JP6450224B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  Conventionally, in order to prevent the wear from progressing at the shoulder portion earlier than the center portion of the tread and to improve uneven wear resistance, the outer contour of the tread tread formed by a plurality of arcs in the cross-sectional view in the tire width direction is used. Various tires that define the radius of curvature of each arc have been proposed (for example, Patent Document 1).

JP-A-9-71107

  By the way, in recent years, it has been desired to further cope with the environment in the tire, for example, to extend the life of the tire, and even in such a tire, it is required to sufficiently improve the uneven wear resistance of the shoulder portion of the tread. It was done.

  Then, an object of this invention is to provide the pneumatic tire which can fully improve the uneven wear resistance in the shoulder part of a tread.

The pneumatic tire of the present invention includes a plurality of circumferential grooves continuously extending in the tire circumferential direction on the tread surface, at least one central land portion formed between the circumferential grooves, and the circumferential grooves. A pneumatic tire comprising a shoulder circumferential groove on the outermost side in the tire width direction and a pair of shoulder land portions formed between tread contact ends, and the tire is attached to an applicable rim and has a predetermined internal pressure. In the tire width direction cross-sectional view of the tread, the region inside the tire width direction with the shoulder circumferential groove as a boundary is an arc C1 having a radius of curvature CR1 and a tire width of the arc C1. A region adjacent to the outer side in the tire width direction with the shoulder circumferential groove as a boundary on the tread surface is formed by an arc C2 having a radius of curvature CR2 smaller than the radius of curvature CR1. The arc C2 is formed adjacent to the outer side in the tire width direction and includes an arc C3 having a curvature radius CR3 smaller than the curvature radius CR2. When the tread ground half width is W, the curvature radius CR3 is equal to the tread ground half width W. 1.0-1.5 Baidea is, land portion width of the shoulder land portion is characterized 0.4-0.6 Baidea Rukoto the tread half width W.
According to the present invention, uneven wear resistance at the shoulder portion of the tread can be sufficiently improved. Moreover, the uneven wear resistance at the shoulder portion and the central portion can be further improved.

In the present invention, the above-mentioned “applied rim” is an industrial standard effective in the area where tires are produced and used. In Japan, JATMA YEAR BOOK of JATMA (Japan Automobile Tire Association), in Europe, ETRTO STANDARDS MANUAL of (The European Tire and Rim Technical Organization), US TRA (The TIRE and RIM Association, Inc.) YEAR BORU of the standard size (ETRTOURING of the standard rim (ETRTOURUSRUM) and the standard rim (ETRMAUR of the applicable size). In YEAR BOOK, “Design Rim”. In addition, the state where the tire mounted on the application rim is “filled with a predetermined internal pressure” refers to a state where the tire is mounted on the application rim and has an air pressure (maximum air pressure) corresponding to the maximum load capacity. “Maximum load capacity” refers to the maximum load capacity of a single wheel in the applicable size / ply rating described in the above JATMA YEAR BOOK.
Hereinafter, unless otherwise specified, the dimensions and the like of each element of the tread are measured in a no-load state in which a tire is mounted on an applicable rim and filled with a predetermined internal pressure.

In the present invention, the “tread surface” means a road surface when a tire mounted on an applicable rim and filled with a predetermined internal pressure is rolled with a load corresponding to the maximum load capacity applied. It refers to the outer peripheral surface over the entire circumference of the tire that will come into contact. Furthermore, the “tread ground contact end” refers to the outermost position of the tread surface in the tire width direction. The “tread grounding half width W” refers to half of the length measured along the tire width direction from the tire equatorial plane to the tread grounding end.
Further, in the present invention, “with a shoulder circumferential groove as a boundary” means that the center position in the tire width direction of the shoulder circumferential groove is a boundary in a cross-sectional view in the tire width direction.

In the present invention, the “land portion width” refers to a length of the land portion measured along the tire width direction. When the “land portion width” varies in the tire circumferential direction, the average land portion is measured. The width is the “land width”.
Here, in the pneumatic tire of the present invention, the negative rate of the tread surface is preferably 20 to 30%.

  In the pneumatic tire of the present invention, a groove and / or sipe is disposed in the shoulder land portion, and a land portion end adjacent to the opening portion of the groove or sipe to the tread surface is chamfered. preferable. According to this configuration, both wet performance and uneven wear resistance at the shoulder portion of the tread can be achieved.

  In the present invention, “sipe” refers to a groove having a groove width of 1.5 mm or less in a cross-sectional view in a direction orthogonal to the extending direction of the sipe.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic tire which can fully improve the uneven wear resistance in the shoulder part of a tread can be provided.

It is an expanded view which shows the tread pattern of the pneumatic tire which concerns on one Embodiment of this invention. FIG. 2 is a tire width direction cross-sectional view of a tread portion of the pneumatic tire of FIG. 1. (A) is a figure which shows the cross section which follows the aa 'line of the pneumatic tire of FIG. 1, (b) is a figure which shows the cross section along the bb' line of the pneumatic tire of FIG. is there.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a development view showing a tread pattern of a pneumatic tire (hereinafter also referred to as a tire) according to an embodiment of the present invention. Although the tire of this embodiment is not illustrated, a carcass having a radial structure extending in a toroidal shape between the bead portions, a belt disposed on the outer side in the tire radial direction of the carcass of the tread portion, and the tire radial direction of the belt And a tread that is disposed outside and forms a tread surface.

  As shown in FIG. 1, the tire according to this embodiment has a plurality of circumferential grooves 1 that continuously extend in the tire circumferential direction on the tread tread T, and in the illustrated example, linearly extends 4 continuously in the tire circumferential direction. A circumferential groove 1 is provided. In addition, although the illustrated circumferential groove 1 extends linearly in the tire circumferential direction, it can be formed in a zigzag or wave-like extending form. Moreover, although the groove width of the circumferential groove | channel 1 is the same in the example of illustration, it can also differ, respectively.

Further, this tire has at least one central land portion 2 formed between the circumferential grooves 1 and three circumferential land grooves 2 in the illustrated example, and a circumferential groove (shoulder circumference) of the circumferential grooves 1 on the outermost side in the tire width direction. Directional groove) 1s and a pair of shoulder land portions 3 formed between the tread grounding ends E are disposed.
In this tire, two central land portions 2 adjacent to the central land portion 2 through which the tire equatorial plane CL passes among the three central land portions 2 have different land widths. When the central land portion 2 on the one side (right side in the figure) is relatively large outside in the tire mounting direction, the rigidity of the central land portion 2 can be increased and the steering stability during cornering can be improved. .
In the illustrated tire, the width of the land portion of each shoulder land portion 3 is the same, and the central land portion 2 through which the tire equatorial plane CL passes, and the one side with respect to the central land portion 2. The land width of the central land portion 2 adjacent to the other side opposite to the other side (left side in the figure) is the same, but the relationship between the land width of each shoulder land portion 3 and each central land portion 2 is Can be arbitrary.

  Each central land portion 2 can be provided with a groove 4 and / or a sipe 5, and in the illustrated example, the central land portion 2 on one side (right side in the figure) of the central land portion 2 has both ends. Is provided with a lateral groove 41 that opens in both circumferential grooves 1 that define the central land portion 2, and a lateral groove 42 that extends from the circumferential groove 1 on the other side (left side in the figure) and terminates in the central land portion 2. Has been. Further, in the illustrated example, the central land portion 2 through which the tire equatorial plane CL passes extends from the sipe 51 that opens to both circumferential grooves 1 that define the central land portion 2, and the other circumferential groove 1. There is a lateral groove 43 that terminates in the land. Further, in the illustrated example, the other side central land portion 2 includes a sipe 52 that opens in both circumferential grooves 1 that define the central land portion 2, and a sipe 53 that opens only in the other circumferential groove 1. , And a notch 44 opened to the circumferential groove 1 on one side.

Each shoulder land portion 3 can be provided with a groove 6 and / or a sipe 7. In the illustrated example, each of the shoulder land portions 3 is provided with a groove (lateral groove) 6 and a sipe 7. Yes. Specifically, the shoulder land portion 3 on one side is provided with a first shoulder lateral groove 61 and a second shoulder lateral groove 62 located between the first shoulder lateral grooves 61 adjacent in the tire circumferential direction. Yes. The first shoulder lateral groove 61 has one end opened to the tread grounding end E and the other end connected to a sipe 72 opened to the circumferential groove 1 (shoulder circumferential groove 1s) in the land portion of the shoulder land portion 3. . The second shoulder lateral groove 62 has one end opened to the tread grounding end E and the other end terminated in the shoulder land portion 3. Further, the shoulder land portion 3 is provided with a notch portion 63 that opens to the shoulder circumferential groove 1s.
Further, as shown in FIG. 1, a sipe 71 extending from the circumferential groove 1 (shoulder circumferential groove 1s) to the tread ground contact E is disposed on the shoulder land portion 3 on the other side (left side in the figure). ing.

  In this embodiment, the tread tread T has a plurality of circumferential grooves 1, a plurality of land portions 2, 3, and a plurality of grooves 4, 6 and sipes 5, 7 in each land portion 2, 3 as described above. Is disposed, from the viewpoint of wet performance and wear performance, the negative rate of the tread surface T (groove area ratio to the area of the tread surface T) is preferably 20 to 30%, more preferably 23. ~ 28%.

Incidentally, in the tire of this embodiment, as shown in FIG. 2, the tread surface T is formed by a plurality of circular arcs having different radii of curvature in a sectional view in the tire width direction. Specifically, in the tread tread T, a region on the inner side in the tire width direction with respect to the shoulder circumferential groove 1s (that is, the region includes the outer contour of all the central land portions 2) is an arc C1. And an arc C2 adjacent to the outer side in the tire width direction of the arc C1, and the tread tread T has a region on the outer side in the tire width direction with the shoulder circumferential groove 1s as a boundary (that is, the shoulder land portion 3 in the region). Is formed including an arc C3 adjacent to the outer side of the arc C2 in the tire width direction. In the illustrated example, the arc C1 intersects the tire equator plane CL at the center thereof, the arc C2 is located on both sides (outer in the tire width direction) of the arc C1, and the tread tread T has a shoulder circumferential groove 1s as a boundary. The outer region in the tire width direction is formed by an arc C2 and an arc C3 located on both sides of the arc C2 (outer in the tire width direction). In addition, the arcs C1 to C3 are smoothly connected to each other (tangents at the connection points are matched).
Further, the radii of curvature CR1 to CR3 of the respective arcs C1 to C3 are different from each other and become smaller as CR1 changes to CR3. When the tread ground half width is W, the curvature radius CR3 is equal to 1 of the tread ground half width W. 0 to 1.5 times.
In the cross-sectional view of the tread portion shown in FIG. 2, sipes and grooves are omitted, and only circumferential grooves are provided.

  Therefore, in this embodiment, in the cross-sectional view in the tire width direction, a region on the inner side in the tire width direction with respect to the shoulder circumferential groove 1s in the tread surface T is defined by the arc C1 having the curvature radius CR1 and the curvature radius CR1. The tread tread T is formed with an arc C2 having a small radius of curvature CR2, and the outer region in the tire width direction with the shoulder circumferential groove 1s as a boundary including the arc C3 having a radius of curvature CR3 smaller than the radius of curvature CR2. By setting the curvature radius CR3 to 1.0 to 1.5 times the tread grounding half width W, the grounding pressure in the tire width direction of the tread becomes uniform, and the uneven wear resistance at the shoulder portion is improved. be able to. It should be noted that by setting the radius of curvature CR3 to 1.0 or more of the tread ground half width W, the ground contact pressure at the shoulder portion is prevented from becoming too small, and the curvature radius CR3 is set to 1.5 of the tread ground half width W. By setting it as the following, it can prevent that the ground contact pressure of a shoulder part becomes large too much.

  Further, from the same viewpoint, the radius of curvature CR3 is more preferably 1 to 1.2 of the tread ground half width W.

  In the present invention, the curvature radii CR1 to CR3 are preferably 0.15 <CR2 / CR1 <0.4, and / or 0.05 <CR3 / CR1 <0.15. . By setting the curvature radii CR1, CR2 within the above range and / or the curvature radii CR1, CR3 within the above range, the curvature radius CR2 or the curvature radius CR3 with respect to the curvature radius CR1 becomes too small or too large. , The contact pressure in the tire width direction of the tread can be effectively made uniform, and uneven wear resistance at the shoulder portion can be further improved.

  Further, the radius of curvature CR1 is preferably 15 to 20 times the tread grounding half width W, and more preferably 17 to 18 times the tread grounding half width W. The radius of curvature CR2 is preferably 2 to 4 times the tread grounding half width W, and more preferably 2.5 to 3 times the tread grounding half width W.

Further, in the present invention, for the arcs C1 to C3 forming the outer contour of the tread surface T, the connecting point where the arcs C1 and C2 are connected and the connecting point where the arcs C2 and C3 are connected are connected from the tire equatorial plane CL to the tire width. If the lengths measured along the direction are the lengths L1 and L2, respectively, the lengths L1 and L2 are
0.3 ≦ L1 / W ≦ 0.5 and / or 0.6 ≦ L2 / W ≦ 0.9
It is preferable that According to this configuration, the distribution of contact pressure in the tire width direction can be adjusted more appropriately, and uneven wear resistance at the shoulder portion can be further improved. From the same viewpoint, the lengths L1 and L2 are
0.3 ≦ L1 / W ≦ 0.4 and / or 0.6 ≦ L2 / W ≦ 0.7
It is more preferable that

Here, the wider the land width of the shoulder land portion 3, the more uniform the contact pressure in the shoulder land portion 3. However, if the land width is too wide, the land portion of the central land portion 2 on the inner side in the tire width direction. There is a tendency that the width is reduced as a whole and the rigidity of the central land portion 2 is lowered as a whole, and therefore, the central portion of the tread is likely to be worn. Therefore, in the present invention, the width of the land portion of the shoulder land portion 3 is preferably 0.4 to 0.6 times the tread ground half width W, thereby further improving the uneven wear resistance at the shoulder portion and the central portion. Can be improved. From the same viewpoint, it is more preferable that the land width of the shoulder land portion 3 is 0.4 to 0.5 times the tread ground half width W.
Further, from the viewpoint of preventing the rigidity of the central land portion 2 from decreasing and suppressing the wear of the central portion of the tread, the land width of one central land portion 2 is 0.2 times the tread ground half width W or more. It is preferable that

  Further, as described above, in this embodiment, as shown in FIG. 1, the groove 6 and / or the sipe 7 can be disposed in the shoulder land portion 3 (in the drawing, both the groove 6 and the sipe 7 are disposed). However, the land end 31 adjacent to the opening to the tread surface T of the groove 6 and / or the sipe 7 is preferably chamfered (in the drawing, the groove of the shoulder land portion 3 on one side). 6 and the land end 31 adjacent to the opening of the sipe 7 is chamfered). According to this configuration, it is possible to achieve both wet performance and uneven wear resistance at the shoulder portion of the tread. Specifically, in order to ensure wet performance, it is effective to increase the groove volume and improve drainage, but on the other hand, if the groove volume is too large, the rigidity of the land portion will decrease. The shoulder land portion 3 may be easily worn. Therefore, by chamfering the land portion end 31 adjacent to the opening of the groove 6 and / or sipe 7 disposed in the shoulder land portion 3, the drainage performance is improved by the enlarged opening of the groove 6 and / or sipe 7. On the other hand, since the groove volume is not greatly increased, uneven wear can be suppressed, and therefore both wet performance and uneven wear resistance at the shoulder portion of the tread can be achieved.

In addition, the groove | channel 6 adjacent to the land part edge 31 chamfered specifically, as shown to Fig.3 (a), the 1st groove part 6a located in a land part, and the said 1st groove part 6a. And a second groove portion 6b including an opening that opens to the tread surface T. In a cross section in a direction perpendicular to the extending direction of the groove 6, the first groove portion 6a has a substantially constant groove width, and the second groove portion 6b has a groove width larger than that of the first groove portion 6a. The groove width gradually increases toward the opening on the tread surface T.
Further, as shown in FIG. 3B, the sipe 7 adjacent to the chamfered land portion end 61 has a sipe portion 7a located inside the land portion and an upper end portion of the sipe portion 7a on the outer side in the tire radial direction. And an enlarged portion 7b including an opening that opens to the tread surface T. In a cross section in a direction perpendicular to the extending direction of the sipe 7, the sipe portion 7a has a substantially constant groove width, and the enlarged portion 7b has a width larger than that of the sipe portion 7a, and an opening at the tread surface T. The width gradually increases toward the part. In this embodiment, the sipe portion 7a of the sipe 7 has a groove width of 1.5 mm or less.

  Further, in this embodiment, as shown in FIG. 1, the land portion end 31 adjacent to the groove 6 and the sipe 7 disposed in the shoulder land portion 3 is chamfered, but is disposed in the shoulder land portion 3. Either the groove 6 or the sipe 7 may be used. In this embodiment, it is preferable that the land portion 31 adjacent to the groove 6 and / or the sipe 7 disposed in the shoulder land portion 3 is chamfered, but the groove disposed in the central land portion 2. The end of the land adjacent to 4 and sipe 5 can also be chamfered. Further, the land portion end 31 adjacent to the sipe 7 disposed on the shoulder land portion 3 on one side is chamfered, but the land portion end adjacent to the sipe 7 disposed on the shoulder land portion 3 on the other side is chamfered. 31 can also be chamfered. Moreover, the chamfering shape of the land portion end 31 adjacent to the groove 6 and the sipe 7 can be arbitrarily set. In FIG. 3, the land portion ends 31 on both sides are chamfered, but the land portion end 31 is chamfered only on one side. It may be.

  As mentioned above, although embodiment of this invention was described with reference to drawings, the pneumatic tire of this invention is not limited to said example, A change can be added suitably. For example, in the illustrated tire, four circumferential grooves are provided to divide three central land portions, and various grooves and sipes are provided on the central land portion and the shoulder land portions. However, as long as a plurality of circumferential grooves, at least one central land portion, and a pair of shoulder land portions are provided, any tread pattern can be obtained. .

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to the following Example at all.

The tire of Example 1 has a tire size of 195 / 65R15 and has a tread pattern as shown in FIG. Specifically, the tires of Example 1 have curvature radii CR1 to CR3 of 1300 mm, 210 mm, and 70 mm, respectively, and lengths L1 and L2 obtained by measuring the connection points of the arcs C1 to C3 from the tire equatorial plane, respectively. The land width of the shoulder land portion is 35 mm, and the end of the land portion adjacent to the sipe and groove disposed on the shoulder land portion on one side is chamfered.
The tires of Examples 2 to 6, Reference Examples 7 and 8, and Comparative Examples 1 to 2 are the same as the tire of Example 1 except that the tires are changed as shown in Table 1.
In the conventional tire, the outer contour of the tread surface is formed only by the arcs C1 and C2 having the curvature radii CR1 and CR2, the curvature radii CR1 and CR2 are 900 mm and 200 mm, respectively, and the connecting point of the arcs C1 and C2 is the tire equator. The length L1 measured from the surface is 25 mm, and is the same as that of the tire of Example 1 except that the length L1 is changed as shown in Table 1.

Each of the above test tires was evaluated by the following method, and the results are shown in Table 1.
[Uneven wear resistance]
Each of the above test tires was attached to a rim having a rim size of 6J and the internal pressure was set to 230 kPa, and then the tire was caused to travel 10,000 km. Then, after running, the amount of wear at the shoulder from the new article was measured and compared. The evaluation result is shown by an index in which the result of each sample tire is the reciprocal and the tire of the conventional example is set to 100, and the larger this value, the better the uneven wear resistance at the shoulder.
[Wet performance]
Each of the above test tires was mounted on a rim having a rim size of 6J and the internal pressure was set to 230 kPa, and then the vehicle was run on a straight road with a water depth of 6 mm on a test course to measure the speed when a hydroplaning phenomenon occurred. . The evaluation result is indicated by an index in which the tire of the conventional example is set to 100, and the larger this value, the better the wet performance.

As shown in Table 1, the tires of Examples 1 to 6 and Reference Examples 7 and 8 are of Comparative Examples 1 and 2 in which the radius of curvature CR3 is outside the range of 1.0 to 1.5 of the tread ground half width W. It can be seen that the uneven wear resistance is sufficiently improved as compared with the tire. Further, the tires of Examples 1 to 6 were wet compared to the tires of Reference Examples 7 and 8 in which the land width of the shoulder land portion was outside the range of 0.4 to 0.6 times the tread ground half width. It can be seen that the performance is improved.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic tire which can improve the uneven wear resistance in the shoulder part of a tread can be provided.

1: circumferential groove, 1 s: shoulder circumferential groove, 2: central land portion, 3: shoulder land portion, 31: land portion end, 4: groove (disposed in the central land portion), 5, 51, 52, 53: Sipe (disposed in the central land) 41, 42, 43: Transverse groove, 44: Notched portion, 6: Groove (disposed in the shoulder land portion), 61: First shoulder lateral groove, 62: First 2 shoulder lateral grooves, 63: notch portion, 6a: first groove portion, 6b: second groove portion, 7, 71, 72: sipe (disposed on the shoulder land portion), 7a: sipe portion, 7b: enlarged portion C1, C2, C3: Arc, CL: Tire equatorial plane, CR1, CR2, CR3: Radius of curvature, E: Tread contact edge, L1, L2: Length, T: Tread tread, W: Tread contact half width

Claims (3)

A plurality of circumferential grooves extending continuously in the tire circumferential direction on the tread surface, at least one central land portion formed between the circumferential grooves, and an outermost shoulder in the tire width direction of the circumferential grooves A pair of shoulder land portions formed between a circumferential groove and a tread grounding end, and a pneumatic tire comprising:
In a cross-sectional view in the tire width direction in a no-load state in which a tire is mounted on an applicable rim and filled with a predetermined internal pressure,
Of the tread surface, a region on the inner side in the tire width direction with respect to the shoulder circumferential groove is adjacent to an arc C1 having a radius of curvature CR1 and an outer side in the tire width direction of the arc C1 and being smaller than the radius of curvature CR1. Formed with arc C2 of CR2,
Of the tread surface, a region on the outer side in the tire width direction with the shoulder circumferential groove as a boundary is adjacent to the outer side in the tire width direction of the arc C2 and includes an arc C3 having a curvature radius CR3 smaller than the curvature radius CR2. And
When the tread half width is W, the radius of curvature CR3 is Ri 1.0-1.5 Baidea the tread half width W,
Land portion width of the shoulder land portion is characterized 0.4-0.6 Baidea Rukoto the tread half width W, a pneumatic tire. The pneumatic tire according to claim 1, wherein a negative rate of the tread surface is 20 to 30% . Grooves and / or sipes are disposed in the shoulder land portion,
The pneumatic tire according to claim 1 or 2, wherein a land portion end adjacent to an opening to the tread surface of the groove or sipe is chamfered.

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