JPH0540070A - Device for measuring unbalance of rotor - Google Patents

Abstract

PURPOSE:To carry out correct measure with a simple operation, by controlling automatically the gain of an amplifier and the cut-off frequency of a filter to correction values, on the basis of a detected judgment result. CONSTITUTION:A Fourier transform means 54 makes detection signals of a rotation detecting means 50 and an oscillation detecting means 52 given through the first and second filter amplification means 51, 52, Fourier transform respectively; and outputs them to an unbalance operation means 55 for operating the unbalance quantity of a rotor and that position. On the other hand, the means 54 outputs them also to a judging means 56. In the means 56, the peak frequency of a frequency spectrum transforming the detection signal of the means 50 is detected, and whether the value transforming the detection signal of the means 52 is in a fixed range or not is judged. The cut-off frequencies of the means 51, 53 and the gain of the means 53 are automatically controlled according to the peak frequency, on the basis of the judgment result, in a controlling means 57. Before the real measurement, the states of the detection signals of the means 50, 51 can be automatically controlled in the states suitable for the measurement, and the unbalance measurement can be carried out correctly and in a short time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for measuring the amount of unbalance of a rotating body such as a propeller shaft of a vehicle.

[0002]

2. Description of the Related Art As a conventional unbalance measuring device,
For example, there is one as shown in FIG. In FIG. 10, 1 is a transmission extension, 2 is a first propeller shaft, 3 is a center bearing, 4 is a second propeller shaft, 5 is a differential gear, and 6, 7 and 8 are joints for connection,
The above part is the structure of the drive system of the vehicle. Further, 10 is a reflective tape adhered to the second propeller shaft 4, 11
Irradiates the second propeller shaft 4 with light, and the reflective tape 1
It is an optical fiber sensor that detects a rotation speed by detecting a reflected wave from zero. Further, 12 is an amplifier for converting the output of the optical fiber sensor 11 into a voltage output, 13 is an acceleration sensor bonded to the lower part of the differential gear, 14 is an acceleration sensor amplifier, and 15 is an unbalance calculation device.

In the above apparatus, the optical fiber sensor amplifier 12 outputs a pulse voltage having a cycle corresponding to the rotation speed as shown in FIG. When the above-mentioned signal is Fourier-transformed by the unbalance calculation device 15, FIG.
As shown in (b), at a constant rotation speed, a peak spectrum occurs at a predetermined frequency fp. Similarly, the output of the acceleration sensor 14 is as shown in FIG. 12 (a), and the result of Fourier transforming it is as shown in FIG. 12 (b). The Fourier transform result of the optical pulse shown in FIG. 11 (b) is shown by the following (Equation 1) formula, and the Fourier transform result of the acceleration sensor signal shown in FIG. 12 (b) is shown by the following (Equation 2) formula, The phase difference θ between the light pulse and the acceleration is the following (Equation 3)
It can be calculated by a formula.

[0004]

[Equation 1]

[0005]

[Equation 2]

[0006]

[Equation 3]

When the weights attached to the propeller shaft are exchanged twice for the above measurement, as shown in FIG. 13, a vector of magnitude | Fy ₁ (ω) | and a phase angle of θ ₁ Two vectors having a magnitude of | Fy ₂ (ω) | and a phase angle of θ ₂ are obtained, and a combined vector of these two becomes an unbalanced vector of the propeller shaft. Therefore, if a balance weight having a size and a phase angle θx corresponding to the vector W in the direction opposite to the above-described combined vector is attached to the propeller shaft, the imbalance of the propeller shaft can be eliminated.

[0008]

In the conventional unbalance measuring device as described above, the level of the detection signal changes depending on the mounting position of the acceleration sensor 13, and the vibration level changes depending on the rotation speed of the propeller shaft. However, since it becomes very large at the resonance point, the detection signal of the acceleration sensor changes significantly. When the level of vibration detection is low, the S / N becomes small due to being buried in the vibration of the engine, and when the level is too high, there is a fear of scale over. In such a case, accurate measurement should be performed. Can not. And when the unbalance amount is calculated based on the inaccurate measurement result and the balance weight is attached to the propeller shaft, the vibration may increase further, and it is difficult to perform accurate balance adjustment.
There was a problem. In addition, in order to perform accurate measurement, at the stage where the sensors are mounted on the vehicle to be inspected, the inspector checks the sensor input in advance, and the sensor mounting position, amplifier gain, and It is necessary to adjust the cut-off frequency of the filter, etc., and if there is a scale-over at the resonance point, it is necessary to readjust each time. There was a problem of becoming.

The present invention has been made in order to solve the problems of the prior art as described above, and provides an unbalance measuring device for a rotating body, which enables an accurate unbalance measurement to be easily performed by a simple operation. The purpose is to

[0010]

In order to achieve the above object, the present invention is constructed as described in the claims. FIG. 1 is a block diagram showing the configuration of the present invention. In FIG. 1, reference numeral 50 denotes a rotation detecting unit that outputs a signal according to the rotation speed of the rotating body, and corresponds to, for example, the optical fiber sensor 22 in FIG. 2 described later. Also, 51 is
It is a first filter amplifying means capable of filtering and amplifying the output of the rotation detecting means 50 and having an adjustable cutoff frequency, and corresponds to, for example, a filter 25 and an amplifier 27 in FIG. 2 described later. Further, reference numeral 52 denotes a vibration detecting means that is attached to the support portion of the rotating body and detects the vibration of the support portion, and corresponds to, for example, the acceleration sensor 21 in FIG. 2 described later. Reference numeral 53 is a second filter amplifying means that filters and amplifies the output of the vibration detecting means 52 and that can adjust the cutoff frequency and the gain. For example, the filter amplifying means 53 is provided in the filter 24 and the amplifier 26 shown in FIG. Equivalent to.
Further, 54 is a Fourier transforming means for Fourier-transforming the signals of the rotation detecting means 50 and the vibration detecting means 52, which are given through the first filter amplifying means 51 and the second filter amplifying means 53, respectively. Details of the Fourier transform will be described later. Further, 55 is an unbalance calculation means for calculating the unbalance amount and the unbalance position of the rotating body from the conversion result of the Fourier transform means 54. The above calculation will be described later in detail with reference to FIG. Further, 56 detects the peak frequency of the frequency spectrum obtained by converting the detection signal of the rotation detecting means 50 by the Fourier transforming means 54, and converts the detection signal of the vibration detecting means 52 by the Fourier transforming means 54 within a predetermined range. Is a determining means for determining whether or not The detection judgment calculation will be described in detail later with reference to FIGS. 3 and 4. The above-mentioned Fourier transform means 54, unbalance calculation means 55, and determination means 56 correspond to the calculation section 23 in FIG. 2 described later, and can be configured using, for example, a microcomputer. Further, 57, based on the detection judgment result of the judgment means 56, the cutoff frequencies of the first and second filter amplification means 51 and 53 according to the peak frequency, and the second filter amplification according to the judgment result. The gain of the means 53 is
It is an adjusting unit that automatically adjusts, and corresponds to, for example, the variable frequency oscillator 30, the relays 31 and 32, and the calculation unit 23 shown in FIG. Further, reference numeral 58 is a display means for displaying the calculation result of the unbalance calculation means 55, and corresponds to, for example, a printer 29 for making a hard copy such as a thermal printer shown in FIG.

[0011]

As described above, in the present invention, the first and second filter amplifying means 51 and 53, the determining means 56, and the adjusting means 58, whose cutoff frequency and gain can be adjusted, are provided, and the Fourier transforming means 54 converts them. Based on the result, the gain of the amplifier and the cutoff frequency of the filter are automatically adjusted to appropriate values. Therefore, before performing the actual unbalance measurement,
Since the state of the detection signals of the rotation detection means (optical fiber sensor) and the vibration detection means (acceleration sensor) is automatically adjusted to a state suitable for measurement, the pretreatment process of measurement is greatly simplified and accurate. Unbalance measurement can be performed easily in a short time.

[0012]

FIG. 2 is a block diagram of an embodiment of the present invention. Incidentally, the mounting state of the vehicle drive system and each sensor when measuring the imbalance of the propeller shaft of the vehicle is the same as in FIG. In FIG. 2, 21 is
It is an acceleration sensor that detects the vibration of the support part of the rotating body,
This corresponds to the acceleration sensor 13 in FIG. Also, 22
Is an optical fiber sensor for detecting the rotation speed of the rotating body, and corresponds to the optical fiber sensor 11 in FIG. Further, 24 and 25 are filters. The cutoff frequencies of these filters are variable according to the signal of the variable frequency oscillator 30. Further, 26 and 27 are amplifiers, and the amplifier 26 has a variable gain according to the opening and closing of the contacts 33 and 34 of the relays 31 and 32. Further, reference numeral 23 is a calculation unit, which is composed of, for example, a microcomputer. Further, 28 is a liquid crystal display, and 29 is a printer.
The variable frequency oscillator 30 is, for example, a crystal oscillator, and the oscillation frequency is variable according to a control signal (for example, a 3-bit signal) given from the arithmetic unit 23. Further, the relays 31 and 32 open and close the contacts 33 and 34 according to the control signal given from the arithmetic unit 23.

Next, the operation of this embodiment will be described. First, a method of frequency spectrum analysis and Fourier transform will be briefly described. In the frequency spectrum analysis, first, as shown in FIG. 7, for example, the sensor output (time axis) waveform is A / D converted into a digital discrete system,
For example, it is represented as a digital value of 1024 points. Then, the Fourier transform thereof is performed to express it as a frequency spectrum distribution as shown in FIG. Before performing the Fourier transform, data of 1024 points is multiplied by a window function (weighting function) as shown in FIG. This is necessary when performing a discrete Fourier transform on a finite number of data, and the characteristic of FIG. 8 is the Hanning window (Ha
nnings window) characteristic. This Hanning window has a characteristic of W (N) = 0.5-0.5 cos (2πN / 1024). Next, general Fourier transform is performed by the following equation (4).

[0014]

[Equation 4]

It should be noted that g (t) is a function, and here, indicates the value of the sensor (on the time axis). When the above equation (4) is represented by a digitalized discrete Fourier transform, the following equation (5) is obtained.

[0016]

[Equation 5]

In the above equation (5), g _n = g (nΔt) F _m = F ( _m Δω), where (m = 0 to N-1) K = m × n, and

[0018]

[Equation 6]

[0019] In the equations (5) and (6), N is the number of samples (1024 in the example), Δt is the sampling period, and the acquired data g ₀ to g _n-1
It can be calculated by multiplying the sin and cos functions to obtain the sum. Power spectrum at a certain frequency x | F
_x | ² is | F _x | ² = (F _XR ) ² + (F _XI ) ² (Equation 7) where F _{XR is} the real part of the FFT operation result F _{XI is} the imaginary part of the FFT operation result, 0 to N-1 at intervals of a predetermined frequency Δf in the memory of the microcomputer that constitutes the arithmetic unit 23.
Written up. FIG. 9 shows this.
Further, normally, in order to improve the accuracy of the analysis result, the results of Fourier transform of several to several tens blocks are averaged and the spectrum is displayed as shown in FIG.

Next, the operation of the embodiment will be described. When a power switch (not shown) is turned on, the microcomputer constituting the arithmetic unit 23 operates according to the flow chart of a predetermined program written in the ROM (FIGS. 3 to 6 described later). 3 to 6 are flowcharts showing the calculation of the present invention. FIGS. 3 and 4 are programs showing the calculation of the preprocessing, FIG. 5 is a main program showing the calculation of the main measurement, and FIG. 6 is a predetermined sampling cycle. This is an interrupt processing program for performing A / D conversion in.

First, the preprocessing operation of FIGS. 3 and 4 will be described. In FIG. 3, first, in P1, initial values are set in the RAM and the register of the microcomputer forming the arithmetic unit 23. Next, in P2, it is determined whether the start switch for measurement is on or off, and if it is on, the lamp indicating that analysis is in progress is turned on in P3. Then P
4, the cutoff frequency fmax of the filters 26 and 27 is
Set the initial value of. When measuring the balance of the propeller shaft, the rotation speed of the propeller shaft is 10000rp.
Cutoff frequency f because m (frequency 167 Hz) or less
The arithmetic unit 23 outputs a 3-bit command signal so that the max becomes, for example, 200 Hz, and the oscillation frequency of the variable frequency oscillator 30 is set. According to this frequency, the filter 24,
A cutoff frequency of 25 is set. Next, in P5, the sampling number Ns and the average number AV are set. For example, if the number of averages AV = 4, then the number of samplings Ns = 1024 × 4 = 4096. Next, in P6, the sampling period ΔT is set. The sampling period ΔT is the cutoff frequency f as described above.
If max 200 Hz, ΔT = 1/2 · fmax (sampling theorem), and the sampling period ΔT = 2.5 msec. Next, in P7, the timer interrupt is permitted. With this timer interrupt permission, the interrupt flowchart shown in FIG. 6 is executed in the ΔT cycle.

In FIG. 6, the pulse signal from the optical fiber sensor of channel 1 and the signal from the acceleration sensor of channel 2 are A / D converted and stored in a predetermined memory area. And the sampling number Ns = 40
When it reaches 96 times, the sampling end flag SPEND =
Then, the timer interrupt is terminated and the program returns to the program of FIG.

Next, in P8 of FIG. 3, the judgment flag SPEND during sampling is checked to make SPEND = 1.
When, that is, when sampling is completed,
Proceed to the next Fourier transform process. Channel 1 on P9
Fourier transform operation of the data (optical fiber sensor data) is performed. In this calculation, first, the sampled data of channel 1 is multiplied by the Hanning window function shown in FIG.
Fourier transform the block. Next, in P10, the average value of the conversion results of the four blocks is calculated. Next, in P11, the peak frequency fp of the frequency spectrum of the Fourier transform result is obtained. Next, at P12, the Fourier transform is similarly performed on the data of channel 2 (acceleration sensor data). Then, in P13, the average value and the gain of the Fourier transform result are obtained. Next, in P14,
The conversion result of the optical fiber sensor signal and the acceleration sensor signal is displayed on the liquid crystal display 28. From P14 of FIG. 3 to FIG.
Continue to P15.

In P15 to P17, the filters 24 and 25 are used.
Officially set the cutoff frequency of. First, in P15, a value twice the peak frequency of the spectrum is calculated from the Fourier transform result of the optical fiber sensor signal of channel 1. When the object to be measured is a propeller shaft, the peak frequency is around 55 Hz to 80 Hz, and good measurement can be performed by setting the cutoff frequency to about twice that value. Next, in P16, a value closest to the above value is retrieved from the ROM frequency table, and P
At 17, the search value is output and a 3-bit signal is sent to the variable frequency oscillator 30 shown in FIG. For example, "000" for 100 Hz, "001" for 200 Hz, 200
In the case of Hz, "010" is sent and the variable frequency oscillator 30
The output frequency is changed by changing the internal division ratio. The cutoff frequency of the filter is set by applying the signal of the variable frequency oscillator 30 set as described above to the filters 24 and 25. Next, in P18, the level of the value obtained by Fourier transforming the output of the acceleration sensor of channel 2 is checked, and in P19 to P22, the processing level is 0 to 0.
The amplification factor of the amplifier 26 is set so as to be between 20 dB. Specifically, by controlling the relays 31 and 32, the contact 3
The gain of the amplifier 26 is adjusted by turning on / off the switches 3 and 34.

In this embodiment, the case where the table look-up method is used as the method for setting the cutoff frequency and the amplification factor is described, but the constant setting method and the level matrix (the comparator is operated at the signal level). , A method of controlling with a relay or the like) or the like.

After the preprocessing is performed as described above, the main measurement operation shown in FIG. 5 is performed. In FIG. 5, P31 to P
The portion 36 is the same as P2 to P8 in FIG. However, since the cutoff frequency of the filter is set to the optimum value in the preprocessing of FIG. 4, it is unnecessary to set the cutoff frequency. Next, after P37, Fourier transform processing is performed. First, in P37, the sampled data of channel 1 (optical fiber sensor data) is multiplied by the Hanning window function of FIG. Then P
In 38, Fourier transform is performed on one block of 1024-point data. Then, in P39 and P40, the number of times of termination is judged, and this routine is repeated until AV = 4 times. Next, in P41, the AV count block (4
When the Fourier transform of (block) is completed, the average power spectrum | F _AV (ω) | ² of AV times is obtained. Then P
At 42, the maximum value of the power spectrum | F _AV (ω) | ² is obtained, and the frequency at that time is set to fp. Then P
At 43, the Fourier transform is similarly performed on the data of channel 2 (acceleration sensor data). Note that P43
Is shown in one part, the contents of which are described in P37.
Is the same as P40. Next, in P44, the average value of the results obtained in P43 is calculated. Next, after P45, the unbalance amount calculation is performed. Since two measurements are required to obtain the unbalance vector, 1 is added to the count C _NT in P45. Next, in P46, C _NT
If it is 2 and it is NO (that is, C _NT = 1)
Is the phase difference between the first and second channels at P47,
After storing the gain of channel 2 in the memory, return to the start and perform the second measurement. When C _NT is 2 in P46, in P48 the phase difference and gain of the first and second times,
That is, the unbalance vector is calculated from the first vector and the second vector, and the weight of the balancer added to the propeller shaft and the angle of the mounting position with the reflection tape 10 as the reference position are used as the liquid crystal display 34 and the printer 3.
Output to 5. Next, at P49, the counter C _NT = 0 is set, and a standby state for the next imbalance measurement is set.

Although not shown in the above embodiment, when the input signal judgments are all OK in the above-mentioned preprocessing results, the blue lamp is lit up, the measurement start is displayed, or the main measurement start switch is activated. You may comprise so that it may become. Further, in the above embodiment, an example of measuring the vibration of the first rotation is described, but the vibration of the second rotation and the third rotation can be similarly measured. Further, it can be applied not only to the propeller shaft but also to balancing other rotating bodies such as unbalance of tire rotation.

[0028]

As described above, in the present invention, the first and second filter amplifying means 51 and 53 and the judging means 5 whose cutoff frequency and gain can be adjusted.
6. The adjusting means 57 is provided, and the gain of the amplifier and the cutoff frequency of the filter are automatically adjusted to appropriate values based on the result of conversion by the Fourier transforming means 54. Therefore, the state of the detection signals of the rotation detection means (optical fiber sensor) and the vibration detection means (acceleration sensor) is automatically adjusted to a state suitable for measurement before the actual imbalance measurement is performed. The processing steps are greatly simplified, and the effect that accurate imbalance measurement can be easily performed in a short time is obtained.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram of an embodiment of the present invention.

FIG. 3 is a part of a flow chart showing the calculation contents of preprocessing in the embodiment of the present invention.

FIG. 4 is another part of the flowchart showing the calculation contents of the preprocessing in the embodiment of the present invention.

FIG. 5 is a main flowchart showing a calculation process of main measurement according to the embodiment of the present invention.

FIG. 6 is a flowchart showing a part of arithmetic processing in the embodiment of the present invention.

FIG. 7 is an example diagram of an acceleration sensor output waveform in frequency spectrum analysis.

FIG. 8 is a characteristic diagram of a weighting function and shows a Hanning window characteristic.

FIG. 9 is a characteristic diagram showing an example of a frequency spectrum distribution after Fourier transform.

FIG. 10 is a schematic diagram showing an example of a conventional method for measuring unbalance of a rotating body.

FIG. 11 is a diagram showing a rotation sensor signal and its Fourier transform result.

FIG. 12 is a diagram showing an acceleration sensor signal and a Fourier transform result thereof.

FIG. 13 is a diagram showing an unbalance vector.

[Explanation of symbols]

 1 ... Transmission extension 2 ... 1st propeller shaft 3 ... Center bearing 4 ... 2nd propeller shaft 5 ... Differential gears 6, 7, 8 ... Joint 10 ... Reflective tape 11 ... Optical fiber sensor 12 ... Optical fiber sensor amplifier 13 ... Acceleration sensor 14 ... Acceleration sensor amplifier 15 ... Unbalance calculation device 21 ... Acceleration sensor 22 ... Optical fiber sensor 23 ... Calculation unit 24, 25 ... Filter 26, 27 ... Amplifier 28 ... Liquid crystal display 29 ... Printer 30 ... Variable frequency oscillator 31 , 32 ... Relays 33, 34 ... Relay contacts 50 ... Rotation detecting means 51 ... First filter amplifying means 52 ... Vibration detecting means 53 ... Second filter amplifying means 54 ... Fourier transforming means 55 ... Unbalance calculating means 56 ... Determining means 57 ... Adjusting means 8 ... display means

Claims (1)

[Claims] 1. A rotation detecting means for outputting a signal according to a rotation speed of a rotating body, and a first filter amplifying means for filtering and amplifying an output of the rotation detecting means and capable of adjusting a cutoff frequency. A vibration detecting means which is attached to a supporting portion of the rotating body and detects vibration of the supporting portion; and a second filter which filters and amplifies an output of the vibration detecting means and which can adjust a cutoff frequency and a gain. Amplifying means, Fourier transforming means for Fourier transforming the signals of the rotation detecting means and the vibration detecting means through the first and second filter amplifying means, respectively, and the result of transforming by the Fourier transforming means The unbalance calculation means for calculating the unbalance amount and the unbalance position and the detection signal of the rotation detection means are converted into the Fourier transform signal. Detecting means for detecting the peak frequency of the frequency spectrum converted by the above, and determining whether or not the value obtained by converting the detection signal of the vibration detecting means by the Fourier transforming means is within a predetermined range; Adjustment for automatically adjusting the cutoff frequencies of the first and second filter amplifying means in accordance with the determination result and the gain of the second filter amplifying means in accordance with the determination result based on the determination result. An unbalance measuring device for a rotating body, comprising: a means for displaying the calculation result of the unbalance calculating means.