JP5166059B2 - Tire design method and tire. - Google Patents

Description

  The present invention relates to a tire, and more particularly to a tire design method that ensures straight running stability of a vehicle regardless of the vehicle weight, and a tire to which the tire design method is applied.

  Conventionally, tires for passenger cars have a residual cornering force (hereinafter referred to as “PRCF” as appropriate) so that the road surface cant (the inclination of the road surface provided for draining rainwater) can travel straight with respect to the weight of the vehicle to be mounted. .) Is applied.

Since the tread pattern contributes to the generation of the residual cornering force, various tread patterns capable of obtaining a suitable residual cornering force with respect to the road surface cant have been studied (for example, see Patent Document 1).
JP-A-5-58114

  In recent years, tires are increasingly used in vehicles of the same size but with various weights. However, depending on the inclination angle of the road surface cant (hereinafter referred to as a cant angle) and the load borne by the tire (hereinafter referred to as the tire load), the PRCF required to ensure straight running stability is Different. Therefore, in the market, tires that ensure straight running stability regardless of tire load, in other words, tires that can obtain the residual cornering force required to ensure straight running stability according to tire load are desired. It is rare.

  In consideration of the above facts, the present invention provides a tire design method capable of obtaining a residual cornering force necessary for ensuring straight running stability in accordance with a tire burden load, and a tire designed by the tire design method. The purpose is to provide.

  In general, when a vehicle travels on a traveling path R having a cant, a force as shown in FIG. Note that θ shown in FIG. 3 indicates a cant angle, W indicates a tire burden load, and DF indicates a force with which the tire T attempts to lower the cant. As shown in FIG. 3, the force DF that causes the tire T to lower the cant of the travel path R is generated in a direction parallel to the road surface of the travel path R, and can be obtained by W × sin θ. Further, the force DF for lowering can be canceled by generating (acting) on the tire T a force that is in the opposite direction and equal in magnitude to the force DF for lowering. The straight running stability of the vehicle is ensured by canceling the force DF to be lowered. Here, the present inventor paid attention to the residual cornering force generated during traveling as a force for canceling the force DF to be lowered.

  The residual cornering force is roughly divided into a force caused by a belt component generated by deformation of the belt cord (hereinafter referred to as a belt component) and a tread block that receives a load and is twisted. It is comprised by the force (henceforth a pattern component) resulting from a pattern component.

  The belt component generated by the belt cord deformation is generated, for example, by about 10 N per 1 kN load in a belt material used for a normal passenger car tire. This belt component is obtained by sticking the belt such that the belt cord is inclined with respect to the tire circumferential direction (or tire width direction). Specifically, when the belt cord is tilted upward as viewed from the tire outer peripheral side, a belt component in the right direction with respect to the traveling direction of the tire is obtained, and the belt cord is viewed from the tire outer peripheral side. By tilting leftward, the belt component in the left direction with respect to the traveling direction of the tire can be obtained. For this reason, a belt component in the left direction is generated in countries with right-hand traffic (climbing to the left with respect to the direction of travel), and a belt with a right-hand direction in countries with left-hand traffic (road cant in the direction of going up with respect to the direction of travel). Ingredients are often generated. Further, since the outermost layer belt contributes the most to the generation of the belt component, the direction in which the belt component is generated is determined by the cord direction (upward or leftward) of the outermost layer belt. When there is one belt, that belt is the outermost belt.

  In addition, since the belt component depends on the strength of the cord and the like, for example, if a belt having an excellent cord strength such as for LT is used, the belt component becomes a large value. That's not true.

The pattern component is based on the circumferential groove provided at the position (including the line) closest to the line that bisects the ground contact edge (end of the contact width) at 80% normal load and the tire equatorial plane. As
The manner of occurrence is different between the reference circumferential groove in the tire width direction (tire equatorial plane side) and the tire width direction outer side (side away from the tire equatorial plane). On the inner side in the tire width direction of the reference circumferential groove, a pattern component is generated mainly by a longitudinal shear force generated in the ground contact surface. Specifically, in a block formed by a lug groove that rises to the right when viewed from the tire outer peripheral surface side, a pattern component in the left direction with respect to the traveling direction is generated. In the formed block, a pattern component in the right direction with respect to the traveling direction is generated. If the angle of the lug groove with respect to the tire width direction is halved, the amount of pattern component generated per load is approximately halved and the angle can be doubled. For example, the amount of pattern components generated per load is approximately doubled.

  Further, on the outer side in the tire width direction of the reference circumferential groove, a pattern component is generated mainly by a lateral shearing force generated in the ground contact surface. Specifically, in a block formed by a lug groove that rises to the right when viewed from the tire outer peripheral surface side, a pattern component in the right direction with respect to the traveling direction is generated. In the formed block, a pattern component in the left direction with respect to the traveling direction is generated. If the angle of the lug groove with respect to the tire width direction is halved, the amount of pattern component generated per load is approximately halved and the angle can be doubled. For example, the amount of pattern components generated per load is approximately doubled.

  The present inventor has intensively studied in consideration of the above, and completed a tire design method capable of generating the residual cornering force necessary to cancel out the force DF that varies depending on the tire load. It came to do.

  That is, a tire designing method according to claim 1 of the present invention includes a tread having a plurality of circumferential grooves and a plurality of blocks defined by a plurality of lug grooves intersecting the circumferential grooves, and the tire of the tread. A tire design method comprising: at least one belt having a plurality of cords provided radially inward and parallel to each other, wherein a cant angle of a traveling road is set and the cant angle is set The first step of calculating the force of the tire to lower the cant according to the tire burden load, and obtaining the inclination from the calculated relationship between the force of lowering and the tire burden load, and the outermost layer during running The angle of the belt cord with respect to the tire width direction, the angle of the outer lug groove defining the outermost block in the tire width direction with respect to the tire width direction, and the outermost block The inclination obtained from the relationship between the resultant force of the force in the tire traveling direction and the direction orthogonal to the tire traveling direction, which contributes to the generation of the angle with respect to the tire width direction of the inner lug groove defining the inner block in the inner side in the ear width direction, is the first The angle of the outermost layer of the belt cord with respect to the tire width direction, the angle of the outer lug groove with respect to the tire width direction, and the angle of the inner lug groove with respect to the tire width direction so as to be equal to the inclination obtained in the step And a second step of setting.

Next, a tire designing method according to claim 1 will be described.
In the first step, the cant angle of the traveling road is set, and the force at which the tire attempts to lower the cant at the set cant angle is calculated according to the tire burden load. The inclination is determined from the relationship between the calculated force to drop and the tire load.
In the second step, during traveling, the angle of the cord of the outermost layer belt with respect to the tire width direction, the angle of the outer lug groove with respect to the tire width direction, and the angle of the inner lug groove with respect to the tire width direction are orthogonal to the tire traveling direction. The angle of the outermost belt cord with respect to the tire width direction and the outer lug so that the inclination obtained from the relationship between the resultant force (PRCF) of the direction and the tire load is equal to the inclination obtained in the first step An angle of the groove with respect to the tire width direction and an angle of the inner lug groove with respect to the tire width direction are set.

  Here, the tire is designed so that the direction of the resultant force (PRCF) generated by the tire during traveling is opposite to the direction in which the tire attempts to lower the cant, that is, the direction in which the force to lower the tire is canceled. By mounting, the traveling force and the resultant force cancel each other out when traveling on the traveling path of the set cant angle, and the straight running stability of the vehicle is ensured. In addition, even if the vehicle to be installed or the number of passengers is changed and the tire burden load fluctuates, the inclination obtained from the relationship between the resultant force (PRCF) generated by the tire and the tire burden load is Residual cornering required to ensure straight running stability according to the changed tire burden load, because it is set to be equal to the slope determined from the relationship between the force to lower the cant and the tire burden load. You can get a force. As a result, the straight running stability of the vehicle is ensured.

  A radial tire according to claim 2 of the present invention is characterized by being designed by the tire design method according to claim 1.

  According to the tire designing method of the present invention, it is possible to design a tire capable of obtaining a residual cornering force necessary to ensure straight running stability in accordance with a tire burden load.

[First Embodiment]
A first embodiment of a tire designed by the tire designing method of the present invention will be described with reference to FIGS. The tire according to the present embodiment is a pneumatic radial tire 10 for passenger cars (hereinafter, referred to as a tire), and is a left-hand traffic with a cant angle θ of 2 degrees on average (a cant rising to the right in the traveling direction F). Designed for. The tire size is 195 / 65R15.

  As shown in FIG. 1, the tire 10 includes a bead portion 14 in which a pair of left and right bead cores 16 are embedded, a toroidal shape extending from one bead core 16 to the other bead core 16, and an end portion of the tire 10 being engaged with the bead core 16. A combined carcass 12, a belt 18 provided outside the carcass 12 in the tire radial direction, and a tread 20 provided outside the belt 18 in the tire radial direction are provided. In addition, the conventionally well-known thing can be used for the tire structural member which comprises the tire 10. FIG.

(belt)
As shown in FIG. 2, the belt 18 is formed by embedding a plurality of belt cords 18C provided in parallel with each other in a covering rubber. The belt cord 18C is inclined at an angle φ with respect to the tire width direction on the tire equatorial plane CL. FIG. 2 is a partial cross-sectional view of the tire 10 viewed from the tire outer peripheral side, and the belt cord 18C of the present embodiment is inclined upward as viewed in FIG.

(Tread, groove)
As shown in FIG. 2, the tread 20 is formed with center circumferential grooves 30 extending in the tire circumferential direction on both sides of the equatorial plane CL, and the shoulder circumferential direction on the outer side in the tire width direction of both center circumferential grooves 30. A groove 32 is formed. The shoulder circumferential groove 32 of the present embodiment is provided at a position (including the line) closest to a line that bisects the ground contact end 20E and the tire equatorial plane CL at 80% normal load. Yes.

  Further, the tread 20 extends at an angle B1 with respect to the tire width direction, and a first center lug groove 40 that partitions a block-shaped land portion (first center block 50) between both the center circumferential grooves 30. , And extending at an angle B2 with respect to the tire width direction, and a block-shaped land portion (second center block 52) is defined between both shoulder circumferential grooves 32 and both center circumferential grooves 30. A center lug groove 42 is formed. In addition, the 1st center lug groove 40 and the 2nd center lug groove 42 of this embodiment incline in the same direction with respect to a tire width direction, and left-up as seen in FIG.

  Further, the tread 20 has shoulder lug grooves 44 extending from both shoulder circumferential grooves 32 outward in the tire width direction and defining block-like land portions (shoulder blocks 54) on the outer sides in the tire width direction of both shoulder circumferential grooves 32. Is formed. The shoulder lug groove 44 is inclined at an angle A with respect to the tire width direction, and the inclined direction is opposite to the second center lug groove 42. That is, the shoulder lug groove 44 is inclined upward as viewed in FIG.

Below, the design procedure of the tire 10 is demonstrated.
(First step)
First, the cant angle θ of the travel path R that uses the tire 10 is set. Next, at the set cant angle θ, the force DF at which the tire 10 tries to lower the cant is calculated according to the tire burden load W using DF = Wsin θ (see FIG. 4). Then, as shown in FIG. 5, the horizontal axis (X axis) is the tire burden load W, the vertical axis (Y axis) is the force DF that is going to be lowered, and the force DF that is going to be lowered at each angle θ and the tire burden load. A straight line indicating a relationship with W is obtained, and an inclination m of the straight line is obtained.

(Second step)
Next, the cant direction of the travel path R (whether it is rising to the right or rising to the traveling direction F) is set. In the present embodiment, the cant direction of the traveling path R is set to rise to the right with respect to the traveling direction F.

  Then, the angle φ, the angle A, and the angle B (so that the slope of the straight line indicating the relationship between the PRCF generated when the tire 10 travels and the tire burden load W are equal to the slope m of the straight line obtained in the first step. An average value of the angle B1 and the angle B2) is set. Note that the values of the angle φ, the angle A, and the angle B to be set can be obtained by a calculation formula to be described later, or can be obtained by inputting each component of the tire in a behavior simulation for measuring the behavior of the tire. Evaluation may be performed and the measurement value may be used as a reference.

  The operation and effect of the tire 10 designed by the tire design procedure described above will be described. When the vehicle 10 on which the tire 10 is mounted travels on the traveling path R having a cant that rises to the right with respect to the traveling direction F (cant angle θ), a force DF that attempts to lower the cant acts on the tire 10. However, since the force DF to be lowered is canceled out by the PRCF generated in the tire 10 during traveling, the straight running stability of the vehicle is ensured. Even if the vehicle on which the tire 10 is mounted or the number of passengers is changed to change the tire burden load W, the PRCF and the tire burden load with respect to the slope m of the straight line obtained in the first step. Since the tire 10 is designed so that the slopes of the straight lines representing the relationship with W are equal, it is possible to obtain a residual cornering force necessary to ensure straight running stability according to the changed tire load W. it can. As a result, the straight running stability of the vehicle is ensured.

  Next, a calculation formula for obtaining the residual cornering force (PRCF) will be described. First, PRCF assumes that the force generated in the right direction with respect to the traveling direction F is + (plus), and the force generated in the left direction with respect to the traveling direction F is − (minus). In addition, the inclination direction of each lug groove formed in the tread 20 with respect to the tire circumferential direction is defined as + for upward to the right and − for upward to the left as viewed from the tire outer peripheral surface side.

  Usually, in left-handed countries, the road surface cant rises to the right, so a right force, that is, a positive force is required to prevent the vehicle from flowing to the left. In order to generate a force in the + direction, the belt is usually combined so that the force is generated in the direction of the belt (the cord direction of the belt) in the + direction (the right direction with respect to the traveling direction). Here, assuming that the tire burden load per tire is XkN, the belt 18 generates a force of 10 × XkN, for example, when the angle φ of the belt cord 18C with respect to the tire width direction is 62 to 68 degrees.

  On the other hand, the first center lug groove 40 and the second center lug groove 42 on the inner side in the tire width direction from the shoulder circumferential groove 32 generate a positive PRCF when the inclination direction rises to the left (an angle of −). When, for example, a force of (−B / 45 degrees) × 10 × XN is generated.

  Further, the shoulder lug groove 44 on the outer side in the tire width direction from the shoulder circumferential groove 32 generates a positive PRCF when the inclination direction is upward (+ angle), and when the angle is B, for example, (A / 7.5) ) Generate a force of × 10 × XN.

  Therefore, the PRCF at the load XkN is the sum of them, and is obtained by PRCF at the load XkN = 10 × XN + (− B / 45 degrees) × 10 × XN + (A / 7.5 degrees) × 10 × XN.

  Here, when the PRCF at the load XkN of the first embodiment is substituted into the equation for obtaining the PRCF at the load XkN, the gradient K1 × XN = 10 × XN + (− B / 45 degrees) × 10 × XN + (A / 7.5 degrees) × 10 × XN. In the first embodiment, since the cant angle θ is 2 degrees on average, the straight line obtained in the first step is a straight line of θ = 2 degrees shown in FIG. 5, and the slope m is approximately 34.8. Substituting this approximately 34.8, the relational expression of 111.6 = 6 × A−B is obtained. That is, if the values of the angle A and the angle B satisfy the relational expression of 111.6 = 6 × A−B, the vehicle can travel straight on the travel path R even if the vehicle weight varies. Note that each coefficient of the force generated with respect to the load X described above can be obtained by actual measurement experimental data, calculation of a contribution rate by simulation, or the like.

  For example, if the shoulder lug groove is bent, the load dependence can be controlled nonlinearly. However, if the vehicle weight changes as a result of vehicle simulation, the required PRCF is the load On the other hand, it is preferable that the shoulder lug groove is not bent because it is linear.

  In addition, since the tire 10 of the first embodiment is designed for a left-handed road with a cant angle θ of an average of 2 degrees (a cant rising to the traveling direction F), 111.6 = 6 × If the relational expression A-B is satisfied, straight running stability can be obtained, but when the cant angle θ is the same and the tire is designed for a right-hand traffic (a cant that rises to the left with respect to the traveling direction F), A relational expression of −111.6 = 6 × a−b is obtained based on the above-described calculation formula of PRCF at the time of load X. If this relational expression is satisfied, straight running stability is obtained.

Needless to say, the present invention is not limited to the above-described embodiments, and can be implemented with various modifications within the scope of the claims.
Also, the contact surface at 80% normal load means that the tire is mounted on the applicable rim specified in JATMA YEAR BOOK (2008 edition, Japan Automobile Tire Association Standard), and the applicable size and ply rating in JATMA YEAR BOOK Is filled with 80% of the internal air pressure (maximum air pressure) corresponding to the maximum load capacity (internal pressure-load capacity correspondence table) and placed perpendicular to the flat plate and loaded with the maximum load capacity. The contact surface of the tread is a contact surface, and the contact shape indicates the shape of the contact surface. When the TRA standard or ETRTO standard is applied at the place of use or manufacturing, the respective standards are followed.

(Test example)
In order to confirm the effect of improving the performance of the tire according to the present invention, tires having a tire size of 195 / 65R15 are prepared and mounted on the domestic passenger car A or the domestic passenger car B, respectively, and the sensory evaluation of the driver trained in the vehicle flow in each tire I went there. Table 1 shows the test results for domestic passenger car A, and Table 2 shows the test results for domestic passenger car B. The evaluations in the table indicate that 最 も is the best, ○ is good, and x is not good.

(Test conditions)
As the test tires, tires each having a two-layer belt (cross belt) were used.
The actual vehicle travel path used in the test was a cant that was raised to the right with respect to the traveling direction, and had a variation in cant angle between 1.5 and 2.5 degrees.
When the test tire was mounted on a domestic passenger car A, the heavy load on the tire (front wheel) was 4.5 kN per wheel.
When the test tire was mounted on a domestic passenger car B, the heavy load on the tire (front wheel) was 3.9 kN per wheel.

Next, tires of Examples 1 to 3 and Comparative Examples 1 and 2 that have been tested by being mounted on a domestic passenger car A will be described.
In the tire of Example 1, the angle φ, the angle A, and the angle B were set so that 6A-B was 72.5.
In the tire of Example 2, the angle φ, the angle A, and the angle B were set so that 6A-B was 111.6.
In the tire of Example 3, the angle φ, the angle A, and the angle B were set so that 6A-B was 151.7.
In the tire of Comparative Example 1, the angle φ, the angle A, and the angle B were set so that 6A-B was 60.
In the tire of Comparative Example 2, the angle φ, the angle A, and the angle B were set so that 6A-B was 160.
In addition, Table 1 shows values of the angle φ, the angle A, and the angle B of the tires of Examples 1 to 3 and Comparative Examples 1 and 2.

Next, tires of Examples 4 to 6 and Comparative Examples 3 and 4 that were mounted on a domestic passenger car B and tested were described.
In the tire of Example 4, the angle φ, the angle A, and the angle B were set so that 6A-B was 72.5.
In the tire of Example 5, the angle φ, the angle A, and the angle B were set so that 6A-B was 111.6.
In the tire of Example 6, the angle φ, the angle A, and the angle B were set so that 6A-B was 151.7.
In the tire of Comparative Example 3, the angle φ, the angle A, and the angle B were set so that 6A-B was 60.
In the tire of Comparative Example 4, the angle φ, the angle A, and the angle B were set so that 6A-B was 160.
Table 2 shows the values of the angle φ, the angle A, and the angle B of the tires of Examples 4 to 6 and Comparative Examples 3 and 4.

(Test results)
As can be seen from Tables 1 and 2, the tires of Examples 1 to 6 are at a level where there is no problem with vehicle flow. This is because Example 1 and Example 4 can generate a PRCF equivalent to the tire designed by the tire designing method of the present invention with the cant angle θ set to 1.5 degrees. Further, in Example 3 and Example 6, PRCF equivalent to the tire designed by the tire designing method of the present invention with the cant angle θ set to 2.5 degrees can be generated. For this reason, in the traveling road used for the test, the favorable result is represented. On the other hand, since the tires of Comparative Examples 1 to 4 are designed with the cant angle θ set outside the range of 1.5 to 2.5 degrees, the amount of PRCF generated is not an appropriate value. Vehicle flow is occurring. The tires of Example 2 and Example 5 can generate PRCF equivalent to the tire designed by the tire design method of the present invention with the cant angle θ set to 2 degrees, so that the best results are obtained. Has been obtained.

FIG. 2 is a half sectional view showing a half of a cross section along the tire width direction of the tire according to the first embodiment of the present invention. It is a fragmentary sectional view of the top view showing the tread pattern of the tire concerning a 1st embodiment of the present invention. It is explanatory drawing which shows the force which acts on the tire on a travel path. It is a table | surface showing the relationship between cant angle (theta), the tire burden load W, and force DF which a tire tends to descend. It is a graph which shows the relationship between DF which a tire tends to go down and tire burden load W.

Explanation of symbols

10 Pneumatic radial tire (tire)
18 belt 18C belt cord (belt cord)
20 tread 30 center circumferential groove (circumferential groove)
32 Shoulder circumferential groove (circumferential groove)
40 1st center lug groove (lug groove)
42 Second center lug groove (lug groove)
44 Shoulder lug groove (lug groove)
50 1st center block (block)
52 Second Center Block (Block)
54 Shoulder Block (Block)
A Angle B Angle φ Angle DF Force to move down F Traveling direction PRCF Residual cornering force
R road W tire load θ cant angle

Claims (2)

A tread having a plurality of blocks defined by a plurality of circumferential grooves and a plurality of lug grooves intersecting the circumferential grooves;
A tire design method comprising: at least one belt having a plurality of cords provided in parallel to each other and provided inside the tread in the tire radial direction,
The cant angle of the road is set, the force at which the tire attempts to lower the cant at the set cant angle is calculated according to the tire burden load, and the inclination is determined from the relationship between the calculated lower force and the tire burden load. A first step to find,
During traveling, the angle of the belt cord of the outermost layer with respect to the tire width direction, the angle of the outer lug groove defining the outermost block in the tire width direction with respect to the tire width direction, and the inner side in the tire width direction with respect to the outermost block The inclination obtained from the relation between the resultant force of the tire traveling direction and the orthogonal force that contributes to the generation of the angle of the inner lug groove defining the block with respect to the tire width direction and the tire burden load was obtained in the first step. A second step of setting an angle of the outermost layer belt cord with respect to the tire width direction, an angle of the outer lug groove with respect to the tire width direction, and an angle of the inner lug groove with respect to the tire width direction so as to be equal to an inclination; When,
A method for designing a tire, comprising:   A tire designed by the tire designing method according to claim 1.

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