JP2018103855A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve both of the braking performance and the driving stability.SOLUTION: An area ratio As/(As+Am+Ac) of shoulder land parts 38 in a tread part 14 is 0.40-0.52 (As: area of a pair of shoulder land parts 38, Am: area of a pair of mediate land parts 40, Ac: area of a center land part 36). In a cross section in a tire-width direction with a normal rim assembly inner pressure unfilled, Dc/Db is 0.86-0.98, where Db is a distance from a tire equator plane CL to a tread end 50, and DC is a distance from the tire equator plane CL to a belt end 24A, with a rubber thickness Tg at the belt end 24A being larger than a rubber thickness Th at the tread end 50 (Tg>Th).SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a pneumatic tire.

  In the pneumatic tire, for the purpose of improving various performances, each component in the tire cross-sectional shape is designed and the like (for example, see Patent Document 1).

  For example, in order to improve the braking performance of a pneumatic tire, there is a method of increasing the ground contact area of the tire. Specifically, there is a method of expanding the tread width in the tire cross-sectional shape, particularly increasing the ground contact area of the shoulder land portion. is there. However, when the contact area is increased, as a contradiction, the steering stability in the high G region where high gravitational acceleration acts is deteriorated, and the limit behavior of the steering stability is impaired.

International Publication No. 2011/126077

  In view of the above points, an embodiment of the present invention aims to achieve both braking performance and steering stability.

  A pneumatic tire according to an embodiment of the present invention includes a pair of bead portions, a pair of sidewall portions extending radially outward from the bead portions, and radially outer ends of the pair of sidewall portions. A tread portion connected to form a ground plane; a carcass layer extending across the pair of bead portions; and a belt disposed on an outer peripheral side of the carcass layer in the tread portion; and the tread portion The center land portion located in the center portion in the tire width direction, the pair of shoulder land portions located in the tire width direction end portion of the tread portion, and the center land portion by four circumferential main grooves extending in the tire circumferential direction And a pair of mediate land portions located between the shoulder land portions. The tread portion has an area of the pair of shoulder land portions, an area of the pair of mediate land portions, and an area of the center land portion within the contact width as As, Am, and Ac, respectively, As / (As + Am + Ac). The area ratio of the shoulder land part represented by is 0.40 or more and 0.52 or less. Further, in the cross section of the tire in the tire width direction in which the normal rim assembly internal pressure is not filled, the distance from the tire equator surface to the tread end is Db, the distance from the tire equator surface to the belt end is Dc, and Dc / Db is 0.86 or more. 0.98 or less, Tg> Th, where Tg is the rubber thickness at the belt end and Th is the rubber thickness at the tread end.

  According to this embodiment, it is possible to achieve both braking performance and steering stability.

The figure which shows the tire width direction cross section of the pneumatic tire which concerns on one Embodiment. Development view showing the tread pattern of the pneumatic tire 1 is an enlarged view of the main part of FIG.

  Hereinafter, embodiments will be described with reference to the drawings.

  A pneumatic tire according to an embodiment shown in FIGS. 1 and 2 includes a pair of left and right bead portions 10, a pair of left and right sidewall portions 12 extending outward from the bead portion 12 in the tire radial direction, and tires of the sidewall portions 14. A tread portion 14 that connects the radially outer ends and forms a ground contact surface. In this example, the shape of the cross section in the tire width direction shown in FIG. 1 is bilaterally symmetric, and the left half is not shown.

  In the figure, reference sign CL indicates a tire equatorial plane corresponding to the center in the tire width direction. Here, the tire radial direction is a direction perpendicular to the tire rotation axis, and is indicated by a symbol RD in the drawing. The inner side in the tire radial direction is a direction approaching the tire rotation axis, and the outer side in the tire radial direction is a direction away from the tire rotation axis. The tire width direction is a direction parallel to the tire rotation axis, and is indicated by a symbol WD in the drawing. The inner side in the tire width direction is a direction approaching the tire equatorial plane CL, and the outer side in the tire width direction is a direction away from the tire equatorial plane CL. The tire circumferential direction is a circumferential direction around the tire rotation axis, and is indicated by an arrow CD in the figure.

  A ring-shaped bead core 16 is embedded in each of the pair of bead portions 10. A bead filler 18 made of hard rubber that is tapered toward the outer side in the tire radial direction is provided on the outer side in the tire radial direction of the bead core 16.

  The pneumatic tire includes a carcass layer 20 that extends between the pair of bead portions 10 and extends in a toroidal shape. The carcass layer 20 reaches the bead portion 10 from the tread portion 14 through the side wall portions 12 on both sides, and is folded back from the inner side to the outer side in the tire width direction around the bead core 16 at the bead portion 10. Is locked. The carcass layer 20 is composed of at least one carcass ply formed by arranging carcass cords made of organic fiber cords so as to be substantially perpendicular to the tire circumferential direction CD and covering them with rubber. It is composed of carcass plies.

  A belt 24 is provided between the carcass layer 20 and the tread rubber 22 on the outer peripheral side of the carcass layer 20 in the tread portion 14. The belt 24 includes at least two cross belt plies in which belt cords are arranged at an inclination angle of 10 ° to 35 ° with respect to the tire circumferential direction CD. In this example, the first belt 24 is arranged on the inner side in the tire radial direction. This is a two-layer structure of a belt ply 26 and a second belt ply 28 disposed on the outer peripheral side thereof. Among these, the first belt ply 26 is the widest maximum width belt ply, and the outer end in the tire width direction corresponds to the belt end 24 </ b> A that is the end in the tire width direction of the belt 24.

  In this example, a belt reinforcing layer 30 is provided on the outer side in the tire radial direction of the belt 24, that is, between the belt 24 and the tread rubber 22. The belt reinforcing layer 30 is configured by a cap ply having a cord that extends substantially parallel to the tire circumferential direction CD.

  As shown in FIG. 2, four circumferential main grooves extending in the tire circumferential direction CD are provided on the surface of the tread portion 14 at intervals in the tire width direction WD. The four circumferential main grooves are a pair of center main grooves 32, 32 located on both sides of the tire equatorial plane CL, and a pair of shoulder main grooves 34, 34 located on the outer side in the tire width direction of each center main groove 32. is there. The circumferential main groove generally has a groove width (opening width) of 5 mm or more.

  The tread portion 14 includes a center land portion 36 located at the center portion in the tire width direction and a pair of shoulder land portions 38 located at end portions in the tire width direction of the tread portion 14 by the four circumferential main grooves 32 and 34. , 38 and a pair of mediate land portions 40, 40 located between the center land portion 36 and the shoulder land portion 38. The center land portion 36 is a land portion on the tire equator that is sandwiched between the pair of center main grooves 32 and 32. The mediate land portion 40 is a land portion sandwiched between the center main groove 32 and the shoulder main groove 34. The shoulder land portion 38 is a land portion partitioned by the shoulder main groove 34 on the outer side in the tire width direction.

  These land portions 36, 38, 40 are provided with a number of penetrating or non-penetrating lateral grooves 42 extending in the direction intersecting with the circumferential main grooves 32, 34, respectively, and the center land portion 36 is arranged in the tire circumferential direction CD. An extending sub-groove 44 is provided. As a result, a predetermined tread pattern is formed on the surface of the tread portion 14. In this example, the pneumatic tire is a tire for which the rotation direction is not specified. Therefore, the tread pattern is point-symmetric with respect to an arbitrary point on the tire equator in the developed view shown in FIG.

  In the pneumatic tire according to the embodiment, the tread portion 14 includes the area of the pair of shoulder land portions 38, 38, the area of the pair of mediate land portions 40, 40, and the center land in the contact width Cw (see FIG. 2). The area ratio (Sh ratio) of the shoulder land portion 38 represented by As / (As + Am + Ac) is set to 0.40 or more and 0.52 or less, with the area of the portion 36 being As, Am, and Ac, respectively. As described above, by increasing the area ratio of the shoulder land portion 38, the ground contact pressure of the shoulder land portion 38 that greatly contributes to braking can be reduced, and the braking performance can be improved. Further, when the Sh ratio is 0.52 or less, it is possible to suppress the cornering power from being excessively high under a high load, and to suppress a reduction in the limit behavior of the steering stability. The Sh ratio is preferably 0.43 to 0.50.

  Here, the contact width Cw refers to the contact ends 46 on both sides that attach a pneumatic tire to a regular rim, place it vertically on a flat road surface filled with a regular internal pressure, and ground to the road surface when a regular load is applied. , 46. 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, a standard rim for JATMA, “Design Rim” for TRA, and ETRTO. "MeasuringRim". The normal 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. The maximum air pressure is JATMA, and the table is "TRAIRE LIMITS AT VARIOUS COLD INFLATION" The maximum value described in “PRESSURES”, “INFLATION PRESSURE” in the case of ETRTO, is 180 kPa when the tire is for a passenger car. In addition, the normal load is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. If it is JATMA, it is the maximum load capacity, and if it is TRA, the maximum load described in the above table. If the value is ETRTO, it is “LOAD CAPACITY”, but if the tire is for a passenger car, the load is equivalent to 88% of the load.

  As is the width of the shoulder land portion 38 (that is, the width from the tire width direction inner edge 38A to the ground contact end 46) Ws (see FIG. 2) in the tire circumferential direction CD, and is a pair of shoulders. This is the total area of the land portions 38, 38 and is the area excluding narrow grooves such as the lateral grooves 42.

  Am is the area of the entire circumference of the tire circumferential direction CD with the width Wm of the mediate land portion 40, the total area of the pair of mediate land portions 40, 40, and the area excluding narrow grooves such as the lateral grooves 42 It is.

  Ac is the area of the entire circumference in the tire circumferential direction CD in the width Wc of the center land portion 36, and is an area excluding narrow grooves such as the lateral groove 42 and the auxiliary groove 44.

  Further, in the pneumatic tire according to the embodiment, the dimensions are set as in the following (1) to (6) in the cross section in the tire width direction in the normal rim assembly internal pressure unfilled state shown in FIG.

  Here, the tire width direction cross section is a cross section along the tire width direction WD, and can also be referred to as a tire meridian direction cross section. The normal rim assembly internal pressure unfilled state is a state in which a pneumatic tire is mounted on a normal rim, and no internal pressure is applied. Therefore, when measuring the following dimensions, a pneumatic tire cut along the tire width direction WD may be used. Specifically, when a pneumatic tire is cut in a thickness of about 5 cm along the tire width direction WD and a sample is measured, each dimension is measured in a state where a pair of bead portions of the sample is fixed at a normal rim position. Good.

(1) 0.68 ≦ Db / Da ≦ 0.88
Here, Da is a distance from the tire equatorial plane CL to the tire maximum width position 48, and the tire maximum width position 48 along the tire width direction WD from the tire equatorial plane CL (that is, perpendicular to the tire equatorial plane CL). Is the length of the line segment extending to Da is a half width of the maximum tire width, but since the cross-sectional shape is bilaterally symmetrical, hereinafter it may be simply referred to as the maximum tire width Da for convenience.

  The tire maximum width position 48 is a position on the outermost side of the surface of the sidewall portion 12 in the tire width direction WD, and is a position on the surface of the sidewall portion that takes the tire maximum width. The maximum tire width is also referred to as a cross-sectional width, and is a width excluding protrusions such as patterns and letters on the sidewall surface.

  Db is the distance from the tire equatorial plane CL to the tread end 50 that is the tire width direction end of the tread portion 14, and is the length of a line segment extending from the tire equatorial plane CL to the tread end 50 along the tire width direction WD. is there. Although Db is a half width of the tread width, since the cross-sectional shape is left-right symmetric, hereinafter, it may be simply referred to as the tread width Db for convenience.

  The tread end 50 is a tire width direction end of the tread portion 14 that defines the maximum contact width of the tire, and more specifically, an arc that defines the profile of the shoulder land portion 38 in the tire width direction cross section shown in FIG. 52 is a midpoint of an arc 56 that defines a tire surface profile that connects 52 and an arc 54 that defines the profile of the sidewall portion 12 (the outer contour in the tire radial direction from the tire maximum width position 48). As shown in FIGS. 1 and 3, the boundary region between the tread portion 14 and the sidewall portion 12 is gently connected via an arc 56. In FIG. 3, reference numeral 52 </ b> A indicates an outer end in the tire width direction of the arc 52, reference numeral 54 </ b> A indicates an outer end in the tire radial direction of the arc 54, and these 52 </ b> A and 54 </ b> A correspond to both ends of the arc 56.

  As in (1) above, by setting Db / Da to be not less than 0.68 and not more than 0.88, that is, the tread width Db is set within the range of 68 to 88% of the tire maximum width Da, the tread width is reduced. The braking performance can be improved by increasing the contact shape and the tension distribution. Db / Da is more preferably 0.70 to 0.85, and still more preferably 0.75 to 0.80.

(2) 0.86 ≦ Dc / Db ≦ 0.98
Here, Dc is the distance from the tire equatorial plane CL to the belt end 24A, which is the end of the belt 24 in the tire width direction, and the length of the line segment extending from the tire equatorial plane CL to the belt end 24A along the tire width direction WD. That's it. Dc is a half width of the belt width, but since the cross-sectional shape is bilaterally symmetric, hereinafter, it may be simply referred to as belt width Dc for convenience.

  As in (2) above, by setting Dc / Db to be 0.86 or more and 0.98 or less, that is, by setting the belt width Dc within the range of 86 to 98% of the tread width Db, the tread width Db While obtaining the effect of improving the braking performance due to the expansion and the area expansion of the shoulder land portion 38, the limit behavior of the steering stability can be suppressed from deteriorating, and both the braking performance and the steering stability can be achieved. Specifically, when Dc / Db is 0.86 or more, the ground pressure of the shoulder land portion 38 can be lowered and the braking performance can be improved, and when Dc / Db is 0.98 or less, An excessive increase in cornering power at high loads can be suppressed, and deterioration of the critical behavior of steering stability can be suppressed. Dc / Db is more preferably 0.90 to 0.95.

(3) Tg> Th
Here, Tg is the rubber thickness at the belt end 24A, that is, the rubber thickness from the tire surface at the position in the tire width direction of the belt end 24A. Specifically, as shown in FIG. 3, the tire thickness in the normal to the tire surface profile at the point E, where the tire radial direction line L1 passing through the belt end 24A intersects the tire surface is a point E, and the tire This is the length of the line segment from the surface point E to the belt reinforcing layer 30.

  Th is the rubber thickness at the tread end 50. Specifically, as shown in FIG. 3, the rubber thickness is normal to the tire surface profile at the tread end 50, and is the length of the line segment from the tread end 50 located on the tire surface to the belt reinforcing layer 30. is there.

  As described in (3) above, by setting the rubber thickness Tg at the belt end 24A to be larger than the rubber thickness Th at the tread end 50, the occurrence of local non-grounding parts can be suppressed and the ground pressure can be made uniform. It is possible to suppress the deterioration of the braking performance.

(4) 0.50 ≦ Dd / Db ≦ 0.64
Here, Dd is the distance from the tire equatorial plane CL to the tire width direction inner edge 38A of the shoulder land portion 38, and the length of the line segment extending from the tire equatorial plane CL to the inner edge 38A along the tire width direction WD. That's it. An inner edge 38A in the tire width direction of the shoulder land portion 38 coincides with an opening end of the shoulder main groove 34 on the outer side in the tire width direction.

  As in (4) above, Dd / Db is 0.50 or more and 0.64 or less, that is, the distance Dd to the inner edge 38A of the shoulder land portion 38 is set within a range of 50 to 64% of the tread width Db. By doing so, the following effects are exhibited. That is, when Dd / Db is 0.50 or more, it is possible to prevent the cornering power at a high load from becoming too large. Moreover, when Dd / Db is 0.64 or less, it is possible to suppress an increase in contact pressure at the shoulder land portion 38 and to suppress deterioration in braking performance. Dd / Db is more preferably 0.55 to 0.60.

(5) 0.84 ≦ Tf / Te ≦ 1.00
Here, Te is the rubber thickness at the tire equatorial plane CL. Specifically, as shown in FIG. 3, the rubber thickness at the normal line to the tire surface profile at the tire equatorial plane CL, and the length of the line segment from the tire surface to the belt reinforcing layer 30 at the normal line.

  Tf is the rubber thickness at the tire width direction inner edge 38A of the shoulder land portion 38. Specifically, as shown in FIG. 3, the rubber thickness is normal to the tire surface profile at the inner edge 38 </ b> A, and is the length of the line segment from the inner edge 38 </ b> A of the tire surface to the belt reinforcing layer 30. .

  As in (5) above, Tf / Te is 0.84 or more and 1.00 or less, that is, the rubber thickness Tf at the tire width direction inner edge 38A of the shoulder land portion 38 is the rubber thickness at the tire equatorial plane CL. By setting it to 84 to 100% of Te, the following effects are exhibited. That is, when Tf / Te is 0.84 or more, it is possible to secure the ground contact property at the inner edge 38A and suppress the deterioration of the braking performance due to the decrease in the ground contact area of the shoulder land portion 38. Further, when Tf / Te is 1.00 or less, the contact length at the shoulder land portion 38 is larger than the contact length at the center land portion 36, thereby suppressing uneven contact pressure and braking performance. Can be prevented. Tf / Te is more preferably 0.90 to 0.95.

(6) 0.60 ≦ Tg / Te ≦ 0.74, 0.60 ≦ Th / Te ≦ 0.74
Thus, the rubber thickness Tg at the belt end 24A and the rubber thickness Th at the tread end 50 are both set within the range of 60 to 74% with respect to the rubber thickness Te at the tire equatorial plane CL. The effect of is produced. That is, when Tg / Te and Th / Te are 0.60 or more, these portions can be easily grounded, the ground contact area of the shoulder land portion 38 can be secured, and the effect of improving the braking performance can be enhanced. Can do. In addition, since Tg / Te and Th / Te are 0.74 or less, an increase in the contact length of the shoulder land portion 38 during normal load can be suppressed, so that the contact pressure of the shoulder land portion 38 during braking is reduced. It can be suppressed that the braking performance is deteriorated due to the excessive increase. Tg / Te is more preferably 0.65 to 0.72, and Th / Te is more preferably 0.62 to 0.70.

  According to the present embodiment as described above, the belt as described above is used to improve the steering stability in the high G region while improving the braking performance by increasing the tread width and increasing the area ratio of the shoulder land portion 38. By setting the width, it is possible to achieve both braking performance and steering stability.

  In the above embodiment, the case where the tire cross-sectional shape is bilaterally symmetrical has been described as an example. However, it is not always necessary to be bilaterally symmetric. .

  Examples and comparative examples were performed on pneumatic tires for passenger cars having a tire size of 205 / 60R16. About each tire of an Example and a comparative example, the basic composition is as having demonstrated in the said embodiment, and as shown in following Table 1, each specification was set and the tire was made as an experiment. Each prototype tire was evaluated for handling stability and braking performance. The evaluation method is as follows.

  Steering stability: A prototype tire was mounted on a 16 × 6.0 rim, filled with an internal pressure of 230 kPa, mounted on a test vehicle, and subjected to sensory evaluation using an actual vehicle. The evaluation was performed by evaluating the stability of the vehicle when turning back and cornering at successive corners, and using an index with a comparative example as 100. The larger the index, the better the steering stability.

  ・ Brake performance: A prototype tire is mounted on a 16 × 6.0 rim, filled with an internal pressure of 230 kPa, mounted on a test vehicle, and the braking distance is measured when the running speed is changed from 100 km / h to 0 km / h. The reciprocal of the braking distance is expressed as an index with the value of Comparative Example 1 being 100. The larger the index, the shorter the braking distance and the better the braking performance.

  The results are as shown in Table 1. Compared with Comparative Example 1 in which the tread width Db is narrow, in Comparative Example 2, the braking performance was improved by increasing the tread width Db, but the steering stability was lowered. In Comparative Example 3, although the tread width Db was enlarged, the area ratio (Sh ratio) of the shoulder land portion 38 was small, and the effect of improving the braking performance was not obtained. In Comparative Example 4, the belt width Dc was small compared to Comparative Example 2, and the braking performance was degraded. In Comparative Example 5, since the rubber thickness Tg at the belt end 24A was smaller than the rubber thickness Th at the tread end 50, the braking performance was lower than that of Comparative Example 2.

  On the other hand, in the case of Examples 1 to 11, the tread width Db is enlarged in order to improve the braking performance, and in particular, the area ratio (Sh ratio) of the shoulder land portion 38 is enlarged. By setting the rubber thickness Tg at the belt end 24 </ b> A to be larger than the rubber thickness Th at the tread end 50, the braking performance and the steering stability can be achieved at a high level.

  Although some embodiments have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention.

DESCRIPTION OF SYMBOLS 10 ... Bead part, 12 ... Side wall part, 14 ... Tread part, 20 ... Carcass layer, 24 ... Belt, 24A ... Belt end, 32 ... Center main groove, 34 ... Shoulder main groove, 36 ... Center land part, 38 ... Shoulder land portion, 38A ... Inner edge in the tire width direction, 40 ... Medium land portion, 48 ... Tire maximum width position, 50 ... Tread edge, CL ... Tire equator, CD ... Tire circumferential direction, RD ... Tire radial direction, WD ... Tire Width direction, Cw: Contact width, Da: Distance from tire equator plane to tire maximum width position, Db: Distance from tire equator plane to tread edge, Dc: Distance from tire equator plane to belt edge, Dd: Tire equator The distance from the surface to the inner edge in the tire width direction of the shoulder land portion, Te ... the rubber thickness at the tire equator surface, Tf ... the inner edge in the tire width direction of the shoulder land portion Rubber thickness at the rubber thickness, rubber thickness at Tg ... belt end, Th ... tread edge

Claims (5)

A pair of bead portions, a pair of sidewall portions extending outward in the tire radial direction from these bead portions, a tread portion that configures a ground contact surface by connecting the radially outer ends of the pair of sidewall portions; and A carcass layer extending across a pair of bead portions, and a belt disposed on the outer peripheral side of the carcass layer in the tread portion,
The tread portion includes four circumferential main grooves extending in the tire circumferential direction, a center land portion located at the tire width direction center portion, and a pair of shoulder land portions located at the tire width direction end portions of the tread portion, In the pneumatic tire divided into a pair of mediate land portions located between the center land portion and the shoulder land portion,
The tread portion has an area of the pair of shoulder land portions, an area of the pair of mediate land portions, and an area of the center land portion within the contact width as As, Am, and Ac, respectively, As / (As + Am + Ac). The area ratio of the shoulder land portion represented by is 0.40 or more and 0.52 or less,
In the cross section of the tire width direction in the normal rim assembly internal pressure unfilled state,
The distance from the tire equator plane to the tread edge is Db, the distance from the tire equator plane to the belt edge is Dc, and Dc / Db is 0.86 or more and 0.98 or less,
Tg> Th, where Tg is the rubber thickness at the belt end, and Th is the rubber thickness at the tread end.
A pneumatic tire characterized by that.   2. The pneumatic tire according to claim 1, wherein Db / Da is not less than 0.68 and not more than 0.88, where Da is a distance from the tire equatorial plane to the tire maximum width position in the tire width direction cross section.   The tire width direction cross section WHEREIN: Dd / Db is 0.50 or more and 0.64 or less, where Dd is the distance from the tire equatorial plane to the tire width direction inner edge of the shoulder land portion. Pneumatic tires.   In the tire width direction cross section, Tf / Te is 0.84 or more and 1.00 or less, where Te is the rubber thickness at the tire equatorial plane and Tf is the rubber thickness at the tire width direction inner edge of the shoulder land portion. The pneumatic tire according to any one of claims 1 to 3.   The tire width direction cross section WHEREIN: The rubber | gum thickness in a tire equator surface is set to Te, and both Tg / Te and Th / Te are 0.60 or more and 0.74 or less, The any one of Claims 1-4. Pneumatic tires.

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