JP5952713B2 - 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.

  An automobile tire generates a cornering force when a slip angle is given during traveling. This cornering force generates a moment in the vehicle and turns the vehicle body to turn.

  Further, the cornering force increases as the slip angle increases, and the proportionality constant between them is called cornering power. In this specification, for the sake of convenience, the cornering force when the slip angle is 1 ° is defined as the cornering power. Conventionally, this cornering power has been used as an index for evaluating the cornering performance of an automobile tire.

By the way, conventionally, various methods for estimating the cornering power from the physical properties of each part of the tire have been proposed. For example, in the following Non-Patent Document 1, the following formula (3) is proposed as a cornering power estimation formula.
... (3)







Where CP: cornering power (N / deg)
Cy: Lateral stiffness of tread rubber Ky: Lateral stiffness of carcass E: Elastic constant of belt layer I: Secondary moment of inertia of belt layer around Z axis (mm ⁴ )
l: Maximum length of ground contact surface in the circumferential direction (mm)
w: Maximum width in the tire axial direction of the contact surface (mm)

  However, since most of the physical property values and the like input to the cornering power estimation formula represented by the above formula (3) are abstract physical quantities, they are not useful for practical tire design and are not practical. .

  Therefore, the inventors have improved the practicality by replacing the physical property value represented by the above formula (3) with a specific design factor determined when designing the tire in Patent Document 1 below. A method for predicting the cornering performance of automobile tires is proposed.

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

JP 2012-159378 A

  However, although the prediction method of Patent Document 1 can improve the efficiency of tire design, it is not sufficient and there is room for further improvement.

  As a result of extensive research, the inventors have found that, among the design factors used to predict the cornering power of Patent Document 1, the maximum width in the tire axial direction of the belt ply has little effect on the cornering power. To complete the invention.

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

Among the present inventions, the invention described in claim 1 includes a step of predicting the cornering power of an automobile tire using the following formula (1).
... (1)



CP: Cornering power (N / deg)
l: Maximum circumferential length of tire contact surface (mm)
w: Maximum width of tire ground contact surface in the axial direction (mm)
Tg: Elastic modulus of the tread rubber in the twist direction (MPa)
α: Angle of belt cord with respect to tire axial direction (°)
Ky: Tire lateral spring (N / mm)
K: Pattern lateral rigidity (N / mm) of land part of tread part
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 )
a1-a6: Constant

In the invention according to claim 2, when the siping is provided in the tread portion of the automobile tire, the value K ′ corrected by the following expression (2) is used in the expression (1). The method for predicting the cornering performance of the automobile tire described in the above.
... (2)
Where W: width of the tread land (mm)
L: Circulating component length in the circumferential direction (mm)
hs: Depth of siping (mm)

  According to a third aspect of the present invention, the cornering power is predicted in a state in which the automobile tire is assembled on a regular rim, filled with a regular internal pressure, and loaded with 5 to 30% of the regular load. The method for predicting cornering performance of an automobile tire according to claim 1 or 2.

  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, “Design Rim” for TRA, ETRTO Then "Measuring Rim".

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

  “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 specified for JATMA, and the table “TIRE LOAD LIMITS AT for TRA” The maximum value described in “VARIOUS COLD INFLATION PRESSURES”, or “LOAD CAPACITY” for ETRTO.

  The method for predicting cornering performance of an automobile tire according to the present invention includes a step of predicting the cornering power 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.

  Moreover, in the prediction method of the present invention, there is no need to set the maximum width in the tire axial direction of the belt ply that has been input conventionally. This is based on the fact that the inventors have found that the maximum width of the belt ply hardly affects the prediction of cornering power. Therefore, according to the prediction method of the present invention, the cornering power can be easily predicted while maintaining the correlation with the actually measured cornering power.

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 of the cornering power estimated with the prediction method of this embodiment, and the measured cornering power.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
The method for predicting the cornering performance of an automobile tire of the present invention (hereinafter sometimes simply referred to as “prediction method”) includes a step of predicting the cornering power CP, and evaluates the cornering performance of the automobile tire. In the present specification, as described above, the cornering power CP is defined by the cornering force when the slip angle is 1 °.

  As shown in FIG. 1, an automobile tire (hereinafter, simply referred to as a “tire”) 1 evaluated by the prediction method of the present embodiment is configured as a passenger car tire, for example, from the tread portion 2 to the side. A carcass 6 extending from the wall portion 3 to the bead core 5 of the bead 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 2G is disposed on the outer side in the tire radial direction of the belt layer 7. 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 on the outer surface of the tread rubber 2G. 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 sipings 16 (shown in FIG. 3B) which are cuts having a groove width of 1.5 mm or less.

  As shown in FIG. 1, the carcass 6 has a body portion 6 a that extends from the tread portion 2 through the sidewall portion 3 to the bead portion 4, and a bead core 5 that is continuous with the body portion 6 a and embedded in the bead portion 4. Are formed of two carcass plies including the folded portion 6b, that is, the inner carcass ply 6A and the outer carcass ply 6B. “Inside, outside” is 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 ° with respect to the tire equator C are overlapped so as to intersect each other. A bead apex 8 extending from the bead core 5 to the outer side in the tire radial direction is disposed between the main body portion 6a and the folded portion 6b of the inner and outer carcass plies 6A and 6B. The bead apex rubber 8 is made of, for example, a hard rubber having a JIS durometer A hardness of 75 to 90 degrees, and reinforces the bead portion 4 as appropriate. 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 with the belt cord inclined at a small angle of, for example, 10 to 35 ° with respect to the tire equator C, that is, the inner belt ply 7A and the outer belt ply 7B. Overlaid in the crossing direction. In the belt layer 7 of the present embodiment, end portions 7e in the tire axial direction are located in the vicinity of both ends of the tread portion 2 in the tire axial direction.

  And in the process of estimating the cornering power of the tire of this embodiment, the following formula (1) not including the maximum width in the tire axial direction of the belt ply as a design factor is used.

... (1)



CP: Cornering power (N / deg)
l: Maximum circumferential length of tire contact surface (mm)
w: Maximum width of tire ground contact surface in the axial direction (mm)
Tg: Elastic modulus of the tread rubber in the twist direction (MPa)
α: Angle of belt cord with respect to tire axial direction (°)
Ky: Tire lateral spring (N / mm)
K: Pattern lateral rigidity (N / mm) of land part of tread part
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 )
a1-a6: Constant

  In the above formula (1), among the design factors used to predict the cornering power in Patent Document 1, the maximum width BW between the end portions 7e and 7e in the tire axial direction of the belt plies 7A and 7B is Not included. This is because the tread portion 2 hardly touches over the end portion 7e in the tire axial direction of the belt plies 7A and 7B during normal running when a load lower than the normal load is applied. This is because the difference in the maximum width BW is considered not to affect the cornering power.

  The above formula (1) indicates that the load applied to the tire 1 during normal running, that is, the rim is assembled to the normal rim, the normal internal pressure is filled, and a load of 5 to 30% of the normal load is applied. It is desirable to predict under low load conditions. If the load applied to the tire 1 exceeds 30% of the normal load, the tire 1 may be grounded beyond the end portions 7e of the belt plies 7A and 7B. Conversely, if the load applied to the tire 1 is less than 5% of the normal load, the load becomes excessively small and the prediction accuracy may be reduced. From such a viewpoint, the load applied to the tire 1 is more preferably 10% or more of the normal load, and more preferably 30% or less. In the present embodiment, it is desirable that the dimensions and the like of each part of the tire are specified in a low load state.

  As shown in FIG. 2, the circumferential maximum length l of the ground contact surface of the tire is specified by the maximum circumferential length of the ground contact surface 14 of the tread portion 2. The maximum width w of the tire contact surface is specified by the maximum width in the tire axial direction.

The torsional direction elastic modulus Tg of the tread rubber is a complex elastic modulus G * of the tread rubber 2G in the tread part 2 in the torsional direction. RDA III).
Initial strain: 0%
Dynamic distortion (amplitude): ± 2%
Frequency: 10Hz
Measurement temperature: 30 ° C

  When the tread rubber 2G has a multilayer structure, the twist direction elastic modulus Tg is the value of the twist direction elastic modulus of the rubber layer that is grounded.

  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 close to the outer surface side of the tread portion 2 (in this embodiment, the outer side). Belt ply 7B).

  In the present embodiment, a lateral spring Ky of the tire is used instead of the lateral stiffness Ky of the carcass of Patent Document 1. This is because the lateral stiffness of the carcass and the lateral spring of the tire are proportional to each other. The lateral spring Ky of the tire measures, for example, a lateral tire deformation amount t (mm) when a longitudinal load of 4.1 kN and a lateral load of 2.0 kN is applied to the tire 1, and the lateral load of 2.0 kN is measured. It is obtained by dividing by the tire deformation amount t (mm). Thereby, cornering power can be predicted more easily.

  Further, the pattern lateral stiffness K of the land portion 13 of the tread portion 2 in the above formula (1) is the tread grounding end on the grounding surface 14 of the tread portion 2 when grounded on a plane as shown in FIG. 2e and 2e are specified in the following manner for all land portions 13 in the entire circumference range sandwiched between tire circumferential direction lines Le and Le.

  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.

  The pattern lateral stiffness K is a known design factor in the process of predicting cornering power, such as the height h of the land portion 13 of the tread portion 2, the Young's modulus Ey of the tread rubber 2G, the shear stiffness G of the tread rubber 2G, It can be obtained from the sectional secondary moment Im of the land portion 13 in the ground contact surface 14 of the tread portion 2 and the sectional area A of the land portion 13 in the ground contact surface 14 of the tread portion 2.

  As shown in FIG. 1, the height h of the land portion 13 of the tread portion 2 is the maximum height from the outer surface of the belt ply 7B disposed on the outermost side in the tire radial direction to the tread outer surface 2S. Specified by Further, the cross-sectional area A of the land portion 13 of the tread portion 2 includes tire radial direction lines 21e and 21e passing through the grounding ends 2e and 2e of the tread portion 2, the outer surface of the belt ply 7B on the outermost side in the tire radial direction, and the tread portion. In the region surrounded by the two outer surfaces 2S, the cross section 20 of each land portion 13 is specified. Further, the cross-sectional secondary moment Im of the land portion 13 of the tread portion 2 is specified in the cross-section 20 of each land portion 13 of the tread portion 2.

The tread rubber Young's modulus Ey and the tread rubber shear stiffness G mean the elastic modulus of the tread rubber against elongation and shear, and are determined by the type of tread rubber. The shear rigidity G of the tread rubber is a value measured using a torsion type high output viscoelasticity measuring device (Dynamic Analyzer RDAIII) manufactured by Rheometric Scientic under the following conditions. The Young's modulus Ey of the tread rubber is a value measured using a tensile type viscoelasticity measuring machine (Visco Elastic Spectorometer Type-3) manufactured by Iwamoto Seisakusho Co., Ltd. under the following conditions.
Initial strain: 0%
Dynamic distortion (amplitude): ± 2%
Frequency: 10Hz
Measurement temperature: 30 ° C

As shown in FIG. 3B, when the siping 16 is present in the block 15, the value K ′ corrected by the following equation (2) is used in consideration of the decrease in the lateral rigidity of the block 15. It is preferred that
... (2)
Where W: width of the tread land (mm)
L: Length of circumferential component of siping (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. .

  The constants a1 to a6 are obtained by substituting the measured cornering power of the six tires 1 into the cornering power CP of the above equation (1) and substituting the design factors (parameters) of the respective tires into the above equation (1). It is obtained by solving six simultaneous equations that hold. In addition, the actual value of the cornering power of this embodiment is measured by the cornering force when the slip angle is 1 degree for the low-load tire 1 using an indoor test machine.

  FIG. 4 shows a graph in which the cornering power predicted by the above formula (1) is X and the measured cornering power is Y in a plurality of tires having different design factors such as the carcass 6 and the belt layer 7. As shown in this graph, it can be confirmed that the cornering power predicted using the above equation (1) has a very high correlation with the measured cornering power. Thus, since the prediction method of the present invention can be easily predicted by substituting specific design factors of the tire constituent members into the above formula (1) without actually measuring the cornering power, the practicality is high. Tire design with excellent cornering performance can be made more efficient. Moreover, in the prediction method of the present invention, it is not necessary to input the maximum width of the belt ply in the tire axial direction. Therefore, according to the prediction method of the present invention, the cornering power can be easily predicted while maintaining the correlation with the actually measured cornering power.

  The constants a1 to a6 are preferably obtained using tires 1 having different tire sizes. Thereby, the cornering power can be obtained with higher accuracy.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

Using the above formula (1), cornering power was predicted for 158 tires having different tire constituent members, and the cornering power of those tires was actually measured. A graph plotted with the predicted cornering power as X and the measured cornering power as Y is shown in FIG.
The common specifications are as follows.
Constant a1: 0.362
Constant a2: 0.2
Constant a3: 243
Constant a4: 0.1
Constant a5: 4.2
Constant a6: 0.56

The constants a1 to a6 in the above equation (1) are obtained by solving six simultaneous equations established by substituting the measured cornering power of the six tires and the design factor of each tire into the above equation (1). I was asked.
Details of the design factors for the six tires are shown in Table 1.

Moreover, the cornering power when different loads were applied to the tire having the basic structure of FIG. 1 was predicted using the above formula (1). Similarly, the cornering power when different loads were applied was measured. Then, for each load, a correlation coefficient between the predicted cornering power CP1 and the actually measured cornering power CP2 was calculated. The result shows that the closer the value is to 1, the higher the correlation.
The test results are shown in Table 2.

  As a result of the test, as shown in FIG. 4 and Table 2, it was confirmed that the cornering power predicted by the prediction method of the present invention had a very high correlation with the actually measured cornering power. Therefore, the prediction method of the present invention can easily predict the cornering power simply by substituting the design factor, and thus it has been confirmed that the tire design is highly practical and can improve the efficiency of tire design with excellent cornering performance. Further, in the prediction method of the present invention, it is not necessary to input the maximum width of the belt ply that has been input conventionally, so that it was confirmed that the cornering power can be predicted easily in a short time. Furthermore, it has been confirmed that the prediction method of the present invention predicts cornering power with high accuracy by limiting it to the normal traveling where a load of 5 to 30% of the normal load is applied.

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 9 Clinch rubber 10 Bead reinforcement layer

Claims (3)

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




CP: Cornering power (N / deg)
l: Maximum circumferential length of tire contact surface (mm)
w: Maximum width of tire ground contact surface in the axial direction (mm)
Tg: Elastic modulus of the tread rubber in the twist direction (MPa)
α: Angle of belt cord with respect to tire axial direction (°)
Ky: Tire lateral spring (N / mm)
K: Pattern lateral rigidity (N / mm) of land part of tread part
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 )
a1-a6: Constant
In the above formula (1), when siping is provided in the tread portion of the automobile tire, the value K ′ corrected by the following formula (2) is used. Prediction method.
... (2)
Where W: width of the tread land (mm)
L: Circulating component length in the circumferential direction (mm)
hs: Depth of siping (mm)   The automobile according to claim 1 or 2, wherein the cornering power is predicted in a state in which the automobile tire is assembled on a regular rim, filled with a regular internal pressure, and loaded with 5 to 30% of a regular load. For predicting cornering performance of automobile tires.