JPS63217245A - Dynamic balance testing machine - Google Patents

Abstract

PURPOSE:To improve measurement accuracy by providing a mixing circuit which mixes both detection signals of 1st and 2nd vibration detectors at a ratio corresponding to their output levels between the 1st and 2nd vibration detectors and an A/D converter. CONSTITUTION:A body 2 to be tested is rotated to detect vibrations caused by its unbalance by the 1st and 2nd vibration detectors 10a and 10b. The 1st and 2nd vibration detectors 10a and 10b output detection signals corresponding to the quantity of the unbalance, so those detection signals are both inputted to a mixing circuit 12. The mixing circuit 12 mixes both detection signals at the ratio corresponding to their output levels to make common component that the detection signals contain cancel each other. Consequently, only a component which contains the unnecessary unbalance quantity is led out of the mixing circuit 12. The signal from the mixing circuit 12 is digitized by an A/D converter 28, so the input signal at the time of A/D conversion is handled as a 100% effective signal. Consequently, the measurement accuracy of two-surface separate arithmetic processing can be improved.

Description

[Detailed description of the invention] (b) Industrial application fields The present invention relates to a dynamic balance tester.

(b) Prior art and its problems In general, there are two types of dynamic balance testing machines: hard type in which the bearing of the rotary drive shaft that rotates the specimen is fixed, and soft type in which the bearing is supported so that it can vibrate with a leaf spring or the like. There is something. In particular, the latter method has the advantage of providing highly accurate measurement results because of its high detection sensitivity.

Conventional 0. As shown in Fig. 2, in this type of soft type motion tester, vibration detectors d3, d are placed on the bearing that holds the rotational drive shaft a of the specimen. Each vibration detector d3, d detects the vibration generated as the rotation of
, and the detection signal output is connected to an A/D (not shown).
There is a device that is capable of performing so-called two-plane separation arithmetic processing in which the amount of unbalance in the two left and right planes S8 and S is determined based on these detection signal data after being digitized by a converter.

The two-plane separation calculation for determining the amount of imbalance between the two left and right surfaces S8 and S is based on the following principle. Now, P: Amount of unbalance on the left measuring surface Q: Amount of unbalance on the right measuring surface L: Detection signal of the left vibration detector R: Detection signal of the right vibration detector A: Amount of unbalance on the left measuring surface Influence coefficient B on the left measurement surface: Influence coefficient C that the amount of unbalance on the left measurement surface exerts on the right measurement surface C: Influence coefficient D that the amount of unbalance on the right measurement surface exerts on the left measurement surface D: Amount of unbalance on the right measurement surface Assuming that each position is given as a vector quantity as an influence coefficient on the right measurement surface,
The following relational expression holds true.

L=A-P+C-Q (1)I
N=B−P+D−Q (2) Therefore, a similar well-balanced specimen is prepared in advance, and a known weight giving a predetermined unbalance m P + is added to the left measurement surface of this specimen. In this case, the unbalance mQ on the right measurement surface is zero, so the left and right detection signals are L+,
If Rt, equations (1) and (2) are t, ,=A fist P.

It l= B '' P r , and the influence coefficient ASB is determined from this. Also, a predetermined unbalance mQ is placed on the right measurement surface of the specimen.

Add a known weight that gives . In this case, the unbalance mP on the left measurement surface is zero, so if the left and right detection signal ratio, force is 2, and R2, equations (1) and (2) are L *=
C-Q t Rt=D-Q l , and thereby the influence coefficients C and D are determined.

Therefore, if each influence coefficient ASB%C, D is determined in advance, then the actual specimen is rotated and each vibration detector dlq da detects the vibration on the left and right sides. If the signal R and R are measured, the amount of unbalance P between the left and right surfaces Sr and SR can be obtained from equations (1) and (2).

Q can be calculated.

By the way, like a thin-walled specimen, the distance between the bearings is a,
If the distance between the two surfaces of the specimen is extremely small compared to , the difference in the amount of unbalance between the left and right sides will be relatively small. Then, the output levels of the detection signals obtained by the left and right vibration detectors d2 and d become similar to each other, and the absolute output levels of the detection signals themselves are large (even though the difference between the two signal levels is small. Therefore, the proportion that can be used as a valid signal becomes extremely small, and if both detection signals are digitized as they are, the resolution of the A/D converter will be substantially reduced.

For example, if the output levels (current values) of the detection signals output from the left and right vibration detectors respectively have values of 100" and "99", the level difference between the two is "
1" (= 100-99). On the other hand, when these detection signals are digitized using an 8-bit A/D converter, the resolution is 1/256 of the full scale range. If the level "100" corresponds to the full scale range of the A/D converter, then the level difference "l" between both detection signals will be at most "2.0" after A/D conversion.
It only gives a level difference of 56". This is as if noise is mixed into the active ingredient, and the measurement accuracy is significantly lower than when calculating the amount of imbalance based only on the active ingredient. I will do it.

The present invention has been made in view of the above circumstances, and has been developed to improve the measurement accuracy of a soft-type movement tester that performs two-plane separation arithmetic processing compared to the conventional one. The purpose is to obtain measurements and results with sufficient accuracy even when the distance between the two surfaces of the specimen is small compared to the previous method.

(C) Means for Solving the Problems In order to achieve the above object, the present invention provides a method for detecting vibrations caused by rotation of a specimen by disposing the specimen on two different planes perpendicular to the rotational drive axis of the specimen. Between the first and second vibration detectors that respectively detect the circular vibration detectors and the A/D converter that digitizes each detection signal output of these circular vibration detectors, A mixing circuit is provided that mixes the signals at a ratio according to their output levels to cancel common components contained in the detection signals.

(d) Effect Therefore, in the dynamic balance tester of the present invention, by rotating the specimen, vibrations caused by the unbalance of the specimen are detected by the eleventh and second vibration detectors.

Since the first and second vibration detectors output respective detection signals corresponding to the amount of imbalance, both of these detection signals are input to the mixing circuit. The mixing circuit mixes both detection signals at a ratio according to their output levels to cancel common components contained in the detection signals. Therefore, only the component containing the necessary amount of unbalance is extracted from the mixing circuit. Then, the signal taken out from the mixing circuit is digitized by the A/D converter, so the input signal at the time of A/D conversion is
% can be treated as a valid signal. For this reason,
The measurement accuracy of the two-plane separation calculation process can be improved.

(E) Embodiment FIG. 1 is an overall configuration diagram of a dynamic balance tester of the present invention. In the same figure, the symbol ! 2 shows the entire motion testing machine, 2 is the specimen, 4 is the rotating drive shaft fixed to the specimen 2,
Bearings 6a and 6b hold the rotary drive shaft 4 at the left and right ends, respectively, and are supported so as to vibrate by springs 8a and 8b.

Reference numerals 10a and 10b are eleventh and second vibration detectors of a moving coil type, each of which detects vibrations of the bearing parts caused by unbalance of the specimen 2.

The circular vibration detectors 10a and IOb output analog detection signals proportional to the magnitude of the unbalance amount.

I2 is a mixing circuit that mixes both detection signals from the first and second vibration detectors 10a and IQb at a ratio according to their output levels to cancel common components contained in the detection signals. That is, this mixing circuit 12 includes four resistors R1, R3, R
3 and R4, and two pre-stage amplifiers 16a, 16b. First and second vibration detectors 10a, 10b are connected to the two input parts of the bridge circuit 14, respectively. Pre-stage amplifiers 16aS and 16b are respectively connected to the two outputs of the circuit.

In addition, the resistors (R8 and R4) or (R1 and R3) at opposite positions of the bridge circuit 14 are interlocked with each other, and when the value of one of the resistors R, (or Rt) is set, the resistor R4 at the opposite position (or R5) is also configured to be set to the same value.

Reference numeral 18 denotes a photocell for detecting the rotation of the rotary drive shaft 4, and a reference phase signal synchronized with the rotation of the specimen 2 is output from this photocell 18 by detecting a reflective mark etc. attached to the rotary drive shaft 4. Output. 20 is a waveform shaping circuit that shapes the reference phase signal from the photocell 18 into a pulse waveform; 22a and 22b are the pre-stage amplifiers 16a;
16b, respectively.

Further, 24a and 24b are first and second filter circuits that extract only the synchronous component synchronized with the rotation of the specimen 2 using the reference phase pulse given from the waveform shaping circuit 20 from the detection signal output amplified by the respective amplifiers 22a and 22b. It is.

26 is a multiplexer that alternately switches and inputs each output of the first and second filter circuits 24a and 24b, 28 is an A/D converter that digitizes each detection signal selected by the multiplexer 26, and 30 is an A/D converter. Based on the detection signal data digitized by the converter 28, the above-mentioned (1) and (
2) An arithmetic processing circuit that calculates the amount of unbalance between the left and right sides of the specimen 2 according to the formula; 32 is a display that displays the calculation results of the arithmetic processing circuit 30;

Next, the operation of the dynamic balance tester 1 of the present invention will be explained.

When the specimen 2 is rotated, vibrations caused by the amount of unbalance are transmitted to the first and second vibration detectors 10a and 10, respectively.
b, detected by the circular vibration detector 10a.

10b outputs detection signals corresponding to the left and right winter grass balance amounts and whose phases are shifted by 180° from each other. Both of these detection signals are then input to the mixing circuit 12.

Now, if the output level (current value) of the detection signal of the first vibration detector 10a and the detection signal of the second vibration detector tab have a ratio of, for example, 100:99, then The resistance of the bridge circuit 14 is adjusted so that the output signal becomes minimum. That is, R,=R,=9
9 to Ω, R, == R3=100 to Ω, and
If both the first and second pre-stage amplifiers 16a and 16b have an amplification factor of 100 times, the signal output of the first pre-stage amplifier 16a is (
100/99-99/100)X 1oO=2, 2nd
The signal output of the front stage amplifier 16b is (100/100-99
/99)X100=O.

Conversely, if the output level (current value) of the detection signal of the first vibration detector 10a and the detection signal of the second vibration detector tab have a ratio of, for example, 99:100, then The resistance of the bridge circuit 14 is adjusted so that the output signal becomes minimum.

That is, R, = R4 = 100Ω, R* = Rs
= 99Ω, then the first pre-stage amplifier 16a
The output signal is (10G/100-99/99)X 1
00601 Second pre-stage amplification W16b (7) Signal output Lt
(100/99-99/100)X100=2. Therefore, from the mixing circuit 12, only the components containing the necessary amount of unbalance are taken out.

Then, the signal taken out from the mixing circuit 12 is sent to the amplifier 2.
After being amplified by 2a and 22b, the filter circuit 24a12
4b, is digitized by an A/D converter 28 via a multiplexer 26. Therefore, amplifiers 22a, 22b
Assuming that a circuit with an amplification factor of about 50 times is used as the input signal, and that the full scale of the 8-bit A/D converter 28 corresponds to the input signal level "loo", in the above example, the mixing circuit I2 The level "2" signal extracted from the A/D converter 28 is treated as a 100% valid signal. Even if the amplification factor of the amplifiers 22a and 22b is 1, the A/D converter 28 has an amplification factor of 2/25.
6 = A signal corresponding to 5.12 times the resolution becomes effective, resulting in an improvement twice that of the conventional method. As a result, the measurement accuracy of the two-plane separation calculation process after A/D conversion is improved.

In this embodiment, the mixing circuit 12 is connected to the vibration detector 10.
Although it is provided between the aS 10b and the amplifiers 22a, 22b, it is not limited thereto as long as it is between the vibration detectors 10a, 10b and the A/D converter 28.

(f) Effects As described above, according to the present invention, only the essential active ingredients can be extracted by mixing the detection signals obtained from the left and right 11th and second vibration detectors in the mixing circuit. A/D conversion is possible with high resolution. This improves the measurement accuracy in the subsequent two-plane separation calculation process, making it possible for bearings to obtain sufficiently accurate measurement results even when the distance between the two surfaces of the specimen is small compared to the distance between them. Excellent effects such as

[Brief explanation of the drawing]

Figure 1 is an overall configuration diagram of the motion testing machine of the present invention, Figure 2
The figure is an explanatory diagram for performing a two-plane separation III calculation using a moving test machine. l...Dynamic balance tester, 2...Specimen, 10a. 10b...First and second vibration detectors, 12...Mixing circuit, 28...A/D converter, 3o... Arithmetic processing circuit.

Claims (3)

[Claims] (1) First and second vibration detectors that are arranged on two different planes perpendicular to the rotational drive axis of the specimen and detect vibrations accompanying the rotation of the specimen, and the first and second vibrations. An A/D converter that digitizes each detection signal output of the detector, and a two-plane separation unit that calculates the amount of unbalance on the left and right sides of the specimen based on the detection signal data converted by the A/D converter. In a motion balance testing machine equipped with an arithmetic processing circuit that performs arithmetic processing, both detection signals from the first and second vibration detectors are provided between the first and second vibration detectors and the A/D converter. A motion balance tester characterized in that it is provided with a mixing circuit that cancels common components contained in detection signals by mixing them at a ratio according to their output levels. (2) The dynamic balance tester according to claim 1, wherein the mixing circuit includes a bridge circuit combining resistors. (3) The dynamic balance tester according to claim 1, wherein the mixing circuit includes a resistor and a differential amplifier.