JP2007099245A - Road surface condition presumption device and road surface condition presumption method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately provide a road surface friction coefficient based on wheel information even if a tire constituting a wheel is worn. <P>SOLUTION: The road surface condition presumption devices for presuming the road surface condition of a traveling road of the vehicle 10 are provided on the respective wheels 14 and are provided with an acceleration sensor 21g for detecting vibration of the corresponding wheel 14; a frequency analysis part 32 for obtaining a vibration level in a predetermined frequency band area by frequency-analyzing the detection result of the acceleration sensor 21g; a memory device 31 for storing a plurality of maps for specifying correlation of the vibration level and a road surface friction coefficient μ according to the wearing degree of the tire constituting the wheel 14; and a friction coefficient obtaining part 34 for obtaining the road surface friction coefficient μ on the traveling road of the vehicle 10 by selecting the map used for presumption of the road surface friction coefficient μ based on the wearing degree of the tire defined from a usage time of the tire and using the selected map and the vibration level obtained by the frequency analysis part 32. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a road surface state estimation device and a road surface state estimation method for estimating a road surface state of a traveling road of a vehicle based on wheel information related to a plurality of wheels provided in the vehicle.

  2. Description of the Related Art Conventionally, an apparatus that estimates a road surface state of a traveling path of a vehicle based on wheel information related to a plurality of wheels provided in the vehicle is known (see, for example, Patent Document 1). In this apparatus, the vibration information signal of the wheel detected by the acceleration sensor attached to the wheel rim of the wheel is subjected to frequency analysis, and the vibration level in a predetermined frequency band is detected. Then, the road surface friction coefficient is estimated from the detected vibration level using a table indicating the relationship between the road surface friction coefficient and the vibration level. Also, as this type of device, there is known a device that estimates a road surface friction coefficient based on tire air pressure information of a running vehicle detected by a pressure sensor (see, for example, Patent Document 2). In this apparatus, the pressure fluctuation level of the pressure fluctuation spectrum obtained by frequency analysis of the minute vibration component (AC component) on the time axis of the pressure signal from the pressure sensor is detected, and the detected pressure fluctuation level and the road surface condition are detected. Further, the road surface friction coefficient μ and the like are estimated using a table showing the relationship with the running state of the tire.

As a system for monitoring the wear of the tire contact surface, at least one of the radial and lateral accelerations of the tire is detected, and at least one resonance frequency is determined for at least one of these accelerations. Also known is a system for determining the wear of a tire contact surface by comparing at least one resonance frequency with at least one stored frequency (see, for example, Patent Document 3).
JP 2003-182476 A JP 2003-182475 A JP 2001-215175 A

  Here, the tires constituting the wheels are worn with the passage of time, and when the wear of the tires progresses, the rubber of the tread portion decreases and the block rigidity of the tread portion changes, and the vibration level also changes accordingly. . For this reason, even if the road surface friction coefficient is estimated based on the vibration information of the wheel as described above, it is difficult to accurately estimate the road surface friction coefficient because the vibration level changes due to tire wear.

  Therefore, an object of the present invention is to provide a road surface state estimation device and a road surface state estimation method that can accurately acquire a road surface friction coefficient based on wheel information even when a tire constituting a wheel is worn.

  A road surface state estimation device according to the present invention is provided for each wheel in a road surface state estimation device that estimates a road surface state of a traveling road of a vehicle based on wheel information related to a plurality of wheels provided in the vehicle. Vibration detection means for detecting the vibration of the corresponding wheel, vibration level acquisition means for acquiring the vibration level in a predetermined frequency band by frequency analysis of the detection result of the vibration detection means, and the degree of wear of the tires constituting the wheel And a storage means for storing a plurality of maps defining the correlation between the vibration level and the road surface friction coefficient, and a map used for estimating the road surface friction coefficient based on the degree of wear of the tire determined from the tire usage time. At the same time, the road surface friction coefficient in the traveling road of the vehicle is acquired using the selected map and the vibration level acquired by the vibration level acquisition means. Characterized in that it comprises a friction coefficient obtaining means.

  This road surface state estimation device obtains a vibration level in a predetermined frequency band by performing frequency analysis on the detection result of the vibration detection means for detecting the vibration of the wheel, and based on the acquired vibration level, a road surface friction coefficient on the traveling road, That is, the road surface friction coefficient between the wheel tire and the traveling road surface is acquired. In the storage means of this road surface state estimation device, a plurality of maps that define the correlation between the vibration level and the road surface friction coefficient are stored in accordance with the degree of tire wear. From these maps, a map used for estimating the road surface friction coefficient is selected based on the degree of tire wear determined from the tire usage time, and the vehicle travel path is selected using the selected map and vibration level. The road surface friction coefficient at is acquired. As described above, in this road surface state estimation device, since the road surface state is estimated in consideration of the degree of wear of the tires constituting the wheels, the road surface friction coefficient between the tires of the wheels and the traveling road surface is accurately obtained. Is possible.

  The road surface state estimating device according to the present invention may further include a determination unit that determines whether or not the road surface friction coefficient on the traveling road is substantially constant, and the friction coefficient acquisition unit is configured to determine the road surface friction coefficient on the traveling road by the determination unit. Is determined to be substantially constant, it is preferable to select a map corresponding to the degree of tire wear determined from the tire usage time.

  In this way, when the road friction coefficient on the road on which the vehicle is traveling is approximately constant, a map corresponding to the tire wear degree determined from the tire usage time is used for estimating the road friction coefficient. It becomes possible to acquire the road surface friction coefficient with high accuracy.

  Further, the friction coefficient acquisition means selects a map corresponding to the degree of wear that is one step lower than the degree of wear determined from the tire usage time when the judgment means determines that the road surface friction coefficient on the road is not substantially constant. Good.

  As described above, when the road surface friction coefficient on the road is not substantially constant, it is considered that the wear of the tire has not progressed, and the wear degree is one step lower than the wear degree determined from the use time of the tire. The map should be used to estimate the road surface friction coefficient.

  Further, the determination means preferably determines whether or not the road surface friction coefficient on the traveling road is substantially constant based on at least one of an outside air temperature around the vehicle and weather information.

  In general, when the outside air temperature around the vehicle is high to some extent, or when it is not raining or snowing, the road surface friction coefficient on the traveling road of the vehicle is often a relatively high value and generally constant. Therefore, based on at least one of the outside air temperature and the weather information as described above, it is possible to accurately determine whether or not the road surface friction coefficient on the traveling road of the vehicle is substantially constant.

  The vibration detection means is provided on each wheel, and each wheel is provided with wheel-side communication means for transmitting the detection result of the vibration detection means to the vehicle body side, and the vibration level acquisition means, storage means, and friction The coefficient acquisition means is preferably provided in the vehicle body, and the vehicle body is preferably provided with vehicle body side communication means for receiving a signal transmitted from the wheel side communication means.

A road surface state estimation method according to the present invention is a road surface state estimation method for estimating a road surface state of a traveling path of a vehicle based on wheel information related to a plurality of wheels provided in the vehicle.
(A) detecting the vibration of the wheel;
(B) obtaining a vibration level in a predetermined frequency band by performing frequency analysis on the vibration of the wheel detected in step (a);
(C) From the maps prepared in advance so as to define the correlation between the vibration level and the road surface friction coefficient according to the degree of wear of the tire constituting the wheel, the degree of wear of the tire determined from the tire usage time Selecting a map to be used for estimating the road surface friction coefficient based on;
(D) including a step of acquiring a road surface friction coefficient on the traveling road of the vehicle using the vibration level acquired in step (b) and the map selected in step (c).

  ADVANTAGE OF THE INVENTION According to this invention, even if the tire which comprises a wheel wears, it becomes possible to acquire a road surface friction coefficient accurately based on wheel information.

  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 showing a vehicle including a wheel information processing apparatus according to the present invention. A vehicle 10 shown in the figure includes four traveling wheels 14 and one spare wheel 15 provided on a vehicle body 12, a steering device (not shown) for steering a steering wheel of the traveling wheels 14, and these traveling wheels. 14 is provided with an internal combustion engine, a motor, a hybrid power unit or the like as a travel drive source (not shown) for driving the drive wheels. Each wheel 14 and 15 includes a wheel and a tire, respectively.

  Each of the wheels 14 and 15 is provided with a TPMS valve 20 that functions as a tire pressure adjusting valve. Each TPMS valve 20 is attached to an attachment hole provided in a wheel rim of the wheel via a grommet made of elastic rubber, a washer, a bolt, and the like. A valve cap (not shown) of the TPMS valve 20 protrudes to the outside of the wheel rim. By removing this valve cap and connecting a hose of an air supply device to a valve port (not shown), air can be supplied to the internal space of the tire. It becomes.

  Each TPMS valve 20 has a housing (not shown). In this housing, as shown in FIG. 2, an air pressure sensor 21a, an acceleration sensor 21g, a wheel side communicator 22, a control circuit 23, and a battery 24 are accommodated. Thereby, each TPMS valve | bulb 20 functions also as a means which can transmit the wheel information acquired regularly while acquiring the tire pressure and wheel acceleration (wheel vibration) as wheel information, respectively.

  The air pressure sensor 21a is a semiconductor sensor, for example, and detects the air pressure in the tire internal space, and the acceleration sensor 21g detects the acceleration in the width direction or radial direction (vertical direction) of the corresponding traveling wheel 14 as wheel vibration. The wheel side communicator 22 can wirelessly transmit a signal indicating the detection value of the air pressure sensor 21a and the detection value of the acceleration sensor 21g periodically at a predetermined cycle. The control circuit 23 is mounted on an IC chip or the like, and controls the air pressure sensor 21a, the acceleration sensor 21g, and the wheel side communication device 22. The battery 24 supplies power to the air pressure sensor 21a, the acceleration sensor 21g, the wheel side communicator 22 and the control circuit 23. The TPMS valve 20 may further include a temperature sensor that detects the temperature in the tire internal space, a ground pressure sensor, and the like.

  Further, in the vehicle 10 of the present embodiment, a unique ID code is assigned to each wheel side communication device 22 included in the TPMS valve 20 of each wheel 14. In the present embodiment, for example, the wheel side communication device 22 of the TPMS valve 20 mounted on the right front wheel 14 is assigned ID code = 1, and the wheel side communication of the TPMS valve 20 mounted on the left front wheel 14 is performed. ID code = 2 is assigned to the machine 22 and ID code = 3 is assigned to the wheel side communication machine 22 of the TPMS valve 20 attached to the right rear wheel 14 and the TPMS valve 20 attached to the left rear wheel 14. ID code = 4 is assigned to the wheel side communicator 22, and ID code = 5 is assigned to the wheel side communicator 22 of the TPMS valve 20 attached to the spare wheel 15. The signal periodically transmitted from each wheel-side communication device 22 includes an ID code indicating the transmission-side wheel-side communication device 22 together with the detection values by the air pressure sensor 21a and the acceleration sensor 21g. That is, each wheel side communicator 22 periodically transmits a signal including information detected by the air pressure sensor 21a and the acceleration sensor 21g and its own ID code as information.

  On the other hand, as shown in FIGS. 1 and 2, the vehicle body 12 of the vehicle 10 has an electronic control unit as processing means for performing various controls using information transmitted from the wheel side communication device 22 of the TPMS valve 20. (Hereinafter referred to as “ECU”) 30 is mounted. The ECU 30 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 storage device 31, and the like. As shown in FIG. 1, the vehicle body side communication device 25, a sensor, a switch, and an alarm device 27 are connected to the ECU 30. Further, the ECU 30 is connected to the in-vehicle battery 29 via the ignition switch 28 of the vehicle 10. When the ignition switch 28 is turned ON, electric power is supplied from the in-vehicle battery 29 to the vehicle body side communication device 25, the sensor group, the alarm device 27, the ECU 30, and the like.

  The vehicle body side communication device 25 performs signal transmission / reception with the wheel side communication device 22 included in the TPMS valve 20 of each wheel 14, and receives a signal wirelessly transmitted from the wheel side communication device 22. It gives to ECU30. Sensors connected to the ECU 30 include an outside air temperature sensor 26 that detects outside air temperature around the vehicle 10, a wheel speed sensor (not shown) that is provided for each wheel 14 and detects the speed of the corresponding wheel 14, and the like. . The warning device 27 issues a warning to the driver under a predetermined condition under the control of the ECU 30, and includes, for example, a warning display device provided on the instrument panel of the vehicle 10. As shown in FIGS. 1 and 2, the ECU 30 includes a odometer 40 that measures (integrates) the mileage of the vehicle 10, a wiper switch 41 that controls the operation of a wiper (not shown), and A navigation system 42 and the like are connected.

  When the vehicle 10 configured as described above travels, the air pressure sensor 21a of each TPMS valve 20 detects the air pressure of the wheel 14 (15), and the acceleration sensor 21g detects wheel vibration. 22, a signal indicating the detected value of the air pressure sensor 21a, the detected value of the acceleration sensor 21g, and its own ID is periodically wirelessly transmitted to the vehicle body side communication device 25. When the vehicle body side communication device 25 receives a signal from the wheel side communication device 22, the ECU 30 stores (registers) the ID included in the signal received by the vehicle body side communication device 25 in the storage device. When the ID matches one of the IDs, a predetermined process using the received signal is executed.

  In the present embodiment, the wheel vibration information detected by the acceleration sensor 21g among the wheel information from each wheel 14 is used for estimating the road surface friction coefficient μ of the traveling path of the vehicle 10. That is, the road surface information estimation device according to the present invention is configured by the acceleration sensor 21g of each TPMS valve 20, the ECU 30, and the like. For this reason, the ECU 30 of the vehicle 10 includes the frequency analysis unit 32, the tire wear degree acquisition unit 33, and the friction coefficient acquisition. Part 34 is constructed. The frequency analysis unit 32 analyzes the frequency of the wheel vibration information from each wheel 14 (TPMS valve 20) received by the vehicle body side communication device 25, and the frequency at which the vibration level changes characteristically in the frequency spectrum of the wheel vibration. The vibration level in the band is detected for each wheel 14 and a signal indicating the detected vibration level is given to the friction coefficient acquisition unit 34. In addition, the frequency band in which a vibration level changes characteristically is contained in the range of 10-10000 Hz, for example.

In addition, the tire wear degree acquisition unit 33 estimates the tire usage time of each wheel 14 based on the accumulated travel distance of the vehicle 10 measured by the odometer 40 using, for example, a predetermined function equation or the like. Above, the degree of wear according to the estimated usage time of the tire is obtained. Then, the tire wear degree acquisition unit 33 gives a signal indicating the obtained wear degree to the friction coefficient acquisition unit 34. In the present embodiment, the estimated usage time (allowable usage time) from when the tire is new to when the tire is changed is divided into a plurality of usage time zones, and the wear degrees W ₀ , W corresponding to the respective usage time zones. ₁ , W ₂ ..., W _n are assigned. In this embodiment, when a new tire is mounted on the wheel 14 by exchanging the tire, a signal indicating that the tire is new is displayed on the wheel side until the corresponding wheel 14 rotates by a predetermined amount. It is transmitted from the communication device 22 to the vehicle body side communication device 25. Therefore, when the tire is replaced, the tire wear degree acquisition unit 33 determines the tire for the wheel 14 based on the travel distance of the vehicle 10 from the time when the signal indicating that the tire is new is received from the wheel 14. Estimate usage time.

Further, the storage device 31 of the ECU 30 stores a map that defines the correlation between the vibration level in the predetermined frequency band and the road surface friction coefficient (dynamic friction coefficient) μ between the tire of each wheel 14 and the traveling road. Yes. Here, as shown in FIG. 3, when the road surface friction coefficient μ decreases, the vibration level increases due to slippage of the tread portion of the tire. Further, when the tire is worn, the rubber in the tread portion is decreased and the block rigidity of the tread portion is changed. Therefore, as the tire wear proceeds, the vibration level under the same road surface friction coefficient μ is lowered. For this reason, in the present embodiment, a map that prescribes the correlation between the vibration level and the road surface friction coefficient μ is previously provided for each of the wear degrees W _{0 to} W _n assigned to a plurality of use time zones from a new article to a tire change. Has been created. A plurality of maps corresponding to the degree of wear W _{0 to} W _n are obtained by actually measuring the vibration of the wheel while running a test vehicle equipped with a wheel including an acceleration sensor on a road surface having a different road surface friction coefficient μ at a predetermined speed. It is created by performing this for a plurality of tires having different wear states.

  The friction coefficient acquisition unit 34 selects a map used for estimating the road surface friction coefficient μ from the storage device 31 based on the signal from the tire wear degree acquisition unit 33, and is acquired by the frequency analysis unit 32 while using the selected map. A road surface friction coefficient μ on the traveling road of the vehicle 10 is obtained based on the vibration level thus determined.

  Next, an estimation procedure of the road surface friction coefficient μ on the traveling road of the vehicle 10 will be described with reference to FIG.

  The routine shown in FIG. 4 is repeatedly executed every predetermined time for each traveling wheel 14 while the vehicle 10 is traveling. At the execution timing of the routine of FIG. 4 for a traveling wheel 14, the friction coefficient acquisition unit 34 of the ECU 30 acquires the outside air temperature around the vehicle 10 from the outside air temperature sensor 26, and displays the operation state of the wiper switch 41 as weather information. (S10). Further, the friction coefficient acquisition unit 34 acquires the vibration level sent from the frequency analysis unit 32 in S10. Further, the tire wear degree acquisition unit 33 of the ECU 30 estimates the tire usage time of each wheel 14 based on the accumulated travel distance of the vehicle 10 measured by the odometer 40 and then calculates the estimated tire usage time. A corresponding wear degree is obtained, and a signal indicating the obtained wear degree is given to the friction coefficient obtaining unit 34 (S12).

  When the friction coefficient acquisition unit 34 receives a signal indicating the tire wear degree from the tire wear degree acquisition unit 33, the friction coefficient acquisition unit 34 next determines whether or not the road surface friction coefficient μ of the traveling path of the vehicle 10 at that time is substantially constant. Determine (S14). In the present embodiment, the friction coefficient acquisition unit 34, when the outside air temperature acquired in S10 is equal to or higher than a predetermined temperature and the wiper switch 41 is not turned on, the road surface friction coefficient μ of the traveling path of the vehicle 10. Is substantially constant (Yes in S14). In addition, the friction coefficient acquisition unit 34 is configured so that the road surface friction coefficient μ of the traveling path of the vehicle 10 is approximately when the outside air temperature acquired in S10 is below a predetermined temperature or when the wiper switch 41 is ON. It is determined that it is not constant (No in S14).

  That is, as the traveling road of the vehicle 10, it is assumed that the asphalt road is the most frequent. Therefore, the outside temperature around the vehicle 10 is high to some extent, and the driving road of the vehicle 10 is not used during rainy weather or snowfall. The road surface friction coefficient μ is considered to be substantially constant at a relatively high value. Therefore, the accuracy of whether or not the road surface friction coefficient μ on the traveling road of the vehicle 10 is substantially constant by performing the determination process based on the outside air temperature and the operating state of the wiper as weather information as in the present embodiment. It is possible to judge well. In S14, when determining whether or not the road surface friction coefficient μ on the traveling road of the vehicle 10 is substantially constant, only one of the outside air temperature and the weather information (operating state of the wiper) is set as the determination criterion. In addition, information on the traveling environment of the vehicle 10 from the navigation system 42, the slip ratio during acceleration / deceleration, and the like may be taken into consideration.

  The friction coefficient acquisition unit 34 determines that the road surface friction coefficient μ of the traveling path of the vehicle 10 is substantially constant because the outside air temperature is equal to or higher than the predetermined temperature and the wiper switch 41 is not turned on (in S14). Yes), a map corresponding to the degree of tire wear determined from the tire usage time is selected from a plurality of maps stored in the storage device 31 (S16). Then, the friction coefficient acquisition unit 34 reads the road surface friction coefficient μ corresponding to the vibration level acquired in S10 from the map selected in S16, and the value is obtained between the tire of the target wheel 14 and the traveling road surface. Is stored in a predetermined storage area as the road surface friction coefficient μ (S18).

  As described above, in the vehicle 10, by analyzing the frequency of the detection result of the acceleration sensor 21g that detects the vibration of the wheel 14, the vibration level in the predetermined frequency band is acquired, and the road surface friction on the traveling road based on the acquired vibration level. The coefficient μ is acquired. At this time, the road surface state is estimated in consideration of the degree of wear of the tires constituting the wheels 14. That is, a plurality of maps that define the correlation between the vibration level and the road surface friction coefficient μ are stored in the storage device 31 of the ECU 30 according to the degree of tire wear. Then, a map used for estimating the road surface friction coefficient μ is selected from these maps based on the tire wear degree determined from the tire usage time (S16), and the selected map and vibration level are used. A road surface friction coefficient μ on the travel path of the vehicle 10 is acquired. As a result, in the vehicle 10, the road surface friction coefficient μ between the tire of the wheel 14 and the traveling road surface can be obtained with high accuracy. Further, when it is determined that the road surface friction coefficient μ on the traveling road on which the vehicle 10 is traveling is approximately constant, a map corresponding to the degree of tire wear determined from the tire usage time is used to estimate the road surface friction coefficient μ. If it is used for, it becomes possible to acquire the road surface friction coefficient μ with high accuracy.

On the other hand, the friction coefficient acquisition unit 34 determines that the outside air temperature is lower than the predetermined temperature or the wiper switch 41 is ON and the road surface friction coefficient μ of the traveling path of the vehicle 10 is not substantially constant ( No) in S14, a map corresponding to the degree of wear that is one step lower than the degree of tire wear determined from the tire usage time is selected from a plurality of maps stored in the storage device 31 (S20). For example, if the wear degree of the tire of the wheel 14 to be obtained at S12 is W _1, a negative determination in S14 is made, in S20, the map is selected corresponding to the tire wear degree W ₀ Will be. However, when the wear degree of the tire of the wheel 14 to be obtained at S12 is the lowest level of W _0, negative determination at S14 is also made, in S20, corresponding to the wear degree W ₀ A map is selected.

  Then, the friction coefficient acquisition unit 34 reads the road surface friction coefficient μ corresponding to the vibration level acquired in S10 from the map selected in S20, and the value between the tire of the target wheel 14 and the traveling road surface. The road surface friction coefficient μ is stored in a predetermined storage area (S18). As described above, when it is determined that the road surface friction coefficient μ on the traveling road of the vehicle 10 is not substantially constant, it is determined that the wear of the tire has not progressed, and the wear degree determined from the tire use time is determined. However, a map corresponding to the degree of wear that is one step lower may be used to estimate the road surface friction coefficient μ.

  In the above-described embodiment, the acceleration sensor 21g that detects the wheel vibration is provided for the TPMS valve 20 mounted on the wheel of each wheel 14, but is not limited thereto. That is, an acceleration sensor for detecting wheel vibrations may be provided for each traveling wheel, and may be provided directly on either the wheel or the tire. When the acceleration sensor is provided on the tire, a plurality of acceleration sensors may be arranged in the circumferential direction on the inner surface of the tread portion of the tire. Further, the acceleration sensor may be provided in a component member of the suspension located in the vicinity of each wheel. In this case, the acceleration sensor detects vibration of the wheel transmitted to the component member of the suspension.

It is a schematic block diagram which shows the vehicle provided with the road surface state estimation apparatus by this invention. It is a control block diagram of the road surface state estimation apparatus by this invention. It is a graph for demonstrating the correlation with the vibration level and road surface friction coefficient in case the abrasion degree of a tire changes. 2 is a flowchart for explaining a procedure for estimating a road surface friction coefficient in the vehicle of FIG. 1.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Vehicle, 12 Car body, 14, Running wheel, 15 Spare wheel, 20 TPMS valve, 21a Air pressure sensor, 21g Acceleration sensor, 22 Wheel side communication machine, 23 Control circuit, 24 Battery, 25 Car body side communication machine, 26 Outside temperature sensor , 27 Alarm device, 28 Ignition switch, 29 On-board battery, 30 ECU, 31 Storage device, 32 Frequency analysis unit, 33 Tire wear degree acquisition unit, 34 Friction coefficient acquisition unit, 40 Odometer, 41 Wiper switch, 42 Navigation system .

Claims (6)

In a road surface state estimating device for estimating a road surface state of a traveling road of the vehicle based on wheel information related to a plurality of wheels provided in the vehicle,
Vibration detecting means provided for each wheel, and detecting vibration of the corresponding wheel;
Vibration level acquisition means for acquiring a vibration level in a predetermined frequency band by frequency analysis of the detection result of the vibration detection means;
Storage means for storing a plurality of maps defining the correlation between the vibration level and the road surface friction coefficient according to the degree of wear of the tires constituting the wheels;
The vehicle is selected based on the degree of wear of the tire determined from the tire usage time, and the vehicle is selected using the selected map and the vibration level acquired by the vibration level acquisition means. A road surface state estimating device comprising: friction coefficient acquisition means for acquiring a road surface friction coefficient on the traveling road.   It further comprises determination means for determining whether or not the road surface friction coefficient on the travel road is substantially constant, and the friction coefficient acquisition means is determined by the determination means to be substantially constant on the road surface friction coefficient. The road surface state estimating device according to claim 1, wherein a map corresponding to a degree of wear of the tire determined from a usage time of the tire is selected.   The friction coefficient obtaining means responds to a degree of wear that is one step lower than the degree of wear determined from the use time of the tire when the judgment means determines that the road surface friction coefficient on the travel road is not substantially constant. The road surface state estimating apparatus according to claim 2, wherein a map is selected.   3. The determination unit according to claim 2, wherein the determination unit determines whether or not a road surface friction coefficient on the traveling road is substantially constant based on at least one of an outside air temperature around the vehicle and weather information. 4. The road surface state estimating device according to 3.   The vibration detection means is provided on each wheel, and each wheel is provided with wheel side communication means for transmitting the detection result of the vibration detection means to the vehicle body side, the vibration level acquisition means, and the storage And the friction coefficient acquisition means are provided in a vehicle body of the vehicle, and the vehicle body is provided with vehicle body side communication means for receiving a signal transmitted from the wheel side communication means. The road surface state estimating device according to any one of claims 1 to 4. In the road surface state estimation method for estimating the road surface state of the traveling road of the vehicle based on wheel information related to a plurality of wheels provided in the vehicle,
(A) detecting vibration of the wheel;
(B) obtaining a vibration level in a predetermined frequency band by frequency-analyzing the vibration of the wheel detected in step (a);
(C) Wear of the tire determined from the use time of the tire from a plurality of maps prepared in advance so as to define the correlation between the vibration level and the road surface friction coefficient according to the degree of wear of the tire constituting the wheel. Selecting a map to be used for estimating the road friction coefficient based on the degree;
(D) A road surface state estimation method including the step of acquiring a road surface friction coefficient on the traveling road of the vehicle using the vibration level acquired in step (b) and the map selected in step (c).

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