JP2017013672A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of improving performances of driveability and partial wear resistance while maintaining drainage.SOLUTION: A pneumatic tire 1 has several lateral grooves 4 extending toward a direction crossing with a tire circumferential direction on a tread 2. At least one lateral groove 4 has a groove bottom 15, a pair of groove walls 16, 16 extending from the groove bottom 15 toward the outside in a tire radial direction, and at least one link part 17 linking between the groove walls 16, 16 at a tread ground plane 2S side. Further, the tire has between the link part 17 and groove bottom 15, a hollow part 18 maintaining a drain path along the longitudinal direction of the lateral groove 4.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire that can improve steering stability performance and uneven wear performance while maintaining drainage performance.

  The tread portion of the pneumatic tire is provided with a plurality of lateral grooves that divide the block or the block-like land portion. In addition, in order to improve the circumferential rigidity of the block of the tread portion and the like and improve the steering stability performance and the uneven wear performance, for example, a tie bar having a raised groove bottom of a lateral groove is provided.

International Publication No. 2007/072717 Pamphlet

  However, with the tie bar as described above, the circumferential rigidity of the block or the like could be increased, but there was room for further improvement. It is also conceivable to provide a tie bar having a large raised height in order to further increase the circumferential rigidity of the block or the like. However, such a tie bar also has a problem in that the groove volume of the lateral groove is reduced and the drainage performance is likely to be reduced.

  The present invention has been devised in view of the actual situation as described above, and includes a connecting portion that connects the groove walls on the tread ground surface side, and a hollow portion between the connecting portion and the groove bottom. Basically, the main object is to provide a pneumatic tire capable of improving the steering stability performance and the uneven wear performance while maintaining the drainage performance.

  The present invention relates to a pneumatic tire having a plurality of lateral grooves extending in a direction intersecting with the tire circumferential direction in a tread portion, wherein at least one of the lateral grooves includes a groove bottom and an outer side in the tire radial direction from the groove bottom. A pair of extending groove walls and at least one connecting portion for connecting the groove walls on the tread ground surface side, and between the connecting portion and the groove bottom, along the longitudinal direction of the lateral groove. It has a hollow portion for maintaining a drainage path.

  In the pneumatic tire according to the present invention, it is preferable that an outer surface of the connecting portion in a tire radial direction forms the tread grounding surface.

  In the pneumatic tire according to the present invention, it is desirable that the thickness of the lateral groove of the connecting portion in the groove depth direction gradually decreases from the groove wall side toward the groove center side of the lateral groove.

  In the pneumatic tire according to the present invention, it is preferable that the length of the connecting portion along the longitudinal direction of the lateral groove gradually increases from the tread ground surface side toward the groove bottom side.

  In the pneumatic tire according to the present invention, it is desirable that the height of the hollow portion in the tire radial direction is substantially the same over the entire region in the longitudinal direction of the connecting portion.

  In the pneumatic tire according to the present invention, the tread portion includes at least one main groove extending continuously in a tire circumferential direction, and the main groove includes a shoulder main groove arranged on the most tread grounding end side. Preferably, the lateral groove includes a shoulder lateral groove extending between the shoulder main groove and the tread grounding end, and the connecting portion is provided in the shoulder lateral groove.

  In the pneumatic tire according to the present invention, it is preferable that an inner end in the tire axial direction of the connecting portion is disposed along a groove edge on the outer side in the tire axial direction of the shoulder main groove.

  In the pneumatic tire according to the present invention, in a normal state in which a rim is assembled on a normal rim and a normal internal pressure is filled, a load of 50% of the normal load is applied and the camber angle is set to a plane at a 0 degree angle. The connecting portion is preferably disposed across the tread grounding end of the tread portion.

  In the present specification, unless otherwise specified, the dimensions of each part of the tire are values specified in a normal state in which a rim is assembled on a normal rim and a normal internal pressure is filled.

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

  The “regular internal pressure” is the air pressure defined by the standard for each tire. The maximum air pressure for JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” for ETRA, Then, “INFLATION PRESSURE” is set, but when the tire is for a passenger car, the pressure is uniformly set to 180 kPa.

  In the pneumatic tire of the present invention, a plurality of lateral grooves extending in the direction intersecting with the tire circumferential direction are provided in the tread portion. The at least one lateral groove has a groove bottom, a pair of groove walls extending from the groove bottom to the outside in the tire radial direction, and at least one connecting portion that connects the groove walls on the tread ground surface side.

  For example, a block or block-shaped land portion divided by a horizontal groove is a tire on the tread ground contact surface side that is the free end side, with the corner of the groove bottom and groove wall as a fulcrum when contacting the road surface. Large deformation in the circumferential direction. Such deformation reduces the circumferential rigidity of the block or the like. Unlike the conventional tie bar, the connecting portion of the present invention connects the groove walls on the tread ground surface side, so that deformation on the free end side such as a block can be effectively suppressed. Therefore, the connecting portion can effectively increase the circumferential rigidity of the block or the like, and can improve the steering stability performance and the uneven wear performance.

  Moreover, it has a hollow part which maintains the drainage path along the longitudinal direction of a horizontal groove between a connection part and a groove bottom. Such a hollow portion can be smoothly guided along the longitudinal direction of the lateral groove without hindering water in the lateral groove. Therefore, the pneumatic tire of the present invention can maintain drainage performance.

It is an expanded view which shows an example of the tread part of the pneumatic tire of this embodiment. It is A1-A1 sectional drawing of FIG. FIG. 2 is an exploded view showing an enlarged center land portion and middle land portion of FIG. 1. It is an expanded view which expands and shows the outer middle land part and shoulder land part of FIG. It is A2-A2 sectional drawing of FIG. It is A3-A3 sectional drawing of FIG. It is an expanded view which shows the connection part of other embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a development view illustrating an example of a tread portion of the pneumatic tire according to the present embodiment. 2 is a cross-sectional view taken along line A1-A1 of FIG. A pneumatic tire (hereinafter sometimes simply referred to as “tire”) 1 of the present embodiment is configured as a tire for a passenger car. The tread portion 2 of the tire 1 of the present embodiment is provided with at least one main groove 3 extending continuously in the tire circumferential direction and a plurality of lateral grooves 4 extending in a direction intersecting with the tire circumferential direction.

  The main groove 3 of the present embodiment includes a pair of center main grooves 3A, 3A arranged on both sides of the tire equator C, and a pair of shoulder main grooves 3B, 3B arranged most on the tread grounding end 2t side. Yes. Accordingly, the tread portion 2 includes a center land portion 5A between the pair of center main grooves 3A and 3A, a middle land portion 5B between the center main groove 3A and the shoulder main groove 3B, and the shoulder main groove 3B and the tread. It is divided into a shoulder land portion 5C between the ground contact end 2t.

  The “tread grounding end 2t” is an edge that can be identified by a clear edge in appearance. If the tire 1 in the normal state is loaded with a normal load and the tread portion 2 is grounded to the flat surface with a camber angle of 0 degree, the grounding that touches the flat surface on the outermost side in the tire axial direction is performed. The end is defined as a tread grounding end 2t.

  “Regular load” is the load that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum load capacity is specified for JATMA, and the table “TIRE LOAD LIMITS AT for TRA” If the maximum value described in “VARIOUS COLD INFLATION PRESSURES”, ETRTO, “LOAD CAPACITY” is used, but if the tire 1 is for a passenger car, the load is equivalent to 88% of the load.

  The center main groove 3A and the shoulder main groove 3B are formed as straight grooves extending linearly along the tire circumferential direction. Such straight grooves can smoothly drain the water film between the tread ground contact surface 2S of the tread portion 2 and the road surface in the tire circumferential direction. Therefore, the center main groove 3A and the shoulder main groove 3B can improve drainage performance. The groove widths W1a and W1b of the center main groove 3A and the shoulder main groove 3B are preferably about 3% to 10% of the tread ground contact width TW, which is the distance in the tire axial direction between the tread ground contact ends 2t and 2t. Further, the groove depths D1a and D1b (shown in FIG. 2) of the center main groove 3A and the shoulder main groove 3B are preferably about 6 mm to 10 mm.

  The tread portion 2 of the present embodiment is provided with a middle sub-groove 6 extending in the tire circumferential direction between the center main groove 3A and the shoulder main groove 3B. Thus, the middle land portion 5B is divided into an inner middle land portion 5Ba between the center main groove 3A and the middle sub groove 6 and an outer middle land portion 5Bb between the middle sub groove 6 and the shoulder main groove 3B. Has been.

  The middle sub-groove 6 is formed as a straight groove extending linearly along the tire circumferential direction. Such middle sub-groove 6 can smoothly drain the water film between the tread ground contact surface 2S of the middle land portion 5B and the road surface in the tire circumferential direction, and can improve drainage performance. Further, the groove width W2 of the middle sub groove 6 is set to be smaller than the groove width W1a of the center main groove 3A. Thereby, the middle subgroove 6 can prevent the rigidity reduction of the middle land portion 5B, and can improve the steering stability performance. The groove width W2 of the middle sub groove 6 is desirably about 0.5% to 1.0% of the tread ground contact width TW. Moreover, the groove depth D2 of the middle sub-groove 6 is desirably about 1.0 mm to 3.0 mm.

  The lateral groove 4 of the present embodiment includes a center lateral groove 4A provided in the center land portion 5A, an inner middle lateral groove 4B provided in the inner middle land portion 5Ba, an outer middle lateral groove 4C provided in the outer middle land portion 5Bb, and a shoulder land portion. A shoulder lateral groove 4D provided in 5C is included.

  FIG. 3 is an expanded view showing the center land portion 5A and the middle land portion 5B of FIG. The center lateral groove 4A extends from the center main groove 3A inward in the tire axial direction and terminates without reaching the tire equator C. The center lateral groove 4A is inclined with respect to the tire axial direction. Such a center lateral groove 4A can smoothly drain the water film between the tread ground contact surface 2S of the center land portion 5A and the road surface to the center main groove 3A, and can improve drainage performance. Further, since the center lateral groove 4A is formed as a lug groove that terminates without reaching the tire equator C, it is possible to suppress a decrease in rigidity of the center land portion 5A. The groove width W3a of the center lateral groove 4A is desirably about 1.0% to 2.0% of the tread grounding width TW (shown in FIG. 1). The groove depth D3a (shown in FIG. 2) of the center lateral groove 4A is preferably about 2.0 mm to 6.0 mm. Further, the angle α3a of the center lateral groove 4A with respect to the tire circumferential direction is preferably 40 degrees to 60 degrees.

  The inner middle lateral groove 4B extends from the center main groove 3A to the outer side in the tire axial direction and terminates without reaching the middle sub groove 6. Further, the inner middle lateral groove 4B is inclined with respect to the tire axial direction. Furthermore, the inner middle lateral groove 4B is disposed on an extension line extending from the outer end in the tire axial direction of the adjacent central lateral groove 4A across the center main groove 3A to the outer side in the tire axial direction. Such an inner middle horizontal groove 4B smoothly discharges the water film between the tread grounding surface 2S of the inner middle land portion 5Ba and the road surface to the center main groove 3A while preventing the rigidity of the inner middle land portion 5Ba from being lowered. sell. The groove width W3b and groove depth D3b (shown in FIG. 2) of the inner middle lateral groove 4B are preferably in the same range as the groove width W3a and groove depth D3a (shown in FIG. 2) of the center lateral groove 4A. Further, the angle α3b of the inner middle lateral groove 4B with respect to the tire circumferential direction is preferably about 50 to 70 degrees.

  FIG. 4 is an expanded view showing the outer middle land portion 5Bb and the shoulder land portion 5C of FIG. 1 in an enlarged manner. The outer middle lateral groove 4 </ b> C extends from the shoulder main groove 3 </ b> B inward in the tire axial direction and terminates without reaching the middle sub-groove 6. The outer middle lateral groove 4C is inclined with respect to the tire axial direction. The outer middle lateral groove 4C smoothly discharges the water film between the tread grounding surface 2S of the outer middle land portion 5Bb and the road surface to the shoulder main groove 3B while preventing the rigidity of the outer middle land portion 5Bb from decreasing. sell. The groove width W3c and groove depth D3c (shown in FIG. 2) of the outer middle lateral groove 4C are the same as the groove width W3a (shown in FIG. 3) and the groove depth D3a (shown in FIG. 2) of the center lateral groove 4A. The same range is desirable. Further, the angle α3c of the outer middle lateral groove 4C with respect to the tire circumferential direction is preferably about 60 to 80 degrees.

  The shoulder lateral groove 4D extends in the tire axial direction between the shoulder main groove 3B and the tread ground contact end 2t. Further, the shoulder lateral groove 4D extends smoothly from the shoulder main groove 3B to the tread ground contact end 2t while gradually increasing the angle α3d in the tire circumferential direction. Such a shoulder lateral groove 4D can smoothly discharge the water film between the tread ground surface 2S of the shoulder land portion 5C and the road surface along the inclination of the shoulder lateral groove 4D. The groove width W3d of the shoulder lateral groove 4D is desirably about 1.0% to 4.0% of the tread ground contact width TW (shown in FIG. 1). Further, the groove depth D3d (shown in FIG. 2) of the shoulder lateral groove 4D is desirably about 3.0 mm to 7.5 mm. Furthermore, the angle α3d of the shoulder lateral groove 4D is desirably 70 degrees to 90 degrees.

  As shown in FIG. 1, the center land portion 5A is formed as a straight rib extending linearly in the tire circumferential direction on the tire equator C. Such a center land portion 5A can increase the circumferential rigidity, and can improve the straight running stability performance. Note that the maximum width W4a in the tire axial direction of the center land portion 5A is desirably about 12.0% to 14.0% of the tread ground contact width TW.

  As shown in FIG. 3, the center land portion 5A is provided with a chamfer 11a cut into a substantially triangular shape at an acute corner portion formed by the center main groove 3A and the center lateral groove 4A. Such a chamfer 11a can suppress the occurrence of damage such as chipping at an acute corner portion. Further, the chamfer 11a can cause a disturbance in the vibration in the air column formed between the center main groove 3A and the road surface. Therefore, the chamfer 11a can effectively suppress the generation of noise due to air column resonance.

  As shown in FIG. 1, the inner middle land portion 5Ba is formed as a straight rib extending linearly in the tire circumferential direction. Such an inner middle land portion 5Ba can increase the circumferential rigidity, and can improve the straight running stability performance and the steering stability performance. Note that the maximum width W4b in the tire axial direction of the inner middle land portion 5Ba is desirably about 5.0% to 8.0% of the tread ground contact width TW.

  As shown in FIG. 3, the inner middle land portion 5Ba is provided with a chamfer 11b cut into a substantially triangular shape at an acute corner portion formed by the center main groove 3A and the inner middle lateral groove 4B. Such a chamfer 11b can also suppress the occurrence of damage such as chipping at an acute corner. Further, the chamfer 11b can effectively suppress the generation of noise due to air column resonance in the center main groove 3A together with the chamfer 11a of the center land portion 5A.

  As shown in FIG. 1, the outer middle land portion 5Bb is formed as a straight rib extending linearly in the tire circumferential direction. Such outer middle land portion 5Bb can also increase the circumferential rigidity, and can improve the straight running stability performance and the steering stability performance. Note that the maximum width W4c in the tire axial direction of the outer middle land portion 5Bb is desirably about 5.0% to 8.0% of the tread ground contact width TW.

  The shoulder land portion 5C is divided into a plurality of shoulder blocks 12 by a shoulder main groove 3B, a tread grounding end 2t, and a shoulder lateral groove 4D.

  The shoulder block 12 is formed in a horizontally long rectangular shape in which the maximum width W4d in the tire axial direction is larger than the maximum length L4d in the tire circumferential direction. Such a shoulder block 12 can improve tire axial rigidity, and can improve steering stability performance. The maximum width W4d of the shoulder block 12 is desirably about 10.0% to 20.0% of the tread ground contact width TW. The maximum length L4d of the shoulder block 12 is preferably about 7.0% to 17.0% of the tread ground contact width TW (shown in FIG. 1).

  5 is a cross-sectional view taken along line A2-A2 of FIG. 6 is a cross-sectional view taken along line A3-A3 of FIG. The at least one lateral groove 4 of the present invention includes a groove bottom 15, a pair of groove walls 16, 16 extending from the groove bottom 15 to the outside in the tire radial direction, and at least one connecting portion 17 connecting the groove walls 16, 16. Are provided. The connecting portion 17 of the present embodiment is provided in the shoulder lateral groove 4D.

  The connecting portion 17 connects the groove walls 16 and 16 on the tread ground surface 2S side. Further, a hollow portion 18 is provided between the connecting portion 17 and the groove bottom 15 along the longitudinal direction of the lateral groove 4.

  Thus, unlike the conventional tie bar which raises the groove bottom 15, for example, the connecting portion 17 connects the groove walls 16 and 16 on the tread ground surface 2S side. For this reason, the connecting portion 17 is greatly deformed in the tire circumferential direction on the tread ground contact surface 2S side, which is the free end side of the shoulder block 12, with the corner 21 of the groove bottom 15 and the groove wall 16 as a fulcrum. Can be prevented.

  Therefore, the tire 1 of the present invention can effectively increase the circumferential rigidity of the shoulder block 12 and improve the steering stability performance. Moreover, the connection part 17 can suppress the slip of the shoulder block 12 and a road surface resulting from a deformation | transformation of the shoulder block 12. FIG. Therefore, the connecting portion 17 can improve the uneven wear performance. Further, the connecting portion 17 can reduce the pumping sound caused by the deformation of the shoulder lateral groove 4D. Therefore, the connection part 17 can improve noise performance.

  Further, the deformation with the corner 21 as a fulcrum as described above tends to be larger in the block on the tread ground contact end 2t side where the outer diameter is smaller than that on the tire equator C side. Since the connection part 17 of this embodiment is provided in the shoulder lateral groove 4D which divides the shoulder block 12 (shown in FIG. 4), the deformation of the shoulder block 12 can be effectively suppressed.

  The connecting portion 17 is provided with a hollow portion 18 that can maintain the drainage path of the lateral groove 4. For this reason, the connection part 17 can guide smoothly along the longitudinal direction of shoulder lateral groove 4D, without inhibiting the water in shoulder lateral groove 4D. Therefore, the tire 1 of the present invention can maintain drainage performance.

  The outer surface 17s of the connecting portion 17 in the tire radial direction preferably forms the tread contact surface 2S together with the outer surface 12s of the shoulder block 12 in the tire radial direction. Thereby, the connection part 17 can prevent effectively the deformation | transformation of the shoulder block 12 which becomes easy to become large in the tread grounding surface 2S side. Further, the connecting portion 17 can prevent a step from being formed between the adjacent shoulder blocks 12 and 12. Therefore, since the connection part 17 can be earth | grounded smoothly between the adjacent shoulder blocks 12 and 12, the fall of the noise performance resulting from the vibration at the time of driving | running | working can be prevented.

  As shown in FIG. 5, in the cross section orthogonal to the longitudinal direction of the lateral groove 4, the thickness W6 of the lateral groove 4 of the connecting portion 17 in the groove depth direction is from the groove walls 16, 16 side to the groove center side of the lateral groove 4. It is desirable to gradually decrease toward. Thereby, as for the connection part 17 of this embodiment, the hollow part 18 is formed in the curve shape (arch shape) which protrudes on the radial direction outer side. The connecting portion 17 can increase the height H7 of the hollow portion 18 in the tire radial direction on the groove center side while maintaining the rigidity on the groove walls 16 and 16 side. Therefore, the connection part 17 can improve drainage performance, maintaining steering stability performance and uneven wear performance.

  In order to effectively exhibit the above action, the minimum thickness W6s of the lateral groove 4 of the connecting portion 17 in the groove depth direction is set to the groove depth D3 of the lateral groove 4 (in this embodiment, the groove of the shoulder lateral groove 4D). 20% to 50% of the depth D3d (maximum value) (shown in FIG. 2) is desirable. If the minimum thickness W6s exceeds 50% of the groove depth D3 of the lateral groove 4, the cross-sectional shape of the hollow portion 18 becomes small, and there is a possibility that the drainage performance cannot be sufficiently exhibited. Conversely, if the minimum thickness W6s is less than 20% of the groove depth D3 of the lateral groove 4, the rigidity of the connecting portion 17 may not be sufficiently maintained on the groove center side. From such a viewpoint, the minimum thickness W6s is more preferably 45% or less of the groove depth D3 of the lateral groove 4, and more preferably 25% or more.

  Further, the maximum thickness W6m in the groove depth direction of the lateral groove 4 of the connecting portion 17 is the groove depth D3 of the lateral groove 4 (in this embodiment, the groove depth D3d (maximum value) of the shoulder lateral groove 4D (shown in FIG. 2). 35) to 60% of)) is desirable. If the maximum thickness W6m is less than 35% of the groove depth D3 of the lateral groove 4, the rigidity of the connecting portion 17 may not be sufficiently maintained. Conversely, if the maximum thickness W6m exceeds 60% of the groove depth D3 of the lateral groove 4, the cross-sectional shape of the hollow portion 18 becomes small, and there is a possibility that the drainage performance cannot be sufficiently exhibited. From such a point of view, the maximum thickness W6m is more preferably 40% or more of the groove depth D3 of the lateral groove 4, and more preferably 55% or less.

  As shown in FIG. 6, the connecting portion 17 desirably has a length L6 of 10 mm to 15 mm along the longitudinal direction of the lateral groove 4. If the length L6 is less than 10 mm, the circumferential rigidity of the shoulder block 12 cannot be sufficiently increased, and the steering stability performance and uneven wear performance may not be sufficiently improved. On the other hand, if the length L6 exceeds 15 mm, the groove volume of the lateral groove 4 may be reduced, and the drainage performance may not be maintained. From such a viewpoint, the length L6 is more preferably 11 mm or more, and more preferably 14 mm or less.

  Further, it is desirable that the length L6 of the connecting portion 17 gradually increases from the tread grounding surface 2S side toward the groove bottom 15 side. Thereby, since the connection part 17 can raise the rigidity by the side of the groove bottom 15 relatively, and can suppress a deformation | transformation of the shoulder block 12, it can improve steering stability performance and drainage performance. Further, the connecting portion 17 can prevent the length L6 from gradually shortening due to wear of the tire 1. Accordingly, the connecting portion 17 can suppress changes in appearance due to the wear of the tire 1.

  In the cross section along the longitudinal direction of the lateral groove 4, the length L6m of the connecting portion 17 on the groove bottom 15 side is desirably 105% to 120% of the length L6s of the connecting portion 17 on the tread grounding surface 2S side. If the length L6m on the groove bottom 15 side of the connecting portion 17 is less than 105% of the length L6s on the tread grounding surface 2S side of the connecting portion 17, the rigidity on the groove bottom 15 side of the connecting portion 17 is sufficient. May not be improved. On the contrary, even if the length L6m on the groove bottom 15 side of the connecting portion 17 exceeds 120% of the length L6s on the tread grounding surface 2S side of the connecting portion 17, the rigidity on the tread grounding surface 2S side of the connecting portion 17 remains. There is a possibility that the deformation of the shoulder block 12 on the tread grounding surface 2S side cannot be sufficiently prevented. From such a viewpoint, the length L6m of the connecting portion 17 on the groove bottom 15 side is more preferably 108% or more of the length L6s of the connecting portion 17 on the tread grounding surface 2S side, and more preferably 117%. % Or less is desirable.

  From the same viewpoint, in the cross section along the longitudinal direction of the lateral groove 4, the angle α8 formed by the virtual extension line 23 extending the outer end 17o of the connecting portion 17 in the tire axial direction to the groove bottom 15 and the groove bottom 15 is 80 to 90 degrees is desirable. Thereby, in the outer end 17o side of the connection part 17, the external appearance change by abrasion of the tire 1 can be prevented effectively.

  The height H7 of the hollow portion 18 in the tire radial direction is substantially the same over the entire region in the longitudinal direction of the connecting portion 17 (longitudinal direction of the lateral groove 4) in the cross section along the longitudinal direction of the lateral groove 4. Is desirable. Thereby, the hollow part 18 can be smoothly guided along the longitudinal direction of the shoulder lateral groove 4D without inhibiting the flow of water in the shoulder lateral groove 4D. Therefore, the tire 1 can improve drainage performance. Note that “substantially the same” allows a range in which the difference between the maximum value and the minimum value of the height H7 of the hollow portion 18 in the longitudinal direction of the connecting portion 17 is 0.7 mm or less. .

  As shown in FIG. 5, the maximum height H7m in the tire radial direction of the hollow portion 18 is the groove depth D3 of the lateral groove 4 (in this embodiment, the groove depth D3d (maximum value) of the shoulder lateral groove 4D) (FIG. 2). To 50% to 80%)))). If the maximum height H7m of the hollow portion 18 is less than 50% of the groove depth D3 of the lateral groove 4, water in the shoulder lateral groove 4D may not be smoothly guided. Conversely, if the maximum height H7m of the hollow portion 18 exceeds 80% of the groove depth D3 of the lateral groove 4, the thickness W6 of the connecting portion 17 becomes small, and the rigidity of the connecting portion 17 may be reduced. From such a viewpoint, the maximum height H7m of the hollow portion 18 is more preferably 55% or more of the groove depth D3 of the lateral groove 4, and more preferably 75% or less.

  From the same viewpoint, the minimum height H7s of the hollow portion 18 in the tire radial direction is the groove depth D3 of the lateral groove 4 (in this embodiment, the groove depth D3d (maximum value) of the shoulder lateral groove 4D (shown in FIG. 2)). ) Of 40% or more, more preferably 45% or more, and 65% or less, more preferably 60% or less.

  As shown in FIG. 2, in the tread rubber 2G disposed in the tread portion 2, the complex elastic modulus E * 1 of the first region T1 in which the connecting portion 17 is formed is the second region T2 other than the first region T1. It is desirable to be larger than the complex elastic modulus E * 2. The inner end T1i of the first region T1 is disposed on the inner side in the tire axial direction than the inner end 17i (shown in FIG. 4) of the connecting portion 17 in the tire axial direction. Further, the outer end T1o of the first region T1 is disposed on the outer side in the tire axial direction of the outer end 17o of the connecting portion 17 in the tire axial direction.

  Thereby, in this embodiment, since the rigidity of the connection part 17 can be improved relatively, the circumferential direction rigidity of the shoulder block 12 can be improved. Accordingly, the connecting portion 17 can improve the steering stability performance and the uneven wear performance.

  In the present embodiment, the complex elastic modulus E * 1 is set in the entire region from the tread ground contact surface 2S to the belt layer 8 in the first region T1. For this reason, the rigidity of the groove bottom 15 (shown in FIG. 5) and the groove walls 16 and 16 (shown in FIG. 5) of the shoulder lateral groove 4D adjacent to the connecting portion 17 and the connecting portion 17 can be set to be the same. . Therefore, the connection part 17 of this embodiment can prevent the damage resulting from the difference in rigidity between the connection part 17 and the shoulder lateral groove 4D.

  The complex elastic modulus E * 1 of the first region T1 is desirably 105% to 150% of the complex elastic modulus E * 2 of the second region T2. If the complex elastic modulus E * 1 is less than 105% of the complex elastic modulus E * 2, the steering stability performance and uneven wear performance may not be sufficiently improved. On the contrary, when the complex elastic modulus E * 1 exceeds 150% of the complex elastic modulus E * 2, the difference in rigidity between the first region T1 and the second region T2 increases, and the steering stability performance and noise performance decrease. In addition, the connecting portion 17 may be damaged. From such a viewpoint, the complex elastic modulus E * 1 is preferably 110% or more and preferably 140% or less of the complex elastic modulus E * 2.

The complex elastic moduli E * 1 and E * 2 are values measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. under the following conditions in accordance with JIS-K6394.
Initial strain: 10%
Amplitude: ± 1%
Frequency: 10Hz
Deformation mode: Tensile temperature: 70 ° C

  The distance in the tire axial direction (not shown) between the inner end T1i of the first region T1 and the inner end 17i of the connecting portion 17 can be set as appropriate. Further, the distance (not shown) in the tire axial direction between the outer end T1o of the first region T1 and the outer end 17o of the connecting portion 17 can be set as appropriate. These distances are preferably set to 1.0 mm to 3.0 mm, for example.

  As shown in FIGS. 4 and 6, in the connecting portion 17 of the present embodiment, the inner end 17i in the tire axial direction is disposed along the groove edge 3Bo on the outer side in the tire axial direction of the shoulder main groove 3B. Thereby, since the connection part 17 can ensure the groove volume of shoulder lateral groove 4D by the side of the tread grounding end 2t (shown in FIG. 1), the drainage performance can be effectively maintained.

  As an example of a method for forming such a connecting portion 17, first, a tire having the tread portion 2 in which the connecting portion 17 is not formed is manufactured through a vulcanization process using a vulcanization mold. And the inside of the area | region in which the connection part 17 is formed is cut along the shoulder lateral groove 4D so that the shoulder lateral groove 4D and the shoulder main groove 3B communicate. Thereby, the connection part 17 which has the hollow part 18 can be formed.

  By the way, for example, in the rear tires of FF vehicles and 4WD vehicles, the load factor is relatively small, and therefore, slippage between the shoulder block 12 and the road surface is likely to occur on the tread ground contact end 2t (shown in FIG. 1) side. Such sliding of the shoulder block 12 causes a decrease in uneven wear performance. FIG. 7 is a development view showing a connecting portion 17 according to another embodiment of the present invention. In addition, about the cross-sectional shape and each dimension of the connection part 17 of this embodiment, it is set to the same range as all the embodiments.

  The connecting portion 17 of this embodiment is disposed on the tread grounding end 2t side. Such a connecting portion 17 can suppress slip on the tread grounding end 2t side of the shoulder block 12 in a tire having a relatively small load factor (for example, a rear tire of an FF vehicle or a 4WD vehicle). Therefore, the connection part 17 can maintain uneven wear performance.

  In order to effectively exhibit such an action, the connecting portion 17 is in a state where a load of 50% of the normal load is applied to the normal state and is grounded on a plane with a camber angle of 0 degrees (hereinafter simply referred to as a normal state). In the “half-load load state”), it is desirable that the tread grounding end 2h in the half-load load state is disposed across the tread grounding end 2h. Thereby, the connection part 17 can suppress reliably the slip in the tread grounding end 2h of the shoulder block 12 in the tire (for example, rear tire of FF vehicle, 4WD vehicle, etc.) whose load load factor is comparatively small.

  Further, in the half load load state, the distance L9a in the tire axial direction between the outer end 17o of the connecting portion 17 and the tread ground contact end 2h in the half load load state is preferably 5.0 mm to 8.0 mm. If the distance L9a is less than 5.0 mm, the connecting portion 17 may not be disposed across the tread grounding end 2h due to displacement of the tread grounding end 2h due to a load change. On the other hand, if the distance L9a exceeds 8.0 mm, the groove volume of the lateral groove 4 may decrease, and the drainage performance may not be maintained.

  From the same viewpoint, in the half load load state, the distance L9b in the tire axial direction between the inner end 17i of the connecting portion 17 and the tread ground contact end 2h in the half load load state is preferably 5.0 mm or more, preferably Is 8.0 mm or less.

  Note that the slip of the shoulder block 12 as described above tends to occur on the vehicle inner side of both sides in the tire axial direction. For this reason, when the tread portion 2 is a tire having a directional pattern in which the mounting direction to the vehicle is designated, it is desirable that the connecting portion 17 is disposed at least inside the vehicle. As a result, the tire 1 can improve the uneven wear performance while preventing a decrease in drainage performance outside the vehicle.

  Further, when the connecting portion 17 is disposed on the tread grounding end 2t side as in this embodiment, the shoulder block 12 has a substantially triangular corner portion formed by the shoulder main groove 3B and the shoulder lateral groove 4D. It is desirable to provide a chamfer 11d cut into a shape. Such a chamfer 11d can also effectively suppress damage such as chipping at an acute corner and noise generation due to air column resonance.

  As shown in FIG. 1, the connecting portion 17 of the present embodiment is provided in the shoulder lateral groove 4D, but may be provided in, for example, the center lateral groove 4A, the inner middle lateral groove 4B, or the outer middle lateral groove 4C. . As a result, the connecting portion 17 is divided into the center land portion 5A, the inner middle land portion 5Ba, and the outer middle land portion 5Bb, each block shape being divided by the center lateral groove 4A, the inner middle lateral groove 4B and the outer middle lateral groove 4C. The deformation of the land portions 7A, 7Ba, 7Bb can be suppressed. Therefore, the connection part 17 can improve the circumferential rigidity of each block-shaped land part 7A, 7Ba, 7Bb, and can improve steering stability performance and uneven wear performance. Further, the connecting portion 17 may be provided at any position of the center lateral groove 4A, the inner middle lateral groove 4B, the outer middle lateral groove 4C, or the shoulder lateral groove 4D.

  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.

[Example A]
Tires having the basic structure shown in FIG. 1 and having the connecting portion and the hollow portion shown in FIG. 4 and Table 1 were manufactured and evaluated. For comparison, a tire having no connection part and a hollow part (Comparative Example 1) and a tire having only the connection part (Comparative Example 2) were also manufactured and evaluated in the same manner. The common specifications are as follows.
Tire size: 205 / 55R16
Rim size: 16 × 6.5JJ
Internal pressure: 230 kPa
Vehicle: 2000cc domestic FF vehicle Regular load: 5.41kN
Tread contact width TW: 176mm
Center main groove:
Groove width W1a / TW: 5.3%
Groove depth D1a: 7.8 mm
Shoulder main groove:
Groove width W1b / TW: 5.8%
Groove depth D1b: 7.8 mm
Middle minor groove:
Groove width W2 / TW: 0.7%
Groove depth D2: 1.5 mm
Center lateral groove:
Groove width W3a / TW: 1.5%
Groove depth D3a: 3.0 mm
Angle α3a: 50 degrees Inner middle lateral groove:
Groove width W3b / TW: 1.5%
Groove depth D3b: 3.0 mm
Angle α3b: 60 degrees Outer middle lateral groove:
Groove width W3c / TW: 1.0%
Groove depth D3c: 3.0 mm
Angle α3c: 70 degrees Shoulder lateral groove:
Groove width W3d / TW: 1.5% to 3.0%
Groove depth D3d (maximum value): 6.8 mm
Angle α3d: 80 degrees to 90 degrees Center land:
Maximum width W4a / TW: 13.5%
Inner middle land:
Maximum width W4b / TW: 6.7%
Outer middle land:
Maximum width W4c / TW: 6.7%
Shoulder block:
Maximum width W4d / TW: 17.3%
Maximum length L4d / TW: 15.4%
Complex elastic modulus E * 2 in the second region: 3.5 MPa
The test method is as follows.

<Uneven wear performance>
Each test tire was assembled on the rim and filled with the internal pressure, and the wear energy during braking and driving was measured using a wear energy measuring device. Next, during braking and driving, the ratio U1 / U2 between the wear energy U1 on the rear side of the shoulder block and the wear energy U2 on the first side of the shoulder block was calculated. The ease of partial wear (heel & toe wear) was evaluated from the ratios U1 / U2 for braking and driving. The evaluation results are indicated by an index with Comparative Example 1 as 100. The larger the value, the better the uneven wear.

<Steering stability>
Each test tire was assembled to the four wheels of the vehicle after assembling the rim on the rim and filling the internal pressure. Then, two people traveled on a dry asphalt road test course, and the characteristics of steering wheel response, rigidity, grip, etc. were evaluated by sensory evaluation of the driver. The evaluation results are indicated by an index with Comparative Example 1 as 100. The larger the value, the better.

<Noise performance>
Each test tire was assembled to the four wheels of the vehicle after assembling the rim on the rim and filling the internal pressure. And the noise level resulting from the pattern noise at the time of a vehicle passing the dry paved road surface was measured. The evaluation result is displayed as an index with the comparative example 1 being 100, using the reciprocal of the measured value. The larger the value, the less pattern noise and the better.

<Drainage performance>
Each test tire was assembled to the four wheels of the vehicle after assembling the rim on the rim and filling the internal pressure. Then, on the asphalt road surface with a radius of 102 m, on the course provided with a puddle with a depth of 6 mm and a length of 20 m, the vehicle entered while increasing the speed stepwise, and the lateral acceleration (lateral G) was measured, and 60 km / h The average lateral G of the front wheels at a speed of ˜90 km / h was calculated. The evaluation results are indicated by 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 was confirmed that the tire of the example can improve the steering stability performance and the uneven wear performance while maintaining the drainage performance. Moreover, it has confirmed that the tire of an Example can improve noise performance.

[Example B]
Tires having the basic structure shown in FIG. 1 and having the connecting portion and the hollow portion shown in FIG. 7 and Table 2 were manufactured and evaluated. The common specifications are the same as those in the example A. The test method is the same as that of Example A except for the following “actual vehicle uneven wear performance”.

<Real car uneven wear performance>
Each test tire was assembled to the four wheels of the vehicle after assembling the rim on the rim and filling the internal pressure. Next, a total of 340 km traveled on a highway and general roads (including urban areas and mountain roads). Then, at three locations on the tire circumference on the tread ground contact side, uneven wear (heel & toe) is determined from a ratio V1 / V2 between the wear amount V1 on the rear side of the shoulder block and the wear amount V2 on the first side of the shoulder block. Ease of wear was evaluated. The evaluation results are indicated by an index with Comparative Example 1 as 100. The larger the value, the better the uneven wear.
Table 2 shows the test results.

  As a result of the test, it was confirmed that the tire of the example can improve the steering stability performance and the uneven wear performance while maintaining the drainage performance. Moreover, it has confirmed that the tire of an Example can improve noise performance.

1 Pneumatic tire.
2 Tread part 4 Horizontal groove 17 Connecting part 18 Hollow part

Claims (8)

A pneumatic tire having a plurality of lateral grooves extending in a direction intersecting with the tire circumferential direction in the tread portion,
The at least one lateral groove has a groove bottom, a pair of groove walls extending from the groove bottom to the outside in the tire radial direction, and at least one connecting portion that connects the groove walls on the tread ground surface side,
A pneumatic tire having a hollow portion that maintains a drainage path along a longitudinal direction of the lateral groove between the connecting portion and the groove bottom.   The pneumatic tire according to claim 1, wherein an outer surface in a tire radial direction of the connecting portion forms the tread contact surface.   3. The pneumatic tire according to claim 1, wherein a thickness of the connecting portion in the groove depth direction of the lateral groove gradually decreases from the groove wall side toward the groove center side of the lateral groove.   The pneumatic tire according to any one of claims 1 to 3, wherein a length of the connecting portion along the longitudinal direction of the lateral groove gradually increases from the tread ground surface side toward the groove bottom side.   The pneumatic tire according to any one of claims 1 to 4, wherein the height of the hollow portion in the tire radial direction is substantially the same throughout the longitudinal direction of the connecting portion. The tread portion includes at least one main groove extending continuously in the tire circumferential direction,
The main groove includes a shoulder main groove arranged on the most tread grounding end side,
The lateral groove includes a shoulder lateral groove extending between the shoulder main groove and the tread grounding end,
The pneumatic tire according to claim 1, wherein the connecting portion is provided in the shoulder lateral groove.   The pneumatic tire according to claim 6, wherein an inner end in the tire axial direction of the connecting portion is disposed along a groove edge on the outer side in the tire axial direction of the shoulder main groove. In a state where a rim is assembled to a normal rim and a normal internal pressure is filled, a load of 50% of the normal load is applied and the camber angle is set to a flat surface at 0 degrees.
The pneumatic tire according to claim 6, wherein the connecting portion is disposed across a tread grounding end of the tread portion.

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