JP4729096B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire capable of improving noise performance by suppressing heel and toe wear of a shoulder land while maintaining drainage performance.

  Pneumatic tires, especially passenger car tires, are required to have excellent quietness. In general, one of the causes of noise during tire running is heel and toe wear in the tread land portion. The heel and toe wear is a kind of partial wear in which the tread land part (heel) or kicking side (toe side) wears greatly due to the shearing force acting on the tread land part during driving and braking.

  The pattern stiffness of the tire is not uniform in the circumferential direction due to variable pitch arrangement and inevitable non-circularity in manufacturing. For this reason, heel and toe wear tends to promote growth at local positions in the tire circumferential direction. Such local wear causes a load fluctuation in the tire circumferential direction starting from the local wear, which causes the local wear to grow further (abnormal wear) and generate large running noise. Therefore, in order to improve the quietness of the tire, it is important to suppress heel and toe wear that causes abnormal wear over a long period of time.

  Conventionally, in order to suppress heel and toe wear, a rib pattern in which only circumferential grooves continuous in the tire circumferential direction are provided has been proposed. However, the rib-patterned pneumatic tire has the disadvantages that it cannot maintain sufficient drainage performance, and the driving force and braking force on ice roads and wet roads with a small road surface friction coefficient are significantly reduced.

  In order to improve the above-mentioned drawbacks, a rib lug pattern has been proposed in which the crown land portion of the tread portion is used as a rib while the lug groove is provided in the shoulder land portion. In such a rib lug pattern, while driving noise is suppressed by the crown rib, driving or braking force can be exhibited at the shoulder land portion having the lug groove.

  Related technologies include the following.

JP-A-6-55913

  The inventors have conducted further research on forming the lug groove in the shoulder land portion, and as a result, the drainage performance is improved by forming the shoulder land portion by combining the inner lug groove, the outer lug groove and the intermediate slot. It was found that the heel and toe wear of the shoulder land portion can be suppressed for a long time while maintaining the noise performance.

  As described above, the present invention provides a pneumatic tire, in particular a pneumatic tire for passenger cars, that can suppress the heel and toe wear of the shoulder land portion over a long period of time while maintaining the drainage performance, and thus improve the noise performance. The main purpose is to do.

The invention according to claim 1 of the present invention is a pneumatic tire comprising a pair of shoulder circumferential grooves extending continuously in the tire circumferential direction on the tread portion, in the tire circumferential direction,
In the shoulder land portion formed between the shoulder circumferential groove and the ground contact end,
An inner lug groove extending from the shoulder circumferential groove outward in the axial direction of the tire and being interrupted before the ground contact edge;
An outer lug groove that breaks in front of the shoulder circumferential groove without crossing the inner lug groove extending from the ground contact end inward in the tire axial direction; and
An intermediate slot extending in the tire axial direction is formed between the inner lug groove and the outer lug groove,
The intermediate slot is discontinuous without the inner end in the tire axial direction being inside the outer end in the tire axial direction of the inner lug groove and reaching the shoulder circumferential groove, and the outer end in the tire axial direction is the outer lug groove of the tire As the shoulder land portion continues in the tire circumferential direction without interruption by being interrupted without reaching the ground contact end outside the axial direction of the inner end in the axial direction ,
The intermediate slot includes an outer inclined surface from the outer end toward the groove bottom and an inner inclined surface from the inner end toward the groove bottom in a cross section perpendicular to the tread tread along the length direction thereof.
The angle θo of the outer inclined surface with respect to the normal line of the tread surface extending from the outer end of the intermediate slot to the inner side in the tire width direction is the angle θo of the inner inclined surface with respect to the normal line of the tread surface extending from the inner end of the intermediate slot to the inner side of the tire width direction. It is characterized by being larger than the angle θi .

  The invention according to claim 2 is the pneumatic tire according to claim 1, wherein the width Ws of the shoulder land portion in the tire axial direction is 15 to 26% of the tread ground contact width TW.

  According to a third aspect of the present invention, the overlap length in the tire axial direction between the inner lug groove and the intermediate slot and the overlap length in the tire axial direction between the intermediate slot and the outer lug groove are both shoulders. The pneumatic tire according to claim 1 or 2, which is 1.0 to 20.0% of a width Ws in a tire axial direction of a land portion.

  In the invention according to claim 4, the ground contact length CL in the tire circumferential direction on the tire equator is formed on the ground surface which is assembled to the regular rim and filled with the regular internal pressure and is loaded with a regular load and grounded to the plane. And a ground contact shape factor which is a ratio CL / SL to a tire contact length SL in the tire circumferential direction at a shoulder position separating a distance of 40% of the tread contact width from the tire equator is 1.05 to 1.35. The pneumatic tire according to any one of 1 to 3.

The invention according to claim 5 is the pneumatic tire according to claim 1 , wherein the angle θo is not less than 20 degrees and not more than 45 degrees .

  According to a sixth aspect of the present invention, the tread portion includes a pair of crown circumferential grooves on the inner side of the shoulder circumferential groove, and a crown rib continuous in the tire circumferential direction is formed between the pair of crown circumferential grooves. The pneumatic tire according to any one of claims 1 to 5, wherein a middle rib continuous in the tire circumferential direction is formed between the crown circumferential groove and the shoulder circumferential groove.

The invention according to claim 7 is a directional tire in which a rotation direction is designated by a character or a mark on a side wall portion , and at the outer end position of the inner lug groove, the inner lug groove and the rearmost The pneumatic tire according to any one of claims 1 to 6, wherein the distance in the tire circumferential direction from the wear-side intermediate slot is 25 to 40% of the arrangement pitch of the intermediate slot in the tire circumferential direction.

  The invention according to claim 8 is the pneumatic tire according to any one of claims 1 to 7, wherein the inner lug groove, the outer lug groove and the intermediate slot are all inclined in the same direction with respect to the tire axial direction. is there.

  The pneumatic tire of the present invention intersects the shoulder land portion with the inner lug groove extending from the shoulder circumferential groove outward in the tire axial direction and before the ground contact end, and at least the inner lug groove extending inward in the tire axial direction from the ground contact end. An outer lug groove that is interrupted in front of the shoulder circumferential groove and an intermediate slot that extends between the inner lug groove and the outer lug groove in the tire axial direction is formed. In this way, the inner land groove, the outer surface lug groove and the intermediate slot are distributed and arranged on the shoulder land portion in different positions in the tire axial direction, thereby increasing the driving force or braking force in the shoulder land portion and draining. Performance degradation can be prevented.

  Further, the intermediate slot is interrupted without the inner end in the tire axial direction reaching the inner circumferential edge of the inner lug groove and the shoulder circumferential groove, and the outer end in the tire axial direction is the outer lug groove. The shoulder land portion is continuous in the tire circumferential direction without interruption by being interrupted without reaching the ground contact end on the outer side in the tire axial direction than the inner end in the tire axial direction. Such a shoulder land portion maintains high rigidity in the tire circumferential direction without impairing drainage performance. In particular, since the land portions sandwiched between the lug grooves or between the intermediate slots are connected to each other in the tire axial direction, the tire circumferential rigidity is high, and heel and toe wear hardly occurs. Therefore, the pneumatic tire of the present invention can suppress heel and toe wear over a long period of time and improve noise performance and ride comfort.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a developed view of a tread portion 2 of a pneumatic tire (not shown) of the present embodiment, and FIG. 2 is a partial sectional view thereof.

  In the present embodiment, a directional tire in which the rotation direction R is designated is shown as a pneumatic tire. The rotation direction R is clearly indicated by characters or marks on the sidewall portion (not shown). Further, the pneumatic tire of the present embodiment is configured as a radial tire for passenger cars.

  The tread portion 2 has a pair of shoulder circumferential grooves 3 extending continuously in the tire circumferential direction on the most ground contact end e side, and a pair of crown circumferences extending continuously in the tire circumferential direction inside the shoulder circumferential grooves 3. Directional grooves 4 are formed. Accordingly, the tread portion 2 includes a shoulder land portion 5 between the shoulder circumferential groove 3 and the ground contact e, a crown land portion 6 between the pair of crown circumferential grooves 4 and 4, and a crown circumferential groove. 4 and the middle land portion 7 between the shoulder circumferential grooves 3 are divided.

  Here, the “grounding end” e is obtained when a normal load is applied to a tire in a normal state in which a rim is assembled on a normal rim and a normal internal pressure is filled, and the tread portion 2 is grounded 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 “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, “Design Rim” for TRA. “Or“ Measuring Rim ”if ETRTO.

  In addition, the “regular internal pressure” is an air pressure determined by each standard for each tire in the standard system including the standard on which the tire is based. TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES "Maximum value", ETRTO, "INFLATION PRESSURE".

  Further, the “regular load” is a load determined by each standard for each tire in a standard system including a standard on which the tire is based. “JATMA” is “maximum load capacity”, and TRA is a table. The maximum value described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". If it is ETRTO, it will be "LOAD CAPACITY". .

  In the present embodiment, the shoulder circumferential groove 3 and the crown circumferential groove 4 are formed as straight grooves along the tire circumferential direction in order to reduce drainage resistance. However, as long as each circumferential groove 3 and 4 extends continuously in the tire circumferential direction, it may have a non-linear shape such as a zigzag shape or a wave shape.

  The groove widths of the circumferential grooves 3 and 4 can be appropriately determined according to the tire size and the like. However, if the groove width is too large, the rigidity of the tread portion 2 tends to be reduced. There is a tendency to get worse. In order to prevent a significant decrease in the tread rigidity while ensuring sufficient drainage, the groove widths GW1 and GW2 of the circumferential grooves 3 and 4 are preferably 3% or more, more preferably 4%, of the tread ground contact width TW. The above is desirable, and it is preferably 7% or less, more preferably 6% or less.

  In the present embodiment, the groove width GW1 of the shoulder circumferential groove 3 is formed larger than the groove width GW2 of the crown circumferential groove 4. More preferably, the groove width GW1 is formed to be about 1.3 to 1.6 times the groove width GW2. This is useful for enhancing drainage on the grounding end e side.

  In addition, unless otherwise indicated, the dimension of each part of a tire shall be the value measured in the said no-load normal state. Further, the groove width is measured in a direction perpendicular to the longitudinal direction of the groove.

  In the pneumatic tire of the present embodiment, the crown land portion 6 and the middle land portion 7 are formed as ribs extending continuously in the tire circumferential direction. Each of the land portions 6 and 7 is formed with lug-shaped small grooves 12 and circumferential narrow grooves 13 for adjusting the rib rigidity, but continues in the circumferential direction without being divided in the tire axial direction. The crown land portion 6 and the middle land portion 7 are particularly preferable in that there is no fear of heel and toe wear and generation of noise during traveling can be suppressed. In addition, it is desirable to provide a tapered surface 14 that descends toward the edge end on the edge on the acute angle side formed by the small groove 12 and the crown circumferential groove 4 to prevent rubber chipping or the like.

  In the shoulder land portion 5, an inner lug groove 8, an outer lug groove 9, and an intermediate slot 10 are formed. In addition to the lug grooves 8 and 9 and the intermediate slot 10, the shoulder land portion 5 of the present embodiment is not provided with other circumferential grooves or lateral grooves.

  3, the inner lug groove 8 extends from the shoulder circumferential groove 3 outward in the tire axial direction, and the outer end 8o in the tire axial direction does not communicate with the ground contact e. It is interrupted before that. The inner lug grooves 8 are spaced apart in the tire circumferential direction with a substantially constant arrangement pitch Pi. Needless to say, the arrangement pitch Pi may be changed within the range of the pitch variation since it is “substantially constant”.

  The outer lug groove 9 extends at least inward in the tire axial direction from the ground contact end e, and the inner end 9i in the tire axial direction is disconnected in front of the shoulder circumferential groove 3 without communicating with the shoulder circumferential groove 3. In addition, the outer lug grooves 9 of the present embodiment are spaced apart in the tire circumferential direction, and the arrangement pitch Po thereof is substantially the same as the arrangement pitch Pi of the inner lug grooves 8.

  Further, the outer lug groove 9 is provided without intersecting with the inner lug groove 8. That is, the outer lug groove 9 and the inner lug groove 8 are provided at different positions in the tire circumferential direction (that is, shifted in phase in the tire circumferential direction).

  Further, the outer lug groove 9 is preferably extended from the outer side in the tire axial direction of the ground contact end e to the inner side in the tire axial direction as in the present embodiment. During turning, the region outside the tire axial direction of the ground contact edge e is also grounded, so it is advantageous to extend the lug groove to the outside of the ground contact edge e in the tire axial direction from the viewpoint of improving the drainage performance at the time of turning. It is.

  The intermediate slot 10 extends between the inner lug groove 8 and the outer lug groove 9 in the tire axial direction. The inner end 10 i in the tire axial direction of the intermediate slot 10 is interrupted inside the outer end 8 o of the inner lug groove 8 and without reaching the shoulder circumferential groove 3. Accordingly, the inner lug groove 8 and the intermediate slot 10 have an overlap length L1 in the tire axial direction.

  Further, the outer end 10 o in the tire axial direction of the intermediate slot 10 is interrupted without reaching the ground contact end e on the outer side in the tire axial direction than the inner end 9 i of the outer lug groove 9. Accordingly, the intermediate slot 10 and the outer lug groove 9 have an overlap length L2 in the tire axial direction.

  Further, the intermediate slots 10 are spaced apart in the tire circumferential direction, and the arrangement pitch Pc thereof is substantially the same as that of the outer lug grooves 9 and the inner lug grooves 8. Further, the intermediate slot 10 is provided without intersecting (communicating with) both the lug grooves 8 and 9. That is, the intermediate slot 10 is provided with a phase shifted from the outer lug groove 9 and the inner lug groove 8 at different positions in the tire circumferential direction. Such lug grooves 8 and 9 and the intermediate slot 10 are continued in the tire circumferential direction without interrupting the shoulder land portion 5.

  In this way, the shoulder land portion 5 is provided with the inner lug grooves 8, the outer lug grooves 9, and the intermediate slots 10 dispersedly at different positions in the tire axial direction and the tire circumferential direction, so that driving force or braking force is provided. While increasing, the fall of the drainage performance in the shoulder land part 5, and the fall of a driving force and a braking force can be prevented.

  Further, since the shoulder land portion 5 is continuous in the tire circumferential direction, its rigidity is maintained high, and each land between the inner lug grooves 8 and 8, between the outer lug grooves 9 and 9, or between the intermediate slots 10 and 10. Since the portions are connected to each other in the tire axial direction, the rigidity in the tire circumferential direction is high, and as a result, heel and toe wear hardly occurs. Therefore, the pneumatic tire of the present invention can suppress heel and toe wear over a long period of time and improve noise performance and ride comfort.

  The shoulder land portion 5 may be divided by a narrow groove that does not substantially affect its rigidity. Such a narrow groove may include, for example, a tread pattern decorative narrow groove (not shown) having both a groove width and a groove depth of 1.5 mm or less.

  The width Ws of the shoulder land portion 5 in the tire axial direction is preferably 15% or more of the tread contact width TW, more preferably 20% or more, and preferably 26% or less, more preferably 25% or less. . When the width Ws of the shoulder land portion 5 is less than 15% of the tread ground contact width TW, the driving force and the braking force that tend to decrease in the crown land portion 6 and the middle land portion 7 tend not to be sufficiently secured. Moreover, there is a possibility that the lateral rigidity at the time of turning may be lowered. On the contrary, if the width Ws of the shoulder land portion 5 exceeds 26% of the tread ground contact width TW, the width of the crown land portion 6 and the middle land portion 7 is reduced, and the lateral rigidity thereof is lowered and the center wear easily occurs. Therefore, it is not preferable.

  Further, the overlapping length L1 of the inner lug groove 8 and the intermediate slot 10 in the tire axial direction and the overlapping length L2 of the intermediate slot 10 and the outer lug groove 9 in the tire axial direction are both of the above-mentioned shoulder land portion 5. The width Ws is 1.0% or more, more preferably 5.0% or more, and preferably 20.0% or less, more preferably 15.0% or less. When the overlapping lengths L1 and L2 are less than 1.0% of the width Ws of the shoulder land portion 5, the drainage tends to be lowered, and the steering stability during rainy weather tends to be lowered. Conversely, 20.0% If it exceeds, the pattern rigidity of the shoulder portion is lowered, and the steering stability on the dry road surface tends to be lowered.

  Further, the lengths GL1, GL2 and GL3 in the tire axial direction of the inner lug groove 8, the outer lug groove 9 and the intermediate slot 10 extending over the shoulder land portion 5 are not particularly limited and can be variously determined. In order to maintain the rigidity balance of the shoulder land portion 5, the groove lengths GL1 to GL3 are preferably 45% or more of the width Ws of the shoulder land portion 5, more preferably 48% or more, and preferably 60%. Below, 50% or less is more desirable.

  Further, the groove depth GD1 (shown in FIG. 2) of the inner lug groove 8, the outer lug groove 9, and the intermediate slot 10 is preferably about 0.7 to 1.2 times the groove depth GD2 of the shoulder circumferential groove 3. Is desirable. If the groove depth GD1 of the lug groove or the like is less than 0.7 times the groove depth GD2 of the shoulder circumferential groove 3, the lug groove or the like may disappear early due to wear, resulting in a decrease in driving or braking force. On the contrary, if it exceeds 1.2 times, the rigidity of the shoulder land portion 5 is lowered, and heel and toe wear is likely to occur, and the fuel efficiency may be deteriorated.

  Further, the groove width GW3 (shown in FIG. 1) of the inner lug groove 8, the outer lug groove 9 and the intermediate slot 10 extending over the shoulder land portion 5 is not particularly limited, but if it is too small, the drainage performance deteriorates. On the contrary, if it is too large, the pattern rigidity of the shoulder land portion 5 is lowered, and there is a possibility that the steering stability is lowered and the heel and toe wear is accelerated. From such a viewpoint, the groove width GW3 such as the lug groove is preferably 3 mm or more, more preferably 5 mm or more, and preferably 7 mm or less, more preferably 6 mm or less. In particular, the groove width GW3 is preferably set to be about 9 to 11% of the arrangement pitch Pi of the lug grooves.

  Further, as shown in FIG. 3, the inner lug groove 8, the outer lug groove 9 and the intermediate slot 10 extending over the shoulder land portion 5 are preferably set to an angle θa of 20 degrees or less with respect to the tire axial direction. When the angle θa exceeds 20 degrees, the drainage performance toward the vehicle outer side at the lug grooves 8 and 9 and the slot 10 tends to deteriorate. On the other hand, if the lug grooves 8, 9 and the slot 10 extend parallel to the tire axial direction, the noise performance may be deteriorated. From such a viewpoint, the angle θa is preferably greater than 0 degree, more preferably 5 degrees or more and 20 degrees or less with respect to the tire axial direction. Each angle θa of the lug grooves 8 and 9 and the intermediate slot 10 is specified by an angle formed by a straight line connecting both ends of the groove center line and the tire axial direction, as shown in FIG.

In the present embodiment, the inner lug groove 8, the outer lug groove 9, and the intermediate slot 10 are all inclined in the same direction (that is, upward to the right in FIG. 1) with respect to the tire axial direction. For example, in the left shoulder land portion 5 in FIG. 1, the lug grooves 8 to 10 are sequentially grounded from the inner side to the outer side in the tire axial direction. For this reason, the water film on the road surface can be effectively discharged to the grounding end side by the pressure accompanying the rotation of the tire, and the drainage can be improved. On the other hand, the right side of the shoulder land portion 5 in FIG. 1, the lug grooves 8 to 10, sequentially ground from the outside to the inside in the tire axial direction. For this reason, the water film on the road surface can be guided to the shoulder circumferential groove 3 having a large groove width and drained by the pressure accompanying the rotation of the tire.

  In order to effectively exhibit the above-described action, as shown in FIG. 3, at the position of the outer end 8o of the inner lug groove 8 in the tire axial direction, the inner lug groove 8 and the closest rear landing side The distance X1 in the tire circumferential direction with respect to the intermediate slot 10 (the distance between the groove center lines) is 25 to 40%, more preferably 30 to 36% of the arrangement pitch Pc of the intermediate slot 10 in the tire circumferential direction. Is desirable.

  When the distance X1 is less than 25% of the arrangement pitch Pc in the tire circumferential direction of the intermediate slot 10, there is a possibility that uneven wear may concentrate on a portion having low rigidity between these grooves, and conversely exceeds 40%. In such a case, drainage performance may be reduced. From the same viewpoint, at the position of the outer end 10o of the intermediate slot 10 in the tire axial direction, the distance in the tire circumferential direction between the intermediate slot 10 and the outer lug groove 9 on the rear landing side closest to the intermediate slot 10 (between the groove center lines). X2 is preferably 25 to 40%, more preferably 30 to 36% of the arrangement pitch Pc of the intermediate slot 10.

  As described above, when the inner lug groove 8, the intermediate slot 10, and the outer lug groove 9 are spaced apart at substantially equal pitches in the tire circumferential direction, and the deviation amount thereof is restricted as described above, the inner lug groove 8 The intermediate slot 10 and the outer lug groove 9 can be repeatedly grounded almost uniformly in this order. Accordingly, drainage performance is exhibited in a well-balanced manner over the entire area of the shoulder land portion 5, and it is useful for the shoulder land portion 5 to be uniformly worn.

  As shown in FIG. 4, in the shoulder land portions 5 on both sides, the lug grooves or the like 8 to 10 may be inclined in a symmetric direction with respect to the tire equator C so that the lug grooves 8 to 10 are sequentially grounded from the inside in the tire axial direction.

  Further, as shown in FIG. 5, the ground contact shape factor is preferably 1.05 to 1.35 in the ground contact surface FP that is loaded with a normal load from the normal state and grounded to the plane with a camber angle of 0 degree. . Here, the ground contact shape factor is the contact position CL in the tire circumferential direction on the tire equator C and the shoulder position S separating the distance 0.4 TW of 40% of the tread contact width from the tire equator C on the ground contact surface FP. It is represented by the ratio CL / SL with the contact length SL in the tire circumferential direction. The shoulder position S represents a representative position of the shoulder portion that passes through the shoulder land portion 5 and is prone to heel and toe wear.

  As a result of various experiments by the inventors, it has been found that most of the heel and toe wear that causes noise contributes greatly to the shearing force during driving and braking, particularly the shearing force during braking. . Therefore, in order to more effectively suppress the heel and toe wear of the shoulder land portion 5, the contact length CL on the tire equator C and the contact length at the shoulder position on the contact surface FP when traveling straight ahead. It is effective to optimize the relationship with SL and reduce the slip of the shoulder land portion 5 during braking. For this reason, in the pneumatic tire of the present embodiment, the ground contact shape factor is set in the above-described range.

  That is, it is not preferable that the ground contact shape factor is less than 1.05 because the ground contact pressure of the shoulder land portion 5 during traveling may increase excessively, leading to heel and toe wear, shoulder wear, and the like. On the other hand, when the ground contact shape factor exceeds 1.35, the difference in outer diameter between the tire equator position and the shoulder position S becomes large, dragging occurs in the shoulder land portion 5 during braking, and heel and toe wear is likely to occur. . From such a viewpoint, the ground contact shape factor is more preferably 1.10 or more, further preferably 1.15 or more, and preferably 1.25 or less, more preferably 1.20 or less. It should be noted that the shoulder positions on both sides of the tire equator C preferably satisfy the above-mentioned ground shape factor. The contact shape factor can be adjusted to a desired value by adjusting the position of the tire equator C of the tread portion 2 and the outer diameter and the tread profile at the shoulder position S.

  FIG. 6 shows a cross section taken along the line B-B of FIG. 3, that is, a cross section perpendicular to the tread surface 2 a along the length direction of the intermediate slot 10. As is apparent from FIG. 6, the intermediate slot 10 of the present embodiment includes an outer inclined surface 11o from the outer end 10o toward the groove bottom 10b, and an inner inclined surface 11i from the inner end 10i toward the groove bottom 10b. Consists of.

  In the present embodiment, the angle θo of the outer inclined surface 11o with respect to the normal line N1 of the tread tread surface 2a extending inward in the tire width direction from the outer end 10o of the intermediate slot 10 is inward in the tire width direction from the inner end 10i of the intermediate slot 10. It is set larger than the angle θi of the inner inclined surface 11i with respect to the normal line N2 of the tread surface 2a. Such an outer inclined surface 11o serves to easily drain the water filled in the intermediate slot 10 to the ground end side. However, if the angle θo becomes excessively large, the groove volume of the intermediate slot 10 may be reduced or may disappear early due to wear. Therefore, the angle θo is preferably 20 degrees or more, more preferably 30 degrees or more, Further, it is preferably 45 degrees or less, more preferably 40 degrees or less.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be implemented with various modifications.

  In order to confirm the effect of the present invention, a radial tire for a passenger car having a tire size of 225 / 50R17 was prototyped based on the specifications in Table 1. Various performances were tested on them. The test method is as follows.

<Heel and toe wear amount>
Run the test track with each test tire mounted on the right front wheel of the vehicle under the following conditions, and wear on the toe side and heel side at the land part between the inner lug groove and the land part between the outer lug groove of the shoulder land The amount difference (heel and toe wear amount) was measured and the average value was calculated. The smaller the value, the better.
Rims: 17 × 7.5J
Air pressure: 230kPa
Vehicle: 3000cc domestic FR passenger car Test course surface: Dry asphalt Traveling distance: 7000km

<Noise performance>
Using a vehicle with the same conditions as described above, a smooth road surface was run at a speed of 50 km / h, and the magnitude of the pattern noise was evaluated by the driver's feeling. The result is a score of Comparative Example 1 being 100, and the larger the value, the smaller the pattern noise and the better.

<Drainage performance>
On the asphalt road surface with a radius of 100m, on the course with a puddle with a depth of 5mm and a length of 20m, the vehicle is approached while increasing the speed stepwise, and the lateral acceleration (lateral G) is measured, 50-80km / The average lateral G of the front wheels at the speed of h was calculated. The results were displayed as an index with the average lateral G of Comparative Example 1 as 100. The larger the value, the better.
<Steering stability>
Using the above-mentioned vehicle, a driver on a dry asphalt road test course was run, and the characteristics relating to steering response, rigidity, grip, etc. were evaluated by sensory evaluation of the driver. The results are displayed with a score of Comparative Example 1 as 100. The larger the value, the better.
Table 1 shows the test results.

  As a result of the test, it was confirmed that the tire of the example improved the noise performance by suppressing the heel and toe wear of the shoulder land portion while maintaining the drainage performance as compared with the comparative example.

It is an expanded view of the tread part of this embodiment. It is the fragmentary sectional view. It is a principal part enlarged view of the shoulder land part of FIG. It is an expanded view of the tread part which shows other embodiment of this invention. It is a diagram which shows the ground-contact plane of the pattern of FIG. It is BB sectional drawing of FIG. It is an expanded view of the tread part of the pneumatic tire of a comparative example. It is an expanded view of the tread part of the pneumatic tire of a comparative example.

Explanation of symbols

2 Tread portion 3 Shoulder circumferential groove 4 Crown circumferential groove 5 Shoulder land portion 6 Crown land portion 7 Middle land portion 8 Inner lug groove 9 Outer lug groove 10 Intermediate slot

Claims (8)

A pneumatic tire having a pair of shoulder circumferential grooves extending continuously in the tire circumferential direction on the tread portion, with the most ground contact end side,
In the shoulder land portion formed between the shoulder circumferential groove and the ground contact end,
An inner lug groove extending from the shoulder circumferential groove outward in the axial direction of the tire and being interrupted before the ground contact edge;
An outer lug groove that breaks in front of the shoulder circumferential groove without crossing the inner lug groove extending from the ground contact end inward in the tire axial direction; and
An intermediate slot extending in the tire axial direction is formed between the inner lug groove and the outer lug groove,
The intermediate slot is discontinuous without the inner end in the tire axial direction being inside the outer end in the tire axial direction of the inner lug groove and reaching the shoulder circumferential groove, and the outer end in the tire axial direction is the outer lug groove of the tire As the shoulder land portion continues in the tire circumferential direction without interruption by being interrupted without reaching the ground contact end outside the axial direction of the inner end in the axial direction ,
The intermediate slot includes an outer inclined surface from the outer end toward the groove bottom and an inner inclined surface from the inner end toward the groove bottom in a cross section perpendicular to the tread tread along the length direction thereof.
The angle θo of the outer inclined surface with respect to the normal line of the tread surface extending from the outer end of the intermediate slot to the inner side in the tire width direction is the angle θo of the inner inclined surface with respect to the normal line of the tread surface extending from the inner end of the intermediate slot to the inner side of the tire width direction. A pneumatic tire characterized by being larger than the angle θi .
  The pneumatic tire according to claim 1, wherein a width Ws of the shoulder land portion in the tire axial direction is 15 to 26% of a tread contact width TW.   The overlapping length of the inner lug groove and the intermediate slot in the tire axial direction and the overlapping length of the intermediate slot and the outer lug groove in the tire axial direction are both the width Ws of the shoulder land portion in the tire axial direction. The pneumatic tire according to claim 1 or 2, which is 1.0 to 20.0%.   In the contact surface that is assembled to the normal rim and filled with the normal internal pressure and is contacted to the plane by applying a normal load, the contact length CL in the tire circumferential direction on the tire equator and the contact width of the tread from the tire equator 4. The contact form factor, which is a ratio CL / SL to a contact length SL in the tire circumferential direction at a shoulder position separating a distance of 40%, is 1.05 to 1.35. 5. Pneumatic tire. The pneumatic tire according to claim 1, wherein the angle θo is not less than 20 degrees and not more than 45 degrees .
The tread portion includes a pair of crown circumferential grooves on the inner side of the shoulder circumferential grooves,
A crown rib continuous in the tire circumferential direction is formed between the pair of crown circumferential grooves, and a middle rib continuous in the tire circumferential direction is formed between the crown circumferential groove and the shoulder circumferential groove. The pneumatic tire according to any one of 1 to 5. It is a directional tire whose direction of rotation is designated by letters or marks on the sidewall portion , and at the outer end position of the inner lug groove, the tire circumference between the inner lug groove and the intermediate slot on the rear landing side closest thereto The pneumatic tire according to any one of claims 1 to 6, wherein the distance in the direction is 25 to 40% of the arrangement pitch of the intermediate slots in the tire circumferential direction.
  The pneumatic tire according to any one of claims 1 to 7, wherein the inner lug groove, the outer lug groove, and the intermediate slot are all inclined in the same direction with respect to the tire axial direction.

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