JPH09159562A - Pneumatic pressure detection device for tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the cost of a system and improve mountability on a vehicle by providing a means for detecting a quantity of state on a spring in a vertical direction, a means for extracting a resonance frequency band component under the spring, and a air pressure detection means for a tire. SOLUTION: This device is equipped with at least one on-spring vertical quantity state detection means (a) mounted on a vehicular spring for detecting a vertical quantity of state thereon, an under-spring resonance frequency band component extraction means (b) for extracting a resonance frequency band component under the spring from the vertical quantity of state detected with the means (a), a tire air pressure detection means (c) for detecting the air pressure of a tire from the level of the under-spring resonance frequency band component. As a result, the air pressure can be detected with a single sensor. In addition, a sensor mounted for controlling an attenuation characteristic is used for the same purpose. According to this construction, the cost of the device can be reduced, due to system cost reduction, and mountability on a vehicle can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire air pressure detecting device for detecting an abnormality in tire air pressure while a vehicle is running.

[0002]

2. Description of the Related Art Conventionally, as a tire air pressure detecting device for a vehicle, for example, one disclosed in Japanese Patent Laid-Open No. 5-330322 is known.

This conventional tire air pressure detection device calculates the resonance frequency in the vertical direction and the front-rear direction under the spring of the vehicle based on the wheel speed signal from the wheel speed sensor provided in each wheel, and uses this resonance frequency as the resonance frequency. Based on this, the tire pressure condition is detected.

[0004]

However, in the conventional device, as described above, in order to detect the tire pressure based on the wheel speed, it is necessary to provide a wheel speed sensor for each wheel. Therefore, the cost of the system becomes high, and the wiring from the wheel speed sensor provided under the spring to the electronic control device on the spring becomes complicated and difficult, resulting in poor vehicle mountability.

The present invention has been made by paying attention to the above-mentioned conventional problems, and it is possible to detect the tire air pressure based on the signal of at least one sensor provided on the spring, whereby the cost of the system can be reduced. An object of the present invention is to provide a tire air pressure detection device that can be reduced and improved in vehicle mountability.

[0006]

In order to achieve the above object, a tire pressure detecting device according to claim 1 of the present invention comprises:
As shown in the claim correspondence diagram of FIG. 1, at least one on-spring sprung vertical state amount detecting means a for detecting the sprung vertical state amount, and the sprung vertical state amount. Unsprung resonance frequency band component extraction means b for extracting unsprung resonance frequency band components from the sprung up / down direction state quantity detected by the detection means a, and sprung up / down direction detected by the unsprung resonance frequency band component extraction means b The tire air pressure detecting means c for detecting the tire air pressure from the level of the unsprung resonance frequency band component of the state quantity is used as the means.

Further, in the tire air pressure detecting device according to the second aspect, the tire air pressure detecting means c causes the unsprung resonance frequency band component of the sprung up / down direction state quantity detected by the unsprung resonance frequency band component extracting means b. Is compared with the level of the unsprung resonance frequency band component when the tire air pressure is normal, whereby the tire air pressure is detected.

Further, in the tire pressure detecting device according to the third aspect, the unsprung resonance frequency band component extracting means b estimates the unsprung vertical state amount from the sprung vertical state amount based on a predetermined transfer function. The unsprung vertical state quantity estimating means d is provided, and the unsprung resonance frequency band component is extracted from the unsprung up and down state quantity estimated by the unsprung up and down state quantity estimating means d.

Further, in the tire pressure detecting device according to the fourth aspect, the sprung vertical state amount detected by the sprung vertical state amount detecting means a is defined as the sprung vertical acceleration.

Further, in the tire air pressure detecting device according to the fifth aspect, the sprung vertical state amount detecting means a is provided for each wheel.

[0011]

In the tire pressure detecting device according to the first aspect of the present invention, as described above, the spring on the basis of the sprung vertical state amount detected by the sprung vertical state amount detecting means a provided on the spring of the vehicle is used. The lower resonance frequency band component extraction means b extracts the unsprung resonance frequency band component of the sprung vertical state quantity, and the tire air pressure detection means c detects the tire air pressure from the level of the unsprung resonance frequency band component. To do.

That is, the tire air pressure is detected based on the signal of at least one sensor provided on the sprung, whereby the cost of the system can be reduced and the vehicle mountability can be improved.

Further, in the tire air pressure detecting device according to the fifth aspect, by providing the sprung vertical state amount detecting means a for each wheel, it is possible to identify the wheel position where the tire air pressure is lowered.

[0014]

An embodiment of the present invention will be described with reference to the drawings. (First Embodiment) FIG. 2 is a structural explanatory view showing a tire air pressure detecting device according to a first embodiment of the present invention, which is interposed between a vehicle body and four wheels and has four shock absorbers S.
A _FL , SA _FR , SA _RL , SA _RR (Note that in describing the shock absorber, these four are collectively referred to, and when describing their common configuration, they are simply indicated as SA. The lower reference numbers indicate the wheel position, _FL indicates the front wheel left, _FR indicates the front wheel right, _RL indicates the rear wheel left, and _RR indicates the rear wheel right.) Then, each shock absorber SA _FL , SA _FR , SA _RL , S
Position near the A _RR (hereinafter, referred to as the wheel position) to the vehicle body, sprung mass vertical acceleration sensor for detecting a vertical acceleration G sprung (hereinafter, vertical referred G sensor) 1 (1 _FL, 1 _FR,
1 _RL , 1 _RR ) is provided, and the pulse of each shock absorber SA is provided in the vicinity of the driver's seat based on the signal from each vertical G sensor 1 (1 _FL , 1 _FR , 1 _RL , 1 _RR ). A control unit 4 that outputs a drive control signal to the motor 3 is provided.

The above-mentioned configuration is shown in the system block diagram of FIG. 3, in which the control unit 4 comprises an interface circuit 4a, a CPU 4b, and a drive circuit 4c, and the interface circuit 4a is provided with each of the vertical G sensors 1 _FL. , 1 _FR , 1 _RL , 1 _RR sprung vertical acceleration G _FL ,
The G _FR , G _RL , and G _RR signals are input.

As shown in the block diagram of FIG. 4, the interface circuit 4a determines the tire air pressure at each wheel from the sprung vertical accelerations G _FL , G _FR , G _RL , and G _RR signals at each wheel position. A signal processing circuit for determining the unsprung low-frequency processed signal Gj-p as a signal is provided.

The configuration of the signal processing circuit will be described below with reference to the block diagram of FIG. First, at B1, from the sprung vertical acceleration G (G _FL , G _FR , G _RL , G _RR ) signals, as shown in FIG.
As shown in the time chart of (1), bandpass filter processing for obtaining the high-frequency unsprung resonance frequency band component Gj is performed. That is, a second-order bandpass filter BPF (11 Hz) is used as this bandpass filter.

At B2, the unsprung resonance frequency band component G
The unsprung low-frequency processed signal Gj-p is created by calculating the absolute value of the peak value of j and holding the absolute value of the peak value until the absolute value of the next peak value is detected (FIG. 7).
reference).

5A is a frequency characteristic diagram of the sprung vertical acceleration, and FIG. 5B is a frequency characteristic diagram of the unsprung resonance frequency component signal Gj. As shown in FIG. In addition, the level of the unsprung resonance frequency component signal Gj is lower when the tire air pressure is lower than when the tire air pressure is normal. Therefore, by judging this level change with a threshold value, it is possible to detect the variation state of the tire air pressure.

Next, among the control operations of the control unit 4, the tire air pressure detection operation will be described with reference to the flow chart of FIG. 6 and the time chart of FIG.

In the flowchart of FIG. 6, first, at step 101, the unsprung low-frequency processed signal Gj-p of each wheel is compared with a predetermined threshold value Gj-v, and the unsprung low of one of the four wheels is lowered. Only the frequency processed signal Gj-p is less than the predetermined threshold value Gj-v, and the unsprung low frequency processed signal G of the other wheels is
jp It is judged whether or not the predetermined threshold value Gj-v is exceeded, and if YES, the routine proceeds to step 102, where after the timer is started (Tt = Time-Ton), the routine proceeds to step 104. If NO, step 103
And the timer count Tt is reset to 0 (Tt =
After 0), the routine proceeds to step 106 where the tire pressure normality determination process is performed.

In step 104, it is determined whether or not the timer count Tt has passed a predetermined time Δt, and YES.
If it is, the routine proceeds to step 105 where the tire pressure abnormality determination processing is performed. On the other hand, if NO, the routine proceeds to step 106 where the tire pressure normality determination process is performed.

With the above, one flow is completed, and thereafter, the above flow is repeated.

As the tire pressure abnormality determination processing performed in step 106, blinking of an alarm lamp provided in the passenger compartment, alarm sound or voice abnormality notification processing is performed, and in step 106 described above. As the tire pressure normality determination processing that is performed, reset processing of the abnormality notification processing, normality confirmation processing, and the like are performed. Then, by performing the above-described abnormality determination processing for each wheel, it is possible to specify the abnormality-occurring wheel.

As described above, in the tire air pressure detecting device of this embodiment, each tire air pressure can be detected based on the signals of the vertical G sensor 1 provided on the spring at each wheel position. Since it can be shared with the vertical G sensor 1 installed for damping force characteristic control,
It is possible to reduce the system cost and improve the in-vehicle performance.

Next, another embodiment of the present invention will be described. In the description of the other embodiments, the same components as those in the first embodiment will be designated by the same reference numerals and the description thereof will be omitted, and only different points will be described.

(Second Embodiment) In the tire air pressure detecting device of the second embodiment, by observing the level fluctuation of two different frequency (10 Hz, 11 Hz) components in the unsprung resonance frequency band components. The tire pressure drop is detected, which will be described in detail below.

First, of the control operations of the control unit 4, the sprung vertical acceleration G at each wheel position.
The configuration of a signal processing circuit for obtaining two tire pressure determination signals from (G _FL , G _FR , G _RL , G _RR ) will be described based on the block diagram of FIG. B1 and B2 of this signal processing circuit are the same as B1 and B2 of the signal processing circuit shown in FIG. 4 of the first embodiment, and the unsprung low frequency processed signal Gj-H of 11 Hz is created. .

Further, in B3 of this signal processing circuit, as shown in the time chart of FIG. 11, from the sprung vertical acceleration G (G _FL , G _FR , G _RL , G _RR ) signals, the unsprung mass of 10 Hz is obtained. Bandpass filtering is performed to obtain the resonance frequency component GjL. That is, a second-order bandpass filter BPF (10 Hz) is used as this bandpass filter.

In the subsequent B4, the unsprung resonance frequency band component G
The unsprung low-frequency processed signal Gj-L is created by calculating the absolute value of the peak value of jL and holding the absolute value of the peak value until the absolute value of the next peak value is detected (Fig. 1).
1).

9 (a) is a frequency characteristic diagram of both unsprung resonance frequency components GjH and GjL when the tire pressure is normal, and FIG. 9 (b) is both springs under reduced tire pressure. It is a frequency characteristic diagram of the lower resonance frequency components GjH and GjL. As shown in the characteristic diagram, the signal level of the 10 Hz unsprung resonance frequency component GjL is higher when the tire pressure is lower than when the tire pressure is normal. , On the contrary, 11
With the unsprung resonance frequency component GjH of Hz, the signal level is lower when the tire pressure is lower than when the tire pressure is normal. Therefore, the fluctuation state of the tire air pressure can be detected by determining the level change at these two points by the threshold value.

Next, among the control operations of the control unit 4, the tire air pressure detection operation will be described based on the flowchart of FIG. 10 and the time chart of FIG. Incidentally, steps 202 to 206 in this embodiment.
Is the same as the contents of steps 102 to 106 of the block diagram shown in FIG. 6 of the first embodiment, the detailed description thereof will be omitted.

First, in step 200, the first unsprung low-frequency processed signal Gj-H for each wheel is set to a predetermined threshold value Gf.
Determine if it is less than H, YES (Gj-H <GfH)
If so, the tire air pressure may be abnormal, so the routine proceeds to step 201, and NO (Gj-H ≧ Gf
If it is H), the tire pressure is normal, so the routine proceeds to step 203.

In step 201, the second unsprung low frequency processed signal Gj-L for each wheel is set to a predetermined threshold value GfL.
It is judged whether or not it exceeds, and YES (Gj-L> GfL)
If so, the tire pressure may be abnormal, so the routine proceeds to step 202, and NO (Gj-L ≤ Gf
If L), the tire pressure is normal, so the routine proceeds to step 203.

As described above, also in the tire air pressure detecting device of this embodiment, each of the tire air pressure detecting devices according to the first and second embodiments is based on the signals of the vertical G sensor 1 provided on the spring at each wheel position, as in the first embodiment. Since the tire pressure can be detected and can be shared with the vertical G sensor 1 installed for damping force characteristic control, the system cost can be reduced and the in-vehicle performance can be improved. can get.

(Third Embodiment) As shown in the block diagram of FIG. 12, the tire air pressure detecting device of the third embodiment has a transfer function Ga ₍ from the sprung vertical acceleration to the unsprung vertical speed) at B0 thereof. _{S) Based on} (the following formula (1)), the unsprung vertical velocity is estimated from the sprung vertical acceleration G detected by the G sensor 1, and the unsprung resonance frequency band component is extracted from the unsprung vertical velocity in the subsequent B1. It is something that is done. Since the processing contents of B1 and B2 are substantially the same as those of B1 and B2 of the block diagram of FIG. 4 in the first embodiment, detailed description thereof will be omitted.

Ga _(S) = (M ₁ · s ² + c ₁ · s + k ₁ ) / (c ₁ · s ² + k ₁ · s) (1) In addition, M ₁ is sprung A mass, c ₁ is a damping coefficient of the suspension, and k ₁ is a spring constant of the suspension. Also,
This equation is obtained by Laplace transforming the equation of motion.

As described above, in the tire air pressure detecting device of this embodiment, the same effect as that of the first embodiment can be obtained, and since the comparison is made by the unsprung behavior directly influenced by the tire air pressure, the judgment is made. The effect that it can be performed more accurately is obtained.

Although the embodiment has been described above, the specific structure is not limited to this embodiment, and the present invention includes a design change and the like within a range not departing from the gist of the invention.

For example, in the embodiment, the vertical G sensor as the sprung vertical state amount detecting means is provided at each wheel position, but the variation of the tire air pressure can be detected by providing at least one G sensor. it can.

Further, in the embodiment, as the abnormality determination processing of the tire pressure, only the abnormality is notified in the vehicle interior. However, in the shock absorber at the wheel position where the abnormality is detected, the damping force characteristic is changed to the soft side. The control can prevent damage to the tires and wheels.

[0042]

As described above, the first aspect of the present invention is as follows.
In the tire air pressure detection device described above, as described above, at least one on the spring of the vehicle, sprung vertical direction state amount detection means for detecting the sprung vertical direction state amount,
An unsprung resonance frequency band component extracting means for extracting an unsprung resonance frequency band component from the sprung up and down state quantity detected by the sprung up and down state quantity detecting means and an unsprung resonance frequency band component extracting means. The tire air pressure detecting means for detecting the tire air pressure from the level of the unsprung resonance frequency band component of the sprung up-down direction state quantity is provided with one sensor, and Since it can be shared with a sensor installed for damping force characteristic control, there is an effect that the cost can be reduced by the cost reduction of the system and the vehicle mountability can be improved.

Further, in the tire air pressure detecting device according to the fifth aspect of the present invention, by providing the sprung vertical state amount detecting means for each wheel, it is possible to specify the wheel position where the tire air pressure is lowered. become.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims showing a tire pressure detection device of the present invention.

FIG. 2 is a structural explanatory view showing a tire air pressure detecting device of a first embodiment of the present invention.

FIG. 3 is a system block diagram showing the tire air pressure detection device of the first embodiment.

FIG. 4 is a block diagram showing a configuration of a signal processing circuit for obtaining an unsprung low-frequency processed signal in the device of the first embodiment.

FIG. 5 is a sprung vertical acceleration (a) in the device of the first embodiment.
FIG. 3 is a frequency characteristic diagram of an unsprung resonance frequency component (b).

FIG. 6 is a flowchart showing a tire air pressure detection operation of the control operations of the control unit in the first embodiment device.

FIG. 7 is a time chart for explaining a tire pressure abnormality determination operation based on an unsprung resonance frequency band component and an unsprung low-frequency processed signal in the first embodiment device.

FIG. 8 is a block diagram showing a configuration of a signal processing circuit for obtaining an unsprung low-frequency processed signal in the tire air pressure detection device of the second embodiment.

FIG. 9 is a frequency characteristic diagram (A) of both unsprung resonance frequency components when the tire pressure is normal in the second embodiment device and a frequency characteristic diagram (B) of both unsprung resonance frequency components when the tire pressure is abnormal.

FIG. 10 is a flowchart showing a tire pressure detection operation of the control operations of the control unit in the second embodiment device.

FIG. 11 is a time chart for explaining a tire pressure abnormality determination operation based on an unsprung resonance frequency band component and an unsprung low-frequency processed signal in the second embodiment device.

FIG. 12 is a block diagram showing a configuration of a signal processing circuit for obtaining an unsprung low-frequency processed signal in the device of the third embodiment.

[Explanation of symbols]

 a sprung vertical state quantity detecting means b unsprung resonance frequency band component detecting means c tire air pressure detecting means d unsprung vertical state quantity estimating means

Claims (5)

[Claims] 1. A sprung vertical condition amount detecting means for detecting at least one sprung vertical condition amount provided on a spring of a vehicle, and a sprung member detected by the sprung vertical condition amount detecting means. An unsprung resonance frequency band component extracting means for extracting an unsprung resonance frequency band component from the up-and-down state quantity; and an unsprung resonance frequency band component of the unsprung up-and-down state quantity detected by the unsprung resonance frequency band component extracting means. A tire air pressure detection device comprising: a tire air pressure detection means for detecting a tire air pressure from a level. 2. The level of the unsprung resonance frequency band component of the sprung up / down direction state amount detected by the unsprung resonance frequency band component extraction means is determined by the tire air pressure detection means when the tire air pressure is normal. The tire air pressure detection device according to claim 1, wherein the tire air pressure detection device is configured to detect the tire air pressure by comparing with the level of the unsprung resonance frequency band component. 3. The unsprung resonance frequency band component extracting means includes unsprung up and down state quantity estimating means for estimating the unsprung up and down state quantity based on a predetermined transfer function from the sprung up and down direction quantity. The tire air pressure detection device according to claim 1 or 2, wherein the unsprung resonance frequency band component is extracted from the unsprung up and down state quantity estimated by the unsprung up and down state quantity estimation means. . 4. The tire pneumatic pressure according to claim 1, wherein the sprung vertical state amount detected by the sprung vertical state amount detecting means is a sprung vertical acceleration. Detection device. 5. The sprung vertical state quantity detecting means is provided for each wheel.
The tire air pressure detection device according to any one of 1.