DE3428914A1 - Induction sensor - Google Patents

Abstract

In an induction sensor for scanning vibrations, having two magnets which are fixedly mounted on the end face with mutually like poles and in whose common end space there is arranged a movable annular permanent magnet having poles which are unlike with respect to the fixedly mounted magnets, the aim is to achieve the object of providing an induction sensor for scanning vibrations which has small dimensions, can be exposed to large accelerations and amplitudes of vibration, and whose robust design ensures reliable operation even in a nonuniform temperature field. The invention achieves this object when a first coil is wound in a pseudo-bifilar manner around a fixedly mounted sleeve in which the movable magnet moves, and a second coil, which is wound in a pseudo-bifilar manner around an element fixedly attached on both sides, is arranged in a cavity of the movable annular magnet.

Description

Prvni bimenska.strojjirnakoncernov ^ podnik, Brno, Olomoucka 7/9

--- . - Czechoslovakia -

Induction transmitter

The invention relates to an induction transmitter for scanning vibrations with two on the end face with one another co-rotating poles firmly attached magnets, in their common end space a movable ring-shaped permanent one Magnet is arranged with opposite poles opposite the fixed magnets.

Vibration is one of the most important parameters that characterize the operating condition of the machines. Measuring Vibration is very important in high-speed machines and facilities, especially in power engineering and in transport, e.g. for gas and steam turbines, compressors, fans, coal mills, vibration feeders, Turfcoladem, Aircraft engines etc.

In the above-mentioned devices, in particular in plug-in engines and energetic devices, the vibration transmitters are often elevated temperatures and a great acceleration as well as a vibration amplitude that reaches values of a few thousand microns in certain operating conditions. In stable operation, the vibration amplitude in high-speed rotary machines is only a few microns.,

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Further requirements for the vibration transmitter are small Dimensions and light weight, a linear characteristic in the "whole frequency range, a small Wäraedrift and Resistance to electromagnetic interference.

There are currently induction sensors used to scan vibrations, where a permanent magnet on one elastic membrane is suspended between two firmly attached coils Coils induce an electromotive force, which is amplified and measured with a suitable apparatus. Of the Disadvantage of this encoder is .darin that under difficult conditions, especially with a large increase in - vibration amplitude, the membranes burst and that their frequency characteristics are also not linear.

In another known induction transmitter for sensing vibrations, the movable, permanent magnet is in a Sleeve arranged and fastened on both sides with two springs. An induction coil is attached around the sleeve. When moving of the movable magnet, the electrical motor force is induced in the coil. «The disadvantage of this encoder is there in a lower sensitivity under the influence of the friction in the sleeve due to the torque that is passed through the springs are exerted on the permanent magnet and that presses it against the sleeve walls. Further limits the weight and the own spring frequency, the application of these donors to a relatively narrow. Frequency and acceleration range. In addition, these donors are difficult to manufacture.

There are also induction transmitters for sensing vibrations known in which a movable permanent magnet in a magnetic formed by two fixed magnets Field is suspended and in which movable magnets oppose the fixed magnets

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-current poles are arranged. The movable magnet moves in a Sleeve Shirt he se, which jam around an induction coil is wound pseudobi filar "During the movement of the permanent magnet in the coil, the electromotive force is induced, which is amplified and measured. These induction sensors are very reliable and have good linear characteristics, but the intensity of the signals and the sensitivity of the sensors depends on their size, which is disadvantageous. _z ■ "

Another well-known induction transmitter with an in the magnetic The movable permanent magnet has a suspended field inside the movable permanent magnet Induction coil that has an annular shape. This encoder has small dimensions, a low thermal drift, tolerates large accelerations and vibration amplitudes and is very resistant to electromagnetic Disruptions. The disadvantage of these transmitters is that they give weak signals and that they are more sensitive exhibit at a small acceleration.

A known method for scanning vibrations is measurement with piezoelectric vibration transmitters. Here the ability of some crystals to convert mechanical forces into electrical voltage is used, which causes the Vibrations resulting accelerations of the mass of the piezoelectric encoder is proportional. The advantage of this Method consists on the one hand in the ability to withstand a large acceleration and vibration amplitude, on the other hand in the small dimensions. The disadvantages here are the weak signals and the great sensitivity to the uneven temperature field of the environment.

The invention eliminates the disadvantages of the prior art. It is the object of the invention, "/ induction transmitter for Ab-

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to create vibrations that have small dimensions and are exposed to large accelerations and vibration amplitudes can be_and_whose robust construction reliable operation guaranteed even in an uneven temperature field.

The essence of the invention is that a first pseudobifilar coil is wound around a permanently attached sleeve is in which the movable magnet moves, and that a second pseudobifilar coil wound around a body fixed on both sides in a cavity of the movable one annular magnet is arranged. ~~ - ~~~

Both coils are mutually switched through in such a way that the movement of the moving coil in the individual coils? .Magnets generated electromotive force is added together. An induction transmitter constructed in this way has small dimensions and can withstand considerable acceleration and * large vibration amplitudes. Its sturdy construction ensures reliable operation and the uneven temperature field does not affect its characteristics the end. The encoder body made of ferritic material guarantees effective magnetic damping of the movement of the moving one Magnets and good shielding of both induction coils against electromagnetic interference.

It is useful if both firmly attached magnets have an annular shape.

To achieve good shielding of both induction coils against electromagnetic interference, it is advantageous to when the immovable sleeve is made of Teflon and when the movable annular permanent magnet is in an anti-friction sleeve is firmly attached. This also ensures a small amount of friction and therefore a high level of sensitivity of the Donor. The electrical signals of the so equipped encoder

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much stronger than with similar donors.

The essence of the invention is based on one below Execution shown schematically in the drawing. Example in more detail "explained.

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The drawing shows an axial section of the invention

according to ö

The induction generator consists of a closed cylinder body 5 made of ferritic material, in which with inserts "6.7 made of non-magnetic material one immovable sleeve 4 is permanently installed. Uin this is one first coil 5 pseudabifilar wound. The firmly attached Magnets 10, 11 are firmly attached in the inserts 6, 7. The body 8 is also in these insoles the second coil 9 firmly attached. This coil 9 is also wound in a pseudobifilar manner. The movable one ring-shaped permanent magnet is provided with an anti-friction sleeve 2 and moves see in a fixed Sleeve 4 # The second pseudobifilar coil 9 wound on the body 8 is in the cavity of this movable one Magnet 1 attached. Both firmly attached magnets 10, 11 are synchronous with poles, whereas the movable magnet 1 opposite the fixed magnets 10, 11 has opposite poles. The mutually opposite poles of the fixed magnets 10, 11 opposite the movable permanent magnets 1 form repulsive axial forces, so that the magnetic field as elastic Pressure elements with very advantageous characteristics acts.

In the embodiment described, the fixed sleeve is made of Teflon, whereas the anti-friction sleeve 2 of the movable magnet 1 is formed from a chromium-plated brass. This means that when the

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.movable ring-shaped permanent magnets emerging - Frictional forces reduced to a minimum · By having the . pseudobifilar incited coils 3.9 both the outer ones as well as the inner lines of force of the movable annular permanent magnet 1 are induced at a considerable electromotive force in motion. The robust design of the encoder ensures its reliable operation. The external disturbing electro-magnetic Signals are effectively shielded by the ferritic body 5. In addition, the ferritic body 5 enables the closure of the magnetic circuit of the movable ring-shaped permanent magnet and, consequently, the damping the undesired oscillation of this magnet, while maintaining sufficient sensitivity of the giver.

When attaching the induction transmitter to a vibrating object, e.g. the bearing of a gas turbine, the ring-shaped permanent magnet 1 begins opposite one another compared to the pseudobifilar wound coils 3.9 » the firmly attached necks 4, dea body 8 and opposite move the fixed magnet 10, 11 au. At this Movement intersects the outer and also the inner lines of force of the moving annular permanent magnet 1 the winding of the coils 3.9 »in which the electrical Force is induced · Hit a suitable circuit of the coils 3.9, the electromotive forces of both The coils are added together and the resulting electromotive force is further amplified using a suitable apparatus and measured. The magnetic damping of the movement of the movable annular permanent magnet 1 allows It does not vibrate too much if the machine's vibration frequency is close to the induction transmitter's own frequency or at higher harmonic multiples of this frequency lies.

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Claims (3)

Patent a η s ρ r ü ehe: _ - ^J ΐ, induction transmitter for scanning vibrations with " two magnets firmly attached to the end face with mutually sliding poles, in their common Frontal area a movable, ring-shaped permanent magnet with magnets fixed opposite the - ™ ~ opposing poles is arranged, characterized by '".. -. ^ ³ ^ —___ that a first pseudobifilar coil (3) is wound around a firmly attached sleeve (4) in which the movable magnet moves, and that a second paeudobifilar is wound around a body (8) firmly attached to both sides in one Cavity of the movable annular magnet is arranged, .._... '., _T * "■""' 2. Induction transmitter according to claim 1, ■ - characterized in that that both fixed magnets (10,11) have a ring-shaped Own porm. 3. Induction generator according to claim 1, .. characterized,. jl that the immovable sleeve is made of Teflon '^;;'* i and that the movable ring-shaped permanent magnet £ 3) is firmly attached in an anti-friction sleeve (2). _ ν EPOCQPY