JP4653832B2 - Pneumatic tire - Google Patents

Description

  The present invention provides a plurality of parallelogram-shaped blocks in a tread portion by an inclined lateral groove that inclines toward the rear side in the tire rotation direction toward the outer side in the tire axial direction and a circumferential joint groove that connects between the inclined lateral grooves. The present invention relates to a pneumatic tire having a directional pattern.

  For example, as illustrated in FIG. 10A, in the tread portion, an inclined lateral groove a extending from the position near the tire equator C toward the rear side in the tire rotation direction toward the outer side in the tire axial direction, and in the tire circumferential direction. A circumferential joint groove b that connects between the adjacent inclined lateral grooves a and a, and a directional pattern in which the inclination angle α of the inclined lateral groove a with respect to the tire circumferential direction is sequentially increased outward in the tire axial direction. Tires are known (see, for example, Patent Document 1).

JP-A-5-246214 (FIG. 1)

  In the tire having such a pattern, when the tire rotates, the inclined lateral groove a sequentially contacts the tire axial direction inner end a1, so that the water in the groove flows along the streamline from the tire equator side to the tread end side. It can be discharged efficiently and can exhibit excellent wet grip performance. In addition, since the inclination angle α of the inclined lateral groove a sequentially increases toward the outer side in the tire axial direction, the pattern rigidity in the circumferential direction is high on the tire equator side, and the pattern rigidity in the lateral direction is set high on the tread end side. , It has the advantage that it can also exhibit excellent dry handling stability.

  However, in the pattern, the block j divided by the inclined lateral groove a and the circumferential joint groove b has a parallelogram shape having an acute corner portion d1 and an obtuse corner portion d2, as shown in FIG. 10B. Will be formed. Further, since the rigidity is inevitably lowered at the acute corner portion d1, there is a problem that uneven wear is induced from the acute corner portion d1. In particular, since the acute angle corner portion d1f on the first arrival side is subjected to compressive strain, there is a problem that uneven wear occurs more significantly than the acute angle corner portion d1r on the rear arrival side that receives tensile strain.

  In the prior art, the chamfer e is applied to the acute angle corner part d1 to secure the rigidity of the acute angle corner part d1, but if the chamfer e is small, the uneven wear suppression is insufficient, and conversely, There is a problem that the ground contact area is reduced and the steering stability is lowered.

  Therefore, the present invention can ensure the rigidity of the acute corner corner portion while suppressing chamfering while maintaining excellent wet grip performance and suppressing chamfering particularly in the acute corner portion where uneven wear is particularly noticeable. An object of the present invention is to provide a pneumatic tire capable of improving uneven wear.

In order to achieve the object, the invention of claim 1 of the present application provides
A plurality of inclined lateral grooves that incline toward the rear side in the tire rotation direction toward the outer side in the tire axial direction from the vicinity of the tire equator to a position beyond the tread contact edge, and spaced apart in the tire circumferential direction;
TECHNICAL joint between the inclined lateral grooves adjacent in the tire circumferential direction, and by providing a four circumferential connecting grooves which are spaced axially,
A pneumatic tire in which a plurality of parallelogram blocks divided by the inclined lateral grooves and the circumferential joint grooves are formed in the tread portion,
The inclination angle α of the inclined lateral groove with respect to the tire circumferential direction sequentially increases toward the outer side in the tire axial direction,
Further, the inclined lateral groove is on the outer side in the tire axial direction and on the most tread grounding end side with respect to the innermost intersection position intersecting with the innermost circumferential joint groove arranged on the tire equator side among the plurality of circumferential joint grooves. In the range of the region on the inner side in the tire axial direction than the outermost intersection position intersecting with the outermost circumferential joint groove arranged in the groove depth of the inclined lateral groove is substantially constant,
The innermost circumferential joint groove and the outermost circumferential joint groove extend from the first arrival side end to the rear arrival side end and have a constant groove depth Dg, and
The circumferential joint groove between the innermost circumferential joint groove and the outermost circumferential joint groove has a groove depth Dgf at the first arrival side end in the tire rotation direction from a groove depth Dgr at the rear arrival side end. The groove depth is gradually reduced toward the first arrival side end.

  In the invention of claim 2, the groove depth Dgf at the first arrival side end of the circumferential joint groove is 20 to 80% of the groove depth Dgr at the rear arrival side end.

  In the invention of claim 3, the inclined lateral groove has an inclination angle αi of 10 to 35 ° with respect to the tire circumferential direction at the inner end in the tire axial direction, and an inclination angle αo with respect to the tire circumferential direction of the tread ground contact end of 40 to 40 °. It is characterized by 90 °.

In the invention of claim 4, the groove depth Dg of the innermost circumferential joint groove is in the range of 90 to 100 % of the groove depth Dy of the inclined lateral groove 3 at the innermost intersection position. Yes.

The invention of claim 5, wherein the circumferential joint angle β with respect to the tire circumferential direction of the groove, is characterized in that it has a large enough circumferential dovetail groove of the outer tire axial direction.

  In the invention of claim 6, the groove width Wy of the inclined lateral groove is such that the groove width Wyo at the outermost intersection position is larger than 1.0 times and less than three times the groove width Wyi at the innermost intersection position. It is characterized by that.

  In the invention according to claim 7, the parallelogram-shaped block has an acute angle corner portion and an obtuse angle corner portion, and the inclined lateral groove is inclined with respect to the normal line of the tread surface of the groove wall on the subsequent wear side. The angle θr is gradually increased from the obtuse angle side corner portion toward the acute angle side corner portion.

In the invention of claim 8, the parallelogram-shaped block has an acute angle corner portion and an obtuse angle corner portion, and the inclined lateral groove is inclined with respect to the normal line of the tread surface of the groove wall on the landing side. The angle θr is gradually increased from the acute angle corner portion toward the obtuse angle side corner portion. In the invention of claim 9, a pair of innermost circumferential seam grooves are formed on both sides of the tire equator, and circumferential ribs extending continuously on the tire equator are formed between the innermost circumferential seam grooves. It is characterized by being formed.

  Further, the inclination angle α, the groove width Wy and the like of the inclined lateral groove are values specified on the tread surface side.

  The “tread grounding end” means the outer end in the tire axial direction of the tread grounding surface that comes into contact when a regular load is applied to a tire in a state where a rim is assembled on a regular rim and filled with a regular internal pressure. 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, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO means "Measuring Rim". The “regular internal pressure” is the air pressure defined by the standard for each tire. If JATMA, the maximum air pressure is specified. If TRA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, ETRTO Means "INFLATION PRESSURE", but in the case of passenger car tires, it is 180 kPa. The “regular load” is a load determined by the standard for each tire. The maximum load capacity in the case of JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the case of TRA, If it is ETRTO, it is "LOAD CAPACITY".

  As described above, the inclined lateral grooves incline toward the rear side in the tire rotation direction from the position near the tire equator toward the outer side in the tire axial direction, and at that time, the inclination angle α with respect to the tire circumferential direction is set to the outer side in the tire axial direction. It is increasing towards. Accordingly, the wet grip performance and the dry steering stability can be exhibited at a high level in cooperation with the circumferential joint groove that connects between the inclined lateral grooves.

  On the other hand, at least one of the circumferential joint grooves has a groove depth Dgf at the first arrival side end of the circumferential joint groove that is smaller than the groove depth Dgr at the rear arrival side end, and further toward the first arrival side end. The groove depth is gradually reduced. Thereby, the rigidity of the acute angle corner portion on the first arrival side in the parallelogram block can be relatively increased, and uneven wear resistance can be improved. In addition, since the size of the chamfer can be minimized, a decrease in steering stability can be suppressed accordingly. Furthermore, since the change of the groove depth in the circumferential joint groove is smooth, it is possible to maintain excellent wet grip performance.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a development view in which the tread surface of the pneumatic tire of the present invention is developed on a plane.

In FIG. 1, the pneumatic tire 1 according to the present embodiment includes a plurality of inclined lateral grooves 3 that extend from a position near the tire equator C to a position beyond the tread ground contact Te in the tread portion 2 and spaced apart in the tire circumferential direction. When, it is provided and the circumferential connecting grooves 4 of the plurality of which are spaced between the inclined lateral grooves 3, 3 adjacent in the tire circumferential direction in adoptive and axially.

  The “position in the vicinity of the tire equator C” means a region having a width Y of 10% or less of the tread contact width TW with the tire equator C as the center. If the distance h from the tire equator C to the inner end 3i of the inclined lateral groove 3 in the tire axial direction exceeds Y / 2, the drainage is insufficient on the tire equator side, and the wet grip performance is deteriorated.

  Next, each of the inclined lateral grooves 3 inclines toward the outer side in the tire rotational direction toward the outer side in the tire axial direction, and then the inclination angle α of the inclined lateral grooves 3 with respect to the tire circumferential direction increases outward in the tire axial direction. It is increasing gradually. Therefore, the inclined lateral groove 3 is grounded sequentially from the tire axial inner end 3i side to the outer end 3o side during tire rotation, and the water in the groove is efficiently discharged to the outside of the tread grounding end Te along the streamline. Yes. That is, excellent wet grip performance can be exhibited. Moreover, since the inclination angle α gradually increases toward the outer side in the tire axial direction, the circumferential pattern rigidity can be set higher on the tire equator side, and the lateral pattern rigidity can be set higher on the tread grounding end side. Sex can also be set at a high level.

  In this example, as shown in FIGS. 2 and 3, the case where the inclined lateral groove 3 increases the inclination angle α stepwise is exemplified. Specifically, the inclined lateral groove 3 includes a first inclined portion 3A closest to the tire equator with the inclination angle α1 and a second inclined portion 3B having an inclination angle α2 continuous on the outer side thereof and on the outer side thereof. It is formed as a bent groove composed of a third inclined portion 3C having a continuous inclination angle α3 and a fourth inclined portion 3D having a continuous inclination angle α4. The inclination angle α satisfies α1 <α2 <α3 <α4. The inclined lateral groove 3 may be an arc-shaped groove whose inclination angle α changes continuously.

  Next, between the inclined lateral grooves 3 and 3 adjacent in the tire circumferential direction, a plurality of circumferential joint grooves 4 that connect the adjacent inclined lateral grooves 3 and 3 to each other are provided in the tire axial direction. As a result, a large number of parallelogram blocks 6 are formed in the tread portion 2, which are divided by the inclined lateral grooves 3 and the circumferential joint grooves 4.

From the viewpoint of drainage performance, the number of the circumferential connecting grooves 4 disposed between the inclined lateral grooves 3, 3, from the viewpoint of balance between the drainage and block rigidity in particular, is preferably four.

In this example, a case where four circumferential splice grooves 4 are arranged is illustrated. Specifically, between the inclined lateral grooves 3 and 3,
A first circumferential joint groove 4A that joins the inner ends 3i of the first inclined portion 3A;
A second circumferential joint groove 4B that joins the vicinity of the bent portions of the first inclined portion 3A and the second inclined portion 3B;
A third circumferential joint groove 4C that connects the vicinity of the bent portions of the second inclined portion 3B and the third inclined portion 3C, and the third inclined portion 3C and the fourth inclined portion 3D. A fourth circumferential joint groove 4D that joins the vicinity of the bent portions is formed.

  As a result, circumferential ribs 5 extending continuously on the tire equator C are formed between the first circumferential joint grooves 4A and 4A. Between the first and second circumferential joint grooves 4A and 4B, between the second and third circumferential joint grooves 4B and 4C, and between the third and fourth circumferential joint grooves 4C and 4D, respectively. The first block 6A, the second block 6B, and the second block 6B having a parallelogram shape having an acute angle corner portion C1 having an apex angle smaller than 90 ° and an obtuse angle side corner portion C2 having an apex angle of 90 ° or more. 3 blocks 6C are formed.

  In the case of the tread pattern of this example, the inclined portions 3 </ b> A to 3 </ b> D form a straight line having a small resistance to water flow, while the vicinity of the bent portion where the resistance increases is connected by the circumferential joint groove 4. For this reason, the effect of resistance at the bent portion is alleviated, and it is possible to obtain an advantage that more excellent drainage can be ensured, such as smoothing the flow of water as a whole groove. As shown in FIG. 3, the vicinity of the bent portion means a region range J having a width equal to or less than 11% of the tread grounding width Tw around the bending point ip where the groove center line i of the inclined lateral groove 3 is bent. means.

  As shown in FIG. 4, the position where the inclined lateral groove 3 intersects with the innermost circumferential joint groove 4 i arranged on the tire equator side is defined as the innermost intersection position Pi, and the inclined lateral groove 3 is A position that intersects with the outermost circumferential joint groove 4o arranged on the most tread grounding end side is defined as an outermost intersection position Po. At this time, from the viewpoint of drainage, the inclined lateral groove 3 has a groove depth Dy (in a region range outside the innermost intersection position Pi and outside the outermost intersection position Po and inside the tire axis direction Po. (Shown in FIG. 5) is substantially constant. That is, the inclined lateral groove 3 does not have a partial raised portion such as a tie bar that can become water resistance within the region range, and the groove bottom is formed smoothly with a constant depth. In this example, the innermost circumferential joint groove 4i corresponds to the first circumferential joint groove 4A, and the outermost circumferential joint groove 4o corresponds to the fourth circumferential joint groove 4D. .

  Here, as in this example, the outermost circumferential joint groove 4o is inclined with respect to the tire circumferential direction, and at the intersection position Pof with the inclined lateral groove 3 at the first arrival side end Ef and at the rear arrival side end Er. When the crossing position Por with the inclined lateral groove 3 is displaced in the tire axial direction, the crossing position located more outward in the tire axial direction (in this example, the crossing position Por at the rear landing side end Er) It is adopted as the outermost intersection position Po. Also, in this example, the case where the innermost circumferential joint groove 4i is arranged in parallel with the tire circumferential direction is illustrated, but if it is inclined, it is located more inside in the tire axial direction. The intersection position is adopted as the innermost intersection position Pi.

  Further, in the inclined lateral groove 3, the inclination angle αi at the inner end 3i in the tire axial direction (corresponding to the inclination angle α1 in this example) is in the range of 10 to 35 °, and the tire at the position of the tread ground contact end Te. It is also preferable that the inclination angle αo with respect to the circumferential direction (corresponding to the inclination angle α4 in this example) is in the range of 40 to 90 ° in order to discharge water more smoothly along the streamline. At this time, the difference (αo−αi) between the inclination angles αi and αo is more preferably 20 ° or more.

Next, in the tire of the present embodiment , the second and third circumferential joint grooves 4B and 4C each have a groove depth Dgf of the first arrival side end Ef greater than a groove depth Dgr of the rear arrival side end Er. The depth change groove 10 is formed to be small and the groove depth Dg is gradually decreased toward the first arrival side end Ef.

  FIG. 5 representatively shows a cross-sectional view (cross-sectional view taken along the line II in FIG. 4) along the groove center line of the second circumferential joint groove 4B. As shown in FIG. 5, the groove depth Dgf of the first arrival side end Ef of the depth changing groove 10 is smaller than the groove depth Dgr of the rear arrival side end Er, and the groove depth Dg is equal to the rear arrival side end Er. It gradually decreases from the first end Ef toward the first arrival side. As the gradual decrease, as in this example, the reduction ratio is constant, that is, the groove depth Dg can be changed in a linear function. For example, the groove depth Dg can be changed in a quadratic function.

  Thus, by setting the second circumferential joint groove 4B as the depth change groove 10, the rigidity of the acute-angle corner section C1f on the first arrival side among the four corner sections in the second block 6B is relatively set. Can be enhanced. Further, by using the third circumferential joint groove 4C as the depth changing groove 10, the rigidity of the acute corner portion C1f on the first arrival side in the third block 6C can be relatively increased. And by this rigidity improvement, generation | occurrence | production of the uneven wear of the said acute angle side corner part C1f of the said arrival side can be suppressed. Moreover, since the change of the groove depth Dg in the depth change groove 10 is smooth, the wet grip performance can be maintained high.

  For the above effect, in the depth changing groove 10, the groove depth Dgf at the first arrival side end is preferably 20 to 80% of the groove depth Dgr at the rear arrival side end. If it exceeds 80%, the rigidity of the sharp corner C1f is not sufficiently increased. Conversely, if it is less than 20%, the drainage performance tends to decrease, for example, it becomes difficult for water from the inclined lateral groove 3 to flow. Therefore, the lower limit value of the groove depth Dgf is more preferably 40% or more of the groove depth Dgr, and the upper limit value is more preferably 60% or less of the groove depth Dgr. The groove depth Dgr at the rear arrival side end is in the range of 90 to 100% of the groove depth Dy of the inclined lateral groove 3, and in particular, Dgr = Dy is a balance between drainage and block rigidity. From the viewpoint of

  On the other hand, in this example, as the first circumferential joint groove 4A (corresponding to the innermost circumferential joint groove 4i), the groove depth Dg is constant from the first arrival side end Ef to the rear arrival side end Er. It is formed by a constant depth groove 11. The groove depth Dg of the constant depth groove 11 is set to a range of 90 to 100% of the groove depth Dy of the inclined lateral groove 3 at the innermost intersection position Pi, in this example, 100%. This is because the importance of drainage is the highest on the tire equator side. Therefore, in this example, the uneven wear of the acute angle corner portion C1f on the first arrival side in the first block 6A is the same as the conventional chamfering. 13, the first circumferential joint groove 4 </ b> A is made to have a constant depth groove 11, thereby ensuring drainage and, in turn, wet grip performance.

  In this example, the fourth circumferential joint groove 4D (corresponding to the outermost circumferential joint groove 4o) is also formed by the constant depth groove 11. This is because the inclination angle α of the inclined lateral groove 3 increases toward the outer side in the tire axial direction. That is, the apex angle of the acute corner corner portion C1f on the first arrival side in the trapezoidal shoulder block 14 formed between the fourth circumferential joint groove 4D and the tread ground contact Te is the same in the other blocks 6A to 6C. This is because it is larger than the apex angle of the acute-angle corner portion C1f, has high rigidity, and is difficult to cause uneven wear. However, the fourth circumferential joint groove 4D can be formed by the depth changing groove 10 as in the case of the second and third circumferential joint grooves 4B and 4C.

  In the present example, in the four circumferential joint grooves 4A to 4D, the angle β of the groove width center with respect to the tire circumferential direction is set to be larger as the circumferential joint groove on the outer side in the tire axial direction. As a result, the block rigidity in the tire axial direction of the blocks 6A to 6C, 14 increases sequentially toward the outer side in the tire axial direction, and steering stability can be improved, for example, turning performance can be improved. The angle βa of the first circumferential joint groove 4A is in the range of 0 to 5 °, and in this example, 0 °, and the angle βd of the fourth circumferential joint groove 4D is in the range of 8 to 20 °. In this example, the angle is 10 °.

  FIG. 6 illustrates a cross-sectional view perpendicular to the groove center line of the depth changing groove 10 (a cross-sectional view taken along the line II-II in FIG. 4). As shown in FIG. 6, in this example, the inclination angle γb of the groove wall surface 10 sb on the tread ground end side with respect to the normal line of the tread surface among the groove wall surfaces 10 s on both sides arranged in the depth change groove 10 is It is set smaller than the inclination angle γa of the groove wall surface 10sa on the tire equator side. As a result, wet grip properties can be improved while ensuring the rigidity of the acute corner corner C1f on the first arrival side in the second and third blocks 6B and 6C. As in the case of the depth changing groove 10, also in the constant depth groove 11, the inclination angle γb of the groove wall surface at the tread contact end may be set smaller than the inclination angle γa of the groove wall surface on the tire equator side. preferable.

  Next, from the viewpoint of drainage, in the groove width Wy of the inclined lateral groove 3, as shown in FIG. 3, the groove width Wyo at the outermost intersection position Po is 1 of the groove width Wyi at the innermost intersection position Pi. It is preferable that it is larger than 0.0 times and not larger than 3 times. At this time, it is preferable that the groove width Wy is sequentially increased toward the outer side in the tire axial direction. In this example, the groove width WyB of the second inclined portion 3B is equal to the groove width WyC of the third inclined portion 3C, and is larger than the groove width WyA of the first inclined portion 3A, and the fourth inclined portion. The case where it is smaller than the 3D groove width WyD is shown. WyA <WyB = WyC <WyD. If the groove width ratio (WyD / WyA), that is, the ratio (Wyo / Wyi) is less than 1.0, the drainage performance decreases. If it exceeds 3.0, the rigidity of the shoulder block 14 decreases and the steering stability decreases. Cause a decline.

  Next, as shown as a representative of the second block 6B in FIGS. 7A and 7B, each of the acute corner corner portions C1 of the blocks 6A to 6C and 14 has its apex p. A chamfer 13 cut obliquely is formed to increase the rigidity of the acute corner portion C1. However, in the second and third blocks 6B and 6C, as described above, the second and third circumferential joint grooves 4B and 4C are the depth change grooves 10, so that the acute angle corner portion on the first arrival side is formed. The rigidity of C1f is increased. Therefore, the chamfer 13f formed at the acute corner corner C1f on the first arrival side of the second and third blocks 6B and 6C is the chamfer 13r formed on the acute corner corner C1r on the rear arrival side, or another block 6A. , 14 can be formed sufficiently smaller than the chamfer 13 formed at the acute-angle corner portion C1. Thereby, the ground contact area can be increased, which helps to improve the steering stability.

    FIG. 8 shows another embodiment of the inclined lateral groove 3. 8A is a plan view showing a part of the inclined lateral groove 3, and FIG. 8B is a sectional view taken along line III-III. As shown in FIG. 8, in this example, among the groove wall surfaces 3s on both sides arranged in the inclined lateral groove 3, at least the inclination angle θr of the groove wall surface 3sr on the rear arrival side with respect to the normal line of the tread surface is set to the obtuse angle side corner. It is gradually increased from the portion C2f toward the acute angle corner portion C1f. Thereby, the rigidity of the acute angle corner portion C1f on the first arrival side can be further increased. At this time, it is preferable that the inclination angle θf of the groove wall surface 3sf on the first arrival side with respect to the normal line of the tread surface is gradually increased from the obtuse angle side corner portion C2r toward the acute angle side corner portion C1r. Thereby, the rigidity of the acute angle corner portion C1r on the rear arrival side can be increased.

  However, as shown in FIGS. 9A and 9B, the inclination angle θr of the groove wall surface 3sr on the rear landing side with respect to the normal line of the tread surface is directed from the acute corner portion C1f to the obtuse corner portion C2f. Can be increased gradually. In this case, the removal effect of the water film by the acute angle side corner portion C1f is improved, wet grip properties are improved, and rigidity at the acute angle side corner portion C2f can be improved. For drainage, it is preferable that the inclination angle θf of the groove wall surface 3sf on the first arrival side with respect to the normal line of the tread surface is gradually increased from the acute corner portion C1r toward the obtuse corner portion C2r.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  Using the tread pattern shown in FIG. 1 as a reference pattern, a passenger car radial tire having a tire size of 225 / 45R17 according to the specifications shown in Table 1 was prototyped. Each sample tire was tested for wet grip performance and uneven wear resistance, and the results were compared with each other.

Except for the specifications shown in Table 1, each tire has substantially the same specifications, and a part thereof is shown below.
<Inclined lateral groove>
Inclination angle α1 (= αi): 20 degrees Inclination angle α2: 38 degrees Inclination angle α3: 55 degrees Inclination angle α4 (= αo): 80 degrees (difference αo-αi): 60 degrees Groove depth Dy : 8.0mm
<Circumferential seam>
・ Number: 4 <block>
・ First block (parallelogram shape)
... Vertical angle of acute corner part C1f: 20 degrees-Second block (parallelogram shape)
... Vertical angle of acute corner C1f: 33 degrees ・ Third block (parallelogram shape)
... Vertical angle of sharp corner C1f: 47 degrees -Shoulder block (trapezoidal shape)
... Vertical angle of sharp corner C1f: 70 degrees

  In Table 1, “the size of the chamfer of the acute corner portion on the first arrival side” in the block was compared based on the size of the chamfer formed on the tire of Comparative Example 1.

(1) Wet grip performance:
A sample tire is mounted on all wheels of a vehicle (3000 CC, FR vehicle) under the conditions of a rim (7.5 × 17) and internal pressure (180 kPa), and a water depth of 5 mm and a length of 20 m on an asphalt road surface with a radius of 100 m. On the course with a puddle, the speed was increased stepwise, the lateral acceleration (lateral G) was measured, and the average lateral G of the front wheels at a speed of 50-80 km / h was calculated (lateral hydroplaning) test). A result is displayed by the index | exponent which sets the comparative example 1 to 100, and it is so favorable that a numerical value is large.

(2) Uneven wear resistance:
Using the vehicle, the test course on the dry asphalt road surface was run for 8000 km, and the uneven wear state after running was visually evaluated. A result is displayed by the index | exponent which sets the comparative example 1 to 100, and it is excellent in uneven wear resistance, so that a numerical value is large.

It is an expanded view which expands and shows one Example of the tread pattern of the pneumatic tire of this invention. It is an expanded view which expands and shows a part. It is the schematic explaining the shape of an inclination horizontal groove. It is a development view of a tread pattern for further explaining the inclined lateral groove and the circumferential joint groove. It is II sectional drawing of FIG. 4 which shows the cross section along the groove | channel centerline of the circumferential joint groove. It is II-II sectional drawing of FIG. 4 which shows a cross section orthogonal to the groove | channel centerline of a depth change groove | channel. (A) is the top view to which the 2nd block was expanded, (B) is the fragmentary perspective view which shows the chamfering 13. FIG. (A) is a top view which shows the other Example of an inclination horizontal groove, (B) is the III-III sectional drawing. (A) is a top view which shows the further another Example of an inclination horizontal groove, (B) is the IV-IV sectional drawing. (A) is a developed view showing an example of a conventional tread pattern, and (B) is an enlarged view of a block for explaining the problem.

Explanation of symbols

2 Tread portion 3 Inclined transverse groove 4 Circumferential seam groove 4i Inner circumferential seam groove 4o Outermost circumferential seam groove 6 Block C Tire equator C1 Acute angle corner C2 Obtuse corner area Ef First arrival side Er Last arrival side End Te Tread grounding end Pi Innermost intersection position Po Outermost intersection position

Claims (9)

In the tread part,
A plurality of inclined lateral grooves that incline toward the rear arrival side in the tire rotation direction toward the outer side in the tire axial direction from the position near the tire equator to the position beyond the tread ground contact edge, and spaced apart in the tire circumferential direction,
TECHNICAL joint between the inclined lateral grooves adjacent in the tire circumferential direction, and by providing a four circumferential connecting grooves which are spaced axially,
A pneumatic tire in which a plurality of parallelogram blocks divided by the inclined lateral grooves and the circumferential joint grooves are formed in the tread portion,
The inclination angle α of the inclined lateral groove with respect to the tire circumferential direction sequentially increases toward the outer side in the tire axial direction,
Further, the inclined lateral groove is on the outer side in the tire axial direction and on the most tread ground contact end side with respect to the innermost intersection position intersecting with the innermost circumferential joint groove arranged on the tire equator side among the plurality of circumferential joint grooves. In the range of the region on the inner side in the tire axial direction from the outermost intersection position intersecting with the outermost circumferential joint groove arranged in the groove depth of the inclined lateral groove is substantially constant,
The innermost circumferential joint groove and the outermost circumferential joint groove extend from the first arrival side end to the rear arrival side end and have a constant groove depth Dg, and
The circumferential joint groove between the innermost circumferential joint groove and the outermost circumferential joint groove has a groove depth Dgf at the first arrival side end in the tire rotation direction, and a groove depth Dgr at the rear arrival side end. A pneumatic tire characterized in that the groove depth is gradually reduced toward the first arrival side end.   2. The pneumatic tire according to claim 1, wherein a groove depth Dgf of a first arrival side end of the circumferential joint groove is 20 to 80% of a groove depth Dgr of a second arrival end.   The inclined lateral grooves have an inclination angle αi with respect to the tire circumferential direction at the inner end in the tire axial direction of 10 to 35 °, and an inclination angle αo with respect to the tire circumferential direction at the position of the tread ground contact end of 40 to 90 °. The pneumatic tire according to claim 1 or 2. Any said groove depth Dg of the circumferential connecting grooves in the uppermost, the of claims 1 to 3, characterized in that 90 to 100% of the slope lateral groove 3 depth Dy of the innermost intersection The pneumatic tire according to Crab. 5. The pneumatic tire according to claim 1, wherein an angle β of the circumferential joint groove with respect to the tire circumferential direction is larger as the circumferential joint groove on the outer side in the tire axial direction is larger.   The groove width Wy of the inclined lateral groove is such that the groove width Wyo at the outermost intersection position is greater than 1.0 times and less than three times the groove width Wyi at the innermost intersection position. The pneumatic tire in any one of -5.   The parallelogram-shaped block has an acute angle corner portion and an obtuse angle side corner portion, and the inclined lateral groove has an inclination angle θr with respect to the normal line of the tread surface of the groove wall on the landing side, and the obtuse angle side corner. The pneumatic tire according to any one of claims 1 to 6, wherein the pneumatic tire is gradually increased from the portion toward the acute-angle corner portion.   The parallelogram-shaped block has an acute angle corner portion and an obtuse angle corner portion, and the inclined lateral groove has an inclination angle θr with respect to a normal line of the tread surface of the groove surface on the landing side, and the acute angle corner. The pneumatic tire according to claim 1, wherein the pneumatic tire is gradually increased from the portion toward the obtuse angle side corner portion. 9. A pair of innermost circumferential seam grooves are formed on both sides of the tire equator, and circumferential ribs extending continuously on the tire equator are formed between the innermost circumferential seam grooves. The pneumatic tire according to any one of the above.

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