JP2010215180A - Method for estimating force applied to tire and pneumatic tire used therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the estimation accuracy of the longitudinal force, the lateral force and the vertical force to be applied to a tire. <P>SOLUTION: In a pneumatic tire, three or more (n-sets of) sensor units G are mounted on a side wall part 3 on one side Each sensor unit comprises a first strain sensor 10A in which the maximum gain line K1 is arranged in the tire radial direction, a second strain sensor 10B in which the maximum gain line K2 is inclined at the angle θa of 30-60° with respect to the maximum gain line K1, and a third strain sensor 10C in which the maximum gain line K3 is inclined in the other side at the angle θb of 30-60° with respect to the maximum gain line K1, and forms a W-shaped array. The estimation method includes a strain measuring step of obtaining the outputs of total 3n-sets of sensors by each sensor unit, and a rosette analysis step of obtaining three sensor outputs for each sensor unit, i.e., the maximum main strain data ε<SB>max</SB>, the minimum main strain data ε<SB>min</SB>, and the maximum shear strain data γ<SB>max</SB>for each sensor unit. The method is capable of estimating the longitudinal force Fx, the lateral force Fy and the vertical force Fz based on the total 3n-sets of analysis data. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an estimation method for estimating longitudinal force, lateral force, and vertical force acting on a tire by measuring tire strain at a sidewall portion with a strain sensor, and a pneumatic tire used therefor.

In recent years, for example, as shown in FIG. 4, n strain sensors a are attached to one side wall of the tire at different positions in the tire circumferential direction, and tire strain is simultaneously measured at a predetermined tire rotation angle position Q. together, the n-number of simultaneous sensor output t ₁ ~t _n obtained by this, the longitudinal force Fx acting on the tire lateral force Fy, and vertical force Fz (hereinafter, referred 3 component force is collectively referred to Have been proposed (see, for example, Patent Document 1). In the figure, the case of n = 4 is shown.

Here, the tire strain ε measured by each strain sensor a appears only as the sum of the strain εx caused by the longitudinal force Fx, the strain εy caused by the lateral force Fy, and the strain εz caused by the vertical force Fz. However, at different circumferential positions, the relationship between the longitudinal force Fx and its strain εx, the relationship between the lateral force Fy and its strain εy, and the relationship between the vertical force F and its strain εz are different for each circumferential position. , Each has a characteristic of appearing differently. Therefore using this characteristic varies with the use of the n-number of sensor outputs t ₁ ~t _n measured simultaneously in the circumferential direction position, then the 3 component force Fx exerted, Fy, be estimated, respectively to separate the Fz Is possible.

Specifically, in this technique, prior load application tests are performed in which the longitudinal force Fx, the lateral force Fy, and the vertical force Fz are different, and the tire strain ε when the tire reaches a predetermined tire rotation angle position Q is calculated. The n strain sensors are measured simultaneously for each load application condition. And this with the n sensor outputs t ₁ ~t _n obtained by analyzing the number of load application test data consisting of a load application condition at that time, the longitudinal force Fx and the sensor output t ₁ ~t _n relationship _{Fx = fx (t 1, t} 2 ··· t n), lateral force Fy and the sensor output _t 1 ~t _n and relationship _{Fy = fy (t 1, t} 2 ··· t n), vertical obtaining force Fz and relationship _Fz = fz between the sensor output _t 1 ~t _n a _{(t 1, t 2 ··· t} n) in advance.

Then, the actual sensor output t _{1 to} t _n measured when the tire reaches the predetermined tire rotation angle position Q in actual vehicle travel is applied to the prior relational expression, thereby acting on the tire during actual measurement. It is possible to estimate the longitudinal force Fx, the lateral force Fy, and the vertical force Fz, respectively. In Patent Document 1, the following determinant is exemplified as the relational expression.
┌Fx┐ ┌A ₁ B ₁ C ₁ ┐-1 ┌t ₁ ┐
│Fy│ = │A ₂ B ₂ C ₂ │ │t ₂ │
_{└Fz┘ └A 3 B 3 C 3 ┘} └t 3 ┘

Japanese Patent Laid-Open No. 2005-126008

  However, in the case of the arrangement of the conventional strain sensor, there is a problem that it is difficult to improve the estimation accuracy of the three component forces Fx, Fy, and Fz. The reason is that the output form of the strain sensor by the longitudinal force Fx and the output form of the strain sensor by the lateral force Fy are similar, so it is difficult to separate the three component forces Fx, Fy, Fz, and the relationship described above. This is presumably because the accuracy of the expression is reduced.

  For example, in the case of a conventional strain sensor arrangement, when a longitudinal force Fx is applied to the tire, each strain sensor a1 to a4 detects a tensile strain, as conceptually shown in FIG. When a lateral force Fy is applied to the tire, the strain sensors a1 to a4 detect tensile strains as conceptually shown in FIG. 5B. When the compression force Fz is applied to the tire, the strain sensors a2 and a3 detect the tensile strain and the strain sensors a1 and a4 detect the compressive strain as conceptually shown in FIG. As shown in Table 1 that summarizes the results, the longitudinal force Fx and the lateral force Fy show similar output forms in which the strain sensors a1 to a4 detect tensile strains, respectively. As a result, when analyzing the load addition test data and obtaining a prior relational expression, it becomes unclear whether the strain is derived from longitudinal force or lateral force, and the error increases, and the accuracy of the relational expression is increased. It is thought to decrease.

  Therefore, the present invention provides n sensor units in which three strain sensors are arranged in a W shape at different positions in the tire circumferential direction, and each sensor unit obtained by rosette analysis of three sensor outputs for each sensor unit. Based on associating the maximum principal strain data, the minimum principal strain data, and the maximum shear strain data with the three component forces Fx, Fy, Fz, the accuracy of the prior relational expression can be improved, and the three component forces Fx, Fy An object of the present invention is to provide a method for estimating a force acting on a tire that can improve the estimation accuracy of Fz, and a pneumatic tire used therefor.

In order to achieve the above object, the invention of claim 1 of the present application estimates the longitudinal force, lateral force, and vertical force acting on the tire based on the sensor output of the strain sensor that measures the tire strain in the sidewall portion of the tire. A method,
N or more sensor units of three or more that are attached to the sidewall portion on at least one side of the tire at intervals in the tire circumferential direction;
Using a tire angle distortion sensor that detects the rotational angle position of the tire,
In addition, each of the sensor units includes a first strain sensor in which a gain maximum line K1 that maximizes the gain is arranged in the tire radial direction, and an angle that the gain maximum line K2 is 30 to 60 ° with respect to the gain maximum line K1. A second strain sensor tilted to one side in the tire circumferential direction at θa, and a third strain tilted to the other side in the tire circumferential direction at an angle θb of 30-60 ° with respect to the maximum gain line K1 of the gain maximum line K3. And a W-shaped arrangement in which the first to third strain sensors are arranged adjacent to each other in the tire circumferential direction.
A strain measurement step for obtaining a total of 3n sensor outputs composed of three sensor outputs for each sensor unit by simultaneously measuring tire strain by strain sensors of the respective sensor units at a predetermined tire rotation angle position Q;
By performing rosette analysis on the three sensor outputs for each sensor unit, the rosette for obtaining three pieces of analysis data, that is, the maximum principal strain data ε _max , the minimum principal strain data ε _min , and the maximum shear strain data γ _max for each sensor unit. An analysis step;
And a calculation step for obtaining estimated values of the longitudinal force Fx, the lateral force Fy, and the vertical force Fz based on a total of 3n pieces of analysis data obtained by the rosette analysis step.

According to a fourth aspect of the present invention, there is provided a pneumatic tire comprising a strain sensor used for estimating a longitudinal force, a lateral force and a vertical force acting on a tire based on a sensor output obtained by measuring tire strain at a sidewall portion. ,
Provided with three or more n sensor units attached at intervals in the tire circumferential direction on at least one side wall portion of the tire,
Each of the sensor units includes a first strain sensor in which a gain maximum line K1 that maximizes the gain is arranged in the tire radial direction, and an angle θa in which the gain maximum line K2 is 30 to 60 ° with respect to the gain maximum line K1. The second strain sensor tilts to one side in the tire circumferential direction, and the third strain sensor tilts the gain maximum line K3 to the other side in the tire circumferential direction at an angle θb of 30 to 60 ° with respect to the gain maximum line K1. And a W-shaped arrangement in which the first to third strain sensors are adjacent to each other in the tire circumferential direction.

  In the present invention, a sensor unit in which three strain sensors are arranged in a W shape is used, and n of the sensor units are arranged at different positions in the tire circumferential direction. Therefore, sensor outputs from the three strain sensors constituting the sensor unit are obtained from each sensor unit, and the three sensor outputs are subjected to rosette analysis, so that the position of each sensor unit is It is possible to obtain three pieces of analysis data that are maximum principal strain data, minimum principal strain data, and maximum shear strain data acting on the. That is, a total of 3n pieces of analysis data can be obtained.

  On the other hand, as a result of the inventor's research, the correlation between the longitudinal force Fx and the 3n analysis data, the correlation between the lateral force Fy and the 3n analysis data, and the vertical force Fz and the above It has been found that the correlation between 3n pieces of analysis data is higher than that when 3n sensor outputs are used. Then, the estimation accuracy of the longitudinal force Fx, lateral force Fy, and vertical force Fz is improved by establishing relational expressions using the 3n pieces of analysis data for the longitudinal force Fx, lateral force Fy, and vertical force Fz. It becomes possible to make it.

It is sectional drawing which shows the pneumatic tire used for the estimation method of the force which acts on the tire of this invention. (A) is a top view which shows one Example of a sensor unit, (B) is a side view which shows the direction of the gain maximum line. It is the schematic explaining the attachment position of a sensor unit. It is a side view of the tire explaining arrangement | positioning of the conventional strain sensor. (A)-(C) are the conceptual diagrams explaining the tire distortion in each sensor position when 3 component force acts.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the pneumatic tire 1 according to this embodiment includes a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and the inside of the tread portion 2. And a belt layer 7 disposed on the outer side in the radial direction of the carcass 6.

  The carcass 6 is formed of one or more, in this example, one carcass ply 6A in which carcass cords are arranged at an angle of, for example, 70 to 90 ° with respect to the tire circumferential direction. The carcass ply 6A includes a series of ply turn-up portions 6b that are turned back from the inside in the tire axial direction around the bead core 5 on both sides of the ply main body portion 6a straddling the bead cores 5 and 5. Further, a bead apex rubber 8 for reinforcing a bead having a triangular cross section extending from the bead core 5 to the outer side in the tire radial direction is disposed between the ply main body portion 6a and the ply folded portion 6b.

  The belt layer 7 is formed of two or more belt plies, in this example, two belt plies 7A and 7B in which belt cords are arranged at an angle of, for example, 10 to 35 ° with respect to the tire circumferential direction. By crossing each other, the belt rigidity is increased, and the substantially entire width of the tread portion 2 is firmly reinforced with a tagging effect. In this example, on the outer side in the radial direction of the belt layer 7, a band layer 9 in which band cords are arranged at an angle of 5 degrees or less with respect to the tire circumferential direction for the purpose of improving high-speed running performance and high-speed durability. Is provided.

  In the tire 1 according to the present embodiment, three or more n sensor units G each including three strain sensors 10 are attached to at least one sidewall portion 3 at intervals in the tire circumferential direction. . The axle is provided with a tire angle distortion sensor (not shown) such as a resolver or an encoder that detects the rotational phase angle of the tire 1.

  In this example, as conceptually shown in FIG. 3, only one side wall portion 3 has three (n = 3) sensor units G, one circumferential line centered on the tire axis i. The case where it attaches at equal intervals on j is illustrated. The region Y (shown in FIG. 1) to which the sensor unit G is to be attached is separated from the inside and outside in the radial direction by a distance L of 25% of the tire cross-section height h, centering on an intermediate height position M of the tire cross-section height h. An area range is preferable, and in particular, an area range closer to the intermediate height position M with the distance L being set to 20% and further 15% of the tire cross-section height h is preferable. The tire cross-sectional height h means a radial height from the bead base line BL to the tread surface on the tire equator.

  Next, as shown in FIGS. 2A and 2B, the sensor unit G includes a first strain sensor 10A in which a gain maximum line K1 that maximizes the gain is arranged in the tire radial direction, and a maximum gain. The second strain sensor 10B in which the line K2 is inclined to one side in the tire circumferential direction at an angle θa of 30 to 60 ° with respect to the maximum gain line K1, and the maximum gain line K3 is 30 to 30 with respect to the maximum gain line K1. A W-shaped array composed of a third strain sensor 10C tilted to the other side in the tire circumferential direction at an angle θb of 60 ° and adjacent to the first to third strain sensors 10A to 10C in the tire circumferential direction. Eggplant. The angle θa and the angle θb are set to the same angle.

  Each of the first to third strain sensors 10A to 10C is formed by a pair of one magnet 11 and one magnetostrictive sensor element 12 facing the magnet 11 with a gap therebetween, and the sensor unit G Is formed as a block-shaped mold body 20 in which the three magnets 11 and the three magnetostrictive sensor elements 12 are integrated via an elastic material 13. As the magnetostrictive sensor element 12, a Hall element, an MR element (magnetoresistance effect element), a TMF-MI element, a TMF-FG element, an amorphous strain sensor, etc. can be adopted, and particularly compactness, sensitivity, and ease of handling. From the viewpoints of the above, a Hall element can be preferably employed. In the first to third strain sensors 10 </ b> A to 10 </ b> C, it is important that the elastic members 13 can be elastically deformed flexibly following the movement of the side wall portion 3. Is adopted. In particular, thermoplastic elastomer (TPE) can be molded by plastic molding such as cast molding and injection molding, and can be suitably employed from the viewpoint of manufacturing the first to third strain sensors 10A to 10C.

  Here, in the sensor unit G, the magnetostrictive sensor elements 12 are arranged on the radially inner side, and the gap between the magnetostrictive sensor elements 12 is larger than the gap between the magnets 11. The character arrangement is preferable. The reason is that if the distance between the magnetostrictive sensor elements 12 is small (the distance between the magnets 11 is large), that is, if the magnetostrictive sensor elements 12 are brought close to each other, each magnetostrictive sensor element 12 receives. The magnetic flux density is close. As a result, it can no longer be determined from the change in the magnetic flux density which of the three magnets 11 has changed the distance to the magnet 11, which tends to reduce the measurement accuracy. Further, if the magnetostrictive sensor element 12 is arranged on the outer side in the radial direction (that is, on the tread side), the wiring from the magnetostrictive sensor element 12 becomes long. As a result, the wiring is liable to interfere with the road surface due to traveling, which causes disadvantages in measurement accuracy and wiring durability. In this case, since the magnet 11 is located radially inward (that is, on the rim side), when the rim is formed of a magnetic material such as iron, the magnetic field changes, which adversely affects measurement accuracy.

  In the sensor unit G, the magnet 11 in the first strain sensor 10A opposes the magnetic pole of the sensor element facing surface S1 facing the magnetostrictive sensor element 12, and the sensor element counteracts in the second and third strain sensors 10B and 10C. It is preferable to make it different from the magnetic pole of the surface S1. In this case, the magnetic pole surface S2 opposite to the sensor element facing surface S1 faces each other. At this time, the adjacent magnetic pole surfaces S2 are different magnetic poles, so that the magnets 11 attract each other. As a result, the arrangement of the magnets 11 when the sensor unit G is manufactured can be stabilized, and the manufacturing efficiency and the manufacturing accuracy can be improved. On the contrary, when the adjacent magnetic pole surfaces S2 are the same magnetic pole, the magnets 11 repel each other, so that the magnets 11 are easy to move during manufacturing, and the manufacturing efficiency and manufacturing accuracy tend to be reduced.

  Each of the strain sensors 10A to 10C preferably includes a transmission means for transmitting the measured tire strain output to an electronic control unit (ECU) of the vehicle control system. This transmitting means is composed of a semiconductor in which a transmission / reception circuit, a control circuit, a memory, etc. are made into a chip, and an antenna. When receiving an interrogation radio wave from the electronic control unit (ECU), this is used as electric energy, The distortion output data in the memory can be transmitted as a response radio wave.

Next, a method for estimating the three component forces Fx, Fy, and Fz will be described using the pneumatic tire 1.
The estimation method is:
(A) At the predetermined tire rotation angle position Q, the tire strain is simultaneously measured by the strain sensors 10A to 10C of each of the sensor units G, whereby three sensor outputs t _a , t _b , t _{c for} each sensor unit G are obtained. A strain measurement step for obtaining a total of 3n sensor outputs t _{a1 to} t _an , t _{b1 to} t _bn , t _{c1 to} t _cn ,
(B) By performing rosette analysis on the three sensor outputs t _a , t _b , and t _c for each sensor unit G, the maximum principal strain data ε _max , the minimum principal strain data ε _min , and the maximum shear for each sensor unit G A rosette analysis step for obtaining three pieces of analysis data d _a , d _b and d _c which are strain data γ _max ;
(C) Estimating the longitudinal force Fx, lateral force Fy, and vertical force Fz based on a total of 3n pieces of analysis data d _{a1 to} d _an , db _{1 to} db _bn , d _{c1 to} d _cn obtained by this rosette analysis step A calculation step for calculating a value;
It is comprised including.

In the strain measurement step, a tire rotation angle position Q for measuring tire strain is set in advance, and when the running tire 1 reaches the tire rotation angle position Q, each sensor unit G Measure tire strain at the same time. As a result, _a total of 3n sensor outputs t _{a1 to} t _an , t _{b1 to} t _bn , and t _{c1 to} t _{cn including} three sensor outputs t _a , t _b and t _{c for} each sensor unit G can be obtained. .

  In this example, as illustrated in FIG. 3, first, a coordinate system around the tire axis i (where one of the tire rotation directions is set) is set to 0 ° as a vertical line passing vertically through the tire axis i toward the ground contact surface. The sensor unit G sequentially arranged on the plus side from the 0 ° reference line X0 is distinguished as the first to nth sensor units G1 to Gn. A tire rotation position at which the phase angle β of the first sensor unit G1 is a predetermined value, for example, 0 °, is set as the tire rotation angle position Q. For example, when the phase angle β is + 15 °, + 30 °, or + 45 ° can be set as the tire rotation angle position Q, the tire rotation angle position Q can be set as appropriate.

Next, in the rosette analysis step, a known rosette analysis process is performed on the three sensor outputs t _a , t _b and t _c for each sensor unit G. Thus, for each sensor unit G, three pieces of analysis data d _a , d _b , d that are maximum principal strain data ε _max , minimum principal strain data ε _min , and maximum shear strain data γ _max acting on the position of each sensor unit. a _c 3 single analysis data _{d a, d b,} obtains the _{d c.}

When the angles θa and θb are 45 °, by rosette analysis,
The maximum principal strain data ε _max , the minimum principal strain data ε _min , and the maximum shear strain data γ _max can be obtained by the following equations.
d _a = ε _max = [t _b + t _c + √2 {(t _c −ta _a ) ² + (t _b −ta _a ² )}] / 2
_{d b = ε min = [t} b + t c -√2 {(t c -t a) 2 + (t b -t a) 2}] / 2
d _c = γ _max = √2 {(t _c −t _a ) ² + (t _b −t _c ) ² }

Next, in the calculation step, the longitudinal force Fx and analysis data obtained in advance are calculated using a total of 3n pieces of analysis data d _{a1 to} d _an , d _{b1 to} d _bn , d _{c1 to} d _cn obtained in the rosette analysis step. _{d a1 ~d an, d b1 ~d} bn, d c1 ~d cn a relationship _{Fx = fx (d a1 ··· d} an, d b1 ··· d bn, d c1 ··· d cn), lateral force Fy and analysis data _{d a1 ~d an, d b1 ~d} bn, relational expression of the _{d c1 ~d cn Fy = fy (} d a1 ··· d an, d b1 ··· d bn, d c1 · .., D _cn ), vertical force Fz, and analysis data d _{a1 to} d _an , d _{b1 to} d _bn , d _{c1 to} d _cn , relational expression Fz = fz (d _a1 ... D _an , d _{b1. d bn, d c1 ··· d cn} ), from, Zorezore Estimate Fx0, Fy0, is determine by calculating the FZ0.

Here, the prior relational expression can be obtained by a prior load application test in which the longitudinal force Fx, the lateral force Fy, and the vertical force Fz are different from each other. That is, the tire strain when the tire reaches a predetermined tire rotation angle position Q is simultaneously measured by the 3n strain sensors for each of various different load application conditions. This is subjected to rosette analysis processing to obtain 3n pieces of analysis data d _{a1 to} d _an , d _{b1 to} d _bn , and d _{c1 to} d _cn, and a large amount consisting of the analysis data and the load application conditions at that time By analyzing the load application test data, the above-mentioned relational expression Fx = fx (d _a1 ... D _an , d _b1 ... D _bn , d _c1 ... D _cn ),
Fy = fy (d _a1 ... D _an , d _b1 ... D _bn , d _c1 ... D _cn ),
Fz = fz (d _a1 ... D _an , d _b1 ... D _bn , d _c1 ... D _cn ),
Can be obtained in advance. As an example, in the load addition test data, for example, Fx, Fy, and Fz that are inputs are objective variables, and d _{a1 to} d _an , d _{b1 to} d _bn , and d _{c1 to} d _cn that are outputs are explanatory variables. The relational expression can be obtained by multiple regression.

Thus, the estimation accuracy of the longitudinal force Fx, the lateral force Fy, and the vertical force Fz can be improved by establishing the relational expressions for the longitudinal force Fx, the lateral force Fy, and the vertical force Fz using 3n pieces of analysis data. It becomes possible. In the sensor unit G, when the angles θa and θb between the maximum gain lines are out of the range of 30 to 60 °, the maximum principal strain data ε _max , the minimum principal strain data ε _min , and the maximum shear strain data γ _max . The accuracy is reduced. For this reason, the angles θa and θb preferably have a lower limit of 40 ° or more and an upper limit of 50 ° or less, particularly preferably 45 °.

  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.

  In order to confirm the operation and effect of the present invention, n sensor units G (total number of strain sensors: 3n) are attached to the side wall portion on one side and equidistantly mounted on the same circumferential line j. A tire (size 225 / 55R17) was prototyped. Each of the first to third strain sensors 10A to 10C constituting the sensor unit G is composed of a pair of one magnet and one Hall element, and the angles θa and θb between the maximum gain lines are both 45 °. is there.

  For comparison, a pneumatic tire of the same size in which a strain sensor 10A is attached only to one side wall portion was made as a comparative example. Comparative Example 2 and Example 1 have the same total number of strain sensors.

Based on the estimation method of the present invention, tire strain is simultaneously measured by each strain sensor at a predetermined tire rotation angle position, and the sensor output obtained thereby is applied to a relational expression obtained in advance. These estimated values Fx0, Fy0, and Fz0 are calculated and obtained. The estimated values Fx0, Fy0, and Fz0 are compared with the three component forces Fx, Fy, and Fz that are actually measured using a six-component force meter to evaluate the estimation accuracy, and the results are shown in Table 4. Shown in The estimation accuracy is evaluated as follows.
Δ--The accuracy of the estimated value is slightly low: (Δ + is slightly better than Δ)
○ --The accuracy of the estimated value is good:
◎ --The accuracy of the estimated value is excellent:

  As shown in Table 2, it can be confirmed that in the estimation method of the example, the estimation accuracy is improved as compared with the comparative example using the same number of strain sensors.

  By using the information of the three component forces estimated in the present invention, it is possible to improve vehicle safety and reduce occupant fatigue. For example, estimate the load (vertical force) for each wheel that changes depending on the number of passengers, the layout of the passengers, the loading position of the load, etc., and use this information to optimize the brake distribution for each wheel during normal braking or ABS operation Thus, the safety of the vehicle can be improved. Further, by transmitting the vertical force information to the electronically controlled suspension, the damping force of the shock absorber is changed, and the optimum damping force in the situation is improved, so that ride comfort is improved and occupant fatigue can be reduced.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 3 Side wall part 10A 1st strain sensor 10B 2nd strain sensor 10C 3rd strain sensor 11 Magnet 12 Magnetostrictive sensor element 13 Elastic material 20 Mold body K1, K2, K3 Maximum gain line G Sensor unit

Claims (7)

An estimation method for estimating a longitudinal force, a lateral force, and a vertical force acting on a tire by a sensor output of a strain sensor that measures tire strain at a sidewall portion of the tire,
N or more sensor units of three or more that are attached to the sidewall portion on at least one side of the tire at intervals in the tire circumferential direction;
Using a tire angle distortion sensor that detects the rotational angle position of the tire,
In addition, each of the sensor units includes a first strain sensor in which a gain maximum line K1 that maximizes the gain is arranged in the tire radial direction, and an angle that the gain maximum line K2 is 30 to 60 ° with respect to the gain maximum line K1. A second strain sensor tilted to one side in the tire circumferential direction at θa, and a third strain tilted to the other side in the tire circumferential direction at an angle θb of 30-60 ° with respect to the maximum gain line K1 of the gain maximum line K3. And a W-shaped arrangement in which the first to third strain sensors are arranged adjacent to each other in the tire circumferential direction.
A strain measurement step for obtaining a total of 3n sensor outputs composed of three sensor outputs for each sensor unit by simultaneously measuring tire strain by strain sensors of the respective sensor units at a predetermined tire rotation angle position Q;
By performing rosette analysis on the three sensor outputs for each sensor unit, the rosette for obtaining three pieces of analysis data, that is, the maximum principal strain data ε _max , the minimum principal strain data ε _min , and the maximum shear strain data γ _max for each sensor unit. An analysis step;
A force acting on the pneumatic tire, including a calculation step for obtaining estimated values of the longitudinal force Fx, the lateral force Fy, and the vertical force Fz based on a total of 3n pieces of analysis data obtained by the rosette analysis step Estimation method.   2. The estimation of the force acting on the pneumatic tire according to claim 1, wherein the sensor units are arranged at equal intervals in the tire circumferential direction on one circumferential line centered on the tire axis. Method.   The calculation step includes a relational expression between the analysis data and the longitudinal force Fx obtained in advance at the tire rotation angle position Q, a relational expression between the analysis data and the lateral force Fy, and a relation between the analysis data and the vertical force Fz. 3. The method for estimating a force acting on a tire according to claim 1, wherein estimated values of the longitudinal force Fx, the lateral force Fy, and the vertical force Fz are calculated based on an equation. A pneumatic tire including a strain sensor used for estimating front-rear force, lateral force, and vertical force acting on a tire based on a sensor output obtained by measuring tire strain in a sidewall portion,
Provided with three or more n sensor units attached at intervals in the tire circumferential direction on at least one side wall portion of the tire,
Each of the sensor units includes a first strain sensor in which a gain maximum line K1 that maximizes the gain is arranged in the tire radial direction, and an angle θa in which the gain maximum line K2 is 30 to 60 ° with respect to the gain maximum line K1. The second strain sensor tilts to one side in the tire circumferential direction, and the third strain sensor tilts the gain maximum line K3 to the other side in the tire circumferential direction at an angle θb of 30 to 60 ° with respect to the gain maximum line K1. And a W-shaped arrangement in which the first to third strain sensors are arranged adjacent to each other in the tire circumferential direction.   5. The pneumatic tire according to claim 4, wherein the sensor units are arranged at equal intervals in the tire circumferential direction on one circumferential line centered on the tire axis.   Each of the first to third strain sensors includes one magnet and one magnetostrictive sensor element facing the magnet, and the sensor unit uses the first to third strain sensors as an elastic material. The pneumatic tire according to claim 4, wherein the pneumatic tire is a molded body integrated with each other.   The first strain sensor is characterized in that the magnetic pole of the sensor element facing surface where the magnet faces the magnetostrictive sensor element is different from the magnetic pole of the sensor element facing surface in the second and third strain sensors. The pneumatic tire according to claim 6.