JP5452338B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a tire that can exhibit high dry grip properties and uneven wear resistance while suppressing a decrease in drainage, and more particularly to a pneumatic tire suitable as a racing tire such as a gymkhana.

  As a tread pattern of a high-performance tire on the premise of running in a race such as a gymkana competition in addition to running on a public road, as shown in FIG. 6, from the tread ground contact Te side toward the tire equator C, the tire circumferential direction The one using the inclined main groove b extending while reducing the angle α has been proposed (see Patent Document 1). In such a tread pattern, since the inclined main groove b is inclined along the streamline of water, the wet grip performance with excellent drainage can be exhibited. In the example of FIG. 6, although the inclined main groove b is branched into two inclined groove portions b1 and b2, since the inclined main grooves b and b do not intersect with each other, the tread portion is subdivided into a plurality of blocks. Therefore, there is an advantage that the pattern rigidity is relatively large and high dry grip properties can be exhibited.

  However, even with such a tread pattern, the dry grip and uneven wear resistance are not sufficient for race running, and further improvements are desired.

  Specifically, the pattern stiffness on the tire equator side is relatively insufficient, and the wear on the tire equator side becomes severe and the wear life of the tire is impaired. On the tread ground end side, the pattern stiffness is on the tire equator side. Compared with this, there is a tendency that the grounding property is deteriorated and the dry grip property is deteriorated. However, when the tread pattern is formed by the inclined main groove, especially when the tread pattern is formed by the inclined main groove that is not branched, the pattern pattern is limited. difficult. In order to adjust the pattern stiffness, for example, it may be proposed to reduce the groove width of the inclined main groove toward the tire equator side. Since the drainage is reduced, the wet grip performance cannot be maintained.

JP 2000-127715 A

  Therefore, the present invention provides a chamfered portion made of an inclined surface on the groove wall surface on the tire equator side of the inclined main groove, and gradually increases the inclination angle of the chamfered portion from the tread grounding end side toward the tire equator side. Basically, the groove bottom width of the groove is gradually reduced from the tread grounding end side toward the tire equator side, and the change in the groove opening width of the inclined main groove is kept low to suppress the drainage, that is, the decrease in wet grip performance. However, the pattern stiffness on the tire equator side can be made relatively higher than the tread grounding end side to optimize the overall pattern stiffness, and the wear life can be increased by suppressing uneven wear on the tire equator side. An object of the present invention is to provide a pneumatic tire capable of improving the dry grip property by increasing the ground contact property on the ground contact end side and securing a wide ground contact area.

In order to solve the above-mentioned problem, the invention of claim 1 of the present application is directed to the tread portion while gradually decreasing the angle α with respect to the tire circumferential direction without intersecting with other grooves from the tread ground contact side toward the tire equator. A pneumatic tire with a sloping main groove that extends,
In the inclined main groove, the angle α at the inner end position where the inclined main groove is closest to the tire equator is in the range of 0 to 30 °,
In addition, the inclined main groove has an equatorial side chamfered portion that cuts the intersection with an inclined surface at an intersection where the groove wall surface on the tire equator side and the tread surface intersect.
The angle β with respect to the normal direction of the tread surface of the equator side chamfered portion gradually increases from the tread ground contact end side toward the tire equator side,
In addition, the inclined main groove gradually decreases as the groove bottom width WB, which is a groove width at a reference height position separating a distance of 1.6 mm from the groove bottom toward the tread surface, from the tread grounding end side toward the tire equator side. It is characterized by that.

  In the invention of claim 2, the inclined main groove includes a groove wall surface on the tire equator side and a groove wall surface on the tread grounding end side, each having an angle θ with respect to the normal direction of the tread surface within a range of 0 to 10 °. It is characterized by that.

  In the invention of claim 3, the equator side chamfered portion is characterized in that the chamfer width in the groove width direction of the inclined main groove is gradually increased from the tread grounding end side toward the tire equator side.

  According to a fourth aspect of the present invention, the inclined main groove has a grounding end side surface chamfering portion in which the groove wall on the tread grounding end side and the tread surface intersect with each other, and the intersection is cut off by an arc surface having a radius of curvature R. It is characterized by that.

  In the invention of claim 5, the radius of curvature R of the side edge chamfered portion gradually increases from the tread grounded end side toward the tire equator side, and the radius of curvature Ri at the inner end position is the largest at the tread grounded end. It is characterized by being 1.1 to 10.0 times the radius of curvature Ro at the approaching outer end position.

  According to a sixth aspect of the present invention, the inclined main groove includes a grounding end formed by an intersection of the equator side groove side edge formed by the intersection of the equator side chamfered portion and the tread surface, and a groove wall surface of the tread grounding end side and the tread surface. The groove opening width WO between the side groove side edges is gradually reduced from the tread ground contact side toward the tire equator side.

  Further, in the invention of claim 7, the inclined main groove is provided with a turn-up portion that turns back from the inner end position toward the tread ground contact end side with different inclination directions with respect to the tire circumferential direction.

  The “tread grounding end” means the maximum width position in the tire axial direction on the tread grounding surface that can be grounded when a normal load is applied to a tire that is assembled with a normal rim and filled with a normal internal pressure. The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO means "Measuring Rim". The “regular internal pressure” is the air pressure defined by the standard for each tire. The maximum air pressure for JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” for ETRA, Means "INFLATION PRESSURE", but in the case of passenger car tires, it is 180 kPa. The “regular load” is a load determined by the standard for each tire. The maximum load capacity in the case of JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the case of TRA, If it is ETRTO, it is “LOAD CAPACITY”, but if the tire is for a passenger car, the load is equivalent to 88% of the load.

  Further, in the provision of “slip prevention requirements” in the “Safety Standard for Road Transport Vehicles”, in the case of automobile tires, the groove depth of the remaining groove is defined as a wear limit of 1.6 mm. The limit “height position separating 1.6 mm from the groove bottom toward the tread surface” is defined as the reference height position X, and the groove width at this reference height position X is defined as the groove bottom width WB. ing.

  As described above, according to the present invention, the groove bottom width WB of the inclined main groove is gradually decreased from the tread grounding end side toward the tire equator side, and the chamfering formed of an inclined surface is formed on the groove wall surface of the inclined main groove on the tire equator side. The angle c of the chamfered portion is gradually increased from the tread ground contact end side toward the tire equator side.

  Thus, by making the groove bottom width WB small on the tire equator side, the pattern rigidity on the tire equator side can be relatively increased, and the wear resistance can be improved. On the tire equator side, the chamfer width increases due to an increase in the inclination angle β of the chamfered portion. Therefore, the increase in the chamfering width counteracts the decrease in the groove bottom width WB, so that the change in the groove opening width of the inclined main groove can be kept low, and the drainage on the tire equator side is suppressed and the wet grip is suppressed. The performance can be maintained.

  On the other hand, on the tread grounding end side, the pattern rigidity is decreased by increasing the groove bottom width WB, so that the grounding property is improved and a wide grounding area can be secured. That is, dry grip properties can be improved. In addition, the reduction of the chamfer width further achieves a large ground contact area. Moreover, since the rigidity of the tread portion as a whole is optimized, the steering response is enhanced and it is possible to contribute to the improvement of the steering stability.

It is an expanded view which shows one Example of the tread pattern of the pneumatic tire of this invention. It is an enlarged view of an inclined main groove. It is AA sectional drawing of FIG. It is BB sectional drawing of FIG. It is a fragmentary perspective view which exaggerates and shows an inclined main groove. It is an expanded view which shows an example of the tread pattern of the conventional tire.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, the pneumatic tire 1 of the present embodiment has an angle α with respect to the tire circumferential direction without crossing other grooves from the tread contact end Te side toward the tire equator C toward the tread portion 2. An inclined main groove 3 extending while gradually decreasing is provided. In this example, an inclined sub-groove 4 that is inclined in the same direction as the inclined main groove 3 and does not intersect with other grooves is disposed outside the inclined main groove 3 in the tire axial direction. A tread pattern is formed by a unit pattern including the inclined sub-groove 4.

  The tread pattern is a left-right symmetric pattern, and the unit pattern is formed on both sides of the tire equator C and at symmetrical positions around the tire equator C. Note that the pattern on one side and the pattern on the other side of the tire equator C are arranged out of phase in the tire circumferential direction. The inclined main groove 3 and the inclined sub-groove 4 are inclined toward the first arrival side from the tread contact end Te side toward the tire equator C, and accordingly, when the tire rotates, water on the road surface is contacted along the streamline on the contact surface. It can be discharged efficiently. The “first arrival side” means a side that contacts the road surface first when the tire rotates.

  Next, the inclined main groove 3 is a closed-type main groove whose both ends are cut off in the tread portion 2, and the angle α at the inner end position Pi closest to the tire equator C (sometimes referred to as αi for convenience). Is in the range of 0 to 30 °. If this angle αi exceeds the above range, the drainage is reduced and the wet grip performance is adversely affected. Further, the angle α (sometimes referred to as αo for the sake of convenience) at the outer end position Po where the inclined main groove 3 is closest to the tread ground contact Te is not particularly restricted, but the range of 40 to 80 ° is the steering stability and the wet grip. It is preferable from the viewpoint of performance.

  The angle α is defined as the angle of the width center line j of the groove bottom width WB with respect to the tire circumferential direction. The groove bottom width WB is defined as a reference height position X separating a distance h of 1.6 mm from the groove bottom 6 toward the tread surface S, that is, a groove width at the wear limit, as shown in FIGS. The

  In the inner end position Pi, the distance Li from the tire equator C to the inclined main groove 3 is preferably in the range of 1 to 5% of the tread ground contact width Tw, and the outer end position Po is inclined from the tread ground contact Te. The distance Lo to the main groove 3 is preferably in the range of 10 to 20% of the tread ground contact width Tw. If the distance Li is less than 1% of the tread contact width Tw, sufficient rigidity on the tire equator C side cannot be ensured. Conversely, if the distance Li exceeds 5%, the wet grip performance becomes insufficient. If the distance Lo is less than 10% of the tread ground contact width Tw, the rigidity on the tread ground contact Te side is insufficient, and if it exceeds 20%, the wet grip performance is insufficient.

  Further, as shown in FIGS. 3 to 5, the inclined main groove 3 has an equatorial side chamfered portion 8 in which the intersection point Jc where the groove wall surface 7 on the tire equator side and the tread surface S intersect is cut out by the inclined surface 8S. With

  In the present invention, as shown in FIGS. 3 and 4 which are AA sectional view and BB sectional view of FIG. 2, a groove width direction which is a direction orthogonal to the groove length direction of the inclined main groove 3 is shown. In the cross section, the equator side chamfer 8 has an angle β with respect to the normal direction n of the tread surface S that gradually increases from the tread ground contact Te side toward the tire equator C side, and the groove bottom width WB is equal to the tread surface width WB. It gradually decreases from the ground contact Te side toward the tire equator C side. At this time, the chamfering width W8 in the groove width direction of the equator side chamfered portion 8 gradually increases from the tread ground contact end Te toward the tire equator C side.

  As relative, the angle β in the AA cross section on the tire equator C side is expressed as βa, the groove bottom width WB is expressed as WBa, the chamfering width W8 is expressed as W8a, and the angle β in the BB cross section on the tread ground contact Te side. Is expressed as βb, the groove bottom width WB is expressed as WBb, and the chamfer width W8 is expressed as W8b, βa> βb, WBa <WBb, W8a> W8b.

  By configuring in this way, on the tire equator C side, the groove bottom width WB is small, the pattern rigidity is relatively increased, and the wear resistance is improved. Moreover, on the tire equator C side, the chamfering width W8 increases due to an increase in the angle β of the equator side chamfered portion 8. Therefore, the increase in the chamfering width W8 counteracts the decrease in the groove bottom width WB, and the change in the groove opening width W0 of the inclined main groove 3 is suppressed to a low level. For this reason, a decrease in drainage on the tire equator C side is suppressed, and wet grip performance can be maintained.

  On the other hand, on the tread grounding end Te side, the pattern rigidity decreases due to the relative increase in the groove bottom width WB, so that the grounding performance is improved and a large grounding area can be secured. That is, dry grip properties are improved. In addition, the reduction of the chamfering width W8 further achieves a large ground contact area. Moreover, since the rigidity of the tread portion 2 as a whole is optimized, the steering wheel response is enhanced, and it is possible to contribute to the improvement of the steering stability.

  The angle β has a maximum value βmax at the inner end position Pi and a minimum value βmin at the outer end position Po. The groove bottom width WB has a minimum value WBmin at the inner end position Pi and a maximum value WBmax at the outer end position Po. The chamfering width W8 has a maximum value W8max at the inner end position Pi, and a minimum value WBmin at the outer end position Po. The maximum value βmax, maximum value WBmax, maximum value W8max, minimum value βmin, minimum value WBmin, and minimum value W8min are appropriately set according to the tread pattern, groove size, tire size, and the like.

  Here, the angle γ with respect to the normal direction n of the tread surface S of the groove wall surface 7 on the tire equator side of the inclined main groove 3 and the groove wall surface 10 on the tread ground contact end side is substantially in the groove length direction. It is constant. The angle γ is smaller than the minimum value βmin of the angle β and is preferably in the range of 0 to 10 °. When this angle γ increases beyond 10 °, the groove volume becomes relatively small, the drainage performance of the tread as a whole decreases, and the difference (β−γ) from the angle β of the equatorial side chamfered portion 8 increases. As a result, the effect by the equator chamfered portion 8 tends not to be sufficiently achieved. Therefore, the upper limit value of the angle γ is more preferably 5 ° or less, and in this example, the case of 0 ° is shown.

  Further, in the inclined main groove 3, the equator side groove side edge Ei formed by the intersection of the equator side chamfer 8 and the tread surface S and the ground end side groove formed by the intersection of the groove wall surface 10 on the tread ground end side and the tread surface S are formed. The groove opening width WO between the side edges Eo can be made substantially constant in the groove length direction. However, gradually decreasing the groove opening width WO from the tread ground contact Te side to the tire equator C side optimizes the pattern rigidity and suppresses uneven wear on the tire equator C side, while at the tread ground contact Te side. It is preferable for improving the dry grip property by improving the ground contact property.

  In this case, when the groove opening width WO in the AA cross section on the tire equator C side is expressed as WOa and the groove opening width WO in the BB cross section on the tread grounding end Te side is expressed as WOb, WOa <WOb Further, the groove opening width WO has a minimum value WOmin at the inner end position Pi and a maximum value WOmax at the outer end position Po. From the viewpoint of suppressing a decrease in drainage on the tire equator C side, the difference between the maximum value WOmax and the minimum value WOmin (WOmax−WOmin) is preferably 10% or less of the tread ground contact width Tw.

  Further, in this example, the inclined main groove 3 has a grounding end side surface chamfered at a crossing portion Je where the groove wall surface 10 on the tread grounding end side and the tread surface S intersect with each other by an arc surface 11S having a radius of curvature R. The unit 11 is provided. In the ground contact edge chamfer 11, the radius of curvature R gradually increases from the tread ground contact edge Te side toward the tire equator C side, and the curvature radius Ri at the inner end position Pi is equal to the curvature radius at the outer end position Po. It is 1.1 to 10.0 times Ro. As described above, by providing the ground contact end side surface chamfering portion 11 made of the circular arc surface 11S, uneven wear at the intersecting portion Je is suppressed. In addition, since the radius of curvature R is large on the tire equator C side, it is possible to further suppress a decrease in drainage on the tire equator C side while optimizing the pattern rigidity. If the radius of curvature Ri is less than 1.1 times the radius of curvature Ro, the above-mentioned effect of the ground contact edge side chamfer 11 cannot be obtained. .

  In the present example, the inclined main groove 3 is provided with a turn-back portion 3A that turns back from the inner end position Pi toward the tread ground contact end Te side with different inclination directions with respect to the tire circumferential direction. The angle θ of the folded portion 3A with respect to the tire circumferential direction is not particularly limited, but a range of ± 10 ° of the angle α at the inner end position Pi is preferable in terms of balance. The cross-sectional shape of the folded portion 3A is substantially equal to the cross-sectional shape of the inclined main groove 3 at the inner end position Pi. The folded portion 3A terminates with a distance K1 from the inclined main groove 3 adjacent in the circumferential direction, and the distance K1 is preferably 0.2 times or less of the tread grounding width Tw.

  The inclined sub-groove 4 is formed at a substantially intermediate position between the inclined main grooves 3 and 3 adjacent to each other in the circumferential direction. In this example, the inclined sub-groove 4 has an inclination angle substantially equal to the inclined main groove 3 and has a tread grounding end Te. It extends to. The inner end of the inclined sub-groove 4 terminates at a distance K2 from the folded portion 3A.

  In this example, the inclined sub-groove 4 is formed as a substantially Z-shaped groove in which the groove bottom width WB is substantially constant and the groove bottom 4S is displaced stepwise in the groove width direction by a displacement amount δ. Yes. In particular, in this example, the inclined sub-groove 4 is also formed with an equatorial side chamfer 20 made of an inclined surface at an intersection where the groove wall surface on the tire equator side and the tread surface intersect with each other. In the equatorial side chamfering portion 20A in the groove portion 4A, the inclination angle and the chamfering width are constant, and in the equatorial side chamfering portion 20B in the auxiliary groove portion 4B on the outer side in the tire axial direction, the inclination angle and the chamfering width are constant. Yes. Also, the difference in chamfer width between the equator side chamfers 20A and 20B is equal to the displacement δ, whereby the equator side groove side edge Fi of the inclined sub-groove 4 is formed in a smooth arc line shape. . However, the inclined sub-groove 4 can be formed in substantially the same configuration as the inclined main groove 3.

  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.

  A tire with a tire size of 255 / 40R17 based on the tread pattern shown in Fig. 1 was prototyped according to the specifications shown in Table 1, and the initial response, wet grip performance, dry grip performance, wear resistance performance, and running performance were tested. Compared. Except as described in Table 1, the specifications are substantially the same.

In each tire, the inclined main groove has an angle αi at the inner end position Pi of 17 degrees, an angle αo at the outer end position Po of 53 degrees, and an angle γ of each groove wall surface of 0 degrees.
Also, in Table 1,
In * 1, βa> βb means that the angle β gradually increases from the tread ground contact end side toward the tire equator side.
In * 2, WBa <WBb means that the groove bottom width WB gradually decreases from the tread ground contact end side toward the tire equator side.
In * 3, W8a> W8b means that the chamfer width W8 gradually increases from the tread ground contact end side toward the tire equator side.
In * 4, WOa <WOb means that the groove opening width WO gradually decreases from the tread ground contact end side toward the tire equator side.
In * 5, Ra> Rb means that the radius of curvature R gradually increases from the tread contact end side toward the tire equator side.

(1) Driving test A sample tire was mounted on all wheels of a passenger car (2000cc, 4WD) under the conditions of a rim (9J × 17) and internal pressure (230kPa), and the vehicle traveled on a closed course of 1.5km per lap. The initial responsiveness (handle responsiveness) and dry grip performance were determined by a five-point method using Comparative Example 1 as three points by sensory evaluation of a professional driver.

  The running performance was time-attacked 5 times on the test course, and the best time at that time was compared.

  In addition, the wear resistance was determined by visual inspection of the initial responsiveness, the dry grip performance, and the running condition after the running test by a five-point method using Comparative Example 1 as three points.

  The wet grip performance was determined by running the test course in a wet road surface state, and the grip performance at that time was determined by a five-point method using Comparative Example 1 as three points by sensory evaluation of a professional driver.

  As shown in Table 1, it can be confirmed that the tires of the examples can improve wear resistance, handle response, dry grip performance and the like while suppressing a decrease in wet grip performance.

2 Tread portion 3 Inclined main groove 3A Folded portion 6 Groove bottom 7 Groove wall surface 8 Equatorial side surface chamfered portion 8S Inclined surface 10 Groove wall surface 11 Ground end side chamfered portion 11S Arc surface C Tire equator Ei Equatorial side groove side edge Eo Ground end side groove side edge Jc Intersection Je Intersection n Normal direction Pi Inner end position Po Outer end position S Tread surface Te Tread grounding end X Reference height position

Claims (7)

A pneumatic tire having an inclined main groove extending in a tread portion from the tread ground contact side toward the tire equator without gradually intersecting with other grooves and gradually decreasing an angle α with respect to the tire circumferential direction,
In the inclined main groove, the angle α at the inner end position where the inclined main groove is closest to the tire equator is in the range of 0 to 30 °,
In addition, the inclined main groove has an equatorial side chamfered portion that cuts the intersection with an inclined surface at an intersection where the groove wall surface on the tire equator side and the tread surface intersect.
The angle β with respect to the normal direction of the tread surface of the equator side chamfered portion gradually increases from the tread ground contact end side toward the tire equator side,
In addition, the inclined main groove gradually decreases as the groove bottom width WB, which is a groove width at a reference height position separating a distance of 1.6 mm from the groove bottom toward the tread surface, from the tread grounding end side toward the tire equator side. A pneumatic tire characterized by having been made. Claim the inclined main groove, the groove wall surface of the tire equator side, and the groove wall surface of the tread end side, an angle γ with respect to the normal direction of the tread surface, characterized in that the ranges of 0 ° The pneumatic tire according to 1 .
  3. The pneumatic tire according to claim 1, wherein the equator side chamfering portion gradually increases the chamfering width in the groove width direction of the inclined main groove from the tread ground contact end side toward the tire equator side.   The inclined main groove includes a grounding end side surface chamfering portion where a groove wall on the tread grounding end side and the tread surface intersect with each other, and the intersection is cut out by an arc surface having a radius of curvature R. The pneumatic tire according to any one of 1 to 3.   The curvature radius R of the side surface chamfered portion gradually increases from the tread ground contact end side toward the tire equator side, and the curvature radius Ri at the inner end position is the curvature radius Ro at the outer end position closest to the tread ground contact end. The pneumatic tire according to claim 4, wherein the pneumatic tire is 1.1 to 10.0 times as large as 5.   The inclined main groove is a groove between the equator side groove side edge formed by the intersection of the equator side chamfered portion and the tread surface and the ground end side groove side edge formed by the intersection of the groove wall surface of the tread ground end side and the tread surface. The pneumatic tire according to any one of claims 1 to 5, wherein the opening width WO is gradually reduced from the tread ground contact end side toward the tire equator side.   The inclined main groove includes a folded portion that turns back from the inner end position toward the tread contact end side with a different inclination direction with respect to the tire circumferential direction. Pneumatic tires.

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