JP2022165827A - Tire air pressure monitoring system - Google Patents

Abstract

To provide a tire air pressure monitoring system that can grasp a timing suitable for executing an adjustment of tire air pressure.SOLUTION: A tire air pressure monitoring system is applied to a vehicle 10 having a plurality of wheels 10a-10d including tires mounted on a vehicle body 11. The tire air pressure monitoring system comprises tire sensors 2 including air pressure detecting parts 21 that detect tire air pressure of the plurality of wheels 10a-10d, an on-vehicle machine 3 and a meter 5. The on-vehicle machine 3 creates a variation prediction model which predicts variations of tire air pressure at the present time and thereafter, and estimates the number of days required until the tire air pressure falls below a preset abnormal pressure value. The meter 5 notifies information for prompting the tire air pressure to be adjusted before the number of days estimated by the on-vehicle machine 3 elapses.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to tire pressure monitoring systems.

In order to drive the vehicle safely, some systems of this type alert the user when tire pressure falls below regulatory thresholds. Further, for example, in the alarm device described in Patent Document 1 below, a rapid decrease in tire air pressure is determined, and an alarm is issued when the tire is punctured.

JP 2014-159206 A

However, conventional tire pressure monitoring systems and warning devices issue warnings only when the tire pressure becomes inappropriate. . This leads to lower fuel consumption and deterioration of tire condition. Even if the tire pressure was displayed on the display inside the vehicle, many users would not be able to read the tire condition from the tire pressure value, and it would be difficult to know when to adjust the tire pressure. .

An object of the present disclosure is to provide a tire pressure monitoring system capable of grasping appropriate execution timing of tire pressure adjustment.

The invention according to claim 1,
A tire pressure monitoring system applied to a vehicle (10) in which a plurality of wheels (10a, 10b, 10c, 10d) including tires are attached to a vehicle body (11),
a tire sensor (2) including an air pressure detector (21) for detecting tire air pressure of a plurality of wheels;
A day estimating unit (331) for creating a predictive change model for predicting the amount of change in tire air pressure after the present, and estimating the number of days required for the tire air pressure to fall below a predetermined abnormal pressure value based on the predictive change model. When,
a notification unit (5) for notifying information for prompting adjustment of tire air pressure before the number of days estimated by the number of days estimation unit elapses.

According to this, the user or the like is notified of information for prompting adjustment of the tire air pressure before the tire air pressure becomes equal to or less than the abnormal pressure value. Therefore, it is possible for the user or the like to grasp the appropriate execution timing of the adjustment of the tire air pressure. This is effective in improving fuel efficiency and suppressing deterioration of tire conditions.

It should be noted that the reference numerals in parentheses attached to each component etc. indicate an example of the correspondence relationship between the component etc. and specific components etc. described in the embodiments described later.

1 is an overall configuration diagram of a tire pressure monitoring system according to an embodiment; FIG. 1 is a block configuration diagram of a tire sensor; FIG. 2 is a block configuration diagram of an in-vehicle device; FIG. FIG. 4 is an explanatory diagram for explaining changes in tire air pressure over time; It is an explanatory view for explaining a factor influencing tire air pressure. FIG. 5 is an explanatory diagram for explaining changes in tire air pressure due to differences in region and season; This is an explanation for explaining changes in maximum and minimum temperatures in a certain area. It is an explanatory view for explaining a temperature change model. FIG. 4 is an explanatory diagram for explaining a linear prediction model of changes in tire air pressure caused by leaks; FIG. 4 is an explanatory diagram for explaining the relationship between outside air temperature and tire pressure; It is an explanation for explaining a method of setting the leak coefficient in consideration of the outside air temperature. It is an explanation for explaining the leak change model. It is an explanatory view for explaining a prediction change model. 4 is a flowchart showing a flow of tire air pressure prediction processing executed by an in-vehicle device; It is an explanatory view for explaining a prediction result of tire air pressure.

An embodiment of the present disclosure will be described with reference to FIGS. 1-15. FIG. 1 is a diagram showing a tire pressure monitoring system (hereinafter referred to as TPMS) having a tire pressure detection function. Front, rear, left, and right shown in FIG. 1 indicate the front, rear, left, and right of the vehicle 10 . Further, hereinafter, when the four wheels 10a to 10d attached to the vehicle 10 are separately described, the four wheels 10a to 10d are referred to as the front left wheel FL, the front right wheel FR, the rear left wheel RL, and the rear right wheel RR. is sometimes written as

As shown in FIG. 1, the TPMS includes a plurality of tire sensors 2 and vehicle-mounted device 3 . The TPMS monitors the tire air pressure using each tire sensor 2 and the on-vehicle device 3, and notifies the user of the monitoring result via the notifying unit such as the meter 5 or the like. In addition, the TPMS uses information obtained by using the mobile communication device 6 to create a predicted change model ΔP(t) of the tire pressure from now on, and based on the predicted change model ΔP(t) The number of days required for the tire air pressure to drop below a predetermined abnormal pressure value _Pth is estimated.

The tire sensors 2 are attached to the respective wheels 10a to 10d, and detect the air pressure of the tires attached to the wheels 10a to 10d. do. The in-vehicle device 3 is attached to the vehicle body 11 side of the vehicle 10, receives the frame transmitted from the tire sensor 2, and performs various processing and calculations based on the information stored therein to determine the tire Perform air pressure detection.

As shown in FIG. 2, the tire sensor 2 includes an air pressure detection unit 21, an acceleration sensor 22, a first microcomputer 23, and a tire radio 24. Each unit is driven by power supplied from a battery (not shown). be done.

The air pressure detection unit 21 includes a pressure sensor 21a and a temperature sensor 21b, and outputs a detection signal corresponding to tire air pressure and a detection signal corresponding to temperature. The acceleration sensor 22 is used to detect the rotation angle of the tire sensor 2 and the travel speed (that is, vehicle speed) of the vehicle 10 . The acceleration sensor 22 is composed of, for example, a biaxial acceleration sensor capable of detecting radial acceleration and circumferential acceleration of each wheel 10a-10d.

The first microcomputer 23 constitutes a control section of the tire sensor 2, and includes a CPU, memories such as ROM and RAM, I/O, and the like. The first microcomputer 23 executes predetermined processing according to programs stored in the internal memory. The memory stores individual ID information including a unique tire ID for identifying each tire sensor 2 and a unique vehicle ID for identifying the own vehicle.

The first microcomputer 23, for example, receives the detection signals of the pressure sensor 21a and the temperature sensor 21b, processes them and processes them as necessary, and frames the information about the tire air pressure together with the ID information of each tire sensor 2. Store in

Further, the first microcomputer 23 monitors the detection signal of the acceleration sensor 22 and performs vehicle travel determination to determine the angle of each tire sensor 2 and whether the vehicle 10 is running. After creating the frame, the first microcomputer 23 transmits the frame from the tire wireless device 24 to the vehicle-mounted device 3 based on the result of vehicle travel determination. Hereinafter, the information about the tire air pressure is simply referred to as tire information. Specifically, the first microcomputer 23 repeatedly transmits frames at predetermined timings while the vehicle 10 is running.

The tire radio 24 includes a first transmission/reception circuit 241 and a first communication antenna 242 . The first transmission/reception circuit 241 is a communication circuit that bi-directionally communicates with the vehicle-mounted device 3 through the first communication antenna 242 . The first transmission/reception circuit 241 performs wireless communication based on a communication method such as BLE. BLE is an abbreviation for Bluetooth (registered trademark) Low Energy. Note that the first transmission/reception circuit 241 may perform wireless communication based on a communication method other than BLE.

The first communication antenna 242 is an antenna for two-way communication with the vehicle-mounted device 3 . The tire sensor 2 is provided with the tire wireless device 24 so that not only unidirectional communication from the tire sensor 2 to the vehicle-mounted device 3 but also two-way communication with the vehicle-mounted device 3 is possible.

The tire sensor 2 configured in this manner detects the tire air pressure and the internal temperature of the tire, and when the vehicle 10 is running, the tire sensor 2 performs frame transmission at the timing when the angle of the tire sensor 2 reaches a predetermined angle.

On the other hand, the in-vehicle device 3 is provided on the vehicle body 11 . As shown in FIG. 3, the vehicle-mounted device 3 includes a vehicle-mounted wireless device 31, a second microcomputer 33, and the like. The in-vehicle device 3 is connected to a meter 5, a mobile communication device 6, and the like through an in-vehicle LAN (Local Area Network) such as a CAN (Controller Area Network).

The vehicle-mounted wireless device 31 includes a second communication antenna 311 and a second transmission/reception circuit 312 . The second communication antenna 311 is an antenna for two-way communication with each tire sensor 2 . The second communication antenna 311 is used not only for receiving frames and the like sent from each tire sensor 2 but also for transmitting signals to each tire sensor 2 . The second communication antenna 311 may be an internal antenna arranged inside the main body of the vehicle-mounted device 3, or may be an external antenna extending a wire from the main body.

The second transmission/reception circuit 312 is a communication circuit that bi-directionally communicates with each tire sensor 2 through the second communication antenna 311 . The second transmission/reception circuit 312 performs wireless communication based on a communication method such as BLE. The second transmitting/receiving circuit 312 functions as an input section that inputs transmission frames from the respective tire sensors 2 received by the second communication antenna 311 and transmits the frames to the second microcomputer 33 . When the second transmission/reception circuit 312 receives the frame through the second communication antenna 311 , it transmits the received signal to the second microcomputer 33 .

The second microcomputer 33 constitutes a control section in the vehicle-mounted device 3, and includes a CPU, memories such as ROM and RAM, I/O, and the like. The second microcomputer 33 executes a tire air pressure detection process and a tire air pressure prediction process according to a program stored in an internal memory. The details of the tire air pressure detection process and the tire air pressure prediction process will be described later.

The meter 5 plays a role of displaying various information as a display unit provided in the vehicle compartment. The meter 5 displays various information when the power is turned on, specifically when an accessory (hereinafter referred to as ACC) switch or a start switch such as an ignition switch IG is turned on. The display by the meter 5 is basically performed when the power is turned on.

The meter 5 is arranged at a place that can be visually recognized by the driver, and is configured by, for example, a multi-information display installed in the instrument panel of the vehicle 10, a display of a navigation device, or the like. For example, when a signal indicating that the tire air pressure has decreased is sent from the vehicle-mounted device 3, the meter 5 specifies the corresponding wheel 10a to 10d and displays the tire air pressure decrease to notify the driver of the corresponding wheel. Notification of a decrease in tire pressure in 10a to 10d. In this embodiment, the meter 5 constitutes a "notifying section".

The mobile communication device 6 is a wireless communication unit for communicating with a communication destination outside the vehicle 10 . When the ignition switch IG is turned on, the mobile communication device 6 enters an active state and wirelessly connects with the wireless base station 61 connected to the communication network 62, whereby the service center 63 and the cloud connected to the communication network 62 are connected. communicate with server 64;

The service center 63 provides the on-vehicle device 3 with predicted values of the outside air temperature after the current time included in the weather forecast, etc. communicate.

The cloud server 64 is a server created in a cloud environment, and stores various kinds of information regarding past outside temperature fluctuations and the like. The in-vehicle device 3 can acquire various types of information stored in the cloud server 64 via the communication network 62 .

The TPMS configured in this way monitors the tire air pressure of each of the wheels 10a to 10d through tire air pressure detection processing and tire air pressure prediction processing. The tire air pressure detection process and the tire air pressure prediction process are periodically or irregularly executed by the vehicle-mounted device 3 of the TPMS.

In the tire pressure detection process, the tire pressures of the wheels 10a to 10d to which the tire sensors 2 are attached are detected. Specifically, the vehicle-mounted device 3 calculates the tire pressure conversion value at a predetermined temperature based on the ID information and tire information stored in the transmission frame from each tire sensor 2, thereby tire pressure detection. Then, an electric signal corresponding to the tire air pressure detection result is output to the meter 5 through an in-vehicle LAN such as CAN. For example, the vehicle-mounted device 3 outputs to the meter 5 a signal indicating the tire pressure of each of the wheels 10a-10d. The in-vehicle device 3 detects a decrease in tire air pressure by comparing the tire air pressure detection result with a predetermined abnormal pressure value Pth. As a result, the meter 5 is informed that the tire pressure of one of the four wheels 10a to 10d or one of the tires has decreased, and is displayed through the meter 5. FIG. In this manner, in the tire air pressure detection process, as shown in FIG. 4, an alarm is issued when the tire air pressure drops to the abnormal pressure value Pth.

However, if the warning is given after the tire air pressure has decreased to the abnormal pressure value Pth, the driver is likely to continue driving as long as there is no warning. This leads to lower fuel consumption and deterioration of tire condition.

Further, since the temperature of the tires rises when the vehicle 10 is driven, the temperature of the tires tends to be higher immediately after the driver gets off the vehicle than immediately before the driver gets on the vehicle. The tire pressure increases when the tire temperature is high, and decreases when the tire temperature is low. Therefore, the tire pressure tends to be lower immediately after the driver gets in the vehicle than immediately before the driver gets off the vehicle. In many cases, the tire air pressure drops to the abnormal pressure value Pth during the period from when the driver gets off the vehicle to when he/she gets on the vehicle the next day, and an alarm is issued.

In view of this, the TPMS of the present disclosure executes tire pressure prediction processing in the vehicle-mounted device 3 . The tire pressure prediction process creates a prediction change model for the tire pressure from now onwards, estimates the number of days the tire pressure will remain below the abnormal pressure value based on the prediction change model, and This is a process of notifying information for prompting adjustment of air pressure.

[Factors affecting tire pressure]
As shown in FIG. 5, factors affecting tire pressure include external factors and factors of the tire itself. External factors include, for example, the outside air temperature that varies depending on the season, tire temperature variations during running of the vehicle 10, load, and the like. In addition, the factors of the tire itself are caused by air leaks such as slow leaks. Defective air valves, etc. can be mentioned.

Thus, the external factors and the factors of the tire itself are fundamentally different and have a low correlation. For this reason, in order to accurately predict changes in tire pressure from now on, it is necessary to consider the amount of change in tire pressure caused by changes in outside temperature, which is an external factor, and the amount of change in tire pressure caused by air leaks, which is a factor in the tires themselves. It is desirable to estimate the amount separately.

[Amount of change in tire pressure due to change in outside temperature]
As mentioned above, tire pressure is affected by ambient temperature. The amount of change in tire pressure due to changes in outside temperature varies with different regions and seasons. For example, as shown in FIG. 6, regions with a high outside temperature tend to have a larger decrease in tire air pressure than regions with a low outside temperature. In addition, there is a tendency that the amount of decrease in tire air pressure is greater in seasons when the outside temperature is high than in seasons when the outside temperature is low. In addition, as shown in FIG. 7, for example, the outside air temperature changes greatly even during the day and also changes greatly depending on the season.

For this reason, it is difficult to estimate the amount of change in tire air pressure caused by changes in the outside air temperature only from the information stored in advance in the vehicle-mounted device 3 . Based on the weather forecast for the area where the vehicle 10 is located and past changes in the outside temperature, the outside temperature after the present is predicted, and based on the predicted outside temperature, the amount of change in the tire pressure caused by the change in the outside temperature is estimated. is desirable.

Therefore, the in-vehicle device 3 estimates the amount of change in the tire air pressure caused by the change in the outside air temperature using, for example, the temperature change model ΔP _Tf (t) represented by the formula M1 in FIG. "s" in the formula M1 of FIG. 8 is the air pressure variation rate [kPa/° C.] due to temperature, and is set to a value of about 1.5, for example. “T(t)” is the predicted value of the outside air temperature on the tth day from the present. “T ₀ ” is, for example, the outside air temperature on the day when the tire pressure is adjusted.

[Amount of change in tire pressure caused by air leak]
On the other hand, as shown in FIG. 9, tire air pressure decreases over time due to air leaks. If the amount of decrease in tire air pressure per day is constant, the amount of change in tire air pressure due to air leaks can be easily estimated by a linear prediction model ΔP _N (t) given by Equation M2 below.

ΔP _N (t)=k ₀ t+q (M2)
"t" in the above formula M2 is the number of days from the present to the prediction date. "k" is a leak coefficient corresponding to the amount of tire air pressure decrease (leak amount) per day. Also, "q" is an intercept coefficient corresponding to the tire pressure on the day of pressure adjustment. This linear prediction model ΔP _N (t) can be obtained by regression analysis, for example.

However, the amount of leakage per day is not constant and changes with changes in the outside temperature. FIG. 10 shows the relationship between changes in tire pressure over a year, the leak coefficient k corresponding to the leak amount for each month, and the mean value _Tmean of the outside air temperature for each month. As shown in FIG. 10, the monthly leak coefficient k varies in the same manner as the mean value _Tmean of the outside air temperature.

Considering this fact, it is desirable to set the leak coefficient k every month according to the outside temperature. As shown in FIG. 11, the leak coefficient ki in the i-th month from the present is the current leak coefficient k ₀ , the mean value of the outside air temperature for the most recent month _{Tmean_0} , the mean value of the outside temperature in the i-th month _{Tmean_i} , It can be obtained based on a predetermined coefficient r. The mean value _{Tmean_i} of the i-th month outside temperature can be estimated based on the predicted value of the outside temperature after the present included in the weather forecast.

Then, the amount of change in the tire air pressure due to the air leak on the tth day ( _d months, tm days later) from the present is estimated with high accuracy based on the leak change model ΔP _Nf (t) shown by the formula M3 in FIG. 12 . can be done. Note that " _tn " indicates the current number of days.

Here, ΔP _N , which is one item of the leak change model ΔP _Nf (t), is the amount of change in tire air pressure due to natural leak from the previous pressure adjustment to the present. ΔP _N is obtained by removing the amount of change in tire air pressure caused by the change in outside air temperature from the amount of change in tire air pressure from the previous pressure adjustment to the present. The second item of the leak change model ΔP _Nf (t) is the amount of change in tire pressure due to air leak after d months (the number of days obtained by multiplying "d" by "30") from the present. Furthermore, the third item of the leak change model ΔP _Nf (t) is the amount of change in the tire pressure caused by the air leak after the fractional number of days tm has elapsed. In the leak change model ΔP _Nf (t), a value (=30ki) obtained by multiplying the leak coefficient ki of the i-th month by "30" is calculated as the amount of change in the tire pressure of the i-th month.

[Prediction change model of tire pressure]
The TPMS uses the temperature change model ΔP _Tf (t) and the leak change model ΔP _Nf (t) to create a prediction change model ΔP(t) that predicts the amount of change in tire air pressure from now on. The predictive change model ΔP(t) is the sum of the temperature change model ΔP _Tf (t) and the leak change model ΔP _Nf (t), as shown in formula M4 in FIG.

[Prediction processing of tire air pressure]
Next, the flow of tire air pressure prediction processing executed by the in-vehicle device 3 will be described with reference to the flowchart of FIG. 14 . The tire air pressure prediction process shown in FIG. 14 is started, for example, when the tire air pressure is adjusted.

As shown in FIG. 14, in step S100, the in-vehicle device 3 acquires the tire air pressure and the outside air temperature on the tire pressure adjustment day via the tire sensor 2 and other ECUs, and stores the acquired tire air pressure and the outside air temperature. They are stored in the memory as initial values P ₀ and T ₀ . In addition, the vehicle-mounted device 3 acquires the time _t0 when the tire pressure is adjusted via another ECU.

Subsequently, in step S110, the in-vehicle device 3 determines whether or not the elapsed time since the tire pressure adjustment or the elapsed time since the previous tire pressure prediction is 24 hours or more. As a result, if the elapsed time is 24 hours or more, the vehicle-mounted device 3 proceeds to step S120 and newly acquires the tire air pressure Pt and the outside air temperature Tt via the tire sensor 2 or another ECU.

Subsequently, in step S130, the in-vehicle device 3 calculates the amount of change in the tire air pressure from when the tire air pressure was adjusted and the amount of change _ΔPT in the tire air pressure caused by the change in the outside air temperature. Then, in step S140, the in-vehicle device 3 calculates a leak amount ΔP _N (=ΔP−ΔP _T ), which is the amount of change in tire air pressure caused by the air leak.

Subsequently, in step S150, the in-vehicle device 3 creates a linear prediction model ΔP _N (t) of the amount of change in tire air pressure due to air leaks based on the leak amount ΔP _N for the most recent month. The linear prediction model ΔP _N (t) can be created, for example, by regression analysis using time t as an explanatory variable and the amount of change in tire pressure as an objective variable.

Subsequently, in step S160, the in-vehicle device 3 calculates the mean value _{Tmean_0} of the outside temperature of the area where the vehicle 10 is used in the most recent month, Estimate _{mean_i} . The average value _{Tmean_0} is calculated based on the data of the outside air temperature Tt stored in the memory of the vehicle-mounted device 3, for example. Also, the mean value T _{mean_i} is estimated based on the predicted value of the outside air temperature after the current time included in the weather forecast or the like obtained from the service center 63 . The mean values _{Tmean_0} and _{Tmean_i} of the outside air temperature may be calculated based on the outside air temperature data stored in the cloud server 64, for example.

Subsequently, in step S170, the vehicle-mounted device 3 calculates the leak coefficient ki for the i-th month after the present. As shown in FIG. 11, the i-th month leak coefficient ki is the current leak coefficient k ₀ , the most recent one-month average outside temperature T mean — 0 , the i-th month average T _mean — _i , and a predetermined It is obtained based on the coefficient r.

Subsequently, in step S180, the in-vehicle device 3 creates a leak change model ΔP _Nf (t) that predicts the amount of change in tire air pressure due to air leak on the tth day from the present ( _d months, tm days later). . This leak change model ΔP _Nf (t) is the same as the formula M3 shown in FIG.

Subsequently, in step S190, the vehicle-mounted device ₃ calculates an estimated warning date t3, which is the number of days required for the tire air pressure to become the abnormal pressure value _Pth or less, using the predictive change model ΔP(t). The estimated warning date _t3 can be calculated by solving the following inequality M5 and formula M6.

P ₀ −ΔP(t ₃ )≦P _th (M5)
ΔP(t ₃ )=ΔP _Tf (t ₃ )+ΔP _Nf (t ₃ ) (M6)
Note that the temperature change model ΔP _Tf (t ₃ ) in Equation M6 is a model shown in Equation M7 below using the predicted value T _MIN (t ₃ ) of the lowest outside temperature (minimum temperature) in a day.

ΔP _Tf (t ₃ )=s(T _MIN (t ₃ )−T ₀ ) (M7)
Subsequently, in step S200, the vehicle-mounted device ₃ determines whether or not the estimated warning date t3 is less than 30 days. As a result, if the estimated warning date t3 is not less than 30 days, the vehicle-mounted device ₃ returns to step S110. On the other hand, if the estimated warning date t3 is less than ₃₀ days, in step S210, the vehicle-mounted device 3 transmits information prompting adjustment of the tire air pressure to the meter 5 side to inform the user of the information. Return to S110.

Here, a predictive change model ΔP(t) for predicting the amount of change in tire air pressure after the present time is created in the in-vehicle device 3, and based on the predictive change model ΔP(t), the tire air pressure is abnormal pressure value P _th The number of days estimating unit 331 is configured to estimate the number of days required to achieve the following. Further, in the in-vehicle device 3, the configuration for predicting the outside air temperature after the present constitutes an outside air temperature prediction unit 332. FIG.

The vehicle-mounted device 3 of the TPMS described above creates a predictive change model ΔP(t) that predicts the amount of change in tire air pressure from the present onward, and based on the predictive change model ΔP(t), the tire air pressure is an abnormal pressure value. Estimate the number of days required to reach P _th or less. Then, before the number of days elapses, the meter 5 notifies information for prompting adjustment of the tire air pressure. According to this, before the tire air pressure becomes the abnormal pressure value _Pth or less, the user or the like is notified of information for prompting adjustment of the tire air pressure. Therefore, it is possible for the user or the like to grasp the appropriate execution timing of the adjustment of the tire air pressure. This is effective in improving fuel efficiency and suppressing deterioration of tire conditions.

(1) Predictive change model ΔP(t) includes temperature change model ΔP _Tf (t) for estimating the amount of change in tire pressure caused by changes in outside air temperature, and ΔP Tf (t) for estimating the amount of change in tire pressure caused by air leaks. and a leak change model ΔP _Nf (t). Then, the in-vehicle device 3 calculates the amount of change in tire air pressure estimated by the temperature change model ΔP _Tf (t) and the amount of change in tire air pressure estimated by the leak change model ΔP _Nf (t) based on Estimate the number of days. Tire pressure changes due to the influence of outside temperature and air leaks. Therefore, by using the predictive change model ΔP(t) that predicts the tire pressure after the current time in consideration of the outside air temperature and air leak, it is possible to accurately estimate the timing when the tire pressure drops below the abnormal pressure value _Pth . can.

(2) The leak change model ΔP _Nf (t) corrects the amount of change in the tire pressure caused by the air leak in a predetermined period according to the predicted value of the outside air temperature for each predetermined period, and integrates the values obtained by this correction. value is used to estimate the amount of change in tire pressure caused by air leaks. The amount of change in tire pressure caused by an air leak is affected by the outside air temperature. Therefore, by estimating the amount of change in tire air pressure caused by leakage in consideration of the outside air temperature, it is possible to improve the accuracy of estimating the amount of change in tire air pressure from now on.

(3) The temperature change model ΔP _Tf (t) estimates the amount of change in tire pressure due to changes in outside air temperature using the lowest outside air temperature of the day in the predicted outside air temperature. Considering the safety of the vehicle 10, it is desirable to estimate the shortest number of days during which the tire pressure is equal to or less than the abnormal pressure value _Pth . Tire pressure decreases as the outside temperature decreases and increases as the outside temperature rises. The amount of change in tire air pressure caused by outside air temperature increases as the outside air temperature decreases. Therefore, for example, when estimating the amount of change in tire air pressure due to a change in the outside air temperature in a state where the outside air temperature is high, the amount of change in tire air pressure is likely to be small, and the tire air pressure is less than or equal to the predetermined abnormal pressure value _Pth . The number of days required to achieve this tends to be long. Further, when estimating the amount of change in tire air pressure due to changes in the outside air temperature when the outside air temperature is low, the amount of change in tire air pressure tends to increase, and the tire air pressure does not fall below the predetermined abnormal pressure value _Pth . The number of days required for Therefore, in order to improve the safety of the vehicle 10, it is desirable to use the lowest outside air temperature in a day to estimate the amount of change in tire pressure from now on, as indicated by the black diamond points in FIG. According to this, the tire air pressure warning is performed early, and the safety of the vehicle 10 is improved.

(Other embodiments)
Although representative embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and can be modified in various ways, for example, as follows.

As in the above-described embodiment, the leak change model ΔP _Nf (t) calculates the amount of change in tire pressure caused by an air leak based on the integrated value of the amount of change in tire pressure corrected according to the predicted value of the outside air temperature. Although it is desirable to estimate as, it is not limited to this. The leak change model ΔP _Nf (t) may be, for example, estimated as a change in tire pressure caused by air leak based on the linear prediction model ΔP _N (t). Further, the leak change model ΔP _Nf (t) may be estimated as a change in tire pressure caused by air leak, for example, based on a non-linear prediction model.

As in the above embodiment, the temperature change model ΔP _Tf (t) is used to estimate the amount of change in tire pressure due to changes in outside temperature using the lowest outside temperature of the day in the forecast of outside temperature. Although it is desirable to be, it is not limited to this. Even if the temperature change model ΔP _Tf (t) is designed to estimate the amount of change in tire pressure due to changes in the outside temperature using the average outside temperature and the highest outside temperature in the outside temperature prediction values, good.

As in the above embodiment, the predictive change model ΔP(t) preferably includes the temperature change model ΔP _Tf (t) and the leak change model ΔP _Nf (t), but is not limited to this.
The predictive change model ΔP(t) may estimate the amount of change in tire air pressure based on one of the temperature change model ΔP _Tf (t) and the leak change model ΔP _Nf (t).

The tire sensor 2 and the vehicle-mounted device 3 of the above-described embodiment are configured to be able to communicate bidirectionally based on the BLE communication method, but are configured to be able to communicate bidirectionally based on a communication method other than BLE. may

In the above-described embodiment, the TPMS of the present disclosure is applied to the vehicle 10 having four wheels 10a to 10d. can be applied.

In the above-described embodiments, it goes without saying that the elements that make up the embodiments are not necessarily essential unless explicitly stated as essential or clearly considered essential in principle.

In the above-described embodiments, when numerical values such as the number, numerical value, amount, range, etc. of the constituent elements of the embodiment are mentioned, when it is explicitly stated that they are essential, and in principle they are clearly limited to a specific number It is not limited to that particular number, unless otherwise specified.

In the above-described embodiments, when referring to the shape, positional relationship, etc. of components, etc., the shape, positional relationship, etc., unless otherwise specified or limited in principle to a specific shape, positional relationship, etc. etc. is not limited.

The controller and techniques of the present disclosure are implemented on a dedicated computer provided by configuring a processor and memory programmed to perform one or more functions embodied by the computer program. good too. The controller and techniques of the present disclosure may be implemented in a dedicated computer provided by configuring the processor with one or more dedicated hardware logic circuits. The control unit and technique of the present disclosure is a combination of a processor and memory programmed to perform one or more functions and a processor configured by one or more hardware logic circuits. It may be implemented on one or more dedicated computers. The computer program may also be stored as computer-executable instructions on a computer-readable non-transitional tangible storage medium.

10 vehicle 10a to 10d wheel 2 tire sensor 21 air pressure detection unit 331 number of days estimation unit 4 meter (notification unit)

Claims (4)

A tire pressure monitoring system applied to a vehicle (10) in which a plurality of wheels (10a, 10b, 10c, 10d) including tires are attached to a vehicle body (11),
a tire sensor (2) including an air pressure detection unit (21) for detecting tire air pressure of the plurality of wheels;
A day estimating unit for creating a predictive change model for predicting the amount of change in the tire air pressure after the present, and estimating the number of days required for the tire air pressure to become equal to or less than a predetermined abnormal pressure value based on the predictive change model. (331) and
a notification unit (5) for notifying information for prompting adjustment of the tire air pressure before the number of days estimated by the number of days estimation unit elapses;
tire pressure monitoring system. Equipped with an outside temperature prediction unit (332) that predicts the outside temperature after the present,
The predictive change model includes a temperature change model for estimating the amount of change in the tire pressure caused by changes in the outside temperature, and a leak change model for estimating the amount of change in the tire pressure caused by an air leak,
The number of days estimating unit estimates the number of days based on a sum of the amount of change in the tire air pressure estimated by the temperature change model and the amount of change in the tire air pressure estimated by the leak change model. Item 1. The tire pressure monitoring system according to item 1. The leak change model corrects the amount of change in the tire pressure caused by the air leak in a predetermined period according to the outside air temperature predicted by the outside air temperature prediction unit for each predetermined period. 3. The tire pressure monitoring system according to claim 2, wherein the amount of change in the tire pressure caused by the air leak is estimated using an integrated value of values. wherein the temperature change model estimates the amount of change in the tire pressure caused by the change in the outside temperature using the lowest outside temperature in a day among the outside temperatures predicted by the outside temperature prediction unit. 4. A tire pressure monitoring system according to Item 2 or 3.

Images