JP5749441B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

In this type of pneumatic tire, various means have been conventionally proposed as means for reducing rolling resistance, for example, as shown in Patent Document 1 below, but it is also conceivable to simply reduce the thickness of the tread portion. .
However, in this case, since the depth of the circumferential groove is inevitably reduced, it is necessary to maintain the hydroplaning performance by increasing the width of the circumferential groove to suppress a decrease in the internal volume of the circumferential groove.

JP-A-5-246208

  However, in such a pneumatic tire, since the contact area of the tread portion is reduced by increasing the width of the circumferential groove, the lateral force generated in the pneumatic tire during cornering is reduced and the cornering power is reduced. As a result, the handling stability may be reduced.

  The present invention has been made in view of such circumstances, and provides a pneumatic tire capable of reducing rolling resistance while maintaining hydroplaning performance without deteriorating steering stability. Objective.

In order to solve the above problems and achieve such an object, in the pneumatic tire of the present invention, a plurality of circumferential grooves extending in the tire circumferential direction are formed in the tread portion at intervals in the tire width direction. Each of the pair of side wall surfaces defining the circumferential grooves of the tires is a pneumatic tire that gradually extends away from the inner side toward the outer side in the tire radial direction, and the thickness of the tread portion is the tire outer diameter. 0.0120 times or more and 0.0155 times or less, and the depth of the circumferential groove is 0.725 times or more and 0.800 times or less of the thickness of the tread portion, and the widths of the plurality of circumferential grooves are added together. A total width is 0.2 times or more and 0.3 times or less of the tread contact width, and a pair of first side wall surfaces that individually define end circumferential grooves positioned at both ends in the tire width direction among the plurality of circumferential grooves. Each perpendicular to the outer surface of the tread The angle of inclination is different from each other, and among the plurality of circumferential grooves, the perpendicular to at least one of the pair of second side wall surfaces that define an inner circumferential groove located on the inner side in the tire width direction than the end circumferential groove The inclination angle is larger than the smaller one of the inclination angles of the pair of first side wall surfaces , and is positioned on both ends in the tire width direction on the tread portion by the plurality of circumferential grooves. A shoulder rib and an inner rib positioned between the shoulder ribs, and the inclined angle of at least one of the pair of side wall surfaces defining the inner rib is the pair of first ribs. It is characterized by being larger than the smaller one of the inclination angles of one side wall surface .

According to this invention, the thickness of the tread portion is 0.0120 times or more and 0.0155 times or less of the tire outer diameter, and the depth of the circumferential groove is 0.725 times or more and 0.800 times the thickness of the tread portion. Since the total width of the plurality of circumferential grooves is not less than 0.2 times and not more than 0.3 times the tread ground contact width, the rolling resistance can be reduced while maintaining the hydroplaning performance.
In addition, when the thickness of the tread portion is smaller than 0.0120 times the tire outer diameter, for example, durability and ride comfort may be lowered, or it may be difficult to maintain hydroplaning performance. When it becomes larger than twice, it becomes difficult to reduce rolling resistance. Further, when the depth of the circumferential groove is smaller than 0.725 times the thickness of the tread portion, for example, durability may be lowered, or maintenance of hydroplaning performance may be difficult. When it becomes large, there is a possibility that, for example, durability is lowered or steering stability is lowered. Furthermore, if the total width of the plurality of circumferential grooves is less than 0.2 times the tread contact width, it becomes difficult to maintain the hydroplaning performance, and if it exceeds 0.3 times, the steering stability may be greatly reduced. is there.
Further, the inclination angle of at least one of the pair of second side wall surfaces defining the inner circumferential groove is the smaller of the inclination angles of the pair of first side wall surfaces defining the end circumferential groove. Therefore, the ribs defined by the plurality of circumferential grooves on the tread portion can be made difficult to fall down in the tire width direction, and the tread portion caused by such deformation of the ribs can be achieved. The reduction of the ground contact area can be suppressed. Accordingly, it is possible to suppress a decrease in lateral force generated in the pneumatic tire during cornering, and it is possible to prevent a decrease in steering stability.
The larger of the inclination angles of at least one of the pair of second side wall surfaces defining the inner circumferential groove, the inclination angle of each of the pair of first side wall surfaces defining the end circumferential groove. It may be equivalent to the inclination angle.

  Here, the inclination angles of the pair of second side wall surfaces are equal to each other, and the inclination angle of the first side wall surface located inside the tire width direction among the pair of first side wall surfaces. And may be larger than the inclination angle of the first side wall surface located outside in the tire width direction.

  In this case, it is possible to reliably suppress the inner ribs between the shoulder ribs located at both ends in the tire width direction from falling down in the tire width direction among the plurality of ribs. Therefore, for example, the above-described effects can be effectively achieved at a low load when the contact area of the tread portion is relatively small and the ratio of the tire equator portion to the contact area is relatively high.

  Further, the mounting direction to the vehicle is clearly indicated, and in each of the plurality of circumferential grooves, of the pair of side wall surfaces, the inclination of the side wall surface located on the vehicle outer side is greater than the side wall surface located on the vehicle inner side. It can be bigger.

  In this case, in each of the plurality of circumferential grooves, of the pair of side wall surfaces, the side wall surface positioned on the vehicle outer side has a larger inclination angle than the side wall surface positioned on the vehicle inner side. When a vertical compressive load is applied to the entering tire, a shearing force toward the vehicle inner side along the tire width direction is generated in each of the plurality of ribs. Therefore, it is possible to increase the lateral force generated in the pneumatic tire during cornering, and it is possible to more reliably prevent the steering stability from being lowered.

  According to the pneumatic tire according to the present invention, it is possible to reduce rolling resistance while maintaining hydroplaning performance without reducing steering stability.

It is a part of sectional drawing which follows the tire width direction of the pneumatic tire shown as one Embodiment which concerns on this invention. It is a part of sectional drawing which follows the tire width direction of the pneumatic tire shown as another embodiment which concerns on this invention.

Hereinafter, an embodiment of a pneumatic tire according to the present invention will be described with reference to FIG.
In the pneumatic tire 1 of the present embodiment, as shown in FIG. 1, a steel belt layer 16 is interposed between a crown portion 12 a of a carcass 12 extending in a toroidal shape between a pair of left and right bead cores 11 and a tread portion 13. Is provided. In the illustrated example, the steel belt layer 16 has a two-layer structure in which a first steel cord layer 14 and a second steel cord layer 15 are laminated in the tire radial direction. Further, in each of the steel cord layers 14 and 15, steel cords extending in directions inclined with respect to the tire width direction H and the tire circumferential direction in the creeping direction perpendicular to the tire radial direction are inclined in the creeping direction. A plurality of them are embedded in a direction orthogonal to the direction. The extending directions of the steel cords embedded in the steel cord layers 14 and 15 are opposite to each other. In the state where the steel cord layers 14 and 15 are laminated in the tire radial direction as described above, The steel cords embedded in the steel cord layers 14 and 15 intersect with each other in a plan view of the tread portion 13.

  In the illustrated example, each of the first and second steel cord layers 14 and 15 has a center portion in the width direction at the center portion in the tire width direction H of the pneumatic tire 1 (hereinafter referred to as a tire equator portion CL). In the state where it is positioned at, it extends continuously over the entire circumference in the tire circumferential direction. Further, the first steel cord layer 14 is disposed on the inner side in the tire radial direction than the second steel cord layer 15 and is formed wider than the second steel cord layer 15.

  The tread portion 13 is formed with a plurality (four in the illustrated example) of circumferential grooves 18 and 19 extending in the tire circumferential direction at intervals in the tire width direction H. The pair of side wall surfaces 21 and 22 that define the circumferential grooves 18 and 19 separately extend in directions that gradually move away from each other in the tire radial direction from the inside to the outside. Further, the plurality of circumferential grooves 18 and 19 are arranged in line symmetry with respect to the tire equator CL at a position where the tire equator CL is avoided in the tread portion 13. By these circumferential grooves 18 and 19, the outer peripheral surface of the tread portion 13 is partitioned into a plurality of ribs 20.

Here, in the present embodiment, the thickness C of the tread portion 13 is 0.0120 times or more and 0.0155 times or less of the tire outer diameter E. The thickness C of the tread portion 13 is, for example, about 0.01405 times the tire outer diameter E. Further, the depth D of the circumferential grooves 18 and 19 is 0.725 to 0.800 times the thickness C of the tread portion 13. The depth D of the circumferential grooves 18 and 19 is, for example, about 0.785 times the thickness C of the tread portion 13. Further, the total width obtained by adding the widths B of the plurality of circumferential grooves 18 and 19 is not less than 0.2 times and not more than 0.3 times the tread ground contact width TW. The total width of the plurality of circumferential grooves 18 and 19 is, for example, about 0.25 times the tread grounding width TW.
Here, the thickness C of the tread portion 13 is a distance in the tire radial direction between the outer peripheral surface of the tread portion 13 and the outer peripheral surface of the second steel cord layer 15. Further, the width B of the circumferential groove 18 is the width of the outer end of each circumferential groove 18 in the tire radial direction.

  And in this embodiment, the outer periphery of the tread part 13 of each of a pair of 1st side wall surface 21 which respectively defines the end peripheral groove 18 located in the both ends of the tire width direction H among several peripheral grooves 18 and 19. The inclination angles θ1 and θ2 and θ7 and θ8 with respect to the perpendicular L perpendicular to the surface are different from each other. In addition, among the plurality of circumferential grooves 18 and 19, at least one of the pair of second side wall surfaces 22 that individually define the inner circumferential groove 19 positioned on the inner side in the tire width direction H than the end circumferential groove 18. The inclination angles θ3, θ4, θ5, and θ6 with respect to the perpendicular L are larger than the smaller inclination angles θ1 and θ8 of the pair of first side wall surfaces 21 among the inclination angles θ1 and θ2 and θ7 and θ8. . In the example shown in the figure, between the two end circumferential grooves 18, the smaller ones of the inclination angles θ1 and θ2 and θ7 and θ8 of the pair of first side wall surfaces 21 are equal to each other. It has become.

  Further, in the present embodiment, the inclination angles θ3 to θ6 of the pair of second side wall surfaces 22 that respectively define the plurality of inner circumferential grooves 19 are made equal to each other, and the two end circumferential grooves 18 are formed on the respective end circumferential grooves 18. Of the pair of first side wall surfaces 21 separately defined, the inclination angle θ2 is equal to the inclination angle θ2 of the first side wall surface 21 located inside the tire width direction H, and located outside the tire width direction H. It is larger than the inclination angles θ1 and θ8 of the first side wall surface 21.

  In the illustrated example, the inclination angles θ2 to θ7 are 10 ° or more larger than the inclination angles θ1 and θ8. For example, the inclination angles θ2 to θ7 are about 20 °, and the inclination angles θ1 and θ8 are about 5 °. The two end circumferential grooves 18 are formed symmetrically with respect to the tire equator portion CL, and the two inner circumferential grooves 19 positioned between the end circumferential grooves 18 have the same shape and size. Yes. Further, the widths B of the plurality of circumferential grooves 18 and 19 are all equal to each other, and the depths D of these circumferential grooves 18 and 19 are all equal to each other.

  As described above, according to the pneumatic tire 1 of the present embodiment, the thickness C of the tread portion 13 is 0.0120 times or more and 0.0155 times or less of the tire outer diameter E, and the circumferential grooves 18 and 19 The depth D is 0.725 times or more and 0.800 times or less of the thickness C of the tread portion 13, and the total width of the plurality of circumferential grooves 18 and 19 is 0.2 times or more and 0.3 times the tread grounding width TW. Since it is less than twice, rolling resistance can be reduced while maintaining hydroplaning performance.

  Further, the inclination angles θ3 to θ6 of at least one of the pair of second side wall surfaces 22 that respectively define the plurality of inner circumferential grooves 19 are defined as a pair of second circumferential grooves 18 that individually define the two end circumferential grooves 18. Each of the side wall surfaces 21 is larger than the smaller inclination angles θ1 and θ8 of the inclination angles θ1 and θ2 and θ7 and θ8, and thus is partitioned by the plurality of circumferential grooves 18 and 19 on the tread portion 13. The rib 20 can be made difficult to fall down in the tire width direction H, and a reduction in the contact area of the tread portion 13 due to the deformation of the rib 20 can be suppressed. Therefore, it is possible to suppress a decrease in lateral force generated in the pneumatic tire 1 during cornering, and it is possible to prevent a decrease in steering stability.

Further, in the present embodiment, the inclination angles θ2 to θ7 are equal to each other, and the inclination angles θ1 and θ8 of the first side wall surface 21 located outside the tire width direction H of the pair of first side wall surfaces 21 are the same. Therefore, the inner ribs 20 between the shoulder ribs 20 located at both ends in the tire width direction H among the plurality of ribs 20 can be reliably prevented from falling in the tire width direction H. become.
Therefore, for example, at the time of a low load in which the contact area of the tread portion 13 is relatively small and the ratio of the tire equator portion CL to the contact area is relatively high, the above-described effects can be effectively achieved.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

For example, the circumferential grooves 18 and 19 are not limited to the above embodiment, and may be changed as appropriate.
For example, instead of the circumferential grooves 18 and 19 shown in FIG. 1, circumferential grooves 18 and 19 as shown in FIG. 2 may be employed. Hereinafter, only differences from the circumferential grooves 18 and 19 shown in FIG. 1 will be described with reference to FIG.

In the pneumatic tire 2 shown in FIG. 2, among the pair of side wall surfaces 21 and 22, the side wall surfaces 21 and 22 positioned on the vehicle outer side O are closer to the vehicle inner side I in all the circumferential grooves 18 and 19. The inclination angle is larger than the side wall surfaces 21 and 22 located.
In the illustrated example, all of the plurality of circumferential grooves 18 and 19 have the same shape and size. Of the pair of side wall surfaces 21, 22, the inclination angles θ1, θ3, θ5, θ7 of the side wall surfaces 21, 22 located on the vehicle outer side O are the inclinations of the side wall surfaces 21, 22 located on the vehicle inner side I. The angles θ2, θ4, θ6, and θ8 are greater than 10 °. For example, the inclination angles θ1, θ3, θ5, θ7 of the side wall surfaces 21, 22 located on the vehicle outer side O are about 20 °, and the inclination angles θ2, θ4, θ6 of the side wall surfaces 21, 22 located on the vehicle inner side I are θ8 is about 5 °. Further, in the present embodiment, a mark (not shown) that clearly indicates the mounting direction to the vehicle is provided on the outer surface of the pneumatic tire 2.

  In this case, in each of the plurality of circumferential grooves 18 and 19, of the pair of side wall surfaces 21 and 22, the side wall surfaces 21 and 22 positioned on the vehicle outer side O are more than the side wall surfaces 21 and 22 positioned on the vehicle inner side I. Since the inclination angle is large, when a compressive load in the vertical direction is applied to the pneumatic tire 2, each of the ribs 20 is sheared toward the vehicle inner side I along the tire width direction H. Force will be generated. Therefore, it is possible to increase the lateral force generated in the pneumatic tire 2 during cornering, and it is possible to more reliably prevent the steering stability from being lowered.

  In addition, it is possible to appropriately replace the constituent elements in the above-described embodiments with well-known constituent elements without departing from the gist of the present invention, and the above-described modified examples may be appropriately combined.

Next, the verification test about the effect demonstrated above was implemented.
The pneumatic tires of Examples 1 and 2, Comparative Examples 1 and 2 and the conventional example are each mounted on a front-wheel-drive sedan type vehicle and run on a test course. The driving stability is evaluated by the index to be used, the rolling resistance test is conducted with the smooth drum and force type in accordance with ISO18164, the rolling resistance is evaluated with the index based on the conventional example, and the test course The above-mentioned vehicle was run above, and the running speed of the vehicle when the hydroplaning phenomenon occurred was measured, and the hydroplaning performance was evaluated with an index based on the conventional example.

Here, in each of the pneumatic tires of Examples 1, 2, Comparative Examples 1, 2 and the conventional example, the width B of the circumferential grooves 18 and 19, the thickness C of the tread portion 13, and the depth of the circumferential grooves 18 and 19. D and at least one of the inclination angles θ1 to θ8 are made different so that the tire size (215 / 60R16), the tread contact width TW (about 180 mm), the tire outer diameter E (about 644 mm), and the circumferential grooves 18, 19 The number of (4) was all the same. Among these, the pneumatic tire 1 shown in FIG. 1 was adopted as Example 1, and the pneumatic tire 2 shown in FIG. 2 was adopted as Example 2.
Table 1 shows the main dimensions of the pneumatic tires of Examples 1 and 2, Comparative Examples 1 and 2 and the conventional example.

The test results are shown in Table 2.
In addition, it has shown that rolling resistance is so favorable that a numerical value is small, and hydroplaning performance has shown that it is so favorable that a numerical value is large.

  As a result, in the pneumatic tires 1 and 2 of Examples 1 and 2, the rolling resistance is reduced while maintaining the hydroplaning performance without lowering the steering stability as compared with the pneumatic tire of the conventional example. It was confirmed that In addition, it was confirmed that the pneumatic tires 1 and 2 of Examples 1 and 2 can improve steering stability as compared with the pneumatic tire of Comparative Example 1.

  The rolling resistance can be reduced while maintaining the hydroplaning performance without reducing the steering stability.

1, 2 Pneumatic tire 13 Tread 18 End circumferential groove (circumferential groove)
19 Inner circumferential groove (circumferential groove)
21 1st side wall surface (side wall surface)
22 Second side wall surface (side wall surface)
B Width of circumferential groove C Thickness of tread portion D Depth of circumferential groove E Tire outer diameter H Tire width direction L Vertical TW Tread contact width θ1-θ8 Inclination angle

Claims (3)

A plurality of circumferential grooves extending in the tire circumferential direction are formed in the tread portion at intervals in the tire width direction, and a pair of side wall surfaces that define these circumferential grooves separately from the inner side to the outer side in the tire radial direction. A pneumatic tire extending gradually away from each other in accordance with
The thickness of the tread portion is 0.0120 times or more and 0.0155 times or less of the tire outer diameter, and the depth of the circumferential groove is 0.725 times or more and 0.800 times or less of the thickness of the tread portion. The total width of each circumferential groove is 0.2 to 0.3 times the tread contact width,
Of the plurality of circumferential grooves, the inclination angles with respect to the perpendicular perpendicular to the outer circumferential surface of the tread portion of each of the pair of first side wall surfaces that respectively define end circumferential grooves positioned at both ends in the tire width direction are different from each other,
Among the plurality of circumferential grooves, an inclination angle with respect to the perpendicular of at least one of the pair of second side wall surfaces that define the inner circumferential groove located on the inner side in the tire width direction than the end circumferential groove is the pair of the circumferential grooves. It is larger than the smaller one of the inclination angles of the first side wall surfaces ,
On the tread portion, shoulder ribs located at both ends in the tire width direction and inner ribs located between these shoulder ribs are partitioned by the plurality of circumferential grooves,
The inclination angle of at least one of the pair of side wall surfaces defining the inner rib is larger than the smaller one of the inclination angles of the pair of first side wall surfaces. A featured pneumatic tire. The pneumatic tire according to claim 1,
The angle of inclination of each of the pair of second side wall surfaces is equal to each other and is equal to the angle of inclination of the first side wall surface located on the inner side in the tire width direction of the pair of first side wall surfaces. A pneumatic tire characterized by being larger than the inclination angle of the first side wall surface located outside in the tire width direction. The pneumatic tire according to claim 1,
The mounting direction to the vehicle is clearly indicated,
In each of the plurality of circumferential grooves, of the pair of side wall surfaces, the side wall surface located on the vehicle outer side has a larger inclination angle than the side wall surface located on the vehicle inner side. tire.

Images