JP6439416B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire in which a tread pattern is formed in a tread portion.

In order to improve wet steering stability including the drainage of the pneumatic tire, the tread portion of the tire is provided with a main groove extending in the circumferential direction and a lug groove extending in the width direction. In order to improve the wet performance, it is necessary to increase the groove area ratio. On the other hand, when the groove area ratio is increased, noise during traveling increases. Further, when the groove area ratio is increased, the ground contact area of the tire is reduced, so that the grip force of the tire is reduced, and the steering stability may be reduced. For this reason, in order to reduce noise and improve steering stability, it is required to reduce the groove area ratio.
In order to satisfy the contradictory tire performance in a balanced manner, the width and number of tire circumferential main grooves provided in the tread portion and the inclination angle and width of the lug grooves have been devised.

  By the way, in the tire which attaches importance to the steering stability, in order to increase the grip force, by increasing the interval between the plurality of circumferential main grooves, the length in the tire width direction of the land portion sandwiched between the circumferential main grooves is increased. Increasing the rigidity increases the rigidity of the land. Further, in order to maintain wet steering stability, lug grooves are provided in the region of the land portion sandwiched between the circumferential main grooves. In particular, the land region including the tire center line has a great influence on the wet steering stability, and thus a large number of lug grooves are provided in this region. For this reason, a groove area ratio becomes large in the area | region of the land part containing a tire center line.

  On the other hand, when the interval between the plurality of circumferential main grooves is increased, the contact length in the tire circumferential direction at the land portion sandwiched between the circumferential main grooves is shorter at the center in the tire width direction and longer at both ends in the tire width direction. Tend to be. For this reason, the ground contact shape tends to be a non-uniform shape that becomes concave at the center in the tire width direction at the front end and the rear end. In such a non-uniform contact shape, uneven wear in which both end portions in the tire width direction having a long contact length are worn more easily than the center portion in the tire width direction is likely to occur. In addition, if the ground contact shape is not uniform, there is a problem that steering stability is lowered.

  It has also been attempted to improve uneven wear resistance by causing the tread surface of the land portion to protrude beyond the virtual tread profile (see, for example, Patent Document 1).

JP 2014-118123 A

By the way, if there is a lug groove extending in the tire width direction between two adjacent circumferential main grooves, the amount of rubber in the tread portion decreases in the vicinity of the lug groove, and the rigidity of the land portion decreases. For this reason, the nonuniformity of the ground contact shape that occurs when the interval between the plurality of circumferential main grooves is widened varies depending on the groove area of the land portion. For this reason, even if the tread surface of the land portion protrudes uniformly, it is not possible to eliminate the decrease in steering stability and uneven wear.
Then, an object of this invention is to provide the pneumatic tire which can improve steering stability and abrasion resistance by making the contact | ground shape of a land part uniform.

A first aspect of the present invention is a pneumatic tire having a tread portion provided with a tread pattern,
The tread portion is
A plurality of regions extending in the tire circumferential direction in the tire width direction and defined by three or more circumferential main grooves having different groove widths;
Each region has a different groove area ratio;
The tread of the land portion of each region protrudes outward in the tire radial direction with respect to the reference contour line of the tread portion,
In the region where the groove area ratio is 0% or more and less than 5%, the protrusion amount of the tread from the reference contour line is 0.05 mm or more and less than 0.15 mm,
In the region where the groove area ratio is 5% or more and 10% or less, the protruding amount of the tread surface from the reference contour line is 0.15 mm or more and 0.25 mm or less .

  According to the above-described aspect, the larger the groove area ratio of each region defined by the circumferential main groove, the larger the land surface tread surface of each region protrudes from the reference contour line, so that when the ground is grounded by this protrusion amount The amount of deformation can be offset and the ground contact shape can be made uniform. For this reason, steering stability and abrasion resistance can be improved.

1 is a perspective view showing a pneumatic tire 10 according to a first embodiment of the present invention. It is an expanded view which shows the tread pattern of the pneumatic tire 10 which is 1st Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Whole tire description)
Hereinafter, the pneumatic tire of this embodiment will be described. FIG. 1 is a tire cross-sectional view showing a cross section of a pneumatic tire (hereinafter referred to as a tire) 10 of the present embodiment.
The tire 10 is, for example, a passenger car tire. Passenger car tires are tires defined in Chapter A of JATMA YEAR BOOK 2012 (Japan Automobile Tire Association Standard). In addition, the present invention can also be applied to small truck tires defined in Chapter B and truck and bus tires defined in Chapter C.
The numerical value of the dimension of each pattern element specifically explained below is a numerical example in the tire for passenger cars, and the pneumatic retirement according to the present invention is not limited to these numerical examples.

  The tire circumferential direction described below refers to the direction of rotation of the tread surface (both rotation directions) when the tire 10 is rotated about the tire rotation axis, and the tire radial direction refers to the tire rotation axis. The radial direction extending orthogonally refers to the tire radial direction outer side, which is the side away from the tire rotation axis in the tire radial direction. The tire width direction means a direction parallel to the tire rotation axis direction, and the tire width direction outside means both sides of the tire 10 away from the tire center line CL.

(Tire structure)
The tire 10 includes a pair of bead cores 11, a carcass ply layer 12, and a belt layer 14 as a skeleton material, and a tread rubber member 18, a side rubber member 20, and a bead filler rubber around these skeleton materials. It mainly includes a member 22, a rim cushion rubber member 24, and an inner liner rubber member 26.

The pair of bead cores 11 has an annular shape, and is disposed at both ends in the tire width direction and at inner ends in the tire radial direction.
The carcass ply layer 12 is composed of one or a plurality of carcass ply materials 12a and 12b in which organic fibers are covered with rubber. The carcass ply materials 12 a and 12 b are formed in a toroidal shape by being wound between a pair of bead cores 11.
The belt layer 14 includes a plurality of belt members 14 a and 14 b and is wound around the outer side of the carcass ply layer 12 in the tire radial direction in the tire circumferential direction. The width in the tire width direction of the belt material 14a on the inner side in the tire radial direction is wider than the width of the belt material 14b on the outer side in the tire radial direction.
The belt members 14a and 14b are members in which a steel cord is covered with rubber. The steel cord of the belt material 14a and the steel cord of the belt material 14b are arranged to be inclined at a predetermined angle, for example, 20 to 30 degrees with respect to the tire circumferential direction. The steel cord of the belt material 14a and the steel cord of the belt material 14b are inclined in directions opposite to each other with respect to the tire circumferential direction and cross each other. The belt layer 14 suppresses the expansion of the carcass ply layer 12 due to the filled air pressure.

A tread rubber member 18 is provided outside the belt layer 14 in the tire radial direction. Side rubber members 20 are connected to both ends of the tread rubber member 18. The tread rubber member 18 includes a two-layer rubber member including an upper layer tread rubber member 18a provided on the outer side in the tire radial direction and a lower layer tread rubber member 18b provided on the inner side in the tire radial direction. A rim cushion rubber member 24 is provided at the inner end in the tire radial direction of the side rubber member 20. The rim cushion rubber member 24 comes into contact with a rim on which the tire 10 is mounted. A bead filler rubber member 22 is provided outside the bead core 11 in the tire radial direction so as to be sandwiched between carcass ply layers 12 wound around the bead core 11. An inner liner rubber member 26 is provided on the inner surface of the tire 10 facing the tire cavity region filled with air surrounded by the tire 10 and the rim.
In addition, the tire 10 includes a belt cover layer 28 that covers the outer surface of the belt layer 14 in the tire radial direction. The belt cover layer 28 is made of organic fibers and rubber that covers the organic fibers.

  Although the tire 10 has the tire structure shown in FIG. 1, the tire structure of the pneumatic tire of the present invention is not limited to this.

  FIG. 2 is a development view showing the tread pattern 30 of the pneumatic tire 10. In the tire 10 of the present invention, a tread pattern 30 is formed in a tread portion T as shown in FIG. The tire 10 having the tread pattern 30 can be suitably used for a passenger car tire. Here, the case where the right side in FIG. 2 is the side disposed on the inner side in the vehicle width direction when mounted on the vehicle and the left side in FIG. 2 is the side disposed on the outer side in the vehicle width direction when mounted on the vehicle will be described. .

The tire 10 of the present embodiment has a predetermined tire rotation direction and is mounted on the vehicle so as to rotate in the tire rotation direction R of FIG. 2 when the vehicle moves forward. On the surface of the side rubber member 20 of the tire 10, symbols and information (cereal symbols) for designating the direction of this rotational movement are displayed. In the present embodiment, although not shown, a cereal symbol is provided on the surface of the left side rubber member 20 in FIG. When the tire 10 rotates in the tire rotation direction R, the tread portion T rotates from the top to the bottom in FIG. 2, and the position in contact with the road surface of the tread portion T moves from the bottom to the top in FIG.
In FIG. 2, the symbol CL indicates the center line of the tire. The tread pattern 30 contacts the road surface in the tire width direction region indicated between the contact ends E1 and E2 in a state where the tire 10 is mounted on the vehicle.

  Here, the distance between the grounding ends E1 and E2 is the grounding width W. The ground contact ends E1 and E2 are at both ends of the ground contact surface in the tire width direction when the tire 10 is assembled to a specified rim, filled with a specified internal pressure, and grounded on a horizontal plane under the condition of 80% of the specified load. is there.

  In the present embodiment, the tire width direction W refers to the direction of the rotation center axis of the tire 10 and is the left-right direction in FIGS. Further, the tire circumferential direction C refers to the rotation direction R of the tire 10 and the opposite direction, and is a direction perpendicular to the paper surface of FIG.

  The tread pattern 30 includes a plurality of circumferential main grooves 31, 32, 33, 34, a circumferential sub groove 35, and a plurality of lug groove groups.

The first circumferential main groove 31, the second circumferential main groove 32, the third circumferential main groove 33, the fourth circumferential main groove 34, and the circumferential sub-groove 35 are arranged from the tire ground contact edge E1 side to the tire ground contact edge E2. It is provided in this order toward the side.
The first circumferential main groove 31, the second circumferential main groove 32, the third circumferential main groove 33, the fourth circumferential main groove 34, and the circumferential sub-groove 35 extend in the tire circumferential direction and extend over the entire circumference of the tire. It is provided in an annular shape. In the present embodiment, the first circumferential main groove 31 and the second circumferential main groove 32 are provided closer to the ground contact end E1 than the tire center line CL, and the third circumferential main groove 33 and the fourth circumferential main groove. 34 and a circumferential sub-groove 35 are provided on the ground contact end E2 side of the tire center line CL.

The first lug groove group includes a plurality of first lug grooves 41. The plurality of first lug grooves 41 are provided apart from each other in the tire circumferential direction in a region L1 between the first circumferential main groove 31 and the second circumferential main groove 32.
Each of the first lug grooves 41 starts from a position separated from the first circumferential main groove 31 and the second circumferential main groove 32, and travels in the direction opposite to the tire rotation direction R, and the first circumferential main groove 31. It is inclined toward the side and opens in the first circumferential main groove 31. For this reason, the land portion of the region L1 is continuous in the tire circumferential direction.

The second lug groove group includes a plurality of second lug grooves 42. The plurality of second lug grooves 42 are provided apart from each other in the tire circumferential direction in a region L2 between the second circumferential main groove 32 and the third circumferential main groove 33.
Each of the second lug grooves 42 starts from a position separated from the second circumferential main groove 32 and the third circumferential main groove 33, and travels in the direction opposite to the tire rotation direction R, and the second circumferential main groove 32. It is inclined toward the side and opens in the second circumferential main groove 32. For this reason, the land portion of the region L2 is continuous in the tire circumferential direction. In the present embodiment, the start end of each second lug groove 42 is provided closer to the ground contact end E1 than the tire center line CL.

The third lug groove group includes a plurality of third lug grooves 43. The plurality of third lug grooves 43 are provided apart from each other in the tire circumferential direction in a region L3 between the third circumferential main groove 33 and the fourth circumferential main groove 34.
Each of the third lug grooves 43 starts from a position separated from the third circumferential main groove 33 and the fourth circumferential main groove 34, and travels in the direction opposite to the tire rotation direction R, and the third circumferential main groove 33. It is inclined toward the side and opens in the third circumferential main groove 33. For this reason, the land portion of the region L3 is continuous in the tire circumferential direction.

The fourth lug groove group includes a plurality of fourth lug grooves 44. The plurality of fourth lug grooves 44 are provided apart from each other in the tire circumferential direction in a region L4 between the fourth circumferential main groove 34 and the circumferential sub-groove 35.
Each of the fourth lug grooves 44 starts from a position separated from the fourth circumferential main groove 34 and the circumferential sub-groove 35 and goes in the direction opposite to the tire rotation direction R, and on the fourth circumferential main groove 34 side. It is inclined toward the fourth circumferential main groove 34 and is opened. For this reason, the land portion of the region L4 is continuous in the tire circumferential direction.

By providing the lug groove group, the groove area ratios in the regions L1 to L4 are different. In the present embodiment, the groove area ratio of the region L2 is the largest, the groove area ratio of the region L1 is next to the region L2, the groove area ratio of the region L3 is next to the region L1, and the groove area ratio of the region L4. Is next to the area L3.
When the lug groove group is provided, when the lug grooves 41 to 44 are in the vicinity of the front end of contact, the land portions of the regions L1 to L4 contact the road surface so that the curvature in the tire width direction and the tire circumferential direction becomes zero. Transforms into Since the deformation amount increases as the groove area ratio of each of the regions L1 to L4 increases, the ground contact shape may be nonuniform if the groove area ratios of the regions L1 to L4 are different. The same applies to the rear end of the ground.

In this embodiment, according to the groove area ratio of each area | region L1-L4, the maximum protrusion amount from the reference | standard outline B of a tread is enlarged as the land part of an area | region where a groove area ratio is large. Specifically, since the region with a larger groove area ratio has a larger deformation amount when grounded, the tread of the land portion of each of the regions L1 to L4 protrudes from the reference contour line B according to the deformation amount. . The larger the groove area ratio of each of the regions L1 to L4, the larger the tread of the land portion of each of the regions L1 to L4 protrudes from the reference contour line B indicated by a broken line in FIG. The grounding shape can be made uniform.
For this reason, steering stability and abrasion resistance can be improved.
In the present embodiment, P2>P1>P3> P4, where P1 to P4 are the maximum protrusion amounts from the reference contour line B of the tread surface of the land portion in each of the regions L1 to L4. In addition, since the area | region L4 has the smallest groove area, the protrusion amount P4 from the reference | standard outline B of the tread of the land part of the area | region L4 may be zero.

  Here, the “reference contour line” is a curve fitting (with respect to the four connecting ends of the groove wall and the tread surface of the two circumferential main grooves defining the target land portion in the tire radial cross section ( A curved arc).

Here, the “connection end” is the apex of the corner formed by the groove wall of the circumferential main groove and the tread of the land, and is formed by the groove wall of the circumferential main groove and the tread of the land. If the corner is chamfered, it is the intersection of the chamfered surface and the land tread.
With respect to the position of the connection end, an arc-shaped regression curve can be obtained using the least square method, and this can be used as the reference contour B.

  The maximum protrusion amount from the reference contour line B of the tread of each land portion is preferably 0.05 mm to 2.00 mm. If the maximum protrusion amount is smaller than 0.05 mm, the effect of improving the ground contact shape cannot be obtained sufficiently. On the other hand, when the maximum protrusion amount is larger than 2.00 mm, uneven wear occurs in the center portion of each land portion in the tire width direction.

  The protruding shape from the reference contour line B of the tread of each land portion may be an arbitrary quadratic curve shape (for example, an arc, a parabola, a hyperbola, etc.) passing through both ends of each land portion in the tire radial cross section. Good. As the groove area ratio of each of the regions L1 to L4 is larger, the area of the region surrounded by the tread surface of the land portion and the reference contour line B in the cross section in the tire radial direction is increased, thereby reducing the amount of tread rubber reduction due to the lug groove. It is possible to compensate for the decrease in rigidity of the land portion.

  As an example of increasing the amount of protrusion from the reference contour line B of the tread as the land portion of the region where the groove area ratio is large, for example, when the groove area ratio is 0% or more and less than 5%, the protrusion of the tread from the reference contour B When the amount is 0.05 mm or more and less than 0.15 mm and the groove area ratio is 5% or more and 10% or less, the protruding amount of the tread from the reference contour line B can be 0.15 mm or more and 0.25 mm or less. By setting the protruding amount in this way, uneven wear can be suppressed in a tire having a groove area ratio excluding the circumferential main groove of 10% or less.

[Experimental example]
In order to examine the effects of the tire 10 of the present invention, tires provided with tread patterns having the specifications shown in Tables 1 and 2 below were produced, and the tire performance was evaluated.

The tire size was 215 / 60R17 96H.
In the tires of the conventional examples, comparative examples, reference examples 1 to 8, and examples 1 and 2 , tires having a tread pattern similar to that shown in FIG. 2 were used. The groove area ratios and the protrusion amounts P1 to P3 in the regions L1 to L3 are as shown in Tables 1 and 2, respectively. Note that the protrusion amount P4 in the region L4 is 0 mm.

  As the tire performance of the prototype tire described above, steering stability and uneven wear were evaluated as follows.

[Maneuvering stability]
A passenger car equipped with the above tires was run on a test course, and the driver's steering stability performance was evaluated. The tire pressure was 240 kPa. The evaluation with the tire of the conventional example was evaluated with an index with the reference value (100), and the higher the index, the better the steering stability.

[Uneven wear]
After running the test course for 10,000 km on a vehicle equipped with a new tire, the difference in the amount of wear between the center portion and both end portions in the tire width direction in the region between the second circumferential main groove 32 and the third circumferential main groove 33 Asked. Evaluation was performed using an index with the reciprocal of the amount of wear in the conventional tire as a reference value (100). The higher the index, the better the uneven wear performance.

Comparing Reference Examples 5 to 8 in Table 2 with Examples 1 and 2 , the protrusion amount when the groove area ratio is 0% or more and less than 5% is 0.05 mm or more and less than 0.15 mm, and the groove area ratio is 5 It can be seen that the steering stability and the uneven wear performance are further improved by setting the protrusion amount when the ratio is not less than 10% and not more than 10% to be not less than 0.15 mm and not more than 0.25 mm.

  As mentioned above, although the pneumatic tire of this invention was demonstrated in detail, this invention is not limited to the said embodiment, Of course, in the range which does not deviate from the main point of this invention, you may make a various improvement and change. is there.

CL center line E1, E2 Grounding end T tread portion 30 tread pattern 31 first circumferential main groove 32 second circumferential main groove 33 third circumferential main groove 34 fourth circumferential main groove 35 circumferential subgroove 41 first Lug groove 42 Second lug groove 43 Third lug groove 44 Fourth lug groove

Claims (1)

A pneumatic tire having a tread portion provided with a tread pattern,
The tread portion is
A plurality of regions extending in the tire circumferential direction in the tire width direction and defined by three or more circumferential main grooves having different groove widths;
Each region has a different groove area ratio;
The tread of the land portion of each region protrudes outward in the tire radial direction with respect to the reference contour line of the tread portion,
In the region where the groove area ratio is 0% or more and less than 5%, the protrusion amount of the tread from the reference contour line is 0.05 mm or more and less than 0.15 mm,
In the region where the groove area ratio is 5% or more and 10% or less, the amount of protrusion of the tread surface from the reference contour line is 0.15 mm or more and 0.25 mm or less .

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