JP3182836B2 - Tire balance detection 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 tire balance detecting device for detecting a tire balance state.

[0002]

2. Description of the Related Art Conventionally, tire balance adjustment is performed only for a tire alone, and is not performed after the tire is mounted on a vehicle unless the tire is replaced by puncture or the like. However, the aging of tires varies greatly depending on the usage conditions, and when the tires become unbalanced (uneven wear, standing wave phenomenon, etc.), the unsprung vibration of the tires increases, and the tires lose control of the tire's contact with the ground. There is a problem of deteriorating stability and riding comfort. Therefore, to solve this problem,
It is necessary to detect the balance state of the tire even while the vehicle is running.

Therefore, a method has been considered in which an acceleration sensor is attached to the unsprung portion of the suspension, and the unsprung vibration component of the tire is extracted from the output signal of the acceleration sensor to detect the balance state of the tire.

[0004]

However, the normal acceleration sensor is, as shown in FIG.
Is detected by the gauge unit 102, and the gauge unit 102 is easily affected by the vibration from the road surface. Therefore, there is a problem in durability as a sensor, and there is a problem that long-term detection accuracy cannot be sufficiently ensured.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a tire balance detecting device capable of accurately detecting a tire balance state.

[0006]

In order to achieve the above object, a tire balance detecting device according to the present invention comprises: a rotation speed output means for outputting a signal corresponding to a rotation speed of a wheel; Vibration frequency component extraction means for extracting a signal containing a vibration frequency component, order component extraction means for extracting a signal of the order component of the wheel rotation speed per unit time from the signal containing the vibration frequency component of the tire, and the order component Detecting means for detecting the balance state of the tire based on the signal of the rotation speed output means
Is the anti-skid control device mounted on the vehicle
It is characterized by being shared with a wheel speed sensor .

[0007]

According to the above configuration, an anti-skip mounted on a vehicle is provided.
Speed output shared with wheel speed sensor of
A signal containing a tire vibration frequency component is extracted from the rotation speed of the wheel by the force means, and a signal of the order component of the wheel rotation speed per unit time is extracted from the extracted signal containing the tire vibration frequency component, and the order component is extracted. The balance state of the tire is detected based on the signal. Here, when the tire enters an unbalanced state, the magnitude of the signal of the order component of the wheel rotation speed per unit time of the signal including the vibration frequency component of the tire changes, so the signal of the extracted order component is Of the tire can be detected based on the size of the tire.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration diagram showing the entire configuration of the first embodiment.

As shown in FIG. 1, the tires 1a to 1a of the vehicle
A wheel speed sensor is provided corresponding to 1d. Each wheel speed sensor includes gears 2a to 2d and pickup coils 3a to 3d. Gears 2a to 2d
Are coaxially mounted on the rotating shafts (not shown) of the tires 1a to 1d and are made of a disk-shaped magnetic material. The pickup coils 3a to 3d are connected to these gears 2a to 2d
Are mounted at predetermined intervals in the vicinity of the gears 2a to 2a.
2d, that is, an AC signal having a cycle corresponding to the rotation speed of the tires 1a to 1d is output. Pickup coil 3
AC signals output from a to 3d are output from a waveform shaping circuit R
Well-known electronic control unit (ECU) consisting of OM, RAM, etc.
4 to perform predetermined signal processing including waveform shaping. The result of the signal processing is input to the display unit 5, and the display unit 5 notifies the driver of the balance state of each of the tires 1a to 1d. The display unit 5 may independently display the balance state of each of the tires 1a to 1d, or provide one warning lamp and turn on when one of the tires becomes unbalanced. May be warned.

[0010] The tire unbalance state mentioned here has two meanings. One is related to the basic structure of a tire, and a tire is a composite material product made of fiber, steel wire, rubber, etc., and most of the tire is manually changed, such as partial dimensional change, rigidity change and asymmetry on the periphery. Therefore, when the tire rolls, the tire receives an abnormal force or a synchronously varying force from the road surface when the tire rolls. When these forces become abnormal, it causes a decrease in the straightness of the vehicle and abnormal vibration.

A prominent example in this case is a standing phenomenon that occurs when the tire pressure is low at a high speed. The tire undulates due to the waving phenomenon of the tire.

The second is weight balance. Since the balance of the tire is balanced by the balance weight, there is almost no problem.However, uneven wear of the tire often occurs while the vehicle is running, and the weight is unbalanced due to misalignment of the mounting position of the tire. A balance may occur.

Here, the principle of detecting the tire balance in this embodiment will be described first. When the vehicle travels on, for example, a paved asphalt road surface, the tire receives vertical and longitudinal forces due to minute irregularities on the road surface, and the tire vibrates in the vertical and longitudinal directions. The tire vibration component of the vehicle can be extracted from the detection signal of the wheel speed sensor. This is because, as a result of detailed studies by the inventors, it has been found that the detection signal of the wheel speed sensor includes a vibration frequency component of a tire (Japanese Patent Application No. 3-294622). At this time, when the wheel speed fluctuates relatively largely, the frequency characteristics of the wheel speed fluctuation at the time of the tire vibration are as shown in FIG.
When the wheel speed fluctuates in a relatively narrow range with respect to the frequency characteristics of FIG. 2, as shown in FIG. 3, the frequency characteristics of the wheel speed fluctuation show a peak value at a certain interval, and the peak value is , The order of wheel rotations per unit time (integer multiple). This order component appears as shown in FIG. 4 even when the vehicle is subjected to a constant speed test on a bench such as a chassis roller (the roller is a smooth surface), and the cause is caused by unbalance of the tire itself. It turned out to be.

Thus, according to the present embodiment, the anti-skid control device (ABS) whose number of mounted vehicles is increasing in recent years.
Since a vehicle or the like equipped with a vehicle is already equipped with a wheel speed sensor for each tire, the tire balance can be detected without adding any new sensors.

FIG. 5 is a flowchart showing the processing executed by the ECU 4. Note that the ECU 4 controls each wheel 1a.
In order to perform the same processing for .about.1d, the flowchart of FIG. 5 shows only the flow of processing for one wheel. In addition, in the following description, the suffix of each code is omitted. Further, the flowchart shown in FIG. 5 shows an example in which it is particularly detected that the tire has become unbalanced, and a warning is issued to the driver.

In FIG. 5, in step 100, after the AC signal (FIG. 6) output from the pickup coil 3 is shaped into a pulse signal, the pulse interval is divided by the time between the pulse signal and the wheel speed v. Is calculated. As shown in FIG. 7, the wheel speed v usually includes many frequency components including a tire vibration frequency component. In step 110, as shown in FIG. 8, the wheels from the difference Δv and time Δt taken during the wheel speed v _n1 that is calculated on the wheel speed v _n and _first n computed in the n-th step 100 The speed change rate dv is calculated.

[0017]

Dv = Δv / Δt At this time, the wheel speed v is calculated (n ₁ −n) times during the time ΔT, and this (n ₁ −n) is calculated by the FFT calculation described later. It is desirable that n ₀ be the required number of data.

[0018] At step 120, it determines the calculated wheel speed variation rate dv is to or less than a predetermined value dv ₀ at step 110. The process of step 120 is performed to determine whether the vehicle speed at which the vehicle is traveling is a vehicle speed at which tire balance can be detected by the detection method of the present embodiment. That is, in the present embodiment, the tire balance is detected based on the magnitude of the order component of the wheel rotation included in the vibration frequency component of the tire. However, if the wheel speed v is not within a certain range, the wheel rotation is detected. Is difficult to detect. Therefore, in order to clarify the order component, the tire balance is detected only when the wheel speed fluctuation dv is small. Needless to say, when the vehicle is traveling at a constant speed at a constant wheel speed, the ideal state is obtained.

In step 120, if the judgment is affirmative, the process proceeds to step 130, and if the judgment is negative, the process returns to step 100. In step 130, a frequency analysis (FFT) operation is performed on the wheel speed v, and the number of operations N is counted. FIG. 9 shows an example of the result of performing the FFT operation.

As shown in FIG. 9, when the FFT calculation is performed on the wheel speed obtained when the vehicle actually travels on a general road, frequency characteristics usually become very random. This is because the shape (size and height) of the minute unevenness existing on the road surface is completely irregular, and therefore, the frequency characteristic varies for each wheel speed data. Therefore, in the present embodiment, in order to reduce the fluctuation of the frequency characteristics as much as possible, an average value of the results of the FFT operations performed a plurality of times is obtained. Therefore, in step 140, step 130
It is determined whether or not the number N of FFT operations in has reached a predetermined number n ₀ . When the number of calculations N has not reached the predetermined number n ₀ , the processing from step 100 to step 130 is further repeatedly executed. On the other hand, when the number of operations N has reached the predetermined number of times n ₀ , step 1
Proceeding to 50, an averaging process is performed. In this averaging process, as shown in FIG. 10, an average value of each FFT operation result is obtained, and an average value of the gain of each frequency component is calculated. By such averaging processing, FFT by road surface
It is possible to reduce the variation in the calculation result.

Next, in step 160, based on the FFT operation result smoothed by the averaging process,
By comparing the magnitude v _P of the primary component of the wheel rotation speed with the predetermined value v _T , it is determined whether or not the tire is in an unbalanced state. When it is determined that the magnitude v _{P of the} primary component is larger than the predetermined value v _T , the process proceeds to step 170 on the assumption that the tire is unbalanced, and a warning is displayed on the display unit 5 to the driver.

Next, a second embodiment of the present invention will be described. In the above-described first embodiment, the FFT operation and the averaging process are performed to detect the order component of the wheel rotation speed. However, in the second embodiment, a band-pass filter (BPF) is used regardless of the FFT operation and the averaging process. The process is characterized in that the order component of the wheel rotation speed is detected.

For this reason, in the second embodiment, only a part of the processing contents in the ECU 4 is different from the first embodiment, and the configuration is common to the first embodiment. Therefore, the description of the configuration is omitted, and only the differences in the processing contents in the ECU 4 will be described. That is, in the second embodiment, steps 130 to 160 in the flowchart shown in FIG. 5 are changed to the processing shown in FIG.

In FIG. 11, at step 132, the maximum value v _H and the minimum value v _L of the wheel speed within the time Δt required to calculate the wheel speed change rate dv are calculated.
For example, if the fluctuation of the wheel speed v is as shown in FIG. 8, the maximum value v _H = v _n1 and the minimum value v _L = v _n . At this time, it is clear that the magnitude of the primary component of the wheel rotation speed is between the minimum value v _L and the maximum value v _H. In step 134, the maximum value v _H calculated in step 132,
The minimum value v _{by L} dividing the at circumferential length per wheel revolution, the maximum value v _H, the cutoff frequency cf _H band filters corresponding respectively to the minimum value v _L (BPF), cf _L
Is calculated. In step 136, the cutoff frequency c
f _H, determining the time waveform f of frequencies close to cut high frequency and low frequency components of the wheel speed v at bandpass filter is determined by cf _L (BPF) in the primary component of the wheel speed. Thereafter, the process proceeds to step 138, where a time waveform f having a frequency close to the first-order component of the wheel rotation speed as shown in FIG.
An unbalanced state of the tire is detected by determining whether or not it is within a range of predetermined determination values v _I and −v _I. At this time, if the time waveform f is out of the range of the determination values v _I , −v _I , it is determined that the tire is unbalanced, and Step 1 is performed.
Proceeding to 70, the display unit 5 displays a warning to the driver.

The present invention is not limited to the above embodiment.
However, unless deviating from the purpose, for example,
Various modifications are possible. In step 160 of the first embodiment, the primary
Component size v_PTo a predetermined value v_TShowed an example to compare with
However, the size of the second and third order components (v _P2, V
_P3) To a predetermined value (v_T2, V_T3)
Thus, the unbalanced state of the tire may be detected.
Also in the second embodiment, the secondary and tertiary components of the wheel rotation speed are used.
Time waveform with a frequency close to the minute
May be detected.

Further, in the determination at step 160,
Is the magnitude v of the primary component of the wheel rotation speed _PIs a predetermined value v_TYo
Even if it becomes larger, proceed to step 170 immediately.
First, set the number of times and time to appropriate values,_P> V_TShape
If the state continues for more than the set value, proceed to step 170
You may do it.

The wheel speed sensor may be a sensor that utilizes the Hall effect for detection.

[0028]

As described in detail above, according to the present invention, a vehicle
Wheel speed sensor of anti-skid control device mounted on both
A signal containing the tire vibration frequency component is extracted from the wheel rotation speed by the rotation speed output means shared with the vehicle, and a signal of the order component of the wheel rotation speed per unit time is extracted from the signal containing the extracted tire vibration frequency component. Is extracted, and the balance state of the tire is detected based on the signal of the order component.
Here, since the magnitude of the signal of the order component changes according to the balance state of the tire, the balance state of the tire can be accurately detected from the rotation speed of the wheel.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a state of resonance frequencies in a vertical direction and a longitudinal direction below a spring of a vehicle.

FIG. 3 is a characteristic diagram showing a state of an order component of a wheel rotation speed when traveling on an asphalt road surface.

FIG. 4 is a characteristic diagram showing a state of an order component of a wheel rotation speed when a constant speed test is performed.

FIG. 5 is a flowchart showing processing contents of the electronic control device of the first embodiment.

FIG. 6 is a waveform diagram showing an output voltage waveform of a wheel speed sensor.

FIG. 7 is a waveform diagram showing a fluctuation state of a wheel speed v calculated based on a detection signal of a wheel speed sensor.

FIG. 8 is an explanatory diagram for calculating a wheel speed change rate dv.

9 is a characteristic diagram showing a result of performing a frequency analysis operation on the wheel speed v having the waveform shown in FIG. 6;

FIG. 10 is an explanatory diagram for explaining an averaging process in the first embodiment.

FIG. 11 is a flowchart illustrating a difference in processing content between the second embodiment and the first embodiment.

FIG. 12 is a time waveform diagram of a frequency close to the first order component of the wheel rotation speed.

FIG. 13 is a structural diagram of an acceleration sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tire 2 Gear 3 Pickup coil 4 Electronic control unit (ECU) 5 Display

Continuation of front page (56) References JP-A-62-149503 (JP, A) JP-A-59-26029 (JP, A) JP-A-5-133383 (JP, A) JP-A-5-221208 (JP) JP-A-5-254316 (JP, A) JP-A-5-294118 (JP, A) JP-A-5-330322 (JP, A) JP-A-5-213018 (JP, A) 6-115328 (JP, A) JP-A-6-122304 (JP, A) "Automotive Technology Handbook"<1stvolume> Fundamentals and Theory, 1st edition, Japan Society of Automotive Engineers, December 1990 1st, pp. 264-288 (58) Fields investigated (Int. Cl. ⁷ , DB name) B60C 23/00-23/08 G01L 17/00 G01M 17/02 G01M 1/16

Claims (6)

(57) [Claims] 1. A signal corresponding to a rotation speed of a wheel is output.
Rotation speed output means, including a vibration frequency component of a tire from the rotation speed of the wheel
A vibration frequency component extracting means for extracting a signal;
The order component that extracts the signal of the order component of the wheel rotation speed
Extraction means;  The balance of the tire based on the signal of the order component
Detecting means for detecting a state;  Equipped, The rotation speed output means includes an anti-rotation speed sensor mounted on a vehicle.
Shared with wheel speed sensor of skid control device That
Characteristic tire balance detection device. 2. The method according to claim 1, further comprising determining means for determining a change rate of the rotation speed of the wheel, and determining that the tire balance can be detected when the change rate of the rotation speed is equal to or less than a predetermined value. The tire balance detection device according to claim 1 . 3. A vehicle comprising a determining means for determining whether or not the rotational speed of the wheel is within a predetermined range, wherein when the determining means makes an affirmative determination, it is determined that the vehicle speed is capable of detecting a tire balance. The tire balance detection device according to claim 1 or 2, wherein Wherein said order component, relative to the rotational speed signal of the wheel, tire balance detection according to any one of claims 1 to 3, characterized in that detecting by performing a FFT operation apparatus. Wherein said order component is a tire balance detecting device according to any one of claims 1 to 3, characterized in that the detecting by the FFT calculation and averaging process with respect to the rotational speed of the signal of the wheel. Wherein said order component is a tire balance detecting device according to any one of claims 1 to 5, characterized in that detecting by performing a bandpass filter process with respect to the rotational speed signal of the wheel .