JPS58200166A - Measuring system for contactless tachometer - Google Patents

Abstract

PURPOSE:To obtain a contactless tachometer free from electromagnetic induction noise by detecting the rotation or passage of a magnetic field due to a mechanical rotor having magnets properly arranged with a magnetic field measuring apparatus comparing a light source, a magnetism detecting section and a photometry section. CONSTITUTION:A magnetic field measuring apparatus comprises a measuring section A, a transmisssion section B and a detector section C. Light from a light source 9 is focused to a half mirror 5 through a lens 8 and most thereof is lead to the detector section C through an optical fiber 1 while a part thereof to a light receiver 7. The detector section C provides a focused output of a lens 10 to a magnetic garnet film 3 through a polarizer 2. Faraday rotation of the film 3 due to a magnetic field applid thereto 3 is measured as change in the intensity of light with a light receiver 6 through a polarizer 4 and a lens 11. Therefore, the comparison of outputs from the light receivers 6 and 7 enables the measurement of a magnetic field applied to the film 3. A magnet 13 is arranged on a rotary table 14 adapted to rotate synchronizing a rotating shaft 15 of a rotary instrument 16 securely close to the detector section C thereby enabling the rotation of the instrument 16 free from electromagnetic induction noise.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a measurement method of a non-contact mechanical rotation speed measuring device.

Conventional non-contact type non-contact tachometers use the magnetoresistive effect described in the Proceedings of the National Conference of the Institute of Electronics and Communication Engineers in 1981, page 161, or in the August 18, 1980 issue of Nikkei Mechanical, page 88. Examples include rotating needles, specifically electronic water meters. A magnetic thin film is used as the detection part of this rotating needle, and the measurement principle is to measure the change in electrical resistance of the magnetoresistive element over time. Therefore, electrical wiring is used for signal transmission, and it is susceptible to noise due to electromagnetic induction, making it unsuitable for use as a rotating needle in generators, motors, etc., for example.

An object of the present invention is to provide a measurement system for an optical non-contact tachometer that is free from electrical noise such as electromagnetic induction.

In order to achieve the above object, the present invention has developed an optical 7 eyebar magnetic flux needle that utilizes the fact that the Faraday rotation ability changes depending on the magnitude of the magnetic field, in place of the conventional magnetic field detector using the magnetoresistive effect. It is described in Japanese Patent Application No. 55-112742 filed on August 18, 1955, and by using a nine-magnetic field measuring device, a measurement method of an optical non-contact tachometer that is not affected by electromagnetic induction noise at all was realized. .

Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 shows the configuration of an embodiment of the measurement method according to the present invention. The magnetic field measurement device in this method includes a measurement section A1 and a transmission section B1.
It consists of a detection section C. The light emitted from the light source 9t is focused on the half mirror 5 by the lens 8, a part of which enters the light receiver 7, but most of the light is introduced into the optical fiber 1. Furthermore, lens IO
After being focused by K, the light becomes directly polarized by the polarizer 2, undergoes Faraday rotation by the magnetic garnet film, passes through the analyzer 4 and the lens 11, and reaches the light receiver 6. When a perpendicular magnetic field is applied to the magnetic garnet film, the magnitude of one revolution of 7 Arad changes depending on the magnitude of the magnetic field, and the light intensity of the light receiver 6 changes. Therefore, by comparing the signal intensities p and q output from the light receiver 7.6, the magnetic field Is perpendicular to the magnetic garnet film can be measured. When the magnet 13 is fixed on the rotary table 14 near the magnetic field measuring detector C, the magnet 13 rotates in synchronization with the rotating shaft 150 of the rotary device 16. A magnetic field is generated from the north pole of the magnet 13 toward the south pole. FIG. 2 shows the half-plane positional relationship as the angle II-a formed by the magnetic garnet film 3 and the magnet 13. The color loss of the magnetic field at the center 0 point is H
When M is assumed, the vertical magnetic field Ha becomes Hm=Hvsia#.

The signal strength I at the comparator 12 is electrically processed so as to be proportional to Ha.

In FIG. 3, a samarium cobalt magnet is used as the magnet 13, and (YSmLuGdCa)s(
F e Ge ) m Os t % He- as light source 9
This is an example in which the rotation speed of a generator with an output of 100,000 kl was detected using Nev-za. Signal intensity I' is shown as a function of time. The measurement result was 12056.2 rpm, which matched the mechanically measured value with an accuracy of ±o, trpm.

Figure 4 shows the configuration of another embodiment of the measurement method according to the present invention. Figure 4 shows an example in which the positional relationship between the detection unit and the magnetic field generating magnet is different from the embodiment shown in Figure 1.
1 shown. In this case too, A,
Portion B is the same as in FIG. 1 and is omitted in FIG. 4.

In this implementation, the magnets 13 are located near the end of a large rotary table and move circumferentially as it rotates. Therefore, a magnetic field is applied to the magnetic garnet m only for a short time when it approaches the detection part C, and a pulse-like output I is obtained. FIG. 5 shows the output characteristics of a generator installed on the same generator as in the embodiment shown in FIG. 1. Although the signal strength is smaller than that in Fig. 43, the time width of the signal is small, so it is possible to input other information to the optical fiber and process it all at once. For example, as in yet another embodiment shown in FIG. 6, the detection sections C can be arranged in series to form a detection section C1 and a detection section C2. If the magnets 13 are placed on two rotary tables with opposite polarities, the directions of the magnetic fields when they cross CI and C2 will be opposite, resulting in two pulse trains with opposite signs and different pulse heights and pulse widths. is obtained. By performing an operation to separate these two pulses in the measuring section A, it is possible to know the respective rotational speeds or relative phase difference of the two rotating bodies. It is obvious from this embodiment that more detection units can be connected in series or installed in parallel.

According to the present invention, it is possible to construct a non-contact tachometer that is completely unaffected by electrical noise and has a high degree of measurement accuracy and excellent maintainability.

It is obvious that the rotating body of the present invention can be applied to any mechanical rotating body other than a generator, such as electric motors, engines, Kameoka rotating parts, and automobile tachometers. It is also obvious that the present invention can be applied to flow rate needles, air volume needles, wind vanes, and speed darkness meters, which are measuring devices based on rotation as a basic principle. It is also obvious that a coil may be attached around the magnet in order to excite the magnet.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the measurement method according to the present invention, Fig. 2 is a plan view showing the magnitude relationship between the magnetic garnet film and the magnet in the above embodiment, and Fig. 3 is the output in the above embodiment. Figure 4 is a block diagram of another embodiment of the measurement method according to the present invention; Figure 5 is a diagram showing measurement results according to the embodiment of Figure 4; Figure 6 (2) is a diagram showing measurement results of signal strength; FIG. 7 is a block diagram of still another embodiment of the measurement method according to the present invention, and is a diagram showing the measurement results according to the implementation sequence of FIG. 6. M...Measurement section, B...Transmission section, C...Detection section, l
...Optical fiber, 2...Polarizer, 3...Magnetic garnet film, 4...Analyzer, 5...Normal mirror, 6
．． 7... Light receiver, 8... Lens, 9... Light source, 1
0.11... Lens, 12... Comparison detector, 13.
... Magnet, 14... Rotating table, 15... Rotating shaft, 16... Rotating equipment C generator). Agent Patent Attorney Toshiyuki Usuda ¥11゛ Mi No. 2 Figure 3 Figure #IfJ4 th) i'i5 (2) ¥16 Figure 7 Figure sec,)

Claims (1)

[Claims] 1. A light source, a magnetic field detection section made of a medium having Faraday rotation ability, a measurement section that measures light from the detection section, and optical coupling between the light source, the detection section, and the measurement section. The first part is a magnetic field measuring device consisting of a magnetic transmission line, and the second part is a magnetic field generating device having a magnet (ferromagnetic material) placed on or inside an arbitrary mechanical rotating body. A measurement method for a non-contact tachometer, characterized in that the rotation of a rotating body is measured by detecting the rotation or passage of a magnetic field from a second part in a first part. 2. A tachometer measurement method according to item 1, wherein a magnetic garnet thin film is used as the medium having Faraday rotation ability.