JP2007307980A - Method and device for calculating ground contact length of tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for calculating the ground contact length while a tire rolls based on the measurement time series data of the acceleration of a tread part of the rolling tire. <P>SOLUTION: Firstly, the measurement time series data of the acceleration in the radial direction of a tire tread part on the tire circumference is obtained. The acceleration data in the vicinity of the ground contact is extracted from the obtained measurement time series data, and a first ground contact length candidate is obtained from the time series waveform shape of the acceleration data. A second ground contact length candidate is obtained by calculating the deflection shape of the tire in the vicinity of the ground contact. Further, any one candidate of the first ground contact length candidate and the second ground contact length candidate is selected as the ground contact length according to the result of the frequency spectrum of the acceleration data in the vicinity of the ground contact. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for calculating a contact length of a tire when the tire rolls on a road surface.

Conventionally, the contact length of a rolling tire has been obtained by performing a running simulation of the rolling tire using a finite element model. With this acquisition method, the contact length cannot be acquired in a short time in terms of the time required to create the finite element model and the calculation time of the simulation. For this reason, the contact length during rolling (dynamic contact length) and the deformed shape of the tire are substituted with the contact length during non-rolling and the deformed shape of the tire.
However, since the flexure shape on the circumference of the tire that affects the contact length and contact shape of the rolling tire has a great influence on the tire performance, the contact length is obtained by measuring the rolling tire. Therefore, it has been required to judge the tire performance.

On the other hand, in Patent Documents 1 to 3 below, an acceleration sensor is attached to the tire, measurement data of the acceleration of the rolling tire is obtained, and a power spectrum and a vibration spectrum are obtained from the obtained measurement data to obtain the rolling data. A method for estimating the road surface state, a method for determining the timing at which the tread portion contacts the road surface from radial acceleration measurement data, and the like are disclosed.
However, in Patent Documents 1 to 3, when the rolling tire has no squeal noise generated due to a large slip angle, the contact length of the rolling tire is calculated using the acceleration measurement data. However, in a state where a squealing noise is generated, it is extremely difficult to specify the contact area due to vibration on the measurement data, and the contact length of the rolling tire cannot be calculated.

JP 2002-340863 A JP 2003-182476 A Japanese translation of PCT publication No. 2002-511812

  Therefore, the present invention can accurately determine the contact length during rolling of the tire based on the measurement time series data of the acceleration of the tread portion of the rolling tire. It is an object of the present invention to provide a tire contact length calculation method and a tire contact length calculation apparatus capable of accurately obtaining the length.

In order to achieve the above object, the present invention is a method for calculating a contact length of a tire when the tire rolls on a road surface, and at least an acceleration in a radial direction on the tire circumference of the rolling tire. Obtaining measurement time-series data of acceleration including acceleration, extracting acceleration data near the ground from the acquired measurement time-series data, and integrating the time-series waveform shape or acceleration data of this acceleration data by second-order time integration. Step of obtaining a first contact length candidate from the tire deflection shape obtained, and extracting acceleration data in the vicinity of the contact from the acquired measurement time series data, and regressing the acceleration data into a regression equation to determine the deflection shape of the tire in the vicinity of the contact Calculating a second contact length candidate by calculating the acceleration, and an acceleration in the vicinity of the contact acquired from the measurement time series data Selecting one candidate as a contact length from the first contact length candidate and the second contact length candidate according to the result of the frequency spectrum of the data. Provide a method for calculating the contact length.
Here, the acceleration measurement time-series data including at least the radial acceleration includes radial acceleration data among the radial acceleration, the circumferential acceleration, and the width acceleration as measurement time-series data. Say.

The result of the frequency spectrum of the acceleration data is a maximum peak value in a frequency band of 500 Hz to 1500 Hz, and when the maximum peak value is a predetermined value or less, the first contact length candidate is selected as a contact length, When the maximum peak value is larger than a predetermined value, it is preferable to select the second contact length candidate as the contact length.
Further, in the step of obtaining the first contact length candidate, the two points when the time series waveform of the acceleration data crosses the acceleration 0 are set as the corresponding points of the tire stepping edge and the kicking edge, and the distance between the two points. Is preferably obtained as the first contact length candidate.
Further, in the step of obtaining the second contact length candidate, the second-order differential function of a deflection function representing a peak shape having one extreme value and a curve asymptotic to 0 on both sides of the extracted acceleration data is obtained. Using the least square regression to determine the value of the parameter of the deflection function, to calculate the deflection shape near the ground contact from the deflection function determined using the value of the parameter of the deflection function, based on the calculated deflection shape of the tire, It is preferable to obtain the second contact length candidate.

  The present invention also relates to a method for calculating a contact length of a tire when the tire rolls on a road surface, and a measurement time series including at least radial acceleration on the tire circumference of the rolling tire. In the frequency spectrum of acceleration data near the ground acquired from the measurement time-series data in the step of acquiring data, when the maximum peak value in the frequency band of 500 Hz to 1500 Hz is less than or equal to a predetermined value, the measurement on the acquired tire circumference The acceleration data near the ground is extracted from the time series data, the contact length is obtained from the time series waveform shape of the acceleration data or the tire deflection shape obtained by integrating the acceleration data on the second floor, and the maximum peak value is If larger than the predetermined value, the acceleration data near the ground is extracted from the measured time series data on the tire circumference. The acceleration data by regression to regression provides a contact length calculating method of a tire characterized by having the steps of: obtaining a contact length by calculating the deflection shape of the tire in the ground near.

When the maximum peak value is less than or equal to a predetermined value, the two points when the time series waveform of the acceleration data crosses acceleration 0 are taken as the corresponding points of the tire stepping edge and the kicking edge, and the distance between the two points Is preferably obtained as the contact length.
Further, when the maximum peak value is larger than a predetermined value, the extracted acceleration data uses a second-order differential function of a deflection function representing a peak shape having one extreme value and a curve asymptotic to 0 on both sides thereof. The value of the deflection function parameter is determined by performing a least-squares regression, and the deflection shape in the vicinity of the ground contact is calculated from the deflection function determined using the parameter value of the deflection function, and the ground contact is calculated based on the calculated tire deflection shape. It is preferable to determine the length.

  Further, the present invention is an apparatus for calculating a contact length of a tire when the tire rolls on a road surface, and is a measurement time series of acceleration including at least radial acceleration on the tire circumference of the rolling tire. An acquisition unit that acquires data, and a calculation unit that calculates the contact length of the tire using the acquired measurement time-series data on the tire circumference, the calculation unit is a measurement time series on the acquired tire circumference First processing for obtaining a first contact length candidate from a tire shape obtained by extracting acceleration data near the ground from the data and integrating the time-series waveform shape of the acceleration data or the second-order time integration of the acceleration data. And acceleration data near the ground is extracted from the measured time series data on the tire circumference, and this acceleration data is regressed to a regression equation to calculate the deflection shape of the tire near the ground. A second processing unit for obtaining a second ground contact length candidate, and depending on a result of a frequency spectrum of acceleration data near the ground acquired from the measurement time series data, the first ground contact length candidate and the There is provided a tire contact length calculation apparatus, comprising: a selection unit that selects one candidate as a contact length from the second contact length candidates.

  In the present invention, one of the first contact length candidates and the second contact length candidates is set as the contact length according to the result of the frequency spectrum of the acceleration data near the contact acquired from the acceleration measurement time series data. Since the selection is made, the contact length during rolling of the tire can be accurately obtained even in a state where a squeal noise is generated. By providing this vehicle contact length information to the vehicle control device, it is possible to contribute to stable vehicle control. In addition, by notifying the driver of the contact length information, it is possible to avoid danger from sudden slipping of the tire.

  Hereinafter, a tire contact length calculation method and a tire contact length calculation apparatus according to the present invention will be described in detail with reference to preferred embodiments shown in the accompanying drawings.

  FIG. 1 is a block diagram showing an apparatus configuration of an embodiment of a tire contact length calculation apparatus according to the present invention for carrying out the tire contact length calculation method according to the present invention, and FIG. 2 is a line II-II in FIG. It is sectional drawing. In the embodiment shown in FIGS. 1 and 2, the acceleration including at least the radial acceleration of the rolling tire on the inner peripheral surface (the inner liner surface) of the tread portion of the tire is measured by an acceleration sensor. Although the acceleration measurement time series data is obtained, an acceleration sensor may be provided in the tread portion, the belt portion, or the like to obtain the measurement time series data of the acceleration of the rolling tire.

  A tire contact length calculation device 10 shown in FIG. 1 is a device that calculates the contact length of a rolling tire by using acceleration measurement data (acceleration data) including acceleration in the radial direction in the tread portion 1a of the tire 1. is there. The acceleration of the tread portion 1a of the tire 1 is detected by an acceleration sensor 2 fixed to an inner liner portion 1b provided on the inner periphery of the tread portion 1a of the tire. The acceleration measurement time series data at this time is transmitted from a transmitter (not shown) provided on the rolling tire to the receiver 3 and amplified by the amplifier 4 and then input to the tire contact length calculation device 10. The measurement time series data may be transmitted, for example, by providing a transmitter on a wheel assembled in a tire and transmitting the measurement time series data of the acceleration sensor 2 from the transmitter to the receiver 3. A transmission function may be provided and the acceleration sensor 2 may be configured to transmit directly to the receiver 3. Further, an amplifier that amplifies the time series data of the acceleration sensor 2 may be provided on the wheel together with the transmitter, and the acceleration measurement time series data received by the receiver may be supplied to the tire ground contact length calculation device 10.

  As the acceleration sensor 2, for example, a semiconductor acceleration sensor disclosed in Japanese Patent Application No. 2003-134727 (Japanese Patent Laid-Open No. 2004-340616) filed earlier by the applicant of the present application is exemplified. Specifically, the semiconductor acceleration sensor includes a Si wafer having a diaphragm formed in the outer peripheral frame portion of the Si wafer, and a pedestal for fixing the outer peripheral frame portion, and a weight is provided at the center of one surface of the diaphragm. And a plurality of piezoresistors are formed on the diaphragm. When acceleration is applied to the semiconductor acceleration sensor, the diaphragm is deformed, and the resistance value of the piezoresistor changes due to the deformation. A bridge circuit is formed so that this change can be detected as acceleration information.

  By fixing the acceleration sensor 2 to the inner peripheral surface of the tread portion 1a of the tire, radial, circumferential and width accelerations acting on the tread portion 1a of the rolling tire can be measured. In addition to this, the acceleration sensor 2 may be an acceleration pickup using a piezoelectric element, or a strain gauge type acceleration pickup combined with a strain gauge.

The tire contact length calculation device 10 to which the acceleration time series data amplified by the amplifier 4 is supplied includes a data acquisition unit 12, a signal processing unit 14, a calculation unit 16, and a data output unit 18. Each of these parts is defined by a subroutine or subprogram that functions on the computer. That is, by executing software on a computer having the CPU 20 and the memory 22, the tire ground contact length calculating device 10 is configured by installing each of the above parts.
Further, the tire ground contact length calculation device of the present invention may be a dedicated device in which the function of each part is configured by a dedicated circuit instead of a computer.

  The data acquisition unit 12 is a part that acquires, as input data, measurement time series data of acceleration for at least one rotation of the tire amplified by the amplifier 4. Data supplied from the amplifier 4 is analog data, which is sampled at a predetermined sampling frequency and converted into digital data.

  The signal processing unit 14 is a part that extracts acceleration data in the radial direction from digitized acceleration measurement time-series data and performs a smoothing process using a filter. Specific processing will be described later.

  The calculation unit 16 is a part for obtaining the contact length of the rolling tire based on the acceleration data obtained by the signal processing unit 14. When calculating the contact length, the calculation unit 16 determines a first contact length candidate from the time series waveform of the acceleration data, and further calculates a tire deflection shape (tire deflection distribution) near the contact from the acceleration data. Thus, the second contact length candidate is obtained. In other words, the calculation unit 16 calculates the second ground contact by calculating the tire deflection distribution near the ground contact from the first processing unit for obtaining the first ground contact length candidate from the time series waveform of the acceleration data and the acceleration data. A second processing unit for obtaining a length candidate, and further selecting one of the first contact length candidates and the second contact length candidate as the contact length according to the result of the frequency spectrum of the acceleration data The selection part to perform is provided. Specific processing will be described later.

  The data output unit 18 is a part that uses the calculated tire contact length and other information, for example, the rotation trajectory of the tire tread portion obtained based on the acceleration data, as output data. The output data of the contact length is sent to the vehicle control device 24 that controls the traveling speed of the vehicle and the steering angle of the tire according to the contact length of the tire.

FIG. 3 is a flowchart showing a flow of a tire contact length calculation method performed by the tire contact length calculation apparatus 10.
First, it is determined whether or not wheel rotation has started (step S100). The start of wheel rotation is determined using a measuring instrument such as a vehicle speedometer.
After the wheel rotation is started, the measurement time series data of acceleration amplified by the amplifier 4 is supplied to the data acquisition unit 12, sampled at a predetermined sampling frequency, and digitized measurement data is acquired (step S102).

  Next, the acquired measurement time series data is supplied to the signal processing unit 14, and first, smoothing processing by a low-pass filter is performed (step S104). Further, radial acceleration data in the vicinity of the ground is extracted from the measured time series data subjected to the smoothing process (step S106). Since the measurement time series data supplied to the signal processing unit 14 includes a lot of noise components, the noise components are removed by the smoothing process, and smooth measurement time series data of radial acceleration is obtained. The cutoff frequency of the filter changes depending on the tire running speed (rolling speed) and noise components. For example, when the rolling speed (running speed) is 60 (km / hour), the cutoff frequency is 2 kHz. The In addition, a smoothing process may be performed using a moving average process or a trend model instead of the filter.

  Next, a first contact length candidate is obtained from the time-series waveform shape of the acceleration data in the vicinity of the extracted contact (step S108). Specifically, the two points when the time-series waveform of the acceleration data in the radial direction crosses acceleration 0 are taken as the corresponding points of the tire stepping end (front end) and kicking end (rear end), and between these two points The distance between the two points is calculated by multiplying the time difference by the traveling speed obtained by a speedometer or the like provided in the vehicle, and this calculated value is set as the first contact length candidate. The zero acceleration line is obtained by extracting the centrifugal force component from the time-series waveform of the acceleration data in the radial direction. For example, when the time series waveform of the acceleration data in the radial direction near the ground is a waveform as shown in FIG. A corresponding point. The first contact length candidate is calculated by multiplying the time difference Δt between the two points by the running speed of the tire at this time.

Furthermore, a second contact length candidate is obtained by calculating the deflection shape of the tire in the vicinity of the contact using the deflection function from the extracted acceleration data in the radial direction (step S110).
Hereinafter, the second contact length candidate will be described more specifically. FIG. 5A shows a graph of an example of measurement time series data of acceleration in the radial direction. FIG. 5A shows a measurement in which the value of the radial acceleration Az is taken on the vertical axis and the time axis t (seconds) is taken on the horizontal axis, and the slip angle changes from 0 ° to a slip angle of 20 ° in about 1 second. Time series data is shown.

In the measurement time series data Az (t) of the acceleration in the radial direction, a time t _c when the radial acceleration is minimized is temporarily set as a time passing through the grounding center. For example, Qc ± 57.5 degrees (± 57.5 can be set by the operator), where Qc is the tire rotation phase angle (angle θ with reference to point O in FIG. 1) at time t = t _c Is extracted as acceleration data in the vicinity of the ground contact, and further as data to be regressed for regression to a deflection function described later.

The regression data is subjected to least square regression using the following formulas (1-1) and (1-2). D ² T (s) / ds ² in the expression (1-2) corresponds to a second-order differential function of the deflection function T (t) having a peak shape represented by the expression (2-1) described later. . Note that B (s) (function represented by a fifth-order polynomial) in the expression (1-2) represents the background component acceleration other than the acceleration of the deflection deformation of the tire. The background component B (s) uses a fifth-order polynomial as a function of the background component B (s) so that it gradually changes in the area of the regression data, but other functions may be used. The parameters determined by the least square regression process at this time are parameters that determine t _c and T (s) (T (t)) and B (s). Specifically, the parameters are shown in Expression (2-1). A, c, d, and coefficients e _{0 to} e ₅ of the formula (1-3). The method of least squares regression is not particularly limited in the present invention, but can be suitably performed using, for example, the Newton-Raphson method. Note that the measurement time series data Az (t) includes a low-frequency background component caused by the acceleration component of the centrifugal force (centripetal force) and the gravitational acceleration component during rolling of the tire, and therefore uses the polynomial B (s). Regress low frequency background components. Thereby, the low frequency background component included in the measurement time series data Az (t) can be removed in the calculation of the deflection shape using the deflection function.

In general, the amount of deflection of the tread portion of the tire rolling on the road surface increases from the state where the amount of deflection is approximately 0 to the front end of the stepping on the tire near the ground contact, near the position directly below the load (ground contact center position). The peak shape is maximum and the amount of deflection asymptotically approaches 0 from the kicking end. This peak shape shows an asymmetric shape during cornering and braking / driving. On the other hand, the peak shape represented by the deflection function T (t) in the following equation (2-1) is approximately in the vicinity of the center (t = 0), where the vertical axis represents the value of T (t) and the horizontal axis represents t. It has a peak shape having a peak value and a curve in which both ends are asymptotic toward 0. Expression (2-1) is an example of an asymmetric Gaussian function. Here, the asymmetrical Gaussian function is different from the symmetrical Gaussian function G (x) = e · exp (−At ² ) (A is a parameter) in that the curve shape is different in a region where t is positive and negative. = −∞, t = + ∞, the convergence to 0 is defined as a function having the same property. Therefore, by using T (t) in the following equation (2-1) as a deflection function, the actual tire deflection shape can be suitably reproduced.

Here, the deflection function T (t) is a so-called asymmetric Gaussian function whose symmetry is broken, as shown in FIG. 6A and FIG. 5B showing the second order differential function, depending on the parameter c. The distribution of the amount of deflection during cornering or braking / driving of the tire can be obtained using this asymmetry.
The peak shape of the deflection function T (t) shown in FIGS. 6A and 6B and the equation (2-1) is an example in which the peak value (extreme value) is positive, that is, the maximum value is shown. Even when a peak value is negative, that is, a function indicating a minimum value is used, it can be used in the same manner by reversing the positive and negative values of the parameter that defines the value of the deflection function T (t).

As described above, among the parameters whose values are obtained by the least square regression, the values (a, c, d) of the parameters t _c and T (t) excluding the coefficients e _{0 to} e ₅ are obtained. The deflection shape (deflection amount distribution) is calculated from the deflection function defined by using the deflection function. The least square regression process as described above is performed by the calculation unit 16. Furthermore, the value of each parameter and the peak value (the value with the largest displacement) in the deflection amount distribution are stored in the memory 20 as data.

In such a process, the parameter value of the deflection function can be calculated for each rotation of the tire. Therefore, when setting the time t _c for the acceleration sensor 2 to pass through the ground contact center as a parameter, the past ground contact center is determined. by using the time t _c that the acceleration sensor 2 passes to estimate the time t _c for use in the process during the next tire revolution, it is possible to provisionally set. That is, based on the values of time t _c (t _c1, t _c2 ... T _ci ) obtained as parameter values in the past tire rotation, t _{c (i + 1)} = t _ci + (t _ci + −t _{c (i−1)} ) (where i is a natural number), a temporary value of the contact center time t _c of the next rotation can be set. Based on this, the operation of repeatedly extracting the acceleration data in a range corresponding to ± 57.5 degrees as the regression data area with respect to the tire rotation phase angle Q _{c at} time t _c is repeatedly performed, and the tire is measured during the acceleration measurement period. Can be obtained continuously for each rotation.

  Based on the parameter values calculated by the least square regression, the tire rotation path and the tire second contact length candidate are obtained as follows. First, since the parameter values (a, c, d) of the tire deflection function T (t) are known, they are expressed by the deflection function T (t) using the tire radius r of the tire to be measured. A curve is developed as a displacement on an arc having a radius r and added to calculate a rotation trajectory. Thereafter, the second contact length candidate of the tire at the time of rolling is obtained in the calculation unit 16.

FIG. 7 is a diagram illustrating a method for obtaining the second contact length candidate from the tire deflection shape (deflection amount distribution).
In the same figure, a horizontal line (dot-dash line in FIG. 7) in contact with the lowest point of the tire rotation trajectory (solid line in FIG. 7), and an arcuate rotation trajectory with zero deflection (dotted line in FIG. 7) And A and B, and the tire rotation center is O. At this time, the angle ∠COD formed by the points C and D provided on the horizontal line and the rotation center O has an angle of 50 to 95%, more preferably 60 to 75% of the angle ∠AOB formed by the intersections A and B. Thus, the points C and D are determined (a ratio of 50 to 95%, more preferably 60 to 75% is referred to as an adjustment ratio). The length between the points C and D is set as a second contact length candidate during tire rotation. In FIG. 7, a straight line portion between points C and D indicated by a thick solid line is a grounding portion. As a result, a second contact length candidate that is rolling is obtained from the tire rotation path. The adjustment ratio varies depending on the tire size, tire structure, etc., so that the contact length of the rolling tire at an extremely low traveling speed, for example, 10 km / hour corresponds to the actual measurement of the contact length of the stationary tire. Alternatively, the adjustment ratio value is set in advance so that the contact length of the rolling tire corresponds to the contact length of the rolling tire calculated by the finite element method. In the present invention, as will be described later, it is preferable to correct the adjustment ratio so that the first contact length candidate and the second contact length candidate are continuously connected.

  In the present embodiment, T (t) shown in the above equation (2-1) is used as the deflection function of the peak shape, but this is an example, and the present invention is not limited to this. For example, the functions shown in the following equations (3-1), (3-2), (3-3), and (3-4) can be used as the deflection function T (t).

The above is the description of step 110.
Returning to FIG. 3, in parallel with step S108 and step S110, frequency analysis is performed on the acceleration data near the ground extracted in step S106, and the maximum peak value in the frequency band of 500 to 1500 Hz is detected ( Step S112). Specifically, the acceleration data near the ground is subjected to FFT (Fast Fourier Transformation) processing to detect the maximum peak value in the frequency band of 500 to 1500 Hz. The maximum peak value in the frequency band of 500 to 1500 Hz is detected when the rolling tire emits a squealing noise due to a large slip angle, and the first contact length candidate calculated in step S108 is grounded. This is to determine whether it is appropriate to select the length.

  The acceleration measurement time series data shown in FIG. 5A is radial acceleration data when the slip angle is changed from 0 degrees to 20 degrees per second. In FIG. 5 (a), when the slip angle gradually increases and the acceleration sensor 2 passes through the grounded portion 11 times, the slip angle becomes a large slip angle of 20 degrees, a squeal noise is generated, and the acceleration varies greatly. is doing. When the slip angle is increased and a squealing sound is generated, the tire and the road surface vibrate greatly in a frequency band of 500 to 1500 Hz. This vibration also changes the position of the stepping-in end and the kicking-out end of the tire ground contact. In particular, since the vibration causes the kicking end to fluctuate greatly, it is difficult to obtain the contact length in the calculation in step S108 for obtaining the contact length by specifying the stepping-in end and the kicking-out end of the contact. Even if the contact length can be obtained, an accurate contact length cannot be obtained. For example, in the acceleration data in the vicinity of the ground at about 0.9 seconds in FIG. 5A, an appropriate point crossing the acceleration 0 cannot be obtained, and the kicking end cannot be specified.

  Therefore, in order to determine whether the first contact length candidate in step S108 can be calculated and the selection result is appropriate, the highest peak in the frequency band of 500 to 1500 Hz representing the level of the squeal sound level. The magnitude of the value is determined (step S114). That is, when the maximum peak value in the frequency band of 500 Hz to 1500 Hz is equal to or less than a predetermined threshold, the first contact length candidate calculated in step S108 is selected as the contact length (step S116), and the maximum peak value is If it is larger than the threshold, the second contact length candidate obtained in step S110 is selected as the contact length (step S118). That is, if the first contact length candidate is not an appropriate and accurate contact length, the second contact length candidate is set as the contact length. The second contact length candidate uses the least square regression of the acceleration data in the vicinity of the contact using Equation (1-2). Therefore, even when the first contact length candidate is not an appropriate and accurate contact length, the acceleration data is used. Therefore, a relatively appropriate contact length candidate can be calculated.

  FIGS. 8A to 8C are graphs showing measurement time-series data of radial acceleration when a squeal sound is generated and frequency analysis results at that time. As shown in FIG. 8A, the measurement time series data vibrates greatly. When the frequency analysis is performed, the acceleration data near the ground extracted from the measurement time series data at this time has a large peak in the frequency band of 500 to 1500 Hz as shown in FIG. This peak is vibration based on squeal noise. It can also be seen that the maximum peak value at this time increases with the slip angle, as shown in FIG. Depending on the level of the maximum peak value, it is determined whether the first contact length candidate calculated in step 108 is a contact length or the second contact length candidate calculated in step 110 is a contact length. select.

  Originally, since the calculation method in step S108 directly obtains the contact length using the uneven shape of the time series waveform of the measurement time series data, the first contact length candidate calculated by this method is accurate and appropriate. Although there is a value, when a squealing sound is generated, it is difficult to specify the position of the kicking end. For this reason, the second contact length candidate calculated in step S110 is selected as the contact length.

The contact length obtained in this way is supplied to the vehicle control device 24 and used for controlling the vehicle (step S118). For example, the contact length is used for controlling the traveling speed of the vehicle and for active control of the steering angle of the wheels. Further, the calculation unit 16 obtains the contact length of each tire for each wheel of the vehicle, for example, four wheels, the ratio of the contact length of the inner and outer wheels during cornering, or the ratio of the contact length of the front and rear wheels during braking / driving. If the ratio exceeds a predetermined threshold, the contact length information can be used to alert the vehicle driver. In addition, information on the contact length can be displayed on the instrument panel of the vehicle to notify the vehicle driver.
Such processes of steps S102 to S118 are continuously performed until the wheel stops (until the vehicle traveling speed becomes a predetermined value or less) (step S120).

  When a vehicle is steered, a slip angle is generated by giving a steering angle to the wheels from a straight traveling state, and in some cases, the slip angle is large enough to generate a squeal noise. In this case, when no squeal noise is generated or is small, the acceleration data in the radial direction in the tire tread portion has a small vibration component in the frequency band of 500 to 1500 Hz. For this reason, the first contact length candidate calculated in step S108 is selected as the contact length. However, when the steering angle further increases and a squeal noise is generated and the maximum peak value in the frequency band of 500 to 1500 Hz of the acceleration data in the radial direction exceeds the threshold value, the second contact length candidate calculated in step S110 is obtained. Switched to ground contact length. At this time, the second contact length candidate is used when calculating the second contact length candidate so that the second contact length candidate is continuously connected to the previous contact length determined by selecting the first contact length candidate. The points C and D can be determined by correcting the adjustment ratio within the range of 50 to 95%, more preferably within the range of 60 to 75%.

FIG. 9 shows the result of measuring the contact length for a passenger car tire (tire size 185 / 60R15) under the conditions of an air pressure of 230 kPa, a load of 3.43 kN, a slip angle of 0 to 20 degrees, and a speed of 80 km / hour. . According to FIG. 9, it is a figure which shows the change of the contact length when the acceleration sensor 2 is provided in the area | region of the shoulder part vicinity of a tire internal peripheral surface. The line L ₁ is a line in which the first contact length candidate calculated in step S108 is the contact length, and the line L ₂ is the second contact length candidate calculated in step S110. Line. By appropriately correcting the adjustment ratio, the line L ₁ and the line L ₂ are connected with continuity as shown in FIG.

  In the present invention, in addition to the above embodiment, first, the maximum peak value in the frequency band of 500 to 1500 Hz is detected by frequency analysis of radial acceleration in the vicinity of the ground contact of the tire, and according to the level of the maximum peak value. The contact length may be determined by performing any one of steps S108 and S110. That is, when the maximum peak value is less than or equal to the threshold, the first contact length candidate calculated in step S108 is calculated as the contact length, and when the maximum peak value is greater than the threshold, the second calculated in step S110. The contact length candidates may be calculated as the contact length.

  In the said embodiment, although the acceleration sensor 2 was provided in the internal peripheral surface (surface of an inner liner part) of a tire tread part, the acceleration sensor 2 may be embedded in a tread part. Further, the position in the tire width direction of the acceleration sensor 2 may be a shoulder region in addition to the center region of the tire tread portion, and the arrangement position is not particularly limited. In addition to the case where one acceleration sensor 2 is used for one tire, a plurality of acceleration sensors 2 may be provided for one tire, and the plurality of acceleration sensors 2 may be provided by changing positions in the tire circumferential direction. Alternatively, a plurality of acceleration sensors may be provided at different positions in the tire width direction. When a plurality of acceleration sensors are provided by changing the position in the tire width direction, the contact length at each position in the tire width direction can be obtained, so that the approximate contact shape of the tire can be obtained.

  In addition, the calculation of the first contact length candidate in step S108 is performed when the first contact length candidate is obtained from the time-series waveform shape of acceleration, and the time-series data of the acceleration in the tire circumferential direction is used instead of the radial acceleration. The first contact length candidate can also be calculated using. Further, similarly to the method described in Japanese Patent Application No. 2004-335417 filed by the same applicant as the present application, displacement data is obtained by performing time integration of the second floor of the radial acceleration data of the tire. It is also possible to obtain the tire deflection shape due to tire contact from the data, and obtain the first contact length candidate using the method shown in FIG. 7 for this shape.

  The tire contact length calculation method and tire contact length calculation apparatus of the present invention have been described in detail above, but the present invention is not limited to the above-described embodiment, and various improvements can be made without departing from the scope of the present invention. Of course, changes may be made.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram illustrating a configuration of an embodiment of a tire contact length calculation apparatus according to the present invention that implements a tire contact length calculation method according to the present invention. FIG. 2 is a tire cross-sectional view along the line II-II shown in FIG. 1. 2 is a flowchart showing a flow of a tire contact length calculation method performed by the tire contact length calculation apparatus shown in FIG. 1. It is a figure explaining calculation of the 1st contact length candidate in the contact length calculation method of the tire shown in FIG. (A)-(c) is a figure explaining the calculation method of the deflection | deviation shape of the tire in the contact length calculation method of the tire shown in FIG. (A) And (b) is a figure explaining the deflection function used in the case of calculation of the 2nd contact length candidate. It is a figure explaining the calculation method of the 2nd contact length candidate in the contact length calculation method of the tire shown in FIG. (A)-(c) is a figure explaining the vibration component contained in acceleration data. It is a figure which shows an example of the contact length calculated with the contact length calculation method of the tire which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tire 1a Tread part 2 Acceleration sensor 10 Ground contact length calculation apparatus 12 Data acquisition part 14 Signal processing part 16 Calculation part 18 Data output part 24 Vehicle control apparatus

Claims (8)

A method for calculating a contact length of a tire when the tire rolls on a road surface,
Acquiring measurement time series data of acceleration including at least radial acceleration on the tire circumference of the rolling tire;
The acceleration data near the ground is extracted from the acquired measurement time series data, and the first ground contact length candidate is obtained from the shape of the time series waveform of the acceleration data or the tire deflection shape obtained by integrating the acceleration data on the second floor. Seeking steps,
Extracting the acceleration data near the ground from the acquired measurement time series data, regressing the acceleration data into a regression equation to calculate the deflection shape of the tire near the ground, and obtaining a second ground length candidate;
One candidate is selected as a contact length from the first contact length candidate and the second contact length candidate according to the result of the frequency spectrum of the acceleration data near the contact acquired from the measurement time series data. And a tire contact length calculation method.   The result of the frequency spectrum of the acceleration data is a maximum peak value in a frequency band of 500 Hz to 1500 Hz, and when the maximum peak value is a predetermined value or less, the first contact length candidate is selected as a contact length, and the maximum The tire contact length calculation method according to claim 1, wherein when the peak value is larger than a predetermined value, the second contact length candidate is selected as a contact length.   In the step of obtaining the first contact length candidate, two points when the time series waveform of acceleration data crosses acceleration 0 are set as corresponding points of the stepping-in end and the kicking-out end of the tire, and the distance between the two points is defined as the distance between the two points. The tire contact length calculation method according to claim 1, wherein the tire contact length calculation method is obtained as a first contact length candidate.   In the step of obtaining the second contact length candidate, the extracted acceleration data is obtained by using a second-order differential function of a deflection function representing a peak shape having one extreme value and having a curve asymptotic to 0 on both sides thereof. The value of the deflection function parameter is determined by least square regression, and the deflection shape in the vicinity of the ground is calculated from the deflection function determined using the value of the deflection function parameter. Based on the calculated deflection shape of the tire, the first The contact length calculation method for a tire according to any one of claims 1 to 3, wherein two contact length candidates are obtained. A method for calculating a contact length of a tire when the tire rolls on a road surface,
Acquiring measurement time series data of acceleration including at least radial acceleration on the tire circumference of the rolling tire;
In the frequency spectrum of acceleration data near the ground acquired from the measured time series data, when the maximum peak value in the frequency band of 500 Hz to 1500 Hz is equal to or less than a predetermined value, the measured time series data on the tire circumference The acceleration data is extracted, and the contact length is obtained from the shape of the time series waveform of this acceleration data or the tire deflection shape obtained by integrating the acceleration data on the second floor. If the maximum peak value is greater than the predetermined value, it is acquired. Extracting the acceleration data in the vicinity of the contact from the measured time series data on the tire circumference, and obtaining the contact length by calculating the deflection shape of the tire in the vicinity of the contact by regressing the acceleration data into a regression equation. A method for calculating a contact length of a tire.   When the maximum peak value is less than or equal to a predetermined value, the two points when the time series waveform of the acceleration data crosses acceleration 0 are taken as corresponding points of the tire stepping edge and kicking edge, and the distance between the two points is grounded The tire contact length calculation method according to claim 5, which is calculated as a length.   When the maximum peak value is larger than a predetermined value, the extracted acceleration data is minimized using a second-order differential function of a deflection function representing a peak shape having one extreme value and having a curve asymptotic to 0 on both sides thereof. The value of the deflection function parameter is determined by square regression, the deflection shape near the ground contact is calculated from the deflection function determined using the value of the deflection function parameter, and the contact length is calculated based on the calculated tire deflection shape. The tire contact length calculation method according to claim 5 or 6. A device for calculating a contact length of a tire when the tire rolls on a road surface,
An acquisition unit that acquires acceleration measurement time-series data including at least radial acceleration on the tire circumference of the rolling tire;
An arithmetic unit that calculates the contact length of the tire using the measured time series data on the tire circumference,
The arithmetic unit extracts the acceleration data near the ground from the acquired measurement time series data on the tire circumference, and the deflection of the tire obtained by integrating the time series waveform shape or acceleration data of the acceleration data with the second floor time integration. The first processing unit for obtaining the first contact length candidate from the shape, and the acceleration data near the ground is extracted from the measured time series data on the tire circumference, and the acceleration data is regressed to a regression equation to approximate the ground contact According to the result of the frequency spectrum of the acceleration data in the vicinity of the ground obtained from the second processing unit that obtains the second ground contact length candidate by calculating the deflection shape of the tire, and the measurement time-series data, the first A selection unit for selecting one of the contact length candidates and the second contact length candidate as a contact length. Apparatus.

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