JP3131201B2 - Tire pressure drop detection method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a device for detecting a decrease in air pressure of a tire of a vehicle.

[0002]

2. Description of the Related Art As a device for detecting a decrease in tire air pressure, a device for judging an abnormal air pressure by a disturbance observer described in Japanese Patent Application Laid-Open No. 8-22221, No. 2221, the frequency characteristic of the tire rotation speed signal is FFT
In some cases, an abnormality in the air pressure is determined by acquiring the data using the (Fast Fourier Transform) method. The former detection by the disturbance observer detects a decrease in tire air pressure by obtaining an air pressure change amount using an estimated value of the disturbance and an estimated value of the torsion angle. In the latter detection by FFT, a decrease in tire air pressure is detected by detecting the resonance frequency from the frequency characteristics, utilizing the relationship that the lower the resonance frequency is, the lower the air pressure is.

[0003]

However, detection of a decrease in air pressure by a disturbance observer complicates the process. Also, when detecting the air pressure drop by detecting the resonance frequency,
If a peak frequency is detected within a predetermined frequency range, it is determined that the air pressure is within a normal range. Therefore, if there is a peak frequency due to other factors within this frequency range, it may not be possible to detect it even though the air pressure is lowered.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and a device which are simple in processing and capable of accurately detecting a decrease in tire air pressure.

[0005]

In order to achieve the above object, a method and apparatus for detecting a decrease in tire air pressure according to the present invention are provided.
And the maximum target frequency of up to the natural frequency or frequencies close to a torsion natural frequency of the axial center of the tire at the time of air 圧最 sized tires air pressure is sufficient, the air pressure
There was determined the minimum target frequency consisting of a minimum natural frequency or frequencies close to a central axis torsional natural frequency around the tire when the air 圧最 small tire has dropped, run
From torsional vibration is detected in the line, the maximum for the maximum calculated tire in a subject frequency Contact <br/> pre said minimum target frequency torsional vibration amplitude respectively only torsional vibration amplitude of the tire in the minimum target frequency calculating a ratio of the torsional vibration amplitudes in our <br/> Keru tires target frequency, the ratio starve
If it is below the threshold value, a decrease in tire air pressure is detected.

According to the structure of the method and the apparatus, the torsional vibration characteristics of the tire, that is, the frequency pattern changes depending on the air pressure, that is, the higher the air pressure, the larger the amplitude of the higher frequency region. Because we use
It is only necessary to determine the torsional vibration amplitude of the tire at the predetermined maximum natural frequency or a frequency close thereto and the minimum natural frequency or the frequency close thereto, and it is not necessary to obtain the torsional vibration amplitude of the tire over a wide range of frequencies. Therefore, the process of analyzing the torsional vibration characteristics of the tire is simple. Also, since only the torsional vibration amplitude of the tire at the maximum target frequency consisting of the maximum natural frequency or a frequency close thereto and the torsional vibration amplitude of the tire at the minimum target frequency consisting of the minimum natural frequency or a frequency close to it are determined. If there is a frequency peak due to other factors, it will be the maximum target frequency or the minimum frequency.
As long as the frequency does not correspond to the target frequency , the detection of the decrease in the air pressure does not become inaccurate. Furthermore, even if the force acting on the tire is random, the ratio of the torsional vibration amplitude is determined,
A decrease in tire air pressure can be accurately detected.

In a preferred embodiment of the method and apparatus for detecting a decrease in tire air pressure according to the present invention, when determining the torsional vibration amplitude of the tire, a rotation speed is detected to output a rotation pulse of the tire, and a pulse time for each pulse is obtained. Generate an interval signal. According to this configuration, since the fact that the torsional vibration characteristics of the tire are obtained from the rotation pulse of the tire is used, it is possible to detect a decrease in the air pressure of the tire without providing a complicated detection device.

[0008] In a preferred embodiment of the method and apparatus for detecting a decrease in tire air pressure according to the present invention, a pulse time interval for each of the pulses is determined based on the maximum target frequency and the previous frequency.
The Fourier coefficients are calculated, respectively, in serial minimum target frequency, wherein the Fourier coefficients in the maximum target frequency
Calculating a torsional vibration amplitude of the tire at the maximum target frequency, wherein the Fourier coefficients in the minimum target frequency
The torsional vibration amplitude of the tire at the minimum target frequency is calculated. According to this configuration, a decrease in tire air pressure can be detected by obtaining a Fourier coefficient, so that the calculation process is simple. Also, the maximum target frequency and the minimum target frequency
Since only the Fourier coefficients in the numbers need to be obtained, there is no calculation processing for other frequencies, and the processing is quick.

In a preferred embodiment of the method and apparatus for detecting a decrease in tire air pressure according to the present invention, an analog pulse time interval signal is generated from a pulse time interval for each of the pulses, and the maximum target of the analog pulse time interval signal is generated.
The components in the frequency extracted by a first analog filter to obtain the torsional vibration amplitude of the tire in the maximum target frequency, prior to the analog pulse time interval signal
The component at the minimum target frequency is extracted by the second analog filter to determine the torsional vibration amplitude of the tire at the minimum target frequency . According to this configuration, the first
And the second analog filter can extract components at the maximum target frequency and the minimum target frequency ,
Air pressure drop can be detected with a simple circuit configuration.

First, the principle of the present invention will be described.
2. Description of the Related Art Wheels of vehicles such as motorcycles are generally configured by attaching a tire generally formed of rubber to an outer periphery of a wheel generally formed of metal. The tire dynamic analysis model is
Is as shown in FIG. 1, a relatively stiff belt side portion 2 and the rim 3 of the wheel periphery, the torsion spring 10 and the damping coefficient C _i of the spring constant k _i, which is connected in parallel to form the outer periphery of the tire 1 Can be represented as being connected by a plurality of sets of connecting elements including the dampers 11. The angular displacement of the belt side 2 is θ ₁ and the angular displacement of the rim side 3 is θ ₂
When equation of motion relates to the moment of inertia I _1, and the moment of inertia I ₂ of the belt side portions 2 of the rim 3, the following equation (1) and (2).

(Equation 1)

Next, from equations (1) and (2), the angular displacement θ
₂ (ω) can be expressed by the following equation (3).

(Equation 2) Here, ζ is a damping ratio in the vibration system of the analytical model of FIG. 1, and η is a ratio of the moment of inertia of the belt side portion 2 to the moment of inertia of the rim side portion 3. ω ₀ is the natural angular frequency of free vibration of the belt side alone in the vibration system of the analysis model of FIG. As shown in equation (6), natural angular frequency omega ₀ is dependent on the spring constant k, the spring constant k decreases as tire pressure is reduced, the natural angular frequency omega ₀
Is also smaller.

From equation (3), the angular displacement θ of the rim side 3 is
₂ (ω) torsional vibration amplitude characteristic | θ ₂ (ω) | can be expressed by the following equation (7).

(Equation 3)

From equation (7), two angular frequencies ω ₁ and ω ₂
Amplitude of torsional vibration of rim side 3 at the time | θ ₂ (ω ₁ ) |, |
The ratio M of θ ₂ (ω ₂ ) | can be expressed by the following equation (8).

(Equation 4) As is apparent from equation (8), the ratio M of the torsional vibration amplitude does not depend on the force F applied to the tire. Therefore, even if the force acting on the tire is random, the reduction of the air pressure of the tire can be accurately detected by calculating the ratio in this manner.

FIG. 2 shows the characteristics of the ratio M of the torsional vibration amplitude represented by the equation (8) as a function of the natural frequency f ₀ (= ω ₀ / 2π). The characteristic shown in FIG. 2 is that the natural frequency of the tire with the sufficient air pressure is 86 Hz at the maximum air pressure and the natural frequency of the tire with the low air pressure is 74 Hz at the minimum air pressure. And the maximum object consisting of the maximum natural frequency or a frequency close to it
The frequency f ₁ (= ω ₁ / 2π) is 90 Hz, and the minimum target frequency f consisting of the minimum natural frequency or a frequency close thereto is
₂ (= ω ₂ / 2π) is set to 70 Hz. Note that the damping ratio ζ = 0.025 and the moment of inertia ratio η = 0.
It is one.

As is apparent from FIG. 2, the natural frequency f₀
From the natural frequency 86Hz at the time of tire pressure maximum
As the natural frequency at the minimum pressure drops to 74 Hz, f₁
And f _TwoIs smaller. Accordingly
Therefore, if this vibration amplitude ratio M is used, the tire air pressure becomes sufficient.
From tired pressure to tire pressure drop.
Indicates that they can be separated. The present invention takes advantage of this property.
It is a thing.

Therefore, according to the present invention, since it is not necessary to determine the torsional vibration amplitude of the tire for a wide range of frequencies, the process of analyzing the torsional vibration characteristics of the tire is simplified. Further, since the torsional vibration amplitude ratio M is obtained from the torsional vibration amplitudes at the _two angular frequencies ω ₁ and ω ₂ , even if a frequency peak exists due to other factors, the peak frequency is 2 As long as it does not correspond to the _two frequencies f ₁ and f ₂ , a decrease in air pressure can be detected.

[0017]

Next, a first embodiment of the present invention will be described. As shown in FIG. 3, the tire pressure drop detecting device according to the present embodiment includes a front wheel FW provided on a motorcycle.
This is a device for detecting a decrease in the air pressure of the tire 1a of the rear wheel RW and the tire 1b of the rear wheel RW, and includes a rotation pulse output means 21 composed of an electromagnetic pickup for detecting the rotation speed of the front wheel FW and the rear wheel RW. As shown in FIG. 4, the electromagnetic pickup 21 is held by a non-rotating mounting bracket 22 supported by a suspension (a front fork or a swing arm) of the wheels FW and RW, and an axle 23 of the wheels FW and RW.
, Each of which detects a number of teeth 24a of the detected part 24 that rotates together with the wheel 20 (FIG. 3). Therefore, the electromagnetic pickup 21 is mounted on the rim side 3 shown in FIG.
It will detect the angular displacement theta _2. A detected part cover 25 that covers the detected part 24 is also held by the mounting bracket 22. The rotation pulse signal generated by the electromagnetic pickup 21 is input to the processing means 30 (FIG. 3) via the lead 26, and is also input to a speedometer (not shown) to indicate the speed of the vehicle.

Returning to FIG. 3, the present apparatus also includes a maximum target vibration _f0max which is a torsional natural frequency around the axis of the tire when the air pressure of the tire is at a maximum, or a maximum target vibration comprising a frequency close thereto. Storage means 31 for storing a number f _max and a minimum target frequency f _min consisting of a minimum natural frequency f _0min which is a torsional natural frequency around the axis of the tire when the tire air pressure is at a minimum or a frequency close to the minimum natural frequency f _0min. Is provided. The apparatus further includes two pulse time interval signal generation means for the front wheel FW and the rear wheel RW for generating pulse time interval signals S2 and S2 from the respective pulses output by the electromagnetic pickups 21 and 21 for the front wheel FW and the rear wheel RW. 3
2, 32. The present apparatus further comprises a torsional vibration amplitude quantifying means 33,
Is the maximum target frequency f _max for the pulse time interval for each pulse output by the electromagnetic pickups 21 and 21.
A Fourier coefficient calculating means 34 for calculating a Fourier coefficient at the minimum target frequency f _min, and a maximum target frequency f
Maximum target frequency from the Fourier coefficients in _max and the minimum target frequency f _{mi n} f _max and the minimum target frequency f _min
Torsional vibration amplitude | θ ₂ (f _max ) |, |
θ ₂ (f _min ) |

The apparatus for detecting a decrease in tire air pressure further includes a torsional vibration amplitude | at a maximum target frequency f _max |
torsional vibration amplitude ratio calculating means 36 for calculating the ratio M between θ ₂ (f _max ) | and the torsional vibration amplitude | θ ₂ (f _min ) | of the tire at the minimum target frequency f _min , based on this ratio M Determining means 37 for determining a decrease in tire air pressure, and an informing means 38 for notifying that the decrease in tire air pressure has been determined.
And

Next, the operation of the apparatus according to this embodiment will be described. First, the maximum and minimum target frequencies f _max and f _min stored in the storage means 31 are determined. The maximum and minimum target frequency f _max, f _min is an operator on the basis of the previously measured maximum natural frequency f _0max air pressure at the maximum tire, and the minimum natural frequency f _0min when tire pressure minimum Is determined. Specifically, the maximum target frequency f _max is made from the maximum natural frequency f _0max or frequency in the vicinity thereof, the minimum target frequency f _min is a minimum natural frequency f _0min or frequency of the vicinity thereof. Incidentally, the natural frequency f _0max during air pressure maximum and minimum tire, f _0min, because those corresponding to the model of the tire, it is sufficient to measure for each model. In the example shown the characteristics in FIG. 2 described above, in advance the maximum natural frequency f _0max during air pressure maximum of the measured tire 86 Hz, the minimum natural frequency f _0min at the minimum is 74 Hz, the storage means 31 the maximum target frequency f _max stored in at 90 Hz, the minimum target frequency f _min is 70 Hz.

With the maximum and minimum target frequencies f _max and f _min determined in this way stored in the storage means 31, the apparatus according to the present embodiment provides the tire 1a of the front wheel FW during the running of the motorcycle. And a decrease in air pressure of the tire 1b of the rear wheel RW. Since the processing for detecting the air pressure drop for each tire is the same, the processing for detecting the air pressure drop of the tire 1 corresponding to any of the tires will be described below without specifying the tire 1a of the front wheel FW or the tire 1b of the rear wheel RW. It will be described as.

First, while the motorcycle is running, an electromagnetic pick
Each time the up 21 detects the tooth 24a (FIG. 4),
A pulse shown by the detection signal S1 is generated in FIG. Each pal
Time interval t_1,t_Two, ... t_iIs not constant, tire 1
Fluctuates due to the torsional vibration of This detection signal S1 is
As shown in FIG. 3, the pulse time interval through lead 26
The signal is input to the signal generator 32. Pulse time interval signal generation
The generating means 32, as shown in FIG.
Pulse time interval t for 2,... I,._1,t _2,…
t_i, ... t_nPulse time interval by giving a level equivalent to
A signal S2 is generated. The number of pulses per unit time is
The number is n because it is determined by the rotation speed of the wheel
And n pulses whose time intervals fluctuate as shown in FIG.
On the other hand, in FIG. 5 (b), n
A pulse is assigned and the time interval is represented by the pulse height. What
Contact, pulse time interval t_1,t_2,... t_iFluctuation of tire 1
Showing vibration of wheel 20 caused by torsional vibration of
Therefore, the vibration characteristics of the pulse time interval signal S2
Of the rim side portion 3 (FIG. 1) of the tire 1 expressed by the equation (3)
Angular displacement θ_Two(ω) is a torsional vibration characteristic.

[0023] Thus, the present invention is that the electromagnetic pickup 21 outputs a rotation pulse, the pulse time interval _{t 1, t 2, ... t} i, ... t n that torsional vibration characteristics of the tire can be obtained from The electromagnetic pickup 21
It is possible to detect a decrease in the air pressure of the tire 1 with only a simple detecting means such as

Next, returning to FIG. 3, the Fourier coefficient calculating means 34 to which the pulse time interval signal S2 has been input, calculates the Fourier coefficient of the pulse time interval signal S2 at the maximum target frequency f _max and the minimum target frequency f _min . Calculate the coefficient. Specifically, first, the Fourier coefficient calculating means 34 calculates
The average pulse time interval Δt is calculated. The average pulse time interval Δt can be represented by the following equation (9).

(Equation 5) Here, n is the number of pulses in the unit time described above.

Next, the pulse numbers N _max , N for m periods (m is an integer) at the maximum and minimum target frequencies f _max , f _min shown in the following equations (10) and (11).
Calculate _min .

(Equation 6)

Using these, the following equations (14) and (1)
Fourier coefficients A _max in the maximum target frequency f _{ma x} represented by 5), B _max and the following formula (16), the Fourier coefficients A at the minimum target frequency f _min of the formula (17)
_min and B _min are calculated.

(Equation 7) Note that, for the number of pulses N _max and N _min for m periods, the pulse time interval is given to each of a sine (sin) and a cosine (cos) based on a value obtained by dividing the average pulse time interval Δt by the cycle of the target frequency. By multiplying by t _i and taking the sum, the sine wave component and the cosine wave component of the frequency component of the target frequency can be obtained.

Thus, the Fourier coefficient calculating means 34
The calculated Fourier coefficient A_max, B _max, A_min, B
_minIs used in the torsional vibration amplitude calculating means 35. Right
The torsional vibration amplitude calculating means 35 calculates the maximum target frequency f_maxTo
Time interval t for each pulse in_1,t_2,... t_i
Vibration amplitude, that is, the maximum target frequency f_maxThailand in
Amplitude of torsional vibration of gear 1 | θ_Two(f_max) | Square and minimum
Target frequency f_minPulse time for each pulse at
Interval t_1,t_2,... t_iVibration amplitude, that is, the minimum target frequency
Torsional vibration amplitude of tire | θ_Two(f_min) | 2
To the power of | Θ_Two(f_max) ｜^TwoAnd | θ
_Two(f_min) ｜^TwoIs represented by the following equations (18) and (19).
It is.

(Equation 8)

Next, the torsional vibration amplitude ratio calculating means 36
The torsional vibration amplitude of the tire at the maximum target frequency f _{max with} respect to the square of the torsional vibration amplitude | θ ₂ (f _min ) | of the tire at the minimum target frequency f _min represented by the following equation (20) | θ ₂ ( f _max) | to calculate the square of the ratio M ² of.

(Equation 9)

The torsional vibration of the tire calculated as described above
Amplitude squared ratio M^TwoIs determined by the determination means 37
It is determined whether the value is equal to or less than the value. For example, the thresholdof
If it is 1.00 or less, as shown in FIG.
Since it is determined that the temperature has decreased, the determination means 37
Is determined to be decreasing. Thus, the format
When the determining means 37 determines a decrease in tire air pressure, for example,
Notifier such as the warning lamp controller in the meter
A signal is sent to the stage 38, and the warning means 38
Flashes to indicate that the air pressure is low.
Notify the driver.

[0030] Thus, the present apparatus, the Fourier coefficients A _{ma x} at the Fourier coefficient calculation means 34, 34, B _max,
By calculating A _min and B _min , a decrease in the air pressure of the tire 1 can be detected, so that the calculation process is simple. Further, only the Fourier coefficients at the maximum target frequency f _max and the minimum target frequency f _min need to be obtained, and there is no calculation processing at other frequencies, so that the processing is quick.

Next, a second embodiment of the present invention will be described.
I do. Tire air pressure drop detecting device according to the present embodiment
Is, as shown in FIG.
Only the configuration differs from the device according to the first embodiment. Torsional vibration
The amplitude quantifying means 33 outputs a signal to each pulse 1, 2,.
Lus time interval t_1,t_2,... t_iPal showing (FIG. 5 (b))
Analog signal corresponding to the envelope from the time interval signal S2.
Pulse time interval signal S_aTo generate the front wheel FW and
Analog pulse time interval signal generating means 4 for rear wheel RW
4, 44 and the analog pulse time interval signal S_a, S
_aTo the maximum target frequency f_maxExtract the components in
1 analog filter 45, 45, and analog pulse
Interval signal S_a, S_aTo the minimum target frequency f_minSmell
Second analog filters 46 and 46 for extracting components
Having. The apparatus also includes a first analog filter 4
5, 45 and the second analog filter 46, 46
Vibration signal θ at a specific frequency output from_Two(f
_max), Θ_Two(f_max), Θ_Two(f_min), Θ_Two(f_min)
The torsional vibration amplitude | θ_Two(f_max) |, | Θ_Two(f
_max) |, | Θ_Two(f_min) |, | Θ_Two(f_min) | Output
Torsional vibration amplitude output means 47, 47, 47, 47
Prepare.

Next, the operation of the apparatus according to this embodiment will be described. Prior to running of the motorcycle, based on the maximum target frequency f _{ma x} in the storage unit 31 is stored, the first analog filter 45, 45 is the maximum target frequency f
It is adjusted to pass only the signal component of _max . Further, based on the minimum target frequency f _min stored in the storage means 31, the second analog filters 46, 46 are adjusted so as to pass only the signal component of the minimum target frequency f _min .

In this embodiment, similarly to the first embodiment, the tire 1a of the front wheel FW or the tire 1b of the rear wheel RW is not specified, and the air pressure of the tire 1 corresponding to any of the tires will be described below. The process will be described as a drop detection process.

The pulse time interval signal S1 is a discrete signal shown in FIG. 5 (b) generated by the pulse time interval signal generating means 31 by the analog pulse time interval signal generating means 44, a continuous analog signal S _a Is converted. The analog signal S _a is input to both the first and second analog filters 45, 46, being extracted by the first analog filter 45, the maximum target frequency f of the torsional vibration characteristics of the tire 1 a vibration signal theta ₂ torsion in _max (f _max), being extracted by the second analog filter 46, the vibration signal torsional at the minimum target frequency f _min of the torsional vibration characteristics of the tire 1 theta
₂ (f _min ).

The torsional vibration signals θ ₂ (f _max ), θ ₂ (f
_min )), the torsional vibration amplitude quantifying means 47 takes out the torsional vibration amplitudes | θ ₂ (f _max ) | and | θ ₂ (f _min ) | and inputs the torsional vibration amplitude ratio calculating means 36 to the first torsional vibration amplitude ratio calculating means 36.
The processing is performed in the same manner as in the embodiment.

As described above, the components at the maximum target frequency f _max and the minimum target frequency f _min can be extracted by the first and second analog filters 45 and 46.
Air pressure drop can be detected with a simple circuit configuration.

In the first and second embodiments, the air pressure drop detecting device provided in the motorcycle has been described. However, the device according to the present invention is not limited to the motorcycle, but may be provided in any vehicle.

[0038]

As described above, according to the present invention, the torsional vibration characteristics of the tire, that is, the frequency pattern changes depending on the air pressure, that is, the higher the air pressure, the larger the amplitude of the higher frequency region. Since it is used, it is sufficient to determine the torsional vibration amplitude of the tire at the predetermined maximum natural frequency or a frequency close to it and the minimum natural frequency or a frequency close to it, and the torsional vibration amplitude of the tire over a wide range of frequencies is determined. No need to ask. Therefore, the process of analyzing the torsional vibration characteristics of the tire is simple. Also, since only the torsional vibration amplitude of the tire at the maximum target frequency consisting of the maximum natural frequency or a frequency close thereto and the torsional vibration amplitude of the tire at the minimum target frequency consisting of the minimum natural frequency or a frequency close to it are determined. If there is a frequency peak due to other factors, it is the maximum frequency of interest or the minimum
Unless it corresponds to the elephant frequency , the detection of the air pressure drop will not be inaccurate. Further, even if the force acting on the tire is random, the ratio of the amplitude of the torsional vibration is determined, so that a decrease in the air pressure of the tire can be detected with high accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram showing a dynamic analysis model of a tire.

FIG. 2 is a characteristic diagram of a torsional vibration amplitude ratio with respect to a natural frequency.

FIG. 3 is a schematic configuration diagram showing a tire air pressure drop detecting device according to the first embodiment of the present invention.

FIG. 4 is a schematic side view showing a rotation pulse output unit and a tire in the tire air pressure drop detecting device according to the first embodiment of the present invention.

5A and 5B are diagrams showing signals processed by the tire pressure drop detecting device according to the first embodiment of the present invention. FIG. 5A shows a signal S1 detected by a rotation pulse output unit.
(B) is a pulse time interval signal S generated from the signal S1.
FIG.

FIG. 6 is a schematic configuration diagram showing a tire pressure drop detecting device according to a second embodiment of the present invention.

DESCRIPTION OF SYMBOLS 1 ... tire, 21 ... rotation pulse output means, 31 ... storage means, 32 ... pulse time interval signal generation means, 33 ... torsional vibration amplitude quantification means, 34 ... Fourier coefficient calculation means, 35
... torsional vibration amplitude calculating means, 36 ... torsional vibration amplitude ratio calculating means, 37 ... determining means, 44 ... analog pulse time interval signal generating means, 45 ... first analog filter, 46
... second analog filter, A _max , B _max , A _min ,
_Bmin : Fourier coefficient, M: Torsional vibration amplitude ratio, S2:
Pulse time interval signal, f _max … maximum target frequency, f _min
... minimum target frequency, f _0max ... maximum natural frequency, f _0min ...
Minimum natural frequency, | θ ₂ (f _max ) |, | θ ₂ (f _min ) |
… Torsional vibration amplitude.

Continuing from the front page (72) Inventor Hidekazu Kobayashi 1-1, Kawasaki-cho, Akashi-shi, Hyogo Kawasaki Heavy Industries, Ltd. Inside the Akashi Plant (72) Inventor, Akitetsu Inoue 1-1, Kawasaki-cho, Akashi-shi, Hyogo Kawasaki Heavy Industries, Ltd. (72) Inventor Takashi Shin-Oda 1-1, Kawasaki-cho, Akashi-shi, Hyogo Kawasaki Heavy Industries, Ltd. Inside the Akashi Factory (56) References JP-A-8-1001085 (JP, A) JP-A-7 -47829 (JP, A) JP-A-8-2221 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60C 23/00-23/06

Claims (8)

(57) [Claims] 1. A damping maximum target air pressure of up to the natural frequency or frequencies close to a central axis torsional natural frequency around the tire when the air 圧最 sized tires is sufficient
And oscillating number, the minimum target frequency <br/> and consisting of minimum natural frequency or frequencies close to a torsion natural frequency of the axial center of the tire at the time of air 圧最 small tire whose air pressure has dropped determined from torsional vibration is detected during travel, the maximum determined target frequency and the tire in the minimum target frequency torsional vibration amplitude respectively only the torsional oscillation amplitude of the tire in the minimum target frequency
A tire pressure drop detection method for calculating a ratio of the torsional vibration amplitude of the tire at the maximum target frequency to the tire pressure drop if the ratio is equal to or less than a threshold value . 2. The tire pressure drop detecting method according to claim 1, wherein when calculating the torsional vibration amplitude of the tire, a tire rotation speed is detected, a rotation pulse is output, and a pulse time interval signal for each pulse is generated. . 3. The method according to claim 2, wherein the maximum target frequency and the pulse time interval for each of the pulses are determined.
The Fourier coefficients are calculated respectively in the minimum target frequency, the maximum from the Fourier coefficients in the maximum target frequency
Calculating a torsional vibration amplitude of the tire in the subject frequency, the minimum from the Fourier coefficients in the minimum target frequency
A method for detecting a decrease in tire air pressure for calculating a torsional vibration amplitude of a tire at a target frequency . 4. The analog pulse time interval signal according to claim 2, wherein an analog pulse time interval signal is generated from a pulse time interval for each of the pulses, and a component of the analog pulse time interval signal at the maximum target frequency is set to a first frequency . Extracted by an analog filter to determine the torsional vibration amplitude of the tire at the maximum target frequency, The component at the minimum target frequency of the analog pulse time interval signal is extracted by a second analog filter, A method for detecting a decrease in tire air pressure for obtaining a torsional vibration amplitude of a tire at the minimum target frequency . 5. A vibration maximum target air pressure of up to the natural frequency or frequencies close to a central axis torsional natural frequency around the tire when the air 圧最 sized tires is sufficient
And oscillating number, the minimum target frequency <br/> and consisting of minimum natural frequency or frequencies close to a torsion natural frequency of the axial center of the tire at the time of air 圧最 small tire whose air pressure has dropped Storage means for storing, torsional vibration amplitude quantifying means for respectively obtaining only the torsional vibration amplitude of the tire at the maximum target frequency and the minimum target frequency from the torsional vibration detected during traveling, and the tire at the minimum target frequency the torsional vibration amplitude
Wherein the maximum target torsion calculating the ratio of the torsional vibration <br/> amplitude of the tire in the oscillation frequency amplitude ratio calculation means, the tire pressure if the ratio is below the threshold value is lowered against
A tire pressure drop detecting device, comprising: a judging means for judging that the tire pressure has decreased. 6. A pulse time interval signal generating means for detecting a rotation speed of a tire and outputting a rotation pulse, and a pulse time interval signal generating means for generating a pulse time interval signal for each detected pulse. A tire pressure drop detection device comprising: 7. The method of claim 6, wherein the torsional vibration amplitude dosing means, for the pulse time intervals for each pulse, the highest
A Fourier coefficient calculation means for calculating the Fourier coefficients in a large target frequency and the minimum target frequency, the maximum target frequency or the minimum pairs from the Fourier coefficients in the maximum target frequency or the minimum target frequency
A torsion vibration amplitude calculating means for calculating a torsional vibration amplitude of the tire at an elephant frequency , respectively. 8. The analog pulse time interval signal generating means according to claim 6, wherein said torsional vibration amplitude quantifying means generates an analog pulse time interval signal from a pulse time interval for each of said pulses. From the maximum subject vibration
A first analog filter for extracting a component in a number ; and the minimum target oscillation from the analog pulse time interval signal.
A second analog filter for extracting a component in the number .