JPS6138565A - Detector of number of revolution, speed, or the like - Google Patents

Abstract

PURPOSE:To perform high-reliability measurement under an electromagnetic noise and make the optical axis alignment work unnecessary to eliminate the impossibility of measurement due to the deviation of optical axis, by leading an electromotive force, which is generated in a coil when a moving magnet passes it, to a light intensity modulating element. CONSTITUTION:A coil 30 is fixed near an optional point of the locus of a circularly moved magnet 11 so that this coil 30 is linked sufficiently to the magnetic flux generated from the magnet 11. The light intensity modulating element includes two optical waveguides 21 and 22 formed on a substrate 20 consisting of a crystal having the electrooptic effect, for example, an LiNbO3 crystal. A pair of electrodes 31 are provided on parts close to each other of optical waveguides 21 and 22, and a voltage induced in the coil 30 is applied to these electrodes 31. The optical signal led to the optical waveguide 21 through an optical fiber 41 has the intensity modulated and is led to an optical fiber 42 and is converted photoelectrically by a photoelectric transducer 43 and is inputted to a counter 46 through a low pass filter 44 and a level discriminating circuit 45 to obtain a detection signal indicating the number of revolution of a disc 10.

Description

[Detailed Description of the Invention] Background of the Invention [Technical Field of the Invention] This invention relates to the number of rotations, rotation speed, angular velocity, and angular position of a rotating body, the velocity of an object periodically moving on a fixed path,
This invention relates to a device that detects the period, position, and velocity of other objects using optical signals.

[Description of the Prior Art] Optical transmission has the excellent feature of not being affected by electromagnetic noise, and is therefore 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 made 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 the 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, and the resulting photodetection signal is The disadvantage is that the strength is 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. Furthermore, there is a high possibility that the optical axis will shift due to photographing or the like.

Summary of the Invention and Purpose of the Invention The present invention utilizes the features of optical measurement, which enable highly reliable measurement and low-loss long-distance transmission even under electromagnetic noise, while eliminating the hassle of optical axis alignment. It is an object of the present invention to provide a detection device for detecting rotational speed, speed, etc., which does not require additional work and does not cause a situation in which measurements cannot be made due to optical axis deviation.

[Structure, operation, and effect 1 of the invention The device for detecting rotational speed, speed, etc. according to the present invention detects a 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 object. An element that is fixed to a member and generates an electromotive force when a magnetic flux generating part passes relatively near it, such as a coil, and modulates the intensity of light guided from a light source by applying the generated electromotive force information about the movement of the object, e.g. rotational speed,
The light intensity modulating element is provided with a means for creating speed data, etc., and the light intensity modulation element is formed on a substrate having an electro-optic effect and has two leading wavepaths having mutually adjacent portions, and mutually adjacent portions of the two leading wavepaths. It is characterized by comprising a pair of electrodes which are provided on top of the electrode and to which the generated electromotive force is applied.

The parts of the optical waveguide that are close to each other constitute a directional coupler, and applying a voltage to the electrodes changes the coupling strength and degree of phase matching, so the output light intensity of the directional coupler changes. is modulated by the applied voltage. The output light intensity of the directional coupler is modulated each time the magnetic flux generation section passes near the electromotive force generation element. By measuring the time intervals, data such as the number of rotations 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 [Configuration of rotational speed detection device] In FIG. 1, a circle is placed on the axis for which the rotational speed is to be detected, such as the output shaft of a motor or a shaft connected thereto (the path shown).
(10) is fixed at its center, a circle! One permanent magnet (11) is embedded around (10). A magnet (11) that moves circularly as the disk (10) rotates.
At any point on the trajectory, the coil (30) is arranged so as to face the magnet (indicated by the chain line (Ila)) that has reached this point in the vicinity, and is fixed at that position by a suitable fixing member.゛The magnet (11) is a disk (1
It is also possible to provide it on the peripheral surface of 0). Also in this case,
The coil (30) 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 stone (11) on the disk (10), the disk (10) itself may be made of ferromagnetic material or the disk (10) may be
) may be fitted with a ferromagnetic ring to magnetize this ferromagnetic material.

The light intensity modulation element is a crystal that produces an electro-optic effect, for example, a 2-layer crystal formed on a L i Nb Oa crystal substrate (20).
It includes two leading wavepaths (21) (22). These optical waveguides (21) and (22) have portions adjacent to each other, and these adjacent portions constitute a directional coupler. A pair of electrodes (31) are formed on portions of the optical waveguides (21) and (22) that are close to each other. Both ends of the coil (30) are connected to these electrodes (31), respectively. 13, a voltage induced in the coil (30) is applied between these electrodes (31).
) (22) is formed, for example, by thermally diffusing Ti into the substrate (20), and the electrode ff1 (31) is formed by vapor depositing A/.

Light from a light source (not shown) is sent through an optical fiber (41) and guided to a leading waveguide (21) on the substrate (20) via a suitable optical coupler. The generally intensity-modulated light output from the same leading waveguide (21) is likewise guided into the optical fiber (42) via a suitable light attenuator. The optical signal of the optical fiber (42) is converted into an electrical signal by the photoelectric conversion element (43). This electric signal (a) is sent to a level discrimination circuit (signal (1)) through a low-pass filter (44), and further is sent to a pulse or square wave signal (C
) is input to the counter (46).

A detection signal representing the number of rotations of the disc (10) is obtained from the counter (46).

[Voltage generated in the coil] When the disk (10) rotates once, the magnet (11) generates a voltage in the coil (3).
0〉 once. At this time, the magnetic flux generated from the magnet (11) interlinks with the coil (30), and the interlinked magnetic flux number density (Ii) changes with time, so the electromotive force occurs. This electromotive force V is given by the following equation.

V=-nc(dΦ/dt) where nC is the number of turns of the coil, and Φ is the number of magnetic fluxes interlinking with the coil.

To simplify the explanation, as shown in Figure 2, a magnet (
11), the surface facing the coil (30) (hereinafter referred to as the magnet surface) and the coil (30) are both circular and have the same diameter. If the shape of the coil and magnet surface is square or other shape, even if these sizes are different,
There is only a slight hole in the waveform of the electromotive force, etc., and there is no substantial difference from the case shown in FIG.

FIG. 3 shows the number Φ of magnetic flux interlinking with the coil (30), its time change (dΦ/dt), and the electromotive force V generated in the coil (30). Magnet (11) and coil (30)
The flux linkage number Φ changes when the two move toward each other and when they move away from each other, and its time change (dΦ/dt) takes positive and negative values. Therefore, positive and negative electromotive force V is generated in the coil (30) twice: when they approach each other and when they move away from each other.

A unidirectional coupler for modulating light intensity in a light intensity modulating element causes exchange of light power between two parallel optical waveguides that are close to each other. Leading wavepath (21) and (2
A directional coupler configured by mutually close parts of 2) and
It is assumed that the interaction length, coupling coefficient, phase constant, etc. are set so that 0% of the power is transferred to the optical waveguide (22) used.

death! Since Nb0a is a crystal with an electro-optic effect, when an electric field is applied to this crystal, its refractive index changes. When the voltage generated from the coil (30) is applied to the electrode (31), the refractive index of the optical waveguide (21) (22) directly under the electrode changes, and the phase of the leading waveguide (21) (22) changes at these parts. The constant changes (Z cut L i N
b 03 case), or the coupling strength (coupling coefficient) changes by changing the refractive index between the optical waveguide parts (Y cut i Nb 03 case). By changing the coupling strength and phase matching, the leading waveguide (21)
In the directional coupler/device constructed from the adjacent portions of (22), the transition flatness of the optical power changes.

Figure 4 shows the output light intensity of the optical waveguides (21) and (22) in the case of a Y-cut LtNtlO3 substrate.
is shown on the horizontal axis.

In the embodiment shown in FIG. 1, the interaction length is set to a. The solid line is the output light intensity of the leading waveguide (22),
The broken line indicates the output light intensity of the leading waveguide (21). When the voltage applied to the electrode (31) is 0, the optical waveguide (2
2), the light with the maximum intensity is output, and no light is output from the optical waveguide (21). A certain voltage Valfi electrode (31
), the output light intensity of the optical waveguide (21) becomes maximum, and the output light intensity of the optical waveguide (22) becomes 0. In this way, the output light intensity of the optical waveguide (21) changes depending on the voltage applied between the electrodes (31).

Effect of L rotation speed detection device] FIG. 5 shows the output signal (a) of the photoelectric conversion element (43), the output signal (b) of the low-pass filter (44), and the output signal ( C) is shown. These waveforms are obtained when the absolute value of the voltage V generated by the coil (30) is equal to or smaller than the above-mentioned voltage Va.

The waveform of the output signal <a> of the photoelectric conversion element (43) is the same as the intensity waveform of the light obtained in the optical waveguide (21).

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 nc of the coil (30) are constant, the voltage generated in the coil (30) is equal to the disc (
10) It depends on the number of rotations, and the higher the number of rotations, the higher the voltage. Positive and negative voltages are generated when the magnet (11) passes near the coil (30), so if the absolute value of this generated voltage is less than Va, the signal (a) has two pulse-like components. appears. As the rotation speed of the circle 8N (10) increases, the time T for the magnet (11) to pass near the coil (30) becomes shorter, and the absolute value of the voltage ■ generated in the coil (30) increases, so 1 The number of pulse-like components occurring in the signal <a> increases during each pass. Therefore, as the rotation speed increases, the signal (a')
contains more high-order harmonic components.

The low-pass filter (44) receives a signal (a) corresponding to the lowest rotational speed within the rotational 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, for any value of rotational speed, the signal (b) contains circle a3 (10
) comes to appear one pulse-like component for one rotation.

This pulsed component of the signal (b) is processed by the level discrimination circuit (
45), the level is discriminated by the threshold value (S) set, and the waveform is shaped (signal (C)).

The counter (46) measures the pulse interval (pulse interval Pt) included in the signal (C), or counts the number of pulses within a certain period of time C1. These timing results or counting results represent the rotational speed, rotational speed, or angular velocity of the disk (10).

[Modification] In the above embodiment, the waveform outputted from the leading waveguide (21) is
Although the light output from the optical waveguide (22) is used to detect the rotation speed, it is also possible to use the light output from the optical waveguide (22). Further, the interaction length of the directional coupler can be set arbitrarily.

Furthermore, as shown by the chain line (35) in FIG.
When a Zener diode (35) is connected in parallel to 30), one of the positive and negative voltages generated in the coil (30) can be cut due to its rectifying action.
On the other hand, the absolute value of the voltage applied to the electrode (31) can be kept below a certain value (Zener voltage). If the Zener voltage is set below the voltage ■a mentioned above, the signal <a
The pulse-like component appearing in > is always one per one rotation of the disk (10), and the filter (44) can be omitted, and the range of detected rotational speed is limited by the pass band of the filter (44). Therefore, it is possible to widen the rotational speed measurement range.

Various types of rectifier circuits and clip circuits can be used in addition to Zener diodes. If necessary, you can connect a resistor in series with the coil (30).

In the above embodiment, one permanent magnet (11
), but if a plurality of permanent magnets are provided at equal angular intervals, the accuracy of rotational speed and angular velocity detection will be increased. In addition, when detecting a specific angular position of the disk (10), multiple permanent magnets are not placed at equal angular intervals,
The arrangement state is the detection signal (for example, the level discrimination circuit (45)
A specific arrangement state is assumed as appearing in the output signal (C)). Also, by making the strength of a specific magnet stronger than other magnets, the output signal (a) of the photoelectric conversion element (43)
A specific angular position may be detected based on the difference in waveforms appearing in the angular position.

The substrate (20) 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 guide waveguide can also be manufactured using various techniques and materials depending on the type of substrate other than thermal diffusion of Ti. In addition, it is also possible to ground one of the electrodes (31).The electrodes can be made of a material other than AI, such as lithium.This invention is applicable not only to physical quantities related to the rotation of a rotating body, but also to fixed two-dimensional or three-dimensional It can also be applied to the measurement of physical quantities related to the movement of objects that periodically reciprocate on a path.
If two permanent magnets are installed on one object that moves relatively, by measuring the time interval during which these two magnets pass near the coil, it can be determined that the object moves back and forth throughout its circumference. You can measure the speed of an object even if it is not moving.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an example of a rotation speed detection device, Fig. 2 is a diagram showing the size and shape of the permanent magnet and coil, and Fig. 3 is a diagram showing the size and shape of the permanent magnet and coil.
A graph showing the number of magnetic fluxes interlinking with the coil, their changes, and the electromotive force generated in the coil. Figure 4 is a graph showing changes in the output light intensity of the optical waveguide. Figure 5 is the output of each circuit shown in Figure 1. FIG. 3 is a waveform diagram showing an example of a signal waveform. (10)...Disc, (11)...Permanent magnet, (20
) - Electro-optic crystal substrate (light intensity modulation element), (2
1) (22)... Leading wave path, (30)... Coil,
(31)...electrode, (43)...photoelectric conversion element, (
44)...Low pass filter, (45)...Level discrimination circuit, (4G)...Counter. that's all

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; The light intensity modulating element has an element that modulates light intensity by applying the generated electromotive force, and a means for creating information regarding the movement of a moving object from a change in the modulated light intensity, and the light intensity modulating element has an electro-optic effect. two optical waveguides formed on a substrate having portions close to each other;
1. A detection device for detecting rotational speed, speed, etc., comprising a pair of electrodes provided on mutually close portions of two optical waveguides and to which generated electromotive force is applied.