JP2004085297A - Method and apparatus for measuring properties of tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily and simply evaluate properties of a tire which exert influence on the frequency band ≥ 100 Hz of road noises and so on. <P>SOLUTION: To measure properties of a rotating test tire T using a rotating drum 12, which has a smooth drum surface 12a, a single protrusion 12b which is narrower in width than the supporting surface of the test tire T when the test tire T is put on and touches the drum surface 12a, and is enveloped by the test tire T when the test tire T treads on, is formed on the drum surface 12a. The test tire T is rotated on the drum surface 12a, and the movement of the test tire T generated, when the test tire T treads on the single protrusion 12b is measured. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a tire characteristic measuring method and a tire characteristic measuring device for measuring tire characteristics during rolling by rolling a test tire.
[0002]
[Prior art]
Noise in a frequency band of 100 to 500 Hz, which is measured in a passenger compartment of a traveling car or the like, causes the tire to vibrate due to slight irregularities on the road surface, and this vibration is transmitted through the rotation axis of the tire and the suspension of the car. This is known as road noise that propagates as sound in the passenger compartment. This road noise is treated as one of noises to be reduced not only by tire manufacturers but also by vehicle manufacturers.
[0003]
Conventionally, various studies have been made as a method for evaluating tire characteristics that affect the road noise.
For example, the tire is suspended from the ceiling using a spring or the like to make the tire free, and the surface of the tread portion of the tire is hit with an impulse hammer or the like to obtain a transfer function of the tire (by hammering). Evaluate the superiority or inferiority of tire characteristics with respect to road noise from the transfer function.
[0004]
On the other hand, in order to comprehensively evaluate tire characteristics affecting road noise, a plurality of protrusions are randomly arranged on the circumference of the drum surface of the indoor drum to simulate a road surface that generates road noise ( "In-vehicle noise test and evaluation", Automotive Technology, Vol.28, No.4, p274-282, 1974; "Road noise reduction by sensitivity analysis", Automotive Technology, Vol.42, No.12, p1575-1579. 1988), and a method of reproducing a pseudo road surface around the drum surface of an indoor drum ("Road noise of passenger cars", Automobile Technology, Vol. 19, No. 5, p377-387, 1965) has been proposed.
[0005]
[Problems to be solved by the invention]
However, the method of evaluating tire characteristics that affect road noise by hammering is that when hitting using an impulse hammer etc., it is performed in a no-load state with the tire in a free state, so it is in a state where it is grounded to the road surface It is different from the running condition of rolling. For this reason, it may not always be possible to evaluate the superiority or inferiority of the tire characteristics with respect to actual road noise.
Further, when the tire mounted on the vehicle is in a non-rolling state, the tire is vibrated from the road surface side where the tire comes into contact with the ground, and the axial force fluctuation generated in the axial force of the tire is obtained, whereby the transfer function of the tire can be obtained. In this case, since the rolling state of the tire is not reproduced, it may not always be possible to evaluate the superiority or inferiority of the tire characteristics with respect to actual road noise.
Further, the transfer function of the tire obtained by these methods is mainly formed by being governed by the mass and rigidity of the tread portion and the belt portion, which are tire components, and the rigidity around the bead portion. There is a problem in that the magnitude of the vibration excited in the tread portion due to the unevenness of the road surface is not taken into consideration, and the tire characteristics with respect to road noise cannot be correctly evaluated.
[0006]
On the other hand, in order to comprehensively evaluate the tire characteristics, a method of randomly arranging a plurality of protrusions on the circumference of the drum surface of the indoor drum or reproducing a pseudo road surface on the circumference of the drum surface of the indoor drum is used. Because the road surface shape is constant, it is necessary to change the random arrangement of the protrusions or change the pseudo road surface to evaluate the effect when the road surface shape changes, which can easily and easily affect road noise There is a problem that it is not possible to measure the tire characteristics that give the tire.
[0007]
In general, tire characteristics that affect road noise are classified into vibration (input characteristics) excited on the ground contact portion of the tire due to unevenness of the road surface and vibration transmission rate (transmission characteristics) for transmitting the vibration to the tire shaft. It is understood that the above-described measurement method and the method of determining the axial force fluctuation of the tire by vibrating the tire from the road surface correspond to the method of evaluating the transfer characteristic, and that a plurality of methods are randomly arranged on the circumference of the drum surface. The method of arranging the projections and reproducing the pseudo road surface on the circumference of the drum surface of the indoor drum can be considered as a comprehensive evaluation in consideration of both the input characteristics and the transfer characteristics.
In any case, it is not possible to evaluate the magnitude of the vibration excited on the ground contact portion of the tire due to the unevenness of the road surface, that is, it is not possible to mainly evaluate the input characteristics among the tire characteristics.
[0008]
Therefore, the present invention provides a tire characteristic measuring method and a tire characteristic measuring device capable of easily and easily evaluating tire characteristics that affect a frequency band of 100 Hz or more such as road noise in order to solve the above problem. The purpose is to do.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a tire characteristics measuring method for measuring tire characteristics of a rolling test tire using a rotating drum having a smooth drum surface,
The drum surface is narrower than the contact width of the test tire when it comes into contact with the drum surface, and when the test tire is stepped on, a single projection is provided to envelope the test tire,
Rolling a test tire on the drum surface, by measuring the response of the test tire when the test tire steps on the single protrusion, a tire characteristic measuring method characterized by measuring the characteristics of the test tire provide.
[0010]
It is preferable that the single protrusion is attached to a predetermined position in the width direction of the drum surface by a detachable means. Further, it is preferable that the mounting position of the single protrusion is set so as to be in contact with the tread rubber portion of the test tire.
[0011]
Also, the measurement of the response of the test tire is performed by taking in the signal of the axial force of the test tire in synchronization with the position of the single protrusion on the drum surface, and measuring the axial force when the test tire passes through the single protrusion. This is preferably performed by acquiring the average waveform of the time waveform of the fluctuation of. In this case, in the measurement of the response of the test tire, it is preferable to obtain a spectrum waveform when passing through the single protrusion by performing frequency analysis using the obtained average waveform of the fluctuation of the axial force.
It is preferable that the single projection has a height of 5 mm or less.
[0012]
Further, the present invention is a tire characteristic measuring device for measuring the tire characteristics of the test tire during rolling,
Having a tire drum surface for rolling the test tire, the width is smaller than the contact width of the test tire when it is grounded on this drum surface, and when the test tire is stepped on, a single protrusion that envelopes the test tire is provided on the drum surface. A rotating drum provided,
There is provided a tire characteristic measuring device, comprising: measuring means for measuring characteristics of a test tire by measuring behavior of the test tire generated when the test tire steps on the single protrusion.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the tire characteristic measuring method of the present invention will be described in detail based on preferred embodiments shown in the attached drawings.
[0014]
FIG. 1A is an example of a tire characteristic measuring device of the present invention, and is a configuration diagram showing a schematic configuration of a road noise characteristic measuring device (hereinafter, referred to as a measuring device) 10 for implementing a tire characteristic measuring method of the present invention. It is.
The measuring device 10 includes a rotating drum 12 for rolling the test tire T on the drum surface while contacting the drum surface, and a mounting hub for rotatably supporting the test tire T in a free wheel state, and the mounting hub is hung on the rotation axis of the tire. A tire stand 14 provided with a load cell 13 for measuring a load (tire axial force), an amplifier 16 for amplifying a tire axial force signal from the load cell, and a processing unit 18 for taking in the amplified tire axial signal and measuring tire characteristics. And a drive motor 20 for driving the rotary drum 12.
[0015]
The rotating drum 12 is provided with a single protrusion 12b on a smooth drum surface 12a without unevenness (maximum height _Ry ( _Rmax ) ≦ 6.3 μm) where the test tire T is in contact with the ground, and the single protrusion 12b is tested. When passing through the tire T, a small striking force is generated.
[0016]
Here, the single projection is a projection that is narrower than the contact width of the test tire T on the drum surface 12a and wraps (envelopes) the periphery of the single projection when the test tire T is stepped on. The protrusions are arranged such that only one protrusion exists in the ground surface of the tire T. In addition, the single protrusion is opposed to a continuous protrusion in which a plurality of protrusions are close to each other and the test tire does not contact the drum surface 12a between the protrusions. Therefore, around the single protrusion, the surface of the tread portion of the test tire T and the smooth drum surface 12a act so as to come into contact with each other. That is, the test tire T does not completely ride on the single protrusion 12b, and the surface of the tread portion of the test tire T contacts the smooth drum surface 12a.
The single protrusions 12b are provided to simulate one of a plurality of minute irregularities on the road surface on which road noise is generated.
[0017]
The size of the single protrusion 12b varies depending on the size of the test tire T and the state of the tire internal pressure of the test tire T. For example, in the case of a tire for a passenger car, when the single protrusion 12b is formed in a cylindrical shape, the cross-sectional shape is 10 mm or less in diameter. In this case, the height is preferably 5 mm or less. The reason for limiting the height of the single protrusion is that the thickness of the tread portion of the passenger car tire is approximately 5 to 10 mm, and as described later, among the tire characteristics that affect road noise, the tire is easily affected by the tread portion. This is for obtaining the tire characteristics in consideration of the input characteristics.
In addition, the single protrusion 12b is not limited to a cylindrical shape, and may have any shape. For example, a shape obtained by cutting a rectangular parallelepiped shape, a hemispherical shape, or a spherical shape by a plane may be used. In the case of a shape obtained by cutting a spherical shape in a plane, for example, in a passenger car tire, the height is set to be 5 mm or less when the spherical shape has a diameter of 10 mm or less.
[0018]
It is preferable that one single protrusion 12b is provided on the drum surface 12a, but a plurality of single protrusions 12b may be provided on the drum surface 12a. In this case, the test tire T rolls and is arranged so that only one single protrusion 12b is included in the ground contact surface of the test tire T. This arrangement is for accurately measuring the vibration excited by one single projection 12b when the rolling test tire T passes through the single projection 12b, as described later.
Therefore, in order to accurately measure the vibration excited by one single projection 12b, it is necessary to measure until the vibration completely converges. Therefore, preferably, one single projection 12b is provided on the drum surface 12a. Is preferred.
[0019]
As shown in FIG. 1B, on the circumference of the drum surface 12a, there are provided portions 12c in which female screws are cut at regular intervals in the width direction of the drum surface 12a, and male screws provided on the single protrusion 12b. And the single projection 12b is attached to a desired position by means that can be attached to and detached from the drum surface 12a. The unused female screw portion of the portion 12c is sealed by a dummy member so as to be flush with the drum surface 12a.
The single protrusion 12b can be attached to and detached from the drum surface 12a and can be attached to a desired position in the width direction. Therefore, by measuring the tire characteristics against road noise while changing the position of the single protrusion 12b, the tire against road noise can be measured. The characteristic can be obtained as a distribution in the width direction.
[0020]
The tire stand 14 is configured such that a mounting hub is movable in a direction perpendicular to the drum surface 12a so as to apply a desired contact load to the test tire T, and a load cell 13 is provided on the mounting hub.
The load cell 13 measures an axial force generated on the rotation axis (center axis) of the test tire T in at least one of a direction perpendicular to the drum road surface 12a, a circumferential direction of the drum surface 12a, and a width direction of the drum surface 12a. Thus, it is possible to measure the fluctuation of the axial force acting on the test tire T when the test tire T passes through the single protrusion 12b.
The axial force signal obtained by the load cell 13 is sent to the amplifier 16 and amplified.
The amplified axial force signal is sent to the processing unit 18.
[0021]
The processing unit 18 obtains an axial force variation when the test tire T passes through the single protrusion 12b from the amplified axial force signal, performs a frequency analysis on the axial force variation, and performs a predetermined frequency band, for example, 100 to 500 Hz. , 100 to 300 Hz, the overall power value is calculated, and the tire characteristics of the test tire T with respect to road noise are evaluated.
[0022]
Specifically, the axial force signal of the test tire T is taken in synchronism with the position of the single protrusion 12b on the drum surface 12a, and the average of the time waveform of the axial force fluctuation when the test tire T passes through the single protrusion 12a. Get the waveform. A method of acquiring an average waveform by synchronization is, for example, to provide a mark such as a notch or a reflector at a specific position on the circumference of the rotary drum 12 and to pass a detection signal by passing the mark such as the notch or the reflector. An output detection sensor is provided on the rotating drum 12, and the detection signal is used as a trigger signal to sample and average the axial force signal sent from the amplifier 16.
Thereafter, the obtained average waveform of the axial force fluctuation is frequency-analyzed to obtain a spectrum waveform of the axial force fluctuation generated in the test tire T when the test tire T passes through the single protrusion 12b, and a spectrum in a predetermined frequency band is obtained. The superiority of the tire characteristics with respect to road noise is evaluated based on the overall value of the waveform. The reason why the average waveform of the axial force fluctuation is obtained is to remove a noise component included in the axial force fluctuation and a uniformity component inherent in the test tire T because the axial force fluctuation due to the single protrusion 12b is small.
Such a processing unit 18 may be a well-known FFT (Fast Fourier Transformation) analyzer, or may be configured by a computer that performs functions by executing a program.
[0023]
The drive motor 20 is connected to a rotating shaft of the rotating drum 12, and rotates the rotating drum 12 at a desired speed.
[0024]
In such a measuring device 10, first, the width of the contact area of the test tire T is narrower than the contact width of the test tire T when the test tire T is in contact with the drum surface 12a. Is attached to a predetermined position in the width direction of the drum surface 12a. The position in the width direction where the single protrusion 12b is attached is attached such that the single protrusion 12b does not abut on a circumferential groove extending in the circumferential direction of the test tire T and abuts on the tread rubber portion of the test tire T.
Next, the test tire T is grounded to the drum surface 12a so as to have a desired grounding load. Thereafter, the drive motor 20 is driven to start rotating at a desired rolling speed.
Thus, the test tire T is rolled on the drum surface 12a, and the axial force generated when the test tire T steps on the single protrusion 12b is measured by the load cell 13.
[0025]
The axial force signal generated by the load cell is amplified by the amplifier 16 and sent to the processing unit 18.
In the processing unit 18, the axial force signal of the test tire T is fetched in synchronization with the position of the single protrusion 12b on the drum surface 12a, and the time waveform of the axial force change when the test tire T passes through the single protrusion 12b is obtained. An average waveform is obtained.
Thereafter, the obtained average waveform of the axial force fluctuation is subjected to frequency analysis, and a spectrum waveform of the axial force fluctuation generated in the test tire T when passing through the single protrusion 12b is obtained. Then, the overall value of the spectrum waveform in the predetermined frequency band is calculated. Based on the calculated overall value, the superiority or inferiority of the tire characteristics with respect to road noise is evaluated.
[0026]
【Example】
To confirm the validity of the above measurement method, tire characteristics were measured for two types of passenger car tires (size: P155 / 80R13) A and B.
Before the measurement of the tire characteristics of the tires A and B, the road noise generated when the vehicle travels on a road noise-generating road surface under the conditions of an internal pressure of 210 (kPa) and a traveling speed of 60 (km / hour) in a rear seat in the vehicle. It was measured. The measurement was performed using the well-known precision sound level meter with the A characteristic. FIG. 2 shows a spectrum waveform of the sound pressure of road noise as a measurement result.
According to this, it can be seen that the tire A has a higher road noise level in the frequency band of 100 to 300 Hz, and further 100 to 500 Hz, as compared with the tire B.
[0027]
FIG. 3 is a diagram showing a spectrum waveform of a fluctuation of an axial force in a contact load direction of a tire measured by the method of the present invention described above. For the tires A and B, the load was 3000 (N), the rolling speed was 60 (km / H), and the average number of times of obtaining the average waveform of the axial force fluctuation was 16 times. The spectral waveform is the result of the frequency band from 0 to 300 Hz.
According to this, in the frequency band of 100 to 300 Hz, the variation in axial force of the tire B is uniformly reduced as compared with the tire A, and the tire characteristics of the tire B are evaluated to be superior to the tire characteristics of the tire A. This evaluation result corresponds to the result of the noise level shown in FIG.
[0028]
FIG. 4A illustrates a conventional hammering method. The tread portion of the tire suspended from the ceiling by a spring is hit with an impulse hammer, and the response at the center axis (rotation axis) of the tire is determined using an acceleration pickup attached to a rim on which the tire is mounted.
FIG. 4B shows an example of a transmissivity which is a kind of the vibration transfer function obtained by the method shown in FIG.
As shown in FIG. 4B, it can be seen that the value of the transmissivity of the tire B is partially larger than that of the tire A in the region of 100 to 300 Hz or 100 to 500 Hz. That is, the tire B is evaluated to be inferior in tire characteristics to road noise as compared with the tire A. However, this evaluation result contradicts the result of the noise level shown in FIG.
[0029]
FIG. 5A illustrates a conventional method different from FIG. 4A. The tire is grounded on the vibration surface of the vibrator, the tire is vibrated using the vibrator, and the acceleration generated on the center axis (rotation axis) of the tire is picked up by an acceleration pickup attached to a rim mounted on the tire. To determine the response of the tire's axis of rotation.
FIG. 5B shows an example of a transmissibility (acceleration of the center axis of the tire with respect to acceleration of the exciter), which is a kind of the vibration transfer function obtained by the method of FIG. 5A.
As shown in FIG. 5 (b), it can be seen that there is no difference in transmission rate between tire A and tire B in tire B in the frequency band of 100 to 300 Hz or 100 to 500 Hz. That is, the tire A and the tire B are evaluated as having the same tire characteristics with respect to road noise. However, this evaluation result does not correspond to the result of the noise level shown in FIG.
[0030]
As described above, according to the results of the conventional example shown in FIGS. 4B and 5B, it is not possible to obtain a result that the tire B has better tire characteristics with respect to road noise than the tire A. However, according to the result of the embodiment shown in FIG. 3, the evaluation result corresponding to the result of the noise level of the road noise shown in FIG. 2 can be obtained.
From the above, it can be said that the tire characteristic measuring method of the present invention can evaluate tire characteristics with respect to road noise extremely well.
[0031]
As described above, the tire characteristic measuring method and the tire characteristic measuring device of the present invention have been described in detail. However, the present invention is not limited to the above-described embodiment, and various improvements and modifications are made without departing from the gist of the present invention. Of course, you can.
For example, instead of measuring the axial force fluctuation of the test tire, the test tire is made movable using a suspension mechanism so as to enable the translational movement of the rotation axis of the test tire, and the acceleration generated on the rotation axis of the test tire. May be measured, or the fluctuation of the force acting on the rotating shaft of the rotating drum or the fluctuation of the force acting on the drum surface may be measured as a reaction to the fluctuation of the axial force of the test tire. At least, the drum surface is provided with a single protrusion that is narrower than the contact width of the test tire when it comes into contact with the drum surface, and when the test tire is stepped on, the test tire may be configured to envelope the single protrusion. The method for measuring the behavior of the tire is not limited.
[0032]
【The invention's effect】
As described above in detail, according to the present invention, on the drum surface on which the test tire rolls, a single projection having a width smaller than the contact width of the test tire when it is grounded on the drum surface is provided, and the test tire is stepped on. At this time, since the test tire is enveloped, by measuring the response when the test tire passes through the single protrusion, tire characteristics that affect road noise can be easily and easily evaluated.
[Brief description of the drawings]
FIGS. 1A and 1B are configuration diagrams showing a configuration of an example of a tire characteristic measuring device of the present invention.
FIG. 2 is a diagram illustrating an example of a spectrum waveform of a road noise of a tire.
FIG. 3 is a diagram showing an example of a spectrum waveform obtained by the tire characteristic measuring method of the present invention.
FIG. 4A is a diagram illustrating an example of a conventional tire characteristic measuring method, and FIG. 4B is a diagram illustrating an example of a spectrum waveform obtained by the method described in FIG.
FIG. 5A is a diagram illustrating another example of a conventional tire characteristic measuring method, and FIG. 5B is a diagram illustrating an example of a spectrum waveform obtained by the method described in FIG.
[Explanation of symbols]
Reference Signs List 10 Road noise characteristic measuring device 12 Rotary drum 12a Drum surface 12b Single protrusion 13 Load cell 14 Tire stand 16 Amplifier 18 Processing unit 20 Drive motor

Claims (7)

Using a rotating drum having a smooth drum surface, a tire characteristic measuring method for measuring the tire characteristics of the test tire during rolling,
The drum surface has a width smaller than the contact width of the test tire when it is in contact with the drum surface, and when the test tire is stepped on, a single projection is provided to envelope the test tire,
A tire characteristic measuring method, comprising: measuring a characteristic of a test tire by rolling the test tire on the drum surface and measuring a response of the test tire when the test tire steps on the single protrusion. The tire characteristic measuring method according to claim 1, wherein the single protrusion is attached to a predetermined position in a width direction of the drum surface by a detachable means. The tire characteristic measuring method according to claim 2, wherein the mounting position of the single protrusion is set so as to be in contact with a tread rubber portion of the test tire. The measurement of the response captures the signal of the axial force of the test tire in synchronization with the position of the single protrusion on the drum surface, and the time waveform of the change in the axial force when the test tire passes through the single protrusion. The tire characteristic measuring method according to any one of claims 1 to 3, which is performed by acquiring an average waveform. The tire characteristic measurement method according to claim 4, wherein the measurement of the response is performed by performing frequency analysis using the acquired average waveform of the fluctuation of the axial force to obtain a spectrum waveform when passing through the single protrusion. The tire characteristic measuring method according to any one of claims 1 to 5, wherein the single protrusion has a height of 5 mm or less. A tire characteristic measuring device for measuring tire characteristics of a test tire during rolling,
Having a tire drum surface for rolling the test tire, the width is narrower than the contact width of the test tire when it is grounded on this drum surface, and when the test tire is stepped on, a single projection that envelopes the test tire is provided on the drum surface. A rotating drum provided,
A measuring device for measuring characteristics of the test tire by measuring a behavior of the test tire generated when the test tire depresses the single protrusion, thereby measuring a characteristic of the test tire.

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