JP4495223B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire having a tread pattern having a lateral groove extending across a ground contact end, and is particularly useful as a studless tire.

  Generally, in a studless tire, a groove is formed deeper and wider than a normal tire. This is a contrivance to improve the running performance on icy and snowy road surfaces with a low friction coefficient. According to such studless tires, a large amount of snow that has been compacted during running on icy and snowy roads is filled into the grooves and pushed in the grooves. A large driving force or braking force can be generated by utilizing the shear force of the hardened snow column (snow column shear force).

  However, in recent years, due to the influence of global warming, snow on the road surface melts as the temperature rises, and the icy and snowy road surface often becomes a sherbet state containing a lot of moisture. Such a sherbet-like icy and snowy road surface (hereinafter referred to as a sherbet road surface) cannot step on and harden snow, so that it is difficult to generate sufficient driving force and braking force even for studless tires.

  In Patent Document 1 below, a studless tire is proposed in which a tread is provided with a number of anti-slip holes or anti-slip chips, and water drain grooves are formed in communication with them. However, in this tire, since the groove width of the drainage groove connecting the respective parts is narrow, it is sufficient that the snow in the sherbet state is not smoothly discharged from the inside of the groove when traveling on the sherbet road surface, and a state close to aquaplaning is generated. Driving performance is difficult to obtain.

  Further, in order to improve the running performance on the sherbet road surface, a method is considered in which the lateral groove is formed to spread toward the tread end side and the snow in the sherbet state is discharged out of the groove. However, in this case, the rigidity of the block facing the lateral groove is partially reduced at a portion where the groove width is wide, so that there is a problem that uneven wear tends to occur.

  The following Patent Documents 2 and 3 disclose tires in which concave portions are provided on the wall surface of the block facing the lateral groove to adjust the compression rigidity of the block and the coefficient of friction of the wall surface. However, these are intentionally and positively different forms of the stepping side and kicking side of the block, so uneven wear such as toe and heel wear is caused by the difference in rigidity between the stepping side and the kicking side. It is likely to occur.

Patent Document 4 listed below describes a tire which is a wall surface of a shoulder block facing a lateral groove and has a recess on the outer side in the tire width direction from the ground contact end. However, this concave portion extends to the outer end of the shoulder block as the design end, and is not suitable for discharging snow in a sherbet state out of the groove. In the first place, this tire merely improves the fall limit performance of the vehicle by easily compressing and deforming the shoulder block by the recess, and does not disclose a structure useful as a studless tire.
Japanese Patent Laid-Open No. 7-81318 JP 2001-63319 A JP 2002-29223 A JP 2006-51927 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pneumatic tire that can improve running performance on a sherbet-like icy and snowy road surface without reducing uneven wear resistance. is there.

The above object can be achieved by the present invention as described below. That is, the pneumatic tire according to the present invention is a pneumatic tire having a tread pattern having a lateral groove extending across the ground contact end, and a discharge groove extending in the tire width direction is formed on a wall surface of a land portion facing the lateral groove. The discharge groove is open to the outside of the tread on the outer side in the tire radial direction with respect to the inlet portion disposed in the vicinity of the ground contact end in an unexposed state on the tread surface and the extended line of the groove bottom line. An outlet portion, and the groove depth of the discharge groove gradually increases toward the outer side in the tire width direction, and the groove wall closer to the tread surface of the discharge groove has a tire radial direction toward the outer side in the tire width direction. It is inclined and extends outward .

  According to the pneumatic tire of the present invention, when traveling on a sherbet road surface, snow in a sherbet state that has entered the lateral groove can be discharged to the outside of the tread laterally through the discharge groove. The discharge groove is formed by enlarging the volume of the lateral groove, and the outlet portion is opened on the outer side in the tire radial direction from the extension line of the groove bottom line, so that snow in a sherbet state can be discharged smoothly. Moreover, since the inlet portion of the discharge groove is disposed in the vicinity of the ground contact end in a state where it is not exposed on the tread surface, the rigidity of the land portion where the discharge groove is formed can be ensured. As a result, the running performance on the sherbet-like icy and snowy road surface can be improved without reducing the uneven wear resistance.

In the present invention, the groove depth of the discharge groove you gradually increases outward in the tire width direction. According to such a configuration, the effect of discharging snow in the sherbet state can be enhanced, and the running performance on the sherbet road surface can be suitably improved. In addition, since the groove depth is small at the inlet portion of the discharge groove, the rigidity of the land portion where the discharge groove is formed is maintained, and uneven wear hardly occurs.

In the present invention, the groove wall on the side closer to the tread surface of the discharge groove, Ru extends inclined outward in the tire radial direction toward the outer side in the tire width direction. According to such a configuration, it is possible to shorten the snow removal path and enhance the discharge effect as compared with the case where the discharge groove extends parallel to the tire width direction. In addition, since the angle formed by the groove wall on the side near the tread surface of the discharge groove and the outer wall on the side of the tread can be increased, a decrease in uneven wear resistance can be suppressed.

  In the present invention, it is preferable that the inlet portion of the discharge groove reaches the groove bottom of the lateral groove. According to such a configuration, the entrance portion of the discharge groove is kept away from the tread surface, and the rigidity of the land portion where the discharge groove is formed can be ensured satisfactorily, so that uneven wear such as toe and heel wear hardly occurs.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a development view showing an example of a tread pattern in the pneumatic tire of the present invention. FIG. 2 is a tire meridian cross-sectional view showing the main part of the pneumatic tire, and corresponds to a cross section taken along the line AA in FIG. FIG. 3 is a perspective view showing a main part of the pneumatic tire. These all show the unworn state when new.

  In the present embodiment, an example is shown in which the land portion of the tread surface is divided into five rows of blocks 1 by four circumferential grooves 3a to 3d. Each block 1 is formed with a number of wavy sipes, and the running performance on icy and snowy road surfaces with a low friction coefficient is enhanced by the edge effect and water removal effect of the sipe. The lateral groove 2 is formed linearly along the tire width direction WD, and divides the block 1 into the tire circumferential direction PD.

  As shown in FIG. 1, the pneumatic tire of the present invention includes a tread pattern having a lateral groove 2 extending across the ground contact CE. In the present invention, the lateral grooves 2 may be inclined with respect to the tire width direction WD or may be formed in a zigzag shape. The ground contact edge CE is the outermost position in the tire width direction when a tire that is assembled with a regular rim and loaded with a regular internal pressure and a regular load is grounded on a flat road surface.

  The regular rim corresponds to a standard rim defined in JATMA, “Design Rim” defined in TRA, or “Measuring Rim” defined in ETRTO. The normal internal pressure corresponds to the maximum air pressure specified by JATMA, the maximum value described in the TRA table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, or “INFLATION PRESSURE” specified by ETRTO. The normal load corresponds to the maximum load capacity defined by JATMA, the maximum value described in the table of TRA, or “LOAD CAPACITY” defined by ETRTO.

  The shoulder block 10 is a block 1 that is disposed on the outer side in the tire width direction of the circumferential grooves 3a and 3d that are the outermost of the four circumferential grooves 3a to 3d. The ground contact edge CE is located on the shoulder block 10 and the outer edge of the shoulder block 10 in the tire width direction is the design edge DE.

  As shown in FIGS. 2 and 3, the shoulder block 10 gradually decreases the land portion height toward the outer side in the tire width direction, and the design end DE is positioned on the inner side in the tire radial direction from the extension line L of the groove bottom line. To do. The groove bottom line is a line extending in the tire width direction through the groove bottoms of the circumferential grooves 3a to 3d, and the extension line L is an imaginary line when the groove bottom line is extended outward in the tire width direction. It is. Usually, the groove bottom line is configured by combining a plurality of curves (about three if only one side in the width direction of the tire), but an extension line extending from the inner side of the ground contact edge CE in the tire width direction is extended. L may be used.

  A discharge groove 4 extending in the tire width direction is formed on the wall surface 10 a of the shoulder block 10 facing the lateral groove 2. The discharge groove 4 opens to the outside of the tread laterally on the outer side in the tire radial direction with respect to the inlet portion 41 disposed in the vicinity of the ground contact CE without being exposed on the tread surface and the extension line L of the groove bottom line. And an outlet portion 42.

  When traveling on the sherbet road surface, snow in the sherbet state that has entered the lateral groove 2 is discharged to the outside of the tread through the discharge groove 4. The discharge groove 4 is formed by enlarging the volume of the lateral groove 2, and the outlet 42 is opened on the outer side in the tire radial direction from the extension line L of the groove bottom line. To discharge. On the other hand, when the discharge groove reaches the design end DE, the snow discharge path is longer than necessary, and an advantageous effect cannot be obtained.

  In addition, since the inlet portion 41 of the discharge groove 4 is disposed in the vicinity of the ground contact CE without being exposed on the tread surface, the rigidity of the land portion where the discharge groove 4 is formed, that is, the shoulder block 10 is secured. The Thus, the discharge groove 4 is designed not only to simply expand the volume of the lateral groove 2 but also to ensure the rigidity of the shoulder block 10 so that snow in a sherbet state can be discharged smoothly. . According to such a tire, the running performance on the sherbet road surface can be enhanced without reducing the uneven wear resistance.

  The discharge groove 4 preferably has a groove depth X of the outlet portion 42 of 0.3 mm or more, and more preferably 1 mm or more. Similarly, the groove width Y is preferably 0.5 mm or more, and more preferably 2 mm or more. If the groove depth X is less than 0.3 mm or the groove width Y is less than 0.5 mm, the effect of discharging snow in a sherbet state tends to be insufficient.

  In this embodiment, the groove depth of the discharge groove 4 is formed so as to gradually increase toward the outer side in the tire width direction. Thus, the groove depth is small on the inlet 41 side of the discharge groove 4 that has a large contribution to the block rigidity, and the groove depth increases on the outlet 42 side that has a large contribution to the effect of discharging snow in the sherbet state. Therefore, the running performance on the sherbet road surface can be effectively enhanced without reducing the uneven wear resistance.

  In the present invention, the discharge grooves 4 are preferably formed on the respective wall surfaces 10a before and after the tire block in the tire circumferential direction as in the present embodiment. As a result, the difference in rigidity between the step-in side and the kick-out side of the shoulder block 10 can be reduced as much as possible, and the occurrence of toe and heel wear can be suppressed.

  The inlet 41 of the discharge groove 4 may be located on the inner side in the tire width direction than the ground contact edge CE. However, from the viewpoint of suppressing a reduction in rigidity of the shoulder block 10, the width W of the shoulder block 10 from the ground contact edge CE. It is preferable that the inlet 41 is not overhanging at a position exceeding 10%. The width W of the shoulder block 10 referred to here is a width dimension measured on the inner side in the tire width direction with reference to the ground contact CE as shown in FIG.

  In the present embodiment, the groove wall 4a on the side close to the tread surface of the discharge groove 4 is inclined and extended outward in the tire radial direction toward the outer side in the tire width direction. As a result, the snow removal path is shortened compared to the discharge groove extending in parallel with the tire width direction, and the effect of discharging the sherbet-like snow can be enhanced. In addition, since the angle θ formed by the groove wall 4a and the outer wall on the side of the tread can be increased, it is possible to secure rigidity at this portion and suppress a decrease in uneven wear resistance.

  Furthermore, in this embodiment, the inlet 41 of the discharge groove 4 reaches the groove bottom of the lateral groove 2. As a result, the entrance portion 41 is moved away from the tread surface, and the rigidity of the land portion where the discharge groove 4 is formed, that is, the shoulder block 10 is secured satisfactorily, thereby suppressing the occurrence of uneven wear such as toe and heel wear. it can.

  The pneumatic tire of the present invention is particularly useful as a studless tire (winter tire) because it can improve the running performance on the sherbet road surface and has a tread pattern that hardly causes uneven wear such as toe and heel wear. . In the studless tire, a relatively soft rubber is used for the tread, and its rubber hardness (rubber hardness measured according to JISK6253 durometer hardness test (type A)) is, for example, 43 to 65 °.

  The pneumatic tire of the present invention is the same as a normal pneumatic tire except that the discharge groove as described above is formed, and any conventionally known material, shape, structure, manufacturing method, etc. can be adopted in the present invention. .

[Other Embodiments]
(1) In the above-described embodiment, the example in which the discharge groove extends linearly in the tire width direction is shown. However, the present invention is not limited to this, and for example, the outlet portion 42 is formed to be thick as shown in FIG. This is also a preferred embodiment. Moreover, you may extend the discharge groove 4 in the tire width direction in the shape as shown in FIG. These increase the volume of the outlet portion 42 as compared with the above-described embodiment, and can improve the effect of discharging snow in a sherbet state.

  (2) In the above-described embodiment, the example in which the discharge groove is formed on the wall surface of the shoulder block has been described. However, in the present invention, a shoulder rib can be used instead of the shoulder block. When the shoulder rib is employed, a lateral groove extending across the grounding end may be formed in a state where the end is closed, and the discharge groove as described above may be formed on the wall surface facing the lateral groove.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. In addition, each performance evaluation of the tire was performed as follows.

(1) Driving performance on a sherbet road surface Tires are mounted on a real vehicle (3000cc class sedan) and run on a sherbet road surface (depth of sherbet is about 8mm), running straight, turning, braking, etc. at a speed of 40km / h. Then, it was evaluated by a driver's sensory test. In addition, evaluation is shown by an index display when the conventional product (Comparative Example 1) is set to 100, and a larger value indicates a better result.

(2) Wear resistance performance When the tire is mounted on a real car (3000 cc class sedan) and running on a dry paved road for 8000 km, the amount of step wear (maximum difference in height before and after the block edge due to wear) is measured. evaluated. In addition, evaluation is shown by an index display when the conventional product (Comparative Example 1) is set to 100, and a larger value indicates a better result.

Comparative example 1 (conventional product)
A pneumatic tire of size 205 / 65R15 having a tread pattern in which no discharge groove is formed in FIG. The maximum depth of the transverse groove was 9 mm, and the groove width of the transverse groove was 6 mm.

Example 1
A pneumatic tire of the size 205 / 65R15 having the tread pattern shown in FIG. The shape of the discharge groove is as shown in FIGS. 1 to 3 (groove depth 1.5 mm, groove width 2.5 mm), and other tire specifications were the same as in Comparative Example 1. The results of each performance evaluation are shown in Table 1.

  As shown in Table 1, in Comparative Example 1, the running performance on the sherbet road surface is not improved as in the case of a normal studless tire. On the other hand, in the embodiment, the running performance on the sherbet road surface can be improved without reducing the uneven wear resistance.

The expanded view which shows an example of the tread pattern in the pneumatic tire of this invention Tire meridian cross-sectional view showing the main part of the pneumatic tire of FIG. The perspective view which shows the principal part of the pneumatic tire of FIG. Sectional drawing of the principal part in another embodiment of this invention Sectional drawing of the principal part in another embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Block 2 Horizontal groove 3a-3d Circumferential groove | channel 4 Discharge groove | channel 4a Groove wall 10 Shoulder block 10a Wall surface 41 Inlet part 42 Outlet part CE Grounding edge DE Design end L Extension line of groove bottom line

Claims (2)

In a pneumatic tire having a tread pattern having a transverse groove extending across the ground contact edge,
A discharge groove extending in the tire width direction is formed on the wall surface of the land portion facing the lateral groove, and the discharge groove is not exposed on the tread surface and is disposed in the vicinity of the ground contact end, and the groove bottom line An outlet portion that is open to the outside of the tread laterally outside the extension line in the tire radial direction ,
The groove depth of the discharge groove gradually increases toward the outer side in the tire width direction, and the groove wall on the side near the tread surface of the discharge groove extends toward the outer side in the tire width direction so as to incline toward the outer side in the tire radial direction. A featured pneumatic tire. The pneumatic tire according to claim 1, wherein an inlet portion of the discharge groove reaches a groove bottom of the lateral groove.

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