JPH10142253A - Vibration detection sensor and vibration measuring device using the same - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To measure the vibration of an object to be measured optically by bringing the object into contact with the object to be vibrated. Make it easy. SOLUTION: The vibration detection sensor 10 according to the present invention includes: a housing 12 which vibrates together with the object to be measured M by being brought into contact with the object to be vibrated; a weight 14 accommodated in the housing 12; The coil springs 161 and 162 that support the weight 14 swingably with respect to the housing 12, the reflecting plate 18 fixed to the weight 14, and the laser light L emitted from one end 201 is reflected by the reflecting plate 18. The optical fiber 20 has one end 201 fixed to the housing 12 so as to be incident on the one end 201 again.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration detecting sensor for measuring the vibration of an object to be measured by bringing the object into contact with a vibrating object, and a vibration measuring device using the same.

[0002]

2. Description of the Related Art Conventionally, as a vibration measuring device for measuring the vibration of an object to be measured by bringing the object into contact with a vibrating object to be measured, an apparatus using a piezoelectric material is generally used. Since this vibration measuring device directly converts the vibration of an object into an electric signal, there is a problem that the vibration measuring device is easily affected by electric noise such as electromagnetic waves. Therefore, a vibration measuring device that solves this problem is disclosed in Japanese Patent Application Laid-Open No. 5-60781. This vibration measuring device is to convert the vibration of an object into an optical signal once, and to convert the optical signal into an electric signal, thereby eliminating the influence of electric noise.

FIG. 5 is a block diagram showing a conventional vibration measuring device disclosed in the above publication. Hereinafter, description will be given based on this drawing.

A conventional vibration measuring device 70 comprises a semiconductor laser 72, an optical fiber 76 connecting the semiconductor laser 72 and the coupler 74, and a coupler for splitting light emitted from the semiconductor laser 72 into two optical fibers 78 and 80. 74 and a coupler 74 provided at the distal ends of the optical fibers 78 and 80.
Reflectors 82 and 84 for reflecting the light branched from the optical fiber again in the direction of the coupler 74, and a weight 86 fixed to the optical fiber 80.
An optical fiber 80 connecting the coupler 74 and the photodiode 88; and optical fibers 78 and 80 in the direction of the coupler 74.
And a photodiode 90 that receives one of two branches of the interference light due to the reflected light from the coupler 74.

The light emitted from the semiconductor laser 72 is split into two by a coupler 74 in a direction of a reflector 82 and a direction of a reflector 84. The lights respectively reflected by the reflection plates 82 and 84 return to the coupler 74 again, where they are multiplexed and interfere. The interference light is bifurcated by the coupler 74, one of which is incident on the photodiode 88, and the interference light output intensity is converted into an electric signal. Here, it is assumed that the weight 86 is brought into contact with an object to be measured (not shown). When the weight 86 feels acceleration, a stress is generated in the portion of the optical fiber 80 fixed to the weight 86. As a result, the effective refractive index of the optical fiber 80 changes, and the phase of light propagating in the optical fiber 80 changes. Since only one of the lights undergoes a phase change due to the application of the acceleration, the interference state of the two lights changes, and the intensity of the interference light changes in response to the application of the acceleration, whereby the acceleration of the object to be measured is detected.

[0006]

However, in the conventional vibration measuring device 70, four optical fibers 76, 90,
Numerous optical components such as 78, 80, two reflectors 82, 84 and coupler 74 are required. Moreover, the two optical fibers 76 and 90 are connected to the semiconductor laser 72 around the coupler 74.
And the photodiode 88, and the other two optical fibers 78 and 80 are also connected to the two reflectors 8 around the coupler 74.
2, 84, and the weight 86 is brought into contact with only one of the optical fibers 80.
78 and 80 are complicatedly intersected. Therefore, in the conventional vibration measuring device 70, the optical system is complicated, so that the size is increased and the adjustment of the optical axis and the focus is complicated.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to make it possible to optically measure the vibration of an object to be measured by bringing the object into contact with the object being vibrated, to achieve a reduction in size and weight, and to achieve manufacturing and An object of the present invention is to provide a vibration detection sensor and a vibration measuring device using the same, which can be easily operated.

[0008]

According to a first aspect of the present invention, there is provided a vibration detection sensor, comprising: a housing which vibrates together with a vibrating object by being brought into contact with the vibrating object; and a weight accommodated in the housing. An elastic body that swingably supports the weight with respect to the housing, a reflector fixed to the weight, and a laser beam emitted from one end reflected by the reflector and again applied to the one end. An optical fiber whose one end is fixed to the housing so as to be incident.

[0009] Hereinafter, the laser light before reflection is referred to as irradiation light, and the laser light after reflection is referred to as reflected light. The irradiation light is emitted from one end of the optical fiber, and the reflected light is incident again on one end of the optical fiber. Here, when the vibration detection sensor is brought into contact with the measured object, the housing vibrates together with the measured object. On the other hand, the weight remains stationary in the coordinate system for measurement due to the action of the elastic body. Therefore, the reflector is stationary with the weight, and one end of the optical fiber is vibrating with the housing, so that the distance between the reflector and one end of the optical fiber is synchronized with the vibration of the DUT. Expand and contract. As a result, the reflected light changes to a frequency corresponding to the vibration of the device under test due to the Doppler effect, so that a laser beam containing a beat wave signal consisting of a mixed wave of irradiation light and reflected light is obtained from the other end of the optical fiber. Can be Thus, with an optical system consisting of only one optical fiber and one reflector,
Information on the vibration of the device under test is obtained optically.

According to a second aspect of the present invention, there is provided the vibration detecting sensor according to the first aspect, wherein a liquid that is in contact with the weight and has a light transmitting property is sealed in the housing. As described above, the weight is stationary with respect to the coordinate system for measurement, but swings with respect to the housing. Therefore, if the liquid that comes into contact with the weight is sealed in the housing,
Due to the frictional force between the weight and the liquid, the swing of the weight, especially at a high frequency, is suppressed. The liquid only needs to have a light-transmitting property to the extent that the liquid does not interfere with the measurement by absorbing the laser light.

According to a third aspect of the present invention, there is provided a vibration measuring apparatus.
Or the vibration detection sensor according to 2, a laser light source for irradiating the laser light to the other end of the optical fiber, and an electric power from a mixed wave of the irradiation light and the reflected light of the laser light obtained at the other end of the optical fiber. A mixing circuit for extracting a typical beat wave signal, and a vibration calculating circuit for calculating a vibration of the device under test based on the beat wave signal extracted by the mixing circuit.

When the vibration detection sensor is brought into contact with the vibrating object, the weight and the reflector remain stationary, but the housing and one end of the optical fiber vibrate together with the object. On the other hand, laser light is emitted from a laser light source toward the reflector via an optical fiber. At this time, the reflected light from the reflector changes to a frequency corresponding to the vibration of the measured object due to the Doppler effect. Therefore, a beat wave signal is included in the mixed wave of the irradiation light and the reflected light, and the beat wave signal is extracted by the mixing circuit. In the beat wave signal, a high-frequency portion and a low-frequency portion are formed corresponding to the time when the device under test approaches or moves away from the laser light source. The vibration calculation circuit calculates a frequency, a cycle, an amplitude, a speed, an acceleration, and the like relating to the vibration of the measured object based on the beat wave signal.

[0013]

1 and 2 show a first embodiment of a vibration detecting sensor according to the present invention. FIG. 1 is a sectional view and FIG.
Is an exploded perspective view. Hereinafter, description will be made based on this drawing.

The vibration detecting sensor 10 according to the present embodiment is configured to contact the object
The housing 12 vibrates together, the weight 14 accommodated in the housing 12, coil springs 161 and 162 as elastic bodies for supporting the weight 14 swingably with respect to the housing 12, and The reflecting plate 18 as a reflector provided, and the one end 201 is connected to the housing 12 so that the laser beam L emitted from the one end 201 is reflected by the reflecting plate 18 and is incident on the one end 201 again.
And an optical fiber 20 fixed to the optical fiber.

The housing 12 has a bottomed cylindrical main body 121.
And a lid 122 mounted on the main body 121. The material of the housing 12 is preferably a metal or a synthetic resin having a property of not absorbing vibration. A female screw is formed on the main body 121, and a male screw is formed on the lid 122,
The main body 121 and the lid 122 are screwed together with the O-ring 123 interposed therebetween.

A through hole 124 is formed at the center of the lid 122. One end 201 of the optical fiber 20 and a SELFOC lens 202 that is in contact with the one end 201 are fixed to the through hole 124 by fitting or bonding. The Selfoc lens 202 is for condensing the laser light L, and is not always necessary. The weight 14 is
Made of columnar metal. The weight of the weight 14 and the spring constants of the coil springs 161 and 162 are selected so that the weight 14 does not vibrate due to the vibration of the housing 12. The reflection plate 18 is a disk having a mirror surface on one side, and is fixed to the weight 14 by bonding or fitting.

Next, the operation of the vibration detection sensor 10 will be described. Hereinafter, the laser beam L before reflection on the reflection plate 18 is referred to as irradiation light Lf, and the laser beam L after reflection is referred to as reflection light Lr.

The irradiation light Lf is applied to one end 201 of the optical fiber 20.
The reflected light Lr exits from the optical fiber 20 through the Selfoc lens 202 again, and enters the one end 201 of the optical fiber 20 through the Selfoc lens 202. Here, the detection surface 125 of the vibration detection sensor 10 is brought into contact with the measured object M. Then, the housing 12 vibrates together with the measured object M. On the other hand, the weight 14 remains stationary by the action of the coil springs 161 and 162. Therefore, the reflection plate 1
8 is stationary with the weight 14, and the SELFOC lens 202 is vibrating with the housing 12, so that the distance between the reflector 18 and the SELFOC lens 202 is
The object M expands and contracts in synchronization with the vibration of the object M. As a result, the reflected light Lr changes to a frequency corresponding to the vibration of the device under test M due to the Doppler effect. Obtained from the other end 203 of the fiber 20. in this way,
An optical system including only one optical fiber 20 and one reflecting plate 18 optically obtains information on the vibration of the device under test M.

3 to 5 show a second embodiment of the vibration detecting sensor according to the present invention. FIG. 3 is a sectional view, and FIGS.
FIG. Hereinafter, description will be made based on this drawing. However, the same parts as those in FIG.

The vibration detection sensor 30 of the present embodiment is the same as the vibration detection sensor 10 of the first embodiment, except that a liquid 34 that is in contact with the weight 32 and has translucency is sealed in the housing 12. The weight 32 has a liquid 34.
Through holes 321 to 324 are formed.
The weight 32 is stationary with respect to the coordinate system for measurement, but swings with respect to the housing 12. Therefore, weight 3
When the liquid 34 that comes into contact with the liquid 2 is sealed in the housing 12, the swing of the high frequency weight 32 is particularly suppressed by the frictional force between the weight 32 and the liquid 34. Thereby, high frequency noise included in the vibration of the device under test M can be removed. Note that a weight 36 shown in FIG. 5 may be used instead of the weight 32 shown in FIG. The weight 36 has a long groove 3 serving as a flow path of the liquid 34.
61 to 364 are formed.

FIG. 6 is a block diagram showing an embodiment of the vibration measuring device according to the present invention. FIG. 7 is a waveform chart showing the operation of the vibration measuring device of FIG. Hereinafter, description will be made based on these drawings.

The vibration measuring device 40 includes the vibration detecting sensor 10
And a laser light source 42 for irradiating the other end 203 of the optical fiber 20 with the laser light L, and an electric signal from the mixed wave of the irradiation light Lf of the laser light L obtained at the other end 203 of the optical fiber 20 and the reflected light Lr. Mixing circuit 44 for extracting a simple beat wave signal fd
And a vibration calculation circuit 46 that calculates the vibration of the device under test M based on the beat wave signal fd extracted by the mixing circuit 44.

The laser light source 42 includes a semiconductor laser 42a
A driving circuit 42b for driving the semiconductor laser 42a;
It comprises a photodiode 42c for converting a self-mixed wave of the irradiation light Lf of the laser light L and the reflected light Lr into an electric signal, and an optical system (not shown). For example, the semiconductor laser 42a and the photodiode 42c are an LT030 series manufactured by Sharp Corporation and the driving IC is an IR3C01 series manufactured by Sharp Corporation.

The mixing circuit 44 includes an amplifier, a limiter, a DC component blocking capacitor, and the like.

The vibration calculating circuit 46 includes a frequency-voltage converting circuit 48 for converting the beat wave signal fd extracted by the mixing circuit 44 into a voltage corresponding to the frequency, and a voltage waveform converted by the frequency-voltage converting circuit 48. DUT M based on Vb
And a pulsing circuit 5 for generating a fixed number of pulse signals P _FD for one cycle of the beat wave signal fd extracted by the mixing circuit 44.
2 and an amplitude calculating circuit 54 that counts the pulse signal P _FD generated from the pulsing circuit 52 for one cycle calculated by the cycle calculating circuit 50.

The frequency-voltage conversion circuit 48 is, for example,
This is a frequency discrimination circuit used for demodulation of M waves. In the beat wave signal fd, a high-frequency portion and a low-frequency portion are formed corresponding to the time when the device under test M approaches or moves away from the laser light source 42 (FIG. 7 (3)). Accordingly, the frequency-voltage conversion circuit 48 converts the high-frequency portion into a high-voltage voltage waveform and the low-frequency portion into a low-voltage voltage waveform Vb (FIG. 7 (4)). That is, the period of the voltage waveform Vb is twice as long as the period Tm of the device under test M (FIG. 7A).

The period calculating circuit 50 includes a comparator 501 for pulsing the voltage waveform Vb output from the frequency-voltage converting circuit 48 with a threshold Vs, and a comparator 5.
01 and a pulse signal V inverted by the inverter 502.
c, a timing signal generating circuit 503 for outputting a reset signal S _RE , an enable signal S _EN , and a latch signal S _LA .
An oscillator 504 for generating a clock pulse CP;
A counter circuit 505 for resetting the count value by the reset signal S _RE with counting the clock pulses CP by the enable signal S _EN, latch circuit 506 for holding the count value of the counter circuit 505 by the latch signal S _LA
And a microcomputer 507 which inputs the count value held by the latch circuit 506 and calculates the period Tm and the reciprocal frequency fm based on the count value.

The pulsing circuit 52 is a comparator for generating one pulse signal _PFD per one cycle of the beat wave signal fd.

The amplitude calculation circuit 54 supplies the enable signal S _EN
The counter circuit 54 counts the pulse signal P _FD by the reset signal and resets the count value by the reset signal S _RE.
1, a latch circuit 542 for holding the count value of the counter circuit 541 by the latch signal _SLA , and the count value held by the latch circuit 542 are input, and the amplitude Lm of the device under test M is calculated based on the count value. And a microcomputer 543.

FIG. 8 is a block diagram showing an example of the timing signal generation circuit 503 in the vibration measuring device 40. FIG. 9 is a time chart showing the operation of the timing signal generation circuit 503. Hereinafter, description will be made based on these drawings.

The timing signal generation circuit 503 includes JK flip-flops 561 and 562 and an AND gate 56.
3,564 and an inverter 565.

The JK flip-flops 561 and 562 are
Since the J and K terminals are connected to the power supply voltage Vcc, they operate as T flip-flops whose outputs are inverted each time a clock pulse is input. As a result, the JK flip-flop 561 operates at the rising edge of the pulse signal Vc, and outputs a pulse signal Ve having a cycle twice as long as the pulse signal Vc (FIGS. 9A and 9B). That is, the cycle of the pulse signal Ve matches the cycle Tm of the device under test M. Similarly, the JK flip-flop 562 operates at the rising edge of the pulse signal Ve, and outputs the enable signal _SEN having a cycle twice as long as the pulse signal Ve (FIG. 9 (3)). The inverter 565 is connected so as to obtain an inverted output of the pulse signal Vc. The AND gate 563 is connected such that when the enable signal _SEN is “0”, the pulse signal Ve is “1”, and the pulse signal Vc is “0”, the latch signal _SLA becomes “1”. AND gate 56
4 indicates that the enable signal _SEN is "0" and the pulse signal Ve
Are connected so that the reset signal _SRE becomes "1" when the pulse signal Vc is "0" and the pulse signal Vc is "0".

Therefore, as shown in FIGS. 9 (3) to 9 (5), only the enable signal _SEN becomes “1” during one cycle of the pulse signal Ve, and the latch signal S _{LA is provided in} a half cycle of the next pulse signal Ve. Only the reset signal _SRE becomes "1" in the remaining half cycle. Thus, FIG. 9 (6)
As shown in (7), the counter circuits 505 and 541 and the latch circuits 506 and 542 operate.

Next, the overall operation of the vibration measuring device 40 will be described with reference to FIG.

When the vibration detection sensor 10 is brought into contact with the vibrating object M, the weight 14 and the reflection plate 18 remain stationary, but the housing 12 and one end 20 of the optical fiber 20 remain.
1 vibrates together with the object M to be measured. On the other hand, the laser light source 4
The laser beam L is transmitted from the optical fiber 20 to the reflector 18 via the optical fiber 20.
Irradiated toward At this time, the reflected light Lr from the reflecting plate 18 has changed to a frequency corresponding to the vibration of the device under test M due to the Doppler effect. Therefore, the mixed wave of the irradiation light Lf and the reflected light Lr includes the beat wave signal fd, and the beat wave signal fd is extracted by the mixing circuit 44. The beat-wave signal fd is converted by the frequency-voltage conversion circuit 48 into a voltage waveform Vb having a period twice as long as the period Tm of the device under test M as described above. Therefore, by calculating the cycle of the voltage waveform Vb by the cycle calculation circuit 50,
The period Tm and the frequency fm are obtained.

Each time the device under test M moves by half the wavelength λ of the laser beam L, one cycle of the beat wave signal fd is formed. Therefore, when one pulse signal P _FD is generated in one cycle of the beat wave signal fd by the pulsing circuit 52, the number of pulses counted by the amplitude calculating circuit 54 within one cycle Tm of the vibration of the device M is measured. Corresponds to the magnitude of the amplitude Lm of the vibration of the DUT M.

According to the vibration measuring device 40, since the beat wave signal fd is converted into the voltage waveform Vb having a period twice as long as the period Tm of the DUT M, the period of the voltage waveform Vb is calculated by the period calculating circuit. By calculating at 50, the period Tm of the DUT M can be obtained. Therefore, the measurement at the frequency level of the laser beam L as in the related art can be performed at a frequency lower than the periodic level Tm of the device under test M. As a result, when the frequency of the beat wave signal fd is high, the measurement accuracy of the period Tm, the frequency fm, and the like of the device under test can be improved.

Further, a pulse signal P _FD corresponding to one cycle of the beat wave signal fd is generated from the pulsing circuit 52, and the pulse signal P _FD is counted by the amplitude calculating circuit 54 for one cycle of the vibration of the object M. Thus, the amplitude Lm can be measured at the same time as the period Tm and the frequency fm of the DUT M. Furthermore, the speed and the acceleration of the DUT M can be measured based on the cycle Tm and the amplitude Lm.

It is needless to say that the present invention is not limited to the above embodiment. For example, when the measurement of the amplitude Lm is not required, the pulse generator 52 and the amplitude calculator 54 may be eliminated. Further, the cycle calculation circuit 5
In the above embodiment, 0 is used to determine the period Tm by digital processing. However, the value 0 may be obtained by analog processing.

[0040]

According to the vibration detecting sensor and the vibration measuring device according to the first, second, or third aspect, a housing that vibrates together with the object to be measured by being brought into contact with the object that is vibrating; Weight, an elastic body that swingably supports the weight in the housing, a reflector fixed to the weight, and a laser beam emitted from one end reflected by the reflector and incident again on one end. And an optical fiber fixed at one end to the housing so that a laser beam including a beat wave signal composed of a mixed wave of irradiation light and reflected light can be obtained from the other end of the optical fiber. it can. Therefore, with an optical system consisting of only one optical fiber and one reflector,
Since information on the vibration of the object to be measured can be obtained optically, downsizing and weight reduction can be achieved by reducing the number of parts, and optical adjustment can be simplified, so that manufacturing and operation can be simplified.

According to the vibration detecting sensor of the second aspect,
By enclosing the translucent liquid in the housing while contacting the weight, the high-frequency weight is prevented from swinging due to the frictional force between the weight and the liquid. Can be removed.

According to the vibration measuring device of the third aspect, the vibration detecting sensor of the first or second aspect, a laser light source for irradiating the other end of the optical fiber with laser light, and the other end of the optical fiber can be obtained. A mixing circuit for extracting an electrical beat wave signal from a mixed wave of the irradiation light of the laser light and the reflected light, and a vibration calculation circuit for calculating a vibration of the device under test based on the beat wave signal extracted by the mixing circuit. Is provided, the frequency, cycle, amplitude, speed, acceleration, and the like relating to the vibration of the measured object can be easily measured simply by bringing the vibration detection sensor having a small size and excellent operability into contact with the measured object.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of a vibration detection sensor according to the present invention.

FIG. 2 is an exploded perspective view of the vibration detection sensor of FIG.

FIG. 3 is a sectional view showing a second embodiment of the vibration detection sensor according to the present invention.

4 is a perspective view of a main part showing a first example of a weight in the vibration detection sensor of FIG. 3;

FIG. 5 is a perspective view of a main part showing a second example of a weight in the vibration detection sensor of FIG. 3;

FIG. 6 is a block diagram showing one embodiment of a vibration measuring device according to the present invention.

7 is a waveform chart showing the operation of the vibration measuring device of FIG. 6, wherein FIG. 7 (1) shows the vibration of the object to be measured, FIG. 7 (2) shows the speed of the object to be measured, and FIG. 3) is a beat wave signal, FIG. 7 (4) is a voltage waveform, FIG. 7 (5) is a pulse signal, and FIG. 7 (6) is a pulse signal.

FIG. 8 is a block diagram showing an example of a timing signal generation circuit in the vibration measuring device of FIG.

9 is a time chart showing the operation of the timing signal generation circuit of FIG. 3, and FIG. 9 (1) is a pulse signal,
9 (2) shows a pulse signal, FIG. 9 (3) shows an enable signal, and FIG. 9 (4) shows a latch signal.
FIG. 9 (6) shows the operation of the counter circuit, and FIG. 9 (7) shows the operation of the latch circuit.

FIG. 10 is a block diagram showing a conventional vibration measuring device.

[Explanation of symbols]

10, 30 Vibration detection sensor 12 Housing 14, 32, 36 Weight 18 Reflector (reflector) 20 Optical fiber 40 Vibration measuring device 42 Laser light source 44 Mixing circuit 46 Vibration calculation circuit 48 Frequency-voltage conversion circuit 50 Period calculation circuit 52 Pulsing circuit 54 Amplitude calculation circuit 161, 162 Coil spring (elastic body) 201 One end of optical fiber 203 The other end of optical fiber fd Beat wave signal M DUT L laser light Lf Irradiation light of laser light Lm Vibration of DUT vibration period Vb frequency of the pulse signal Tm measured object is output from the reflected light P _FD pulsing circuit of the amplitude Lr laser beam - voltage voltage waveform output from the conversion circuit

Claims (3)

[Claims] A housing that vibrates together with the object to be measured when the object comes into contact with the object to be vibrated, a weight accommodated in the housing, and the weight swingable with respect to the housing. An elastic body supported on the weight, a reflector fixed to the weight, and one end fixed to the housing such that laser light emitted from one end is reflected by the reflector and re-enters the one end. And an optical fiber. 2. The vibration detecting sensor according to claim 1, wherein a liquid that is in contact with the weight and has a light transmitting property is sealed in the housing. 3. The vibration detection sensor according to claim 1, wherein the laser light source irradiates the other end of the optical fiber with laser light, and the irradiation light of the laser light obtained at the other end of the optical fiber. A vibration circuit comprising: a mixing circuit that extracts an electric beat wave signal from a mixed wave with the reflected light; and a vibration calculation circuit that calculates a vibration of the device under test based on the beat wave signal extracted by the mixing circuit. measuring device.