JP2804223B2 - Pneumatic tire - Google Patents

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 the tire rotates, is reduced to increase the uniformity of the tire.

[0002]

2. Description of the Related Art In uniformity of a tire, RFV is an important factor such as generation of vibration during running, and this RFV tends to increase as running speed increases. In addition, the vibration of the tire increases with the increase of the RFV, and the steering stability and the riding comfort decrease.

[0003]

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

As a result of repeated investigations and studies on the stabilization of the RFV, the inventors have found that the ratio of the length of the carcass and the ratio of the flatness of the carcass to the design contour of the tire base are important factors. I knew that

The present invention can stabilize the RFV and suppress the generation of vibration during traveling by regulating the flatness ratio and the carcass length of the carcass in a certain range as a ratio to the basic contour dimension of the tire. The aim is to provide a pneumatic tire that can enhance steering stability and ride comfort.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a folded portion for turning around the bead core is integrally formed on a main body portion extending from the tread portion through the sidewall portions on both sides to the radially inner end of the bead core of the bead portion. A pneumatic tire provided with a provided carcass and a belt layer disposed inside a tread portion and radially outside of the carcass and specified by the JATMA standard, wherein the tire is mounted on a standard rim and filled with a normal internal pressure and has no load. Carcass height (mm) CH which is the height from the bead baseline of this tire in the meridional section to the maximum height point at the midpoint of the thickness of the carcass body in the radial direction.
And the carcass flatness 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, and the carcass body Carcass length CL, which is the length of the body along the midpoint of the thickness of the tire, and JAT
The tire section height (mm) TH, which is obtained by subtracting the rim diameter mm (RO) obtained by multiplying the nominal diameter of the rim by 25.4 from the outer diameter (design dimension mm) TO specified by MA and dividing by 2, and the tire section width (mm) Tire flatness ratio TF (= TH /
TW) and the tire standard length T obtained by adding the tire cross-sectional width (mm) TW to twice the tire cross-sectional height (mm) TH.
L, the case flatness ratio F (= CF / TF), which is the ratio of the carcass flatness ratio CF to the tire flatness 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 expression.

Here, the JATMA standard is defined by the Japan Automobile Tire Association, which is examined by a committee composed of experts from the industry, neutral organizations, and users. It is specified in detail. New settings and revisions are being made successively while reflecting the world situation.

Accordingly, the JATMA standard referred to in the present application includes the current tire standard established by the association and the tire standard established by the association in the future. Also J
Includes all JIS standards, ISO standards, and other foreign standards that are compatible with ATMA standards.

Regarding the radial ply tire 65 series (1993) for passenger cars specified in JATMA,
Table 1 shows some of them.

[0010]

[Table 1]

Here, the design dimension is a dimension that is a reference for tire design, and the growth dimension is a dimension including dynamic growth accompanying running of the tire. Further, the new dimension is measured by a predetermined method for a new tire, and this dimension includes a design tolerance and a manufacturing tolerance.

Further, the standard rim means a standard rim attached to the tire of each type and size, and the tire cross-sectional width TW means a no-load tire mounted on the standard rim and filled with a normal internal pressure. In the state, it refers to the width of the tire width including the pattern or characters on the side of the tire, excluding the pattern, characters, and the like from the total width of the tire.

[0013]

The acting force of the RFV increases as the tire speed increases. For a plurality of tires having the same configuration in the 65 series passenger car radial ply tires shown in Table 1, the first order RFV value (GL) at low speed (20 km / H) and the first order RFV value (GH) at high speed (120 km / H) And the respective ratios GH: G
L was determined.

At the time of measurement, the air pressure was 2.0 kg / cm ² , the load and the rim used were measured using a high-speed uniformity machine and in accordance with the uniformity measurement method specified in JASO C607. For example, if the tire size is 205
For a / 65R tire, the load is 468 kgf.
FIG. 3 shows an example of the measurement result.

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

As the running speed increases, the rate at which the RFV increases, that is, the value of the RFV speed increasing rate α decreases, the RFV decreases, and the occurrence of vibration decreases.

Further, as to the radial tires of the 65 series, ie, 205 / 65R15, the relationship between the composition ratio and the RFV speed increase rate α as shown in Table 2 and FIG. investigated. As a result, the RFV speed increase rate α was found to be largely related to the carcass length CL and the carcass flatness CF in the cross section of the carcass in the tire axial direction, whereby the carcass length CL and the carcass flatness were compared. It has been confirmed that by restricting to a certain range, the rate of increase of the RFV speed can be reduced.

Further, in order to apply the carcass length CL and the carcass flattening factor CF not only to the tire size 205 / 65R15 but also to the 65 series passenger car radial tires, and further to the general radial tires for passenger cars specified in JATMA, It is preferable to regulate the ratio based on a design dimension which is a basic dimension.

In the present invention, the basic dimensions and dimensional ratio of the tire are defined as follows. Tire section height (design dimensions) TO = ｛outer diameter (design dimensions)
TO− (nominal diameter of rim) × 25.4． / 2 Tire flatness TF = (tire cross-section height TO) / (tire cross-section width TH) Tire standard length TL = (tire cross-section height TO) × 2 +
(Tire section width TH) The tire section height TO, the tire flatness factor TF, and the tire standard length TL are basic values for regulation, and these values are independent of the structure of the carcass and their respective sizes. Is a constant for the tire of.

On the other hand, the dimensions of the carcass in the formed tire are defined as follows. The measurement of the dimensions is performed in a no-load state when the tire is mounted on the standard rim J and filled with the normal internal pressure.

Carcass height CH = the height from the tire bead baseline to the maximum height at the midpoint of the carcass thickness in the tire radial direction in the tire meridian section Carcass width CW = maximum at the midpoint of the carcass Carcass flatness CF = (carcass height CH) / (carcass width CW) and carcass length CL = the tire of the main body along the midpoint of the thickness of the main body of the carcass Length in the meridional section These values 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.
Exceeding the thickness will reduce the cross-sectional thickness of the tread portion 2 and impair durability. Carcass length C against tire standard length TL
The case length ratio L (= CL / TL), which is the ratio of L, is 0.8
5 or more and 0.89 or less.

In addition, the case flatness ratio F and the carcass length ratio L must satisfy the following equation (1). F ≧ 1.85L−0.71 (1) Here, when F = 1.85L−0.71, the aforementioned RF
V speed increase rate α is 1.4 and F ≧ 1.85L−0.7
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 RFV increase is small even at a high speed, the occurrence of tire vibration can be suppressed, and therefore, the basic dimensions of the tire are not changed. Steering stability and ride comfort can be improved.

[0024]

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, 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.

The pneumatic tire 1 has a bead core 5 of a bead portion 4 extending from a tread portion 2 to a sidewall portion 3.
A carcass 6 having a folded portion 6b which is turned around the bead core 5 from the inside to the outside in the tire axial direction on a body portion 6a reaching the radial inner end 5a of the carcass 6, and the tread portion 2 outside the carcass 6 Belt layer 7 arranged inside
In this embodiment, a bead apex 8 is provided which rises from the radially outward surface of the bead core 5 to a position between the main body portion 6a of the carcass 6 and the folded portion 6b.

In the present embodiment, the carcass 6 is made of one carcass ply. The carcass ply is made of a carcass cord made of an organic fiber such as nylon, polyester, rayon, aromatic polyamide or the like.
Radial or semi-radial arrangements are arranged side by side at an angle of 90 °, and the carcass ply is formed as a sheet by topping the carcass cord.

In this embodiment, the belt layer 7 includes two belt plies 7A and 7B, and each of the belt plies 7A and 7B
Belt cords made of organic fibers such as nylon, polyester, rayon, and aromatic polyamide or steel are inclined at an angle of 10 to 70 ° with respect to the tire equator C, and are arranged so as to cross each other between the belt plies 7A and 7B. You.

In the present embodiment, the belt width WB is formed to be 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 is insufficient, while if it exceeds 1.1 times, the rubber thickness in the buttress portion 3a of the shoulder portion 3 becomes small and there is a risk of breakage. .

The carcass height CH, carcass width CW
The measurement of the carcass length CL is performed by assembling the rim into a measuring rim having the same basic dimensions as the standard rim J, filling the normal internal pressure, and using the midpoint m of the carcass thickness t as a reference. In FIG. 2, reference numerals with parentheses indicate those indicated by design dimensions.

[0030]

[Specific example] JAT with a tire size of 205 / 65R15
Tires having dimensions shown in Table 2 (Examples 1 to 3) were manufactured as prototype tires having the configuration shown in FIGS.
The V speed increase rate α was investigated. In addition, the tires (comparative examples 1 to 4) outside the configuration of the present application were also investigated and their performances were compared.

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

[0032]

[Table 2]

FIG. 4 also shows contour lines indicating the isotopes of the RFV speed fluctuation rate α. As a result of the test, it was confirmed that the example had an RFV speed fluctuation rate α of 1.4 or less, and 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 has the following features.
As described above, since the carcass flatness ratio and the carcass length ratio with respect to the design dimensions of the tire are regulated, the RFV can be reduced without changing the basic dimensions of the tire, the uniformity of the tire can be increased, and the steering stability and riding comfort can be improved. Moreover, since all of the regulation values are set based on the design dimensions of the tire, RFV measures can be easily and quickly taken for existing tires.

[Brief description of the 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 part 3 Side wall part 4 Bead part 5 Bead core 5a Inner end 6 Carcass 6a Main body part 6b Turnback part 7 Belt layer CF Carcass flattening ratio CH Carcass height CL Carcass length CW Carcass width F Case flattening ratio J Standard rim L Case Length Ratio RO Rim Diameter TF Tire Flatness TH Tire Section Height TL Tire Standard Length TO Outer Diameter TW Tire Section Width X Bead Baseline m Intermediate Point t Thickness α RFV Speed Increase Rate

Continuation of front page (56) References JP-A-6-48108 (JP, A) JP-A-3-204313 (JP, A) JP-A-2-225102 (JP, A) JP-A-1-160404 (JP) JP-A-3-169709 (JP, A) JP-A-51-39803 (JP, A) JP-A-4-215502 (JP, A) JP-A-57-182501 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) B60C 9/00-9/26

Claims (1)

(57) [Claims] 1. A carcass having a body portion integrally provided with a folded portion which turns around the bead core from a tread portion through a sidewall portion on both sides to a tire radial inner end of a bead core of the bead portion; A pneumatic tire defined by the JATMA standard having a belt layer disposed inside and radially outside of the carcass, wherein the tire has a bead base in a meridional section of a tire mounted on a standard rim and filled with a normal internal pressure and having no load. The carcass height (mm) CH, which is the height from the line to the maximum height point at the midpoint of the thickness of the carcass body in the radial direction, and the largest tire axis at the midpoint of the carcass body thickness Carcass flatness ratio C, which is the ratio to the carcass width (mm) CW, which is the width in the direction
F (= CH / CW), the carcass length CL which is the length of the main body along the thickness midpoint of the main body of the carcass, and the outer diameter (design dimension mm) defined by JATMA for this tire. The tire is the ratio of the tire section height (mm) TH obtained by subtracting the rim diameter mm (RO) obtained by multiplying the nominal diameter of the rim by 25.4 from TO and dividing by 2, and the tire section width (design dimension mm) TW. The flatness ratio TF (= TH / TW) and the carcass flatness ratio with respect to the tire flatness ratio TF at a tire standard length TL obtained by adding the tire cross-sectional width (mm) TW to twice the tire cross-sectional height (mm) TH A case flatness ratio F (= CF / TF) which is a ratio of CF is 0.89 or more and 1.00 or less, and a case length ratio L (= CL) which is a ratio of the carcass length CL to the tire standard length TL. / T
L) is not less than 0.85 and not more than 0.89, and the case flatness ratio F and the case length ratio L satisfy the following relational expression. F ≧ 1.85L−0.71