JP5377059B2 - tire - Google Patents

Description

  The present invention relates to a tire, and more particularly to a structure of a tire tread for improving WET brake performance.

Conventionally, as a tread pattern excellent in braking / driving force, a lug pattern having a lug groove extending in a direction crossing the tire circumferential direction, or a rib-shaped land portion partitioned by a circumferential groove extending in the tire circumferential direction And a rib / lag type pattern having a lug groove whose one end terminates in the land portion, or a block pattern having a plurality of blocks defined by a circumferential groove and a lug groove. In the tire having the above tread pattern, the friction coefficient between the road surface and the tire is increased by the lug groove, thereby improving the tire grip and improving the braking / driving force of the tire.
In addition, a sipe extending in the tire width direction (width direction sipe) is formed in the land portion of the tire such as a block, and the drainage effect and edge effect of this sipe further improve the braking / driving performance on WET roads and snowy roads. A way to increase it has been proposed. However, on the other hand, since the sipe in the width direction is formed, the block collapses and the contact area is reduced. As a result, the contact effect is reduced and the tire slip increases. Therefore, a three-dimensional sipe whose shape also changes in the depth direction is formed on the block, and when the block collapses, the wall surfaces of the three-dimensional sipe are brought into contact with each other to improve block rigidity, and the block collapses. A method for suppressing the deformation of the dust has been proposed (see, for example, Patent Document 1).
In addition, when the block collapses on the wall surface of the block, a protrusion that contacts the wall surface facing the wall surface is provided, or a bridging piece that connects the wall surfaces facing each other is provided. Thus, a method for suppressing the collapse deformation of the block has also been proposed (see, for example, Patent Documents 2 and 3).

JP-A-11-105512 JP-A-1-175507 JP-A-2-57407

As a result of observing the ground contact state of the block when the braking force is applied to the tire running on the WET road by the paint method, the block end portion to be grounded first when the block 50 is grounded is the front end portion, and the block to be grounded later When the end portion is the rear end portion, at the initial stage of braking, as shown in FIG. 10A, the block 50 is deformed, and an ungrounded region is generated due to the rear end portion B of the block 50 being lifted. At the end, as shown in FIG. 10 (b), it was found that in addition to the lift of the rear end B, an ungrounded region caused by the entrainment of the front end A occurred. As described above, when the ungrounded area is formed in the block 50, there is a problem that the ground contact area of the tire is reduced and the WET brake performance is deteriorated.
As shown in FIG. 11, the rising of the rear end B and the entrainment of the front end A are caused by shear stress and bending stress acting on the block 50, and tensile stress acting on the rear side of the block 50 on the ground contact surface side. This is presumably because compressive stress acts on the front side of the ground surface and the block 50 is further compressed to the road surface side by the load. The WET brake performance is evaluated by the time or distance traveled until the vehicle stops when the vehicle running on the WET road is braked. The larger the tire contact area, the higher the WET brake performance. Is expensive.
As a result of studies by the present inventors, the ratio of the actual contact area (straight line) decreases as the compression angle α, which is the angle formed by the groove bottom 51 and the groove wall 52 when the block 50 is deformed, as shown in FIG. It was found that the ratio of the ground contact area during braking to the ground contact area during traveling was small, and the WET brake performance was degraded.
FIG. 12 is a graph showing the results of examining the ratio between the compression angle α and the actual ground contact area when the hardness of the tread rubber is changed, and the relationship between the compression angle α and the WET brake performance. It was expressed as an index (WET brake performance index) when the current rubber was used as the rubber. From this figure, it can be seen that the higher the hardness of the tread rubber, the larger the compression angle α, and the higher the compression angle α, the higher the WET brake performance. That is, it was found that the WET brake performance greatly depends on the compression angle α.

In order to increase the compression angle α, it is conceivable to improve the WET brake performance by using a highly rigid rubber as the tread rubber. However, simply increasing the rigidity of the tread rubber will improve the ride comfort, etc. In addition to affecting other properties, changing the rubber type is accompanied by a change in production conditions such as vulcanization conditions, so it is not a preferable solution at present.
On the other hand, the method of providing a plurality of protrusions that come into contact with one wall surface of the sipe when contacting the other wall surface, and the method of providing a protrusion portion that contacts the wall surface on the side facing the wall surface on the wall surface of the block were divided by sipe. Since the small blocks or the blocks support each other, the collapse of the blocks can be suppressed to some extent, but it is difficult to increase the compression angle α and improve the WET brake performance.

  The present invention has been made in view of conventional problems, and an object of the present invention is to provide a tire capable of increasing the compression angle α and improving the WET brake performance without changing the rubber type of the tread rubber. And

As a result of detailed examination of the deformation behavior of the block when the braking force is applied to the tire running on the WET road, the inventors have found that the deformation amount of the block during braking is close to the groove bottom behind the input. Because of the increase in size, the protrusion of the lug groove is provided on the side wall facing the lug groove of the block, or conversely, a protrusion is provided on the bottom of the lug groove. It has been found that if the pressure is suppressed at the bottom, a large compression angle α can be obtained, and the WET brake performance can be improved.
That is, the invention according to claim 1 of the present application includes a circumferential groove provided in a tire tread extending along the tire circumferential direction, a lug groove intersecting the circumferential groove, and the circumferential groove and the lug groove. And a plurality of blocks partitioned by the length of the lug groove extending in the extending direction of the lug groove, and when the block is tilted in the tire front-rear direction during braking, the protruding length abuts against the bottom of the lug groove includes a rod-shaped projection having, a sipe extending in a direction crossing the tire circumferential direction, the rod-like protrusions, the block end side of the ground after the one wall on the side facing to said lug grooves of the block provided only on the wall surface, Rukoto end in the depth direction of the sipes, located between the end portion of the tread surface side and the end portion of the lug groove bottom side of the bar-shaped projections of said bar-shaped projections It is characterized by.
As a result, when the braking force is applied to the tire running on the WET road, the land portion that is inclined in the front-rear direction of the tire can be supported by the bottom portion of the lug groove that is hardly deformed via the protrusion. It is possible to increase the compression angle α at the time of collapse. Therefore, it is possible to suppress a decrease in the contact area and improve the WET brake characteristics.
Further, the depth of the sipe can be increased, and even when the land portion falls down in the front-rear direction of the tire, the opening of the sipe can be sufficiently maintained, so that the drainage performance and edge effect due to the sipe can be sufficiently exhibited.

It is a figure which shows an example of the tread pattern of the tire which concerns on embodiment of this invention. It is a figure which shows an example of the shoulder block provided with the reinforcement block which concerns on this Embodiment. It is a figure for demonstrating the deformation | transformation state of the shoulder block provided with the reinforcement block when a vehicle brakes on the WET road. It is a figure which shows the other form of the reinforcement block based on this invention. It is a figure which shows the other form of the reinforcement block based on this invention. It is a figure which shows the relationship between the volume ratio of a reinforcement block, and a compression angle. It is a figure which shows the relationship between the volume ratio of a reinforcement block, and the ratio of an actual contact area. It is a figure which shows the relationship between a compression angle, the ratio of an actual contact area, and a prediction WET brake performance index. It is a figure which shows the protrusion provided in the groove bottom of the lug groove which concerns on this invention. It is a figure which shows the deformation | transformation state of a block when braking force acts on the tire currently drive | working a WET road. It is a figure for demonstrating compression angle (alpha) in the collapse of a block. It is a figure which shows the relationship between the hardness of a tread rubber, compression angle (alpha), and WET brake performance.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a development view of a tread pattern of a tire 10 according to an embodiment of the present invention. Four tread grooves 12 to 15 extending along the tire circumferential direction are formed on the tread 11 of the tire 10. The circumferential grooves 12, 13, the circumferential grooves 13, 14, and the circumferential grooves 14, 15 define three rib-like land portions 16 extending in the tire circumferential groove, respectively. Among the circumferential grooves 12 to 15, the circumferential grooves 12 and 15 located on the outer side in the tire width direction are circumferential grooves provided on the shoulder portion 11 </ b> S of the tire 10. Lug grooves 17 communicating with the directional grooves 12 and 15 and extending in the direction intersecting with the circumferential grooves 12 and 15 are provided. A plurality of shoulder blocks 18 are defined by the circumferential groove 12 and the lug groove 17 or the circumferential groove 15 and the lug groove 17.
As shown in FIG. 2, the shoulder block 18 is located on the circumferential groove 12 side (or the circumferential groove 15 side) that is close to the center CL of the tread 11 and serves as a tire tread when the vehicle is traveling straight ahead. The flat part 18a and the inclination part 18b which is located in the tire width direction outer side and the height reduces according to the profile of the said tire 10 are provided. The flat portion 18a is provided with a plurality of sipes 19 extending in the tire width direction and having a zigzag shape when viewed from the tread surface side.

Here, of the two side walls 18p, 18q facing the lug groove 17 of the shoulder block 18, the side wall 18p, which is the side wall on the block end side to be grounded first when the shoulder block 18 is grounded, is replaced with the front side wall, When the side wall 18q, which is the side wall on the block end side to be grounded later, is used as the rear side wall, in the tire 10 of the present example, as shown in FIG. One protrusion (hereinafter referred to as a reinforcement block) 20 having a protruding length that comes into contact with the bottom portion 17k of the lug groove when the block 18 is inclined in the tire longitudinal direction is provided.
In detail, the reinforcing block 20 is a side wall 18q on the rear side of the shoulder block 18, and is located at a position near the groove bottom 17 with a depth d from the surface 18s of the shoulder block 18 toward the groove bottom 17 of the lug groove 17. Is provided. This reinforcing block 20 is a rod-shaped block having a substantially semicircular cross section and extending in the extending direction of the lug groove 17, and one end 20a thereof is located at the substantially center of the flat portion 18a of the rear side wall 18q, and the like. The end 20b is located at the boundary between the flat portion 18a and the inclined portion 18b. The one end 20a is referred to as the start end of the reinforcing block 20, and the other end 20b is referred to as the end.
Further, when the length of the tire width direction of the reinforcing block 20 has a length L of the reinforcing block 20, this length L is about half the length L ₀ of the flat portion 18a. Further, when the end of the reinforcing block 20 on the shoulder block surface 18s side is 20c and the end of the lug groove on the bottom 17k side is 20d, the distance between the end 20c and the end 20d is the thickness D, and the reinforcing Let the protrusion length of the block 20 be the height H of the reinforcing block 20.
In this example, the protrusion length H and the depth d of the reinforcing block 20 are applied when the vehicle is braked on a WET road at a predetermined speed (for example, 40 km / h), and the shoulder block 18 is inclined in the tire longitudinal direction. In addition, the size is set such that the reinforcing block 20 comes into contact with the bottom portion 17k of the lug groove.
Further, in this example, the sipe 19 provided in the tire width direction provided on the tread surface side of the shoulder block 18, the end 19 k in the depth direction of the shoulder block is the center in the thickness direction of the reinforcing block 20. The sipe 19 was formed so as to be positioned between the end 20c on the 18s side and the end 20d on the bottom 17k side of the lug groove.

When a brake is applied while the vehicle is traveling on a WET road, a braking force as shown by a thick arrow in FIG. 3 is input to the tire 10, and the shoulder blocks 18A and 18B are compressed in a direction perpendicular to the road surface. Shears rearward and bends rearward to incline in the tire longitudinal direction. As shown in the figure, the shoulder block 18A is a shoulder block that contacts the ground first when the vehicle moves forward, and the shoulder block 18B is a shoulder block that contacts the ground later when the vehicle moves forward.
When the shoulder block 18A does not have the reinforcing block 20, as shown by the broken line in the figure, the groove bottom 17k of the lug groove 17 of the shoulder block 18A and the rear side wall 18q which is the groove wall of the lug groove 17 are formed. The compression angle α ₀ which is an angle is small. On the other hand, the tire 10 of the present example is provided with a reinforcing block 20 on the rear side wall 18q that abuts against the bottom 17k of the lug groove when the shoulder block 18A is inclined in the tire longitudinal direction. The block 20 abuts against the bottom 17k of the lug groove that divides the shoulder block 18A and the shoulder block 18B, thereby suppressing the collapse of the shoulder block 18A. That is, since the reinforcing block 20 functions as a so-called replacement rod of the shoulder block 18A, the compression angle α can be made larger than the compression angle α ₀ .
The reason why the reinforcing block 20 is received by the bottom portion 17k of the lug groove is that the tread rubber of the shoulder block 18B is deformed so as to be inclined in the tire longitudinal direction, whereas the tread rubber of the bottom portion 17k of the lug groove is almost deformed. Because it does not. Accordingly, when the reinforcing block 20 is brought into contact with the bottom portion 17k of the lug groove as in this example, the reinforcing block 20 is not provided with the reinforcing block 20, but the reinforcing block 20 is disposed on the side wall 18p on the front side of the shoulder block 18B. Compared with the case where it is made to contact | abut, the fall of the said shoulder block 18A can be made small. That is, since the compression angle α can be increased, the actual contact area ratio can be increased and the WET brake performance can be improved.
In this example, since the deep sipe 19 is formed so that the end 19k in the depth direction of the sipe 19 is positioned at the center of the reinforcing block 20 in the thickness direction, drainage performance and edge effect by the sipe are formed. And the opening of the sipe 19 can be sufficiently maintained even when the shoulder block 18 falls down. Therefore, the edge effect can be exhibited while maintaining the drainage performance due to sipe, so that the WET brake performance can be further improved.

As described above, in the embodiment according to the present invention, the side wall 18q on the rear side of the shoulder block 18 is separated by d in the depth direction of the lug groove 17 from the surface of the flat portion 18a that becomes the tire tread when the vehicle is traveling straight ahead. One end 20a that protrudes from the position is positioned substantially at the center of the flat portion 18a, and the other end 20b extends in the extending direction of the lug groove 17 provided at the boundary between the flat portion 18a and the inclined portion 18b. A rod-shaped reinforcing block 20 is provided, and the protruding length D of the reinforcing block 20 is set so that the shoulder block 18 contacts the bottom 17k of the lug groove when the shoulder block 18 is inclined in the tire front-rear direction. Since the shoulder block 18 is prevented from falling when tilted in the front-rear direction, the compression angle α of the shoulder block 18 is increased. Can Kusuru. Therefore, the actual contact area ratio can be increased, and the WET brake performance can be improved. Moreover, since the reinforcement block 20 is comprised from the rod-shaped block extended in a tire width direction, the shoulder block 18 can be supported stably.
Further, the shoulder block 18 is provided with a sipe 19 extending in the tire width direction, and the end 19k in the depth direction of the sipe 19 is positioned at the center of the reinforcing block 20 in the thickness direction. The edge effect can be exhibited while maintaining the performance.
Further, since the reinforcement block 20 of this example does not contact the bottom portion 17k of the lug groove when the fall of the shoulder block 18 is small, the reinforcement block 20 does not function during SNOW traction. Therefore, the WET brake performance can be improved without affecting the SNOW traction performance.

In the embodiment, the tire 10 having the tread pattern including the rib-like land portion 16 and the plurality of shoulder blocks 18 has been described, but the present invention is not limited thereto, and the lug pattern, Any tire having a tread pattern with lug grooves such as a block pattern can be applied. In this case, the reinforcing block 20 may be provided on the side surface of the land portion facing the lug groove 17.
In addition, the cross-sectional shape of the reinforcing block 20 is not limited to a semicircular shape, and any shape may be used as long as the tip is trapezoidal and the shoulder block 18 contacts the bottom portion 17k of the lug groove with a certain contact area. . Further, the sipe 19 is not limited to the one extending in the tire width direction, and may be extended in a direction intersecting the tire circumferential direction.
Further, in place of the reinforcing block 20, a protrusion that contacts the bottom portion 17k of the lug groove when the shoulder block 18 falls to the bottom portion 17k side of the lug groove of the side wall 18q on the rear side of the shoulder block 18 is predetermined in the tire width direction. The same effect can be obtained even if they are arranged with an interval of.

Further, in the above example, the start end 20a of the reinforcing block 20 is positioned substantially at the center of the flat portion 18a of the rear side wall 18q, and the end 20b is positioned at the boundary between the flat portion 18a and the inclined portion 18b. As shown in (a), the position of the reinforcing block 20 in the tire width direction may be changed, for example, by positioning the starting end 20a on the circumferential groove 15 (or circumferential groove 12) side of the rear side wall 18q. . In addition, as an optimal position for increasing the compression angle α, it is preferable to provide the reinforcing block 20 at the center of the shoulder block 18 as in this example shown in FIG.
Further, the position in the depth direction is preferably closer to the groove bottom 17k of the lug groove 17 as in this example. For example, as shown in FIG. 4B, when the depth d is reduced, the compression angle α is reduced. In addition, when the protrusion length H of the reinforcing block 20 is increased while the depth d is shallow, the rigidity of the reinforcing block 20 is slightly decreased, and the compression angle α may be decreased. Therefore, the reinforcing block 20 is preferably provided near the groove bottom 17k of the lug groove 17.

In order to increase the compression angle α, it is advantageous that the volume of the reinforcing block 20 is large. As a method of increasing the volume, the length L of the reinforcing block 20 is lengthened as shown in FIGS. 5A and 5B, or the cross-sectional shape is cut as shown in FIG. What is necessary is just to change the shape of the reinforcement block 20 so that an area may become large. Further, as shown in FIG. 5D, a reinforcing block 20 ′ having the same structure as the reinforcing block 20 may be provided not only on the rear side wall 18q but also on the front side wall 18p. In this case, the reinforcing block 20 ′ on the front side wall 18p does not contact the bottom portion 17k of the lug groove, but contacts the reinforcing block 20 on the rear side wall 18p, so that the reinforcing block only on the rear side wall 18p. The compression angle α is larger than when 20 is provided.
FIG. 6 is a diagram illustrating the relationship between the volume of the reinforcing block and the compression angle α. The horizontal axis represents the volume (volume ratio) of the reinforcing block when the volume of the reinforcing block 20 of this example shown in FIG. 2 is 1, and the vertical axis represents the compression angle α (deg.). In the figure, No. 1 ● indicates that there is no reinforcing block, No. 2 ● indicates a reinforcing block in FIG. 4A, No. 3 ● indicates a reinforcing block in this example shown in FIG. ● in 4 is the reinforcing block in Fig. 5 (a), ● in No. 5 is the reinforcing block in Fig. 5 (d), ● in No. 6 is the reinforcing block in Fig. 5 (b), and ● in No. 7 is the figure The reinforcing block of 5 (c) and the ● in No. 8 are the reinforcing blocks of FIG. 4 (b). Although depending on the position of the reinforcing block, the larger the volume ratio of the reinforcing block, the larger the compression angle α. Further, as shown in FIG. 7, the larger the volume ratio, the larger the ratio of the actual ground contact area. 6 and 7 also show that the larger the compression angle α, the larger the actual contact area ratio. Therefore, the magnitude of the WET brake performance predicted from the compression angle α (predicted WET brake performance index) can be estimated from the graphs of FIGS.
FIG. 8 is a diagram showing the relationship between the ratio of the compression angle α and the actual ground contact area and the relationship between the compression angle α and the predicted WET brake performance index predicted from the compression angle α. It can be seen that the area ratio is large and the predicted WET brake performance index is high.

  In the above example, the reinforcing block extends in the extending direction of the lug groove 17 on the side wall 18q on the rear side of the shoulder block 18 and contacts the bottom 17k of the lug groove when the shoulder block 18 is inclined in the tire longitudinal direction. 20 is provided to suppress the fall of the shoulder block 18, but as shown in FIGS. 9A and 9B, when the shoulder block 18 inclines in the tire longitudinal direction at the bottom 17k of the lug groove. Even if a rod-shaped protrusion 30 that contacts the side wall 18q on the rear side of the shoulder block 18 is provided to suppress the collapse of the shoulder block 18 block at the groove bottom 17k of the lug groove 17, a large compression angle α can be obtained. Can be secured.

  Thus, according to the present invention, it is possible to provide a tire capable of increasing the compression angle α and improving the WET brake performance without changing the rubber type of the tread rubber. Can be improved.

10 tires, 11 treads, 12-15 circumferential grooves, 16 rib-like land portions,
17 lug groove, 17k bottom of lug groove, 18 shoulder block,
18a flat part, 18b inclined part, 18p front side wall, 18q rear side wall,
19 Sipe, 20 Reinforcement block (protrusion).

Claims (1)

A tire provided with a circumferential groove provided in a tire tread and extending along a tire circumferential direction, a lug groove intersecting the circumferential groove, and a plurality of blocks defined by the circumferential groove and the lug groove. There,
A rod-like protrusion that extends in the extending direction of the lug groove and has a protruding length that comes into contact with the bottom of the lug groove when the block is inclined in the tire longitudinal direction during braking ;
And a sipe extending in a direction crossing the tire circumferential direction,
The bar-shaped protrusion is provided only on the wall surface on the block end side to be grounded after the wall surface facing the lug groove of the block,
Tire terminating in the depth direction of the sipe, characterized that you have located between the end portion of the tread surface side and the end portion of the lug groove bottom side of the bar-shaped projections of said bar-shaped projections.

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