JP5798414B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire that improves mud performance and drainage performance while suppressing deterioration of noise performance.

  For example, in an all-season tire traveling on a mud road surface, the tread portion is divided into a plurality of blocks by a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of lateral grooves extending in the tire axial direction. A pattern is adopted. Conventionally, in order to improve mud performance and drainage performance, the groove depth and width of the lateral groove are increased to increase the shearing force against the traction and mud pressed in the lateral groove, and also smooth drainage to the grounding end side That is known.

  However, in the above-described method, the groove volume of the lateral groove increases, and resonance vibration of air (air column resonance sound) generated in the circumferential groove is easily discharged from the lateral groove to the grounding end side, and noise performance is deteriorated. There was a problem. Thus, there is a tradeoff between improving the mud performance and drainage performance and ensuring the noise performance, and it has been difficult to achieve both. Related technologies include the following.

Japanese Patent Laid-Open No. 11-245625

  The present invention has been devised in view of the above problems, and is based on improving the shape of the shoulder lateral groove extending from the shoulder circumferential groove to the tire axial direction outside, while suppressing the deterioration of noise performance. The main object is to provide a pneumatic tire capable of improving the mud performance and drainage performance.

  The invention according to claim 1 of the present invention includes a shoulder circumferential groove extending continuously from the shoulder circumferential direction to the tire circumferential direction on the tread portion, the tire circumferential direction groove extending outwardly in the tire axial direction from the shoulder circumferential groove. By providing a plurality of extending shoulder lateral grooves, a pneumatic tire in which a shoulder block row in which shoulder blocks are spaced in the tire circumferential direction along the ground contact end is formed, and the shoulder lateral grooves are An inner portion extending from the shoulder circumferential groove at a first angle α1 of 10 to 20 degrees with respect to the tire axial direction, and connected to the inner portion and from the first angle α1 with respect to the tire axial direction. An intermediate portion extending at an incline at a second angle α2, and an outer portion connected to the intermediate portion and extending at an angle α3 smaller than the second angle α2 with respect to the tire axial direction. In addition, the shoulder lateral groove includes a first shoulder lateral groove having a large average groove width from an inner end in the tire axial direction to a ground contact end, and a second shoulder lateral groove having a smaller average groove width than the first shoulder lateral groove. Alternately formed in the tire circumferential direction, the intermediate portion of the shoulder lateral groove has an anti-inclined side groove edge that is a groove edge opposite to the side inclined with respect to the tire axial direction. The amount of deviation, which is the distance in the tire circumferential direction between the inner end and the outer end in the tire axial direction of the side groove edge, is 20 to 50% of the groove width in the tire circumferential direction at the inner end in the tire axial direction of the anti-tilt side groove edge.

  In the invention according to claim 2, the groove width in the tire circumferential direction of the first shoulder lateral groove gradually increases from the inner end in the tire axial direction to the ground contact end of the first shoulder lateral groove, and the inner width of the second shoulder lateral groove is increased. 2. The pneumatic tire according to claim 1, wherein a groove width in the tire circumferential direction is constant from the inner end to the outer end in the tire axial direction of the inner portion.

  According to a third aspect of the present invention, the length in the tire axial direction of the inner portion of the first shoulder lateral groove is smaller than the length in the tire axial direction of the inner portion of the second shoulder lateral groove. Tire.

The invention according to claim 4 is the pneumatic tire according to any one of claims 1 to 3, wherein a groove width Wg1 of the shoulder circumferential groove in the tire axial direction is 4 to 10% of a tread ground contact width TW. is there.

Further, in the invention according to claim 5, the shoulder circumferential groove includes an outer groove portion extending along the tire circumferential direction on the outer side in the tire axial direction, and an inner side extending along the tire circumferential direction in the tire axial direction from the outer groove portion. A trapezoidal wave-shaped zigzag including a groove portion and a transition groove portion obliquely extending from the inner groove portion to the outer groove portion is formed, from the groove edge on the outer side in the tire axial direction of the inner groove portion to the groove edge on the outer side in the tire axial direction of the outer groove portion. 5. The pneumatic tire according to claim 4 , wherein a protruding amount Lb that is a distance in the tire axial direction is 0.5 to 0.8 times the groove width Wg <b> 1.

  The pneumatic tire of the present invention has a shoulder circumferential groove extending continuously in the tire circumferential direction on the tread portion, and a plurality of tires extending from the shoulder circumferential groove to the tire axial direction outside the grounded end. By providing the shoulder lateral groove, a shoulder block row in which shoulder blocks are spaced in the tire circumferential direction along the ground contact end is formed.

  The shoulder lateral groove includes an inner portion extending from the shoulder circumferential groove at a first angle α1 of 10 to 20 degrees with respect to the tire axial direction, and connected to the inner portion and the first angle. The intermediate portion extends at a second angle α2 larger than α1 and the outer portion is connected to the intermediate portion and extends at an angle α3 smaller than the second angle α2. Such shoulder lateral grooves have mud performance and drainage because the inner and outer parts, which have a relatively small angle with respect to the tire axial direction, easily discharge mud and drainage from the shoulder longitudinal groove to the grounding end when turning. Can increase performance. In addition, since the intermediate portion having a relatively large angle with respect to the tire axial direction disturbs and reduces the resonance vibration (air column resonance sound) of the air generated in the shoulder circumferential groove, the noise performance can be improved.

  The shoulder lateral groove includes a first shoulder lateral groove having a large average groove width from an inner end in the tire axial direction to a ground contact end, and a second shoulder lateral groove having a smaller average groove width than the first shoulder lateral groove. It is formed alternately in the direction. That is, since the first and second shoulder lateral grooves having different groove areas (groove volumes) are alternately arranged in the shoulder block row, the peak of the pitch sound is effectively suppressed. Accordingly, the noise performance of the pneumatic tire of the present invention is further improved.

  The intermediate portion of the shoulder lateral groove has an anti-inclined groove edge which is a groove edge opposite to the side where the intermediate portion is inclined with respect to the tire axial direction. And the amount of deviation which is the distance in the tire circumferential direction between the outer ends is set to 20 to 50% of the groove width in the tire circumferential direction at the inner end in the tire axial direction of the anti-tilt side groove edge. Such shoulder lateral grooves reduce air column resonance noise by colliding and absorbing the groove wall of the anti-tilt side groove edge, effectively suppressing discharge to the ground end, and when traveling straight, the anti-tilt side groove edge The tire circumferential direction component ensures soil discharge and drainage to the ground contact end. Therefore, the pneumatic tire of the present invention can further improve the noise performance and improve the drainage performance and mud performance in a well-balanced manner.

It is an expanded view of the tread part which shows the pneumatic tire of one Embodiment of this invention. It is an enlarged view of the right half of FIG. FIG. 3 is an enlarged view of the vicinity of a shoulder circumferential groove in FIG. 2.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the pneumatic tire of this embodiment (hereinafter, simply referred to as “tire”) is preferably used as an all-season tire for a four-wheel drive vehicle, for example, and a tread portion thereof. 2 includes a pair of shoulder circumferential grooves 3 that extend most continuously on the ground contact end Te side in the tire circumferential direction, and a pair that extends on the tire equator C side continuously in the tire circumferential direction from the shoulder circumferential grooves 3. Center circumferential grooves 4 are provided. Thus, the tread portion 2 has a pair of shoulder land portions 5 extending between the shoulder circumferential groove 3 and the ground contact Te, and a pair of middle land portions extending between the center circumferential groove 4 and the shoulder circumferential groove 3. A pair of center land portions 7 extending between the portion 6 and the pair of center circumferential grooves 4 and 4 are formed. Therefore, the tire 1 of this embodiment includes a total of five land portions in the tread portion 2.

  Here, the “grounding end” Te is obtained when a normal load is loaded on a normal rim that is assembled with a normal rim and filled with a normal internal pressure, and a normal load is applied to a flat surface with a camber angle of 0 degrees. Is defined as the ground contact position on the outermost side in the tire axial direction. The distance in the tire axial direction between the ground contact Te and Te is determined as the tread ground contact width TW. Further, the dimensions and the like of each part of the tire are values in the normal state unless otherwise specified.

  The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, “Standard Rim” for JATMA and “Design Rim” for TRA. For ETRTO, use "Measuring Rim".

  The “regular internal pressure” is the air pressure defined by each standard for each tire in the standard system including the standard on which the tire is based, and is “maximum air pressure” for JATMA and table for TRA. The maximum value described in TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES is "INFLATION PRESSURE" for ETRTO, but 180 kPa for tires for passenger cars.

  Furthermore, “regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. “Maximum load capacity” for JATMA, “TIRE” for TRA The maximum value described in “LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” is “LOAD CAPACITY” if it is ETRTO, but if the tire is for a passenger car, the load is equivalent to 88% of the above load.

  In the shoulder land portion 5, shoulder lateral grooves 8 extending from the shoulder circumferential groove 3 outward in the tire axial direction beyond the ground contact end Te are provided in the tire circumferential direction. Thereby, the shoulder land portion 5 is formed with a shoulder block row 9R in which a plurality of shoulder blocks 9 divided by the shoulder circumferential groove 3, the ground contact Te and the shoulder lateral groove 8 are arranged in the tire circumferential direction along the ground contact Te. Is done.

  The shoulder circumferential groove 3 includes an outer groove portion 10 extending outside in the tire axial direction along the tire circumferential direction, an inner groove portion 11 extending along the tire circumferential direction in the tire axial direction from the outer groove portion 10, and the inner side. It is formed in a trapezoidal wavy zigzag including a transition groove portion 12 extending obliquely from the groove portion 11 to the outer groove portion 10. Since the transition groove portion 12 extending obliquely has a tire axial direction component, it is easy to grasp mud in the groove of the transition groove portion 12 and obtains a large shearing force against the mud pressed in the groove. be able to. Moreover, the outer side groove part 10 and the inner side groove part 11 which extend along a tire circumferential direction are useful for improving a soil removal property.

  As shown in FIG. 2, the transition groove portion 12 includes a first transition piece 12 </ b> A extending between the inner groove portion 11 and the outer groove portion 10 so as to incline toward one side (downward in the present figure) with respect to the tire axial direction. And the second transition piece 12B extending in a direction opposite to the first transition piece 12A (upward to the right in the figure). That is, in the shoulder circumferential groove 3 of the present embodiment, the outer groove portion 10, the first transition piece 12A, the inner groove portion 11 and the second transition piece 12B are sequentially formed in the trapezoidal wavy zigzag.

  Further, as shown in FIG. 3, the shoulder circumferential groove 3 is a tire axial distance from the groove edge 11 e on the outer side in the tire axial direction of the inner groove part 11 to the groove edge 10 e on the outer side in the tire axial direction of the outer groove part 10. The protruding amount Lb is preferably formed to be 0.5 to 0.8 times the groove width Wg1 of the shoulder circumferential groove 3 in the tire axial direction. That is, if the protruding amount Lb is smaller than 0.5 times the groove width Wg1, the shearing force against the mud pressed in the shoulder circumferential groove 3 may be reduced. If it exceeds, the soil resistance and drainage resistance will increase, and the mud performance and drainage performance may be deteriorated.

  In order to exhibit the above-mentioned action more effectively, the angle θ1 of the groove center line 12G of the transition groove portion 12 with respect to the tire axial direction is preferably 35 degrees or more, more preferably 40 degrees or more, and preferably 60 degrees. Degrees or less, more preferably 55 degrees or less are desirable.

  Further, the groove width Wg1 of the shoulder circumferential groove 3 in the tire axial direction is preferably formed to 4.0 to 10.0% of the tread ground contact width TW. When the groove width Wg1 is increased, the groove volume is increased and the noise performance is deteriorated, and the rigidity of the land portions 5 and 6 may be reduced. On the other hand, when the groove width Wg1 is reduced, the soil drainage drainage using the tire rolling is deteriorated and the mud performance and drainage performance are deteriorated. For this reason, the groove width Wg1 is more preferably 6% or more of the tread ground contact width TW, and more preferably 8% or less. Moreover, about the groove depth D1 (not shown) of the shoulder circumferential direction groove | channel 3, in order to exhibit the above-mentioned effect | action effectively, 9.0-10.0 mm is desirable, for example.

Further, in the present embodiment, the center circumferential groove 4 is also similar to the shoulder circumferential groove 3, and in this embodiment, the outer groove portion 4 a extends outside in the tire axial direction along the tire circumferential direction, and the inner side in the tire axial direction extends in the tire circumferential direction. A trapezoidal wave-shaped zigzag including an inner groove portion 4b extending along and a transition groove portion 4c extending obliquely from the inner groove portion 4b to the outer groove portion 4a is formed. Thereby, also in a crown part, the effect | action similar to the shoulder circumferential groove | channel 3 is acquired, and a mud performance can be improved by extension. In addition, the shape of the shoulder circumferential groove 3 and the center circumferential groove 4 is not limited to such an aspect, and various shapes can be adopted.

  Further, the groove width Wg2 (shown in FIG. 2) and the groove depth D2 (not shown) in the tire circumferential direction of the center circumferential groove 4 can be variously determined according to customary practice. For example, the groove width Wg2 is determined by the tread. The ground contact width TW is desirably 2.0 to 6.0%, and the groove depth D2 is desirably 9.0 to 10.0 mm.

  Further, as shown in FIG. 1, with respect to the position where the shoulder circumferential groove 3 is disposed, for example, the tire axial distance L1 between the amplitude center line 3G and the ground contact Te is preferably the tread ground contact width TW. 15% or more, more preferably 20% or more is desirable, preferably 35% or less, and more preferably 30% or less. Further, with respect to the position where the center circumferential groove 4 is disposed, for example, the tire axial direction distance L2 between the amplitude center line 4G and the tire equator C is preferably 4% or more of the tread ground contact width TW, more preferably 4 0.5% or more is desirable, preferably 9.0% or less, and more preferably 8.5% or less. By setting to such a range, the rigidity balance of the land portions 5, 6 and 7 can be further improved, and uneven wear resistance can be improved.

As shown in FIG. 2, the shoulder lateral groove 8 includes an inner portion 13 extending from the shoulder circumferential groove 3 at a first angle α1 of 10 to 20 degrees with respect to the tire axial direction, and the inner portion 13. And an intermediate portion 14 that is inclined at a second angle α2 that is larger than the first angle α1, and an outer portion that is connected to the intermediate portion 14 and extends at an angle α3 that is smaller than the second angle α2. Part 15. Such a shoulder lateral groove 8 can easily remove mud and drainage in the shoulder circumferential groove 3 through the inner side portion 13 and the outer side portion 15 having a relatively small angle with respect to the tire axial direction during cornering. Therefore, mud performance and drainage performance can be improved. Further, the intermediate portion 14 having a relatively large angle with respect to the tire axial direction disturbs and reduces the resonance vibration (air column resonance sound) of the air generated in the shoulder circumferential groove at the groove wall of the intermediate portion 14. Noise performance can be improved.

  Moreover, the inner side part 13, the intermediate | middle part 14, and the outer side part 15 of this embodiment incline in the same direction with respect to a tire axial direction, and are extended to the earthing | grounding end Te. Such a shoulder lateral groove 8 can more smoothly discharge mud and drainage in the shoulder circumferential groove 3 to the grounding end Te side, and is useful for further improving drainage performance and mud performance.

  When the first angle α1 is less than 10 degrees, mud in the shoulder circumferential groove 3 cannot be smoothly discharged to the ground contact Te side, mud performance and drainage performance deteriorate, and the shoulder circumferential groove 3 and shoulder lateral groove The rigidity of the shoulder block 9 in the vicinity of the connection with the belt 8 may be reduced, and uneven wear may occur. If the first angle α1 exceeds 20 degrees, the edge component in the tire axial direction becomes small, and the mud performance deteriorates. For this reason, the angle α1 is more preferably 12 degrees or more, and more preferably 18 degrees or less.

  The intermediate portion 14 is formed at a second angle α2 that is larger than the first angle α1 of the inner portion 13. That is, the second angle α2 is not particularly limited as long as it is larger than 20 degrees, but preferably, the difference (α2−α1) between the second angle α2 and the first angle α1 is 20 to 20 degrees. 40 degrees is desirable. That is, when the difference (α2−α1) becomes small, the tire circumferential direction component of the groove wall 14b of the intermediate portion 14 becomes small, and the air column resonance noise cannot be absorbed and diffused, and the noise performance may be deteriorated. On the contrary, when the difference (α2−α1) increases, drainage resistance and the like at the intermediate portion 14 increase during turning, so that the drainage and drainage smoothly from the shoulder circumferential groove 3 and the inner portion 13 toward the grounding end Te side. It becomes difficult to be excavated. For this reason, the angle difference (α2−α1) is more preferably 25 degrees or more, and more preferably 35 degrees or less.

  The outer portion 15 is formed at a third angle α3 that is smaller than the second angle α2 of the intermediate portion 14, but in order to exhibit the above-described action more effectively, the outer portion 15 and the third angle α3 The difference (α2−α3) from the second angle α2 is preferably 30 degrees or more, more preferably 35 degrees or more, and preferably 50 degrees or less, more preferably 45 degrees or less.

  Further, the shoulder lateral groove 8 is an average groove from the inner end 8i in the tire axial direction (intersection of the groove center line 8G of the shoulder lateral groove 8 and the groove edge 3e on the grounding edge Te side of the shoulder circumferential groove 3) to the grounding edge Te. The first shoulder lateral groove 8A having a relatively large width (average over the tire axial direction of the groove width perpendicular to the longitudinal direction of the groove) and a second shoulder having the average groove width Wa smaller than the first shoulder lateral groove 8A The lateral grooves 8B are alternately formed in the tire circumferential direction. Accordingly, the first and second shoulder lateral grooves 8A and 8B having different groove areas (groove volumes) are alternately arranged in the shoulder block row 9R, so that the peak of the pitch sound during tire rolling is effectively reduced. Is done. Therefore, the noise performance of the pneumatic tire 1 of the present invention is further improved.

  When the ratio Wa1 / Wa2 between the average groove width Wa1 (not shown) of the first shoulder lateral groove 8A and the average groove width Wa2 (not shown) of the second shoulder horizontal groove 8B is increased, the drainage performance and the soil removal performance are improved. The deterioration or the effect of providing the intermediate portion 14 is not sufficiently exhibited, and the noise performance may be deteriorated. On the contrary, when the ratio Wa1 / Wa2 is small, there is a possibility that the pitch sound cannot be effectively reduced. For this reason, the ratio Wa1 / Wa2 is preferably greater than 1.0, more preferably 1.2 or more, and preferably 2.0 or less, more preferably 1.5 or less.

  Further, as shown in FIG. 3, the intermediate portion 14 of the shoulder lateral groove 8 has an anti-inclined side groove edge 16 which is a groove edge opposite to the side where the intermediate portion 14 is inclined with respect to the tire axial direction. Yes. The amount of deviation Lc, which is the distance in the tire circumferential direction between the inner end 16i in the tire axial direction and the outer end 16e of the anti-tilt side groove edge 16, is a groove in the tire circumferential direction at the inner end 16i in the tire axial direction of the anti-tilt side groove edge 16. It needs to be set to 20 to 50% of the width Ws1. That is, when the deviation Lc is less than 20% of the groove width Ws1, the intermediate column 14 cannot absorb and diffuse the air column resonance sound in the shoulder circumferential groove 3 and noise performance deteriorates. On the contrary, if the amount of displacement Lc exceeds 50% of the groove width Ws1, it becomes difficult for the soil and drainage in the shoulder circumferential groove 3 to be discharged to the grounding end Te side during turning, and the mud performance and drainage performance deteriorate. To do. For this reason, the deviation Lc is preferably 25% or more of the groove width Ws1, and preferably 45% or less.

  Thus, in the tire 1 of the present invention, the shoulder lateral groove 8 extending from the shoulder circumferential groove 3 beyond the ground contact Te has a relatively large angle with respect to the tire axial direction and the intermediate portion 14 having a relatively large angle with respect to the tire axial direction. By providing the inner part 13 and the outer part 15 which are small in size, noise performance, mud performance and drainage performance are improved in a well-balanced manner.

  Further, the groove width WsA in the tire circumferential direction of the first shoulder lateral groove 8A of the present embodiment gradually increases from the tire axial direction inner end 8A1 to the ground contact end Te of the first shoulder lateral groove 8A. On the other hand, the groove width WsB in the tire circumferential direction of the inner portion 13B of the second shoulder lateral groove 8B of the present embodiment is constant from the inner end 13B1 to the outer end 13B2 in the tire axial direction of the inner portion 13B. Such first shoulder lateral grooves 8A are more smoothly drained and drained toward the ground contact Te when turning, and help to improve mud performance and drainage performance. Further, the inner portion 13B of the second shoulder lateral groove 8B is useful for ensuring a large rigidity of the shoulder block 9 and improving uneven wear resistance. That is, by alternately providing the first shoulder lateral grooves 8A and the second shoulder lateral grooves 8B in the tire circumferential direction, the drainage performance and the mud performance are improved in a well-balanced manner while ensuring the rigidity of the shoulder block 9.

  Further, as shown in FIG. 2, the tire axial direction length La1 of the inner side portion 13A of the first shoulder lateral groove 8A is formed smaller than the tire axial direction length La2 of the inner side portion 13B of the second shoulder lateral groove 8B. ing. Such a shoulder lateral groove 8 further helps to reduce air column resonance while ensuring the rigidity of the shoulder block 9. Therefore, the tire 1 of the present embodiment improves the mud performance, drainage performance, noise performance, and uneven wear resistance in a well-balanced manner. In addition, when the tire axial direction length La2 of the said inner side part 13B becomes large too much, there exists a possibility that soil discharging property or drainage property may deteriorate. Therefore, the ratio La2 / La1 between the tire axial direction length La1 and the tire axial direction length La2 is preferably 1.1 or more, more preferably 1.2 or more, and preferably 1.4. Hereinafter, 1.3 or less is desirable.

  Further, as shown in FIG. 3, the shoulder lateral groove 8 of the present embodiment is connected across the front and rear ends in the tire circumferential direction of the groove edge 12Be on the ground contact Te side of the second transition piece 12B. Thereby, since the rigidity of the shoulder block 9 in the vicinity of the connection between the shoulder lateral groove 8 and the second transition piece 12B is secured, uneven wear can be suppressed.

  The groove depth D3 (not shown) of the shoulder lateral groove 8 is preferably 90 to 100% of the groove depth D1 of the shoulder circumferential groove 3, for example, from the viewpoint of achieving both mud performance, drainage performance, and noise performance. .

  Next, the middle land portion 6 and the center land portion 7 of this embodiment will be described. As shown in FIGS. 1 and 2, the middle land portion 6 is provided with middle lateral grooves 20 that are inclined from the shoulder circumferential groove 3 to the center circumferential groove 4 in the tire circumferential direction. Accordingly, the middle land portion 6 includes a middle block row 21R in which a plurality of middle blocks 21 partitioned by the shoulder circumferential groove 3, the center circumferential groove 4, and the middle lateral groove 20 are arranged in the tire circumferential direction along the ground contact Te. Formed as.

  The middle lateral groove 20 includes an equal width portion 20a extending from the center circumferential groove 4 with a constant groove width, an enlarged portion 20b connected to the equal width portion 20a and gradually increasing in groove width, and the enlarged portion 20b and the shoulder circumference. It comprises a gradually increasing portion 20c extending between the directional grooves 3 and gradually increasing at a rate that the groove width is smaller than that of the enlarged portion 20b. Such a middle lateral groove 20 increases the rigidity of the middle block 21 on the tire equator C side where the contact pressure is high when traveling straight, and effectively drains and discharges the soil in the center circumferential groove 4 on the shoulder circumferential groove 3 side. In addition, the air column resonance sound in the center circumferential groove 4 is prevented from flowing toward the shoulder circumferential groove 3. Therefore, the tire 1 of the present embodiment is further effectively improved in uneven wear resistance, drainage performance, mud performance, and noise performance. It is desirable that the middle lateral groove 20 be inclined in the direction opposite to the shoulder lateral groove 8 in order to effectively exhibit the above action regardless of the rotation direction of the tire.

  Further, the middle land portion 6 includes a middle outer lug groove 22 that inclines in the tire axial direction from the shoulder circumferential groove 3 and terminates without contacting the center circumferential groove 4, and a center circumferential groove. In-middle lug grooves 23 that are inclined toward the outer side in the tire axial direction from 4 and terminate without contacting the shoulder circumferential groove 3 are spaced apart in the tire circumferential direction. Such middle outer lug groove 22 and middle inner lug groove 23 increase the edge component in the tire axial direction while ensuring the rigidity of the middle land portion 6 and serve to increase the traction and improve the mud performance. The middle outer lug groove 22 and the middle inner lug groove 23 are preferably inclined in the same direction in order to maintain the rigidity of the middle land portion 6 high.

  Further, the center land portion 7 is provided with a center lug groove 24 extending in the tire axial direction from the center circumferential groove 4 toward the tire equator C and terminating without reaching the tire equator C. Such a center lug groove 24 increases the edge component in the tire axial direction while ensuring rigidity in the vicinity of the tire equator C where the ground pressure acts greatly during straight traveling, and thus increases traction and improves mud performance. Useful.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, it cannot be overemphasized that this invention can be deform | transformed and implemented in various aspects, without being limited to embodiment of illustration.

Pneumatic tires (size: 285 / 60R18) having the pattern of FIG. 1 and based on the specifications in Table 1 were manufactured and tested for their respective performance. The common specifications are as follows.
Tread contact width TW: 114mm
<Shoulder circumferential groove>
Groove depth D1: 10.0 mm
<Center circumferential groove>
Groove depth D2: 10.0mm
<Shoulder lateral groove>
Groove depth D3 / D1: 100%
Second angle α2 of the middle portion of the first shoulder lateral groove: 35 degrees First angle α1: 10 degrees of the inner portion of the second shoulder transverse groove Second angle α2 of the second shoulder lateral groove α2: 35 degrees Second The third angle α3: 2 degrees of the outer portion of the shoulder lateral groove The test method is as follows.

<Noise performance>
A sample tire is mounted on all wheels of a vehicle (domestic 4600cc, 4WD vehicle) under the conditions of a rim 18 × 8.5JJ and internal pressure (230 kPa), and the road noise measurement path (asphalt rough road) at a speed of 60 km / h. In-vehicle noise during driving was collected with a microphone installed at the driver's seat window side ear position, and the sound pressure level of the peak value of the air column resonance sound in the narrow band around 240 Hz was measured. The evaluation is shown by an index with the reciprocal of Comparative Example 1 being 100, and the larger the numerical value, the better.

<Mad performance>
Under the above-mentioned vehicle conditions, a single driver on the mud road test course was run, and braking force, turning performance, etc. were evaluated comprehensively based on the driver's feeling. Evaluation is based on a score of Comparative Example 1 being 100, and the larger the value, the better.

<Traction performance>
The same test course under the above vehicle conditions was run by a professional test driver, and the degree of transmission of driving force to the road surface was evaluated by the driver's feeling. The comparative example 1 is set as 100, and the larger the value, the better.

<Uneven wear resistance>
Under the above vehicle conditions, a dry asphalt tire test course was run for 30 km by limit running, and the presence or absence of ribs, blocks, uneven wear, etc. were visually observed. The evaluation is indicated by a score with Comparative Example 1 being 100, and the larger the numerical value, the better the uneven wear resistance.

<Drainage performance>
Under the above vehicle conditions, the vehicle is approached while increasing the speed stepwise on a course with a water depth of 10 mm and a length of 20 m on an asphalt road surface with a radius of 100 m, and the lateral acceleration (lateral G) is measured. The average lateral G of the front wheels at a speed of 50 to 80 km / h was calculated. The results were expressed as an index with Comparative Example 1 as 100. The larger the value, the better.
The test results are shown in Table 1.

  As a result of the test, it can be confirmed that the tires of the examples have improved various performances as compared with the comparative examples.

2 tread portion 3 shoulder circumferential groove 8 shoulder lateral groove 8A first shoulder lateral groove 8B second shoulder lateral groove 9 shoulder block 9R shoulder block row 13 inner portion 14 intermediate portion 14e anti-tilt side groove edge 15 outer portion Lc tire axis of anti-tilt side groove edge Deviation amount 16i between the inner and outer ends in the tire direction inner end Te of the anti-tilt side groove edge Te Ground end Wa Average groove width Ws1 Groove width in the tire circumferential direction at the inner end in the tire axial direction of the anti-tilt side groove edge

Claims (5)

The tread portion is provided with a shoulder circumferential groove extending continuously in the tire circumferential direction on the most grounded end side, and a plurality of shoulder lateral grooves extending beyond the grounded end from the shoulder circumferential groove outward in the tire axial direction. According to the pneumatic tire in which a shoulder block row in which shoulder blocks are spaced in the tire circumferential direction along the ground contact end is formed,
The shoulder lateral groove includes an inner portion extending at a first angle α1 of 10 to 20 degrees with respect to the tire axial direction from the shoulder circumferential groove, and an inner portion connected to the inner portion and extending in the tire axial direction. An intermediate portion extending at an inclination of a second angle α2 larger than the angle α1 of 1 and an outer portion connected to the intermediate portion and extending at an angle α3 smaller than the second angle α2 with respect to the tire axial direction. Become
In addition, the shoulder lateral groove includes a first shoulder lateral groove having a large average groove width from an inner end in the tire axial direction to a grounding end, and a second shoulder lateral groove having a smaller average groove width than the first shoulder lateral groove. Alternately formed in the direction,
The intermediate portion of the shoulder lateral groove has an anti-inclined side groove edge that is a groove edge opposite to the side where the intermediate portion is inclined with respect to the tire axial direction,
The amount of deviation, which is the distance in the tire circumferential direction between the inner end and the outer end in the tire axial direction of the anti-tilt side groove edge, is 20 to 50% of the groove width in the tire circumferential direction at the inner end in the tire axial direction of the anti-tilt side groove edge. A pneumatic tire characterized by being. The groove width in the tire circumferential direction of the first shoulder lateral groove gradually increases from the inner end in the tire axial direction of the first shoulder lateral groove to the ground contact end,
2. The pneumatic tire according to claim 1, wherein a groove width in a tire circumferential direction of an inner portion of the second shoulder lateral groove is constant from an inner end to an outer end in a tire axial direction of the inner portion.   The pneumatic tire according to claim 1 or 2, wherein a tire axial direction length of an inner part of the first shoulder lateral groove is smaller than a tire axial direction length of an inner part of the second shoulder lateral groove. The pneumatic tire according to any one of claims 1 to 3, wherein a groove width Wg1 in the tire axial direction of the shoulder circumferential groove is 4 to 10% of a tread ground contact width TW. The shoulder circumferential groove includes an outer groove portion extending in the tire circumferential direction on the outer side in the tire axial direction, an inner groove portion extending in the tire axial direction on the inner side in the tire axial direction from the outer groove portion, and the outer groove portion from the inner groove portion. A trapezoidal wave-shaped zigzag including a transition groove extending obliquely in the groove,
A protruding amount Lb, which is a distance in the tire axial direction from a groove edge on the outer side in the tire axial direction of the inner groove portion to a groove edge on the outer side in the tire axial direction of the outer groove portion, is 0.5 to 0.8 times the groove width Wg1. The pneumatic tire according to claim 4 .

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