Driving assistance systems

Abstract

This technology allows drivers to check the rolling resistance performance of their tires while they are in use. [Solution] The driving assistance device comprises a coefficient identification unit and an output unit. The coefficient identification unit identifies the rolling resistance coefficient of the tires included in the vehicle based on data acquired while the vehicle is in motion. The output unit outputs at least one of the identified rolling resistance coefficient and the grade to which the rolling resistance coefficient belongs to a display located inside the vehicle.

Description

[Technical Field]

[0001] This invention relates to technology for assisting vehicle operation. [Background technology]

[0002] Patent Document 1 discloses a driving support device for improving vehicle fuel efficiency by controlling tire temperature. This driving support device calculates the rolling resistance of the tires based on the vehicle speed and tire temperature. Then, it calculates the energy consumed during travel along the route from the starting point to the destination based on the travel distance and the rolling resistance. According to Patent Document 1, the driving support device can accurately calculate fuel efficiency for each route. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2012-101762 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] As disclosed in Patent Document 1, tire rolling resistance is a factor that affects a vehicle's fuel efficiency. For this reason, tires that boast higher rolling resistance performance are available on the market, primarily for the purpose of improving fuel efficiency and electric energy consumption. However, it is extremely difficult for the average tire consumer (typically a vehicle driver) to verify the rolling resistance performance of such tires or to experience it firsthand while driving. Therefore, there has been a need for a technology that allows drivers to confirm the rolling resistance performance of tires under actual usage conditions.

[0005] The present invention aims to provide a technology that allows drivers to check the rolling resistance performance of tires while they are in use. [Means for solving the problem]

[0006] A driving assistance device according to a first aspect of the present invention comprises a coefficient identification unit and an output unit. The coefficient identification unit identifies the rolling resistance coefficient of the tires included in the vehicle based on data acquired while the vehicle is in motion. The output unit outputs at least one of the identified rolling resistance coefficient and the grade to which the rolling resistance coefficient belongs to a display located inside the vehicle.

[0007] The driving assistance device relating to the second viewpoint is the driving assistance device relating to the first viewpoint, further comprising a temperature acquisition unit for acquiring the temperature of the tire, and the coefficient identification unit for identifying the rolling resistance coefficient based on the acquired temperature of the tire.

[0008] The third-party driving assistance device is a driving assistance device relating to the first or second party, wherein the temperature acquisition unit selects a heat generation / heat dissipation model for the tire according to the driving state of the vehicle, and derives a temperature change of the tire corresponding to the duration of the driving state according to the selected heat generation / heat dissipation model for the tire.

[0009] The driving assistance device relating to the fourth viewpoint is a driving assistance device relating to either the first viewpoint or the third viewpoint, wherein the temperature acquisition unit rejects the temperature change of the tire if the calculated temperature change of the tire exceeds a predetermined threshold per unit time, and does not use it to calculate the temperature of the tire.

[0010] The driving assistance device relating to the fifth viewpoint is a driving assistance device relating to any of the first viewpoints or the fourth viewpoint, further comprising a weight estimation unit that estimates the weight of the vehicle based on the rolling resistance coefficient.

[0011] The driving assistance device relating to the sixth viewpoint is a driving assistance device relating to either the first viewpoint or the fifth viewpoint, wherein the output unit generates a notification screen to notify the driver of the vehicle when at least one of the rolling resistance coefficient and the grade changes in a direction that worsens or improves the vehicle's fuel consumption rate or power consumption rate, and outputs it to the display.

[0012] The driver assistance device relating to the seventh viewpoint is a driver assistance device relating to either the first viewpoint or the sixth viewpoint, wherein the output unit generates a notification screen to notify the driver of the vehicle when the acquired tire temperature exceeds a predetermined threshold and outputs it to the display.

[0013] The driver assistance device relating to the eighth viewpoint is a driver assistance device relating to either the first viewpoint or the seventh viewpoint, wherein the output unit generates a notification screen to notify the driver of the vehicle when the estimated weight of the vehicle exceeds a predetermined threshold based on the vehicle's maximum load capacity, and outputs it to the display.

[0014] The driving assistance device relating to the ninth viewpoint is a driving assistance device relating to either the first viewpoint or the eighth viewpoint, further comprising: a storage unit that stores time-series data of at least one of the following: data acquired while the vehicle is running, the rolling resistance coefficient, and the grade; and an analysis unit that performs statistical analysis on at least one of the following: data acquired while the vehicle is running, the rolling resistance coefficient, and the grade, based on the time-series data.

[0015] The driver assistance device relating to the 10th viewpoint is a driver assistance device relating to any of the 1st viewpoint to the 9th viewpoint, further comprising a storage unit that stores time-series data of the estimated weight of the vehicle, and an analysis unit that performs statistical analysis of the weight of the vehicle based on the time-series data.

[0016] The driver assistance device relating to the 11th viewpoint is a driver assistance device relating to any of the 1st viewpoint to the 10th viewpoint, further comprising a data transmission unit that transmits data acquired while the vehicle is running, the rolling resistance coefficient, and at least one of the grades to a device outside the vehicle.

[0017] The driver assistance device relating to the 12th viewpoint is a driver assistance device relating to either the 1st viewpoint or the 11th viewpoint, further comprising a data transmission unit that transmits the estimated weight of the vehicle to a device outside the vehicle.

[0018] A driving assistance device relating to the 13th viewpoint is a driving assistance device relating to either the 1st viewpoint or the 12th viewpoint, further comprising a notification unit that notifies a predetermined device outside the vehicle when the estimated weight of the vehicle exceeds a predetermined threshold based on the vehicle's maximum load capacity.

[0019] The driver assistance system relating to the 14th viewpoint comprises a driver assistance device relating to either the 1st viewpoint or the 13th viewpoint, and a server device that is communicably connected to the driver assistance device, the server device having a receiving unit that receives data transmitted by the data transmission unit, a trend identification unit that analyzes the received data and identifies the driving tendencies of the driver of the vehicle equipped with the driver assistance device, and a transmitting unit that transmits the identified driving tendencies for the vehicle to the driver assistance device.

[0020] The driving assistance system relating to the 15th perspective includes a driving assistance device relating to either the 1st perspective or the 13th perspective, and a server device that is communicatively connected to the driving assistance device, the server device having a receiving unit that receives notifications from the notification unit, a location identification unit that identifies the location where the driving assistance device that sent the notification is located, an alert generation unit that generates an alert warning of the possibility of an overloaded vehicle being present at the identified location, and an alert transmission unit that transmits the alert to an information processing terminal located in another vehicle within a predetermined area including the location. [Effects of the Invention]

[0021] According to the present invention, the driver can check the rolling resistance performance of the tires while they are in use. [Brief explanation of the drawing]

[0022] [Figure 1] A schematic diagram of a vehicle equipped with a driver assistance system according to one embodiment of the present invention. [Figure 2] A block diagram showing the electrical configuration of a driver assistance system equipped with driver assistance devices. [Figure 3] An example of a table that classifies tire rolling resistance coefficients into grades. [Figure 4A] A block diagram showing an example of the electrical configuration of an external device. [Figure 4B] A block diagram showing an example of the electrical configuration of another external device. [Figure 5] A flowchart illustrating the process for determining the rolling resistance coefficient. [Figure 6] A flowchart illustrating the process for determining the rolling resistance coefficient. [Figure 7A] A diagram illustrating the tire heat generation model when a vehicle is moving in a straight line at a constant speed. [Figure 7B] A diagram illustrating the tire's heat dissipation model when stopped. [Figure 7C] A diagram illustrating the heat generation model of tires when a vehicle is accelerating, decelerating, or turning. [Figure 8] Graph showing tire temperature-rolling resistance coefficient. [Figure 9] Example of a status screen configuration. [Figure 10] A flowchart illustrating the processing flow performed by an external device. [Figure 11] A flowchart showing the processing flow performed by another external device. [Modes for carrying out the invention]

[0023] Hereinafter, with reference to the drawings, an embodiment of the driver assistance device and a driver assistance system including the same of the present invention will be described.

[0024] <1. Configuration of the driver assistance system> Figure 1 is a schematic diagram showing the configuration of a vehicle 1 equipped with the driver assistance device 2 according to this embodiment, and Figure 2 is a block diagram showing the electrical configuration of the driver assistance system 10 (hereinafter also simply referred to as "system 10") equipped with the driver assistance device 2. The vehicle 1 is a four-wheeled vehicle and is equipped with a left front wheel, a right front wheel, a left rear wheel, and a right rear wheel. The left front wheel, right front wheel, left rear wheel, and right rear wheel are each equipped with a tire T FL ,T FR ,TRL ,T RR The following is installed. Vehicle 1 may be a gasoline-powered vehicle, an electric vehicle (EV), or a hybrid vehicle. The driver assistance device 2 controls the tires T included in Vehicle 1 while the vehicle is in motion. FL ,T FR ,T RL ,T RR The system identifies the rolling resistance coefficient (RRC), determines the current driving state of vehicle 1 based on the identified rolling resistance coefficient, and provides feedback to the driver. In addition, it analyzes the driver's driving tendencies based on the rolling resistance coefficient and other sensing data acquired for vehicle 1, and provides comprehensive driving assistance to improve fuel efficiency or electric energy efficiency, or to maintain appropriate driving.

[0025] The system 10 according to this embodiment comprises a driver assistance device 2, a display 3, an outside temperature sensor 4, a wheel speed sensor 5, and an external device 8. The display 3, outside temperature sensor 4, and wheel speed sensor 5 are mounted on the vehicle 1, similar to the driver assistance device 2, and are each connected to the driver assistance device 2 via a communication line 6. The driver assistance device 2 can independently provide driving assistance to the driver of the vehicle 1 by operating in conjunction with the display 3, outside temperature sensor 4, and wheel speed sensor 5. However, by connecting the driver assistance device 2 to the external device 8 via a network 7 for data communication, it can provide more comprehensive driving assistance or services to users of the system 10 other than the driver of the vehicle 1. The external device 8 may be other driver assistance devices 2 or server devices 9A and 9B (see Figures 4A and 4B) owned by a public institution or private business, as will be described later. The network 7 is not particularly limited as long as it enables wireless data communication between the vehicle's ECU, server device, general-purpose computer, smartphone or other information processing terminal, and may be the internet or a closed network independent of the internet. The following describes the various components of System 10.

[0026] [Driving assistance system] The driving support device 2 is composed of an in-vehicle ECU (Electronic Control Unit) as hardware, and includes a ROM (Read Only Memory) 20, a storage unit 21, a controller 22, a data communication unit 23, and a RAM (Random Access Memory) not shown in the figure. A program 200 for controlling the operations of each part of the vehicle 1 is stored in the ROM 20. The driving support device 2 is manufactured by writing the program 200 from a storage medium 201 such as a CD-ROM or a USB memory into the ROM 20. Note that the program 200 may be written into and stored in the storage unit 21 instead of the ROM 20.

[0027] The controller 22 is composed of, for example, a microcontroller. By reading and executing the program 200 from the ROM 20, the controller 22 virtually operates as a temperature acquisition unit 220, a coefficient identification unit 221, a determination unit 222, an output unit 223, a rotational speed acquisition unit 224, a driving force acquisition unit 225, an acceleration acquisition unit 226, a weight estimation unit 227, and an analysis unit 228. The temperature acquisition unit 220 according to the present embodiment acquires the outside air temperature of the vehicle 1 from an outside air temperature sensor 4 described later, and calculates the temperature of the tire T FL ,T FR ,T RL ,T RR by the method described later. The coefficient identification unit 221 identifies the rolling resistance coefficient based on the temperature of the tire T FL ,T FR ,T RL ,T RR . The determination unit 222 determines the grade to which the identified rolling resistance coefficient belongs among the predefined hierarchical grades of the rolling resistance coefficient. As described later, the vehicle running state regarding fuel consumption or electricity cost is associated with this grade, and when the determination unit 222 determines the above grade, the vehicle running state regarding fuel consumption or electricity cost is automatically determined. The output unit 223 appropriately generates a screen for transmitting information to the driver and outputs this to the display 3. The RAM is appropriately used for the calculations by the controller 22.

[0028] The rotation speed acquisition unit 224 receives the tire speed from the wheel speed sensor 5 (described later) T FL ,T FR ,T RL ,T RR The rotational speeds of each tire are acquired. The driving force acquisition unit 225 acquires the driving force F of the vehicle 1. The acceleration acquisition unit 226 acquires the longitudinal acceleration α of the vehicle 1. In this embodiment, the acceleration acquisition unit 226 calculates the longitudinal acceleration α based on the acquired rotational speeds of each tire. The weight estimation unit 227 estimates the weight M of the vehicle 1 based on the rolling resistance coefficient, driving force F, and longitudinal acceleration α identified by the coefficient identification unit 221. The estimated weight M of the vehicle 1 is also used for driving assistance by the driving assistance device 2.

[0029] The storage unit 21 is composed of a non-volatile, rewritable storage device such as a solid-state drive or a hard disk. The storage unit 21 of this embodiment stores coefficient calculation information 210 necessary for calculating the rolling resistance coefficient. The coefficient calculation information 210 includes, for example, the tire T FL ,T FR ,T RL ,T RR The coefficient calculation information 210 includes the dynamic load radius D, the tanδ of the rubber composition constituting each tire, the specific heat c (J / (g·K)), the heat generation / dissipation model of the tire described later, a coefficient for calculating the braking friction coefficient, and the relationship between the tire temperature and the rolling resistance coefficient. The coefficient calculation information 210 is read out as appropriate by the temperature acquisition unit 220 and the coefficient identification unit 221 and used as described later.

[0030] Furthermore, the memory unit 21 stores grade information 211. The grade information 211 includes thresholds that define the range of rolling resistance coefficients for classifying the rolling resistance coefficient of the tire into predetermined grades, and the grades themselves. As shown in Figure 3, the grade information 211 in this embodiment is a table that includes five grades, thresholds that define the range of rolling resistance coefficients of the tire corresponding to each grade, and the driving state of the vehicle 1 associated with the five grades. The five grades are grades according to the JATMA grading system and are represented as "AAA", "AA", "A", "B", and "C", respectively. From the viewpoint of improving fuel efficiency or electric energy efficiency, "AAA" represents the best rolling resistance performance, and "C" represents the worst rolling resistance performance. The driving state of the vehicle 1 is determined according to each grade, and in this embodiment, these are referred to as "Eco Mode", "Semi-Eco Mode", "Normal Mode", "Semi-Sport Mode", and "Sport Mode", respectively. In this way, by associating the rolling resistance coefficient of the tires with the driving status of Vehicle 1, the driver can more easily understand the current driving status through the status screen described later.

[0031] Furthermore, time-series data 212 is stored in the memory unit 21. The time-series data 212 is data calculated or acquired over a certain period of time in the rolling coefficient identification process and weight estimation process described later, and is accumulated in a time-series format. The time-series data 212 includes at least one of the following: time-series data of rolling resistance coefficient, time-series data of grade, time-series data of tire temperature, time-series data of estimated vehicle weight, time-series data of tire rotation speed, time-series data of driving force, time-series data of vehicle speed, time-series data of longitudinal acceleration, time-series data of accelerator pedal depression, time-series data of brake pedal depression, time-series data of steering angle, time-series data of yaw rate, time-series data of lateral acceleration, and time-series data of tire pressure. These time-series data 212 are used for statistical analysis by the analysis unit 228. In this statistical analysis, the state of vehicle 1 is analyzed based on the time-series data, and a driving improvement method based on the state of vehicle 1 is proposed to the driver.

[0032] The data communication unit 23 is a known communication module for connecting to the network 7. The controller 22 is connected to the network 7 via the data communication unit 23 and performs data communication with an external device 8. The external device 8 is mainly assumed to be other driver assistance devices 2 or a server device 9A (see Figure 4A) described later. The data communication unit 23 corresponds to the data transmission unit of the present invention.

[0033] The notification unit 24 is a communication module for sending specific notifications to specific external devices 8. Examples of specific external devices 8 include server devices 9B (see Figure 4B) owned by local government administrative agencies (such as police stations) or public organizations that manage road traffic. A specific notification is, for example, a notification informing a vehicle 1 that it may be overloaded. In other words, the notification unit 24 sends notifications of higher urgency or public interest to designated agencies compared to the data transmitted and received by the data communication unit 23. These notifications may include current location information from a satellite positioning system acquired by the car navigation system installed in the vehicle 1. The communication method of the notification unit 24 is not particularly limited; it may be communication via the network 7 or not. For example, the notification unit 24 may be configured to send notifications to the nearest communication base from the vehicle 1's current location among the communication bases used by the aforementioned administrative agencies or public organizations.

[0034] [display] The display 3 can be any device capable of displaying various information to the driver, and can be implemented in any form, such as a liquid crystal display element, liquid crystal monitor, organic EL display, plasma display, or touch panel display. The position of the display 3 can also be selected as appropriate, but it is preferable to place it in a location easily visible to the driver, such as on the instrument panel. If the display 3 is connected to a car navigation system, it is also possible to use the car navigation system's monitor as the display 3.

[0035] [Outside temperature sensor] The outside temperature sensor 4 can be any sensor that can detect the temperature outside the vehicle 1 and output a detection signal. The location where the outside temperature sensor 4 is installed can be selected as appropriate, but it is preferable to install it in a location that is less affected by the heat generated by the engine or battery of the vehicle 1.

[0036] [Wheel speed sensor] Any wheel speed sensor 5 can be used as long as it can detect the rotational speed of the left front wheel, right front wheel, left rear wheel, and right rear wheel while the vehicle is in motion and output a detection signal. For example, a sensor that measures rotational speed from the output signal of an electromagnetic pickup can be used, or a sensor that generates electricity using rotation, such as a dynamo, and measures rotational speed from the voltage at that time can be used. The mounting position of the wheel speed sensor 5 is not particularly limited and can be appropriately selected depending on the type of sensor, as long as it is possible to detect the rotational speed of each wheel. The wheel speed sensor 5 may also constitute an indirect tire pressure monitoring system (TPMS) in the vehicle 1.

[0037] [External device] Figure 4A is a block diagram showing the electrical configuration of the server device 9A as an external device 8. The server device 9A is configured as a general-purpose server computer in terms of hardware and includes a ROM 90A, a storage unit 91A, a CPU (Central Processing Unit) 92A, a data communication unit 93A, and RAM (not shown). The ROM 90A stores a program 900A for controlling the operation of each part of the server device 9A. The server device 9A is manufactured when the program 900A is written to the ROM 90A from a storage medium 901A such as a CD-ROM or USB memory. Note that the program 900A may also be written to and stored in the storage unit 91A instead of the ROM 90A. Typically, the server device 9A is a server computer owned by a private business (e.g., an automobile insurance company, an automobile maintenance company, etc.) that provides driving-related services to the driver of a vehicle 1, and the program 900A is configured appropriately according to the type of service.

[0038] The CPU 92A virtually operates as a trend identification unit 920A by reading and executing program 900A from ROM 90A. Based on various data received from multiple driver assistance devices 2 (2A, 2B, ...), the trend identification unit 920A identifies the driving tendencies of the drivers of vehicles 1 (1A, 1B, ...) equipped with each driver assistance device 2. Furthermore, based on the identified driving tendencies, the trend identification unit 920A identifies methods to further improve fuel efficiency or electric power consumption, or methods to drive more appropriately, and generates feedback information to provide each driver with feedback on their driving tendencies and methods for improving driving. The data received from the driver assistance devices 2 includes data on at least one of the rolling resistance coefficient and grade of each tire, which are identified by the driver assistance devices 2. Furthermore, the data received from the driver assistance system 2 may include at least one of the following: sensing data acquired by the driver assistance system 2 (e.g., rotational speed data of each tire, accelerator pedal depression amount, brake pedal depression amount, steering angle, yaw rate, lateral acceleration) or data derived by the driver assistance system 2 (e.g., rolling resistance coefficient, grade, tire pressure, tire temperature, tire temperature change, estimated vehicle weight, driving force, longitudinal acceleration, etc.).

[0039] The memory unit 91A consists of a non-volatile, rewritable storage device such as a solid-state drive or a hard disk. Various data received from each of the multiple driver assistance devices 2 are stored in the memory unit 91A for each different vehicle 1 (driver assistance device 2). In addition, feedback information generated by the trend identification unit 920A is stored for each different vehicle 1 (driver assistance device 2).

[0040] The data communication unit 93A is a known communication module for connecting to the network 7. In particular, the data communication unit 93A is used to receive data from each of the multiple driver assistance devices 2 and to transmit the above-mentioned feedback information to each of the multiple driver assistance devices 2. The data communication unit 93A corresponds to the receiving unit and transmitting unit of the present invention.

[0041] Figure 4B is a block diagram showing the electrical configuration of the server device 9B as an external device 8. The server device 9B is configured as a general-purpose server computer in terms of hardware and includes a ROM 90B, a storage unit 91B, a CPU (Central Processing Unit) 92B, a receiving unit 93B, an alert transmission unit 94B, and RAM (not shown). The ROM 90B stores a program 900B for controlling the operation of each part of the server device 9B. The server device 9B is manufactured when the program 900B is written to the ROM 90B from a storage medium 901B such as a CD-ROM or USB memory. Note that the program 900B may also be written to and stored in the storage unit 91B instead of the ROM 90B. As described above, the server device 9B is a server computer owned by an administrative agency or public organization, and the program 900B is configured appropriately according to the operations performed by the administrative agency or public organization.

[0042] The memory unit 91B is composed of a non-volatile, rewritable storage device such as a solid-state drive or a hard disk. The memory unit 91B may store information such as that of the vehicle 1 equipped with the driver assistance device 2 that sent the aforementioned notification via the notification unit 24.

[0043] The CPU 92B virtually operates as a location identification unit 920B and an alert generation unit 921B by reading and executing program 900B from ROM 90B. The location identification unit 920B identifies the location of vehicle 1, which is equipped with the driver assistance device 2, based on current location information included in a notification received from the driver assistance device 2. Alternatively, the location identification unit 920B identifies the location (area) of vehicle 1, which is equipped with the driver assistance device 2, based on information identifying the communication base that first received the notification. The alert generation unit 921B generates an alert directed at the driver of another vehicle located near vehicle 1, depending on the content of the notification received from the driver assistance device 2. For example, if the notification indicates that vehicle 1 may be driving with an overload, the alert generation unit 921B generates an alert warning that an overloaded vehicle (a vehicle that may hinder safe driving or violates laws and regulations) may be located nearby.

[0044] The receiving unit 93B is a known communication device and receives notifications transmitted by the notification unit 24 of the driver assistance device 2.

[0045] The alert transmission unit 94B transmits the alert generated by the alert generation unit 921B to information processing terminals located in vehicles 1C, 1D, ... other than the vehicle 1 that sent the notification. The other vehicles 1C, 1D, ... are vehicles located within a predetermined area including the location identified by the location identification unit 920B. The information processing terminals located in the other vehicles may be driver assistance devices 2C, 2D, ... other than the driver assistance device 2 that sent the notification, or in-vehicle devices other than driver assistance devices installed in the other vehicles 1C, 1D, ... or portable information processing terminals 9C, 9D, ... such as general-purpose smartphones carried by the driver. The alert transmission unit 94B may send alerts to individual information processing terminals via the network 7, or it may send alert signals simultaneously to information processing terminals located within the predetermined area without identifying individual information processing terminals. When sending alerts to individual information processing terminals, this can be done, for example, via a dedicated application installed on the information processing terminal.

[0046] <2. Rolling coefficient determination process> Figures 5 and 6 are flowcharts showing the flow of the rolling resistance coefficient determination process. Referring to Figures 5 and 6 below, while vehicle 1 is in motion, tire T FL ,T FR ,T RL ,T RR The process for determining the rolling resistance coefficient and the subsequent operation of the driving assistance device 2 will be explained. The process shown in Figures 5 and 6 starts, for example, when the power supply of the vehicle 1's electrical system is turned ON, and is repeated at predetermined intervals until the power supply is turned OFF.

[0047] Steps S1 to S3 are steps in which the temperature acquisition unit 220 determines the driving state of the vehicle 1 in order to appropriately select the tire heat generation / heat dissipation model described later. Specifically, the temperature acquisition unit 220 first determines whether or not the vehicle 1 is in motion (step S1). This determination can be made based on the rotational speed of the engine or motor that drives the vehicle 1, or based on the presence or absence of detection signals from each wheel speed sensor 5. If it is determined that the vehicle 1 is not in motion (NO), that is, that it is stationary, then step S5 is executed. Step S5 will be described later. If it is determined that the vehicle 1 is in motion (YES), then step S2 is executed.

[0048] Furthermore, when vehicle 1 is in motion, the rotational speed acquisition unit 224 acquires the tire T at a predetermined period. FL ,T FR ,T RL ,T RR The rotational speeds V1 to V4 (rpm) in time series are acquired. The rotational speed acquisition unit 224 acquires detection signals from the wheel speed sensors 5 corresponding to each wheel at a predetermined sampling period, and the tire T FL ,T FR ,T RL ,T RRThe rotational speeds V1 to V4 (rpm) are converted over time. Also, when vehicle 1 is in motion, the driving force acquisition unit 225 acquires the time-series driving force F (N) of vehicle 1 at a predetermined period. If vehicle 1 is an engine vehicle, for example, the driving force acquisition unit 225 acquires the engine torque, differential reduction ratio, power transmission efficiency, and tire torque. FL ,T FR ,T RL ,T RR The time-series driving force F is calculated from the dynamic load radius D. Furthermore, when vehicle 1 is in motion, the acceleration acquisition unit 226 acquires the time-series longitudinal acceleration α (m / s²) of vehicle 1 at a predetermined period. 2 The following is obtained. Note that the longitudinal acceleration α can be calculated, for example, based on the detection signals from each wheel speed sensor 5.

[0049] In step S2, the temperature acquisition unit 220 determines whether or not the vehicle 1 is accelerating or decelerating. This determination can be made, for example, based on the amount the accelerator pedal of the vehicle 1 is pressed, the amount the brake pedal is pressed, or values ​​such as the longitudinal acceleration α described above. For example, if these values ​​are above a predetermined threshold, the temperature acquisition unit 220 can determine that the vehicle 1 is accelerating or decelerating. If it is determined that the vehicle 1 is accelerating or decelerating (braking) (YES), then step S6 is executed. Step S6 will be described later. If it is determined that the vehicle 1 is not accelerating or decelerating (NO), that is, neither acceleration nor deceleration (braking) is occurring, then step S3 is executed.

[0050] In step S3, the temperature acquisition unit 220 determines whether or not vehicle 1 is in a constant-speed straight-line state. This determination can be made based on values ​​such as the steering angle acquired from the vehicle 1's steering angle sensor, the yaw rate acquired from the vehicle 1's yaw rate sensor, and the lateral acceleration acquired from the lateral acceleration sensor. For example, if these values ​​are below a predetermined threshold, the temperature acquisition unit 220 can determine that vehicle 1 is in a constant-speed straight-line state. If it is determined that vehicle 1 is not in a constant-speed straight-line state (NO), that is, that it is turning, then step S11 is executed. Step S11 will be described later. If it is determined that vehicle 1 is in a constant-speed straight-line state, then step S4 is executed.

[0051] [Derivation of temperature change ΔT1] In step S4, the temperature acquisition unit 220 acquires the tire temperature during one constant-speed straight-line drive. FL ,T FR ,T RL ,T RR The temperature change ΔT1 is derived. First, the temperature acquisition unit 220 calculates the vehicle speed V (m / s) of vehicle 1 based on the rotational speeds V1 to V4 of each tire described above. The vehicle speed V is calculated, for example, by multiplying the average value of V1 to V4 (rpm) by πD (m) and dividing by 60. Alternatively, if vehicle 1 is connected to a satellite positioning system such as GPS (Global Positioning System), the vehicle speed V is calculated, for example, based on the time-series current position information received from the satellite positioning system. Note that the average value of the vehicle speed V calculated during the duration t1 (s) of a single constant-speed straight drive may be used as the vehicle speed V.

[0052] Next, the temperature acquisition unit 220 calculates the work W (=F × V × t1) (J) performed during a single constant-speed straight-line drive, based on the driving force F (N) of the vehicle 1 and the duration t1 (s) of that drive. The temperature acquisition unit 220 further converts the work W into heat quantity Q (cal) according to the following formula. Heat quantity Q represents the total amount of heat generated by the tires during the constant-speed straight-line drive of t1 (s). Q = W / 4.19

[0053] On the other hand, if we denote the temperature change that occurs in each tire during constant-speed straight driving as ΔT1(°C), Q=mcΔT1 (1) It can be expressed as follows: where m(g) is the total weight of the tires, and c(J / (g·K)) is the specific heat of the tires, which are fixed values ​​stored in the memory unit 21 beforehand. The temperature acquisition unit 220 calculates the temperature change ΔT1 (=Q / mc) based on equation (1). When the tires are moving in a straight line at a constant speed, the temperature change of the tires with respect to time is as shown by the curve in Figure 7A. As can be seen from Figure 7A, the rate of temperature rise of the tires with respect to time is generally constant immediately after the start of moving in a straight line at a constant speed, and gradually decreases from the initial value as time passes. Furthermore, the above rate of temperature rise also differs depending on the tanδ of the rubber composition that makes up the tire, and it is larger as tanδ is larger and smaller as tanδ is smaller. From this, the work W or heat Q is set such that the temperature change ΔT1 approximates the curve in Figure 7A, for example, the tire T FL ,T FR ,T RL ,T RR This correction may be appropriately adjusted depending on the tanδ and duration t1. This correction can be applied, for example, to tire T FL ,T FR ,T RL ,T RR The tire type (summer, studless, all-season, etc.) and the correction coefficient corresponding to the labeling are predetermined and stored in the memory unit 21, etc., and the correction can be performed by multiplying the above ΔT1 (=Q / mc) by the correction coefficient. FL ,T FR ,T RL ,T RR The type of tire may be identified by reading from an information storage device such as an RFID embedded in the tire, for example. The initial temperature of the tire can be the temperature obtained by the ambient temperature sensor 4, for example. The ambient temperature is also obtained by the ambient temperature sensor 4 in step S15, which will be described later, but the temperature acquisition unit 220 may be configured to acquire the ambient temperature at any time. The above is the method for deriving the temperature change ΔT1 according to the tire heat generation model when the vehicle 1 is moving in a straight line at a constant speed, which is performed in step S4. The temperature change ΔT1 is the temperature of the tire T FL ,TFR ,T RL ,T RR Individual values ​​may be calculated, or a common value may be calculated.

[0054] [Derivation of temperature change ΔT4] In step S5, the temperature acquisition unit 220 detects the tire T while it is stationary. FL ,T FR ,T RL ,T RR The temperature change ΔT4 is derived. When the tire is stopped, the temperature change of the tire over time is as shown in the curve in Figure 7B. As can be seen from Figure 7B, the rate of temperature decrease of the tire over time is roughly constant immediately after stopping, and gradually decreases from the initial value as time passes. The temperature acquisition unit 220 derives the temperature change ΔT4 according to the tire's stopping heat dissipation model based on this curve. The stopping heat dissipation model only needs to be able to derive the temperature change ΔT4 (°C) from the initial temperature based on the elapsed time after stopping, and may be, for example, a regression equation of elapsed time-temperature change identified from a large number of datasets. The initial temperature of the tire can be, for example, the temperature acquired by the ambient temperature sensor 4. Also, as shown in Figure 7B, the larger the specific heat c of the tire, the smaller the temperature change from the initial temperature, and the smaller the specific heat c, the larger the temperature change from the initial temperature. For this reason, multiple different models may be identified as the stopping heat dissipation model according to the specific heat c of the tire and stored in the storage unit 21 in advance. The temperature acquisition unit 220 may appropriately select a model from among several different stop heat dissipation models that corresponds to the specific heat c of the tire.

[0055] [Derivation of temperature change ΔT3] When vehicle 1 is accelerating or decelerating, the change in tire temperature over time is as shown in the curve in Figure 7C. As can be seen from Figure 7C, the rate of temperature increase of the tire over time is generally constant immediately after acceleration or deceleration, and gradually decreases from the initial value as time passes. The temperature acquisition unit 220 derives the temperature change ΔT3 according to the tire heat generation model based on this curve. The tire heat generation model can be any model that can derive the temperature change ΔT3 (°C) from the initial temperature based on the elapsed time after acceleration or deceleration, and may be, for example, a regression equation of elapsed time-temperature change identified from a large number of datasets. The initial temperature of the tire can be, for example, the temperature acquired by the ambient temperature sensor 4. However, as shown in Figure 7C, the rate of temperature increase of the tire over time also changes depending on the magnitude of the slip angle and the friction coefficient of the tire. Specifically, the larger the slip angle, the greater the rate of temperature increase; the smaller the slip angle, the smaller the rate of temperature increase; the smaller the friction coefficient, the greater the rate of temperature increase; and the larger the friction coefficient, the smaller the rate of temperature increase. In this embodiment, multiple different tire heat generation models are identified, corresponding to two or more slip angles and two or more friction coefficients, and are stored in the memory unit 21 in advance.

[0056] In step S6, the temperature acquisition unit 220 is set to the tire T FL ,T FR ,T RL ,T RRThe braking friction coefficient μ1 is calculated. The braking friction coefficient μ1 is the friction coefficient between each tire and the road surface, and as long as the vehicle 1 is driving normally, the tires are not slipping, and the slip ratio is below a certain value, it can be said to be proportional to the driving force F. For this reason, by identifying a conversion factor for converting the braking friction coefficient μ1 from the driving force F and storing it in advance in the memory unit 21, the temperature acquisition unit 220 can calculate the braking friction coefficient μ1 based on this conversion factor and the driving force F. The driving force F used to calculate the braking friction coefficient μ1 can be appropriately selected based on time-series data of the driving force F. For example, the driving force F based on the average value of torque data sampled within a predetermined speed range (speed window) relative to the vehicle speed of the vehicle 1 can be selected. Multiple speed ranges can be defined relative to the vehicle speed of the vehicle 1, for example, in increments of 10 km / h. Furthermore, if the tires are spinning freely, the braking friction coefficient μ1 can be calculated based on the driving force F calculated based on the torque immediately before the spinning occurs, and a conversion factor.

[0057] In step S7, the temperature acquisition unit 220 acquires the temperature of the tire T during acceleration or deceleration. FL ,T FR ,T RL ,T RR One of two or more slip angles is assigned to each tire. The assigned slip angle may be selected based on the steering angle, yaw rate, etc. For example, if there are two or more applicable slip angles based on the steering angle, yaw rate, etc., the smallest of the applicable ones may be assigned to each tire.

[0058] In step S8, the temperature acquisition unit 220 selects the most suitable tire heat generation model according to the braking friction coefficient μ1 and slip angle, and derives the tire temperature change ΔT3 based on the selected heat generation model. The temperature change ΔT3 is the tire temperature FL ,T FR ,T RL ,T RR Individual values ​​may be calculated, or a common value may be calculated.

[0059] In step S9, the temperature acquisition unit 220 determines whether the temperature change per unit time calculated based on ΔT3 is below a predetermined threshold. The predetermined threshold is, for example, 60°C / s. When the temperature change per unit time exceeds 60°C, it is considered that the temperature change is due to sudden braking. The heat generated in the tire during sudden braking is generated on the surface of the tread and is dissipated instantaneously, so it is considered to have little effect on the temperature at the center of the cross-section of the tread. Therefore, by rejecting such values ​​in step S10, a more accurate temperature change ΔT can be calculated. Also, since sudden braking is considered to be when some kind of emergency occurs in the vehicle 1, there is little need to notify the rolling resistance coefficient or issue any kind of alarm in the steps described later. For these reasons, the above determination is performed in step S9. If it is determined in step S9 that the temperature change per unit time is below the predetermined threshold (YES), then step S14 is performed. On the other hand, if it is determined that the temperature change per unit time exceeds the predetermined threshold (NO), then step S10 is performed.

[0060] In step S10, the temperature acquisition unit 220 rejects the temperature change ΔT3 derived in step S8. At this time, the temperature acquisition unit 220 does not use the temperature change ΔT3 derived in step S8 to calculate the temperature change ΔT in step S14. After step S10, step S1 is executed again.

[0061] [Derivation of temperature change ΔT2] When vehicle 1 is turning, the change in tire temperature over time is as shown by the curve in Figure 7C. In other words, when vehicle 1 is turning, the same heat generation model as when accelerating or decelerating can be used.

[0062] In step S11, the temperature acquisition unit 220 is set to the tire T FL ,T FR ,T RL ,T RRTo any one of two or more slip angles, assign a slip angle. The assigned slip angle may be determined based on, for example, the steering angle, yaw rate, etc. The temperature acquisition unit 220 can, for example, assign a larger slip angle when the turning radius is considered to be smaller, and assign a smaller slip angle when the turning radius is considered to be larger. Also, the temperature acquisition unit 220 can, for example, assign a larger slip angle to a tire to which a larger driving force is assigned, and assign a smaller slip angle to a tire to which a smaller driving force is assigned or a driven tire.

[0063] In step S12, the temperature acquisition unit 220 determines the turning friction coefficient μ2 of the tire T FL ,T FR ,T RL ,T RR . The turning friction coefficient μ2 is determined based on at least one of the slip angle and the turning radius assigned in step S11. Data of the turning friction coefficient μ2 corresponding to at least one of the slip angle and the turning radius of the tire T FL ,T FR ,T RL ,T RR is determined in advance and stored in the storage unit 21 or the like.

[0064] In step S13, the temperature acquisition unit 220 selects the most suitable tire heat generation model according to the turning friction coefficient μ2 and the slip angle, and derives the tire temperature change ΔT2 based on the selected heat generation model. The temperature change ΔT2 may be calculated as individual values for the tire T FL ,T FR ,T RL ,T RR or may be calculated as common values.

[0065] In step S14, the temperature acquisition unit 220 sums up the temperature changes derived in steps S4, S5, S9, and S13, and derives the total temperature change ΔT (=ΔT1 + ΔT2 + ΔT3 + ΔT4). Note that ΔT4 is a negative value. The total temperature change ΔT is for the tire T FL ,T FR,T RL ,T RR Individual values may be calculated, or a common value may be calculated.

[0066] In step S15, the temperature acquisition unit 220 acquires the outside air temperature. The temperature acquisition unit 220 may acquire the outside air temperature at a certain point in time, for example, based on the detection signal of the outside air temperature sensor 4. Also, the temperature acquisition unit 220 may acquire the average value of the outside air temperature during the time elapsed while steps S1 to S14 are performed once as the outside air temperature.

[0067] In step S16, the temperature acquisition unit 220 calculates the temperature T of the tire. The temperature T of the tire is calculated by adding the derived temperature change ΔT to the outside air temperature acquired in step S14. When the temperature change ΔT is derived for each tire, the temperature T of the tire is calculated for each tire.

[0068] In step S17, the coefficient identification unit 221 identifies the rolling resistance coefficient of the tire based on the temperature T calculated in step S16. As shown in FIG. 8, the rolling resistance coefficient of the tire depends on the temperature of the tire. Therefore, for example, by previously storing data of a curve as shown in FIG. 8 in the storage unit 21, the coefficient identification unit 221 can identify the rolling resistance coefficient of the tire based on the temperature T of the tire. When the temperature T is calculated for each tire, the rolling resistance coefficient for each tire can be identified.

[0069] In step S18, the coefficient identification unit 221 determines whether the rolling resistance coefficient identified in step S17 is less than a predetermined threshold. Generally, the rolling resistance coefficient between a railway wheel and rails is considered to be 1 or less. Since tires have more viscous elements than railway wheels, it is unlikely that the identified rolling coefficient will be equivalent to the rolling resistance coefficient between a railway wheel and rails. For this reason, the predetermined threshold can be, for example, 1. If it is determined that the rolling resistance coefficient is less than the predetermined threshold (YES), step S19 is executed. On the other hand, if it is determined that the rolling resistance coefficient is less than the predetermined threshold (NO), step S20 is executed.

[0070] In step S19, the coefficient identification unit 221 rejects the rolling resistance coefficient identified in step S17. In other words, that rolling resistance coefficient is not used for driving assistance. Furthermore, the coefficient identification unit 221 may discard the data used to identify that rolling resistance coefficient (erase it from RAM or storage unit 21). After step S19, step S1 is executed again.

[0071] In step S20, the determination unit 222 determines the grade to which the rolling resistance coefficient belongs based on the grade information 211. In this embodiment, once the grade is determined, the driving state associated with the grade is also automatically determined, as shown in Figure 3. If the rolling resistance coefficient for each tire is specified, the grade to which the rolling resistance coefficient of each tire belongs may be determined, or the grade to which the average value of the rolling resistance coefficients of all tires belongs may be determined. The driving state can also be determined as appropriate according to a predetermined algorithm.

[0072] In step S21, the output unit 223 generates a status screen W1 and outputs it to the display 3. Figure 9 shows an example of the configuration of the status screen W1. The status screen W1 displays at least one of the rolling resistance coefficient identified by the coefficient identification unit 221 and the grade determined by the determination unit 222. In the example in Figure 9, the value of the rolling resistance coefficient is displayed in area R2, and the determined grade is displayed in area R3 in a manner that distinguishes it from other grades among all grades. In the example in Figure 9, only one value of the rolling resistance coefficient and grade are displayed, but in addition to or instead of this, (multiple) rolling resistance coefficient values ​​and grades for each tire may be displayed, or they may be displayed on a separate screen that can be accessed from the status screen W1. The status screen W1 displays the date, the owner's name of vehicle 1, the model name of vehicle 1, and tire T in area R1. FL ,T FR ,T RL ,T RR Information that identifies the tire T FL ,T FR ,T RL ,T RR Information that can be stored in the memory unit 21, such as the start date and time of use, may be displayed. In addition, the status screen W1 may display in area R2 the tire status, such as the tire pressure acquired by another system of the vehicle 1, such as TPMS, and the tire temperature derived in step S16, as well as the latest vehicle weight estimated in the load estimation process described later. In addition, the driving mode determined from the grade may be displayed in area R4 of the status screen W1. Area R4 may also display further advice for improving fuel efficiency and electric power consumption, such as a message prompting adjustment to the target tire pressure calculated based on the tire status displayed in area R2.

[0073] In step S22, the analysis unit 228 determines at least one of the following: whether the grade determined in step S20 has decreased (worsened) compared to a grade determined in the past; whether the tire pressure has decreased to an alarm level; and whether the tire temperature calculated in step S16 is above a predetermined threshold (e.g., 100°C) and is high temperature. The analysis unit 228 can, for example, read past grade data from the time-series data 212 of the storage unit 21 and compare it with the current grade to make a determination about the grade. Alternatively, the analysis unit 228 can receive the determination result from the TPMS regarding whether the tire pressure has decreased to an alarm level. If at least one of the above is determined to be YES, then step S23 is executed. On the other hand, if all of the above are determined to be NO, then step S24 is executed.

[0074] In step S23, the output unit 223 generates a notification screen to inform the driver of the judgment result in step S22 and displays it on the display 3. For example, if the grade determined in step S20 has worsened, the output unit 223 generates a notification screen including icons and text information to inform the driver of this and displays it on the display 3. This notification screen may include advice to improve the grade, such as a message prompting the driver to adjust the tire pressure to the target pressure. Also, for example, if the tire pressure has decreased to a warning level, the output unit 223 generates a notification screen to inform the driver of this and displays it on the display 3. This notification screen may include advice to improve driving, such as a message prompting the driver to adjust the tire pressure. Furthermore, for example, if the tires are hot, the output unit 223 generates a notification screen to inform the driver that the tires are hot and displays it on the display 3. This notification screen may include advice to normalize the tire temperature, such as interrupting driving. The notification screen may be generated separately from the status screen, or it may be used in conjunction with the status screen.

[0075] After step S23, step S1 may be executed again. However, if the determination in the previously executed step S1 was that the vehicle is stationary (NO), and the determination in the next executed step S1 is that the vehicle is in motion (YES), then a change in the load of vehicle 1 (such as passengers getting on or off, loading or unloading cargo) may occur. Therefore, before executing step S1 again, step S24 is executed to determine whether or not the previously estimated weight of vehicle 1 should be updated.

[0076] In step S24, the weight estimation unit 227 determines whether or not the load of vehicle 1 may have changed. Based on the progression of the determination result in step S1 described above, the weight estimation unit 227 can determine whether or not vehicle 1 has moved from a stationary state to a driving state. However, the weight estimation unit 227 may make this determination by another method. If it is determined that there is a possibility that the load has changed (YES), then step S25 is executed. If it is determined that there is no possibility that the load has changed (NO), then step S27, which will be described later, is executed.

[0077] Step S25 is a step in which the weight estimation unit 227 estimates the current weight M of vehicle 1 based on the rolling resistance coefficient identified in step S17. The current weight M of vehicle 1 is calculated by dividing the rolling resistance of the tires after stopping (RR) by the rolling resistance coefficient (RRC) identified before stopping. That is, it is calculated as M = RR / RRC. On the other hand, the equation of motion for vehicle 1 is expressed as F = Mα + RR, using the driving force F and longitudinal acceleration α of vehicle 1. Using this, M = F / (α + RRC), and the weight M of vehicle 1 can be estimated from the rolling resistance coefficient, driving force F, and longitudinal acceleration α. ​​If the rolling resistance coefficient for each tire is calculated as the rolling resistance coefficient, for example, the average value of the rolling resistance coefficients for each tire can be substituted into RRC in the above formula. Here, if the estimated weight M is less than or equal to the weight M0 of vehicle 1 alone, the weight estimation unit 227 may reject it. In this case, the driver assistance device 2 may skip step S26 and perform step S1 again.

[0078] In step S26, the weight estimation unit 227 determines whether the vehicle 1 is in an overloaded state. The weight estimation unit 227 can perform this determination based on, for example, the estimated weight M and a predetermined threshold value M1. The predetermined threshold value M1 is the upper limit of the weight of the vehicle 1, which is predetermined based on the maximum load (the weight of passengers and cargo) defined by law for the vehicle 1. That is, if M1≧M, it can be determined that the vehicle 1 is not in an overloaded state, and if M1<M, it can be determined that the vehicle 1 is in an overloaded state. When it is determined in step S26 that the vehicle 1 is not in an overloaded state (NO), then step S27 is executed next. When it is determined that the vehicle 1 is in an overloaded state (YES), then step S28 is executed next.

[0079] In step S27, the data communication unit 23 transmits the data calculated or acquired during the execution of the series of steps S1 to step S25, together with the data for identifying the vehicle 1, to the server device 9A. This data includes at least one of the rotational speeds V1 to V4, the vehicle speed V, the driving force F, the longitudinal and lateral accelerations α, the depression amount of the accelerator pedal, the depression amount of the brake pedal, the steering angle, the yaw rate, the lateral acceleration, the temperature of the tire, the air pressure of the tire, the estimated weight M, the rolling resistance coefficient, and the grade. The data for identifying the vehicle 1 can be, for example, the production number of the vehicle 1, the vehicle registration number, the ID registered by the driver in the server device 9A, etc. When the server device 9A receives this data, it performs the processing (see FIG. 10) described later. After step S27, in the driving support device 2, step S1 is executed again.

[0080] In step S28, the output unit 223 generates a notification screen for notifying the driver that the vehicle 1 is in an overloaded state (or there is a possibility thereof) and displays it on the display 3. In addition to this, the output unit 223 may emit a warning buzzer and a voice warning of the overloaded state or the possibility thereof from the speaker of the vehicle 1.

[0081] In step S29, the notification unit 24 generates a notification indicating that the vehicle is overloaded or potentially overloaded, and sends it to the server device 9B. Upon receiving this notification, the server device 9B performs the processing described later (see Figure 11). After step S29, step S27 described above is executed.

[0082] In the driver assistance device 2, as steps S1 to S28 above are repeatedly executed, the data deemed valid (not rejected) is stored in the storage unit 21 as the time-series data 212 described above. When the time-series data 212 has been stored for a predetermined period or for a predetermined number of data points, the analysis unit 228 performs a statistical analysis of the time-series data 212. The output unit 223 creates an analysis result screen showing the analysis results by the analysis unit 228 and displays it on the display 3. The analysis result screen includes at least one of the following examples: a notification, a message, and a graph of time-series data over a certain period.

[0083] For example, the analysis unit 228 determines whether the rolling resistance coefficient and at least one of its grades have decreased within a certain period, based on time-series data of both. The analysis unit 228 also determines whether the tire pressure was maintained at the normal level or whether it was decreasing during the same period, based on time-series data of the tire pressure. For example, if at least one of the rolling resistance coefficient and grade has decreased and the tire pressure is decreasing, the analysis results screen displays a notification that the rolling resistance coefficient has deteriorated and a message suggesting that the tire pressure be adjusted. For example, if at least one of the rolling resistance coefficient and grade has decreased and the tire pressure is maintained at the normal level, the analysis results screen displays a notification that the tire pressure is maintained normally but the rolling resistance coefficient has deteriorated and a message suggesting that the tire be replaced. For example, if the rolling resistance coefficient or grade is maintained at a constant level and the tire pressure is maintained normally, the analysis results screen displays a notification that both the tire pressure and the rolling resistance coefficient are maintained. This analysis results screen may include a message suggesting that the tire pressure be adjusted to a higher level than the normal internal pressure in order to improve the rolling resistance coefficient or grade, if necessary. Preferably, the message suggesting tire pressure adjustment should include a recommended pressure.

[0084] For example, the analysis unit 228 counts the number of times the tire temperature exceeds a predetermined threshold within a certain period, based on time-series data of the tire temperature. The analysis results screen displays the number of times the tire temperature exceeds the predetermined threshold, and the timing at which the tire temperature exceeds the predetermined threshold (e.g., during cornering or acceleration / deceleration). The analysis results screen may also include a message suggesting that the driver refrain from driving that causes the tire temperature to rise, such as sudden acceleration / deceleration or cornering at high speeds.

[0085] For example, the analysis unit 228 calculates the period during which vehicle 1 has been overloaded based on the estimated time-series data of vehicle weight. For example, if vehicle 1 has been overloaded up to the present, the analysis results screen will display the duration of the overloaded state and a message suggesting that the cargo be unloaded.

[0086] <3-1. Processing of external devices> Figure 10 is a flowchart showing the processing flow performed by the server device 9A as a component of the system 10. In step S31, the data communication unit 93A of the server device 9A determines whether or not it has received data from the driver assistance device 2. If it is determined that data has been received (YES), then step S32 is executed.

[0087] In step S32, the data communication unit 93A stores the received data in the storage unit 91A based on the data identifying the vehicle 1. The storage unit 91A generates an area for each vehicle 1 (1A, 1B, ...) registered in the server device 9A to store the data transmitted from the driver assistance devices 2 (2A, 2B, ...). As a result, the storage unit 91A builds a database for multiple vehicles 1 (1A, 1B, ...).

[0088] In step S33, the trend identification unit 920A identifies the driving tendencies of the driver of vehicle 1 based on the data received by the data communication unit 93A. The driver's driving tendencies are, for example, tendencies during acceleration / deceleration and cornering, such as "acceleration is rapid / gradual", "deceleration is rapid / gradual", and "acceleration during cornering is rapid / gradual". The above driving tendencies can be subdivided into, for example, at least one of the vehicle speed range, timing, strength, and duration for which the driver tends to press the accelerator pedal and brake pedal during acceleration / deceleration and cornering. These are identified based on at least one of the following: vehicle speed, longitudinal acceleration α, steering angle, yaw rate, lateral acceleration, etc. The trend identification unit 920A may further identify tendencies regarding the condition of the tires, such as "tire air pressure is approximately normal / tends to decrease / tends to increase".

[0089] In step S34, the trend identification unit 920A generates feedback information based on the driving trend identified in step S33. The feedback information includes, for example, the identified driving trend, and advice on maintaining the rolling resistance performance of the tires and advice on preventing tire wear, based on the identified driving trend. For example, if the driver's driving trend is identified as gradual acceleration and deceleration, but accelerating when turning, the feedback information may include the identified driving trend and advice that gradual acceleration when turning can suppress excessive wear. Furthermore, if the tire condition is identified as having a tendency towards depressurization, the feedback information may include the identified trend and advice that adjusting the tire pressure will improve the rolling resistance coefficient and grade. Preferably, this advice includes a recommended tire pressure. The data format of the feedback information is not particularly limited, but can be, for example, text data or screen data.

[0090] The trends identified in step S33 are stored in the memory unit 91A and can be used by a private company that owns the server device 9A. For example, if the private company is an automobile insurance company, the trends identified in step S33 can be used to calculate automobile insurance premiums.

[0091] In step S35, the data communication unit 93A transmits the generated feedback information to the driver assistance device 2.

[0092] When the data communication unit 23 of the driver assistance device 2 receives feedback information transmitted by the data communication unit 93A, it stores it in the storage unit 21 or RAM. The output unit 223 displays the stored feedback information on the display 3.

[0093] <3-2. Processing of external devices> Figure 11 is a flowchart showing the processing flow performed by the server device 9B as a component of the system 10. In step S41, the receiving unit 93B of the server device 9B determines whether or not it has received a notification from the driver assistance device 2. If it is determined that a notification has been received (YES), then step S42 is executed.

[0094] In step S42, the location identification unit 920B identifies the location (area) of the notification sender, that is, the location (area) where the vehicle 1 that sent the notification is located.

[0095] In step S43, the alert generation unit 921B generates alerts for the drivers of nearby vehicles 1C, 1D, ... of vehicle 1. The alerts may notify drivers of the possibility of an overloaded vehicle traveling nearby and urge them to pay attention to their surroundings. The data format of the alerts is not particularly limited, but can be, for example, text data or screen data.

[0096] In step S44, the alert transmission unit 94B transmits the generated alert to an information processing terminal located within the vehicle 1C, 1D, ... The information processing terminals that receive the alert may be in-vehicle devices, driver assistance devices 2C, 2D, ... and information processing terminals 9C, 9D, ... as described above.

[0097] When each information processing terminal receives an alert from the alert transmission unit 94B, it displays it on the display of that information processing terminal. If the information processing terminal is an in-vehicle device other than the driver assistance device 2, the display can be, for example, a monitor device for a car navigation system installed in vehicles 1C, 1D, ...

[0098] <4. Features> According to the driver assistance device 2 of the above embodiment, the driver of vehicle 1 can check the rolling resistance performance of the tires being used. Rolling resistance performance is a factor related to the fuel efficiency and electric energy consumption of vehicle 1, and by checking this in a timely manner, the driver can determine whether or not they have actually selected tires with good rolling resistance performance. In addition, according to the driver assistance device 2 of the above embodiment, useful messages are output to improve fuel efficiency and electric energy consumption, or to extend the life of the tires. This provides driver assistance and enhances the driver's awareness of driving.

[0099] According to the system 10 of the above embodiment, it is possible to provide services to improve traffic safety not only to vehicle drivers but also to private businesses and government agencies.

[0100] <5. Variation> 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 invention. For example, the following modifications are possible. Furthermore, the gist of the following modifications can be combined as appropriate.

[0101] (1) Display 3 may be a display independent of Vehicle 1. For example, it may be a display on an information processing terminal carried by the driver of Vehicle 1 and brought into Vehicle 1.

[0102] (2) The method for determining the rolling resistance coefficient is not limited to the method of the above embodiment. The rolling resistance coefficient is, for example, the tire T FL ,T FR ,T RL ,T RR The tire T may be determined by a known method based on temperature and vehicle speed V. FL ,T FR ,T RL ,T RR The temperature of the tire T FL ,T FR ,T RL ,TRR The temperature may be obtained by a temperature sensor provided in at least one of the following. In other words, the outside temperature sensor 4 may be omitted. Furthermore, the tire T FL ,T FR ,T RL ,T RR When starting to use the tire T FL ,T FR ,T RL ,T RR The rolling resistance coefficient (catalog value) of the tire T can be stored as an initial value in the memory unit 21, and thereafter the current rolling resistance coefficient can be calculated by continuously calculating the change in the rolling resistance coefficient. The change in the rolling resistance coefficient is calculated as the tire T FL ,T FR ,T RL ,T RR It can be calculated from the temperature change.

[0103] (3) The driving assistance device 2, in addition to the rolling resistance coefficient, also considers the tire T during driving. FL ,T FR ,T RL ,T RR The wet grip performance may also be specified. Wet grip performance can be specified, for example, based on the slip ratio. In the JATMA grading system, tires that have a rolling resistance performance of "AAA," "AA," or "A" and a wet grip performance of "a," "b," "c," or "d" are considered fuel-efficient tires that contribute to improved fuel economy. For this reason, the wet grip performance may be notified to the driver in accordance with the said grading system.

[0104] (4) The method for obtaining the driving force F is not particularly limited. For example, if the vehicle 1 is equipped with a wheel torque sensor, the driving force F can be obtained based on the detection signal output by the wheel torque sensor. The method for obtaining the longitudinal acceleration α is also not particularly limited.

[0105] (5) When the status screen, notification screen, or analysis results screen is displayed, advertisements for tires, automobile insurance, or automobile maintenance services may also be displayed. The advertisements may be displayed in a manner that switches between the above screens, or they may be displayed in a manner that is incorporated into the above screens. Furthermore, the rolling resistance coefficient grade and driving conditions according to the above embodiment are merely examples in accordance with the JATMA grading system and may be changed as appropriate.

[0106] (6) Statistical analysis may be performed by a device other than the driver assistance device 2, for example, the server device 9A. Also, identification of driving trends and feedback may be performed by the driver assistance device 2 instead of the server device 9A. Time series data 212 may be stored in a device other than the driver assistance device 2, for example, the server device 9A, in addition to or instead of the driver assistance device 2. Also, at least one of the statistical analysis, identification of driving trends, and feedback may be omitted.

[0107] (7) The weight estimation of vehicle 1 may be performed by a device other than the driver assistance device 2, for example, server device 9A. The processing performed by server devices 9A and 9B may be shared among multiple devices. Furthermore, weight estimation and subsequent processing may be omitted.

[0108] (8) The heat generation / heat dissipation model of the tire according to the above embodiment may be modified as appropriate. For example, the heat generation model of the tire may take into account heat dissipation by airflow while driving.

[0109] (9) In step S23 of the above embodiment, if the grade determined in step S20 is lower than the grade determined in the past, the driver is notified of this fact. However, in addition to or instead of this, if the grade determined in step S20 is higher (improved) than the grade determined in the past, a notification screen may also be generated and the driver is notified of this fact. With such a configuration, the driver can feel that they have selected tires with good fuel efficiency or electric efficiency, and that the selected tires are actually contributing to an improvement in fuel efficiency or electric efficiency. [Explanation of Symbols]

[0110] 1. Vehicles 1A-1D 2, 2A~2D Driving Assistance System 3 displays 8 External device 9A, 9B Server Equipment 10. Driver assistance systems

Claims

1. A coefficient identification unit identifies the rolling resistance coefficient of the tires included in the vehicle based on data acquired while the vehicle is in motion, An output unit that outputs at least one of the identified rolling resistance coefficient and the grade to which the rolling resistance coefficient belongs to to a display located inside the vehicle. Equipped with, Driving assistance system.

2. Temperature acquisition unit that acquires the temperature of the aforementioned tire Furthermore, The coefficient identification unit identifies the rolling resistance coefficient based on the acquired tire temperature. The driving support device according to claim 1.

3. The temperature acquisition unit selects a heat generation / heat dissipation model for the tire according to the driving state of the vehicle, and derives the temperature change of the tire according to the duration of the driving state, in accordance with the selected heat generation / heat dissipation model for the tire. The driving support device according to claim 2.

4. The temperature acquisition unit rejects the temperature change of the tire if the calculated temperature change of the tire exceeds a predetermined threshold per unit time, and does not use it to calculate the temperature of the tire. The driving support device according to claim 3.

5. A weight estimation unit estimates the weight of the vehicle based on the rolling resistance coefficient. Furthermore, The driving support device according to claim 1.

6. The output unit generates a notification screen to inform the vehicle driver when at least one of the rolling resistance coefficient and the grade changes in a direction that worsens or improves the vehicle's fuel consumption rate or power consumption rate, and outputs it to the display. The driving support device according to claim 1.

7. The output unit generates a notification screen to inform the vehicle driver if the acquired tire temperature exceeds a predetermined threshold, and outputs it to the display. The driving support device according to claim 2.

8. The output unit generates a notification screen to inform the driver of the vehicle if the estimated weight of the vehicle exceeds a predetermined threshold based on the vehicle's maximum load capacity, and outputs it to the display. The driving support device according to claim 5.

9. A storage unit that stores time-series data of at least one of the following: data acquired while the vehicle is in motion, the rolling resistance coefficient, and the grade. Based on the aforementioned time-series data, an analysis unit performs statistical analysis on at least one of the data acquired during the vehicle's operation, the rolling resistance coefficient, and the aforementioned grade. Furthermore, The driving support device according to claim 1.

10. A storage unit that stores time-series data of the estimated weight of the vehicle, An analysis unit performs a statistical analysis of the vehicle's weight based on the aforementioned time-series data. Furthermore, The driving support device according to claim 5.

11. A data transmission unit transmits data acquired while the vehicle is in motion, the rolling resistance coefficient, and at least one of the aforementioned grades to a device outside the vehicle. Furthermore, The driving support device according to claim 1.

12. A data transmission unit transmits the estimated weight of the vehicle to an external device of the vehicle. Furthermore, The driving support device according to claim 5.

13. A notification unit notifies a predetermined device outside the vehicle if the estimated weight of the vehicle exceeds a predetermined threshold based on the vehicle's maximum load capacity. Furthermore, The driving support device according to claim 5.

14. A driving support device according to claim 11 or 12, A server device that is communicatively connected to the aforementioned driving assistance device, A receiving unit that receives data transmitted by the aforementioned data transmission unit, A trend identification unit analyzes the received data and identifies the driving tendencies of the driver of a vehicle equipped with the driver assistance device, A transmitting unit transmits the identified driving tendencies for the vehicle to the driving support device. A server device having Equipped with, Driver assistance system.

15. The driving support device according to claim 13, A server device that is communicatively connected to the aforementioned driving assistance device, A receiving unit that receives notifications from the aforementioned notification unit, A location identification unit that identifies the location where the driver assistance device that sent the aforementioned notification is located, An alert generation unit that generates an alert warning of the possibility of an overloaded vehicle being present at the identified location, An alert transmission unit that transmits the alert to an information processing terminal located in another vehicle within a predetermined area including the aforementioned position, and A server device having Equipped with, Driver assistance system.

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