JPH0781305A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To restrict the vibration of a tire when a car is running by setting a ratio of a carcass oblateness to a tire oblateness into a range of a prescribed value and setting a ratio of carcass length to tire-specification-length into another range of a prescribed value together with making a case oblateness ratio greater than or equal to a value obtained by subtracting a prescribed value from a case length ratio multiplied by a prescribed number. CONSTITUTION:With regard to a carcass oblateness CF, which is a ratio between a carcass height CH and a carcass width, carcass length CL, a tire oblateness (TF), or ratio between cross sectional height of the tire TH and a design, cross sectional width of the tire, and tire specification length TL, a case oblateness ratio F, or a ratio of the carcass oblateness CF to the tire oblateness (TF), should be over than 0.89 and less than 1.00. In addition, a case length ratio L, or a ratio of the carcass length CL to the tire specification length TL, should be over 0.85 and less than 0.89. Meanwhile, the case oblateness ratio F and the case length ratio L should satisfy the following condition: F>=1.85L-0.71.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire in which radial force variation (hereinafter referred to as RFV), which is a vertical load fluctuation force generated when a tire rotates, is reduced to improve the uniformity of the tire.

[0002]

2. Description of the Related Art In the uniformity of tires, RFV is an important factor such as generation of vibration during running, and RFV tends to increase as running speed increases. Further, as the RFV increases, the vibration of the tire increases, which deteriorates steering stability and riding comfort.

[0003]

Therefore, in order to suppress the vibration of the tire during high speed running, it is a requirement that RFV is not increased even at high speed.

The inventors conducted extensive research and studies on the stabilization of the RFV, and as a result, the ratio of the length of the carcass and the flatness ratio of the carcass to the design contour shape of the tire base is an important factor. I was able to know that

According to the present invention, RFV can be stabilized by controlling the flatness of the carcass and the carcass length within a certain range as a ratio to the basic design dimension of the tire design, and the generation of vibration during running can be suppressed. However, the purpose of the present invention is to provide a pneumatic tire that can improve driving stability and riding comfort.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a folded-back portion that is folded back around the bead core is integrally formed in a main body portion that extends from a tread portion to sidewall inner portions of both sides of a bead portion to a tire radial inner end. A pneumatic tire defined by the JATMA standard, comprising a carcass provided and a belt layer arranged inside the tread portion and outside in the radial direction of the carcass, the tire being an unloaded tire mounted on a standard rim and filled with a normal internal pressure. Carcass height (mm) CH which is the height from the bead baseline of this tire to the maximum height point at the midpoint of the thickness of the carcass body in the meridional section in the radial direction.
And the carcass flatness ratio CF (= CH / CW) which is the ratio of the carcass width (mm) CW which is the maximum width in the tire axial direction at the midpoint of the thickness of the carcass body part, and the carcass body part Carcass length CL, which is the length of the body along the midpoint of the thickness of the tire, and JAT for this tire
The tire cross-section height (mm) TH obtained by subtracting the rim diameter mm (RO) obtained by multiplying the nominal rim diameter by 25.4 from the outer diameter (design dimension mm) TO specified by MA and dividing by 2 and the tire cross-section width ( Tire flatness ratio TF (= TH / which is the ratio with design dimension mm) TW
TW), and a tire standard length T obtained by adding the tire cross-section width (mm) TW to twice the tire cross-section height (mm) TH
In L, the case aspect ratio F (= CF / TF), which is the ratio of the carcass aspect ratio CF to the tire aspect ratio TF, is 0.89 or more and 1.00 or less, and the tire standard length T
Case length ratio L, which is the ratio of carcass length CL to L
(= CL / TL) is 0.85 or more and 0.89 or less, and the case flatness ratio F and the case length ratio L satisfy the following relational expressions.

[0007] The JATMA standard is considered by the Japan Automobile Tire Manufacturers Association by a committee consisting of experts from industry, neutral organizations, and users, and is based on JIS, while maintaining conformity with ISO. It is specified in detail. In addition, new settings and revisions are being made one after another while reflecting the world situation.

Therefore, the JATMA standard referred to in the present application includes the current tire standard established by the above-mentioned association, and further the tire standard established in the future by the association. See J
It includes all JIS standards, ISO standards, and foreign standards that are compatible with the ATMA standard.

Regarding the radial ply tires for passenger cars 65 series (1993) specified in JATMA,
Some of them are shown in Table 1.

[0010]

[Table 1]

Here, the design dimension is a dimension that serves as a reference for tire design, and the growth dimension is a dimension that includes dynamic growth as the tire runs. Further, the new dimension is a measurement of a new tire according to a predetermined method, and this dimension includes a design tolerance and a manufacturing tolerance.

Further, the standard rim means a standard rim mounted on the tire of each model and size, and the tire section width TW means the no-load in which the standard rim is attached to the standard rim and filled with a normal internal pressure. In the state, it refers to the width obtained by removing the above-mentioned patterns and characters from the total width of the tire, which is the tire width including the patterns or characters on the tire side.

[0013]

The action force of the RFV increases as the tire speed increases. For a plurality of tires of the same construction in the 65 series passenger car radial ply tires shown in Table 1, the RFV primary value (GL) at low speed (20 km / H) and the RFV primary value (GH) at high speed (120 km / H) And the ratio of GH: G
I asked for L.

At the time of measurement, the air pressure was 2.0 kg / cm ² , the load and the rim used were high speed uniformity machines and the uniformity measurement method defined in JASO C607 was applied. For example, if the tire size is 205
For a / 65R tire, the load is 468 kgf.
An example of the measurement result is shown in FIG.

Based on the measurement results of FIG. 3, a regression line having a correlation between the two is obtained by using the method of least squares, and the slope GH: GL of this line is defined as the RFV velocity increase rate α.

As the rate of increase in RFV due to the increase in traveling speed, that is, the smaller the value of the RFV speed increase rate α, the smaller the RFV, the less the occurrence of vibration.

Further, regarding the 205 / 65R15 which is the 65 series passenger car radial tire, as shown in Table 2 and FIG. 4, the relationship between the composition ratio and the RFV speed increase rate α is shown for a plurality of types of tires having different composition dimensions. investigated. As a result, it has been found that the RFV speed increase rate α is largely related to the carcass length CL and the carcass flatness ratio CF in the tire axial cross section of the carcass, whereby the carcass length CL and the carcass flatness ratio are calculated. It was confirmed that it is possible to reduce the RFV speed increase rate by limiting the RFV speed to a certain range.

Furthermore, in order to apply the carcass length CL and the carcass flatness factor CF to not only the tire size 205 / 65R15 but also the 65 series passenger car radial tires, and further to the passenger car radial tires defined by JATMA, the tires are It is better to regulate the ratio with the design dimension which is the basic dimension.

In the present invention, the basic size and size ratio of the tire are defined as follows. Tire cross-section height (design dimension) TO = {outer diameter (design dimension)
TO- (nominal diameter of rim) × 25.4} / 2 Tire flatness TF = (tire section height TO) / (tire section width TH) Tire standard length TL = (tire section height TO) × 2 +
(Tire cross-section width TH) These tire cross-section height TO, tire flatness TF, and tire standard length TL are basic values for regulation. Each of these values is independent of the size of the carcass. In the tire of, it becomes a constant.

On the other hand, the size of the carcass in the formed tire is defined as follows. The measurement of the dimensions is carried out in a non-loaded state when the tire is attached to the standard rim J and filled with the normal internal pressure.

Carcass height CH = the height from the bead baseline of the tire in the tire meridian to the maximum height at the midpoint of the carcass thickness in the radial direction of the tire Carcass width CW = the maximum at the midpoint of the carcass The carcass flatness ratio CF = (carcass height CH) / (carcass width CW), and the carcass length CL = the tire of the main body along the midpoint of the thickness of the main body of the carcass. Length in meridional section These figures are the fluctuation values subject to regulation.

Here, the case flatness ratio F (= CF / T) which is the ratio of the carcass flatness ratio CF to the tire flatness ratio TF.
F) is 0.89 or more and 1.00 or less. When the case flatness ratio F is less than 0.89, the cross-sectional thickness of the tread portion 2 becomes too thick and the tire weight increases, while 1.00
If it exceeds, the cross-sectional thickness of the tread portion 2 becomes thin and the durability is impaired. The carcass length C relative to the tire standard length TL
The case length ratio L (= CL / TL), which is the ratio of L, is 0.8
It is set to 5 or more and 0.89 or less.

In addition, the case flatness ratio F and the carcass length ratio L must satisfy the relationship of the following expression (1). F ≧ 1.85L−0.71 (1) Here, in the case of F = 1.85L−0.71, the above-mentioned RF
V speed increase rate α is 1.4 and F ≧ 1.85L-0.7
In No. 1, the RFV speed increase rate α is 1.4 or less.
That is, by satisfying the expression (1), the RFV speed increase rate α becomes 1.4 or less, the increase of RFV is small even at the high speed, and the vibration of the tire can be suppressed, so that the basic size of the tire is not changed. Driving stability and riding comfort can be improved.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 and 2, a pneumatic tire 1 includes a tread portion 2, a pair of sidewall portions 3 and 3 extending inward in the tire radial direction from both sides thereof, and a bead portion 4 extending inward of the sidewall portion 3. Have.

Further, in the pneumatic tire 1, the bead core 5 of the bead portion 4 extends from the tread portion 2 to the sidewall portion 3.
A carcass 6 having a folded-back portion 6b that is folded back around the bead core 5 from the inner side in the tire axial direction toward the outer side on the main body portion 6a reaching the inner end 5a in the tire radial direction, and the tread portion 2 outside the carcass 6 Belt layer 7 arranged inward
In this embodiment, a bead apex 8 is provided which rises from the radially outward surface of the bead core 5 between the main body portion 6a of the carcass 6 and the folded-back portion 6b.

In the present example, the carcass 6 is made of one carcass ply, and the carcass ply has a carcass cord made of organic fibers such as nylon, polyester, rayon, and aromatic polyamide at 75 to the tire equator C.
The carcass ply is formed as a sheet body by forming a radial or semi-radial arrangement in which the carcass plies are inclined and arranged side by side at an angle of 90 °.

The belt layer 7 is composed of two belt plies 7A and 7B in this example, and each of the belt plies 7A and 7B is
Belt cords made of organic fibers such as nylon, polyester, rayon, aromatic polyamide or steel are inclined at an angle of 10 to 70 ° with respect to the tire equator C, and are arranged in a direction intersecting with each other between the belt plies 7A and 7B. It

In this embodiment, the belt width WB is formed in the range of 0.8 to 1.1 times the tread width WT.
If it is less than 0.8 times, the rigidity of the shoulder region of the tread portion 2 will be insufficient, while if it exceeds 1.1 times, the rubber thickness at the buttress portion 3a of the shoulder portion 3 will be small and there is a risk of damage. .

The carcass height CH and the carcass width CW
Also, the carcass length CL is measured with the rim assembled to a measuring rim having the same basic dimensions as the standard rim J, filled with the normal internal pressure, and with the midpoint m of the carcass thickness t as a reference. Further, in FIG. 2, the reference numerals in parentheses indicate the design dimensions.

[0030]

[Specific example] JAT with tire size 205 / 65R15
Regarding the tires conforming to the MA standard and having the configurations shown in FIGS. 1 and 2, the tires (Examples 1 to 3) having the dimensions shown in Table 2 were experimentally manufactured and their RF
The V speed increase rate α was investigated. Note that tires (Comparative Examples 1 to 4) having a configuration other than that of the present application were also investigated and their performances were compared.

The test results are shown in Table 2, and a diagram showing the relationship between the carcass flatness ratio and the carcass length ratio L is shown in FIG.

[0032]

[Table 2]

Incidentally, FIG. 4 also shows contour lines showing the same points of the RFV velocity fluctuation rate α. As a result of the test, the RFV velocity fluctuation rate α of the example was 1.4 or less, and it was confirmed that the RFV could be suppressed by the regulation of the case length ratio L and the case flatness ratio F described above.

[0034]

As described above, the pneumatic tire of the present invention is
As described above, since the carcass flatness ratio and the carcass length ratio with respect to the design size of the tire are regulated, the RFV can be reduced without changing the basic size of the tire, the uniformity of the tire can be enhanced, and the steering stability and the riding comfort can be improved. Moreover, since all of the above regulation values are established on the basis of the tire design dimensions, it is possible to easily and promptly take RFV measures for existing tires.

[Brief description of drawings]

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

FIG. 2 is a sectional view showing its basic dimensions.

FIG. 3 is a graph showing an example of determining an RFV speed increase rate.

FIG. 4 is a graph showing measured values in relation to a carcass length ratio and a carcass flatness ratio.

[Explanation of symbols] 2 tread portion 3 sidewall portion 4 bead portion 5 bead core 5a inner end 6 carcass 6a main body portion 6b folded portion 7 belt layer CF carcass flatness ratio CH carcass height CL carcass length CW carcass width F case flatness ratio Ratio J Standard rim L Case length ratio RO Rim diameter TF Tire flatness TH Tire sectional height TL Tire standard length TO Outer diameter TW Tire sectional width X Bead baseline m Intermediate point t Thickness α RFV Speed increase rate

Claims (1)

[Claims] 1. A carcass integrally provided with a turn-back portion that turns back around the bead core in a main body portion from a tread portion to sidewall end portions on both sides to a tire radial inner end of a bead core of the bead portion, and a tread portion. A pneumatic tire defined by the JATMA standard, which comprises a belt layer disposed inside and on the outer side in the radial direction of the carcass, wherein a bead base of this tire in a meridional section of an unloaded tire mounted on a standard rim and filled with a normal internal pressure. The carcass height (mm) CH, which is the height from the line to the maximum height point at the carcass body thickness midpoint, and the maximum tire axis at the carcass body thickness midpoint Carcass flatness C, which is the ratio to the carcass width (mm) CW, which is the width in the direction
F (= CH / CW), and a carcass length CL that is the length of the main body along the midpoint of the thickness of the main body of the carcass, and the outer diameter (design dimension mm) specified by JATMA for this tire. A tire that is the ratio of the tire section height (mm) TH obtained by subtracting the rim diameter mm (RO), which is obtained by multiplying the nominal rim diameter by 25.4 from TO, and the tire section width (mm) TW. The flatness ratio TF (= TH / TW) and the tire standard length TL obtained by adding the tire cross-section width (mm) TW to twice the tire cross-section height (mm) TH, the carcass flatness ratio with respect to the tire flatness ratio TF The case flatness ratio F (= CF / TF), which is the ratio of CF, is 0.89 or more and 1.00 or less, and the case length ratio L (= CL is the ratio of the carcass length CL to the tire standard length TL). / T
L) is 0.85 or more and 0.89 or less, and the case flatness ratio F and the case length ratio L satisfy the following relational expression. F ≧ 1.85L−0.71