JP2019026010A - tire - Google Patents

Abstract

[Problem] To provide a tire capable of improving the resistance to rocking of a main groove and suppressing cracks in the groove bottom.
A tire 1 is provided with a main groove 3 extending continuously in a tire circumferential direction in a tread portion 2. The main groove 3 includes a maximum width portion 4 where the groove width measured on the tread tread 2a is maximum and a minimum width portion 5 where the groove width is minimum, and the groove width changes between these. Yes. The groove bottom 4a of the maximum width portion 4 is provided with a stone biting prevention protrusion 8 that locally protrudes outward in the tire radial direction. The protrusion 8 is a tire having a height in the center portion in the tire circumferential direction that is larger than both ends in the tire circumferential direction.
[Selection] Figure 1

Description

  The present invention relates to a tire, and more particularly to a tire having a groove bottom provided with a protrusion for preventing stone biting.

  A main groove for drainage is usually provided in the tread portion of the tire. When traveling on a gravel road that is not paved with such tires, so-called stone biting may occur in which stones are caught in the main groove. When the tire is run with the stone bite generated, the trapped stone spreads the main groove and moves to the groove bottom side, causing a problem of cracking at the groove bottom.

  In order to suppress the cracks, for example, it is known to provide a stone biting prevention protrusion that locally protrudes outward in the tire radial direction at the bottom of the main groove.

Japanese Patent No. 5134662

  However, in recent years, it has been desired to further improve the stone biting performance and suppress groove bottom cracks.

  The present invention has been devised in view of the above problems, and a main object of the present invention is to provide a tire capable of improving the stone-resisting performance of the main groove and suppressing cracks in the groove bottom.

  The present invention is a tire provided with a main groove continuously extending in a tire circumferential direction in a tread portion, wherein the main groove has a maximum width portion where a groove width measured on a tread surface is maximized; And a minimum width portion having a minimum groove width, and the width of the groove changes between them, and the bottom of the maximum width portion has a stone bite locally raised outward in the tire radial direction. Protrusion portions for prevention are provided, and the height of the central portion in the tire circumferential direction is greater than the both end portions in the tire circumferential direction.

  In the tire according to the present invention, the main groove has a pair of groove walls that connect between the groove bottom and the tread surface, and the pair of groove walls has a distance from the groove bottom side. It is desirable that the angle of the pair of groove walls with respect to the normal line standing on the tread surface is gradually increased from the minimum width portion toward the maximum width portion. .

  In the tire according to the present invention, it is desirable that the width of the groove bottom is substantially constant.

  In the tire according to the present invention, the protrusion is disposed across the position of the maximum width portion of the main groove in the tire circumferential direction, and the position where the height of the protrusion is the largest is the maximum of the main groove. It is desirable to align the position of the large part.

  In the tire according to the present invention, it is preferable that the length of the protrusion in the tire circumferential direction gradually decreases toward the outer side in the tire radial direction in a cross-sectional view along the longitudinal direction of the main groove.

  In the tire according to the present invention, it is desirable that the width of the protrusion in the tire axial direction gradually increases from both ends in the tire circumferential direction toward the center in the tire circumferential direction.

  In the tire according to the present invention, the groove width of the maximum width portion is desirably 1.3 to 1.5 times the groove width of the minimum width portion.

  In the tire according to the present invention, the width of the groove bottom is preferably 0.3 to 0.5 times the groove width of the minimum width portion.

  In the tire according to the present invention, it is desirable that the width of the protrusion in the tire axial direction is not less than 0.3 times and less than 1.0 times the width of the groove bottom.

  In the tire according to the present invention, the length in the tire circumferential direction of the protrusion is 0.3 to 0.5 times the length in the tire circumferential direction between the maximum width portion and the minimum width portion. Is desirable.

  In the tire according to the present invention, it is preferable that the height of the protrusion in the tire radial direction is 0.25 to 0.35 times the groove depth of the main groove.

  The tire of the present invention is provided with a main groove whose groove width varies between the maximum width portion and the minimum width portion. Such a main groove can move a stone sandwiched between the main grooves toward the maximum width portion having a smaller resistance by using a driving force or a braking force due to rolling of the tire. On the other hand, the groove bottom of the maximum width portion is provided with a protruding portion having a height in the central portion in the tire circumferential direction that is larger than both ends in the tire circumferential direction. For this reason, the stone that has moved to the maximum width portion is gradually pushed out toward the outer side in the tire radial direction and discharged as the contact with the protrusion proceeds.

It is an expanded view of the tread part of the tire of one embodiment of the present invention. It is an enlarged view of the main groove of FIG. It is a perspective view of the main groove of FIG. (A) is the sectional view on the AA line of FIG. 1, (b) is the sectional view on the BB line of FIG. (A) is sectional drawing of the main groove of other embodiment, (b) is sectional drawing of other embodiment. It is CC sectional view taken on the line of FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a development view of a tread portion 2 of a tire 1 showing an embodiment of the present invention. In this embodiment, a pneumatic tire for a small truck is shown as a preferable aspect. However, it goes without saying that the present invention can be applied to tires 1 of other categories such as for passenger cars, motorcycles, and heavy loads.

  As shown in FIG. 1, the tread portion 2 of the present embodiment is provided with a main groove 3 that extends continuously in the tire circumferential direction.

  The main groove 3 of the present embodiment includes a pair of shoulder main grooves 3A and 3A arranged closest to the tread end Te side, and a pair of crown main grooves 3B arranged between the shoulder main groove 3A and the tire equator C, 3B. In the present invention, the main groove 3 is not limited to four such grooves, and may be an embodiment in which, for example, two to four are provided.

  The “tread end Te” is obtained when a normal load is loaded on a normal rim that is assembled with a normal rim and filled with a normal internal pressure, and a normal load is applied to the flat tire with a camber angle of 0 degrees. It is determined as the ground contact position on the outermost side in the tire axial direction. In the normal state, the distance in the tire axial direction between the tread ends Te and Te is determined as the tread width TW. When there is no notice in particular, the dimension of each part of the tire 1 is a value measured in a normal state.

  The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, “standard rim” for JATMA, “Design Rim” for TRA, “ETRTO” If so, it is "Measuring Rim".

  “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. “JATIMA” is the “maximum air pressure”, TRA is the table “TIRE LOAD LIMITS” The maximum value described in "AT VARIOUS COLD INFLATION PRESSURES", or "INFLATION PRESSURE" in ETRTO. When the tire is for a passenger car, the normal internal pressure is 180 kPa.

  “Regular load” is the load determined by each standard for each tire in the standard system including the standard on which the tire is based. “JATMA” is “Maximum load capacity”, TRA is “TIRE LOAD” The maximum value described in “LIMITS AT VARIOUS COLD INFLATION PRESSURES”, or “LOAD CAPACITY” in ETRTO. When the tire is for a passenger car, the normal load is a load corresponding to 88% of the load.

  FIG. 2 is an enlarged view of the main groove 3. FIG. 3 is a perspective view of the main groove 3. As shown in FIGS. 2 and 3, the main groove 3 includes a maximum width portion 4 where the groove width W measured on the tread tread surface 2 a is maximum, and a minimum width portion 5 where the groove width W is minimum. And the groove width W is changing between these. Such a main groove 3 can move a stone sandwiched between the main grooves 3 to the maximum width portion 4 having a smaller resistance by using a driving force or a braking force due to rolling of the tire 1. The tread surface 2a is a portion that contacts the road surface when the tire 1 rolls.

  The groove bottom 4a of the maximum width portion 4 is provided with a stone biting prevention protrusion 8 that locally protrudes outward in the tire radial direction. The protrusion 8 has a height h (shown in FIG. 4A) of the central portion 10 in the tire circumferential direction that is greater than both end portions 9 and 9 in the tire circumferential direction. As a result, as described above, the stone moved to the maximum width portion 4 side is pushed out from the central portion 10 side to the tire radial direction outer side of the main groove 3 through the end portion 9 as the contact with the projection portion 8 proceeds. Discharged. Therefore, the main groove 3 of the present embodiment has excellent stone biting performance.

  In the present embodiment, the main groove 3 has a maximum width portion 4 and a minimum width portion 5 arranged alternately along the longitudinal direction of the main groove 3. Thereby, the above-mentioned effect is exhibited over the tire circumferential direction.

  The main groove 3 has a groove width W that gradually increases from the minimum width portion 5 toward the maximum width portion 4. As a result, the resistance to the stone gradually decreases from the minimum width portion 5 toward the maximum width portion 4, so that the stone sandwiched between the main grooves 3 moves smoothly from the minimum width portion 5 side toward the maximum width portion 4 side. obtain.

  In the main groove 3 of the present embodiment, the groove center line 3k extends linearly along the tire circumferential direction. Such a main groove 3 has excellent stone biting performance and drainage performance. In addition, the main groove 3 is not limited to such an aspect, For example, the groove centerline 3k may extend in zigzag shape or circular arc shape.

  In the present embodiment, the main groove 3 has groove edges 3e and 3e on both sides extending in the tire circumferential direction extending in a linear zigzag shape. Further, the groove edges 3e and 3e on both sides of the main groove 3 are inclined at the same angle α with respect to the tire circumferential direction. Such a main groove 3 facilitates the movement of the stone in the main groove 3 while maintaining a small resistance to the stone in the main groove 3 (the force for sandwiching the stone). In addition, the main groove 3 is not limited to such an aspect, For example, the groove edge 3e, 3e of both sides may extend in a wave shape (illustration omitted). The main groove 3 may be configured such that one groove edge 3e extends along the tire circumferential direction and the other groove edge 3e extends while being inclined with respect to the tire circumferential direction.

  The groove width Wa of the maximum width portion 4 is desirably 1.3 to 1.5 times the groove width Wb of the minimum width portion 5. When the groove width Wa of the maximum width portion 4 is less than 1.3 times the groove width Wb of the minimum width portion 5, the change in resistance to the stone is small, and there is a possibility that the stone cannot move in the main groove 3. When the groove width Wa of the maximum width portion 4 exceeds 1.5 times the groove width Wb of the minimum width portion 5, the rigidity step in the tire axial direction of the tread portion 2 becomes large, and the steering stability performance may be deteriorated. The groove width Wa of the maximum width portion 4 is preferably 7.0 to 14.0 mm, and more preferably 7.0 to 12.0 mm, for example.

  From the same viewpoint, the length L1 in the tire circumferential direction between the maximum width portion 4 and the minimum width portion 5 is desirably 2.0 to 3.5 times the groove width Wa of the maximum width portion 4.

  FIG. 4A is a cross-sectional view taken along line AA in FIG. As shown in FIG. 4A, the main groove 3 includes a groove bottom 3a and a pair of groove walls 3b and 3b connecting the groove bottom 3a and the tread surface 2a.

  The groove bottom 3a of the present embodiment is formed in a straight line extending along a virtual line 3c that connects between the tread treads 2a and 2a. In addition, the groove bottom 3a is not limited to such an aspect, For example, as shown to Fig.5 (a), the aspect formed in the circular arc shape convex inward in the tire radial direction may be sufficient. In this embodiment, both ends 3i and 3i of the groove bottom 3a are connected to the groove walls 3b and 3b via arc portions 3f and 3f having a radius of curvature r smaller than the radius of curvature of the groove bottom 3a. As shown in FIG. 5B, the groove bottom 3a may be formed on the groove center line 3k in an arc shape having a minimum radius of curvature at the groove bottom 3a. In the case of this aspect, a region from the position where the depth is maximum to 10% of the groove depth D is defined as the groove bottom 3a.

  As shown in FIG. 4A, the groove wall 3b of the present embodiment is formed in a straight line between the groove bottom 3a and the tread surface 2a. The groove wall 3b is not limited to such an embodiment, and may be formed, for example, in a convex arc shape toward the outside of the main groove 3 (shown in FIG. 5B).

  The pair of groove walls 3b and 3b are inclined such that the distance W1 therebetween increases from the groove bottom 3a side toward the tread surface 2a. Such a groove wall 3b generates a reaction force to the outer side in the tire radial direction with respect to the stone sandwiched between the main grooves 3, and therefore, the effect of suppressing the penetration of the stone into the groove bottom 3a side and the outside of the main groove 3 of the stone Exhibits the effects of emissions.

  FIG. 4B is a cross-sectional view taken along line BB in FIG. As can be understood from FIGS. 3 and 4, the angle θ with respect to the normal n standing on the tread surface 2 a of the pair of groove walls 3 b and 3 b gradually increases from the minimum width portion 5 toward the maximum width portion 4. . As a result, the force for sandwiching the stone toward the maximum width portion 4 side is effectively reduced, so that the stone sandwiched in the main groove 3 is easily moved to the maximum width portion 4 side.

  Although not particularly limited, the angle θa of the groove wall 3b in the maximum width portion 4 is preferably 15 to 35 degrees from the viewpoint of exerting the above-described effect while ensuring the rigidity of the tread portion 2. Moreover, as for the said angle (theta) b of the groove wall 3b in the minimum width part 5, 5-20 degree is desirable. Further, it is desirable that the angle θ is increased by 0.2 to 0.6 degrees / mm from the minimum width portion 5 toward the maximum width portion 4, and more preferably, it is increased by 0.4 degrees / mm.

  In the present embodiment, the width W2 of the groove bottom 3a of the main groove 3 is substantially constant. For this reason, while the smooth movement main of the stone in the main groove 3 is ensured, the smooth flow of the waste_water | drain in the groove | channel 3 is ensured.

  The width W2 of the groove bottom 3a is preferably 0.3 to 0.5 times the groove width Wb of the minimum width portion 5. When the width W2 of the groove bottom 3a is less than 0.3 times the groove width Wb of the minimum width portion 5, the drainage performance may be deteriorated. When the width W2 of the groove bottom 3a exceeds 0.5 times the groove width Wb of the minimum width portion 5, the angle θb of the groove wall 3b becomes small in the minimum width portion 5 and the stone sandwiched in the main groove 3 There is a possibility that the reaction force outward in the tire radial direction is reduced.

  FIG. 6 is a cross-sectional view taken along the line CC of FIG. As shown in FIG. 6, in the cross-sectional view along the longitudinal direction of the main groove 3, the protrusion 8 is disposed across the circumferential direction of the tire in the present embodiment, and the protrusion 8 The position where the height h is the largest is aligned with the position of the maximum width portion 4. That is, the position where the height h of the protrusion 8 is the largest is located at the maximum width part 4 where the resistance to the stone is the smallest, so that the stone in the main groove 3 is more effectively removed from the protrusion 8. It is discharged to the outside of the groove 3 in the tire radial direction.

  The protrusion 8 has a tire circumferential length La that gradually decreases outward in the tire radial direction. Such a protrusion 8 can effectively push up the stone from the end 9 of the protrusion 8 toward the central portion 10 as described above, and thus exhibits excellent stone biting performance.

  The protrusion 8 is formed in a trapezoidal shape in the sectional view. In addition, the shape of the protrusion part 8 is not limited to such an aspect, For example, the shape which is line-symmetrical about the maximum width part 4 containing circular arc shape and triangular shape may be sufficient (illustration omitted). In addition, each shape is not limited to the shape in a strict meaning, and if it is an aspect which demonstrates the effect which pushes up the stone in the main groove 3, it is a shape which can be understood as the shape at a glance. Good.

  The length L (maximum length) of the protrusion 8 in the tire circumferential direction is desirably 0.3 to 0.5 times the length L1 between the maximum width portion 4 and the minimum width portion 5. When the length L of the protrusion 8 is less than 0.3 times the length L1, the chance of contact between the stone and the protrusion 8 is reduced, and the stone may not be discharged smoothly. When the length L of the protrusion 8 exceeds 0.5 times the length L1, the groove volume becomes small, and the drainage performance may be deteriorated.

  The height h of the protrusion 8 is preferably 0.25 to 0.35 times the groove depth D of the main groove 3. When the height h of the protrusion 8 is less than 0.25 times the groove depth D of the main groove 3, there is a possibility that the stone cannot be effectively discharged out of the main groove 3. When the height h of the protruding portion 8 exceeds 0.35 times the groove depth D of the main groove 3, the protruding portion 8 is likely to buckle and the stone pushing force is reduced, so that the stone cannot be discharged. There is a fear. Moreover, the groove volume of the main groove 3 becomes small and there exists a possibility that drainage performance may deteriorate.

  As shown in FIGS. 2 and 3, it is desirable that the width w of the protrusion 8 in the tire axial direction gradually increases from both end portions 9 and 9 in the tire circumferential direction toward the central portion 10 in the tire circumferential direction. Such a protruding portion 8 has a pair of side surfaces 8a, 8a extending in the tire circumferential direction to generate a reaction force that moves the stone toward the both end portions 9, 9 side, and therefore, between the protruding portion 8 and the groove wall 3b. To prevent stones from being caught in

  In the present embodiment, the width w of the protrusion 8 in the tire axial direction is the maximum at the groove bottom 3 a of the central portion 10. As a result, the side surface 8a also generates a reaction force that moves the stone to the outside in the tire radial direction, and thus more effectively suppresses the stone from being sandwiched between the protrusion 8 and the groove wall 3b. Moreover, such a protrusion 8 contacts the groove bottom 3a with a large area. For this reason, since the chip | tip of the protrusion part 8 etc. are suppressed, it has further high stone-resisting performance.

  In order to effectively exhibit the above-described action, the contour shape at the groove bottom 3a of the protrusion 8 is preferably, for example, a hexagonal shape or a barrel shape.

  The width w of the protrusion 8 in the tire axial direction is desirably 0.3 times or more and less than 1.0 times the width W2 of the groove bottom 3a. When the width w of the protruding portion 8 is less than 0.3 times the width W2 of the groove bottom 3a, the rigidity of the protruding portion 8 is lowered, and there is a possibility that a rubber chip or the like may occur due to contact with a stone. When the width w of the protrusion 8 is 1.0 times or more the width W2 of the groove bottom 3a, that is, when the protrusion 8 is formed so as to connect between the groove walls 3b and 3b, the groove volume of the main groove 3 There is a risk that drainage performance will deteriorate.

  Such a protrusion 8 of the present invention is preferably provided in the main groove 3 on the tire equator C side, which in the present embodiment is likely to bite by stone, due to the large contact pressure acting, in this embodiment, the crown main groove 3B. However, the protrusion 8 may be provided in the shoulder main groove 3A.

  When a lateral groove (not shown) extending in the tire axial direction communicates with the main groove 3 provided with the protrusion 8, the stone moving in the main groove 3 is sandwiched between the lateral grooves, so that the movement of the stone is suppressed, and the stone resistant The biting performance may be reduced. For this reason, it is desirable that the lateral groove is not communicated with the main groove 3 provided with the protrusion 8. In the present specification, the lateral groove refers to a groove-like body having a groove width measured by the tread surface 2a of 1.5 mm or more.

  As mentioned above, although embodiment of this invention was explained in full detail, it cannot be overemphasized that this invention is not limited to exemplary embodiment, and can be deform | transformed and implemented in a various aspect.

A tire of size 205 / 85R16 having the basic pattern of FIG. 1 was prototyped based on the specifications in Table 1, and the stone biting performance of each sample tire was tested. The main common specifications and test methods for each sample tire are as follows.
Maximum groove width Wa of main groove: 14mm
Minimum groove width Wb of main groove: 10 mm (excluding Comparative Example 1)
Maximum width portion and minimum width portion length L1: 20 mm (excluding Comparative Example 1)
Groove depth D of main groove: 10.5mm
Groove bottom width W2: 4.0 mm (Example 4 is the minimum value)
Projection height h: 3.0 mm (excluding Comparative Example 1)
Protrusion width w: 2.0 mm (excluding Comparative Example 1)
Projection length L / L1: 50% (excluding Comparative Example 1)

<Stone-resistant performance>
Each sample tire was mounted on all wheels of a 3000 cc light truck under the following conditions. Then, the test driver drove the test course on the unpaved gravel road surface, and the occurrence of stone biting (stone biting performance) after running was evaluated by visual inspection of the test driver. The result is indicated by the number of stone bites generated in one center main groove. The smaller the value, the better.
Rim: 5.5J
Internal pressure: 600kPa
Longitudinal load: 29.4kN
Mileage: 10km
Table 1 shows the test results.

  As a result of the test, it was confirmed that the tire of the example had improved stone biting performance as compared with the tire of the comparative example. Thereby, it is understood that the crack of the groove bottom is suppressed in the tire of the example as compared with the tire of the comparative example.

DESCRIPTION OF SYMBOLS 1 Tire 2 Tread part 2a Tread surface 3 Main groove 4 Maximum width part 4a Groove bottom 5 Minimum width part 8 Projection part 9 End part 10 Center part

Claims (11)

In the tread portion, a tire provided with a main groove extending continuously in the tire circumferential direction,
The main groove includes a maximum width portion where the groove width measured on the tread tread is the maximum, and a minimum width portion where the groove width is the minimum, and the groove width changes between them. ,
On the groove bottom of the maximum width portion, there is provided a protrusion for preventing stone biting that locally protrudes outward in the radial direction of the tire,
The height of the central portion in the tire circumferential direction is larger than the both end portions in the tire circumferential direction,
tire. The main groove has a pair of groove walls that connect between the groove bottom and the tread surface.
The pair of groove walls are inclined such that the distance between them increases from the groove bottom side toward the tread surface.
The tire according to claim 1, wherein an angle of the pair of groove walls with respect to a normal line standing on the tread surface is gradually increased from the minimum width portion toward the maximum width portion.   The tire according to claim 1 or 2, wherein a width of the groove bottom is substantially constant. The protrusion is disposed across the tire circumferential direction at the position of the maximum width of the main groove,
The tire according to any one of claims 1 to 3, wherein a position where the height of the protrusion is the largest is aligned with a position of a maximum width portion of the main groove.   The tire according to any one of claims 1 to 4, wherein the protrusion has a tire circumferential length that gradually decreases outward in the tire radial direction in a cross-sectional view along the longitudinal direction of the main groove.   The tire according to any one of claims 1 to 5, wherein a width of the protruding portion in the tire axial direction gradually increases from both end portions in the tire circumferential direction toward a central portion in the tire circumferential direction.   The tire according to any one of claims 1 to 6, wherein a groove width of the maximum width portion is 1.3 to 1.5 times a groove width of the minimum width portion.   The tire according to any one of claims 1 to 7, wherein a width of the groove bottom is 0.3 to 0.5 times a groove width of the minimum width portion.   The tire according to any one of claims 1 to 8, wherein a width of the protrusion in the tire axial direction is not less than 0.3 times and less than 1.0 times the width of the groove bottom.   The length in the tire circumferential direction of the protrusion is 0.3 to 0.5 times the length in the tire circumferential direction between the maximum width portion and the minimum width portion. The tire described in Crab.   The tire according to any one of claims 1 to 10, wherein a height of the protrusion in a tire radial direction is 0.25 to 0.35 times a depth of the main groove.

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