Patent Application
20170225515
This disclosure relates to a pneumatic tire.
Conventionally, in order to improve the steering stability of pneumatic tires, methods have been adopted such as providing a plurality of land portions defined on the tread surface with a ribbed shape, the land portions being defined by circumferential main grooves extending continuously in the tread circumferential direction and by the tread edges (for example, see JP 2012-236455 A (PTL 1)).
PTL 1: JP 2012-236455 A
In the pneumatic tire disclosed in PTL 1, however, the rigidity of the land portions increases, which may reduce the quietness during ground contact and the ride comfort. Also, in the pneumatic tire of PTL 1, the land portions have a completely ribbed shape, without being divided in the tread width direction, and therefore may have insufficient drainage performance.
Therefore, it would be helpful to provide a pneumatic tire that improves the ride comfort, quietness, and drainage performance while maintaining the steering stability.
A summary of this disclosure is as follows.
A pneumatic tire of this disclosure includes: on a tread surface, a plurality of circumferential main grooves extending continuously in a tread circumferential direction and a plurality of land portions defined by the circumferential main grooves and tread edges; wherein an intermediate land portion on one side in a tread width direction, adjacent to a tire equatorial plane side of an outermost circumferential main groove on the one side, is formed into blocks only by sipes extending in the tread width direction; wherein an intermediate land portion on another side in the tread width direction, adjacent to the tire equatorial plane side of an outermost circumferential main groove on the other side, is formed in a ribbed shape; and wherein intermediate land portion lug grooves are formed in the intermediate land portion on the other side, with one end opening into the outermost circumferential main groove on the other side, and another end terminating within the intermediate land portion on the other side.
The “tread surface” refers to the entire outer circumferential surface of the tire that comes into contact with the road surface when the tire is attached to an applicable rim, filled to a prescribed internal pressure, and rolled while being placed under a load corresponding to the maximum load capability. As used herein, an “applicable rim” refers to a standard rim specified by the standards below in accordance with tire size (“Design Rim” in the YEAR BOOK of the below-mentioned TRA, and “Measuring Rim” in the STANDARDS MANUAL of the below-mentioned ETRTO), “prescribed internal pressure” refers to air pressure specified by the standards below in accordance with the maximum load capability, and the “maximum load capability” refers to the maximum mass that the tire is allowed to bear according to the standards below. The standards are determined by valid industrial standards for the region in which the tire is produced or used, such as the “YEAR BOOK” of the “Tire And Rim Association, Inc.” (TRA) in the United States of America, the “STANDARDS MANUAL” of the “European Tyre and Rim Technical Organisation” (ETRTO) in Europe, and the “JATMA YEAR BOOK” of the “Japan Automobile Tyre Manufacturers Association” (JATMA) in Japan.
The “groove” refers to an opening with a width of greater than 1.5 mm that opens to the tread surface when the pneumatic tire is mounted on an applicable rim and filled to prescribed internal pressure, with no load applied. On the other hand, a “sipe” is a thin cut, inward from the surface of the land portion, such that the width of the opening to the tread surface is 1.5 mm or less, preferably 1 mm or less, and even more preferably 0.7 mm or less when the pneumatic tire is mounted on an applicable rim and filled to prescribed internal pressure, with no load applied.
“Extending in the tread width direction” does not refer to “extending in exactly the tread width direction” but refers to extending in a direction having a component in the tire width direction.
Stating that the circumferential main grooves “extend continuously in the tread circumferential direction” refers to extending continuously towards the tread circumferential direction and includes the cases of extending continuously towards the tread circumferential direction in a zigzag shape and of extending towards the tread circumferential direction while curving.
The “tread edge” refers to the outermost position in the tread width direction of the aforementioned “tread surface.”
A “ribbed shape” refers to the land portion not being divided by grooves or sipes into blocks in the tread circumferential direction.
The statement below that one end of the lug grooves on the equatorial plane side “opens to the circumferential main groove at a position corresponding to an opening position of the intermediate land portion lug groove to the circumferential main groove” refers to the opening position of the intermediate land portion lug grooves and the opening position of the lug grooves on the equatorial plane side partially overlapping in the tread circumferential direction.
According to this disclosure, a pneumatic tire that improves the ride comfort, quietness, and drainage performance while maintaining the steering stability can be provided.
In the accompanying drawings:
The following describes embodiments of this disclosure in detail with reference to the drawings.
As illustrated in
In the example illustrated in
Furthermore, as illustrated in
In the illustrated example, the outermost land portion 31 and the outermost land portion 35 are formed to have equivalent dimensions in the tread width direction. Also, the intermediate land portion 32, central land portion 33, and intermediate land portion 34 are formed to have equivalent dimensions in the tread width direction.
Lug grooves 41 on the tread edge side are formed in the outermost land portion 31 of this embodiment, with one end opening to the tread edge TE1 and the other end terminating within the outermost land portion 31. Sipes 51 are further formed in the outermost land portion 31 of this embodiment, with the inward end in the tread width direction terminating within the outermost land portion 31. The outer edge, in the tread width direction, of the sipes 51 of this embodiment opens to the tread edge TEL The sipes 51 of this embodiment have a width of 0.7 mm. As referred to here, the width of the sipe is the dimension in a direction perpendicular to the extending direction of the sipe. In this embodiment, the sipes 51 are formed so that the inward end in the tread width direction of the sipes 51 is positioned further outward in the tread width direction than the inward end in the tread width direction of the lug grooves 41 on the tread edge side.
The intermediate land portion 32 on one side in a tread width direction, adjacent to the tire equatorial plane CL side of the outermost circumferential main groove 21 on the one side, is formed into blocks only by sipes 52 extending in the tread width direction. The sipes 52 of this embodiment have a width of 0.7 mm.
The sipes 52 of this embodiment are formed at an inclination relative to the tread width direction. The sipes 52 may, for example, be formed at an inclination of 10° to 50° relative to the tread width direction. By setting the inclination angle of the sipes 52 relative to the tread width direction to be within this range, the steering stability can be maintained even as a large force is applied in the tread circumferential direction and the tread width direction, and the water film in the intermediate land portion 32 can effectively be removed. The sipes 52 of this embodiment are inclined at approximately 30° relative to the tread width direction.
In this embodiment, each block 32a forming the intermediate land portion 32 is formed approximately as a parallelogram with a pair of sides defined by the circumferential main grooves 21 and 22 and extending in the tread circumferential direction, and a pair of sides defined by the sipes 52. In this embodiment, among the corners of each block 32a, corners 32b and 32c with an obtuse angle formed by the sipe 52 and the circumferential main grooves 21 and 22 are chamfered to form chamfered portions 32d and 32e.
As illustrated in
The central land portion 33 of this embodiment is formed into blocks by sipes 53 extending in the tread width direction. The sipes 53 of this embodiment have a width of 0.7 mm.
The sipes 53 of this embodiment are formed at an inclination relative to the tread width direction. The sipes 53 may, for example, be formed at an inclination of 10° to 50° relative to the tread width direction. By setting the inclination angle of the sipes 53 relative to the tread width direction to be within this range, the steering stability can be maintained even as a large force is applied in the tread circumferential direction and the tread width direction, and the water film in the central land portion 33 can effectively be removed. The sipes 53 of this embodiment are inclined at approximately 30° relative to the tread width direction.
In this embodiment, each block 33a forming the central land portion 33 is formed approximately as a parallelogram with a pair of sides defined by the circumferential main grooves 22 and 23 and extending in the tread circumferential direction, and a pair of sides defined by the sipes 53. In this embodiment, among the corners of each block 33a, corners 33b and 33c with an obtuse angle formed by the sipe 53 and the circumferential main grooves 22 and 23 are chamfered to form chamfered portions 33d and 33e.
As illustrated in
In this embodiment, as illustrated in
In this embodiment, the blocks 32a of the intermediate land portion 32 and the blocks 33a of the central land portion 33 are formed to have the same shape. In this embodiment, the chamfered portions 32d and 32e are formed in the corners 32b and 32c of the blocks 32a, and the chamfered portions 33d and 33e are formed in the corners 33b and 33c of the blocks 33a. Therefore, the shock is lessened when the corners 32b and 32c and the corners 33b and 33c, which are highly rigid, contact the ground, thus yielding even better ride comfort.
The intermediate land portion 34 on the other side in the tread width direction, adjacent to the tire equatorial plane CL side of the outermost circumferential main groove 24 on the other side, is formed in a ribbed shape. Lug grooves 42 are formed in the intermediate land portion 34, with one end opening into the circumferential main groove 24 and the other end terminating within the intermediate land portion 34.
Sipes 54 are formed in the intermediate land portion 34 of this embodiment, with one end opening into the circumferential main groove 23 adjacent on the equatorial plane side and the other end terminating within the intermediate land portion 34. By providing such sipes 54, the rigidity balance of the intermediate land portion 34 in the tread width direction can be made uniform, and the ride comfort can be further improved while maintaining the quietness.
The sipes 54 of this embodiment are formed at an inclination relative to the tread width direction. The sipes 54 may, for example, be formed at an inclination of 10° to 50° relative to the tread width direction. By setting the inclination angle of the sipes 54 relative to the tread width direction to be within this range, the steering stability can be maintained even as a large force is applied in the tread circumferential direction and the tread width direction, and the water film in the intermediate land portion 34 can effectively be removed. The sipes 54 of this embodiment are inclined at approximately 30° relative to the tread width direction.
In this embodiment, the corner 34a with an obtuse angle formed by the sipe 54 and the circumferential main groove 23 has a chamfered portion 34b formed by chamfering.
As illustrated in
As illustrated in
In this embodiment, as illustrated in
Lug grooves 43 on the tread edge side are formed in the outermost land portion 35 of this embodiment, with one end opening to the tread edge TE2 and the other end terminating within the outermost land portion 35. Sipes 55 are further formed in the outermost land portion 35 of this embodiment, with the inward end in the tread width direction terminating within the outermost land portion 35.
The outer edge, in the tread width direction, of the sipes 55 of this embodiment opens to the tread edge TE2. The sipes 55 of this embodiment have a width of 0.7 mm. In this embodiment, the sipes 55 are formed so that the inward end in the tread width direction of the sipes 55 is positioned further outward in the tread width direction than the inward end in the tread width direction of the lug grooves 43 on the tread edge side.
In this embodiment, the extending length of the sipes 51 formed in the outermost land portion 31 is configured to be greater than the extending length of the sipes 55 formed in the outermost land portion 35.
Furthermore, lug grooves 44 on the equatorial plane side are formed in the outermost land portion 35 of this embodiment, with one end opening to the outermost circumferential main groove 24 at a position corresponding to an opening position, to the circumferential main groove 24, of the lug groove 42 formed in the intermediate land portion 34, and the other end terminating within the outermost land portion 35. The lug grooves 44 on the equatorial plane side do not overlap in the tread width direction with the lug grooves 43 on the tread edge side.
In this way, in the tire according to an embodiment of this disclosure, the intermediate land portion 32 on one side in the tread width direction, adjacent to the tire equatorial plane CL side of the outermost circumferential main groove 21 on the one side, is formed into blocks only by sipes 52 extending in the tread width direction; the intermediate land portion 34 on the other side in the tread width direction, adjacent to the tire equatorial plane CL side of the outermost circumferential main groove 24 on the other side, is formed in a ribbed shape; and lug grooves 42 are formed in the intermediate land portion 34 on the other side, with one end opening into the outermost circumferential main groove 24 on the other side, and the other end terminating within the intermediate land portion 34 on the other side.
The following describes the effects of the tire according to this embodiment when mounting the tire onto a vehicle so that the intermediate land portion 34 at the other side is on the outside while the tire is mounted on the vehicle.
In order to improve the steering stability, it is effective to provide the land portions with a ribbed shape, but upon providing all of the land portions with a ribbed shape, the high rigidity of the land portions may prevent sufficient ride comfort, quietness, and drainage performance from being obtained.
By contrast, in the tire according to an embodiment of this disclosure, the intermediate land portion 32 that is on the inside while the tire is mounted on a vehicle is formed into blocks by only the sipes 52, thereby lowering the rigidity of the intermediate land portion 32 and improving the ride comfort and quietness. Since the intermediate land portion 32 is formed into blocks by only the sipes 52, the pattern noise that would occur if the intermediate land portion 32 were formed into blocks by grooves can be prevented, and a reduction in the footprint area can be suppressed while maintaining steering stability.
On the other hand, the intermediate land portion 34 that is on the outside while the tire is mounted on the vehicle is provided with a ribbed shape to satisfy the high rigidity required during cornering. The steering stability is thus maintained, and by providing the lug grooves 42, the drainage performance can also be improved.
Therefore, the pneumatic tire of this embodiment can improve the ride comfort, quietness, and drainage performance while maintaining the steering stability.
In this disclosure, lug grooves 41 and 43 on the tread edge side are preferably formed in the outermost land portions 31 and 35 in the tread width direction defined by the outermost circumferential main grooves 21 and 24 in the tread width direction and by the tread edges TE1 and TE2, with one end of the lug grooves 41 and 43 on the tread edge side opening to the tread edge TE1 or TE2 and the other end terminating within the outermost land portion 31 or 35. By forming such lug grooves 41 and 43, the rigidity of the outermost land portions 31 and 35 can be ensured, while allowing further improvement in the drainage performance. Therefore, the drainage performance can be further improved without reducing the steering stability.
Furthermore, in this disclosure, as described above, sipes 51 and 55 are preferably further formed in the outermost land portions 31 and 35, an inward end in the tread width direction of each sipe terminating within the outermost land portion 31 or 35, and the extending length of the sipe 51 formed in the outermost land portion 31 on the one side is preferably greater than the extending length of the sipe 55 formed in the outermost land portion 35 on the other side. By forming such sipes 51 and 55, the ride comfort and quietness can be further improved, and the rigidity on the outside while the tire is mounted on the vehicle becomes greater than the rigidity on the inside while the tire is mounted on the vehicle, allowing improvement in the steering stability during cornering.
Also in this disclosure, as described above, lug grooves 44 on the equatorial plane side are preferably formed in the outermost land portion 35 on the other side, with one end opening to the circumferential main groove 24 at a position corresponding to an opening position of the intermediate land portion lug groove 42 to the circumferential main groove 24, and the other end terminating within the outermost land portion 35 on the other side, and the lug grooves 44 on the equatorial plane side do not overlap in the tread width direction with the lug grooves 43 on the tread edge side. By adopting this configuration, even if the lug grooves 44 on the equatorial plane side are formed, a reduction in the rigidity of the outermost land portion 35 due to formation of the lug grooves 44 on the equatorial plane side can be suppressed, thereby further improving the drainage performance while maintaining the steering stability.
As another feature of this disclosure, as described above, sipes 54 are preferably formed in the intermediate land portion 34 on the other side, with one end opening into the circumferential main groove 23 adjacent on the equatorial plane CL side and the other end terminating within the intermediate land portion 34 on the other side. By forming such sipes 54, the rigidity of the intermediate land portion 34 in the tread width direction can be made uniform, thereby further improving the ride comfort while maintaining the quietness. It is also possible to suppress a reduction in the quietness and ride comfort occurring when forming grooves on the inside while the tire is mounted on the vehicle, which tends to yield high ground contact pressure during regular running.
As yet another feature of this disclosure, as described above, four circumferential main grooves 2 are preferably formed on the tread surface, and the tire preferably further includes a central land portion 33 extending across the tire equatorial plane CL between the intermediate land portion 32 on the one side and the intermediate land portion 34 on the other side, the central land portion 33 being formed into blocks by sipes 53 extending in the tread width direction. By adopting this configuration, the occurrence of pattern noise in the central land portion 33 can be suppressed, and a reduction in the footprint area can be suppressed, thereby maintaining the quietness and steering stability.
As still another feature of this disclosure, as described above, the sipes 52 in the intermediate land portion 32 on the one side are preferably formed at an inclination relative to the tread width direction, and among corners of each block 32a in the intermediate land portion 32 on the one side, corners 32b and 32c with an obtuse angle formed by the sipes 52 and the circumferential main grooves 21 and 22 are preferably chamfered. Inclining the sipes 52 ensures the rigidity necessary during cornering. Also, by chamfering, the rigidity of the corners 32b and 32c with an obtuse angle formed by the sipes 52 and the circumferential main grooves 21 and 22 can be reduced, thereby reducing the shock when the corners 32b and 32c contact the road surface and improving the ride comfort.
Embodiments of this disclosure have been described, but this disclosure is in no way limited to the above embodiments. For example, the number of circumferential main grooves formed on the tread surface may be three or may be five or more. A variety of other changes and modifications may be made.
To verify the effects of the tire disclosed herein, prototypes of tires according to Examples 1 to 8 and tires according to Comparative Examples 1 and 2 and a Conventional Example were produced, and tests were run to evaluate the performance of the tires. Table 1 below lists the specifications of each tire. The tests were performed by assembling the above tires with a tire size of 215/55R17 onto an applicable rim, applying an internal pressure of 230 kPa, and mounting the tires onto a vehicle so that the intermediate land portion 34 was on the outside while the tire was mounted on the vehicle.
Each of the above tires was run on a dry road surface, and the driving performance was evaluated based on the driver's sensory perception. The results were evaluated as relative values, with the evaluation result for the tire according to Comparative Example 1 as 100. The larger the value is, the better the steering stability is.
Each of the above tires was run over a wet road surface with a water depth of 6 mm on a test course, and the braking distance from the start of braking at a speed of 80 km/h until a full stop was measured. The results were evaluated as the inverse of the braking distance ratio, with the evaluation result for the tire according to Comparative Example 1 as 100. The larger the value is, the better the drainage performance is.
The noise generated from the lateral side of the tire when the tire was run at a speed of 80 km/h on an indoor drum test machine under the conditions stipulated by the JASO C606 standard was measured to evaluate an air column resonance sound. The results were evaluated as relative values, with the evaluation result for the tire according to Comparative Example 1 as 100. The larger the value is, the better the quietness is.
On a dry course, a test driver rode over five varieties of road surfaces with different degrees of pavement roughness and subjectively evaluated the ride comfort of the tire during the test drive based on the vibration and sound transmitted to the inside of the vehicle. Specifically, an index serving as a comparative evaluation was calculated, with the evaluation result of Comparative Example 1 being 100. Table 1 shows the results of the evaluation. A higher index indicates that the tire has better ride comfort.
As shown in Table 1, the tires in accordance with Examples 1 to 8 all have improved ride comfort, quietness, and drainage performance as compared to the tire in accordance with Comparative Example 1, while maintaining steering stability.
In Comparative Example 2, the intermediate land portion 32 is formed into blocks by lateral grooves, and therefore the steering stability is worse than in Comparative Example 1.
In the Conventional Example, the intermediate land portions are provided with a ribbed shape, and therefore the steering stability and quietness are worse than in Comparative Example 2.
A comparison of Example 1 and Example 2 shows that Example 1, in which the chamfered portions 32d and 32e are formed in the block 32a of the intermediate land portion 32, has higher ride comfort.
A comparison of Example 2 and Example 3 shows that Example 2, in which the sipes 52 are inclined, has higher steering stability.
A comparison of Example 2 and Example 4 shows that Example 2, in which the sipes 53 are formed, has higher steering stability and quietness.
A comparison of Example 4 and Example 5 shows that Example 4, in which the sipes 54 are formed, has higher steering stability, quietness, and ride comfort.
A comparison of Example 5 and Example 6 shows that Example 5, in which the lug grooves 44 on the equatorial plane side are formed, has higher steering stability and drainage performance.
A comparison of Example 6 and Example 7 shows that Example 6, in which the sipes 51 and 55 are formed, has higher steering stability and drainage performance.
A comparison of Example 7 and Example 8 shows that Example 7, in which the lug grooves 41 and 43 on the tread edge side are formed, has higher drainage performance.
According to this disclosure, a pneumatic tire that improves the ride comfort, quietness, and drainage performance while maintaining the steering stability can be provided.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-176204 | Aug 2014 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2015/003979 | 8/7/2015 | WO | 00 |
