JP2006327554A - Tire air pressure monitoring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire air pressure monitoring device capable of warning reduction of the air pressure of the tire in advance. <P>SOLUTION: In the tire air pressure warning controller 5 provided with a pressure sensor 10a for detecting the tire air pressure, reduction degree of the tire air pressure indicating reduction tendency of the tire air pressure is calculated and a time required for reducing the tire air pressure to a set air pressure is presumed from the reduction degree of the tire air pressure. When the time required for reducing the tire air pressure to the set air pressure becomes a set time or shorter, the fact is informed to a driver. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention belongs to a technical field of a tire pressure monitoring device that transmits each tire pressure to a receiving device provided on the vehicle body side by a pneumatic sensor provided on each tire.

As this type of technology, a technique is disclosed in which a warning signal is generated when the tire air pressure is equal to or lower than a threshold value set based on the recommended tire air pressure (see, for example, Patent Document 1).
JP 2002-225519 A

  However, in the above prior art, a warning signal is generated when the threshold value is lowered to the threshold value. Therefore, in a situation where it is not possible to deal with immediately, for example, when driving on a highway or a mountain road, the tire pressure is insufficient and a warning is generated. When this occurs, there is a problem that the driver may be confused.

  The present invention has been made paying attention to the above problem, and an object of the present invention is to provide a tire pressure monitoring device capable of predicting a warning of tire pressure drop in advance.

  In order to achieve the above object, in the present invention, in a tire pressure monitoring device that is attached to a tire and includes tire pressure detecting means for detecting the tire pressure, a tire pressure reduction degree indicating a tendency of the tire pressure to decrease is calculated. Air pressure reduction degree calculation means, reduction time estimation means for estimating a reduction time required for the tire air pressure to drop to the set air pressure based on the tire air pressure reduction degree, and notification means for informing the driver of the estimated reduction time And provided.

  In the tire pressure monitoring apparatus according to the present invention, the tire pressure is notified to the driver when the tire pressure drops to the set pressure, which is the pressure at which the tire should be refilled with air. You can know if the pressure drops to air pressure.

  Hereinafter, the best mode for realizing the tire pressure monitoring device of the present invention will be described based on the first embodiment.

  First, the configuration will be described.

  FIG. 1 is a system diagram showing a vehicle to which the tire pressure monitoring device according to the first embodiment is applied. Transmitter A is provided in each of tires 1, 2, 3, and 4 and transmits tire pressure information and the like. , B, C, D, receivers E, F, G, H that receive transmission signals from transmitters A, B, C, D, and signals received by receivers E, F, G, H A tire pressure alarm controller 5 for processing tire pressure information and the like.

  Transmitters A, B, C, and D are attached to the road wheels of the front and rear tires 1, 2, 3, and 4, respectively, and detect the tire pressure and the tire internal temperature of each tire. The temperature information in the tire is transmitted to the receivers E, F, G, and H by radio signals.

  The receivers E, F, G, and H receive each information transmitted from the transmitters A, B, C, and D and input the information to the tire pressure alarm controller 5.

  The tire pressure warning controller 5 performs ID registration for each tire and displays on the in-vehicle display 6 tire pressure information of the tires 1, 2, 3, and 4 of the front and rear wheels specified by the registration. If it is determined that at least one of the tires 1, 2, 3, and 4 of the front and rear wheels has decreased to a set air pressure Ps or less, a lamp lighting command is output to the warning lamp 7.

  FIG. 2 is a detailed view showing the tire pressure monitoring device of the first embodiment.

  The transmitters A, B, C, and D include a pressure sensor (tire pressure detecting means) 10a for detecting tire pressure, a temperature sensor (tire temperature detecting means) 10b for detecting tire temperature, and an integrated circuit for specific applications. ASIC 10c, a transmitter 10d, a transmitting antenna 10e, and a centrifugal force switch 10f that is open (OFF) in a region where the acting centrifugal force is small and is closed (ON) in a region where the centrifugal force is large. Each is composed. Then, with the opening / closing of the centrifugal force switch 10f installed to ensure the battery life as a trigger, it is a long transmission interval (for example, 1 hour) in the extremely low speed traveling region including the stop, and short in the region where the vehicle speed is higher than that. The transmission cycle is changed into two stages such as a transmission interval (for example, 1 minute).

  Each of the receivers E, F, G, and H includes a reception antenna 11a that receives transmission data from the transmitters A, B, C, and D, and a tuner 11b that is a reception circuit.

  The tire pressure alarm controller 5 receives 5V power supply circuit 5a, a microcomputer 5b that receives received data from each tuner 11b and performs various information processing, and each tire 1, 2, 3, 4 based on the received data. A display drive circuit 5c for outputting a display drive command for displaying tire pressure information and a temperature rise in the tire to the in-vehicle display 6, and a tire pressure warning command at the time of pressure drop by judging the pressure information and temperature information of the mounted tire from the received data Or a warning lamp output circuit 5d that outputs to the warning lamp 7 when an abnormal temperature rises, and an EEPROM 5e that is a memory that can electrically erase stored information for ID registration.

  Next, the operation will be described.

  In the present embodiment, the tire pressure warning controller 5 determines that the warning pressure is lower than at least one of the tires 1, 2, 3, and 4 of the front and rear wheels. A lamp lighting command is output to 7. The warning lamp 7 is lit based on a lighting command from the air pressure alarm controller 5 and notifies the driver of a decrease in tire air pressure.

  In the conventional tire pressure monitoring device, as in the warning lamp 7 described above, when the tire pressure drops below the set air pressure Ps, the driver is notified of the drop in air pressure. However, even if the warning lamp 7 is turned on after the tire air pressure falls below the set air pressure Ps, the driver can recognize the decrease in the tire air pressure when the tire air pressure is already below the set air pressure Ps. As a result, the tires 1, 2, 3, 4 have a state where the air pressure is not sufficient.

  Therefore, in this embodiment, the tire pressure drop (drop speed) Pg is estimated based on the tire pressure data detected by the pressure sensor 10a, and the tire pressure falls from the tire pressure drop to the set pressure Ps. The reduction time (in this example, the number of days Dth) was calculated. The driver is notified when the calculated number of days Dth falls below the set number of days Dr.

[Notification of tire pressure drop due to tire pressure tendency]
FIG. 3 is a flowchart showing a flow of processing executed in the tire air pressure alarm controller 5 of the present embodiment.

  In step S1, it is determined whether conditions for a stable data acquisition environment described later are satisfied. When the condition for the stable data acquisition environment is satisfied, the process proceeds to step S2, and when the condition for the stable data acquisition environment is not satisfied, the process ends. This step S1 corresponds to the stable data acquisition environment judging means of the present invention.

  In step S2, the air pressure data of each tire 1, 2, 3, 4 detected by the pressure sensor 10a when the conditions for the stable data acquisition environment are satisfied are read, and the process proceeds to step S3.

  In step S3, the tire air pressure data detected by the pressure sensor 10a is corrected according to the tire internal temperature detected by the temperature sensor 10b, and the process proceeds to step S4. The processing in step S3 corresponds to the correcting means of the present invention.

  In step S4, the air pressure decrease degree Pg is calculated based on the air pressure data corrected in step S3, and the process proceeds to step S5. The processing in step S4 corresponds to the air pressure reduction degree calculation means of the present invention.

  In step S5, the number of days Dth of decrease until the tire air pressure decreases to the set air pressure Ps is estimated from the air pressure decrease degree Pg, and the process proceeds to step S6. The processing in this step S5 corresponds to the reduction time estimation means of the present invention.

  In step S6, it is determined whether or not the number of days Dth until the tire air pressure decreases to the set air pressure Ps is equal to or less than the set number of days Dr. If the number of days Dth until the tire air pressure drops to the set air pressure Ps is less than or equal to the set number of days Dr, the process proceeds to step S7, and if not less than the set number of days Dr, the process ends.

  In step S7, the driver is notified of a decrease in tire air pressure by a screen display on the in-vehicle display 6 or the like.

  Below, the process performed in said control flow is demonstrated in detail.

[Stable data acquisition conditions]
In this embodiment, the tire pressure drop Pg is estimated based on tire pressure data detected by the pressure sensor 10a. In order to estimate the tire pressure drop Pg with high accuracy, it is necessary to calculate it based on stable air pressure data that is not subject to disturbance.

  Therefore, in the present embodiment, the pressure sensor 10a can acquire stable air pressure data that is not subject to disturbance, and the tire air pressure decrease degree Pg is estimated based on air pressure data when a condition of a stable data acquisition environment described later is satisfied. did.

  The conditions for the stable data acquisition environment are when the vehicle is stopped and the door is unlocked by the keyless remote control, or the door is unlocked by inserting the key into the key cylinder of the door, or the operation of turning on the ignition. At least one operation is performed, and so on. In an environment where the conditions for the stable data acquisition environment are in place, the change in the temperature in the tire is small as in driving, and the tire internal temperature is also stable because it often takes some time after the vehicle stops. In addition, there is little influence of weight changes due to passengers getting on and off. Therefore, the pressure sensor 10a can acquire stable air pressure data that is not subject to disturbance.

[Tire pressure correction]
The tire air pressure detected by the pressure sensor 10a varies depending on the temperature in the tire. Therefore, in this embodiment, the tire air pressure detected by the pressure sensor 10a is corrected according to the temperature inside the tire detected by the temperature sensor 10b. Hereinafter, a method for correcting the tire air pressure according to the tire internal temperature will be described.

The following equation holds according to Boyle-Charles' law.
(Absolute pressure) / (Absolute temperature) = (Constant) ... (1)
Therefore, the tire air pressure detected by the pressure sensor 10a is P0 [kPa] (gauge pressure), the tire internal temperature detected by the temperature sensor 10b is Te0 [° C], the standard temperature is Teb [° C] (for example, 20 [° C]), When the atmospheric pressure is Pa [kPa] and the tire air pressure converted to the pressure at the standard temperature is Pf [kPa] (gauge pressure), the following equation is established.
(P0 + Pa) / (Te0 +273) = (Pf + Pa) / (Teb +273)… (2)
Therefore,
Pf = [{(P0 + Pa) × (Teb +273)} / (Te0 +273)] − Pa (3)

  Although an example of the tire pressure correction method has been described above, other methods may be used to correct the tire pressure. The tire pressure correction method using other methods is disclosed in, for example, Japanese Patent Application Laid-Open No. 2002-225519 and Japanese Patent Application Laid-Open No. 2004-189170, and the description thereof is omitted.

  Hereinafter, the tire pressure alarm controller 5 performs processing using the tire pressure Pf converted to the pressure in the standard temperature state.

[Calculation of tire pressure drop]
Next, a method for calculating the tire pressure drop Pg will be described.

FIG. 4A is a table in which the air pressure data acquired by the pressure sensor 10a read by the tire air pressure alarm controller 5 and acquired when the conditions of the stable data acquisition environment are satisfied are arranged along the elapsed time. . The elapsed time is, for example, the air pressure data detected in a state where the above-mentioned stable data acquisition environment condition is satisfied, based on the time when the tires 1, 2, 3, 4 are replenished with air. Indicates the time of reading. The time when air is replenished to each tire 1, 2, 3, 4 is set to the time when the air pressure data d (0) is read when both of the following two conditions are satisfied.
d (0) −d (-1) ≧ ΔP (4)
d (1) −d (0) ≦ ΔP (5)
Here, d (0) indicates the current air pressure data, d (-1) indicates the previous air pressure data, d (1) indicates the next air pressure data, and ΔP indicates the measurement error of the pressure sensor 10a.

FIG. 4B is a graph showing the table of FIG. When the approximate curve of each data is obtained, if the air pressure is P and the elapsed time is T, it is expressed by the following equation.
P = -0.6798T + 214.27 (6)
In this embodiment, the air pressure decrease degree Pg is defined as a tire air pressure decrease speed, which corresponds to the slope (−0.6798) of the equation (6). The air pressure decrease degree Pg may not be calculated based on all data, but may be calculated from, for example, air pressure data read in the last three times.

[Estimated number of days of decline (hours)]
If the elapsed time T is calculated by substituting the difference between the current tire pressure and the set air pressure Ps in the air pressure P in the equation (6), the time required for the set air pressure Ps to decrease can be obtained. The number of days Dth until decreasing to Ps can be estimated. When the estimated number of days Dth is equal to or less than the set number of days (set time) Dr (for example, 7 days), the driver is notified of a decrease in tire air pressure. The set air pressure Ps is, for example, an air pressure that is 20% lower than the recommended air pressure of each of the tires 1, 2, 3, and 4. The set number of days Dr may be changed according to the driving history of the driver. For example, when the operation frequency is low, the set number of days Dr is set long, and when the operation frequency is high, the set number of days Dr is set short. According to this configuration, it is possible to give a sufficient margin for replenishing air to a driver having any driving frequency.

[Tire pressure drop notification method]
FIG. 5 shows an example of a method for notifying the driver of a decrease in tire air pressure, and shows a screen displayed on the in-vehicle display 6 or the like. For example, if it is determined that the tire air pressure of the tire 1 for the left front wheel falls to the set air pressure Ps in the number of days less than or equal to the set number of days Dr, the frame indicating the left front wheel tire 1 is set more than the other tires 2, 3, 4. Largely displayed, and the current tire pressure and the number of days until the tire pressure drops to the set pressure Ps are displayed in the frame. In addition, as in the case of the other tires 2, 3, and 4, even when it is not determined that the tire air pressure is reduced to the set air pressure Ps in the number of days less than the set number of days Dr, Only the tire pressure is displayed.

  The screen display of the in-vehicle display 6 or the like is not limited to that described above, and other screen displays may be used. For example, change the color of the frame indicating the tire that the tire pressure is determined to decrease to the set air pressure Ps in the number of days less than the set number of days Dr, or blink the frame display, or display the characters in the frame large Alternatively, the text in the frame may be displayed as “Check tire”. Also, the number of days Dth until the set air pressure Ps drops may be displayed at all times. If the number of days Dth exceeds the set number of days Dr, “OK” is displayed. When the number of days Dth falls below the set number of days Dr, the number of days Dth is displayed. You may make it do.

  The notification of the tire pressure drop to the driver is performed every time the ignition is turned on, but may be performed when the tire pressure approaches the set air pressure Ps even during traveling.

  With the above operation, the driver recognizes in advance the decrease in tire air pressure of each tire 1, 2, 3, 4 and refills the air before the air pressure of each tire 1, 2, 3, 4 falls below the set air pressure Ps. It can be performed. Therefore, it is possible to prevent the air pressure of each tire 1, 2, 3, 4 from becoming the set air pressure Ps or less.

  Next, the effect will be described.

  (1) The number of days Dth until the tire pressure drops to the set pressure Ps is estimated from the current tire pressure data and the pressure drop Pg, and the estimated number of days Dth is notified to the driver. Therefore, the driver can recognize the state of the tire pressure in advance, and can perform air replenishment or the like before the air pressure of each tire 1, 2, 3, 4 becomes equal to or lower than the set air pressure Ps. Therefore, it is possible to reduce the occurrence of a state in which the air pressure becomes equal to or lower than the set air pressure Ps during traveling where it is difficult to cope with air replenishment.

  (2) Since the air pressure decrease degree Pg is the tire air pressure decrease rate, the number of days Dth until the tire air pressure decreases to the set air pressure Ps can be estimated. Therefore, the driver can recognize the state of the tire air pressure in advance, and can perform air replenishment or the like before the air pressure of each of the tires 1, 2, 3, 4 becomes equal to or lower than the set air pressure Ps. Therefore, it is possible to reduce the occurrence of a state in which the air pressure falls below the set air pressure Ps during traveling.

  (3) It is determined whether or not the pressure sensor 10a is in an environment where stable air pressure data can be acquired without being disturbed, and the air pressure decrease degree Pg is calculated using the air pressure data acquired in an environment where stable air pressure data can be acquired. I tried to do it. Therefore, it is possible to calculate the air pressure decrease degree Pg with high accuracy. Moreover, since the air pressure data used for calculation of the air pressure decrease degree Pg can be reduced and the memory in the tire air pressure alarm controller 5 can be designed to be small, the cost can be reduced.

  (4) When the vehicle is stopped, at least one of the door unlocking operation by the keyless remote controller, the door unlocking operation by inserting the key into the door key cylinder, or the operation of turning on the ignition is performed. In this case, it is determined that the conditions for the stable data acquisition environment are satisfied. Therefore, the change in the temperature inside the tire is small as in traveling, and the tire internal temperature is also stable because in many cases a certain amount of time has passed since the vehicle stopped. In addition, there is little influence of weight changes due to passengers getting on and off. Therefore, the pressure sensor 10a can acquire stable air pressure data that is not subject to disturbance, and the air pressure decrease degree Pg is calculated using the air pressure data. Therefore, the air pressure decrease degree Pg can be calculated with high accuracy.

  (5) The driver is informed of a decrease in tire air pressure every time the ignition is turned on or when the tire air pressure approaches the set air pressure Ps. Therefore, the driver can recognize the tire pressure state at an early stage.

  (6) When the tire pressure drop notification to the driver is displayed on the in-vehicle display 6 when the current tire pressure and the number of days until the tire pressure drops to the set air pressure Ps are less than the set number of days, the number of days is displayed. . Therefore, the driver can recognize the tire pressure state at an early stage.

  (7) The tire air pressure detected by the pressure sensor 10a is corrected according to the temperature inside the tire detected by the temperature sensor 10b. Accordingly, it is possible to reduce the influence of the tire temperature change in the calculation of the air pressure decrease degree Pg, and to estimate the time until the tire air pressure decreases to the set air pressure Ps more accurately.

  (8) The set time Ts is set longer when the driving frequency is low, and is set shorter when the driving frequency is high. Therefore, since a driver with low driving frequency can be notified of a decrease in tire air pressure at an early stage, the driver can be made to recognize the decrease in tire air pressure more reliably.

  As mentioned above, although the tire pressure monitor of the present invention has been described based on the first embodiment, the specific configuration is not limited to this embodiment, and the gist of the invention according to each claim of the claims is described. Design changes and additions are permissible without departing.

  For example, in this embodiment, the tire pressure drop is notified by the screen display of the in-vehicle display 6, but may be notified by voice or the like.

  In the embodiment, the tire pressure monitoring device in a vehicle equipped with four tires such as a passenger car is shown, but the tire pressure monitoring device in a small vehicle equipped with three tires or a large vehicle equipped with five or more tires may be used. Can be applied.

It is a whole system figure of the amount of vehicles equipped with a tire pressure monitor device. It is detail drawing which shows a tire pressure monitoring apparatus. It is a flowchart which shows the flow of the process performed in a tire pressure warning controller. It is a table | surface and a graph of air pressure data. It is a figure which shows the example of the alerting | reporting method of a tire pressure fall.

Explanation of symbols

5 Tire pressure alarm controller 6 In-vehicle display 10a Pressure sensor 10b Temperature sensor

Claims (9)

In a tire air pressure monitor device that is attached to a tire and includes tire air pressure detecting means for detecting tire air pressure,
An air pressure decrease degree calculating means for calculating a tire air pressure decrease degree indicating a tire air pressure decrease tendency of the tire air pressure;
A reduction time estimation means for estimating a reduction time required for the tire air pressure to decrease to a set air pressure based on the tire air pressure decrease degree;
Informing means for informing the driver of the estimated decrease time;
A tire pressure monitoring device comprising: In the tire pressure monitoring device according to claim 1,
The tire pressure monitoring device according to claim 1, wherein the tire pressure drop calculation means calculates a tire pressure drop rate of the tire pressure as the tire pressure drop rate. In the tire pressure monitoring device according to claim 1 or 2,
Comprising a stable data acquisition environment determination means for determining a stable data acquisition environment, which is an environment in which the tire pressure detection means can acquire the tire pressure data without receiving disturbance,
The tire pressure monitoring device according to claim 1, wherein the tire pressure drop calculating means calculates the tire pressure drop based on the tire pressure detected by the tire pressure detecting means in the stable data acquisition environment. In the tire pressure monitoring device according to claim 3,
When the stable data acquisition environment judging means is at a stop of the vehicle and performs at least one of a door unlocking operation, a door opening operation, or an operation of turning on an ignition switch, A tire air pressure monitoring device that determines that the stable data acquisition environment is set. In the tire pressure monitoring device according to any one of claims 1 to 4,
The tire pressure monitoring device characterized in that the notification means notifies a driver every time an ignition switch is turned on or when the set pressure is approached. In the tire pressure monitoring device according to any one of claims 1 to 5,
The informing means displays the tire pressure on the in-vehicle display and the decrease time when the decrease time is equal to or less than a set time. The tire pressure monitoring device according to any one of claims 1 to 6,
A tire temperature detecting means attached to the tire for detecting the tire temperature;
Correction means for correcting the data of the tire air pressure according to the tire temperature;
With
The tire pressure drop calculating means calculates the tire pressure drop level based on the corrected tire pressure data. In the tire pressure monitoring device according to any one of claims 1 to 7,
The tire pressure monitoring device, wherein the notification means sets the set time short when the driving frequency of the driver is high, and sets the set time long when the driving frequency of the driver is low. A tire air pressure monitoring device, which is attached to a tire, detects tire air pressure, estimates a time taken for the tire air pressure to decrease to a set air pressure, and notifies the driver of the estimated time.

Images