JP3333698B2 - Tire pressure detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire pressure detecting device for detecting a tire pressure condition such as a puncture in a vehicle.

[0002]

2. Description of the Related Art A tire pressure detecting device monitors a tire pressure condition during running of a vehicle and informs a driver or the like of a tire abnormality such as tire deflation. The tire pressure detecting device detects the tire pressure directly. 5-1.
No. 33831 discloses a tire pressure detecting device (first tire pressure detecting device).
As in the conventional example), there is an apparatus that focuses on the correlation between the tire air pressure and the tire resonance frequency and uses the tire resonance frequency (resonance point method). In the first conventional example, the spectrum of the vibration component of the wheel speed is obtained by fast Fourier transform (FFT) calculation of the wheel speed (see FIG. 14), the resonance frequency of the tire is detected, and as shown in FIG. If it falls below the threshold, it is determined that an air leak such as a puncture has occurred in the tire, and a warning is issued.

Japanese Patent Application Laid-Open No. Sho 63-305011 does not provide an absolute evaluation of detecting tire air pressure based on a resonance frequency as in the first prior art, but indirectly detects a tire air pressure state (such as occurrence of puncture). A method for detecting a reduced pressure tire of a vehicle is disclosed. In this method for detecting a reduced pressure tire of a vehicle (second conventional example), the angular velocities of four wheels are detected, and the sum of the angular velocities of two pairs of wheels located on a diagonal line is calculated. If the values are within the values, the angular velocity of each wheel is compared with the average value of the angular velocities of the four wheels to relatively evaluate the decrease in air pressure.

[0004]

However, the first problem is to be solved.
In the conventional example, since the wheel speed includes other resonance frequencies that become noise in addition to the resonance frequency of the tire, the quality of the S / N ratio affects the detection accuracy of the tire air pressure. As for the S / N ratio, the driving wheels decrease in the high speed range, and the practical limit speed of the first conventional example is about 60 to 100 km / h.

In the second conventional example, there is no limitation on the vehicle speed as in the first conventional example, but only relative determination of one wheel can be made, and it is not known which of the two diagonal wheels is abnormal. .

Accordingly, an object of the present invention is to provide a tire pressure detecting device capable of performing absolute evaluation of a tire pressure state even in a high-speed range.

[0007]

According to the first aspect of the present invention, the resonance frequency extraction means detects the resonance of the tire mounted on each wheel from the wheel speed of each wheel detected by the wheel speed detection means when the vehicle is running. The frequency is extracted, and the determination unit determines the air pressure state of the tire of the wheel based on the resonance frequency, the deviation of the rotational state of the left and right wheels in the driven wheels and the left and right wheels of the drive wheels based on the wheel speed. A rotation state value calculation means for calculating a rotation state value depending on a difference in rotation state deviation, and a vehicle speed exceeding a preset upper limit value
The amount of change over time and the vehicle speed of the rotation state value from
A rotational state value change amount calculating means and a resonance frequency change amount calculating means for calculating a temporal change amount of the resonance frequency of the driven wheel after the above, and a resonance when the tire air pressure changes stored in the storage means. Correction means for converting the change over time in the resonance frequency of the driven wheel into a change over time in the rotation state value based on the relationship between the frequency and the rotation state value, and correcting the change over time in the rotation state value with the converted change over time. When the vehicle speed becomes equal to or higher than the <br/> upper limit, based on the stored relationship in the storage unit, the vehicle speed with time variation of the corrected rotational state value by the correction means from equal to or more than the upper limit value in terms of change over time in the resonance frequency of the drive wheels, the vehicle speed is above the upper limit value exceeds previous estimates the resonance frequency of the drive <br/> wheels from the resonance frequency and the temporal variation amount of the drive wheel the drive wheel resonance frequency estimate Means Therefore, the determination means is set so that the tire pressure state of the drive wheel is determined based on the resonance frequency estimated by the drive wheel resonance frequency estimation means at the vehicle speed equal to or higher than the upper limit value.

[0008] The correction means eliminates the influence of the time-dependent change in the rotational state value of the driven wheel due to a decrease in the tire air pressure from the time-dependent change in the rotation state value. Only the components that depend on the change over time in the drive wheel bias remain. By converting the corrected rotational state value over time, the amount of change over time of the resonance frequency of the drive wheel due to a decrease in tire air pressure is known. Thus, from the resonance frequency of the drive wheel before the vehicle speed exceeds the upper limit value and the amount of change over time in the resonance frequency of the drive wheel, the resonance frequency of the drive wheel with reduced tire pressure can be estimated with good accuracy, and the limit speed is increased. be able to.

The deviation may be a wheel speed ratio as in claim 2 or a wheel acceleration ratio as in claim 3.

According to the present invention, when the resonance frequency of the driving wheel cannot be detected before the vehicle speed exceeds the upper limit,
The determination means is set so as to determine the tire pressure state of the drive wheel based on the amount of change over time in the rotation state value corrected by the correction means.

In the corrected amount of change in the rotational state value with time, only a component that depends on the change with time in the bias of the drive wheel due to the decrease in tire air pressure remains. Therefore, even when the vehicle rapidly accelerates, for example, when the resonance frequency of the drive wheel before the vehicle speed exceeds the upper limit cannot be detected and the resonance frequency of the drive wheel cannot be estimated, the corrected rotation state value The tire pressure state of the drive wheel can be relatively determined from the amount of change with time.

According to the fifth aspect of the present invention, when the amount of change over time in the rotational state value cannot be calculated, the determining means determines the tire pressure state of the drive wheel based on the rotational state value calculated by the rotational state value calculating means. Is set to be determined.

When the vehicle suddenly accelerates and the vehicle speed exceeds the upper limit value, it is impossible to calculate the time-dependent change in the rotation state value at a very early stage. Since the wheel speed is larger than the wheel speed of the wheel, the presence or absence of abnormality in the tire pressure is reflected in the rotation state value. Therefore, even if the vehicle suddenly accelerates in a state where the air pressure of a certain tire has decreased since the start of traveling and the vehicle speed exceeds the above upper limit, an abnormality in the air pressure of the tire can be detected early.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 shows a tire pressure detecting device according to the present invention. The vehicle on which the tire pressure detecting device is mounted is an FR vehicle in which an engine is mounted in an engine room at a front portion of the vehicle and rear wheels are driving wheels. Wheel speed sensors 1a and 1 serving as wheel speed detecting means provided for each tire of the vehicle.
b, 1c, 1d, an arithmetic processing device 2 having the wheel speed sensors 1a to 1d as inputs, and a warning device 3 for warning a driver of a decrease in tire air pressure when a warning signal is issued from the processing device 2. It is composed. Wheel speed sensors 1a-1d
Among them, two (for example, 1a and 1b) correspond to the front wheels, and the remaining two (for example, 1c and 1d) correspond to the rear wheels.

The arithmetic processing unit 2 is composed of a microcomputer or the like.
It is executed on software of the arithmetic processing unit 2 based on the pulse signals from a to 1d. The functional configuration of the arithmetic processing device 2 is as follows. The wheel speed data input as pulse signals from the wheel speed sensors 1a to 1d is calculated by the wheel speed calculating unit 2a, the FFT calculating unit 2b, the averaging unit 2c, the moving average processing unit 2d, the resonance frequency The data is input to the differential pressure determination value calculator 2j and the resonance frequency storage 2f via the calculator 2e. The wheel speed data is input from the wheel speed calculator 2a to the differential pressure determination value calculator 2j and the wheel speed deviation value storage 2i via the wheel speed deviation calculator 2g and the wheel speed deviation average processor 2h. It has become. Resonance frequency storage unit 2f and wheel speed deviation value storage unit 2
i is constituted by the memory of the microcomputer.
The data read from the resonance frequency storage unit 2f and the wheel speed deviation value storage unit 2i are combined with the data from the resonance frequency calculation unit 2e and the wheel speed deviation average processing unit 2h together with the differential pressure determination value calculation unit 2j and the air pressure drop determination unit. After 2k, the data is processed into determination data of the tire pressure state and output to the alarm device 3.

FIG. 2 shows the flow of the main routine from the calculation of the wheel speed executed by the arithmetic processing unit 2 to the warning of the decrease in air pressure. Step (hereinafter referred to as S) 100
F and S100R denote a front wheel resonance frequency detection subroutine and a rear wheel resonance frequency detection subroutine, in which resonance frequencies are extracted based on front wheel speed and rear wheel speed, respectively.
In S200, a wheel speed deviation value D is calculated based on the four wheel speeds. The wheel speed deviation value D is determined by the wheel speed sensors 1a to 1d.
This is given as a function of the wheel speeds of the front, rear, left and right wheels detected by, and details of the calculation will be described later.

FIG. 3 shows the flow of the resonance frequency calculation subroutine, which is the same for the front wheels and the rear wheels. S
Reference numeral 110 denotes an operation of a wheel speed calculating unit 2a which constitutes a wheel speed detecting means together with the wheel speed sensors 1a to 1d. Each wheel is calculated from the number of pulse signals input from the wheel speed sensors 1a to 1d within a predetermined time, for example, 5 ms. Is calculated.

Steps S120 to S170 are operations as resonance frequency extracting means. S120 is an operation of the FFT operation unit 2b, in which the wheel speed of each wheel is subjected to FFT operation to obtain spectrum data. In the spectral data, each component value has a resolution of F _lsb
(Hz) for each discrete frequency. Next, the number-of-operations counter N is incremented by 1 and temporarily stored in the result storage memory B (N) (S130).

[0019] Compare At subsequent S140 computation number counter N with a predetermined value n _0. If N <n ₀ returns to S110. If N ≧ n ₀ , that is, FFT for wheel speed
If the calculation (S120) is performed n ₀ times, the process proceeds to S150.

In step S150, the averaging unit 2c operates to read the results of the n ₀ FFT operations from the result storage memory B (N) and average them. This is because the shape (size and height) of the unevenness existing on the road surface is not constant, and the results of the FFT calculation include random variations, which are to be removed. S160 is the operation of the moving average processing unit 2d, and S150
The smoothing process is performed on the averaged spectrum data by moving average to remove high frequency components in advance, thereby improving the detection accuracy of the resonance frequency.

S170 is an operation of the resonance frequency calculation unit 2e, which is a resonance frequency calculation subroutine by the center of gravity method.
The resonance frequency is determined from the smoothed spectrum data by the centroid method.

FIG. 4 shows a detailed procedure of a resonance frequency calculation subroutine by the center of gravity method. First, in step S171, the component value F is calculated using Equation (1) for the frequency range to which the centroid method is applied.
The sum S of (i) is calculated. Here, i is an index corresponding to the frequency, and the frequency range to which the centroid method is applied is i =
F _{ws to} F _we .

[0023]

(Equation 1)

In S172, S 'is reset to 0 and i is set to F _ws -1. Next, i is incremented by 1 (S173), and F (i) is added to S 'and updated (S174). In S175, S 'is compared with S / 2. S173 to S175 are repeated until S ′ reaches S / 2, and i at that time corresponds to the frequency at which the component value is located at the center of gravity. Thus the i obtained by multiplying the resolution F _lsb obtain resonance frequency F _k (S176). Thereafter, the resonance frequency of the right front wheel is F _k (FR) and the left front wheel is F _k (F
L), the right rear wheel is F _k (RR), and the left rear wheel is F _k (R
L).

FIG. 5 shows a subroutine for calculating the wheel speed deviation value in S200 (FIG. 2). The wheel speed deviation value calculation subroutine is an operation part as a rotation state value calculation means. S21
Reference numerals 0 to 230 denote operations of the wheel speed deviation value calculation unit 2g.
0, S220, the ratio F of the right wheel and the left wheel which is deviated with respect to the detected wheel speed for each of the front wheel and the rear wheel.
_d and R _d are calculated by the equations (2) and (3) (S21).
0, S220), the wheel speed deviation value D, which is the rotation state value, is calculated from the equation (4), and the number-of-calculations counter N is incremented by 1 (S230). _{F d = FR / FL ···· (} 2) R d = RR / RL ···· (3) D = F d -R d ···· (4)

[0026] In S240, compares the number of operations counter N and the predetermined number n _0. If N <n ₀ returns to S210.
If N ≧ n ₀ , that is, the calculation of the wheel speed deviation value D (S
If (210 to 230) is performed n ₀ times, the process proceeds to S250.

In step S250, the wheel speed deviation value averaging unit 2i operates to average the n ₀ wheel speed deviation values D which are temporarily stored, and returns the result to the main routine (FIG. 2). Note that the average value of the wheel speed deviation values D is also referred to as a wheel speed deviation value D.

FIG. 6 explains the behavior of the wheel speed deviation value D. All because wheel tire pressure of the equal 4-wheel wheel speed during straight running normal left and right front wheels wheel speed ratio F _d, the left and right wheel speed ratio R _d of the rear wheel is both 1, the wheel speed deviation D is It becomes 0. The front wheels during turning for left and right turning radius is different, the front wheels of the right and left wheel speed ratio F _d to and below the 1 by turning direction. On the other hand, the rear wheels in particular shows the same behavior as the front wheels in a high speed region, the right and left wheel speed ratio R _d of the rear wheel is equal to the left and right front wheels wheel speed ratio F _d. Therefore, the wheel speed deviation value D is determined by the left and right wheel speed ratios F _d , R
The changes in _d cancel each other out and always take the same value regardless of whether the vehicle is traveling straight or turning.

[0029] Then for example if the right tire pressure of the front wheel is lowered, the wheel speed is the left and right front wheels wheel speed ratio even when the linear because increases with decreasing pressure F _d
Increase. On the other hand, since the rear wheels have the same wheel speed on the left and right,
The left and right wheel speed ratio _Rd remains 1. Therefore, the wheel speed deviation value D changes to the positive side in accordance with the amount of decrease in the tire pressure. The wheel speed deviation value D also changes when the tire air pressure of the other wheels decreases, but when the tire air pressure on the left side of the front wheel or the right side of the rear wheel decreases, the wheel speed deviation value D takes a negative value.

In S100 and S200, the resonance frequencies _Fk (FR), _Fk (FL), _Fk (RR), Fk
_k (RL) and the wheel speed deviation value D, and then S30
Go to 0.

Steps S300 to S1100 are the operations of a part of the air pressure drop judging section 2k as judging means. Other parts will be described later. In S300 and S500, the resonance frequencies _Fk (FR) and _Fk (FL) of the front wheels are compared with the threshold value _Fsh . The Threshold Level Sshorudo value F _sh is set to the resonance frequency when the air pressure is recognized that there is a risk of deflation. Front wheel resonance frequency F _k (FR), F
_k (FL) outputs a warning signal to the warning device 3 if beyond the F _sh (S400, S600). As the warning signal, the amount of decrease in the air pressure is output as a numerical value, and the driver can absolutely evaluate the decrease in the air pressure by the numerical value from the warning device 3.

Next, the vehicle speed V is compared with a limit speed _Vsh which is an upper limit value (S700). If the vehicle speed V is equal to or lower than the limit speed _Vsh , it is determined that there is no problem in detecting the resonance frequency, and the resonance frequency F of the rear wheel is determined. _k (RR) and F _k (RL) are respectively compared with predetermined values F _sh (S800, S1000), and if they exceed F _sh , a warning signal is output to the warning device 3 (S900, S900).
1100). Resonance frequency F _k of the rear wheels at the limit speed V _sh is S100R (RR), is set based on detection accuracy of the F _k (RL).

The subsequent S1200 is resonant at the operating frequency storage unit 2f, S100F, resonance frequencies of the respective wheels that are used to determine the calculated pressure drop in the 100R F _k (F
R), F _k (FL), F _k (RR), and F _k (RL) are respectively set to reference values F _k (*) _std (where *: FR, FL,
(RR, RL).

In step S1300, the wheel speed deviation value D calculated in step S200 by the operation of the wheel speed deviation value storage unit 2i is updated and stored as a reference value D _std .

The vehicle speed V in S700 proceeds to S1400 if the limit speed V _sh above. S1400 is a differential pressure determination value calculation subroutine, which is an operation of the differential pressure determination value calculation unit 2g.

FIG. 7 shows a detailed flow of the differential pressure determination value calculation subroutine. S1410 is an operation as a rotation state value change amount calculating means, and the reference value D _std stored in the memory is used.
Is read, and the differential pressure determination value ΔD ′ is calculated by equation (5). ΔD ′ = DD _std (5)

Step S1420 is an operation as a resonance frequency change amount calculating means, which calculates a temporal decrease amount of the front wheel resonance frequency by the equations (6) and (7). ΔF _k (FR) = F _k (FR) _std −F _k (FR) (6) ΔF _k (FL) = F _k (FL) _std −F _k (FL) (7)

Steps S1430 and S1440 are operations as correction means. In step S1430, the front wheel differential pressure correction value FDC
Is calculated by Expression (8). In the equation, the coefficient C is a coefficient for converting the resonance frequency and the wheel speed deviation value when the tire air pressure decreases, and is stored in the memory as the storage means. The coefficient C is obtained in advance by an experiment or the like that simulates an actual running state. For example, when the tire pressure drops by 100 kPa, the differential pressure judgment value is 5/1000 and the resonance frequency drop amount is 8
If it is Hz, C becomes 1600.

[0039]

(Equation 2)

The right side of the above equation (8) represents the amount of change in the deviation of the wheel speed of the left and right front wheels caused by the difference between the right and left tire air pressures. It becomes negative if the air pressure drop of the left front tire is large.

Next, the differential pressure determination value ΔD ′ is corrected by the equation (9) using the front wheel differential pressure correction value FDC (S144).
0). In the equation, ΔD is a corrected differential pressure determination value. ΔD = ΔD′−FDC (9)

As described above, the front wheel differential pressure correction value FDC represents the amount of change in the deviation of the wheel speed of the left and right front wheels caused by the difference between the right and left tire air pressures of the front wheels. It only depends on changes in the rear tire pressure.

Steps S1500 to S1900 are other operations of the air pressure drop judging section 2k. In S1500, it is determined whether the differential pressure determination value ΔD is positive or negative. The differential pressure determination value ΔD depends only on the tire pressure of the rear wheel as described above, and takes a negative value if the tire pressure of the right rear tire is decreasing, and takes a negative value if the tire pressure of the left rear wheel is decreasing. If the value is positive. And ΔD
Is negative, it is determined that the air pressure of the right rear tire has decreased, and the flow proceeds to S1600.

In the first half of S1600, the drive wheel resonance frequency is estimated.
Operation as a means to reduce the tire pressure on the right rear wheel.
The amount of change in the resonance frequency is determined. Tire pressure drops
The resonance frequency and wheel speed deviation value at the time of
Therefore, the amount of change in the resonance frequency is given by C · ΔD
Can be Resonance frequency at the start of the change in resonance frequency
Is the resonance frequency reference value F stored in the memory._k(RR)
_stdIt is. Also, when the air pressure of the right rear tire drops,
ΔD becomes a negative value. Thus, the resonance frequency reference value F _k(R
R)_stdFrom the memory, and the resonance frequency of the right rear wheel
And F_k(RR)_std+ C · ΔD.

In the latter half of S1600, the air pressure drop judging unit 2k
In the operation of the remaining part of
_In comparison with _sh , if Fsh is exceeded, a warning signal is output to the warning device 3 (S1700). As the warning signal, the amount of decrease in air pressure is output as a numerical value in the same manner as in the case where the vehicle speed V does not exceed the limit speed _Vsh in a low speed range based on the estimated resonance frequency.

If the differential pressure determination value ΔD is positive, it is determined that the air pressure of the left rear wheel tire has decreased, and the flow advances to S1800.
In S1800, the procedure in S1600 is executed by substantially replacing the right rear wheel with the left rear wheel. However, when the air pressure of the left rear tire decreases, ΔD becomes a negative value. Is F _k (RL) _std −C ·
Estimate as ΔD. The estimated value of the resonance frequency of the left rear wheel is F _sh
Is exceeded, a warning signal is output to the warning device 3 as in the case of the right rear wheel (S1700) (S1900).

FIG. 8 shows changes over time in the resonance frequency and the vehicle speed. When the tire air pressure decreases due to puncture or the like, the resonance frequency also decreases. Until the vehicle speed V exceeds the limit speed _Vsh , the resonance frequency is directly calculated, and the resonance frequency is compared with a warning threshold value _Fsh to warn of an abnormal air pressure condition of the tire (resonance point method). When the vehicle speed V exceeds a limit speed V _sh, the rear wheel is calculated by the estimation on the basis of these and difference pressure determination value ΔD last resonance frequency before the resonance frequency reference value exceeds a warning threshold resonance frequency estimated The value is compared with the value _Fsh to warn of an abnormality in the air pressure state of the tire.

(Second Embodiment) FIG. 9 shows a second embodiment of the present invention. Which was provided with a rear wheel frequency existence determining unit 2l between the differential pressure determination value calculation unit 2j and the air pressure drop judgment unit 2k in Figure 1 of the first embodiment, the vehicle speed V in S700 of FIG. 2 is a limit speed V _sh Flow when exceeding (S1400
1900) is another judgment of air pressure drop based on a differential pressure judgment value.
It has been changed to a warning subroutine (FIG. 10). FIG. 1 shows a subroutine for determining / warning air pressure based on the differential pressure determination value.
It is shown in FIG. In the figure, steps denoted by the same reference numerals as those in FIG. 3 described in the first embodiment perform substantially the same operation, and therefore, the description will be focused on differences from the first embodiment.

In FIG. 11, in S2010, the resonance frequencies F _k (FR) _std and F _k (FL) of the front tires are set.
It is determined whether or not _std has already been detected. If not, F _k (FR) and F _k (F
L) is _defined as F _k (FR) _std and F _k (FL) _std (S2020).

Subsequently, it is determined whether or not the reference value D _std of the wheel speed deviation has been detected.
The differential pressure determination value D calculated in 200 (FIG. 10) is set to D _std (S2040), and this routine ends.

If the reference value D _std of the differential pressure determination value has been detected (S2030), the differential pressure determination value calculation subroutine (S1400) is executed as in the first embodiment, and the differential pressure determination value ΔD is obtained.

The subsequent step S2050 is the operation of the rear wheel resonance frequency existence judging unit 21 to determine the resonance frequency F _k (R
R) Determine if _std and F _k (RL) _std have been detected. At a very early stage immediately after traveling, the rear wheel resonance frequency reference value required for estimating the rear wheel resonance frequency has not yet been stored. Therefore, for example, when the vehicle speed V exceeds the limit vehicle speed _Vsh when the vehicle speed V exceeds the limit vehicle speed _Vsh by vigorously accelerating from the parking area or the like to the driving lane, the vehicle speed V becomes the limit vehicle speed _Vsh.
, The resonance frequency of the rear wheel before being exceeded cannot be detected. Therefore, different procedures are executed depending on whether the rear-wheel resonance frequency reference value is stored or not. Rear tire resonance frequency F _k (RR) _std and F _k (RL)
_{If std} has been detected, S150 is performed in the same manner as in the first embodiment.
Execute 0-1900.

The resonance frequency F _k (RR) of the rear wheel tire
If _std and F _k (RL) _std has not yet been detected (S2050), the magnitude of the difference pressure determination value [Delta] D in S2060 | comparing the threshold value D _sh | ΔD. Since the differential pressure determination value ΔD depends only on the change in the tire pressure difference of the rear wheels, if any one of the tires of the rear wheels has a decreased pressure, it is largely biased to either positive or negative. Threshold value D _sh is the value of the differential pressure determination value ΔD which may determine the pressure drop and stored in the memory of the processing unit 2 is preset by an experiment or the like.

[0054] | ΔD | when is greater than D _sh is, ΔD
Is determined (S2070). Rear left wheel speed ratio R _d if the air pressure of the right rear wheel is only to decrease the difference pressure determination value ΔD from increasing takes a negative value. Therefore, the differential pressure determination value ΔD
If the sign of is negative, a warning signal for warning of a decrease in the air pressure of the right rear wheel is output to the warning device 3 (S2080). Conversely, if the sign of the differential pressure determination value ΔD is positive, the decrease in the air pressure of the left rear wheel is determined. A warning signal for warning is output to the warning device 3 (S209)
0).

[0055] In S2060, | ΔD | is D _sh
If it is smaller, the tire pressure state is determined to be normal.

(Third Embodiment) FIG. 12 shows a third embodiment of the present invention. In FIG. 9 of the second embodiment, a wheel speed deviation default determination unit 2m is provided before the differential pressure determination value calculation unit 2j.
In this embodiment, the air pressure drop judgment / warning subroutine based on the differential pressure judgment value in FIG. 11 is changed to another air pressure drop judgment / warning subroutine using the differential pressure judgment value. FIG. 13 shows a subroutine for determining / warning the air pressure based on the differential pressure determination value. In the figure, FIG. 11 shown in the description of the second embodiment
The steps denoted by the same reference numerals perform substantially the same operation, and therefore, the description will focus on the differences from the second embodiment.

In the tire pressure detecting device of the second embodiment, even if the vehicle speed V exceeds the limit vehicle speed _{Vsh due} to vigorous acceleration from the parking area or the like to the traveling lane, the resonance frequency of the rear wheel cannot be extracted. By calculating the differential pressure determination value ΔD (S1400 in FIG. 11), the tire pressure state of each rear wheel can be determined. However, since the differential pressure determination value ΔD requires data at two time points, the tire pressure is extremely low and a large wheel speed deviation is generated, and the vehicle is accelerated vigorously from the parking area to the traveling lane to join the vehicle. exceeding the limit speed V _sh, the first differential pressure determination value Δ
A time lag occurs before D is calculated, and even if a puncture or the like occurs on the rear wheel, it cannot be known early.

Therefore, in this embodiment, in FIG.
If the reference value D _std of the wheel speed deviation value has not been detected yet (S2030), the wheel speed deviation value D is set to the reference value D _std (S2040), and the magnitude | D | compared with the values D _dsh, an alarm signal is larger than the default value D _dsh the warning device 3 (S302
0). As a result, when the air pressure of any one of the rear wheels is low from the start of traveling and the vehicle speed V exceeds the limit vehicle speed _Vsh immediately after the start of traveling, an abnormality in the tire air pressure state can be known at an early _stage .

In each of the above embodiments, the deviation of the rotation state of the left and right wheels is used as the wheel speed ratio. The bias may be the wheel acceleration ratio.

The rotation state value is a wheel speed deviation value represented by a difference between the front and rear wheel speed ratio of the left and right wheel speed ratios. A function that depends on the rotation and cancels the change in the degree of rotation of the left and right wheels due to the turning can be used.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first tire pressure detection device of the present invention.

FIG. 2 is a first flowchart illustrating the operation of the first tire pressure detecting device of the present invention.

FIG. 3 is a second flowchart illustrating the operation of the first tire pressure detecting device of the present invention.

FIG. 4 is a third flowchart illustrating the operation of the first tire pressure detecting device of the present invention.

FIG. 5 is a fourth flowchart illustrating the operation of the first tire air pressure detecting device of the present invention.

FIG. 6 is a schematic diagram for explaining the operation of the first tire pressure detecting device of the present invention.

FIG. 7 is a fifth flowchart illustrating the operation of the first tire air pressure detecting device of the present invention.

FIG. 8 is a graph illustrating the operation of the first tire pressure detecting device of the present invention.

FIG. 9 is a configuration diagram of a second tire pressure detection device of the present invention.

FIG. 10 is a first flowchart illustrating the operation of the second tire pressure detecting device of the present invention.

FIG. 11 is a second flowchart illustrating the operation of the second tire pressure detecting device of the present invention.

FIG. 12 is a configuration diagram of a third tire pressure detection device of the present invention.

FIG. 13 is a flowchart illustrating the operation of the third tire pressure detecting device of the present invention.

FIG. 14 is a first graph illustrating the operation of one conventional tire pressure detecting device.

FIG. 15 is a second graph illustrating the operation of one conventional tire pressure detecting device.

[Explanation of symbols]

1a to 1d Wheel speed sensor (wheel speed detecting means) 2 Arithmetic processing unit 2a Wheel speed calculating unit (wheel speed detecting means) 2b FFT calculating unit (resonant frequency extracting means) 2c Average processing unit (resonant frequency extracting means) 2d Moving average Processing unit (resonance frequency extraction unit) 2e Resonance frequency calculation unit (resonance frequency extraction unit) 2f Resonance frequency storage unit 2g Wheel speed deviation value calculation unit (rotation state value calculation unit) 2h Wheel speed deviation value average processing unit (rotation state value) Calculation means) 2i Wheel speed deviation value storage unit 2j Differential pressure judgment value calculation unit (Rotation state value change amount calculation means,
Storage unit, correction unit) 2k air pressure drop determining unit (drive wheel resonance frequency estimating unit,
Judgment unit) 2l Rear wheel resonance frequency existence judgment unit (judgment unit) 2m Wheel speed deviation default judgment unit (judgment unit)

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Yuichi Inoue 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Co., Ltd. 72) Inventor Shinjiro Fukada 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside DENSO Co., Ltd. 41, No. 41, Chuchu-Yokomichi, Nagakute-cho, Aichi-gun Examiner, Masaya Deguchi in Toyota Central Research Laboratory, Inc. (56) References JP-A-5-133383 (JP, A) JP-A-6-328920 (JP, A) JP-A-8-216636 (JP, A) JP-A-8-156536 (JP, A) JP-A-6-286432 (JP, A) JP-A-7-178107 (JP, A) ) (58) investigated the field (Int.Cl. ^7, DB name) B60C 23/00 - 23/06 G01L 17/00

Claims (5)

(57) [Claims] When a vehicle is running, a wheel speed detecting means for sequentially detecting a wheel speed of each wheel, and a resonance frequency of a tire attached to each wheel is extracted from each wheel speed detected by the wheel speed detecting means. In a tire pressure detecting device comprising: a resonance frequency extracting unit; and a determining unit that determines a tire air pressure state based on the resonance frequency, a left and right side of a driven wheel based on a wheel speed detected by the wheel speed detecting unit. A rotation state value calculating means for calculating a rotation state value dependent on a difference between the rotation degree deviation of the wheels and the rotation state deviations of the left and right wheels in the driving wheels, and a resonance when the tire air pressure changes in advance. storage means for storing a relationship between the frequency and the rotational state value, it equal to or greater than the upper limit of the vehicle speed is preset
A rotational state value change amount calculating means for calculating a temporal change amount of the rotational state value from the I or the vehicle speed is equal to or more than the upper limit value
The resonance frequency change amount calculating means for calculating the change amount of the resonance frequency of the driven wheel over time, and the change amount of the resonance frequency of the driven wheel over time to the change amount of the rotation state value based on the relationship stored in the storage means. converted, a correction means for correcting the amount of change over time in rotation state values with time variation that is converted, when the vehicle speed becomes equal to or higher than the <br/> upper limit, based on the stored relationship in the memory means, the correction means The corrected rotation state value over time
The resonance frequency of the drive wheel is converted into a change over time in the resonance frequency of the drive wheel after the vehicle speed exceeds the upper limit, and the resonance frequency of the drive wheel is estimated from the resonance frequency of the drive wheel before the vehicle speed exceeds the upper limit and the change over time. A driving wheel resonance frequency estimating unit that determines the tire pressure state of the driving wheel based on the resonance frequency estimated by the driving wheel resonance frequency estimating unit when the vehicle speed becomes equal to or higher than the upper limit value. A tire pressure detection device, wherein the setting is made to make a determination. 2. The tire pressure detecting device according to claim 1, wherein the deviation is a wheel speed ratio. 3. The tire pressure detecting device according to claim 1, wherein the deviation is a wheel acceleration ratio. 4. The tire air pressure detecting device according to claim 1, wherein the determining means determines whether the resonance frequency of the driving wheel before the vehicle speed exceeds the upper limit value cannot be extracted. A tire pressure detecting device which is set so as to determine a tire pressure condition based on a rotational state value temporal change amount corrected by the correction means. 5. The tire pressure detecting device according to claim 1, wherein the determination means calculates the tire pressure by the rotation state value calculation means when the rotation state value change with time cannot be calculated. A tire pressure detection device set to determine a tire pressure state of a drive wheel based on a rotation state value.