PNEUMATIC TIRE

Abstract

In the pneumatic tire in which not less than three main grooves 1 extending in the tire circumferential direction R are formed and ribs 2 are formed by the main grooves 1, upper edges 11 of the main groove 1 when the tire is new extend in a linear manner in the tire circumferential direction R, the bottom 12 of the main groove 1 extends in a zigzag manner in the tire circumferential direction R, the sidewalls 13 of the main groove 1 is provided with concave portions and convex portions, and in the concave portion of at least one of the sidewalls 13 of the main groove 1, the protrusions 3 that is joined to the bottom 12 of the main groove 1 and to the sidewall 13. Further, the pneumatic tire may be provided with sipes or notches that extend from the concave portion to the inner side of the rib 2 in the tire width direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing the tread pattern of the pneumatic tire of the present invention when the tire is new.

FIG. 2 is an oblique perspective view showing a part of the main groove in FIG. 1.

FIG. 3 is a schematic view showing the tread pattern of the pneumatic tire of the present invention when the tire is new.

FIG. 4 is an oblique perspective view showing a part of the main groove in FIG. 3.

FIG. 5 is a schematic view showing the tread pattern of the pneumatic tire of the present invention when the tire is new.

FIG. 6 is an oblique perspective view showing a part of the main groove in FIG. 5.

FIG. 7 is a cross-section view taken along the line A-A in FIGS. 1, 3, and 5, respectively.

FIG. 8 is an enlarged view showing the bottom of the main groove in FIG. 1.

FIG. 9 is an enlarged view showing the bottom of the main groove in FIG. 3.

FIG. 10 is an enlarged view of the bottom of the main groove in FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, using figures, the explanation goes on for the embodiment for carrying out the pneumatic tire of the present invention. FIG. 1 is a schematic view showing the tread pattern of the pneumatic tire of the present invention when the tire is new. In the figure, ribs 2 are formed by the main grooves 1 that extend in the tire circumferential direction R. Upper edges 11 of the main grooves 1 when new extend in a linear manner in the tire circumferential direction R. On the other hand, the bottoms 12 of the main grooves 1 extend in a zigzag manner in the tire circumferential direction R. As a result, the generation of uneven wear at the ribs 2 from a time of a new product to the initial stage of wear can be inhibited. The traction performance and the braking performance are improved since the bottoms of the main grooves 1 extend in a zigzag manner thereafter.

FIG. 2 is an oblique perspective view showing a part of the main groove. The sidewall 13 of the main groove 1 is provided with concave portions 14 and convex portions 15 alternately. In the concave portions 14, the protrusions 3 that are joined to the bottom 12 of the main groove 1 and to the sidewall 13 is provided. Therefore, even when a stone should be caught in the main groove 1, the stone can be inhibited from proceeding into the groove by the protrusions 3, thereby capable of preventing the catching of stones. In addition, since the protrusions 3 are not continuous and are arranged with spaces provided, the drainage performance of the main grooves 1 cannot be damaged.

Since the protrusions 3 are joined to the sidewall 13, no crack is generated at the joining portion of the groove bottom 12 and the protrusions 3. As the wear progresses and when the protrusions 3 appear on the tread surface, the traction performance and the braking performance are improved by the protrusions 3. For information, although the protrusions 3 may be provided at least one sidewall 13, they may be provided at both sidewalls 13.

FIG. 3 is a schematic view showing the tread pattern of the pneumatic tire when the tire is new in another embodiment and FIG. 4 is an oblique perspective view showing a part of the main groove. Although the operational effect of the protrusions 3 is just like that observed in the tires of FIGS. 1 and 2, the sipes 4 extending from the concave portion 14 of the sidewall 13 to the inner side of the rib 2 in the tire width direction are formed. By the sipes 4, the rigidity of the concave portions 14 of the sidewall 13 with improved rigidity by the protrusions 3 is lowered. As a result, the difference in the rigidity between the concave portions 14 and the convex portions 15 of the sidewall 13 becomes smaller, which can inhibit the uneven wear. For information, it is preferable that the depth of the sipes 4 is the depth that can reach to the protrusions 3 and that the length of the sipes 4 is 5 to 15% of the width of the rib 2. When the sipes 4 are too short, the effect of narrowing the rigidity difference between the concave portions 14 and the convex portions 15 is small. On the other hand, when the sipes 4 are too long, the rigidity of the concave portions 14 becomes too small.

FIG. 5 is a schematic view showing the tread pattern of the pneumatic tire when the tire is new in another embodiment and FIG. 6 is an oblique perspective view showing a part of the main groove. Although the operational effect of the protrusions 3 is just like that observed in the tires of FIGS. 1 and 2, instead of the sipes, notches 5 extending from the concave portion 14 of the sidewall 13 to the inner side of the rib 2 in the tire width direction are formed. By the notches 5, the rigidity of the concave portions 14 of the sidewall 13 with improved rigidity by the protrusions 3 is lowered as is the case of using the sipes 4. As a result, the difference in the rigidity between the concave portions 14 and the convex portions 15 of the sidewall 13 becomes smaller, which can inhibit the uneven wear. For information, it is preferable that the depth of the notches 5 is the depth that can reach to the protrusions 3, that the length of the notches 5 is 5 to 15% of the width of the rib 2, and that the width that opens to the sidewall 13 of the notches 5 is 2 to 8 mm. When the notches 5 are too short or when the opening width is too narrow, the effect of narrowing the rigidity difference between the concave portions 14 and the convex portions 15 is small. On the other hand, when the notch 5 is too long or when the opening width is too wide, the rigidity of the concave portion 14 becomes too small.

FIG. 7 is a cross-section view taken along the line A-A in FIGS. 1, 3, and 5, respectively. It is preferable that the height H from the groove bottom 12 of the protrusions 3 is 10 to 40% of the depth D of the main groove 1. When the height H is less than 10% of the depth D, sometimes, the effect of inhibiting the catching of stones is low and when the height H exceeds 40% of the depth D, sometimes, the drainage performance of the main groove 1 is damaged.

FIGS. 8 to 10 are enlarged views of the bottoms of the main grooves in FIG. 1, FIG. 3, and FIG. 5, respectively and the groove bottoms 12 are shaded. W1 is the distance from the protrusions 3 to the opposing sidewall 13 in the groove bottom. W2 is the space of the adjacent protrusions 3 in the groove bottom. In order to secure the satisfactory drainage performance, it is necessary that there is no great changes in the width of the groove bottom 12. Therefore, it is preferable that the larger value between W1 and W2 is not greater than twice as the smaller value between W1 and W2. In FIGS. 8 to 10, although W2 is larger than W1, depending on the size of the protrusions 3, W1 sometimes becomes larger than W2 or vice versa.

Further, when the groove width in the bottom 12 except the protrusions 3 is defined as W, it is preferable that the smaller value between W1 and W2 is 50 to 70% of W. When the smaller value is less than 50% of W, sometimes the drainage performance is degraded, and when the smaller value exceeds 70% of W, since the protrusions 3 are small, sometimes inhibition of the catching of stones cannot be achieved. Further, from the view point of securing drainage, it is preferable to make L1 shorter than L2 when L2 is defined to be the circumferential length of the protrusions 3 at the farther side from the sidewall 13 and when L1 is defined to be the circumferential length at the near side from the sidewall 13.

EXAMPLE

The pneumatic tires of the present invention of the Examples were test produced and the evaluation was made by installing the tires on a truck with a live load of 10 tons (axle constitution of 2-D). For information, the tread patterns of Examples 1 to 3 were the patterns shown in FIGS. 1, 3, and 5, respectively. The depth D of the main grooves 1 was 14.5 mm, the height H of the protrusion 3 is 3 mm, and W, W1, and W2 in FIGS. 8 to 10 were 7 mm, 4.5 mm, and 6.5 mm, respectively, and L1 and L2 were 23 mm and 17 mm, respectively, and the width of the ribs 2 was 38 mm. The length of the sipes 4 of the Example 2 was 2.5 mm, and the length of the notches 5 of the Example 3 was 4 mm, and the opening width of the notches 5 at the sidewall 13 was 5.5 mm.

The tires of the Conventional Examples 1 to 3 were the tires that had the same patterns as those of the Examples 1 to 3 but were not provided with the protrusions. However, the tire of the Conventional Example 2 is provided with the same sipes of that of the Example 2, and the tire of the Conventional Example 3 is provided with the same notches of that of the Example 3, respectively. Although the tire of the Conventional Example 4 has the same pattern as that of the Example 1, it is the tire with the groove bottom extending in a linear manner and with the protrusions arranged at the center of the groove bottom with the width of 3 mm, height of 3 mm, the circumferential length of 6 mm, and at the spaces of 2 mm. Also, the tire size of all the tires was set to be 11R22.5 and the installed rim size was set to be 22.5×7.50, and the inner pressure was set to be 700 kPa.

According to the Table 1, the tire of the present invention can prevent the generation of catching of stones, while maintaining the drainage performance, and further, capable of improving the traction performance at the time of wear. For information, the evaluation methods in each item shown in the Table 1 are as follows. All are the indexes defining the value in the Conventional Example 1 to be 100, and the greater value shows the good performance.

(1) Drainage Performance

Driving on a wet road with water depth of 3 mm accelerating the speed gradually from 50 km per hour and then showing the speed at which hydro planning phenomena occurred (when the change in response from the steering wheel was felt) and the average value by five drivers were observed.

(2) Traction Performance

Driving on a dried road from 60 km per hour and the braking distance was measured. The shorter braking distance shows the good traction performance.

(3) Performance of Preventing Catching of Stones

After driving 10,000 km on a general road, the number of the stones caught in the main grooves was measured.

	TABLE 1
				Conventional	Conventional	Conventional	Conventional
	Example 1	Example 2	Example 3	Example 1	Example 2	Example 3	Example 4
Drainage	100	100	100	100	100	100	100
performance when
the tire is new
Traction	100	100	100	100	100	100	100
performance when
the tire is new
Drainage	95	95	95	100	100	100	60
performance with
80% wear
Traction	110	110	110	100	100	100	90
performance with
80% wear
Catching of stones	120	120	120	100	100	100	135
prevention
performance

Claims

1. A pneumatic tire with not less than three main grooves extending in the tire circumferential direction formed and ribs formed by the main grooves, wherein upper edges of the main groove when the tire is new extend in a linear manner in the tire circumferential direction, the bottom of the main groove extends in a zigzag manner in the tire circumferential direction, the sidewalls of the main groove is provided with concave portions and convex portions, and in the concave portions of at least one of the sidewalls of the main groove, the protrusions that are joined to the bottom of the main groove and to the sidewall are provided.

2. The pneumatic tire as set forth in claim 1, provided with the protrusions at both sidewalls of the main groove.

3. The pneumatic tire as set forth in claim 1, wherein height H from the groove bottom of the protrusions is 10 to 40% of depth D of the main groove.

4. The pneumatic tire as set forth in claim 1, wherein W1 is defined the distance from the protrusion to the opposing sidewall in the groove bottom and W2 is defined the space between the adjacent protrusions in the groove bottom, the larger value between W1 and W2 is not greater than twice as the other value, the smaller value between W1 and W2 is 50 to 70% of the groove width W in the groove bottom except for the protrusions.

5. The pneumatic tire as set forth in claim 1, wherein the circumferential length L2 of the protrusions at the farther side from the sidewall is shorter than the circumferential length L1 of the protrusions at the near side from the sidewall.

6. A pneumatic tire with not less than three main grooves extending in the tire circumferential direction formed and ribs formed by the main grooves, wherein upper edges of the main groove when the tire is new extend in a linear manner in the tire circumferential direction, the bottom of the main groove extends in a zigzag manner in the tire circumferential direction, the sidewalls of the main groove are provided with concave portions and convex portions, in the concave portions of at least one of the sidewalls of the main groove, the protrusions that are joined to the bottom of the main groove and to the sidewall, and the pneumatic tire is provided with sipes that extend from the concave portion to the inner side of the rib in the tire width direction.

7. The pneumatic tire as set forth in claim 6, provided with the protrusions at both sidewalls of the main groove.

8. The pneumatic tire as set forth in claim 6, wherein height H from the groove bottom of the protrusions is 10 to 40% of depth D of the main groove.

9. The pneumatic tire as set forth in claim 6, wherein W1 is defined the distance from the protrusion to the opposing sidewall in the groove bottom and W2 is defined the space between the adjacent protrusions in the groove bottom, the larger value between W1 and W2 is not greater than twice as the other value, the smaller value between W1 and W2 is 50 to 70% of the groove width W in the groove bottom except for the protrusions.

10. The pneumatic tire as set forth in claim 6, wherein the circumferential length L2 of the protrusions at the farther side from the sidewall is shorter than the circumferential length L1 of the protrusions at the near side from the sidewall.

11. A pneumatic tire with not less than three main grooves extending in the tire circumferential direction formed and ribs formed by the main grooves, wherein upper edges of the main groove when the tire is new extend in a linear manner in the tire circumferential direction, the bottom of the main groove extends in a zigzag manner in the tire circumferential direction, the sidewalls of the main groove is provided with concave portions and convex portions, in the concave portions at least one of the sidewalls of the main groove, the protrusions that are joined to the bottom of the main groove and to the sidewall, and the pneumatic tire is provided with notches that extend from the concave portions to the inner side of the rib in the tire width direction.

12. The pneumatic tire as set forth in claim 11, provided with the protrusions at both sidewalls of the main groove.

13. The pneumatic tire as set forth in claim 11, wherein height H from the groove bottom of the protrusions is 10 to 40% of depth D of the main groove.

14. The pneumatic tire as set forth in claim 11, wherein W1 is defined the distance from the protrusion to the opposing sidewall in the groove bottom and W2 is defined the space between the adjacent protrusions in the groove bottom, the larger value between W1 and W2 is not greater than twice as the other value, the smaller value between W1 and W2 is 50 to 70% of the groove width W in the groove bottom except for the protrusions.

15. The pneumatic tire as set forth in claim 11, wherein the circumferential length L2 of the protrusions at the farther side from the sidewall is shorter than the circumferential length L1 of the protrusions at the near side from the sidewall.