Wheel load estimation device, wheel load estimation method and wheel load estimation program

Abstract

To highly accurately estimate wheel load.SOLUTION: A wheel load estimation device comprises a tire information acquisition part, a wheel speed acquisition part, a frequency characteristic ratio calculation part, a load ratio calculation part, and a wheel load calculation part. The tire information acquisition part acquires kind information for specifying the kind of a tire. The wheel speed acquisition part acquires wheel speed information representing wheel speed of each wheel of a vehicle. The frequency characteristic ratio calculation part calculates a front and back frequency characteristic ratio and a left and right frequency characteristic ratio. The load ratio calculation part calculates each of a front and back load ratio and a left and right load ratio. The wheel load calculation part calculates a wheel load ratio representing a relative wheel load. The load ratio calculation part calculates each of the front and back load ratio and the left and right load ratio on the basis of a first relation identification information and second relation identification information. The first relation identification information and the second relation identification information are obtained according to the kind of the tire.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a technique for estimating the wheel load of a tire included in a vehicle. [Background technology]

[0002] Patent Document 1 discloses a wheel load estimation device capable of accurately estimating wheel loads with simple equipment. This wheel load estimation device estimates the load ratio of each wheel by utilizing the fact that the frequency characteristics of rotating wheels change with changes in wheel load. More specifically, Patent Document 1 derives gain integral values ​​of the frequency spectrum for each of the two front wheels, two rear wheels, two left wheels, and two right wheels from the output signals of wheel speed sensors that detect the wheel speeds of each wheel. According to Patent Document 1, the front-to-rear and left-to-right ratios of these gain integral values ​​are approximately linearly related to the front-to-rear and left-to-right wheel load ratios, respectively. Therefore, by calculating coefficients that specify this linear relationship in advance, the load ratio of each wheel can be estimated using the gain integral values ​​derived based on the output signals of the wheel speed sensors for each wheel. Furthermore, by separately estimating the total vehicle weight, the wheel load of each wheel can be estimated. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-113373 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the frequency characteristics of the wheel speeds differ depending on the type of tire. Therefore, depending on the tire included in the vehicle, the linear relationship between the front-rear ratio of the gain integral value and the front-rear ratio of the wheel load may deviate from the predetermined linear relationship, which may reduce the accuracy of the wheel load estimation. The same applies to the linear relationship between the left-right ratio of the gain integral value and the left-right ratio of the wheel load.

[0005] An object of the present invention is to provide a wheel load estimation device, a wheel load estimation method, and a wheel load estimation program that can estimate wheel loads with high accuracy. [Means for solving the problem]

[0006] A wheel load estimation device according to a first aspect of the present invention is a wheel load estimation device that estimates wheel loads of tires included in a vehicle, and includes a tire information acquisition unit, a wheel speed acquisition unit, a frequency characteristic ratio calculation unit, a load ratio calculation unit, and a wheel load calculation unit. The tire information acquisition unit acquires type information that identifies the type of the tire. The wheel speed acquisition unit acquires wheel speed information that indicates the wheel speed of each wheel of the vehicle. The frequency characteristic ratio calculation unit calculates, based on the wheel speed information, a front-rear frequency characteristic ratio that changes with a change in a front-rear load ratio, which is the ratio of a load acting on a front wheel of the vehicle to a load acting on a rear wheel of the vehicle, and a left-right frequency characteristic ratio that changes with a change in a left-right load ratio, which is the ratio of a load acting on a left wheel of the vehicle to a load acting on a right wheel of the vehicle. The load ratio calculation unit calculates the front-rear load ratio and the left-right load ratio based on the front-rear frequency characteristic ratio and the left-right frequency characteristic ratio, respectively. The wheel load calculation unit calculates, for at least one wheel of the vehicle, a wheel load ratio that represents a relative wheel load between wheels included in the vehicle based on the front-rear load ratio and the left-right load ratio. The load ratio calculation unit calculates the front-rear load ratio and the left-right load ratio based on first relationship specifying information that specifies a relationship between the front-rear frequency characteristic ratio and the front-rear load ratio and second relationship specifying information that specifies a relationship between the left-right frequency characteristic ratio and the left-right load ratio, respectively, and the first relationship specifying information and the second relationship specifying information are determined according to the type of the tire.

[0007] A wheel load estimation device according to a second aspect is the wheel load estimation device according to the first aspect, wherein at least one of the tires includes a tag that electromagnetically stores the type information.

[0008] A wheel load estimation device according to a third aspect is a wheel load estimation device according to the first or second aspect, wherein the first relationship identification information and the second relationship identification information are stored in a computer external to the vehicle, and the load ratio calculation unit acquires the first relationship identification information and the second relationship identification information from the external computer.

[0009] A wheel load estimation system according to a fourth aspect includes the wheel load estimation device according to the first aspect, at least one tire including a tag that electromagnetically stores the type information, and a reader that reads the type information from the tag.

[0010] A wheel load estimation method according to a fifth aspect is a wheel load estimation method executed by one or more computers for estimating wheel loads of tires included in a vehicle, and includes the following. Obtaining type information that identifies the type of tire Obtaining wheel speed information representing the wheel speed of each wheel of the vehicle. Calculating, based on the wheel speed information, a front-rear frequency characteristic ratio that changes with a change in a front-rear load ratio, which is the ratio of a load acting on a front wheel of the vehicle to a load acting on a rear wheel of the vehicle, and a left-right frequency characteristic ratio that changes with a change in a left-right load ratio, which is the ratio of a load acting on a left wheel of the vehicle to a load acting on a right wheel of the vehicle. Calculating the front-to-rear load ratio and the left-to-right load ratio based on the front-to-rear frequency characteristic ratio and the left-to-right frequency characteristic ratio, respectively. Calculating a wheel load ratio representing a relative wheel load between wheels included in the vehicle for at least one wheel of the vehicle based on the front-rear load ratio and the left-right load ratio. Calculating the front-rear load ratio and the left-right load ratio includes calculating the front-rear load ratio and the left-right load ratio based on first relationship specifying information that specifies a relationship between the front-rear frequency characteristic ratio and the front-rear load ratio, and second relationship specifying information that specifies the relationship between the left-right frequency characteristic ratio and the left-right load ratio, and the first relationship specifying information and the second relationship specifying information are determined according to the type of tire.

[0011] A wheel load estimation program according to a sixth aspect is a wheel load estimation program for estimating wheel loads of tires included in a vehicle, and causes one or more computers to perform the following. Obtaining type information that identifies the type of tire Obtaining wheel speed information representing the wheel speed of each wheel of the vehicle. Calculating, based on the wheel speed information, a front-rear frequency characteristic ratio that changes with a change in a front-rear load ratio, which is the ratio of a load acting on a front wheel of the vehicle to a load acting on a rear wheel of the vehicle, and a left-right frequency characteristic ratio that changes with a change in a left-right load ratio, which is the ratio of a load acting on a left wheel of the vehicle to a load acting on a right wheel of the vehicle. Calculating the front-to-rear load ratio and the left-to-right load ratio based on the front-to-rear frequency characteristic ratio and the left-to-right frequency characteristic ratio, respectively. Calculating a wheel load ratio representing a relative wheel load between wheels included in the vehicle for at least one wheel of the vehicle based on the front-rear load ratio and the left-right load ratio. Calculating the front-rear load ratio and the left-right load ratio includes calculating the front-rear load ratio and the left-right load ratio based on first relationship specifying information that specifies a relationship between the front-rear frequency characteristic ratio and the front-rear load ratio, and second relationship specifying information that specifies the relationship between the left-right frequency characteristic ratio and the left-right load ratio, and the first relationship specifying information and the second relationship specifying information are determined according to the type of tire. [Effects of the Invention]

[0012] According to the present invention, the wheel load of a tire included in a vehicle can be estimated with higher accuracy. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram showing a state in which a wheel load estimation device according to an embodiment of the present invention is mounted on a vehicle; [Figure 2] FIG. 2 is a block diagram showing the electrical configuration of the wheel load estimation device. [Figure 3]4 is a flowchart showing the flow of a wheel load estimation process. [Figure 4] FIG. 10 is a schematic diagram of a wheel load estimation system according to a modified example. [Figure 5] FIG. 1 is a diagram showing an example of a database configuration. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, a wheel load estimation device, a wheel load estimation method, and a wheel load estimation program according to an embodiment of the present invention will be described with reference to the drawings.

[0015] <1. Configuration of wheel load estimation device> FIG. 1 is a schematic diagram showing a state in which a wheel load estimation device 2 according to this embodiment is mounted on a vehicle 1. The vehicle 1 is a four-wheel vehicle, and has a left front wheel FL, a right front wheel FR, a left rear wheel RL, and a right rear wheel RR. Each of the wheels FL, FR, RL, and RR has a tire T FL ,T FR ,T RL ,T RR The wheel load estimation device 2 estimates the load of these wheels FL, FR, RL, RR (or tires T FL ,T FR ,T RL ,T RR ) and has the function of estimating the wheel load acting on the vehicle.

[0016] The estimated wheel load data is used for various controls that assist the vehicle 1 in traveling. For example, the estimated wheel load data is transmitted to a brake control system and used for brake control. The estimated wheel load data is also transmitted to a tire pressure monitoring system (TPMS) or the like mounted on the wheels FL, FR, RL, and RR and used to determine tire deflation. If a tire deflation is detected based on the estimated wheel load data, the TPMS can issue a warning via the warning indicator 3 mounted on the vehicle 1. Some TPMS systems determine tire deflation from changes in the tire's dynamic load radius, but the tire's dynamic load radius is affected not only by tire deflation but also by the wheel load. Therefore, if this system is adopted, tire deflation can be accurately determined by canceling the influence of the wheel load from the tire's dynamic load radius based on the estimated wheel load data. The estimated wheel load data can also be used to detect overloading or uneven loading of the vehicle 1. If such a condition is detected, a warning can be issued via the warning indicator 3 mounted on the vehicle 1. Overloading refers to a state in which the vehicle 1 is loaded with a load that exceeds the allowable load, and uneven loading refers to a state in which the load within the vehicle 1 is unevenly distributed in certain areas.

[0017] Tire T of this embodiment FL ,T FR ,T RL ,T RR At least one of the tags 8A includes a tag 8A that electromagnetically stores type information for identifying the type of tire. More specifically, the tag 8A is configured, for example, as a known RFID tag with a built-in memory for storing information, and the tag 8A is used to identify the type of tire T. FL ,T FR ,T RL ,T RRThe type information for identifying the type of tire is embedded inside the rubber that constitutes the tire. The type information for identifying the type of tire may be information that can identify the tire name and tire size of the tire. The memory of the tag 8A may further store individual identification information for identifying individual tires, specification information indicating specifications other than tire size, manufacturing information related to manufacturing such as the manufacturing date, etc.

[0018] In this embodiment, the information stored in the memory of the tag 8A can be read out contactlessly by the reader 8B. The reader 8B is a device that is installed in, for example, the vehicle 1 and is connected to the wheel load estimation device 2 so as to be able to communicate data with the tag 8A. The reader 8B transmits a request signal to the tag 8A to request that the tag 8A transmit type information. In response to the request signal, the tag 8A transmits the type information stored in the memory to the reader 8B. Upon receiving the type information, the reader 8B notifies the wheel load estimation device 2 of the type information. In this way, the reader 8B can be configured as a known RFID reader or a known RFID reader / writer. At least one tire including the tag 8A and the reader 8B, together with the wheel load estimation device 2, constitute the wheel load estimation system 10 according to this embodiment.

[0019] In this embodiment, the tire T FL ,T FR ,T RL ,T RR The wheel load is estimated based on the wheel speeds (rotational speeds) of the wheels FL, FR, RL, and RR. Each of the wheels FL, FR, RL, and RR is equipped with a wheel speed sensor 6, which detects information indicating the wheel speed of the wheel to which it is attached (hereinafter referred to as wheel speed information) at a predetermined sampling period ΔT. The wheel speed sensors 6 are connected to the wheel load estimation device 2 via communication lines 5, and the wheel speed information detected by each wheel speed sensor 6 is transmitted to the wheel load estimation device 2 in real time.

[0020] Any type of wheel speed sensor 6 can be used as long as it can detect the wheel speeds of the wheels FL, FR, RL, and RR while the vehicle is moving. For example, a sensor of the type that measures wheel speed from the output signal of an electromagnetic pickup can be used, or a sensor of the type that generates electricity using rotation, like a dynamo, and measures wheel speed from the resulting voltage can be used. The installation position of the wheel speed sensor 6 is not particularly limited, and can be selected appropriately depending on the type of sensor, as long as it is capable of detecting wheel speed.

[0021] In this embodiment, the current total weight of the vehicle 1 is estimated based on the wheel torque WT of the vehicle 1. In this embodiment, a wheel torque sensor (hereinafter referred to as a WT sensor) 7 is installed on the left front wheel, which is one of the driving wheels. The WT sensor 7 detects the wheel torque of the vehicle 1. The WT sensor 7 is connected to the wheel load estimation device 2 via a communication line 5, and information on the wheel torque detected by the WT sensor 7 is transmitted to the wheel load estimation device 2 in real time.

[0022] The WT sensor 7 is not particularly limited in structure or installation position as long as it can detect the wheel torque of the drive wheels of the vehicle 1. Various types of WT sensors are commercially available, and their configurations are well known, so a detailed description will be omitted here. It is also possible to detect wheel torque without using the WT sensor 7; for example, wheel torque can be estimated from engine torque obtained from an engine control device.

[0023] FIG. 2 is a block diagram showing the electrical configuration of the wheel load estimation device 2. As shown in FIG. 2, the wheel load estimation device 2 is an on-board computer installed in the vehicle 1, and includes an I / O interface 21, a CPU (Central Processing Unit) 22, a ROM (Read Only Memory) 23, a RAM (Random Access Memory) 24, and a non-volatile rewritable storage device 25. The I / O interface 21 is a communication device for communicating with external devices such as the wheel speed sensor 6, the WT sensor 7, and an alarm indicator 3 (described later). The ROM 23 stores a program 29 for controlling the operation of each part of the vehicle 1. The program 29 is written to the ROM 23 from a storage medium 20 such as a CD-ROM. The CPU 22 reads and executes the program 29 from the ROM 23, thereby virtually operating as a tire information acquisition unit 220, a wheel speed acquisition unit 221, a torque acquisition unit 222, a total weight calculation unit 223, a frequency characteristic ratio calculation unit 224, a load ratio calculation unit 225, and a wheel load calculation unit 226. The operation of each of the units 220 to 226 will be described in detail later. The storage device 25 is configured with a hard disk, a flash memory, or the like. The program 29 may be stored in the storage device 25 instead of the ROM 23. The RAM 24 and the storage device 25 are used as appropriate for the calculations of the CPU 22.

[0024] In this embodiment, the storage device 25 or the ROM 23 stores in advance first relationship specifying information and second relationship specifying information for multiple types of tires that may be mounted on the wheels FL, FR, RL, and RR. The first relationship specifying information and second relationship specifying information are information that are referenced by the wheel load estimation device 2 in the wheel load estimation process described below. The first relationship specifying information and second relationship specifying information are specified in advance for each type of tire based on data acquired during test runs conducted, for example, on a test vehicle of the same model as the vehicle 1, with the types of tires mounted on the wheels and wheel load conditions for each tire changed.

[0025] The warning indicator 3 can be realized in any form, such as a liquid crystal display element or an LCD monitor, as long as it can inform the user that an uneven tire loading or the like has occurred. The mounting position of the warning indicator 3 can also be selected appropriately, but it is preferable to install it in a location that is easy for the driver to see, such as on the instrument panel. If the wheel load estimation device 2 is connected to a car navigation system, the monitor for the car navigation system can also be used as the warning indicator 3. If a monitor is used as the warning indicator 3, the warning can be displayed as an icon or text information on the monitor.

[0026] <2. Wheel load estimation processing> 3 is a flowchart showing the flow of the wheel load estimation process. FL ,T FR ,T RL ,T RR The wheel load estimation process shown in Fig. 3 starts, for example, when the vehicle 1 starts traveling and ends when the vehicle 1 stops traveling.

[0027] First, the tire information acquisition unit 220 acquires the tire information of the tire T currently mounted on the wheels FL, FR, RL, and RR. FL ,T FR ,T RL ,T RR It is determined whether or not at least one of the type information items has already been stored in the storage device 25 (step S1). If it is determined that at least one of the type information items has already been stored in the storage device 25 (YES), step S3 is then executed. FL ,T FR ,T RL ,T RR If it is determined that none of the above type information is stored in the storage device 25 (NO), step S2 is then executed.

[0028] In step S2, the tire information acquisition unit 220 acquires information about the tire T via the reader 8B. FL ,T FR ,T RL,T RR The tire information acquisition unit 220 transmits a request signal to the tag 8A and requests the reader 8B to transfer the type information received from the tag 8A to the reader 8B. FL ,T FR ,T RL ,T RR and stores it in the storage device 25. The request to the reader 8B may be triggered by an operation on the wheel load estimation device 2 by a user (typically, the driver of the vehicle 1). In this case, the tire information acquisition unit 220 may generate a screen prompting the user to perform a predetermined initialization operation (for example, pressing a predetermined button), and display it on the warning display 3. In this embodiment, once the type information is stored in the storage device 25, the same type information is referenced in subsequent wheel load estimation processes. Therefore, it is preferable that the wheel load estimation device 2 be configured so that the type information can be appropriately overwritten and updated by the user performing the initialization operation after changing tires, etc.

[0029] In step S3, the wheel speed acquisition unit 221 acquires time-series rotation speed signals from the wheel speed sensors 6 attached to the wheels FL, FR, RL, and RR. The wheel speed acquisition unit 221 converts the acquired rotation speed signals into time-series rotation speed signals for the wheels FL, FR, RL, and RR (or tires T FL ,T FR ,T RL ,T RR ) into rotational speeds V1 to V4, which are temporarily stored in the RAM 24 or in the storage device 25.

[0030] Next, the torque obtaining unit 222 obtains the output signal of the WT sensor 7 (step S4). The torque obtaining unit 222 temporarily stores the obtained output signal of the WT sensor 7 in the RAM 24, or stores it in the storage device 25. The torque obtaining unit 222 also converts the output signal of the WT sensor 7 into wheel torque.

[0031] Next, the total weight calculation unit 223 calculates the current total weight M of the vehicle 1 (step S5). In this embodiment, the total weight M is calculated based on the following equation of motion. In the equation, WT is the wheel torque derived in step S3. α is the longitudinal acceleration of the vehicle 1, and is calculated from the wheel speeds V1 to V4. g is the gravitational acceleration, and θ is the road surface gradient. θ can be calculated, for example, from data from a satellite positioning system such as GPS mounted on the vehicle 1. WT=Mα+Mg·sinθ

[0032] Since various methods are known for estimating the total weight M of vehicle 1, further detailed explanation will be omitted here, but for a deeper understanding, reference can be made to, for example, Patent No. 5346659 and Patent No. 4926258 of the present applicant.

[0033] Next, the frequency characteristic ratio calculation unit 224 evaluates the frequency characteristics of the waveform signals of the wheel speeds V1 to V4 (step S6). Specifically, the frequency characteristic ratio calculation unit 224 time-differentiates the time-series data of the wheel speeds V1 to V4 to calculate accelerations A1 to A4, where A1 to A4 are the rotational accelerations of the wheels FL, FR, RL, and RR, respectively. Next, the frequency characteristic ratio calculation unit 224 performs a fast Fourier transform on the accelerations A1 to A4 to derive their respective frequency spectra. The frequency characteristics can be evaluated not only by fast Fourier transform processing, but also by time-series estimation using an autoregressive model and the variance of the time-series data, etc.

[0034] Next, the frequency characteristic ratio calculation unit 224 calculates the gain integral value for each of the two front wheels (FL+FR), two rear wheels (RL+RR), two left wheels (FL+RL), and two right wheels (FR+RR) based on the frequency spectra of the wheels FL, FR, RL, and RR derived in step S6 (step S7). As described above, the gain integral value represents the magnitude of the gain. In this embodiment, the frequency spectrum is integrated over a band from 0 to the Nyquist frequency to calculate the gain integral value, but integration may be limited to a band where the influence of the load is significantly apparent. In addition, the front, rear, left, and right integration intervals do not necessarily have to be the same. Hereinafter, the gain integral values ​​for the two front wheels, two rear wheels, two left wheels, and two right wheels will be referred to as the front wheel gain, rear wheel gain, left wheel gain, and right wheel gain, respectively.

[0035] Subsequently, the load ratio calculation unit 225 calculates the front-rear frequency characteristic ratio R1 and the left-right frequency characteristic ratio R2 according to the following equations (step S8). R1 = rear wheel gain / front wheel gain R2 = Right wheel gain / Left wheel gain

[0036] Next, the load ratio calculation unit 225 calculates the front-rear load ratio L1 and the left-right load ratio L2 (step S9). More specifically, the load ratio calculation unit 225 reads out first relationship specifying information and second relationship specifying information from the storage device 25 based on the type information stored in the storage device 25. In this embodiment, as disclosed in Patent Document 1, L1 and L2 are calculated from R1 and R2, respectively, by utilizing the fact that L1 and R1 are generally linearly related and that L2 and R2 are also generally linearly related. Therefore, the first relationship specifying information is constants c1 and d1 that specify the linear relationship between L1 and R1 as shown in the following equation, and the second relationship specifying information is constants c2 and d2 that specify the linear relationship between L2 and R2 as shown in the following equation. L1=c1×R1+d1 L2=c2×R2+d2

[0037] Next, the load ratio calculation unit 225 calculates the front axle load ratio x and the rear axle load ratio y, and calculates the wheel load ratio L based on x and y. FL , LFR , L RL , L RR is calculated (step S10). The front axle load ratio x is the ratio of the sum of the wheel loads of the two front wheels to the total weight M of the vehicle 1. The rear axle load ratio y is the ratio of the sum of the wheel loads of the two rear wheels to the total weight M of the vehicle 1. x and y are calculated using the following formulas. x=1 / (1+L1) y=1-x=L1 / (1+L1)

[0038] In addition, the wheel load ratio L calculated here FL , L FR , L RL , L RR are indices that represent the relative wheel loads among the wheels FL, FR, RL, and RR, respectively. FL , L FR , L RL , L RR are defined as the ratios of the wheel loads of the wheels FL, FR, RL, and RR to the total weight M of the vehicle 1, and are calculated according to the following formula: L FL =x / (1+L2) L FR =xL FL L RL =y / (1+L2) L RR =yL RL

[0039] Next, the wheel load calculation unit 226 calculates the wheel load ratio L FL , L FR , L RL , L RR and the total weight M of the vehicle 1, the wheel loads of the wheels FL, FR, RL, and RR are calculated according to the following formula (step S11). FL wheel: M×L FL FR wheels: M x L FR RL wheel: M×L RL RR wheel: M×L RR

[0040] The wheel load estimation process is then completed. However, the wheel load estimation device 2 may further determine whether or not an unbalanced load has occurred based on at least one of the wheel load ratio calculated in step S10 and the wheel load calculated in step S11. If it is determined that an unbalanced load has occurred, the wheel load estimation device 2 may be configured to generate an alarm and output it via the alarm display 3.

[0041] <3. Features> According to the above embodiment, the first relationship specifying information and the second relationship specifying information stored in advance in the wheel load estimation device 2 are referenced in accordance with the tire type information, and the wheel load is estimated using the first relationship specifying information and the second relationship specifying information suitable for the combination of the vehicle 1 and the tire. Therefore, the wheel load can be estimated more accurately than when using, as the first relationship specifying information and the second relationship specifying information, general-purpose data acquired from test runs under conditions of combinations of multiple types of vehicles 1 and multiple types of tires.

[0042] <4. Modifications> Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention. For example, the following modifications are possible. Furthermore, the gist of the following modifications can be combined as appropriate.

[0043] (1) The configurations of the tag 8A and the reader 8B are not limited to those in the above embodiment. For example, the tag 8A may be configured to transmit type information in accordance with other wireless communication standards, such as Bluetooth (registered trademark). In this case, the reader 8B may be a mobile information terminal (smartphone, tablet, laptop computer, etc.) that the user can carry and bring into the vehicle 1, or the wheel load estimation device 2 may also function as the reader 8B.

[0044] (2) In the above embodiment, the wheel load ratio and wheel load are calculated for each wheel, but these may be calculated for only some of the wheels FL, FR, RL, and RR. Also, if only the wheel load ratio is required in another control system of the vehicle 1, steps S4, S5, and S11 may be omitted.

[0045] (3) The order in which the steps of the wheel load estimation process according to the above embodiment are executed can be changed as appropriate. For example, steps S4 to S5 may be executed before step S3.

[0046] (4) The method for calculating the front-rear load ratio L1 and the left-right load ratio L2 is not limited to the method described in the above embodiment. For example, the front-rear load ratio L1 can be expressed as a linear combination of the ratio of the gain integral value of the two front wheels to the gain integral value of the two rear wheels in a first frequency band and the ratio of the gain integral value of the two front wheels to the gain integral value of the two rear wheels in a second frequency band, each weighted by a predetermined coefficient. For details of this method, refer to Japanese Patent Application Laid-Open No. 2024-029666, a publication of the present applicant. When calculating the front-rear load ratio L1 using the method disclosed in this publication, the first relationship identification information corresponds to a weighting coefficient for the gain integral value ratio in the first frequency band and the gain integral value ratio in the second frequency band. Similarly, when the left and right load ratios (first left and right load ratio L2 and second left and right load ratio L3) are calculated using the method disclosed in the same publication, the second relationship specifying information corresponds to a weighting coefficient of the gain integral value ratio in the first frequency band and the gain integral value ratio in the second frequency band for the front left and right wheels, and a weighting coefficient of the gain integral value ratio in the first frequency band and the gain integral value ratio in the second frequency band for the rear left and right wheels.

[0047] (5) In the above embodiment, the storage device 25 of the wheel load estimation device 2 stores the first relationship identifying information and the second relationship identifying information corresponding to multiple tire type information. However, the first relationship identifying information and the second relationship identifying information may be stored not in the wheel load estimation device 2 but in a computer 9 external to the vehicle 1 to which the wheel load estimation device 2 is connected for data communication, as shown in FIG. 4 . The computer 9 may be configured as a general-purpose server computer that is connected for data communication with the wheel load estimation devices 2 of multiple vehicles 1 and transmits the first relationship identifying information and the second relationship identifying information in response to a request from the wheel load estimation device 2. The computer 9, together with the wheel load estimation device 2, at least one tire including a tag 8A, and a reader 8B, constitutes a wheel load estimation system 10X according to a modified example. The computer 9 includes a CPU 90, a ROM 91, a RAM 92, a communication unit 93, and a non-volatile rewritable storage device 94. The ROM 91 stores a program 95 for controlling the operation of the computer 9. The CPU 90 reads and executes the program 95, causing the computer 9 to function as a server computer. The RAM 92 and the storage device 94 are used as appropriate for the calculations of the CPU 90. The communication unit 93 is a communication device for performing data communication with other computers such as the wheel load estimation device 2 via a network.

[0048] The storage device 94 stores first relationship specifying information and second relationship specifying information associated with a plurality of combinations of vehicle information and tire type information, as shown in Fig. 5, for example. The vehicle information is information that specifies the model of the vehicle on which the wheel load estimation device 2 is mounted. That is, the storage device 94 stores a database 940 of first relationship specifying information and second relationship specifying information corresponding to a plurality of combinations of the vehicle 1 and tires. It is preferable that this database 940 be updatable.

[0049] If the determination in step S1 of the above embodiment is NO (i.e., if the tire T FL ,T FR ,T RL ,T RRIf all the type information has not been acquired yet), in step S2, the computer 9 acquires at least one piece of tire type information from each tag 8A and transmits the acquired tire type information and the vehicle information of the vehicle 1 on which the wheel load estimation device 2 is mounted to the computer 9. When the computer 9 receives the type information and vehicle information from the wheel load estimation device 2, the computer 9 refers to the database 940 to identify data of the first relationship identifying information and the second relationship identifying information that match the combination of the received type information and vehicle information, and transmits this to the wheel load estimation device 2. In this way, the tire information acquisition unit 220 acquires the first relationship identifying information and the second relationship identifying information from the computer 9.

[0050] In the above embodiment, the device that directly communicates with the computer 9 may be a device other than the wheel load estimation device 2 that is connected to the wheel load estimation device 2 so as to be able to communicate data with the computer 9. For example, the reader 8B may acquire tire type information from the tag 8A and transmit this information together with vehicle information to the computer 9, and acquire the first relationship specifying information and the second relationship specifying information from the computer 9.

[0051] (6) The tire type information may be acquired by the wheel load estimation device 2 without using the tag 8A. For example, the tire information acquisition unit 220 may generate a screen that allows the user to input or select tire type information, display this on the warning display 3, etc., and acquire the tire type information based on the user's input or selection operation. In other words, the tire T FL ,T FR ,T RL ,T RR may not include tag 8A.

[0052] (7) The tire type information does not need to be acquired for all tires included in the vehicle 1, but only needs to be acquired for at least one tire included in the vehicle 1. In other words, it is assumed that the same type of tire is installed on the vehicle 1. [Explanation of symbols]

[0053] 1 vehicle 2. Wheel load estimation device (on-board computer) 8A Tag 8B Leader 9 Computers (server equipment) 220 Tire Information Acquisition Unit 221 Wheel speed acquisition section 224 Frequency characteristic ratio calculation section 225 Load ratio calculation section 226 Wheel load calculation section V1 Rotational speed of the left front tire V2 Rotational speed of the right front tire V3 Left rear tire rotation speed V4 Right rear tire rotation speed

Claims

1. A wheel load estimation device that estimates a wheel load of a tire included in a vehicle, a tire information acquisition unit that acquires type information that identifies the type of the tire; a wheel speed acquisition unit that acquires wheel speed information representing a wheel speed of each wheel of the vehicle; a frequency characteristic ratio calculation unit that calculates, based on the wheel speed information, a front-rear frequency characteristic ratio that changes with a change in a front-rear load ratio, which is the ratio of a load acting on a front wheel of the vehicle to a load acting on a rear wheel of the vehicle, and a left-right frequency characteristic ratio that changes with a change in a left-right load ratio, which is the ratio of a load acting on a left wheel of the vehicle to a load acting on a right wheel of the vehicle; a load ratio calculation unit that calculates the front-rear load ratio and the left-right load ratio based on the front-rear frequency characteristic ratio and the left-right frequency characteristic ratio, respectively; a wheel load calculation unit that calculates a wheel load ratio representing a relative wheel load between wheels included in the vehicle for at least one wheel of the vehicle based on the front-rear load ratio and the left-right load ratio; Equipped with the load ratio calculation unit calculates the front-rear load ratio and the left-right load ratio based on first relationship identification information that identifies a relationship between the front-rear frequency characteristic ratio and the front-rear load ratio, and second relationship identification information that identifies a relationship between the left-right frequency characteristic ratio and the left-right load ratio, The first relationship specifying information and the second relationship specifying information are determined according to the type of the tire. Wheel load estimation device.

2. At least one of the tires includes a tag that electromagnetically stores the type information. The wheel load estimation device according to claim 1 .

3. the first relationship specifying information and the second relationship specifying information are stored in a computer external to the vehicle; the load ratio calculation unit acquires the first relationship identification information and the second relationship identification information from the external computer. The wheel load estimation device according to claim 1 or 2.

4. The wheel load estimation device according to claim 1 ; At least one tire including a tag that electromagnetically stores the type information; a reader that reads the type information from the tag; Equipped with Wheel load estimation system.

5. 1. A wheel load estimation method executed by one or more computers for estimating wheel loads of tires included in a vehicle, comprising: acquiring type information that identifies the type of the tire; obtaining wheel speed information representing a wheel speed of each wheel of the vehicle; calculating, based on the wheel speed information, a front-rear frequency characteristic ratio that changes with a change in a front-rear load ratio, which is the ratio of a load acting on a front wheel of the vehicle to a load acting on a rear wheel of the vehicle, and a left-right frequency characteristic ratio that changes with a change in a left-right load ratio, which is the ratio of a load acting on a left wheel of the vehicle to a load acting on a right wheel of the vehicle; calculating the front-rear load ratio and the left-right load ratio based on the front-rear frequency characteristic ratio and the left-right frequency characteristic ratio, respectively; calculating a wheel load ratio representing a relative wheel load between wheels included in the vehicle for at least one wheel of the vehicle based on the front-rear load ratio and the left-right load ratio; Including, calculating the front-rear load ratio and the left-right load ratio includes calculating the front-rear load ratio and the left-right load ratio based on first relationship specifying information specifying a relationship between the front-rear frequency characteristic ratio and the front-rear load ratio, and second relationship specifying information specifying the relationship between the left-right frequency characteristic ratio and the left-right load ratio, The first relationship specifying information and the second relationship specifying information are determined according to the type of the tire. Wheel load estimation method.

6. A wheel load estimation program for estimating a wheel load of a tire included in a vehicle, acquiring type information that identifies the type of the tire; obtaining wheel speed information representing a wheel speed of each wheel of the vehicle; calculating, based on the wheel speed information, a front-rear frequency characteristic ratio that changes with a change in a front-rear load ratio, which is the ratio of a load acting on a front wheel of the vehicle to a load acting on a rear wheel of the vehicle, and a left-right frequency characteristic ratio that changes with a change in a left-right load ratio, which is the ratio of a load acting on a left wheel of the vehicle to a load acting on a right wheel of the vehicle; calculating the front-rear load ratio and the left-right load ratio based on the front-rear frequency characteristic ratio and the left-right frequency characteristic ratio, respectively; calculating a wheel load ratio representing a relative wheel load between wheels included in the vehicle for at least one wheel of the vehicle based on the front-rear load ratio and the left-right load ratio; on one or more computers, calculating the front-rear load ratio and the left-right load ratio includes calculating the front-rear load ratio and the left-right load ratio based on first relationship specifying information specifying a relationship between the front-rear frequency characteristic ratio and the front-rear load ratio, and second relationship specifying information specifying the relationship between the left-right frequency characteristic ratio and the left-right load ratio, The first relationship specifying information and the second relationship specifying information are determined according to the type of the tire. Wheel load estimation program.

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