JP3214265B2 - Apparatus and method for testing and determining brake noise - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for evaluating a brake noise for evaluating a so-called brake noise generated during braking by a brake dynamometer.

[0002]

2. Description of the Related Art In a motor vehicle, a braking device is one of the most important safety devices, and it must operate reliably and stably regardless of running conditions. For this reason, it has come to be carried out to test a brake device of an automobile using a brake dynamometer in advance. In the test, there is a method of determining a brake sound (brake squeal). Conventionally, the following method has been adopted as a method for determining the brake sound.

(1) A method in which a certain noise level threshold value is set for each noise frequency, and a noise level value exceeding the threshold value is determined as brake squeal (method shown in FIG. 6A). (2) Noise level value Is set in the following way: a. A method of setting a threshold value for each frequency by a frequency analyzer or a computer device (the method shown in FIG. 6B) b. A method of storing a noise frequency in a state where the brake is not sounding in a frequency analysis device or a computer device, and using this as a threshold value (method shown in FIG. 6C). In the method of FIGS. When the waveform becomes as shown in FIG. 6D, the waveform is determined as brake squeal.

[0004]

Although the conventional brake squeal test method described above can determine the brake squeal, this determination method measures the noise level and frequency when the brake squeal occurs, and measures the noise level. The brake temperature, the brake fluid pressure, the braking torque, the vibration value of each part, the rotation speed, and the like are measured, and the cause of the brake squeal is analyzed. However, the above-described determination method has a problem that the data amount is considerably large because the noise level is extracted by comparing the threshold value with a set value. Also, since the evaluation of the noise level extracted differs depending on the method of setting the threshold value, the setting of the threshold value is important, but the setting of the threshold value usually depends on experience, and the test results differ depending on the operator. There was a lot of fear.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a brake noise test / determination apparatus and method which facilitate determination of brake noise and facilitate pursuit of the cause of the noise. And

[0006]

In order to achieve the above object, the present invention provides a brake dynamometer, a brake body to be tested set in the brake dynamometer, and a brake to be tested. A noise measurement device provided at a position closest to a brake portion of the main body, first and second vibration measurement devices provided at two locations of the brake main body under test, and a noise output of the noise measurement device are supplied, A first fast Fourier transformer for comparing the noise spectrum data with a previously measured background noise measurement value and outputting the noise spectrum data of the difference, and a vibration output of the first and second vibration measurement devices are supplied, and a vibration spectrum is supplied to the output. Second and third fast Fourier transformers for transmitting data;
A noise and vibration spectrum data obtained by the fast Fourier transformer is inputted, and the computer is provided with a computer which processes the data to determine brake squeal.

A second step of obtaining a waveform peak point from a noise waveform output from a noise measuring device provided at a position closest to a brake portion of the brake body to be tested;
The second step of obtaining the peak point of the waveform from the vibration waveform output from the first and second vibration measuring devices provided on the brake body to be tested matches the peak point of the waveform obtained in the first and second steps. And a third step of determining that brake squeal has occurred when a peak point has been detected.

In the third invention, a peak point of a noise waveform obtained by subtracting a certain noise level threshold or a noise waveform in a state where the brake is not sounding from a measured noise waveform of the brake body under test is compared with a peak point of a vibration waveform. Thereafter, when there is a region where the frequency bands of the noise and the vibration at each peak point coincide with each other, it is determined that the brake noise is present.

According to a fourth aspect of the present invention, a brake sound test is performed by attaching a brake body to be tested to a dynamometer, and a noise measuring device is provided near the brake body to be tested, and a vibration measuring device is provided to the brake body. When the peak points of the waveforms of the noise signal and the vibration signal detected by the measuring device fall within a certain frequency range, it is determined that the brake noise is generated.

[0010]

The noise measuring device measures the noise coming from the brake during braking, the first and second vibration measuring devices measure the vibration sound of the brake body, and the measured values of the noise measuring device are transmitted to the first high-speed Fourier transformer. The measured values of the first and second vibration measuring devices are converted into vibration spectrum data by the second and third fast Fourier transformers. After conversion, both data are processed by a computer to determine brake squeal.

[0011]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention. In FIG. 1, reference numeral 11 denotes a brake dynamometer composed of an electric motor, a flywheel, a torque meter, and the like (not shown). There is a chassis dynamometer for testing and a brake dynamometer with roller for testing with only one wheel. A brake to be tested (not shown) is set in the brake dynamometer 11. The noise measuring device 12 is arranged at the position closest to the brake under test, and the first and second vibration measuring devices 13 and 14 for measuring the vibration of the brake main body are arranged at two places on the brake main body. The values measured by the measuring devices 12 to 14 are respectively the first to third fast Fourier transformers (FFT1 to FFT).
3) Input to 15 to 17 to calculate. The first fast Fourier transformer 15 is configured to receive a background noise measurement value measured in advance, which will be described later, and to compare the background noise measurement value with a calculated value. The calculation outputs of the first to third fast Fourier transformers 15 to 17 are input to a computer 19 provided in a brake control system 18 and processed.

The analog signal of the sound pressure of the noise at the position closest to the brake measured by the noise measuring device 12 is sampled at a high speed by the first fast Fourier transformer 15 and
FT calculation and comparison with the background noise measurement value,
The difference is output. In addition, the first and second vibration measuring devices 1
Analog signals of the vibrations of the brake body measured at 3 and 14 are sampled at high speed by the second and third fast Fourier transformers 16 and 17 in the same manner as described above, and then subjected to FFT calculation.

First to third fast Fourier transformers 15-1
Reference numeral 7 converts the time-axis waveform data output from each of the measuring devices 12 to 14 into waveform data (spectral waveform data) on the frequency axis by performing an FFT operation. FIG. 2A shows the time axis waveform data before the FFT operation is performed, and FIG.
This is the spectrum waveform data after the FT operation. A plurality of spectrum waveform data obtained in this way are measured over one measurement section. Then, the maximum value of each frequency band (point) is extracted for all frequency bands from the obtained plurality of spectral waveform data, and one peak waveform data is created by each of the Fourier transformers 15 to 17. The created peak waveform data is input to the computer 19. The numbers of points and frequencies in FIG. 2B are examples.

Here, the above-mentioned background noise will be described.
Background noise is noise at the time of constant speed rotation during non-braking, and automatically measures and captures data at each speed set before the test. This background noise measurement is performed as shown in FIG. First, the following items are set before measurement for background noise measurement.

(A) Measurement speed When an arbitrary measurement speed is set and the background noise measurement is started, the operation is automatically performed up to the set speed, and the background noise and the speed at that time are automatically measured.

(B) Measurement Time In FIG. 4, a time ts for background noise measurement is set, and the spectrum waveform data obtained at each measurement speed is an average waveform within the measurement time set here.

The background noise peak waveform data obtained under the above measurement conditions is stored and stored. The stored background noise peak waveform data is supplied to the first fast Fourier transformer 15 and the background noise peak waveform data is compared with the data measured by the noise measuring device 12, and the difference is determined by the first high speed Fourier transformer 15. The output from the Fourier transformer 15 is input to the computer 19.

It is assumed that the noise spectrum output from the first fast Fourier transformer 15 has a waveform as shown in FIG. 5A. When the vibration spectrum at that time (the waveforms of the second and third fast Fourier transformers 16 and 17) has the waveform shown in FIG. 5B, the coincidence between the brake squeal peak point and the peak point of the vibration spectrum waveform is set in advance. It is determined whether or not it is within the determined frequency collation band BPW (the area indicated by the broken line in the figure). For example, when the line segment of the solid line X is lowered from the peak point of the noise spectrum waveform in FIG. 5A to the vibration spectrum waveform in FIG. Is determined. Similarly, when the solid line Y and Z line segments are lowered from the peak point of the noise spectrum waveform of FIG. 5A to the vibration spectrum waveform of FIG. 5B, when the peak of the vibration waveform falls within the frequency collation bandwidth BPW, It is determined that the brake noise is heard. This determination process is performed by the computer 19.

As a test method for evaluating the squeal noise during braking as described above, the brake squeal was performed when the frequency of the peak point of the vibration waveform of each component constituting the brake coincided with the noise waveform. Determination became easier. In the above embodiment, the noise measurement is performed at one location and the vibration measurement is performed at two locations. However, the measured rotation speed range during braking is divided into “high-speed” and “high-medium-constant”. Then, the number of noise and vibration measurement channels may be increased in order to measure the measured noise waveform and the measured vibration waveform in each area. This is to divide the frequency band for extracting the peak point, and to improve the accuracy of the brake noise determination and the sampling frequency. Further, the number of vibration measurement points may be increased, and the condition of the brake noise determination may be changed by comparing the OR or AND of the logical condition of the peak point of each vibration waveform with the peak point of the noise waveform.

[0020]

As described above, according to the present invention,
Since the noise and vibration at the time of brake squeal are simultaneously captured, the cause of the squeal can be easily pursued. Also,
Since the squeal determination during brake braking is performed not only based on the threshold but also based on the vibration waveform, not only the determination is facilitated, but also the cause of the brake squeal is easily evaluated for each brake component. . Furthermore, in the brake test, several thousand braking operations are performed in one operation pattern, and the brake squeal is determined for each braking operation, and the brake temperature, the brake fluid pressure, the braking torque, the rotation speed, the vibration value of each part, etc. Measurement, the amount of data becomes enormous, but if it is easy to judge that the brake has sounded, the saved data amount can be reduced by only setting the amount of data to be saved at the frequency of the sound. There is.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIGS. 2A and 2B are waveform diagrams before and after calculation by a fast Fourier transformer.

FIGS. 3A and 3B are waveform diagrams after calculation by a fast Fourier transformer.

FIG. 4 is a waveform chart for background noise measurement.

5A and 5B are waveform diagrams showing brake squeal detection means.

FIG. 6 is an explanatory diagram of a conventional brake noise determination method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Brake dynamometer 12 ... Noise measuring equipment 13, 14 ... First and second vibration measuring equipment 15-17 ... First to third fast Fourier transformer 18 ... Brake control system 19 ... Computer

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01H 3/00 G01M 17/007

Claims (4)

(57) [Claims] 1. A brake dynamometer, a brake body under test set on the brake dynamometer, a noise measuring device provided at a position closest to a brake portion of the brake body under test, and the brake body under test The first and second vibration measuring devices provided at the two locations and the noise output of the noise measuring device are supplied, compared with a previously measured background noise measurement value, and the noise spectrum data of the difference is output. A first fast Fourier transformer, second and third fast Fourier transformers to which vibration outputs of the first and second vibration measuring devices are supplied, and to output vibration spectrum data to the outputs; A computer that receives noise and vibration spectrum data obtained by a Fourier transformer and processes these data to determine brake squeal; A test determination apparatus for a brake sound. 2. A first step of obtaining a waveform peak point from a noise waveform output from a noise measuring device provided at a position closest to a brake portion of a brake body under test, and a first and a second step provided on the brake body under test. 2 Obtain the waveform peak point from the vibration waveform output from the vibration measurement device.
And a third step of determining a brake squeal when a peak point coincides with a peak point of the waveform obtained in the first and second steps. 3. After comparing a peak point of a noise waveform obtained by subtracting a certain noise level threshold or a noise waveform in a state where the brake is not sounding from a measured noise waveform of a brake body under test with a peak point of a vibration waveform, A brake sound test determination method characterized in that it is determined that brake noise is present when there is an area where the frequency bands of noise and vibration at each peak point match. 4. A test for testing a brake sound by attaching a brake body under test to a dynamometer, wherein a noise measuring device is provided near the brake body under test, and a vibration measuring device is provided on the brake body. A brake sound test determination method, wherein a brake noise is determined when a waveform peak point of a noise signal and a vibration signal detected by a device falls within a certain frequency range.