JP2009220779A - Pneumatic tire for off-road - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire for an off-road capable of enhancing traction performance without deteriorating off-road ride quality. <P>SOLUTION: The pneumatic tire has lug grooves 3 extending in an inclined manner with respect to the tread width direction, and division grooves 7 for dividing a land 5 demarcated by the lug grooves 3 into five blocks 5A. The division groove depth (h) of the division groove 7 is smaller than the lug groove depth (g) of the lug groove 3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an off-road pneumatic tire, and more particularly, to an off-road pneumatic tire including a lug groove extending in the tread width direction.

  Conventionally, off-road pneumatic tires mounted on off-road vehicles such as construction vehicles have not only the traction performance that is the driving force by which the tire kicks the ground, but also the ride comfort when traveling on the road. There is a strong demand for superiority.

For example, the land portion located in the tread center portion is continuously arranged with respect to the tire circumferential direction (including those that are intermittently divided by narrow grooves extending in the tread width direction), and the lug groove located in the tread shoulder portion. An off-road pneumatic tire that improves ride comfort is specified (see, for example, Patent Document 1).
Japanese Patent Laying-Open No. 2005-186703 (FIGS. 1 to 3)

  However, in the conventional off-road pneumatic tire described above, since the land portion located in the tread center portion is continuously arranged in the tire circumferential direction, the ride comfort is improved, but the land portion (block ) Is small enough to improve on-road traction performance.

  Therefore, the present invention has been made in view of such a situation, and provides an off-road pneumatic tire capable of improving traction performance without deteriorating riding comfort on-road. With the goal.

  The inventors have found the following regarding traction performance and ride comfort. That is, as a factor of the traction performance, there is an edge force applied to an edge portion of a land portion (block or the like) formed in the tread pattern. This edge force is the total pressure (edge amount × edge pressure) applied to the stepped-side edge portion formed in the tread pattern when the tire rolls.

  As a method for controlling the edge amount, it is conceivable to increase the number of blocks by increasing the number of grooves within one pitch among pitches that are units in which the tread pattern is repeated in the tire circumferential direction.

  In addition, as a method for controlling the edge pressure, the number of grooves and the groove width are increased within one pitch, and the negative ratio that is the ratio of the groove to the ground contact surface of the tread portion is increased, whereby the pressure per unit area of the block is reduced. It can be increased.

  On the other hand, as a factor of ride comfort, there is a vibration performance generated when the block contacts the road surface. This vibration performance is affected by the impact on the block that is struck against the road surface when the tire rolls and the action that the block deformed in the tire circumferential direction within the contact surface tries to return to the original state when the block comes out of the contact surface. .

  Considering this, the present invention has the following features. First, the first feature of the present invention is provided with a lug groove extending incline with respect to the tread width direction, and a dividing groove that divides a land portion defined by the lug groove into five blocks, and the depth of the dividing groove. The gist of the present invention is that the depth (h) of the split groove, which is the depth, is shallower than the depth (g) of the lug groove, which is the depth of the lug groove.

  According to such a feature, the lug groove extends inclining with respect to the tread width direction, and the dividing groove divides the land portion into five, thereby improving the edge force (edge amount × edge pressure), Traction performance can be improved.

  In addition, the fact that the split groove depth (h) is shallower than the lug groove depth (g) suppresses the vibration performance generated by the block coming into contact with the road surface and deteriorates the on-road riding comfort. Can be eliminated.

  Specifically, since the rigidity is reduced on the surface side of each block, it is possible to mitigate the impact on the block that is struck against the road surface during tire rolling. On the other hand, when a block kicks off the road surface, the first block to be kicked out of one land portion is grounded by another block connected to the same land portion. It is possible to suppress the deterioration of the action of the block that is generated when getting out of the ground returning to the original state.

  As a result, it is possible to suppress the vibration performance generated when the block contacts the road surface and improve the traction performance without deteriorating the on-road riding comfort.

  Another feature is that the divided groove width (W1), which is a width orthogonal to the extending direction of the divided grooves, is narrower than the lug groove width (W2), which is a width orthogonal to the extending direction of the lug grooves. To do.

  According to this feature, the split groove width (W1) is narrower than the lug groove width (W2), thereby improving the rigidity of the base side of the block, and the block generated when the block comes out from the ground contact surface Deterioration of the action to return can be further suppressed.

  Another feature is summarized as satisfying the relationship of 0.4 ≦ h / g ≦ 0.7, where the depth of the divided grooves is “h” and the deepest lug groove depth is “g”.

  According to such a feature, by satisfying the relationship of 0.4 ≦ h / g ≦ 0.7, the block comes into contact with the road surface while balancing the rigidity on the surface side of the block and the rigidity on the base side of the block. The vibration performance generated by this can be further suppressed.

  Another feature is that, on a parallel line extending substantially parallel to the tire equator line, the pitch length which is the length in the tire circumferential direction of the pitch (p) which is a unit in which the tread pattern is repeated in the tire circumferential direction is set to “e”, The gist is to satisfy the relationship of 0.24 ≦ d / e ≦ 0.36, where “d” is the lug circumferential length which is the length of the lug groove.

  According to such a feature, by satisfying the relationship of 0.24 ≦ d / e ≦ 0.36, it is possible to suppress a decrease in the rigidity of the block, and to reduce the on-road riding comfort without deteriorating the on-road riding comfort. It is possible to prevent stones and the like from being caught in the lug grooves and the dividing grooves.

  According to the present invention, it is possible to provide an off-road pneumatic tire capable of improving traction performance without deteriorating on-road riding comfort.

  Next, an example of an off-road pneumatic tire according to the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  Hereinafter, the configuration of the off-road pneumatic tire according to the present embodiment will be described. FIG. 1 is a perspective view showing an off-road pneumatic tire according to the present embodiment, and FIG. 2 is a partial perspective view showing a tread pattern of the off-road pneumatic tire according to the present embodiment. FIG. 3 is a development view showing a tread pattern of the off-road pneumatic tire according to the present embodiment, and FIG. 4 is a partial cross-sectional view of the tread pattern of the off-road pneumatic tire according to the present embodiment. FIG.

  An off-road pneumatic tire according to the present embodiment (hereinafter referred to as a pneumatic tire 1) is a general radial tire for a construction vehicle (for example, a dump truck) including a bead portion, a carcass layer, and a belt layer (not shown). Tires mounted on trucks, graders, excavator loaders, wheel loaders, wheel crane construction vehicles).

  As shown in FIGS. 1 to 3, the pneumatic tire 1 includes a lug groove 3 extending in the tread width direction, and a division groove 7 that divides a land portion 5 partitioned by the lug groove 3 into five blocks 5A. It has.

The lug groove 3 is inclined with respect to the tread width direction. Specifically, as shown in FIG. 3, the lug groove angle (a) that is an angle inclined with respect to the tread width direction of the lug groove 3 is 30 ° to tan ⁻¹ (tire outer periphery / tread width TW). It is preferable to satisfy the relationship.

  Here, the tire outer periphery indicates the tire outer periphery on the tire equator line CL. Further, the tread width TW indicates the maximum width in the tread width direction in which the tread pattern is formed.

For example, when the tire outer periphery is 664 mm and the tread width TW is 412 mm, tan ⁻¹ (664/412) = 58.18, and the lug groove angle (a) is preferably smaller than 58.18 °. I understand. That is, tan ⁻¹ (tire outer circumference / tread width TW) means that the lug groove 3 always extends from one end in the tread width direction to the other end in the tread width direction while the pneumatic tire 1 makes one round. I mean.

When the lug groove angle (a) is smaller than 30 °, when the block 5A kicks off the road surface, the first block 5A kicked out of one land portion and the last block 5A kicked out are: Since they are kicked out almost at the same time, it may not be possible to suppress the deterioration of the action of the block 5A, which occurs when the block 5A comes out of the ground surface, trying to return to the original state. On the other hand, if the lug groove angle (a) is larger than the angle calculated by tan ⁻¹ (tire outer circumference / tread width TW), the lug groove 3 extends in the tire circumferential direction (becomes a rib pattern), Since the edge amount is smaller than when the lug groove 3 is inclined, the traction performance may not be ensured.

  The dividing groove 7 is inclined in the direction opposite to the lug groove 3. Specifically, as shown in FIG. 3, the dividing groove angle (b) that is an angle inclined with respect to the tread width direction of the dividing groove 7 is preferably 30 ° or more.

  If the split groove angle (b) is smaller than 30 °, a large amount of edge enters the road surface at the time of rolling of the tire, so it is difficult to mitigate the impact on the block 5A hit against the road surface. The vibration performance generated when the block 5A is in contact with the road surface may not be suppressed.

  Further, as shown in FIGS. 4A and 4B, the division groove depth (h) that is the depth of the division groove 7 is the lug groove depth (g) that is the depth of the lug groove 3. It is set shallower.

  If the block groove depth (h) is deeper than the lug groove depth (g), the rigidity of the block 5A as a whole is lowered, and the block 5A generated when the block 5A comes out of the grounding surface tries to return. It may not be possible to suppress the deterioration of the action, and the on-road riding comfort may deteriorate.

  In particular, it is preferable that the relationship 0.4 ≦ h / g ≦ 0.7 is satisfied, where “h” is the depth of the divided grooves and “g” is the deepest lug groove depth.

  If the groove depth ratio (h / g), which is the value of the ratio of the lug groove depth (g) to the divided groove depth (h), is less than 0.4, the rigidity of the block 5A is too high, The impact on the block 5A, which is struck against the road surface when the tire rolls, may increase the on-road riding comfort. On the other hand, if the groove depth ratio (h / g) is larger than 0.7, the rigidity of the entire block 5A is reduced, and the block 5A generated when the block 5A comes out of the grounding surface tends to return to the original state. The deterioration of the action cannot be suppressed, and the riding comfort on the road may be deteriorated.

  Further, as shown in FIGS. 4A and 4B, the divided groove width (W1), which is a width orthogonal to the extending direction of the dividing groove 7, is a width orthogonal to the extending direction of the lug groove. It is set narrower than a certain lug groove width (W2).

  If the dividing groove width (W1) is wider than the lug groove width (W2), the edge force (edge amount × edge pressure) is reduced as the block 5A becomes smaller. May fall.

  The angle of the corner of the block 5A, that is, the block angle (c) that is the intersection angle between the lug groove 3 and the dividing groove 7 is preferably 60 ° to 110 °.

  If the block angle (c) is smaller than 60 °, the corners of the block 5A are too acute, and the block 5A may be lost during off-road driving, making it difficult to ensure durability. It may become. On the other hand, if the block angle (c) is larger than 110 °, since a large amount of edge enters the road surface at the time of rolling the tire, it is difficult to mitigate the impact on the block 5A hit against the road surface. The vibration performance generated when the block 5A is in contact with the road surface may not be suppressed.

  Here, on the parallel line extending substantially parallel to the tire equator line CL, the pitch length which is the length in the tire circumferential direction of the pitch (p) which is a unit in which the tread pattern is repeated in the tire circumferential direction is defined as “e”, and the lug When the circumferential length of the lug, which is the length of the groove, is “d”, it is preferable to satisfy the relationship of 0.24 ≦ d / e ≦ 0.36.

  If the parallel line ratio (d / e), which is the ratio of the pitch length (e) to the lug circumferential length (d), is smaller than 0.24, the lug circumferential length (d) is too short ( That is, the lug groove width (W2) is too narrow), and off-road stones may be caught in the lug groove 3. On the other hand, when the parallel line upper ratio (d / e) is larger than 0.36, the lug circumferential length (d) becomes longer (that is, the lug groove width (W2) becomes wider), so that the block 5A becomes smaller. As a result, the rigidity of the entire block 5A decreases, and it may not be possible to suppress the deterioration of the action of the block 5A, which is generated when the block 5A comes out of the ground contact surface.

  Moreover, it is preferable that block length (B) which is the length of the block 5A orthogonal to the extending direction of the land part 5 is 2 to 4% with respect to the tire outer periphery.

  When the block length (B) is shorter than 2% with respect to the tire outer periphery, the lug circumferential length (d) becomes longer (that is, the lug groove width (W2) becomes wider), that is, the block 5A In some cases, the block 5A becomes smaller and the rigidity of the entire block 5A is reduced, so that the deterioration of the action of the block 5A, which is generated when the block 5A comes out of the ground surface, tries to return to the original state may not be suppressed. On the other hand, when the block length (B) is longer than 4% with respect to the tire outer periphery, the number of blocks 5A arranged in the entire tread portion is reduced, and the edge force (edge amount × edge pressure) is reduced. May not be improved.

(Action / Effect)
According to the pneumatic tire 1 according to the present embodiment described above, the lug groove 3 extends while being inclined with respect to the tread width direction, and the dividing groove 7 divides the land portion 5 into five edges. The traction performance can be improved by improving the force (edge amount × edge pressure).

  Further, since the division groove depth (h) is shallower than the lug groove depth (g), the vibration performance generated when the block 5A is grounded and struck during rolling of the tire is suppressed, and on-road riding is suppressed. It is possible to eliminate the deterioration of comfort.

  Specifically, since the rigidity is low on the surface side of each block 5A, it is possible to mitigate the impact on the block 5A that is hit against the road surface when the tire rolls. On the other hand, when the block 5A kicks off the road surface, the block 5A that is first kicked out of the one land portion 5 is grounded by another block 5A that is connected by the same land portion 5, so that the movement is restricted. Thus, it is possible to suppress the deterioration of the action of the block 5A, which is generated when the block 5A comes out of the ground plane, trying to return to the original state.

  As a result, the vibration performance generated by the block 5A coming into contact with the road surface can be suppressed, and the traction performance can be improved without deteriorating the on-road riding comfort.

  Further, since the division groove width (W1) is narrower than the lug groove width (W2), the base side rigidity of the block 5A is improved, and the block 5A generated when the block 5A comes out of the ground surface is restored. It is possible to further suppress the deterioration of the action to be attempted.

  In addition, by satisfying the relationship of 0.4 ≦ h / g ≦ 0.7, the block 5A is in contact with the road surface by providing a balance between the rigidity on the surface side of the block 5A and the rigidity on the base side of the block 5A. The vibration performance generated by the above can be further suppressed.

  Furthermore, according to this feature, by satisfying the relationship of 0.24 ≦ d / e ≦ 0.36, the rigidity reduction of the block 5A is suppressed, and the on-road riding comfort is not deteriorated. It is possible to prevent stones on the road from getting caught in the lug grooves and split grooves.

[Other Embodiments]
Although the contents of the present invention have been disclosed through the embodiments of the present invention as described above, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention.

  Specifically, the pneumatic tire 1 has been described as a general radial tire for a construction vehicle including a bead portion, a carcass layer, and a belt layer (not shown), but is not limited thereto. Of course, a tire other than a radial tire (for example, a bias tire) may be used.

  From this disclosure, various alternative embodiments, examples, and operational techniques will be apparent to those skilled in the art. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

  Next, in order to further clarify the effects of the present invention, test results performed using pneumatic tires according to Comparative Example 1 and Examples 1 to 7 below will be described. In addition, this invention is not limited at all by these examples.

  Data regarding each pneumatic tire is measured under the following conditions.

・ Tire size: 17.5R25
・ Rim size: 14.00 / 1.5
・ Tire circumference: 1362mm
・ Tread width: 412mm
・ Block length: 145mm
・ Lug groove depth: 40mm
-Number of pitches: 30 pitches-Vehicle type: Wheel loader In the pneumatic tire 100 according to the comparative example, as shown in FIG. Tilt alternately. Moreover, in the pneumatic tire 100 according to Comparative Examples 1 to 3, the dividing groove 105 that divides the land portion 103 into the blocks 103 </ b> A is formed by the lug groove 101.

  In the pneumatic tires according to Examples 1 to 7, the tread pattern described in the above-described embodiment is formed (see FIGS. 1 to 4). In the pneumatic tires according to Examples 1 to 7, the lug groove inclination angle (a), the division groove angle (b), the block angle (c), the groove depth ratio (h / g), the parallel line upper ratio (d / E) is different, and each configuration is shown in Table 1.

The vibration performance (riding comfort) and traction performance of the pneumatic tires according to these comparative examples and Examples 1 to 7 will be described with reference to Table 1.

<Vibration performance (riding comfort)>
A vehicle equipped with each pneumatic tire was run on-road, and the driver evaluated the vibration performance (riding comfort). In addition, it evaluates with a 10-point perfect score, and it is excellent in vibration performance, so that a numerical value is large.

  As a result, it was found that the pneumatic tires according to Examples 1 to 7 were superior to the pneumatic tire according to the comparative example in vibration performance generated when the block was grounded and struck during tire rolling. It was. In particular, in the pneumatic tires according to Examples 2, 3, 4, and 6, the groove depth ratio (h / g) satisfies the relationship of 0.4 to 0.7, and thus is 7 points or more, and the vibration performance is improved. It turns out that it is excellent.

<Traction performance>
The vehicle equipped with each pneumatic tire was run on-road, the traction performance of the pneumatic tire according to the comparative example was set to “100”, and the traction performance of other pneumatic tires was indexed. The higher the index, the better the traction performance.

  As a result, it was found that the pneumatic tires according to Examples 1 to 7 were superior in traction performance as compared with the pneumatic tires according to Comparative Examples 1 to 3.

<Comprehensive evaluation>
As described above, the air satisfies the relationship that the groove depth ratio (h / g) is 0.4 to 0.7 and the parallel line ratio (d / e) is 0.24 to 0.36. It was found that the entering tire can eliminate both stones and the like between the lug grooves and the split grooves when off-road, and at the same time, can achieve both a high level of on-road riding comfort and traction performance.

1 is a perspective view showing an off-road pneumatic tire according to the present embodiment. It is a partial perspective view which shows the tread pattern of the pneumatic tire for off-road concerning this Embodiment. It is a development view showing a tread pattern of an off-road pneumatic tire according to the present embodiment. It is a partial cross section figure of the tread pattern of the pneumatic tire for off-road concerning this embodiment. It is a perspective view which shows the pneumatic tire for off-road concerning a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pneumatic tire 3 ... Lug groove 5 ... Land part 5A ... Block 7 ... Dividing groove

Claims (4)

Lug grooves extending obliquely with respect to the tread width direction;
A dividing groove that divides the land portion defined by the lug groove into five blocks;
An off-road pneumatic tire characterized in that a division groove depth (h) which is a depth of the division groove is shallower than a lug groove depth (g) which is a depth of the lug groove.   The division groove width (W1) which is a width orthogonal to the extending direction of the division groove is narrower than the lug groove width (W2) which is a width orthogonal to the extension direction of the lug groove. The pneumatic tire for off-road as described in 1.   The relationship of 0.4 ≦ h / g ≦ 0.7 is satisfied, where the division groove depth is “h” and the deepest lug groove depth is “g”. Off-road pneumatic tire.   On the parallel line extending substantially parallel to the tire equator line, the pitch length which is the length in the tire circumferential direction of the pitch (p) which is a unit in which the tread pattern is repeated in the tire circumferential direction is “e”, and the length of the lug groove 2. The off-road pneumatic tire according to claim 1, wherein a relation of 0.24 ≦ d / e ≦ 0.36 is satisfied, where the length in the circumferential direction of the lug is “d”.

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