JP3887128B2 - Combination of front and rear tires - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a combination of a tire for a front wheel and a tire for a rear wheel that can achieve both wet performance, noise performance, and dry steering stability performance at a high level.
[0002]
[Prior art and problems to be solved by the invention]
In general, in order to improve the hydroplaning performance of a vehicle, for example, the groove area formed in the tire is increased, in other words, the land ratio is decreased. However, a decrease in the land ratio causes a decrease in steering stability on a dry road surface. Particularly in high-performance tires that are installed in sports cars, etc., the groove area is smaller than usual to increase grip and rigidity, so a decrease in the land ratio reduces the handling stability of this type of tire. There is a problem of greatly lowering.
[0003]
In order to prevent such a decrease in steering stability, for example, in an FR vehicle, the width of the rear wheel tire may be increased as compared with the front wheel tire. However, when the clearance on the body side is small, the body and the tire may interfere with each other, and this method alone has not yet achieved a sufficient effect.
[0004]
The present invention has been devised in view of the above problems, and is based on limiting the land ratio of the front wheel tire and the rear wheel tire having a specific tread pattern to a certain range. The object is to provide a combination of front and rear wheel tires that can achieve high performance, noise performance, and dry steering stability performance at a high level.
[0005]
[Means for Solving the Problems]
The invention according to claim 1 of the present invention extends on the tread surface in the range of 0 to 15 ° with respect to the tire circumferential line without crossing the tire equator starting from the inner end located in the vicinity of the tire equator. The tire includes an inclined groove that includes a steeply inclined portion and a gently inclined portion that is continuous with the steeply inclined portion and extends in the same direction within an angle that is greater than 15 ° and equal to or less than 60 °. A combination of front and rear wheel tires on both sides of the equator,
The inner end is independent without intersecting with other grooves, and the inclined grooves are sequentially grounded from the inner end side to the road surface,
In the ground contact surface that is assembled to the regular rim and filled with the regular internal pressure and loaded with a regular load and grounded to a flat surface,
Before wheel tire is 50-60% of the land ratio is the ratio of contact area to the total area of the ground plane surrounded by the outer peripheral contour of the ground surface,
And the rear wheel tire has a land ratio larger than that of the front wheel tire and 60 to 70%,
Groove width of the steep portion of the front wheel tires is larger than the groove width of the steep portion of the rear wheel tires,
In addition, each land portion formed between the steeply inclined portions of the adjacent inclined grooves of the front wheel tire has a land width that is 1.0 mm to 4.0 mm smaller than the groove width of the steeply inclined portion of the front wheel tire. Including a narrow part,
In addition, each land portion formed between the steeply inclined portions of the adjacent inclined grooves of the rear wheel tire is characterized in that the land portion width is equal to or greater than the groove width of the steeply inclined portion of the rear wheel tire . .
[0006]
Here, the “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, Or, for ETRTO, “Measuring Rim”. In addition, “regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is JATMA, and the table “TIRE LOAD LIMITS” is TRA. The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO, but 180 kPa when the tire is for passenger cars. In addition, “regular load” is the load that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum load capacity is JATMA, and the table “TIRE LOAD LIMITS” is TRA. The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”. If ETRTO, “LOAD CAPACITY”.
[0007]
It is preferable that the steeply inclined portion and the gently inclined portion of the inclined groove are smoothly connected, and the gently inclined portion gradually increases the angle with respect to the tire circumferential direction.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a development view of the tread pattern of the front wheel tire 1F, and FIG. 2 shows a development view of the tread pattern of the rear wheel tire 1R. First, the portions common to the tires 1F and 1R will be described. .
[0009]
Each tire 1F, 1R of the present embodiment has a plurality of inclined grooves 3 provided on both sides of the tire equator C on the tread surface 2. The inclined groove 3 includes a steeply inclined portion 3a and a gently inclined portion 3b. As shown in an enlarged view of FIG. 3, the steeply inclined portion 3a has an angle θ1 that is 0 to 15 ° with respect to the tire circumferential line without crossing the tire equator C starting from the inner end i located in the vicinity of the tire equator. Extends at a small angle.
[0010]
The inner end i is independent and does not intersect with other grooves. Such an independent inner end i can substantially prevent an air column tube having both ends open when the inclined groove 3 is grounded, and can suppress tire noise. For example, in an air column tube with one end closed, the frequency of resonance noise is shifted to approximately half, that is, to a lower frequency side than an air column tube with both ends open. Therefore, the inclined groove 2 having the inner end i as in the present example can shift the resonance noise to the low frequency side when it contacts the road surface, and the noise frequency can be distributed, so that the passing noise and the road surface can be reduced. Can be reduced, as well as in-vehicle noise.
[0011]
In the present embodiment, the central portion Cr of the tread of each tire 1F, 1R does not have a groove useful for drainage extending continuously in the tire circumferential direction. Thereby, resonance noise is further reduced. The “tread central portion” Cr is a ground contact width TW centered on the tire equator C (a ground surface tire that is assembled on a normal rim and filled with a normal internal pressure and is loaded with a normal load and grounded on a flat surface). It is defined as a region of 50% of the tire axial distance between the outermost ends in the axial direction. The “substantially useful groove for drainage” does not include a narrow groove having a width of 2.0 mm or less, or a groove that does not exhibit a substantial drainage effect such as siping.
[0012]
Further, as shown in FIG. 3, the inner end i of the inclined groove 3 is illustrated as being separated from the tire equator C by a small distance L in this example. The small distance L is preferably about 2% or less of the ground contact width TW, for example. If this small distance L is too large, the water film drainage effect in the tread center portion Cr, particularly in the vicinity of the tire equator C, tends to decrease. In addition, since the steeply inclined portion 3a extending at a small angle with respect to the tire circumferential direction line is provided on the tire equator side, excellent drainage that is not substantially different from the circumferential grooves conventionally formed on both sides of the tire equator. Can exhibit sex. The inner end i may be positioned on the tire equator C.
[0013]
Further, the gently inclined portion 3b extends in the same direction in a range where the angle θ2 that is connected to the steeply inclined portion 3a and the tire circumferential direction is greater than 15 ° and not more than 60 °. Such a gently inclined portion 3b is particularly useful for maintaining the pattern rigidity of the tread central portion Cr, and can contribute to improving the steering stability performance such as increasing the dry grip.
[0014]
In addition, the steeply inclined portion 3a and the gently inclined portion 3b may extend at constant angles θ1 and θ2, respectively. In this example, the steeply inclined portion 3a and the gently inclined portion 3b extend in the tire axial direction toward the tire axial direction. An example of gradually increasing the angle is shown. The angles θ1 and θ2 of the steeply inclined portion 3a and the gently inclined portion 3b are measured at the groove center line Gc, and when these curves smoothly, the angle formed between the tangent to the groove center line and the tire circumferential line Can be measured as
[0015]
As shown in FIG. 3, the intersection P where the steeply inclined portion 3a and the gently inclined portion 3b intersect is, for example, 0.25 times the tire axial direction length WG between the inner end i and the outer end 3e of the inclined groove. It is desirable to provide a distance S of ˜0.70 times, more preferably 0.35 to 0.65 times, at a position separated from the tire equator C. Thereby, wet grip performance and dry grip performance can be improved in a well-balanced manner.
[0016]
Further, the outer end 3e of the inclined groove 3 terminates in communication with a vertical groove 4 extending continuously in the tire circumferential direction at the tread shoulder portion Sh which is the outside of the tread center portion Cr in this example. Therefore, the inclined groove 3 can effectively discharge the waste water in the inclined groove to the outside of the tire by using the vertical groove 4. The outer end 3e of the inclined groove 3 in the tire axial direction may extend to the tread edge e.
[0017]
The pneumatic tire of the present embodiment, the inclined grooves 3, Ru is rotated so as to ground sequentially road surface from the inner end toward i. As a result, the water film on the wet road surface can be effectively discharged from the inner end i of the steeply inclined portion 3a through the steeply inclined portion 3a having a low flow resistance and from the gently inclined portion 3b to, for example, the vertical groove 4. Further, in this example, the vertical groove 4 is provided with small inclined grooves 5i, 5o extending in and out of the tire axial direction from the vertical groove 4, and further using these small inclined grooves 5i, 5o to further drainage. Can be increased.
[0018]
As described above, each of the tires 1F and 1R basically has the same tread pattern.
In the combination of the front wheel tire 1F and the rear wheel tire 1R of the present embodiment, a grounding surface that is assembled on a regular rim and filled with a regular internal pressure and is loaded with a regular load and grounded on a flat surface (FIG. 1, FIG. 2, the outer peripheral contour line E is indicated by a dotted line.) In the front wheel tire 1F, the ratio of the ground contact area to the total area (groove area + ground contact area) of the ground contact surface surrounded by the outer peripheral contour line E of the ground contact surface The land ratio is set to 50 to 60%, and in the rear wheel tire 1R, the land ratio is set to be larger than the land ratio of the front wheel tire and 60 to 70%.
[0019]
The inventors have four types of tires having the land ratios of 48%, 57%, 63%, and 72% in the tire having the pattern of FIGS. A tire size of 215 / 45ZR17 and a mounting rim size of 7J × 17) was made as a prototype. Then, a test tire having a land ratio of 57% is mounted on the front tire 1F, and test tires having different land ratios are sequentially mounted on the rear tire 1R (test vehicle: domestic FR passenger car, displacement 2500cc, internal pressure 230 kPa). The vehicle was tested for steering stability and anti-hydroplaning performance (hereinafter sometimes simply referred to as “hydro-resistance”).
[0020]
Regarding the driving stability, the stability when the dry asphalt road surface was lane-changed at a speed of 120 km / H with the test vehicle was evaluated by the driver's feeling by a 10-point method. In addition, the hydroplaning resistance is shown by indexing this test vehicle by turning the test vehicle 100R circularly at a speed of 70km / h on an asphalt road with a depth of 10mm and measuring the maximum remaining lateral G. It is.
[0021]
FIG. 4 shows the result. From the figure, it can be confirmed that when the land ratio of the rear wheel tire 1R is increased, the steering stability is improved, but the hydro-resistant performance is lowered. However, when the land ratio of the rear wheel tire 1R is limited to a range of 60 to 70%, it can be confirmed that there is substantially no decrease in hydro-resistant performance and both performances are maintained in a relatively balanced manner. .
[0022]
On the other hand, the land ratio of the rear wheel tire 1R is set to 63% which is included in the preferable range, and test tires having different land ratios are sequentially mounted on the front wheel tire 1F so that the steering stability and the hydro-resistant performance are the same. Tested. FIG. 5 shows the result of the test. As a result of the test, in order to improve the steering stability and the hydro-proof performance in a well-balanced manner, when the land ratio of the rear wheel tire 1R is 63%, the land ratio of the front wheel tire 1F is set to 50 to 60%. Is good. Further, the inventors further trial manufactured tires with various land ratios, and tried to make the land ratio of the front wheel tire 1F 50 to 60%, more preferably 55 to 58%. It was found that the land ratio of 1R is larger than the land ratio of the tire for the front wheels and is preferably 60 to 70%, more preferably 62 to 66%.
[0023]
Further, when the land ratio of the front wheel tire 1F is made smaller than that of the rear wheel tire 1R, the front wheel tire 1F has the groove width Wf of the steeply inclined portion 3a set to the steeply inclined portion 3a of the rear wheel tire 1R. It shall be the greater than the groove width Wr. The steeply inclined portion 3a is located in the vicinity of the tire equator C having a high contact pressure and is inclined at a small angle with respect to the tire circumferential direction. This is because it becomes higher than the groove.
[0024]
As for the gently inclined portion 3b, in this example, the front wheel tire 1F and the rear wheel tire 1R have the same groove width. This is preferable in that a decrease in pattern rigidity of the tread central portion Cr of the front wheel tire 1F can be minimized and a decrease in steering stability can be suppressed. The groove widths Wf and Wr are specified as the maximum groove width when the groove width of the steeply inclined portion 3a changes, and are measured in a direction perpendicular to the direction in which the grooves extend.
[0025]
The groove width Wf of the steeply inclined portion 3a of the front wheel tire 1F is, for example, 2 to 9%, preferably 2.5% or more, more preferably 4 to 8%, and more preferably 4 to 7% of the ground contact width TW. % Is preferable, but the lower limit is more preferably 6 mm or more. The groove depth of the steeply inclined portion 3a is preferably 7 mm or more. The difference (Wf−Wr) between the groove width Wf of the steeply inclined portion 3a of the front wheel tire 1F and the groove width Wr of the steeply inclined portion 3a of the rear wheel tire is 0.5 mm or more, more preferably 1 It is preferable that the thickness is 0.0 mm or more.
[0026]
Further, in the front wheel tire 1F of the present embodiment, land portions 9, 10 and the like that are in contact with the road surface are formed between the inclined grooves 3, 3, etc., but in this example, the land width Ws is the groove width Wf. The smaller narrow portions 6 and 7 are included. In this example, as shown in FIG. 1, the narrow portions 6 and 7 are rib-like land portions 9 (that is, steeply inclined portions 3a of adjacent inclined grooves) sandwiched between the steeply inclined portions 3a and 3a on both sides of the tire equator. 3a) and on each side of the tire equator C, the wing-like land portion 10 formed between the steeply inclined portions 3a and 3a (that is, the steeply inclined portion 3a of the adjacent inclined groove, And a land portion formed between 3a ). Here, the width of the land portion is measured at a right angle to the direction in which the land portion extends, and is specified by the minimum width. The narrow portions 6 and 7 are provided in the tread center portion Cr, respectively. For this reason, in the front wheel tire 1F, the water film removal near the tire equator is further promoted, and the hydro-resistant performance can be further improved. The difference (Wf−Ws) between the groove width Wf and the (minimum) width Ws of the small width portion is set to 1.0 to 4.0 mm, preferably 2.0 to 4.0 mm.
[0027]
In contrast, in the rear wheel tire 1R, the widths of the rib-like land portion 9 and the wing-like land portion 10 are both set to be equal to or greater than the groove width Wr of the steeply inclined portion 3a. That is, in the rear wheel tire, the land portion width of the land portion formed between the steeply inclined portions of the adjacent inclined grooves of the rear wheel tire is equal to or greater than the groove width of the steeply inclined portion. Since the rear wheel tire 1R that contributes greatly to the steering stability does not include the narrow portions 6 and 7 as described above, the rigidity at the tread central portion Cr can be increased and the steering stability can be improved.
[0028]
Although the embodiment of the present invention has been described in detail above, the front wheel tire 1F and the rear wheel tire 1R may be the same size, but the rear wheel tire is preferably larger.
[0029]
【The invention's effect】
As described above, in the combination of the front wheel tire and the rear wheel tire of the present invention, wet performance, noise performance, and dry steering stability performance can be achieved at a high level.
[Brief description of the drawings]
FIG. 1 is a diagram showing a tread pattern of a front wheel tire according to an embodiment.
FIG. 2 is a diagram showing a tread pattern of a rear wheel tire according to the present embodiment.
FIG. 3 is an enlarged view of an inclined groove.
FIG. 4 is a graph showing the relationship between hydro-resistant performance, steering stability, and land ratio.
FIG. 5 is a graph showing the relationship between hydro-resistant performance, steering stability, and land ratio.
[Explanation of symbols]
1F Front wheel tire 1R Rear wheel tire 2 Tread surface 3 Inclined groove 3a Steeply inclined portion 3b Slowly inclined portion

Claims (2)

On the tread surface, a steep slope extending from 0 to 15 ° with respect to the tire circumferential direction line without crossing the tire equator starting from the inner end located in the vicinity of the tire equator, and continuous to the steep slope And a tire for a front wheel and a rear wheel provided with inclined grooves on both sides of the tire equator, including a gently inclined portion extending in the same direction in an angle greater than 15 ° and not more than 60 ° with respect to the tire circumferential line. A combination of tires for
The inner end is independent without intersecting with other grooves, and the inclined grooves are sequentially grounded from the inner end side to the road surface,
In the grounding surface that is assembled to the regular rim and filled with the regular internal pressure and loaded with a regular load and grounded to a flat surface,
Before wheel tire is 50-60% of the land ratio is the ratio of contact area to the total area of the ground plane surrounded by the outer peripheral contour of the ground surface,
And the rear wheel tire has a land ratio larger than that of the front wheel tire and 60 to 70%,
Groove width of the steep portion of the front wheel tires is larger than the groove width of the steep portion of the rear wheel tires,
In addition, each land portion formed between the steeply inclined portions of the adjacent inclined grooves of the front wheel tire has a land width that is 1.0 mm to 4.0 mm smaller than the groove width of the steeply inclined portion of the front wheel tire. Including a narrow part,
In addition, each land portion formed between the steeply inclined portions of the adjacent inclined grooves of the rear wheel tire has a land width that is equal to or larger than the groove width of the steeply inclined portion of the rear wheel tire. A combination of front and rear tires.   The combination of a front wheel tire and a rear wheel tire according to claim 1, wherein the steeply inclined portion and the gently inclined portion are smoothly connected, and the slowly inclined portion gradually increases an angle with respect to the tire circumferential direction.

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