JP5981952B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire having improved performance on snow while maintaining steering stability on a dry road surface.

  The following Patent Document 1 proposes a pneumatic tire in which the shape of the sipe provided in the tread portion and the width of the belt layer are improved. Such a pneumatic tire suppresses the growth of the outer diameter of the tread portion due to the inner pressure filling, and consequently maintains the sipe width substantially constant. For this reason, the sipe edge effect is enhanced.

JP 2011-143891 A

  However, even in the pneumatic tire of Cited Document 1, further improvement has been demanded for compatibility between the handling stability on the dry road surface and the performance on snow.

  The present invention mainly provides a pneumatic tire that improves on-snow performance while maintaining steering stability on a dry road surface based on improving the shape of the middle lateral groove provided in the middle land portion. It is aimed.

The present invention provides a tread portion having a pair of shoulder main grooves extending continuously in the tire circumferential direction on both sides of the tire equator and closest to the tread grounding end, and continuously between the pair of shoulder main grooves in the tire circumferential direction. By providing the center main groove extending, a middle land portion divided by the shoulder main groove and the center main groove is provided on both sides of the tire equator, and the shoulder main groove has an outer shoulder in the tire axial direction. A pneumatic tire provided with a land portion , wherein each middle land portion is provided with a plurality of middle lateral grooves extending obliquely with respect to a tire axial direction, and each middle lateral groove communicates with the shoulder main groove. An outer end portion and an inner end portion terminating in the middle land portion, the groove width of the outer end portion gradually increases toward the outer side in the tire axial direction, and a groove bottom is formed at the outer end portion. Raised mid Tie bars disposed et al is, the shoulder land portion includes a plurality of shoulder lateral grooves which terminate extending and within the shoulder land portion from the tread ground contact edge on the inner side in the tire axial direction, and the inner end in the tire axial direction of the shoulder lateral grooves A first shoulder sipe communicating with the shoulder main groove is provided; a shoulder tie bar having a raised groove bottom is provided at the inner end of the shoulder lateral groove; It has a depth smaller than the groove depth of the shoulder lateral groove at the position of the tie bar .

  In the pneumatic tire of the present invention, the maximum groove depth of the middle lateral groove is 0.6 to 0.75 times the groove depth of the shoulder main groove, and the middle groove is determined from the maximum groove depth of the middle horizontal groove. The middle tie bar height minus the groove depth at the tie bar position is 1.0 to 1.4 mm, and the length of the middle tie bar in the tire axial direction is 2.5 to 5.5 mm. desirable.

  In the pneumatic tire of the present invention, the center main groove includes a first center main groove provided on one side of the tire equator and a second center main groove provided on the other side of the tire equator, It is desirable that a center rib extending continuously in the tire circumferential direction is provided between the first center main groove and the second center main groove.

  In the pneumatic tire of the present invention, the center rib includes a first center sipe extending from the first center main groove and terminating in the center rib, and extending from the second center main groove and terminating in the center rib. It is desirable that a plurality of center sipe pairs including the second center sipe are provided in the tire circumferential direction.

  In the pneumatic tire of the present invention, the distance between the inner end in the center rib of the first center sipe and the inner end in the center rib of the second center sipe in the center sipe pair It is desirable to change periodically for each sipe pair.

  In the pneumatic tire of the present invention, a distance in the tire axial direction between the inner end of the first center sipe and the inner end of the second center sipe in the center sipe pair is constant for each center sipe pair. It is desirable that

  The pneumatic tire of the present invention has a pair of shoulder main grooves extending continuously in the tire circumferential direction on both sides of the tire equator and closest to the tread ground end side in the tread portion, and between the pair of shoulder main grooves in the tire circumferential direction. By providing the center main groove extending continuously, the middle land portion divided by the shoulder main groove and the center main groove is provided on both sides of the tire equator. Each middle land portion is provided with a plurality of middle lateral grooves extending obliquely with respect to the tire axial direction.

  Each middle lateral groove has an outer end portion communicating with the shoulder main groove and an inner end portion terminating in the middle land portion. Such middle lateral grooves increase the rigidity of the middle land portion in the tire axial direction and maintain steering stability on the dry road surface.

  The groove width of the outer end portion gradually increases toward the outer side in the tire axial direction. Such an outer end increases the volume of the middle lateral groove and exhibits a large snow column shear force. Moreover, such an outer end portion fills a groove with a large amount of snow when the tire slides, and exerts a greater snow column shear force.

  A middle tie bar with a raised groove bottom is provided at the outer end. Such a middle tie bar increases the rigidity in the tire circumferential direction on the outer side in the tire axial direction of the middle land portion, and maintains steering stability on a dry road surface. Moreover, the middle tie bar makes it difficult for snow to get stuck in the middle lateral groove.

  As described above, the pneumatic tire of the present invention can improve on-snow performance while maintaining steering stability on a dry road surface.

It is an expanded view of the tread part of the pneumatic tire of one embodiment of the present invention. It is AA sectional drawing of FIG. It is an enlarged view of the middle land part of FIG. It is BB sectional drawing of the middle horizontal groove of FIG. It is an enlarged view of the center rib of FIG. It is an enlarged view of the shoulder land part of FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a development view of a tread portion 2 of a pneumatic tire (hereinafter sometimes simply referred to as “tire”) 1 of the present embodiment. The pneumatic tire 1 of this embodiment is suitably used for, for example, a passenger car.

  As shown in FIG. 1, the tread portion 2 is provided with a pair of shoulder main grooves 3 and 3 and a pair of center main grooves 4 and 4.

  Each shoulder main groove 3 continuously extends in the tire circumferential direction on both sides of the tire equator C and on the tread ground contact end Te side. The shoulder main groove 3 of the present embodiment has a substantially constant groove width and extends linearly.

  The “tread grounding end Te” is a flat surface with a normal load applied to a normal tire 1 which is assembled with a normal rim (not shown) and filled with a normal internal pressure, and which is not loaded, with a camber angle of 0 °. This is the ground contact position on the outermost side in the tire axial direction when touching the ground.

  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, “Standard Rim” for JATMA, “Design Rim” for TRA, For ETRTO, "Measuring Rim".

  The “regular internal pressure” is the air pressure determined by each standard for each tire in the standard system including the standard on which the tire is based, and is “maximum air pressure” for JATMA, and “TIRE LOAD” for TRA. The maximum value described in “LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” in the case of ETRTO.

  The “regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. “JAMATA” indicates “maximum load capacity”, and TRA indicates “TIRE” The maximum value described in “LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, or “LOAD CAPACITY” in the case of ETRTO.

  The center main groove 4 extends continuously between the shoulder main grooves 3 and 3 in the tire circumferential direction. The center main groove 4 of the present embodiment has, for example, a substantially constant groove width and extends linearly. The center main groove 4 of the present embodiment includes a first center main groove 5 provided on one side of the tire equator C and a second center main groove 6 provided on the other side of the tire equator C. The center main groove 4 may be only one extending on the tire equator C, for example.

  The groove width W1 of the shoulder main groove 3 and the groove width W2 of the center main groove 4 are, for example, 4.0 to 6.0% of the tread grounding width TW. The shoulder main groove 3 and the center main groove 4 exhibit excellent on-snow performance while maintaining the steering stability on the dry road surface. The tread contact width TW is the distance in the tire axial direction between the tread contact ends Te and Te of the tire 1 in the normal state.

  FIG. 2 shows a cross-sectional view of the tire 1 corresponding to the position AA in FIG. As shown in FIG. 2, the groove depth d1 of the shoulder main groove 3 and the groove depth d2 of the center main groove 4 are preferably, for example, 6.0 to 9.0 mm.

  As shown in FIG. 1, the tread portion 2 includes a pair of middle land portions 10 and 10 divided by a shoulder main groove 3 and a center main groove 4, a first center main groove 5, and a second center main groove. 6, and a shoulder land portion 30 provided on the outer side in the tire axial direction of each shoulder main groove 3 is provided.

  FIG. 3 shows an enlarged view of the middle land portion 10. As shown in FIG. 3, middle lateral grooves 11 that are inclined with respect to the tire axial direction are spaced apart in the tire circumferential direction in the middle land portion 10.

  Each middle lateral groove 11 includes an outer end portion 12 communicating with the shoulder main groove 3, an inner end portion 13 terminating in the middle land portion 10, and a main body portion 14 between the outer end portion 12 and the inner end portion 13. have. Such middle lateral grooves 11 enhance the rigidity of the middle land portion 10 on the inner side in the tire axial direction, and maintain steering stability on a dry road surface.

  The inner end portion 13 is provided, for example, on the inner side in the tire axial direction from the center line 10c of the middle land portion 10. Thereby, the volume of the middle lateral groove 11 is ensured and the performance on snow is enhanced.

  The main body 14 has a substantially constant groove width W4. The groove width W4 of the main body 14 is, for example, 2.5 to 4.0 mm. Such a main body 14 exhibits excellent on-snow performance while maintaining steering stability on a dry road surface.

  The groove width W5 of the outer end portion 12 gradually increases toward the outer side in the tire axial direction. Such an outer end 12 increases the volume of the middle lateral groove 11 and exhibits a large snow column shear force. Moreover, such an outer end 12 fills the groove with a large amount of snow when the tire slides, and exerts a greater snow column shear force.

  The outer end portion 12 includes, for example, a first edge 12a extending substantially linearly and a second edge 12b curved substantially arcuately. Such an outer end portion 12 effectively guides snow into the middle lateral groove 11 and enhances the snow column shear force.

  4 shows a cross-sectional view of the middle lateral groove 11 taken along the line BB. As shown in FIG. 4, a middle tie bar 15 having a raised groove bottom is provided at the outer end portion 12 of the middle lateral groove 11. Such a middle tie bar 15 increases the rigidity in the tire circumferential direction on the outer side in the tire axial direction of the middle land portion 10 and maintains steering stability on a dry road surface.

  Conventionally, a groove having a flat groove bottom face has a problem that it is easy for snow to be in close contact with the groove bottom face, and snow is easily clogged in the groove. The middle tie bar 15 of the present invention reduces the adhesion of snow in the groove and effectively discharges snow in the groove as the tire rotates. For this reason, it becomes difficult to clog snow in the middle lateral groove 11.

  The length L1 of the middle tie bar 15 in the tire axial direction is preferably 2.5 mm or more, more preferably 3.5 mm or more, preferably 5.5 mm or less, more preferably 4.5 mm or less. Such a middle tie bar 15 exhibits the above-described effects while maintaining the volume of the middle lateral groove 11.

  The middle tie bar height h1 obtained by subtracting the groove depth d4 at the position of the middle tie bar 15 from the maximum groove depth d3 of the middle lateral groove 11 is preferably 0.8 mm or more, more preferably 1.0 mm or more, preferably Is 1.8 mm or less, more preferably 1.4 mm or less. When the middle tie bar height h1 is smaller than 0.8 mm, the above-described effect may be reduced. When the middle tie bar height h1 is larger than 1.4 mm, the pumping sound of the middle lateral groove 11 may be increased.

  The maximum groove depth d3 of the middle lateral groove 11 is preferably 0.6 times or more, more preferably 0.65 times or more, and preferably 0.75 times or less, more preferably the groove depth d1 of the shoulder main groove 3. Is 0.7 times or less. Such middle lateral grooves 11 enhance the performance on snow while maintaining the rigidity of the middle land portion 10 and maintaining the steering stability on the dry road surface.

  As shown in FIG. 3, the middle land portion 10 of the present embodiment includes, for example, a first middle sipe 16 provided on the inner side in the tire axial direction of the middle lateral groove 11 and a first middle sipe 16 provided between each middle lateral groove 11. 2 middle sipes 17 are provided. In this specification, “sipe” means a cut having substantially no width, and is distinguished from a drainage groove.

  The first middle sipe 16 communicates between the center main groove 4 and the inner end 13 of the middle lateral groove 11. The first middle sipes 16 are inclined in the same direction as the middle lateral grooves 11. Such a first middle sipe 16 improves on-ice performance while suppressing uneven wear of the middle land portion 10. Moreover, the first middle sipe 16 as described above allows the air in the middle lateral groove 11 to escape appropriately, thereby reducing the pumping sound of the middle lateral groove 11.

  For example, the second middle sipe 17 has one end 17 a communicating with the shoulder main groove 3 and the other end 17 b terminating in the middle land portion 10. The second middle sipe 17 is, for example, convex on one side (upward in FIG. 3) in the tire circumferential direction and curved in an arc shape. Such a second middle sipe 17 improves on-ice performance while suppressing uneven wear of the middle land portion 10.

  FIG. 5 shows an enlarged view of the center rib 20. As shown in FIG. 5, the center rib 20 extends continuously in the tire circumferential direction. The center rib 20 of the present embodiment is provided with only sipes and is not provided with drainage grooves. Thereby, the rigidity of the center rib 20 is enhanced, and excellent steering stability on a dry road surface is exhibited.

  The center rib 20 is provided with a plurality of center sipe pairs 23 including a first center sipe 21 and a second center sipe 22 in the tire circumferential direction, for example.

  The first center sipe 21 extends from the first center main groove 5 and terminates in the center rib 20 without straddling the tire equator C, for example. For example, the second center sipe 22 extends from the second center main groove 6 and terminates in the center rib 20 without straddling the tire equator C. Such first center sipe 21 and second center sipe 22 enhance the performance on ice while maintaining the rigidity of the center rib 20.

  The first center sipe 21 and the second center sipe 22 are inclined in the same direction. The first center sipe 21 and the second center sipe 22 are at least partially opposed to each other in the tire axial direction.

  For example, the distance L2 between the inner end 21b of the first center sipe 21 and the inner end 22b of the second center sipe 22 in the center sipe pair 23 is preferably periodically changed for each center sipe pair 23. . Such a center sipe pair 23 turns white noise when the center rib 20 contacts the ground, and improves noise performance.

  The distance L2 is preferably not less than 0.25 times the width W6 of the center rib 20, more preferably not less than 0.35 times, preferably not more than 0.65 times, more preferably not more than 0.55 times. As a result, the handling stability on the dry road surface and the performance on snow can be balanced.

  The distance L3 in the tire axial direction between the inner end 21b of the first center sipe 21 and the inner end 22b of the second center sipe 22 in the center sipe pair 23 is desirably constant for each center sipe pair 23, for example. Accordingly, uneven wear of the center rib 20 near the inner end 21b of the first center sipe 21 and the inner end 22b of the second center sipe 22 is suppressed.

  FIG. 6 shows an enlarged view of the shoulder land portion 30. As shown in FIG. 6, the shoulder land portion 30 is provided with a plurality of shoulder lateral grooves 31 extending in the tire axial direction and communicating with the tread ground contact end Te.

  The shoulder lateral groove 31 has an inner end portion 32 that terminates in the shoulder land portion 30. Such a shoulder lateral groove 31 improves on-snow performance while maintaining steering stability on a dry road surface.

  As shown in FIG. 2, for example, a shoulder tie bar 35 with a raised groove bottom is preferably provided at the inner end 32 of the shoulder lateral groove 31. Such a shoulder tie bar 35 alleviates a decrease in rigidity of the shoulder land portion 30 due to the shoulder lateral groove 31 and smoothes the rigidity distribution of the shoulder land portion 30. Accordingly, the steering stability on the dry road surface is improved while the uneven wear of the shoulder land portion 30 is suppressed.

  As shown in FIG. 6, the shoulder land portion 30 includes, for example, a first shoulder sipe 36 provided on the inner side in the tire axial direction of each shoulder lateral groove 31 and the shoulder lateral groove 31 provided between each shoulder lateral groove 31. A second shoulder sipe 37 extending along the tire circumferential direction and a third shoulder sipe 38 extending linearly in the tire circumferential direction are provided.

  For example, the first shoulder sipe 36 communicates between the shoulder main groove 3 and the inner end portion 32 of each shoulder lateral groove 31. The first shoulder sipe 36 has a depth smaller than the groove depth at the position of the shoulder tie bar 35 (shown in FIG. 2, hereinafter the same). Such a first shoulder sipe 36 reduces the pumping sound of the shoulder lateral groove 31 while smoothing the rigidity distribution of the shoulder land portion 30.

  The second shoulder sipe 37 has, for example, one end 37 a communicating with the tread grounding end Te and the other end 37 b terminating in the shoulder land portion 30. The other end 37 b of the second shoulder sipe 37 is located, for example, on the outer side in the tire axial direction than the inner end 32 of the shoulder lateral groove 31. Such a second shoulder sipe 37 improves the performance on ice while smoothing the rigidity distribution of the shoulder land portion 30.

  For example, the third shoulder sipe 38 communicates between the inner end portions 32 of the shoulder lateral grooves 31. The third shoulder sipe 38 has a depth smaller than the groove depth at the position of the shoulder tie bar 35. Such a third shoulder sipe 38, in combination with the shoulder tie bar 35 and the first shoulder sipe 46, smoothes the rigidity distribution of the shoulder land portion 30 and achieves both steering stability and riding comfort. Moreover, such a third shoulder sipe 38 exhibits a large edge effect in the tire axial direction, and improves turning performance on ice.

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

A pneumatic tire of size 215 / 60R16 having the basic pattern of FIG. 1 was prototyped based on the specifications in Table 1. As a comparative example, a tire without a middle tie bar was manufactured as a prototype. Each test tire was tested for handling stability on dry roads, performance on snow, and noise performance. The common specifications and test methods for each test tire are as follows.
Wearing rim: 16 × 6.5J
Tire internal pressure: front wheel 210 kPa, rear wheel 200 kPa

<Operation stability on dry road>
The driving stability of the following test vehicle when traveling on a dry road course was evaluated by the driver's sensuality. A result is a score which makes a comparative example 100, and shows that steering stability is excellent, so that a numerical value is large.
Test vehicle: displacement 1800cc, front-wheel drive vehicle Test tire mounting position: all wheels

<Snow performance>
The performance on the snow when running on a snowy road with the test vehicle was evaluated by the driver's sensuality. A result is a score which makes a comparative example 100, and shows that performance on snow is excellent, so that a numerical value is large.

<Noise performance>
The in-vehicle noise when traveling on the road noise measuring road (asphalt rough road) at a speed of 100 km / h with the test vehicle was measured under the following conditions. The evaluation is the reciprocal of the value of the vehicle interior noise, and is represented by an index with the value of the comparative example being 100. The larger the value, the lower the vehicle interior noise and the better.
Measurement method: The sound pressure level of the peak value of the air column resonance sound near the narrow band 240 Hz is measured with a microphone. Microphone position: Driver's seat window side ear test The test results are shown in Table 1.

  As a result of the test, it was confirmed that the pneumatic tire of the example improved on-snow performance while maintaining steering stability on a dry road surface.

2 tread portion 3 shoulder main groove 4 center main groove 10 middle land portion 11 middle lateral groove 12 outer end portion 13 inner end portion 15 middle tie bar

Claims (6)

A pair of shoulder main grooves extending continuously in the tire circumferential direction on both sides of the tire equator and closest to the tread grounding end in the tread portion, and a center main groove extending continuously in the tire circumferential direction between the pair of shoulder main grooves Are provided on both sides of the tire equator, a middle land portion divided by the shoulder main groove and the center main groove is provided, and a shoulder land portion is provided on the outer side in the tire axial direction of each shoulder main groove. It was a pneumatic tire,
Each middle land portion is provided with a plurality of middle lateral grooves extending inclining with respect to the tire axial direction,
Each of the middle lateral grooves has an outer end portion communicating with the shoulder main groove, and an inner end portion terminating in the middle land portion,
The groove width of the outer end portion gradually increases toward the outer side in the tire axial direction,
The said outer end portion, a middle tie bars provided we are the groove bottom is raised,
The shoulder land portion includes a plurality of shoulder lateral grooves extending inward in the tire axial direction from the tread grounding end and terminating in the shoulder land portion, an inner end portion of the shoulder lateral groove in the tire axial direction, and the shoulder main groove. A first shoulder sipe communicating with each other,
A shoulder tie bar with a raised groove bottom is provided at the inner end of the shoulder lateral groove,
The pneumatic tire according to claim 1, wherein the first shoulder sipe has a depth smaller than a depth of the shoulder lateral groove at the position of the shoulder tie bar . The maximum groove depth of the middle lateral groove is 0.6 to 0.75 times the groove depth of the shoulder main groove,
The middle tie bar height obtained by subtracting the groove depth at the position of the middle tie bar from the maximum groove depth of the middle lateral groove is 1.0 to 1.4 mm,
The pneumatic tire according to claim 1, wherein a length of the middle tie bar in a tire axial direction is 2.5 to 5.5 mm. The center main groove includes a first center main groove provided on one side of the tire equator and a second center main groove provided on the other side of the tire equator,
The pneumatic tire according to claim 1, wherein a center rib extending continuously in a tire circumferential direction is provided between the first center main groove and the second center main groove.   The center rib includes a first center sipe extending from the first center main groove and terminating in the center rib, and a second center sipe extending from the second center main groove and terminating in the center rib. The pneumatic tire according to claim 3, wherein a plurality of sipe pairs are provided in the tire circumferential direction. The distance between the inner end of the center sipe in the center rib of the first center sipe and the inner end of the center sipe in the center rib of the second center sipe changes periodically for each of the center sipe pairs. The pneumatic tire according to claim 4 . The pneumatic tire according to claim 5, wherein a distance in the tire axial direction between the inner end of the first center sipe and the inner end of the second center sipe in the center sipe pair is constant for each center sipe pair. tire.

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