JP2994989B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention can reduce the passing noise,
The present invention also relates to a pneumatic tire capable of improving hydroplaning performance.

[0002]

2. Description of the Related Art In recent years, global environmental issues and safety issues have become important issues. Items related to pneumatic tires for passenger cars include reducing passing noise,
And improving hydroplaning performance, which is various performances when traveling on a water film.

[0003] Generally, the passing noise has a close relationship with the contact shape of the tire on the road surface during running, and this is shown in the graph of FIG. In this graph, the vertical axis represents the passing noise level dB (A), and the horizontal axis represents the contact width (mm) at which the tread contacts the road surface. As is clear from this graph, the noise level of the passing noise is reduced. To do so, it is better to reduce the contact width.

[0004] The hydroplaning performance during cornering of a vehicle is closely related to the ratio of the contact length to the contact width (contact length / contact width) in the tread contact shape, and this relationship is shown. This is the graph of FIG. As is clear from this graph, it can be understood that the lateral hydroplaning performance (index) is superior as the contact length is larger and the contact width is smaller.

[0005] In summary, in order to reduce the passing noise and improve the hydroplaning performance of the pneumatic tire, it is preferable to reduce the tread contact width and increase the tread length.

Conventionally, such a tire has a ratio (SH / SW) between the tire maximum sectional width SW and the tire maximum height SH.
Can be embodied only by performing high flattening to increase the flattening rate, which is a percentage of about 70% to about 80%, in a super flat tire for a passenger car or the like in which the flattening rate is less than 50%, for example. It was considered impossible.

[0007]

However, in the pneumatic tire highly flattened as described above, the lateral rigidity of the tire is reduced due to the relatively large size of the sidewall portion, which is the sidewall portion of the tire. Needless to say, especially when the cornering speed of the vehicle is low,
Another problem arises: poor handling stability.

The inventor of the present invention has solved the above problem by realizing that the passing noise and the hydroplaning performance can be made compatible and the cornering limit can be increased by a method completely different from the conventional method of flattening. I did my best research.

First, in the case of a conventional tire including a highly flat tire, as shown in FIG. 23, an outer portion a of the tire t is strongly pressed against a road surface by a lateral force acting at the time of cornering, but the inner portion of the tire t The portion b tends to rise from the road surface, and it has been found that the change in the contact shape of the tire, that is, the change in the footprint is significantly large based on such a phenomenon.

FIG. 24 (A) shows the results of footprint measurement of such a conventional tire, in which the state at a slip angle of 0 ° is shown by a solid line, and the state at a slip angle of 4 ° is shown by a broken line. I have.

As is apparent from this figure, the conventional tires have undergone a completely different shape change, for example, from a horizontally long rectangular shape when traveling straight, to a triangular shape given a slip angle. Can be confirmed. In general,
After the footprint becomes such a triangular shape,
The tires can no longer support the lateral force from the road, reaching the cornering limit and losing road grip.

In addition, in the conventional tire, when the slip angle increases, the distribution of the footprint with respect to the tire equator c is significantly different between the left and right. This means that in the contact area of the tire at the time of cornering, the distribution of the frictional force is biased to one side with respect to the tire equator c, and the frictional force generated between the tire and the road surface is effectively used. Is not at all remarkable.

At the time of cornering, a load variation occurs in each tire of the vehicle due to centrifugal force, and the applied load increases on the tires outside the cornering. Here, the present inventor measured a change in footprint due to an increase in the load of the highly flat tire, and obtained the results shown in FIG. As is clear from the figure, it has been found that the contact width of the conventional tire hardly changes even when the load increases, and that the conventional tire undergoes non-similar deformation in which only the contact length increases.

Generally, at the time of cornering, the tire is required to increase the grip force in the lateral direction. Therefore, in the above-described change in the shape of the footprint, the effect of increasing the limit of the cornering can hardly be expected. .

According to the present inventors, in order to solve the above-mentioned problems based on the above research results, the tire must firstly have a small contact width when traveling straight, and secondly, have a footprint even when a slip angle occurs. Of the shape of the tread is small, and thirdly, when the load acting on the tire increases, the footprint must have a substantially similar expansion change. It has been found that it is better to define the cross-sectional shape of the tire and thus the shape of the tire outer surface.

The tire outer surface shape is such that the radius of curvature RC of the tire outer surface is substantially equal to the tire maximum cross section from the tire equator point CP in the tire meridional section in a normal state where the tire is mounted on the wheel rim and filled with the normal internal pressure. Basically, gradually decrease to the width position,
And half the width of the tire's maximum cross-section from the equatorial plane C (SW
/ 2) was found to be embodied by restricting points on the outer surface of the tire at positions separated by 60%, 75%, 90% and 100% within a certain range, and completed the present invention. It was done.

That is, an object of the present invention is to provide a pneumatic tire which can achieve both passing noise and hydroplaning performance and can increase the limit at the time of cornering.

[0018]

According to the first aspect of the present invention, there is provided a carcass comprising a carcass ply which is locked by turning around a bead core of a bead portion from a tread portion through a sidewall portion, and a radius of the carcass in the tread portion. Pneumatic tire having a breaker disposed on the outer side in the direction, wherein the tire equatorial plane C in a tire meridional section in a normal state mounted on a wheel rim and filled with a normal internal pressure.
When a point on the outer surface of the tire, which is separated from the tire by a distance SP of 45% of the maximum sectional width (SW) of the tire, is P, the radius of curvature RC of the outer surface of the tire gradually increases from the tire equatorial point CP to the point P. And the tire equatorial plane C
From the half width (SW / 2) of the maximum cross-sectional width of the tire to 60
%, 75%, 90% and 100% distances X60, X75, X
The radial distance between each point on the tire outer surface separating 90 and X100 from the tire equatorial point CP is represented by Y60 and Y60, respectively.
75, Y90 and Y100, and SH as the tire section height, 0.05 <Y60 / SH≤0.1 0.1 <Y75 / SH≤0.2 0.2 <Y90 / SH≤0. 4 0.4 <Y100 / SH ≦ 0.7.

As means for gradually reducing the radius of curvature RC of the tire outer surface from the tire equator to the point P, the tire equatorial surface C
The radius of curvature RC at a distance x in the tire axis direction from
The following equation (1) RC = 1 / (C · e ^Bx + A · x) (1) (where e is the base of natural logarithm and e ^Bx is an exponential function,
A, B, and C are constants).

Further, as in the third aspect of the present invention, the outer surface of the tire covers a range from the tire equatorial plane C to the point P,
Five or more arcs having different radii of curvature may be continuously formed, and each of the radii of curvature may be reduced from the tire equator side to the tire axial direction outer side.

Further, in the invention according to claim 4, the breaker includes:
The maximum width BW in the tire axial direction is set to 0.85 to 1.0 times the maximum cross-sectional width (SW) of the tire. Contact width (CW), which is the axial distance between the outermost ends in the axial direction of the tire where the outer surface of the tire contacts the ground at 80% of the
Is set to 50% to 65% of the tire maximum sectional width (SW).

[0022]

According to the first aspect of the present invention, the curvature of the tire outer surface extends from the tire equator plane C to the tire maximum sectional width position in the normal tire meridional section mounted on the wheel rim and filled with the normal internal pressure. As the radius RC gradually decreases, 60%, 75%, 90%, and 1 of half the width (SW / 2) of the tire maximum sectional width from the tire equatorial point CP.
By defining the points on the outer surface of each tire that separate the distances X60, X75, X90 and X100 of 00% from the tire equator point CP at a certain radial distance, the passing noise and hydroplaning are as follows. Performance can be compatible, and the limit at the time of cornering can be raised.

That is, in FIG. 18A, the footprint at a slip angle of 0 ° is indicated by a solid line, and the footprint at a slip angle of 4 ° is indicated by a broken line. As is clear from these figures, the footprint has a vertically long elliptical shape whose major axis is the tire equator c, regardless of the slip angle. As a result, the contact width is small and the contact length is large. Passing noise can be reduced, and hydroplaning performance can be improved.

In addition, even when the slip angle changes, it can be confirmed that the vertically long elliptical shape can be maintained almost as it is, that is, the shape of the footprint does not change. This means that during cornering, the frictional force between the tire and the road surface in the tire contact area is reduced by the tire equator c.
It can be seen that a substantially uniform region on the left and right can be distributed over a wide range, and the cornering limit can be increased.

In FIG. 2B, the footprint when a load of 350 kgf is applied per tire is indicated by a solid line, and the footprint when the load of 550 kgf is applied is indicated by a broken line. As is apparent from this figure, it can be understood that the tire of the present invention has a similar enlarged deformation in which the footprint and the contact length both increase as the load increases as the load increases.

Generally, in the above-mentioned conventional high flat tire,
There is a place where the radius of curvature suddenly changes on the tire outer surface from the shoulder part of the tread to the sidewall part,
Therefore, it is considered that the change in the ground contact shape due to the slip angle was remarkably large, and the similar deformation occurred even when the load was increased.

On the other hand, in the tire according to the first aspect of the present invention, the radius of curvature of the outer surface of the tire can be gradually reduced from the tire equator to almost the maximum cross-sectional width of the tire. In addition, by providing a "potential contact area" on the tread that can contact only when the load increases, the footprint is similarly deformed, increasing the cornering limit and raising the handling stability to a remarkably high level It is sighing.

Such an operation and effect can be exerted regardless of the flatness of the tire. Particularly, when a super-flat tire having a flatness of 50% or less is used, the rigidity of the sidewall portion is increased. It is exhibited even more.

The radius of curvature RC of the tire outer surface can be continuously reduced by using an exponential function, for example, as in the second aspect of the present invention, or a constant area of the tire outer surface can be reduced, as in the third aspect of the present invention. It is possible to preferably adopt monotonically decreasing, for example, by dividing by combining arcs having five or more different radii of curvature and decreasing each of the radii of curvature from the tire equator side toward the tire axial direction outer side. . When connecting arcs with different radii of curvature,
More preferably, the arcs are smoothly joined by matching the tangents of the arcs at the arc joint.

In order to maintain the shape of the outer surface of the tire as described above, a breaker having a width that is 0.85 to 1.0 times the maximum sectional width (SW) of the tire is provided as in the invention of claim 4. Is preferably arranged radially outward of the carcass, and in particular, a highly rigid "tag effect" is given to the tread portion.

The contact width (CW), which is the axial distance between the outermost ends in the axial direction of the tire where the outer surface of the tire is in contact with the normal rim in a state of 80% of the normal load, is assembled on the normal rim. , 50% to 65% of the maximum section width (SW) of the tire
%, It is preferable that both the passing noise and the hydroplaning performance can be remarkably improved, and the potential contact area can be largely secured.

The potential contact area on the outer surface of the tire is as follows:
Although it differs depending on the running conditions, it is possible to secure the tire almost up to the vicinity of the maximum sectional width position.

[0033]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing the inner structure of the tire in the right half and the outline of the cross section of the tire in the left half. The pneumatic tire has a tire size 215 mounted on a wheel rim having a rim size of 16 × 7 1/2. 1 shows an example of a / 45 passenger car tire.

The pneumatic tire has a carcass 6 composed of a carcass ply having a folded portion 6A which is rolled up from the inside to the outside at the bead core 5 of the bead portion 4 from the tread portion 2 to the sidewall portion 3, and the carcass 6 at the tread portion 2. And a breaker 7 disposed radially outward of

In the tread portion 2, the tread rubber 9 forming the outer surface thereof is, in this embodiment, a tire maximum sectional width position M.
Therefore, a tread end N which is an axial end of the tread portion 2 is set to be equal to the tire maximum sectional width position M. Thus, the tread width TW, which is the distance between the tread ends N, N in the tire axial direction,
Is set equal to the tire maximum sectional width SW.

The tread rubber 9 has a JISA hardness of 5
About 0 ° to 80 ° can be preferably adopted. The sidewall rubber 10 has a JISA hardness of 35 ° to 65 ° in this example.
The degree can be preferably adopted.

The tread portion 2 determines the thickness of the tread rubber 9 measured along the tire radial direction by the tire equatorial plane C.
, The carcass 6 and the breaker 7 become substantially parallel to the cross section of the tire outer surface described later.

As shown in FIG. 2, the tread portion 2 may be one in which the tread rubber 9 terminates at a position axially inward of the tire cross-sectional maximum width position M. Therefore, in this case, the tread width TW of the tread portion 2 is increased. Is set to about 0.85 to 0.9 times the maximum sectional width SW of the tire.
In this embodiment, the side wall rubber 10 is longer than that of FIG. 1, and is preferable in that the flexibility at the side wall portion 3 is enhanced and the potential ground region can be smoothly grounded.

Next, the pneumatic tire shown in FIG. 1 has a bead apex 11 made of hard rubber extending radially outward from the radially outer surface of the bead core 5, and in this embodiment, a chafer 12 comprises the bead core 5, the bead apex 11 The carcass is provided with cushioning properties by being wound up around the periphery of the bead, and the clinch apex 13 made of hard rubber is arranged along the outer surface of the bead portion, whereby the bead portion 4 can be appropriately reinforced. .

The carcass 6 is one or more, in this example, one.
Consists of carcass plies. The carcass 6 preferably uses an organic fiber cord having a relatively low elasticity such as nylon, rayon, or polyester, and in this example, the polyester cord is arranged to be inclined in a radial direction of about 65 to 90 degrees with respect to the tire equator. Are illustrated.

The breaker 7 may be made of an organic fiber cord such as rayon, nylon, polyester or the like, or a steel cord or the like in the tire circumferential direction at 5 ° to 50 °, preferably 10 ° to 45 °, more preferably 15 °. It has breaker plies arranged at an inclination of about 30 °, and in this example, breaker plies 7A, 7B, 7 using an aramid cord.
C shows the three cords formed by overlapping the cords in a direction in which the cords cross each other.

In this example, the breaker plies 7A have a wider width as they are located inward in the tire radial direction, and the maximum width BW in the tire axial direction is the maximum sectional width (SW) of the tire.
0.85 to 1.0 times of the outer surface 2 of the tire
A, in particular, is preferred in that a hammer effect can be imparted over the entire area of the tread portion 2 and the shape of the tire outer surface described later can be maintained.

The breaker 7 can reduce the number of breaker plies to, for example, two. In addition, as shown in FIG. 3, the breaker 7 has two breaker plies 7A, 7B.
B and a band-like ply or one organic fiber cord in which a plurality of organic fiber cords are arranged in parallel and topped in a radially outer side of the breaker plies 7A and 7B, at an angle of substantially 0 ° with respect to the tire circumferential direction. And a jointless layer 8 which is formed by spirally winding with the above.

At this time, the width B3 of the jointless layer 8 in the tire axial direction is preferably larger than the maximum widths B1 and B2 of the respective breaker plies 7A and 7B in the axial direction of the tire, and is preferably the maximum width BW of the breaker. Thereby, the breaker plies 7A and 7B are given a strong hoop effect by the jointless layer 8 forming an extremely shallow angle with respect to the tire circumferential direction, and the shape of the tire outer surface 2A can be more reliably maintained.

The aramid cord used in this example has a strength of 1500 d / 3 and a strength of 85 per cord.
By adopting the high-strength cord of kgf, breaker 7
The layer of each ply or the jointless layer 7C may have no cord breakage.

The aramid code is JIS L
By setting the elongation under a constant load specified in 1017 to about 0.9%, the elongation of the cord can be restricted to a range where the outer shape of the tire can be maintained without impairing the manufacturing process, and the cross-sectional shape of the outer surface 2A of the tire can be adjusted. Over its entire life.

When such a jointless layer 8 is incorporated in the breaker 7, the ply peeling off at the time of high-speed rotation of the tire can be suppressed, and the high-speed durability can be improved. It is also preferable in that the tire durability can be increased.

Further, as shown in FIG. 1, when the outer surface of the breaker 7 is mounted on the wheel rim J and filled with the normal internal pressure, the outer surface of the breaker 7 is separated from the tire equatorial plane C outward in the tire axial direction in the tire meridian section. , The radius of curvature is formed so as to gradually decrease in accordance with the cross-sectional shape of the tire outer surface 2A described later.

Next, in the present invention, in a normal state where the tire is mounted on the wheel rim J and filled with the normal internal pressure,
The tire outer surface 2A, which is the tire outer surface in the tire meridian section, is defined as follows.

First, in the normal state, a distance SP of 45% of the tire maximum sectional width (SW) from the tire equatorial plane C is used.
When a point on the tire outer surface 2A separating the tire is defined as P, and a point where the tire equatorial plane C and the tire outer surface 2A intersect is defined as a tire equatorial point CP, a radius of curvature RC of the tire outer surface 2A is calculated from the tire equatorial point CP to the above-mentioned point. It is set so as to gradually decrease until reaching P.

Also, 60%, 75%, 90% and 1% of half width (SW / 2) of the tire maximum sectional width from the tire equatorial plane C.
Points on the outer surface of each tire separating the 00% distances X60, X75, X90 and X100 are designated as P60, P75, P90 and P100. The radial distances between the points P60, P75, P90 and P100 on the outer surface of each tire and the tire equator point CP are defined as Y60, Y75, Y90 and Y100.

Further, assuming that the tire section height which is the height in the radial direction from the bead base BL to the tire equator point CP in the normal state is SH, the radial distances Y60, Y75, Y90 and Y100 are respectively It is characterized by satisfying the following relationship. 0.05 <Y60 / SH≤0.1 0.1 <Y75 / SH≤0.2 0.2 <Y90 / SH≤0.4 0.4 <Y100 / SH≤0.7

FIG. 4 shows an example of a range RYi satisfying the above-mentioned relationship, where RY60 = Y60 / SH RY75 = Y75 / SH RY90 = Y90 / SH RY100 = Y100 / SH. As is clear from the figure, when the flatness is less than 50%, the conventional passenger car and truck tires in which the tread surface, the breaker, the belt, and the like are as flat as possible are different from the tire structure of the present invention. Can be understood to be completely different.

The ranges RY60, RY75, RY90 and R
The reasons for setting the upper and lower limits of Y100 are as follows. First, when each of the ranges Ri is smaller than each of the lower limits, the outer surface 2A of the tire is flattened around the tread portion 2, so that the contact width of the tire is widened and the passing noise cannot be reduced. In addition, the contact shape is often a butterfly shape, so that a sufficient grip force cannot be obtained due to uneven contact pressure, and the tread wear is inferior.

Conversely, when each of the ranges RYi is larger than each of the upper limits, the outer surface of the tire is extremely convex around the tread portion 2, so that the contact width is extremely small and the contact length is extremely small. This is because, although the hydroplaning performance is excellent, the grip performance and the wandering performance are significantly inferior and cannot be adopted. In addition, such a tire is not preferable because the contact pressure is significantly increased in the vicinity of the tire equator of the tread, causing uneven wear.

For a pneumatic tire, the required tire flatness, maximum tire cross-section width, maximum tire height, and the like can be substantially determined from standards such as JATMA and ETRTO by determining the tire size in advance. RY
The ranges of 75, RY90 and RY100 can be easily calculated. Accordingly, the radius of curvature RC of the tire outer surface 2A gradually decreases from the tire equatorial point CP to the point P, and RY60, RY75, RY90, and R at each position.
It can be determined as appropriate by drawing smoothly so as to satisfy the range of Y100.

Incidentally, such a pneumatic tire is mounted on a regular rim J and is grounded at an axial distance between the outermost ends in the tire axial direction where the tire outer surface 2A is grounded at 80% of the normal load. Preferably, the width CW (shown in FIG. 2) forms 50% to 65% of the tire maximum sectional width SW.

When the contact width CW is less than 50% of the maximum sectional width SW of the tire, the contact width tends to be small, and the wandering performance is reduced, such as easy wobbling due to a rut. It tends to cause uniformity and tends to reduce wear performance.

Also, the contact width CW is equal to the tire maximum sectional width SW.
If it exceeds 65%, the contact width tends to be large, and it tends to be difficult to achieve both passing noise and hydroplaning performance.

Incidentally, in the tire meridional section,
In the present example, a portion formed from the tire maximum cross-sectional width position M to the flange contact point BP where the tire is in contact with the rim flange is formed by continuously reducing the radius of curvature from the tire maximum cross-sectional width position M by gradually decreasing the radius of curvature. But besides this,
For example, it can be appropriately determined by adopting a constant radius of curvature in the vicinity of the tire maximum cross-sectional width position M, or by joining with a smooth curve.

As described above, by regulating the radius of curvature of the tire outer surface 2A in the tire meridional section, the pneumatic tire can be mounted on the tire equatorial point CP in the tire meridian section.
To the tire maximum cross-sectional width position M, the tire outer surface shape substantially continuously curved, and consequently the tread cross-sectional shape.

In such a tire outer shape, even when a slip angle occurs, there is almost no change in the shape of the footprint. Further, when the load increases, the footprint can contact the ground only when the load increases. As described above, as a result of the similar deformation by the “target contact area”, the limit at the time of cornering can be increased while achieving both passing noise and hydroplaning performance.

Next, the tire outer surface 2A is specifically determined.
Possible modes will be described below. The tire outer surface 2A
Is given by the following formula (1) RC = 1 / (C · e ^BX + A · x) (1) at a position apart from the equatorial plane C by a distance x in the tire axial direction. it can. Where e is the base of the natural logarithm and e ^BX is an exponential function.

The above constants A, B, and C can be arbitrarily determined according to the size of the tire and the like. The constant A decreases the radius of curvature RC from the tire equatorial plane C toward the outside in the axial direction. Determine the degree. Also constant B
Is, rather than the tire equator,
It acts to reduce the radius of curvature. Further, the constant C
Defines the radius of curvature at the tire equatorial point CP.

On the basis of such an exponential function,
To C, the radius of curvature RC of the tire outer surface 2A in the tire meridional section smoothly decreases from the tire equator point CP to the point P, and the tire outer surface 2A RY60, RY75, RY90 and RY100 at each of the above positions can be satisfied.

When a tire having a flatness of 45% is realized by using the above equation (1), typical values of the constants A to C and examples of various tire dimensions are given for each tire size. Are shown in Table 1. In addition, the tire outer surface contour (right half) in the meridional section of each tire is shown in FIGS.

[0067]

[Table 1]

As is clear from these tables and figures, in the case of a tire having a flatness of 45%, the constant A in the above equation (1) is used.
Is approximately in the range of 5 × 10 ^{−5 to} 13 × 10 ⁻⁵ , and the constant B
Is approximately in the range of 2.3 × 10 ^{−2 to} 2.8 × 10 ⁻² , and the constant C is in the case of adopting the range of 4.8 × 10 ^{−4 to} 12.8 × 10 ⁻⁴ , Each tire maximum section width SW
Decrease with the increase in

Similarly, using the above equation (1), the
Table 2 shows examples of the values of the constants A to C and various tire dimensions when 0% of the tire is embodied for each tire size. 8 to 10 show the outline (right half) of the tire outer surface in a meridional section of each tire, respectively.

[0070]

[Table 2]

In the case of a tire having an aspect ratio of 40%, the above equation is used.
The constant A in (1) is approximately 4.0 × 10 ^-Five~ 8.5 × 10
^-FiveAnd the constant B is approximately 2.3 × 10^-2~ 2.8 ×
10^-2, And the constant C is 4.0 × 10^-Four~ 8.
3 × 10^-FourIs the case where
The width decreases with an increase in the maximum sectional width SW.

Table 3 shows the cases where the flattening ratio is 35% and 30%, and Table 4 shows the cases where the flattening ratio is 50%. Also, the tire outer surface contour in the meridional section of each tire is shown in correspondence with FIGS.

[0073]

[Table 3]

[0074]

[Table 4]

As described above, by using the above equation (1) and determining the constants A, B, and C so as to satisfy the range of RYi for each tire size, in this example, the tire maximum is calculated from the tire equator point CP. The radius of curvature of the tire outer surface can be gradually reduced to the cross-sectional width position M.

In the above table, JATMA, ETR
Because there are sizes that are not described in standards such as TO,
Nominal values are used for the tire maximum section width SW and the tire section height SH. Therefore, for example, in the case of the 215/45 size, the tire maximum sectional width SW is 215 mm, and the tire sectional height SH is 215 × 0.45 and 96.8 mm. The design dimensions of the standards such as JATMA and ETRTO may be slightly different from the nominal values. However, when actually designing these tires, the above formula (1) is appropriately modified so as to conform to each standard. be able to.

In each table, the nominal dimensions of the rim type are not described. This is because if the tire maximum sectional width SW and the flatness are determined, the sectional shape does not change even if the rim diameter is different. Therefore, in the case of the 215/45 size, 215 / 45R15, R16 , R17, etc., respectively.

As described above, by appropriately setting each of the constants A to C in the above formula (1) according to the tire size or the flatness, a smooth and continuous tire outer surface 2A satisfying the requirements of claim 1 is satisfied. This is preferable in that the contour can be determined.

Further, as another embodiment in which the tire outer surface 2A can be defined, the range from the tire equatorial plane C of the tire outer surface 2A to the point P is different by 5 or more, preferably 7 or more, more preferably 10 or more. An arc having a radius of curvature may be formed continuously, and the radius of curvature may be reduced from the equator side of the tire toward the outside in the tire axial direction.

FIG. 17 shows a tire outer surface 2A in a tire meridional section determined by such a method.
In this example, the axial region from the tire equatorial point CP to the point P is equally divided into ten sections n1 to n10 (accordingly,
The section between the points P and P is divided into 20), and each section is formed by connecting circular arcs C1 to C10 having different radii of curvature R1 to R10.

Here, the radius of curvature Ri in each section ni of the tire outer surface 2A can be calculated using, for example, the above-described equation (1). In this case, R1>R2>R3>...> R1
Each radius of curvature can be determined so as to be zero.

Here, R1 to R10 specifically exemplify those defined as follows (unit: mm). R1 = 887.46 R2 = 468.74 R3 = 309.38 R4 = 224.56 R5 = 171.36 R6 = 134.55 R7 = 107.40 R8 = 86.47 R9 = 69.87 R10 = 56.44

In this embodiment, the point P and the tire maximum sectional width position M are connected by an arc C11 having a radius of curvature R11 smaller than the radius of curvature R10.

Further, in the present example, when connecting arcs having different radii of curvature, the outer surface of the tire is made smoother by joining the joints JT of adjacent arcs so that the tangents T of the arcs coincide with each other. Although a preferred embodiment is illustrated, the invention is not limited to this.

In the present invention, since the curvature radius RC of the tire outer surface 2A in the tire meridian section is gradually reduced from the tire equator point CP to the point P, as shown in FIG. As the outer surface of the tread portion 2 also moves toward the tread end N, the camber amount Lc (mm), which is the radial distance between the tire equator point CP and a point U on an arbitrary tire outer surface, increases.

In general, when a curved surface such as a sphere is pressed against a plane, a lateral stress is generated at the end of the contact area along the plane toward the center of the contact area. It gets bigger as it gets tighter. Therefore, when the vicinity of the tread end N where the camber amount Lc (mm) is large contacts the road surface when the vehicle goes straight as in the present invention, the tire equator which is the center of the contact surface as shown in FIG. A large lateral stress τ is generated to shrink the tread contact surface toward the side c. Also, this lateral stress τ is
If the frictional force with the road surface is exceeded, the contact portion slides with the road surface.

The wear of the tire outer surface 2A, especially the tread portion 2, is generally proportional to the work due to the transverse stress τ, ie, [transverse stress] × [slip amount]. τ is large and uneven wear easily occurs.

In this embodiment, as shown in FIG. 19, the tire outer surface 2A has a tire equatorial plane C and a tread end N
A plurality of sipes 15 having a groove width of, for example, 1 mm or less extending linearly in the circumferential direction of the tire are provided in between, and a pattern having ribs 16 sandwiched between the sipes 15 as a tread pattern is exemplified. doing.

Such a siping 15 has a small groove width of, for example, 1 mm or less. During cornering of the vehicle, the groove wall surfaces are brought into contact with each other by a remarkably large lateral force acting on the tread portion 2. Closing the groove width, it will be possible to integrate each rib adjacent to each other,
It does not reduce the tread rigidity at the time of cornering, and helps to improve the cornering limit.

On the other hand, the siping 15 brings about an appropriate deformation to close the groove wall of the rib against the lateral stress acting when the vehicle travels straight, and the gap between the outer surface of the tread portion 2 and the road surface. This is preferable in that side slip can be reduced and uneven wear of the tread portion 2 can be suppressed.

The depth of the groove of the siping 15 is preferably about 4 mm to 12 mm, more preferably about 4 mm to 10 mm. In addition to the linear shape, a zigzag pattern, a wave pattern, or a combination thereof can be appropriately used. .

[0092] In addition, the tire outer surface 2A may be formed with various pattern grooves such as extremely wide water retaining grooves, and may include one or more extremely wide grooves depending on the required pattern performance. May be. In addition, as shown in FIG. 20, a wide center groove which is popular in recent years, and left and right wide main grooves 20 sandwiching the tire equatorial plane C, and a plurality of sipes 15 arranged axially outside the wide main groove 20 are provided. The present invention can be modified in various forms, such as a pattern having a lateral groove 21 extending obliquely outward in the tire axial direction from the wide main groove 20 toward the tread end N, and is preferably used for automobiles, more preferably for passenger cars. Can be adopted as a tire for automobiles. When the above-described various grooves are formed in the tread portion 2, the tire outer surface in the meridional section of the tire can be specified as a virtual outer surface that smoothly connects between points where the groove wall and the tire surface intersect.

(Specific example) The tire size is 215 / 45R
16, the rim size is 16 × 7JJ, the tire of the present invention having the tread pattern shown in FIG. 1, Table 5 and FIG. 20 is prototyped (Examples 1 to 6) to test the performance, and the same tire size, rim size, tread A test was also performed on a tire having a pattern other than the configuration of the present invention (Comparative Examples 1 and 2) and a tire having a conventional structure (Conventional Examples 1 and 2) in which the tire outer surface centering on the tread portion forms a single arc. Was.

The tire of Conventional Example 1 has a tire size of 185 / 65R14 (rim size 14 × 5 1 / 2JJ),
The tire of Conventional Example 2 has a tire size of 205 / 55R1.
5 (rim size 15 × 6 1/2 JJ), and the air pressure of all tires is 2000 kgf / cm ² and 2000c.
The vehicle was mounted on the four wheels of the front-wheel drive vehicle c and the following test was performed.

A) Passing noise test In accordance with the actual vehicle coasting test specified in JASO / C / 606, the vehicle is caused to coast on a straight test course (asphalt road surface) at a passing speed of 60 km / h for a distance of 50 m and the course. 6. Lateral from the running center line at the midpoint of
The maximum level of passing noise dB (A) was measured by a stationary microphone installed at a position of 5 m and 1.2 m from the road surface.

B) Lateral hydroplaning test A 100 m radius asphalt road surface, a water depth of 5 mm and a length of 2
The vehicle was entered on a course provided with a puddle of 0 m while increasing the speed stepwise, the lateral acceleration (lateral G) was measured, and the average lateral G at a speed of 70 to 90 km / h was calculated. The results are expressed as an index with Conventional Example 1 being 100, and the wet performance and cornering limit can be evaluated. The larger the numerical value, the better.

C) Grip test A dry asphalt road surface having a radius of 50 m was turned, and the maximum lateral G that can be turned constantly was measured. The cornering limit can be evaluated, and the larger the value, the better.

D) Wandering test The wandering test was carried out at a speed of 80 km / h in the rut, and the degree of wobble of the vehicle was evaluated by a ten-point method according to the driver's sensuality. The larger the value, the smaller the fluctuation and the better the wandering performance.

E) Abrasion test A running test was performed on a regular road and a highway at a legal speed of 10,000 km, and the abrasion amount of the crown and the shoulder of the front wheel, which is a driving wheel, was measured. The amount of wear at the shoulder) was calculated. The measurement positions of the wear amount were measured at points S1 and S2 shown in FIG. Table 5 shows the test results.

[0100]

[Table 5]

As is clear from the test results, it can be understood that the tire of the present invention can achieve both passing noise and hydroplaning performance, and the cornering limit is significantly increased.

[0102]

As described above, in the tire of the present invention, by specifying the tread cross-sectional shape as described above, the passing noise can be reduced, the hydroplaning performance can be improved, and the limit speed at the time of cornering can be significantly increased. .

[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 another embodiment of the present invention.

FIG. 3 is a sectional view showing another embodiment of the present invention.

FIG. 4 is a diagram showing a range of RYi at each position on an outer surface of a tire.

FIG. 5 is a diagram showing an outer surface of a tire according to the present invention.

FIG. 6 is a diagram showing an outer surface of a tire according to the present invention.

FIG. 7 is a diagram showing an outer surface of a tire according to the present invention.

FIG. 8 is a diagram showing an outer surface of a tire according to the present invention.

FIG. 9 is a diagram showing an outer surface of a tire according to the present invention.

FIG. 10 is a diagram showing an outer surface of a tire according to the present invention.

FIG. 11 is a diagram showing an outer surface of a tire according to the present invention.

FIG. 12 is a diagram showing an outer surface of a tire according to the present invention.

FIG. 13 is a diagram showing an outer surface of a tire according to the present invention.

FIG. 14 is a diagram showing an outer surface of a tire according to the present invention.

FIG. 15 is a diagram showing an outer surface of a tire according to the present invention.

FIG. 16 is a diagram showing an outer surface of a tire according to the present invention.

FIG. 17 is a diagram showing an outer surface of a tire according to another embodiment of the present invention.

FIGS. 18A and 18B are diagrams showing the footprint of the tire of the present invention.

FIG. 19 is a development view of a tread pattern that can be employed in the present invention.

FIG. 20 is another developed view of a tread pattern that can be employed in the present invention.

FIG. 21 is a graph showing a relationship between a contact width of a tire and a noise level.

FIG. 22 is a graph showing a relationship between (contact length / contact width) and lateral hydroplaning performance.

FIG. 23 is a sectional view showing a posture of a conventional tire during cornering.

FIGS. 24A and 24B are diagrams showing footprints of conventional tires.

FIG. 25 is a diagram illustrating a tire contact area for explaining a lateral stress as viewed from a road surface side.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Breaker J Wheel rim 2A Tire outer surface C Tire equatorial plane CP Tire equatorial point N Tread end SW Tire maximum section width SH Tire section height

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B60C 3 / 00,9 / 18 B60C 11 / 00,15 / 06

Claims (5)

(57) [Claims] 1. A carcass comprising a carcass ply that is locked by turning around a bead core of a bead portion from a tread portion through a sidewall portion and a breaker disposed radially outside the carcass in the tread portion. A pneumatic tire, which is mounted on a wheel rim and filled with a normal internal pressure in a normal tire meridional section, is 45% of a tire maximum sectional width (SW) from the tire equatorial plane C.
When a point on the tire outer surface separated by a distance SP of P is P, the radius of curvature RC of the tire outer surface gradually decreases from the tire equatorial point CP to the point P, and from the tire equatorial plane C Each point on the outer surface of the tire, which is separated by a distance X60, X75, X90 and X100 of 60%, 75%, 90% and 100% of the half width (SW / 2) of the tire maximum sectional width, and the tire equator point CP When the radial distances between them are Y60, Y75, Y90 and Y100, respectively, and the tire section height is SH, 0.05 <Y60 / SH≤0.1 0.1 <Y75 / SH≤0.2 A pneumatic tire which satisfies a relationship of 0.2 <Y90 / SH≤0.4 and 0.4 <Y100 / SH≤0.7. 2. The distance X10 from the tire equatorial point CP.
The tire outer surface up to a point on the tire outer surface separating 0
The radius of curvature RC at a position apart from the tire equatorial plane C by a distance x outward in the tire axial direction is represented by the following equation (1) RC = 1 / (Ce ^BX + ^Ax ) (1) (where e is E ^BX is an exponential function,
The pneumatic tire according to claim 1, wherein A, B, and C are constants. 3. The tire outer surface has a range from the tire equatorial plane C to the point P formed by connecting arcs having five or more different radii of curvature, and the respective radii of curvature are set in the tire axial direction from the tire equator side. The pneumatic tire according to claim 1, wherein the size of the pneumatic tire decreases toward the outside. 4. The breaker has a maximum width B in the tire axial direction.
W is the tire maximum sectional width (SW) of 0.85-1.
The pneumatic tire according to claim 1, wherein the pneumatic tire has 0 times. 5. The contact width (C), which is the axial distance between the outermost ends in the axial direction of the tire where the pneumatic tire is assembled to a regular rim and the outer surface of the tire contacts the ground at 80% of the regular load.
The pneumatic tire according to claim 1, wherein W) is 50% to 65% of a tire maximum sectional width (SW).