RU218106U1 - Fiber Optic Reflective Type Vibration Sensor - Google Patents

Abstract

The utility model relates to the field of industrial vibration measurements for the purpose of monitoring and diagnosing the technical condition of rotary machines with the possibility of using in the presence of flammable or explosive gases and liquids. The fiber-optic vibration sensor of the reflective type contains a housing made of two parts of the base and a cover laid on the base and hermetically fixed. The body material is selected according to the requirements of operation. Two grooves are located on the base of the sensor, in one, a light-conducting fiber is laid through a hole in the rear wall, directed to a reflective plate fixed on the front wall of the housing, in such a way that the core of the light-conducting fiber is directed to the media separation of the reflecting surface, in the second groove there is a guide fiber for formation of an elastic element. The elastic element, made in the form of a pair of fibers, ensures the sensitivity of the sensor to only one axis. Quartz fiber is used as an elastic element, which eliminates the need for special elastic elements. The sensor is attached with a threaded connection to the measurement object. Reflective surface made in the form of an interface between the absorption and reflection bands, made by sawing a plate with a reflective coating at a right angle. The technical result consists in simplifying the design and production while maintaining the technical characteristics. 5 ill.

Description

The proposed utility model relates to the field of industrial vibration measurements for the purpose of monitoring and diagnosing the technical condition of rotary machines with the possibility of using in the presence of flammable or explosive gases and liquids.

The fiber-optic vibration sensor of the reflective type contains a housing made of two parts of the base and a cover laid on the base and hermetically fixed. The body material is selected according to the requirements of operation. Two grooves are located on the base of the sensor, in which a light-conducting fiber is laid through a hole in the rear wall, directed to a reflective plate fixed on the front wall of the housing, in such a way that the core of the light-conducting fiber is directed to the media separation of the reflecting surface, in the second groove there is a guide fiber for formation of an elastic element. The elastic element, made in the form of a pair of fibers, ensures the sensitivity of the sensor to only one axis. Quartz fiber is used as an elastic element, which eliminates the need for special elastic elements. The sensor is attached with a threaded connection to the measurement object. Reflective surface made in the form of an interface between the absorption and reflection bands, made by sawing a plate with a reflective coating at a right angle. Due to the structure of the reflective surface, the vibration sensor is sensitive mainly to one axis, and the adjustment to the separation of media makes it more sensitive to small vibration displacements.

The technical result consists in simplifying the design and production while maintaining the technical characteristics. Expansion of the arsenal of measuring devices.

Technical field

This utility model relates to the field of industrial vibration measurements for the purpose of monitoring and diagnosing the technical condition of rotary machines, as well as analyzing the vibrational behavior of structures. In particular, the utility model relates to fiber optic sensors designed to monitor the vibration of machines also in conditions of the possible presence of flammable or explosive gases and liquids.

Prior Art

Known fiber-optic converter of physical quantities, which can be used as a sensitive element in gravimeters, seismic receivers, as well as in accelerometers, vibration transducers. The sensitive element includes an inertial mass fixed on the light guides forming the elastic element, at least one optically conjugated pair of transmitting and receiving fiber light guides, one of which is part of the elastic element. The light guides of the elastic element can be a flat or three-dimensional figure (RF patent 2164339. 2000 Bull. No. 27). Under the action of the measured acceleration on the inertial mass, the end face of the transmitting light guide is displaced relative to the end face of the receiving light guide, causing modulation of the transmitted optical power.

The main disadvantage of the known device is the difficulty of aligning the two fibers relative to each other. This design is not able to perceive and reflect high amplitudes and impacts, and such a design and technology is difficult to manufacture.

Known fiber-optic vibration converter applicable to solve the problem of vibration control under vibration loads of large electrical machines. The fiber-optic vibration transducer contains a carrier base, a vibration element, optical light guides, relative to the ends of which a reflective surface is formed at a distance, each of the optical light guides simultaneously performs the function of supplying and removing a luminous flux, the carrier base from a single crystal plate is made in one piece with the vibration element, light guides are fixed above and below the supporting base, the axes of which are perpendicular to the reflecting surface, and the continuation of the axes of these light guides cross its upper and lower boundaries (RF patent 2537474, 2015, Bull. No. 1).

The disadvantages of the known device are the vulnerability to thermal effects, changes in stiffness characteristics with temperature changes, as well as material fatigue are not indicated. Due to the fact that in this design, not the fiber itself is used as an elastic element, certain restrictions and requirements are imposed on the material, which complicates and increases the cost of such a design.

The closest device of the same purpose to the claimed utility model in terms of a combination of features is a fiber-optic sensing element (Patent US 008995798, 2014). The invention is based on the back reflection of a beam from a surface with areas of different reflection coefficient and the passage of this beam into the fiber. When vibration occurs, the end of the fiber begins to oscillate, as a result of which it deviates from its original position. When crossing the boundary of the section, the intensity of the reflected beam changes and, falling back into the waveguide, is detected by the photodetector.

The disadvantages of the known device include the fact that the deviation of the fiber in the direction of the transverse measurement is not limited, which makes the sensor sensitive to transverse vibrations. Such a design can hardly be called easy to manufacture, although it is carried out by etching, the creation of attenuator zones is strictly regulated by an angle of 70 degrees, which makes such a design very demanding. This device is taken as a prototype.

The known device allows the production of fiber optic sensors, in particular vibration sensors, which are practically unaffected by very strong electromagnetic fields, which can operate at high temperatures.

Signs of the prototype, coinciding with the essential features of the claimed utility model, are the use of fiber as an elastic element, as well as the presence of a reflective element. A source of electromagnetic radiation connected by means of a fiber light guide and a sensitive element made in the form of an end face of a fiber light guide and a reflective element placed in the device case, and a photodetector included in the information processing unit.

The task to be solved by the claimed technical solution is to expand the arsenal of technical means for recording vibrations that allow continuous recording of vibrations of a controlled object without the need to adjust the operating point before operating the device.

The problem was solved due to the fact that in the proposed fiber-optic vibration sensor of the reflective type, the design of the reflective element was developed, made in the form of an interface between the media of the absorption band with a reflection coefficient k1 and reflection with a reflection coefficient k2>k1. An elastic element in the form of a pair of fibers has been developed, which ensures the sensitivity of the sensor to only one axis. A configuration of a single-axis and a two-axis reflective-type fiber-optic sensor has been developed. The adjustment of the fiber end in the sensitive part of the sensor to the media separation of the periodic reflective element is proposed, the proposed adjustment increases the sensitivity of the sensor and preserves the amplitude-frequency characteristics.

Features of the proposed technical solution, different from the prototype - elastic element, made in the form of a pair of fibers providing sensor sensitivity to only one axis; a reflective surface made in the form of an interface between the absorption and reflection bands, fixed on the base of the device body; design of single-axis and dual-axis reflective type fiber optic sensor;

Distinctive features in combination with the known ones make it possible to simplify the design of the reflective surface without loss of sensitivity by adjusting the reflective element to the media separation. The elastic element makes it possible to implement a uniaxial and biaxial reflective type sensor. Perform continuous registration of vibrations of the controlled object in the absence of the need to adjust the operating point before operating the device. The arsenal of technical means for recording vibrations is expanding.

The proposed device is illustrated by the drawings shown in Fig.1-5.

In FIG. 1 is a diagram of a fiber optic device.

In FIG. 2 shows the design of a single-axis fiber optic reflective type vibration sensor.

In FIG. Figure 3 shows the alignment of the fiber end to the reflective plate of a single-axis sensor.

In FIG. 4 shows the signal recorded from the sensor, with a vibration of 100 Hz.

In FIG. 5 shows a variant of a two-axis fiber-optic vibration sensor of the reflective type.

The fiber-optic device (figure 1) contains a source of electromagnetic radiation - a laser 1, a y-splitter 2, a fiber-optic uniaxial vibration sensor of the reflective type 3, a photodetector 4 included in the information processing unit (personal computer PC). The vibration sensor 3 is connected to the source of electromagnetic radiation 1 and the photodetector 4 by means of a fiber light guide through a y-splitter 2. In the claimed design, signal registration is possible using both coherent and incoherent radiation sources.

A fiber-optic uniaxial vibration sensor (Fig. 2) contains a housing made of two parts of the base (10) and a cover (7) laid on the base and hermetically fixed. The body material is selected according to the requirements of operation. Two grooves (9) are located on the base of the sensor, in which a light-conducting fiber (5) is laid through an opening (6) in the rear wall, directed to a reflective plate (11) fixed on the front wall of the housing, in such a way that the core of the light-conducting fiber is directed to section of media (Fig. 3) of the reflective surface. In the second groove there is a guide fiber (13) for forming an elastic element. The sensor is fixed with a threaded hole (8) to the object to be measured.

The elastic element in the sensor is made of two quartz fibers, which are placed in grooves (9) on the base (10) of the sensor. One light-conducting fiber (5) is used to transmit and receive a signal, the second guide fiber (13) is laid in the housing parallel to the light-conducting fiber in the same plane. The fibers are fixed to each other by a seismic mass (12) at the end of the free part of the fibers. Using a pair of fibers solves the problem of rigidity in a plane perpendicular to the measurement plane, which makes the sensor sensitive to only one axis.

In the proposed solution, quartz fibers are used as an elastic element, which are a fairly reliable material - homogeneous, elastic with a vitreous structure, which eliminates the need for special elastic elements. As a fiber light guide, a single-mode or multimode fiber light guide can be used.

The reflective element (11) is made in the form of two strips, an attenuation strip with a reflection coefficient k1(15) and a strip with a reflective coating with a reflection coefficient k2>k1 (14). The structure is made by sawing a plate (11) coated with a reflective coating at a right angle.

It should be noted that in the presented design there is the possibility of varying the operating range at the assembly stage by changing the length of the free end of the fiber and the seismic mass, the values of the resonant frequencies were calculated by a mathematical model.

The device operates as follows, the radiation from the source 1 through the fiber 5, resistant to bending, is directed to the vibration sensor 3 (figure 1, 2). When exposed to vibration, the free end of the fiber oscillates, as a result of which it deviates from the equilibrium position, the radiation from the end of the fiber, shifting to a reflective or attenuating surface, modulates the signal. The modulated radiation, reflected from the surface, returns to the fiber and propagates further along the light guide 5 in the opposite direction, subsequently being recorded by the photodetector module. The signal from the photodetector 4 is processed using specialized programs on a PC. In FIG. 4 shows the signal recorded from the sensor, with a vibration of 100 Hz.

Thus, the proposed device allows continuous registration of vibrations of a controlled object without the need to adjust the operating point before operating the device. Thereby expanding the arsenal of technical means for recording vibrations.

With a slight modification of the design, it is possible to implement a two-axis sensor, figure 5 shows a variant of a two-axis fiber-optic vibration sensor of the reflective type. For such a modification, it is required to add another bundle of light guide and guide fibers, turning it 90 degrees. Also, the reflective element is replaced by a plate made in the form of a square to form two media interfaces for the vertical and horizontal directions, respectively. The first bundle of light-conducting and guiding fibers, forming an elastic element in a two-axis sensor, is sensitive to vertical vibrations, the second bundle of fibers is sensitive to horizontal vibrations. Both bundles are adjusted to the separation of the attenuation media (15) and the reflective surface (14).

Claims (1)

A fiber-optic uniaxial vibration sensor of a reflective type, containing a body made of two parts - a base and a cover laid on the base and hermetically fixed, two grooves are located on the base of the sensor, in one, a light-conducting fiber is laid through the hole in the rear wall, directed to the reflective plate , fixed on the front wall of the housing, in such a way that the core of the light-conducting fiber is directed to the media separation of the reflecting surface, in the second groove there is a guide fiber for forming an elastic element, the sensor is attached by means of a threaded connection to the measurement object, characterized in that the elastic element is made in in the form of a pair of fibers, providing the sensitivity of the sensor to only one axis, a single-mode or multimode fiber light guide is used as a fiber light guide, the reflective element is made in the form of two strips, an attenuation strip with a reflection coefficient k1 and a strip with a reflective coating with a reflection coefficient k2>k1.

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