JPS6291825A - Seismic type vibration measuring instrument - Google Patents

Abstract

PURPOSE:To simplify the constitution, and to prevent the accuracy from being deteriorated, by lowering a natural frequency by interposing an elastic body between a dead weight and a piezoelectric element, so that an electric signal being proportional to a displacement can be obtained. CONSTITUTION:On the upper part of a piezoelectric element 102, a dead weight 104 is fixed through an elastic body 103. As for the elastic body 103, its dimension is set to thickness by which a natural frequency becomes lower than a working frequency. An output signal from the element 102 is outputted as an output 124 for alarm through a pre-amplifier 121, a BPF 122, and an amplitude detector 123. Also, an output signal from the BPF 122 goes round the detector 123 and inputted to an analyzer 125. That is, the natural frequency is lowered by interposing the elastic body 103 between the dead weight (mass) 104 and the element 102, so that an electrical signal being proportional to a displacement can be obtained, therefore, an integrator, etc., become unnecessary. Accordingly, the constitution is simplified, and an integral control action by the integrator is not executed, therefore, deterioration of the accuracy caused by an integration is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a seismo-type vibration measuring device for detecting imaging in various rotational regions III.

[Prior Art] In general, the li I 1ll + constant can be roughly divided into cases using a standard that can be regarded as stationary in space, that is, a fixed point, and cases using a so-called seismo system. In other words, it is not impossible to use the above-mentioned base plate to measure the vibration of a machine mounted on a heavy and sturdy plywood board.In this case, it is sufficient to measure the relative motion of the object to be measured with respect to the base plate. , there is no equivalence problem in principle.

However, in reality, fixed points can only be used in extreme cases, and most vibration measurements are made using the seismic system described above.

The above-mentioned seismo system is a basic frame fixed to the measurement target,
A system consisting of a single weight mounted within this base frame, and usually also includes a damping element.

Furthermore, when measuring vibrations, it is detected using an optical or electrical conversion element.

Therefore, a conventional Seismo type vibration measuring device will be explained with reference to FIGS. 7 to 11. FIG. 7 is a diagram showing the configuration of the Seismo pattern vibration vJ measuring device, in which symbol A is a counter-dyed object to be measured, and a piezoelectric acceleration transducer 1 is installed on this object A to be measured.

That is, the reference numeral 2 in the figure is a base frame, and within this base frame 2, a piezoelectric element 3 and a mass 4 are installed integrally.

The reason why the piezoelectric element 3 and the mass 4 are combined in this way is as follows. In other words, an inertial force proportional to the speed of the piezoelectric element 4 acts on the pressure element 3, and by taking out the output of the piezoelectric element 3, the acceleration increases. This is because it can be detected with high accuracy, and it is also compact and robust. Note that the reference numeral 5 in the figure is a fixing screw.

Examples of the structure of the piezoelectric acceleration transducer 1 are shown in FIGS. 9 to 11. The piezoelectric acceleration transducer shown in FIG. 9 is a compression type, and FIG. 10 is a sectional view taken along line XX in FIG. 9. Reference numeral 11 in the figure represents a case (base frame), and a connector 12 is attached to the lower part of this case 11. Case 11 above
Inside, a piezoelectric element 14 is installed integrally with a pawn 15 via an insulating plate 13. Further, the reference numeral 16 in the figure is a preload screw, and the reference numeral 17 is a preload spring. Also the 10th
Number 18 in the figure is a mounting screw. Furthermore, the piezoelectric acceleration transducer 1 shown in FIG. 11 is of the compression type, and is designated by the same reference numerals as those of the compression type described above.

The output from the piezoelectric element 3 is inputted to a preamplifier 21 as shown in FIG. . From there, a II reward signal 27 is output.

Further, a signal bypassing the amplitude detector 26 is output to the analyzer 29.

[The problem that the invention aims to solve] The above configuration has the following problems.

That is, generally machine vibration monitoring or vibration meter 1111
For example, displacement amplitude or imaging amplitude is used to prevent high frequency noise. However, when attempting to obtain the displacement amplitude using the vibration device described above, it is necessary to convert the acceleration signal into a displacement signal using bandpass filters 22, 25 and integrators 23, 24 (the configuration becomes complicated). At the same time, there was also a cost problem.
When measuring with the configuration shown in the figure, the relative sensitivity to the frequency of each part changes as shown in Figure 8, so the required S/N ratio (signal to noise ratio) of the displacement signal is In order to ensure this, a wide dynamic range is required for the route amplifier 21, bandpass filters 22, 25, and integrators 23, 24, and as a result, expensive circuits or devices are required, leading to an increase in cost. In addition, FIG. 8(A) shows the change in relative sensitivity to frequency at the outlet of the preamplifier 111 and width filter 21, and FIG.
8(C) is the outlet of the integrator 23, FIG. 8(D) is the outlet of the integrator 24, and FIG. 8(E) is the bandpass filter 25.
shows the change in relative sensitivity to frequency at the exit of . Furthermore, the band pass filters 22J5 and 25
, or the transfer characteristics of integrators 23 and 24 are strictly v
A? ! ! It is extremely difficult to do so, and the obtained displacement signal has a problem of poor transfer characteristics.

The present invention has been made based on the above points, and its purpose is to eliminate the various problems mentioned above while retaining the characteristics of the pressure I8 type, simplify the structure, reduce costs, and It is an object of the present invention to provide a seismo-type vibration measuring device that facilitates signal processing and enables highly accurate vibration measurement.

Means for Solving Problem F] That is, the seismo-type vibration measuring device according to the present invention is a seismo-type vibration measuring device that is equipped with a piezoelectric acceleration transducer in which a plow and a piezoelectric element are installed within a base frame fixed to a measurement target. The type vibration measuring device is characterized in that a neutral body is interposed between the weight and the piezoelectric element to lower the natural frequency and obtain an electric signal proportional to displacement.

[Function] In other words, by interposing an elastic body between the mass and the piezoelectric element, the unique one! The '71 number is set lower than the frequency used so that a force proportional to the displacement acts on the piezoelectric element.

[Effects] Therefore, since the detected electric signal is already proportional to the displacement, a conventional integrator is not required, the configuration can be simplified, and signal processing is also facilitated. Further, since there is no integral operation, it is possible to effectively prevent a decrease in the opening degree.

Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 to 6. First, the configuration of the piezoelectric acceleration transducer 100 will be described with reference to FIGS. 1 and 2. The piezoelectric acceleration transducer 100 shown in FIG. 1 is a compression type, and the number 1 in the figure is
01 is a case.

A piezoelectric element 102 is installed inside this case 101. A weight 104 is fixed above the piezoelectric element 102 via an elastic body 103. For example, rubber or plastic is used as the elastic body, and the size and thickness are such that the natural frequency is lower than the operating frequency. Further, the elastic body 103 and the piezoelectric element 102 or the weight 104 are fixed using adhesive or bolts. In addition, the above case 1
A mounting screw 105 is attached to the lower end of the case 101, and a connector 106 is attached to the side of the case 101. It is fixed to the object to be measured 111 via the mounting screw 105 as shown in FIG.

The output signal from the piezoelectric element 102 is transmitted to the front neck width device 12.
1 is input. The signal is roughly input to the S-width detector 123 via a band-pass filter 122 . Attack width detector 123
The output signal from is output as the alarm output 124. Further, the output signal from the bandpass filter 122 bypasses the amplitude detector] 23 and is input to the analyzer 125.

The operation will be explained based on the above configuration. First, the configuration of the piezoelectric acceleration transducer 100 according to this embodiment is schematically shown in FIG. 5. It is assumed that the converter mounting section is undergoing sinusoidal gt vibration as shown in the figure. In this embodiment, the elastic body 103 lowers the specific SvJ number and serves as a port for detecting the force transmitted to the 1li104.

Therefore, it is sufficient to detect the force transmitted to the elastic pair 103, which is calculated by the following formula.

m-C-k<y-x)-c(C-C)・・・・・・(
1) Here, if z=(y-x) and x=X-sin (ωt), the above formula (I> becomes as follows.

m-i+c-c+ni-z-m-ω2 ・X・5in(ω
t) ・・・・・・
- (n) The force detected by the piezoelectric element 102 is the product of the relative displacement and the dynamic stiffness. That is, Z
When (Z/X) is determined as -Z-3in (ωt-φ), it becomes as shown in FIG. Figure 6 is a diagram showing the values of relative displacement (Z, /' Things become power.

However: Spring term C: is a reduction term. In the case of an elastic body such as rubber, (k+1・C・ω
) is constant, so that above a certain vibration frequency shown in FIG. 6, a constant force approximately proportional to the displacement is transmitted. Incidentally, FIG. 4 shows changes in the relative sensitivity with respect to the frequency seen at the exits of the preamplifier 121 and the bandpass filter 122.

According to this embodiment, the following effects can be achieved.

(1) First, in the case of this embodiment, since the electric signal detected is proportional to the displacement, there is no need for an integrator or the like as in the conventional case, and the configuration is greatly simplified. The device can be made more compact.

(2) Furthermore, as described above, since there is no integration operation by an integrator, it is possible to prevent a decrease in accuracy due to integration.

Although the above embodiment has been described with respect to a compression type piezoelectric acceleration transducer, the present invention is not limited to this, and can be similarly applied to a completely new type of piezoelectric acceleration transducer shown in FIG. .

[Brief explanation of drawings]

FIGS. 1 to 6 are diagrams showing one embodiment of the present invention.
The figure is a cross-sectional view showing the configuration of a compression type piezoelectric acceleration transducer.
FIG. 2 is a sectional view showing the configuration of a helical/V-shaped piezoelectric acceleration transducer, FIG. 3 is a diagram showing the overall configuration of the vibration measuring device, and FIG. Figure 4 (B), which shows the relationship between relative sensitivity and the number of #J, shows the relative sensitivity at the exit of the bandpass filter 122! 7I
Figure 5 is a diagram schematically showing the piezoelectric acceleration transducer to explain the action, Figure 6 is a diagram showing the relative displacement and transfer angle values with respect to the frequency ratio. , 7th
11 are diagrams showing a conventional example, FIG. 7 is a diagram showing the configuration of a vibration measuring device, and FIG. 8 (A> to (E) is a preamplifier and each bandpass filter. A diagram showing the relationship between relative sensitivity and frequency at the exit. Figure 9 is a perspective view of a compression type piezoelectric acceleration transducer. Figure 10 is a sectional view taken along line XX in Figure 9. Figure 11 is a spiral type piezoelectric. It is a sectional view of a type acceleration transducer. 1oo... Piezoelectric type acceleration transducer, 101... Case (base frame), 102... Piezoelectric element, 103... Elastic body, 104... Mass. Applicant sub-agent Patent attorney Takehiko Suzue (A) (B) Figure 8, Figure 9vl:J

Claims (1)

[Claims] In a seismo type vibration measuring device equipped with a piezoelectric acceleration transducer in which a weight and a piezoelectric element are installed within a base frame fixed to a measurement target, an elastic body is interposed between the weight and the piezoelectric element. A seismo-type vibration measuring device characterized in that it is configured to obtain an electric signal proportional to displacement by lowering the natural frequency.