JP2011051408A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suggest a pneumatic tire allowing improvement of on-snow performance without affecting braking performance on a dry road surface. <P>SOLUTION: The pneumatic tire includes tread patterns based on a plurality of blocks 3 divided and formed by a plurality of peripheral grooves 1 provided along a rotating direction of the tire and a plurality of lateral grooves 2 provided along a width direction of the tire. The blocks 3a and 3b arrayed on a shoulder side, of the blocks 3, include lug grooves 4 having each one end opened to the peripheral grooves 1 by being passed through the side walls of the blocks 3a and 3b. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pneumatic tire suitable for running on a snowy road surface, and aims to improve snow performance, particularly traction performance, without impairing braking performance on a dry road surface.

  As pneumatic tires suitable for traveling on snowy road surfaces, pneumatic tires with tread patterns based on blocks partitioned by multiple circumferential grooves and lateral grooves are applied, snow performance (traction performance, In order to improve the braking performance and the like, conventionally, a large number of sipes and width direction grooves are arranged in each block to increase the edge length.

  By the way, in this kind of pneumatic tire, when the number of sipes formed per block is too large, the pattern rigidity in the tire circumferential direction is lowered and the traction performance on the snowy road surface is lowered. In addition, there was a cause of affecting the braking performance on the dry road surface.

  As prior art related to pneumatic tires suitable for running on icy and snowy roads, a block row is formed by a circumferential main groove and a transverse groove, and one or more transverse sipes are arranged in each block. By providing narrow grooves extending in the circumferential direction through the rows and setting the sum of the areas of the narrow grooves on the ground contact surface to 0.02 to 0.08 times the total ground contact area, the contact pressure distribution can be varied depending on the tire running conditions. There is known a pneumatic radial tire that easily follows even when it changes greatly and exhibits a sufficient edge effect (see, for example, Patent Document 1).

  In addition, by providing a circumferential narrow groove on the shoulder block and arranging a circumferential sipe on the outer block piece, it improves skid resistance and wandering performance on icy and snowy road characters, and damages the tread shoulder part There is also known a pneumatic radial tire that has been prevented and improved in durability (see, for example, Patent Document 2). However, in this type of pneumatic tire, the braking performance on the dry road surface is particularly described above. The current state of the art is still not sufficient.

Japanese Patent Laid-Open No. 7-329517 Japanese Patent No. 3133800

  An object of the present invention is to propose a pneumatic tire capable of improving snow performance without impairing braking performance on a dry road surface.

The present invention comprises a tread pattern based on a plurality of blocks defined by a plurality of circumferential grooves provided along the direction of rotation of the tire and a plurality of lateral grooves provided along the width direction of the tire. In pneumatic tires,
Among the blocks, a pneumatic tire is characterized in that a block arranged on a shoulder side is provided with a lug groove that penetrates the side wall of the block and has one end opened in the circumferential groove.

  In the pneumatic tire having the above-described configuration, among the lug grooves, the lug groove that opens in the circumferential groove on the shoulder side has a longer groove length than the lug groove that opens in the circumferential groove on the center side in the width direction of the tire. Is preferred.

  Of the lug grooves, the lug groove that opens to the seed groove on the shoulder side may have a shorter groove length than the lug groove that opens to the circumferential groove on the center side in the width direction of the tire.

  The lug groove is preferably provided in the central area in the circumferential direction of the block.

  The block arranged on the shoulder side includes a block on the circumferential groove side adjacent to the block arranged on the shoulder side from the block ground end when grounded under a normal internal pressure and normal load specified by JATMA. It is desirable to provide a circumferential narrow groove that is located substantially in the middle between the end of the groove and opens the groove end in each of the transverse grooves. In this case, the lug groove is one region divided by the circumferential narrow groove. The other region divided by the circumferential narrow groove is cut along the substantial width direction of the tire in the circumferential central region of the block and penetrates the block side wall to open one end of the circumferential groove. It is possible to provide lateral narrow grooves (transverse sipes).

  Specifically, it is preferable to apply the circumferential narrow groove having a groove width of 2 mm or less and a groove depth of 60 to 65% of the groove depth of the circumferential groove. The opening end has a notch recess having a width of 11 to 18% relative to the block length and a length of 16 to 26% relative to the block width, and the lug groove is arranged in the substantial length direction of the block. It is preferable to use one that is located in the middle and has a groove width of 7.5 to 11.5% with respect to the length of the block.

  Further, it is desirable to give the lateral narrow groove and the lug groove an angle with respect to an axis along the width direction of the tire, of which the lug groove has a groove angle of 20 to 50 ° with respect to the axis. It shall have. The lug groove and the lateral groove can have a substantially equal groove angle.

  A snow column effect is obtained by providing a lug groove with one end opened in the peripheral groove through the side wall of the block arranged on the shoulder side, contributing to improvement of traction performance and opening both ends. As compared with the case where the lag groove is provided, a decrease in the block rigidity is suppressed.

  Of the lug grooves, the groove length of the lug groove that opens in the circumferential groove on the shoulder side can be made longer than the lug groove that opens in the circumferential groove on the center side in the width direction of the tire. Performance is particularly dominant on the shoulder side.)

  Among the lug grooves, the length of the lug groove that opens in the circumferential groove on the shoulder side is shorter than the lug groove that opens in the circumferential groove on the center side in the width direction of the tire, so that the braking performance can be improved (traction The center is dominant in performance.)

  By providing the lug groove in the central region in the circumferential direction of the block, it is possible to increase the edge length while suppressing a decrease in the rigidity of the block, thereby improving the snow performance.

  As the circumferential narrow groove, it is the actual middle between the grounding end of the block when grounded under the normal internal pressure and normal load specified by JATMA and the block end on the circumferential groove side adjacent to the shoulder block. And the groove ends are opened in the lateral grooves, so that the distribution of contact pressure in the block changes, and the grip force of the block edge by the lug groove (width direction groove) in the block improves, and the road surface on snow. The traction performance (snow traction performance) is improved. This also maintains the balance of lateral rigidity in the block, and prevents the block from falling over when the vehicle is turning.

  The lug groove is positioned in one region divided by the circumferential narrow groove, and the lateral narrow groove is provided in the other region partitioned by the circumferential narrow groove, so that the circumferential rigidity in the block is provided. The balance of the vehicle is maintained, the falling of the block during braking is suppressed, the grip on the road surface on the snow is secured, and the snow traction performance is improved.

It is the figure which showed embodiment of the pneumatic tire according to this invention about the tread pattern. It is the figure which showed other embodiment of the pneumatic tire according to this invention about the principal part of the block. It is the figure which showed the relationship between the braking performance on a dry road surface, and snow traction performance.

Hereinafter, the present invention will be described more specifically with reference to the drawings.
FIG. 1 is a diagram schematically showing a part of a tread pattern of a pneumatic tire according to the present invention on a plane. The pneumatic tire according to the present invention is assumed to be a general radial tire, and its internal structure is not particularly different from that of the conventional structure, and therefore the tire cross section is not shown.

  In FIG. 1, 1 is a circumferential groove provided in the direction of rotation of the tire, 2 is a lateral groove provided along the width direction of the tire, and 3 is a block defined by the circumferential groove 1 and the lateral groove 2. . The block 3 is composed of a row of blocks 3a and 3b arranged on the shoulder side and a row of width direction central blocks 3c located between the blocks 3a and 3b arranged on the shoulder side. A tread pattern is formed based on the plurality of blocks 3.

  Reference numeral 4 denotes lug grooves provided in the blocks 3a and 3b arranged on the shoulder side. One end of the lug groove 4 is opened through the side walls of the shoulder side blocks 3a and 3b. In this example, the lug groove 4 is only shown in the circumferential groove on the shoulder side, and when the lug groove (not shown) opened in the circumferential groove on the center side in the width direction of the tire is provided. The brake performance is improved by having a longer groove length than that, and the traction performance is shorter by the groove length shorter than the lug groove opening in the circumferential groove on the center side in the width direction of the tire. Is improved.

  Reference numeral 5 denotes a lateral narrow groove (lateral sipe) provided in the central region in the circumferential direction of the blocks 3a and 3b arranged on the shoulder side. The lateral narrow groove 5 functions as a sipe, and is cut along the substantial width direction of the tire, and one end is opened in the circumferential groove 1 through the block side wall. In the example, it is connected to the lug groove 4, and a notch recess 5 a is formed at the opening end.

Reference numeral 6 denotes a circumferential narrow groove provided in the blocks 3a and 3b arranged on the shoulder side. The circumferential narrow groove 6 is a block on the circumferential groove 1 side adjacent to the blocks 3a and 3b arranged on the shoulder side from the block ground end when grounded under a normal load and a normal internal pressure specified by JATMA. The groove ends 6a and 6b are respectively opened in the lateral grooves 2 and the lug grooves 4 are shoulder-side regions 3a ₁ and 3b divided by the circumferential narrow grooves 6. _A lateral sipe 5 is located in the other region 3 a ₂ , 3 b ₂ located at ₁ and divided by the circumferential narrow groove 6.

  Here, the normal load refers to the maximum load (maximum load capacity) of a single wheel at the applicable size specified in the JATMA standard, and the normal internal pressure refers to the maximum load of a single wheel described in the above standard. Air pressure corresponding to (maximum load capacity).

  In order to ensure the performance on snow, it is effective to increase the number of grooves in the red part or widen the groove width, which makes it possible to securely grip and prevent slipping on the road surface on snow. In order to obtain sufficient braking performance when driving on a dry road surface, it is effective to maintain the rigidity of the tread sufficiently high in order to increase the ground contact area of the tread surface block in contact with the road surface. Although the performance is a contradiction, by adopting the tread pattern with the above configuration, the performance required for driving on snow (especially grip force) and the braking performance required for driving on dry road Both (the rigidity of the tread portion) can be ensured.

  In the present invention, the circumferential narrow grooves 6 are provided in the blocks 3a and 3b arranged on the shoulder side. The reason for this is that, conventionally, in order to improve the snow traction performance, the lateral grooves are simply added. However, this greatly reduced the block rigidity and had an effect on the braking performance on the dry road surface. By providing the circumferential narrow groove 6, the lateral groove was not added. The ground contact pressure distribution is changed, whereby the grip force of the block edge by the lug groove 4 provided in the block can be improved, and the snow traction performance is improved. By providing the circumferential narrow groove 6, the allowance for block rigidity is reduced, and the braking performance on the dry road surface can be ensured. In consideration of turning performance on snow, it is particularly effective to provide the circumferential narrow grooves 6 in the blocks 3a and 3b arranged on the shoulder side.

  The groove width t of the circumferential narrow groove 6 is preferably 2 mm or less. The reason is that if the groove width t of the circumferential narrow groove 6 is larger than 2 mm, the rigidity of the block is greatly reduced, and it becomes difficult to ensure the braking performance in the traveling on the dry road surface.

  In addition, the groove depth of the circumferential narrow groove 6 is preferably 60 to 65% of the groove depth of the circumferential groove 1. The reason for this is that the deeper the groove depth, the better the grip force on the road surface on snow, but if the groove depth of the circumferential narrow groove 6 exceeds 65% of the groove depth of the circumferential groove 1, This is because the grip force maintained by the balance of rigidity at the end of the groove falls due to a decrease in the ground pressure at the block edge. On the other hand, the groove depth of the circumferential narrow groove 6 is the groove depth of the circumferential groove 1. If it is less than 60%, the grip force on the snowy road surface is insufficient and sufficient snow traction performance cannot be obtained.

  The position of the circumferential narrow groove 6 is changed from the block ground end when grounded under the normal internal pressure and normal load defined by JATMA to the block end on the circumferential groove side adjacent to the block arranged on the shoulder side. By being in the middle in the middle, the balance of the rigidity in the lateral direction in the block is maintained, and the collapse of the block during turning is suppressed.

  The lug groove 4 is preferably provided in the central area in the circumferential direction of the blocks 3a and 3b (substantially the middle in the length direction). The reason is that the lug groove 4 is located in the substantial middle in the length direction of the blocks 3a and 3b. By providing, the balance of the rigidity of the circumferential direction in a block is maintained, and the fall of the block at the time of braking is suppressed.

  In general, a wider groove width T of the lug groove 4 is advantageous from the viewpoint of securing a grip force on snow, but if it exceeds 11.5% of the length of the blocks 3a and 3b, the rigidity of the block decreases. Therefore, there is a concern about the influence on the braking performance when traveling on a dry road surface. When the length of the blocks 3a and 3b is less than 7.5%, the grip force on the road surface on snow is insufficient, and sufficient snow traction performance is ensured. There is also a concern that this is not possible. For this reason, in this invention, it is desirable to set the groove width of the lug groove 4 in the range of 7.5 to 11.5% of the length of the blocks 3a and 3b.

  Further, the groove angle θ of the lug groove 4 (an angle formed with the straight line when a straight line parallel to the tire rotation axis is used as a reference) is preferably 20 to 50 °. This is because the present invention focuses on improving the snow traction performance, but the actual performance of the tire must also take into account the lateral force that acts during cornering, etc. This is because it is necessary to gain power in a balanced manner. If the groove angle θ is less than 20 °, the snow traction force can be secured. However, if the groove angle θ exceeds 50 °, the snow traction performance will be sufficiently exerted when a cross flow occurs during cornering. Therefore, in the present invention, the groove angle θ of the lug groove 4 is set to 20 to 50 °.

  The groove angle between the lug groove 4 and the lateral groove 2 should be substantially equal, because the groove angle between the lug groove 4 and the lateral groove 2 is made substantially equal so that the snow traction performance is efficiently improved. It is because it can be obtained.

  One lug groove 4 and one lateral narrow groove 5 are preferably provided for each block, thereby ensuring grip on the road surface on snow and improving snow traction performance.

  In the present invention, the lateral narrow groove 5 is preferably arranged in the central area in the circumferential direction of the blocks 3a and 3b (substantially the middle in the longitudinal direction), but this allows the balance of rigidity in the circumferential direction in the block to be balanced. This keeps the block from falling down during braking.

  Although the notch recess 5a can be provided at the opening end of the circumferential narrow groove 6, it is possible to improve the snow traction performance without reducing the block rigidity.

If the width n ₁ of the notch recess 5a is less than 11% in comparison with the block length (length along the circumferential direction of the block), sufficient snow performance cannot be obtained, whereas it exceeds 18% in comparison with the block length. Then, the block rigidity is lowered, and there is a concern about the influence on the braking performance. Therefore, in the present invention, the width n ₁ of the notch recess 5a is set to 11 to 18% in comparison with the block length.

Length n ₂ of the notch recesses 5a, in less than 16% block length compared, it is impossible to obtain sufficient snow performance, whereas, will fall block rigidity exceeds 26% block length compared the brake There is concern about the impact on performance. Therefore, in the present invention, the length _{n 2} of the cut-out recess 5a is a 16-26% block length compared.

  The circumferential narrow groove 6 can have a waveform shape with a constant amplitude as shown in FIG. By imparting such a corrugated shape to the circumferential narrow groove 6, it is possible to suppress a decrease in block rigidity and improve snow traction performance. When the circumferential narrow groove 6 having a corrugated shape is applied, the number of peaks (or valleys) formed in one portion (each portion divided by the lug groove 4 and the lateral narrow groove 5) is What has about 3-5 pieces is good. This is because if the number of peaks (or valleys) is less than 3, or more than 5, there is a concern of affecting the lateral force.

  Table 1 shows a pneumatic radial tire of a size: 225 / 65R17 having a tread pattern as shown in FIG. 1 and assembled to an applicable rim, and a normal internal pressure (210 kPa) and a normal load (4.90 kN). Under a loaded condition, a running test (simulation) was performed, and snow traction performance with respect to the groove width t of the circumferential narrow groove 6 (the groove depth was about 65% of the groove depth of the circumferential groove 1). (If the contact pressure becomes higher, the edge will be better able to bite into the snow, and as a result, the snow performance will improve. Therefore, the “block edge length in the tire circumferential direction (or sipe edge length) x contact pressure” Investigating the effects of braking performance on the dry road surface (braking performance) (block stiffness in the tire circumferential direction was used as an index of dry braking performance). And it shows the results (Yes displayed by an index, indicating that the larger the index is a good.).

  From Table 1, the snow traction performance tends to improve as the width of the circumferential narrow groove 6 increases, but the braking performance on the dry road surface decreases as the width of the groove widens. When the influence of the above is taken into consideration, it is apparent that the upper limit of the groove width of the circumferential narrow groove 6 is about 2.0 mm.

  FIG. 3 is a diagram showing the results of investigating the effects on snow traction performance and braking performance on a dry road surface when the groove width t of the circumferential narrow groove 6 is kept constant and the groove depth is changed.

  When the groove depth of the circumferential narrow groove 6 is increased, the block rigidity tends to decrease, and it is clear that about 65% of the groove depth of the circumferential groove takes an appropriate value from the balance with the dry braking performance. This is because, if the groove depth of the circumferential narrow groove 6 is too deep, the rigidity of the region on the lug groove side of the block is lowered and the contact pressure is lowered, so that there is an appropriate value for the groove depth. It is shown that.

  Table 2 shows the results of investigating the effects of snow traction performance and braking performance on a dry road surface with respect to the width of the notch recess 5a (based on a block length comparison of 14%).

From Table 2, although the snow traction performance is improved in accordance with the width n ₁ of the cutout recess 5a is widened, the width n ₁ of the cutout recess 5a has gone down and becomes 22%, which, as a block This is because the rigidity itself drops and the contact pressure decreases, and the edge works effectively. On the other hand, at 7%, the snow traction performance is greatly reduced compared to the standard. It is thought that the edge does not work effectively. The dry braking performance, has become smaller as becomes wider n ₁ of the cutout recess 5a, as the range does not affect the running by the actual vehicle, the range of 11 to 18% in the block length compared.

  Table 3 shows the results of investigating the effects of snow traction performance and dry braking performance on the length of the notch recess 5a (compared to the block width) (based on the block width of 21%). .

From Table 3, although the length n ₂ Snow be varied traction performance is not much variation in the notch recesses 5a, in the case of 10%, there is a tendency that the snow traction performance is slightly reduced at the reference comparison. This length n ₂ of the cutout recess 5a is considered to be because transmitted forces on the snow surface is not sufficient in 10% block width compared becomes insufficient. On the other hand, the dry braking performance, and decreases with increasing length n ₂ becomes longer notch recess 5a, as the range does not affect the running by the actual vehicle, the range of 16 to 26% in the block width compared.

  Table 4 shows the effect on snow traction performance and dry braking performance when the circumferential narrow groove 6 having the amplitude shown in FIG. 2 is applied (waveform shape (period: 3 mm, amplitude: 2 mm)). The results are shown (based on a straight circumferential narrow groove).

  From Table 4, when the circumferential narrow groove 5 is corrugated, the snow traction performance tends to improve as the number of mountains increases, but the lateral force is conversely reduced, and in particular, the number of mountains is 1. In the case of ˜2 or 6 or more, the demerit with respect to performance is larger than the merit of giving the corrugated shape to the circumferential narrow groove 6. For this reason, even if the circumferential direction narrow groove 6 is made into a waveform shape, the number of peaks is preferably about 3 to 5. As for the braking performance on the dry road surface, it is clear that the same value is maintained regardless of the number of peaks.

EXAMPLE A pneumatic radial tire having a tread pattern as shown in FIG. 1 and having a size as shown in Table 5: 225 / 65R17 is manufactured, and the tire is assembled to an applied rim. Under a condition of 210 kPa) and a normal load (4.90 kN), a running test using an actual vehicle was performed under the following conditions to investigate snow traction performance and braking performance (brake performance) on a dry road surface. The results are also shown in Table 5.

Driving conditions when investigating snow traction performance:
Evaluation with acceleration time from 10km / h to 40km / h

Driving conditions when investigating braking performance on dry roads:
Evaluation at a braking distance of 100 km / h → 0 km / h

  From Table 5, in the pneumatic tires that satisfy even one of the conditions defined in the present invention (Compliance Examples 1 and 2), it is clear that the snow traction performance and the braking performance on the dry road surface are improved. When all the conditions were satisfied (Compliance Example 3), it was confirmed that both the snow traction performance and the braking performance on the dry road surface were more effective than the compatible tires 1 and 2. Note that the comparative tire 3 has a high improvement effect when only the traction is viewed, but the lateral force on the snow road surface is extremely reduced (about 88 as compared with the reference tire), and is therefore displayed as a comparative example.

  A pneumatic tire that can improve snow performance without affecting braking performance on a dry road surface can be applied.

1 Circumferential groove 2 Horizontal groove 3 Block 4 Lug groove 5 Lateral narrow groove 5a Notch recess 6 Circumferential narrow groove

Claims (6)

A pneumatic tire comprising a tread pattern based on a plurality of blocks defined by a plurality of circumferential grooves provided along a tire rotating direction and a plurality of lateral grooves provided along a tire width direction. In
A pneumatic tire characterized in that, among the blocks, a block arranged on the shoulder side is provided with a lug groove penetrating the side wall of the block and having one end opened in the circumferential groove.   2. The pneumatic tire according to claim 1, wherein a lug groove that opens to a circumferential groove on a shoulder side among the lug grooves has a longer groove length than a lug groove that opens to a circumferential groove on a center side in the width direction of the tire.   2. The pneumatic tire according to claim 1, wherein a lug groove that opens to a circumferential groove on a shoulder side among the lug grooves has a groove length shorter than a lug groove that opens to a circumferential groove on a center side in the width direction of the tire.   The pneumatic tire according to claim 1, wherein the lug groove is provided in a central region in a circumferential direction of the block. Block end on the circumferential groove side adjacent to the block arranged on the shoulder side from the block ground end when the block arranged on the shoulder side is grounded under normal internal pressure and normal load specified by JATMA Is provided in the middle in the middle, to provide a circumferential narrow groove opening the groove end in the transverse groove,
The lug groove is located in one region partitioned by the circumferential narrow groove, and the other region partitioned by the circumferential narrow groove is in the substantial width direction of the tire in the circumferential central region of the block. Formed along the side wall of the block opposite to the lug groove to form a transverse narrow groove having one end opened in the circumferential groove,
The circumferential narrow groove has a groove width of 2 mm or less and a groove depth of 60 to 65% of the groove depth of the circumferential groove. The lateral narrow groove is compared with a block length at an opening end thereof. It has a notch recess having a width of 11 to 18% and a length of 16 to 26% compared to the block width, and the lug groove is located in the middle of the substantial length direction of the block and the length of the block And having a groove width of 7.5 to 11.5%,
The lateral narrow groove and the lug groove are provided with an angle with respect to an axis along a tire width direction, and the lug groove has a groove angle of 20 to 50 degrees with respect to the axis. Item 5. The pneumatic tire according to any one of Items 1 to 4.   The pneumatic tire according to claim 1, wherein the lug groove has a groove angle substantially equal to the lateral groove.

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