JP2007106243A - Tire information acquisition device and tire information acquisition method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire information acquisition device and tire information acquisition method enabling to precisely calculate friction coefficient in the anteroposterior direction between a tire and road surface. <P>SOLUTION: A vehicle 10 comprises a plurality of acceleration sensors 26 disposed at least on the circumference of the tire 18 for detecting accelerations at the respective circumferential positions of the tire 18, and ECU 100. Based on the detection values of the acceleration sensors 26 of the tire 18, the ECU 100 acquires the ground contact length L of the tire 18 on the anteroposterior direction of the vehicle, and load Fz imposed on the tire 18 in the height direction of the tire based on the detected value of each acceleration sensor of the tire 18, and lateral force Fy imposed on the tire 18 in the width direction of the tire, and calculates the longitudinal friction coefficient μx between the tire 18 and the road surface. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a tire information acquisition device and a tire information acquisition method for acquiring information related to a tire of a vehicle.

Conventionally, there is known a vehicle tire in which a strain gauge for detecting the strain of rubber in a corresponding portion is embedded in at least one of a tread portion, a sidewall portion, and a bead portion. By using this type of tire, Based on the output value of the strain gauge, the contact state between the tire and the road surface can be grasped (see, for example, Patent Document 1). Conventionally, there has been known a tire in which a piezoelectric element that generates a voltage by deformation is embedded, and a conductive wire that generates a magnetic field by power feeding from the piezoelectric element extends over the entire circumference of the tire. (For example, see Patent Document 2). A vehicle body of a vehicle on which the tire is mounted is provided with a magnetic field sensor that detects a magnetic field of a conductive wire embedded in the tire and generates a current. In this vehicle, the tire contact length is obtained from the time interval, the wheel speed, and the tire radius from the start to the end of contact of the tire obtained based on the current value from the magnetic field sensor, and based on the tire contact length. It is checked whether the tire pressure is abnormally reduced. Furthermore, a mark formed on the inner peripheral surface of the crown portion of the tire, mark position detection means provided on a wheel rim, etc., and a tire that detects deformation of the tire from the position of the mark detected by the mark position detection means A tire deformation detection means including a deformation detection means is also known (see, for example, Patent Document 3). Further, Patent Document 4 adds to the tire by detecting and comparing the contact length indicators having a 1: 1 correspondence with the contact length of the tire such as the contact time of the tire tread portion at a plurality of positions of the tire. A method for estimating the lateral force that is present is disclosed.
JP 2003-226120 A Japanese Patent Laid-Open No. 2003-066871 JP-A-9-193627 JP 2005-205956 A

  As described above, a device for detecting the deformation state of a tire has been proposed in the past. However, in recent years, from the viewpoint of executing vehicle motion control such as ABS control and vehicle stabilization control (VSC) with high accuracy, a tire is used. There is a growing need for a technology that can accurately calculate the longitudinal friction coefficient between the road and the road surface.

  Therefore, an object of the present invention is to provide a tire information acquisition device and a tire information acquisition method that can accurately calculate a longitudinal friction coefficient between a tire and a road surface.

  A tire information acquisition device according to the present invention is a tire information acquisition device for acquiring information related to a tire of a vehicle, and a plurality of tire information acquisition devices are arranged in the tire circumferential direction with respect to the tire, and based on respective detection values. Acceleration obtaining means for obtaining acceleration in a predetermined direction of the tire, front and rear contact length obtaining means for obtaining a contact length in the vehicle longitudinal direction of the tire based on each acceleration of the tire, and a load in the tire height direction acting on the tire Load acquisition means to acquire, lateral force acquisition means to acquire lateral force in the tire width direction acting on the tire, tire contact length acquired by the front and rear contact length acquisition means, load acquired by the load acquisition means and lateral Friction coefficient calculation means for calculating a front-rear friction coefficient between the tire and the road surface based on the lateral force acquired by the force acquisition means Characterized in that it comprises a.

  The tire information acquisition device includes a plurality of acceleration acquisition means, front and rear contact length acquisition means, load acquisition means, lateral force acquisition means, and friction coefficient calculation means. A plurality of acceleration acquisition means are arranged at least in the tire circumferential direction with respect to the tire, and each calculates acceleration in a predetermined direction of the tire. The front-rear contact length acquisition unit acquires the contact length L of the tire in the front-rear direction of the vehicle based on, for example, the time interval between peaks in the acceleration waveform obtained from the detection value of each acceleration acquisition unit of the tire. The load acquisition means acquires the load Fz in the tire height direction acting on the tire, and the lateral force acquisition means acquires the lateral force Fy in the tire width direction acting on the tire. Then, the friction coefficient calculation means calculates the front-rear direction friction coefficient μx between the tire and the road surface based on the tire contact length L, the load Fz, and the lateral force Fy.

Here, if the friction coefficient in the tire width direction between the tire and the road surface is μy and the contact length in the tire width direction is W,
μy / μx ∝ W / L
Therefore, the ratio of the friction coefficient μx and μy is
μy / μx = α (W / L) + β (1)
(Where α and β are coefficients determined in advance by experiment and analysis). In addition, between the lateral force Fy acting on the tire and the load Fz,
Fy = μy · Fz (2)
The relationship is established.

Therefore, from the equations (1) and (2), the longitudinal friction coefficient μx between the tire and the road surface is
μx = μy / {α (W / L) + β} = Fy / Fz / {α (W / L) + β} (3)
Represented as: As a result, if the contact length W in the tire width direction is constant, the contact length L of the tire acquired by the front and rear contact length acquisition means, the load Fz acquired by the load acquisition means, and the lateral force acquisition means If the friction coefficient calculating means executes the process of substituting the lateral force Fy to the above equation (3), the longitudinal friction coefficient μx between the tire and the road surface can be accurately calculated and obtained. Further, the longitudinal friction coefficient μx can be used for, for example, ABS control, vehicle stabilization control (VSC), or the like.

  Furthermore, it is preferable to further include a longitudinal force calculating means for calculating a force in the vehicle longitudinal direction acting on the tire based on the load acquired by the load acquiring means and the longitudinal friction coefficient calculated by the friction coefficient calculating means.

That is, if the longitudinal friction coefficient μx calculated by the friction coefficient calculating means as described above is used, the force Fx in the vehicle longitudinal direction acting on the tire is
Fx = μx · Fz (4)
Can be obtained with high accuracy.

  Further, the acceleration acquisition means is provided in a plurality of rows in the tire width direction with respect to the tire, and the lateral force acquisition means determines the contact lengths of the tires in the vehicle longitudinal direction obtained from the detection values of the acceleration acquisition means in each row. It is preferable to obtain the lateral force based on the ratio.

  Thus, when the acceleration acquisition means is provided in a plurality of rows in the tire width direction for the tire, the contact length in the vehicle longitudinal direction of the tire obtained for each row of the acceleration acquisition means is the magnitude of the lateral force Fy acting on the tire. It changes according to. Therefore, according to this aspect, the lateral force Fy acting on the tire in the tire width direction can be accurately obtained.

  And each acceleration acquisition means is arrange | positioned in the tread part inner surface of a tire, and it is preferable if the acceleration of the tire in a tire circumferential direction or a tire radial direction is detected.

That is, if the change in the tire acceleration in the tire circumferential direction or the tire radial direction is grasped, the contact length L of the tire in the vehicle front-rear direction can be accurately obtained from the time interval between peaks in the acceleration waveform.
The acceleration acquisition means may be an acceleration sensor that directly detects the acceleration of the tire in the tire circumferential direction or the tire radial direction, or a strain gauge is provided on the inner surface of the tread portion of the tire and the detection is performed. The acceleration of the tire in the tire circumferential direction or the tire radial direction may be calculated by differentiating the distortion amount as a value with a vehicle-mounted control device. In this case, the acceleration acquisition means in the claims includes a strain gauge and a control device.

  The tire information acquisition method according to the present invention is a tire information acquisition method for acquiring information related to a tire of a vehicle, based on detection values of a plurality of acceleration acquisition means arranged at least in the tire circumferential direction with respect to the tire. Obtaining a contact length of the tire in the vehicle longitudinal direction, obtaining a load in a tire height direction acting on the tire, obtaining a lateral force acting on the tire in a tire width direction, and contacting the tire And calculating a longitudinal friction coefficient between the tire and the road surface based on the length, load and lateral force.

  According to the present invention, it is possible to accurately calculate the longitudinal friction coefficient between the tire and the road surface.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram illustrating a vehicle including a tire information acquisition device according to the present invention, and FIG. 2 is a partial cross-sectional view illustrating wheels provided in the vehicle of FIG. A vehicle 10 shown in FIG. 1 includes four wheels 14 provided on a vehicle body 12, a steering device (not shown) that steers steering wheels among these four wheels 14, and among these four wheels 14. A driving drive source (not shown) for driving the driving wheels, a braking device, and the like are provided. Each wheel 14 includes a wheel 16 and a tire 18. In the present embodiment, a so-called run flat tire is adopted as the tire 18 constituting the wheel 14. However, it goes without saying that a general hollow tire other than the run-flat tire may be adopted as the tire 18.

  As shown in FIG. 2, the tire 18 is a so-called side-reinforced run-flat tire that enables run-flat running when the air pressure decreases. As shown in FIG. 2, the tire 18 includes a pair of bead portions 181 in which a bead core 180 is embedded, a pair of sidewall portions 182 extending from the bead portion 181 outward in the tire radial direction, and both sidewall portions 182. An extended tread portion 183. A carcass 184 made of, for example, a single fiber material is embedded in the pair of bead portions 181, the pair of sidewall portions 182 and the tread portion 183, and the tread portion 183 is positioned outside the carcass 184. A belt layer 185 is embedded. Reinforcing rubber 187 is embedded in each sidewall portion 182 so as to be located inside the inner liner 186.

  Each reinforcing rubber 187 has high rigidity, and supports the entire tire 18 with respect to the wheel 16 when the air pressure in the tire internal space 188 defined by the wheel 16 and the tire 18 decreases due to puncture or the like. As a result, run-flat driving is enabled. Further, a driving type or a pasting type balance weight 17 is appropriately attached to the wheel 16. Note that the tire 18 provided in the vehicle 10 is not limited to a side-reinforced run-flat tire, and the entire tire 18 is supported to the wheel 16 when the air pressure in the tire internal space 188 decreases. A core-type run flat tire including a child may be used.

  As shown in FIGS. 1 and 2, each wheel 14 described above is equipped with a TPMS valve 20 that functions as a tire pressure adjusting valve. Each TPMS valve 20 is attached to a mounting hole 16b provided in the wheel rim 16a of the wheel 16 via a grommet 19 made of elastic rubber, a washer, and a bolt. The grommet 19 has a predetermined rigidity and keeps the tire internal space 188 airtight. Further, the valve cap 20a of the TPMS valve 20 protrudes to the outside of the wheel rim 16a. If the valve cap 20a is removed and a hose of an air supply device is connected to a valve port (not shown), the tire inner space 188 is formed. Air can be supplied. As shown in FIG. 2, each TPMS valve 20 has a housing 21 protruding into the tire internal space 188, and the air pressure in the tire internal space 188 is stored in the housing 21 as wheel information. An air pressure sensor 22 to detect is disposed.

  Each of the wheels 14 is provided with a plurality of (eight in the present embodiment) acceleration sensors 26. As shown in FIG. 2, each acceleration sensor 26 is fixed to the inner surface of the tread portion 183 of the tire 18, and detects acceleration in the tire circumferential direction of the tire 18 as wheel information at each installation location. As shown in FIG. 3, a plurality of acceleration sensors 26 are provided in the tire circumferential direction and in a plurality of rows in the tire width direction with respect to the inner surface of the tread portion 183. In the tire circumferential direction, at least three (four in the present embodiment, four at 90 ° intervals) acceleration sensors 26 may be disposed on the inner surface of the tread portion 183.

Further, in the present embodiment, two rows of acceleration sensors 26 are provided at intervals W, and each acceleration sensor 26 in the tire outer row and each acceleration sensor 26 in the tire inner row are the tire 18. Are arranged adjacent to each other in the width direction. The interval W between the columns of the acceleration sensors 26 is substantially equal to the width of the tread portion 183, and the value W can be regarded as the contact length in the tire width direction of the tire 18. Each acceleration sensor 26 may detect acceleration in the tire radial direction of the tire 18 as wheel information at the installation location. Further, three or more rows of acceleration sensors 26 may be provided for the tire 18 of each wheel 14.
The acceleration acquisition means may be an acceleration sensor that detects the acceleration of the tire in the tire circumferential direction or the tire radial direction, or a strain gauge is provided on the inner surface of the tread portion of the tire, and the detected value The tire acceleration in the tire circumferential direction or the tire radial direction may be calculated by differentiating the amount of distortion with an on-vehicle control device.

  FIG. 4 is a control block diagram of the tire information acquisition apparatus according to the present invention. As shown in the figure, in the housing 21 of the TPMS valve 20, in addition to the air pressure sensor 22, a TPMS communication device 23, a control circuit 24, and a battery 25 are accommodated. Thereby, each TPMS valve | bulb 20 functions as a means which can transmit the acquired wheel information regularly while acquiring the tire pressure as wheel information, respectively. The air pressure sensor 22 is a semiconductor sensor, for example, and detects the air pressure in the tire internal space. The TPMS communication device 23 is capable of periodically wirelessly transmitting a signal indicating the detection value of the air pressure sensor 22 at a predetermined cycle (for example, every 3 minutes). The control circuit 24 is mounted on an IC chip or the like and controls the air pressure sensor 22 and the TPMS communication device 23. The battery 25 supplies power to the air pressure sensor 22, the TPMS communication device 23 and the control circuit 24. The TPMS valve 20 may further include a temperature sensor that detects the air temperature in the tire interior space, a ground pressure sensor, and the like.

  Each acceleration sensor 26 provided on the tire 18 is connected to a communication device (transmitter) 28 via an amplifier 27, and each wheel 14 is connected to the acceleration sensor 26, the amplifier 27, and the communication device. A battery 29 for supplying electric power to 28 is provided. The amplifier 27, the communication device 28, and the battery 29 are disposed at appropriate positions of the corresponding wheel 14, for example, the outer peripheral surface of the wheel 16. The amplifier 27 amplifies the output of the corresponding acceleration sensor 26 and gives it to the communication device 28. The communication device 28 can wirelessly transmit a signal indicating the output value of each acceleration sensor 26 at a cycle of, for example, about 10 to 20 msec. It is.

  Further, as shown in FIGS. 1 and 4, a plurality of (four in the present embodiment) vehicle body side communication devices 30 are arranged on the vehicle body 12 of the vehicle 10 so as to correspond to the respective wheels 14. . Each vehicle body side communication device 30 can transmit and receive signals indicating wheel information and the like to and from the TPMS communication device 23 and the communication device 28 provided on the corresponding wheel 14. The vehicle body 12 may be provided with a single vehicle body side communication device capable of transmitting and receiving signals indicating wheel information and the like between the TPMS communication device 23 and the communication device 28 provided on each wheel 14. . Each vehicle body side communication device 30 is connected to an electronic control unit (hereinafter referred to as “ECU”) 100 mounted on the vehicle body 12 as shown in FIGS. 1 and 4. Each vehicle body side communication device 30 receives a signal wirelessly transmitted from the TPMS communication device 23 or the communication device 28 of the corresponding wheel 14 and gives the received information to the ECU 100. Wheel information from the TPMS communication device 23 and the communication device 28 is stored and held by a predetermined amount in a predetermined storage area (buffer) of the ECU 100, and the ECU 100 performs various controls using information received from each vehicle body side communication device 30. Execute.

  The ECU 100 includes a CPU that executes various arithmetic processes, a ROM that stores various control programs, a RAM that is used as a work area for data storage and program execution, an input / output interface, a memory, and the like. The ECU 100 is connected to a sensor group 101 and an alarm device 102 as shown in FIGS. The sensor group 101 includes, for example, a wheel speed sensor 101 a (see FIG. 4) that is provided for each wheel 14 and detects the speed of the corresponding wheel 14. The warning device 102 issues a warning to the driver under predetermined conditions under the control of the ECU 100, and includes, for example, a warning display device provided on the instrument panel of the vehicle 10.

  By the way, in the vehicle 10 described above, for example, the ECU that controls the braking device cooperates with the ECU that controls the traveling drive source, the ECU that controls the steering device, and the like to stabilize the behavior of the vehicle 10. Integrated control of driving, steering and braking (VDIM: Vehicle Dynamics Integrated Management) is executed. In such integrated control, from the viewpoint of executing vehicle motion control with high accuracy, the longitudinal friction coefficient μx between the tire 18 and the road surface and the force Fx in the longitudinal direction of the vehicle acting on the tire 18 are accurately obtained. Is required. For this reason, in the vehicle 10 of the present embodiment, the above-described ECU 100 causes the longitudinal friction coefficient μx between the tire 18 and the road surface and the force in the longitudinal direction of the vehicle to act on the tire 18 based on the wheel information from each wheel 14. Fx is calculated.

  FIG. 5 is a flowchart showing a routine for determining the longitudinal friction coefficient μx between the tire 18 and the road surface and the force Fx in the vehicle longitudinal direction acting on the tire 18. The routine shown in the figure is executed for each wheel 14 every predetermined time by the ECU 100 while the vehicle 10 is traveling. When it is time to execute the routine of FIG. 5 for a certain wheel 14, the ECU 100 determines each acceleration sensor based on the acceleration information from each acceleration sensor 26 of the wheel 14 (tire 18) stored in a predetermined storage area. The time interval Δt between the peaks in the acceleration waveform obtained from the 26 detected values is obtained (S10).

  Here, each acceleration sensor 26 detects acceleration in the tire circumferential direction of the tire 18 at the installation location as described above. Therefore, as shown in FIG. 6, a signal indicating a large acceleration value (peak value) is output from the acceleration sensor 26 located near the front end of the ground contact portion of the tire 18 that rotates while the vehicle 10 is traveling. Similarly, a signal indicating a large acceleration value (peak value) is output from the acceleration sensor 26 located near the rear end of the ground contact portion of the tire 18 that rotates while the vehicle 10 is traveling, as shown in FIG. Therefore, in S10, the ECU 100 calculates the time interval Δt between the peaks in the acceleration waveform based on the sampling time of the acceleration sensor 26, the number of data samples between the peaks of the acceleration waveform, and the like.

When the time interval Δt is calculated, the ECU 100 determines that the time interval Δt and the wheel speed indicated in the signal from the wheel speed sensor 101a corresponding to the corresponding wheel 14 and the tire radius that is known in advance are applicable. The contact length L in the vehicle longitudinal direction of the tire 18 of the wheel 14 is calculated (S12). In the present embodiment, since the acceleration sensors 26 are provided in two rows for the tires 18 of the respective wheels 14 as described above, in S12, the calculation is performed based on signals from the acceleration sensors 26 of the respective rows. The average value of the contact length obtained from the time interval Δt is calculated as the contact length L. That is, the contact length obtained from the time interval Δt calculated based on the signal from the acceleration sensor 26 in the inner row of the tire 18 is Li, and is calculated based on the signal from the acceleration sensor 26 in the outer row of the tire 18. When the contact length obtained from the time interval Δt is Lo, the contact length L in the vehicle front-rear direction of the tire 18 is
L = (Li + Lo) / 2
Is calculated as

  As described above, the plurality of acceleration sensors 26 are disposed on the inner surface of the tread portion 183 of the tire 18, and by detecting the acceleration of the tire 18 in the tire circumferential direction or the tire radial direction, the tire circumferential direction or the tire radial direction is detected. The change in acceleration of the tire 18 can be grasped, and the contact length L of the tire 18 in the vehicle front-rear direction can be accurately obtained from the time interval Δt between peaks in the acceleration waveform.

  When the contact length L of the tire 18 in the vehicle front-rear direction is calculated, the ECU 100 calculates the load Fz in the tire height direction (vehicle vertical direction) acting on the tire 18 and the lateral force Fy acting on the tire 18 in the tire width direction. Obtain (S14). In S14, the ECU 100 obtains the load Fz based on the ground contact length L of the tire 18 in the vehicle front-rear direction calculated in S12 and the tire air pressure detected by the air pressure sensor 22 of the TPMS valve 20. In the present embodiment, a map or a function formula that defines the correlation between the contact length L of the tire 18 in the longitudinal direction of the vehicle, the tire air pressure, and the load Fz is determined in advance and stored in the storage device of the ECU 100. The load Fz is acquired using the map or function expression.

  Further, in S14, the ECU 100 determines the contact length Li obtained from the time interval Δt calculated based on the signal from the acceleration sensor 26 in the inner row of the tire 18 and the signal from the acceleration sensor 26 in the outer row of the tire 18. The lateral force Fy acting on the tire 18 in the tire width direction is obtained from the ratio with the contact length Lo obtained from the time interval Δt calculated on the basis thereof. In the present embodiment, a map or a function formula that defines the correlation between the ratio between the contact length Li on the tire inner side and the contact length Lo on the tire outer side and the lateral force Fy is determined in advance and stored in the storage device of the ECU 100. The ECU 100 acquires the lateral force Fy using the map or the function formula. As described above, when the acceleration sensor 26 is provided for the tire 18 in a plurality of rows (two rows) in the tire width direction, the contact lengths Li and Lo in the vehicle longitudinal direction of the tire 18 obtained for each row of the acceleration sensor 26 are: It changes according to the magnitude of the lateral force Fy acting on the tire. Therefore, if the ratio between the contact lengths Li and Lo is used, the lateral force Fy acting on the tire 18 in the tire width direction can be accurately obtained.

When the contact length L, the load Fz, and the lateral force Fy in the vehicle longitudinal direction of the tire 18 are obtained as described above, the ECU 100 determines the longitudinal friction coefficient (dynamic friction coefficient) between the tire 18 and the road surface based on these values. ) Μx is calculated (S16). That is, in S16, using the equation (3) obtained from the above equations (1) and (2), the longitudinal friction coefficient μx between the tire 18 and the road surface is
μx = Fy / Fz / {α (W / L) + β}
Is calculated as At this time, as a value W indicating the contact length of the tire 18 in the tire width direction, the interval W between the rows of the acceleration sensors 26 is substituted into the equation (3). Accordingly, it is possible to accurately calculate the longitudinal friction coefficient μx between the tire 18 and the road surface, and the obtained longitudinal friction coefficient μx can be used for the vehicle integrated control described above.

  Further, the ECU 100 calculates the vehicle front-rear direction force Fx acting on the tire 18 based on the front-rear frictional coefficient μx between the tire 18 and the road surface calculated in S16 (S18). That is, using the longitudinal friction coefficient μx calculated as described above, the force Fx in the vehicle longitudinal direction acting on the tire 18 can be accurately calculated as Fx = μx · Fz from the equation (4). And the force Fx in the vehicle front-back direction calculated in this way is also used for vehicle integrated control.

  Note that in the vehicle 10 according to the present embodiment, integrated control of driving, steering and braking of the vehicle 10 is executed, and the directional friction coefficient μx calculated through the routine of FIG. The force Fx is provided, but is not limited to this. That is, it goes without saying that the directional friction coefficient μx calculated through the routine of FIG. 5 and the force Fx in the longitudinal direction of the vehicle can be used for, for example, general ABS control or vehicle stabilization control (VSC).

It is a schematic block diagram which shows the vehicle provided with the tire information acquisition apparatus by this invention. It is a fragmentary sectional view which shows the wheel with which the vehicle of FIG. 1 was equipped. It is a schematic diagram which shows the arrangement | positioning aspect of the acceleration sensor in the tire of the wheel with which the vehicle of FIG. 1 was equipped. It is a control block diagram of the tire information acquisition apparatus by this invention. 2 is a flowchart showing a routine for obtaining a longitudinal friction coefficient between a tire and a road surface and a force acting on the tire in the longitudinal direction of the vehicle in the vehicle of FIG. 1. It is a schematic diagram which shows the relationship between the ground contact state of a tire and the acceleration waveform obtained from the detected value of the acceleration provided in the tire.

Explanation of symbols

  10 vehicle, 12 vehicle body, 14 wheel, 16 wheel, 18 tire, 20 TPMS valve, 22 air pressure sensor, 23 TPMS communication device, 24 control circuit, 25 battery, 26 acceleration sensor, 27 amplifier, 28 communication device, 29 battery, 30 Vehicle side communication device, 100 ECU, 101 sensor group, 101a wheel speed sensor, 102 alarm device, 183 tread part, 188 tire internal space.

Claims (5)

In a tire information acquisition device for acquiring information related to vehicle tires,
A plurality of at least the tire circumferential direction with respect to the tire, an acceleration acquisition means for obtaining acceleration in a predetermined direction of the tire based on respective detection values;
Front and rear contact length acquisition means for acquiring a contact length in the vehicle longitudinal direction of the tire based on each acceleration of the tire;
Load acquisition means for acquiring a load in a tire height direction acting on the tire;
Lateral force acquisition means for acquiring lateral force in the tire width direction acting on the tire;
Based on the contact length of the tire acquired by the front and rear contact length acquisition means, the load acquired by the load acquisition means and the lateral force acquired by the lateral force acquisition means, the front and rear between the tire and the road surface A tire information acquisition apparatus comprising: a friction coefficient calculation unit that calculates a directional friction coefficient.   The apparatus further comprises a longitudinal force calculation means for calculating a force in the vehicle longitudinal direction acting on the tire based on the load acquired by the load acquisition means and the longitudinal friction coefficient calculated by the friction coefficient calculation means. The tire information acquisition device according to claim 1.   The acceleration acquisition means is provided in a plurality of rows in the tire width direction with respect to the tire, and the lateral force acquisition means is a contact length in the vehicle longitudinal direction of the tire obtained from a detection value of the acceleration acquisition means of each row. The tire information acquiring apparatus according to claim 1, wherein the lateral force is acquired based on a ratio between the two.   4. The acceleration according to claim 1, wherein each acceleration acquisition unit is disposed on an inner surface of a tread portion of the tire and detects acceleration of the tire in a tire circumferential direction or a tire radial direction. Tire information acquisition device. In a tire information acquisition method for acquiring information related to a vehicle tire,
Acquiring a contact length in the vehicle front-rear direction of the tire based on detection values of at least a plurality of acceleration acquisition means arranged in the tire circumferential direction with respect to the tire;
Obtaining a load in a tire height direction acting on the tire;
Obtaining a lateral force in the tire width direction acting on the tire;
Calculating a longitudinal friction coefficient between the tire and a road surface based on the contact length of the tire, the load, and the lateral force.

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