JP5629631B2 - Tire pressure monitoring system - Google Patents

Description

  The present invention relates to a tire pressure monitoring system.

  Conventionally, as described in Patent Document 1, for example, a tire pressure monitoring system for monitoring the tire pressure of a vehicle is known. The system includes a sensor unit with a wireless communication function provided in each tire of a vehicle. This sensor unit detects the temperature and air pressure of the tire and transmits a radio signal. This radio signal includes temperature information and air pressure information to be detected, and identification information unique to itself. This radio signal is received by a monitoring device provided in the main body of the vehicle. The device is connected to an initiator that transmits a transmission request signal for requesting each sensor unit to transmit a radio signal. Thus, the apparatus can receive a radio signal after designating the tire unit mounting position (left front, left rear, right front, right rear) of the sensor unit. And the said apparatus monitors the presence or absence of abnormality of the air pressure of each tire based on the temperature information and air pressure information contained in the received radio signal. When it is determined that any one of the tires has an abnormal air pressure, the device warns that through a display device in the passenger compartment. The driver can recognize which of the tires is abnormal through the warning. The monitoring device is connected to a communication unit capable of wireless communication with a portable device carried by the user. The apparatus transmits a wireless signal including temperature information and air pressure information associated with the tire position to the portable device through the communication unit. The portable device is provided with an indicator that can display information of the received radio signal. When the portable device receives the wireless signal, the portable device displays the temperature information and the air pressure information included in the signal in a manner associated with the tire position. By visually recognizing this display, the user of the vehicle can consider an appropriate air pressure based on the temperature information and air pressure information displayed on the indicator.

JP 2010-191540 A

In the system of Patent Document 1, an appropriate air pressure must be examined by the user himself. In addition, normally, the vehicle has a tire pressure adjustment value (target adjustment value) that is necessary for driving safely. This target adjustment value indicates that the tire is sufficiently cooled. , that is defined on the assumption that is equal to the tire temperature and the outside air temperature. However, it is assumed that many users do not understand this precondition. Further, when adjusting the tire air pressure, it is not always possible to make the tire cool enough. Generally, it is assumed that there are few users who have equipment capable of adjusting tire pressure. Such users often adjust the tire pressure using equipment installed at a gas station or the like. At that time, it is assumed that the user drives the vehicle and moves to the gas station. In this case, the tire temperature increases as the vehicle travels. In such a situation, it is difficult for a user who understands the preconditions for the target adjustment value to study the air pressure suitable for the tire temperature.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a tire pressure monitoring system capable of easily adjusting a tire pressure to an appropriate value.

In order to solve the above-mentioned problem, the invention according to claim 1 periodically transmits a radio signal provided in each tire of the vehicle and including temperature information, air pressure information, and identification information unique to itself. A sensor unit, a receiver provided in the vehicle and receiving the radio signal transmitted from the sensor unit, and the temperature information included in the radio signal also provided in the vehicle and received by the receiver use, to calculate the actual reference value is pneumatically appropriate to the temperature of the tire, and a control means for calculating the threshold value serving as the presence or absence of acceptance criteria of decrease in tire air pressure using the actual reference value The control means displays the actual reference value through a display means provided in a vehicle, and further determines whether or not the air pressure information is below the threshold value and falls below In pressure monitoring system in case of notification via the notification means to that effect, the control unit displays on the display means the highest value among the lowest value and the actual reference values of all tires of the air pressure information of all the tires This is the gist.

Usually, the air pressure displayed on the vehicle is the air pressure required when the tire is sufficiently cooled. It is assumed that many users do not have an adjustment device for adjusting the tire pressure of the vehicle. Such a user adjusts the air pressure at a gas station or the like where an adjusting device is installed. In this case, the user travels the vehicle and moves to a gas station or the like. However, with this movement, the tire warms up. When the tire pressure in the warmed state is adjusted with the air pressure displayed on the vehicle, the adjusted air pressure is lower than the air pressure displayed on the vehicle when the tire cools down. If it falls below, there is an effect such as a reduction in fuel consumption. In that respect, according to the configuration, if the air pressure is adjusted in accordance with the actual reference value displayed on the display means, the air pressure adjustment suitable for the actual tire temperature can be performed. For this reason, even when a tire gets cold, it is suppressed that it falls below the air pressure displayed on the vehicle. That is, the tire pressure can be easily adjusted to an appropriate value.
In addition, when the lowest value of the air pressure information of all tires and the highest value of the actual reference values of all tires are displayed on the display means, the displayed air pressure information is lower than the displayed actual reference value. In addition, the user can be prompted to adjust the tire air pressure. If the tire air pressure is adjusted to the actual reference value displayed on the display means, even if the tire cools, it is maintained at an appropriate air pressure.

The invention described in claim 2, in a tire pressure monitoring system according to claim 1, wherein the vehicle is provided with an outside air temperature sensor for measuring the outside air temperature, said control means is pre-determined through Kigaiki temperature sensor The gist is to calculate the actual reference value with the outside air temperature as the cold temperature of the tire .

The target adjustment value of the air pressure set for the tire is determined on the assumption that the air pressure is adjusted at a cold temperature, which is a temperature at which the tire is sufficiently cooled. According to this configuration, it is possible to measure the outside air temperature, which is the temperature when the tire is sufficiently cooled , by the outside air temperature sensor . Therefore, for example, compared with the case of calculating the actual reference value using the lowest tire temperature of the tire temperature mounted on the vehicle or the lowest tire temperature in a certain period in the past as the cold temperature, etc. The control means can calculate the actual reference value more accurately. That is, if the tire air pressure is adjusted with the actual reference value calculated based on the outside air temperature, the vehicle can be driven with a tire having a more appropriate air pressure value.

The invention according to claim 3 is the tire pressure monitoring system according to claim 1 or 2, wherein the display means is a display in a meter of a vehicle.
According to this configuration, the actual reference value can be displayed on the in-meter display that is easily visible to the driver of the vehicle. Thereby, it is easy for the driver to confirm the actual reference value, and it is not necessary to provide a separate display device in the vehicle.

  According to a fourth aspect of the present invention, in the tire pressure monitoring system according to any one of the first to third aspects, the vehicle includes a replenishment detection unit that detects a state in which fuel is replenished, and the control. The gist is to display an actual reference value on the display means when it is determined that the fuel is replenished via the replenishment detection unit.

  In many cases, an adjusting device capable of adjusting the air pressure is installed in a place where fuel is supplied, for example, a gas station. According to this configuration, the actual reference value is displayed on the display device when the vehicle is refueling at a gas station or the like. For this reason, the user can visually recognize the actual reference value without performing a special operation. Then, the tire air pressure can be adjusted according to the actual reference value.

  The present invention can provide a tire pressure monitoring system that can easily adjust the tire pressure to an appropriate value.

The block diagram which shows schematic structure of the tire pressure monitoring system in this embodiment. The list figure which shows the structure of the table data memorize | stored in the monitoring apparatus on the vehicle side. The relationship figure which shows the relationship between tire pressure and tire temperature.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. In this example, a so-called direct type (valve type) system in which a sensor unit provided integrally with an air valve is built in a tire, and tire pressure information directly detected by the sensor unit is wirelessly transmitted to the vehicle body side. Is adopted.

<System overview>
First, an overview of the tire pressure monitoring system will be described. As shown in FIG. 1, the system 11 includes four sensor units 14 provided on four tires 13 of the vehicle 12 and a monitoring device 16 provided on a vehicle body 15 of the vehicle 12. Each sensor unit 14 detects the temperature and air pressure of the tire, and transmits a radio signal including the detected temperature information and air pressure information and identification information (ID code) unique to itself at a predetermined period (for example, 15 seconds). Send. The radio signal from each sensor unit 14 is received by the monitoring device 16. Based on the identification information included in the received wireless signal, the monitoring device 16 determines whether the pneumatic information included in the wireless signal is one of its four tires 13. And the monitoring apparatus 16 monitors the air pressure of the four tires 13 based on each air pressure information. If an abnormality is detected in the pressure of any of the tires, an abnormality occurs in any of the tires 13 through a display device 17 provided in an instrument panel or the like that is visible to the driver in the passenger compartment. Warn you. Further, the monitoring device 16 calculates the optimum air pressure corresponding to the temperature based on the temperature information included in the radio signal. Then, for example, the calculated air pressure is displayed on the in-meter display 35 as display means for displaying the travel distance of the vehicle.

<Sensor unit>
The sensor unit 14 is integrally provided at the inner end of an air valve (not shown) of the tire 13. As shown in the enlarged upper part of FIG. 1, the sensor unit 14 includes a temperature sensor 21, an air pressure sensor 22, a transmitter 23, and a control circuit 24.

  The temperature sensor 21 detects the air temperature (tire temperature) inside the tire 13 and inputs the detection result to the control circuit 24. The air pressure sensor 22 measures the air pressure inside the tire 13 and inputs the measurement result to the control circuit 24. The control circuit 24 comprehensively controls each part of the sensor unit 14. The storage device 25 of the control circuit 24 stores various control programs and identification information (ID code) unique to itself. The control circuit 24 generates an electrical signal including identification information unique to itself, temperature information acquired through the temperature sensor 21, and air pressure information acquired through the air pressure sensor 22, and transmits the electrical signal at a predetermined control cycle. 23 is transmitted as a radio signal. The transmitter 23 modulates the electrical signal generated in the control circuit 24 and wirelessly transmits the modulated electrical signal.

<Monitoring device>
Next, the monitoring device 16 will be described in detail. As shown in FIG. 1, the monitoring device 16 includes a receiver 31, a control device 32 as control means, an outside air temperature sensor 36, and a travel distance sensor 37. The receiver 31 receives a radio signal from each sensor unit 14. The outside air temperature sensor 36 measures the outside air temperature. The travel distance sensor 37 measures the travel distance of the vehicle. The control device 32 performs overall control of the system. The control device 32 monitors the state of each tire 13 based on the outside air temperature measured through the outside air temperature sensor 36 and the temperature information and air pressure information included in the wireless signal received through the receiver 31. That is, the table data 34 shown in FIG. 2 is stored in the storage device 33 of the control device 32. The table data 34 is information indicating the relationship between the identification information ID1 to ID4 for the number of sensor units 14 and the initial value (reference value) P0 of the air pressure of each tire 13. The initial value is a value indicating an appropriate air pressure (cold air pressure) in a state where the attached tire 13 is sufficiently cooled. In this example, the proper air pressure of each tire 13 is the same. The registration of the identification information and the initial value of the air pressure is performed in a state where the tire air pressure is known to be appropriate (normal), such as when the vehicle is shipped or the tire 13 is replaced. Note that the state where the tire is cooled sufficiently, is that the state and the tire temperature and the outside air temperature is equal. The storage device 33 stores an ideal gas equation of state derived from Boyle-Charles' law. The state equation is represented by the following equation (A). However, P is pressure (air pressure), V is volume, n is the amount of substance, R is a gas constant, and T is temperature (absolute temperature). From this relational expression and the target adjustment value (initial value) of the tire pressure, the control device 32 calculates an actual reference value that is the optimum air pressure for the tire temperature. More specifically, the actual reference value, a target adjustment value of tire pressure at high tire temperature than the outside air temperature.

PV = nRT (A)
Here, the actual reference value when the tire temperature is T3 (T2 <T3) when the outside air temperature is T1, T2 (T1 <T2) as shown in FIG. 3 will be described. The air pressure required for each tire is the reference value P0 when the outside air temperature is T1 or T2. When equation (A) is solved for P, the following equation (B) is obtained.

P = n · R / V · T (B)
Here, since the gas constant R and the volume V are constant, when R / V is replaced with the constant A, the equation (B) can be expressed as the following equation (C).

P = nAT (C)
That is, the tire air pressure P is proportional to the gaseous substance amount n and the temperature T. From this equation (C), when the tire is filled with gas such that the tire is sufficiently cooled and the outside air temperature is T1 so that the tire air pressure becomes the reference value P0, the amount of substance of the gas filled in the tire is n1. On the other hand, when the tire is filled with gas such that the tire is sufficiently cooled and the outside air temperature is T2 so that the tire air pressure becomes the reference value P0, the amount of the gas filled in the tire is n2. In addition, the relationship of the following formula | equation (D) is materialized between substance amount n1, n2.
n1 × T1 = n2 × T2 (D)
In this way, even when the tire is filled with air so that the tire pressure is the same reference value P0 when the tire is sufficiently cooled, the amount of gas filled in the tire varies depending on the outside air temperature. . Precisely, when the tire is filled with air in a state where the outside air temperature is high, the amount of gas substance filled in the tire is smaller than when the tire is filled with air while the outside air temperature is low. Since the tire is a closed space, there is no change in the amount of the gaseous substance filled in the tire due to a change in the tire temperature. Accordingly, as shown in FIG. 3, the actual reference value when the tire is filled with air in the state where the outside air temperature, which is the temperature when the tire is sufficiently cooled, is T1, and the actual tire temperature is T3. Is P1, and the actual reference value for filling the tire with air in a state where the outside air temperature is T2 and the actual tire temperature is T3 is P2. In this way, when the outside air temperature, which is the temperature when the tire is sufficiently cooled, is different , the actual reference value is different even at the same tire temperature.

  The control device 32 compares the identification information included in the wireless signal received through the receiver 31 with the identification information stored in its own storage device 33, so that the air pressure information included in the wireless signal is converted into the tire 13 of the own vehicle. To determine if it is. Moreover, the control apparatus 32 determines the presence or absence of abnormality of the air pressure of each tire 13 based on the said air pressure information. That is, when calculating the previous actual reference value, the control device 32 calculates an air pressure determination threshold value that serves as a determination criterion for determining whether the tire air pressure is normal or abnormal based on the actual reference value, and stores this in the storage device 33. To do. In this example, the air pressure determination threshold is 80% of the actual reference value. Then, the control device 32 determines whether or not the tire air pressure is normal by comparing the air pressure information included in the received radio signal with the air pressure determination threshold value stored in the storage device 33. When an abnormality is detected in the air pressure of any one of the tires 13, the control device 32 generates a display control signal to warn to that effect. The display device 17 displays a warning that an abnormality has occurred in any of the tires according to the display control signal generated by the control device 32.

  Further, the control device 32 displays the travel distance of the vehicle measured through the travel distance sensor 37, the received actual air pressure value, and the calculated actual reference value on the in-meter display 35. The actual air pressure value displayed on the in-meter display 35 indicates the lowest value among the air pressure values of the four tires 13. This is because it is easy for the user to recognize this when the air pressure decreases. Similarly, the actual reference value displayed on the in-meter display 35 indicates the highest value among the actual reference values of the four tires 13. This is because if the user adjusts the air pressure in accordance with the highest actual reference value, the air pressure exceeding the actual reference value can be adjusted in all four tires.

  The display content of the in-meter display 35 is switched by operating a trip switch 38 that protrudes in the vicinity thereof, in this example, on the right side of the in-meter display 35. In this example, switching is performed in the order of travel distance, actual air pressure value, and actual reference value.

  Furthermore, the control device 32 includes a determination unit 40 that determines whether or not fuel has been replenished based on a value indicated by a fuel gauge 39 that is part of the meter. For example, when the driving source for driving the vehicle is an engine (internal combustion engine), the determination unit 40 determines that the fuel has been replenished when the gasoline as the fuel has increased. When the determination unit 40 determines that the fuel has been replenished, the control device 32 switches the display on the in-meter display 35 to the previous actual reference value display.

<In-meter indicator display process>
In the tire pressure monitoring system 11 configured as described above, each sensor unit 14 detects the temperature and air pressure of the tire on which the sensor unit 14 is mounted, and also detects the detected temperature information, air pressure information, and its own. A radio signal including identification information (ID code) is transmitted at a predetermined cycle (here, 15 seconds). The radio signal is received by the receiver 31.

  The control device 32 compares the identification information included in the radio signal received by the receiver 31 with the table data 34 to determine whether the received radio signal corresponds to the tire 13 of the host vehicle. Next, the control device 32 calculates an actual reference value and an air pressure determination threshold value for each tire from the temperature information of each tire 13. Then, the actual tire air pressure is compared with the air pressure determination threshold value for each tire. If any of the tire air pressures falls below the air pressure determination threshold value, the control device 32 notifies the fact through the display device 17 as shown in FIG.

  Further, the control device 32 selects the tire pressure to be displayed on the in-meter display 35 from the four tire pressures. The tire pressure selected here indicates the lowest value of the four tire pressures. Similarly, the control device 32 selects an actual reference value to be displayed on the in-meter display 35 from the four actual reference values. The tire pressure selected here indicates the highest value among the four actual reference values.

  The control device 32 displays the selected tire pressure, the actual reference value, and the travel distance of the vehicle acquired through the travel distance sensor 37 on the in-meter display 35 according to the operation of the trip switch 38. For this reason, the user can confirm the tire pressure indicating the lowest value and the actual reference value indicating the highest value by switching the display of the in-meter display 35 through the operation of the trip switch 38. When the user who has visually recognized the actual reference value adjusts the air pressure of each tire 13 according to the actual reference value, the proper air pressure can be maintained even when the tire is cooled. This is because the actual reference value is determined based on the target air pressure of the outside air temperature, which is the temperature when the tire is cold.

  Further, when the determination unit 40 determines that the fuel has been replenished, the control device 32 switches the display on the in-meter display 35 to the display of the actual reference value. With this configuration, the user can easily recognize the actual reference value when fuel is supplied at the gas station. Normally, an adjustment device capable of adjusting the tire air pressure is installed in the gas station, and thus the user can adjust the air pressure of each tire 13 to an appropriate value using the adjustment device.

As described above in detail, according to the present embodiment, the following effects can be obtained.
(1) The actual reference value corresponding to the tire temperature is displayed on the display 35 in the meter. The user can know the actual reference value at which the air pressure is maintained at an appropriate value even when the tire temperature is lowered through visual recognition of the in-meter display 35, so that the air pressure can be easily adjusted.

  (2) The outside temperature sensor 36 is provided in the monitoring device 16. Thereby, it is possible to measure the outside air temperature, which is the temperature when the tire is sufficiently cooled. Therefore, the actual reference value calculated based on this temperature is an accurate value.

  (3) The actual reference value is displayed on the display 35 in the meter. Thereby, it is easy for the driver to confirm the actual reference value, and it is not necessary to separately provide a display device in the vehicle 12.

  (4) A determination unit 40 for determining supply of fuel (gasoline) is provided. And when it is judged that the gasoline is replenished through the determination part 40, the control apparatus 32 changed the display of the display 35 in a meter to the display of the previous actual reference value. With this configuration, the user can easily recognize the actual reference value when fuel is supplied at the gas station. Usually, since an adjustment device capable of adjusting the tire air pressure is installed in the gas station, the user can adjust the air pressure of each tire 13 to an appropriate value.

In addition, you may change the said embodiment as follows.
In the above embodiment, the actual reference value is displayed on the in-meter display 35, but other display methods may be used. For example, a navigation display or an indicator for displaying the outside air temperature may be used. Even in this way, the user can recognize the actual reference value. Then, the tire pressure can be adjusted to the actual reference value.

  -In the said embodiment, the outside temperature sensor does not need to be provided. In this case, the temperature (reference temperature) in a state where the tire is sufficiently cooled is calculated based on the temperature information measured by the temperature sensor 21 of the sensor unit 14. For example, the lowest tire temperature among the tire temperatures attached to the vehicle 12 or the lowest tire temperature in a past fixed period may be used as the reference temperature. Even in this case, the user can recognize the actual reference value through the in-meter display 35. The tire pressure can be adjusted to the actual reference value.

  In the above embodiment, the determination unit 40 that determines this based on the value indicated by the fuel meter 39 is provided as a supply detection unit that detects the supply of fuel. However, the supply of fuel may be detected by other methods. . For example, a detection unit that detects opening and closing of the lid of the fuel filler opening is provided. Then, when it is determined that the lid is open through this detection unit, the display on the meter display 35 is switched to the actual reference value. Even if comprised in this way, the effect similar to the said embodiment can be acquired.

  In the above embodiment, the internal combustion engine vehicle in which the vehicle 12 uses gasoline as fuel has been described. However, if the vehicle 12 is an electric vehicle that uses electric power as fuel, the determination unit 40 supplies fuel according to the value of the battery voltage or the like. May be judged. Even if comprised in this way, the effect similar to the said embodiment can be acquired.

  In the above embodiment, the tire with the highest actual reference value among the four tires is displayed on the in-meter display 35, but may be displayed for each tire. In addition, the actual air pressure is displayed as the lowest of the four tires, but may be displayed for each tire.

  In the above embodiment, the air pressure determination threshold is 80% of the actual reference value, but is not limited to this value. For example, it may be 80% of the cold air pressure. Even if it does in this way, the effect similar to the said embodiment can be acquired.

  In the above embodiment, when the actual reference value is displayed on the in-meter display 35, it is necessary to operate the trip switch 38 to switch the display on the in-meter display 35. However, a predetermined condition is satisfied. If so, the display may be automatically switched to another display (travel distance display). For example, the display on the meter display 35 may be switched from the actual reference value to another display when the display of the actual reference value has elapsed, or when the vehicle has traveled a predetermined distance after the actual reference value is displayed. .

DESCRIPTION OF SYMBOLS 11 ... Tire pressure monitoring system, 12 ... Vehicle, 13 ... Tire, 14 ... Sensor unit, 15 ... Vehicle body, 16 ... Monitoring device, 17 ... Display device (notification means), 21 ... Temperature sensor, 22 ... Air pressure sensor, 23 ... Transmitter 24 ... Control circuit 25 ... Storage device 31 ... Receiver 32 ... Control device (control means) 33 ... Storage device 34 ... Table data 35 ... In-meter display (display device) 36 ... Outside air Temperature sensor, 37 ... travel distance sensor, 38 ... trip switch, 39 ... fuel gauge, 40 ... determining unit.

Claims (4)

A sensor unit that is provided in each tire of the vehicle and periodically transmits a radio signal including its temperature information, air pressure information, and identification information unique to itself,
A receiver provided in a vehicle for receiving the radio signal transmitted from the sensor unit;
An actual reference value that is an air pressure suitable for the temperature of the tire is calculated using the temperature information included in the radio signal that is also provided in the vehicle and received by the receiver, and the actual reference value is and control means for calculating the threshold value serving as acceptance criteria of whether the decrease in tire air pressure by using,
The control means displays the actual reference value through a display means provided in the vehicle, and further determines whether or not the air pressure information is below the threshold value, and if not, notifies the fact through the notification means. In tire pressure monitoring system ,
The said control means is a pneumatic pressure monitoring system which displays on the said display means the lowest value among the pneumatic information of all the tires, and the highest value among the actual reference values of all the tires . In the tire pressure monitoring system according to claim 1,
The vehicle includes an outside temperature sensor for measuring outside temperature,
The control means, a tire pressure monitoring system for calculating the actual reference value outside air temperature to be pre-determined through Kigaiki temperature sensor as a cold temperature of the tire. In the tire pressure monitoring system according to claim 1 or 2,
The tire pressure monitoring system, wherein the display means is a display in a vehicle meter. In the tire pressure monitoring system according to any one of claims 1 to 3,
The vehicle includes a supply detection unit that detects a state in which fuel is supplied.
The control means is a tire air pressure monitoring system that displays an actual reference value on the display means when it is determined that the fuel is replenished via the replenishment detection unit.

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