CA1158352A - Vibration transducer - Google Patents
Vibration transducerInfo
- Publication number
- CA1158352A CA1158352A CA000377002A CA377002A CA1158352A CA 1158352 A CA1158352 A CA 1158352A CA 000377002 A CA000377002 A CA 000377002A CA 377002 A CA377002 A CA 377002A CA 1158352 A CA1158352 A CA 1158352A
- Authority
- CA
- Canada
- Prior art keywords
- bush
- permanent magnet
- movable permanent
- induction
- vibration transducer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Reciprocating, Oscillating Or Vibrating Motors (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An induction vibration transducer for measuring vibrations or shocks comprising a bush having an inner surface and provided with an antifriction insert on its inner surface. Two fixed magnets each mounted at one end of the bush have opposite confronting poles. A movable permanent magnet is mounted for reciprocation within the bush between the two fixed magnets, each repelling a confronting pole of this movable permanent magnet. Two induction coils each having a geometrical axis conforming with the axis of the bush, are wound around empty spaces formed in the bush between the movable permanent magnet and the two fixed magnets when the movable permanent magnet is in a central position, and are mounted for delivering a resultant electromotive force corresponding to the sum of electromotive forces induced in the two induction coils during a movement of the movable permanent magnet. This vibration transducer has relatively small dimensions and also withstands an uneven temperature field.
An induction vibration transducer for measuring vibrations or shocks comprising a bush having an inner surface and provided with an antifriction insert on its inner surface. Two fixed magnets each mounted at one end of the bush have opposite confronting poles. A movable permanent magnet is mounted for reciprocation within the bush between the two fixed magnets, each repelling a confronting pole of this movable permanent magnet. Two induction coils each having a geometrical axis conforming with the axis of the bush, are wound around empty spaces formed in the bush between the movable permanent magnet and the two fixed magnets when the movable permanent magnet is in a central position, and are mounted for delivering a resultant electromotive force corresponding to the sum of electromotive forces induced in the two induction coils during a movement of the movable permanent magnet. This vibration transducer has relatively small dimensions and also withstands an uneven temperature field.
Description
115~35~
The present invention concerns a vibration transducer for measuring vibrations and shocks, especiall~ vibrations formed during the func-tion o~ machines and mechanical equip-ment.
Vibrations are one oE the important parameters charac-terizing the working conditions and the operating mode oE
a machine. It is of utmost importance to measure and evo-luate vibrations, particularly of high-speed rotating mach.ines and of equipment working in long service, such as steam and gas turbines.
In the mentioned energetic e~uipment the vibration transducers are e~posed very often to hi.gh temperatures, to a high acceleration and an important amplitude a-ttaining in certain phases of the operating mode the value of even several hundreds micrometers, whereas in the current opera-tion the vibration amplitude value is only few micrometers.
Besides that the vibration transducers should have small dimensions and weight, a linear characteristic within the whole measuring range and should be resistant against the electromagnetic interference.
Induction vibra-tion transducers are presently known, where a permanent magnet is suspended in an elas-tic membrane between two rigidly fixed coils. When the transducer moves there is induced in the coils an elec-tromotive orce.
which by a suitable equipment is amplified and measured. Such induction transducers have the disadvantage that under hard conditions, especially when the vibration amplitude is largely increased, their membranes are cracking.
Another known induction vibration transducer consists of a transducing coil and of two magnetic ringsO The inner movable magnetic ring is mounted with clearance in the cylindrical cavi-ty of the outer rigid magnetic riny. In the . ~:
a~5~352 narrow intercylindrical space between the two magnetic rings there is arranged a thi~ -transducing coil in a guIde bush.
The oscillation of the inner movable magnetic ring induces in the transducing coil an electromotive force which is ampliEied and measured in a suitable way. The disadvantage of this type of the vibration transducer is a relatively weak signal and an imperfect guide of the inner movable magnetic ring within the outer rigid magnetic ring which guide causes an increased friction during the operation and counter-running of the mutually moving parts. Thereby particularly is small vibration amplitudes, a considerable non-linearity in dependance of the induced electromotive force on the relative speed of the mac3netic rings is develop-ped. For these reasons -the use of this induction transducer is restricted only to measuring in the vertical direction.
Another known induction transducer has in a guide profile above a rigidly moun-ted solid magnet arranged concen-trically~a thin disc transducing coil above which coil is arranged an axially movable magnet. Owing to the oppositely polarized magnets~in their common front space are Eormed axial repulsive forces which forces function as a pushing elastic element holding the movable magnet in a permanent suspension above the solid magnet. This type of induction transducer makes possible to measure vibrations just in the vertical direction likewise.
There is known also an induction vibration transducer formed by a movable permanent ma~net mounted in a bush and ~llatcrally Li~cd by two sprillgs. ~ro~nl~ the busll is arrancJed an induction coil. When -the movable magnet moves there i5 induced an electromotive force in the coil which force is amplified, measured and evaluated in a suitable manner. However, this type of transducer has a lower sensitivity ow:ing to the ~ 15835~
friction in the bush and owing -to the twisting moment trans-mitted through springs to the permanent magnet and pushing the same to the walls of the bush~ Besides -that the mass and the proper frequence of the springs restricts the use of these transducers to a relatively small zone of frequency and acceleration. Likewise it is very difficult and costly to make springs with a precise characteristic and precise dimensions.
For measuring vibrations, particularly in -the said energetic equipment, there are used piezoelectric vibration transducers. In these piezoelectric transducers is made use of the capacity of some crystals to transduce mechanical forces to the electric tension proportional to the mass - acceleration of the piezoelectric transducer formed during the vibration. This electric tension is then again amplified, measured and evaluated with a suitable equipment. The advan-tage of the piezoelectric transducers is their capacity to withstand big acceleration and vibra-tion amplituaes and also their small dimensions. However they give weak signals.
Therefore, the respective amplifying equipment has to be in a relatively small distance from the piezoelectric trans-ducer. Besides that the piezoelectric transducers are very sensitive to the ambiant uneven temperature field.
The present invention aims at eliminating the ma~ority of the said disadvantages of the known vibrations t~ansducers.
According to the invention, there is provided an induction vibration transducer for measuring vibrations or shocks comprising a bush having an inner surface and provided with an antifriction insert on its inner surface, two fixed magnets each mounted at one end of the bush and having opposite confronting poles 7 a movable permanent magnet mounted for reciprocation within the bush be-tween the two f~xed magne-ts each repelling a confronting pole of ~lis movable permc~nent macJnet, and two induction^coils each having a geome-trical axis conforming with the axis of the bush. _ _ _ ~ ~5~3S2 The two induction coils are wound around empty spaces formed in the bush between the movable permanent magnet and -the two fixed magnets when the movable permanent magnet is in a contral position, and are mounted for delivering a resuItant electromotive force corresponding to the sum of electromotive forces induced in the two induction coils during a movement of the movable permanent magnet.
The permanent magnet may be provided with an antifriction wrapping.
The induction vibration transducer according to the invention may have relatively small dimensions and may withstand considerable acceleration amplitudes. It may also withstand an uneven temperature ~ield and can give a relatively strong ou-tput signal making thus possible to locate the amplifying and measuring equipment in a greater distance. Its sensitivity can be very good and it.may withstand temperatures up to.250C while keeping its linear characteristic of the output electromotive force in dependence of the speed.
Two embodiments of the invention are shown in the accompanying drawings.
FigO 1 shows the axial section of one embodiment;
Fig. 2 shows the axial section of another embodi-ment.
As shown in Fig. 1, the induction.vibration transducer consists of a closed cylindrical body 7 in the cavity of which is fixed a bush 2 with frontally concentric-ally arranged solid magnets 5,6. Between the said solid magnets 5/6 in the common front space in the cylindrical opening of the bush 2 is concentrically arranged an axially movable cylindrical permanen-t magnet 1. The mutually consequent poles orien-tation of the said solid magnets 5,6 and towards the same unconsequently poles orientated movable permanent magnet 1 Eorm axial repulsive forces both in the first front poles space 9 between the first _ ~ _ i'' .
, solid magnet 5 and the movable permanent magnet 1 as well as in the second front poles space 1~5~3~2 10 between the second solid m~net 6 and the mo~able perma-nent maynet l~ The magnetic fields in the said front poles spaces 9,10 function as pushing elastic elements with a very advantageous characteristic. The said repulsive forces of the magnetic fields acting in the poles spaces 9,10 prevent at the same time in any stationary position of the induction vibration transducer the direct contact of the permanent movable magnet 1 with any of the solid magnets 5l6. There is provided a frontally through ventil-lQ lation opening 12 in the movable permanent magnet 1 whichmagnet is provided in i-ts ou-ter cylindrical surface with an antifriction wrapping 8. The material of the slipping sur~ace of the antiEriction wrapping 8 and the material of the bushing 2 are chosen with regard to the minimal mutual friction factor. In the outer cylindrical surface of the bush 2 there are made two peripheral recesses wherein are arranged pseudobifiliary induction coils 3,4. The coil winding in the bifillary arrangement consists of two coil conductor warps arranged in one coil space and made by two conductors of an approximately same length. The conductor of one warp is wound in counter sense towards the concluctor of the second warp. Both conduc-tors are wound alternatively in immediate vicinity, being mutually conductivitely connected in the middle of the total length of the coil winding. The scope of this ~ifiliary arrangement of the coil winding is to compensate mutually the magnetic fields formed during the passage of the electric current through both coil conduc-tor warps.
Under this invention the concept of the pseudobifiliary arrangement of the coil winding means the arrangement of both coil conductor warps into two independent coil spaces. In the shown embodiment, the first coil conductor warp of the ~irst ' tl5~3~2 1 induction coil 3 is axiall~ offset towards the second coil conductor warp of the second inductio~ coil.4, In such a pseudobifiliary arrangement the magnetic fields formed ~; during the passage of the electric current through both conductor warps are compensated only partially~ On the other hand the pseudobifiliary arrangement makes it possible to increase the total electromotive force induced during the given axial movement of the permanent magnet 1 in the opening of the bush 2. ~uch an arrangement weakens besides that the in-terference influence, if any, of the outer magnetic fields. This weakening effect is assisted also by making the body 7 of ferromagnetic material.
In the second embodiment shown in ~ig~ 2, the bush 2 is in its cylindrical opening provided with a thin cylindrical . anti~riction insert 11. The bush 2 is made of ceramics and the antiEriction insert 11 of polytetrafluoroethylene also . known commercially as teflon. This prevents sticking of the permanent magnet 1 in the cylindrical opening of the bush 2.
It guarantees the dimensional stability of the bush 2 even during relativel~ high temperature changes. Otherwise this second embodiment is the same as the first one.
. When fixing the induction vibration transducer to an oscillating object, such as the bearing pedesta1 of a turbine, the permanent magnet 1 starts moving towards the remaining parts of transducer, i.e. towards its body 7 with the bush 2, .~ solid magnets 5,6 and induction coils 3,~. During this . movement, the lines of fo.rce of the permanent magnet 1 inter~
sect the winding of the inductions.coils 3,~ in which coils is induce.d the resulting electromotive force amplified and measured then with a suitable equipment. With the described pseudobifiliary arrange~ent of the induction coils 3,~, this resulting electromoti~e force i.s the sum of the partial electro~
~h 1 1~83~2 motive forces formed separately in the first induction coil 3 and in the second induction coil. 4, being thus of the maximal value.
The present invention concerns a vibration transducer for measuring vibrations and shocks, especiall~ vibrations formed during the func-tion o~ machines and mechanical equip-ment.
Vibrations are one oE the important parameters charac-terizing the working conditions and the operating mode oE
a machine. It is of utmost importance to measure and evo-luate vibrations, particularly of high-speed rotating mach.ines and of equipment working in long service, such as steam and gas turbines.
In the mentioned energetic e~uipment the vibration transducers are e~posed very often to hi.gh temperatures, to a high acceleration and an important amplitude a-ttaining in certain phases of the operating mode the value of even several hundreds micrometers, whereas in the current opera-tion the vibration amplitude value is only few micrometers.
Besides that the vibration transducers should have small dimensions and weight, a linear characteristic within the whole measuring range and should be resistant against the electromagnetic interference.
Induction vibra-tion transducers are presently known, where a permanent magnet is suspended in an elas-tic membrane between two rigidly fixed coils. When the transducer moves there is induced in the coils an elec-tromotive orce.
which by a suitable equipment is amplified and measured. Such induction transducers have the disadvantage that under hard conditions, especially when the vibration amplitude is largely increased, their membranes are cracking.
Another known induction vibration transducer consists of a transducing coil and of two magnetic ringsO The inner movable magnetic ring is mounted with clearance in the cylindrical cavi-ty of the outer rigid magnetic riny. In the . ~:
a~5~352 narrow intercylindrical space between the two magnetic rings there is arranged a thi~ -transducing coil in a guIde bush.
The oscillation of the inner movable magnetic ring induces in the transducing coil an electromotive force which is ampliEied and measured in a suitable way. The disadvantage of this type of the vibration transducer is a relatively weak signal and an imperfect guide of the inner movable magnetic ring within the outer rigid magnetic ring which guide causes an increased friction during the operation and counter-running of the mutually moving parts. Thereby particularly is small vibration amplitudes, a considerable non-linearity in dependance of the induced electromotive force on the relative speed of the mac3netic rings is develop-ped. For these reasons -the use of this induction transducer is restricted only to measuring in the vertical direction.
Another known induction transducer has in a guide profile above a rigidly moun-ted solid magnet arranged concen-trically~a thin disc transducing coil above which coil is arranged an axially movable magnet. Owing to the oppositely polarized magnets~in their common front space are Eormed axial repulsive forces which forces function as a pushing elastic element holding the movable magnet in a permanent suspension above the solid magnet. This type of induction transducer makes possible to measure vibrations just in the vertical direction likewise.
There is known also an induction vibration transducer formed by a movable permanent ma~net mounted in a bush and ~llatcrally Li~cd by two sprillgs. ~ro~nl~ the busll is arrancJed an induction coil. When -the movable magnet moves there i5 induced an electromotive force in the coil which force is amplified, measured and evaluated in a suitable manner. However, this type of transducer has a lower sensitivity ow:ing to the ~ 15835~
friction in the bush and owing -to the twisting moment trans-mitted through springs to the permanent magnet and pushing the same to the walls of the bush~ Besides -that the mass and the proper frequence of the springs restricts the use of these transducers to a relatively small zone of frequency and acceleration. Likewise it is very difficult and costly to make springs with a precise characteristic and precise dimensions.
For measuring vibrations, particularly in -the said energetic equipment, there are used piezoelectric vibration transducers. In these piezoelectric transducers is made use of the capacity of some crystals to transduce mechanical forces to the electric tension proportional to the mass - acceleration of the piezoelectric transducer formed during the vibration. This electric tension is then again amplified, measured and evaluated with a suitable equipment. The advan-tage of the piezoelectric transducers is their capacity to withstand big acceleration and vibra-tion amplituaes and also their small dimensions. However they give weak signals.
Therefore, the respective amplifying equipment has to be in a relatively small distance from the piezoelectric trans-ducer. Besides that the piezoelectric transducers are very sensitive to the ambiant uneven temperature field.
The present invention aims at eliminating the ma~ority of the said disadvantages of the known vibrations t~ansducers.
According to the invention, there is provided an induction vibration transducer for measuring vibrations or shocks comprising a bush having an inner surface and provided with an antifriction insert on its inner surface, two fixed magnets each mounted at one end of the bush and having opposite confronting poles 7 a movable permanent magnet mounted for reciprocation within the bush be-tween the two f~xed magne-ts each repelling a confronting pole of ~lis movable permc~nent macJnet, and two induction^coils each having a geome-trical axis conforming with the axis of the bush. _ _ _ ~ ~5~3S2 The two induction coils are wound around empty spaces formed in the bush between the movable permanent magnet and -the two fixed magnets when the movable permanent magnet is in a contral position, and are mounted for delivering a resuItant electromotive force corresponding to the sum of electromotive forces induced in the two induction coils during a movement of the movable permanent magnet.
The permanent magnet may be provided with an antifriction wrapping.
The induction vibration transducer according to the invention may have relatively small dimensions and may withstand considerable acceleration amplitudes. It may also withstand an uneven temperature ~ield and can give a relatively strong ou-tput signal making thus possible to locate the amplifying and measuring equipment in a greater distance. Its sensitivity can be very good and it.may withstand temperatures up to.250C while keeping its linear characteristic of the output electromotive force in dependence of the speed.
Two embodiments of the invention are shown in the accompanying drawings.
FigO 1 shows the axial section of one embodiment;
Fig. 2 shows the axial section of another embodi-ment.
As shown in Fig. 1, the induction.vibration transducer consists of a closed cylindrical body 7 in the cavity of which is fixed a bush 2 with frontally concentric-ally arranged solid magnets 5,6. Between the said solid magnets 5/6 in the common front space in the cylindrical opening of the bush 2 is concentrically arranged an axially movable cylindrical permanen-t magnet 1. The mutually consequent poles orien-tation of the said solid magnets 5,6 and towards the same unconsequently poles orientated movable permanent magnet 1 Eorm axial repulsive forces both in the first front poles space 9 between the first _ ~ _ i'' .
, solid magnet 5 and the movable permanent magnet 1 as well as in the second front poles space 1~5~3~2 10 between the second solid m~net 6 and the mo~able perma-nent maynet l~ The magnetic fields in the said front poles spaces 9,10 function as pushing elastic elements with a very advantageous characteristic. The said repulsive forces of the magnetic fields acting in the poles spaces 9,10 prevent at the same time in any stationary position of the induction vibration transducer the direct contact of the permanent movable magnet 1 with any of the solid magnets 5l6. There is provided a frontally through ventil-lQ lation opening 12 in the movable permanent magnet 1 whichmagnet is provided in i-ts ou-ter cylindrical surface with an antifriction wrapping 8. The material of the slipping sur~ace of the antiEriction wrapping 8 and the material of the bushing 2 are chosen with regard to the minimal mutual friction factor. In the outer cylindrical surface of the bush 2 there are made two peripheral recesses wherein are arranged pseudobifiliary induction coils 3,4. The coil winding in the bifillary arrangement consists of two coil conductor warps arranged in one coil space and made by two conductors of an approximately same length. The conductor of one warp is wound in counter sense towards the concluctor of the second warp. Both conduc-tors are wound alternatively in immediate vicinity, being mutually conductivitely connected in the middle of the total length of the coil winding. The scope of this ~ifiliary arrangement of the coil winding is to compensate mutually the magnetic fields formed during the passage of the electric current through both coil conduc-tor warps.
Under this invention the concept of the pseudobifiliary arrangement of the coil winding means the arrangement of both coil conductor warps into two independent coil spaces. In the shown embodiment, the first coil conductor warp of the ~irst ' tl5~3~2 1 induction coil 3 is axiall~ offset towards the second coil conductor warp of the second inductio~ coil.4, In such a pseudobifiliary arrangement the magnetic fields formed ~; during the passage of the electric current through both conductor warps are compensated only partially~ On the other hand the pseudobifiliary arrangement makes it possible to increase the total electromotive force induced during the given axial movement of the permanent magnet 1 in the opening of the bush 2. ~uch an arrangement weakens besides that the in-terference influence, if any, of the outer magnetic fields. This weakening effect is assisted also by making the body 7 of ferromagnetic material.
In the second embodiment shown in ~ig~ 2, the bush 2 is in its cylindrical opening provided with a thin cylindrical . anti~riction insert 11. The bush 2 is made of ceramics and the antiEriction insert 11 of polytetrafluoroethylene also . known commercially as teflon. This prevents sticking of the permanent magnet 1 in the cylindrical opening of the bush 2.
It guarantees the dimensional stability of the bush 2 even during relativel~ high temperature changes. Otherwise this second embodiment is the same as the first one.
. When fixing the induction vibration transducer to an oscillating object, such as the bearing pedesta1 of a turbine, the permanent magnet 1 starts moving towards the remaining parts of transducer, i.e. towards its body 7 with the bush 2, .~ solid magnets 5,6 and induction coils 3,~. During this . movement, the lines of fo.rce of the permanent magnet 1 inter~
sect the winding of the inductions.coils 3,~ in which coils is induce.d the resulting electromotive force amplified and measured then with a suitable equipment. With the described pseudobifiliary arrange~ent of the induction coils 3,~, this resulting electromoti~e force i.s the sum of the partial electro~
~h 1 1~83~2 motive forces formed separately in the first induction coil 3 and in the second induction coil. 4, being thus of the maximal value.
Claims (5)
1. An induction vibration transducer for measuring vibrations or shocks comprising a bush having an inner surface and provided with an antifriction insert on said inner surface, two fixed magnets each mounted at one end of the bush and having opposite confronting poles, a movable permanent magnet mounted for reciprocation within said bush between said two fixed magnets each repelling a confronting pole of this movable permanent magnet, and two induction coils each having a geometrical axis conforming with the axis of the bush, said two induction coils being wound around empty spaces formed in the bush between the movable permanent magnet and said two fixed magnets when said movable permanent magnet is in a central position, and being mounted for delivering a resultant electromotive force corresponding to the sum of electromotive forces induced in the two induction coils during a movement of the movable permanent magnet.
2. An induction vibration transducer according to claim 1, wherein said movable permanent magnet has an axial opening.
3. An induction vibration transducer according to claim 1, wherein said induction coils are wound into peripheral recesses formed in the outer surface of said bush.
4. An induction vibration transducer according to claim 1, wherein the movable permanent magnet is provided with an antifriction wrapping.
5. An induction vibration transducer according to claim 1, further comprising an outer housing made of a ferromagnetic material.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000377002A CA1158352A (en) | 1981-05-06 | 1981-05-06 | Vibration transducer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000377002A CA1158352A (en) | 1981-05-06 | 1981-05-06 | Vibration transducer |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1158352A true CA1158352A (en) | 1983-12-06 |
Family
ID=4119902
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000377002A Expired CA1158352A (en) | 1981-05-06 | 1981-05-06 | Vibration transducer |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1158352A (en) |
-
1981
- 1981-05-06 CA CA000377002A patent/CA1158352A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |