JP2012247351A - Tire balance testing method and tire balance testing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly accurately check an unbalanced state of tires even in the area where a rotation speed of tires is not fixed, and to shorten a check cycle time as further as possible, as a result.SOLUTION: According to a tire balance testing method, a load generated in a spindle shaft 2 holding tires T is measured in the state of installing a plurality of tires T for which mounting angles of the tires T to the spindle shaft 2 are made different, and at various rotation speeds. From the measured balance load, correction data in the case of rotation acceleration or rotation deceleration of the tires T are determined. In the case of actual measurement, a balance load generated in the rotating spindle shaft 2 is measured and the measured balance load is corrected by using the correction data, thereby measuring an unbalanced state of the tires T.

Description

  The present invention relates to a tire balance test technique for detecting a balance force (unbalance force) generated when a tire is rotated, and more particularly to a technique that can shorten a test cycle time in a tire balance test.

In a tire production line, a test for measuring a balance force (unbalance force) generated when a tire is rotated is performed using a tire balance tester. The balance force is measured by pressing a tire fixed to a spindle shaft against a rotating drum and rotationally driving the tire shaft or the rotating drum to measure a fluctuating force generated in the tire as a load waveform.
FIG. 1 shows a schematic diagram of a typical tire balance testing machine.

As shown in this figure, a spindle cell to which a tire is attached via a rim is supported so as to be freely rotatable, and a load cell in which the balance force generated in the tire during rotation, the direction, and the rotation phase are provided in the apparatus. And the balance force of the tire is measured by various methods based on the obtained detection value.
A general dynamic balance calculation method based on the balance force obtained by such an apparatus is shown below.

  As shown in FIG. 2, the detected load F1 by the upper load cell and the detected load F2 by the lower load cell can be expressed in complex numbers having amplitude and phase with respect to the reference signal from the frequency analysis of the test data. Here, assuming that B1 and B2 are the balance loads of the upper and lower surfaces of the tire, the balance loads B1 and B2 are as shown in Formula (1) based on the detected loads F1 and F2.

In addition, as shown in FIG. 2, a, b, c, d are distances from the center in the width direction of the tire to each part, and the detected loads F1, F2 and balance loads B1, B2 are expressed by complex numbers.
By the way, in an actual tire balance test, disturbance (rotational speed component) is included in the detected loads F1 and F2. This disturbance is mainly caused by the eccentricity of the rim provided at the upper end of the spindle shaft. Here, this is called “unbalanced load unique to the device”.

  This unbalanced load unique to the device can be expressed by a vector as a rim eccentric vector Ua. As shown in the vector diagram (unbalanced vector diagram) of FIG. 3A, the rim eccentric vector Ua includes a rim unbalance vector Uar caused by a rim mass nonuniformity with respect to the spindle axis, and a rim-tire fitting portion. This is a combined vector with the apparent unbalance vector Uas of the tire caused by the deviation between the center line and the spindle shaft. That is,

It is.
The detection unbalance vector U _D in which the detected loads F1 and F2 obtained from the load cell are expressed as vectors is a combination of the unbalance vector Ut of the tire itself and the rim eccentric vector Ua.

It becomes.
That is, as shown in equation (3), the detection unbalance vectors U _D detected by the load cell, is clear that the eccentricity vector Ua of the rim is included as an error, the correct balance of only tires without correction Measurement (Ut measurement) is not possible.
For this reason, various detection load correction means have been conventionally employed (Patent Documents 1 and 2).

  For example, Patent Literature 1 uses a test apparatus that measures the vibration of the rotating part accompanying rotation of the tire by attaching a tire to the rotating part, and changes the rotation angle of the tire with respect to the rotating part. However, correction data for removing the influence of eccentricity and distortion of the rotating part from the measurement result by storing the data obtained by performing the measurement a plurality of times, storing the data obtained by the plurality of measurements, and combining the stored data The correction method in the dynamic balance test of obtaining

That is, Patent Document 1 performs measurement by changing the tire mounting phase with respect to the rim a plurality of times (divided into n equal parts), and synthesizes the obtained waveform data to remove the tire unbalance component and perform balance correction. This is a method of obtaining only correction load data for the purpose.
Patent Document 2 discloses an adapter that rotates with a test specimen mounted thereon, an unbalance detection unit that detects an unbalance of the rotating test specimen, and n types (n Is a natural number equal to or greater than 3) in the attachment mode, the first storage means for storing data of n detection unbalance vectors obtained from the unbalance detection section, and n stored in the first storage means Computing means for obtaining coordinates of the center of the circle passing through the respective tips or the vicinity of the detected unbalance vectors and obtaining a vector symmetric with respect to the origin with respect to the vector of the center coordinates of the circle with respect to the origin, and the vector thus obtained With respect to the detected unbalance vector obtained from the unbalance detection unit at the time of actual measurement. It discloses a dynamic balancing machine that includes a correcting means for adding an eccentricity correction vector stored in the serial second storage means.

That is, in Patent Document 2, the correction load can be calculated even when the tire mounting phase is unknown, and the measured load vector at three or more arbitrary tire mounting phases is plotted on the complex plane, and the least square method is used. Use it to draw a circle and find its center point. The obtained center is the balance correction load vector.
By the way, in the tire balance test, in addition to improving the measurement accuracy, reduction of the cycle time of the test is an issue.

  For example, in a tire balance test, about 2 seconds are required for acceleration of tire rotation, about 2 seconds are required for deceleration, and the inspection time during steady rotation is often about 5-6 seconds. Therefore, the tire balance test requires about 9 to 10 seconds for one tire. If the inspection can be performed at the time of acceleration or deceleration of the tire rotation, the inspection time at the steady rotation can be shortened accordingly, and the inspection time can be shortened by about 2 to 4 seconds as a whole. Significant shortening is possible.

As a balance measuring method for the purpose of shortening the cycle time as described above, it is conceivable to use a region where the speed is not constant such as an acceleration part or a deceleration part of the tire rotation as described above. The technique of Patent Document 4 has been developed.
Patent Document 3 discloses rotational position signal output means for outputting a plurality of predetermined rotational position signals per rotation of a specimen, vibration detection means for detecting vibrations generated by applying rotation to the specimen, and specimen A rotation speed calculation means for calculating the rotation speed data, a storage means for storing the rotation speed data calculated by the rotation speed calculation means in association with the rotation position signal output from the rotation position signal output means, A filtering means for obtaining a waveform data of an unbalanced signal by applying a digital filter to the vibration data detected by the vibration detecting means in association with the rotational position signal output from the position signal output means; A correction based on the rotational speed data stored in the storage means is performed on the waveform data of the obtained unbalance signal. Waveform data correcting means, waveform data corrected by the waveform data correcting means, and a function including an undetermined coefficient desired to be matched with the waveform data is applied to the least square method to determine the undetermined coefficient. Disclosed is an unbalance measuring device which is provided with unbalance calculating means for calculating an unbalance vector from a coefficient and outputting the result, so that unbalance measurement can be performed even if the rotation of the specimen is not constant speed rotation. To do.

  On the other hand, Patent Document 4 is a balance testing machine for measuring the unbalanced force of the object to be measured by detecting an unbalance force when the object to be measured that is rotatably supported is rotated by a force detection means. A speed and rotational position measuring means for measuring the angular velocity and rotational position of the rotating object to be measured, an unbalance force detected by the force detection means, and the speed and speed when the unbalance force is detected. Disclosed is a balance testing machine comprising dynamic unbalance calculation means for calculating dynamic unbalance of the measurement object using the angular velocity and rotation position of the measurement object measured by the rotation position measurement means.

JP 2000-234980 A Japanese Patent Publication No. 7-50011 Japanese Unexamined Patent Publication No. 2000-97795 JP 2000-221096 A

  Correction methods such as Patent Document 1 and Patent Document 2 are effective for improving measurement accuracy in a tire balance test, but both methods assume measurement at a constant rotation speed of the spindle shaft. Only after the acceleration has finished and the tire has reached a certain number of revolutions, can it be measured satisfactorily. In other words, it cannot be applied as it is to the balance load measured when the rotational speed changes as in the case of acceleration / deceleration of the spindle shaft, and there is a difficulty in that measurement cannot be performed during acceleration / deceleration time. Therefore, the cycle time (test time) of the tire balance test cannot be shortened.

  Therefore, the inventors of the present application have made extensive studies in order to reduce the cycle time of the tire balance test. As a result, Patent Document 3 and Patent Document 4 have found that the unbalanced load is proportional to the square of the tire rotational speed, but cannot be completely expressed by the square of the speed. As a result of investigating the error component, it has been found that an error component that does not depend on the rotational speed, in other words, an unbalanced component specific to the apparatus is included, and that correction that takes into account such component is necessary.

FIG. 3 (b) shows an actual measurement waveform (dark solid line) of the balance load obtained by a conventional tire balance tester. On the other hand, a waveform indicated by a light solid line is a balance load calculated by correcting the tire balance load as being proportional to the square of the rotational speed in accordance with the idea of Patent Documents 3 and 4. It is clear that the curves do not match.
Therefore, the inventors of the present application consider that there is a term that does not depend on the rotational speed when considering rotational correction and rotational deceleration of a tire when considering correction for calculating an accurate balance load even during rotational acceleration. Based on the above, the inventors have focused on “unbalance components that do not depend on rotational speed”, which the engineer has not paid attention to, and have developed a new correction method that takes into account such unbalance components. That is, the inventors have come up with a method for obtaining “correction data (data for correcting measurement values) at the time of tire rotation acceleration or rotation deceleration” in consideration of an unbalance component that does not depend on the rotation speed.

  As described above, the present invention is a correction method that enables calculation of an accurate tire balance load even in a region where the tire rotation speed is not constant in a tire balance test, in other words, a tire during rotation acceleration or rotation deceleration. An object of the present invention is to provide a tire balance test technique that can inspect the unbalanced state of a tire with high accuracy by using a balance load and that can shorten the inspection cycle time as much as possible.

In order to achieve the above-described object, the present invention takes the following technical means.
That is, the tire balance test method according to the present invention is a method for measuring tire unbalance using a tire balance tester having a spindle shaft that rotatably holds the tire, and the tire mounting angle with respect to the spindle shaft. The balance load generated on the spindle shaft holding the tire is measured at various rotational speeds in a plurality of tire installation states that are different from each other, and the tire is accelerated or decelerated from the measured balance load. Correction data at the time is obtained, and at the time of actual measurement, the balance load generated on the rotating spindle shaft is measured, and the measured balance load is corrected using the correction data, thereby measuring the tire imbalance. It is characterized by that.

  Preferably, the balance load Fa to be measured has a term Ft caused by unbalance of the tire itself, a term Fz2 proportional to the square of the rotational speed of the spindle shaft, and a term Fz0 independent of the rotational speed of the spindle shaft. It is expressed as a function, and the load balance of the spindle shaft is measured based on the measured balance load in a plurality of tire installation states with different tire mounting angles with respect to the spindle shaft and at a plurality of rotational speeds. A term Fz2 proportional to the square of the rotational speed and a term Fz0 that does not depend on the rotational speed of the spindle shaft are obtained, and a term Fz2 that is proportional to the square of the obtained rotational speed of the spindle shaft and a term Fz0 that does not depend on the rotational speed of the spindle shaft. May be the correction data.

Preferably, the tire mounting angle is known in the plurality of tire installation states.
Preferably, in the plurality of tire installation states, the tire attachment angle is unknown and the tire installation states may be three or more different states.
On the other hand, a tire balance testing machine according to the present invention includes a spindle shaft that rotatably holds a tire, a housing that rotatably supports the spindle shaft via a bearing portion, and a spindle shaft that holds a rotating tire. A measurement unit that measures the balance load generated in the vehicle, and an unbalance calculation unit that corrects the balance load measured by the measurement unit and calculates the unbalanced state of the tire using the tire balance test method described above. It is provided.

  According to the tire balance test technique according to the present invention, even in a region where the tire rotation speed is not constant, the unbalanced state of the tire can be inspected with high accuracy, and the inspection cycle time can be shortened as much as possible. .

It is the figure which showed the structure of the tire balance testing machine. It is the figure which showed the force which acts on the tire balance testing machine under test. (A) is the vector diagram which decomposed | disassembled and displayed the tire balance load to each component, (b) is the figure which showed the measurement waveform of the tire balance load by the conventional tire balance testing machine. It is the figure which showed on the complex plane the force which acts on a tire in different tire rotation speed. It is the flowchart which showed the procedure of the tire balance test method of this embodiment. It is the figure which showed on the complex plane the force which acts on a tire in different tire rotation speed, and is the figure which showed the balance load vector on the complex plane, the approximate circle, and the center point of the approximate circle. It is the figure which showed the result of having measured the balance load of the tire. It is the figure which showed the result of having analyzed (corrected) the balance load of a tire using the measuring method concerning the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
A tire balance testing machine 1 according to the present invention will be described hereinafter with reference to the drawings.
The tire balance testing machine 1 of the present embodiment is a test apparatus that measures a balance load (unbalance force) generated when the tire T is rotated at a high speed.
As schematically shown in FIG. 1, the tire balance testing machine 1 includes a spindle shaft 2 that holds a tire T, and a housing 3 that rotatably supports the spindle shaft 2 around its axis. .

The spindle shaft 2 is a rod body whose axis is directed vertically, and a rim that protrudes in a bowl shape toward the radially outer side is formed at an upper end portion thereof. The rim is formed to have an outer diameter that matches the inner periphery of the tire T, and the tire T can be held from the inner periphery side.
The housing 3 is a cylindrical body having an inner diameter larger than the outer diameter of the spindle shaft 2, and rotatably supports the spindle shaft 2 via a pair of upper and lower bearing portions 5 provided on the inner wall of the cylindrical body. . The housing 3 is connected to a fixed frame 7 via a load cell 6 (measurement unit) that can measure a force component in one direction (see FIG. 1). In the example of FIG. 1, the housing 3 is attached to the fixed frame 7 via a pair of upper and lower load cells 6.

The rotational driving force of the driving motor 8 is transmitted to the spindle shaft 2 through the belt 9, and as a result, the spindle shaft 2 rotates around the vertical axis.
The balance load generated in the rotating tire T is measured by the load cell 6 and sent to the unbalance calculation unit 10 as a waveform signal of the balance load (unbalance force). The two load cells 6 measure the balance loads F1 and F2 in the direction shown in FIG. 2 among the unbalanced loads caused by the eccentricity generated from the tire T.

The unbalance calculation unit 10 calculates the balance loads B1 and B2 of the tire T using the relationship shown in the above-described equation (1) based on the balance loads F1 and F2 measured by the load cell 6 as a measurement unit. To do.
Further, the unbalance calculation unit 10 obtains correction data for removing the influence of the eccentricity and distortion of the rotating portion existing in the tire balance tester 1 from the balance load measured in advance, and at the time of the tire balance test. The balance load measured in the region where the rotational speed changes is corrected using the correction data, and the unbalanced state of the tire T is detected. The unbalance calculation unit 10 is configured by a computer or the like.

Hereinafter, a correction method performed by the unbalance calculation unit 10 and a tire balance load calculation method using this correction method will be described.
[First Embodiment]
If the tire balance load measuring method according to the first embodiment is outlined, it has the following three steps.

(i) In a certain tire T, the load generated on the spindle shaft 2 holding the tire T is measured in an installation state where the mounting angles are different and under various rotational speed conditions.
(ii) From the measured load, correction data for removing the influence of eccentricity and distortion of the rotating portion existing in the tire balance testing machine 1 is obtained.
(iii) At the time of actual measurement, the load generated on the spindle shaft 2 is measured while rotating the tire T while the rotational speed is changed, and the measured load is corrected using the correction data, whereby the balance load of the tire T is corrected. Measure.

  Specifically, the measured load Fa includes a term Ft caused by the unbalance of the tire T itself, a term Fz2 proportional to the square of the rotational speed of the spindle shaft 2, and a term Fz0 that does not depend on the rotational speed of the spindle shaft 2. It is expressed as a function having In addition, the load is measured at a plurality of tire T installation states with different mounting angles of the tire T with respect to the spindle shaft 2 and at a plurality of rotational speeds, and the measured actual load and the above function are calculated. By calculating the undetermined coefficient so that the square of the difference is minimized, a term Fz2 proportional to the square of the rotational speed of the spindle shaft 2 and a term Fz0 independent of the rotational speed of the spindle shaft 2 are obtained. The term Fz2 proportional to the square of the calculated rotational speed of the spindle shaft 2 and the term Fz0 independent of the rotational speed of the spindle shaft 2 are used as correction data.

Hereinafter, the calculation procedure will be described in detail.
First, correction data for the detected load F1 detected by the upper load cell 6 and the detected load F2 detected by the lower load cell 6 are obtained.
For this purpose, first, let Fa be the load vector detected by the load cell 6 when the tire T is attached to the rim and rotated at the rotational angular velocity ω (rad / sec). At that time, the balance load generated by the tire T (the load caused by the unbalance of the tire T itself and the balance load to be obtained) is Ft, and the component due to the eccentricity and distortion of the rotating portion existing in the tire balance testing machine 1 In other words, the unbalance component unique to the apparatus is set to Fz0. This Fz0 is a component that does not depend on the rotational speed of the spindle shaft 2. Further, a component proportional to the square of the rotation speed of the spindle shaft 2 is set as Fz2. Note that Fa, Ft, Fz0, and Fz2 are represented as vectors, and these vectors have periodic variability, and therefore are represented by complex numbers in this embodiment.

  The tire balance load Fa detected by the load cell 6 is expressed by Equation (4).

At this time, Fz is the unbalanced force unique to the device as shown in Equation (5).

Here, if Fz0 and Fz2 are obtained in advance as correction data, the original balance load Ft of the tire T can be calculated from Equation (4) using the actual measurement value Fa. Fz0 and Fz2 are calculated by the method of least squares based on measurement waveforms at various rotational speeds and installation phases of the plurality of tires T.
It should be noted that the correction data Fz2 varies depending on the tire mass. When the tire mass changes, it is necessary to identify correction data based on the tire mass. Since Fz2 is proportional to the tire mass, it can be expressed by a function using the mass as a parameter based on a plurality of tire mass data.

Now, a method of calculating Fz0 and Fz2 when the installation angle of the tire T (relative angle with respect to the spindle shaft 2) is known will be described.
When the tire T installation angles with respect to a plurality of experimental rims are φ1, φ2, φ3... (Reference position is arbitrary), and the loads observed at that time are Fa1, Fa2, Fa3. )become that way.

  Here, the unknowns are Fz0, Fz2, and Ft. As a method for calculating these unknowns, the balance load measurement data at the tire T angles φ1, φ2, and φ3 are set as fex1, fex2, fex3,..., And Fa1, Fa2, Fa3,. The unknowns Fz0, Fz2, and Ft are calculated so as to be expressed as fa1, fa2, fa3... and minimize the square of the error with fex1, fex2, fex3. The rotation angle waveform data (fa (θ)) of Fa is expressed by Expression (7).

  Here, Re means the real part of a complex number, and is numerical data equivalent to the measured load data fex. Since the value of ω is a function of the rotation angle θ, it is expressed as ω (θ). Fz0, Fz2, and Ft are obtained so that J in Expression (8) is minimized. n is a test data number.

Note that the accuracy increases as the angle range to which the least squares method is applied is selected so that the number of waveforms of periodic fluctuation due to imbalance is as large as possible.
In summary, if Fz0 and Fz2 are obtained in advance as correction data so that Equation (8) is minimized, the balance load Ft inherent to the tire T can be calculated from Equation (4) using the actual measurement value Fa. By using these Fz0 and Fz2 as correction data, it is possible to inspect the unbalanced state of the tire T with high accuracy even in a region where the rotational speed of the tire T is not constant (rotation acceleration region, rotation deceleration region), and consequently an inspection cycle. The time can be shortened as much as possible.
[Second Embodiment]
Next, a second embodiment of the method for measuring the tire balance load will be described.

The measurement method of this embodiment is a method of handling the tire T installation angle (relative angle) as unknown. It is known that even if a slight error exists in the mounting position of the tire T, the measurement result is affected. Therefore, if this method is used to eliminate the influence, it is possible to accurately measure and correct the balance load.
Here, the calculation method in three different types of tire T installation phases is shown. When the load generated by the unbalance of the tire T itself in the tire experiments 1 to 3 (the installation phases are different from each other) is Ft1, Ft2, and Ft3, the expression (4) becomes the expression (9).

Since there is no information on the tire T installation angle, equation (9) has many unknowns and cannot be solved by the same mathematical method as in the first embodiment. Therefore, in Equation (9), a method is considered in which a term independent of the rotational speed and a rotational speed squared term are independently calculated for each experimental data, and then each formula is identified.
That is, since Fz2 and Ft of the velocity square term cannot be obtained separately, assuming that Fz2 + Ft = Ft ′, the respective coefficients Fz0 and Ft ′ are calculated from the equations shown in Equation (10).

For Fz0 in equation (10), the variable name is changed for each experiment. The reason for this is that Fz0 should originally have the same value, but because there is a difference in calculating Fz0 and Ft ′ for each data, each is a separate parameter.
The least square method is applied to the calculation of these coefficients in the same manner as described above. The rotation angle waveform data of Fa is expressed by Expression (11). n is a tire experiment number.

Next, Fz0, n and Ft ′, n are obtained so that Jn represented by Expression (12) is minimized.

  After calculating each parameter, that is, after Ft ′ and Fz0 are known, unbalanced load vectors Fa1, Fa2, and Fa3 at a plurality of rotation speeds are calculated from the equation (10), and at each rotation speed as shown in FIG. Create an approximate circle for the calculated value of to find the center point. At that time, a vector from the coordinate origin to the center point of the approximate circle is an unbalance component unique to the apparatus at each rotation speed, that is, correction data, and corresponds to Fz shown in Expression (5). This technique is the technique disclosed in FIG. 1 of Japanese Patent Laid-Open No. 01-142429, etc., and is usually used by those skilled in the art.

  Next, based on the calculation results of Fz at a plurality of spindle shaft rotation speeds, the unbalanced force inherent to the apparatus at an arbitrary rotation speed can be expressed in accordance with Equation (5) using a component Fz0 and a square component Fz2 that are independent of Fz. Represent in the form. In this case, if the approximate circle centers obtained at the rotational angular velocities ω1, ω2,..., Ωn are Fz ′ (ω1), Fz ′ (ω1),. Can be divided into a real part and an imaginary part and combined into a matrix consisting of n expressions (Expression (13)).

Expression (13) can be expressed as Expression (13) ′, and the undetermined coefficient matrix [Fz02] is obtained using a pseudo inverse matrix (Expression (13) ″). This corresponds to the least square method used in the first embodiment.
Although the equation is described with n = 3 as the number of experiments, the accuracy of the approximate circle in FIG. 4 increases and the identification accuracy of the correction data increases as the number of experiments increases.

  In summary, the correction data Fz0 and Fz2 can be calculated in advance also by the method disclosed in the second embodiment, and using the obtained Fz0 and Fz2 and the actual measurement value Fa, the original tire T is obtained from equation (4). The balance load Ft can be calculated. By using these Fz0 and Fz2 as correction data, the unbalanced state of the tire T can be inspected with high accuracy even in a region where the tire T rotation speed is not constant (rotation acceleration region, rotation deceleration region), and consequently the inspection cycle time. Can be shortened as much as possible.

An embodiment in which the tire balance load is identified (estimated) using the tire balance test method according to the present invention described above will be described below.
That is, the correction data is calculated according to the procedure shown in FIG. 5A, and the unbalance of the tire T is calculated according to the procedure shown in FIG.
First, the tire T to be measured is attached to the rim of the tire balance testing machine 1 in S11 of FIG. Next, rotation of the spindle shaft 2 is started, and in S12, a detection signal (load and phase, rotational speed data) of the load cell 6 during acceleration is acquired.

In S13, it is determined whether or not the required number of experiments has been reached. If not (No in S13), the tire installation angle is changed in S14. If Yes in S13, correction data Fz0 and Fz2 are obtained in S15.
Thereafter, actual measurement of the balance load of the tire T is performed (S16, that is, S21 to S26).

First, in S21 of FIG. 5B, it is determined whether or not the correction data Fz0 and Fz2 for the tire T (tire mass) to be measured exists. If it does not exist, the process of FIG. 5A is performed (S22).
When the correction data Fz0 and Fz2 exist (Yes in S21), in S23, the tire T to be measured is mounted on the tire balance testing machine 1, and balance measurement is performed, and the load, phase, and rotation including during acceleration are performed. Get speed data. Further, in S24, the measurement waveform is corrected with the correction data Fz0 and Fz2 stored in advance, and the tire unbalance load Ft is calculated.

Thereafter, the balance loads B1 and B2 are obtained from the tire unbalance load Ft using the formula (1) and the like. Thereafter, the tire T is replaced in S26.
Next, a tire unbalance calculation method using the correction data in S24 and S25 described above will be described in detail with reference to FIGS.
First, from equation (4), the unbalanced load Ft inherent to the tire T is represented by equation (14).

  On the other hand, rotation angle waveform data ft (θ) equivalent to the experimental value fex (θ) is expressed by Expression (15).

  The original unbalance vector Ft of the tire T is calculated from the waveform of ft (θ) by curve fitting or the like. As an example, it can be calculated by a method of calculating the tire T unbalance vector Ft so that J in Equation (16) is minimized, a sequential least square method, or the like.

Thereafter, Ft is calculated as F1 and F2 for each load cell 6, and the dynamic balance B1 and B2 of the tire T can be calculated from the equation (1).
In addition, in order to improve correction data identification accuracy by applying the least square method, when considering a speed proportional component proportional to the rotational speed ω, the speed proportional component is formulated as an unknown Fz1 (complex number) by the same method, and the least square method is used. In addition to Fz0, Fz2, and Ft, the velocity proportional term Fz1 can be calculated.

  For example, when the speed term Fz1 is taken into consideration, if the load generated when the tire T (mass unknown) is attached is Ft, the detected load Fa at the load cell 6 is expressed by Expression (17).

By applying equation (17) instead of equation (4), identification can be performed in the same procedure as described above.
In addition, since Fz2 in Formula (4) includes the load (mr = rim runout × tire mass) due to rim runout, it varies depending on the tire mass attached. When the tire mass changes, it is necessary to identify the correction load based on the tire mass.

The calculation results for the actually measured values (measured loads F1 and F2 in FIG. 1B) are shown.
Assuming that the installation phase of the tire T is unknown (when there is an installation phase error), the correction load was calculated for the acceleration data from the equations (11) to (13). A calculation example is shown for experimental data in which the tire T installation phase is changed eight times in approximately 45 ° increments.
FIG. 6 shows the result of plotting the unbalanced vector Fan calculated by the equation (10) on the complex plane from the corrected load coefficients Fz0n and Ftn ′ of each experiment (rotational angular velocities ω1 to ω5). The center point becomes the correction load vector Fzn unique to the apparatus at each rotation speed. The coefficients Fz0 and Fz2 can be calculated by equation (13). Although FIG. 6 shows an unbalance vector for the measured load F1, it is necessary to perform the same calculation for F2.

FIG. 7 plots the relationship between the rotational speed and the magnitude of the correction load for each of the measured loads F1 and F2 by substituting the coefficients Fz0 and Fz2 calculated by the expression (13) into the expression (5).
On the other hand, FIG. 8 shows a balance measurement by changing the installation phase angle every 45 ° from 0 ° to 360 ° with a tire T different from the tire T used for calculating the correction data. The result calculated using data is shown. As a comparative example, it is also formulated by taking into consideration only the square term, and the result of calculating the unbalance by calculating the correction coefficient using the formula is also shown.

Since the magnitude of unbalance is essentially constant regardless of the tire T installation phase, it can be said that the closer the calculated value at each installation phase, the better the accuracy. From FIG. 8, the proposed method is more accurate and the validity can be confirmed.
As described above, by adopting the tire balance test method of the present embodiment, the balance load Ft inherent to the tire T can be calculated even when the rotational speed is not constant, and the tire T can be accurately calculated. The unbalanced state can be inspected, and consequently the inspection cycle time can be shortened as much as possible.

  By the way, it should be thought that embodiment disclosed this time is an illustration and restrictive at no points. In particular, in the embodiment disclosed this time, matters that are not explicitly disclosed, for example, operating conditions and operating conditions, various parameters, dimensions, weights, volumes, and the like of a component deviate from a range that a person skilled in the art normally performs. Instead, values that can be easily assumed by those skilled in the art are employed.

DESCRIPTION OF SYMBOLS 1 Tire balance testing machine 2 Spindle shaft 3 Housing 5 Bearing part 6 Load cell (measurement part)
7 Fixed frame 8 Drive motor 9 Belt 10 Unbalance calculation part T Tire

The present invention relates to a tire balancing test technique for detecting unbalance force generated when rotating the tires (unbalanced force), in particular, in the tire balance test, a technique that enables shortening the cycle time of the test .

The tire production line, test for measuring the unbalance force generated when rotating the tire (unbalanced force) is performed using the tire balance testing machine. Measurement of the imbalance force, a tire fixed to the spindle shaft are rotationally driven, and measures the variation force generated in the tire as a load waveform.
FIG. 1 shows a schematic diagram of a typical tire balance testing machine.

As shown in this figure, the spindle shaft tire is mounted through the rim be supported freely rotated, unbalance force magnitude generated in the tire during rotation, provided in the machine direction, the rotational phase detected by the load cell, by a variety of techniques based on the detection value obtained measuring the unbalance force of the tire.
It shows a typical dynamic balance calculation method in which the imbalance forces obtained by such a device based on the following.

As shown in FIG. 2, the detected load F1 by the upper load cell and the detected load F2 by the lower load cell can be expressed in complex numbers having amplitude and phase with respect to the reference signal from the frequency analysis of the test data. Here, if the B1, B2 and unbalanced load of two surfaces of the top, bottom surface of the tire, the unbalance loads B1, B2 is as shown in equation (1) based on the detection load F1, F2.

Incidentally, a, b, c, d are as shown in FIG. 2, the distance to each part from the center in the width direction of the tire, load detected F1, F2 and unbalanced loads B1, B2 is represented by a complex number.
By the way, in an actual tire balance test, disturbance (rotational speed component) is included in the detected loads F1 and F2. This disturbance is mainly caused by the eccentricity of the rim provided at the upper end of the spindle shaft. Here, this is called “unbalanced load unique to the device”.

  This unbalanced load unique to the device can be expressed by a vector as a rim eccentric vector Ua. As shown in the vector diagram (unbalanced vector diagram) of FIG. 3A, the rim eccentric vector Ua includes a rim unbalance vector Uar caused by a rim mass nonuniformity with respect to the spindle axis, and a rim-tire fitting portion. This is a combined vector with the apparent unbalance vector Uas of the tire caused by the deviation between the center line and the spindle shaft. That is,

It is.
A detection unbalance vector U _D in which the detected loads F1 and F2 obtained from the load cell are expressed as a vector is a combination of the unbalance vector Ut of the tire itself and the rim eccentric vector Ua.

It becomes.
That is, as shown in equation (3), the detection unbalance vectors U _D detected by the load cell, is clear that the eccentricity vector Ua of the rim is included as an error, the correct balance of only tires without correction Measurement (Ut measurement) is not possible.
For this reason, various detection load correction means have been conventionally employed (Patent Documents 1 and 2).

  For example, Patent Literature 1 uses a test apparatus that measures the vibration of the rotating part accompanying rotation of the tire by attaching a tire to the rotating part, and changes the rotation angle of the tire with respect to the rotating part. However, correction data for removing the influence of eccentricity and distortion of the rotating part from the measurement result by storing the data obtained by performing the measurement a plurality of times, storing the data obtained by the plurality of measurements, and combining the stored data The correction method in the dynamic balance test of obtaining

That is, Patent Document 1 performs measurement by changing the tire mounting phase with respect to the rim a plurality of times (divided into n equal parts), and synthesizes the obtained waveform data to remove the tire unbalance component and perform balance correction. This is a method of obtaining only correction load data for the purpose.
Patent Document 2 discloses an adapter that rotates with a test specimen mounted thereon, an unbalance detection unit that detects an unbalance of the rotating test specimen, and n types (n Is a natural number equal to or greater than 3) in the attachment mode, the first storage means for storing data of n detection unbalance vectors obtained from the unbalance detection section, and n stored in the first storage means Computing means for obtaining coordinates of the center of the circle passing through the respective tips or the vicinity of the detected unbalance vectors and obtaining a vector symmetric with respect to the origin with respect to the vector of the center coordinates of the circle with respect to the origin, and the vector thus obtained With respect to the detected unbalance vector obtained from the unbalance detection unit at the time of actual measurement. It discloses a dynamic balancing machine that includes a correcting means for adding an eccentricity correction vector stored in the serial second storage means.

That is, in Patent Document 2, the correction load can be calculated even when the tire mounting phase is unknown, and the measured load vector at three or more arbitrary tire mounting phases is plotted on the complex plane, and the least square method is used. Use it to draw a circle and find its center point. The obtained center is an unbalance correction load vector.
By the way, in the tire balance test, in addition to improving the measurement accuracy, reduction of the cycle time of the test is an issue.

  For example, in a tire balance test, about 2 seconds are required for acceleration of tire rotation, about 2 seconds are required for deceleration, and the inspection time during steady rotation is often about 5-6 seconds. Therefore, the tire balance test requires about 9 to 10 seconds for one tire. If the inspection can be performed at the time of acceleration or deceleration of the tire rotation, the inspection time at the steady rotation can be shortened accordingly, and the inspection time can be shortened by about 2 to 4 seconds as a whole. Significant shortening is possible.

As a balance measuring method for the purpose of shortening the cycle time as described above, it is conceivable to use a region where the speed is not constant such as an acceleration part or a deceleration part of the tire rotation as described above. The technique of Patent Document 4 has been developed.
Patent Document 3 discloses rotational position signal output means for outputting a plurality of predetermined rotational position signals per rotation of a specimen, vibration detection means for detecting vibrations generated by applying rotation to the specimen, and specimen A rotation speed calculation means for calculating the rotation speed data, a storage means for storing the rotation speed data calculated by the rotation speed calculation means in association with the rotation position signal output from the rotation position signal output means, A filtering means for obtaining a waveform data of an unbalanced signal by applying a digital filter to the vibration data detected by the vibration detecting means in association with the rotational position signal output from the position signal output means; A correction based on the rotational speed data stored in the storage means is performed on the waveform data of the obtained unbalance signal. Waveform data correcting means, waveform data corrected by the waveform data correcting means, and a function including an undetermined coefficient desired to be matched with the waveform data is applied to the least square method to determine the undetermined coefficient. Disclosed is an unbalance measuring device which is provided with unbalance calculating means for calculating an unbalance vector from a coefficient and outputting the result, so that unbalance measurement can be performed even if the rotation of the specimen is not constant speed rotation. To do.

  On the other hand, Patent Document 4 is a balance testing machine for measuring the unbalanced force of the object to be measured by detecting an unbalance force when the object to be measured that is rotatably supported is rotated by a force detection means. A speed and rotational position measuring means for measuring the angular velocity and rotational position of the rotating object to be measured, an unbalance force detected by the force detection means, and the speed and speed when the unbalance force is detected. Disclosed is a balance testing machine comprising dynamic unbalance calculation means for calculating dynamic unbalance of the measurement object using the angular velocity and rotation position of the measurement object measured by the rotation position measurement means.

JP 2000-234980 A Japanese Patent Publication No. 7-50011 Japanese Unexamined Patent Publication No. 2000-97795 JP 2000-221096 A

Correction methods such as Patent Document 1 and Patent Document 2 are effective for improving measurement accuracy in a tire balance test, but both methods assume measurement at a constant rotation speed of the spindle shaft. Only after the acceleration has finished and the tire has reached a certain number of revolutions, can it be measured satisfactorily. That can not be applied directly for the unbalanced load measured when the rotational speed changes as during acceleration and deceleration of the spindle shaft, acceleration, there is a drawback that can not be performed time measurement of the deceleration. Therefore, the cycle time (test time) of the tire balance test cannot be shortened.

  Therefore, the inventors of the present application have made extensive studies in order to reduce the cycle time of the tire balance test. As a result, Patent Document 3 and Patent Document 4 have found that the unbalanced load is proportional to the square of the tire rotational speed, but cannot be completely expressed by the square of the speed. As a result of investigating the error component, it has been found that an error component that does not depend on the rotational speed, in other words, an unbalanced component specific to the apparatus is included, and that correction that takes into account such component is necessary.

In FIG. 3 (b), the measured waveform of the unbalanced load resulting in the conventional tire balance testing machine (dark solid line) is shown. Meanwhile, the waveform shown by the solid line of light color is, in accordance with the idea of Patent Documents 3 and 4, a load imbalance corrected calculated as tire imbalance load is proportional to the square of the rotational speed. It is clear that the curves do not match.
Accordingly, the present inventors, when considering the compensation for also accurately calculated imbalance force during rotational acceleration, rotational acceleration of the tire during rotation deceleration of the "term that does not depend on the rotation speed exists" Based on this idea, the inventors have focused on “unbalance components that do not depend on rotational speed”, which the engineer has not paid attention to, and have developed a new correction method that takes into account such unbalance components. That is, the inventors have come up with a method for obtaining “correction data (data for correcting measurement values) at the time of tire rotation acceleration or rotation deceleration” in consideration of an unbalance component that does not depend on the rotation speed.

As described above, the present invention is a correction method that enables calculation of an accurate tire unbalance load even in a region where the tire rotation speed is not constant in the tire balance test, in other words, during rotation acceleration or rotation deceleration. utilizing the tire unbalance load can check the unbalance condition of the tire with high precision, and an object thereof is to provide a tire balancing test techniques to be shortened and thus the test cycle time as much as possible.

In order to achieve the above-described object, the present invention takes the following technical means.
That is, the tire balance test method according to the present invention is a method for measuring tire unbalance using a tire balance tester having a spindle shaft that rotatably holds the tire, and the tire mounting angle with respect to the spindle shaft. and at various rotational speeds of a plurality of tires installed state which has been assumed to be different, measure the unbalance load generated in the spindle shaft for holding the tire, from the measured imbalance force during rotational acceleration of the tire or to previously obtain the correction data at the time of rotation deceleration during actual measurement, the measured unbalance load generated in the spindle shaft to rotate, the measured imbalance force is corrected using the correction data, tire non It is characterized by measuring the balance.

Preferably, the imbalance load Fa to be measured, a term Ft due to imbalance of the tire itself, the term Fz2 proportional to the square of the rotational speed of the spindle shaft, and a term Fz0 that does not depend on the rotation speed of the spindle shaft expressed by a function having, and a plurality of rotational speed while measuring the unbalance force in the tire installation state of plural kinds having different mounting angle of the tire with respect to the spindle axis, based on the unbalanced load which is measured, A term Fz2 proportional to the square of the rotational speed of the spindle shaft and a term Fz0 that does not depend on the rotational speed of the spindle shaft are obtained, and the term Fz2 proportional to the square of the rotational speed of the spindle shaft thus obtained is independent of the rotational speed of the spindle shaft. The term Fz0 may be the correction data.

Preferably, the tire mounting angle is known in the plurality of tire installation states.
Preferably, in the plurality of tire installation states, the tire attachment angle is unknown and the tire installation states may be three or more different states.
On the other hand, a tire balance testing machine according to the present invention includes a spindle shaft that rotatably holds a tire, a housing that rotatably supports the spindle shaft via a bearing portion, and a spindle shaft that holds a rotating tire. a measuring unit for measuring the unbalance load generated in using the tire balance test method described above, the corrected unbalance load measured by the measurement unit, and the imbalance calculation unit for calculating a non-balanced state of the tire , Is provided.

  According to the tire balance test technique according to the present invention, even in a region where the tire rotation speed is not constant, the unbalanced state of the tire can be inspected with high accuracy, and the inspection cycle time can be shortened as much as possible. .

It is the figure which showed the structure of the tire balance testing machine. It is the figure which showed the force which acts on the tire balance testing machine under test. (A) is a vector diagram displaying the tire unbalance load decomposed into its components, is a diagram showing a (b) the measurement waveform of the tire unbalance load by conventional tire balance testing machine. It is the figure which showed on the complex plane the force which acts on a tire in different tire rotation speed. It is the flowchart which showed the procedure of the tire balance test method of this embodiment. Is a diagram illustrating the forces acting on the tire at different tire rotation speed on the complex plane is a diagram showing the center point of the approximate circle and the approximate circle unbalanced load vector on the complex plane. A diagram showing the results of measuring the imbalance load of the tire. Using the measurement method according to the present invention and shows the results of the analysis (corrected) unbalanced load of the tire.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
A tire balance testing machine 1 according to the present invention will be described hereinafter with reference to the drawings.
Tire balance testing machine 1 of this embodiment is a test device for measuring the unbalance load (unbalanced force) generated when rotated at a high speed of the tire T.
As schematically shown in FIG. 1, the tire balance testing machine 1 includes a spindle shaft 2 that holds a tire T, and a housing 3 that rotatably supports the spindle shaft 2 around its axis. .

The spindle shaft 2 is a rod body whose axis is directed vertically, and a rim that protrudes in a bowl shape toward the radially outer side is formed at an upper end portion thereof. The rim is formed to have an outer diameter that matches the inner periphery of the tire T, and the tire T can be held from the inner periphery side.
The housing 3 is a cylindrical body having an inner diameter larger than the outer diameter of the spindle shaft 2, and rotatably supports the spindle shaft 2 via a pair of upper and lower bearing portions 5 provided on the inner wall of the cylindrical body. . The housing 3 is connected to a fixed frame 7 via a load cell 6 (measurement unit) that can measure a force component in one direction (see FIG. 1). In the example of FIG. 1, the housing 3 is attached to the fixed frame 7 via a pair of upper and lower load cells 6.

The rotational driving force of the driving motor 8 is transmitted to the spindle shaft 2 through the belt 9, and as a result, the spindle shaft 2 rotates around the vertical axis.
Unbalanced load generated in the tire T during rotation is measured by the load cell 6, it is sent to a disproportionately calculator 10 as a waveform signal of unbalanced load (unbalanced force). Incidentally, the load cell 6 in two places, of the unbalanced load caused by eccentricity generated from the tire T, measuring the unbalance load F1, F2 in the direction shown in FIG.

Imbalance calculator 10, based on the unbalanced load F1, F2 measured by the load cell 6 is the measurement unit, unbalanced load B1 of the tire T by using the relationship shown in equation (1) described above, B2 Is calculated.
Furthermore, unbalance calculation unit 10 from a previously measured unbalanced load, with previously obtained correction data for removing the eccentricity and the effect of distortion of the rotating parts present in the tire balance testing machine 1, the tire balance test sometimes, the imbalance load measured in frequency to the rotational speed is changed is corrected using the correction data of said, is configured to detect the imbalance state of the tire T. The unbalance calculation unit 10 is configured by a computer or the like.

Hereinafter, the correction method performed in disproportionate calculator 10, and described the method for calculating the tire unbalance load using this correction method.
[First Embodiment]
Measurement method of tire unbalance load according to the first embodiment, generally stated, those having the following 3 steps.

(i) In a certain tire T, the load generated on the spindle shaft 2 holding the tire T is measured in an installation state where the mounting angles are different and under various rotational speed conditions.
(ii) From the measured load, correction data for removing the influence of eccentricity and distortion of the rotating portion existing in the tire balance testing machine 1 is obtained.
(iii) during actual measurement, while rotating the tire T while the rotation speed is changed to measure the load generated in the spindle shaft 2, the measured load is corrected using the correction data, the imbalance of the tire T Measure the load.

  Specifically, the measured load Fa includes a term Ft caused by the unbalance of the tire T itself, a term Fz2 proportional to the square of the rotational speed of the spindle shaft 2, and a term Fz0 that does not depend on the rotational speed of the spindle shaft 2. It is expressed as a function having In addition, the load is measured at a plurality of tire T installation states with different mounting angles of the tire T with respect to the spindle shaft 2 and at a plurality of rotational speeds, and the measured actual load and the above function are calculated. By calculating the undetermined coefficient so that the square of the difference is minimized, a term Fz2 proportional to the square of the rotational speed of the spindle shaft 2 and a term Fz0 independent of the rotational speed of the spindle shaft 2 are obtained. The term Fz2 proportional to the square of the calculated rotational speed of the spindle shaft 2 and the term Fz0 independent of the rotational speed of the spindle shaft 2 are used as correction data.

Hereinafter, the calculation procedure will be described in detail.
First, correction data for the detected load F1 detected by the upper load cell 6 and the detected load F2 detected by the lower load cell 6 are obtained.
For this purpose, first, let Fa be the load vector detected by the load cell 6 when the tire T is attached to the rim and rotated at the rotational angular velocity ω (rad / sec). Then, (a load caused by imbalance of the tire T itself, imbalance load to be determined) unbalance load generated by the tire T to Ft, eccentricity and the effect of distortion of the rotating parts present in the tire balance testing machine 1 In other words, the unbalance component unique to the apparatus is set as Fz0. This Fz0 is a component that does not depend on the rotational speed of the spindle shaft 2. Further, a component proportional to the square of the rotation speed of the spindle shaft 2 is set as Fz2. Note that Fa, Ft, Fz0, and Fz2 are represented as vectors, and these vectors have periodic variability, and therefore are represented by complex numbers in this embodiment.

Tire unbalanced load Fa detected by the load cell 6 is as shown in equation (4).

At this time, the unbalance force Fz unique to the apparatus is as shown in Expression (5).

Here, FZ0, be previously seeking Fz2 as correction data, original imbalance load Ft tire T from equation (4) can be calculated using measured values Fa. Fz0 and Fz2 are calculated by the method of least squares based on measurement waveforms at various rotational speeds and installation phases of the plurality of tires T.
It should be noted that the correction data Fz2 varies depending on the tire mass. When the tire mass changes, it is necessary to identify correction data based on the tire mass. Since Fz2 is proportional to the tire mass, it can be expressed by a function using the mass as a parameter based on a plurality of tire mass data.

Now, a method of calculating Fz0 and Fz2 when the installation angle of the tire T (relative angle with respect to the spindle shaft 2) is known will be described.
When the tire T installation angles with respect to a plurality of experimental rims are φ1, φ2, φ3... (Reference position is arbitrary), and the loads observed at that time are Fa1, Fa2, Fa3. )become that way.

Here, the unknowns are Fz0, Fz2, and Ft. As a method of calculating these unknowns, the tire T angle .phi.1, .phi.2, Fex1 measurement data unbalanced load in φ3, fex2, fex3, ... Distant, Fa1 of formula (6), Fa2, Fa3 ... waveform relative to the rotation angle The unknowns Fz0, Fz2, and Ft are calculated so as to be expressed as data fa1, fa2, fa3... And minimize the square of the error with fex1, fex2, fex3. The rotation angle waveform data (fa (θ)) of Fa is expressed by Expression (7).

  Here, Re means the real part of a complex number, and is numerical data equivalent to the measured load data fex. Since the value of ω is a function of the rotation angle θ, it is expressed as ω (θ). Fz0, Fz2, and Ft are obtained so that J in Expression (8) is minimized. n is a test data number.

Note that the accuracy increases as the angle range to which the least squares method is applied is selected so that the number of waveforms of periodic fluctuation due to imbalance is as large as possible.
In summary above, if previously obtained as FZ0, Fz2 formula (8) is minimized as the correction data, original imbalance load Ft tire T from equation (4) can be calculated using measured values Fa. By using these Fz0 and Fz2 as correction data, it is possible to inspect the unbalanced state of the tire T with high accuracy even in a region where the rotational speed of the tire T is not constant (rotation acceleration region, rotation deceleration region), and consequently an inspection cycle. The time can be shortened as much as possible.
[Second Embodiment]
Next, the described second embodiment of the measuring method of the tire unbalance load.

The measurement method of this embodiment is a method of handling the tire T installation angle (relative angle) as unknown. It is known that even if a slight error exists in the mounting position of the tire T, the measurement result is affected. Therefore, using this method to eliminate the influence, it is corrected unbalanced load is accurately measured.
Here, the calculation method in three different types of tire T installation phases is shown. When the load generated by the unbalance of the tire T itself in the tire experiments 1 to 3 (the installation phases are different from each other) is Ft1, Ft2, and Ft3, the expression (4) becomes the expression (9).

Since there is no information on the tire T installation angle, equation (9) has many unknowns and cannot be solved by the same mathematical method as in the first embodiment. Therefore, in Equation (9), a method is considered in which a term independent of the rotational speed and a rotational speed squared term are independently calculated for each experimental data, and then each formula is identified.
That is, since Fz2 and Ft of the velocity square term cannot be obtained separately, assuming that Fz2 + Ft = Ft ′, the respective coefficients Fz0 and Ft ′ are calculated from the equations shown in Equation (10).

For Fz0 in equation (10), the variable name is changed for each experiment. The reason for this is that Fz0 should originally have the same value, but because there is a difference in calculating Fz0 and Ft ′ for each data, each is a separate parameter.
The least square method is applied to the calculation of these coefficients in the same manner as described above. The rotation angle waveform data of Fa is expressed by Expression (11). n is a tire experiment number.

Next, Fz0, n and Ft ′, n are obtained so that Jn represented by Expression (12) is minimized.

  After calculating each parameter, that is, after Ft ′ and Fz0 are known, unbalanced load vectors Fa1, Fa2, and Fa3 at a plurality of rotation speeds are calculated from the equation (10), and at each rotation speed as shown in FIG. Create an approximate circle for the calculated value of to find the center point. At that time, a vector from the coordinate origin to the center point of the approximate circle is an unbalance component unique to the apparatus at each rotation speed, that is, correction data, and corresponds to Fz shown in Expression (5). This technique is the technique disclosed in FIG. 1 of Japanese Patent Laid-Open No. 01-142429, etc., and is usually used by those skilled in the art.

  Next, based on the calculation results of Fz at a plurality of spindle shaft rotation speeds, the unbalanced force inherent to the apparatus at an arbitrary rotation speed can be expressed in accordance with Equation (5) using a component Fz0 and a square component Fz2 that are independent of Fz. Represent in the form. In this case, if the approximate circle centers obtained at the rotational angular velocities ω1, ω2,..., Ωn are Fz ′ (ω1), Fz ′ (ω1),. Can be divided into a real part and an imaginary part and combined into a matrix consisting of n expressions (Expression (13)).

Expression (13) can be expressed as Expression (13) ′, and the undetermined coefficient matrix [Fz02] is obtained using a pseudo inverse matrix (Expression (13) ″). This corresponds to the least square method used in the first embodiment.
Although the equation is described with n = 3 as the number of experiments, the accuracy of the approximate circle in FIG. 4 increases and the identification accuracy of the correction data increases as the number of experiments increases.

In summary, the correction data Fz0 and Fz2 can be calculated in advance also by the method disclosed in the second embodiment, and using the obtained Fz0 and Fz2 and the actual measurement value Fa, the original tire T is obtained from equation (4). unbalanced load Ft can be calculated. By using these Fz0 and Fz2 as correction data, the unbalanced state of the tire T can be inspected with high accuracy even in a region where the tire T rotation speed is not constant (rotation acceleration region, rotation deceleration region), and consequently the inspection cycle time. Can be shortened as much as possible.

With tire balancing test method according to the present invention described above, it was identified tire imbalance load (estimated) described by the following examples.
That is, the correction data is calculated according to the procedure shown in FIG. 5A, and the unbalance of the tire T is calculated according to the procedure shown in FIG.
First, the tire T to be measured is attached to the rim of the tire balance testing machine 1 in S11 of FIG. Next, rotation of the spindle shaft 2 is started, and in S12, a detection signal (load and phase, rotational speed data) of the load cell 6 during acceleration is acquired.

In S13, it is determined whether or not the required number of experiments has been reached. If not (No in S13), the tire installation angle is changed in S14. If Yes in S13, correction data Fz0 and Fz2 are obtained in S15.
After that, the actual measurement of the imbalance load of the tire T (S16, i.e., S21 to S26).

First, in S21 of FIG. 5B, it is determined whether or not the correction data Fz0 and Fz2 for the tire T (tire mass) to be measured exists. If it does not exist, the process of FIG. 5A is performed (S22).
When the correction data Fz0 and Fz2 exist (Yes in S21), in S23, the tire T to be measured is mounted on the tire balance testing machine 1, and balance measurement is performed, and the load, phase, and rotation including during acceleration are performed. Get speed data. Further, in S24, the measurement waveform is corrected with the correction data Fz0 and Fz2 stored in advance, and the tire unbalance load Ft is calculated.

Then, by using a formula (1), determining the unbalanced load B1, B2 from the tire unbalance load Ft. Thereafter, the tire T is replaced in S26.
Next, a tire unbalance calculation method using the correction data in S24 and S25 described above will be described in detail with reference to FIGS.
First, from equation (4), the unbalanced load Ft inherent to the tire T is represented by equation (14).

  On the other hand, rotation angle waveform data ft (θ) equivalent to the experimental value fex (θ) is expressed by Expression (15).

  The original unbalance vector Ft of the tire T is calculated from the waveform of ft (θ) by curve fitting or the like. As an example, it can be calculated by a method of calculating the tire T unbalance vector Ft so that J in Equation (16) is minimized, a sequential least square method, or the like.

Thereafter, Ft is calculated as F1 and F2 for each load cell 6, and the dynamic balance B1 and B2 of the tire T can be calculated from the equation (1).
In addition, in order to improve correction data identification accuracy by applying the least square method, when considering a speed proportional component proportional to the rotational speed ω, the speed proportional component is formulated as an unknown Fz1 (complex number) by the same method, and the least square method is used. In addition to Fz0, Fz2, and Ft, the velocity proportional term Fz1 can be calculated.

  For example, when the speed term Fz1 is taken into consideration, if the load generated when the tire T (mass unknown) is attached is Ft, the detected load Fa at the load cell 6 is expressed by Expression (17).

By applying equation (17) instead of equation (4), identification can be performed in the same procedure as described above.
In addition, since Fz2 in Formula (4) includes the load (mr = rim runout × tire mass) due to rim runout, it varies depending on the tire mass attached. When the tire mass changes, it is necessary to identify the correction load based on the tire mass.

The calculation results for the actually measured values (measured loads F1 and F2 in FIG. 1B) are shown.
Assuming that the installation phase of the tire T is unknown (when there is an installation phase error), the correction load was calculated for the acceleration data from the equations (11) to (13). A calculation example is shown for experimental data in which the tire T installation phase is changed eight times in approximately 45 ° increments.
FIG. 6 shows the result of plotting the unbalanced vector Fan calculated by the equation (10) on the complex plane from the corrected load coefficients Fz0n and Ftn ′ of each experiment (rotational angular velocities ω1 to ω5). The center point becomes the correction load vector Fzn unique to the apparatus at each rotation speed. The coefficients Fz0 and Fz2 can be calculated by equation (13). Although FIG. 6 shows an unbalance vector for the measured load F1, it is necessary to perform the same calculation for F2.

FIG. 7 plots the relationship between the rotational speed and the magnitude of the correction load for each of the measured loads F1 and F2 by substituting the coefficients Fz0 and Fz2 calculated by the expression (13) into the expression (5).
On the other hand, FIG. 8 shows a balance measurement by changing the installation phase angle every 45 ° from 0 ° to 360 ° with a tire T different from the tire T used for calculating the correction data. The result calculated using data is shown. As a comparative example, it is also formulated by taking into consideration only the square term, and the result of calculating the unbalance by calculating the correction coefficient using the formula is also shown.

Since the magnitude of unbalance is essentially constant regardless of the tire T installation phase, it can be said that the closer the calculated value at each installation phase, the better the accuracy. From FIG. 8, the proposed method is more accurate and the validity can be confirmed.
Above As noted, the use of the tire balance test method of this embodiment, the rotational speed is able to calculate the tire T inherent imbalance load Ft even if not constant, the tire T with high accuracy Thus, it is possible to inspect the unbalanced state, and thus to shorten the inspection cycle time as much as possible.

  By the way, it should be thought that embodiment disclosed this time is an illustration and restrictive at no points. In particular, in the embodiment disclosed this time, matters that are not explicitly disclosed, for example, operating conditions and operating conditions, various parameters, dimensions, weights, volumes, and the like of a component deviate from a range that a person skilled in the art normally performs. Instead, values that can be easily assumed by those skilled in the art are employed.

DESCRIPTION OF SYMBOLS 1 Tire balance testing machine 2 Spindle shaft 3 Housing 5 Bearing part 6 Load cell (measurement part)
7 Fixed frame 8 Drive motor 9 Belt 10 Unbalance calculation part T Tire

Claims (5)

A method of measuring tire imbalance using a tire balance tester having a spindle shaft that rotatably holds a tire,
Measuring a balance load generated on the spindle shaft holding the tire in a plurality of tire installation states with different mounting angles of the tire with respect to the spindle shaft and at various rotational speeds;
From the measured balance load, correction data at the time of rotation acceleration or rotation deceleration of the tire is obtained,
A tire balance test method for measuring a tire unbalance by measuring a balance load generated on a rotating spindle shaft at the time of actual measurement and correcting the measured balance load using the correction data. . The balance load Fa to be measured is expressed by a function having a term Ft caused by unbalance of the tire itself, a term Fz2 proportional to the square of the rotational speed of the spindle shaft, and a term Fz0 independent of the rotational speed of the spindle shaft. ,
The balance load is measured at a plurality of rotational speeds with different tire mounting angles with respect to the spindle shaft at a plurality of rotational speeds, and the square of the rotational speed of the spindle shaft is measured based on the measured balance loads. A term Fz2 proportional to, and a term Fz0 that does not depend on the rotational speed of the spindle shaft,
The tire balance test method according to claim 1, wherein the correction data includes a term Fz2 proportional to the square of the calculated rotational speed of the spindle shaft and a term Fz0 not dependent on the rotational speed of the spindle shaft.   The tire balance test method according to claim 2, wherein a tire attachment angle is known in the plurality of tire installation states.   The tire balance test method according to claim 2, wherein, in the plurality of tire installation states, a tire attachment angle is unknown and the tire installation states are three or more different states. A spindle shaft that rotatably holds the tire;
A housing that rotatably supports the spindle shaft via a bearing portion;
A measuring unit for measuring a balance load generated on a spindle shaft holding a rotating tire;
An unbalance calculation unit that corrects a balance load measured by the measurement unit using the tire balance test method according to any one of claims 1 to 4, and calculates a tire unbalance state;
A tire balance testing machine characterized by comprising: