JPS6114519A - Detecting device of number of revolution, speed etc. - Google Patents

Abstract

PURPOSE:To enable to perform the measurement having high reliability even under electromagnetic noise by providing a magnetic flux generating part on a rotary body, detecting the movement of the magnetic flux generating part and modulating the intensity of the light with the detecting output thereof. CONSTITUTION:A permanent magnet 11 is buried on the periphery of a circular disk 10 and when the circular disk 10 is rotated, a voltage is caused on a coil 30 and the voltage thereof is impressed on between electrodes 31, 32. A Mach- Zehnder type light wave guide 25 is consisted of a light wave guide path part 23 for input, two branched light wave guide path parts 21, 22 and light wave guide path part 24 for output, and the light of which intensity is modulated according to the voltage impressed on between electrodes 31, 32 is converted into electrical signal by a photoelectric converting element 43. The electrical signal thereof is transmitted to a level discriminating circuit 45 via a low pass filter 44, further is inputted into a counter 46 as a square wave signal and at the same time the detecting signal showing the number of revolutions of the circular disk 10 is obtd. from the counter 46.

Description

[Detailed Description of the Invention] Background of the Invention [Technical Field of the Invention] This invention relates to the rotational speed, rotational speed, angular velocity 2, angular position of a rotating body, and the velocity of an object that periodically moves on a fixed course. , relates to a device that detects the period, position, speed of other objects, etc. using optical signals.

[Description of prior art]

Optical transmission has the excellent feature of not being affected by electromagnetic noise, so it is suitable for data transmission in environments with a lot of electromagnetic noise. Since optical fibers allow optical data transmission with low loss, data transmission over relatively long distances can also be performed. When the data to be optically transmitted is some kind of measurement data, such as the number of rotations, it is preferable to perform the measurement or detection in the form of light and then optically transmit the measurement data as it is through an optical fiber. This is where the use of optical sensors and optical fiber sensors comes into play. Combining optical sensor detection and optical fiber transmission enables highly reliable measurement and long-distance transmission even in environments with a lot of electromagnetic noise, creating a remote measurement system that uses light.

Now, in a typical optical sensor for measuring rotational speed, rotational speed, angular velocity, etc., a hole is drilled in a part of the periphery of the opaque rotary plate, and a pair of optical fibers are inserted into the hole from both sides. There is something that is opposite. Light from a light source is emitted from one optical fiber and enters the other optical fiber.

As the rotating plate rotates, when the hole reaches the position of the optical fiber, light passes through this hole, and when the other portion faces the optical fiber, the light is blocked. Therefore, an on/off optical signal corresponding to the rotation of the rotating plate is obtained in the other optical fiber.

However, in such an optical sensor, since the light emitted from one of the optical fibers is spread out, only a small portion of the light enters the other optical fiber, which reduces the intensity of the resulting photodetection signal. It has the disadvantage of being low. In order to eliminate this drawback, it is necessary to converge the light emitted from one of the optical fibers using a lens. Since a lens is required, the configuration becomes more complicated and strict optical axis alignment is required. In addition, there is a high possibility that the optical axis will shift due to vibration or the like.

Summary of the Invention [Object of the Invention] This invention utilizes the features of optical measurement, which enable highly reliable measurement and low-loss long-distance transmission even under electromagnetic noise. It is an object of the present invention to provide a detection device for detecting rotational speed, speed, etc., which does not require such troublesome work and does not cause a situation in which measurement cannot be performed due to optical axis deviation.

[Structure, operation, and effects of the invention]

The detection device for detecting the number of rotations, speed, etc. according to the present invention is fixed to one relatively moving object, such as a magnetic flux generating part, such as a permanent magnet, provided on a rotating body, and the other object, such as a fixed member, to generate magnetic flux. An element that generates an electromotive force when a coil passes relatively close to it, such as an element that modulates the intensity of light guided from a light source by applying an electromotive force generated by a coil, and an element that modulates the intensity of light guided from a light source by applying an electromotive force generated by a coil. The present invention is characterized in that it includes means for creating information regarding the movement of a moving object, such as rotation speed and speed data, from changes.

Every time the magnetic flux generator passes near the electromotive force generating element,
The intensity of the light directed from the light source is modulated, eg, the intensity is increased or decreased. Therefore, by counting the number of light intensity modulations in a certain period of time, or
By measuring the time interval between two light intensity modulations, data on the rotational speed and speed of a moving object can be obtained.

Light from a light source is guided to a light intensity modulating element through an optical fiber, and output light (intensity modulated light) from this element is sent to an information generating means through an optical fiber. Since the optical fiber and the light intensity modulation element are easily connected by a known optical connector or the like, there is no need to align the optical axis using a lens as in the past, and there is of course no fear that the optical axis will shift.

Some conventional magnetic rotation speed sensors have a rotating plate around which a permanent magnet is fixed, or a rotating plate whose periphery is magnetized.

This rotational speed sensor uses a magnetoelectric conversion element that responds to the magnetism of a rotating plate to extract an electrical signal representing the rotational speed. According to the present invention, the rotary plate of such a conventional magnetic rotation speed sensor can be used as is and easily modified into an optical measurement and transmission system using an optical fiber.

DESCRIPTION OF EMBODIMENTS [Structure of rotational speed detection device] In FIG. 1, a disk OQ is fixed at the center of a shaft whose rotational speed is to be detected, for example, an output shaft of a motor or a shaft connected thereto (not shown), The disk side rotates together with this axis. One permanent magnet (11) is embedded around this disk GO+. A magnet that moves circularly as the disc side rotates (at any point on the trajectory of 1υ,
A coil (2) is arranged so as to face the magnet (indicated by the m line ('11 a )) that has reached this point in the vicinity thereof, and is fixed at that position by a suitable fixing member.

The magnet OD can also be provided on the circumferential surface of the disk. In this case as well, the coil circle is fixed in such a manner that it interlinks as much as possible with the magnetic flux generated from the magnet (11). Instead of providing the permanent magnet (11) on the disk side, the disk 0
01 The light intensity modulation element may be made of a ferromagnetic material, or a ferromagnetic ring may be fitted around the disk α0), and the ferromagnetic material may be magnetized. For example, it includes a Matsuhatsu Enda type optical waveguide (c) formed on a L I N b Oa crystal substrate (c).

This Matsuhatsu Enda type optical waveguide (c) consists of an input optical waveguide part (2), two branched optical waveguide parts (21) (a) branched from this optical waveguide part at an equal angle), and these optical waveguide parts. (2) Output optical waveguide part where l □ □ ■ is formed on the substrate ■.Both ends of the coil ■ are connected to these electrodes 01) (to), respectively, and the voltage induced in the coil (to) is applied between these electrodes (311□□□). It is marked by a number of marks.

The optical waveguide (to) is formed, for example, by heating Ti in the substrate (2), and the electrode (01) (A) is made of AI! It is made by vapor-depositing.

Light from a light source (not shown) is generally output through an optical fiber (41), and the intensity-modulated light is similarly guided to the optical fiber 142 via a suitable optical coupler. The optical signal of the optical fiber (42) is converted into an electrical signal by the photoelectric conversion element (43). This electrical signal (a) is sent to the level discriminator circuit (45) via the low-pass filter (signal (b)). ) ), and also a pulse or square wave signal (C)
is input into the counter (46) as follows.

A detection signal representing the number of rotations of the disk opening O) is obtained from the counter (46).

[Relationship between permanent magnet and coil]

When the disk aω rotates once, the magnet (11) passes near the coil field once. At this time, the magnetic flux generated from magnet 01) interlinks with coil ■, and the number (density) of the interlinked magnetic flux changes with time, so an electromotive force V is generated in coil 0■ due to mimagnetic induction. . This electromotive force ■ is given by the following equation.

Here n. is the number of turns of the coil, and Φ is the number of magnetic fluxes interlinking with the coil.

The relationship between the sizes of the magnet (11) and the coil (30) is shown in FIGS. 2 and 3. In these figures, the surface of magnet 01) facing the coil +30) (hereinafter referred to as the magnet surface) and the coil (2)) are both shown as circular, but they may also be rectangular or other shapes. The following discussion applies equally.

Figure 2 (A) shows that the diameter of the surface of the magnet (11) is smaller than the diameter of the coil (G); This is a case where the diameter and the diameter of the coil (2) are approximately equal.

FIG. 4 shows the electromotive force V generated in the coil and the coil gloss when the diameter of the surface of the magnet (11) and the diameter of the coil 00 differ by a large width (FIG. 2).

The flux linkage number Φ changes when the magnet (11) and the coil (7) approach and move away, and while the magnet (11) is contained within the coil surface (Fig. 2 (A)) and While the coil (30) is contained within the plane of the magnet (11) (as shown in FIG. 2), the flux linkage number Φ remains approximately constant.

Therefore, positive and negative electromotive forces (2) are generated in the coil (30) twice, at positions somewhat apart in time, when they approach each other and when they move away from each other.

FIG. 5 shows the magnetic flux linkage when the diameter of the surface of the magnet (11) and the diameter of the coil (2) are approximately equal (FIG. 3). In this case, since the magnet (11) and the coil (2) immediately separate when they approach each other, the time during which the linkage magnet Φ remains constant is almost zero, and the positive and negative electromotive force V is applied to the coil (2). occur continuously over time.

In the following explanation, as shown in FIG.
The discussion will proceed on the assumption that the diameter of the surface of and the diameter of the coil ■ are approximately equal. This is because this is easier to explain than the relationship between the magnet (II) and the coil (2) as shown in FIG. However, the present invention is applicable to either the case of FIG. 2 or FIG. 3.

[Relationship between applied voltage and light intensity in the light intensity modulation element]

In Fig. 1, the light propagating through the input optical waveguide section (23) of the Matsuhatsu Enda type optical waveguide (b) is split equally into two branch optical waveguide sections en ), and the output optical waveguide part (combined at 21J. Two branch leading waveguide parts t21)
If the lengths Jl and J2 of E (the length from the branch point to the confluence point as shown by the broken line) are equal, the branched optical waveguide portion t
Since the two lights propagating through 211 (22) are branched from one light, the output moonlight waveguide portion +24
] The phases match when multiplexing. therefore,
If propagation loss is not considered, the output optical waveguide section (towards)
The intensity of the light obtained at the input optical waveguide section (23j) is equal to that at the input optical waveguide section (23j).Generally speaking, the two lights that have propagated through the branch optical waveguide section (21) are combined at the output optical waveguide section (c). When the waves wave, the phase difference between them is 2mπ (
If m is 0 or an integer), light with the same intensity as the light input to the Matsuhatsu Enda type optical waveguide (this is referred to as maximum intensity I m a X) can be obtained from the output optical waveguide. The phase difference between the two lights is 2mπ, which means that the difference in length of the branched optical waveguide part an@ is Δl=l 1−J 2
It is expressed as follows.

Δl=0. 5...(2) Here, n is the refractive index of the leading wavepath, λ. is the wavelength of light in a vacuum.

If the difference in length Δl between the branched optical waveguide portions (21) and (2) has the following relationship, then these optical waveguide portions (2]l(
When the light propagated in c) is combined in the output optical waveguide section (branch), the phase difference becomes ('2m+1)π.

In this case, since two lights of opposite phases are superimposed, the intensity of the light obtained in the output optical waveguide becomes 0.

Now, since L I N b Oa is a crystal with an electro-optic effect, its refractive index changes when an electric field is applied. For example, in the case of a two-cut L I N b Oa, the optical waveguide portion (
2] The refractive index of 1(2) changes as follows.

n = n + −n @r @E1
2 6 a3 K13, K33/K2
200. (4) n2 = 0-Tne Here, K2 is the strength of the electric field in two directions, no is the extraordinary ray refractive index, and K33 is the electro-optical constant.

As is clear from equation (4), when a voltage is applied between the electrodes 131), the refractive index of one side of the branched optical waveguide portion Q112 increases, and the refractive index of the other side decreases. When the refractive index changes, the speed of light propagating through the leading waveguide section Q]1@ changes, so the phase difference when these lights are combined in the output moonlight waveguide section changes. For example, when the lengths of the branched optical waveguide sections (21) and (2) satisfy equation (2), the phase difference when the light propagating through the branched optical waveguide section (211) is combined is (31) If no voltage is applied to (support), it is 2mπ and the intensity I m
Light of a The intensity of the light obtained is 0. The voltages required to change the phase difference of the two lights propagating through the branched optical waveguide section (2) 1 (2) by π are called half-wavelength voltages v, r.

FIG. 6 shows the branched optical waveguide section C! H2; Difference in length Δ of a
Electrode 01) (support) when l satisfies formula (2)
It shows the relationship between the voltage applied between the two and the intensity of light obtained at the output optical waveguide. When the applied voltage is ±2 mvf, light with maximum intensity Im&X is obtained;
The intensity of light becomes 0 when m+1)V□.

FIG. 7 shows the length difference Δl of the branched optical waveguide portion 011 @
It shows the relationship between the voltage applied between the electrodes 011 and the intensity of light obtained in the output optical waveguide (to) when the equation (3) is satisfied. The applied voltage is ±(2m + 1
) ■When x, light of maximum intensity Imax is obtained, and when the applied voltage is ±2 mV, the light intensity becomes O.

As can be seen from equation (1), the voltage V generated in the coil field in Fig. 1 is determined by the number of magnetic fluxes generated by the magnet (111)
), the number of turns nc of the coil (support)), and the chain d Φ Change in the received magnetic flux □, that is, the rotational speed d of the disk (10)
It also changes depending on the rotation speed. The number of flux linkages Φ and the number of turns n. Assuming that is constant, the voltage (2) changes depending on the rotation speed, and the faster the rotation speed, the higher the voltage generated.

Further, the phase difference of the light propagating through the branched optical waveguide portion (211 (22)) also changes depending on the length of the optical waveguide portion to which the electric field is applied, that is, the length of the electrode (311 (32)).

Figures 8 and 9 show the intensity of the light obtained in the output optical waveguide section (two) over time when the disc rotates and the magnet (11) passes near the coil in the configuration shown in Figure 1. This is shown in relation to the axis.

FIG. 8 shows a configuration (the (th 2), corresponds to Figure 6), and Figure 9 shows a configuration (Equation (3), 7).The waveform in FIG. 8 is the same as the waveform in FIG. 9 inverted between light intensity 0 and Imaz, so only FIG. 9 will be described.

As mentioned above, when the magnet (11) passes near the coil (301), positive and negative voltages are generated successively in the coil (301), and the absolute values of these voltages are equal. As shown in , the light intensity is symmetrical with respect to positive and negative voltages with the applied voltage O as the center, and the applied voltage V is ±V7c.
The light intensity reaches its maximum value when . Therefore, coil 00
) is less than V7r, two peaks slightly shifted on the time axis appear in the light intensity, and these peak values do not reach the maximum intensity Imax (
Figure 9 (8), solid line). Then, the absolute value of the voltage V is V,
This is because when the peak value of the light intensity is determined to be the absolute value of the voltage V generated by the coil Ⅰ, the dent in the peak portion of the light intensity waveform becomes smaller than when it is removed (see Figure 7). ).

When the absolute value of the voltage V becomes 2■□, the above-mentioned depression decreases to the intensity O, so that the light intensity waveform substantially has four peaks (FIG. 9(C)).

It is easy to understand that as the absolute value of the voltage ■ becomes higher, more pulse-like waveforms occur in the light intensity.

[Operation of rotation speed detection device]

The low-pass filter (shows the output signal (b) of 4Φ and the output signal (c) of the level discrimination circuit (45), see the same figure) is a disk (see figure (B)) when the rotation speed of 101 is small.
(8) in the same figure shows a case where the rotational speed is higher, and (C) in the same figure shows a case where the rotational speed is even higher. These figures are all under the condition that the difference in length of the branched leading waveguide portion Q1)@ of the Matsuha Tsuenda type leading waveguide (5) satisfies formula (3) (Figs. 7 and 9). ).

The waveform of the output signal (-) of the photoelectric conversion element (431) is the waveform of the output signal (-) of the photoelectric conversion element (431).
is the same as the intensity of light obtained in As is well known, the signal waveform may be inverted depending on the configuration of the element (43). As mentioned above, if the magnetic flux generated by the magnet (11) and the number of turns N of the coil (30) are constant, the voltage generated in the coil (1) is equal to
The voltage depends on the number of rotations, and the higher the number of rotations, the higher the voltage. Figure 10 (4) shows when the absolute value of the generated voltage ■ is lower than V, and Figure 10 (B) shows that when it is almost equal to v9, the same figure shows 0.
This corresponds to the case where 2■ is approximately equal to (see Fig. 9).

As can be seen by comparing Fig. 10 (6) to the working signal (a), as the rotation speed of the disk aα increases, the time T for the magnet (11) to pass near the coil ■ becomes shorter. ,
The number of pulse-like components generated in one pass increases. Therefore, as the number of revolutions )A increases, the signal (&) contains more high-order harmonic components.

Low pass filter (441 is a signal (a) corresponding to the lowest rotation speed within the rotation speed detection range of this detection device)
The pass band is determined to such an extent that a frequency component having one peak is passed for a signal component having two peaks included in the signal component. Therefore, no matter what the rotational speed is, the signal (b) is level-discriminated and waveform-shaped by the threshold value (8) set for one revolution of the disk 00). C)).

The counter (the moth is the interval between pulses contained in the signal (a) (
Pulse interval P,) is measured or a certain period of time ctl'Hi
This is to count the number of pulses in the pulse.

These timing results or counting results represent the rotational speed, rotational speed, or angular velocity of the disk oO1.

[Modified example]
.

In the above embodiment, one permanent magnet Qll is provided on the disk 001, but if a plurality of permanent magnets are provided at equal angular intervals, the accuracy of rotational speed and angular velocity detection will be improved. In addition, when detecting a specific angular position of the disk αQ, it is necessary to arrange the plurality of permanent magnets not at equal angular intervals, but in such a way that the arrangement state appears in the detection signal (for example, the output signal (C) of the level discrimination circuit (451)). In addition, the strength of a specific magnet is made stronger than other magnets, and a specific angular position is determined by the difference in the waveform appearing in the output signal (, ) of the photoelectric conversion element (0). may be detected.

The substrate may be any material as long as it has an electro-optical effect in which its refractive index changes upon application of an electric field. Therefore, the optical waveguide can also be fabricated using various techniques and materials depending on the type of substrate other than thermal diffusion of Ti. Electrode (31
1m changes the refractive index of the optical waveguide section by applying voltage, so it can be used in various shapes or shapes depending on the properties of the substrate.
It can take a placement state. For example, the electrodes C (11(a)) may be arranged to sandwich one branched optical waveguide portion.

It is also possible to ground one of the electrodes. Electrode AI! For example, it can be realized using other materials such as Ti.

Elements that modulate light intensity by applying an electric field include, in addition to those using the above-mentioned Matsuhatsu Enda type leading waveguide, devices that use, for example, a directional coupler between optical waveguides, such as those using Japanese Patent Application No. 57-86178. (Unexamined Japanese Patent Publication No. 58-202
40.6) which utilizes a waveguide optical beam splitter.

The present invention can be applied not only to the measurement of physical quantities related to the rotation speed of a rotating body, but also to the measurement of physical quantities related to the movement of an object that periodically reciprocates on a fixed two-dimensional or three-dimensional path.

In addition, if 21 permanent magnets are installed on one object that moves relatively, the periodic reciprocation of this object can be determined by measuring the time interval during which these two magnets pass near the coil. You can measure the speed of an object without it.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram showing an example of a rotation speed detection device, Figures 2 and 3 are diagrams showing the size and shape of the permanent magnet and coil, and Figures 4 and 5 are diagrams showing the size and shape of the permanent magnet and the coil. These are graphs showing the number of magnetic fluxes, their changes, and the electromotive force generated in the coil. Fig. 4 is a graph for the permanent magnet and coil shown in Fig. 2, and Fig. 5 is a graph for the permanent magnet and coil shown in Fig. 3. Figures 6 and 7 are graphs showing the relationship between the voltage applied to the electrodes provided in the Matsuhatsu Enda type optical waveguide and the light intensity of the output light obtained from the optical waveguide. Figure 7 shows the structure in which the light intensity is set to be maximum when no voltage is applied, Figure 8 shows the structure in which the light intensity is set to zero in the absence of applied voltage. FIG. 9 is a waveform diagram showing the optical intensity of the output light obtained from the Matsuhatsu Enda type optical waveguide when it passes near the permanent magnet in accordance with various applied voltages, and FIG. Figure 9 shows the structure in which the light intensity is set to be maximum when no voltage is applied, and Figure 10 shows the structure in which the light intensity is set to zero when no voltage is applied. Fig. 10 shows the output signal waveforms of each circuit shown in Fig. 1 (A) when the rotational speed is relatively small, and (C) when the rotational speed is about the same 1 and 2 respectively show cases where the number of rotations is relatively large. (101... Disk, (II)... Permanent magnet, (20
)... Electro-optic crystal substrate (light intensity modulation element), (21
1! ... Branch optical waveguide portion of Matsuhatsu Enda type optical waveguide, (5) ... Matsuhatsu Enda type optical waveguide, (30
)... Coil, 01) o21... Electrode, (43)
- Photoelectric conversion element, (441...low-pass filter, +45) - - Leher discrimination circuit, (46) - e-counter. Applicants for the above patents: 4 people other than Tateishi Electric Co., Ltd. (Fig. 2) Application of 9 cylinders (Fig. 7) Fig. 9

Claims (1)

[Claims] A magnetic flux generating section provided on one of objects that move relatively; an element that generates an electromotive force when the magnetic flux generating section passes relatively close to the other object; A device for detecting rotational speed, speed, etc., comprising: an element that modulates light intensity by applying generated electromotive force; and means for creating information regarding the movement of a moving object from changes in the modulated light intensity.