JPH06103239B2 - Dynamic balance tester - Google Patents

Description

The present invention relates to a hard type dynamic balance tester having a bearing structure with high rigidity.

B. Conventional Technology In a conventional hard type dynamic balance testing machine, a piezoelectric element type pickup (load cell etc.) was used as an imbalance detector (pickup).

C. Problems to be Solved by the Invention However, the sensitivity of the piezoelectric element type pick-up is 10%.
0 to 1000pC / G (pC is pico-coulomb, G is weight acceleration), and the output impedance is very high.
Ω), its output signal is very weak (μ
V order).

Further, the piezoelectric element type pickup has a characteristic that the frequency response area is very wide, but the frequency area necessary for the hard type dynamic balance tester is limited to the low frequency area. Since the pickup also detects high-frequency signal components that are not necessary for the test, the level of noise, which is miscellaneous vibration transmitted from the bearing of the bearing and the foundation of the testing machine, is high.

Due to the above synergies, in the conventional dynamic balance testing machine using the piezoelectric element type pickup as the unbalance detector,
There was a problem that the S / N ratio was bad.

This invention is an S / N for a hard type dynamic balance testing machine.
The aim is to improve the ratio.

D. Means for Solving the Problems The present invention has the following configuration in order to achieve such an object.

That is, the present invention is a hard type dynamic balance tester having a bearing structure with high rigidity, in which the left and right bearings that rotatably support the shaft portion of the test body are supported by springs, and the speed proportional to both bearings. Type vibration detector, and means for triple integrating the output signal of the speed proportional type vibration detector with respect to time, and one of the two preset bearings and the two balance correction surfaces of the test body. A means for calculating the dynamic imbalance from the distance, the distance between the two bearings, the value of the triple integral, and the spring coefficient is provided.

E. Operation The operation of the configuration of the present invention will be described, including comparison with the conventional example.

Based on FIG. 3, an arithmetic expression for the correction surface separation is obtained.

In FIG. 3, 1 is a test body, 2 _L and 2 _R are left and right bearings that rotatably support the shaft of the test body 1, 3 _L and 3 _R are shaft bearings 2 _L ,
2 _R is a highly rigid spring that supports _R.

When the unbalanced mass exists in the test body 1, a centrifugal force is generated in the test body 1 as the test body 1 rotates, and the force resulting from this centrifugal force acts on the bearings 2 _L and 2 _R and the spring 3 _L. , 3 against _R bearing 2 _L, 2 _R vibrates.

In the past, the force acting on the bearings 2 _L and 2 _R was detected by the piezoelectric element type pickup which is the force detection type unbalance detector, whereas in the present invention, the bearings 2 _L and 2 _R are caused by the centrifugal force. _The vibration occurring in _R is detected by a velocity proportional type vibration detector (for example, a moving coil type pickup: not shown).

In the left and right balance correction L, R on the test body 1,
Unbalanced masses at the corrected radii _L and _R , respectively
It is assumed that m _L and m _R exist. The spring constants of the springs 3 _L and 3 _R are k _L and k _R , respectively, and the balance correction surface L on the left side and the balance on the right side from the center of the bearing 2 _{L on} the left side along the direction of the rotation axis of the test body 1. Axial distance on the correction surface R
Let a and b be the distance between the centers of the left and right bearings 2 _L and 2 _R (bearing distance) and c.

The test body 1 when rotating at an angular velocity omega, the left and right balance modified surface L, and the centrifugal force acting on the position of the R, respectively _L,
R , the forces acting on the positions of the left and right bearings 2, respectively
_{Let L} and _R.

Centrifugal forces _L and _R acting on the left and right balance correction surfaces _L and _{R
Let L} = m _{L L} ω ² …… F _R = m _{R R} ω ² …… and the left and right bearings 2 _L and 2 _R have amplitude displacements _L and _R , the left and right bearings 2 _L and 2 _R force _{L, R} is to _{receive, L = k L L = k} L ...... R = k R R = k R ...... However, in this case, there is as k _L = k _R = k.

Left and right movement disproportionately _{L, R is, L = m L L ...... R} = m R R ......, from equation ,, wherein _each of ^{_{L = L ω 2 ...... R =}} R ω 2 ...... statics from the balance conditions of _force, L ₊ L ₊ R ₊ a R = 0 ...... moment in the left balancing plane L around the equilibrium _{conditions, L a- R (b-a} ) + R (c-a) = 0 ... Also, from the condition of the moment balance around the correction surface R on the right side, _L b + _R (c−b) _−L (b−a) = 0 ,, _L - If ^{_{(b-a) R ω 2}} + (c-a) and _k R = 0 ...... ,,, expression into _{equation, bk L + (c-b} ) k R - (b-a) L ω ² = 0 ..., If _L and _R are calculated from the equation, The moving coil type pickup is a velocity proportional type vibration detector and generates voltages _{L 1} and _{R 2} proportional to the velocity of the coil and thus to the angular velocity ω. That is, _L ∝ _L ω ...... _R ∝ _R ω ...... Here, the constants A, B, C, D are When the voltage _{L, R} from ,, expression ,, _wherein expressed as _{L = (A L + B R} ) ω 3 ...... R = (C L + D R) ω 3 .......

That is, the generated voltages _L , _{R of} the velocity proportional vibration detector
Is proportional to the simultaneous linear function of the dynamic imbalances _{L 1} and _{R 2} ,
Moreover, it is proportional to the cube of the angular velocity ω.

Here, the voltage _L, and the _R expressed by sin function, triple _{E L = E LO sin (ωt} -φ L) E R = E RO sin (ωt-φ R) These E _L, the E _R for the time t When integrated, And its magnitude is 1 / ω ^{3 of the} original.

Therefore, ω ³ is eliminated from the equation, Becomes From equation, U _L, when obtaining the U _R, That is, the output voltage from the left and right speed proportional vibration detectors
_L, moving left and right on the basis of a value obtained by triple integrating _R disproportionately _L, can be measured _R.

On the other hand, in the case of the piezoelectric element type pickup, the generated voltage is proportional to the dynamic imbalance amount m and ω ^2, and the integral is 2
It becomes a multiple integral.

Since the integration extends the input signal from the velocity proportional vibration detector in time, the noise component is removed by the integration.

This invention is a speed type proportional vibration detector (moving coil type pickup) in a hard type dynamic balance tester.
Therefore, the generated voltage has a characteristic that the generated voltage is proportional to ω ^3, and triple integration is performed due to this. However, triple integration means that the piezoelectric element type pickup This means that the noise suppression effect is superior by one integration as compared with the double integration in the case.

The equation is equivalent to the equation described later, but a detailed method of obtaining the dynamic imbalances _{L 1} and _{R 2} will be described below.

,,, Expression is substituted into Expression, Expression
_{When L} and _R are calculated, In _{formula, L,} both _{R L,} but the coefficient applied to _R is called a influence coefficient, wherein it should be noted _that, for the ^{_{L / ω 2, R / ω}} 2 of 1 / omega ² is As described above, _L (∝ _L ω), _R (∝ _R
ω) is eliminated by triple integration, and the spring constant k (= k _L = k _R ) of the influence coefficient is known. Therefore, in the hard type dynamic balance tester, the unbalance detector is used. Even if a velocity proportional vibration detector is used as a constant, all constants that come into the correction surface separation calculation are dimensions (distances a, b,
It means that it is only c).

The distances a, b, and c can be easily obtained without driving the dynamic balance tester, so after all, the dynamic balance tester is driven and the left and right amplitude displacements are detected by the left and right velocity proportional vibration detectors.
_{Let L} and _R be the generated voltages _{L 1} and
It is possible to obtain the left and right dynamic imbalances _{L 1} and _{R 2} by measuring from _{R and} from the amplitude displacements _{L 1} and _R 2 by the correction surface separation calculation based on the equation.

In the soft type dynamic balance tester, there are not only dimensions but also mass, moment of inertia, etc. as constants that come into the correction surface separation calculation. Therefore, each time the test body changes, a pre-driving using a trial weight is performed. However, in the case of the present invention, no pre-driving is necessary.

Next, let us look at the relationship between the natural frequency of the vibration system and the test rotation speed.

The mass of the test body 1 is M, the masses (parasitic masses) on the springs 3 _L and 3 _R other than the test body 1 such as the bearings 2 _L and 2 _R , and the vibration platform are _Mo , the spring constant is k, and the unbalanced size is large. If the eccentric center of gravity distance that is another expression of E is e, the centrifugal force F when the test body 1 is rotated at the angular velocity ω is F = Meω ² However, the eccentric center of gravity distance e is the unbalanced mass m, If the unbalance radius is r, Is.

Bearing amplitude at this time x _o (amplitude displacement x = x _o · sin (ωt−
θ) is the equation of motion, the damping coefficient is ρ, And ask for a solution. Note that ω _c is the natural frequency of this vibration system, and ζ is damping.

When the disproportionate detector is a soft type, ω ≧ 3ω _c
Holds in the domain of Is approximated by In the case of the hard type, ω ≦ ω _c
It holds in the region of / 3, and at this time, the formula is Is approximated by

As described above, in the case of the hard type, the piezoelectric element type pickup has a wide frequency range of several tens to 100 times the natural frequency ω _c , although the frequency range used is limited to the low frequency range. The noise level was high because it responded in the region.

On the other hand, the velocity proportional vibration detector of the present invention has a low noise level because its frequency response region is about the natural frequency ω _c .

Further, the moving coil type pickup, which is a velocity proportional type vibration detector, can have its sensitivity easily increased by increasing the magnetic flux density of the permanent magnet, increasing the number of turns of the coil, and the like. Therefore, the output impedance can be made sufficiently low (10 ^-3 to 10 ^-4 times) (KΩ order) and the signal level can be increased (V order) as compared with the piezoelectric element type pickup.

As described above, the present invention uses a velocity proportional vibration detector such as a moving coil type pickup as a disproportionate detector in a hard type dynamic balance tester, and therefore, compared with a conventional piezoelectric element type pickup. As a result, the output impedance is low and the frequency response region is narrow, so the S / N ratio is improved.

F. Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of a dynamic balance testing machine according to an embodiment of the present invention.

Left and right bearings 2 _L and 2 _R , which rotatably support the shaft of the test body 1 which is rotated by a motor via a belt or the like, are supported by highly rigid springs 3 _L and 3 _R. The vibration acting on the bearings 2 _L and 2 _R due to the centrifugal force generated in the test body 1 due to imbalance due to the rotation of the test body 1 is a moving coil type pickup 4 _L as a velocity proportional type vibration detector. 4 _R is configured to detect.

Output signal _{L of} moving coil type pickup 4 _L , 4 _R
= (A _L + B _R ) ω ³ , _R = (C _L + D _R )
ω ³ is amplified by the preamplifier 5, and the output signal of the preamplifier 5 is integrator 6a and a double integrator with a bandpass filter.
It is configured to perform triple integration with respect to time by 6b and. By this triple integration, 1 / ω ³ is obtained, the component of the angular velocity ω is eliminated from the signal, the component relating only to the dynamic imbalances _{L 1} and _{R 2} is extracted, and the noise is removed.

The photo mark 7 on the surface of the test body 1
Photo sensor (reference phase detector) 8 that detects each rotation
Is input to the frequency inverse converter 9, and the frequency inverse converter 9 uses a frequency signal inversely proportional to the frequency of the pulse output for each phase in which the unbalanced mass exists as a chopper signal, and the Output to the multiple integrator 6b and the synchronous rectifier 10 at the next stage.

Then, the chopper signal is extracted from the pickup signal input to the double integrator 6b with a bandpass filter and the synchronous rectifier 10 to extract a frequency component synchronized with the rotation speed of the test body 1, that is, a dynamic imbalance signal, and the left side balance correction is performed. Surface L
The X component and the Y component which are perpendicular to each other and the X component and the Y component which are related to the right balance correction surface R are output from the synchronous rectifier 10 as a DC voltage.

These left and right X and Y components are A / with a multiplexer
A can be switched cyclically by the D converter 11
/ D converted, the digital data is introduced into the CPU 12 in the microcomputer.

Connected to the CPU 12 are a memory 13 including a ROM storing a program and a RAM storing various data, a display unit 14 for displaying measurement conditions and measurement results, and a keyboard 15 for inputting measurement conditions and measurement data processing methods. Has been done.

The bearing / balance correction surface distances a, b, the bearing distance c, and the correction radii r _L , r _R are preset in the memory 13 via the keyboard 15.

The CPU 12 corrects the dynamic unbalance amounts _{L 1} and _{R 2} , that is, the unbalanced masses m _L and m _R and the unbalanced angle φ _L , from these preset data and the introduced two sets of the X component and the Y component. φ _R is calculated by calculation, and the result is stored in the memory 13 and displayed on the display unit 14.

Note that FIG. 2 shows the details of the circuit portion for the pickup signal on either the left or right side of the double integrator 6b with the bandpass filter in FIG.

A switching transistor T ₁ is connected to the input side of an integrator 6b ₁ composed of an operational amplifier OP ₁ , a capacitor C ₁ and a resistor R _1, and an input side of an integrator 6b ₂ composed of an operational amplifier OP ₂ , a capacitor C ₂ and a resistor R _2. The integrator 6b ₁ and the integrator 6b ₂ are connected via the connected switching transistor T _2, and the inverter 6b ₃ including the operational amplifier OP ₃ and the resistors R ₃ and R ₄ is connected to the output stage of the inverter 6b ₃ . The output is positively fed back to the drain of the switching transistor T ₁ .

Integrator 6a to 1 at the source of switching transistor T ₂
The signal that has been integrated twice is input, and the chopper signal from the frequency inverse converter 9 is input to the gates of the switching transistors T ₁ and T ₂ .

When the time constants of the integrators 6b ₁ and 6b ₂ match the measurement frequency, the switching transistors T ₁ and T ₂ repeat ON / OFF with a duty factor inversely proportional to the measurement frequency.

Although the integrator is configured by hardware in the above embodiment, it can be implemented by software by a program.

G. Effects of the Invention According to this invention, the following effects are exhibited.

That is, in a hard type dynamic balance tester, a velocity proportional vibration detector such as a moving coil type pickup is used as an unbalance detector, so the output impedance can be made lower than that of a conventional piezoelectric element type pickup. Moreover, since the frequency response region is narrow, the S / N ratio can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a dynamic balance tester according to an embodiment of the present invention, FIG. 2 is a circuit configuration diagram of a double integrator with a bandpass filter, and FIG. 3 is a principle diagram for explaining the operation of the present invention. ,. 1… Test body 2 _L , 2 _R … Bearing 3 _L , 3 _R … Spring 4 _L , 4 _R … Moving coil type pickup (speed proportional vibration detector) 6a… Integrator 6b… Double integrator with bandpass filter (6a, 6b) ... Triple integration means 15 ... Display unit 16 ... Keyboard a, b ... Bearing / balance correction surface distance c ... Bearing distance r _L , r _R ... Correction radius

Claims (1)

[Claims] 1. A hard type dynamic balance testing machine having a bearing structure with high rigidity, wherein left and right bearings that rotatably support a shaft portion of a test body are supported by springs, and both of these bearings are speed proportional type. A vibration detector is provided, and means for triple integrating the output signal of the velocity proportional vibration detector with respect to time,
Means for calculating the dynamic imbalance from the distance between one of the preset bearings and the two balance correction surfaces of the test body, the distance between the bearings, the value of the triple integral, and the spring coefficient. A dynamic balance tester characterized by having and.