JPH0810173B2 - Dynamic balance tester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a dynamic balance testing machine.

(B) Conventional technology and its problems In general, the dynamic balance tester is of a hard type in which the bearing of the rotary drive shaft for rotating the test piece is fixed, and a soft type in which the bearing is vibratably supported by a leaf spring or the like. There are things. In particular, the latter one has an advantage that an accurate measurement result can be obtained because the detection sensitivity is high.

In a conventional soft type dynamic balance tester of this type, as shown in FIG. 2, vibration detectors d ₁ and d ₂ are arranged on a bearing that holds a rotary drive shaft a of a test piece b, and The vibrations generated by the rotation of b are detected by the vibration detectors d ₁ and d ₂ , and the detection signal outputs are digitized by A / D converters (not shown), and then based on these detection signal data. There is a device which is capable of performing a so-called two-face separation calculation process in which the amount of unbalance between the left and right faces s ₁ and s ₂ is obtained.

The above-mentioned two-side separation operation for obtaining the unbalance amount between the two left and right surfaces s ₁ and s ₂ is based on the following principle. Now, P: the amount of unbalance on the left measuring surface Q: amount of the unbalance on the right measuring surface L: Detection signal of the left vibration detector R: Detection signal of the right vibration detector A: The unbalance amount of the left measuring surface Influence coefficient on left measuring surface B: Influence coefficient of unbalance amount of left measuring surface on right side surface C: Influence coefficient of unbalance amount of right side surface on left measuring surface D: Unbalance amount of right side surface Assuming that each value is given as a vector quantity as the coefficient of influence of the value on the right-side constant surface, the following relational expression holds.

L = A ・ P + C ・ Q (1) R = B ・ P + D ・ Q (2) Therefore, prepare a similar balanced test sample in advance, and set a predetermined unbalance amount P _{1 on} the left measurement surface of this test sample. Add a known weight to give In this case, the unbalance amount Q on the right measurement surface is zero, so the left and right detection signals are L ₁ , R ₁
Then, the equations (1) and (2) are L ₁ = A · P ₁ R ₁ = B · P ₁ , and the influence coefficients A and B can be obtained. In addition, a known weight that gives a predetermined unbalance amount Q ₁ is added to the right measurement surface of the test piece. In this case, the unbalance amount P on the left measurement surface
Is zero, so if the left and right detection signal outputs are L ₂ and R ₂ , equations (1) and (2) are L ₂ = C · Q ₁ R ₂ = D · Q ₁ C and D are obtained.

Therefore, if the respective influence coefficients A, B, C and D are obtained in advance, then the actual test piece b is rotated and the vibration detectors d ₁ and d ₂ detect the vibrations on the left and right sides. If each detection signal L, R is measured, from the equations (1) and (2),
The unbalance amounts P and Q of s ₁ and s ₂ can be calculated.

By the way, the distance between bearings l ₁
When the distance l ₂ between the two surfaces of the test piece is extremely small compared to, the left of the left and right unbalance amount becomes relatively small. Then, the output levels of the detection signals obtained by the left and right vibration detectors d ₁ and d ₂ become close to each other, and the difference between the two signal levels is small even if the absolute output level of the detection signal is large. For this reason, the ratio that can be used as an effective signal becomes extremely small, and when both detection signals are directly digitized, the resolution of the A / D converter is substantially reduced.

For example, if the output levels (current values) of the detection signals output from the left and right vibration detectors have values of "100" and "99", for example, 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 detection signal level is "100" and it corresponds to the full-scale range of the A / D converter, the level difference between both detection signals is "1".
Gives a level difference of at most "2.56" after A / D conversion. This is a state in which noise is mixed in the effective component, and the measurement accuracy is significantly reduced compared to the case where the unbalance amount is calculated based on only the effective component.

The present invention has been made in view of such circumstances, in a soft type dynamic balance tester for performing two-sided separation arithmetic processing, to improve the measurement accuracy compared to the conventional,
It is an object of the present invention to obtain a measurement result with sufficient accuracy even when the distance between the two surfaces of the test piece is smaller than the distance between the bearings.

(C) Means for Solving the Problems In order to achieve the above-mentioned object, the present invention is arranged on two different vertical planes of the rotational drive shaft of the test piece, and the vibrations associated with the rotation of the test piece are respectively generated. Both detection signals from the first and second vibration detectors are placed between the first and second vibration detectors to be detected and the A / D converter which digitizes each detection signal output of these both vibration detectors. A mixing circuit is provided for mixing and canceling out the common component contained in the detection signal to take out only the signal component containing the required unbalance amount. This mixing circuit connects four resistors in a bridge shape and The resistors located on opposite sides are configured to exhibit the same resistance value in conjunction with each other, and among the connection points of the resistors of this mixed circuit, a pair of connection points facing each other are used to detect the first and second vibrations. To the A / D converter and the remaining pair of connection points It is provided as an output end to the side.

(D) Operation Therefore, in the dynamic balance tester of the present invention, when the test piece is rotated, the vibrations caused by the imbalance of the test piece are detected by the first and second vibration detectors, respectively. Since the first and second vibration detectors output respective detection signals corresponding to the unbalanced amount, these both detection signals are input to the mixing circuit. The mixing circuit mixes the two detection signals to cancel the common component contained in the detection signal and takes out only the signal component containing the required amount of imbalance. Then, since the signal taken out from the mixing circuit is digitized by the A / D converter, the input signal at the time of A / D conversion can be treated as a 100% effective signal. Therefore, the measurement accuracy of the two-side separation calculation process can be improved.

(E) Example FIG. 1 is an overall configuration diagram of a dynamic balance testing machine of the present invention. In the figure, reference numeral 1 represents the whole of the dynamic balance testing machine, 2 is a specimen, 4 is a rotary drive shaft fixed to the specimen 2, and 6a and 6b are bearings for holding the rotary drive shaft 4 at the left and right ends, respectively. And, it is supported by the springs 8a and 8b so that it can vibrate. Reference numerals 10a and 10b denote first and second moving coil type vibration detectors for detecting the vibrations of the bearing portions caused by the imbalance of the test piece 2. Both of the vibration detectors 10a and 10b output analog detection signals proportional to the magnitude of the unbalance amount.

Reference numeral 12 is a mixing circuit for mixing both detection signals from the first and second vibration detectors 10a and 10b to cancel a common component contained in the detection signal and to extract only a signal component including a necessary unbalanced amount. is there. That is, the mixing circuit 12 includes a circuit 14 in which _four resistors R ₁ , R ₂ , R ₃ and R ₄ are combined in a bridge shape,
It is configured with two front-stage amplifiers 16a and 16b,
Of the connection points of the resistors R _{1 to} R ₄ , a pair of connection points facing each other serve as input terminals for the first and second vibration detectors 10 a, 1 respectively.
0b individually, and the remaining pair of connection points is A / D
Pre-stage amplifiers 16a and 16b are connected as output terminals to the converter 28 side, respectively. Further, the resistors (R ₁ and R ₄ ) or (R ₂ and R ₃ ) at the opposite positions of the circuit 14 are interlocked with each other,
When the value of _one resistance R ₁ (or R ₂ ) is set, the resistance R ₄ (or R ₃ ) at the opposite position is also set to the same value.

Reference numeral 18 denotes a photocell that detects the rotation of the rotary drive shaft 4. The photocell 18 detects a reflection mark or the like attached to the rotary drive shaft 4 to generate a reference position signal that is synchronized with the rotation of the sample 2. Is output. Reference numeral 20 is a waveform shaping circuit for shaping the reference phase signal from the photocell 18 into a pulse waveform, and 22a and 22b are first and second amplifiers respectively connected to the pre-stage amplifiers 16a and 16b. Also, 24a and 24b are waveform shaping circuits for the detection signals amplified by the amplifiers 22a and 22b.
The first and second filter circuits take out only the synchronous component synchronized with the rotation of the sample 2 by the reference phase pulse given from 20.

26 is a multiplexer that alternately switches and inputs the outputs 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 An arithmetic processing circuit for calculating the amount of unbalance between the two left and right surfaces of the sample 2 according to the above-mentioned equations (1) and (2) based on the detection signal data digitized by the converter 28.
Reference numeral 32 is a display for displaying the calculation result of the calculation processing circuit 30.

Next, the operation of the dynamic balance testing machine 1 of the present invention will be described.

When the test piece 2 is rotated, the vibrations caused by the unbalance amount are detected by the first and second vibration detectors 10a and 10b, respectively, and both vibration detectors 10a and 10b correspond to the left and right unbalance amounts. , And the detection signals whose phases are shifted from each other by 180 ° are output. Then, both of these detection signals are input to the mixing circuit 12.

That is, since the left and right vibration detectors 10a and 10b are out of phase with each other by 180 °, the unbalance amounts of the two left and right surfaces are detected by reversing positive and negative. Therefore, assuming that the output levels (voltage values) of the detection signals from the left and right vibration detectors 10a and 10b have a ratio of 100: 99, when V ₀ is the unit reference voltage, the mixing circuit 12
The signals having the output levels of 100V ₀ and −99V ₀ are input to each. Here, the resistance of the bridge circuit 14 is adjusted so that the output signal from the second pre-stage amplifier 16b is minimized. That is, when R ₁ = R ₄ = 99KΩ and R ₂ = R ₃ = 100KΩ are set, the signal output to the first pre-stage amplifier 16a is 1V ₀ ,
The signal output to the pre-stage amplifier 16b becomes 0.

On the contrary, the output level (voltage value) of the detection signal of the first vibration detector 10a and the detection signal of the second vibration detector 10b is, for example, 9
Assuming a ratio of 9: 100, the mixing circuit 12 has 99V
Signals with output levels of ₀ and -100V ₀ are input respectively. Here, the resistance of the bridge circuit 14 is adjusted so that the output signal from the first pre-stage amplifier 16a is minimized. That is, if R ₁ = R ₄ = 100KΩ and R ₂ = R ₃ = 99KΩ are set,
The output signal to the first pre-stage amplifier 16a is 0, the second pre-stage amplifier 1
The signal output to 6b is -1V ₀ . Therefore, the mixing circuit 1
From 2, only the components containing the required unbalance are taken out.

Then, the signal extracted from the mixing circuit 12 is amplified by the amplifier 22.
After being amplified by a and 22b, it is digitized by the A / D converter 28 via the filter circuits 24a and 24b and the multiplexer 26.
Therefore, assuming that the amplifiers 22a and 22b have an amplification factor of about 100 / V ₀ times, and the full scale of the 8-bit A / D converter 28 corresponds to "100" of the input signal level. In the above example, the signal 1V ₀ taken out from the mixing circuit 12 is treated as a 100% effective signal in the A / D converter 28. In the arithmetic processing circuit 30, the A /
Based on the data taken in through the D converter 28, the following arithmetic processing is performed to calculate the unbalanced amounts P and Q of the left and right two surfaces s ₁ and s ₂ .

For example, in the above example, for the mixing circuit 12,
When signals having output levels of 100V ₀ and −99V ₀ are input, the resistance of the bridge circuit 14 is set so that the output signal from the second pre-stage amplifier 16b becomes a minimum, R ₁ = R ₄ = 99.
When KΩ and R ₂ = R ₃ = 100KΩ are set, the output signal of the first front-stage amplifier 16a is 1V ₀ , and the second front-stage amplifier 16b is
Since the output signal of is 0, using the above equations (1) and (2), 1V ₀ = A · P + C · Q 0 = B · P + D · Q, and by solving this binary simultaneous linear equation, The unbalance amounts P and Q of the _two right and left surfaces s ₁ and s ₂ of the sample ₂ are calculated.

Similarly, in the above example, for the mixing circuit 12, 99
The resistance of the bridge circuit 14 is set to R ₁ = R ₄ = 100K so that the output signal from the first pre-stage amplifier 16a becomes minimum when signals having output levels of V ₀ and −100V ₀ are input.
When set to Ω and R ₂ = R ₃ = 99KΩ respectively,
The output signal of the front-stage amplifier 16a is 0, and the output signal of the second front-stage amplifier 16b is 1V _0. Therefore, using the above equations (1) and (2), 0 = A · P + C · Q 1V ₀ = B · P + D・ Q and the unbalanced amounts P and L of the left and right two surfaces s ₁ and s ₂ of the specimen 2 are calculated by solving this two-dimensional simultaneous linear equation.

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

(F) Effect As described above, according to the present invention, since the detection signals obtained from the left and right first and second vibration detectors are mixed by the mixing circuit, only the originally required effective component can be taken out. A / D conversion is possible with sufficient resolution. Therefore, the measurement accuracy in the subsequent two-side separation calculation process improves, so that even if the distance between the two surfaces of the specimen is small compared to the distance between the bearings, it is possible to obtain a measurement result with sufficient accuracy. Excellent effects such as

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a dynamic balance testing machine of the present invention, and FIG.
The figure is an explanatory diagram for performing the two-side separation calculation of the dynamic balance testing machine. 1 ... Dynamic balance tester, 2 ... Specimen, 10a, 10b ...
First and second vibration detectors, 12 ... Mixing circuit, 28 ... A / D converter, 30 ... Arithmetic processing circuit.

Claims (1)

[Claims] 1. A first vibration detector and a second vibration detector which are arranged on two different vertical planes of a rotary drive shaft of the specimen and detect vibrations associated with the rotation of the specimen, and the first and second vibration detectors. A / D converter that digitizes each detection signal output of the detector, and calculates the amount of inconsistency on the left and right sides of the specimen based on the detection signal data digitized by this A / D converter In a dynamic balance testing machine equipped with an arithmetic processing circuit for performing two-sided separation arithmetic processing, the first and second vibration detectors are provided between the first and second vibration detectors and the A / D converter. A mixing circuit is provided for mixing the two detection signals and canceling out the common component contained in the detection signal so as to take out only the signal component containing the necessary unbalance amount. When connected, the resistances on the opposite sides work together to maintain the same resistance. As shown in the figure, among the connection points of the resistors of this mixed circuit, a pair of connection points facing each other are individually connected to the first and second vibration detectors, and the remaining pair of connection points are connected. A dynamic balance testing machine characterized by being provided as an output end to the A / D converter side.