JPS6151252B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for measuring dynamic spring constants of test pieces such as vulcanized rubber.

Generally, as a method for testing the dynamic properties of vulcanized rubber,
According to the method described in "JIS K6394-1976," the load waveform and deflection waveform are measured and recorded, the load amplitude and deflection amplitude, and the phase angle of load and deflection are measured, and the absolute spring constant is calculated using a predetermined formula. , calculate the storage spring constant, loss spring constant and loss coefficient.

Specifically, there are three types of measuring devices that have been conventionally used to carry out the above method, as shown in FIGS. 1, 2, and 3, respectively.

In the measuring device shown in FIG. 1, a lower pedestal b is fixed on a foundation a, and a main body d of a vibration generator c is erected.
With the vibration table e facing upward, a test piece g is placed on it via a test piece mounting plate f, and a load detector h is attached via the test piece mounting plate f, while the above-mentioned main body d
At the upper end, an upper pedestal i is fixed and protrudes left and right, and two cylindrical columns j and j are erected on the upper pedestal i, and a horizontal bar k is vertically connected to the top of the cylindrical columns j and j as a bridge. The load detector h is mounted vertically on the horizontal bar k, and the test piece g and the load detector h are clamped between the horizontal bar k and the lower upper pedestal i. . In addition, LVDT for deflection measurement
(Linear VariabIe DifferentiaI Transformer)
The fixed side of m is fixed to the upper surface of the upper pedestal i, and detects the displacement of the vibration table e.

In the measuring device shown in FIG. 2, a rectangular frame-shaped pedestal n is erected on a foundation a, a vibration generator pedestal r is fixed to the bottom p of the pedestal n, and the vibration generator q is connected to air springs s, A vibrating table e is supported by the pedestal r via s and faces upward, and a test piece g, a load detector h, etc. are sandwiched between it and the upper side t of a pedestal n. The fixed side of the LVDT m for deflection measurement is fixed to the central portion of the upper side t near the attachment point of the load detector h, and detects the displacement of the vibration table e. Note that u is a vertical position setting mechanism that can adjust the vertical position according to the dimensions of the test piece g.

Next, in the conventional measuring device shown in FIG. 3, a vibration generator pedestal r is fixed to a foundation a, and a gate-shaped mount
is directly connected to the vibration generator main body d, and the pedestal n and the vibration generator q are supported by the pedestal r via an air spring s. The fixed side of the LVDT m for deflection measurement is the load detector h located at the center of the upper side t of the mount n.
It is fixed nearby. Furthermore, an acceleration detector v for a masking cell is attached to the load detector h.

By the way, in any of the above-mentioned devices shown in Fig. 1, Fig. 2, and Fig. 3, when viewed from the perspective of vibration transmission of the mechanical structure, resonance of the pedestal, reaction force of the vibration generator, and lateral vibration of the vibration table are observed. The error was large due to error factors such as directional vibration, and measurement with sufficiently high accuracy was impossible.

In particular, there has been an increasing demand to accurately measure dynamic spring constants even in high frequency ranges, such as those of anti-vibration rubber for passenger car engines. The method of reading from the waveform is no longer sufficient, and recently a method has been developed and researched in which the dynamic spring constant is measured by inputting the load signal and deflection signal into a digital transfer function measuring device. The accuracy of this digital transfer function measuring device is generally less than 1% for amplitude and less than 1 degree for phase. Therefore, the accuracy of the dynamic spring constant measuring device is required to be equal to or higher than that, and conventional dynamic spring constant measuring devices such as those illustrated in Figs. 1 to 3 above cannot meet this demand. Nakatsuta.

Here, error factors of the conventional measuring device illustrated in FIGS. 1 to 3 described above will be analyzed.

() Resonance of the mount The force that excites the resonance of the mount is the force applied to the test piece. In both Figures 1, 2, and 3, the load detector h moves not only at the resonant frequency of the pedestal, but also at nearby frequencies, so (mass of the load detector + mass of the test mounting plate on the load detector side) An additional output corresponding to the product of (acceleration of the load detector) is output from the load detector. In Figure 3, it is easy to think that this extra output is detected by the acceleration detector v for the mask canceller and canceled by the electric circuit, but in reality, in the resonance state, the load detector h and the mounting plate f are completely disconnected. Since it is a rigid body and does not vibrate only in the axial direction, cancellation is not possible.
In addition, in the methods shown in Figures 2 and 3, the fixed side of the LVDT m for deflection measurement is fixed to the top of the pedestal n, but when the pedestal n resonates, the axis of the test mounting plate f on the load detector side Since the vibration of the center and the vibration of the fixed point on the top of the frame are different, this causes an error in the deflection measurement.

() Reaction force of the vibration generator The reaction force of the vibration generator is equal in magnitude and opposite in direction to the excitation force of the vibration generator. Assume that the mass of the shaking table is 7Kg, the mass of the test piece mounting plate is 3Kg, the dynamic spring constant of the test piece is 10Kg/mm, and the test piece is 0.1
If a deflection amplitude of mm is applied, the force applied to the specimen is constant regardless of the test diaphragm, and is 1 Kgf.
However, the required excitation force is approximately 40Kg at 100Hz.
f, approx. 160Kgf at 200Hz, approx. 360 at 300Hz
Kgf, which is proportional to the square of the vibration frequency. At high frequencies, a reaction force 100 times greater than the load to be measured will be generated.

In the method shown in Figure 1, the reaction force is absorbed by the foundation, but the upper pedestal i, cylinder j, and horizontal bar k are not completely stationary. Due to these structures, the reaction force is transmitted in a complicated manner, and the reaction force is transmitted to the load detector h.
The fixed side of LVDT m will be moved. now,
Assuming that the equivalent mass of the load detector is 1Kg and the mass of the upper specimen mounting plate is 3Kg, in order to achieve a load amplitude measurement accuracy of 1%, the extra output due to the load detector moving in the axial direction is Must be less than 0.01Kg. Acceleration is 0.01Kgf÷4Kg=
It becomes 0.0025g. It is impossible to achieve such a value with the method shown in FIG.

In addition, in the method shown in Fig. 3, the reaction force causes the vibration generator q and the pedestal n to move in the vertical direction, and this movement is a complete reciprocating motion in the vertical direction, and the vibration generator q and the pedestal n act as completely rigid bodies. As long as this is done, the masking cell will work perfectly and will not produce any measurement errors. However, in reality, torsional movement of pedestal n and rigid body rotational motion of vibration generator q and pedestal n occur below the first resonance frequency of pedestal n, resulting in an output that cannot be canceled by a mask canceller, resulting in an error. .

() Lateral vibration of the shaking table The lateral vibration of the shaking table e cannot be avoided. The causes of lateral vibration are the mismatch between the axis of the guide mechanism of the shaking table e and the axis of the excitation force generation mechanism, and the deviation of the center of gravity of the shaking table from those axes. This becomes noticeable when the resonance of the mechanism is excited. When lateral vibration occurs, pitching or yawing is applied to the vibration table e in addition to the axial reciprocating motion. When pitching, yawing, or their combined motion occurs, the load detector h detects the average value of the load detection plane of those motions, but in any of the methods shown in Figures 1, 2, and 3, deflection detection is not possible. Since the deflection at a specific point on the circumference of the vibration table e is detected, an error occurs. Even with a vibration generator that is said to have relatively little lateral vibration, there are several frequencies within the usable frequency range that generate pitching or yawing of about 3 to 5%. Since there is no factor that determines the phase angle between reciprocating motion and pitching or yawing motion, 2
There is a moment when the phase angle of the two motions becomes 90 degrees. At this time, the measurement error of the phase angle of deflection and load can be calculated from tan ^-1 0.03 to ^{tan -1} 0.05, which is 1.7 to 2.9
degree.

It is an object of the present invention to eliminate all the error factors of the conventional dynamic spring constant measuring device detailed above and to enable extremely highly accurate measurement. Therefore, the first aspect of the invention is characterized in that the vibration table is in an inverted shape facing downward, and a vibration generator is attached to the stand via an air spring with a guide mechanism, and further,
The second invention is characterized in that the displacement detector pedestal and the load detector are attached to a rigid body part such as the bottom or foundation of the pedestal, and the second invention is characterized by two pedestals symmetrically about the vibration axis. A displacement detector is disposed, and the deflection of the test piece at the excitation axis is measured via an average calculation circuit that calculates the average displacement of two points.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

In FIGS. 4 and 5, 1 is a foundation, and a pedestal 2 is fixed on the foundation 1 with its bottom 2a in contact with it, and the pedestal 2 is in the shape of an inverted gate, so to speak. Air spring 3 with a guide mechanism at the upper end position of 2
A vibration generator 4 is attached through the mount 2, and thus the pedestal 2 also serves as a vibration generator pedestal. The vibration generator 4 is placed on the upper end of the pedestal 2 in an inverted configuration with the vibration table 5 facing vertically downward, and the air spring 3 is guided by a guide mechanism to maintain the vibration axis A vertically. supports and guides the vibration generator 4 so that it has a degree of freedom only in the vertical and up-down directions.

FIG. 5 shows an example of an electrodynamic type. In this figure, the vibration generator 4 includes a trunnion shaft 8, which protrudes left and right from an outer container body 7 having an excitation coil 6 therein. 8 is held by the air spring 3 with a guide mechanism, vibrates vertically in the vertical direction, and is vibration-insulated so that the vibration is not transmitted to the pedestal 2. A vibration table 5 is inserted into the outer container body 7, and is held vertically movably by an air spring, a locking arm, etc., and a drive coil 9 fixed to the vibration table 5 generates a predetermined waveform and a predetermined frequency. The vibration of the vibration table 5 is controlled by flowing electricity. (It is also possible to use an electro-hydraulic vibration generator, but it is not shown in the figure.) In FIG.
A vertical position setting mechanism 13 consisting of blocks 10, 11, and 12 is placed, and a load detector 14 is placed on top of it, and a test is performed between the load detector 14 and the vibration table 5. Piece mounting plate 15/test piece 1
6. Clamp the test piece mounting plate 17 like a sandwich and attach it. The vertical position setting mechanism 13 sets the vertical position according to the dimensions of the test piece 16. The block 10 on which the load detector 14 is directly placed has an inverted roof shape, and the left and right sides of the block 10 are Blocks 11 and 12 are abutted and supported from the left and right on the lower slope, and the pair of blocks 11 and 12 are arranged in symmetrical positions on the left and right with the vibration axis A as the center, and the left and right positions of the blocks 11 and 12 are adjusted. By doing so, the upper surface position of the central block 10 can be adjusted up and down, and the dimension from the bottom plate 2a to the lower surface of the load detector 14 can be freely set. Furthermore, as is clear from the figure, the axes of the mounting plate 17, the test piece 16, the mounting piece 15, and the block 10 are placed so as to coincide with the vibration axis A.

Reference numeral 18 denotes a displacement detector for measuring deflection, which is, for example, an eddy current type, and is placed at two points opposite to the target plate 19 protruding from the vibration table 5 and symmetrical to the vibration axis A. Displacement detectors 18, 18 are provided. Furthermore, the respective pedestals 20, 20 of the displacement detectors 18, 18 are erected and fixed from the pedestal bottom 2a.

In this way, the displacement detector pedestal 20 is attached to the pedestal bottom 2a, which is the rigid body part G.
Alternatively, although not shown, it is attached to the foundation 1, which is also the rigid body part G. On the other hand, the load detector 1
4 is placed on the base 1 via rigid blocks 10, 11, and 12, or on the foundation 1 (not shown), and the load detector 14 is also attached to the rigid body part G.

Next, FIG. 6 illustrates the load measurement principle of the load detector 14, which outputs the average value of the load applied to the test piece 16, where 21 is an annular load detection element. When the vibration table 5 causes lateral vibration and pitching/yawing occurs, even if the center 22 of the pitching/yawing is located at the position shown in the lower line of FIG. 6, the average value of the two points B and C will be can be represented by the motion of the vibration axis A.

Similarly, in FIG. 7, the displacement detector 18,
18 are arranged symmetrically around the excitation axis A, the average value of the deflections at the two points D and E corresponds to the deflection of the excitation axis A, and the deflection of the axis A itself. This means that it has been measured.

Therefore, according to the configuration illustrated and explained in FIGS. 6, 7, and 4, even if there is lateral vibration of the vibration table 5,
(load/deflection) value is not affected and no error occurs.

Next, as described above, the outputs of the two displacement detectors 18, 18 symmetrical to the vibration axis A are used to detect the vibration axis A.
An average calculation circuit H for calculating the deflection of the test piece 16 at the time of the test is illustrated in FIGS. 8 and 9. In addition to the eddy current type displacement detectors 18, 18,
There is no problem even if two LVDT type or capacitance type are used. Fig. 8 shows a case in which two detectors, two oscillators, and two detectors are used to add and average the outputs, and Fig. 9 shows two detectors, two oscillators, and two detectors. L ₁ and L ₂ indicate the inductance of the detector coil in the case of the eddy current type, and the inductance of the detection coil in the case of the LVDT type. In either case, the fact that inductance changes in response to displacement is used, so if L ₁ and L ₂ are connected in series, the combined inductance will be L ₁ + L ₂ , and the average displacement can be measured. can. (The LVDT type is composed of an oscillating coil and a receiving coil, but the details are omitted in FIG. 9.) In the case of the capacitive type, the same effect can be achieved by connecting two sets of electrodes in parallel.

The dynamic spring constant measuring device according to the present invention has the above-described configuration, and error factors in vibration transmission of the mechanical structure will be considered.

() Resonance of the pedestal In the present invention, the resonance frequency of the pedestal 2, which corresponds to the vibration generator pedestal, is lower than that of the conventional example shown in Figs. 1 and 3, and is about the same as that of Fig. 2. There are two types of excitation force: a reaction force and a force applied to the test piece 16, but the reaction force is absorbed by the air springs 3 with guide mechanisms and the force applied to the test piece 16.
Since the structure is such that the rigid body part G receives the force applied to the , neither force generates vibration to the extent that it causes a measurement error.

() Reaction force of the vibration generator The main component of the reaction force, that in the direction of the vibration axis A, is absorbed by the air spring 3 and does not cause measurement errors. Among the reaction forces, vibrations in directions other than the direction of the vibration axis A slightly excite the upper end of the pedestal 2 through the guide mechanism, but the bottom 2a, which is the lower end of the pedestal 2, is fixed to the foundation 1. Therefore, the load detector 14 and the displacement detector pedestal 20 do not vibrate to the extent that they cause measurement errors.

() Lateral vibration of the shaking table Deflection is measured by measuring the average value of the deflections at two points symmetrical to the axis A, so it is the same as measuring the deflection at the axis of the test piece 16. On the other hand, since the load detector 14 outputs the average value of the load applied to the test piece 16, the load generated by the lateral vibration can be represented by the movement of the axis of the test piece 16. Therefore, the effect of lateral vibration does not appear in the calculation result obtained by dividing the load by the deflection.

Compared to the conventional measuring devices already explained in FIGS. 1 to 3, the measuring device according to the present invention has very superior effects regarding all error factors ()()(). It became clear.

The present invention has been constructed as described in detail above, and has effectively achieved its intended purpose. In particular, as in the second invention, since the displacement detectors 18, 18 are arranged in pairs at symmetrical positions with respect to the vibration axis A, errors in measurement may occur due to pitching and yawing movements of the vibration table 5. It no longer occurs. In addition, since the vibration generator 4 is attached via the air spring 3 with a guide mechanism,
The reaction force of the vibration generator 4 is no longer transmitted to the lower part of the pedestal 2 and causes errors.

Furthermore, the load detector 14 is connected to the blocks 10, 1
1, 12 and the bottom 2a, the measurement accuracy of the dynamic spring constant is further improved without being affected by vibrations due to the force transmitted through the test piece 16, resonance of the pedestal 2, and screw movement. Significantly improved.

Further, as in the first invention, the vibration table 5 is turned downward in an inverted shape, and the air springs 3, 3 with guide mechanisms are used.
A vibration generator 4 is attached to the pedestal 2 via a
4 is attached to the rigid part G of the bottom 2a of the pedestal 2, the foundation 1, etc., the pedestal 2 has a resonance point within the usable frequency range, but the force that excites resonance is extremely small as described above, and the load The detector 14 and the displacement detector 20 were not vibrated, and the reaction force of the vibration generator 4 did not cause the load detector 14 and the displacement detector pedestal 20 to vibrate, making it possible to achieve a significant improvement in measurement accuracy.

As mentioned above, the present invention can be said to be an excellent invention that was created only after thoroughly analyzing and investigating the measurement error factors that were previously unknown.

[Brief explanation of the drawing]

1, 2, and 3 are front views showing conventional examples. Fig. 4 is a front view showing an embodiment of the present invention, Fig. 5 is a detailed cross-sectional view of main parts, Fig. 6 is an explanatory diagram of the principle of a load detector, Fig. 7 is an explanatory diagram of the principle of a displacement detector, 8 and 9 are electrical circuit diagrams. 1... Foundation, 2... Frame, 2a... Bottom, 3...
...Air spring, 4...Vibration generator, 5...Vibration table,
14...Load detector, 16...Test piece, 18...
Displacement detector, 20... Displacement detector pedestal, A... Vibration axis, G... Rigid body portion, H... Average calculation circuit.

Claims (1)

[Claims] 1. A vibration generator 4 is attached to the pedestal 2 via an air spring 3 with a guide mechanism, with the vibration table 5 facing downward in an inverted shape, and a displacement detector pedestal 20 and a load detector. 14 attached to the rigid body part G of the bottom 2a of the pedestal 2, the foundation 1, etc.. 2. A pedestal 2 whose bottom portion 2a is fixed to the foundation 1, and a vibration table 5 which is oriented vertically downward and is attached to the upper end of the pedestal 2 via an air spring 3 with a guide mechanism that supports and guides only in the vertical up and down direction. A vibration generator 4 and a block 1 placed on the bottom 2a of the pedestal 2
A load detector 14 is placed on the bottom portion 2a via a vertical position setting mechanism 13 consisting of 0, 11, and 12.
and a target plate 1 protruding from the vibration table 5.
9, 19 and symmetrical to the excitation axis A
two displacement detectors 18, 18 disposed on displacement detector pedestals 20, 20 that are erected and fixed on the bottom 2a of the pedestal 2 so as to form a point; The deflection of the test piece 16 held between the vibration table 5 and the load detector 14 at the excitation axis A is measured through an average calculation circuit H that calculates the average displacement of the vibration table 5 and the load detector 14. A dynamic spring constant measuring device characterized by: