JP2019111931A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of suppressing heel-and-toe wear in a shoulder land portion in a region where the hardness of rubber is relatively low on a tread surface having different rubber hardness on the left and right. SOLUTION: In a pneumatic tire, a first rubber 81 forming a region Z1 on one side in the tire width direction of a tread surface Tr and a region Z2 on the other side in the tire width direction thereof are formed to form a first rubber 81. A second rubber 82 that is harder than the hardness, a plurality of shoulder lateral grooves 31 provided on the shoulder land portion 21 at intervals in the tire circumferential direction, and a shoulder land portion 25 provided at intervals in the tire circumferential direction. A plurality of shoulder lateral grooves 35 and a plurality of shoulder lateral grooves 35 are provided. A dividing sipe extending along the tire width direction is provided between the shoulder lateral grooves 31 adjacent to each other in the tire circumferential direction, whereas a sipes are provided between the shoulder lateral grooves 35 adjacent to each other in the tire circumferential direction. It is formed as a non-cypress area. [Selection diagram] Fig. 2

Description

  The present invention relates to a pneumatic tire in which the hardness of rubber forming the tread surface is different on the left and right.

  BACKGROUND Conventionally, pneumatic tires are known in which the hardness of the rubber forming the tread surface is made different between right and left (that is, between one side and the other side in the tire width direction). For example, in Patent Document 1, in the pneumatic tire in which the hardness of the rubber forming the tread surface is made different between the left and right, the hardness of the rubber is relatively increased in the area which is the inside of the vehicle when the vehicle is mounted, A configuration in which the hardness of the rubber is relatively lowered has been proposed.

  Further, with regard to the pneumatic tire in which the hardness of the rubber forming the tread surface differs from side to side, the inventor has the knowledge that the braking performance can be improved by setting the boundary of the rubber in the central portion of the tread surface. ing. Since the loss tangent (tan δ) becomes high around the boundaries of rubber with different hardness and distortion tends to be accumulated, by setting the boundary of the rubber at the center of the tread surface where the contact pressure tends to increase during braking, It is considered that the friction force with the road surface is increased and the braking distance is shortened.

  By the way, in the tire from which the hardness of the rubber | gum which forms a tread surface differs in right and left, there existed a problem of being easy to produce heel and toe wear in the area | region where the hardness of rubber | gum is relatively low. Heel and toe wear tended to occur significantly on shoulder lands where a plurality of lateral grooves were spaced in the circumferential direction of the tire. Patent Document 1 does not disclose any solution to the problem of such heel and toe wear.

JP 2012-76593 A

  The present invention has been made in view of the above-described circumstances, and an object thereof is to suppress heel and toe wear at a shoulder land portion in a region where the hardness of the rubber is relatively low in the tread surface where the hardness of the rubber differs from side to side. It is to provide a pneumatic tire that can be

  The above object can be achieved by the present invention as described below. That is, in the pneumatic tire according to the present invention, the first rubber forming the region on one side in the tire width direction of the tread surface and the region on the other side in the tire width direction of the tread surface form the first rubber Provided in a region on the other side of the tread surface in the tire width direction, and a second rubber having a hardness higher than the hardness of the above, a first shoulder land portion provided on the region on one side in the tire width direction of the tread surface And a plurality of first shoulder lateral grooves provided in the first shoulder land portion at intervals in the tire circumferential direction, and the second shoulder land portions at intervals in the tire circumferential direction. A plurality of second shoulder lateral grooves provided in the shoulder land portion, and a dividing sipe extending along the tire width direction is provided between the first shoulder lateral grooves adjacent in the tire circumferential direction Against Between the second shoulder lateral grooves adjacent to the tire circumferential direction are those formed as a Cypress region sipe is not provided.

  According to this configuration, the region between the first shoulder lateral grooves is divided into regions smaller in tire circumferential length than the first shoulder lateral grooves by the dividing sipe extending along the tire width direction. As a result, the energy difference between the tread-in side and the kick-out side during tire rolling can be reduced between the first shoulder lateral grooves, and heel and toe wear at the first shoulder land portion can be suppressed. Further, in the region on the other side in the tire width direction where the hardness of the rubber is relatively high, the second shoulder lateral groove adjacent in the tire circumferential direction is formed as a cypress region, so the rigidity of the second shoulder land portion Of the rubber that forms the tread surface on the left and right sides of the tread surface.

  It is preferable to provide a display for specifying the mounting direction with respect to the vehicle such that the region on the other side in the tire width direction of the tread surface becomes the region outside the vehicle when the vehicle is mounted. The area outside the vehicle has a large contribution to the steering stability because the ground contact area increases when turning. Therefore, the area | region of vehicle outer side is useful in ensuring steering stability by being formed with rubber | gum with high hardness.

  It is preferable that the number of pitches of the region on one side in the tire width direction of the tread surface be smaller than the number of pitches of the region on the other side in the tire width direction of the tread surface. According to this configuration, the rigidity of the land portion can be enhanced in the region on one side in the tire width direction, in which the hardness of the rubber is relatively low, and the rigidity balance on the left and right of the tread surface can be improved. The pitch length of the first shoulder land portion becomes relatively large according to the relationship of the pitch number, and the kicking side becomes slippery at the time of tire rolling in the region between the first shoulder lateral grooves, but as described above The heel and toe wear is suppressed by the sipes separating between the shoulder lateral grooves of 1.

  It is preferable that the dividing sipe has a deep sipe portion having a relatively large depth and a shallow sipe portion having a relatively small depth and connected to the outer side in the tire width direction of the deep sipe portion. Since the dividing sipe has a shallow sipe portion continuous to the tire width direction outer side of the deep sipe portion, the reduction in rigidity of the first shoulder land portion due to the provision of the dividing sipe is suppressed, and in particular, the rigidity at the time of turning is secured. Useful for

  A notch opened in a circumferential main groove is continuous to the inner side in the tire width direction of the deep sipe portion, and a wall surface of the notch is inclined in a direction to gradually decrease the groove width of the notch toward the inner side in the tire radial direction. Is preferred. Thereby, the ease of movement of the deep sipe portion is suppressed, so uneven wear in the first shoulder land portion due to the difference in rigidity between the region provided with the deep sipe portion and the region provided with the shallow sipe portion Can be suppressed.

  It is preferable that an open sipe opened in the circumferential main groove be continuous with the inside of the first shoulder lateral groove in the tire width direction. Thereby, the rigidity reduction of the first shoulder land portion in the vicinity of the circumferential main groove is suppressed as compared with the case where the end of the first shoulder lateral groove opens in the circumferential main groove, and the heel and Toe wear can be suppressed well.

  It is preferable that the distance in the tire width direction between the boundary position between the first shoulder lateral groove and the open sipe continuous with it and the boundary position between the dividing sipe and the notch continuous with it is within 2 mm. According to this configuration, in the tire width direction, the end portion on the inner side in the tire width direction of the first shoulder lateral groove is disposed at a position close to the end portion on the tire width direction outer side of the notch. As a result, the rigidity balance of the first shoulder land portion in the tire width direction is improved, and partial wear in the tire width direction in the first shoulder land portion can be suppressed.

Tire meridional section in one example of pneumatic tire according to the present invention A plan view showing the tread surface of the pneumatic tire shown in FIG. 1 Top view showing the first shoulder land portion enlarged AA sectional view of FIG. 3 A perspective view showing the periphery of the end of the separating sipe

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

  As shown in FIG. 1, the pneumatic tire T has a pair of bead portions 1, a pair of sidewall portions 2 extending outward from the bead portion 1 in the tire radial direction, and a pair of sidewall portions 2. And a tread portion 3 connected to the direction outer end. In the bead portion 1, an annular bead core 1a formed by rubber-covering a convergent body such as a steel wire and a bead filler 1b disposed on the outer side in the tire radial direction of the bead core 1a are embedded. A carcass 4 is provided between the pair of bead portions 1. The carcass 4 has a toroidal shape as a whole, and the end thereof is wound up so as to sandwich the bead core 1a and the bead filler 1b.

  A belt 5 is provided on the tread portion 3 outside the carcass 4 in the tire radial direction. The belt 5 is composed of a plurality of (two in the present embodiment) belt plies stacked inside and outside. A belt reinforcing material 6 is laminated on the outer side in the tire radial direction of the belt 5. A tread rubber 7 is provided on the outer side in the tire radial direction of the belt reinforcing member 6. The tread rubber 7 includes a cap rubber 8 forming a tread surface Tr which is an outer circumferential surface of the tread portion 3 and a base rubber 9 laminated on the inner side in the tire radial direction of the cap rubber 8. In addition, the cap rubber 8 is formed of two types of rubber, a first rubber 81 and a second rubber 82 described later.

  As shown in FIG. 2, in the present embodiment, four circumferential main grooves 11 to 14 continuously extending in the tire circumferential direction and five land portions 21 to 25 divided by them are provided in the tread surface Tr. And are provided. The five land portions are a pair of shoulder land portions 21 and 25 located at both ends of the tread surface Tr, a center land portion 23 located at the center of the tread surface Tr and passing through the tire equator TE, and the pair It is comprised by a pair of media land parts 22 and 24 arrange | positioned between the shoulder land parts 21 and 25 and the center land part 23. FIG. The pair of shoulder land portions 21 and 25 is provided on the outer side in the tire width direction of the pair of circumferential main grooves 11 and 14 positioned at the outermost side in the tire width direction among the four circumferential main grooves.

  Each of the five land portions is provided with a lateral groove extending in a direction intersecting the tire circumferential direction. Shoulder lateral grooves 31 and 35 extending in the tire width direction are provided in the pair of shoulder land portions 21 and 25, respectively. The lands 22-24 are provided with lateral grooves 32-34, respectively. The pair of shoulder land portions 21 and 25 is provided with cut-shaped sipes 41 and 45, respectively. The sipes 42 and 44 are provided in the pair of media land portions 22 and 24, respectively. Here, the sipe has a groove width of 1.0 mm or less, and the lateral grooves and the notches have a groove width exceeding this.

  The tread pattern provided on the tread surface Tr is not limited to the shape shown in FIG. 2, and other shapes can be adopted, and in particular, a left-right asymmetric pattern centered on the tire equator TE can be preferably applied. Further, in the present embodiment, two circumferential main grooves are formed on both sides of the tire equator TE, but the present invention is not limited to this. At least one circumferential main groove may be formed on both sides of the rubber boundary BL). The circumferential main groove is not limited to the straight groove, but may be formed by a zigzag groove.

  As shown in FIGS. 1 and 2, the pneumatic tire T has a first rubber 81 forming a region Z1 on one side (left side in FIGS. 1 and 2) of the tread surface Tr in the tire width direction, and the tire width of the tread surface Tr. The second rubber 82 forming the area Z2 on the other side (right side in FIGS. 1 and 2), the shoulder land section 21 as the first shoulder land section provided in the area Z1, and the area Z2 A shoulder land portion 25 as a second shoulder land portion, a plurality of shoulder lateral grooves 31 as first shoulder lateral grooves provided in the shoulder land portion 21 at intervals in the tire circumferential direction, and intervals in the tire circumferential direction A plurality of shoulder lateral grooves 35 as second shoulder lateral grooves provided on the shoulder land portion 25 are provided. The second rubber 82 has a hardness higher than that of the first rubber 81. The hardness of rubber refers to "JIS K6253-1-2012 3.2 durometer hardness" measured at 23 ° C.

  The tire T not only has an asymmetrical pattern shape, but also has an asymmetrical tread composition in which the hardness of the rubber forming the tread surface Tr (that is, the cap rubber 8) is different on the left and right. The boundary of rubbers having different hardnesses, that is, the boundary BL between the first rubber 81 and the second rubber 82 is set on the surface of the center land portion 23. Based on this configuration, distortion at the time of braking easily accumulates on the center land portion 23, and braking performance is improved. The hardness difference between the first rubber 81 and the second rubber 82 is set to, for example, 3 to 10 in order to obtain the effect of improving the braking performance. In the tire meridian cross section, the boundary BL between the first rubber 81 and the second rubber 82 extends obliquely with respect to the tire radial direction.

  As shown in FIG. 3 in an enlarged manner, the sipe 41 provided in the shoulder land portion 21 has a dividing sipe 46 provided between the shoulder lateral grooves 31 adjacent in the tire circumferential direction and the tire width direction of the shoulder lateral grooves 31. It includes an open sipe 47 connected to the inside. The dividing sipes 46 extend in the tire width direction. The dividing sipes 46 are provided one by one between the pair of shoulder lateral grooves 31. Therefore, the shoulder lateral grooves 31 and the dividing sipes 46 are alternately arranged at intervals in the tire circumferential direction. The dividing sipes 46 divide the space between the shoulder lateral grooves 31 adjacent in the tire circumferential direction into two equal parts. The shoulder lateral groove 31 and the dividing sipe 46 both cross the ground contact end CE.

  The area between the shoulder lateral grooves 31 is divided by the dividing sipe 46 into an area having a smaller circumferential length in the tire circumferential direction (in the present embodiment, an area having approximately half the circumferential length of the tire). As a result, the energy difference between the tread-in side and the kick-out side at the time of tire rolling can be reduced between the shoulder lateral grooves 31 adjacent in the tire circumferential direction, and heel and toe wear at the shoulder land portion 21 can be suppressed. On the other hand, as shown in FIG. 2, in the region Z2 where the hardness of the rubber is relatively high, the space between the shoulder lateral grooves 35 adjacent in the tire circumferential direction is formed as a cypress region in which no sipes are provided. For this reason, the rigidity of the shoulder land portion 25 is not unnecessarily reduced, and the significance of adopting the asymmetric tread combination (in the present embodiment, improvement of the braking performance) does not fall apart.

  From the viewpoint of securing the steering stability, it is preferable to provide a display for specifying the mounting direction with respect to the vehicle such that the region Z2 on the other side in the tire width direction of the tread surface Tr becomes the region outside the vehicle when the vehicle is mounted. This is because the area outside the vehicle on the tread surface Tr contributes to steering stability because the contact area increases during turning, and it is advantageous for performance to be formed of rubber with high hardness. However, the present invention is not limited to this, and in view of other tire performance, for example, in order to achieve a certain trade-off performance at a high level, a mounting direction opposite to the above may be adopted.

  A display for specifying the mounting direction of the vehicle is provided on, for example, the sidewall portion 2. Specifically, it is conceivable to provide an indication (for example, OUTSIDE) to the effect that the vehicle is on the outer side on the outer surface of the sidewall 2 that is disposed on the outer side of the vehicle when the vehicle is mounted. Instead of or in addition to this, it is conceivable to provide an indication (for example, INSIDE) to the effect that the vehicle is to be the inside of the vehicle on the outer surface of the sidewall portion 2 disposed inside the vehicle when the vehicle is mounted.

  In the present embodiment, the number of pitches in the region Z1 on one side in the tire width direction of the tread surface Tr is smaller than the number of pitches in the region Z2 on the other side in the tire width direction of the tread surface Tr. According to this configuration, the rigidity of the land portion in the region Z1 in which the hardness of the rubber is relatively low can be enhanced, the rigidity balance between the left and right of the tread surface Tr can be improved, and, for example, uneven wear can be suppressed. The number of pitches of the area Z1 is, for example, 50 to 65. The number of pitches of the area Z2 is, for example, 75 to 90. It is preferable that the pitch number of the area Z2 be set to 1.3 to 1.5 times the pitch number of the area Z1. As shown in FIG. 2, the pitch length P1 of the area Z1 is smaller than the pitch length P2 of the area Z2 adjacent thereto. The pitch lengths P1 and P2 are set to include one shoulder lateral groove 31 and 35 respectively. In the present embodiment, a variable pitch in which the pitch lengths P1 and P2 are varied and arranged is applied.

  As shown in FIG. 4, the dividing sipe 46 is a shallow sipe portion having a relatively large depth and a relatively small depth and connected to the tire width direction outer side of the deep sipe portion 46 a. And 46b. Since the dividing sipe 46 has the shallow sipe portion 46 b on the outer side in the tire width direction, the reduction in the rigidity of the shoulder land portion 21 due to the dividing sipe 46 is suppressed, which is particularly useful for securing the rigidity during turning. The depth Da of the deep sipe portion 46 a is set to, for example, 40 to 60% of the depth D 11 of the circumferential main groove 11. The depth Db of the shallow sipe portion 46b is set to, for example, 15 to 35% of the depth Da.

  A notch 50 opened in the circumferential main groove 11 is continuous with the deep sipe portion 46 a on the inner side in the tire width direction. An end on the inner side in the tire width direction of the dividing sipe 46 is apart from the circumferential main groove 11 to the tire width direction outer side, and a notch 50 is interposed between the end and the circumferential main groove 11. As shown in FIG. 5, the wall surface of the notch 50 is inclined in the direction of gradually reducing the groove width of the notch 50 inward in the tire radial direction. In the present embodiment, only one of the wall surfaces 51 of the pair of wall surfaces 51 and 52 of the notch 50 is inclined, but both the wall surfaces 51 and 52 may be inclined.

  In the dividing sipe 46, since the deep sipe portion 46a is more easily moved than the shallow sipe portion 46b, the rigidity is different between the region where the deep sipe portion 46a is provided and the region where the shallow sipe portion 46b is provided. There is concern about uneven wear in the shoulder land portion 21. By connecting the notches 50 having such a shape to the deep sipe portion 46a, the ease of movement of the deep sipe portion 46a can be suppressed to suppress uneven wear. In this embodiment, the notch 50 has a planar shape (opening shape on the surface of the shoulder land portion 21) in which the groove width is gradually increased toward the circumferential main groove 11, and the wall surface 51 is closer to the circumferential main groove 11. The inclination of the is increased.

  In the present embodiment, an open sipe 47 opened in the circumferential main groove 11 is continuous with the inside of the shoulder lateral groove 31 in the tire width direction. An end of the shoulder lateral groove 31 on the inner side in the tire width direction is apart from the circumferential main groove 11 to the outer side in the tire width direction, and an open sipe 47 is interposed between the end and the circumferential main groove 11. The open sipe 47 is shorter than the separator sipe 46. Thereby, compared with the case where the end of the shoulder lateral groove 31 is opened to the circumferential main groove 11, the rigidity reduction of the shoulder land portion 21 in the vicinity of the circumferential main groove 11 is suppressed, and the heel and toe wear is reduced. It can be well suppressed.

  The tire width direction distance X (see FIG. 3) from the boundary position between the shoulder lateral groove 31 and the open sipe 47 connected thereto and the edge of the circumferential main groove 11 is, for example, 7.5 to 9.0 mm. The tire width direction distance Y (see FIG. 3) between the boundary position between the shoulder lateral groove 31 and the open sipe 47 connected thereto and the boundary position between the dividing sipe 46 and the notch 50 connected thereto is preferably within 2 mm. . Thus, in the tire width direction, the inner end of the shoulder lateral groove 31 in the tire width direction is disposed at a position near the outer end of the notch 50 in the tire width direction, so the rigidity of the shoulder land portion 21 in the tire width direction The balance becomes good, and uneven wear in the tire width direction in the shoulder land portion 21 can be suppressed.

  The dimensions of each part of the tire described above are measured with the tire mounted on a regular rim and filled with a regular internal pressure perpendicular to a flat road surface and with a regular load applied, and the tire width contacting the road surface in that state The outermost position in the direction is taken as the ground end CE. The normal load and the normal internal pressure in the standard system including the standard on which the tire is based are the load and air pressure specified by the standard for each tire, for example, in the case of JATMA, the maximum load capacity and the maximum air pressure. The regular rim is a rim which the standard specifies for each tire, and in the case of JATMA, for example, a standard rim.

  The pneumatic tire according to the present invention can be configured the same as a normal pneumatic tire except that the tread surface is configured as described above, and any conventionally known material, shape, structure, manufacturing method, etc. should be adopted. Can.

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

DESCRIPTION OF SYMBOLS 1 bead part 2 sidewall part 3 tread part 7 tread rubber 8 cap rubber 9 base rubber 21 shoulder land part (1st shoulder land part)
25 shoulder land (2nd shoulder land)
31 Shoulder lateral groove (first shoulder lateral groove)
35 Shoulder lateral groove (second shoulder lateral groove)
46 division sipe 46a deep sipe portion 46b shallow sipe portion 47 open sipe 50 notch 51 wall surface 81 first rubber 82 second rubber Z1 tire width direction one side region Z2 tire width direction other side region

Claims (7)

A first rubber forming an area on one side of the tread surface in the tire width direction;
A second rubber that forms a region on the other side in the tire width direction of the tread surface and has a hardness higher than the hardness of the first rubber;
A first shoulder land portion provided in a region on one side in the tire width direction of the tread surface;
A second shoulder land portion provided in a region on the other side in the tire width direction of the tread surface;
A plurality of first shoulder lateral grooves provided on the first shoulder land portion at intervals in the tire circumferential direction;
A plurality of second shoulder lateral grooves provided in the second shoulder land portion at intervals in the tire circumferential direction;
Between the first shoulder lateral grooves adjacent to each other in the tire circumferential direction, a dividing sipe extending along the tire width direction is provided, but between the second shoulder lateral grooves adjacent to each other in the tire circumferential direction A pneumatic tire that is formed as a cypress area without sipe.   The pneumatic tire according to claim 1, further comprising a display for designating a mounting direction with respect to the vehicle such that a region on the other side in the tire width direction of the tread surface becomes a region outside the vehicle when the vehicle is mounted.   The pneumatic tire according to claim 1 or 2, wherein the number of pitches of the region on one side in the tire width direction of the tread surface is smaller than the number of pitches of the region on the other side in the tire width direction of the tread surface.   The divided sipe has a deep sipe portion having a relatively large depth and a shallow sipe portion having a relatively small depth and connected to the outer side in the tire width direction of the deep sipe portion. The pneumatic tire according to any one of the items.   A notch opened in a circumferential main groove is continuous to the inner side in the tire width direction of the deep sipe portion, and a wall surface of the notch is inclined in a direction to gradually decrease the groove width of the notch toward the inner side in the tire radial direction. The pneumatic tire according to claim 4.   The pneumatic tire according to claim 5, wherein an open sipe opened in the circumferential main groove is continuous with an inner side of the first shoulder lateral groove in the tire width direction.   The pneumatic tire according to claim 6, wherein a distance in a tire width direction between a boundary position between the first shoulder lateral groove and the open sipe continuous with it and a boundary position between the dividing sipe and the notch continuous with it is within 2 mm. .

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