JP7517163B2 - Tire pressure notification system - Google Patents

Description

The present invention relates to an air pressure reporting system that obtains and reports the air pressure of tires on vehicle wheels.

In the tire pressure notification system described in Patent Document 1, a judgment threshold is obtained based on the tire pressure and tire temperature, and if the measured tire pressure falls below the judgment threshold, it is determined that the tire is punctured and a warning is issued.

JP 2019-006266 A

The objective of the present invention is to properly determine whether the tire air pressure is adequate and properly notify the tire air pressure status in an air pressure notification system.

In this tire pressure notification system, it is determined whether the acquired tire pressure is equal to or lower than the judgment threshold value, taking into account the temperature change between when the judgment threshold value is set and when the tire pressure is acquired.
Therefore, it is possible to properly determine whether the tire air pressure is appropriate, and to properly notify the tire air pressure state.

1 is a schematic diagram of an entire tire pressure reporting system according to an embodiment of the present invention; FIG. 2 is a block diagram conceptually illustrating a portion of the tire pressure reporting system. FIG. 4 is a diagram showing (a) changes in outside air temperature of a vehicle equipped with the air pressure reporting system, and (b) changes in tire air pressure of the vehicle's wheels. 5 is a flowchart conceptually illustrating a notification control program stored in a storage unit of a tire information processing device of the air pressure notification system. 10 is a flowchart conceptually illustrating another notification control program stored in the storage unit.

The following describes an embodiment of the present invention, an air pressure notification system, with reference to the drawings. The air pressure notification system acquires the air pressure of each tire of a vehicle's multiple wheels individually, determines whether each tire pressure is lower than a judgment threshold, and reports the judgment result.

As shown in FIG. 1, the tire pressure reporting system includes a wheel-side device 12 provided on each of the vehicle's multiple wheels 10, and a management device 16 provided on the vehicle body 14 or outside the vehicle. The management device 16 obtains the tire pressure of each of the multiple wheels 10 through wireless communication between each of the multiple wheel-side devices 12 and the management device 16.

As shown in FIG. 2, each wheel-side device 12 includes an air pressure sensor 20, a tire information creation device 22 mainly composed of a computer, a transmission antenna 24, etc. The air pressure sensor 20 is provided on the tire of the wheel and detects the air pressure inside the tire. The air pressure sensor 20 detects the air pressure of the tire at predetermined set time intervals or in response to a request from the management device 16, and supplies the detected air pressure to the tire information creation device 22. The tire information creation device 22 creates tire information including air pressure information that is information indicating the air pressure of the supplied tire. The created tire information is transmitted to the management device 16 via the transmission antenna 24.

In this embodiment, the management device 16 is provided on the vehicle body 14 and includes a receiving antenna 30, a tire information processing device 32 mainly composed of a computer, a notification device 34, and multiple sensors and switches. The receiving antenna 30 receives tire information transmitted from each of the multiple wheel-side devices 12. The tire information processing device 32 acquires the position of the wheel from which the tire information is transmitted based on the ID information contained in the tire information received by the receiving antenna 30. The tire information processing device 32 also determines whether the tire pressure represented by the air pressure information contained in each piece of tire information is equal to or lower than the judgment threshold value, and controls the notification device 34 or sets the judgment threshold value Pth accordingly. The input/output section of the tire information processing device 32 is connected to the notification device 34, temperature sensor 36, running speed sensor 38, initialization switch 40, threshold value selection switch 42, main switch 44, and the like.

The notification device 34 may include, for example, a warning lamp 34a and a display 34b. In this embodiment, the temperature sensor 36 detects the outside air temperature of the vehicle and is provided on the vehicle body 14. The traveling speed sensor 38 detects the traveling speed of the vehicle in which the tire pressure notification system is mounted and may detect the traveling speed of the vehicle based on, for example, the wheel speed of each of the multiple wheels 10. The main switch 44 may be, for example, an ignition switch, and when the main switch 44 is ON, the vehicle is permitted to travel.

The initialization switch 40 can be operated by an operator. When the initialization switch 40 is turned ON, as described below, the judgment threshold is initialized (reset) and a first temperature, which is the outside air temperature, is acquired and stored. The initialization switch 40 is turned ON when the tire air pressure is refilled (adjusted) or when "Initialization Required" is displayed on the display 34b. When refilling the tire air pressure, the air pressure is adjusted to approach the standard air pressure (which can also be called the set air pressure) P0, which is the air pressure that is preset in the vehicle.

The threshold selection switch 42 is a switch that is operated when the initialization switch 40 is turned ON. By operating the threshold selection switch 42, a selection is made between a case where the judgment threshold is set based on the set air pressure P0 and a case where the judgment threshold is set based on the current air pressure Pi. By operating the threshold selection switch 42, it is possible to switch between a case where the judgment threshold is set based on the set air pressure P0 and a case where the judgment threshold is set based on the current air pressure Pi.

Normally, when the tire air pressure P measured by the air pressure sensor falls below the judgment threshold, this is reported. However, in an enclosed space, Boyle's law holds true between the tire air pressure P, the tire volume V, and the temperature T. Therefore, as the temperature drops, the tire air pressure also drops, making it difficult to determine whether the tire air pressure has truly fallen below the judgment threshold, i.e., whether the amount of air has decreased (whether the air inside the tire has leaked to the outside).

In contrast, in the air pressure notification system described in Patent Document 1, the temperature inside the tire is taken into consideration when determining the judgment threshold value. Because the judgment threshold value is determined taking into account the temperature inside the tire, it is possible to accurately determine whether or not the tire pressure has dropped below the judgment threshold value due to leakage at that temperature. However, the temperature is not necessarily the same when the judgment threshold value is determined and when the tire pressure is measured by the air pressure sensor. Therefore, if the temperature changes between when the judgment threshold value is determined and when the tire pressure is measured, it becomes difficult to determine whether or not the air pressure has dropped below the judgment threshold value due to leakage.

In this embodiment, therefore, when the judgment threshold is set, a first temperature, which is the outside air temperature, is acquired and stored. Then, the tire pressure is measured and it is judged whether it is equal to or lower than the judgment threshold. If the tire pressure is equal to or lower than the judgment threshold, a second temperature, which is the outside air temperature in that case (the outside air temperature when the tire pressure is measured), is acquired, and it is judged whether the value obtained by subtracting the second temperature from the first temperature is smaller than the set temperature. Then, if the tire pressure is equal to or lower than the judgment threshold and the value obtained by subtracting the second temperature from the first temperature is smaller than the set value, it is judged that the tire pressure has dropped below the judgment threshold due to a leak, and an "air pressure refill" is notified.

On the other hand, if the tire pressure is below the judgment threshold and the value obtained by subtracting the second temperature from the first temperature is above the set value, the drop in tire pressure is thought to be mainly due to a drop in outside temperature, but air may also be leaking. Also, since the current outside temperature has dropped by more than the set value from the first temperature when the judgment threshold Pth was previously set, it is desirable to reset the first temperature and judgment threshold. For these reasons, notifications are issued such as "Refill air pressure," "Air pressure drop due to drop in outside temperature," and "Initialization required (resetting of judgment threshold and first temperature)." Note that regulations may stipulate that "Refill air pressure" be notified if the measured air pressure is below the judgment threshold.

In response to the notification of "Air pressure refill" or "Air pressure refill, air pressure drop due to outside temperature drop, initialization required," air pressure refill is performed and the initialization switch 40 is turned ON. In response to the initialization switch 40 being turned ON, an initialization command is issued, and the judgment threshold value is set and the first temperature is obtained and stored.

The storage unit of the tire information processing device 32 stores an air pressure notification program represented by the flowchart in FIG. 4, and the execution unit executes the program at predetermined intervals. When the vehicle is shipped from the factory, the outside air temperature at that time is measured by the temperature sensor 36 and stored as the first temperature. In addition, the judgment threshold value Pth is set to a value obtained by multiplying the set air pressure P0 by a threshold coefficient K (0<K<1) and is stored.

In step 1 (hereinafter abbreviated as S1, and the same applies to the other steps) of the flowchart in FIG. 4, it is determined whether a predetermined processing condition is satisfied. S1 will be described later. In S2, it is determined whether the initialization switch 40 has been turned on, and if the determination is NO, in S3, the air pressure is acquired. In the wheel-side device 12, tire information including air pressure information representing the air pressure measured by the air pressure sensor 20 is created and transmitted. The tire information is received by the receiving antenna 30, and the tire information processing device 32 acquires the air pressure Pi based on the tire information (hereinafter, this may be referred to as the air pressure Pi being measured). In S4, it is determined whether the air pressure Pi is equal to or less than the determination threshold value Pth. If the determination in S4 is NO, the alarm device 34 is not activated.

In S5, it is determined whether the air pressure has returned, for example, whether the air pressure Pi is higher than the determination threshold value Pth. In this case, the determination is YES, and in S6, the warning lamp 34a is turned OFF. If the warning lamp 34a is OFF when S6 is executed, it remains OFF.

In S7, it is determined whether the main switch 42 is OFF. If the determination is YES, the air pressure notification program is terminated, but if the determination is NO, the process returns to S1.

If the judgments in S1 and S2 are NO, the air pressure Pi is obtained in S3, and it is judged in S4 whether it is equal to or lower than the judgment threshold value Pth. If the judgment in S4 is YES, in S8, the second temperature, which is the outside air temperature, is obtained by the temperature sensor 36 and stored (T2). In S9, the warning lamp 34a is turned ON. In S10, it is judged whether the value (T1-T2) obtained by subtracting the second temperature from the first temperature is equal to or higher than the set value ΔTth. If the judgment is NO, in S11, "Air pressure refill" is displayed on the display 34b, and if the judgment in S11 is YES, in S12, "Air pressure refill - air pressure drop due to drop in outside air temperature - initialization required" is displayed on the display 34b.

After that, S5 is executed, but in this case, the determination is NO, so the warning lamp 34a remains ON and the display 34b also remains unchanged.

Thereafter, when air pressure is replenished in response to the notifications in S11 and S12 and the initialization switch 40 is turned ON, the result in S2 becomes YES and the judgment threshold value Pth is set in S13. Based on the operation state of the threshold selection switch 42, the judgment threshold value Pth is set as the set air pressure P0 or the air pressure Pi measured at that time multiplied by the threshold coefficient K (Pth = K * P0 or Pth = K * Pi). If the air pressure drops by (1-K) * P0 or (1-K) * Pi or more from the set air pressure P0 or the air pressure Pi obtained after air pressure replenishment, it is judged that the air pressure in the tire has dropped to the extent that air pressure replenishment is necessary. In S14, the first temperature, which is the outside air temperature, is obtained by the temperature sensor 36 and stored (T1). Then, in S3, the air pressure Pi is measured, and in S4, it is determined whether the measured air pressure Pi is equal to or less than the judgment threshold value Pth set in S13. In this case, the judgment in S4 is NO. Also, since the judgment in S5 is YES, in S6, the warning lamp 34a is turned OFF and the display 34b is erased.

For example, as shown in Fig. 3, when the initialization switch 40 is turned ON, a judgment threshold value Pth is set and a first temperature T1 is acquired. Thereafter, when the air pressure Pi becomes equal to or less than the judgment threshold value Pth, a second temperature T2 is acquired and it is judged whether or not the value (T1-T2) obtained by subtracting the second temperature from the first temperature is equal to or less than a set value ΔTth. When the value obtained by subtracting the second temperature from the first temperature is equal to or less than the set value ΔTth, it is judged that the air pressure has decreased, but when the value is greater than the set value ΔTth, it is judged that the air pressure has decreased mainly due to a decrease in temperature. In this way, in this embodiment, it is possible to appropriately judge whether or not the air pressure of the tire is equal to or less than the judgment threshold value.
The set value ΔTth can be set to a temperature difference where a pressure drop of (1-K)*P0 or (1-K)*Pi or more is considered to be mainly caused by a temperature drop based on Boyle's law. The set value ΔTth can be, for example, about 15°C, but is not limited thereto. The set value ΔTth can also be a variable value. For example, depending on the region and season, there may be a large daily temperature difference, and the air pressure Pi may frequently become equal to or lower than the judgment threshold value Pth due to a temperature drop, which may be annoying. In such a case, it is considered to set the set value ΔTth to a large value.

For example, if the vehicle is shipped from the factory in summer, the first temperature T1 is stored as 35°C, and the judgment threshold is set to the set air pressure P0 multiplied by the threshold coefficient K. Then, in autumn, the outside air temperature falls below 20°C (the outside air temperature drops by more than the set value ΔTth (which can be, for example, about 15°C)), and the air pressure falls below the judgment threshold due to the temperature drop. The judgment in S4 becomes YES, the judgment in S10 becomes YES, and in S12, "Air pressure refill - air pressure drop due to outside air temperature drop - initialization required" is displayed. In response to this display, air pressure is refilled, and the initialization switch 40 is turned ON. This causes the judgment threshold to be reset, and the first temperature to be acquired and stored.

Then, when winter arrives and the outside temperature drops below 4°C, the display 34b similarly displays "Air pressure refill - Air pressure dropping due to outside temperature drop - Initialization required." Air pressure is refilled and the initialization switch 40 is turned ON, causing the judgment threshold to be reset and the first temperature to be acquired and stored.

When the temperature rises from winter to spring and from spring to summer, it is unlikely that the air pressure will drop due to a drop in the outside temperature. However, it may be difficult to accurately detect when the air pressure has fallen below the threshold value, so it is desirable to perform initialization. For example, if the second temperature is 15°C or more higher than the first temperature, the message "Initialization required" may be displayed.

The processing conditions of S1 can be, for example, when the amount of air pressure loss per unit time is equal to or greater than a set amount, when tire information is not received, when a tire change is performed and it becomes necessary to register a tire ID, when a tire is rotated and it becomes necessary to confirm the tire position (correspondence between ID and position), etc. When one or more of these are met, the determination of S1 becomes YES, and the corresponding processing is performed in S15.

For example, if the amount of decrease in air pressure per unit time is equal to or greater than the set amount, the determination in S1 becomes YES, and the rapid pressure reduction determination process is performed in S15. For example, the display 34 may be configured to notify "Check tires in a safe location."
If the tire information is not received, the determination in S1 is YES. Since this is a system abnormality, an abnormality determination process is performed in S15. For example, a "fault occurrence" can be notified.

In addition, when a tire change is performed and it becomes necessary to register the tire ID, a tire position determination process is performed, and when a tire is rotated and it becomes necessary to determine the tire position (correspondence between ID and position), an automatic ID registration process is performed. For example, it is possible to be notified that the ID is being registered, that the tire position is being determined, etc.

The determination threshold value can also be set based on the air pressure after the tire has been driven for a predetermined set time tx after the air pressure has been adjusted. An example of this case is shown in the flow chart of FIG.
If the determination in S2 is YES, in S21 the vehicle is driven for a set time tx, and in S22 the air pressure PH is acquired. Then, in S23, the air pressure PH is multiplied by the threshold coefficient K and set as the HOT pressure determination threshold PHth, which is the determination threshold, and in S24 the first temperature is acquired and stored (T1). Then, in S25, it is determined whether the acquired air pressure Pi is equal to or lower than the HOT determination threshold PHth.

In this way, in this embodiment, after the initialization switch 40 is turned ON, the judgment threshold value PHth is obtained based on the air pressure PH after driving for the set time tx. This is because the method for setting the judgment threshold value may be determined by regulations.

As described above, the wheel-side device 12, the receiving antenna 30, etc. constitute the air pressure acquisition device, the part that stores and executes S13 and S23 of the tire information processing device 32 constitutes the judgment threshold setting unit, and the part that stores and executes S11 and S12 constitutes the notification control unit.

In addition, the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art.

12: Wheel-side device 16: Management device 20: Air pressure sensor 22: Tire information creation device 24: Transmitting antenna 30: Receiving antenna 32: Tire information processing device 34: Notification device 35: Temperature sensor 40: Initialization switch

Patentable inventions

(1) an air pressure acquisition device that acquires air pressure of tires of wheels of a vehicle;
a judgment threshold value setting unit that sets a judgment threshold value to be compared with the air pressure;
an alarm device that notifies the state of the air pressure;
and a notification control unit that, when the air pressure acquired by the air pressure acquisition device is equal to or less than the judgment threshold value set by the judgment threshold value setting unit, causes the notification device to notify the fact,
The air pressure notification system includes a temperature sensor for measuring an outside air temperature,
An air pressure notification system in which the notification control unit causes the notification device to provide an alert in different manners depending on whether the air pressure acquired by the air pressure acquisition device is equal to or lower than the judgment threshold set by the judgment threshold setting unit, and whether the value obtained by subtracting a first temperature, which is the outside air temperature measured by the temperature sensor when the judgment threshold is set by the judgment threshold setting unit, from a second temperature, which is the outside air temperature measured by the temperature sensor when the air pressure is acquired by the air pressure acquisition device, is less than a set value, or whether the value obtained by subtracting the second temperature from the first temperature is equal to or higher than the set value.

The air pressure acquisition device may include an air pressure sensor that directly measures the air pressure in the tire of the wheel, or may estimate the air pressure based on the motion state of the wheel, etc.
The judgment threshold setting unit sets the judgment threshold based on, for example, a standard air pressure (set air pressure) that is predetermined as an appropriate air pressure. The judgment threshold is set to a value obtained by multiplying the set air pressure by a threshold coefficient K. The threshold coefficient K can be a value greater than 0 and less than 1.
The notification device may include one or more of a warning lamp, a display, a speaker, and the like.

(2) The air pressure notification system described in (1) includes a first notification control unit that causes the notification device to notify the user to replenish the air pressure when the air pressure acquired by the air pressure acquisition device is equal to or lower than the judgment threshold value and the value obtained by subtracting the second temperature from the first temperature is smaller than the set value.

(3) The air pressure notification system according to paragraph (1) or (2), further comprising a second notification control unit that, when the air pressure acquired by the air pressure acquisition device is equal to or lower than the judgment threshold value and the value obtained by subtracting the second temperature from the first temperature is equal to or higher than a set value, causes the notification device to notify one or more of refilling the air pressure, setting the judgment threshold value and the first temperature, and notifying that the decrease in air pressure is due to a decrease in temperature.

The setting of the judgment threshold and the first temperature can be referred to as initialization.

(4) An air pressure notification system according to any one of (1) to (3), in which the notification control unit includes a first temperature memory unit that stores a first temperature, which is the outside air temperature detected by the temperature sensor, when setting the judgment threshold value.

(5) The tire pressure notification system includes an initialization switch,
the determination threshold setting unit sets the determination threshold in response to an ON operation of the initialization switch,
An air pressure notification system as described in any one of items (1) to (4), wherein the initialization switch is turned ON when the air pressure is replenished or when the notification device notifies the user that initialization is required.

(6) an air pressure acquisition device that acquires air pressure of tires of wheels of a vehicle;
a judgment threshold value setting unit that sets a judgment threshold value to be compared with the air pressure;
an air pressure determination unit that determines whether the air pressure acquired by the air pressure acquisition device is equal to or less than the judgment threshold value set by the judgment threshold value setting unit,
the air pressure processing system includes a temperature sensor for measuring temperature;
An air pressure processing system in which, when the air pressure acquired by the air pressure acquisition device is equal to or lower than the judgment threshold set by the judgment threshold setting unit, if a value obtained by subtracting a first temperature, which is the temperature measured by the temperature sensor when the judgment threshold is set by the judgment threshold setting unit, from a second temperature, which is the temperature measured by the temperature sensor when the air pressure is acquired by the air pressure acquisition device, is less than a set value, the air pressure determination unit determines that the air pressure has dropped below the judgment threshold due to a leak, and if a value obtained by subtracting the second temperature from the first temperature is equal to or higher than the set value, determines that the air pressure may have dropped below the judgment threshold due to a drop in temperature.

It is not essential that the alarm device notify the tire pressure status.

Claims (1)

An air pressure acquisition device that acquires air pressure of tires of wheels of a vehicle;
a judgment threshold value setting unit that sets a judgment threshold value to be compared with the air pressure;
an alarm device that notifies the state of the air pressure;
and a notification control unit that, when the air pressure acquired by the air pressure acquisition device is equal to or less than the judgment threshold value set by the judgment threshold value setting unit, causes the notification device to notify the fact,
The air pressure notification system includes a temperature sensor for measuring an outside air temperature,
An air pressure notification system in which the notification control unit causes the notification device to provide an alert in different manners depending on whether the air pressure acquired by the air pressure acquisition device is equal to or lower than the judgment threshold set by the judgment threshold setting unit, and whether the value obtained by subtracting the second temperature, which is the temperature measured by the temperature sensor when the air pressure is acquired by the air pressure acquisition device, from the first temperature, which is the temperature measured by the temperature sensor when the judgment threshold is set by the judgment threshold setting unit, is less than a set value, or whether the value obtained by subtracting the second temperature from the first temperature is equal to or higher than the set value.

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