JP2014073793A - Tire air pressure monitoring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire air pressure monitoring system capable of maintaining a relationship between an actual pressure value and a low pressure threshold value in an appropriate state even if the air of a tire slowly leaks.SOLUTION: A TPMS receiver 12 samples pressure data and temperature data in a tire air pressure signal Stp received from a tire air pressure detector 4 to calculate a pressure reduction value (pressure value of slow leakage amount) at a certain reference temperature. When the TPMS receiver 12 is switched to an initial mode, the calculated pressure reduction value is added to the first received pressure data to obtain correction value, and a value obtained by reducing the correction value by 20% is set as a low pressure threshold value for determining tire air pressure.

Description

  The present invention relates to a tire pressure monitoring system that monitors the pressure of each tire based on a tire pressure signal transmitted from a tire pressure detector attached to each tire.

  In recent years, vehicles tend to be equipped with a tire pressure monitoring system for the purpose of safe driving (see Patent Document 1, etc.). The tire pressure monitoring system includes a direct type in which a tire pressure detector is attached to each tire, and the tire pressure is monitored based on a tire pressure signal wirelessly transmitted from each tire pressure detector. When the vehicle body receiver receives the tire pressure signal from the tire pressure detector, it compares the pressure data contained in the signal with the low pressure threshold, and if the pressure data is below the low pressure threshold, it drives that there is a low pressure tire. The person in charge.

  This type of tire pressure monitoring system is provided with an initialization mode for returning the receiver of the vehicle body to the initialization state. The initialization mode is a mode in which, for example, the receiver is initialized by operating an initialization switch provided in the receiver, and the low-pressure threshold value registered in the receiver is returned to the initial value. As an operation of the initialization mode, for example, when the receiver that has been shifted to the initialization mode receives a tire pressure signal from the tire pressure detector, an operation of, for example, -20% of the pressure data included in the tire pressure signal is performed, There are processes such as setting this calculated value as a low pressure threshold.

JP 2001-250186 A

  By the way, for example, when a nail or the like is stuck in the tire, a situation of “slow leak” in which a small amount of air escapes from the tire may occur. Slow leak does not cause air to escape rapidly from the tire, so the vehicle can run for a while. At this time, if the initialization operation is executed in the receiver, the low pressure threshold is set based on the tire that is slowly leaking, that is, the air pressure lower than the appropriate value (normal value). Therefore, since an appropriate low pressure threshold is not set, some countermeasure is required.

  An object of the present invention is to provide a tire pressure monitoring system that can maintain the relationship between the actual pressure value and the low pressure threshold value in an appropriate state even if the tire is slowly leaking.

  A tire pressure monitoring system that solves the above problems includes a tire pressure signal transmitted from a tire pressure detector attached to each tire, and the tire pressure signal is included in the tire pressure signal when the tire pressure signal is received by a receiver of the vehicle body. In the configuration in which the pressure of each tire is monitored by comparing the pressure data and the low pressure threshold, when the pressure data is received from the tire pressure detector when the receiver enters the low pressure threshold setting mode, the pressure An initializing function for initializing a certain value determined from data as the low pressure threshold, collecting the pressure data and temperature data of the tire wirelessly from the tire pressure detector, and calculating a decompression value based on these data An actual pressure value of the tire based on the pressure reduction value calculated in the value calculation means and the low pressure threshold setting mode. Comprising a low-pressure threshold value correction means for correcting the relationship between certain the pressure data and the low pressure threshold.

  According to this configuration, pressure data and temperature data transmitted from the tire pressure detector are collected at the receiver, and a decompression value caused by tire slow leak is calculated based on these data. When the receiver enters the low pressure threshold setting mode, the calculated pressure reduction value is used to correct the relationship between the actual tire pressure value and the low pressure threshold, and the relationship between the actual pressure value and the low pressure threshold is in an appropriate state. Set to. Therefore, even if a slow leak has occurred in the tire, the relationship between the actual pressure value and the low pressure threshold value is maintained in an appropriate state. For this reason, it is possible to ensure the accuracy of tire pressure monitoring.

  In the tire pressure monitoring system, it is preferable that the pressure reduction value calculating means collects the pressure data at a certain reference temperature and calculates the pressure reduction value at the reference temperature. According to this configuration, it is only necessary to collect pressure data at a certain reference temperature, so that the processing can be simplified.

  In the tire pressure monitoring system, the low pressure threshold correction unit corrects the pressure data received first by the pressure reduction value after switching to the low pressure threshold setting mode, and sets the low pressure threshold based on this value. It is preferable to do. According to this configuration, the low pressure threshold value is corrected to an appropriate value as the correction of the relationship between the actual pressure value of the tire and the low pressure threshold value. Therefore, once the low pressure threshold value is corrected, the subsequent tire pressure monitoring operation is performed. The reset low pressure threshold value can be simply used as it is. Therefore, it is possible to simplify the processing performed during normal tire pressure monitoring.

  According to the present invention, the relationship between the actual pressure value and the low pressure threshold value can be maintained in an appropriate state even if the tire is slowly leaking.

The block diagram of the tire pressure monitoring system of one embodiment. The tire pressure-temperature correlation diagram illustrating the low-pressure threshold correction function. FIG. 6 is a tire pressure-temperature correlation diagram illustrating another example of a low-pressure threshold correction function. The pressure-temperature correlation diagram of the tire explaining the low-pressure threshold value correction function of another example.

Hereinafter, an embodiment of a tire pressure monitoring system will be described with reference to FIGS. 1 and 2.
As shown in FIG. 1, the vehicle 1 is provided with a tire pressure monitoring system (TPMS: Tire Pressure Monitoring System) 3 that monitors the tire air pressure and the like of each tire 2 (2a to 2d). In the tire pressure monitoring system 3 of this example, tire pressure detectors 4 (4a to 4d) are attached to the tires 2a to 2d, and tire pressure signals detected by the tire pressure detectors 4a to 4d are wirelessly transmitted to the vehicle body 5. By doing so, the air pressure of the tires 2a to 2d in the vehicle body 5 is a direct type.

  Each tire pressure detector 4 is provided with a controller 6 that controls the operation of the tire pressure detector 4. A tire ID (also referred to as a valve ID) is written and stored in the memory 7 of the controller 6 as a unique ID of each tire 2. The tire pressure detector 4 is provided with a pressure sensor 8 that detects tire pressure, a temperature sensor 9 that detects tire temperature, and an acceleration sensor 10 that detects acceleration (rotation) of the tire 2, and these are the controller 6. It is connected to the. The controller 6 is connected to a transmission antenna 11 capable of transmitting a radio wave in the UHF (Ultra High Frequency) band. The tire air pressure detector 4 transmits a tire air pressure signal Stp to the vehicle body 5 when the tire 2 enters a rotating state, or periodically at a predetermined time interval, for example.

  The vehicle body 5 is provided with a receiver (hereinafter referred to as a TPMS receiver) 12 that receives the tire pressure signals Stp transmitted from the tire pressure detectors 4a to 4d and monitors the tire pressure. The TPMS receiver 12 is provided with a tire pressure monitoring ECU (Electronic Control Unit) 13 that controls the operation of the TPMS receiver 12 and a receiving antenna 14 that can receive radio waves in the UHF band. In the tire 15 of the tire pressure monitoring ECU 13, the tire IDs of the respective tires 2a to 2d are written and stored in association with the tire mounting positions (right front, left front, right rear, and left rear). For example, a display unit 16 installed on an in-vehicle instrument panel or the like is connected to the TPMS receiver 12.

  When the receiving antenna 14 receives the tire pressure signal Stp from the tire pressure detectors 4a to 4d, the TPMS receiver 12 checks the tire ID in the tire pressure signal Stp, and if the ID check is established, the same tire pressure signal is obtained. Check the pressure data in Stp. At this time, if the pressure value is equal to or lower than the low pressure threshold Pmin, the TPMS receiver 12 displays the low pressure tire on the display unit 16 in association with the tire mounting position. The TPMS receiver 12 performs the tire pressure determination for each tire pressure signal Stp received to monitor the tire pressures of the tires 2a to 2d.

  The low pressure threshold Pmin is set to a value of a predetermined ratio with respect to the recommended pressure of the tire 2 (for example, recommended pressure × 0.8), for example. Moreover, since the tire air pressure increases as the temperature of the tire 2 rises, the low pressure threshold value Pmin is set individually for each temperature range. That is, as the tire temperature rises, the recommended pressure of the tire 2 also increases, so that an individual low pressure threshold Pmin is set for each of the divided predetermined temperature ranges. The low pressure threshold Pmin is set for each of the tires 2a to 2d by being associated with the tire ID.

  The tire pressure monitoring system 3 of this example is provided with an initialization function that is executed when the low pressure threshold value Pmin registered in the memory 15 of the tire pressure monitoring ECU 13 is initialized. In this case, the tire pressure monitoring ECU 13 is provided with an initialization function unit 17 that executes an initialization function in the TPMS receiver 12. When the initialization function unit 17 detects that the initialization trigger switch 18 disposed in the TPMS receiver 12 is operated, the initialization function unit 17 sets the operation mode of the TPMS receiver 12 as an initialization mode (low-pressure threshold setting mode) and performs initialization. Execute the function.

  In the initialization function of this example, even when the tires 2a to 2d are slow leaking, the low pressure threshold correction is performed after correcting the low pressure threshold Pmin so that an appropriate low pressure threshold Pmin is registered in the tire pressure monitoring ECU 13. A function is provided. Slow leak refers to a state of air leakage that does not interfere with running, although slight air gradually escapes from the tires 2a to 2d, for example, when nails or the like are stuck into the tires 2a to 2d. say.

  In this case, the tire pressure monitoring ECU 13 includes a sampling unit 19 that collects pressure data and temperature data from the tire pressure signal Stp received by the TPMS receiver 12, and a decompression value (pressure value corresponding to a slow leak) Prp at a predetermined temperature. A reduced pressure value calculating unit 20 for calculating and a low pressure threshold setting unit 21 for setting the low pressure threshold value Pmin based on the calculated reduced pressure value Prp are provided in the initialization mode. Sampling of pressure data and temperature data is performed periodically before initialization. The reference temperature is set to, for example, room temperature. The sampling unit 19 and the reduced pressure value calculating unit 20 are an example of a reduced pressure value calculating unit, and the low pressure threshold setting unit 21 is an example of a low pressure threshold correcting unit.

Next, the operation of the low-pressure threshold correction function of this example will be described with reference to FIGS.
As shown in FIG. 1, the tire pressure detectors 4a to 4d wirelessly transmit a tire pressure signal Stp to the vehicle body 5 at regular or irregular intervals. That is, the tire pressure detectors 4 a to 4 d wirelessly transmit the detected pressure data and temperature data to the vehicle body 5 at a predetermined interval. The sampling unit 19 samples pressure data and temperature data in each of the tires 2a to 2d by reading pressure data and temperature data included in the tire pressure signal Stp every time the tire pressure signal Stp is received by the receiving antenna 14.

  Here, as shown in FIG. 2, if there is a slow leak in the tire 2, the tire air pressure should be lower than the recommended pressure P1. The reduced pressure value calculation unit 20 calculates a reduced pressure value Prp as a pressure value corresponding to the slow leak from sampling data of pressure at a certain reference temperature (normal temperature) T1. In the case of this example, the reduced pressure value calculation unit 20 calculates the difference between the recommended pressure P1 at the reference temperature T1 and the minimum sampling pressure P2 at the reference temperature T1 as the reduced pressure value Prp due to the slow leak. The data sampling of pressure and temperature and the calculation of the pressure reduction value Prp are executed before initialization, periodically or irregularly, and for each of the tire pressure detectors 4a to 4d.

  Subsequently, for example, when the temperature of the tire 2 rises from T1 to T2 (> T1) after driving the vehicle 1, the initialization trigger switch 18 of the TPMS receiver 12 is operated, and the operation mode of the TPMS receiver 12 is initialized. Suppose that it is switched to the conversion mode. At this time, the pressure Pb received at the temperature T2 becomes higher than the pressure P2 received at the reference temperature T1 according to the Boyle Charles' law as the temperature of the tire 2 rises.

  The low pressure threshold setting unit 21 corrects the temperature T2 by adding the pressure reduction value Prp calculated by the pressure reduction value calculation unit 20 to the pressure data in the tire pressure signal Stp received first after switching to the initialization mode. The pressure Pa is calculated. Then, the low pressure threshold setting unit 21 sets a pressure that is −20% to the calculated correction pressure Pa as a low pressure threshold Pmin (= Pa × 0.8). The low pressure threshold value setting unit 21 executes the calculation process of the low pressure threshold value Pmin for each of the tire pressure detectors 4a to 4d. When this low pressure threshold Pmin setting process is completed for all four wheels, the initialization of the low pressure threshold Pmin ends.

According to the configuration of the present embodiment, the following effects can be obtained.
(1) The TPMS receiver 12 samples the pressure data and temperature data received from the tire pressure detector 4, and calculates a pressure reduction value Prp at a certain reference temperature T1. When the TPMS receiver 12 is switched to the initialization mode, the correction pressure Pa is obtained by adding the pressure reduction value Prp to the first received pressure data, and a value obtained by -20% of the correction pressure Pa is set as the low pressure threshold Pmin. To do. Therefore, even if a slow leak has occurred in the tire 2, the low pressure threshold Pmin can be set to an appropriate value taking into account the slow leak. For this reason, the accuracy of tire pressure monitoring can be secured.

  (2) The tire air pressure data is sampled only at a value at a certain reference temperature T1. Therefore, since the pressure data sampling only needs to collect the pressure data at one reference temperature T1, the sampling process can be simplified.

  (3) As a correction of the relationship between the actual pressure value of the tire 2 and the low pressure threshold Pmin, an operation of correcting the low pressure threshold Pmin is executed. Therefore, once the low pressure threshold Pmin is corrected in the initialization mode, the reset low pressure threshold Pmin is simply used as it is during the subsequent operation of the tire pressure monitoring. Therefore, the process performed at the time of normal tire pressure monitoring can be simplified.

Note that the embodiment is not limited to the configuration described so far, and may be modified as follows.
As shown in FIG. 3, pressure data may be sampled in a certain temperature range, and the minimum pressure in the temperature data may be calculated as the reduced pressure value Prp. In this case, since it is possible to take a large number of samples, the effect of optimizing the setting of the low pressure threshold Pmin is enhanced.

  As shown in FIG. 4, a plurality of reference temperatures to be sampled may be set (for example, T1a, T2a, T3a). In this case, for example, if correction is performed with the reduced pressure value Prp obtained with the largest number of samples, the effect of optimizing the accuracy of the low pressure threshold Pmin is enhanced.

-Data sampling may be either regular or irregular. Data sampling may be performed when the vehicle 1 is parked (engine stopped, door locked).
The calculation of the pressure reduction value Prp may be, for example, the difference between the pressure data acquired first in the data sampling and the sampling minimum value.

The calculation of the decompression value Prp may be executed when the TPMS receiver 12 is switched to the initialization mode, for example.
The low pressure threshold value Pmin may be a common value for all four wheels.

The low pressure threshold Pmin is not limited to a calculation method of multiplying the recommended pressure by a predetermined percentage, and various calculation methods such as subtraction of a predetermined value can be applied.
The low pressure threshold Pmin is not limited to being set for each temperature, and may be a single value.

-Switching to the initialization mode is not limited to switching by a switch operation, and various operation modes can be adopted.
The correction of the relationship between the actual pressure value (pressure data) and the low pressure threshold value may be realized by correcting the received pressure data without changing the low pressure threshold value Pmin, for example.

Next, technical ideas that can be grasped from the above-described embodiment and other examples will be described below together with their effects.
(A) The reduced pressure value calculating means calculates a difference between a minimum pressure value in the collected pressure data and a reference pressure value as the reduced pressure value. According to this configuration, it is possible to calculate the reduced pressure value by a simple process.

(B) The reference temperature is a temperature range having a certain range. According to this configuration, it is possible to obtain a large number of samplings, so that the effect of securing correction accuracy is enhanced.
(C) The constant pressure threshold correction means obtains a correction pressure under the current temperature by adding the pressure reduction value to the pressure data received first after switching to the constant pressure threshold setting mode, and calculates the correction pressure. Based on the constant pressure threshold. According to this configuration, it is possible to correct the relationship between the pressure data and the low pressure threshold value with a simple process.

1 ... vehicle,
2 (2a to 2d) ... tyre, 3 ... tyre pressure monitoring system, 4 (4a to 4d) ... tyre pressure detector, 5 ... body, 12 ... receiver (TPMS receiver), 19 ... decompressing pressure calculating means Sampling unit, 20 ... reduced pressure value calculating unit constituting reduced pressure value calculating unit, 21 ... low pressure threshold setting unit as low pressure threshold correcting unit, Stp ... tire pressure signal, Pmin ... low pressure threshold, Prp ... reduced pressure value, T1 ... reference temperature.

Claims (3)

When a tire pressure signal is transmitted from a tire pressure detector attached to each tire and the tire pressure signal is received by a receiver of the vehicle body, by comparing the pressure data included in the tire pressure signal with a low pressure threshold, In the tire pressure monitoring system that monitors the pressure of each tire,
When the receiver is in a low pressure threshold setting mode, when the pressure data is received from the tire pressure detector, an initialization function for initializing a certain value determined from the pressure data as the low pressure threshold is provided.
The pressure data and the temperature data of the tire are collected from the tire pressure detector by radio, and the pressure reduction value calculating means for calculating the pressure reduction value based on these data;
Low pressure threshold correction means for correcting the relationship between the pressure data, which is the actual pressure value of the tire, and the low pressure threshold based on the calculated reduced pressure value in the low pressure threshold setting mode. Tire pressure monitoring system. 2. The tire pressure monitoring system according to claim 1, wherein the pressure reduction value calculating means collects the pressure data at a certain reference temperature and calculates the pressure reduction value at the reference temperature. The low-pressure threshold correction means corrects the pressure data received first after the switching to the low-pressure threshold setting mode with the reduced pressure value, and sets the low-pressure threshold based on this value. Item 3. The tire pressure monitoring system according to Item 1 or 2.