WO2018030001A1

WO2018030001A1 - Road surface state assessment apparatus

Info

Publication number: WO2018030001A1
Application number: PCT/JP2017/023198
Authority: WO
Inventors: 良佑神林; 高俊関澤; 雅士森
Original assignee: 株式会社デンソー
Priority date: 2016-08-11
Filing date: 2017-06-23
Publication date: 2018-02-15

Abstract

A control unit (13) of a tire mounted sensor (1) determines whether a tire 3 has been changed. When the tire (3) has been changed, the control unit (13) changes the threshold value of a road surface state determination condition used for detecting the road surface state from vibration data of the tire (3) detected by an acceleration sensor (12) of the tire mounted sensor (1). For example, the threshold value of the road surface state determination condition is reset upon determining that the tire (3) has been changed, by transmitting an instruction command to the tire mounted sensor (1) through a tool (200) at an automobile maintenance shop, etc.

Description

Road surface condition estimation device

Cross-reference to related applications

This application is based on Japanese Patent Application No. 2016-158311 filed on August 11, 2016 and Japanese Patent Application No. 2017-110485 filed on June 5, 2017, and here The description is incorporated by reference.

The present disclosure relates to a road surface state estimation device that includes a tire mount sensor that detects vibration received by a tire and transmits the vibration data to a vehicle body side system, and estimates a road surface state based on the vibration data.

Conventionally, a tire mount sensor has been provided on the back side of the tire tread, and vibrations applied to the tires are detected by the tire mount sensors, and the detection results of the vibrations are transmitted to the vehicle body system to estimate the road surface condition. There is a device. In this apparatus, an index used for estimating the road surface state, for example, an integrated voltage value of the vibration waveform, is obtained from the vibration waveform detected by the vibration detection unit of the tire mount sensor, and the road surface state is estimated by comparing this index with a threshold value. Is going.

However, since the vibration waveform detected by the vibration detection unit changes depending on the state of the tire, it is preferable to change the threshold value for comparison with an index used for estimating the road surface state according to the state.

As a device for detecting such a tire state, Patent Document 1 proposes a tire wear estimation device that estimates the degree of tire wear.

Japanese Patent No. 5620268

However, at the time of tire replacement, the vibration waveform detected by the vibration detection unit does not gradually change like tire wear, but different vibration waveforms before and after replacement. For this reason, when the tire is replaced, the threshold for comparison with the index used for estimating the road surface condition is completely different from that used before the replacement. When reusing a tire mount sensor, the tire mount sensor attached to the tire that was used before will be attached to the tire after replacement, but in that case, the threshold set based on the tire before replacement will be The road surface condition cannot be estimated accurately.

Also, the device disclosed in Patent Document 1 only detects the degree of wear, and cannot accurately estimate the road surface condition even if the tire is worn.

The present disclosure provides a road surface state estimation device capable of accurately estimating the road surface state even when the tire mount sensor attached to the tire before replacement is reused when the tire is replaced. With the goal.

A road surface state estimation device includes a vibration detection unit that outputs an output voltage corresponding to the magnitude of tire vibration as a detection signal, a signal processing unit that detects a road surface state from vibration data indicated by the detection signal of the vibration detection unit, and a road surface A transmission unit that transmits road surface data indicating a state, a tire mount sensor that is attached to the rear surface of the tire, and a vehicle body side that receives road surface data transmitted from the transmission unit, and road surface data A vehicle body side system having a control unit that estimates a road surface state based on the road surface condition determination condition threshold used when detecting a road surface state from vibration data when a tire is replaced To change.

Thus, when the tire is replaced, the threshold value of the road surface condition determination condition is automatically reset. As a result, when exchanging tires, it is possible to provide a road surface state estimating device capable of accurately estimating the road surface state even when the tire mount sensor attached to the tire before replacement is reused. It becomes.

It is the figure which showed the block configuration of the road surface state estimation apparatus concerning 1st Embodiment. It is a block diagram of a tire mount sensor. It is a cross-sectional schematic diagram of a tire to which a tire mount sensor is attached. It is an output voltage waveform figure of an acceleration sensor at the time of tire rotation. It is the figure which showed the change of the output voltage of an acceleration sensor in the case of drive | working the high micro road surface where road surface (micro | micron | mu) is comparatively large like an asphalt road. It is the figure which showed the change of the output voltage of an acceleration sensor in the case of drive | working on the low micro road surface where road surface (micro | micron | mu) is comparatively small like a frozen road. It is the figure which showed the result of having performed the frequency analysis of the output voltage in the earthing | grounding area about the case where it is drive | working on the high micro road surface, and the case where it is driving on the low micro road surface, respectively. It is the flowchart which showed the detail of the threshold reset process at the time of tire replacement | exchange. It is the flowchart which showed the detail of the threshold reset process at the time of tire replacement demonstrated in 2nd Embodiment. It is a block diagram of the tire mount sensor demonstrated in 3rd Embodiment.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be described with the same reference numerals.

(First embodiment)
A road surface state estimating device 100 to which the tire mount sensor 1 according to the present embodiment is applied will be described with reference to FIGS. The road surface state estimation device 100 according to the present embodiment estimates the road surface state during travel of the vehicle. In the present embodiment, the road surface state is applied to the tire mount sensor 1 applied to the road surface state estimation device 100. A learning function of a threshold value used for estimation of. Hereinafter, the road surface state estimation device 100 of the present embodiment will be specifically described.

As shown in FIGS. 1 and 2, the road surface state estimating device 100 has a tire mount sensor 1 provided on the wheel side and a vehicle body side system 2 including each part provided on the vehicle body side. As the vehicle body side system 2, a receiver 21, a notification device 22, and the like are provided.

The road surface state estimation device 100 detects the vibration of the tire 3 provided to each wheel by the tire mount sensor 1 and travels data such as data indicating the road surface μ between the tire 3 and the road surface during traveling based on the vibration. Data representing the road surface condition inside is generated and transmitted to the receiver 21 side. Hereinafter, the data of the road surface μ is referred to as μ data, and the data indicating the road surface state including the μ data is referred to as road surface data. Further, the road surface state estimation device 100 receives the road surface data transmitted from the tire mount sensor 1 by the receiver 21 and transmits the road surface state indicated by the road surface data from the notification device 22. As a result, it is possible to inform the driver of the road surface condition such as low road surface μ, dry road, wet road or frozen road, and it is possible to warn the driver when the road surface is slippery. Become. Specifically, the tire mount sensor 1 and the receiver 21 are configured as follows.

The tire mount sensor 1 is a tire side device provided on the tire side. As shown in FIG. 2, the tire mount sensor 1 includes a power source 11, an acceleration sensor 12, a control unit 13, an LF (abbreviation of LowＬFrequency) reception circuit 14, and an RF (abbreviation of Radio Frequency) transmission circuit 15. As shown in FIG. 4, it is provided on the back side of the tread 31 of the tire 3. For example, the tire mount sensor 1 is fixed to the tire 3 by being fitted to a rubber bracket 32 bonded to the back surface of the tread 31. The tire mount sensor 1 can be attached to and detached from the rubber bracket 32. When the tire mount sensor 1 is removed from the rubber bracket 32 at the time of tire replacement, the tire mount sensor 1 is fitted again to the rubber bracket 32 attached to the tire 3 after replacement.

The power source 11 is constituted by, for example, a battery and supplies power for driving each part of the tire mount sensor 1.

The acceleration sensor 12 constitutes a vibration detection unit for detecting vibration applied to the tire. For example, the acceleration sensor 12 detects acceleration as a detection signal corresponding to vibration in a tire tangential direction indicated by an arrow X in FIG. 3 in a direction in contact with a circular orbit drawn by the tire mount sensor 1 when the tire 3 rotates. The detection signal is output. More specifically, the acceleration sensor 12 generates an output voltage as a detection signal in which one of the two directions indicated by the arrow X is positive and the opposite direction is negative.

The control unit 13 is a part corresponding to a signal processing unit, and uses the detection signal of the acceleration sensor 12 as a detection signal representing vibration data in the tire tangential direction, obtains road surface data by processing the detection signal, It plays a role of transmitting it to the RF transmission circuit 15.

Specifically, the control unit 13 extracts the ground contact section of the acceleration sensor 12 when the tire 3 rotates based on the detection signal of the acceleration sensor 12, that is, the time change of the output voltage of the acceleration sensor 12. Note that the contact section here means a section in which a portion of the tread 31 of the tire 3 corresponding to the location where the acceleration sensor 12 is disposed is grounded on the road surface. In the case of this embodiment, since the location where the acceleration sensor 12 is disposed is the location where the tire mount sensor 1 is disposed, the portion corresponding to the location where the tire mount sensor 1 is disposed in the tread 31 of the tire 3 is the road surface. It is an agreement with the grounded section. Hereinafter, the arrangement location of the tire mount sensor 1 in the tread 31 of the tire 3, in other words, the arrangement location of the acceleration sensor 12 is referred to as an apparatus arrangement location.

For example, since the high-frequency component included in the detection signal of the acceleration sensor 12 in the contact section represents the road surface state, the control unit 13 extracts the high-frequency component from the detection signal and extracts the high-frequency component as described later. A road surface condition such as road surface μ is detected based on the component.

In this way, when the control unit 13 detects the road surface state, the control unit 13 generates road surface data indicating the road surface state, and performs a process of transmitting it to the RF transmission circuit 15. Thus, road surface data is transmitted to the receiver 21 through the RF transmission circuit 15.

More specifically, the control unit 13 is configured by a known microcomputer including a CPU, ROM, RAM, I / O, and the like, and performs the above-described processing according to a program stored in the ROM. And the control part 13 is provided with the area extraction part 13a, the level calculation part 13b, and the data generation part 13c as a function part which performs those processes.

The section extracting unit 13a extracts the ground section by detecting the peak value of the detection signal represented by the output voltage of the acceleration sensor 12. The output voltage waveform of the acceleration sensor 12 during tire rotation is, for example, the waveform shown in FIG. As shown in this figure, the output voltage of the acceleration sensor 12 takes a maximum value at the start of grounding when the portion corresponding to the device arrangement location starts to ground as the tire 3 rotates. The section extraction unit 13a detects the start of grounding at which the output voltage of the acceleration sensor 12 takes a maximum value as the timing of the first peak value. Furthermore, as shown in FIG. 4, the output voltage of the acceleration sensor 12 takes a minimum value at the end of the grounding when the device arrangement portion is grounded with the rotation of the tire 3 when the grounding is stopped. The section extraction unit 13a detects the end of grounding at which the output voltage of the acceleration sensor 12 takes a minimum value as the timing of the second peak value.

The reason why the output voltage of the acceleration sensor 12 takes a peak value at the above timing is as follows. That is, when the device arrangement place comes into contact with the rotation of the tire 3, the portion of the tire 3 that has been a substantially cylindrical surface in the vicinity of the acceleration sensor 12 is pressed and deformed into a flat shape. By receiving an impact at this time, the output voltage of the acceleration sensor 12 takes the first peak value. In addition, when the device arrangement part moves away from the ground contact surface with the rotation of the tire 3, the tire 3 is released from pressing in the vicinity of the acceleration sensor 12 and returns from a planar shape to a substantially cylindrical shape. By receiving an impact when the tire 3 returns to its original shape, the output voltage of the acceleration sensor 12 takes the second peak value. In this way, the output voltage of the acceleration sensor 12 takes the first and second peak values when the grounding starts and when the grounding ends, respectively. Moreover, since the direction of the impact when the tire 3 is pressed and the direction of the impact when released from the press are opposite directions, the sign of the output voltage is also opposite.

Then, the section extracting unit 13a extracts the ground contact section of the acceleration sensor 12 by extracting the detection signal data including the timings of the first and second peak values, and the level calculating unit 13b indicates that it is in the grounded section. To tell.

Further, since the timing at which the output voltage of the acceleration sensor 12 takes the second peak value is when the grounding of the acceleration sensor 12 is completed, the section extraction unit 13a sends a transmission trigger to the RF transmission circuit 15 at this timing. As a result, road surface data such as μ data created by the data generation unit 13c is transmitted from the RF transmission circuit 15 as will be described later. In this way, data transmission by the RF transmission circuit 15 is not always performed, but only when the acceleration sensor 12 is grounded, so that power consumption can be reduced. Although the timing at which the output voltage of the acceleration sensor 12 takes the second peak value has been described as an example of the data transmission timing from the RF circuit 15, it is needless to say that another timing may be used. In addition, instead of a mode in which data transmission is performed once for each rotation of the tire 3, a mode in which data transmission is performed once for a plurality of rotations or a plurality of times for each rotation may be employed.

The level calculation unit 13b, when notified from the section extraction unit 13a that it is in the grounding section, calculates the level of the high-frequency component caused by the vibration of the tire 3 included in the output voltage of the acceleration sensor 12 during that period. Then, the level calculation unit 13b transmits the calculation result to the data generation unit 13c as road surface data such as μ data. Here, the level of the high-frequency component is calculated as an index representing the road surface state such as the road surface μ. The reason will be described with reference to FIGS. 5A, 5B, and 6. FIG.

FIG. 5A shows a change in the output voltage of the acceleration sensor 12 when traveling on a high μ road surface having a relatively large road surface μ such as an asphalt road. FIG. 5B shows a change in the output voltage of the acceleration sensor 12 when the vehicle is traveling on a low μ road surface where the road surface μ is relatively small to the extent corresponding to the frozen road.

As can be seen from these figures, the first and second peak values appear at the beginning and end of the contact section, that is, at the start and end of the contact of the acceleration sensor 12, regardless of the road surface μ. However, the output voltage of the acceleration sensor 12 changes due to the influence of the road surface μ. For example, when the road surface μ is low, such as when traveling on a low μ road surface, fine high-frequency vibration due to slip of the tire 3 is superimposed on the output voltage. Such a fine high-frequency signal due to the slip of the tire 3 is not superposed when the road surface μ is high, such as when traveling on a high μ road surface.

Therefore, when the frequency analysis of the output voltage during the grounding section is performed for each of the cases where the road surface μ is high and low, the result shown in FIG. 6 is obtained. In other words, in the low frequency range, the level is high when the road surface μ is high or low, but in the high frequency range of 1 kHz or higher, the level is higher when the road surface μ is low than when it is high. . For this reason, the level of the high frequency component of the output voltage of the acceleration sensor 12 serves as an index representing the road surface state.

Therefore, by calculating the level of the high frequency component of the output voltage of the acceleration sensor 12 during the grounding section by the level calculation unit 13b, this can be converted to μ data. Further, from the μ data, for example, when the road surface μ is low, the road surface type corresponding to the road surface μ can be detected as a road surface state, such as determining that the road is frozen.

For example, the level of the high frequency component can be calculated as an integrated voltage value obtained by extracting the high frequency component from the output voltage of the acceleration sensor 12 and integrating the high frequency component extracted during the grounding section. Specifically, the high frequency components of the frequency bands fa to fb that are assumed to change according to the road surface condition and the road surface μ are extracted by filtering or the like, and the voltages of the high frequency components of the frequency bands fa to fb extracted by the frequency analysis are obtained. Integrate to obtain the integrated voltage value. For example, a capacitor (not shown) is charged. In this way, the amount of charge increases when the road surface μ is low, such as when traveling on a low μ road surface, rather than when the road surface μ is high, such as when traveling on a high μ road surface. . Using this charge amount as the μ data, it is possible to estimate the road surface μ such that the larger the charge amount indicated by the μ data, the lower the road surface μ.

The data generation unit 13c generates road surface data based on the calculation result of the level calculation unit 13b. For example, the data generation unit 13c adopts μ data as it is as road surface data, obtains a road surface state such as a frozen road or an asphalt road from μ data, and generates data indicating the road surface data as road surface data. In the case of this embodiment, the road surface state is estimated in the data generation unit 13c. For this reason, the data generation unit 13c stores a threshold value of the road surface condition determination condition used for estimating the road surface condition, and when the tire is changed, the threshold value is reset and stored. It is like that.

The LF reception circuit 14 corresponds to a reception unit, and is a circuit that receives a command input through the tool 200 or the like. For example, when an LF wave including an instruction command is transmitted to the tire mount sensor 1 through the tool 200 in an automobile maintenance shop or the like, the instruction command is transmitted to the control unit 13 through the LF reception circuit 14. When the instruction command is a learning mode transition signal to be described later, the control unit 13 reads the output voltage of the acceleration sensor 12 and assumes that the tire has been changed, and at the data generation unit 13c, Reset the threshold value of the road surface condition determination condition. Specifically, when the control unit 13 acquires information indicating that tire replacement has been performed by the data generation unit 13c, more specifically, when it is determined that tire replacement has been performed, the threshold of the road surface condition determination condition Reset the settings. A method for resetting the threshold value of the road surface condition determination condition will be described later.

The RF transmission circuit 15 constitutes a transmission unit that transmits road surface data such as μ data transmitted from the data generation unit 13 c to the receiver 21. Communication between the RF transmission circuit 15 and the receiver 21 can be performed by a known short-range wireless communication technique such as Bluetooth (registered trademark). The timing for transmitting the road surface data is arbitrary, but as described above, in this embodiment, the road surface data is received from the RF transmission circuit 15 by sending a transmission trigger from the section extracting unit 13a when the ground contact of the acceleration sensor 12 is completed. It is supposed to be sent. In this way, data transmission by the RF transmission circuit 15 is not always performed, but only when the acceleration sensor 12 is grounded, so that power consumption can be reduced.

Further, the road surface data is sent together with the unique identification information (hereinafter referred to as ID information) of the wheels provided in advance for each tire 3 provided in the vehicle. The position of each wheel can be specified by a well-known wheel position detection device that detects which position of the vehicle the wheel is attached to. Therefore, by transmitting road surface data together with ID information to the receiver 21, data on which wheel is detected. Can be determined.

On the other hand, the receiver 21 receives the road surface data transmitted from the tire mount sensor 1, estimates the road surface state based on the road surface data, transmits the estimated road surface state to the notification device 22, and if necessary, from the notification device 22. Inform the driver of the road surface condition. As a result, the driver tries to drive corresponding to the road surface condition, and the danger of the vehicle can be avoided. For example, the road surface state estimated through the notification device 22 may be always displayed, or the estimated road surface state needs to be operated more carefully such as a wet road, a frozen road, a low μ road, or the like. Only when the road surface condition is displayed, the driver may be warned. Further, if the road surface state is transmitted from the receiver 21 to an ECU for executing vehicle motion control such as an electronic control device (hereinafter referred to as ECU) for brake control, the vehicle motion control is performed based on the transmitted road surface state. Can also be executed.

The notification device 22 is composed of a meter display, for example, and is used when notifying the driver of the road surface state. When the notification device 22 is configured by a meter display, the notification device 22 is disposed at a place where the driver can visually recognize the vehicle while driving, for example, in an instrument panel of the vehicle. When the road surface state is transmitted from the receiver 21, the meter display can visually notify the driver of the road surface state by performing display in such a manner that the road surface state can be grasped.

Note that the notification device 22 can also be configured by a buzzer or a voice guidance device. In that case, the notification device 22 can audibly notify the driver of the road surface state by a buzzer sound or voice guidance. In addition, although the meter display device has been exemplified as the notification device 22 that performs visual notification, the notification device 22 may be configured by a display device that displays information such as a head-up display.

As described above, the road surface state estimation device 100 according to the present embodiment is configured. In addition, each part which comprises the vehicle body side system 2 is connected through in-vehicle LAN (abbreviation of Local * AreaNetwork) by CAN (abbreviation for Controller | AreaNetwork) etc., for example. For this reason, each part can communicate with each other through the in-vehicle LAN.

Subsequently, the operation of the tire mount sensor 1 in the road surface state estimation device 100 according to the present embodiment will be described.

As described above, in the tire mount sensor 1, the output voltage waveform is analyzed every time the tire 3 makes one rotation based on the detection signal of the acceleration sensor 12 to obtain road surface data. Then, at the timing when the output voltage waveform becomes the second peak value, a transmission trigger is issued from the control unit 13 to the RF transmission circuit 15, and road surface data is transmitted.

On the other hand, when data transmission is performed from the RF transmission circuit 15, the receiver 21 receives the data, estimates the road surface state based on the road surface data, and transmits the estimated road surface state to the notification device 22. Thereby, a road surface state can be notified to a driver.

Furthermore, when an instruction command is sent to the tire mount sensor 1 through the tool 200 in an automobile maintenance shop or the like, the instruction command is received by the LF receiving circuit 14. When this instruction command is transmitted to the control unit 13 and the instruction command is a learning mode transition signal, the control unit 13 reads the output voltage of the acceleration sensor 12 and resets the threshold value of the road surface condition determination condition. . The instruction command here, specifically the learning mode transition signal, corresponds to “information indicating that tire replacement has been performed” in the present embodiment. And the control part 13 totals the data of the output voltage of the acceleration sensor 12 during the period when the tire 3 rotates two or more, and resets the threshold value of road surface condition determination conditions based on the total result.

For example, in an automobile maintenance factory or the like, the road surface for learning is usually selected as an asphalt road with the highest driving frequency, that is, a high μ road, and road surface condition determination is performed based on vibration data obtained when driving on a high μ road. Reset the various thresholds used. Thereby, in the case of this embodiment, the various threshold values memorize | stored in the data generation part 13c are reset to a new threshold value.

This threshold resetting method will be described with reference to the flowchart of threshold resetting processing shown in FIG. Note that the threshold resetting process shown in FIG. 7 is executed by the control unit 13 every predetermined control cycle based on the power supply from the power supply 11.

First, in step S100, it is determined whether a learning mode transition signal is received as an instruction command transmitted through the tool 200 at the time of tire replacement, that is, whether tire replacement has been performed. If it has been received, the process proceeds to step S110 and subsequent steps. If it has not been received, this process is repeated until it is determined that it has been received. In step S110, the mode is changed to the learning mode, and in steps S120 to S170, a threshold value used as a road surface condition determination condition is reset. In addition, when the control unit 13 transitions to the learning mode, the road surface state determination is interrupted during the period, and various processes for resetting the threshold value are performed without transmitting road surface data.

Specifically, in step S120, processing for transmitting a learning mode transition signal to the vehicle body side system 2 is performed. That is, the control unit 13 outputs a learning mode transition signal indicating the transition to the learning mode to the RF transmission circuit 15 and transmits the learning mode transition signal from the RF transmission circuit 15. Thereby, since it can grasp | ascertain that the tire mount sensor 1 changed to learning mode also in the vehicle body side system 2, it is made not to perform road surface state estimation during the period. Further, in order to inform the driver that the mode has been changed to the learning mode, it may be notified through the notification device 22 that the learning mode is being performed.

Subsequently, in step S130, the output voltage waveform of the acceleration sensor 12 is signal-processed, and an integrated voltage value is calculated by integrating high-frequency components in the ground section, and the integrated voltage values are tabulated. Further, in step S140, it is determined whether or not the number of rotations of the tire 3 has reached a predetermined rotation, for example, 20 rotations, and the processing in step S130 is repeated until the predetermined rotation is reached. Thereby, the integrated voltage value during the period until the rotation speed of the tire 3 reaches a predetermined rotation is tabulated.

Thereafter, the process proceeds to step S150, and the threshold value of the road surface condition determination condition is reset in the control unit 13. For example, the average value of the integrated voltage values collected in step S140 is calculated, and a numerical value obtained by adding a predetermined value to the average value or a value obtained by multiplying a predetermined coefficient is set as the threshold value. Based on this threshold value, the road surface condition can be determined as a high μ road if the integrated voltage value acquired in the future is equal to or lower than the threshold value, and a low μ road if the integrated voltage value exceeds the threshold value.

Also, when resetting the threshold value, it is preferable to reset the threshold value for each vehicle speed or to set the threshold value at the reference vehicle speed. In this way, a threshold value for each vehicle speed or a reference vehicle speed is set, and when the road surface condition is determined, the obtained integrated voltage value is compared with a threshold value corresponding to the vehicle speed. The integrated voltage value thus obtained is corrected to a value converted to a reference vehicle speed and compared with a threshold value. By doing in this way, a road surface state can be determined more correctly. That is, as the vehicle speed increases, the first peak value and the second peak value also increase, and the integrated voltage value of the high frequency component of the output voltage of the acceleration sensor 12 also increases, so that the threshold value is increased as the vehicle speed increases. Or the integrated voltage value is corrected to a value corresponding to the reference vehicle speed. In this way, it is possible to determine the road surface state corresponding to the change in the integrated voltage value due to the vehicle speed.

Here, only the threshold value for determining the high μ road and the low μ road is given as an example, but for example, a threshold value setting for determining the type of road surface such as a snowy road or a wet road is set. It can also be done. In the case of a snowy road, the unevenness of the road surface is large, and therefore, the vibration of the output voltage of the acceleration sensor 12 becomes larger in other regions than in the ground contact section, that is, between the second peak value and the first peak value. For this reason, it is possible to reset the threshold value for determining a normal road such as a snowy road and an asphalt road by analyzing the frequency of the detection signal of the acceleration sensor 12 between the second peak value and the first peak value. In the case of a wet road, the first peak value and the second peak value are not steep, and the manner in which the output voltage of the acceleration sensor 12 changes when reaching the first peak value or the second peak value changes. Furthermore, in the case of a wet road, since it is easy to slip, vibration based on slip increases in the ground contact section. Accordingly, the change amount threshold value that is the threshold value of the change rate of the output voltage of the acceleration sensor 12 when the first peak value or the second peak value is reached, and the integral value threshold value that is the threshold value of the integrated voltage value during the grounding interval are reset. To do. In the future, for example, if the change rate is smaller than the change amount threshold value and the integrated voltage value is larger than the integral value threshold value, it can be determined that the road is a wet road.

Subsequently, the process proceeds to step S160, and the learning mode is changed to the normal mode. Thereby, road surface condition determination is restarted. At this time, the threshold value reset in step S150 is used as the threshold value used for determining the road surface state. And it progresses to step S170 and the process for transmitting a normal mode transition signal with respect to the vehicle body side system 2 is performed. That is, the control unit 13 outputs a normal mode transition signal indicating the transition from the learning mode to the normal mode to the RF transmission circuit 15, and transmits the normal mode transition signal from the RF transmission circuit 15. As a result, the vehicle body side system 2 is also informed that the tire mount sensor 1 has transitioned to the normal mode, that is, has transitioned to the mode in which road surface condition determination is performed. Therefore, in the vehicle body side system 2, road surface state estimation is performed based on the road surface data transmitted from each tire mount sensor 1.

As described above, when a tire is replaced, an instruction command serving as information indicating that the tire has been replaced is transmitted to the tire mount sensor 1 through the tool 200 in an automobile maintenance shop or the like, thereby automatically setting the threshold value of the road surface condition determination condition. Can be reset automatically. Thereby, when performing tire replacement, a road surface state estimation device capable of accurately estimating the road surface state even when the tire mount sensor 1 attached to the tire 3 before replacement is reused. Is possible.

(Second Embodiment)
A second embodiment will be described. In this embodiment, the road surface state is determined by the vehicle body side system 2 with respect to the first embodiment, and the other parts are the same as those in the first embodiment, and therefore different from the first embodiment. Only will be described.

In the first embodiment, the tire mount sensor 1 determines the road surface state and transmits road surface data indicating the result to the vehicle body system 2 so that the vehicle surface system 2 finally estimates the road surface state. . In contrast, the tire mount sensor 1 transmits the integrated voltage value of the high frequency component of the output voltage of the acceleration sensor 12 as road surface data, and the vehicle body side system 2 determines the road surface state based on the road surface data. You can also For example, a threshold value that is a road surface condition determination condition is stored in the vehicle body side system 2, and an integrated voltage value or the like indicated in the road surface data is compared with the threshold value to determine whether the road is a high μ road or a low μ road. The road surface condition can be determined. In this case, the threshold value is stored in the vehicle body side system 2. Therefore, the resetting of the threshold value of the road surface condition determination condition at the time of tire replacement or the like is performed by the vehicle body side system 2.

As described above, the threshold value which is the road surface condition determination condition in the vehicle body side system 2 can be stored, and the road surface condition of the acceleration sensor 12 can be determined. In that case, the threshold resetting process executed by the control unit 13 described in the first embodiment is the process shown in the flowchart of FIG. That is, in steps S200 to S230, processing similar to that in steps S100 to S130 of FIG. 7 is performed, and in step S240, processing for transmitting road surface data such as an integrated voltage value to the vehicle body side system 2 is performed. In step S250, processing similar to that in step S140 in FIG. 7 is performed. As a result, the process of sending road surface data to the vehicle body side system 2 shown in step S240 is performed for a predetermined number of revolutions of the tire 3.

Based on this, the integrated voltage value and the like are aggregated in the vehicle body side system 2. Then, for example, an average value of the integrated voltage values is calculated, and a value obtained by adding a predetermined value to the average value or a value obtained by multiplying a predetermined coefficient is set as the threshold value.

Thereafter, in steps S260 and S270, processing similar to that in steps S160 and S170 in FIG. 7 is performed. As described above, the vehicle body side system 2 can reset the threshold value of the road surface condition determination condition at the time of tire replacement or the like.

(Third embodiment)
A third embodiment will be described. In the present embodiment, the road surface state is determined by the vehicle body side system 2 with respect to the first and second embodiments, and the rest is the same as the first and second embodiments. Only the differences from the first and second embodiments will be described.

In the above embodiment, even if the tool 200 is not used, when the tire mount sensor 1 is reused at the time of tire replacement, information indicating that the tire replacement has been performed is automatically acquired, so that the road surface state is automatically acquired. The threshold value of the determination condition is reset.

As shown in FIG. 9, a fitting detection unit 16 for detecting that the tire mount sensor 1 is fitted to the rubber bracket 32 is provided. The fitting detection unit 16 corresponds to a replacement detection unit that detects that the tire mount sensor 1 is attached to the tire 3 after replacement.

The fitting detection part 16 is comprised by the detection circuit etc. which conduct | electrically_connect by contacting with the conductor part which is provided in the contact surface with the tire mount sensor 1 among the rubber brackets 32, for example. That is, since the detection circuit provided in the tire mount sensor 1 is separated from the conducting portion when it is removed from the rubber bracket 32, the detection circuit is electrically disconnected from the conducting portion when it is attached to the rubber bracket 32 again. Conducted by contact. For this reason, it can detect that the tire mount sensor 1 was attached to the tire 3 after replacement | exchange by switching from a non-conduction state to a conduction | electrical_connection state by a detection circuit. Then, the control unit 13 detects that the switching between the non-conduction state and the conduction state is detected by the fitting detection unit 16 using the change between the non-conduction state and the conduction state as information indicating that the tire has been replaced. Based on the above, it can be determined that the tire has been changed.

As described above, the tire mount sensor 1 includes the fitting detection unit 16, and the fitting detection unit 16 detects that the tire mount sensor 1 is fitted to the rubber bracket 32, thereby performing tire replacement. Determine what happened. In this way, the threshold value of the road surface condition determination condition can be automatically reset. For example, instead of step S100 in FIG. 7, the fitting detection unit 16 determines whether or not the tire mount sensor 1 has been fitted into the rubber bracket 32, and the fitting is detected. In this case, the processing after step S110 is performed. By doing in this way, the threshold value of the road surface condition determination condition is automatically reset.

(Fourth embodiment)
A fourth embodiment will be described. This embodiment is different from the first to third embodiments in that the threshold value of the road surface condition determination condition is changed based on the change in the unevenness of the tread 31, and the others are the first to the third. Since the third embodiment is the same as the third embodiment, only the parts different from the first to third embodiments will be described.

In the present embodiment, the tire mount sensor 1 detects a change in unevenness of the tread 31 of the tire 3 based on the output voltage of the acceleration sensor 12, and automatically switches to the learning mode when the change in unevenness is detected. The threshold value of the road surface condition determination condition is changed.

For example, when the tire 3 is less worn as in a new state, the height of the unevenness due to the grooves formed in the tread 31 is higher than in the state after the wear, and the tire 3 is soft and easily deformed elastically. It is in a state. For this reason, the vibration attenuation rate by the tire 3 is large, and the vibration of the output voltage waveform of the acceleration sensor 12 is small. As the tire 3 wears, the vibration of the output voltage waveform of the acceleration sensor 12 gradually increases.

However, such a change in the output voltage waveform of the acceleration sensor 12 gradually progresses and does not change abruptly when traveling on the same type of road surface. For this reason, for example, an integrated voltage value of a high frequency component of the output voltage of the acceleration sensor 12 when traveling on an asphalt road is stored in the storage unit of the tire mount sensor 1 as past information. For example, since it can be detected that the tire 3 has stopped based on the detection signal of the acceleration sensor 12, the integrated voltage value obtained before the tire 3 stops is stored as past information. When the integrated voltage value obtained at that time is a road surface state suitable for storing, for example, when the road is not an asphalt road, the integrated voltage value obtained when the tire 3 was traveling on the asphalt road before stopping is past information. May be stored. The asphalt road can be determined by, for example, the integrated voltage value being smaller than a stored threshold value, and the integrated voltage value at that time is stored.

And when the change of the integrated voltage value acquired with respect to the integrated voltage value stored as the past information is abrupt, it can be said that the height of the unevenness due to the groove of the tread 31 has changed abruptly. Therefore, it is confirmed that the change of the integrated voltage value was abrupt, for example, that the tire replacement was performed when the difference between the acquired integrated voltage value and the integrated voltage value stored as past information was equal to or greater than the threshold value. As information to be shown, it can be determined that tire replacement has been performed. When it is determined that the tire has been changed in this way, the threshold value of the road surface condition determination condition is reset. At this time, the acquired integrated voltage value needs to be the same as that of the integrated voltage value stored as past information, for example, when traveling on an asphalt road as described above. For this reason, it is also possible to reset the threshold value of the road surface condition determination condition only when the acquired integrated voltage value is smaller than the integrated voltage value stored as past information.

As described above, even when it is assumed that the uneven height due to the groove of the tread 31 has suddenly changed, the threshold value of the road surface condition determination condition can be automatically reset. Also in this case, for example, in place of step S100 in FIG. 7, a process for determining whether or not the height of the recesses and projections in the groove of the tread 31 has changed abruptly is performed. Perform the process. By doing in this way, the threshold value of the road surface condition determination condition is automatically reset.

(Other embodiments)
Although the present disclosure has been described based on the above-described embodiment, the present disclosure is not limited to the embodiment, and includes various modifications and modifications within an equivalent range. In addition, various combinations and forms, as well as other combinations and forms including only one element, more or less, are within the scope and spirit of the present disclosure.

For example, in each of the above embodiments, the case where the resetting of the threshold value of the road surface condition determination condition is performed when the road surface is an asphalt road has been described. This is because the road surface with the highest traveling frequency of the vehicle is an asphalt road. It is. For this reason, the threshold value may be reset when the road surface condition is other than the asphalt road. For example, a desired road surface state can be selected by the tool 200, and a threshold value assumed for the selected road surface form may be set based on the output voltage waveform of the acceleration sensor 12. In this way, it is possible to reset the threshold value in each of various road surface conditions, and it is possible to reset the threshold value more accurately.

Further, in the road surface state estimation device 100 shown in each of the above embodiments, the grounding section is specified from the detection signal of the acceleration sensor 12 that constitutes the vibration detection unit, and the calculation result of the level of the high frequency component in the detection signal in the grounding section It is used as road surface data indicating the road surface condition. However, this is only an example of a method for detecting the road surface state using the detection signal at the vibration detection unit, and even if the road surface state is detected by another method using the detection signal at the vibration detection unit. good.

Further, although the case where the vibration detection unit is configured by the acceleration sensor 12 has been illustrated, the vibration detection unit can also be configured by another element capable of detecting vibration, such as a piezoelectric element. Further, the power source 11 is not limited to a battery, and may be configured by a power generation element or the like. For example, if a vibration detection power generation element is used, the power supply 11 can be configured while the vibration detection power generation element forms a vibration detection unit.

Further, in each of the above embodiments, the receiver 21 has a function as a control unit, and the final road surface state estimation is performed. However, this is merely an example, and a control unit may be provided separately from the receiver 21, or another ECU such as a brake ECU may function as the control unit.

Further, the above embodiments are not irrelevant to each other, and can be appropriately combined unless the combination is clearly impossible. For example, the first embodiment or the second embodiment can be combined with the third embodiment or the fourth embodiment.

Claims

A road surface state estimation device for estimating a road surface state on a traveling road surface of a vehicle,
A vibration detection unit (12) that outputs an output voltage corresponding to the magnitude of vibration of the tire (3) as a detection signal, and a signal processing unit (13) that detects a road surface state from vibration data indicated by the detection signal of the vibration detection unit. ) And a transmission unit (15) for transmitting road surface data representing the road surface state, and a tire mount sensor (1) attached to the back surface of the tire,
A vehicle body side system (2) provided on a vehicle body side, having a control unit (21) for receiving the road surface data transmitted from the transmission unit and estimating a road surface state based on the road surface data;
The said signal processing part is a road surface state estimation apparatus which changes the threshold value of the road surface state determination condition used when detecting a road surface state from the said vibration data, when the said tire is replaced | exchanged.
The road surface state estimation device according to claim 1, wherein the signal processing unit changes a threshold value of the road surface state determination condition when acquiring information indicating that the tire has been replaced.
2. The road surface according to claim 1, wherein the signal processing unit determines whether or not the tire has been replaced, and changes a threshold value of the road surface condition determination condition when it is determined that the tire has been replaced. State estimation device.
The tire mount sensor has a receiving unit (14) for inputting an instruction command sent from the tool (200),
4. The road surface state estimation device according to claim 1, wherein when the instruction command is received from the reception unit, the signal processing unit transitions to a learning mode and changes a threshold value of the road surface state determination. 5.
The tire mount sensor is detachable from the tire, and has a replacement detection unit (16) for detecting that the tire is replaced and attached to the tire after replacement. ,
When the replacement detection unit detects that the tire mount sensor is attached to the replaced tire, the signal processing unit shifts to a learning mode and changes the road surface condition determination threshold value. The road surface state estimation device according to any one of claims 1 to 4.
The signal processing unit stores past information of the road surface data when traveling on a desired road surface, and it is detected that the vehicle is traveling on the desired road surface from the road surface data obtained during traveling. When detecting that the uneven height of the groove of the tread (31) of the tire has changed based on the road surface data and the past information obtained during the traveling, the mode changes to the learning mode and the The road surface state estimation apparatus according to any one of claims 1 to 5, wherein a road surface state determination threshold value is changed.
The signal processing unit includes a section extraction unit (13a) that extracts a grounding section in which a portion corresponding to an arrangement position of the vibration detection unit in the tread during one rotation of the tire is grounded, and the grounding A level calculation unit (13b) that calculates an integrated voltage value obtained by integrating the output voltage of the vibration detection unit as a level of a high-frequency component of the detection signal in the section, and the integrated voltage value as a threshold value for the road surface condition determination The road surface state estimation apparatus according to any one of claims 1 to 6, wherein a threshold value to be compared with is changed.
A road surface state estimation device for estimating a road surface state on a traveling road surface of a vehicle,
A vibration detection unit (12) that outputs an output voltage corresponding to the magnitude of vibration of the tire (3) as a detection signal, and a signal processing unit (13) that detects a road surface state from vibration data indicated by the detection signal of the vibration detection unit. ) And a transmission unit (15) for transmitting road surface data representing the road surface state, and a tire mount sensor (1) attached to the back surface of the tire,
A vehicle body side system (2) provided on a vehicle body side, having a control unit (21) for receiving the road surface data transmitted from the transmission unit and estimating a road surface state based on the road surface data;
The said control part is a road surface state estimation apparatus which changes the threshold value of the road surface state determination condition used when detecting a road surface state from the said vibration data, if the said tire replacement | exchange is performed.
The road surface state estimation device according to claim 8, wherein the control unit changes a threshold value of the road surface state determination condition when acquiring information indicating that the tire has been replaced.
9. The road surface state according to claim 8, wherein the control unit determines whether or not the tire has been replaced, and changes a threshold value of the road surface state determination condition when determining that the tire has been replaced. Estimating device.
The tire mount sensor has a receiving unit (14) for inputting an instruction command sent from the tool (200),
When the signal processing unit receives an instruction command from the receiving unit, the signal processing unit transitions to a learning mode and transmits the road surface data to the vehicle body side system through the transmitting unit,
The road surface according to any one of claims 8 to 10, wherein the control unit changes a threshold value of the road surface state determination based on the road surface data transmitted from the tire mount sensor during the learning mode. State estimation device.
The tire mount sensor is detachable from the tire, and has a replacement detection unit (16) for detecting that the tire is replaced and attached to the tire after replacement. ,
When the replacement detection unit detects that the tire mount sensor is attached to the tire after replacement, the signal processing unit transitions to a learning mode and transmits the road surface data through the transmission unit. To the vehicle side system,
The road surface according to any one of claims 8 to 11, wherein the control unit changes a threshold value of the road surface state determination based on the road surface data transmitted from the tire mount sensor during the learning mode. State estimation device.
The signal processing unit stores past information of the road surface data when traveling on a desired road surface, and it is detected that the vehicle is traveling on the desired road surface from the road surface data obtained during traveling. When detecting that the unevenness height of the groove of the tread (31) of the tire has changed based on the road surface data and the past information obtained during the traveling, the mode changes to the learning mode, Sending the road surface data to the vehicle body side system through the transmitter,
The road surface according to any one of claims 8 to 12, wherein the control unit changes a threshold value of the road surface state determination based on the road surface data transmitted from the tire mount sensor during the learning mode. State estimation device.
The signal processing unit includes a section extraction unit (13a) that extracts a grounding section in which a portion corresponding to an arrangement position of the vibration detection unit in the tread during one rotation of the tire is grounded, and the grounding A level calculation unit (13b) that calculates an integrated voltage value obtained by integrating the output voltage of the vibration detection unit as the level of the high-frequency component of the detection signal in the section, and the integrated voltage as the road surface data through the transmission unit; Send value,
The road surface state estimation device according to any one of claims 8 to 13, wherein the control unit changes a threshold value to be compared with the integrated voltage value as a threshold value for the road surface state determination.