JPS61193074A - Method and device for generating angular velocity signal by magnetic recording regeneration - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] - The present invention relates to the field of rotational speed measurement, and in particular to the recording and playback of individual magnetic regions on a rotating body.
The present invention relates to a method and apparatus for generating a repetitive signal representing the angular velocity of a rotating body in a mode.

BACKGROUND OF THE INVENTION Knowing the rotational or angular velocity of rotating elements is often of critical importance in moving machine applications, research, and diagnostics. To meet the need to obtain angular velocity,
Tachometers based on various operating principles have been developed.

For example, one well-known method is to paint axial stripes on a rotatable shaft and use an optical pickup to pass these stripes past the pickup while the shaft rotates. The purpose is to detect changes in reflected light over time. Another method is to attach a gear or similar device to a rotatable shaft and use a magnetic pick-up to detect and count southerly passages to determine the average speed of the shaft. It is something to do. Also, many other rotational speed/1111 determination methods and devices have been devised, all of which are not perfect for specific applications characterized by varying conditions to obtain rather basic measurements. There are many rotational speed measurement methods that operate satisfactorily, but the unique requirements of other applications preclude their use.

For example, the methods described above require physically attaching extra elements to the rotating body. Even if such attachment is physically possible, the expense required may prohibit it. Optical methods also have the disadvantage that the optical path between the indicator (for example a stripe) and the detector must be clear and free of any obstructions. This method is not always practical, especially where the light may be obscured by atomized oil or other liquids, or by dust or dirt that accumulates on the indicator or detector.

One area where synchronous speed measurement signals are particularly important and where traditional means have proven unsatisfactory is This is the case when torsional vibration is monitored. A signal having a repetition rate proportional to the rotational speed of the rotor is e.g.
Serves as an important input to vibration monitoring equipment as disclosed in US Pat.

If proper corrective action is not taken against undesired torsional vibrations, permanent damage may occur to the rotor or other components of the turbine generator. For maximum reliability in torsional vibration monitoring systems, a reliable rotor speed indication is required that can represent very small changes in the rotor's instantaneous angular velocity.

It is therefore an object of the present invention to generate an electrical signal whose frequency or repetition rate is representative of the instantaneous angular velocity of a rotating body, without the need for special attachments or extra markings on the rotating body. and equipment.

SUMMARY OF THE INVENTION In accordance with the present invention, a plurality of discrete magnetic regions are induced on the surface of a rotating body along a circumferential path located in a plane substantially perpendicular to the axis of rotation of the rotating body to generate a rotational speed signal. do,
This forms separate or individual permanent magnetic regions. This magnetic field can be detected as the rotating body rotates to form a desired response signal representative of the instantaneous angular velocity of the rotating body. In a preferred embodiment, a single probe disposed proximate the rotatable shaft and coupled to an inductive excitation source forms the means for guiding the magnetic region in a first mode of operation and in a second mode of operation. In this mode of operation, it forms means for detecting movement of the magnetic field. The induced excitation sources are synchronized using time-variable signals whose frequency is controlled to be a multiple of the rotational or angular velocity of the shaft so that the induced magnetic field is uniform and continuous around the freely rotatable shaft. and are spaced apart so that the number of regions guided along the circumferential path is independent of the rotational speed of the shaft. Embodiments of the invention are particularly suited for generating signals representative of the angular velocity of the rotor to enable measurements of torsional vibrations in the rotor of large turbine generators.

While the subject matter of the invention is set forth in the claims, the invention will be better understood from the following description taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 illustrates a circuit and apparatus arrangement for generating a signal having a repetition rate or frequency representative of the instantaneous angular velocity or rotational velocity of a rotatable shaft 10. A recording/reproducing probe 12 is disposed adjacent shaft 10 and is adapted to operate in a selected mode. That is, this probe 12 generates magnetic flux in the first recording mode, and this magnetic flux causes the shaft 10 to
induces a small local circumferential permanent magnetic field on the surface of the magnetic field, and in a second sensing or regeneration mode detects the movement of the previously induced magnetic field and generates an electrical signal in response to this movement. do. Shaft 10 may be a large shaft or a rotor of the type typically found in turbine generators in electrical equipment. Recording/playback probe 12
may be an electromagnetic element (described in more detail below).

Switch 13 is operative to select either a first or second mode of operation of probe 12, indicated by switch positions R (record) and P (play), respectively. In the recording mode, the common terminal C of the switch 13
is connected to the terminal R of the switch 13 to connect a circuit for supplying the excitation signal to the probe 12, and for this reason the shaft 1
A sufficiently strong electrical signal is provided to the probe 12 to induce a magnetic field on the surface of the probe 12 . In the preferred embodiment shown in FIG. 1, the magnetic field is guided while shaft 10 is rotating. The synchronization means 14 may consist of a shaft rotation sensor or a variable reluctance pickup that detects physical non-uniformities such as protrusions or notches in the shaft 10. The synchronization means 14 generates a synchronization signal or shaft rotation signal indicative of one complete revolution of the shaft 10;
This signal is coupled via amplifier 16 to inductive excitation source 15 . The inductive excitation source 15 includes a limiter 17, a phase-locked loop (PLL) 18, and a time base generator or divider 2.
0, an active filter 25 with an appropriate passband for the signal frequency determined by the frequency divider 20, and an amplifier 26.

Excitation source 15 can also operate without active filter 25, in which case the value of the divisor of frequency divider 20 can be varied without the need to change the frequency characteristics of active filter 25. A synchronization signal provided to the input of limiter 17 synchronizes the excitation signal provided to probe 12 from inductive excitation source 15 with the angular velocity of shaft 10, thereby creating uniformly spaced magnetic regions on the surface of shaft 10. is generated such that the number of induced magnetic regions along the circumferential path on the surface of shaft 10 is independent of the angular velocity of shaft 10.

That is, the excitation source 15 does not operate at a constant frequency, but rather generates an output or excitation signal having a frequency that is a predetermined multiple of the angular velocity of the shaft 10, such that the circumferential magnetic pattern induced around the shaft 10 is shaft 10
is guaranteed to be guided in a consistent manner on each rotation.

The synchronization signal applied to the input of amplifier 16 may be generated in any convenient manner. In the case of turbine generators for power plants, a generated power signal having a nominal frequency of 60 Hz in the United States is satisfactory as a synchronization signal.

Note, however, that the frequency of the synchronization signal does not need to be exact, but needs to be proportional to the angular velocity of the shaft. The synchronization signal is amplified in an amplifier 16 and its output is supplied to a limiter 17 that limits the amplitude. Therefore, a signal having an approximately constant amplitude and the same frequency as the synchronization signal is obtained at the output of the limiter 17.

The output of limiter 17 is coupled to the first power of phase-locked loop 18 . The phase-locked loop 18 and the time base generator 20 cooperate to form a frequency synthesis circuit that outputs an output signal having a frequency that is an integer multiple of the signal provided to the first input of the phase-locked loop 18 into the phase-locked loop. Generate from 18.

As is well known to those skilled in the art, the operation of phase-locked loop 18 is such that a signal obtained at the output of time base generator 20 and fed to a second or feedback input of phase-locked loop 18 is designed such that the frequency of the signal supplied to the second input of the phase-locked loop 18 is exactly the same as the frequency of the signal supplied to the first input of the phase-locked loop 18. ing. The time base generator 20 consists of a frequency divider or counter, the frequency of which is the output signal of the phase-locked loop 18.
is a selected submultiple of the frequency of the human input signal supplied to the time base generator 20 from the output of . Therefore, the frequency of the second human input signal of the phase-locked loop 18 is adjusted to be exactly equal to the frequency of the first input signal (g) of the phase-locked loop 18, so that the output signal of the phase-locked loop 18 has a frequency that is a multiple of the frequency of the signal at the first input of phase-locked loop 18, with this multiple being exactly equal to the divisor of time base generator 20.

For example, time base generator 20 may be configured to divide the frequency of its input signal by sixty.

In this case, the phase-locked loop 18 maintains the frequency of the signal applied to its second input equal to one cycle per revolution for a signal frequency assumed to be one cycle per revolution at its first input. As a result, a signal having a frequency of 60 cycles/revolution is generated at the output of the phase-locked loop 18.

Active filter 25 has an input coupled to the output of phase-locked loop 18 and provides a narrow band smoothing filter whose passband is centered at the desired excitation frequency. The smoothing action of filter 25 is designed to convert the output signal of phase-locked loop 18, which is approximately square wave in nature, into a sine wave before being applied to power amplifier 26. The output signal of power amplifier 26 is supplied to probe 12 via series resonant capacitor 27 and switch 13. Capacitor 27 in combination with the inductance of probe 12 forms a filter function, so active filter 25 may be omitted if desired.

The probe 12, shown in detail in FIGS. 2 and 3, has a narrow slot 52 extending through and across one end.
A laminated core 51 has a laminated core 51, and a pair of coils 53 and 54 are wound around opposing arms of the core 51. The slots 52 are configured to maintain sufficient magnetic flux communication between the probe 12 and the magnetic region induced on the surface of the shaft 10, such as in the axial direction of the shaft 10, which may occur due to thermal expansion or bearing wear. Preferably, the axial length is sufficiently long to accommodate movement. Furthermore, any magnetic core, such as a toroidal ferrite core, may be used in place of the iron core 51. coil 5
3 and 54 may each be approximately 550 turns of No. 26 AWG wire, for example. Preferably, the coils 53 and 54 are connected in parallel during the recording mode and in series during the playback mode, and the desired connection configuration can be selected with a switch. In FIG. 1, probe 12 is shown as including only a single coil to illustrate its preferred circuit configuration and to facilitate understanding thereof.

In operation, the probe 12 is mounted on a rotatable shaft 1
0 and fixedly disposed proximate the slot 52 to the third
As shown in the figure, it is approximately parallel to the axis of rotation of the shaft 10. The magnetic flux generated in the laminated core 51 by the excitation current supplied from the capacitor 27 (FIG. 1) through the coils 53 and 54 of the probe 12 is substantially confined within the core 51 except for the portion that crosses the slot 52. It is being

When an excitation current is supplied to the coils 53 and 54 of the probe 12, a portion of the magnetic flux is diverted out from the edge of the core 51 defining the slot 52 and passes through the rotating shaft 10. As such, magnetic flux traverses the slot 52, thereby inducing a localized magnetic region on the surface of the shaft 10.

The magnetic pattern thus induced follows the time-varying shape of the excitation current supplied from the amplifier 26 via the capacitor 27 to the coils 53 and 54, and in the case of a sinusoidal excitation current, in the circumferential direction of the shaft 10. The magnetic pattern is approximately sinusoidal. A sine wave is preferred as the excitation signal to avoid inductive effects such as ringing in the case of signals with a more rapid rate of change. Positioning the probe 12 to induce a magnetic region on the surface of the shaft 10 ensures that during the playback mode the probe 12 is placed in a magnetic flux that communicates with the induced magnetic region.

Referring again to FIG. 1, the value of capacitor 27 is selected such that when switch 13 is in the recording position R, probe 12 and capacitor 27 form a series tuned circuit that resonates at the frequency of the excitation signal. As a characteristic of the series resonant circuit, the reactance of the probe 12 (mostly inductive reactance) and the reactance of the capacitor 27 cancel each other out, so that when in the recording mode, the reactance of the probe 1
The current flowing through 2 is generally much higher than could be achieved without the series tuned circuit, thereby enhancing magnetic recording. The value of the capacitor 28 is such that when the switch 13 is in the playback position P, the capacitor 28 is connected in parallel with the probe 12 and resonates at the frequency of the excitation signal used to record the magnetic field on the surface of the shaft 10. selected to form a parallel tuned circuit. In this example where we are monitoring the shaft of a turbine generator,
The resonance frequency is, for example, 3600Hz. A parallel tuned circuit in regeneration mode generates a higher amplitude induced signal at and near the resonant frequency than an untuned circuit. The signal induced in the parallel tuned circuit is applied to the input of amplifier 30. The reproduction signal has a coded frequency proportional to the instantaneous velocity of the shaft 10 and is amplified by the amplifier 2g30. The amplified signal obtained at the output of the amplifier 30 can be used as a human input signal for a torsional vibration monitoring device for a turbine generator of an electrical installation, for example. Of course, capacitor 2
7 and capacitor 28 need not be precisely tuned to their respective predetermined resonant frequencies. However, it will be appreciated that if the circuits are not tuned to their respective predetermined resonant frequencies, the voltages and currents will be less than what can be achieved in a resonantly tuned circuit. Also, each circuit is greatly out of synchrony, and
- It is also possible to set the values of capacitors 27 and 28 such that the voltage and current of the respective circuits are insufficient to produce the desired effect according to the invention.

The operation of the circuit of FIG. 1 for monitoring the instantaneous angular velocity of working shaft 10 is as follows. The switch 13 is initially set to the record mode position R to enable the probe 12 to magnetize a small local area circularly disposed on the surface of the shaft 10. The probe 12 is an amplifier 26
It acts as an electromagnet that induces a magnetic pattern in response to an excitation signal current, preferably sinusoidal, supplied from the capacitor 27 through the capacitor 27 . Preferably, the induced magnetic region is arranged along a circumferential path located within the shaft portion substantially perpendicular to the axis of rotation. Preferably, the inductance of the probe 12, together with the predetermined capacitance of the capacitor 27, forms a series tuned circuit that resonates at the desired frequency of the excitation signal. The excitation signal provided to the probe 12 is synchronized to the rotation of the shaft 10 by a synchronization signal, which is one signal per revolution as described above, obtained from a shaft rotation sensor (14). The frequency of the synchronization signal is multiplied by the phase-locked loop 18 and the time base generator 20, and a signal having a frequency that is an integer multiple of the synchronization signal is supplied to the power amplifier 26 via an active filter 25.

The persistence of the magnetic pattern recorded on shaft 10 depends on the magnetic permeability of the material of shaft 10 as well as the physical environment of shaft 10, such as when exposed to an external magnetic field. However, when a typical shaft is constructed of a magnetic material such as iron, the magnetic pattern is relatively permanent, and thus the magnetization area is shaft 1
0, switch 13 is set to play position 10 and while shaft 10 is rotating,
The rotational speed signal or reproduction signal induced in the probe 12 by the magnetized region can be monitored.

The reproduction signal is generated in a parallel tuned circuit having a capacitor 28 of a predetermined capacity and a probe 28 of a predetermined inductance. This parallel tuned circuit is preferably tuned at the frequency of the excitation signal used to induce the magnetic field on the surface of shaft 10. The reproduction signal is encoded at a frequency that is proportional to the instantaneous angular velocity of the shaft 10, making it possible to detect very small changes in the velocity of the shaft, i.e. on the order of 2.times.10@-5 radians per second.

illustrating and describing what are considered to be preferred embodiments of the invention;
Although the best possible mode of carrying out the invention has been described, it should be understood that various modifications and other uses thereof are possible.

For example, although one electromagnetic probe 12 having two modes of recording and reproduction has been described, when carrying out the present invention, another probe 40 is used as a reproduction probe as shown in FIG. It will be appreciated that it may also be used as a probe for In this case, switch 13 is permanently selected to the R position, or switch 13 is omitted and probe 12 is connected directly to capacitor 27. In this alternative configuration, shaft 10
While rotating, continuous recording and continuous playback are possible. Probe 40 is fixed relative to shaft 10 and disposed circumferentially offset from probe 12 so as to be placed within the magnetic flux due to the magnetic pattern induced by probe 12 on surface -1- of shaft 10.

Capacitor 44 and probe 40 form a parallel tuned circuit, and the capacitance values of capacitor 44 are preferably selected such that the parallel tuned circuit resonates at a predetermined frequency of the excitation signal. The output regeneration signal from the parallel tuned circuit consisting of the probe 40 and capacitor 44 is provided to an amplifier 42 whose output signal is used as an input signal to a torsional vibration monitoring system, such as for a turbine generator in an electrical installation as described above. Ru.

Additionally, shaft 10 does not need to direct magnetic fields while disposed within the desired operating environment.

The magnetic field may be induced onto the surface of the shaft 10 beforehand at a location remote from the final use, since the induced magnetic field is permanent, in which case the aforementioned regeneration circuit will be applied to the surface of the shaft 10. It can be used to detect pre-induced magnetic fields at the final use site. By knowing the frequency of the excitation signal used to induce the magnetic field, the value of capacitor 28 or 44 can be selected to form a parallel tuned resonant circuit.

Thus, there has been illustrated and described a method and apparatus for generating electrical signals having a frequency or repetition rate representative of the instantaneous angular velocity of a rotating body without requiring special mounting or extra markings on the rotating body.

Although a preferred embodiment of the invention has been illustrated, many modifications and changes will occur to those skilled in the art. It is to be understood that the appended claims are intended to cover all such modifications and variations as fall within the true spirit and scope of the invention.

[Brief explanation of the drawing]

1 is a schematic circuit diagram showing a preferred circuit configuration for generating a signal representing shaft rotational speed according to the present invention; FIG. 2 is a schematic circuit diagram of a recording/playback probe suitable for use in the circuit of FIG. 1; FIG. 3 is a perspective view of the preferred embodiment; FIG. 3 shows the recording of FIG.
FIG. 3 is a side view of the reproduction probe. DESCRIPTION OF SYMBOLS 10... Rotatable shaft, 12... Recording/playback probe, 13... Switch, 27... Capacitor, 28... Capacitor, 40... Playback probe, 44... Capacitor .

Claims (1)

[Claims] 1. A speed measuring device for measuring the angular velocity of a rotatable shaft, which is fixed to the shaft and disposed close to the surface of the shaft, and in a first mode. induces a circumferential magnetic pattern on the surface of the shaft, and in a second mode has an output having a frequency representative of the instantaneous angular velocity of the shaft in response to movement of the magnetic pattern while the shaft is rotating. an electromagnetic probe operative to generate a signal; switch means coupled to said probe for switching between said first and second modes; and switch means coupled to said probe via said switch means in said first mode. excitation means having an output for generating an excitation signal applied to the probe during the first mode to induce the magnetic pattern by the probe, wherein the magnetic pattern is controlled at a rotational speed of the shaft; A speed measuring device characterized in that the excitation means includes synchronization means for synchronizing the frequency of the excitation signal and the rotational speed of the shaft so that the frequency of the excitation signal is independent of the rotational speed of the shaft. 2. The speed device according to claim 1, further comprising a first capacitor means, which forms a series resonant circuit together with the probe in the first mode, between the output of the excitation means and the switch means. A speed measuring device, wherein second capacitor means are coupled to said probe and which form a parallel resonant circuit with said probe in said second mode. 3. The speed measuring device according to claim 2, wherein the series resonant circuit and the parallel resonant circuit each resonate at the frequency of the excitation signal. 4. A speed monitoring device for measuring the angular velocity of a rotatable shaft, which is fixed to the shaft and disposed close to the surface of the shaft, and has a circumferential magnetic pattern on the surface of the shaft. a first electromagnetic probe operative to induce a movement of the magnetic pattern while the shaft is rotating, the first electromagnetic probe being fixed to the shaft and disposed within the magnetic flux of the magnetic pattern; a second electromagnetic probe that generates an output signal having a frequency representative of the instantaneous angular velocity of the shaft in response to a second electromagnetic probe coupled to the first probe and generating an excitation signal;
Excitation means for inducing the magnetic pattern by the first probe, and synchronization means for synchronizing the frequency of the excitation signal and the rotational speed of the shaft such that the magnetic pattern is independent of the rotational speed of the shaft. A speed monitoring device comprising: said excitation means comprising; 5. In the speed monitoring device according to claim 4, a first capacitor means forming a series resonant circuit together with the first probe is coupled between the first probe and the excitation means. and wherein second capacitor means are coupled to the second probe to form a parallel resonant circuit with the second probe. 6. The speed monitoring device according to claim 4, wherein the excitation means includes a phase-locked loop that generates the excitation signal, and the synchronization means supplies a synchronization signal to the phase-locked loop. Speed monitoring device containing a rotation sensor. 7. The speed monitoring device according to claim 5, wherein the excitation means includes a phase-locked loop that generates the excitation signal, and the synchronization means supplies a synchronization signal to the phase-locked loop. Speed monitoring device containing a rotation sensor. 8. The speed monitoring device according to claim 5, wherein the series resonant circuit and the parallel resonant circuit each resonate at the frequency of the excitation signal. 9. An apparatus for use in measuring the angular velocity of a rotatable shaft of a turbine generator, the device being fixed in close proximity to the surface of said shaft and in a first mode having a circumferential surface on the surface of said shaft. an electromagnetic device operative to induce a magnetic pattern and, in a second mode, generate an output signal having a frequency representative of the instantaneous angular velocity of the shaft in response to movement of the magnetic pattern while the shaft is rotating; a probe, coupled to the probe and configured to operate in the first mode and in the second mode;
switch means for selectively switching the mode of the switch; and an output coupled to the probe via the switch means in the first mode, and providing an excitation signal to the probe during the first mode. , excitation means for inducing the magnetic pattern by the probe; and first capacitor means coupled between the output of the excitation means and the switch means and forming a series resonant circuit with the probe in the first mode. and second capacitor means coupled to the switch means and forming a parallel resonant circuit with the probe in the second mode. 10. The device according to claim 9, wherein the series resonant circuit and the parallel resonant circuit each resonate at the frequency of the excitation signal. 11. The apparatus of claim 9, wherein the excitation means includes a phase-locked loop, the phase-locked loop controlling the excitation signal in response to a synchronization signal supplied to the phase-locked loop by a shaft rotation sensor. The device that generates it. 12. A device for use in measuring the angular velocity of a rotatable shaft of a turbine generator, the device being fixedly disposed proximate to the surface of the shaft and having a circumferential direction on the surface of the shaft. The first to guide the magnetic pattern
a second electromagnetic probe disposed within the magnetic flux of the magnetic pattern; and an output coupled to the first probe;
excitation means for supplying an excitation signal to the probe to cause the first probe to induce the magnetic pattern; an excitation means coupled between an output of the excitation means and the first probe; Apparatus comprising: first capacitor means forming a series resonant circuit; and second capacitor means coupled to said second probe and forming a parallel resonant circuit therewith. 13. The device according to claim 12, wherein the series resonant circuit and the parallel resonant circuit each resonate at the frequency of the excitation signal. 14. The apparatus of claim 12, wherein the excitation means includes a phase-locked loop, the phase-locked loop controlling the excitation signal in response to a synchronization signal supplied to the phase-locked loop by a shaft rotation sensor. The device that generates it. 15. A method for generating a repetitive signal whose repetition rate is proportional to the instantaneous angular velocity of a rotatable shaft, comprising: inducing a predetermined number of discrete magnetic regions on the surface of said shaft along a circumferential path; A method of detecting movement of the magnetic region while the shaft rotates past stationary sensing means disposed within the magnetic flux of the magnetic region to sense a magnetic field to generate the repetitive signal. 16. The method of claim 15 in which the magnetic region is guided while the shaft is rotating. 17. The method of claim 16, wherein the magnetic region is continuously guided on the surface of the shaft;
A method in which the movement of said magnetic region is detected continuously. 18. The method of claim 16, wherein the predetermined number of discrete magnetic regions is independent of the rotational speed of the shaft. 19. The method of claim 17, wherein the predetermined number of discrete magnetic regions is independent of the rotational speed of the shaft. 20. The method of claim 15, wherein the magnetic region is guided in response to the excitation signal from a series tuned circuit resonant at the frequency of the excitation signal. 21. The method of claim 16, wherein said magnetic region is induced in response to said excitation signal from a series tuned circuit resonant at the frequency of said excitation signal. 22. The method of claim 17, wherein the magnetic region is induced in response to the excitation signal from a series tuned circuit resonant at the frequency of the excitation signal. 23. The method of claim 15, wherein movement of the magnetic region is detected by inducing a current in a parallel tuned circuit including the sensing means and resonant at the frequency of the excitation signal. 24. The method of claim 16, wherein movement of the magnetic region is detected by inducing a current in a parallel tuned circuit including the sensing means and resonant at the frequency of the excitation signal. 25. The method of claim 17, wherein movement of the magnetic region is detected by inducing a current in a parallel tuned circuit including the sensing means and resonant at the frequency of the excitation signal.