JP2001253210A - Pneumatic tire for cart - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the operation stability by improving the grounding follow-up ability under a large fluctuation of load to be generated when cornering at a high speed. SOLUTION: This pneumatic tire for cart has a carcass 5 provided with a tread part 1, a side wall part 2, and a bead part 3 and extended between the bead cores 4 arranged in the bead part 3, and has a tread rubber 6 arranged in the periphery of a crown part of the carcass 5. A mean value (TRc1) of the outline curvature radius over 70% of 50% of a grounding half width (TW/2) from a tire equatorial (CL) to both sides, a mean value(TRc2) of the outline curvature radius over 70% of 50-90% of the grounding half width (TW/2), and the maximum tire width (SW) are set so as to satisfy the following condition: TRc1=50-600 (mm), TRc1/SW=0.35-3.50, TRc2=30-200 (mm), TRc2/SW =0.20-1.20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic cart tire, and more particularly, to optimizing an outer contour of a tread tread in a tire meridian section, thereby reducing a vehicle weight without a suspension mechanism. In a racing kart with the characteristic that, when the cornering and driving force applied to the tire during high-speed cornering, the large change in centrifugal force causes a heavy change in the load on each of the front, rear, left and right wheels, it follows the ground, that is, the cornering tire and the road surface Thus, the performance that enables smooth running without causing a sudden change in the contact state with the ground is improved, and thereby the steering stability is sufficiently improved.

[0002]

2. Description of the Related Art For example, many racing carts
No pneumatic tires for carts have been equipped with a carcass ply cord elasticity to supplement their functions with the tires themselves, because they do not have a suspension mechanism that greatly affects the handling, stability, ride comfort, etc. Rate and, by optimizing the hardness of the tread rubber, etc., ensure steering stability, and adjust the tire case rigidity,
Maneuvering stability is to be ensured by increasing the road surface bending followability of the crown portion and the bending flexibility in the sidewall portion, particularly in its flexible region.

[0003]

However, in recent years,
The remarkable improvement in the performance of the cart itself has made it necessary to ensure sufficient ground following ability and, in turn, steering stability during cornering at higher speeds than in the past. A new problem arises that sufficient steering stability cannot be ensured only by performing appropriate optimization and adjusting the rigidity of the tire case.

SUMMARY OF THE INVENTION An object of the present invention is to solve such a problem of the prior art, and an object of the present invention is to follow a ground contact under a severe load fluctuation occurring at the time of high-speed cornering. By increasing the nature,
An object of the present invention is to provide a pneumatic cart tire with improved steering stability.

[0005]

The pneumatic cart tire according to the present invention is extended toroidally between the bead cores disposed on the respective bead portions so that the side portions are radially outward around the bead cores. A carcass comprising two or more carcass plies, and a tread rubber disposed on an outer peripheral side of a crown portion of the carcass, and a side portion of at least one carcass ply is wound around a bead core in a tire width direction. Turn the carcass ply ply cord from the inside to the outside,
It is formed by an organic fiber cord having an elongation at a constant load of 7% or less while extending at an angle in the range of 5 °, and the tread rubber has a JIS A hardness at room temperature of 20 to 70 degrees. And the tire is mounted on the applicable rim,
The maximum width of the tire under no load filled with the air pressure in the range of 120 (KPa) is assumed to be SW, and the contact width when the load of 1100 (N) is applied, and the 50% point position of the contact half width from the tire equator. The average value of the radius of curvature of the outer contour of the tread surface when there is no load in the meridian cross section of the tire in the range of 70% or more in the region up to and including TRc1 and the position at 50% of the halfway width of the ground from the tire equator. When the average value of the radius of curvature of the outer contour at the time of no load in a range of 70% or more in the region between the point and the 90% point position is TRc2, TRc1 = 50 to 600 (mm), and TRc1 / SW
= 0.35 to 3.50 TRc2 = 30 to 200 (mm) and TRc2 / SW
= 0.20 to 1.20. Here, the “applicable rim” is CIK (COMMISSION INTERNATIONALE DE KAR
TING), and the elongation under a constant load is determined by the chemical fiber tire cord test method of JIS-L1017, and the average value TRc1 of the outer contour radius of curvature and T
When a plurality of radii of curvature exist in the region, Rc2 divides the region into n (n ≧ 20) regions at equal intervals, and TRi = 1, 2, 3,... n TRc1 = (TR ₁ + TR ₂ + TR ₃ +... + T
R _n ) / n TRc2 = (TR ₁ + TR ₂ + TR ₃ +... + T
R _n ) / n.

In this pneumatic cart tire, the ply cord of the carcass ply has an elongation of 7% under a constant load.
By using the following organic fiber cord, it is possible to prevent the tire weight from excessively increasing, etc., to secure the minimum necessary tire case rigidity, and to reduce the JIS A hardness of the tread rubber at normal temperature. By setting the angle to 20 to 70 degrees, both the heat resistance and durability of the tread portion and the grip property of the tread tread surface can be favorably exhibited.

In a pneumatic tire for a racing cart in which the maximum values of the tire width and the outer diameter are restricted in advance by the racing regulation, TRc1 is set to 50 (mm) in order to provide a preferable tread tread contact shape. By setting TRc2 to 30 (mm) or more and securing a minimum necessary outer contour radius of curvature for obtaining a required ground contact surface shape, and obtaining a good outer contour shape of the tread tread surface, As a result, the steering stability can be improved.

On the other hand, by setting TRc1 to 600 (mm) or less and TRc2 to 200 (mm) or less,
It is possible to prevent a sharp decrease in the steering stability when the grip limit is exceeded, which is caused by the tension of the tire contact end portion during high-speed cornering.

The load for defining the half width of the ground is 1
100 (N) is because the maximum load applied to one wheel during cornering is 1100 (N), and when defining TRc1 and TRc2, the outer contour radius of curvature in each of the above regions. The reason why the present invention has no TRc1 or TRc2 in a region of 70% or more is that the existence range of the region is 70% or more in the region means that it covers most of the region. Is thin.

[0010] In addition, the outer contour of the tread tread, so-called flatness, is subject to the constraint that the tire width and the outer diameter of the pneumatic tire for a racing cart do not exceed the maximum width determined by the racing regulation. The relationship TRc1 / SW between the shape radius of curvature and the tire maximum width is set to 0.
By setting the TRc2 / SW at 35 or more and TRc2 / SW at 0.20 or more to obtain a good outer contour shape of the tread tread, respectively, it is possible to improve the ground followability and, consequently, the steering stability. By setting the value to 3.50 or less and setting TRc2 / SW to 1.20 or less, good maneuvering can be achieved in the vicinity of the grip limit, that is, when the vehicle runs at the very limit of the grip force during cornering in a race. Stability can be obtained.

Thus, in the pneumatic cart tire, the handling stability can be improved by improving the following ability under the heavy load fluctuation occurring at the time of high-speed cornering.

More preferably, in such a pneumatic cart tire, TRc1, TRc2, and SW are set such that TRc1 = 50 to 300 (mm) and TRc1 / SW
= 0.35 to 2.36 TRc2 = 30 to 90 (mm) and TRc2 / SW =
0.20 to 0.70, and the maximum contact width of the tread on the tread contact surface when a load of k (N) (k = 200, 1100) is Wk,
The maximum tread contact length when a load of k (N) is applied is Lk, and {(W200 / L200)-(W1100 / L1100)} / (1100-20
0) = θ ₁ , the rate of change of the contact surface rectangular ratio, expressed as a ratio of the maximum contact width Wk to the maximum contact length Lk, relative to the total load θ ₁ , is θ
_{It is} assumed that ₁ ≦ 0.8 × 10 ⁻³ (N ⁻¹ ).

According to this, by setting TRc1 to 50 (mm) or more and TRc2 to 30 (mm) or more, as described above, it is possible to improve the ground followability and, consequently, the steering stability. , TRc1 is 300 (mm)
By setting TRc2 to 90 (mm) or less,
It is possible to more effectively prevent a sudden decrease in the steering stability when the grip limit is exceeded due to the tension of the tire contact end portion during high-speed cornering.

[0014] By setting TRc1 / SW to be 0.35 or more and TRc2 / SW to be 0.20 or more, as described above, it is possible to improve the ground followability and, consequently, the steering stability. Yes, on the other hand, TRc1 / SW
Is set to 2.36 or less, and TRc2 / SW is set to 0.70 or less, it is possible to obtain more excellent steering stability near the grip limit.

In addition, the rate of change of the ground contact surface rectangular ratio with respect to the total load θ
_By setting 1 to be within a predetermined range of 0.8 × 10 ⁻³ (N ⁻¹ ) or less, it is possible to further improve the contact with the ground and, consequently, the steering stability under a severe load variation that occurs during high-speed cornering. Can be.

More preferably, TRc1, TRc2, and SW are set as follows: TRc1 = 50 to 300 (mm), and TRc1 / SW
= 0.35 to 2.36 TRc2 = 30 to 90 (mm) and TRc2 / SW =
0.20 to 0.70, and k (N) (k = 200, 500, 110
{(W200 / L200) − (W500 / L500)} / (where, assuming the maximum tread width of the tread on the tread contact surface under load 0) as Wk and the maximum tread length under load of k (N) as Lk, 500−200) =
θ ₂ {(W500 / L500)-(W1100 / L1100)} / (1100-50
0) = when the theta _3, pairs load variation rate theta ₂ in the low load region of the ground plane rectangle ratio, theta
₂ ≦ 1.5 × 10 ⁻³ (N ^{− 1} ) The load variation rate θ ₃ in the high load area with the ground contact surface rectangular ratio is represented by θ
_{It is} assumed that ₃ ≦ 0.5 × 10 ⁻³ (N ^{− 1} ). According to this, it is possible to further improve the ground following ability in the low load area and the high load area, and furthermore, the steering stability.

Another cart pneumatic tire according to the present invention is toroidally extend between bead cores disposed on respective bead portions and wraps side portions radially outward around the bead cores. Also, a carcass comprising two or more carcass plies, and a tread rubber disposed on the outer peripheral side of the crown portion of the carcass, and at least one side portion of the carcass ply is provided around the bead core from the tire width direction inside. Turned outward, the ply cord of each carcass ply is extended at an angle in the range of 25 to 35 ° with respect to the tire equator, and is formed of an organic fiber cord having an elongation percentage under a constant load of 7% or less. The tread rubber has a JIS A hardness at room temperature of 20 to 70 degrees, and the tire is mounted on the applicable rim, and the tread rubber has a JIS A hardness of 80 to 120.
(KPa) is filled with air pressure, and a ground contact surface rectangular ratio expressed by a ratio of a maximum contact width to a maximum contact length of a tread contact surface in a state where a load of 500 (N) is applied,
0.5 to 1.6.

In this cart pneumatic tire, the load is reduced by 50 in consideration of a general load applied at the time of cornering.
By setting the rectangular ratio to 0.5 or more after setting to 0 (N), the maximum grip force at a large steering angle in cornering is secured, and by setting the rectangular ratio to 1.6 or less, an appropriate value at a small steering angle is obtained. The cornering power can be obtained.

Therefore, even with this pneumatic tire for carts, the steering stability can be improved by increasing the contactability with the ground under the severe load fluctuation that occurs during high-speed cornering.

Preferably, it is used as a front wheel of a racing cart vehicle. According to such a pneumatic tire for carts, in a situation where a heavy load fluctuation is applied between the braking before the cornering and the acceleration of the rising of the cornering, good steering for the steering operation for determining the traveling direction of the vehicle is provided. By using it as a front wheel tire that requires stability, the effect is particularly exhibited.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention in which a rim is assembled to an applied rim of a tire.
FIG. 2 is a cross-sectional view showing an unloaded state filled with an air pressure within a range of 80 to 120 (KPa), where 1 is a tread portion,
Reference numeral 2 denotes a sidewall portion extending inward in the radial direction so as to be connected to each side portion of the tread portion 1, and reference numeral 3 denotes a bead portion provided continuously on the inner peripheral side of the sidewall portion 2.

Here, two inner and outer carcass plies 5a, 5a, 5b are provided between the bead cores 4 arranged in the respective bead portions 3.
The carcass 5 composed of 5b is toroidally extended to reinforce the above 1, 2 and 3, and a tread rubber 6 is disposed on the outer peripheral side of the crown portion of the carcass 5.

The two carcass plies 5a, 5b
At least one of the two ends is folded from the inside to the outside in the tire width direction around the pair of bead cores 4 so that the respective ply cords extend in mutually opposite directions with respect to the tire equator CL. 25 for
Formed at a constant load elongation of 7% or less by an organic fiber cord.
The ISA hardness is 20 to 70 degrees.

Here, the tire is mounted on the applicable rim and filled with air pressure within the range of 80 to 120 (KPa), and the maximum width of the tire at no load is SW, and 1100 (N)
Of the tire equator C
The average value of the outer contour radius of curvature of the tread tread at no load in the tire meridian section in the range of 70% or more in the region from L to the 50% point position of the half-width TW / 2 is TRc1, 5 of halfway width TW / 2 from tire equator
TRc1 = 50-600 (mm), where TRc2 is the average value of the outer contour radius of curvature at the time of no load in a range of 70% or more in the region between the 0% point position and the 90% point position. And TRc1 / SW
= 0.35 to 3.50 TRc2 = 30 to 200 (mm) and TRc2 / SW
= 0.20 to 1.20.

Preferably, TRc1, TRc2 and SW are set as TRc1 = 50 to 300 (mm) and TRc1 / SW
= 0.35 to 2.36 TRc2 = 30 to 90 (mm) and TRc2 / SW =
0.20 to 0.70, and the maximum contact width of the tread when a load of k (N) (k = 200, 1100) is Wk, and the maximum contact length of the tread when a load of k (N) is applied is Lk. , {(W200 / L200)-(W1100 / L1100)} / (1100-20
0) = when the theta _1, a pair of load total variation rate theta ₁ of the ground plane rectangle ratio, theta
₁ ≦ 0.8 × 10 ⁻³ (N ⁻¹ ), and more preferably, the rate of change of load θ ₂ in the low-load region with the contact surface rectangular ratio is θ
₂ ≦ 1.5 × 10 ⁻³ (N ^{− 1} ) The load variation rate θ ₃ in the high load area with the ground contact surface rectangular ratio is represented by θ
₃ ≦ 0.5 × 10 ⁻³ (N ^{− 1} ), and preferably used as a front wheel of a racing cart vehicle.

[0026]

EXAMPLES Examples of the tires of Examples 1 and 2 and the comparative tire will be described below with respect to the lap time during high-speed cornering and the steering stability. The test tire size is 4.5 / 10.0-5, and the example tire 1 has the structure shown in FIG. 1 and has the dimensions shown in the upper part of Table 1. In addition, the example tire 2 and the conventional example tire have the dimensional specifications shown in the upper section of Table 1, respectively.

Here, each of the above three types of tires is used as a front tire of an FSA class machine (chassis: TONYKART, engine: VORTEX), and a circle of 12
The actual vehicle was driven on a circuit of 64.58 m, the lap time was measured, and the feeling evaluation by the test driver regarding the steering stability was performed in 10 levels from 0 to 10 points. Incidentally, in each example, the rear tire used had a tire size of 7.1 / 11.0-5.

As for the lap time, the smaller the value is, the better the result is.
The larger the value, the better the result. Table 1 shows the dimensions of the front tires and the results on lap time and steering stability.

[0029]

[Table 1]

According to the lower part of Table 1, the example tire 2
Compared to the conventional tire, both the lap time and the steering stability are excellent, and the tire 1 of the example is more excellent in both the lap time and the steering stability than the conventional tire. It can be said that this is an optimal example. Regarding the steering stability, Example Tire 2 has improved grip feeling and Example Tire 1 has improved grip feeling and steering wheel responsiveness as compared with the conventional tire. It is.

[0031]

As described above, according to the present invention, by optimizing the outer contour of the tread surface in the tire meridian cross section of the pneumatic tire for a cart, it is possible to reduce the severe load fluctuation occurring at the time of high-speed cornering. It is possible to improve the following contact property under the ground, and as a result, it is possible to improve the steering stability.

[Brief description of the drawings]

FIG. 1 is a transverse sectional view showing an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Bead core 5 Carcass 5a, 5b Carcass ply 6 Tread rubber CL Tire equator SW Tire maximum width TW Tread contact width TRc1 Within the area from the tire equator to 50% of the contact half width. Average value of the radius of curvature of the outer contour of the tread surface when there is no load in the meridian section of the tire in the range of 70% or more.
Average value of the unloaded outer contour radius of curvature of the tread surface in the meridian section of the tire in the range of 70% or more in the area between the 0% point position

Claims (5)

[Claims] 1. A carcass comprising two or more carcass plies, which are toroidally extended between bead cores disposed on respective bead portions and have side portions wound radially outward around the bead cores. And a tread rubber disposed on an outer peripheral side of a crown portion of the carcass, and a side portion of at least one carcass ply is folded around the bead core from the inside in the tire width direction to the outside, and a ply cord of each carcass ply is formed. , 25-3 against the tire equator
The cart is made of an organic fiber cord having an elongation ratio of 7% or less under a constant load while extending at an angle in the range of 5 °, and the tread rubber has a JIS A hardness at room temperature of 20 to 70 degrees. In the pneumatic tire for use, the maximum width of the tire at no load when the tire is mounted on the applicable rim and filled with air pressure in the range of 80 to 120 (KPa) is S
W, the contact width when a load of 1100 (N) is applied, and 70% or more in the region from the tire equator to the position of 50% of the contact half width in the tire meridian cross section, The average value of the outer contour radius of curvature of the tread surface when no load is applied is TRc1, and in the range of 70% or more in the region between the 50% point position and the 90% point position of the halfway width from the tire equator, When the average value of the outer contour curvature radius at no load is TRc2, TRc1 = 50 to 600 (mm), and TRc1 / SW
= 0.35 to 3.50 TRc2 = 30 to 200 (mm) and TRc2 / SW
= 0.20 to 1.20 pneumatic tires for carts satisfying the relationship: 0.20 to 1.20. 2. The TRc1, TRc2, and SW
TRc1 = 50-300 (mm), and TRc1 / SW
= 0.35 to 2.36 TRc2 = 30 to 90 (mm) and TRc2 / SW =
0.20 to 0.70, and the maximum tread width of the tread on the tread contact surface when a load of k (N) (k = 200, 1100) is applied, and the maximum tread of the tread when a load of k (N) is applied Let the length be Lk, {(W200 / L200)-(W1100 / L1100)} / (1100-20
0) = θ ₁ , the total variation rate θ ₁ of the contact surface rectangular ratio expressed by the ratio of the maximum contact width Wk to the maximum contact length Lk with respect to the load θ ₁ ≦ 0.8 × 10
^The pneumatic tire for a cart according to claim 1, wherein the tire is ^-3 (N ^-1 ). 3. TRc1, TRc2, and SW are set as follows: TRc1 = 50 to 300 (mm), and TRc1 / SW
= 0.35 to 2.36 TRc2 = 30 to 90 (mm) and TRc2 / SW =
0.20 to 0.70, and the maximum tread width of the tread on the tread contact surface when a load of k (N) (k = 200, 500, 1100) is Wk, and the tread when a load of k (N) is applied Letting the maximum contact length be Lk, {(W200 / L200)-(W500 / L500)} / (500-200) =
θ ₂ {(W500 / L500)-(W1100 / L1100)} / (1100-50
0) = when the theta _3, pairs load variation rate theta ₂ in the low load region of the ground plane rectangle ratio, theta ₂
≦ 1.5 × 10 ⁻³ (N ⁻¹ ) The load variation rate θ ₃ in the high load area with the contact surface rectangular ratio is represented by θ ₃
3. The pneumatic tire for a cart according to claim 2, wherein ≦ 0.5 × 10 ⁻³ (N ⁻¹ ). 4. A carcass comprising two or more carcass plies, which are toroidally extended between bead cores disposed on respective bead portions and have side portions wrapped around a bead core in a radially outward direction. And a tread rubber disposed on an outer peripheral side of a crown portion of the carcass, and a side portion of at least one carcass ply is folded around the bead core from the inside in the tire width direction to the outside, and a ply cord of each carcass ply is formed. , 25-3 against the tire equator
The cart is made of an organic fiber cord having an elongation ratio of 7% or less under a constant load while extending at an angle in the range of 5 °, and the tread rubber has a JIS A hardness at room temperature of 20 to 70 degrees. In the pneumatic tire for use, the tire is mounted on the applicable rim, filled with air pressure in the range of 80 to 120 (KPa), and the maximum contact width of the tread contact surface when a load of 500 (N) is applied. The contact surface rectangular ratio expressed as a ratio with respect to the maximum contact length is 0.5 to 1.6.
Pneumatic tires for carts. 5. The pneumatic tire for a cart according to claim 1, which is used as a front wheel of a racing cart vehicle.