JP5602037B2 - Method for predicting cornering performance of automotive tires - Google Patents

Description

  The present invention relates to a method for predicting the cornering performance of an automobile tire that is highly practical and useful for improving the efficiency of tire design.

  A lateral force acts on the automobile tire during cornering. Conventionally, a lateral spring constant, which is a ratio of a lateral force and a lateral displacement of a tire caused thereby, is used as an index for evaluating the cornering performance of a tire.

By the way, conventionally, various methods for estimating the lateral spring constant from the physical properties of each part of the tire have been proposed. For example, the following formula (3) has been proposed as an estimation formula for the lateral spring constant.


Where Gy: transverse spring constant (N / mm)
S: Ground contact area (cm ² )
r: Belt layer radius (mm)
Cy: Lateral rigidity of the tread rubber Ky: Lateral rigidity of the carcass E: Elastic constant of the belt layer I: Secondary moment of inertia around the Z axis of the belt layer (mm ⁴ )
φ0: Belt layer rotation angle (°)
r: Belt layer radius (mm)

Hideo Sakai, "From Introduction to Application of Tire Engineering" Grand Prix Publication

  However, since the physical property values and the like input to the lateral spring constant estimation formula represented by the above formula (3) are mostly abstract physical quantities, they are not useful for practical tire design and are not practical. .

  The present invention has been devised in view of the above problems, and has as its main object to provide a method for predicting the cornering performance of an automobile tire that is highly practical and useful for improving the efficiency of tire design. Yes.

The invention according to claim 1 of the present invention includes a step of predicting a lateral spring constant of an automobile tire using the following formula (1), and a method for predicting cornering performance of an automobile tire.

Where Gy: transverse spring constant (N / mm)
S: Tire contact area (cm ² )
Te: Complex elastic modulus (MPa) of tread rubber
r: Belt layer radius (mm)
F: Tangent force during grounding (N)
y: Displacement in the tire axial direction of the land portion of the tread (mm)
h: Land height of the tread (mm)
Ey: Young's modulus of tread rubber (N / cm ² )
G: Shear rigidity of the tread rubber (N / cm ² )
Im: Cross-sectional second moment of land in tread (mm ⁴ )
A: Cross-sectional area of land in the tread (cm ² )
Ap: Air pressure (kPa)
Pn: Number of carcass plies (sheets)
Hi: Height of folded portion of outer carcass ply (mm)
Ho: Height of folded part of inner carcass ply (mm)
Bn: Number of bead reinforcement layers (sheets)
Cw: Maximum thickness of clinch rubber (mm)
Bh: Bead apex height (mm)
Bg: Bead apex rubber hardness (degree)
α: Angle of belt cord with respect to tire axial direction (°)
Bw: Maximum width of belt ply in the tire axial direction (mm)
a1-a14: Constant

Further, in the invention according to claim 2, in the above formula (1), when siping is provided in the tread portion of the automobile tire, the following formula (2) is used. This is a method for predicting cornering performance.

Where W: width of land (mm)
L: Circulating component length in the circumferential direction (mm)
hs: Depth of siping (mm)

  In the present specification, unless otherwise specified, the size of each part of the tire is a value specified in a normal state with no load loaded with a normal rim and filled with a normal internal pressure.

  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, “Standard Rim” for JATMA and “Design Rim” for TRA. "If ETRTO," Measuring Rim ".

  Furthermore, “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. “JAMATA” is the “highest air pressure”, TRA is the table “TIRE LOAD” The maximum value described in LIMITS AT VARIOUS COLD INFLATION PRESSURES is "INFLATION PRESSURE" if it is ETRTO, but it is uniformly 180 kPa if the tire is for passenger cars.

  The method for predicting cornering performance of an automobile tire according to the present invention includes a step of predicting a lateral spring constant of the automobile tire using the above formula (1). The physical property values input to the above formula (1) are all specific design factors determined when designing a tire. Therefore, the prediction method of the present invention is highly practical and can improve the efficiency of tire design with excellent cornering performance.

It is sectional drawing of the pneumatic tire evaluated by the prediction method of the cornering performance of this embodiment. It is a tread expansion | deployment figure of FIG. (A) is a perspective view which shows a block, (b) is a perspective view which shows a block with a siping. It is the graph which showed the correlation with the lateral spring constant estimated with the prediction method of this embodiment, and the measured lateral spring constant.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In the method for predicting the cornering performance of an automobile tire according to the present invention (hereinafter sometimes simply referred to as “prediction method”), the ratio of the lateral force acting on the automobile tire to the lateral displacement caused by the lateral force (lateral force) This includes a step of predicting a lateral spring constant that is a lateral displacement), and evaluates the cornering performance of an automobile tire.

  As shown in FIG. 1, an automobile tire (hereinafter sometimes simply referred to as “tire”) 1 evaluated by the prediction method of the present embodiment is a bead passing from a tread portion 2 to a sidewall portion 3, for example. A carcass 6 reaching the bead core 5 of the portion 4 and a belt layer 7 disposed on the outer side in the tire radial direction of the carcass 6 and inward of the tread portion 2 are provided.

  In the tread portion 2, a tread rubber 2 </ b> G is disposed on the outer side in the tire radial direction of the belt layer 7. On the outer surface of the tread rubber 2G, as shown in FIG. 2, for example, a main groove 11 extending continuously in the tire circumferential direction and a plurality of lateral grooves 12 extending in a direction intersecting with the main groove 11 are provided. A plurality of land portions 13 are divided by the main grooves 11 and the lateral grooves 12. The land portion 13 may be provided with one or two or more of the sipings 16 (shown in FIG. 3B) that are cuts having a groove width of 1.5 mm or less.

  As shown in FIG. 1, the carcass 6 includes a main body portion 6 a extending from the tread portion 2 through the sidewall portion 3 to the bead portion 4, and a bead core 5 connected to the main body portion 6 a and embedded in the bead portion 4. It is composed of two carcass plies including a folded portion 6b whose both ends are folded, that is, an inner carcass ply 6A and an outer carcass ply 6B. The “inner side and outer side” are distinguished by the position of the tire equator C.

  In the inner carcass ply 6A and the outer carcass ply 6B, for example, carcass cords arranged at an angle of 80 to 90 degrees with respect to the tire equator C are overlapped so as to intersect each other. Further, between the inner and outer carcass plies 6A, 6B between the main body portion 6a and the turn-up portion 6b, it is made of hard rubber extending from the bead core 5 in the tire radial direction and JIS durometer A hardness, for example, 75 to 90 degrees. A bead apex rubber 8 is disposed, and the bead portion 4 is appropriately reinforced. The bead portion 4 is provided with a rim displacement preventing clinch rubber 9 that forms the outer surface of the bead portion 4 and a bead reinforcement layer 10 that surrounds the bead core 5 in a U shape.

  The belt layer 7 of the present embodiment has two belt cords arranged at a small angle of, for example, 10 to 35 degrees with respect to the tire equator C, that is, the inner belt ply 7A and the outer belt ply 7B. It is configured by overlapping in directions that intersect each other. A steel cord is employed for the belt cord of the present embodiment.

In the step of predicting the lateral spring constant of the tire 1, the following formula (1) is used. In the present embodiment, as described above, a passenger vehicle tire in which a plurality of blocks 15 are formed in the tread portion 2 is evaluated.

Where Gy: transverse spring constant (N / mm)
S: Tire contact area (cm ² )
Te: Complex elastic modulus (MPa) of tread rubber
r: Belt layer radius (mm)
F: Tangent force during grounding (N)
y: Displacement in the axial direction of the tire in the tread area (mm)
h: Land height of the tread (mm)
Ey: Young's modulus of tread rubber (N / cm ² )
G: Shear rigidity of the tread rubber (N / cm ² )
Im: Cross-sectional second moment of land in tread (mm ⁴ )
A: Cross-sectional area of land in the tread (cm ² )
Ap: Air pressure (kPa)
Pn: Number of carcass plies (sheets)
Hi: Height of folded portion of outer carcass ply (mm)
Ho: Height of folded part of inner carcass ply (mm)
Bn: Number of bead reinforcement layers (sheets)
Cw: Maximum thickness of clinch rubber (mm)
Bh: Bead apex height (mm)
Bg: Bead apex rubber hardness (degree)
α: Angle of belt cord with respect to tire axial direction (°)
Bw: Maximum width of belt ply in the tire axial direction (mm)
a1-a14: Constant

  The ground contact area S is, for example, an area of the ground contact surface 14 in a normal load load state in which the tire 1 is assembled on a normal rim and filled with a normal internal pressure and a normal load is applied to be grounded on a plane.

  The “regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum load capacity is specified for JATMA, and the table “TIRE LOAD LIMITS” is set for TRA. The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”. If ETRTO, “LOAD CAPACITY”.

  The radius r of the belt layer is specified by the radius of the belt layer 7 at the outermost end in the tire radial direction. In this embodiment, it is set as the radius at the outermost end in the tire radial direction of the outer belt ply 7B.

  Cy in the above formula (1) indicates the lateral stiffness of the tread rubber. In this embodiment, Cy is obtained by the product of the complex elastic modulus Te of the tread rubber and the pattern lateral stiffness K of the tire 1.

The complex elastic modulus Te of the tread rubber is a complex elastic modulus of the tread rubber 2G of the tread portion 2, and in accordance with JIS-K6394, a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. is used under the following conditions. It is the value measured using.
Initial strain: 10%
Dynamic distortion (amplitude): ± 2%
Frequency: 10Hz
Deformation mode: Tensile Measurement temperature: 30 ° C

  When the tread rubber 2G has a multilayer structure, the complex elastic modulus Te is the value of the complex elastic modulus of the grounded rubber layer.

  Further, as shown in FIG. 2, the pattern lateral stiffness K in the above formula (1) is the tire circumferential direction lines Le and Le passing through the tread grounding ends 2e and 2e on the grounding surface 14 in the normal load application state. It is specified in the following manner for all land portions 13 in the range of the entire circumference sandwiched between two.

  First, when the land portion 13 is a block 15, as shown in FIG. 3A, it can be modeled as a cantilever beam supported on the inner end side in the tire radial direction. The pattern lateral stiffness K of the land portion 13 is obtained by applying bending and shearing of the beam to this.

  Further, as shown in FIG. 2, for the shoulder block 15S arranged on the tread grounding end 2e side, the width W of the land portion 13 is regarded as Ws which is the length to the tread grounding end 2e, and the pattern lateral stiffness Is calculated.

As shown in FIG. 3B, when the siping 16 is present in the block 15, the value corrected by the following equation (2) is used in consideration of a decrease in the lateral rigidity of the block 15. Is preferred.

Where W: width of land (mm)
L: Circulating component length in the circumferential direction (mm)
hs: Depth of siping (mm)

  Further, when the land portion 13 is a rib that is continuous in the tire circumferential direction, the pattern lateral rigidity is regarded as a block having a circumferential length in the ground contact surface 14 and half the height of the land portion 13. Assume that K is obtained.

  In addition, since the actual block 15 includes various types other than the rectangular shape, the pattern lateral stiffness of each block 15 can be calculated using a quadrature method, coordinate transformation, or the like. .

  Ky in the above formula (1) indicates the lateral rigidity of the carcass. The heights Hi and Ho of the folded portions of the outer and inner carcass plies and the height Bh of the bead apex are specified by the height of the outermost end in the tire radial direction from each bead base line BL. When the carcass 6 is composed of one carcass ply 6A, the height of the outermost end of the carcass ply 6A is substituted for the height Ho of the inner carcass ply folding portion, and 0 is assigned to the height Hi.

  The “bead base line” is a tire axial direction line passing through a bead diameter position defined by a standard based on the tire.

  The bead apex has a rubber hardness Bg in accordance with JIS-K6253, and is a durometer type A hardness in an environment of 23 ° C.

  The number Pn of carcass plies is counted as one if the carcass plies are arranged across the bead core 5 even if the folded portion 6b where both ends of the bead core 5 are folded back is not included.

  E in the above formula (1) represents the elastic constant of the belt layer. When the belt layer 7 includes a plurality of belt plies 7A and 7B as in the present embodiment, the angle α of the belt cord with respect to the tire axial direction is a belt ply (in this embodiment, close to the outer surface side of the tread portion 2). It is specified by the outer belt ply 7B).

  Further, I in the above formula (1) indicates a second moment of section about the Z axis of the belt layer. When the belt layer 7 includes a plurality of belt plies 7A and 7B, the maximum width Bw is specified by a belt ply (outer belt ply 7B in the present embodiment) close to the outer surface side of the tread portion 2.

  For the constants a1 to a14, the actually measured lateral spring constants of the 14 tires 1 are substituted into the lateral spring constant Gy of the above formula (1), and the design factors (parameters) of the respective tires are substituted by the above formulas (1) to ( It is obtained by solving 14 simultaneous equations which are established by substituting into 7).

  The actual value of the lateral spring constant is measured by using a tire static tester, measuring the lateral displacement when a lateral force of 1 kN is applied in the normal load state, and dividing the lateral force by 1 kN. Is required.

  FIG. 4 is a graph plotting the lateral spring constant predicted by the above formula (1) as X and the measured lateral spring constant as Y in a plurality of tires having different tire constituent members such as the carcass 6 and the belt layer 7. Indicated. As shown in this graph, it can be confirmed that the lateral spring constant predicted using the above equation (1) has a very high correlation with the actually measured lateral spring constant. Thus, the prediction method of the present invention can be easily predicted by substituting a specific design factor of the tire constituent member into the above formula (1) without actually measuring the lateral spring constant, and thus has high practicality. In addition, the efficiency of tire design with excellent cornering performance can be improved.

  Further, the constants a1 to a14 can be obtained with higher accuracy by obtaining the constants a1 to a14 using the tires 1 having different tire sizes.

Using the above formula (1), the lateral spring constants were predicted for 246 tires having different tire constituent members, and the lateral spring constants of these tires were actually measured. A graph plotted with the predicted lateral spring constant as X and the actually measured lateral spring constant as Y is shown in FIG.
The common specifications are as follows.
Constant a1: 0.37
Constant a2: 0.11
Constant a3: 1.32
Constant a4: 0.03
Constant a5: 0.12
Constant a6: -3.87
Constant a7: 41.56
Constant a8: 2.27
Constant a9: 0.01
Constant a10: 0.29
Constant a11: 0.01
Constant a12: 0.49
Constant a13: 12.93
Constant a14: -25.94

The constants a1 to a14 are obtained by solving 14 simultaneous equations established by substituting the actually measured lateral spring constants of the 14 tires and the design factor of each tire into the above equation (1). It was.
Table 1 shows the details of the design factors for the 14 tires.

  As a result of the test, the lateral spring constant predicted by the prediction method of the present invention has a correlation coefficient of 0.96 with the actually measured lateral spring constant, has a very high correlation, and can predict the lateral spring constant with high accuracy. Was confirmed. Therefore, since the prediction method of the present invention can be predicted only by substituting the design factor, it has been confirmed that it is highly practical and can improve the efficiency of tire design with excellent cornering performance.

DESCRIPTION OF SYMBOLS 1 Automobile tire 2 Tread part 3 Side wall part 4 Bead part 6A Inner carcass ply 6B Outer carcass ply 7A Inner belt ply 7B Outer belt ply 8 Bead apex rubber 9 Clinch rubber 10 Bead reinforcement layer

Claims (2)

The prediction method of the cornering performance of the tire for motor vehicles characterized by including the process of estimating the transverse spring constant of a tire for motor vehicles using following formula (1).

Where Gy: transverse spring constant (N / mm)
S: Tire contact area (cm ² )
Te: Complex elastic modulus (MPa) of tread rubber
r: Belt layer radius (mm)
F: Tangent force during grounding (N)
y: Displacement in the tire axial direction of the land portion of the tread (mm)
h: Land height of the tread (mm)
Ey: Young's modulus of tread rubber (N / cm ² )
G: Shear rigidity of the tread rubber (N / cm ² )
Im: Cross-sectional second moment of land in tread (mm ⁴ )
A: Cross-sectional area of land in the tread (cm ² )
Ap: Air pressure (kPa)
Pn: Number of carcass plies (sheets)
Hi: Height of folded portion of outer carcass ply (mm)
Ho: Height of folded part of inner carcass ply (mm)
Bn: Number of bead reinforcement layers (sheets)
Cw: Maximum thickness of clinch rubber (mm)
Bh: Bead apex height (mm)
Bg: Bead apex rubber hardness (degree)
α: Angle of belt cord with respect to tire axial direction (°)
Bw: Maximum width of belt ply in the tire axial direction (mm)
a1-a14: Constant The said formula (1) is a method for predicting the cornering performance of the automobile tire according to claim 1, wherein the following formula (2) is used when siping is provided in the tread portion of the automobile tire.

Where W: width of land (mm)
L: Circulating component length in the circumferential direction (mm)
hs: Depth of siping (mm)