JP3129671B2 - Method and apparatus for detecting decrease in tire air pressure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for detecting a decrease in tire air pressure. More specifically, the present invention relates to a method and a device for detecting a decrease in tire air pressure for detecting a decrease in a tire even when the vehicle is traveling at a low speed or a high speed.

[0002]

2. Description of the Related Art In recent years, as one of safety devices for four-wheeled vehicles such as passenger cars and trucks, a device for detecting a decrease in tire air pressure has been proposed, and some of them have been put to practical use.

The importance of a tire pressure drop detecting device has been recognized and developed mainly for the following reasons. That is, when the air pressure decreases, the temperature of the tire increases due to the increase in deflection. As the temperature increases, the strength of the polymer material used in the tire decreases, leading to tire burst. Usually, even if the tire air pressure drops by about 0.5 atm, the driver often does not notice it, so a device that can detect it has been desired.

A method for detecting a decrease in the air pressure in the apparatus for detecting a decrease in the air pressure of the tire is described in, for example, Japanese Patent Application Laid-Open Publication No. H11-64300.
Tires W ₁ , W ₂ , W ₃ and W ₄ (note that tires W ₁ and W ₂ respectively correspond to front left and right tires, and tires W ₃ and W ₄ respectively correspond to rear left and right tires. There is a method based on the difference between the rotational angular velocities F ₁ , F ₂ , F ₃ and F ₄ (hereinafter, collectively referred to as the rotational angular velocities F _i ) of the tires W _i .

[0005] In this way, for example on the basis of a signal outputted from the wheel speed sensor attached to the tire W _i, the rotational angular velocity F _i of the tires W _i are detected for each predetermined sampling period. Here, the detected rotational angular velocities F _i are all the same in the effective rolling radius of the tire W _i (the value obtained by dividing the distance traveled by the vehicle when the tire makes one revolution and dividing it by 2π when the tire rotates freely). In this case, if the vehicle is running straight, all are the same.

On the other hand, the effective rolling radius of the tire W _i varies for example to accommodate changes in tire pressure W _i. That is, when the air pressure of the tire W _i drops, the effective rolling radius smaller than that at a normal internal pressure.
Therefore, the rotational angular velocity F _i of the tire W _i whose air pressure is reduced becomes faster than at the time of normal internal pressure. Therefore, the difference in the rotational angular velocities F _i, can detect decrease in tire air-pressure W _i.

A determination formula for detecting a decrease in the air pressure of the tire W _i due to a difference in the rotational angular speed F _i is, for example, the one shown in the following expression (1) (for example, Japanese Patent Application Laid-Open No. Sho 63-305).
No. 011, JP-A-4-212609).

[0008] Assuming that the effective rolling radii of the respective tires W _i are all the same, the rotational angular velocities F _i are all the same (F ₁ = F ₂ = F ₃ = F ₄ ), so the judgment value D is 0. . Therefore, the threshold values D _TH1 and D _TH2 (where D _TH1 and D _TH2 >
0), and if D <−D _TH1 or D> D _TH2 ... (2) is satisfied, the tire W with reduced air pressure
_It is determined that there is _i , and if it is not satisfied, it is determined that there is no tire W _i with reduced air pressure. Then, when it is determined that there is a tire W _i having a decreased air pressure, an alarm is issued to the driver by, for example, an indicator.

[0009]

However, there is a drawback that erroneous detection may occur depending on the running state of the vehicle only by the determination of the decrease in the air pressure based on the equations (1) and (2). For example, when either the air pressure of one tire W _i of the tires W _i has dropped, the vehicle is, when traveling at a relatively low speed, accurately detect whether the air pressure is decreased However, when the vehicle is running while driving at a relatively high speed, there is a risk of erroneous detection. The reason is that the slip ratio of the decompression wheel at high speed decreases, and the rolling radius increases due to the centrifugal force of the tire.

In view of the circumstances described above, the present invention can accurately detect whether or not the tire air pressure has decreased regardless of the running state of a vehicle, and as a result, an erroneous / non-warning of an alarm (reduced pressure). It is an object of the present invention to provide a method and an apparatus for detecting a decrease in tire air pressure, which can prevent the occurrence of an alarm despite the occurrence of the alarm.

Further, an object of the present invention is to be able to accurately detect whether or not the tire pressure has decreased, irrespective of the speed at which the vehicle is running, among the running conditions of the vehicle, As a result, it is an object of the present invention to provide a method and an apparatus for detecting a decrease in tire air pressure which can prevent erroneous / non-occurrence of an alarm.

[0012]

According to the method of detecting a decrease in tire air pressure of the present invention, the rotational angular velocities of four tires provided in a vehicle are detected, and based on the detected rotational angular velocities, the tires are detected. air pressure is determined whether or not the decrease, if the air pressure is determined to be decreased, a pressure drop detecting method of the tire for generating an alarm, the pre-Symbol rotational angular velocity is detected, A determination value D is obtained based on each of the detected rotational angular velocities, and the absolute value of the determination value D is
When it is larger than a predetermined value , a low speed determination step for determining whether or not the tire air pressure is decreasing, and when the rotational angular velocity is detected, the vehicle speed is equal to or higher than a predetermined threshold value, and only when the vehicle is in the driving state, based on the detected rotational angular velocities, see <br/> contains a high-speed determination step of determining whether the tire pressure has dropped, determining the high-speed Step, the speed of the vehicle is predetermined
The speed above the threshold is divided into regions at regular intervals.
A predetermined number of speeds out of all the speed ranges
Data of a predetermined number of rotational angular velocities accumulate in the
At the point when the
Average the data, then least squares from the averaged data
After obtaining the quadratic function by the method,
The determination value D 'at a high speed is obtained, and the absolute value of the determination value D' is predetermined.
It is characterized in that an alarm is detected when the value is larger than the value .

[0013]

In the high-speed determination step, when the difference between the maximum value and the minimum value of the averaged data is less than a predetermined threshold value, the averaged data in all areas can be set to zero. .

[0015] The high-speed determination step may include a minimum of two.
If there is a risk of misjudgment when calculating from the relationship between the area used for multiplication and the averaged data, the data can be corrected.

In the high-speed determination step, the averaged data can be set to 0 when the high-speed area and the area used for the least squares method are close to each other.

Further, the high-speed determination step includes a minimum of two.
The threshold value for alarm determination can be changed depending on the lower limit speed range of the averaged data used for multiplication.

Further, the high-speed determination step includes a minimum of two.
The averaged data of the lower speed limits used for multiplication can be weighted.

[0019]

Further, the apparatus for detecting a decrease in the air pressure of a tire according to the present invention detects the rotational angular velocities of the four tires provided in the vehicle, and based on the detected rotational angular velocities, the tire air pressure decreases. and it is judged whether or not the that, when the air pressure is determined to be decreased, a pressure drop detecting device of the tire for generating an alarm, a speed detecting means for detecting the speed of the vehicles, the speed Determining means for determining whether or not the speed of the vehicle detected by the detecting means is equal to or higher than a predetermined threshold value; and driving state detecting means for detecting whether or not the vehicle is in a driving state. , The air pressure
Means for determining a decrease in, the respective rotational angular velocity is detected by the rotational angular velocity detecting means, obtains a determination value D based on the detected respective rotational angular velocity are, the absolute of the judgment value D
When the value is larger than a predetermined value, the low-speed determining means for determining whether or not the tire air pressure is decreasing and the rotational angular velocity detecting means detect each of the rotational angular velocities. Only when the speed of the vehicle detected by the detecting means is determined to be equal to or higher than the threshold value and when the driving state detecting means detects that the vehicle is in the driving state, the detected rotational angular velocity is reduced. based on, viewed contains a high-speed determining means for determining whether the tire pressure has dropped, the high-speed determining means, the vehicle
Speeds exceeding a predetermined threshold value are determined at regular intervals.
Area, and then determine
The predetermined number of rotation angular velocities
At the time when the data is accumulated, the condition of the data number is satisfied
The data in the averaged velocity region are averaged, and then the averaged data
After obtaining a quadratic function from the data by the least squares method,
A determination value D 'at a middle to low speed is obtained from the following function, and the determination value D'
Absolute value is characterized by the this <br/> detecting an alarm when greater than a predetermined value.

[0021]

[0022]

Further, the high-speed determination means can set the averaged data in all areas to 0 when the difference between the maximum value and the minimum value of the averaged data is less than a predetermined threshold value. .

The high-speed determining means may correct the data if there is a risk of erroneous determination when performing calculations from the relationship between the area used in the least squares method and the averaged data. it can.

The high-speed determination means can set the averaged data to 0 when the high-speed area and the area used for the least squares method are close.

Further, the high-speed determination means determines a lower limit speed area of the averaged data used in the least squares method.
The threshold value for alarm determination can be changed.

Further, the high-speed determination means can weight the averaged data of the lower limit speed used in the least squares method.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, a plurality of determination means suitable for the running state of a vehicle are provided. Therefore, the determination according to the traveling state of the vehicle can be realized by any of the determination means.

Therefore, when at least one of the plurality of determining means determines that the tire air pressure has decreased, it can be determined that the tire air pressure has reliably decreased. In other words, when all the determination means determine that all the tires have the normal internal pressure, it is possible to reliably determine that the tire has the normal internal pressure.

The present invention focuses on how fast the vehicle is traveling in the running state of the vehicle, and is provided with two determining means, a low speed determining means and a high speed determining means. .

For example, when the air pressure of any of the tires is low, when the vehicle runs at high speed, there is a case where the difference in the rotational angular velocity between the time when the air pressure is low and the time when the internal pressure is normal is almost eliminated. For this reason, there is a possibility that the determination unit that determines that the rotational angular velocity is detected may make an erroneous detection. on the other hand,
According to the investigation by the present applicant, even if the vehicle runs at high speed while the air pressure of any of the tires is low,
When the vehicle is in the driving state, it has been found that as the speed increases from a certain speed, the rotational angular velocity difference between the time when the air pressure decreases and the time when the normal internal pressure decreases decreases in a quadratic function. A method for finding the difference in rotational angular velocity between when the air pressure drops and when the internal pressure is normal has been found.

Therefore, according to the present invention, not only the low speed determining means for determining that the rotational angular velocity is detected, but also, if the rotational velocity is detected and the vehicle speed is equal to or higher than the threshold value, When the condition of the drive state is satisfied, a high-speed determination means for performing determination is prepared. Therefore, regardless of how fast the vehicle is traveling, it is possible to accurately detect whether or not the tire air pressure is decreasing. Therefore, it is possible to prevent erroneous occurrence / non-occurrence of an alarm.

The method and apparatus for detecting a decrease in tire air pressure according to the present invention will be described below with reference to the accompanying drawings. FIG.
1 is a block diagram showing an embodiment of a tire air pressure drop detecting device according to the present invention, FIG. 2 is a block diagram showing an electrical structure of the tire air pressure drop detecting device in FIG. 1, and FIG.
4 and 5 are flowcharts for explaining an alarm generation / stop process in the tire air pressure drop detecting device of FIG.
FIG. 6 is a flowchart for explaining the speed regression depressurization determination of the alarm generation / stop processing in the tire air pressure drop detection device of FIG. 6. FIG. 6 shows that when the vehicle is running at high speed, the longitudinal acceleration is in a positive range and the determination value is increased. FIG. 7 is a diagram for explaining the least squares method, and FIG. 8 is a flowchart for explaining another embodiment of the tire air pressure drop detecting device of the present invention. , FIGS.
0 is a flowchart for explaining the speed regression decompression determination in FIG. 8, FIG. 11 is an explanatory diagram of the erroneous determination, and FIG. 12 is a diagram for explaining the least square method according to another embodiment.

As shown in FIG. 1, the apparatus for detecting a decrease in tire air pressure according to the present invention determines whether or not the air pressure of the _four tires W ₁ , W ₂ , W ₃ and W ₄ provided in the four-wheel vehicle has decreased. A normal wheel speed sensor 1 provided for each of the tires W ₁ , W ₂ , W ₃ and W ₄ is provided. The output of the wheel speed sensor 1 is provided to the control unit 2. The control unit 2 is connected to a display device 3 configured by a liquid crystal display element, a plasma display element, a CRT, or the like for notifying the tire W _{i of} reduced air pressure. Moreover, the tires W _i, so are manufactured to include variations within standards, W _i in a normal internal pressure
Needs to be corrected so that the dynamic load radii are the same.
Therefore, reference numeral 4 is a switch that triggers the above-described correction.

As shown in FIG. 2, the control unit 2 includes an I / O interface 2a necessary for transmitting and receiving signals to and from an external device, and a CPU 2b functioning as a center of arithmetic processing.
And R in which the control operation program of the CPU 2b is stored.
The OM 2c includes a RAM 2d from which data and the like are temporarily written when the CPU 2b performs a control operation, and from which the written data and the like are read.

In the vehicle speed sensor 1, the tire W _i
A pulse signal (hereinafter, referred to as a wheel speed pulse) corresponding to the number of rotations is output. In addition, the CPU 2b calculates the rotational angular velocity F _i of each tire W _i every predetermined sampling period ΔT (sec), for example, ΔT = 1 second, based on the wheel speed pulse output from the wheel speed sensor 1.

Next, an alarm generation / stop process in the method for detecting a decrease in tire air pressure according to the present invention will be described. This processing is realized by software. First, the rotational angular velocity F _i of each tire W _i is calculated based on the wheel speed pulses outputted from the wheel speed sensors 1 per second, as shown in FIG. 3 (step S1). Here, since the tire W _i is manufactured with a variation (initial difference) within the standard, the effective rolling radius of each tire W _i is such that even if all the tires W _i have a normal internal pressure, Not necessarily the same.
Therefore, the rotational angular velocities F _i of the respective tires W _i vary. Therefore, the rotational angular velocity F1 _i corrected to cancel the variation due to the initial difference is calculated (Step S).
2). Specifically, it is corrected with the _{F1 1 = F 1 F1 2 =} mF 2 F1 3 = F 3 F1 4 = nF 4. The correction coefficients m and n are calculated, for example, by calculating the rotational angular velocity F _i on condition that the vehicle is traveling straight, and based on the calculated rotational angular velocity F _i , m = m
It is corrected to be obtained as _{F 1 / F 2, n =} F 3 / F 4.

Then, the speed V, the turning radius R, the lateral G, and the longitudinal acceleration A of the vehicle are calculated based on the F1 _i (step S3).

The rotational angular velocity F _i varies greatly depending on the magnitude of the radius R of the vehicle, the speed V of the vehicle, the lateral acceleration G of the vehicle, and the longitudinal acceleration A (hereinafter simply referred to as longitudinal acceleration). As a result, erroneous determination may be caused.

[0040] That is, when the turning radius R is relatively small, there is a risk that the tires W _i is skidding,
It is highly possible that the variation in the calculated rotational angular velocity F _i becomes large. Further, when the speed V of the vehicle is extremely low speed, since the detection accuracy of the vehicle speed sensor 1 is significantly reduced, it is likely that variations in the rotational angular velocities F _i calculated increases. Further, since the lateral G of the vehicle is relatively large, there is a risk that the tires W _i is skidding,
It is highly possible that the variation in the calculated rotational angular velocity F _i becomes large. Further, rotation absolute value of the longitudinal acceleration A of the vehicle is relatively large, for example because the vehicle is considered slip or effects of a foot brake of the tire W _i due to rapid acceleration or rapid deceleration, which is calculated There is a high possibility that the variation in the angular velocity F _i becomes large. As described above, when there is a high possibility that the rotation angular velocity F _i includes an error, a method of rejecting (eliminating) the rotation angular velocity F _i without using it for detecting a decrease in air pressure is preferable.

Therefore, the turning radius R, the speed V, and the lateral G of the vehicle
And step S2 based on the longitudinal acceleration A of the vehicle
It is determined whether or not to reject the obtained rotational angular velocity F1 _i (step S4).

As a result of the determination in step S4, if the rotational angular velocity F1 _i is not rejected, a determination value D is calculated by the following equation (3) based on the rotational angular velocity F1 _i (step 5). ).

F1 ₁ + F1 _{4 F1 2 + F1 3 D = 2} 2 ···· (3) F1 1 + F1 2 + F1 3 + F1 4 4 Incidentally, the turning radius R of the vehicle in the step S5, the speed V, the calculation of the lateral G and the longitudinal acceleration A of the vehicle ,
This is performed using the rotational angular velocity F1 _i corrected for the initial difference. On the other hand, the effective rolling radius of the tire W _i is the initial difference well, also varies by the turning radius R, the speed V, the lateral G and the longitudinal acceleration A of the vehicle. Therefore, the determination value D obtained in step S5 is influenced by the fluctuation factors including the turning radius R, the speed V, the lateral G, and the longitudinal acceleration A of the vehicle.

Therefore, the turning radius R, the speed V, and the lateral G of the vehicle
In addition, a correction is made to eliminate the influence of the fluctuation factor of the determination value D such as the longitudinal acceleration A (step S6).

Specifically, the correction is made by the following equation (4).

D ′ = D−α1 × horizontal G−α2 × horizontal G × A (4) The D ′ obtained in step S6 is temporarily stored in, for example, the RAM 2d.

[0047] Here, in the formula (4), [alpha] 1 and α2 are coefficients, performs test run when the coefficient [alpha] 1 and α2 are each tire W _i is found to be normal, calculated at that time It is determined in advance based on the determined turning radius R, speed V, lateral G, and longitudinal acceleration A of the vehicle. The coefficients α1 and α2 are stored in advance in, for example, the ROM 2c of the control unit 2.

Using the corrected determination value D 'obtained in step S6, it is determined whether or not the air pressure has decreased by the following equation (5) (step S7). In equation (5), for example, D _TH1 = D _TH2 = 0.1
It is.

D ′ <− D _TH1 or D ′> D _TH2 ... (5) As a result, if the determination value D ′ satisfies the expression (5), it is determined that the air pressure has decreased. If the same determination is performed continuously to some extent, an alarm is generated (step S9). On the other hand, if the determination value D 'does not satisfy the expression (5), it is determined that the air pressure has not decreased, and the alarm is canceled when the same determination is performed several times in succession (step S8). ). That is, instead of performing an alarm or prohibition each time it is determined that the air pressure is low or that the internal pressure is normal, it is performed when the same determination is performed to some extent continuously over a plurality of cycles. Therefore, it is possible to prevent erroneous occurrence / non-occurrence of an alarm due to sudden effects such as noise.

[0050] Incidentally, for example, when the air pressure of any of the tires W _i of the tires W _i has dropped, when the vehicle is relatively low speed traveling, the tire W
_Since the rotation angular velocity F _i of _i is higher than the rotation angular velocity F _i of the tire W _{i having} the normal internal pressure, the determination value D ′ satisfies the equation (5) in step S7. In contrast, when the vehicle is traveling at a relatively high speed, almost no difference between the rotational angular velocities F _i of the tires W _i of the rotational angular velocities F _i and a normal internal pressure of the tire W _i whose air pressure has dropped There is a case. At this time, since the judgment value D 'is likely to be 0, in step 7, all the pneumatic pressure of the tire W _i is thus determined to be normal. Therefore,
In the present embodiment, when the vehicle is in a driving state even at a high speed, the determination value D ′ becomes 2 as the speed increases from a certain speed.
Since the value decreases as a quadratic function (see FIG. 5), the determination value D 'at a low speed by the quadratic function is obtained, even when the vehicle is traveling at a relatively high speed, only when the vehicle is driving. The alarm generation preparation process (hereinafter, referred to as speed regression pressure reduction determination method) is performed again (step 10).

Next, the details will be described with reference to the flowchart of FIG.

First, since the speed regression pressure reduction measurement method is performed only when the vehicle is running at a relatively high speed and in a driving state, the speed V of the vehicle becomes equal to a predetermined threshold value V _TH (for example, V _TH = 120 km / h) and whether or not the longitudinal acceleration A for determining whether the vehicle is in a driving state is equal to or greater than a predetermined threshold value A _TH (for example, A _TH = 0 G) (step S11). ).

As a result, when it is determined that the speed V of the vehicle is less than the threshold value V _TH and the longitudinal acceleration A is less than the threshold value A _TH , the above-described problem does not occur.
It is not necessary to perform the speed regression decompression determination method described later. Moreover, not performed velocity regression pressure judgment method may speed V of the vehicle is the threshold V _TH less than or longitudinal acceleration A is determined to be less than the threshold value A _TH. Therefore step S
The process returns to step S1 without performing the operations from 12 to S25. On the other hand, if the velocity V of the vehicle is the threshold value V _TH or more and the longitudinal acceleration A is determined to be equal to or greater than the threshold value A _TH is then velocity regression pressure judgment process until step S12~S26 described Is performed.

In the velocity regression decompression determination method, first, the current velocity V is divided into regions (step S1).
2). Step S12 will be specifically described. For example, the speed is increased from 120 km / h to 1 every 10 km / h.
If the current speed V is 135 km / h, for example, if the current speed V is 135 km / h, the speed of 120 km / h is in the region of 1 and 135 km / h is in the region of 130 km / h. Will be. The number of areas to be divided is determined by the allowable speed of the vehicle.

When the process is completed, the current determination value D 'and the speed V are stored in the speed area allocated in step S12.
Is added (steps S13 and S14). The steps S13 and S14 will be specifically described. As can be seen from the flowchart of FIG.
It is performed every second, and when it is determined that the vehicle is driving at high speed and driving from the current speed V and the longitudinal acceleration A,
Steps S12 to S26 shown in FIG. 4 are performed. Therefore, when it is determined that the vehicle is running at high speed and is being driven, a process is performed in which the speed V per second and the determination value D 'are put in the corresponding area, and the values are added to the value added up to now. Perform

Next, the number is counted up to count how many data are present in the corresponding speed area (step S15). Here, the steps S11 to S15 are summarized, and the speed V per second and the determination value D ′ that can be used for the processing of the speed regression decompression method that the vehicle is running at a high speed are being driven.
Is added to the divided area, and the number of data in the area is counted.

Next, it is checked whether or not there is a speed area having six or more data in all the areas (step S17). If there is, the average of the judgment value D 'and the speed V that have been added up to that point in the area is obtained (step S18),
The count is incremented to count how many areas with six or more data have been created (step S19). If not, no operation is performed.

If these operations are completed and there are three or more speed regions with six or more data, the speed = 0 km / speed based on the speed V averaged in each region and the determination value D '.
The determination value D '(CrosP) at the time of h is obtained by the least squares method (steps S21 to S22).

To explain the least squares method in detail, if the horizontal axis indicates the speed V and the vertical axis indicates the judgment value D ', the averaged speed V and the corresponding judgment value D' are plotted at three points. (See FIG. 6). Next, assuming a quadratic curve y = ax ² + b passing through the center of these three points, the square of the length of a line drawn from each point so as to be parallel to the y axis is added to the quadratic curve. The method of obtaining a and b that minimizes the sum is the least square method used here. Note that b here
Corresponds to the above-mentioned CrosP.

Further, if there is no speed area having six or more data in three areas, no operation is performed.

Using the determination value D '(CrosP) obtained in the step S22, it is determined whether or not the air pressure has decreased according to the equation (5) (step S2).
3-S26). In the following equation (6), for example, D _HTH1 = D _HTH2 = 0.1.

| CrosP | <−D _HTH1 or | CrosP | <−D _HTH2 (6) As a result, if the determination value CrosP satisfies the expression (6), it is determined that the air pressure has decreased. , An alarm is generated (step S24). On the other hand, if the determination value CrosP does not satisfy Expression (6), it is determined that the air pressure has not decreased, and the alarm is deleted (step S26). When various conditions are met and an alarm is determined, all speed range variables are cleared.

Next, another embodiment of the present invention will be described. Step S ₁ 1 to S ₁ 6 8 are the same as steps S1~S6 in the embodiment, step S ₁
After 5 has been completed, the process proceeds to Step S ₁ 6, then using the determination value D 'after correction is gills in the Step S ₁ 6, performs various judging decompression (Step S ₁ 7). In the pressure reduction determination, it is determined by the following equation (7) whether or not the air pressure has decreased. In equation (7), for example, D _TH1 = D _TH2 = 0.1.

D ′ <− D _TH1 or D ′> D _TH2 ... (7) As a result, if the judgment value D ′ satisfies the expression (7), an alarm flag is set. Clear the flag.

[0065] Then the speed regression pressure judgment (step S ₁ 8) is described below in detail about this. As a result, if the judgment value satisfies the alarm judgment condition, the alarm flag is set, and if not, the alarm flag is cleared. Furthermore, if the alarm flag is set,
Lights an alarm lamp, if it is not set, performs processing such as erasing a warning lamp (step S ₁ 9~S _{1 1}
1).

[0066] Incidentally, as in the embodiment, for example, when the air pressure of any of the tires W _i of the tires W _i has dropped, when the vehicle is relatively low speed traveling, the tire W since the rotational angular velocity F _i of _i is faster than the rotational angular velocity F _i of the tires W _i normal internal pressure, in the step S ₁ 7, the determination value D 'satisfies the warning determination condition. In contrast, when the vehicle is traveling at a relatively high speed, almost no difference between the rotational angular velocities F _i of the tires W _i of the rotational angular velocities F _i and a normal internal pressure of the tire W _i whose air pressure has dropped There is a case. At this time, since the judgment value D 'is likely to be 0, the step S ₁ 7
Oite, the pneumatic pressure of the tire W _i all will be determined to be normal. However, when the vehicle is in a driving state even at high speed, it is known that the determination value D ′ decreases quadratically as the speed increases (see FIG. 6).

Therefore, in this embodiment, the judgment value D 'at the time of low speed is obtained by the quadratic function, and even if the vehicle is traveling at a relatively high speed, the alarm generation preparation process is performed again only during driving. Perform

Next, the details will be described with reference to the flowcharts of FIGS.

First, the speed regression decompression measurement method is performed only when the vehicle is traveling at a relatively high speed and in a driving state. Therefore, the speed V of the vehicle is set to a predetermined threshold value V _TH (for example, V _TH = 85 km / h) or more and a threshold value A _TH (for example, A _TH = 0 G or −0.03 G) for determining the longitudinal acceleration A for determining whether the vehicle is in a driving state.
It is determined whether the whether more (Step S ₁ 13).

As a result, if it is determined that the speed V of the vehicle is less than the threshold value V _TH or the longitudinal acceleration A is less than the threshold value A _TH , the above-described phenomenon does not occur. Do not perform the speed regression decompression judgment method. Therefore Step S ₁ without an operation of step S ₁ 14~S ₁ 25
Go back to 9. On the other hand, step S ₁ 14~S ₁ 25 velocity V of the vehicle when the threshold V _TH or more and the longitudinal acceleration A is determined to be equal to or greater than the threshold value A _TH is described below
The speed regression pressure reduction determination method up to is performed.

[0071] In the speed regression pressure judgment method, starting the first moment of the velocity V since it is divided into regions (step S ₁ 1
4). When Step S ₁ 14 will be described in detail, for example, when the separating speed from 85km / h in the region of from 1 to speed up 155km / h per 5km / h to 14, the speed V at the present time, for example, 100km / h Then, the speed of 85 km / h is 100 km
/ H is in the range of 100 km / h, which is in the area of 4. The number of areas to be divided is determined by the allowable speed of the vehicle.

[0072] we crowded adding judgment value D 'and the speed V of the current to the speed area allocated in step S ₁ 14 When the process is finished (Step S ₁ 15). Step S ₁
More specifically, as can be seen from the flowchart of FIG. 8, the speed regression decompression determination process is performed every second, and it is determined from the current speed V and the longitudinal acceleration A that the vehicle is running at high speed and driving. If it is, so that the process of step S ₁ 14~S ₁ 25 shown in Figure 9-10. Therefore, when it is determined that the vehicle is driving at high speed and driving, a process is performed in which the determination value D 'at that time is put into the corresponding area every second and the value is added to the value added up to now. Do.

Next, increasing one counter to teach how this corresponding data rate within a region number is (Step S ₁ 16). Here, steps S ₁ 14 to S ₁
In summary, the judgment value D 'for each second, which can be used for the processing of the speed regression decompression method that the vehicle is running at high speed and driving, is added to the divided area, and the counter of the corresponding area is increased by one. become.

[0074] Next, it is checked whether all numbers (e.g., 15) to define in advance for region more speed regions of data a number of predetermined (e.g. four regions) (step S ₁ 17). If any, an average and median of the speed range of the judgment value D 'which has crowded adding ever in that region (step S ₁ 18).

[0075] Further, 'threshold difference between the maximum value and the minimum value of predetermined, for example when less than 0.04 mean D in all regions' average D a to 0 (step S ₁ 19
~S ₁ 20). In this case, the alarm determination value finally obtained is set to 0 so that no alarm is detected.

[0076] In the present invention the step S ₁ 19~S ₁ 2
0 is not limited to this, for example, in step S ₁ 19~S ₁ 20, when the operation from the relationship between the area and the average D 'used for least squares, it may become erroneous determination . For example, as shown in FIG. 11, regression data is collected in four speed regions b which are far from the middle and low speeds of the judgment value a obtained by the regression, and the judgment value of the data decreases as the speed increases. If the difference c between the maximum value and the minimum value is still a degree of variation at normal internal pressure of, for example, 0.03 or less, a quadratic regression curve is calculated based on this. If required, there is a possibility that an erroneous determination will be made. Note that d in FIG. 11 is an alarm determination threshold.

[0077] or step S ₁ 19~S ₁ in 20, high-speed region (e.g. 150 km / h or higher) and minimum 2 for use in the multiplication region (are adjacent all example four regions) close when the average D 'Can be zero.

[0078] or in Step S ₁ 19~S ₁ 20, the lower limit speed of the area of the average D '(e.g., 150 km /
h), it is possible to change the threshold value for alarm determination (for example, to provide a variable for doubling the threshold value).

[0079] Further, in step S ₁ 19~S ₁ 20, region lower limit speed of the average D '(e.g., 150 km /
h), the average D 'of the lower limit speeds may be weighted (for example, two).

After these operations, if there are four speed regions having 15 or more data, the judgment value at a low speed based on the intermediate speed V and the average D 'of each region averaged in each region. D 'the (CrosP) determined by the least squares method (step S ₁ 21).

The least-squares method will be described in detail. When the speed V is plotted on the horizontal axis and the decision value D 'is plotted on the vertical axis, the intermediate speed V of each region obtained from the above and the decision value D' corresponding thereto are 4 A point plot will be made (see FIG. 12). Next, assuming a quadratic curve y = ax ² + b passing through the center of these four points, the square of the length of a line drawn from each point so as to be parallel to the y axis is added to this quadratic curve. The method of obtaining a and b that minimizes the sum is the least square method used here.
Here, b corresponds to the above-mentioned CrosP.

If there is no speed area having 15 or more data in the four areas, no particular operation is performed.

[0083] Using the step S ₁ 21 in the obtained judgment values D '(CrosP), by the following equation (8),
It is determined whether the air pressure has decreased (step S).
_{1 22~S 1} 25). In the following equation (8), for example, D _HTH1 = D _HTH2 = 0.1.

CrosP <−D _HTH1 or CrosP <−D _HTH2 (8) As a result, if the determination value CrosP satisfies the expression (8), it is determined that the air pressure has decreased, and the alarm flag is set. set (step S ₁ 23). On the other hand, the judgment value CrosP
If does not satisfy Expression (8), it is determined that the air pressure has not decreased, and the alarm flag is cleared (step S _1).
24). In the case where various conditions makes a determination of matching alarm clear the variables for all speed regions (step S ₁ 25).

[0085]

As described above, according to the present invention,
Since a plurality of determination means suitable for the traveling state of the vehicle are provided, the determination according to the traveling state of the vehicle can be realized by any of the determination means. Therefore, regardless of the running state of the vehicle, it is possible to accurately detect whether or not the tire air pressure is decreasing, and thus it is possible to prevent erroneous / non-warning of an alarm. As a result, the reliability of the driver's warning can be improved, and traffic safety can be improved.

In addition to the low speed judging means for judging when the rotational angular velocity is detected, the condition that, after the rotational angular velocity is detected, the vehicle speed is equal to or higher than a threshold value and the vehicle is being driven. Is satisfied, a high-speed determination means for making a determination is provided, so that regardless of how fast the vehicle is traveling, it is possible to accurately determine whether the tire pressure has decreased or not. Can be detected. Therefore, it is possible to prevent erroneous / non-alarm generation. for that reason,
Since the reliability of the driver's warning can be improved, traffic safety can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a tire air pressure drop detecting device of the present invention.

FIG. 2 is a block diagram showing an electrical configuration of the tire air pressure drop detecting device in FIG. 1;

FIG. 3 is a flowchart for explaining an alarm generation / stop process in the tire air pressure drop detecting device and method in FIG. 1;

FIG. 4 is a flowchart for explaining speed regression pressure reduction determination of an alarm generation / stop process in the tire air pressure drop detection device and method in FIG. 1;

FIG. 5 is a flowchart for explaining speed regression pressure reduction determination of an alarm generation / stop process in the tire air pressure drop detection device and method in FIG. 1;

FIG. 6 is an explanatory diagram showing that, when the vehicle is traveling at high speed, the determination value decreases in a quadratic function with an increase in speed when the longitudinal acceleration is in a positive range.

FIG. 7 is a diagram for explaining the least squares method.

FIG. 8 is a flowchart for explaining another embodiment of the tire air pressure drop detecting device of the present invention.

FIG. 9 is a flowchart for explaining speed regression pressure reduction determination in FIG. 8;

FIG. 10 is a flowchart for explaining speed regression pressure reduction determination in FIG. 8;

FIG. 11 is an explanatory diagram of an erroneous determination.

FIG. 12 is a diagram for describing a least squares method according to another embodiment.

[Explanation of symbols]

1 the wheel speed sensor 2 control unit 3 indicator _{W 1, W 2, W 3} , W 4 tires

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) B60C 23/00-23/08 G01L 17/00

Claims (2)

(57) [Claims] 1. The method according to claim 1, wherein each of the rotational angular velocities of four tires provided in the vehicle is detected, and based on the detected rotational angular velocities, it is determined whether or not the air pressure of the tire is reduced. when it is determined to be, a pressure drop detecting method of the tire for generating an alarm, the pre-Symbol rotational angular velocity is detected, obtains a determination value D based on the detected respective rotational angular velocity were , The absolute value of this determination value D
When the value is greater than a predetermined value , a low speed determination step for determining whether or not the tire air pressure has decreased, and when the rotational angular velocity is detected, the vehicle speed is equal to or higher than a predetermined threshold value. and only when the vehicle is in the driving state, based on the detected rotational angular velocity, viewed contains a high-speed determination step of determining whether the tire pressure has dropped, the high-speed determining step Where the vehicle speed is predetermined
Is divided into regions at regular intervals, and then the speed
A predetermined number of speed ranges out of all speed ranges
When a predetermined number of rotation angular velocity data have accumulated
The data in the speed range that satisfies the condition of the number of data
Are averaged, and then the least squares method is used from the averaged data.
After obtaining a quadratic function, the
A determination value D ′ is obtained, and the absolute value of the determination value D ′ is determined to be a predetermined value.
A method for detecting a decrease in tire air pressure , wherein an alarm is detected when the tire pressure is larger . 2. The method according to claim 1, further comprising: detecting rotational angular velocities of four tires provided in the vehicle, determining whether or not the tire air pressure has decreased based on the detected rotational angular velocities, and reducing the air pressure. when it is determined to be, a pressure drop detecting device of the tire for generating an alarm, a speed detecting means for detecting the speed of the vehicles, the speed of the vehicle detected by the speed detecting means in advance Determining means for determining whether or not the vehicle is greater than or equal to a predetermined threshold, and driving state detecting means for detecting whether or not the vehicle is in a driving state,
Means for determining a decrease in the air pressure, the respective rotational angular velocity is detected by the rotational angular velocity detecting means, obtains a determination value D based on the detected respective rotational angular velocity are, the determination
When the absolute value of the value D is larger than a predetermined value, the low speed determining means for determining whether or not the tire air pressure has decreased and the rotational angular velocity detecting means determine the rotational angular velocity. Only when the speed of the vehicle detected by the speed detecting means is determined to be equal to or higher than the threshold value and the driving state detecting means detects that the vehicle is in the driving state, the detection is performed. was based on the rotation angular velocity, viewed contains a high-speed determining means for determining whether the tire pressure has dropped, the high-speed determining means, the speed of the vehicle is predetermined threshold
The above speeds are divided into regions at regular intervals, and then all
Of all speed ranges, a predetermined number of speed ranges
When a predetermined number of rotation angular velocity data have accumulated,
The data within the speed range that satisfies the data number condition is averaged.
From the averaged data by the least squares method
After finding the quadratic function, judge at medium to low speed from the quadratic function
A value D ′ is obtained, and the absolute value of the determination value D ′ is larger than a predetermined value.
An apparatus for detecting a decrease in air pressure of a tire , wherein an alarm is detected when the threshold is high .