JP2006082734A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire favorably used as a tire for a racer, especially for a racing cart, assuring excellent maneuvering stability in the wet condition by securing a stable gripping performance able to work well with a wide condition about water quantity. <P>SOLUTION: The pneumatic tire is structured so that its shoulder region is free of main grooves having large width continued in the circumferential direction. Circumferential direction large width main grooves 1 having a specified see-through width and groove depth are formed on the tire equator CL and arranged spreading approximately in a bell shape to the left and right approximately centering on the tire equator, while large width main grooves 2 in a bell shape are provided having a specified inclination angle, groove width, and groove depth, in which main grooves 2 adjoining in the circumferential direction have a specified relation about the spacing d1 on the tire equator and the nearest land width d2 where the main grooves 2 approach to the nearest, and the negative rate of the center region is 55-65%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire (hereinafter, also simply referred to as “tire”), and more particularly to a pneumatic tire with improved handling stability when wet, suitable for competitions, particularly racing carts.

  Generally, in a racing wet tire for a racing cart or the like, a tread pattern that emphasizes grip stability when there is a large amount of water on the road surface is adopted with safety as a top priority. However, in such a tread pattern, when the amount of water decreases due to changes in the weather, there is a problem in that the skid at the corner increases due to insufficient rigidity of the pattern block, and performance degradation is observed.

  In particular, since racing cart tires are light in load, there are conventionally used many fine block patterns based on four main grooves that are continuous in the circumferential direction for front tires and five for rear tires. When the amount of water is decreased, a remarkable performance deterioration is observed in that the side slip increases due to the phenomenon of insufficient rigidity of the block and the decrease of the lateral force generated during cornering due to the progress of wear of the shoulder block.

  On the other hand, if a large block pattern is adopted with emphasis on when the amount of water is small, the groove area within the limited ground contact area will decrease, and hydroplaning will occur more easily under conditions where the amount of water is large, and steering stability will be reduced. As a result, it causes a decline. Therefore, in a tire for wet conditions in which the amount of water on the road surface is likely to change, how to exhibit stable grip performance under a wide range of water amounts is a major issue.

On the other hand, for example, in Patent Documents 1 and 2, a circumferential linear groove extending in the tire circumferential direction and a plurality of grooves extending obliquely upward from the tread central area toward the tread end and opening at the tread end. There is described a pneumatic tire that is provided with a plurality of inclined grooves, and that each of the inclined grooves is arranged in a predetermined manner, thereby improving both steering stability and wet drainage on a dry road surface. Further, as a technique for improving drainage performance by improving the tread pattern, for example, Patent Document 3 discloses a pneumatic tire in which hyperbolic curved grooves are provided at predetermined angles on both left and right sides of a main groove provided in the circumferential direction. Is described. Furthermore, Patent Document 4 discloses a technique for arranging an expanded chamfered portion that is aligned under a predetermined condition in order to realize a tread for a pneumatic tire having a wide range of uses on a paved surface and on and off the road. Are listed.
JP-A-4-43105 (Claims etc.) JP-A-4-126612 (Claims etc.) JP-A-4-50006 (Claims etc.) JP 2002-103920 A (Claims etc.)

  As described above, various attempts have been made to improve the tread pattern of pneumatic tires used in wet conditions. However, pneumatic tires with improved handling stability have been demanded for further performance improvement. Is required.

  In particular, in wet tires for racing carts, as described above, conventionally, a block pattern composed of four circumferential main grooves for a front tire and five circumferential main grooves for a rear tire is generally used. As a problem, when the amount of water decreases, the wearing-in side block wears quickly, resulting in a decrease in lateral force generation and a decrease in braking force. As a countermeasure, the block can be enlarged, but the extension of the block pattern based on the conventional circumferential main groove reduces the groove area within the limited contact area of the light-weight racing cart tire. Thus, the problem that the hydroplaning phenomenon tends to occur and the occurrence of uneven wear along the circumferential main groove have not been prevented.

  Accordingly, an object of the present invention is to improve the tread pattern to ensure a stable grip performance that can cope with a wide range of water conditions, so that the pneumatic tire is suitable as a racing tire excellent in handling stability under wet conditions. The object is to provide a pneumatic tire for a tire, in particular a racing cart.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have made the following configuration, so as not to impair drainage and to reduce the lateral force even under conditions where the amount of water is small. It has been found that it is possible to prevent a decrease in pattern rigidity and wear resistance, and to exhibit stable motion performance from a condition with a large amount of water to a condition with a small amount of water. .

That is, the pneumatic tire of the present invention is assembled to a rim of 7-5 inches, filled with an internal pressure of 100 kPa, and the center of the tire occupying TW ₁₁₀ × 35% when the tire contact width is TW ₁₁₀ when a load of 1078 N is applied. A pneumatic tire having an area and shoulder areas on both sides thereof, the shoulder area having no wide main groove continuous in the circumferential direction,
On the tire equator, there is a substantially straight circumferential wide main groove with a see-through width of TW ₁₁₀ × 5 to 9% and a groove depth of tread rubber thickness (Gt) × 65 to 90%,
When viewed from the front of the tire, it expands in a substantially bell shape on both the left and right sides of the tire equator as the center, and the inclination angle with respect to the circumferential direction is 90 ° to 10 ° in the center region and 10 ° to 90 ° in the shoulder region. Has a bell-shaped wide main groove with TW ₁₁₀ x 5 to 8% and groove depth of tread rubber thickness (Gt) x 65 to 90%,
The bell-shaped wide main grooves adjacent to each other in the circumferential direction have a tire circumference x 4.0 to 5.5% on the tire equator, and are closest to both bell-shaped wide main grooves. The land width (d2) has a relationship of 1.5 mm or more, and
The negative rate of the center region is 55 to 65%.

  According to the present invention, in order to substantially reduce the circumferential main groove, a pattern based on a bell-shaped wide main groove is adopted, and the groove area is reduced by eliminating the circumferential main groove from the heavily worn shoulder portion. As a result, it is possible to achieve a significant improvement in wear resistance. As a result, both the hydroplaning property under conditions with a large amount of water and the wear resistance under conditions with a small amount of water are achieved. In addition, it has become possible to realize a pneumatic tire that can exhibit stable steering stability regardless of increase or decrease in the amount of water.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.
FIG. 1A shows a tread pattern of a pneumatic tire according to a preferred example of the present invention. The tire of the present invention is assembled on a rim of 7-5 inches, filled with an internal pressure of 100 kPa, and when a tire ground contact width when a load of 1078 N is applied is TW ₁₁₀ , a center region C occupying TW ₁₁₀ × 35%; Both side shoulder regions S are provided.

  As shown in the figure, in the present invention, first, in order to reduce the wear of the shoulder portion when the amount of water is small, it is necessary not to provide a wide main groove continuous in the circumferential direction in the shoulder region S. The drainage performance under the condition of a large amount of water that is expected to decrease is ensured by adopting the bell-shaped wide main groove 2 and the first and second sub-grooves (gr1, gr2). In order to ensure sufficient drainage in the present invention, it is essential to provide the bell-shaped wide main groove 2, and by providing the first and second sub-grooves (gr1, gr2) as auxiliary, Good drainage can be obtained.

As shown in the figure, the bell-shaped wide main groove 2 is developed in a substantially bell shape on both the left and right sides of the tire equator CL in the front view of the tire, and the inclination angle with respect to the circumferential direction is 90 ° to 10 ° in the center region. 70 ° to 10 °, preferably 10 ° to 90 ° in the shoulder region, preferably 10 ° to 70 °, and the groove width is TW ₁₁₀ × 5 to 8%, preferably TW ₁₁₀ × 5 The groove depth is 7%, and the tread rubber thickness (Gt) × 65 to 90%, preferably (Gt) × 70 to 83%. When considering drainage, it is particularly important that the groove width and groove depth of the bell-shaped wide main groove 2 satisfy these ranges. However, even if the bell-shaped wide main groove 2 is too large, the groove area becomes too large in the limited ground contact area, and a sufficient generating force cannot be obtained due to a decrease in the installation portion with the road surface. .

  Further, in the tire mounted on the rear, the lateral grip force is reduced when traction is applied, but if the drainage is poor when entering the water pool, the lateral grip becomes insufficient, and a side slip is more likely to occur than the front tire. Therefore, in order to ensure the stability of the rear grip in the water pool, it is necessary to place more importance on drainage than the front tire, and it is essential to have a substantially linear circumferential wide main groove 1 on the tire equator CL. It is.

In this circumferential wide main groove 1, in order to ensure drainage, the see-through width is TW ₁₁₀ × 5 to 9%, preferably TW ₁₁₀ × 6 to 8%, and the groove depth is the tread rubber thickness (Gt). It is necessary to secure a certain volume of × 65 to 90%, preferably (Gt) × 70 to 83%. However, if the circumferentially wide main groove 1 is too large, the land area is reduced, and a sufficient generated force cannot be obtained.

  Further, as shown in the drawing, the bell-shaped wide main grooves 2 adjacent to each other in the circumferential direction are closest to each other in the middle region between the center region and the shoulder region, but the two bell-shaped wide main grooves 2 are too close to each other. And the rigidity of the land part in the vicinity of this closest part will fall, and wear resistance will deteriorate. Therefore, it is necessary to ensure 1.5 mm or more about the closest land part width | variety (d2) which both bell-shaped wide main grooves 2 adjoin most, Preferably it is 2-3 mm.

  The distance (d1) between the bell-shaped wide main grooves 2 on the tire equator is tire circumferential length × 4.0 to 5.5%, preferably tire circumferential length × 4.0 to 5.0%. If this distance (d1) is too small, the volume of the block becomes small, and the grip generation force becomes small due to a decrease in block rigidity. On the other hand, if the distance (d1) is too large, the drainage property is deteriorated, and in this case, the grip is lowered. In the example shown in the figure, the bell-shaped wide main groove 2 is developed symmetrically on both the left and right sides with the tire equator CL approximately as the center. However, the present invention is not limited to this. Both sides may be offset from each other in the circumferential direction, and even in this case, the intended effect of the present invention can be obtained without problems.

  In the pattern according to the present invention, in order to improve the wear resistance of the shoulder portion, a wide main groove continuous in the circumferential direction is not provided in the shoulder region. Therefore, drainage in the center region becomes important accordingly. In order to ensure drainage without hydroplaning under conditions with a large amount of water, a negative rate of 55% or more is required in the center region. On the other hand, when the negative rate is higher than 65%, the land portion in the center region is excessively reduced, resulting in a decrease in generated force and wear resistance. Therefore, in the present invention, the negative rate of the center region needs to be 55 to 65%, and preferably the negative rate is 55 to 60%.

  Further, as shown in the drawing, the land portion in the vicinity of the closest portion of the adjacent bell-shaped wide main groove 2 has a narrow width, so that it is possible to secure a width that does not cause a problem with respect to wear resistance. preferable. From this point of view, the angle (α1) of the center land portion 3 formed in the center region by the two bell-shaped wide main grooves 2 as viewed from the closest land portion of the bell-shaped wide main groove 2 is 25 ° or more, and The angle (α2) of the shoulder land portion 4 formed in the shoulder region by the two bell-shaped wide main grooves 2 is preferably set to 25 ° or more.

  In order to improve drainage, a first sub-groove (gr1) communicating between the two bell-shaped wide main grooves 2 is disposed at the closest land portion of the bell-shaped wide main groove 2 adjacent in the circumferential direction. Is preferred. FIG. 1B shows an enlarged sectional view of the first sub-groove (gr1). The first sub-groove (gr1) needs to have a volume sufficient to cause a drainage flow between the adjacent bell-shaped wide main grooves 2. From this point of view, the first sub-groove (gr1) is substantially streamlined in cross section and has a shape in which the land height gradually decreases in an arc parabola as shown in the drawing, and at least the depth of the main groove from the tread surface portion. In the range up to 20%, the groove width is preferably the main groove width × 80 to 250%, and the groove depth is preferably the main groove depth × 60 to 100%. However, if the groove width is too large, the generated force in the center land portion 3 is reduced. Therefore, the groove width is more preferably suppressed to 200% of the main groove width.

  The shoulder land portion 4 is preferably provided with at least one second sub-groove (gr2) for cutting and draining a water film that enters under the land portion having a large shoulder portion. Thus, the shoulder land portion 4 has a substantially fork tip shape as shown in the figure. In order to obtain a stable grip in both the vertical and horizontal directions, the second sub-groove (gr2) has a groove width of main groove width x 30 to 65% and a groove depth of main groove depth x Some volume is required at 40-100%. If the second sub-groove (gr2) is too large, the ground contact area of the shoulder land portion 4 is reduced, and the rigidity is weakened, resulting in a decrease in lateral generation force. Therefore, the groove width is up to 65% of the main groove width. It is preferable to suppress to. Note that the second sub-groove (gr2) may be open at the shoulder end or may not be open depending on the rigidity required for the shoulder land portion 4, and in any case, The desired effect of the present invention can be obtained without problems. A radial sipe groove 6 can be appropriately provided between the second sub-groove (gr2) and the bell-shaped wide main groove 2 as shown in the drawing.

  Further, a radial sipe that communicates with the bell-shaped wide main groove 2 and the circumferential wide main groove 1 in order to cut and drain a water film that enters under the center land portion 3 at the approximate center of the center land portion 3. It is preferable to arrange the grooves 5. However, if the radial sipe groove 5 is too large, the rigidity of the center land portion 3 is insufficient and the wear resistance is deteriorated. Therefore, the radial sipe groove 5 depends on the size of the block of the center land portion 3. The groove width is 0.5 to 2 mm, and the groove depth is the main groove depth x 40 to 80%.

  As described above, the pneumatic tire of the present invention is suitable for racing tires, particularly for racing cart rear tires, and is most effective when used on the rear when the racing cart is wet. .

Hereinafter, the present invention will be described specifically by way of examples.
Under the conditions shown in Table 1 below, pneumatic tires of examples were manufactured, and each tire was mounted on a cart, and an actual vehicle performance test was performed. The test tire of the example (FIG. 2 (b)) was mounted on the rear, and the front tire (FIG. 2 (a)) used a spec suitable for the combination. In addition, as a conventional example, a rear tire (FIG. 3B) having the conditions shown in Table 1 below and a front tire having a specification suitable for the combination (FIG. 3A) are used. A comparison was made.

(1) Test conditions for actual vehicle performance test a. Test course: Water was sprinkled on a part of Mibu International Kart Course, and was run under wet conditions.
b. Part of the course was run with a large amount of water so that drainage could be evaluated.
c. Traveling vehicle: cart FA class vehicle and engine d. Evaluation driver: International competition license driver for cart e. Rim used: (Front) 4.5-5, (Rear) 7.0-5
f. Working internal pressure: (front) 100 kPa, (rear) 100 kPa

(2) Travel results a. Lap Time and Wear The results of evaluating the tires of the examples and the conventional examples with respect to the average lap time and shoulder wear are shown in Table 2 below.

b. Feeling evaluation in a place with a lot of water In the tire of the conventional example, the idling time in a place with a lot of water was long and the handle was taken, but the tire of the example had a strong grip, stable and good Met.

c. Feeling evaluation in a place where the amount of water is medium to small The tire of the example can be easily controlled even if it is moved roughly compared to the conventional example. In addition, the rear was stable when it was shaken from the braking, and the steering wheel was also cut off at the front, making it easy to drive.

d. Comprehensive evaluation The tire of the example had a more stable grip than the tire of the conventional example regardless of the amount of water, and was easy to drive and was able to run in a fast time, and good results were obtained.

It is a fragmentary top view which shows the tread pattern of the pneumatic tire of one suitable example of this invention. (A) is the tread pattern of the front tire used for the Example, (b) is a partial expansion | deployment top view which respectively shows the tread pattern of the rear tire used for the Example. (A) is a tread pattern of the front tire used in the conventional example, and (b) is a partially developed plan view showing the tread pattern of the rear tire used in the conventional example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Circumferential wide main groove 2 Bell-shaped wide main groove 3 Center land part 4 Shoulder land part 5, 6 Radial direction sipe groove gr1 1st subgroove gr2 2nd subgroove

Claims (6)

It has a center area that occupies TW ₁₁₀ x 35% and shoulder areas on both sides when the tire ground contact width is TW ₁₁₀ when it is assembled on a rim of 7-5 inches, filled with an internal pressure of 100 kPa, and a load of 1078 N is applied. The pneumatic tire does not have a wide main groove continuous in the circumferential direction in the shoulder region,
On the tire equator, there is a substantially linear circumferential wide main groove having a see-through width of TW ₁₁₀ × 5 to 9% and a groove depth of tread rubber thickness (Gt) × 65 to 90%,
When viewed from the front of the tire, it is developed in a substantially bell shape on both the left and right sides with the tire equator as the center, and the inclination angle with respect to the circumferential direction is 90 ° to 10 ° in the center region and 10 ° to 90 ° in the shoulder region. Has a bell-shaped wide main groove with TW ₁₁₀ x 5 to 8% and groove depth of tread rubber thickness (Gt) x 65 to 90%,
The bell-shaped wide main grooves adjacent to each other in the circumferential direction have a tire circumference x 4.0 to 5.5% on the tire equator, and are closest to both bell-shaped wide main grooves. The land width (d2) has a relationship of 1.5 mm or more, and
A pneumatic tire characterized by having a negative rate in the center region of 55 to 65%. Seen from the closest landing part of the bell-shaped wide main groove adjacent in the circumferential direction,
The angle (α1) of the center land portion formed in the center region by the double bell-shaped wide main grooves is 25 ° or more, and the angle of the shoulder land portions (α2) formed in the shoulder region by the double bell-shaped wide main grooves ) Is 25 ° or more. The pneumatic tire according to claim 1.   A first sub-groove (gr1) communicating between the two bell-shaped wide main grooves is disposed at the closest land portion of the bell-shaped wide main groove adjacent to the circumferential direction, and the first sub-groove (gr1) The land portion height gradually decreases in a circular arc parabolic shape and has a groove width that is at least 20% of the main groove depth from the tread surface portion. The pneumatic tire according to claim 1 or 2, wherein the groove depth is a main groove depth x 60 to 100%.   At least one second secondary groove (gr2) is disposed in a shoulder land portion formed in a shoulder region by the bell-shaped wide main groove adjacent in the circumferential direction, and the shoulder land portion has a substantially fork tip shape. The second sub-groove (gr2) has a groove width of main groove width x 30 to 65% and a groove depth of main groove depth x 40 to 100%. The pneumatic tire according to any one of claims.   In the center of the center land portion formed in the center region by the bell-shaped wide main groove adjacent in the circumferential direction, there is a radial sipe groove that communicates with the bell-shaped wide main groove and the circumferential wide main groove, The pneumatic tire according to any one of claims 1 to 4, wherein the radial sipe groove has a groove width of 0.5 to 2 mm and a groove depth of 40 to 80%.   It is a rear tire for racing carts, The pneumatic tire according to any one of claims 1 to 5.

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