sipe segment 37 is, for example, not less than 40%, but not more than 60% of the maximum width W7 of the ground contacting top surface 12s of the second middle land portion 12.
Preferably, the length L10 is the same as the length L8 in the tire axial direction of the second oblique portion 22B of the second middle lateral groove 22.
Thereby, while suppressing uneven wear of the second middle land portion 12, the above-mentioned effects can be obtained.
It is preferable that the transverse middle sipe 35 is provided with a chamfer 35c.
For the chamfer 35c, the configuration of the chamfer 30c of the terminating middle sipe 30 shown in
In the present embodiment, it is preferable that the width of the chamfer 35c measured in the direction perpendicular to the length direction of the transverse middle sipe 35 becomes smaller toward the connection 38 between the first sipe segment 36 and the second sipe segment 37.
Thereby, while obtaining the edge effect of the transverse middle sipe 35, uneven wear of the second middle land portion 12 can be suppressed.
As shown in
The crown land portion 10 is provided with a plurality of first sipes 16, a plurality of second sipes 17, and a plurality of third sipes 18.
Each of the first sipes 16 extends from the first longitudinal edge 10a and has a closed end within the ground contacting top surface 10s.
Each of the second sipes 17 extends from the second longitudinal edge 10b and has a closed end within the ground contacting top surface 10s.
Each of the third sipes 18 extends from the first longitudinal edge 10a to the second longitudinal edge 10b.
Each of the first sipes 16 is inclined with respect to the tire axial direction to the first direction toward the second longitudinal edge 10b.
Each of the second sipes 17 is inclined with respect to the tire axial direction to the second direction toward the second longitudinal edge 10b.
Each of the third sipes 18 comprises a first oblique portion 18A and a second oblique portion 18B.
The first oblique portion 18A extends from the first longitudinal edge 10a toward the second longitudinal edge 10b while inclining with respect to the tire axial direction to the first direction.
The second oblique portion 18B extends from the second longitudinal edge 10b toward the first longitudinal edge 10a, while inclining with respect to the tire axial direction to the first direction.
The sipes 16, 17 and 18 having such configurations can provide frictional force in multiple directions when running on snow, and help to improve the on-snow performance.
On the other hand, since the first sipes 16 and the second sipes 17 respectively have the closed ends within the crown land portion 10, it is helpful for maintaining the rigidity of the crown land portion 10 and maintaining the steering stability on dry road surfaces.
Further, as described above, the first sipes 16 and the first oblique portions 18A of the third sipes 18 extend from the first longitudinal edge 10a while inclining to the same direction, and
Thereby, between the first sipes 16 and the third sipes 18, and between the second sipes 17 and the third sipes 18, there are less likely to occur regions where the land portion rigidity is locally reduced, thereby, it becomes possible to more surely maintain the steering stability.
In this embodiment, between every two of the circumferentially adjacent third sipes 18, there are disposed one of the first sipes 16 and one of the second sipes 17. Thus, the third sipes 18 are alternated with pairs of one of the first sipes 16 and one of the second sipes 17 in the tire circumferential direction.
This sipe arrangement makes the rigidity distribution of the crown land portion 10 uniform, and can surely maintain the steering stability on dry road surfaces.
Further, this sipe arrangement reduces the impact sound generated when the crown land portion 10 contacts with the ground, and improves noise performance as well as wear resistance performance of the crown land portion 10.
The first sipes 16 in this example extends linearly at a constant inclination angle toward the above-mentioned first direction. But, the first sipes 16 may be smoothly curved.
The length L3 in the tire axial direction of the first sipes 16 is preferably not less than 30%, more preferably not less than 40%, but preferably not more than 60% more preferably not more than 50% of the maximum width W2 in the tire axial direction of the ground contacting top surface 10s of the crown land portion 10. Such first sipes 16 help to improve the steering stability and on-snow performance in a well-balanced manner.
The angle θ1 of the first sipes 16 with respect to the tire axial direction is preferably not less than 40 degrees, more preferably not less than 50 degrees, but preferably not more than 70 degrees, more preferably not more than 60 degrees. This improves the traction performance and cornering performance in a well-balanced manner when running on snow.
In this embodiment, each of the first sipes 16 is at least partially provided with a chamfer 16c.
For the chamfer 16c of the first sipe 16, the configuration of the chamfer 30c (shown in
In this embodiment, the chamfer 16c is provided on each side of the first sipe 16 in the width direction. But, the chamfer 16c may be provided on only one side of the first sipes 16 in the width direction.
Further, in this embodiment, the chamfer 16c is provided over the entire length of the first sipes 16. Thereby, the ground pressure can be made uniform around the first sipes 16, and the steering stability can be surely improved. Further, such chamfers 16c reduces the impact sound when the first sipe 16 edges contact with the ground, and the noise performance can be improved.
It is preferable that the width of the chamfer 16c is constant over 80% or more of the first sipes 16 in the length direction.
Thereby, uneven wear around the first sipes 16 can be suppressed, and the wear resistance performance can be improved.
The second sipe 17 in this example extends linearly at a certain angle, inclining to the second direction toward the second longitudinal edge 10b. But, the second sipe 17 may be smoothly curved.
The length LA in the tire axial direction of the second sipe 17 is preferably not less than 30%, more preferably not less than 40%, but preferably not more than 60%, more preferably not more than 50% of the maximum width W2 in the tire axial direction of the ground contacting top surface 10s of the crown land portion 10.
Further, it is preferable that the length of the second sipe 17 measured therealong is less than 100%, more preferably from 60% to 75% of the length of the first sipe 16 measured therealong.
Such second sipe 17 helps to improve the steering stability and on-snow performance in a well-balanced manner.
The angle θ2 of the second sipe 17 with respect to the tire axial direction is smaller than the angle θ1 of the first sipes 16 with respect to the tire axial direction.
Specifically, the angle θ2 of the second sipe segment 37 with respect to the tire axial direction is preferably not less than 10 degrees, more preferably not less than 20 degrees, but preferably not more than 40 degrees, more preferably not more than 30 degrees. Such second sipes 17, in cooperation with the first sipes 16, help to improve the traction performance and the cornering performance in a well-balanced manner when running on snow.
In this embodiment, the second sipe 17 is at least partially provided with a chamfer 17c.
For the chamfer 17c of the second sipe 17, the configuration of the chamfer 30c (shown in
It is preferable that the chamfer 17c is provided over the entire length of the second sipe 17.
Preferably, the width of the chamfer 17c of the second sipe segment 37 is constant over 80% or more of the second sipe 17 in the length direction thereof.
This improves the steering stability as well as the noise performance and the wear resistance.
The distance L5 in the tire circumferential direction between
Here, the one pitch length P1 corresponds to the distance in the tire circumferential direction between the ends on the first longitudinal edge 10a side, of the two first sipes 16 adjacent to each other in the tire circumferential direction.
Thereby, the first sipe 16 and the second sipe 17 can work together to improve the on-snow performance, while maintaining the steering stability.
The third sipe 18 in this example is composed of only the first oblique portion 18A and the second oblique portion 18B. Thereby, the third sipe 18 is bent convexly toward one side in the tire circumferential direction.
In this example, the intersection of the first oblique portion 18A and the second oblique portion 18B is positioned in the central part of the ground contacting top surface 10s when divided into three equal parts in the tire axial direction. Thereby, while suppressing uneven wear of the crown land portion 10, the above-mentioned effect can be exhibited. The third sipe 18 is however, not limited to such configuration.
In this example, the first oblique portion 18A of the third sipe 18 extends linearly from the first longitudinal edge 10a toward the second longitudinal edge 10b while inclining to the first direction. However, the first oblique portion 18A may be smoothly curved.
The angle θ3 of the first oblique portion 18A with respect to the tire axial direction is preferably not less than 40 degrees, more preferably not less than 50 degrees, but preferably not more than 70 degrees, more preferably not more than 60 degrees. Thereby, the traction performance and the cornering performance when running on snow are improved in a well-balanced manner.
In this example, the second oblique portion 18B of the third sipe 18 extends linearly from the second longitudinal edge 10b toward the first longitudinal edge 10a while inclining to the first direction. However, the second oblique portion 18B may be smoothly curved.
The angle θ4 of the second oblique portion 18B with respect to the tire axial direction is preferably not less than 10 degrees, more preferably not less than 20 degrees, but preferably not more than 40 degrees, more preferably not more than 30 degrees. Thereby, the traction performance and cornering performance when running on snow are improved in a well-balanced manner.
The angle θ3 of the first oblique portion 18A with respect to the tire axial direction is larger than the angle θ4 of the second oblique portion 18B with respect to the tire axial direction. Thereby, the energy of the impact sound generated when the edges of the first oblique portion 18A and the second oblique portion 18B contact with the ground is dispersed over a wide frequency band, and the noise performance is improved.
The angle θ5 between the first oblique portion 18A and the second oblique portion 18B is, for example, not less than 90 degrees, but not more than 120 degrees. Thereby, the traction performance and the cornering performance when running on snow is improved.
When at least one of the first oblique portion 18A and the second oblique portion 18B is curved, the angle θ5 is defined as an angle between a straight line drawn between both ends of the first oblique portion 18A, and a straight line drawn between both ends of the second oblique portion 18B.
Further, as shown in
As shown, the first shoulder land portion 13 is provided with a plurality of first shoulder lateral grooves 41 and a plurality of first shoulder sipes 42.
In this embodiment, the first shoulder lateral grooves 41 and the first shoulder sipes 42 are arranged alternately in the tire circumferential direction.
The first shoulder lateral groove 41 extends from the first shoulder circumferential groove 5 to at least the first tread edge T1.
The first shoulder lateral groove 41 in this example comprises a portion inclined with respect to the tire axial direction to the first direction toward the axially inside.
The maximum angle θ14 of the first shoulder lateral groove 41 with respect to the tire axial direction is, for example, not less than 10 degrees, but not more than 20 degrees. Such first shoulder lateral grooves 41 help to improve the wet performance and the on-snow performance.
The first shoulder lateral groove 41 is provided with a chamfer 41c. For the chamfer 41c of the first shoulder lateral groove 41, the configuration of the chamfer 21c of the first middle lateral groove 21 (shown in
The first shoulder sipe 42 in this example extends from the first shoulder circumferential groove 5 to the first tread edge T1. But, it may be possible to end the first shoulder sipe 42 before reaching the first tread edge T1.
The first shoulder sipe 42 in this example comprises a portion inclined with respect to the tire axial direction to the first direction toward the axially inside.
The maximum angle θ15 of the first shoulder sipe 42 with respect to the tire axial direction is not less than 10 degrees, but not more than 20 degrees.
It is preferable that the first shoulder sipes 42 extend along the first shoulder lateral grooves 41, and the angular difference between them is not more than 5 degrees.
In cooperation with the first shoulder lateral grooves 41, such first shoulder sipes 42 can provide large traction when running on wet roads and snowy roads.
The first shoulder sipe 42 is provided with a chamfer 42c.
For the chamfer 42c of the first shoulder sipe 42, the configuration of the chamfer 30c (shown in
It is preferable that the chamfer 42c is formed over the entire length of the first shoulder sipe 42, and the width of the chamfer 42c is constant over 80% or more of the length of the first shoulder sipe 42.
Such first shoulder sipes 42 can improve the wet performance while suppressing uneven wear of the first shoulder land portion 13.
The present embodiment is attempted to further improve various performances by optimizing the arrangement of the lateral grooves and the sipes which are adjacent via the circumferential grooves in the plan view of the tread portion 2.
Specifically, in the plan view of the tread portion 2 as shown in
Further, in the plan view of the tread portion 2 as shown in
Thereby, the first sipes 16, the first middle lateral grooves 21 and the first shoulder lateral grooves 41 work together to provide a reaction force when running on snow, and thereby, it becomes possible to further increase the traction on the snow.
As shown, the second shoulder land portion 14 is provided with a plurality of second shoulder lateral grooves 43 and a plurality of second shoulder sipes 44.
In this embodiment, one or two second shoulder sipes 44 are disposed between every two of the circumferential adjacent second shoulder lateral grooves 43.
The second shoulder lateral groove 43 extends from the second shoulder circumferential groove 6 to at least the second tread edge T2.
The second shoulder lateral groove 43 in this example comprises a portion inclined with respect to the tire axial direction to the first direction toward the second tread edge T2 from the second shoulder circumferential groove 6.
The maximum angle θ16 of the second shoulder lateral groove 43 with respect to the tire axial direction is, for example, not less than 10 degrees, but not more than 20 degrees.
Such second shoulder lateral grooves 43 help to improve the wet performance and on-snow performance.
The second shoulder lateral groove 43 is provided with a chamfer 43c. For the chamfer 43c of the second shoulder lateral groove 43, the configuration of the chamfer 21c (shown in
The second shoulder sipe 44 in this example extends from the second shoulder circumferential groove 6 to the second tread edge T2. But, it may be possible to end the second shoulder sipe 44 before reaching the second tread edge T2.
The second shoulder sipe 44 in this example comprises a portion inclined with respect to the tire axial direction to the first direction toward the second tread edge T2 from the second shoulder circumferential groove 6.
The maximum angle θ17 of the second shoulder sipe 44 with respect to the tire axial direction is not less than 10 degrees, but not more than 20 degrees.
It is preferable that the second shoulder sipes 44 extend along the second shoulder lateral grooves 43, and the angular difference between them is not more than 5 degrees. Such second shoulder sipes 44 can improve the wet performance and on-snow performance while suppressing uneven wear of the second shoulder land portion 14.
The second shoulder sipe 44 is provided with a chamfer 44c. For the chamfer 44c of the second shoulder sipe 44, the configuration of the chamfer 30c (shown in
It is preferable that the chamfer 44c is formed over the entire length of the second shoulder sipe 44, and the width of the chamfer 44c becomes smaller toward the second tread edge T2.
In the plan view of the tread portion 2 as shown in
Further, in the plan view of the tread portion 2 as shown in
As a result, the second sipes 17, the second middle lateral grooves 22 and the second shoulder lateral grooves 43 work together to provide a reaction force when running on snow, and thereby, it becomes possible to increase the traction on the snow.
While detailed description has been made of a preferable embodiment of the present disclosure, the present disclosure can be embodied in various forms without being limited to the illustrated embodiment.
Based on the tread pattern shown in
As Comparative example tire Ref.1, a pneumatic tire of size 225/45ZR18 having the tread pattern shown in
As Comparative example tire Ref.2, a pneumatic tire of size 225/45ZR18 having a tread pattern which was the same as the tread pattern shown in
The working example tires and comparative example tires were tested for steering stability on dry road surfaces, wet performance and on-snow performance.
These test tires mounted on wheel rims of size 18×8.0J were attached to a test vehicle (2000 cc rear-wheel drive passenger car) and inflated to 220 kPa (front wheels) and 240 kPa (rear wheels). Then, using the test vehicle, the following tests were conducted.
During running on a dry road surface, a test driver evaluated the steering stability. The results are indicated in Table 1 by an index based on Ref.1 being 100, wherein the higher the index number, the better the steering stability.
During running on a wet road surface, a test driver evaluated the travelling performance. The results are indicated in Table 1 by an index based on Ref. 1 being 100, wherein the higher the index number, the better the wet performance.
During running on a snowy road surface, a test driver evaluated the travelling performance. The results are indicated in Table 1 by an index based on Ref.1 being 100, wherein the higher the index number, the better the on-snow performance.
From the test results, it was confirmed that the comparative example tire Ref.2 and the working example tires Ex.1 to Ex.6 were improved in wet performance and on-snow performance as compared to the comparative example tire Ref.1. This is considered to be due to the improved shape of the second middle lateral grooves. Further, it was confirmed that the working example tires Ex.1 to Ex.6 were improved in steering stability on dry road surfaces as compared to the comparative example tire Ref.2. This is considered to be due to the improved overlapping area.
As described above, it was confirmed that the working example tires Ex.1 to Ex.6 were improved in on-snow performance without sacrificing the steering stability on dry road surfaces.
The present disclosure is as follows:
A tire comprising:
The tire according to Present Disclosure 1, which has an intended mounting direction on a vehicle in which the first tread edge is located outboard of the vehicle when the tire is mounted on the vehicle.
The tire according to Present Disclosure 1 or 2, wherein angles of the first middle lateral grooves with respect to the tire axial direction are not less than 20 degrees but not more than 40 degrees.
The tire according to Present Disclosure 1, 2 or 3, wherein the first oblique portion is inclined with respect to the tire axial direction to a second direction opposite to the first direction toward the second longitudinal edge from the first longitudinal edge of the second middle land portion.
The tire according to any one of Present Disclosures 1 to 4, wherein the length in the tire axial direction of the first oblique portion is not less than 40%, but not more than 60% of the maximum width of the ground contacting top surface of the second middle land portion.
The tire according to any one of Present Disclosures 1 to 5, wherein an angle of the first oblique portion with respect to the tire axial direction is not less than 5 degrees but not more than 25 degrees.
The tire according to any one of Present Disclosures 1 to 6, wherein an angle of the second oblique portion with respect to the tire axial direction is not less than 5 degrees but not more than 25 degrees.
The tire according to any one of Present Disclosures 1 to 7, wherein the angle between the first oblique portion and the second oblique portion is not less than 105 degrees but not more than 135 degrees.
The tire according to any one of Present Disclosures 1 to 8, wherein the first middle lateral groove comprises a first portion provided with a sipe in the groove bottom, and a second portion provided with no sipe in the groove bottom.
The tire according to Present Disclosure 9, wherein the first middle land portion is provided with the first middle lateral grooves in which the first portion is positioned closer to the first tread edge than the second portion, and the first middle lateral grooves in which the second portion is positioned closer to the first tread edge than the first portion.
The tire according to any one of Present Disclosures 1 to 10, wherein in each of the second middle lateral grooves, one of the first oblique portion and the second oblique portion is provided with a sipe in the groove bottom, and the other of the first oblique portion and the second oblique portion is provided with no sipe in the groove bottom.
The tire according to Present Disclosure 11, wherein the second middle land portion is provided with the second middle lateral grooves in which the first oblique portion is provided with the above-said sipe in the groove bottom, and the second middle lateral groove in which the second oblique portion is provided with the above-said sipe in the groove bottom.
The tire according to any one of Present Disclosures 1 to 12, wherein circumferential extents of the second middle lateral grooves overlap in the tire circumferential direction with circumferential extents of the first middle lateral grooves, respectively.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-106272 | Jun 2023 | JP | national |
