JP7037350B2 - Pneumatic tires - Google Patents

Description

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

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

Further, regarding a pneumatic tire in which the hardness of the rubber forming the tread surface is different on the left and right, the present inventor has a finding that the braking performance can be improved by setting the boundary of the rubber at the center of the tread surface. ing. Around the boundary of rubber with different hardness, the loss tangent (tan δ) becomes high and strain tends to accumulate. Therefore, by setting the rubber boundary at the center of the tread surface where the ground pressure tends to be high during braking, the rubber boundary is set. It is considered that the frictional force with the road surface increases and the braking distance is shortened.

By the way, in tires in which the hardness of the rubber forming the tread surface is different on the left and right, there is a problem that heel-and-toe wear is likely to occur in a region where the hardness of the rubber is relatively low. Heel-and-toe wear tended to occur prominently in the land area of the shoulder where a plurality of lateral grooves were provided at intervals in the tire circumferential direction. Patent Document 1 does not disclose any solution to the problem of heel-and-toe wear.

Japanese Unexamined Patent Publication No. 2012-76593

The present invention has been made in view of the above circumstances, and an object thereof is to suppress heel-and-toe wear on the shoulder land portion in a region where the rubber hardness is relatively low on tread surfaces having different rubber hardness on the left and right. It is to provide tires that can be pneumatic.

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 a region on one side of the tread surface in the tire width direction and the first rubber forming a region on the other side of the tread surface in the tire width direction are formed. A second rubber having a hardness higher than that of the tire, a first shoulder land portion provided on one side of the tread surface in the tire width direction, and a region on the other side of the tread surface in the tire width direction. The second shoulder land portion provided, 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 lateral groove provided at intervals in the tire circumferential direction. A plurality of second shoulder lateral grooves provided on the land portion of the shoulder are provided, and a dividing sipe extending along the tire width direction is provided between the first shoulder lateral grooves adjacent to each other in the tire circumferential direction. On the other hand, the space between the second shoulder lateral grooves adjacent to each other in the tire circumferential direction is formed as a cypress region in which a sipe is not provided , and the dividing sipe is a deep sipe having a relatively large depth. A notch having a portion and a shallow sipe portion having a relatively small depth and continuing to the outside in the tire width direction of the deep sipe portion, and opening in the circumferential main groove inward in the tire width direction of the deep sipe portion. The wall surface of the notch is inclined inward in the tire radial direction in a direction in which the groove width of the notch is gradually reduced .

According to such a configuration, the region between the first shoulder lateral grooves is divided into regions having a smaller tire circumferential length by the dividing sipes extending along the tire width direction. As a result, the energy difference between the stepping side and the kicking side when the tire rolls between the lateral grooves of the first shoulder can be reduced, and heel-and-toe wear in the land portion of the first shoulder can be suppressed. Further, in the region on the other side in the tire width direction in which the hardness of the rubber is relatively high, the rigidity of the second shoulder land portion is formed because the space between the second shoulder lateral grooves adjacent to each other in the tire circumferential direction is formed as a cypress region. The structure in which the hardness of the rubber forming the tread surface is different on the left and right is not disdainful.

It is preferable to provide a display for designating the mounting direction with respect to the vehicle so that the region on the other side of the tread surface in the tire width direction becomes the region outside the vehicle when the vehicle is mounted. Since the area outside the vehicle has a large contact area when turning, it contributes greatly to steering stability. Therefore, since the region on the outside of the vehicle is made of rubber having high hardness, it is useful for ensuring steering stability.

It is preferable that the number of pitches in the region on one side of the tread surface in the tire width direction is smaller than the number of pitches in the region on the other side in the tire width direction of the tread surface. According to such a configuration, the rigidity of the land portion can be increased in the region on one side in the tire width direction in which the hardness of the rubber is relatively low, and the left-right rigidity balance of the tread surface can be improved. With this relationship of the number of pitches, the pitch length of the land portion of the first shoulder becomes relatively large, and in the region between the lateral grooves of the first shoulder, the kicking side becomes slippery when the tire rolls, but as described above, the first Heel-and-toe wear is suppressed by separating the shoulder lateral grooves of 1 with a dividing sipe.

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 continuing to the outside in the tire width direction of the deep sipe portion. Since the dividing sipe has a shallow sipe portion that is connected to the outside of the deep sipe portion in the tire width direction, the decrease 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 ensured. Is useful in.

Notches opened in the circumferential main groove are connected to the inside of the deep sipe portion in the tire width direction, and the wall surface of the notch is inclined in a direction in which the groove width of the notch is gradually reduced toward the inside in the tire radial direction. Is preferable. As a result, the ease of movement of the deep sipe portion is suppressed, and therefore, uneven wear in the first shoulder land portion due to the difference in rigidity between the region where the deep sipe portion is provided and the region where the shallow sipe portion is provided. Can be suppressed.

It is preferable that the open sipes opened in the circumferential main groove are connected to the inside of the first shoulder lateral groove in the tire width direction. As a result, the rigidity of the first shoulder land portion in the vicinity of the circumferential main groove is suppressed from being lowered as compared with the case where the end of the first shoulder lateral groove is opened in the circumferential main groove, and the heel and Toe wear can be suppressed satisfactorily.

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 connected to the first shoulder lateral groove and the boundary position between the dividing sipe and the notch connected thereto is within 2 mm. According to such a configuration, in the tire width direction, the inner end portion of the first shoulder lateral groove in the tire width direction is arranged at a position close to the outer end portion of the notch in the tire width direction. As a result, the rigidity balance of the first shoulder land portion in the tire width direction is improved, and uneven wear in the tire width direction in the first shoulder land portion can be suppressed.

Tire meridian cross-sectional view in an example of a pneumatic tire according to the present invention. Top view showing the tread surface of the pneumatic tire shown in FIG. 1st shoulder plan view of the land area enlarged AA sectional view of FIG. 3 Perspective view showing the periphery of the end of the delimiter 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 in the tire radial direction from the bead portions 1, and a pair of sidewall portions 2, respectively. A tread portion 3 connected to the outer end in the direction is provided. An annular bead core 1a formed by rubber-coating a convergent body such as a steel wire and a bead filler 1b arranged on the outer side of the bead core 1a in the tire radial direction are embedded in the bead portion 1. A carcass 4 is provided between the pair of bead portions 1. The carcass 4 has a toroid shape as a whole, and its end is wound so as to sandwich the bead core 1a and the bead filler 1b.

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

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

Each of the five land areas is provided with a lateral groove extending in a direction intersecting the tire circumferential direction. The pair of shoulder land portions 21 and 25 are provided with shoulder lateral grooves 31 and 35 extending along the tire width direction, respectively. Horizontal grooves 32 to 34 are provided in the land portions 22 to 24, respectively. Further, the pair of shoulder land portions 21 and 25 are provided with notched sipes 41 and 45, respectively. The pair of mediat land parts 22 and 24 are also provided with sipes 42 and 44, respectively. Here, the sipe shall have a groove width of 1.0 mm or less, and the lateral groove and the notch shall 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 a left-right asymmetric pattern centered on the tire equator TE can be particularly 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, and the tire equator TE is sandwiched (more specifically, described later). At least one circumferential main groove may be formed on both sides (with the rubber boundary BL in between). The circumferential main groove is not limited to the straight groove, and 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 a tire width of the tread surface Tr. A second rubber 82 forming the region Z2 on the other side of the direction (right side in FIGS. 1 and 2), a shoulder land portion 21 as a first shoulder land portion provided in the region Z1, and a shoulder land portion 21 provided in the region Z2. A shoulder land portion 25 as a second shoulder land portion, a plurality of shoulder lateral grooves 31 as a first shoulder lateral groove provided in the shoulder land portion 21 at intervals in the tire circumferential direction, and a distance in the tire circumferential direction. It is provided with a plurality of shoulder lateral grooves 35 as a second shoulder lateral groove provided on the shoulder land portion 25. 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 a left-right asymmetric pattern shape, but also has an asymmetric tread composition in which the hardness of the rubber (that is, the cap rubber 8) forming the tread surface Tr differs between the left and right. The boundary BL between rubbers having different hardness, 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 during braking tends to accumulate in 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 achieve 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 inclined with respect to the tire radial direction.

As shown in an enlarged manner in FIG. 3, the sipe 41 provided in the shoulder land portion 21 includes a dividing sipe 46 provided between shoulder lateral grooves 31 adjacent to each other in the tire circumferential direction, and a tire width direction of the shoulder lateral groove 31. An open sipe 47 connected to the inside is included. The dividing sipe 46 extends along 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 sipe 46 divides the shoulder lateral grooves 31 adjacent to each other in the tire circumferential direction into two equal parts. Both the shoulder lateral groove 31 and the dividing sipe 46 cross the ground contact end CE.

The region between the shoulder lateral grooves 31 is divided by the dividing sipe 46 into a region having a smaller tire circumferential length (in the present embodiment, a region having approximately half the tire circumferential length). As a result, the energy difference between the stepping side and the kicking side when the tire rolls between the shoulder lateral grooves 31 adjacent to each other in the tire circumferential direction can be reduced, and heel-and-toe wear on 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 to each other in the tire circumferential direction is formed as a cypress region in which no sipes are provided. Therefore, the rigidity of the shoulder land portion 25 is not unnecessarily reduced, and the significance of adopting the asymmetric tread combination (improvement of braking performance in the present embodiment) cannot be dismissed.

From the viewpoint of ensuring steering stability, it is preferable to provide a display for designating the mounting direction with respect to the vehicle so that the region Z2 on the other side of the tread surface Tr in the tire width direction becomes the region outside the vehicle when mounted on the vehicle. This is because the region on the outside of the vehicle of the tread surface Tr has a large contribution to steering stability because the ground contact area becomes large when turning, and it is advantageous in terms of performance to be made of rubber having high hardness. However, the present invention is not limited to this, and in view of other tire performances, for example, in order to achieve both a certain trade-off performance at a high level, a mounting direction opposite to the above may be adopted.

A display for designating the mounting direction with respect to the vehicle is provided, for example, on the sidewall portion 2. Specifically, it is conceivable to provide an indication (for example, OUTSIDE) indicating that the outside of the vehicle is on the outer surface of the sidewall portion 2 arranged on the outside 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) indicating that the inside of the vehicle is on the outer surface of the sidewall portion 2 arranged inside the vehicle when the vehicle is mounted.

In the present embodiment, the number of pitches of the region Z1 on one side of the tread surface Tr in the tire width direction is smaller than the number of pitches of the region Z2 on the other side of the tread surface Tr in the tire width direction. According to such a configuration, it is possible to increase the rigidity of the land portion of the region Z1 where the hardness of the rubber is relatively low, improve the rigidity balance between the left and right sides of the tread surface Tr, and suppress uneven wear, for example. The number of pitches in the region Z1 is, for example, 50 to 65. The number of pitches in the region Z2 is, for example, 75 to 90. The number of pitches in the region Z2 is preferably set to 1.3 to 1.5 times the number of pitches in the region Z1. As shown in FIG. 2, the pitch length P1 of the region Z1 is smaller than the pitch length P2 of the region Z2 adjacent thereto. The pitch lengths P1 and P2 are set so as 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 arranged differently is applied.

As shown in FIG. 4, the dividing sipe 46 has a deep sipe portion 46a having a relatively large depth and a shallow sipe portion having a relatively small depth and connected to the outer side of the deep sipe portion 46a in the tire width direction. It has 46b and. Since the dividing sipe 46 has the shallow sipe portion 46b on the outer side in the tire width direction, the decrease in the rigidity of the shoulder land portion 21 due to the dividing sipe 46 is suppressed, which is particularly useful for ensuring the rigidity at the time of turning. The depth Da of the deep sipe portion 46a is set to, for example, 40 to 60% of the depth D11 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.

Inside the deep sipe portion 46a in the tire width direction, a notch 50 opened in the circumferential main groove 11 is connected. The inner end portion of the dividing sipe 46 in the tire width direction is separated from the circumferential main groove 11 outward in the tire width direction, and a notch 50 is interposed between the end portion and the circumferential main groove 11. As shown in FIG. 5, the wall surface of the notch 50 is inclined inward in the tire radial direction in a direction in which the groove width of the notch 50 is gradually reduced. In the present embodiment, of the pair of wall surfaces 51 and 52 of the notch 50, only one wall surface 51 is inclined, but both wall surfaces 51 and 52 may be inclined.

In the dividing sipe 46, the deep sipe portion 46a is easier to move than the shallow sipe portion 46b, which is caused by the difference in rigidity between the region where the deep sipe portion 46a is provided and the region where the shallow sipe portion 46b is provided. Although there is a concern about uneven wear in the shoulder land portion 21, by connecting the notch 50 having such a shape to the deep sipe portion 46a, the ease of movement of the deep sipe portion 46a can be suppressed and the uneven wear can be suppressed. In the present 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. It is configured so that the inclination of is large.

In the present embodiment, the open sipes 47 opened in the circumferential main groove 11 are connected to the inside of the shoulder lateral groove 31 in the tire width direction. The inner end portion of the shoulder lateral groove 31 in the tire width direction is separated from the circumferential main groove 11 outward in the tire width direction, and an open sipe 47 is interposed between the end portion and the circumferential main groove 11. The open sipe 47 is shorter than the delimiter sipe 46. As a result, as compared with the case where the end portion of the shoulder lateral groove 31 is opened in the circumferential main groove 11, the decrease in the rigidity of the shoulder land portion 21 in the vicinity of the circumferential main groove 11 is suppressed, and heel-and-toe wear is prevented. It can be suppressed well.

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 to the shoulder lateral groove 31 to the edge of the circumferential main groove 11 is, for example, 7.5 to 9.0 mm. Further, 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 to the shoulder lateral groove 31 and the boundary position between the dividing sipe 46 and the notch 50 connected thereto is preferably within 2 mm. .. As a result, in the tire width direction, the inner end portion of the shoulder lateral groove 31 in the tire width direction is arranged at a position close to the outer end portion of the notch 50 in the tire width direction. The balance is good, and uneven wear in the tire width direction in the shoulder land portion 21 can be suppressed.

The above-mentioned dimensions of each part of the tire shall be measured with a tire mounted on a regular rim and filled with regular internal pressure placed vertically on a flat road surface and a regular load applied, and the tire width that touches the road surface in that state. The outermost position in the direction is the grounding end CE. The normal load and the normal internal pressure are the load and the air pressure defined for each tire in the standard system including the standard on which the tire is based. For example, in the case of JATTA, the maximum load capacity and the maximum air pressure. The regular rim is a rim defined by the standard for each tire, and is a standard rim in the case of JATTA, for example.

The pneumatic tire according to the present invention can be configured in the same manner 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. shall be adopted. Can be done.

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

1 Bead part 2 Side wall part 3 Tread part 7 Tread rubber 8 Cap rubber 9 Base rubber 21 Shoulder land part (first shoulder land part)
25 Shoulder land (second shoulder land)
31 Shoulder lateral groove (first shoulder lateral groove)
35 Shoulder lateral groove (second shoulder lateral groove)
46 Separation sipe 46a Deep sipe 46b Shallow sipe 47 Open sipe 50 Notch 51 Wall 81 First rubber 82 Second rubber Z1 Tire width direction One side area Z2 Tire width direction other side area

Claims (5)

The first rubber forming the area on one side of the tread surface in the tire width direction,
A second rubber that forms a region on the other side of the tread surface in the tire width direction and has a hardness higher than that of the first rubber.
A first shoulder land portion provided in a region on one side of the tread surface in the tire width direction, and
A second shoulder land portion provided in the area on the other side of the tread surface in the tire width direction, and
A plurality of first shoulder lateral grooves provided on the land portion of the first shoulder at intervals in the tire circumferential direction, and
A plurality of second shoulder lateral grooves provided on the land portion of the second shoulder at intervals in the tire circumferential direction are provided.
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, whereas between the second shoulder lateral grooves adjacent to the tire circumferential direction. Is formed as a cypress area without sipe ,
The dividing sipe has a deep sipe portion having a relatively large depth and a shallow sipe portion having a relatively small depth and continuing to the outside in the tire width direction of the deep sipe portion.
Notches opened in the circumferential main groove are connected to the inside of the deep sipe portion in the tire width direction, and the wall surface of the notch is inclined in a direction in which the groove width of the notch is gradually reduced toward the inside in the tire radial direction. Pneumatic tires. The pneumatic tire according to claim 1, further comprising a display for designating the mounting direction with respect to the vehicle so that the region on the other side of the tread surface in the tire width direction becomes the region outside the vehicle when mounted on the vehicle. The pneumatic tire according to claim 1 or 2, wherein the number of pitches in the region on one side of the tread surface in the tire width direction is smaller than the number of pitches in the region on the other side in the tire width direction of the tread surface. The pneumatic tire according to any one of claims 1 to 3 , wherein open sipes opened in the circumferential main groove are connected to the inside of the first shoulder lateral groove in the tire width direction. The pneumatic tire according to claim 4 , wherein the distance in the tire width direction between the boundary position between the first shoulder lateral groove and the open sipe connected thereto and the boundary position between the dividing sipe and the notch connected thereto is within 2 mm. ..

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